All-wheel independent steering system

Abstract

The invention discloses an all-wheel independent steering system, belongs to the technical field of vehicle steering system application, and aims to reduce the control difficulty of a coordination algorithm of a control module and solve the problem of complexity of the control system by directly responding to instructions of the control module through split type valve groups (front axle / rear axle independent control), valves in a front wheel steering module and valves in a rear wheel steering module. The left rear wheel steering self-aligning oil cylinder and the right rear wheel steering self-aligning oil cylinder are provided with centering cavities (a cavity A and a cavity E), when steering of the front wheel is controlled and a system breaks down, the centering cavities are kept in the middle position through pre-charging pressure of an energy accumulator, so that the rear wheel is automatically aligned, and the problems that the rear wheel centering and keeping difficulty is large, and the fault returning difficulty is large are solved.

Description

Technical Field

[0001] The present invention belongs to the application field of vehicle steering systems, and particularly relates to an electronically controlled hydraulic all-wheel independent steering system. Background Art

[0002] With the diversification of modern vehicle requirements, traditional vehicles have limitations in terms of mobility, passability, and flexibility. Steering mobility is a decisive factor affecting vehicle mobility. Reducing the low-speed turning radius, enhancing high-speed stability, providing special steering forms such as small-radius turning and diagonal turning through all-wheel independent steering technology has become an effective way to solve the common problem of improving the mobility of wheeled vehicles worldwide. In addition, with the development of technology, independent electric drive technology has been increasingly applied to military and civilian wheeled vehicles worldwide to improve their passability and mobility, which also enables the all-wheel steering technology of wheeled vehicles to get rid of the restriction of "axle", providing a basic condition for realizing all-wheel independent steering. All-wheel independent steering technology takes the wheels as independent execution units. Based on the existing all-wheel steering mobility, it can achieve more complex and flexible steering modes such as lateral and in-situ steering, which is the key technology to improve the mobility of future wheeled vehicles. At the same time, it is also an important support for the future wheeled vehicle to achieve a highly modular and universal technical architecture of "action, drive, steering, and braking".

[0003] With the development of technology, all-wheel independent steering technology has been applied in multiple fields, becoming the main means to improve vehicle mobility worldwide and forming a development consensus. However, the existing all-wheel independent steering systems still have the following problems:

[0004] (1) The control system is complex. A highly complex control system is required to coordinate the steering angles of each wheel, involving the working coordination algorithm of the left and right wheel sensors and actuators, and ensuring the fast and accurate response of the control system under different driving conditions.

[0005] (2) It is difficult to center and maintain the rear wheels. For four-wheel drive and steering vehicles, all-wheel steering at low speeds can improve vehicle mobility. When the vehicle is driving at high speed, it is required to center and maintain the rear wheels in the middle position, which increases the design difficulty of the steering system.

[0006] (3) It is difficult to return to the correct position in case of a failure. In case of unexpected power-off of the system, etc., it is necessary to perform fault centering of the rear wheels, otherwise the vehicle is prone to out-of-control situations. Summary of the Invention

[0007] In view of this, the present invention provides an all-wheel independent steering system, which solves the problems faced by the existing all-wheel independent steering systems.

[0008] The present invention adopts the following technical solutions:

[0009] A full-wheel independent steering system, comprising:

[0010] Front-wheel steering module: including a front axle steering valve group, a left front-wheel steering cylinder, and a right front-wheel steering cylinder. The valves in the front axle steering valve group control the telescopic movement of the piston rods of the two front-wheel steering cylinders to achieve the steering control of the two front wheels;

[0011] Rear-wheel steering module: including a rear axle steering valve group, and a left rear-wheel steering self-aligning cylinder and a right rear-wheel steering self-aligning cylinder provided with chambers A, B, C, D, and E. Chamber D is an unloading chamber. The valves in the rear axle steering valve group control the oil filling or draining of chambers B and C, causing the piston rods of the two rear-wheel steering self-aligning cylinders to telescopic, achieving the steering control of the two rear wheels;

[0012] Automatic self-aligning module: including a left rear accumulator integrated valve group provided with a left rear accumulator and a right rear accumulator integrated valve group provided with a right rear accumulator; when controlling the front-wheel steering and in case of system failure, the left rear accumulator and the right rear accumulator respectively fill chambers A and E of the left rear-wheel steering self-aligning cylinder and the right rear-wheel steering self-aligning cylinder with oil, causing the piston rods of the two rear-wheel steering self-aligning cylinders to be centered, achieving the automatic self-aligning of the two rear wheels;

[0013] Control module: controlling the valves in the front axle steering valve group and the rear axle steering valve group to act.

[0014] Chambers A and E of the left rear-wheel steering self-aligning cylinder and the right rear-wheel steering self-aligning cylinder are centering chambers, chamber B is a rodless steering chamber, and chamber C is a rod steering chamber;

[0015] During normal rear-wheel steering, the oil filling and unloading of chambers B and C are controlled by the action of a proportional valve and a solenoid valve, and chambers A, E, and D are unloaded; during rear-wheel centering, chambers B, C, and D are unloaded, and chambers A and E are filled with oil.

[0016] The cross-sectional areas of chambers A, B, C, and E of the left rear-wheel steering self-aligning cylinder and the right rear-wheel steering self-aligning cylinder are respectively:

[0017]

[0018] Wherein, D A is the inner diameter of the main piston of chamber A, D B is the inner diameter of the cylinder of chamber B, D C is the outer diameter of the main piston of chamber C.

[0019] Furthermore, each of the left front-wheel steering cylinder and the right front-wheel steering cylinder is provided with two oil chambers, namely a rodless chamber and a rod chamber. The telescopic movement of the piston rod is controlled by the oil filling and unloading of the rod chamber and the rodless chamber to achieve the steering of the front wheels;

[0020] The two rodless chambers and the two rod chambers of the left front wheel steering cylinder and the right front wheel steering cylinder are connected by pipelines, and electromagnetic valves are provided on the pipelines.

[0021] Further, it also includes an electric steering pump and a fuel tank assembly. The electric steering pump and the fuel tank assembly include a high-pressure pump and a low-pressure pump, which are used to automatically switch from the high-pressure pump to the low-pressure pump to maintain the system pressure under the control of the control module when the high-pressure pump fails.

[0022] Further, the main path of the front axle steering valve group obtains pressure oil from the electric steering pump and the fuel tank assembly and supplies it to the front axle steering valve group, the rear axle steering valve group, the left rear accumulator integrated valve group, and the right rear accumulator integrated valve group;

[0023] The oil returned from the front axle steering valve group, the rear axle steering valve group, the left rear accumulator integrated valve group, and the right rear accumulator integrated valve group is stored in the fuel tank of the electric steering pump and the fuel tank assembly;

[0024] A main path overflow valve and a main path electromagnetic valve controlled by the control module are connected in parallel on the main path of the front axle steering valve group.

[0025] Further, pressure sensors are provided on the front axle steering valve group and the rear axle steering valve group to monitor the oil circuit pressure in real time and feedback it to the control module. When the pressure exceeds the limit, the control module controls the main path overflow valve to unload.

[0026] Beneficial effects:

[0027] 1. Through the split valve group (independent control of the front axle / rear axle), the valves in the front wheel steering module and the rear wheel steering module directly respond to the instructions of the control module, reducing the control difficulty of the control module's coordination algorithm and solving the problem of complex control systems; the left rear wheel steering self-centering cylinder and the right rear wheel steering self-centering cylinder are designed with a central cavity (cavity A, cavity E). When controlling the front wheel steering and in case of system failure, the central cavity maintains the middle position through the pre-charged pressure of the accumulator, enabling the rear wheels to automatically return to the center, solving the problems of difficult centering and maintaining of the rear wheels, and difficult return to the center in case of failure.

[0028] 2. An integrated hydraulic cylinder that combines the functions of active self-centering and middle position holding is adopted. The drive and self-centering integrated hydraulic cylinder is not only an actuator of the axle independent steering system but also a guarantee for the safety of the entire all-wheel steering system. This device integrates the functions of steering drive, active self-centering, and middle position holding, with a compact structure.

[0029] 3. When the system fails, the accumulator realizes the automatic return of the rear wheels through the pre-charged pressure, which not only reduces energy consumption but also improves the dynamic performance of the system through a fast response mechanism, and at the same time avoids the energy waste caused by the frequent start and stop of the traditional hydraulic system.

[0030] 4. The electric power steering pump and fuel tank assembly includes a dual-source electric power steering pump and a fuel tank. The dual-source electric power steering pump can automatically activate the low-pressure pump in case of high-pressure pump failure, preventing sudden failure of the steering system and enhancing safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Structural diagram of the integrated steering drive and return cylinder provided by the present invention;

[0032] Figure 2 Schematic diagram of the cylinder returning to the middle position after elongation under the fault mode provided by the present invention;

[0033] Figure 3 Schematic diagram of the cylinder returning to the middle position after shortening under the fault mode provided by the present invention;

[0034] Figure 4 Schematic diagram of the cylinder extending to the middle position and then retracting under normal working conditions provided by the present invention;

[0035] Figure 5 Schematic diagram of the cylinder retracting to the middle position and then extending under normal working conditions provided by the present invention;

[0036] Figure 6 Schematic diagram of the cylinder extending from the middle position to the extended state after fault centering provided by the present invention;

[0037] Figure 7 Hydraulic schematic diagram of the all-wheel independent steering system provided by the present invention;

[0038] Figure 8 Schematic diagram of the front axle steering valve group provided by the present invention;

[0039] Figure 9 Schematic diagram of the rear axle steering valve group provided by the present invention;

[0040] Figure 10 Schematic diagram of the rear axle accumulator provided by the present invention;

[0041] Wherein: 1 - Front axle steering valve group; 2 - Rear axle steering valve group; 3 - Left rear accumulator integrated valve group; 4 - Right rear accumulator integrated valve group; 5 - Electric steering pump and fuel tank assembly; 6 - Filter; 7 - Left front wheel steering cylinder; 8 - Right front wheel steering cylinder; 9 - Left rear wheel steering self - centering cylinder; 10 - Right rear wheel steering self - centering cylinder; 11 - Left rear accumulator; 12 - Right rear accumulator; 13 - Main circuit overflow valve; 14 - Main circuit solenoid valve; 15 - Front axle proportional valve; 16 - First solenoid valve in the front axle branch; 17 - Second solenoid valve in the front axle branch; 18 - Third solenoid valve in the front axle branch; 19 - Fourth solenoid valve in the front axle branch; 20 - Fifth solenoid valve in the front axle branch; 21 - Sixth solenoid valve in the front axle branch; 22 - First pressure sensor in the main circuit; 23 - Second pressure sensor in the front axle; 24 - Third pressure sensor in the front axle; 25 - Fourth pressure sensor in the front axle; 26 - Fifth pressure sensor in the front axle; 27 - Rear axle proportional valve; 28 - First solenoid valve in the rear axle branch; 29 - Second solenoid valve in the rear axle branch; 30 - Third solenoid valve in the rear axle branch; 31 - Fourth solenoid valve in the rear axle branch; 32 - Fifth solenoid valve in the rear axle branch; 33 - Sixth solenoid valve in the rear axle branch; 34 - First pressure sensor in the rear axle; 35 - Second pressure sensor in the rear axle; 36 - Third pressure sensor in the rear axle; 37 - Fourth pressure sensor in the rear axle; 38 - First solenoid valve on the left rear; 39 - Second solenoid valve on the left rear; 40 - Left rear check valve; 41 - First pressure sensor on the left rear; 42 - Second pressure sensor on the left rear; 43 - First solenoid valve on the right rear; 44 - Second solenoid valve on the right rear; 45 - Right rear check valve; 46 - First pressure sensor on the right rear; 47 - Second pressure sensor on the right rear. Detailed implementation manners

[0042] The following combines the attached drawings and gives examples to describe the present invention in detail.

[0043] Example 1:

[0044] Referring to Figure 7 、 Figure 8 、 Figure 9 , this embodiment provides a full - wheel independent steering system, including:

[0045] Front - wheel steering module: It includes the front axle steering valve group 1, the left front wheel steering cylinder 7 and the right front wheel steering cylinder 8. The valves in the front axle steering valve group 1 act to control the telescopic movement of the piston rods of the two front - wheel steering cylinders, realizing the steering control of the two front wheels;

[0046] Rear - wheel steering module: It includes the rear axle steering valve group 2 and the left rear wheel steering self - centering cylinder 9 and the right rear wheel steering self - centering cylinder 10 provided with chambers A, B, C, D, and E. Chamber D is the unloading chamber. The valves in the rear axle steering valve group 2 act to control the filling or draining of chambers B and C, causing the piston rods of the two rear - wheel steering self - centering cylinders to telescopic, realizing the steering control of the two rear wheels;

[0047] Automatic centering module: It includes a left rear accumulator integrated valve group 3 provided with a left rear accumulator 11 and a right rear accumulator integrated valve group 4 provided with a right rear accumulator 12; when controlling the front wheel steering and system failure, the left rear accumulator 11 and the right rear accumulator 12 respectively fill the A chamber and the E chamber of the steering self-centering cylinder of the left rear wheel and the right rear wheel with oil, so that the piston rods of the steering self-centering cylinders of the two rear wheels are centered, realizing the automatic centering of the two rear wheels;

[0048] Control module: Controls the valves in the front axle steering valve group 1 and the rear axle steering valve group 2.

[0049] In this way, through the split valve group (independent control of the front axle / rear axle), the valves in the front wheel steering module and the rear wheel steering module directly respond to the control module instructions, reducing the control difficulty of the control module coordination algorithm and solving the problem of complex control system; the left rear wheel steering self-centering cylinder 9 and the right rear wheel steering self-centering cylinder 10 are designed with centering chambers (A chamber, E chamber). When controlling the front wheel steering and system failure, the centering chambers maintain the middle position through the pre-charged pressure of the accumulator, so that the rear wheels are automatically centered, solving the problems of large difficulty in centering and maintaining the rear wheels, and large difficulty in centering during failure.

[0050] In addition, an electric steering pump and fuel tank assembly 5 can be set, so that the electric steering pump and fuel tank assembly 5 includes a high-pressure pump and a low-pressure pump. When the high-pressure pump fails, the dual-source electric steering pump automatically switches from the high-pressure pump to the low-pressure pump under the control of the control module to maintain the system pressure, preventing the steering system from suddenly failing and improving the safety performance. In addition, the oil outlet of the electric steering pump and fuel tank assembly 5 is connected to the filter 6 to filter impurities in the oil.

[0051] Embodiment 2:

[0052] On the basis of Embodiment 1, a specific front axle steering valve group 1 structure is provided. The left front wheel steering cylinder 7 and the right front wheel steering cylinder 8 are each provided with two oil cavities, namely a rodless cavity and a rod cavity. By controlling the filling and unloading of the two cavities of the rod cavity and the rodless cavity, the telescopic movement of the piston rod is controlled to achieve the steering (i.e., deflection) of the front wheels; the two rodless cavities between the left front wheel steering cylinder 7 and the right front wheel steering cylinder 8 and between the two rod cavities are connected by pipelines, and solenoid valves are provided on the pipelines. Moreover, the main circuit of the front axle steering valve group 1 obtains pressure oil from the electric steering pump and fuel tank assembly 5 and supplies it to the front axle steering valve group 1, the rear axle steering valve group 2, the left rear accumulator integrated valve group 3, and the right rear accumulator integrated valve group 4; the oil return of the front axle steering valve group 1, the rear axle steering valve group 2, the left rear accumulator integrated valve group 3, and the right rear accumulator integrated valve group 4 is stored in the fuel tank of the electric steering pump and fuel tank assembly 5; a main circuit overflow valve 13 and a main circuit solenoid valve 14 controlled by a control module are connected in parallel on the main circuit of the front axle steering valve group 1. Pressure sensors are provided on the front axle steering valve group 1 and the rear axle steering valve group 2 to monitor the oil circuit pressure in real time and feedback it to the control module. When the pressure exceeds the limit, the control module controls the main circuit overflow valve 14 to unload.

[0053] More specifically, referring to Figure 8 , the front axle steering valve group 1 includes a main overflow valve 13, a main circuit solenoid valve 14, a front axle proportional valve 15, a first solenoid valve 16 in the front axle branch, a second solenoid valve 17 in the front axle branch, a third solenoid valve 18 in the front axle branch, a fourth solenoid valve 19 in the front axle branch, a fifth solenoid valve 20 in the front axle branch, a sixth solenoid valve 21 in the front axle branch, a first main circuit pressure sensor 22, a second front axle pressure sensor 23, a third front axle pressure sensor 24, a fourth front axle pressure sensor 25, and a fifth front axle pressure sensor 26, where:

[0054] The first pressure oil inlet (P1 port) of the front axle steering valve group 1 is connected to the oil outlet of the filter 6 on the oil tank outlet pipeline of the electric steering pump and oil tank assembly 5, receiving high-pressure oil from the oil outlet of the filter 6; the first oil return port (T1 port) of the front axle steering valve group 1 is connected to the oil tank return port of the electric steering pump and oil tank assembly 5, guiding the hydraulic oil back to the oil tank; the second pressure oil outlet (P2 port) of the front axle steering valve group 1 is connected to the pressure oil inlet (P port) of the rear axle steering valve group 2, providing high-pressure oil for the rear axle steering valve group 2; the second oil return port (T2 port) of the front axle steering valve group 1 is connected to the oil return port (T port) of the rear axle steering valve group 2, combining the oil return of the front axle steering valve group 1 and the oil return of the rear axle steering valve group 2; the third pressure oil outlet (P3 port) of the front axle steering valve group 1 is connected to the pressure oil inlets of the left rear accumulator integrated valve group 3 and the right rear accumulator integrated valve group 4 through a three-way pipe joint, supplying oil to the left rear accumulator integrated valve group 3 and the right rear accumulator integrated valve group 4; the third oil return port (T3 port) of the front axle steering valve group 1 is connected to the oil return ports of the left rear accumulator integrated valve group 3 and the right rear accumulator integrated valve group 4 through a three-way pipe joint, recovering the oil return of the left rear accumulator integrated valve group 3 and the right rear accumulator integrated valve group 4;

[0055] The A1 port on the first branch of the front axle steering valve group 1 is connected to the rod chamber C (piston rod side oil chamber) of the left front wheel steering cylinder 7, and the B1 port on the second branch of the front axle steering valve group 1 is connected to the rodless chamber B (no piston rod side oil chamber) of the left front wheel steering cylinder 7, used to control the telescopic movement of the piston rod of the left front wheel steering cylinder 7 to achieve the steering of the left front wheel; the A2 port on the third branch of the front axle steering valve group 1 is connected to the rod chamber C (piston rod side oil chamber) of the right front wheel steering cylinder 8, and the B2 port on the fourth branch of the front axle steering valve group 1 is connected to the rodless chamber B (no piston rod side oil chamber) of the right front wheel steering cylinder 8, used to control the telescopic movement of the piston rod of the right front wheel steering cylinder 8 to achieve the steering of the right front wheel;

[0056] The main circuit overflow valve 13 is used for the pressure regulation of the all-wheel independent steering system (such as the rated pressure is 13 Mpa); Figure 8 The states of all valves in are the default power-off states. The main circuit solenoid valve 14 is a two-position two-way solenoid valve, and the system builds pressure when powered on; the front axle proportional valve 15 is a three-position four-way proportional valve, switching the oil filling and unloading of the oil circuits of the left front wheel steering cylinder 7 and the right front wheel steering cylinder 8 through the position state command of the control module; the opening and closing of the first solenoid valve 16, the second solenoid valve 17, the third solenoid valve 18, the fourth solenoid valve 19, the fifth solenoid valve 20, and the sixth solenoid valve 21 on the front axle branch determine the telescopic movement of the piston rods of the left front wheel steering cylinder 7 and the right front wheel steering cylinder 8; the main circuit first pressure sensor 22, the front axle second pressure sensor 23 to the front axle fifth pressure sensor 26 feedback the pressure values of the oil circuits where they are located to the control module through analog detection.

[0057] Embodiment 3:

[0058] On the basis of the first embodiment, a specific structure of the rear axle steering valve group 2 is provided. The A chambers and E chambers of the left rear wheel steering self-aligning cylinder 9 and the right rear wheel steering self-aligning cylinder 10 are centering chambers, the B chamber is the rodless steering chamber, and the C chamber is the rod steering chamber; when the rear wheels are steering normally, the filling and unloading of the B chamber and the C chamber are controlled by the actions of the proportional valve and the solenoid valve, and the A chamber, the E chamber, and the D chamber are unloaded; when the rear wheels are centered, the B chamber, the C chamber, and the D chamber are unloaded, and the centering chambers A and E are filled with oil. The cross-sectional areas of the A chamber, B chamber, C chamber, and E chamber of the left rear wheel steering self-aligning cylinder 9 and the right rear wheel steering self-aligning cylinder 10 are respectively:

[0059]

[0060] Among them, D A is the inner diameter of the main piston of the A chamber, D B is the inner diameter of the cylinder of the B chamber, D C is the outer diameter of the main piston of the C chamber.

[0061] More specifically, referring to Figure 7 、 Figure 8 、 Figure 9 , the rear axle steering valve group 2 includes a rear axle proportional valve 27, a first solenoid valve 28 in the rear axle branch, a second solenoid valve 29 in the rear axle branch, a third solenoid valve 30 in the rear axle branch, a fourth solenoid valve 31 in the rear axle branch, a fifth solenoid valve 32 in the rear axle branch, a sixth solenoid valve 33 in the rear axle branch, a first pressure sensor 34 in the rear axle, a second pressure sensor 35 in the rear axle, a third pressure sensor 36 in the rear axle, and a fourth pressure sensor 37 in the rear axle, where:

[0062] The pressure oil inlet (P port) of the rear axle steering valve group 2 is connected to the second pressure oil outlet (P2 port) of the front axle steering valve group 1; the oil return port ((T port) of the rear axle steering valve group 2 is connected to the second oil return port (T2 port) of the front axle steering valve group 1; the C1 port on the first branch of the rear axle steering valve group 2, the B1 on the second branch, and the T1 port on the third branch are respectively connected to the rod chamber C, the rodless chamber B, and the unloading chamber D of the left rear wheel steering self-aligning cylinder 9; the C2 port on the fourth branch of the rear axle steering valve group 2, the B2 port on the fifth branch, and the T2 port on the sixth branch are respectively connected to the rod chamber C, the rodless chamber B, and the unloading chamber D of the right rear wheel steering self-aligning cylinder 10. The rear axle proportional valve 27 switches the filling and unloading of the rear axle cylinder oil circuit through the control module position status command; the opening and closing of the first solenoid valve 28, the second solenoid valve 29, the third solenoid valve 30, the fourth solenoid valve 31, and the fifth solenoid valve 32 in the rear axle branch determine the movement direction of the rear axle cylinder; the first pressure sensor 34 to the third pressure sensor 36 in the rear axle feedback the pressure values of the oil circuits where they are located to the control module through analog detection.

[0063] Embodiment 4:

[0064] On the basis of Embodiment 1, a specific structure of the left rear accumulator integrated valve group 3 and the right rear accumulator integrated valve group 4 is provided.

[0065] Refer to Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 , the left rear accumulator integrated valve group 3 includes a left rear first solenoid valve 38, a left rear second solenoid valve 39, a left rear one-way valve 40, a left rear first pressure sensor 41, and a left rear second pressure sensor 42, where:

[0066] The pressure oil inlet (P4 port) of the left rear accumulator integrated valve group 3 is connected to the pressure oil inlets (P4 port, the left rear accumulator integrated valve group 3 and the right rear accumulator integrated valve group 4 share a pressure oil inlet) of the front axle steering valve group 1 and the right rear accumulator integrated valve group 4 through a three-way pipe joint; the pressure oil return port (T4 port) of the left rear accumulator integrated valve group 3 is connected to the pressure oil return ports (T4 port, the left rear accumulator integrated valve group 3 and the right rear accumulator integrated valve group 4 share a pressure oil return port) of the front axle steering valve group 1 and the right rear accumulator integrated valve group 4 through a three-way pipe joint; the A1 port on the left rear accumulator integrated valve group 3 is connected to the A chamber of the left rear wheel steering self-returning oil cylinder 9, the E1 port on the left rear accumulator integrated valve group 3 is connected to the E chamber of the left rear wheel steering self-returning oil cylinder 9, and the XN1 port on the left rear accumulator integrated valve group 3 is connected to the left rear accumulator 11; the left rear first solenoid valve 38 is default in the connected state, and the left rear second solenoid valve 39 is default in the disconnected state. At this time, the full-wheel independent control system pressure or the pre-charge pressure of the left rear accumulator 11 will fill the A chamber and E chamber of the left rear wheel steering self-returning oil cylinder 9 through the left rear one-way valve 40, realizing the automatic return of the left rear wheel and the right rear wheel when the front wheel steering mode and the system fails and powers off; when the left rear wheel and the right rear wheel need to turn normally, the left rear first solenoid valve 38 and the left rear second solenoid valve 39 are powered on, the A chamber and E chamber of the left rear wheel steering self-returning oil cylinder are unloaded, and the piston rod of the left rear wheel steering self-returning oil cylinder 9 can extend and retract to realize the normal steering of the left rear wheel.

[0067] The right rear accumulator integrated valve group 4 includes a right rear first solenoid valve 43, a right rear second solenoid valve 44, a right rear one-way valve 45, a right rear first pressure sensor 46, and a right rear second pressure sensor 47. Since the structures of the left rear accumulator integrated valve group 3 and the right rear accumulator integrated valve group 4 are the same, except that the left rear accumulator integrated valve group 3 is connected to the left rear wheel self-returning oil cylinder 9, while the right rear accumulator integrated valve group 4 is connected to the right rear wheel self-returning oil cylinder 10, the specific connection method will not be elaborated.

[0068] Embodiment 5:

[0069] On the basis of the above embodiments, the working principle of the all-wheel independent steering system will be introduced in detail.

[0070] I. Working condition decomposition

[0071] The electro-hydraulic all-wheel independent steering system can achieve four-wheel all-wheel steering motion, has the function of coordinated closed-loop control of the front and rear wheels, and has function modes such as front two-wheel steering, four-wheel small-radius steering, four-wheel diagonal steering, and central steering. Through electro-hydraulic servo control, closed-loop control of independent steering of the left front wheel and the right front wheel, and the left rear wheel and the right rear wheel is achieved. The steering function is initially decomposed into:

[0072] (1) Under the default working condition: The front two wheels steer.

[0073] (2) Under the low-speed four-wheel small-radius steering working condition: The steering angles of the front wheels and the rear wheels are the same, and the directions are opposite.

[0074] (3) Under the low-speed four-wheel diagonal steering working condition: The steering angles of the front wheels and the rear wheels are the same, and the directions are the same.

[0075] (4) Under the in-situ central steering working condition: The four wheels cooperate with differential steering at the same angle but in different directions.

[0076] According to the above working conditions, the single-wheel working conditions are further decomposed as shown in Table 1. The steering system receives the vehicle body cornering instruction θ 指令 and the steering mode instruction. θ is the target cornering angle, and θ lf , θ rf , θ lr , θ rr are the target cornering angles of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel respectively, and θ max is the maximum cornering angle of the wheel.

[0077] Table 1 System working condition decomposition

[0078]

[0079]

[0080] II. Wheel movement decomposition

[0081] According to the above working condition decomposition, taking the front wheel as an example, the working state of the hydraulic system is decomposed into the following ten cases according to requirements. Let:

[0082] The cross-sectional area of the rod chamber is A1, with the unit of m 2 ;

[0083] The cross-sectional area of the non-rod chamber is A2, with the unit of m 2 ;

[0084] The force on the rod chamber is F1, with the unit of N;

[0085] The force on the non-rod chamber is F2, with the unit of N;

[0086] System pressure P, unit Mpa;

[0087] Rated flow Q, unit L / min;

[0088] The moving stroke L of the main piston of the oil cylinder, unit m;

[0089] The retraction movement time T1 of the main piston of the oil cylinder, unit t;

[0090] The extension movement time T2 of the main piston of the oil cylinder, unit t;

[0091] Then there is:

[0092]

[0093] The wheel movement directions, the working states of the solenoid valves and proportional valves, the piston forces, and the movement times under each working condition are shown in Table 2. The oil cylinder selection needs to meet Equation (3), where n is the rocker arm length (unit: m), i is the transmission ratio of the vertical axis to the kingpin force, and M r is the single-wheel in-situ steering resistance torque (unit: N·m).

[0094] P·A1·n·i > M r (3)

[0095] Table 2 Wheel movement decomposition

[0096]

[0097]

[0098] III. Principle of the rear-wheel steering self-aligning oil cylinder

[0099] The rear steering wheel is in a time-sharing working condition. It participates in the system work in the all-wheel steering mode state. However, in the case where it does not need to participate in steering or the system has an abnormality, the alignment and neutral position holding capabilities determine the driving safety of the vehicle. Therefore, in the engineering scheme design of this system, an integrated hydraulic cylinder that combines the functions of active alignment and neutral position holding is adopted. The driving and aligning integrated hydraulic cylinder is not only the actuator of the axle independent steering system but also the guarantee of the safety of the entire all-wheel steering system. This device integrates the functions of steering drive, active alignment, and neutral position holding.

[0100] The system structure principle is as Figure 1 shown. The corresponding oil cavities are named after the oil ports. There are a total of five oil cavities, A, B, C, D, and E. The D cavity is always the oil return cavity. The cross-sectional areas of the four cavities A, B, C, and E are respectively:

[0101]

[0102] Among them, DA is the inner diameter of the main piston, D B is the inner diameter of the oil cylinder, D C is the outer diameter of the main piston.

[0103] Cavities B and C communicate with the oil pump, and cavities A and E communicate with the accumulator. They form two independent hydraulic circuits, namely the normal steering circuit and the fault centering circuit respectively. The hydraulic circuit formed by cavities B and C drives the main piston to extend or contract under normal steering conditions; the hydraulic circuit formed by cavities A and E is used to drive the oil cylinder back to the middle position in the system fault mode. Cavity A drives the main piston back to the middle position from the contracted position in the system fault mode, and cavity E drives the main piston back to the middle position from the extended position in the system fault mode. The specific process is as follows:

[0104] (1) Fault mode

[0105] ① Refer to Figure 2 , cavities B and C are unloaded, the accumulator releases pressure to fill oil into cavity E, and the main piston is driven to contract by the floating piston. Cavity E needs to overcome the maximum resistance of wheel rotation and the resistance of the accumulator to fill oil into cavity A. Let F 阻 be the resistance acting on the piston rod of the oil cylinder when the wheel rotates, and there is:

[0106] P 蓄 ·S E >P 蓄 ·S2 + F 阻 (5)

[0107] ② Centering after contraction in the fault state

[0108] Refer to Figure 3 , cavities B and C are unloaded, the accumulator releases pressure to fill oil into cavity A, and the main piston is pushed to extend. Cavity A only needs to overcome the maximum resistance of wheel rotation, that is:

[0109] P 蓄 ·S A >F 阻 (6)

[0110] (2) Normal working condition

[0111] Cavities B and C are the oil cavities of the main oil cylinder, forming another independent hydraulic circuit (normal working circuit). When the system is working normally, the telescopic movement of the main piston is realized by controlling the oil inlet and outlet of cavities B and C. Specifically, it is divided into the following states:

[0112] ① Refer to Figure 4 , under normal conditions, the oil cylinder extends to the middle position and then retracts. Cavities A and E are unloaded, and the oil pump fills oil into cavity C to push the main piston to contract. Cavity C needs to overcome the maximum resistance of wheel rotation, that is:

[0113] P 系 ·SC >F 阻 (7)

[0114] ② Refer to Figure 5 , under normal working conditions, the oil cylinder retracts to the middle position and then extends. The A chamber and the E chamber are unloaded, and the oil pump fills the B chamber to push the main piston to extend. The B chamber needs to overcome the maximum resistance of the wheel rotation, that is:

[0115] P 系 ·S B >F 阻 (8)

[0116] ③ Refer to Figure 6 , after the fault is centered, the oil cylinder is in the middle position and then extends.

[0117] In summary, the above are only the preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An all-wheel independent steering system, characterized in that, Comprising: Front-wheel steering module: It includes a front axle steering valve group (1), a left front-wheel steering cylinder (7) and a right front-wheel steering cylinder (8). The valves in the front axle steering valve group (1) control the telescopic movement of the piston rods of the two front-wheel steering cylinders to achieve the steering control of the two front wheels. Rear-wheel steering module: It includes a rear axle steering valve group (2), a left rear-wheel steering self-aligning cylinder (9) and a right rear-wheel steering self-aligning cylinder (10) provided with an A chamber, a B chamber, a C chamber, a D chamber and an E chamber. The D chamber is an unloading chamber. The valves in the rear axle steering valve group (2) control the oil filling or oil discharging of the B chamber and the C chamber to make the piston rods of the two rear-wheel steering self-aligning cylinders telescopic, so as to achieve the steering control of the two rear wheels. Automatic alignment module: It includes a left rear accumulator integrated valve group (3) provided with a left rear accumulator (11) and a right rear accumulator integrated valve group (4) provided with a right rear accumulator (12). When controlling the front-wheel steering and in case of system failure, the left rear accumulator (11) and the right rear accumulator (12) respectively fill the A chamber and the E chamber of the rear-wheel steering self-aligning cylinders of the left rear wheel and the right rear wheel, so that the piston rods of the two rear-wheel steering self-aligning cylinders are centered, realizing the automatic alignment of the two rear wheels. Control module: Controls the valves in the front axle steering valve group (1) and the rear axle steering valve group (2).

2. The all-wheel independent steering system according to claim 1, characterized in that, The A chamber and the E chamber of the left rear-wheel steering self-aligning cylinder (9) and the right rear-wheel steering self-aligning cylinder (10) are centering chambers, the B chamber is a rodless steering chamber, and the C chamber is a rod steering chamber. When the rear wheels are steering normally, the oil filling and unloading of the B chamber and the C chamber are controlled by the action of the proportional valve and the solenoid valve, and the A chamber, the E chamber and the D chamber are unloaded. When the rear wheels are centered, the B chamber, the C chamber and the D chamber are unloaded, and the A chamber and the E chamber are filled with oil.

3. A full-wheel independent steering system according to claim 2, characterized in that, The cross-sectional areas of the A chamber, the B chamber, the C chamber and the E chamber of the left rear-wheel steering self-aligning cylinder (9) and the right rear-wheel steering self-aligning cylinder (10) are respectively: Among them, D A is the inner diameter of the main piston of chamber A, D B is the inner diameter of the oil cylinder of chamber B, D C is the outer diameter of the main piston of chamber C.

4. A full-wheel independent steering system according to any one of claims 1 to 3, characterized in that, Both the left front-wheel steering cylinder (7) and the right front-wheel steering cylinder (8) are provided with two oil chambers, namely a rodless chamber and a rod chamber. The telescopic movement of the piston rod is controlled by the oil filling and unloading of the rod chamber and the rodless chamber to achieve the steering of the front wheels. The two rodless chambers and the two rod chambers between the left front-wheel steering cylinder (7) and the right front-wheel steering cylinder (8) are connected through pipelines, and solenoid valves are provided on the pipelines.

5. A full-wheel independent steering system according to any one of claims 1 to 3, characterized in that, It further includes an electric steering pump and fuel tank assembly (5). The electric steering pump and fuel tank assembly (5) includes a high-pressure pump and a low-pressure pump, which are used to automatically switch from the high-pressure pump to the low-pressure pump to maintain the system pressure under the control of the control module when the high-pressure pump fails.

6. A full-wheel independent steering system according to any one of claims 1 to 3, characterized in that, The main circuit of the front axle steering valve group (1) obtains pressure oil from the electric steering pump and fuel tank assembly (5) and supplies it to the front axle steering valve group (1), the rear axle steering valve group (2), the left rear accumulator integrated valve group (3) and the right rear accumulator integrated valve group (4). The return oil of the front axle steering valve group (1), the rear axle steering valve group (2), the left rear accumulator integrated valve group (3) and the right rear accumulator integrated valve group (4) is stored in the fuel tank in the electric steering pump and fuel tank assembly (5). A main road of the front axle steering valve group (1) is provided with a main road overflow valve (13) and a main road solenoid valve (14) in parallel, which are controlled by the control module.

7. The all-wheel independent steering system according to claim 6, characterized in that, The front axle steering valve group (1) and the rear axle steering valve group (2) are provided with pressure sensors to monitor the oil circuit pressure in real time and feedback it to the control module. When the pressure exceeds the limit, the control module controls the main road overflow valve (13) to unload.

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