Steering hydraulic system and control method thereof

Abstract

The invention provides a steering hydraulic system which is characterized in that the system comprises a power unit, the power unit is connected with a plurality of damping hydraulic cylinders so as to provide power hydraulic oil for the damping hydraulic cylinders, and a control oil way of each damping hydraulic cylinder comprises a displacement closed-loop control oil way and a hydraulic cylinder damping oil way; pressure sensors are arranged in control oil ways of the damping hydraulic cylinders to monitor oil way pressure values in real time, and the electric control unit is in signal connection with the pressure sensors so as to correspondingly switch the control oil ways of the damping hydraulic cylinders according to the real-time oil way pressure detected by the pressure sensors. Therefore, different corresponding control oil ways are selected for the hydraulic system according to different vehicle running conditions.

Description

Technical Field

[0001] The invention relates to the technical field of articulated vehicle steering control technology, and in particular to a steering hydraulic system and a control method thereof. Background Art

[0002] Compared with ordinary single-section vehicles, articulated buses have many advantages such as large carrying capacity, low construction and operating costs relative to subways, and flexible routes. Therefore, they are widely used in third- and fourth-tier cities in China with relatively low population density, as well as in most cities abroad.

[0003] Traditional articulated buses are composed of two cars, with the front and rear cars connected by an articulated system. In order to ensure the steering stability of the articulated bus and improve riding comfort, the articulated system uses passive shock absorbers to provide shock absorption and damping for vehicle steering.

[0004] With the development of articulated vehicles, articulated buses have gradually developed from a car-type train to a three-car and a four-car train. In order to ensure the stability of steering, the three-car and four-car train must have two axles on each carriage, which greatly affects the space utilization of the articulated bus. In order to improve the space utilization of articulated buses, articulated buses set the axle at the connection between the two carriages, and no axle is set on the carriage, which greatly improves the space utilization of the carriage; when the vehicle turns, the Ackerman steering principle is used to change the axle axis angle such as Figure 1-2 As shown, to achieve stable steering of the vehicle and to change the axle axis angle, active control is required.

[0005] Therefore, it is imperative to develop an articulated vehicle steering stabilization hydraulic system with active control as the main and passive damping as the auxiliary. Summary of the invention

[0006] In order to solve the defects and shortcomings in the prior art, the present invention provides a steering hydraulic system and a control method thereof.

[0007] The technical solution provided by the present invention is as follows: A steering hydraulic system, characterized in that: the system comprises a power unit, and the power unit is respectively connected to a plurality of shock absorbing hydraulic cylinders to respectively provide power hydraulic oil to the plurality of shock absorbing hydraulic cylinders: The control oil circuit of each shock-absorbing hydraulic cylinder includes a displacement closed-loop control oil circuit and a hydraulic cylinder shock-absorbing damping oil circuit; and a pressure sensor is provided in the control oil circuit of each shock-absorbing hydraulic cylinder to monitor the oil circuit pressure value in real time, and the electronic control unit is connected to the pressure sensor signal to switch the control oil circuit of the shock-absorbing hydraulic cylinder accordingly according to the real-time oil circuit pressure detected by the pressure sensor: When the detected real-time oil circuit pressure is within the preset threshold range, the control oil circuit is a displacement closed-loop control oil circuit; When the detected real-time oil circuit pressure exceeds the preset threshold range, the electronic control unit switches the control oil circuit from the displacement closed-loop control oil circuit to the hydraulic cylinder shock-absorbing damping oil circuit and sends an alarm signal to the vehicle; When the reset button is pressed, the control oil circuit is restored to the displacement closed-loop control oil circuit.

[0008] As a further preferred embodiment of the present invention, the power unit includes an oil tank, one end of the oil pump is connected to the inside of the oil tank, and the other end is connected to the control oil circuit of the shock-absorbing hydraulic cylinder through a proportional overflow valve, and the output shaft of the motor is connected to the oil pump to provide driving power for the oil pump.

[0009] As a further preferred embodiment of the present invention, the oil pump is provided with its own unloading pressure, and the proportional relief valve is provided with a relief pressure value, and the following conditions are satisfied: The self-unloading pressure is higher than the pressure value required by the hydraulic system to assist the vehicle in steering; The overflow pressure value is higher than the self-unloading pressure; When the hydraulic system pressure value reaches its own unloading pressure, the oil pump is in idling state.

[0010] As a further preferred embodiment of the present invention, the power unit further includes: Temperature sensor, liquid level sensor and air filter installed on the fuel tank; A cooler and an oil return filter are also connected between the oil tank and the control oil circuit of the shock-absorbing hydraulic cylinder; An oil pump one-way valve, a high-pressure filter, a switch valve and an oil pump accumulator are also connected between the other end of the oil pump and the control oil circuit of the shock-absorbing hydraulic cylinder.

[0011] As a further preferred embodiment of the present invention, the displacement closed-loop control oil circuit includes a proportional servo valve and a servo hydraulic cylinder connected to the other end of the oil pump, and the servo hydraulic cylinder is provided with a displacement sensor connected to the electronic control unit signal.

[0012] As a further preferred embodiment of the present invention, the displacement sensor acquires the real-time displacement of the servo hydraulic cylinder in real time, and sends it to the electronic control unit through the vehicle CAN message. The electronic control unit compares the real-time displacement of the servo hydraulic cylinder with the preset displacement. If there is a deviation in the displacement, the electronic control unit sends a signal to the proportional servo valve to control the servo hydraulic cylinder to extend or retract accordingly, so that the current real-time displacement of the servo hydraulic cylinder is equal to the preset displacement.

[0013] As a further preferred embodiment of the present invention, the hydraulic cylinder shock absorbing and damping oil circuit includes a cylinder accumulator connected to the servo hydraulic cylinder, the interior of the cylinder accumulator is pre-filled with hydraulic oil, the two ends of the cylinder accumulator are respectively connected to the servo hydraulic cylinder via a cylinder overflow valve and an electromagnetic ball valve, and a cylinder check valve is also arranged between the servo hydraulic cylinder and the cylinder accumulator.

[0014] As a further preferred embodiment of the present invention, when in normal driving conditions, the servo hydraulic cylinder reaches the preset displacement position according to the instruction of the electronic control unit, the proportional servo valve is energized, and together with the electronic control unit, the servo hydraulic cylinder and the displacement sensor, a closed-loop displacement control is realized; at this time, the electromagnetic ball valve is energized and closed, and the hydraulic cylinder shock-absorbing and damping oil circuit does not work.

[0015] As a further preferred embodiment of the present invention, when encountering an emergency, the pressure of the displacement closed-loop control oil circuit increases. When it exceeds the preset threshold range, the electronic control unit controls the proportional servo valve and the solenoid ball valve to cut off the power, and the control oil circuit is switched from the displacement closed-loop control oil circuit to the hydraulic cylinder shock-absorbing and damping oil circuit; when the reset button is pressed, the control oil circuit is restored to the displacement closed-loop control oil circuit; when the emergency cannot be eliminated, the hydraulic cylinder shock-absorbing and damping oil circuit provides passive damping to achieve speed limit control of the vehicle.

[0016] Furthermore, the present invention also provides a control method for a steering hydraulic system, characterized in that it comprises the following steps: 1) When the vehicle is powered on, the hydraulic system does not respond; 2) When the vehicle starts, the power unit motor starts, the proportional relief valve loses power, the oil pump runs without load, and the vehicle provides cooling water for the hydraulic system; 3) When the vehicle is in gear, the proportional relief valve is energized, the oil pump is loaded and running, and the power hydraulic oil is provided to the shock-absorbing hydraulic cylinder; at this time, the electromagnetic ball valve is energized, and the shock-absorbing hydraulic cylinder is in the displacement closed-loop control oil circuit; 4) When the vehicle is driving, the vehicle sends a preset displacement instruction of the shock absorbing hydraulic pressure to the electronic control unit 21, and receives the current real-time displacement data of the shock absorbing hydraulic cylinder, and compares the preset displacement instruction of the shock absorbing hydraulic cylinder with the current real-time displacement data: If the preset displacement command is greater than the current real-time displacement data, the electronic control unit sends a signal to the proportional servo valve to control the servo hydraulic cylinder to extend accordingly, so that the servo hydraulic cylinder is adjusted to reach the preset displacement command position; If the preset displacement command is smaller than the current real-time displacement data, the electronic control unit sends a signal to the proportional servo valve to control the servo hydraulic cylinder to retract accordingly, so that the servo hydraulic cylinder is adjusted to reach the preset displacement command position; At this time, the electromagnetic ball valve and the cylinder check valve close the hydraulic cylinder shock-absorbing and damping oil circuit; 5) When an abnormal alarm occurs in the hydraulic system or the vehicle is abnormally powered off, the proportional servo valve is powered off and returns to the neutral disconnected state, the oil pump stops supplying oil to the shock-absorbing hydraulic cylinder, and the hydraulic oil seal in the shock-absorbing hydraulic cylinder is in the servo hydraulic cylinder and its pipeline. At this time, the electromagnetic ball valve is powered off to connect the hydraulic cylinder shock-absorbing damping oil circuit; 6) When the vehicle is moving, If the vehicle's steering wheel is in a straight-ahead state, the tire roll angle will automatically align the vehicle back to a straightened state; If the vehicle turns the steering wheel, the two sections of the vehicle gradually form an angle, and the servo hydraulic cylinder is extended or retracted by the external force applied by the whole vehicle. When the servo hydraulic cylinder extends, the hydraulic cylinder piston compresses the hydraulic oil in the rod chamber, passes through the electromagnetic ball valve, and then passes through the cylinder overflow valve. At the same time, when the hydraulic oil passes through the cylinder check valve, it is blocked by the cylinder check valve and cannot flow to the cylinder accumulator. At this time, the compressed hydraulic oil can only pass through the cylinder overflow valve, generate pressure to overcome the spring force of the cylinder overflow valve, and then enter the cylinder accumulator; When the hydraulic oil in the rod chamber is compressed, the rodless chamber generates a vacuum due to its increased volume. The vacuum negative pressure overcomes the spring force of the cylinder check valve, opens the cylinder check valve, and sucks the pre-filled hydraulic oil in the cylinder accumulator into the rodless chamber of the hydraulic cylinder, so that both the rod chamber and the rodless chamber of the servo hydraulic cylinder are kept full of hydraulic oil. If the vehicle changes its turning direction and the servo hydraulic cylinder changes from extending to retracting, the hydraulic oil in the rod chamber is compressed, generating a damping force, and the rod chamber draws oil from the cylinder accumulator.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention include: 1) The present invention provides an electric drive axle control system and a control method thereof, wherein the control oil circuits of the shock absorbing hydraulic cylinder are all set to include a displacement closed-loop control oil circuit and a hydraulic cylinder shock absorbing damping oil circuit; and the control oil circuit of the shock absorbing hydraulic cylinder is correspondingly switched by an electronic control unit according to the real-time oil circuit pressure detected by a pressure sensor, so that different control oil circuits are selected for the hydraulic system according to different vehicle driving conditions. During normal driving, the current real-time displacement of the servo hydraulic cylinder is equal to the preset displacement through the displacement closed-loop control oil circuit, and when encountering an emergency, the oil supply is stopped and an alarm is sounded. When the emergency cannot be eliminated, the passive damping of the hydraulic cylinder shock absorbing damping oil circuit can be used to realize the vehicle driving back at a limited speed.

[0018] 2) The present invention provides an electric drive axle control system and a control method thereof. A high-pressure filter and a return oil filter are provided in the power unit to prevent the proportional overflow valve from malfunctioning due to cleaning problems; a temperature sensor and a cooler are provided to prevent the hydraulic oil temperature from being too high; a liquid level sensor is provided to prevent the amount of hydraulic oil in the oil tank from being too low, causing the oil pump to be sucked into the air and damage the oil pump; an oil pump accumulator is provided to eliminate pressure fluctuations during system operation, maintain the system pressure to meet the auxiliary steering requirements of the servo hydraulic cylinder, and thereby ensure the stability of the displacement closed-loop control; and an oil pump check valve is provided to prevent oil reflux, which would impact and damage the oil pump.

[0019] 3) The present invention provides an electric drive axle control system and a control method thereof. A displacement sensor is set to obtain the real-time displacement of the servo hydraulic cylinder in real time, and the real-time displacement of the servo hydraulic cylinder is compared with the preset displacement through an electronic control unit. If there is a deviation in the displacement, the electronic control unit sends a signal to the proportional servo valve to control the servo hydraulic cylinder to extend or retract accordingly, which can make the current real-time displacement of the servo hydraulic cylinder equal to the preset displacement in the shortest time, thereby further improving the displacement accuracy and adjustment efficiency of the servo hydraulic cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural side view of a four-unit articulated passenger car in the prior art.

[0021] Figure 2 The figure is a schematic diagram of the structure of a four-set articulated passenger car when turning in the prior art.

[0022] Figure 3 This is a hydraulic oil circuit diagram of the steering hydraulic system provided by the present invention.

[0023] Figure 4 This is a schematic structural diagram of a power unit of a steering hydraulic system provided by the present invention.

[0024] Figure 5 This is a schematic structural diagram of the shock-absorbing hydraulic cylinder provided by the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0027] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] [First embodiment] like Figure 3-5 The figure shows a steering hydraulic system provided by the first embodiment of the present invention, including a power unit 20, which is respectively connected to a plurality of damping hydraulic cylinders to provide power hydraulic oil to the plurality of damping hydraulic cylinders respectively: like Figure 3-4 As shown, in this embodiment, the power unit includes an oil tank 22 for storing hydraulic oil, and a temperature sensor 1, a liquid level sensor 2 and an air filter 3 are correspondingly arranged on the oil tank 22; the temperature sensor is arranged to detect the oil temperature inside the oil tank 22 in real time to avoid the hydraulic oil temperature being too high; the liquid level sensor 2 is arranged to detect the oil level inside the oil tank 22 in real time, so as to avoid too little hydraulic oil in the oil tank, and the oil pump being damaged by suction; the air filter 3 is arranged to filter out sand and dust in the air.

[0029] One end of the oil pump 5 is connected to the inside of the oil tank 22, and the other end is connected to the control oil circuit of the shock absorbing hydraulic cylinder through the proportional relief valve 8. Figure 3 As shown, the proportional relief valve 8 is provided with an electromagnetic coil ST1. When the electromagnetic coil ST1 of the proportional relief valve 8 loses power, the proportional relief valve 8 is disconnected and the oil pump 5 runs without load; when the electromagnetic coil ST1 of the proportional relief valve 8 is energized, the proportional relief valve is closed and the oil pump 5 runs with load.

[0030] The output shaft of the motor 6 is connected to the oil pump 5 to provide driving power for the oil pump 5. The other end of the oil pump 5 is also connected to the control oil circuit of the shock-absorbing hydraulic cylinder via an oil pump one-way valve 7, a high-pressure filter 10, a switch valve 12 and an oil pump accumulator 12. The oil pump one-way valve 7 is provided to prevent oil from flowing back and damaging the oil pump; the high-pressure filter 10 is provided to avoid failure of the proportional relief valve due to cleaning problems; the function of the oil pump accumulator 12 is to eliminate pressure fluctuations during system operation and maintain the system pressure to meet the auxiliary steering requirements of the servo hydraulic cylinder, thereby ensuring the stability of the displacement closed-loop control; the switch valve 11 is used to realize the opening and closing of the oil pump accumulator 12.

[0031] A cooler 4 and an oil return filter 9 are also connected between the oil tank 22 and the control oil circuit of the shock-absorbing hydraulic cylinder. The cooler 4 is provided to prevent the hydraulic oil temperature from being too high, and the oil return filter 9 is provided to ensure the cleanliness of the return oil, thereby preventing the proportional relief valve 8 from malfunctioning due to cleaning problems.

[0032] In this embodiment, the oil pump 5 is provided with its own unloading pressure, and the proportional relief valve 8 is provided with an overflow pressure value, and the following conditions are satisfied: the self-unloading pressure is higher than the pressure value required for the hydraulic system to assist vehicle steering; the overflow pressure value is higher than the self-unloading pressure; this setting allows the oil pump to be in an idling state when the hydraulic system pressure value reaches its own unloading pressure.

[0033] The control oil circuit of each shock-absorbing hydraulic cylinder includes a displacement closed-loop control oil circuit and a hydraulic cylinder shock-absorbing damping oil circuit; and a pressure sensor 17 is provided in the control oil circuit of each shock-absorbing hydraulic cylinder to monitor the oil circuit pressure value in real time, and the electronic control unit is connected to the pressure sensor signal to switch the control oil circuit of the shock-absorbing hydraulic cylinder accordingly according to the real-time oil circuit pressure detected by the pressure sensor: When the detected real-time oil circuit pressure is within the preset threshold range, the control oil circuit is a displacement closed-loop control oil circuit; When the detected real-time oil circuit pressure exceeds the preset threshold range, the electronic control unit switches the control oil circuit from the displacement closed-loop control oil circuit to the hydraulic cylinder shock-absorbing damping oil circuit and sends an alarm signal to the vehicle; When the reset button is pressed, the control oil circuit is restored to the displacement closed-loop control oil circuit; By setting the control oil circuits of the shock-absorbing hydraulic cylinders to include a displacement closed-loop control oil circuit and a hydraulic cylinder shock-absorbing damping oil circuit; and using the electronic control unit to switch the control oil circuits of the shock-absorbing hydraulic cylinders accordingly according to the real-time oil circuit pressure detected by the pressure sensor, different control oil circuits can be selected for the hydraulic system according to different vehicle driving conditions. During normal driving, the current real-time displacement of the servo hydraulic cylinder is equal to the preset displacement through the displacement closed-loop control oil circuit. When encountering an emergency, the oil supply is stopped and an alarm is sounded. When the emergency cannot be eliminated, the passive damping of the hydraulic cylinder shock-absorbing damping oil circuit can be used to enable the vehicle to return to the speed limit state.

[0034] like Figure 3 and Figure 5 As shown, the displacement closed-loop control oil circuit in this embodiment includes a proportional servo valve 13 and a servo hydraulic cylinder 24 connected to the other end of the oil pump 5, and a displacement sensor 14 connected to the electronic control unit signal is arranged in the servo hydraulic cylinder; the displacement sensor obtains the real-time displacement of the servo hydraulic cylinder in real time, and sends it to the electronic control unit through the vehicle CAN message (for example, the displacement can be set to zero in the straight state, and in the non-straight state: the servo hydraulic cylinder extension is positive, and the servo hydraulic cylinder retraction is negative), and the electronic control unit compares the real-time displacement of the servo hydraulic cylinder with the preset displacement. If there is a deviation in the displacement, the electronic control unit sends a signal to the proportional servo valve to control the servo hydraulic cylinder to extend or retract accordingly, so that the current real-time displacement of the servo hydraulic cylinder is equal to the preset displacement, thereby further improving the displacement accuracy and adjustment efficiency of the servo hydraulic cylinder.

[0035] like Figure 3 and Figure 5 As shown, the hydraulic cylinder shock-absorbing and damping oil circuit in this embodiment includes a cylinder accumulator 15 connected to the servo hydraulic cylinder. The interior of the cylinder accumulator is pre-filled with hydraulic oil. The cylinder accumulator can provide hydraulic oil to the interior of the servo hydraulic cylinder, and can also receive hydraulic oil inside the servo hydraulic cylinder; the two ends of the cylinder accumulator are respectively connected to the servo hydraulic cylinder 24 through a cylinder overflow valve 18 and an electromagnetic ball valve 16, so that the hydraulic oil in the rod chamber and the rodless chamber inside the servo hydraulic cylinder can enter the cylinder accumulator through the electromagnetic ball valve and the cylinder overflow valve in turn, and a cylinder check valve 19 is also provided between the servo hydraulic cylinder and the cylinder accumulator. The cylinder check valve prevents the hydraulic oil in the rod chamber and the rodless chamber inside the servo hydraulic cylinder from entering the cylinder accumulator through the cylinder check valve, but can enter the rod chamber or rodless chamber inside the servo hydraulic cylinder from the cylinder accumulator through the cylinder check valve.

[0036] During normal driving conditions, the servo hydraulic cylinder reaches the preset displacement position according to the command of the electronic control unit, the proportional servo valve is energized, and together with the electronic control unit, the servo hydraulic cylinder and the displacement sensor, a closed-loop displacement control is achieved; at this time, the electromagnetic ball valve is energized and closed, and the hydraulic cylinder shock-absorbing and damping oil circuit does not work.

[0037] When encountering an emergency, the pressure in the displacement closed-loop control oil circuit increases. When it exceeds the preset threshold range, the electronic control unit controls the proportional servo valve and the solenoid ball valve to cut off the power, and the control oil circuit switches from the displacement closed-loop control oil circuit to the hydraulic cylinder shock-absorbing and damping oil circuit; when the reset button is pressed, the control oil circuit is restored to the displacement closed-loop control oil circuit; when the emergency cannot be eliminated, the hydraulic cylinder shock-absorbing and damping oil circuit provides passive damping to achieve speed limit control for the vehicle.

[0038] like Figure 3As shown, as one of the preferred embodiments of the present solution, for a four-unit articulated bus, the hydraulic system consists of a power unit 20 and four shock-absorbing hydraulic cylinders, and each axle is equipped with a shock-absorbing hydraulic cylinder to meet the steering requirements of the axle.

[0039] The four shock absorbing hydraulic cylinders are arranged in parallel, namely the first shock absorbing hydraulic cylinder 30 / 1, the second shock absorbing hydraulic cylinder 30 / 2, the third shock absorbing hydraulic cylinder 30 / 3 and the fourth shock absorbing hydraulic cylinder 30 / 4.

[0040] Correspondingly, the proportional servo valve includes a first proportional servo valve 13 / 1, a second proportional servo valve 13 / 2, a third proportional servo valve 13 / 3 and a fourth proportional servo valve 13 / 4. The proportional servo valve in this embodiment is a three-position four-way valve, the middle position is a closed state, and the two sides are respectively connected to the rod chamber and the rodless chamber of the servo hydraulic cylinder in opposite directions, so as to realize the extension and retraction action of the servo hydraulic cylinder; Similarly, each shock-absorbing hydraulic cylinder includes a first servo hydraulic cylinder 24 / 1, a second servo hydraulic cylinder 24 / 2, a third servo hydraulic cylinder 24 / 3 and a fourth servo hydraulic cylinder 24 / 4; wherein the first servo hydraulic cylinder 24 / 1 is respectively connected with a first displacement sensor 14 / 1, a first rod cavity pressure sensor 17 / 1 and a first rodless cavity pressure sensor 17 / 2; the second servo hydraulic cylinder 24 / 2 is respectively connected with a second displacement sensor 14 / 2, a second rod cavity pressure sensor 17 / 3 and a second rodless cavity pressure sensor 17 / 4; the third servo hydraulic cylinder 24 / 3 is respectively connected with a third displacement sensor 14 / 3, a third rod cavity pressure sensor 17 / 5 and a third rodless cavity pressure sensor 17 / 6; the fourth servo hydraulic cylinder 24 / 4 is respectively connected with a fourth displacement sensor 14 / 4, a fourth rod cavity pressure sensor 17 / 7 and a fourth rodless cavity pressure sensor 17 / 8; For example: when the left electromagnetic coil ST2 of the first proportional servo valve 13 / 1 is energized, the first proportional servo valve 13 / 1 works in the left position, and the hydraulic oil enters the rod chamber of the first servo hydraulic cylinder 24 / 1 and flows out from the rodless chamber of the first servo hydraulic cylinder 24 / 1; when the right electromagnetic coil ST3 of the first proportional servo valve 13 / 1 is energized, the first proportional servo valve 13 / 1 works in the right position, and the hydraulic oil enters the rodless chamber of the first servo hydraulic cylinder 24 / 1 and flows out from the rod chamber of the first servo hydraulic cylinder 24 / 1; when the left and right electromagnetic coils of the first proportional servo valve 13 / 1 are de-energized, the first proportional servo valve 13 / 1 works in the middle position and is in a disconnected state; Similarly, when the left electromagnetic coil ST4 of the second proportional servo valve 13 / 2 is energized, the second proportional servo valve 13 / 2 works in the left position, and the hydraulic oil enters the rod chamber of the second servo hydraulic cylinder 24 / 2 and flows out from the rodless chamber of the second servo hydraulic cylinder 24 / 2; when the right electromagnetic coil ST5 of the second proportional servo valve 13 / 2 is energized, the second proportional servo valve 13 / 2 works in the right position, and the hydraulic oil enters the rodless chamber of the second servo hydraulic cylinder 24 / 2 and flows out from the rod chamber of the second servo hydraulic cylinder 24 / 2; when the left and right electromagnetic coils of the second proportional servo valve 13 / 2 are de-energized, the second proportional servo valve 13 / 2 works in the middle position and is in a disconnected state; When the left electromagnetic coil ST6 of the third proportional servo valve 13 / 3 is energized, the third proportional servo valve 13 / 3 works in the left position, and the hydraulic oil enters the rod chamber of the third servo hydraulic cylinder 24 / 3 and flows out from the rodless chamber of the third servo hydraulic cylinder 24 / 3; when the right electromagnetic coil ST7 of the third proportional servo valve 13 / 3 is energized, the third proportional servo valve 13 / 3 works in the right position, and the hydraulic oil enters the rodless chamber of the third servo hydraulic cylinder 24 / 3 and flows out from the rod chamber of the third servo hydraulic cylinder 24 / 3; when the left and right electromagnetic coils of the third proportional servo valve 13 / 3 are de-energized, the third proportional servo valve 13 / 3 works in the middle position and is in a disconnected state; When the left electromagnetic coil ST8 of the fourth proportional servo valve 13 / 4 is energized, the fourth proportional servo valve 13 / 4 works in the left position, and the hydraulic oil enters the rod chamber of the fourth servo hydraulic cylinder 24 / 4 and flows out from the rodless chamber of the fourth servo hydraulic cylinder 24 / 4; when the right electromagnetic coil ST9 of the fourth proportional servo valve 13 / 4 is energized, the fourth proportional servo valve 13 / 4 works in the right position, and the hydraulic oil enters the rodless chamber of the fourth servo hydraulic cylinder 24 / 4 and flows out from the rod chamber of the fourth servo hydraulic cylinder 24 / 4; when the left and right electromagnetic coils of the fourth proportional servo valve 13 / 4 are de-energized, the fourth proportional servo valve 13 / 4 works in the middle position and is in a disconnected state; The two ends of the first cylinder accumulator 15 / 1 are connected to the first servo hydraulic cylinder 24 / 1 through the first cylinder overflow valve 18 / 1 and the first electromagnetic ball valve 16 / 1, the second cylinder overflow valve 18 / 2 and the second electromagnetic ball valve 16 / 2; the two ends of the second cylinder accumulator 15 / 2 are connected to the second servo hydraulic cylinder 24 / 2 through the third cylinder overflow valve 18 / 3 and the third electromagnetic ball valve 16 / 3, the fourth cylinder overflow valve 18 / 4 and the fourth electromagnetic ball valve 16 / 4. ; The two ends of the third cylinder accumulator 15 / 3 are connected to the third servo hydraulic cylinder 24 / 3 via the fifth cylinder overflow valve 18 / 5 and the fifth electromagnetic ball valve 16 / 5, the sixth cylinder overflow valve 18 / 6 and the sixth electromagnetic ball valve 16 / 6; the two ends of the fourth cylinder accumulator 15 / 4 are connected to the fourth servo hydraulic cylinder 24 / 4 via the seventh cylinder overflow valve 18 / 7 and the seventh electromagnetic ball valve 16 / 7, the eighth cylinder overflow valve 18 / 8 and the eighth electromagnetic ball valve 16 / 8; In addition, a first cylinder check valve 19 / 1 and a second cylinder check valve 19 / 2 are provided between the first servo hydraulic cylinder 24 / 1 and the first cylinder accumulator 15 / 1; a third cylinder check valve 19 / 3 and a fourth cylinder check valve 19 / 4 are provided between the second servo hydraulic cylinder 24 / 2 and the second cylinder accumulator 15 / 2; a fifth cylinder check valve 19 / 5 and a sixth cylinder check valve 19 / 6 are provided between the third servo hydraulic cylinder 24 / 3 and the third cylinder accumulator 15 / 3; a seventh cylinder check valve 19 / 7 and an eighth cylinder check valve 19 / 8 are provided between the fourth servo hydraulic cylinder 24 / 4 and the fourth cylinder accumulator 15 / 4.

[0041] [Second embodiment] The second embodiment of the present invention further provides a control method for a steering hydraulic system, comprising the following steps: 1) When the vehicle is powered on, the hydraulic system does not respond; 2) When the vehicle starts, the power unit motor 6 starts, the proportional relief valve 8 loses power, the oil pump 5 runs without load, and the vehicle provides cooling water for the hydraulic system; 3) When the vehicle is in gear, the proportional relief valve 8 is energized, the oil pump 5 is loaded and running, and provides power hydraulic oil to the shock-absorbing hydraulic cylinder; at this time, the electromagnetic ball valve is energized, and the shock-absorbing hydraulic cylinder is in the displacement closed-loop control oil circuit; Figure 3 As shown, at this time, the electromagnetic coil ST14 of the first electromagnetic ball valve 16 / 1 and the electromagnetic coil ST10 of the second electromagnetic ball valve 16 / 2 are energized, and the first shock-absorbing hydraulic cylinder 30 / 1 is in the displacement closed-loop control oil circuit; the electromagnetic coil ST15 of the third electromagnetic ball valve 16 / 3 and the electromagnetic coil ST11 of the fourth electromagnetic ball valve 16 / 4 are energized, and the second shock-absorbing hydraulic cylinder 30 / 2 is in the displacement closed-loop control oil circuit; the electromagnetic coil ST16 of the fifth electromagnetic ball valve 16 / 5 and the electromagnetic coil ST12 of the sixth electromagnetic ball valve 16 / 6 are energized, and the third shock-absorbing hydraulic cylinder 30 / 3 is in the displacement closed-loop control oil circuit; the electromagnetic coil ST17 of the seventh electromagnetic ball valve 16 / 7 and the electromagnetic coil ST13 of the eighth electromagnetic ball valve 16 / 8 are energized, and the fourth shock-absorbing hydraulic cylinder 30 / 4 is in the displacement closed-loop control oil circuit; 4) When the vehicle is driving, the vehicle sends a preset displacement instruction of the shock absorbing hydraulic pressure to the electronic control unit 21, and receives the current real-time displacement data of the shock absorbing hydraulic cylinder, and compares the preset displacement instruction of the shock absorbing hydraulic cylinder with the current real-time displacement data: If the preset displacement command is greater than the current real-time displacement data, the electronic control unit sends a signal to the proportional servo valve to control the servo hydraulic cylinder to extend accordingly, so that the servo hydraulic cylinder is adjusted to reach the preset displacement command position; If the preset displacement command is smaller than the current real-time displacement data, the electronic control unit sends a signal to the proportional servo valve to control the servo hydraulic cylinder to retract accordingly, so that the servo hydraulic cylinder is adjusted to reach the preset displacement command position; At this time, the electromagnetic ball valve and the cylinder check valve close the hydraulic cylinder shock-absorbing and damping oil circuit; 5) When an abnormal alarm occurs in the hydraulic system or the vehicle is abnormally powered off, the proportional servo valve is powered off and returns to the neutral disconnection state, the oil pump 5 stops supplying oil to the shock-absorbing hydraulic cylinder, and the hydraulic oil seal in the shock-absorbing hydraulic cylinder is in the servo hydraulic cylinder and its pipeline. At this time, the electromagnetic ball valve is powered off to connect the shock-absorbing damping oil circuit of the hydraulic cylinder; 6) When the vehicle is moving, If the vehicle's steering wheel is in a straight-ahead state, the tire roll angle will automatically align the vehicle back to a straightened state; If the vehicle turns the steering wheel, the two sections of the vehicle gradually form an angle, and the servo hydraulic cylinder is extended or retracted by the external force applied by the whole vehicle. When the servo hydraulic cylinder extends, the hydraulic cylinder piston compresses the hydraulic oil in the rod chamber, passes through the electromagnetic ball valve, and then passes through the cylinder overflow valve. At the same time, when the hydraulic oil passes through the cylinder check valve, it is blocked by the cylinder check valve and cannot flow to the cylinder accumulator. At this time, the compressed hydraulic oil can only pass through the cylinder overflow valve, generate pressure to overcome the spring force of the cylinder overflow valve, and then enter the cylinder accumulator; When the hydraulic oil in the rod chamber is compressed, the rodless chamber generates a vacuum due to its increased volume. The vacuum negative pressure overcomes the spring force of the cylinder check valve, opens the cylinder check valve, and sucks the pre-filled hydraulic oil in the cylinder accumulator into the rodless chamber of the hydraulic cylinder, so that both the rod chamber and the rodless chamber of the servo hydraulic cylinder are kept full of hydraulic oil. If the vehicle changes its turning direction and the servo hydraulic cylinder changes from extending to retracting, the hydraulic oil in the rod chamber is compressed, generating a damping force, and the rod chamber draws oil from the cylinder accumulator.

[0042] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A steering hydraulic system, characterized in that: The system comprises a power unit (20), wherein the power unit is respectively connected to a plurality of shock absorbing hydraulic cylinders to respectively provide power hydraulic oil to the plurality of shock absorbing hydraulic cylinders: The control oil circuit of each shock-absorbing hydraulic cylinder comprises a displacement closed-loop control oil circuit and a hydraulic cylinder shock-absorbing damping oil circuit; and a pressure sensor (17) is provided in the control oil circuit of each shock-absorbing hydraulic cylinder to monitor the oil circuit pressure value in real time, and the electronic control unit is connected to the pressure sensor signal to switch the control oil circuit of the shock-absorbing hydraulic cylinder accordingly according to the real-time oil circuit pressure detected by the pressure sensor: When the detected real-time oil circuit pressure is within the preset threshold range, the control oil circuit is a displacement closed-loop control oil circuit; When the detected real-time oil circuit pressure exceeds the preset threshold range, the electronic control unit switches the control oil circuit from the displacement closed-loop control oil circuit to the hydraulic cylinder shock-absorbing damping oil circuit and sends an alarm signal to the vehicle; When the reset button is pressed, the control oil circuit is restored to the displacement closed-loop control oil circuit.

2. A steering hydraulic system according to claim 1, characterized in that: The power unit comprises an oil tank (22), one end of the oil pump (5) is connected to the inside of the oil tank (22), and the other end is connected to the control oil circuit of the shock-absorbing hydraulic cylinder via a proportional relief valve (8), and the output shaft of the motor (6) is connected to the oil pump (5) to provide driving power for the oil pump (5).

3. A steering hydraulic system according to claim 2, characterized in that: The oil pump (5) is provided with its own unloading pressure, and the proportional relief valve (8) is provided with a relief pressure value, and the following conditions are satisfied: The self-unloading pressure is higher than the pressure value required by the hydraulic system to assist the vehicle in steering; The overflow pressure value is higher than the self-unloading pressure; When the hydraulic system pressure value reaches its own unloading pressure, the oil pump is in idling state.

4. A steering hydraulic system according to claim 2, characterized in that: The power unit also includes: A temperature sensor (1), a liquid level sensor (2) and an air filter (3) arranged on the oil tank (22); A cooler (4) and an oil return filter (9) are also connected between the oil tank (22) and the control oil circuit of the shock-absorbing hydraulic cylinder; An oil pump check valve (7), a high-pressure filter (10), a switch valve (11) and an oil pump accumulator (12) are also connected between the other end of the oil pump (5) and the control oil circuit of the shock-absorbing hydraulic cylinder.

5. A steering hydraulic system according to claim 2, characterized in that: The displacement closed-loop control oil circuit comprises a proportional servo valve (13) and a servo hydraulic cylinder (24) connected to the other end of the oil pump (5), wherein the servo hydraulic cylinder is provided with a displacement sensor (14) connected to the signal of the electronic control unit.

6. A steering hydraulic system according to claim 5, characterized in that: The displacement sensor obtains the real-time displacement of the servo hydraulic cylinder in real time and sends it to the electronic control unit through the vehicle CAN message. The electronic control unit compares the real-time displacement of the servo hydraulic cylinder with the preset displacement. If there is a deviation in the displacement, the electronic control unit sends a signal to the proportional servo valve to control the servo hydraulic cylinder to extend or retract accordingly, so that the current real-time displacement of the servo hydraulic cylinder is equal to the preset displacement.

7. A steering hydraulic system according to claim 5, characterized in that: The hydraulic cylinder shock absorbing and damping oil circuit comprises a cylinder accumulator (15) connected to a servo hydraulic cylinder, the interior of the cylinder accumulator being pre-filled with hydraulic oil, the two ends of the cylinder accumulator being respectively connected to the servo hydraulic cylinder (24) via a cylinder overflow valve (18) and an electromagnetic ball valve (16), and a cylinder check valve (19) is also provided between the servo hydraulic cylinder and the cylinder accumulator.

8. A steering hydraulic system according to claim 7, characterized in that: During normal driving conditions, the servo hydraulic cylinder reaches the preset displacement position according to the command of the electronic control unit, the proportional servo valve is energized, and together with the electronic control unit, the servo hydraulic cylinder and the displacement sensor, a closed-loop displacement control is achieved; at this time, the electromagnetic ball valve is energized and closed, and the hydraulic cylinder shock-absorbing and damping oil circuit does not work.

9. A steering hydraulic system according to claim 7, characterized in that: When encountering an emergency, the pressure in the displacement closed-loop control oil circuit increases. When it exceeds the preset threshold range, the electronic control unit controls the proportional servo valve and the solenoid ball valve to cut off the power, and the control oil circuit switches from the displacement closed-loop control oil circuit to the hydraulic cylinder shock-absorbing and damping oil circuit; when the reset button is pressed, the control oil circuit is restored to the displacement closed-loop control oil circuit; when the emergency cannot be eliminated, the hydraulic cylinder shock-absorbing and damping oil circuit provides passive damping to achieve speed limit control for the vehicle.

10. A control method for a steering hydraulic system, characterized in that: The following steps are involved: 1) When the vehicle is powered on, the hydraulic system does not respond; 2) When the vehicle is started, the power unit motor (6) starts, the proportional relief valve (8) loses power, the oil pump (5) runs without load, and the vehicle provides cooling water for the hydraulic system; 3) When the vehicle is in gear, the proportional relief valve (8) is energized, and the oil pump (5) is loaded and operated to provide power hydraulic oil to the shock-absorbing hydraulic cylinder; at this time, the electromagnetic ball valve is energized, and the shock-absorbing hydraulic cylinder is in a displacement closed-loop control oil circuit; 4) When the vehicle is driving, the vehicle sends a preset displacement instruction of the shock absorbing hydraulic pressure to the electronic control unit 21, and receives the current real-time displacement data of the shock absorbing hydraulic cylinder, and compares the preset displacement instruction of the shock absorbing hydraulic cylinder with the current real-time displacement data: If the preset displacement command is greater than the current real-time displacement data, the electronic control unit sends a signal to the proportional servo valve to control the servo hydraulic cylinder to extend accordingly, so that the servo hydraulic cylinder is adjusted to reach the preset displacement command position; If the preset displacement command is smaller than the current real-time displacement data, the electronic control unit sends a signal to the proportional servo valve to control the servo hydraulic cylinder to retract accordingly, so that the servo hydraulic cylinder is adjusted to reach the preset displacement command position; At this time, the electromagnetic ball valve and the cylinder check valve close the hydraulic cylinder shock-absorbing and damping oil circuit; 5) When an abnormal alarm is given by the hydraulic system or the vehicle is abnormally powered off, the proportional servo valve is powered off and returns to the neutral disconnected state, the oil pump (5) stops supplying oil to the shock absorbing hydraulic cylinder, and the hydraulic oil seal in the shock absorbing hydraulic cylinder is in the servo hydraulic cylinder and its pipeline. At this time, the electromagnetic ball valve is powered off to connect the shock absorbing damping oil circuit of the hydraulic cylinder; 6) When the vehicle is moving, If the vehicle's steering wheel is in a straight-ahead state, the tire roll angle will automatically align the vehicle back to a straightened state; If the vehicle turns the steering wheel, the two sections of the vehicle gradually form an angle, and the servo hydraulic cylinder is extended or retracted by the external force applied by the whole vehicle. When the servo hydraulic cylinder extends, the hydraulic cylinder piston compresses the hydraulic oil in the rod chamber, passes through the electromagnetic ball valve, and then passes through the cylinder overflow valve. At the same time, when the hydraulic oil passes through the cylinder check valve, it is blocked by the cylinder check valve and cannot flow to the cylinder accumulator. At this time, the compressed hydraulic oil can only pass through the cylinder overflow valve, generate pressure to overcome the spring force of the cylinder overflow valve, and then enter the cylinder accumulator; When the hydraulic oil in the rod chamber is compressed, the rodless chamber generates a vacuum due to its increased volume. The vacuum negative pressure overcomes the spring force of the cylinder check valve, opens the cylinder check valve, and sucks the pre-filled hydraulic oil in the cylinder accumulator into the rodless chamber of the hydraulic cylinder, so that both the rod chamber and the rodless chamber of the servo hydraulic cylinder are kept full of hydraulic oil. If the vehicle changes its turning direction and the servo hydraulic cylinder changes from extending to retracting, the hydraulic oil in the rod chamber is compressed, generating a damping force, and the rod chamber draws oil from the cylinder accumulator.

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