CN108571481B - Oil inlet and return independent regulation retarding control strategy of heavy vehicle electro-hydraulic traveling system - Google Patents

Abstract

The invention provides a slow-speed control strategy for independent adjustment of oil intake and return of a heavy-duty vehicle electro-hydraulic travel system, which decouples the two problems of speed control and negative load suppression. Adjust the displacement of the variable pump, and change the output flow of the variable pump to realize the speed control of the drive motor speed; based on the deviation between the actual speed and the expected speed, the desired acceleration of the system is designed through the acceleration planner, and the actual output acceleration of the system and the expected acceleration are designed. The acceleration deviation is the input of the slow speed adjustment controller, and the control signal of the electro-hydraulic proportional pressure control valve is calculated and output by the controller. The back pressure is continuously and precisely controlled and adjusted, so that the resistance torque generated by the back pressure on the driving motor and the driving torque generated by the overall sliding force of the vehicle are balanced, so as to realize the speed regulation and slow speed control of the driving motor.

Description

Retarding control strategy for independent adjustment of oil in and out of heavy-duty vehicle electro-hydraulic travel system

technical field

The invention belongs to the technical field of engineering vehicle drive and control. The invention relates to a braking system and a control method, in particular to a slow-speed control strategy for independent adjustment of oil intake and return of an electro-hydraulic walking system of a multi-axle hydrostatic driven heavy vehicle under continuous negative load.

Background technique

The closed pump-controlled motor hydrostatic drive system is widely used in the driving and walking system of heavy-duty transportation vehicles such as flatbed trucks and tunnel segment trucks. It has good dynamic performance and control performance, and can realize stepless speed regulation. It has always been a heavy engineering project The main driving method used by the vehicle. When heavy construction vehicles are in long-distance downhill conditions, the brakes are continuously braked to balance the negative load (such as the overall sliding force of the vehicle). The braking performance is seriously degraded, causing potential safety hazards. Therefore, in order to ensure that the heavy vehicle still has the speed regulation function and can drive at a constant speed when going downhill, an auxiliary continuous braking scheme is required. The current solutions for retarding braking of heavy-duty vehicles include hydraulic auxiliary braking, eddy current auxiliary braking, and engine auxiliary braking. However, many heavy-duty transportation vehicles are affected by the installation structure and safety in engineering construction, and the use of hydraulic auxiliary braking and eddy current braking is limited. In addition, the braking force of the engine is limited and cannot be controlled in real time.

The electro-hydraulic retarding control of the vehicle is a method of coordinated control of the system flow and pressure to control the speed and stability of the electro-hydraulic walking system, so as to realize the smooth control of the running speed of the vehicle when the vehicle goes downhill. Vehicle retarding control refers to the controlled and smooth operation of vehicle speed under negative load conditions, simply to make the vehicle running speed controlled and stable within a specified range. The premise of achieving smooth speed is that the driving force of the controlled object must be able to suppress the negative load during speed control. However, the current electro-hydraulic retarding braking technical solutions have some shortcomings:

1) Ordinary four-way inlet and outlet linkage proportional valves and servo valves can control the smooth movement of the controlled object under negative load conditions, but a small valve opening needs to be closed to make the valve-controlled power mechanism work in quadrants II and IV. The coupling problem of negative load and motion control is suppressed, the valve port throttling loss is large, and the heat generation is serious.

2) The negative load is balanced by the continuous braking of the brake. The brake heats up seriously. Long-term use in the downhill and long-slope conditions will cause the braking performance to decline. Intermittent repeated braking can improve this problem to a certain extent, but the speed stability is not stable. it is good.

4) The pump-controlled speed adjustment and the electro-hydraulic proportional balance valve adjust the back pressure scheme, which can decouple the two problems of speed control and negative load suppression. When going down a long slope, there is no need to use the brake to slow down. By arranging a balance on the oil return road The valve is convenient for arranging coolers for forced cooling, and the valve-controlled adjustment back pressure has a fast response speed. The disadvantage is that this solution cannot recover the downhill potential energy.

5) Pump-controlled speed regulation and retarding pump retarding scheme, the remaining part of downhill potential energy that can be absorbed by engine load and other hydraulic circuits is handed over to retarding system for further absorption, and retarding pump can store energy and drive the accumulator Hydraulic motor for cooling fan, the control element is electro-hydraulic proportional relief valve. Although this solution recovers part of the downhill potential energy, the structure is complicated, especially when the additional weight of the recovery device is strictly required, it is difficult to implement, and the response speed is It is slower than the balance valve scheme.

6) The dual-valve independent adjustment scheme can realize the decoupling of speed control and negative load suppression. The system composition is simple and the response speed is fast. This solution, combined with the accumulator, can also supply oil to the cooling circuit, partially recovering the downhill energy. The disadvantage is that the throttling loss is serious, and the system energy rate is lower than that of the pump control regulation.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the present invention provides a slow-speed control strategy for independent adjustment of the oil intake and return of the electro-hydraulic travel system of the multi-axle hydrostatic drive heavy vehicle under continuous negative load. Independent control and adjustment of pressure, decoupling the two problems of speed control and negative load suppression, through the volume control and adjustment of the traveling variable pump in the system oil circuit to realize the speed control of the drive motor speed, and through the bidirectional proportional balance valve in the system oil return circuit The electro-hydraulic proportional pressure control valve of the group realizes continuous self-adaptive control and adjustment of the back pressure, so that the resistance torque generated by the back pressure on the drive motor and the driving torque generated by the overall sliding force of the heavy vehicle are balanced, and the speed regulation of the drive motor can be slowed down. speed control. When going down a long slope, the smooth control of the vehicle speed is realized by the retardation adjustment of the electro-hydraulic retarding control system, which avoids the potential safety hazards caused by the long-term use of the brake to heat up, and improves the speed regulation and stability of the electro-hydraulic walking system of heavy vehicles. Speed control performance reduces the handling requirements for the vehicle driver.

The technical scheme of the present invention is as follows:

A slow-speed control strategy for independent adjustment of oil intake and return of heavy-duty vehicle electro-hydraulic travel system. Under the continuous negative load (such as the following long slope conditions), the slow-speed control strategy of heavy-duty vehicle electro-hydraulic travel system is based on the system oil input and return. Through independent control and adjustment of road flow and pressure, the two problems of speed control and negative load suppression are decoupled, and the displacement of the variable pump is adjusted through the volume control and adjustment of the variable pump in the oil inlet of the system to realize the speed control of the drive motor speed. Based on the deviation between the actual speed and the expected speed of the current system, the desired acceleration of the current system is designed through the acceleration planner, and the continuous adaptive control of the back pressure is realized through the electro-hydraulic proportional pressure control valve of the bidirectional proportional balance valve group in the system oil return circuit. , so that the resistance torque generated by the back pressure on the drive motor and the drive torque generated by the overall sliding force of the heavy vehicle are balanced to realize the speed regulation and slow speed control of the drive motor.

The slow speed control strategy is adjusted by the volume control of the walking variable pump in the oil inlet of the system. The deviation between the actual speed output by the system and the desired speed set by the system is used as the input of the controller, and the output walking variable is calculated by the speed adjustment controller. The real-time control input of the pump adjusts the displacement of the variable pump, thereby changing the output flow of the pump, and realizing the speed control of the drive motor speed.

The slow speed control strategy continuously adjusts the electro-hydraulic proportional pressure control valve of the two-way proportional balance valve group in the slow speed oil return circuit of the system, so that the back pressure of the oil return circuit can be adjusted continuously, so that the driving motor is controlled by the back pressure. A certain acceleration is generated under the combined action of the generated resistance torque and the driving torque generated by the overall sliding force of the vehicle; at the same time, the deviation between the current acceleration and the expected acceleration actually output by the system is used as the input of the slow-speed adjustment controller, and the slow-speed adjustment controller is adjusted by back pressure. The speed controller calculates and outputs the real-time control input of the electro-hydraulic proportional pressure control valve. After the pressure control and adjustment of the electro-hydraulic proportional pressure control valve, the back pressure required for the slow speed adjustment in the oil return circuit is obtained, so as to realize the slow speed of the drive motor. control.

The slow speed control strategy is based on the deviation between the actual speed of the current system and the desired speed, and the desired acceleration of the current system is designed through the desired acceleration planning algorithm of the acceleration planner, wherein the desired acceleration is composed of two parts: the desired acceleration base value and the desired acceleration dynamic value, The base value of the expected acceleration depends on the expected vehicle operating state, and is set to 0 when driving at a constant and steady speed, and the dynamic value of the expected acceleration depends on the comprehensive speed deviation.

The traveling system of the heavy-duty vehicle includes an engine, a transfer case, a coupling, a traveling pump, a charge pump, a filter, a relief valve, a two-way proportional balance valve group, a drive motor, a reduction box, a wheel, and various corresponding sensor devices. and control devices, etc. The two-way proportional balance valve group includes a hydraulic flush valve, an electro-hydraulic proportional pressure control valve, a number of one-way valves and an orifice.

Further, the two-way proportional balance valve group is arranged on the return oil road of the electro-hydraulic walking system of the heavy-duty vehicle, and the back pressure of the system return oil circuit can be continuously and accurately adjusted by continuously adjusting the electro-hydraulic proportional pressure control valve in the two-way proportional balance valve group. Realize the slow speed control of the electro-hydraulic walking system of heavy vehicles, and at the same time arrange a cooler in the system oil return circuit for forced cooling, so as to reduce the temperature of the high-temperature hydraulic oil generated by the throttling control of the electro-hydraulic proportional pressure control valve, so that the system hydraulic oil The temperature is effectively controlled.

The specific process is as follows:

1) When the vehicle is driving on flat ground or climbing conditions, the energy of the closed hydraulic system comes from the engine, passes through the transfer case, and is transmitted to the travel variable pump, and the output pressure oil enters the drive motor through the one-way valve, and the two-way proportional balance is achieved. The hydraulic flush valve in the valve group automatically adjusts the working position of the reversing valve spool according to the pressure difference between the two ends of the spool, switches to the upper working position of the valve, and the oil discharged from the drive motor enters the electro-hydraulic proportional pressure control through the reversing valve. By controlling the current input signal, the electro-hydraulic proportional pressure control valve maintains the maximum opening, and the back pressure of the oil return circuit of the walking system reaches the minimum safe value, so that the motor can obtain the maximum driving torque and minimize the system throttling loss. Taking the deviation between the actual output speed of the system and the desired speed set by the system as the input of the speed adjustment controller, the speed adjustment controller calculates and outputs the real-time control input of the traveling variable pump, and then realizes the system volume by continuously adjusting the displacement of the traveling variable pump. The speed regulation control makes the torque acting on the drive motor in a dynamic balance state, and realizes the speed regulation and speed regulation control of the heavy vehicle walking system.

2) When the vehicle is driving downhill or a long downhill condition, the energy of the closed hydraulic system comes from the power supply of the engine, and part of the energy comes from the sliding force generated by the vehicle under the action of its own gravity. The energy is transmitted through the transfer case. To the walking variable pump, the output pressure oil enters the drive motor through the one-way valve. At this time, the hydraulic flush valve in the two-way proportional balance valve group automatically adjusts the working position of the reversing valve spool according to the pressure difference between the two ends of the spool.

The retarding control of the electro-hydraulic walking system of heavy-duty vehicles is based on the deviation between the actual speed and the desired speed of the current system, and the desired acceleration of the current system is designed through the desired acceleration planning algorithm of the acceleration planner.

With the influence of the gravitational potential energy of the vehicle, the pressure of the retarding braking system rises rapidly, and the back pressure regulating retarding controller continuously outputs the input control signal of the electro-hydraulic proportional pressure control valve based on the deviation signal between the actual acceleration and the expected acceleration of the vehicle. The valve opening of the electro-hydraulic proportional pressure control valve is reduced to an appropriate opening to obtain the back pressure required for the slow speed adjustment in the oil return circuit of the slow brake system, and at the same time cooperate with the speed adjustment controller to reduce the displacement of the traveling variable pump , so as to maintain the torque of the resistance torque generated by the back pressure and the driving torque generated by the overall sliding force of the vehicle acting on the drive motor in a balanced state, so that the vehicle continues to run at a constant speed, so as to realize the slow speed control of the vehicle.

Beneficial effects: the present invention improves the control performance of the hydraulic traveling system of the hydrostatic drive vehicle due to the fast response speed of the valve-controlled adjustment back pressure, and improves the operation efficiency of the vehicle driver when the vehicle driver goes down a long slope

Description of drawings

FIG. 1 is a schematic structural diagram of the present invention.

FIG. 2 is a schematic structural diagram of a two-way proportional balance valve group of the present invention.

FIG. 3 is a schematic diagram of the working principle of the present invention.

In the figure, 1-engine; 2-transfer case; 3-coupling; 4-travel variable pump; 5-charge pump; 6-filter; 7-relief valve; 8-circuit check valve; 9- Cooler; 10-electro-hydraulic proportional pressure control valve; 11-hydraulic flushing valve; 12-drive motor; 13-reduction box; 14-wheel; 15-two-way proportional balance valve group; 16-incoming check valve.

Detailed ways

The present invention will be described below with reference to specific examples. Those skilled in the art can understand that these examples are only for illustrating the present invention, and they do not limit the scope of the present invention in any way.

As shown in Figure 1, the heavy-duty vehicle electro-hydraulic travel system includes an engine 1, a transfer case 2, a coupling 3, a travel variable pump 4, Charge pump 5, filter 6, relief valve 7, two-way proportional balance valve group 15, drive motor 12, reduction box 13 and wheels 14, electrical control device.

As shown in FIG. 2 , the two-way proportional balance valve group 15 includes a hydraulic flush valve 11 , an electro-hydraulic proportional pressure control valve 10 and several loop check valves 8 .

In the above structure, the output torque of the engine 1 is transmitted to the hydraulic braking system through the transfer case 2, and the traveling variable pump 4 is driven through the coupling 3, and the output hydraulic oil from the oil tank enters the driving motor 12 through the dual-inlet check valve 16; The two-way proportional balance valve group 15 is arranged on the oil return road, and a cooler 9 is installed for forced cooling;

Among them, when there is an oil circuit pressure difference between the two ends of the valve core of the hydraulic flushing valve 11, the upper working position of the hydraulic flushing valve 11 is automatically connected, and the output oil of the driving motor enters the electro-hydraulic proportional pressure control valve 10 through the hydraulic flushing valve 11, and outputs the oil. After the pressure is adjusted, it enters the oil inlet chamber of the traveling variable pump 4 through the loop check valve 8, and the overflow oil enters the oil tank after being cooled by the cooler 9.

As shown in Figure 3, the control device includes a speed adjustment controller, a back pressure adjustment retarding controller, a travel variable pump speed sensor, a travel variable pump pressure sensor, a drive motor speed sensor, a motor pressure sensor, and the temperature of the hydraulic oil in the back pressure circuit. sensor; the control device is used to collect the signals of each sensor and realize the slow speed control process; realize the speed regulation control of the driving motor 12 by controlling the volume control and adjustment of the traveling variable pump 4 in the oil inlet circuit; control the bidirectional proportional balance valve group in the oil return circuit 15 Realize the continuous self-adaptive control and adjustment of the back pressure, so that the resistance torque generated by the back pressure on the driving motor 12 and the driving torque generated by the overall sliding force of the heavy vehicle are balanced, and the retarding control of the driving motor is realized.

On the other hand, the traveling variable pump speed sensor is installed on the connecting shaft output from the transfer case 2 to the traveling variable pump 4, and feeds back the speed signal of the traveling variable pump; the traveling variable pump pressure sensor located at the inlet and outlet of the traveling variable pump 4 outputs the traveling variable The pressure signal of the pump inlet and outlet is fed back to the speed adjustment controller of the hydraulic braking system, so as to obtain the input control amount of the pump control volume speed control;

Bearing on the above, the motor pressure sensor is arranged at the inlet and outlet of the drive motor 12, and then the pressure at the inlet oil port of the drive motor is obtained. At the same time, the speed of the motor is output through the speed sensor on the output shaft of the drive motor, and the output signal of the sensor is transmitted to the back pressure. Adjust the controller to obtain the pressure adjustment input control amount of the voltage proportional pressure control valve.

Example 1

When the vehicle is driving on flat ground or climbing conditions, the energy of the closed hydraulic system comes from the engine, passes through the transfer case, and is transmitted to the travel variable pump. The output pressure oil enters the drive motor through the one-way valve, and the two-way proportional balance valve group The medium hydraulic flushing valve automatically adjusts the working position of the reversing valve spool according to the pressure difference between the two ends of the spool. The oil discharged from the drive motor enters the electro-hydraulic proportional pressure control valve through the reversing valve, and the electro-hydraulic pressure is controlled by the current input signal. The proportional pressure control valve maintains the maximum opening degree, and the back pressure of the oil return circuit of the traveling system reaches the minimum safe value, so that the motor can obtain the maximum driving torque T=ΔpD _m , and the throttling loss of the system is minimized. The system volume speed control is realized by continuously adjusting the displacement of the walking variable pump, so that the torque acting on the drive motor is in a dynamic balance state. The speed adjustment controller calculates the real-time control input of the output traveling variable pump, adjusts the displacement of the variable pump, and then changes the output flow of the pump, so as to realize the speed regulation and stable speed control of the heavy vehicle traveling system to maintain the vehicle running at a constant speed. At this time, the vehicle running system mainly realizes the speed regulation and stable speed control of the vehicle through the volume control of the running variable pump and the drive motor.

Δp=p _A -p _B

In the formula, p _A is the inlet pressure of the driving motor, p _B is the pressure of the slow braking system, Δp is the pressure difference between the inlet and outlet of the driving motor, D _m is the displacement of the driving motor, J is the rotational inertia of the driving motor, and B _m is the driving motor Viscous damping coefficient, ω _m is the actual speed of the drive motor, and T _G is the total external load torque.

Example 2

When the vehicle is driving downhill or a long downhill condition, the energy of the closed hydraulic system comes from the power supply of the engine, and part of the energy comes from the sliding driving force generated by the vehicle under the action of its own gravity. Travel variable pump, the output pressure oil enters the drive motor through the one-way valve. At this time, the hydraulic flush valve in the two-way proportional balance valve group automatically adjusts the working position of the reversing valve spool according to the pressure difference between the two ends of the spool.

The retardation control of the electro-hydraulic walking system of heavy vehicles is based on the deviation between the actual speed and the desired speed of the current system, and the desired acceleration α _md of the current system is designed through the desired acceleration planning algorithm of the acceleration planner.

α _md =α _base +K _ad *(ω _md -ω _m )

The expected acceleration α _md is composed of two parts: the expected acceleration base value and the expected acceleration dynamic value, where the expected acceleration base value depends on the expected vehicle operating state, and is set to 0 when driving at a constant speed, and the expected acceleration dynamic value is determined by the comprehensive speed deviation.

a) α _md is the expected base value of acceleration, and is the expected value of acceleration when the walking system runs at a steady speed.

b) Ka _ad *(ω _md -ω _m ) is the expected dynamic value of the pressure, which is determined by combining the speed deviations of each motor.

At this time, through the volume control and adjustment of the traveling variable pump in the oil inlet of the system, the deviation between the actual speed output by the system and the desired speed set by the system is used as the input quantity of the controller, and the real-time output of the traveling variable pump is calculated by the speed adjustment controller. Control the input, adjust the displacement of the variable pump, and then change the output flow of the pump, and realize the speed regulation control of the drive motor speed as an auxiliary cooperation for the slow speed and steady speed control of the vehicle walking system.

With the influence of the gravitational potential energy of the vehicle, the pressure of the retarding braking system rises rapidly. By continuously adjusting the electro-hydraulic proportional pressure control valve of the two-way proportional balance valve group in the oil return circuit of the system, the back pressure can be adjusted continuously, so that the The drive motor generates a certain acceleration under the combined action of the resistance torque generated by the back pressure and the driving torque generated by the overall sliding force of the vehicle. Taking the deviation between the actual output of the system and the expected acceleration as the back pressure to adjust the input control amount of the retarding controller, the controller calculates and outputs the real-time control input signal of the electro-hydraulic proportional pressure control valve. The opening degree is reduced to an appropriate opening degree, so that the pressure of the retarding braking system is controlled at an appropriate size, and the back pressure required for retarding adjustment in the oil return circuit can be obtained, and the retarding control of the drive motor can be realized, so that the heavy vehicle can continue to maintain a constant speed. drive.

In the formula, T ₀ is the sliding torque generated by the gravitational potential energy when the construction transport vehicle goes downhill.

Claims (7)

1. Heavy vehicle electricity liquid traveling system advance oil return independent control slow speed control strategy, its characterized in that: under the action of continuous negative load, a retarding control strategy of the heavy vehicle electro-hydraulic traveling system is independently controlled and adjusted based on the flow pressure of the oil inlet and return paths of the system, so that two problems of speed control and negative load inhibition are decoupled, and the displacement of a variable pump is adjusted through the volume control and adjustment of a traveling variable pump in the oil inlet path of the system, so that the output flow of the variable pump is changed, and the speed regulation control of the rotating speed of a driving motor is realized; based on the deviation between the actual rotating speed and the expected rotating speed of the current system, the expected acceleration of the current system is designed through an acceleration planner, the deviation between the current acceleration and the expected acceleration which are actually output by the system is input into a slow speed regulation controller, the control signal of an electro-hydraulic proportional pressure control valve is resolved and output through the controller, the continuous and accurate control and regulation of the back pressure of a speed-limiting oil return path are realized through the pressure control regulation of the electro-hydraulic proportional pressure control valve in a system oil return path, the resistance torque generated by the system back pressure on a driving motor is balanced with the driving torque generated by the integral glide force of a heavy vehicle, the speed regulation and slow speed control of the driving motor are realized, the back pressure of the oil return path is continuously regulated through the electro-hydraulic proportional pressure control valve of a bidirectional proportional balancing valve group in the slow speed return path of the system, the back pressure of the oil return path is continuously regulated, and the resistance torque generated by the back pressure Generating a certain acceleration by using the lower pressure; meanwhile, the deviation of the current acceleration and the expected acceleration which are actually output by the system is used as the input quantity of the retarding control controller, the real-time control input of the electro-hydraulic proportional pressure control valve is output through resolving by the backpressure control retarding controller, and the backpressure pressure required by retarding control in the oil return path is obtained through pressure control regulation of the electro-hydraulic proportional pressure control valve, so that retarding control of the driving motor is realized.

2. The heavy-duty vehicle electro-hydraulic traveling system oil inlet and return independent regulation retarding control strategy as claimed in claim 1, wherein: the retarding control strategy is controlled and adjusted through the volume of the walking variable pump in the oil inlet path of the system, the deviation between the actual rotating speed output by the system and the set expected rotating speed of the system is taken as the input quantity of the controller, the real-time control input of the walking variable pump is resolved and output by the rotating speed adjusting controller, the displacement of the variable pump is adjusted, the output flow of the pump is changed, and the rotating speed adjusting control of the driving motor is realized.

3. The heavy-duty vehicle electro-hydraulic traveling system oil inlet and return independent regulation retarding control strategy as claimed in claim 1, wherein: the slow speed control strategy is based on the deviation of the actual rotating speed and the expected rotating speed of the current system, the expected acceleration of the current system is designed through an expected acceleration planning algorithm of an acceleration planner, wherein the expected acceleration consists of an expected acceleration basic value and an expected acceleration dynamic value, the expected acceleration basic value depends on the running state of an expected vehicle, the expected acceleration basic value is set to be 0 when the vehicle runs at a constant speed and a stable speed, and the expected acceleration dynamic value is determined by the comprehensive rotating speed deviation.

4. The heavy-duty vehicle electro-hydraulic traveling system oil inlet and return independent regulation retarding control strategy as claimed in claim 1, wherein: the traveling system of the heavy vehicle comprises an engine, a transfer case, a coupler, a traveling pump, an oil replenishing pump, a filter, an overflow valve, a bidirectional proportional balance valve group, a driving motor, a reduction gearbox, wheels, corresponding sensor devices and a control device, wherein the bidirectional proportional balance valve group comprises a hydraulic flushing valve, an electro-hydraulic proportional pressure control valve, a plurality of one-way valves and a throttling hole.

5. The heavy-duty vehicle electro-hydraulic traveling system oil inlet and return independent regulation retarding control strategy of claim 4, characterized in that: the two-way proportional balancing valve group is arranged on a speed-limiting oil return path of an electro-hydraulic traveling system of a heavy vehicle, back pressure of the oil return path of the system is continuously and accurately adjusted by continuously adjusting an electro-hydraulic proportional pressure control valve in the two-way proportional balancing valve group, the slow speed control of the electro-hydraulic traveling system of the heavy vehicle is realized, and meanwhile, a cooler is arranged on the oil return path of the system for forced cooling, so that the temperature of high-temperature hydraulic oil generated by throttling control of the electro-hydraulic proportional pressure control valve is reduced, and the temperature of the hydraulic oil of the system is effectively controlled.

6. The heavy-duty vehicle electro-hydraulic traveling system oil inlet and return independent regulation retarding control strategy of claim 4, characterized in that: when the vehicle runs on flat ground or in a climbing working condition, the energy of a closed hydraulic system is completely transmitted from an engine, the energy is transmitted to a traveling variable pump through a transfer case, output pressure oil enters a driving motor through a one-way valve, a hydraulic flushing valve in a two-way proportional balancing valve set automatically adjusts the working position of a valve core of a reversing valve according to the pressure difference of oil ways at two ends of the valve core, the oil discharged by the driving motor enters an electro-hydraulic proportional pressure control valve through the reversing valve, the electro-hydraulic proportional pressure control valve is kept to be maximum in opening degree through a control current input signal, the back pressure of an oil return path of the traveling system reaches a minimum safety value, the motor obtains maximum driving torque, and the throttling loss of the; the system volume speed regulation control is realized by continuously regulating the displacement of the traveling variable pump, so that the torque acting on the driving motor is in a dynamic balance state, and the speed regulation and stabilization control of the traveling system of the heavy vehicle is realized.

7. The heavy-duty vehicle electro-hydraulic traveling system oil inlet and return independent regulation retarding control strategy of claim 4, characterized in that: when the vehicle runs on a downhill or a long downhill working condition, the energy of the closed hydraulic system is supplied by the engine, part of the energy is supplied by the downward sliding force generated by the vehicle under the action of the gravity of the vehicle, the energy is transmitted to the traveling variable pump through the transfer case, and the output pressure oil enters the driving motor through the one-way valve; under the influence of the gravitational potential energy of the vehicle, the backpressure of an oil return path of the retarding brake system is quickly increased, the backpressure regulating retarding controller continuously outputs an input control signal of the electro-hydraulic proportional pressure control valve based on the current retarding state of the vehicle, the pressure of the retarding brake system is controlled to be in a proper size by reducing the opening degree of a valve port of the electro-hydraulic proportional pressure control valve to a proper opening degree, and meanwhile, the displacement of a traveling variable pump is reduced by matching with a rotating speed regulating controller, so that the resistance torque generated by the backpressure acting on a driving motor and the torque of the driving torque generated by the integral glide force of the vehicle are kept in a balanced state, the vehicle is continuously kept to run at a constant speed, and the retarding speed regulation control of the vehicle is realized.

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