Steering system and control method thereof, and vehicle

Abstract

The present invention discloses a steering system and a control method thereof, and a vehicle. The steering system comprises: a front wheel steering unit, including a front wheel steering axle, a mechanical rod system, a front wheel steering gear, and a front wheel angle sensor; a rear wheel steering unit, including a rear wheel steering axle, an electric hydraulic steering gear, a mechanical rod system, a rear wheel angle sensor, a hydraulic locking cylinder, a locking valve group, and a motor angle sensor; an integrated valve group; an electronic control unit, which is used to receive a vehicle's steering mode signal, a rear axle knob signal, a front wheel angle signal, a vehicle speed signal, a rear wheel angle signal, and a motor angle signal of an electric hydraulic steering gear, and to control the gain and loss of power of the electromagnetic valve in the integrated valve group and the locking valve group, and the action of the electric hydraulic steering gear; and a controller controls the input signal of the electric hydraulic steering gear according to the received angle signal. The present invention utilizes a hydraulic locking cylinder to achieve locking or unlocking of the rear steering wheel, combining the control accuracy of the electronically controlled electric steering and the driving assistance of the hydraulic steering.

Description

Technical Field

[0001] The present invention relates to the field of multi-axle steering vehicles, and in particular to a steering system and a control method thereof, and a vehicle. Background Art

[0002] With the continuous development of science and technology in the automotive field, modern transportation, engineering transport vehicles, and military vehicles are gradually developing in the direction of large-scale and multi-axle. Their speed, number of axles, and load capacity are constantly increasing, and drivers have higher and higher requirements for vehicle controllability, comfort, and safety. For large multi-axle engineering vehicles, their body is long and the axle load is large, so the steering system requirements are more stringent. The traditional front-wheel steering system will make the turning radius of the vehicle too large and aggravate the wear of the tires of the non-steering axle. In order to improve the steering performance of large multi-axle heavy-duty vehicles, mechanical, hydraulic, and electronically controlled steering systems have emerged to achieve multi-axle steering functions. The mechanical multi-wheel steering system has high stability, transmission efficiency, and service life, and is less affected by the external environment and electromagnetic interference, but its spatial arrangement is difficult, and the control accuracy of each wheel is difficult to guarantee. The hydraulic steering system can provide a large driving force, but its motion accuracy is poor; the electronically controlled hydraulic multi-wheel steering system is suitable for multi-axle heavy-duty vehicles traveling at medium and low speeds, but its steering sensitivity and response lag are difficult to meet the high-speed driving requirements of the vehicle, and it is easily affected by power supply and electromagnetic interference during operation. The electronically controlled electric steering system has the advantages of fast dynamic response, high steering control accuracy, strong anti-interference ability, and convenient system detection, but the driving force it generates is relatively small. Patent CN219524009U discloses a system including an angle steering gear, an electric power-assisted circulating ball steering gear, a wheel angle sensor, and a wheel speed sensor. It is characterized in that an electric power steering gear is arranged behind the angle sensor, and the angle transmission device transmits the steering force of the steering wheel to the input shaft of the electric steering gear. The electric steering gear increases the torque and drives the steering wheel to rotate to achieve single-bridge steering; the rear axles are respectively arranged with electric power steering gears, and the controller controls the steering of the axle through signals such as the angle torque sensor, the wheel angle sensor, and the wheel speed sensor. In this scheme, the pure electric steering gear controls and assists the steering of one steering shaft alone, and the coordinated control of the angles of multiple axles is difficult, and it is not suitable for heavy-loaded vehicles. Summary of the invention

[0003] Purpose of the invention: The present invention aims to provide a steering system that combines the control accuracy of electronically controlled electric steering and hydraulic steering; a second purpose of the present invention is to provide a control method for the steering system; a third purpose of the present invention is to provide a vehicle using the steering system.

[0004] Technical solution: The steering system of the present invention comprises:

[0005] A front wheel steering unit, including a front wheel steering axle, a mechanical linkage, a front wheel steering gear and a front wheel angle sensor;

[0006] A rear-wheel steering unit, including a rear-wheel steering axle, an electric hydraulic steering gear, a mechanical linkage, a rear-wheel angle sensor, a hydraulic locking cylinder, a locking valve group, and a motor angle sensor;

[0007] An integrated valve group is connected to the oil tank, oil pump, front wheel steering gear, electric hydraulic steering gear, hydraulic locking cylinder and locking valve group respectively;

[0008] The electronic control unit is used to receive the vehicle's steering mode signal, rear axle knob signal, front wheel angle signal, vehicle speed signal, rear wheel angle signal and motor angle signal of the electric hydraulic steering gear, and control the gain and loss of power of the solenoid valve in the integrated valve group and the locking valve group, as well as the action of the electric hydraulic steering gear;

[0009] A first controller, used for receiving a rear wheel steering angle signal;

[0010] A second controller is used to receive a motor rotation angle signal of the electric hydraulic steering gear;

[0011] The first controller and the second controller control the input signal of the electric hydraulic steering gear according to the received steering angle signal.

[0012] Preferably, a steering assist device is provided in the mechanical lever system.

[0013] Optionally, the front wheel steering gear is a hydraulic power steering gear or an electric hydraulic steering gear or an electric steering gear to realize an unmanned driving assistance function.

[0014] Optionally, the hydraulic locking cylinder and the locking valve group can be replaced by a mechanical locking device or a pneumatically controlled locking device.

[0015] The control method of the steering system of the present invention is as follows: when the vehicle engine is ignited, the steering system enters a rear wheel locking pressure charging mode, the electronic control unit sends a signal, the solenoid valves Y1, Y2, Y3 in the integrated valve group and the solenoid valve Y4 in the locking valve group are all energized, the oil pump draws hydraulic oil from the oil tank, the hydraulic oil flows into the A3 and B3 chambers of the hydraulic locking cylinder through the solenoid valves Y3, Y2, Y4, and is pressurized. When the rear wheel locking pressure threshold is reached, the solenoid valves are all de-energized, and the rear wheels of the vehicle enter a locked state.

[0016] Furthermore, in the front-wheel steering mode, the electronic control unit sends the steering mode signal to the electric hydraulic steering gear, and the electric hydraulic steering gear controls the rear wheels to return to the neutral position. When the rear wheel locking pressure threshold is met, the electronic control unit controls the solenoid valves Y1, Y2, and Y3 in the integrated valve group and the solenoid valve Y4 in the locking valve group to be energized, and the A3 and B3 chambers of the hydraulic locking cylinder are pressurized to complete the locking. The hydraulic oil sucked out by the oil pump passes through the electric hydraulic steering gear circuit and flows back to the oil tank after passing through the return oil filter.

[0017] Furthermore, in the all-wheel steering mode, the electronic control unit controls the solenoid valves Y1, Y2, and Y3 in the integrated valve group to lose power, and the solenoid valve Y4 in the locking valve group to be energized, unlocking the hydraulic locking cylinder, and turning the steering wheel or the electronic control unit to control the front wheel steering gear to achieve front wheel rotation; the electronic control unit detects the front wheel angle through the front wheel angle sensor, determines the rear wheel angle according to the Ackerman principle, and transmits the control signal to the electric hydraulic steering gear to achieve rear wheel rotation. The rear wheel rotation direction is opposite to that of the front wheel. The rear wheel angle sensor feeds back the rear wheel angle signal to the electronic control unit, and the motor angle sensor feeds back the motor angle signal of the electric hydraulic steering gear to the electronic control unit. According to the front and rear wheel angle signals and the motor angle signal, the input signal of the electric hydraulic steering gear is adjusted through the first controller and the second controller to achieve dual closed-loop linear control of the rear wheel angle.

[0018] Furthermore, in crab mode, the difference from manually selecting all-wheel steering mode is that the rear wheels steer in the same direction as the front wheels.

[0019] Furthermore, in the rear-wheel independent steering mode, the electronic control unit adjusts the input signal of the electric hydraulic steering gear according to the opening of the rear-wheel independent steering knob in the cab to achieve rear wheel angle control, and adjusts the input signal of the electric hydraulic steering gear through the first controller and the second controller according to the rear wheel angle signal and the motor angle signal to achieve dual closed-loop linear control of the rear wheel angle.

[0020] Furthermore, a vehicle speed threshold v0 is set. When the vehicle speed v is lower than v0, the electronic control unit switches the steering mode to the all-wheel steering mode; when the vehicle speed v is higher than v0, the electronic control unit switches the steering mode to the front-wheel steering mode.

[0021] The vehicle of the present invention comprises the above-mentioned steering system.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. The front wheel of the present invention adopts a steering gear and a mechanical rod system to realize front wheel steering, and the rear wheel linearly controls the electric hydraulic steering gear angle to regulate the rear wheel steering by detecting the front and rear wheel angles. The driving assistance of the steering system is realized by hydraulic power assistance, and the locking or unlocking of the rear steering wheel is realized by using a hydraulic locking cylinder, combining the control accuracy of the electronically controlled electric steering and the driving assistance of the hydraulic steering; 2. The present invention adopts a hydraulic locking cylinder and a locking valve group, and improves the locking reliability of the rear axle by high-pressure oil; 3. The present invention performs double closed-loop linear control of the electric steering gear through the front and rear wheels and the motor angle, and the control accuracy of the front and rear wheel angle relationship is high, which increases the tire life; 4. The present invention has strong steering self-centering ability, high control accuracy of the front and rear wheel angle relationship, good power assistance effect, is suitable for multi-axle heavy-load steering mode, and can be applied to steering vehicles with two axles or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1is a hydraulic diagram of the steering system of the present invention;

[0024] Figure 2 It is the principle diagram of the control method of the present invention;

[0025] Figure 3 It is a structural schematic diagram of the integrated valve group;

[0026] Figure 4 It is a structural schematic diagram of the locking valve group. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings.

[0028] The steering system of the present invention is characterized by comprising:

[0029] A front wheel steering unit, comprising a front wheel steering axle, a mechanical linkage, a front wheel steering gear 5 and a front wheel angle sensor 6;

[0030] A rear wheel steering unit, comprising a rear wheel steering axle, an electric hydraulic steering gear 8, a mechanical linkage, a rear wheel angle sensor 10, a hydraulic locking cylinder 12, a locking valve group 13 and a motor angle sensor;

[0031] The integrated valve group 9 is respectively connected to the oil tank 1, the oil pumps 3 and 4, the front wheel steering gear 5, the electric hydraulic steering gear 8, the hydraulic locking cylinder 12 and the locking valve group 13;

[0032] The electronic control unit is used to receive the vehicle's steering mode signal, rear axle knob signal, front wheel angle signal, vehicle speed signal, rear wheel angle signal and motor angle signal of the electric hydraulic steering gear 8, and control the gain and loss of power of the solenoid valve in the integrated valve group 9 and the locking valve group 13, and the action of the electric hydraulic steering gear 8;

[0033] A first controller, used for receiving a rear wheel steering angle signal;

[0034] A second controller is used to receive a motor rotation angle signal of the electric hydraulic steering gear;

[0035] The first controller and the second controller control the input signal of the electric hydraulic steering gear according to the received steering angle signal.

[0036] The front wheel steering connects the first steering axle and the second steering axle through the front wheel steering gear 5 and the front steering linkage mechanism. The first steering axle is equipped with a front wheel angle sensor 6. The third steering axle and the fourth steering axle of the rear wheel steering unit are connected through the electric hydraulic steering gear 8 and the rear steering linkage mechanism. The front wheel steering is achieved through the front wheel steering gear 5, the mechanical linkage and the hydraulic power assist. The rear wheel steering detects the front and rear wheel angles through the system and linearly controls the electric hydraulic steering gear 8 angle to achieve the control of the rear wheel angle. The steering assist is still achieved in the form of hydraulics.

[0037] The control method of the steering system of the present invention is as follows:

[0038] When the vehicle engine is started, the steering system first enters the rear wheel locking charging mode, the electronic control unit sends a signal, the solenoid valves Y1, Y2, Y3 in the integrated valve group 9 and the solenoid valve Y4 in the locking valve group 13 are energized, the oil pump 4 draws oil from the oil tank 1, and the hydraulic oil flows into the A3 and B3 chambers of the hydraulic locking cylinder 12 through the solenoid valves Y3, Y2, Y4. The system pressure is determined by the overflow valve Q3. After the charging is completed, the solenoid valves are all de-energized, and the rear wheels of the vehicle enter the locking state.

[0039] When the driver manually selects the front-wheel steering mode, the electronic control unit sends a signal to the electric hydraulic steering gear 8 to control the rear wheels to return to the neutral position. When the vehicle meets the rear wheel locking conditions, the electronic control unit sends a signal to energize the solenoid valves Y1, Y2, Y3 in the integrated valve group 9 and the solenoid valve Y4 in the locking valve group 13, and pressurizes the A3 and B3 chambers of the hydraulic locking cylinder 12 to complete the locking. The oil sucked out by the oil pump 4 flows through the electric hydraulic steering gear 8 through the T2 circuit and directly flows back to the oil tank 1 after passing through the return oil filter 2.

[0040] When the driver manually selects the all-wheel steering mode, the solenoid valves Y1, Y2, and Y3 lose power, the solenoid valve Y4 is energized, and the hydraulic locking cylinder 12 is unlocked. Assuming that the steering wheel turns right, the front wheel steering gear 5 is activated, and the hydraulic oil passes through the oil pump 3, the front wheel steering gear 5, and flows through the B1 circuit to enter the large chamber of the left power-assisting cylinder and the small chamber of the right power-assisting cylinder of the first steering axle and the second steering axle, and the front wheel turns right; the electronic control unit detects the front wheel angle through the front wheel angle sensor 6, obtains the rear wheel angle according to the Ackerman principle, and transmits the control signal to the electric hydraulic steering gear 8. The electric hydraulic steering gear 8 is activated under the input torque of the motor, and the hydraulic oil passes through the oil pump 4, the solenoid valve Y1, the electric hydraulic steering gear 8, and flows through the B2 circuit to enter the left of the third steering axle. The small chamber of the side power-assisting cylinder, the large chamber of the right power-assisting cylinder and the D3 chamber of the hydraulic locking cylinder 12 of the fourth steering axle. At this time, the rear wheel turns left, and the rear wheel angle sensor 10 installed on the rear wheel feeds back the rear wheel steering angle signal to the electronic control unit. The motor angle sensor on the electric hydraulic steering gear 8 feeds back the motor steering angle to the electronic control unit. The system detects the steering angles of the front and rear wheels and the motor in real time, and makes real-time adjustments to the input signal of the electric hydraulic steering gear 8 through the first controller and the second controller to ensure that the real-time steering angle error of the rear wheel is within the required range, thereby realizing double closed-loop linear control of the rear wheel steering angle.

[0041] When the driver manually selects the crab mode, its working principle is similar to that of all-wheel steering, the difference is that the steering direction of the rear wheels is consistent with that of the front wheels, and the electronic control unit detects the steering angle signals of the front and rear wheels and the motor in real time, and adjusts the steering angle of the electric hydraulic steering gear 8 to ensure the steering angle control accuracy of the rear wheels.

[0042] When the driver turns on the rear-wheel independent steering function, the rear wheel angle is adjusted through the rear-wheel independent steering knob in the cab. The electronic control unit adjusts the input signal of the electric hydraulic steering gear according to the size of the knob opening to achieve rear wheel angle control. The rear wheel angle is not affected by the front wheel angle, and the steering accuracy of the rear wheels is guaranteed under the dual closed-loop control of the first controller and the second controller.

[0043] The front-wheel and all-wheel steering modes of the present invention can also be automatically adjusted according to the vehicle speed signal, and the electronic control unit controls whether to switch the steering mode according to the vehicle speed signal. When the vehicle speed v is lower than the set value v0, the electronic control unit switches the steering mode to the all-wheel steering mode; when the vehicle speed v is higher than the set value v0, the vehicle controller switches the steering mode to the front-wheel steering mode.

[0044] Preferably, a power steering device is provided in the mechanical lever system, and the power steering device uses power cylinders 7 and 11.

[0045] Optionally, the front wheel steering gear is an electric steering gear to realize unmanned driving assistance function.

[0046] The vehicle of the present invention comprises the above-mentioned steering system.

Claims

1. A steering system, characterized in that: include: A front wheel steering unit, comprising a front wheel steering axle, a mechanical linkage, a front wheel steering gear (5) and a front wheel angle sensor (6); A rear wheel steering unit comprises a rear wheel steering axle, an electric hydraulic steering gear (8), a mechanical linkage, a rear wheel angle sensor (10), a hydraulic locking cylinder (12), a locking valve group (13) and a motor angle sensor; An integrated valve group (9) is respectively connected to the oil tank (1), the oil pump, the front wheel steering gear (5), the electric hydraulic steering gear (8), the hydraulic locking cylinder (12) and the locking valve group (13); An electronic control unit is used to receive a vehicle steering mode signal, a rear axle knob signal, a front wheel angle signal, a vehicle speed signal, a rear wheel angle signal and a motor rotation angle signal of an electric hydraulic steering gear (8), and control the gain and loss of power of the electromagnetic valve in the integrated valve group (9) and the locking valve group (12), and the action of the electric hydraulic steering gear (8); A first controller, used for receiving a rear wheel steering angle signal; A second controller is used to receive a motor rotation angle signal of the electric hydraulic steering gear; The first controller and the second controller control the input signal of the electric hydraulic steering gear according to the received steering angle signal.

2. The steering system according to claim 1, characterized in that: A steering assist device is arranged in the mechanical lever system.

3. The steering system according to claim 1, characterized in that: The front wheel steering gear (5) is a hydraulic power steering gear or an electric hydraulic steering gear or an electric steering gear.

4. The steering system according to claim 1, characterized in that: The hydraulic locking cylinder (12) and the locking valve group (12) can be replaced by a mechanical locking device or a pneumatically controlled locking device.

5. A control method for a steering system according to any one of claims 1 to 3, characterized in that: When the vehicle engine is started, the steering system enters the rear wheel locking pressure charging mode, the electronic control unit sends a signal, the solenoid valves Y1, Y2, Y3 in the integrated valve group (9) and the solenoid valve Y4 in the locking valve group (12) are all energized, the oil pump draws hydraulic oil from the oil tank (1), and the hydraulic oil flows into the A3 and B3 chambers of the hydraulic locking cylinder (12) through the solenoid valves Y3, Y2, Y4, and is pressurized. When the rear wheel locking pressure threshold is reached, the solenoid valves are all de-energized, and the rear wheels of the vehicle enter the locking state.

6. The control method of the steering system according to claim 5, characterized in that: In the front wheel steering mode, the electronic control unit sends the steering mode signal to the electric hydraulic steering gear (8), and the electric hydraulic steering gear (8) controls the rear wheel to return to the neutral position. When the rear wheel locking pressure threshold is met, the electronic control unit controls the solenoid valves Y1, Y2, and Y3 in the integrated valve group (9) and the solenoid valve Y4 in the locking valve group (12) to be energized, and the A3 and B3 chambers of the hydraulic locking cylinder (12) are pressurized to complete the locking. The hydraulic oil sucked out by the oil pump passes through the circuit of the electric hydraulic steering gear (8) and flows back to the oil tank (1) after passing through the return oil filter (2).

7. The control method of the steering system according to claim 5, characterized in that: In the all-wheel steering mode, the electronic control unit controls the electromagnetic valves Y1, Y2, and Y3 in the integrated valve group (9) to lose power, and the electromagnetic valve Y4 in the locking valve group (12) to be energized, unlocking the hydraulic locking cylinder (12), and turning the steering wheel or the electronic control unit to control the front wheel steering gear (5) to operate, thereby realizing the rotation of the front wheels; the electronic control unit detects the front wheel turning angle through the front wheel angle sensor (6), determines the rear wheel turning angle according to the Ackerman principle, and transmits the control signal to the electric hydraulic steering gear (8) to realize the rotation of the rear wheels. The rotation direction of the rear wheels is opposite to that of the front wheels. The rear wheel angle sensor (10) feeds back the rear wheel angle signal to the electronic control unit, and the motor angle sensor feeds back the motor angle signal of the electric hydraulic steering gear to the electronic control unit. According to the front and rear wheel angle signals and the motor angle signal, the input signal of the electric hydraulic steering gear (8) is adjusted through the first controller and the second controller to realize the double closed-loop linear control of the rear wheel turning angle.

8. The control method of the steering system according to claim 5, characterized in that: In Crab mode, the rear wheels steer in the same direction as the front wheels, unlike in manually selected all-wheel steering mode.

9. The control method of the steering system according to claim 5, characterized in that: In the rear wheel independent steering mode, the electronic control unit adjusts the input signal of the electric hydraulic steering device (8) according to the opening of the rear wheel independent steering knob in the cab to achieve rear wheel angle control, and adjusts the input signal of the electric hydraulic steering device (8) through the first controller and the second controller according to the rear wheel angle signal and the motor angle signal to achieve double closed-loop linear control of the rear wheel angle.

10. The control method of the steering system according to claim 5, characterized in that: The vehicle speed threshold v0 is set. When the vehicle speed v is lower than v0, the electronic control unit switches the steering mode to the all-wheel steering mode; when the vehicle speed v is higher than v0, the electronic control unit switches the steering mode to the front-wheel steering mode.

11. A vehicle, characterized in that: Comprising the steering system described in any one of claims 1-4.

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