An auxiliary accumulator type electro-hydraulic power steering system

Abstract

The present invention discloses an auxiliary accumulator type electro-hydraulic power steering system, comprising: a steering wheel, a steering shaft, an integral recirculating ball type power steering gear, an oil reservoir, a hydraulic pump, a pressure limiting valve, a check valve, an accumulator, a steering wheel torque and rotation angle sensor, an accumulator pressure sensor, an EHPS system controller, a motor controller, a booster motor, an electromagnetic pressure reducing valve, a first electromagnetic switching valve and a second electromagnetic switching valve. In the initial stage of the increase in the rotational speed of the booster motor only under the steering condition, the accumulator and the hydraulic pump together deliver hydraulic oil to the integral recirculating ball type power steering gear, which improves the boost response speed, enables easy and precise control of the boost, the internal pressure of the accumulator is much lower than that of the conventional pressure hydraulic power steering system, and the utilization rate of the pressure oil stored in the accumulator is high, saving energy.

Description

Technical Field

[0001] The present invention relates to a hydraulic power steering system for large vehicles, and more particularly to an auxiliary accumulator type electro-hydraulic power steering system for pure electric large vehicles. Background Art

[0002] The atmospheric pressure type electro-hydraulic power steering system uses a high-pressure accumulator, and the hydraulic oil circuit is often maintained at a high pressure state above 10 Mpa. High requirements are imposed on hydraulic components, and the service life is shortened. The traditional large vehicles generally use the constant flow type hydraulic power steering system. With the development of vehicle electrification, motor and its control technology, the constant flow type electro-hydraulic power steering system has been widely used in pure electric large vehicles. To ensure the system's power assist response speed and avoid the driver's sense of power assist lag caused by the response lag of the power assist motor and hydraulic pump, when the vehicle is in a non-steering condition, the power assist motor and hydraulic pump in the current constant flow type electro-hydraulic power steering system continuously operate at a certain speed, which will inevitably cause waste of energy. Chinese Patent CN107117206 proposes an energy storage type electro-hydraulic power steering device, which uses a double hydraulic pipeline to provide power assist for the steering system, improving the response speed of steering and saving energy. Chinese Patent CN20120035944.2 proposes a new energy bus electro-hydraulic power steering system, which adopts a dual-loop and divided working condition joint control power assist method for the main control loop and the auxiliary control loop, achieving fast response while reducing energy consumption. Chinese Patent CN201720404546.2 proposes a commercial vehicle energy storage electric-hydraulic hybrid power steering system, which greatly reduces the loss of high-pressure hydraulic oil during small-angle steering. However, in the case of large steering power assist demand conditions, the above three solutions all require the accumulator to participate in power assist, and the pressure of the oil stored in the accumulator is equal to or close to the atmospheric pressure type, and the system is in a high-pressure state for a long time; when the accumulator, motor and hydraulic pump supply oil at the same time, the pressure of the oil stored in the accumulator will decrease as the oil is released, increasing the difficulty of precise control of power assist. Summary of the Invention

[0003] In order to overcome the energy waste caused by the continuous operation of the power assist motor in the non-steering condition of the existing constant flow type electro-hydraulic power steering system, or the excessive pressure of the accumulator caused by energy consumption reduction and the difficulty in precisely controlling the power assist magnitude in the later stage of power assist, the present invention provides an auxiliary accumulator type electro-hydraulic power steering system. The pressure of the oil stored in the accumulator of this system is significantly less than the atmospheric pressure type, the power assist is easy to precisely control, the utilization rate of the pressure oil stored in the accumulator is high, and energy is saved.

[0004] The technical solution adopted by the present invention to solve its technical problems is as follows: An auxiliary accumulator type electric hydraulic power steering system, which consists of a mechanical hydraulic part and an electrical part. The mechanical hydraulic part mainly includes: a steering wheel, a steering shaft, an integral recirculating ball type power steering gear, an oil storage tank, a hydraulic pump, an accumulator, a pressure limiting valve, a check valve and corresponding hydraulic pipes; The electrical part mainly includes: a power assist motor, an electromagnetic pressure reducing valve, an EHPS system controller, a motor controller, a steering wheel torque and angle sensor, an accumulator pressure sensor, a first electromagnetic switching valve and a second electromagnetic switching valve. In the steering system, the oil storage tank, the hydraulic pump, the check valve, the first electromagnetic switching valve, the steering control valve in the integral recirculating ball type power steering gear and the power assist cylinder are connected by oil pipes to form the main hydraulic oil circuit for steering assistance; An accumulator is installed on the connecting oil pipe between the check valve and the first electromagnetic switching valve, and an electromagnetic pressure reducing valve, a second electromagnetic switching valve and an accumulator pressure sensor are installed between the accumulator and the main hydraulic pipeline. The oil storage tank, the hydraulic pump, the check valve, the second electromagnetic switching valve, the accumulator and the electromagnetic pressure reducing valve form an auxiliary hydraulic oil circuit, and a pressure limiting valve is installed between the outlet of the hydraulic pump and the oil storage tank. The steering wheel is connected to the integral recirculating ball type power steering gear through the steering shaft, and a steering wheel torque and angle sensor is installed in the middle of the steering shaft. The hydraulic pump is driven by the power assist motor. The EHPS system controller collects the steering wheel torque and angle signals through the steering wheel torque and angle sensor, collects the oil pressure signal stored in the accumulator through the accumulator pressure sensor, and collects the vehicle speed signal through in-vehicle network communication; The output terminals of the EHPS system controller are respectively connected to the first electromagnetic switching valve, the electromagnetic pressure reducing valve, the second electromagnetic switching valve and the motor controller. The EHPS system controller judges whether the vehicle is in a steering condition according to the steering wheel angle signal. If the steering wheel angle is greater than or equal to the free travel, it is in a steering condition, otherwise it is in a non-steering condition. When the vehicle is in a steering condition, the EHPS system controller opens the first electromagnetic switching valve, determines the target speed of the power assist motor in the current condition according to the steering wheel torque, angle signal and vehicle speed signal, and sends it to the motor controller. The motor controller adjusts the speed of the power assist motor according to the target speed; At the same time, in the initial stage of the increase in the speed of the power assist motor, the EHPS system controller determines the target pressure value of the oil output by the electromagnetic pressure reducing valve according to the target speed of the power assist motor (generally less than 50% of the pressure difference between the two sides of the piston of the power assist cylinder in the current steering condition), inputs a certain excitation current to the electromagnetic pressure reducing valve to make the electromagnetic pressure reducing valve output oil at the target pressure. The accumulator and the hydraulic pump together supply hydraulic oil to the steering control valve in the integral recirculating ball type power steering gear, and the accumulator assists in power assistance to improve the power assistance response speed of the whole system; When the main oil passage pressure is greater than or equal to the output pressure of the pressure reducing valve, the pressure reducing valve automatically closes, and the hydraulic pump supplies oil to the steering control valve in the main hydraulic oil circuit alone.When the vehicle is in a non-steering condition, if the accumulator pressure is lower than the set lower limit value, the EHPS system controller opens the second electromagnetic switch valve and sends an accumulator oil replenishment speed signal to the motor controller. The motor controller starts the assist motor to drive the hydraulic pump to pressurize the accumulator. When the set upper limit value of the pressure is reached, the second electromagnetic switch valve is closed and the assist motor stops working. If the internal pressure of the accumulator is higher than the set lower limit value, the system state remains unchanged and the assist motor stops working.

[0005] The beneficial effects of the present invention are as follows: In the initial stage of the increase in the speed of the assist motor, the accumulator and the hydraulic pump together deliver hydraulic oil to the steering control valve in the integral recirculating ball power steering gear, so as to ensure that when the assist motor does not continuously work under non-steering conditions, the system still has a good assist response speed. The accumulator only assists in working in the initial stage of the increase in the speed of the assist motor, and the internal pressure is much smaller than that of the constant-pressure hydraulic power steering system, which can effectively prevent the service life of hydraulic components from being greatly reduced and the internal oil leakage of the system; after the accumulator exits the work, the assist force completely depends on the speed of the assist motor and is not affected by the oil output of the accumulator, and the assist force is easy to accurately control. An electromagnetic pressure reducing valve is provided at the outlet of the accumulator, which is convenient for setting and controlling the oil storage pressure of the accumulator under non-steering conditions, and avoids the unnecessary release of oil in the accumulator caused by the reduction of the oil storage pressure of the accumulator as the vehicle driving speed increases, further saving energy. Description of the Drawings

[0006] Figure 1 It is a structural schematic diagram of the auxiliary accumulator type electro-hydraulic power steering system of the present invention.

[0007] In the figure, 1. Steering wheel, 2. Steering shaft, 3. Steering wheel torque angle sensor, 4. Integral recirculating ball power steering gear, 5. First electromagnetic switch valve, 6. Second electromagnetic switch valve, 7. Pressure limiting valve, 8. Oil storage tank, 9. Hydraulic pump, 10. Check valve, 11. Assist motor, 12. Motor controller, 13. EHPS system controller, 14. Electromagnetic pressure reducing valve, 15. Accumulator pressure sensor, 16. Accumulator. Specific Embodiments

[0008] The technical solutions of the present invention will be further described below in conjunction with the drawings and specific embodiments.

[0009] This embodiment provides an auxiliary accumulator type electro-hydraulic power steering system, as Figure 1As shown in the figure, it is a structural schematic diagram of an auxiliary accumulator type electro-hydraulic power steering system, including a steering wheel 1, a steering shaft 2, a steering wheel torque and rotation angle sensor 3, an integral recirculating ball type power steering gear 4, a first electromagnetic solenoid valve 5, a second electromagnetic solenoid valve 6, a pressure limiting valve 7, an oil storage tank 8, a hydraulic pump 9, a check valve 10, a boost motor 11, a motor controller 12, an EHPS system controller 13, an electromagnetic pressure reducing valve 14, an accumulator pressure sensor 15, and an accumulator 16. The connection relationships of the components of the steering system are as follows: The steering wheel 1 is connected to the upper end of the steering shaft 2, the lower end of the steering shaft 2 is connected to the input end of the recirculating ball type power steering gear 4, the steering wheel torque and rotation angle sensor 3 is installed in the middle of the steering shaft 2, and the hydraulic pump 9 is connected to the motor shaft of the boost motor 11. The hydraulic pump 9 is connected to the oil outlet of the oil storage tank 8 through an oil inlet pipe, the hydraulic pump 9 is connected to the oil inlet of the check valve 10 through an oil outlet pipe, the oil outlet of the check valve 10 is connected to the oil inlet of the first electromagnetic solenoid valve 5 through a pipe, and the oil outlet of the first electromagnetic solenoid valve 5 is connected to the oil inlet of the integral recirculating ball type power steering gear 4 through a pipe and is as close as possible to the oil inlet of the integral recirculating ball type power steering gear 4. The interface of the accumulator 16 is connected to the oil inlet of the electromagnetic pressure reducing valve 14 through a pipe, the oil outlet of the electromagnetic pressure reducing valve 14 is connected to the pipe between the check valve 10 and the first electromagnetic solenoid valve 5, the oil inlet of the accumulator pressure sensor 15 is connected to the pipe between the accumulator 16 and the electromagnetic pressure reducing valve 14, the oil inlet of the second electromagnetic solenoid valve 6 is connected to the oil outlet pipeline of the electromagnetic pressure reducing valve 14 through a pipe, the oil outlet of the second electromagnetic solenoid valve 6 is connected to the oil inlet pipeline of the electromagnetic pressure reducing valve 14 through a pipe, the oil inlet of the pressure limiting valve 7 is connected to the oil outlet pipe of the hydraulic pump 9 through a pipe, the oil outlet of the pressure limiting valve 7 is connected to the oil return port of the oil storage tank 8 through an oil return pipe, and the oil outlet of the integral recirculating ball type power steering gear 4 is connected to the oil return port of the oil storage tank 8 through an oil return pipe. The signal output line of the steering wheel torque and rotation angle sensor 3 is connected to the signal input port of the EHPS system controller 13, the signal output line of the accumulator pressure sensor 15 is connected to the signal input port of the EHPS system controller 13, the network communication interface of the EHPS system controller 13 is connected to the vehicle on-board network interface, the output port of the EHPS system controller 13 is connected to the first electromagnetic solenoid valve 5, the output port of the EHPS system controller 13 is connected to the electromagnetic pressure reducing valve 14, the output port of the EHPS system controller 13 is connected to the second electromagnetic solenoid valve 6, and the output port of the EHPS system controller 13 is connected to the input port of the motor controller 12.

[0010] In Figure 1In the illustrated embodiment, the EHPS system controller 13 determines whether the vehicle is in a steering condition according to the steering wheel angle signal collected from the steering wheel torque angle sensor 3. When the steering wheel angle is greater than or equal to the free travel, the EHPS system controller 13 determines that the vehicle is in a steering condition; otherwise, it is in a non-steering condition. When the vehicle is in a steering condition, the EHPS system controller 13 turns on the first electromagnetic switch valve 5, determines the target speed of the assist motor 11 under the current condition according to the steering wheel torque, angle signal and vehicle speed signal, and sends it to the motor controller 12. The motor controller 12 adjusts the speed of the assist motor 11 according to the target speed, so as to achieve steering assist control. At the same time, in the initial stage of the increase in the speed of the assist motor, the EHPS system controller 13 determines the target pressure of the oil output by the electromagnetic pressure reducing valve 14 according to the target speed of the assist motor 11 (generally lower than 50% of the pressure difference between the two sides of the piston of the assist oil cylinder in the current steering condition), inputs a certain excitation current to the electromagnetic pressure reducing valve 14 to make the electromagnetic pressure reducing valve 14 output oil with the target pressure. The accumulator 16 and the hydraulic pump 9 together supply hydraulic oil to the steering control valve in the integral recirculating ball power steering gear 4, improving the assist response speed of the whole system. When the pressure in the pipeline behind the check valve 10 is greater than or equal to the output pressure of the electromagnetic pressure reducing valve 14, the electromagnetic pressure reducing valve 14 automatically closes, and the hydraulic pump 9 supplies oil to the steering control valve alone. When the vehicle is in a non-steering condition, the EHPS system controller 13 collects the oil pressure signal stored in the accumulator 16 through the accumulator pressure sensor 15, and judges whether the pressure of the oil stored in the accumulator is lower than the preset lower pressure limit value. If the pressure of the oil stored in the accumulator is lower than the lower limit value, the EHPS system controller 13 turns on the second electromagnetic switch valve 6, sends the accumulator oil replenishment speed signal to the motor controller 12, and the motor controller 12 starts the assist motor 11 to drive the hydraulic pump 9 to replenish oil to the accumulator 16. When it reaches the set upper pressure limit value, the second electromagnetic switch valve 6 is closed and the assist motor 11 stops working. If the pressure of the oil stored in the accumulator is higher than the set lower limit value, the system state remains unchanged and the assist motor 11 stops working.

[0011] In this steering system, only in the initial stage of the increase in the speed of the assist motor, the accumulator and the hydraulic pump together supply hydraulic oil to the steering control valve in the integral recirculating ball power steering gear, improving the assist response speed. The assist is easy to control precisely. The internal pressure of the accumulator is much lower than that of the constant pressure hydraulic power steering system, which can effectively prevent the service life of hydraulic components from being significantly reduced and oil leakage inside the system. An electromagnetic pressure reducing valve that can control the output oil pressure according to the input current is provided at the outlet of the accumulator in the system, which can avoid the unnecessary release of oil in the accumulator and further save energy.

[0012] The specific embodiments described above can have various variations and changes within the scope covered by the present invention content and claims. Therefore, the described embodiments do not constitute a limitation on the protection scope of the claims of the present invention.

Claims

1. An auxiliary accumulator type electro-hydraulic power steering system, comprising: Steering wheel, steering shaft, integral recirculating ball power steering gear, first electromagnetic solenoid valve, oil storage tank, hydraulic pump, pressure limiting valve, check valve, accumulator, steering wheel torque and rotation angle sensor, accumulator pressure sensor, EHPS system controller, motor controller, assist motor, electromagnetic pressure reducing valve, and second electromagnetic solenoid valve. The steering wheel is connected to the upper end of the steering shaft, and the lower end of the steering shaft is connected to the input end of the recirculating ball power steering gear. The steering wheel torque and rotation angle sensor is installed in the middle of the steering shaft. The hydraulic pump is connected to the motor shaft of the assist motor. The hydraulic pump is connected to the oil outlet of the oil storage tank through an oil inlet pipe. The oil inlet of the pressure limiting valve is connected to the oil outlet pipe of the hydraulic pump through a pipe. The oil outlet of the pressure limiting valve is connected to the oil return port of the oil storage tank through an oil return pipe. The oil outlet of the integral recirculating ball power steering gear is connected to the oil return port of the oil storage tank through an oil return pipe. The signal output line of the steering wheel torque and rotation angle sensor is connected to the signal input port of the EHPS system controller. The network communication interface of the EHPS system controller is connected to the vehicle on-board network interface to collect vehicle speed signals. It is characterized in that: the hydraulic pump is connected to the oil inlet of the check valve through an oil outlet pipe. The oil outlet of the check valve is connected to the oil inlet of the first electromagnetic solenoid valve through a pipe. The oil outlet of the first electromagnetic solenoid valve is connected to the oil inlet of the integral recirculating ball power steering gear through a pipe. The accumulator interface is connected to the oil inlet of the electromagnetic pressure reducing valve through a pipe. The oil outlet of the electromagnetic pressure reducing valve is connected to the pipe between the check valve and the first electromagnetic solenoid valve. The oil inlet of the accumulator pressure sensor is connected to the pipe between the accumulator and the electromagnetic pressure reducing valve. The oil inlet of the second electromagnetic solenoid valve is connected to the oil outlet pipeline of the electromagnetic pressure reducing valve through a pipe. The oil outlet of the second electromagnetic solenoid valve is connected to the oil inlet pipeline of the electromagnetic pressure reducing valve through a pipe. The signal output line of the accumulator pressure sensor is connected to the signal input port of the EHPS system controller. The output port of the EHPS system controller is connected to the first electromagnetic solenoid valve. The output port of the EHPS system controller is connected to the electromagnetic pressure reducing valve. The output port of the EHPS system controller is connected to the second electromagnetic solenoid valve. The output port of the EHPS system controller is connected to the input port of the motor controller; The EHPS system controller determines whether the vehicle is in a steering condition based on the steering wheel rotation angle signal collected from the steering wheel torque and rotation angle sensor; when the steering wheel rotation angle is greater than or equal to the free travel, the EHPS system controller determines that the vehicle is in a steering condition, otherwise it is in a non-steering condition; When the vehicle is in a steering condition, the EHPS system controller opens the first electromagnetic switch valve, determines the target speed of the assist motor under the current condition according to the steering wheel torque, steering angle signal and vehicle speed signal, and sends it to the motor controller. The motor controller adjusts the speed of the assist motor according to the target speed, so as to achieve steering assist control. At the same time, only in the initial stage of the increase in the speed of the assist motor, the EHPS system controller determines the target pressure of the oil output by the electromagnetic pressure reducing valve according to the target speed of the assist motor, inputs a certain excitation current to the electromagnetic pressure reducing valve to make the electromagnetic pressure reducing valve output oil with the target pressure, and the accumulator and the hydraulic pump together supply hydraulic oil to the steering control valve in the integral recirculating ball power steering gear. When the pressure in the pipeline after the one-way valve is greater than or equal to the output pressure of the electromagnetic pressure reducing valve, the electromagnetic pressure reducing valve automatically closes, and the hydraulic pump supplies oil to the steering control valve alone.

2. The auxiliary accumulator type electro-hydraulic power steering system according to claim 1, characterized in that: An electromagnetic pressure reducing valve that controls the output oil pressure according to the input current is installed between the accumulator interface and the oil pipes connecting the one-way valve and the first electromagnetic switch valve.

3. An auxiliary accumulator type electro-hydraulic power steering system according to claim 1, characterized in that: The EHPS system controller controls the pressure and the on-off of the oil circuit of the hydraulic oil supplied by the accumulator to the integral recirculating ball power steering gear in the initial stage of the increase in the speed of the assist motor under the steering condition.

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