阅读说明：本技术 一种基于电动机－泵／马达的装载机转向系统 (Loader steering system based on motor-pump/motor ) 是由 任好玲 吴标 林添良 陈其怀 李钟慎 付胜杰 缪骋 郭桐 于 2021-07-30 设计创作，主要内容包括：本发明公开一种基于电动机－泵/马达的装载机转向系统,包括电子方向盘、轴角编码器、电控单元、动力电池、两个电机控制器、两个电动机、两个定量泵/马达、多个电磁换向阀、两个先导式比例溢流阀、多个压力传感器、位移传感器、转向油缸、多个单向阀、液压蓄能器、溢流阀及油箱,该轴角编码器、两个压力传感器和位移传感器作为信号输入端连接该电控单元,该多个电磁换向阀作为信号输出端连接该电控单元。该技术方案,通过电动机的电动模式与发电模式转换和泵/马达并利用电动机的变转速调节,能够在控制定量泵输出流量与转向所需流量相匹配的同时实现对回油液压能的回收,并通过液压蓄能器完成对先导式比例溢流阀处溢流损耗的回收再利用。(The invention discloses a loader steering system based on motors-pumps/motors, which comprises an electronic steering wheel, an axial angle encoder, an electric control unit, a power battery, two motor controllers, two motors, two constant delivery pumps/motors, a plurality of electromagnetic directional valves, two pilot type proportional overflow valves, a plurality of pressure sensors, a displacement sensor, a steering oil cylinder, a plurality of one-way valves, a hydraulic energy accumulator, an overflow valve and an oil tank, wherein the axial angle encoder, the two pressure sensors and the displacement sensor are used as signal input ends to be connected with the electric control unit, and the electromagnetic directional valves are used as signal output ends to be connected with the electric control unit. According to the technical scheme, through the conversion of the electric mode and the power generation mode of the motor and the adjustment of the variable rotating speed of the pump/motor by using the motor, the recovery of return oil hydraulic energy can be realized while the output flow of the constant delivery pump is controlled to be matched with the flow required by steering, and the recovery and the reutilization of the overflow loss at the pilot type proportional overflow valve are completed through the hydraulic accumulator.)

1. An electric motor-pump/motor based loader steering system, comprising: the hydraulic control system comprises an electronic steering wheel, a shaft angle encoder, an electric control unit, a power battery, a first motor controller, a second motor controller, a first motor, a first constant displacement pump/motor, a second constant displacement pump/motor, a first electromagnetic directional valve, a second electromagnetic directional valve, a third electromagnetic directional valve, a fourth electromagnetic directional valve, a fifth electromagnetic directional valve, a first pressure sensor, a second pressure sensor, a displacement sensor, a left steering oil cylinder, a right steering oil cylinder, a first check valve, a second check valve, a hydraulic accumulator, a third check valve, a fourth check valve, a first pilot-operated proportional overflow valve, a second pilot-operated proportional overflow valve, a fifth check valve, a sixth check valve, a third pressure sensor, an overflow valve and an oil tank;

the first electric motor and the first fixed displacement pump/motor are coaxially and mechanically connected, and the second electric motor and the second fixed displacement pump/motor are coaxially and mechanically connected; an oil inlet of the first constant delivery pump/motor is connected with an oil tank, and an oil outlet of the first constant delivery pump/motor is connected with an oil inlet of the fifth one-way valve; an oil outlet of the fifth one-way valve is connected with the port A of the first electromagnetic reversing valve and the port B of the fifth electromagnetic reversing valve; the port A of the fifth electromagnetic directional valve is connected with an oil outlet of the fourth one-way valve; an oil inlet of the second constant displacement pump/motor is connected with an oil tank, and an oil outlet of the second constant displacement pump/motor is connected with an oil inlet of the sixth one-way valve; an oil outlet of the sixth one-way valve is connected with a port B of the first electromagnetic reversing valve and a port B of the fourth electromagnetic reversing valve; the port A of the fourth electromagnetic directional valve is connected with an oil outlet of the fourth one-way valve; the C port of the first electromagnetic directional valve is divided into four paths, the first path is connected with an oil inlet of the first pilot type proportional overflow valve, the second path is connected with an oil outlet of the first one-way valve, the third path is connected with a rodless cavity of the left steering oil cylinder, and the fourth path is connected with a rod cavity of the right steering oil cylinder; the D port of the first electromagnetic directional valve is divided into four paths, the first path is connected with the oil inlet of the second pilot type proportional overflow valve, the second path is connected with the oil outlet of the second one-way valve, the third path is connected with the rod cavity of the left steering oil cylinder, and the fourth path is connected with the rodless cavity of the right steering oil cylinder; oil inlets of the first one-way valve and the second one-way valve are connected with an oil tank; the oil outlet of the first pilot-operated proportional overflow valve is connected with the port A of the second electromagnetic directional valve, and the oil outlet of the second pilot-operated proportional overflow valve is connected with the port A of the third electromagnetic directional valve; the port B of the second electromagnetic reversing valve and the port B of the third electromagnetic reversing valve are both connected with an oil inlet of the third one-way valve, and the port T of the second electromagnetic reversing valve and the port T of the third electromagnetic reversing valve are both connected with an oil tank; the port A of the fourth electromagnetic directional valve and the port A of the fifth electromagnetic directional valve are both connected with an oil outlet of the fourth one-way valve; the hydraulic accumulator is connected with an oil outlet of the third one-way valve and an oil inlet of the fourth one-way valve respectively; the first pressure sensor, the second pressure sensor, the third pressure sensor, the displacement sensor and a shaft angle encoder for detecting the rotation angle of the electronic steering wheel are all connected with the electric control unit in an electric signal mode; the electric control unit is electrically connected with the first motor controller, the second motor controller, the first electromagnetic directional valve, the second electromagnetic directional valve, the third electromagnetic directional valve, the fourth electromagnetic directional valve, the fifth electromagnetic directional valve, the first pilot-operated proportional overflow valve and the second pilot-operated proportional overflow valve; the first motor is connected with the power battery through the first motor controller, and the second motor is connected with the power battery through the second motor controller.

2. A motor-pump/motor based loader steering system as claimed in claim 1 wherein: the first and second electric motors each include a motoring mode and a generating mode.

3. A motor-pump/motor based loader steering system as claimed in claim 1 wherein: the first and second fixed displacement pump/motors each include a pump mode and a motor mode.

4. A motor-pump/motor based loader steering system as claimed in claim 1 wherein: and the oil outlet of the third check valve and the oil inlet of the fourth check valve which are connected with the hydraulic accumulator are also connected with overflow valves, and the oil outlets of the overflow valves are communicated with an oil tank.

5. A motor-pump/motor based loader steering system as claimed in claim 1 wherein: the shaft angle encoder can convert a corner signal from the electronic steering wheel into an electric signal and transmit the electric signal to the electronic control unit when the electronic steering wheel controls the loader to steer, and the electronic control unit can control the electromagnet of the first electromagnetic reversing valve to be electrified after receiving the electric signal; the shaft angle encoder can convert a rotation angle signal from the electronic steering wheel into an electric signal and transmit the electric signal to the electronic control unit when the electronic steering wheel controls the loader to drive at a fixed steering angle, and the electronic control unit can control the electromagnet of the first electromagnetic reversing valve to lose power after receiving the electric signal.

Technical Field

The invention relates to an energy-saving control system, in particular to a steering system of a loader based on an electric motor-pump/motor.

Background

The loader is used as an earth and stone square loading engineering machine for shoveling and loading bulk materials, is mainly applied to material loading and unloading in mines, ports, construction sites and road construction sites, has high power, but has low energy utilization rate of a steering system. The realization of energy conservation and emission reduction of the loader is always the goal of the pursuit of the industry, and the loader will develop towards the direction of integration of mechanical, electrical and hydraulic, energy conservation, intellectualization and high efficiency in the future.

With the great development of the engineering machinery industry in China, the loader becomes one of the important pillar industries. Therefore, how to effectively reduce the energy consumption of the hydraulic loader during working becomes a problem which needs to be solved urgently before people. In the aspect of hydraulic element and system energy saving technology, the hydraulic energy loss mainly comprises throttling loss, overflow loss and the like. The throttling loss mainly comprises inlet throttling loss, outlet throttling loss, bypass throttling loss and linkage throttling loss. Different types of hydraulic systems have different types of throttling losses. The overflow loss problem is one of the main reasons that the efficiency of the hydraulic system is low, and especially in the constant delivery pump oil supply throttling speed regulation system, when the external load of the system changes, the flow rate of the oil pump supply oil cylinder in the system is not changed, and the redundant hydraulic oil can only overflow to the oil return tank, which will cause large energy loss.

Disclosure of Invention

In view of the above, the present invention provides a motor-pump/motor based steering system for a loader, which is directed to the disadvantages of the prior art.

To achieve the above object, the present invention provides a motor-pump/motor based loader steering system, the hydraulic control system comprises an electronic steering wheel, a shaft angle encoder, an electric control unit, a power battery, a first motor controller, a second motor controller, a first motor, a first constant displacement pump/motor, a second constant displacement pump/motor, a first reversing valve, a second reversing valve, a third reversing valve, a fourth reversing valve, a fifth reversing valve, a first pressure sensor, a second pressure sensor, a displacement sensor, a left steering oil cylinder, a right steering oil cylinder, a first check valve, a second check valve, a hydraulic accumulator, a third check valve, a fourth check valve, a first pilot type proportional overflow valve, a second pilot type proportional overflow valve, a fifth check valve, a sixth check valve, a third pressure sensor, an overflow valve and an oil tank;

the first electric motor and the first fixed displacement pump/motor are coaxially and mechanically connected, and the second electric motor and the second fixed displacement pump/motor are coaxially and mechanically connected; an oil inlet of the first constant delivery pump/motor is connected with an oil tank, an oil outlet of the first constant delivery pump/motor is connected with an oil inlet of a fifth one-way valve, an oil outlet of the fifth one-way valve is connected with a port A of the first electromagnetic reversing valve and a port B of the fifth electromagnetic reversing valve, and a port A of the fifth electromagnetic reversing valve is connected with an oil outlet of a fourth one-way valve; an oil inlet of the second constant delivery pump/motor is connected with an oil tank, an oil outlet of the second constant delivery pump/motor is connected with an oil inlet of a sixth one-way valve, an oil outlet of the sixth one-way valve is connected with a port B of the first electromagnetic reversing valve and a port B of a fourth electromagnetic reversing valve, and a port A of the fourth electromagnetic reversing valve is connected with an oil outlet of the fourth one-way valve; the port C of the first electromagnetic directional valve is divided into four paths, the first path of the first electromagnetic directional valve is connected with the oil inlet of the second pilot type proportional overflow valve, the second path of the first electromagnetic directional valve is connected with the oil outlet of the first one-way valve, the third path of the first electromagnetic directional valve is connected with the rodless cavity of the left steering oil cylinder, the fourth path of the first electromagnetic directional valve is connected with the rod cavity of the right steering oil cylinder, the port D of the first electromagnetic directional valve is divided into four paths, the first path of the first electromagnetic directional valve is connected with the oil inlet of the first pilot type proportional overflow valve, the second path of the first electromagnetic directional valve is connected with the oil outlet of the second one-way valve, the third path of the first electromagnetic directional valve is connected with the rod cavity of the left steering oil cylinder, and the fourth path of the first electromagnetic directional valve is connected with the rodless cavity of the right steering oil cylinder; oil inlets of the first one-way valve and the second one-way valve are connected with an oil tank; the oil outlet of the first pilot-operated proportional overflow valve is connected with the port A of the second electromagnetic directional valve, and the oil outlet of the second pilot-operated proportional overflow valve is connected with the port A of the third electromagnetic directional valve; the port B of the second electromagnetic reversing valve and the port B of the third electromagnetic reversing valve are both connected with an oil inlet of the third one-way valve, and the port T of the second electromagnetic reversing valve and the port T of the third electromagnetic reversing valve are both connected with an oil tank; the port A of the fourth electromagnetic directional valve and the port A of the fifth electromagnetic directional valve are both connected with an oil outlet of the fourth one-way valve; the hydraulic accumulator is connected with an oil outlet of the third one-way valve and an oil inlet of the fourth one-way valve respectively; the first pressure sensor, the second pressure sensor, the third pressure sensor, the displacement sensor and a shaft angle encoder for detecting the rotation angle of the electronic steering wheel are all connected with the electric control unit in an electric signal mode; the electric control unit is electrically connected with the first motor controller, the second motor controller, the first electromagnetic directional valve, the second electromagnetic directional valve, the third electromagnetic directional valve, the fourth electromagnetic directional valve, the fifth electromagnetic directional valve, the first pilot-operated proportional overflow valve and the second pilot-operated proportional overflow valve; the first motor is connected with the power battery through the first motor controller, and the second motor is connected with the power battery through the second motor controller.

In a preferred embodiment: the first and second electric motors each include a motoring mode and a generating mode.

In a preferred embodiment: the first and second fixed displacement pump/motors each include a pump mode and a motor mode.

In a preferred embodiment: and the oil outlet of the third check valve and the oil inlet of the fourth check valve which are connected with the hydraulic accumulator are also connected with overflow valves, and the oil outlets of the overflow valves are communicated with an oil tank.

In a preferred embodiment: the shaft angle encoder can convert a corner signal from the electronic steering wheel into an electric signal and transmit the electric signal to the electronic control unit when the electronic steering wheel controls the loader to steer, and the electronic control unit can control the electromagnet of the first electromagnetic reversing valve to be electrified after receiving the electric signal; the shaft angle encoder can convert a rotation angle signal from the electronic steering wheel into an electric signal and transmit the electric signal to the electronic control unit when the electronic steering wheel controls the loader to drive at a fixed steering angle, and the electronic control unit can control the electromagnet of the first electromagnetic reversing valve to lose power after receiving the electric signal.

By adopting the technical scheme, the invention has the following beneficial effects:

1. the invention provides a loader steering system based on a motor-pump/motor, which adopts the form that the motor is coaxially connected with a fixed displacement pump, achieves the purpose of controlling the output flow of a hydraulic pump by adjusting the rotating speed of the motor, can effectively solve the matching problem of the flow and the load of the hydraulic pump of the loader, enables the output flow of the hydraulic pump to be matched with the flow required by steering, and simultaneously enables the motor and the hydraulic motor in a power generation mode to convert the hydraulic energy on an oil return path into electric energy to realize energy recovery, thereby improving the cruising ability of the motor loader.

2. The invention provides a loader steering system based on a motor-pump/motor, which realizes the recovery of hydraulic energy lost by overflow through the organic combination operation of an electromagnetic directional valve, a one-way valve, a hydraulic energy accumulator, an overflow valve and the like, and because the hydraulic energy accumulator is communicated with the outlet of a hydraulic pump, when the pressure of a main oil way is lower than the pressure of the hydraulic energy accumulator, the hydraulic energy accumulator can supplement oil for the main oil way, thereby realizing the reutilization of the recovered hydraulic energy, reducing the energy waste and meeting the compensation of the drastic load.

Drawings

FIG. 1 is a schematic diagram of the motor-pump/motor based loader steering system configuration of the present invention;

the attached drawings indicate the following:

1. electronic steering wheel 2, shaft encoder

3. Electric control unit 4 and power battery

5. A first motor controller 6 and a second motor controller

7. First electric motor 8, first fixed displacement pump/motor

9. Second electric motor 10, second fixed displacement pump/motor

11. First electromagnetic directional valve 12 and second electromagnetic directional valve

13. Third electromagnetic directional valve 14, fourth electromagnetic directional valve

15. Fifth electromagnetic directional valve 16, first pressure sensor

17. Second pressure sensor 18, displacement sensor

19. Left steering oil cylinder 20 and right steering oil cylinder

21. First check valve 22, second check valve

23. Hydraulic accumulator 24, third check valve

25. Fourth check valve 26, first pilot type proportional relief valve

27. Second pilot type proportional relief valve 28 and fifth check valve

29. Sixth check valve 30, third pressure sensor

31. Relief valve 32 and oil tank

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention; it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by those skilled in the art without any inventive work are within the scope of the present invention.

In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top/bottom", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "disposed," "sleeved/connected," "connected," and the like, are used in a broad sense, and for example, "connected" may be a wall-mounted connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, a direct connection, an indirect connection through an intermediate medium, and a communication between two elements, and those skilled in the art will understand the specific meaning of the terms in the present invention specifically.

Referring to fig. 1, a specific structure of a preferred embodiment of the present invention is shown, which includes an electronic steering wheel 1, a shaft angle encoder 2, an electronic control unit 3, a power battery 4, a first motor controller 5, a second motor controller 6, a first electric motor 7, a first fixed displacement pump/motor 8, a second electric motor 9, a second fixed displacement pump/motor 10, a first electromagnetic directional valve 11, a second electromagnetic directional valve 12, a third electromagnetic directional valve 13, a fourth electromagnetic directional valve 14, a fifth electromagnetic directional valve 15, a first pressure sensor 16, a second pressure sensor 17, a displacement sensor 18, a left steering cylinder 19, a right steering cylinder 20, a first check valve 21, a second check valve 22, a hydraulic accumulator 23, a third check valve 24, a fourth check valve 25, a first pilot-type proportional overflow valve 26, a second pilot-type proportional overflow valve 27, a fifth check valve 28, a first pilot-type proportional overflow valve 26, a second pilot-type proportional overflow valve 27, a second check valve 28, a third check valve 22, a second pilot-type proportional overflow valve 22, a third electromagnetic directional valve 13, a third electromagnetic directional valve, a fourth electromagnetic directional valve, a second electromagnetic directional control valve, a second electromagnetic control valve, a third electromagnetic control valve, a second electromagnetic control valve, a third electromagnetic control valve, a second electromagnetic control valve, a third electromagnetic control valve, a second electromagnetic control, A sixth check valve 29, a third pressure sensor 30, an overflow valve 31, and an oil tank 32;

wherein: the first electric motor 7 and the first fixed displacement pump/motor 8 are coaxially and mechanically connected, and the second electric motor 9 and the second fixed displacement pump/motor 10 are coaxially and mechanically connected; an oil inlet of the first constant-volume pump/motor 8 is connected with an oil tank 32, an oil outlet of the first constant-volume pump/motor 8 is connected with an oil inlet of a fifth one-way valve 28, an oil outlet of the fifth one-way valve 28 is connected with a port A of the first electromagnetic directional valve 11 and a port B of the fifth electromagnetic directional valve 15, and a port A of the fifth electromagnetic directional valve 15 is connected with an oil outlet of the fourth one-way valve 25; an oil inlet of the second fixed displacement pump/motor 10 is connected with an oil tank 32, an oil outlet of the second fixed displacement pump/motor is connected with an oil inlet of a sixth one-way valve 29, an oil outlet of the sixth one-way valve 29 is connected with a port B of the first electromagnetic directional valve 11 and a port B of the fourth electromagnetic directional valve 14, and a port A of the fourth electromagnetic directional valve 14 is connected with an oil outlet of the fourth one-way valve 25; the port C of the first electromagnetic directional valve 11 is divided into four paths, the first path is connected with the oil inlet of the second pilot type proportional overflow valve 27, the second path is connected with the oil outlet of the first check valve 21, the third path is connected with the rodless cavity of the left steering oil cylinder 19, the fourth path is connected with the rod cavity of the right steering oil cylinder 20, the port D of the first electromagnetic directional valve 11 is divided into four paths, the first path is connected with the oil inlet of the first pilot type proportional overflow valve 26, the second path is connected with the oil outlet of the second check valve 22, the third path is connected with the rod cavity of the left steering oil cylinder 19, and the fourth path is connected with the rodless cavity of the right steering oil cylinder 20; oil inlets of the first check valve 21 and the second check valve 22 are both connected with the oil tank 32; an oil outlet of the first pilot type proportional overflow valve 26 is connected with a port A of the second electromagnetic directional valve 12, and an oil outlet of the second pilot type proportional overflow valve 27 is connected with a port A of the third electromagnetic directional valve 13; the port B of the second electromagnetic directional valve 12 and the port B of the third electromagnetic directional valve 13 are both connected with the oil inlet of the third one-way valve 24, and the port T of the second electromagnetic directional valve 12 and the port T of the third electromagnetic directional valve 13 are both connected with the oil tank 32; the port A of the fourth electromagnetic directional valve 14 and the port A of the fifth electromagnetic directional valve 15 are both connected with an oil outlet of a fourth one-way valve 25; the hydraulic accumulator 23 is respectively connected with an oil outlet of the third one-way valve 24 and an oil inlet of the fourth one-way valve 25; the first pressure sensor 16, the second pressure sensor 17, the third pressure sensor 30, the displacement sensor 18 and the shaft angle encoder 2 for detecting the rotation angle of the electronic steering wheel 1 are all connected with the electronic control unit 3 through electric signals; the electric control unit 3 is in electric signal connection with a first motor controller 5, a second motor controller 6, a first electromagnetic directional valve 11, a second electromagnetic directional valve 12, a third electromagnetic directional valve 13, a fourth electromagnetic directional valve 14, a fifth electromagnetic directional valve 15, a first pilot type proportional overflow valve 26 and a second pilot type proportional overflow valve 27; the first motor 7 is connected with the power battery 4 through the first motor controller 5, and the second motor 9 is connected with the power battery 4 through the second motor controller 6.

The first motor 7 and the second motor 9 are capable of operating in a motoring mode and a generating mode.

The first and second fixed displacement pump/motors 8, 10 are operable in a pump mode and a motor mode.

In this embodiment, when the oil pressure is greater than the set pressure of the first pilot-operated proportional relief valve 26 or the second pilot-operated proportional relief valve 27, the overflow oil enters the hydraulic accumulator 23 through the second electromagnetic directional valve 12 or the third electromagnetic directional valve 13, and the third check valve 24 to charge the hydraulic accumulator 23 with oil, and if the electromagnet of the first electromagnetic directional valve 11 is in a power-off state, that is, the oil in the steering cylinder is in a sealed state, the steering cylinder is replenished with oil through the first check valve 21 or the second check valve 22 to slow down the drift phenomenon of the loader.

In this embodiment, the electronic control unit 3 is communicatively connected with a first pressure sensor 16 for detecting the pressure of the rod cavity of the left steering cylinder 19 and the pressure of the rod-free cavity of the right steering cylinder 20, a second pressure sensor 17 for detecting the pressure of the rod cavity of the left steering cylinder 16 and the pressure of the rod cavity of the right steering cylinder 20, and a third pressure sensor 30 for detecting the pressure of the hydraulic accumulator 23. When the loader turns left, if the oil circuit pressure detected by the first pressure sensor 16 is smaller than the hydraulic accumulator pressure detected by the third pressure sensor 30, the electric control unit 3 controls the electromagnet of the fourth electromagnetic directional valve 14 to be electrified by controlling the current, the fourth electromagnetic directional valve 14 works at the upper position, the oil ports A and B are communicated, and the hydraulic accumulator 23 is used for supplementing oil to the main oil circuit; when the loader turns to the right, if the oil circuit pressure detected by the second pressure sensor 17 is smaller than the hydraulic accumulator pressure detected by the third pressure sensor 30, the electric control unit 3 controls the electromagnet of the fifth electromagnetic directional valve 15 to be electrified by controlling the current, the fifth electromagnetic directional valve 15 works at the upper position, the oil ports A and B are communicated, and the hydraulic accumulator 23 is used for supplementing oil to the main oil circuit. The recycling of the energy recovered by the hydraulic accumulator 23 is realized, and the compensation of the violent change load can be met.

Further, in order to ensure that the oil flow direction in the hydraulic accumulator 23 is fixed, the energy recovery releasing mechanism further comprises a third one-way valve 24 and a fourth one-way valve 25, and in order to ensure that the oil supplement oil does not flow back into the hydraulic pump, the oil outlet of the pump/motor 8 is connected with a fifth one-way valve 28, and the oil outlet of the pump/motor 10 is connected with a sixth one-way valve 29.

In order to improve the safety of the electro-hydraulic system of the invention, as a preferred embodiment of the invention, the oil outlet of the third check valve 24 connected with the hydraulic accumulator 23 and the oil inlet of the fourth check valve 25 are further connected with an overflow valve 31, and the oil outlet of the overflow valve 31 is communicated with the oil tank. When the pressure of the hydraulic accumulator 23 reaches the maximum oil filling pressure, the high-pressure oil overflows back to the oil tank 32 through the overflow valve 31, thereby protecting the hydraulic accumulator 23. At this time, after the third pressure sensor 30 transmits the detected pressure signal to the electronic control unit 3, if the oil pressure detected by the first pressure sensor 16 is greater than the highest oil filling pressure, the electronic control unit 3 controls the electromagnet of the second electromagnetic directional valve 12 to be electrified by controlling the current, so that the oil port a and the oil port T of the second electromagnetic directional valve 12 are communicated, the oil directly returns to the oil tank 32 and does not overflow back to the oil tank through the overflow valve 31, the system heating is reduced, and the system pressure is maintained to be stable through the first pilot-operated proportional overflow valve 26; if the oil pressure detected by the second pressure sensor 17 is greater than the highest oil charging pressure, the electronic control unit 3 controls the electromagnet of the third electromagnetic directional valve 13 to be electrified by controlling the current, so that the oil port a and the oil port T of the third electromagnetic directional valve 13 are communicated, the oil directly returns to the oil tank 32, does not overflow through the overflow valve 31 and returns to the oil tank, the system heating is reduced, and the system pressure is maintained to be stable through the second pilot-operated proportional overflow valve 27.

In this embodiment, the shaft angle encoder 2 can convert a rotation angle signal from the electronic steering wheel 1 into an electrical signal and transmit the electrical signal to the electronic control unit 3 when the electronic steering wheel 1 controls the loader to steer, and the electronic control unit 3 can control the electromagnet of the first electromagnetic directional valve 11 to be powered after receiving the electrical signal, so that the oil port a is communicated with the oil port C, and the oil port B is communicated with the oil port D. Meanwhile, the electronic control unit 3 judges the intention of the driver to turn left and right through the received electric signals transmitted by the shaft angle encoder 2, the first motor 7 is controlled to be in a generator mode by left turning, the second motor 9 is in a motor mode by right turning, the first motor 7 is controlled to be in the motor mode by right turning, and the second motor 9 is in the generator mode by right turning. The displacement sensor 18 transmits a displacement signal of the steering oil cylinder to the electronic control unit 3 to realize displacement closed-loop control, so that the steering angle of the whole vehicle is in proportion correspondence with the rotating angle of the electronic steering wheel 1, and the electronic control unit 3 can control the rotating speed of the motor according to the rotating speed of the electronic steering wheel 1 to achieve the purpose of controlling the output flow of the hydraulic pump, thereby effectively solving the matching problem of the flow and the load of the hydraulic pump of the loader, and simultaneously enabling the motor and the hydraulic motor in a power generation mode to convert the hydraulic energy on an oil return path into electric energy to realize energy recovery.

The above description is only a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto, and any person skilled in the art can make insubstantial changes in the technical scope of the present invention within the technical scope of the present invention, and the actions infringe the protection scope of the present invention are included in the present invention.