CN204161448U - A kind of circulating ball type magnetic fluid electric-controlled hydraulic servo steering device - Google Patents

Abstract

The utility model discloses a recirculating ball type magnetofluid electric control hydraulic power steering device. A steering nut rack piston mechanism driven by a magnetic fluid is arranged inside a recirculating ball steering gear housing to drive a sector gear to drive a steering rocker arm. The electronic control unit passes Adjust the voltage value at both ends of the electrode plate and the polarity of the power supply to realize the control of the magnitude and direction of the power assist of the magnetic fluid electronically controlled hydraulic power steering device. Compared with the electric power steering system, the power booster motor and the complicated deceleration mechanism are omitted, and the structure is simple , reliable operation, low failure rate, small size, easy to arrange on the vehicle. Moreover, the recirculating ball magnetic fluid electronically controlled hydraulic power steering device can achieve the functions that the electric power steering system can accomplish in terms of performance and function. Due to the use of hydraulic system power assistance, the torque brought by the power assist motor in the electric power steering system is avoided. Volatility, higher reliability.

Description

A recirculating ball magnetofluid electronically controlled hydraulic power steering device

technical field

The utility model belongs to the technical field of vehicle engineering, in particular to the power steering technology.

Background technique

Commonly used steering gears are mainly rack and pinion type, worm crank pin type and recirculating ball type. Because the recirculating ball steering gear relies more on rolling friction, it has high transmission efficiency, is relatively light and comfortable to operate, has less wear and tear on mechanical parts, and has a relatively long service life. The recirculating ball steering gear is used on medium and large commercial vehicles. device plays an important role.

Recirculating ball hydraulic power steering is often used in recirculating ball steering gear. Recirculating ball hydraulic power steering is mainly composed of recirculating ball steering gear, hydraulic rotary valve, oil inlet pipe, oil return pipe, oil storage tank, steering oil pump, etc. The oil pump is driven by the automobile engine and provides power hydraulic oil to the circulating ball hydraulic power steering through the oil inlet pipe, and the return oil flows back to the oil storage tank through the oil return pipe. The speed of the steering oil pump in the traditional hydraulic power steering system is determined by the speed of the car engine. Regardless of whether the steering wheel needs to turn, as long as the engine is working, the steering oil pump is working, and there is no speed regulation function. 3% of fuel consumption. In the traditional hydraulic power steering system, due to the use of engine power to drive, the output hydraulic oil flow of the oil pump cannot be adjusted. The oil flow in the rotary valve is controlled by the steering wheel angle. If the designed oil flow is large, it can meet the low speed However, this will lead to poor road feel at high speeds. If the oil flow is designed to be small, it will be the opposite of the above situation, so it is difficult to coordinate the contradiction between the portability and "road feel" of the steering system.

The electric circulating ball hydraulic power steering system uses a motor to drive the steering oil pump to provide hydraulic oil to the hydraulic power steering system. The system collects the signals of the steering wheel torque sensor, steering wheel angle sensor, mileage speed sensor and engine speed sensor through the electronic control unit and feeds them back to the drive motor to realize the regulation of the hydraulic oil flow pumped into the hydraulic power steering by the steering oil pump. When the degree of opening is constant, the pressure of the oil in the hydraulic cylinder is adjusted by the motor, so as to realize the adjustment of the steering power and meet the steering power requirements at high and low speeds. Electro-hydraulic power assist has most of the advantages of mechanical hydraulic power assist, and at the same time reduces energy consumption, and the response is more sensitive. The power steering power can also be adjusted according to parameters such as corner angle and vehicle speed.

However, due to the introduction of many electronic units, the electric recirculating ball hydraulic power steering system has a relatively complicated structure, and its manufacturing and maintenance costs will increase accordingly, and the stability of use is not as reliable as the mechanical hydraulic power steering system.

Utility model content

The technical problem to be solved by the utility model is to provide a recirculating ball type magnetic fluid electric control hydraulic power steering device, which simplifies the structure, reduces the cost and improves the reliability.

In order to solve the above-mentioned technical problems, the utility model adopts the following technical scheme: a recirculating ball type magnetic fluid electric control hydraulic power steering device, including a recirculating ball steering gear housing, and the inside of the recirculating ball steering gear housing includes a straight cavity and a protruding The lower protruding cavity is arranged on the lower side of the middle part of the straight cylinder cavity. There is a steering screw in the straight cylinder cavity. The two ends of the steering screw are supported on the bearings. The steering nut rack is set on the steering screw. The steering nut rack A steel ball and a steel ball guide are provided between the internal thread of the steering screw and the external thread of the steering screw to form a steel ball circulation raceway, and a sector gear is provided in the lower protruding cavity to mesh with the steering nut rack for transmission, and the sector gear drives the steering rocker Arm swings, the recirculating ball steering gear casing is provided with insulating and sealed magnetic fluid chambers on the left and right sides of the steering nut rack respectively, the magnetic fluid chamber is provided with conductive liquid, and the magnetic fluid chambers on both sides pass through the liquid guide The tubes are connected, and a pair of electrode plates are arranged in parallel on the upper and lower inner surfaces of the magnetic fluid cavity. An electric field in the vertical direction is generated between the two electrode plates by powering on. The two electrode plates are electrically connected with the electronic control unit. The magnetic fluid cavity Two strong magnets with opposite magnetic properties are horizontally and symmetrically arranged on the inner surface, and the two strong magnets form a horizontally strong magnetic field in the magnetic fluid cavity, and the directions of the strong magnetic field and the electric field are perpendicular to each other.

Preferably, a conductive liquid reservoir with a one-way valve is connected to the catheter.

Preferably, sealing rings are provided at both ends of the magnetic fluid cavity, and an insulating layer is provided on the inner surface of the recirculating ball steering gear housing, the steering nut rack and the outer surface of the steering screw.

Preferably, the cross section of the magnetic fluid working cavity of the housing of the recirculating ball diverter is rectangular or square.

The utility model recirculating ball type magneto-fluid electronically controlled hydraulic power steering device is equipped with a magnetic-fluid-driven steering nut rack piston mechanism inside the recirculating ball steering gear housing to drive the sector gear to drive the steering rocker arm, and the electronic control unit adjusts the two electrode plates. The terminal voltage value and the polarity of the power supply realize the control of the magnitude and direction of the power assist of the magnetic fluid electronically controlled hydraulic power steering device. Compared with the electric power steering system, the power booster motor and the complicated reduction mechanism are omitted. The structure is simple and the operation is reliable. Low failure rate, small size, easy to arrange on the whole vehicle. Moreover, the recirculating ball magneto-fluid electronically controlled hydraulic power steering device can achieve the functions that the electric power steering system can accomplish in terms of performance and function. Because the hydraulic system is used to assist, the torque brought by the power assist motor of the electric power steering system is avoided. Volatility, higher reliability.

Description of drawings

Below in conjunction with accompanying drawing and specific embodiment the utility model is further described:

Fig. 1 is a schematic diagram of the overall structure of the utility model;

Fig. 2 is a structural diagram of the recirculating ball type magnetic fluid electric control hydraulic power steering device of the utility model;

Fig. 3 is the A-A cross-sectional schematic diagram of the housing of the recirculating ball steering gear of the present invention;

Fig. 4 is the B-B cross-sectional schematic diagram of the recirculating ball diverter housing of the present utility model;

Fig. 5 is the schematic diagram of the electronic control unit of the utility model;

Fig. 6 is the main program flowchart of the electronic control unit in the utility model;

Fig. 7 is the timing interrupt program flow in the electronic control empty unit in the utility model;

Fig. 8 is the flow chart of control mode selection and each control mode in the utility model;

In the figure: 1. Steering gear input shaft, 2. Steering screw, 3. Steering nut rack, 4. Sector gear, 5. Steel ball, 6. Steel ball guide, 7. Steering rocker shaft, 8. First bearing , 9, the second bearing, 10, the first steering gear housing insulation layer, 11, the second steering gear housing insulation layer, 12, the first screw surface insulation layer, 13, the second screw surface insulation layer, 14, the first One steering nut rack insulating layer, 15, the second steering nut rack insulating layer, 16, the first sealing ring, 17, the second sealing ring, 18, the third sealing ring, 19, the fourth sealing ring, 20, the first sealing ring One electrode plate, 21, the second electrode plate, 22, the third electrode plate, 23, the fourth electrode plate, 24, the right magnetic fluid cavity, 25, the left magnetic fluid cavity, 26, the catheter, 27, the single Directional valve, 28, conductive liquid storage, 29, conductive liquid, 30, recirculating ball steering housing, 31, first strong magnet (N pole), 32, second strong magnet (S pole), 33, steering column , 34, steering wheel torque sensor, 35, steering wheel angle sensor, 36, steering gear drive shaft, 37, steering gear screw and nut transmission pair, 38, steering gear rack and gear fan transmission pair, 39, recirculating ball steering gear, 40 , steering rocker arm, 41, steering tie rod, 42, steering wheel, 43, automotive electronic control unit (ECU), 44, steering wheel, 45, the third strong magnet (N pole), 46, the fourth strong magnet (S pole ).

Detailed ways

The utility model mainly includes a control assembly, a recirculating ball steering device and a steering execution assembly, wherein the control assembly includes a mechanical control unit and an electronic control unit.

As shown in Figure 1, steering wheel 44, steering column 33, steering column transmission shaft 36 are mechanical control units, steering wheel 44, steering column 33, steering column transmission shaft 36, recirculating ball steering device 39, steering tie rod 41, steering The wheels 42 are connected successively, and a steering wheel torque sensor 34 and a steering wheel angle sensor 35 are installed on the steering column 33. The vehicle electronic control unit 43 collects the steering wheel torque signal and the steering wheel angle signal through the steering wheel torque sensor 34 and the steering wheel angle sensor 35, and synthesizes The vehicle speed signal, engine speed signal, ignition signal, etc. are processed and finally control the recirculating ball diverter 39. The recirculating ball steering gear 39 is mainly composed of the steering gear screw rod and the nut transmission pair 37, the steering gear rack and the gear fan transmission pair 38, and the steering executive assembly of the vehicle includes a steering rocker arm 40, a steering tie rod 41, and a steering wheel 42.

As shown in FIG. 2 , the recirculating ball steering gear 39 is mainly composed of a recirculating ball steering housing 30 , a steering screw 2 , a steering nut rack 3 , a sector gear 4 , and a steering rocker shaft 7 . The left and right ends of the steering screw 2 are installed inside the recirculating ball steering housing 30 through the first bearing 8 and the second bearing 9 respectively. The external threads of the screw 2 are connected with steel balls 5 and steel ball conduits 6 to form a steel ball circulation raceway. A plurality of steel balls 5 are installed in the steel ball circulation raceway. The rack on the outer side of the steering nut rack 3 and its bottom The sector gear 4 installed on the steering rocker shaft 7 is meshed, and the steering rocker 40 is fixedly installed on the steering rocker shaft 7 by splines.

In the recirculating ball steering gear housing 30, the left and right sides of the steering nut rack 3 are respectively provided with insulating and sealed magnetic fluid chambers, namely the right magnetic fluid chamber 24 and the left magnetic fluid chamber 25. The magnetic fluid chamber is provided with a conductive Liquid 29, the magnetic fluid cavity on both sides communicates through the catheter tube 26, a pair of electrode plates are arranged in parallel on the upper and lower inner surfaces of the magnetic fluid cavity, and an electric field in the vertical direction is generated by powering on between the two electrode plates. The electrode plates are electrically connected with the vehicle electronic control unit 43, and the vehicle electronic control unit changes the strength and direction of the electric field by controlling the voltage value between the two electrode plates and the polarity of the power supply. The two strong magnets form a horizontal strong magnetic field in the magnetic fluid cavity, and the directions of the strong magnetic field and the electric field are perpendicular to each other.

3 to 4, in two pairs of electrode plates (the first electrode plate 20, the second electrode plate 21, the third electrode plate 22, the fourth electrode plate 23), the first electrode plate 20, the second electrode plate The plate 21 is located at the upper and lower ends of the right magnetic fluid cavity 24 , and the third electrode plate 22 and the fourth electrode plate 23 are located at the upper and lower ends of the left magnetic fluid cavity 25 . Among the two pairs of strong magnets, the first strong magnet 31 and the second strong magnet 32 are located on both sides of the left side of the magnetic fluid chamber 25, and the third strong magnet 45 and the fourth strong magnet 46 are located on both sides of the right side of the magnetic fluid chamber 24. .

As shown in Figures 2 to 4, the recirculating ball steering gear housing 30 constitutes a magnetic fluid hydraulic cylinder block, the cross section of which is rectangular or square, and the magnetic fluid hydraulic cylinder body is driven by a steering nut rack 3 (equivalent to the piston) is divided into two independent magnetic fluid chambers (ie, the right magnetic fluid chamber 24 and the left magnetic fluid chamber 25, which are actually equivalent to piston chamber A and piston chamber B). Among the four electrode plates, the first electrode plate 20 and the third electrode plate 22 are connected through the power line and maintain the same voltage value, and the second electrode plate 21 and the fourth electrode plate 23 are also connected through the power line. And keep the same voltage value. In the magnetic fluid cavity 24 on the right side, an electric field in a vertical direction is produced by the electrode plates, and the intensity and direction of the electric field are controlled by the power supply polarity of the voltage value between the electrode plates; An electric field controlled by the electrode plates, the direction of the electric field is the same as the direction of the electric field in the right magnetic fluid cavity 24, and the intensity of the electric field is determined by the voltage value between the electrode plates. The vertical end faces of the two magnetic fluid chambers are all symmetrically placed in parallel with two strong magnets, wherein the first strong magnet 31 and the third strong magnet 45 are the N poles of the strong magnets, and the second strong magnets 32 and the fourth strong magnets 46 are the poles of the magnets. S pole, in two magnetic fluid chambers, produce a strong magnetic field in the horizontal direction perpendicular to the axial direction of the steering nut rack 7 (piston); the two magnetic fluid chambers are filled with conductive liquid 29, the conductive liquid in the two magnetic fluid chambers 29 is connected by catheter 26, and guarantees that conductive liquid 29 can flow freely in two magnetic fluid cavities; The two ends of each magnetic fluid cavity are respectively equipped with sealing rings (the first sealing ring 16, the second sealing ring 17 , the third sealing ring 18, the fourth sealing ring 19), to ensure that the conductive liquid 29 will not leak during work; The parts that can contact the conductive liquid in the outer surface of the nut rack 3 are respectively provided with insulating layers (the first steering gear housing insulating layer 10, the second steering gear housing insulating layer 11, the first screw rod surface insulating layer 12, The second screw rod surface insulation layer 13, the first steering nut rack insulation layer 14, the second steering nut rack insulation layer 15); in order to ensure that the magnetic fluid cavity inside the magnetic fluid hydraulic cylinder is always full of conductive liquid 29, in the cycle A conductive liquid reservoir 28 with a one-way valve 27 is provided on the outside of the ball diverter.

When the driver turns the steering wheel 44, the steering column 33, the steering wheel torque sensor 34, the steering wheel angle sensor 35, the steering gear drive shaft 36 and the steering gear input shaft 1 will rotate together with the steering wheel 44 in the same direction and at the same angle, At this time, the steering gear input shaft 1 drives the steering screw 2 to rotate in the steering nut rack 3, so that the steering nut rack 3 moves along the axial direction of the steering screw 2, and the outer rack of the steering nut rack 3 and the steering rocker arm The sector gear 4 installed on the shaft 7 is meshed, the sector gear 4 drives the steering rocker arm 40 to swing, and the steering rocker arm pulls the steering tie rod 41 to drive the steering wheel 42 to complete the steering action. When the recirculating ball steering gear works, the steering torque required is relatively large, and the power assist system is needed to help the system complete the steering work. The utility model adopts a novel magneto-fluid electronically controlled hydraulic booster system to help the recirculating ball steering gear to complete the steering work.

In the recirculating ball type magnetic fluid electric control hydraulic power steering system, the steering wheel torque sensor 34, the steering wheel angle sensor 35, the steering gear transmission shaft 36 and the steering column 33 are coaxial; the recirculating ball steering gear housing 30 is made into a hydraulic piston cylinder The two ends of the steering nut rack 3 are made into pistons matched with the hydraulic cylinder body, the piston and the steering nut rack are integrated, and the liquid in the hydraulic cylinder pushes the piston, that is, the steering nut rack 3 along the direction of the steering screw 2. The axial direction moves within the hydraulic cylinder.

What the mechanical structure of the recirculating ball steering gear selects is the structural form of existing technology maturity on the vehicle; what the steering wheel torque sensor 34 and the steering wheel angle sensor 35 adopt are also mature technical products, and these two sensors can respectively convert the torque value of the steering wheel and The angle value of the steering wheel is converted into a corresponding linear voltage signal and transmitted to the vehicle electronic control unit 43 .

When the driver turns the steering wheel 44, the automotive electronic control unit 43 will collect the data of the steering wheel torque sensor 34, the steering wheel angle sensor 35, the vehicle speed sensor and the engine speed sensor, and determine the magnitude of the force of the magnetic fluid hydraulic power assist system according to the driving information of the vehicle and direction, by adjusting the voltage value between the two pairs of electrode plates inside the magnetic fluid hydraulic cylinder and the polarity of the power supply to control the magnitude and direction of the Lorentz force received by the conductive liquid 29 in the magnetic fluid hydraulic cylinder, the conductive liquid 29 Under the action of Lorentz force, the piston (steering nut rack 3) is pushed to move along the axial direction of the steering screw 2, and the rack on the outer side of the steering nut rack 3 is in phase with the sector gear 4 installed on the steering rocker shaft 7. Mesh, the sector gear 4 drives the steering rocker shaft 7 to rotate, helping the mechanical recirculating ball steering machine to complete the steering action. The steering force of the steering gear can be adjusted according to different vehicle speeds, which can not only reduce the driver's manipulation burden, but also prevent the driver from losing the sense of the road.

The utility model recirculating ball type magnetic fluid electric control hydraulic power steering device only adopts a simple hydraulic cylinder on the basis of the recirculating ball mechanical steering device, and a pair of electrode plates and a pair of electrode plates and Strong magnets ensure that the generated electric and magnetic fields are perpendicular to each other; complex hydraulic control oil circuits such as steering oil pumps and steering control valves in traditional hydraulic power steering systems are omitted, and the structure is simple and the manufacturing cost is low.

The steering wheel and the steering wheel of the utility model recirculating ball type magnetic fluid electric control hydraulic power steering device are all connected by mechanical parts, with precise control, direct road feeling, sufficient steering power, and the power assist of the steering system can be adjusted according to the vehicle speed information. The active back-to-center function of the steering system can also be realized. The utility model realizes the goals of light steering, energy saving and rapid response, has multiple advantages and has great market prospects.

As shown in Figure 5, the automotive electronic control unit 43 is mainly composed of a CPU, a signal acquisition and processing circuit, an H-bridge drive circuit, a relay drive circuit, a fault monitoring circuit, a fault alarm circuit, a CAN bus communication circuit, and a power processing circuit. Among them, the CPU is an 8-bit or 16-bit single-chip microcomputer, and the drive circuit of the electrode plate adopts an H-bridge circuit. The voltage between the two pairs of electrodes in the hydraulic cylinder and the polarity of the power supply are determined by the four Mosfet tubes Q1, Controlled by Q2, Q3 and Q4, the magnitude and direction of the power boost of the magnetic fluid hydraulic power booster are controlled by adjusting the voltage value and polarity between the two pairs of electrodes. The electronic control unit 43 is provided with an electronic switch (relay) in the drive circuit controlling the voltage at both ends of the electrodes. When the system is abnormal, the switch is cut off quickly to ensure the safety of the system. The fault monitoring circuit and the fault alarm circuit are mainly used to monitor and alarm the working state of the system to improve the safety and reliability of the system. The CAN bus data communication circuit is mainly used for data communication between the electronic control unit of this system and other equipment. The electrode plate driving circuit adopts an H bridge circuit. The automotive electronic control unit is also provided with a detection circuit and a relay switch drive circuit, and after the detection circuit detects that the magnetic fluid electronically controlled hydraulic power steering device fails, the relay switch drive circuit is controlled to cut off the switch of the magnetic fluid electronically controlled hydraulic power steering device . The magnetofluid electronically controlled hydraulic power steering device is directly powered by the vehicle power supply battery.

During the running of the vehicle, when the driver turns the steering wheel 44 , the steering wheel torque sensor 34 and the steering wheel angle sensor 35 will give corresponding signals. The torque sensor outputs a torque signal and converts the torque signal into a voltage signal. The amplitude of the voltage signal is proportional to the torque value of the steering wheel. The zero position of the steering wheel torque signal corresponds to 2.5V of the voltage value; the steering wheel angle sensor outputs the angle signal of the steering wheel And the angle signal of the steering wheel is converted into a voltage signal, the amplitude of the voltage signal is proportional to the angle value of the steering wheel, and the zero position of the steering wheel angle signal corresponds to 2.5V of the voltage value. The steering wheel torque signal, steering wheel angle signal, vehicle speed signal and engine speed signal are input to the electronic control unit 43, and the electronic control unit 43 judges the working mode of the power assist system based on information such as steering wheel torque, steering wheel angle and vehicle speed, and determines the magnitude and direction of power assist of the power assist system , The recirculating ball magnetic fluid hydraulic power steering device can realize a total of three control modes: power control, centering control and damping control, of which power control is the basic control mode. Power assist control: When the vehicle is turning at different speeds, the magnetic fluid electronically controlled hydraulic power steering system can provide different steering assist power. When performing power assist control, it is necessary to reduce the driver's manipulation burden and not make the driver lose the sense of the road; it needs to be considered Handling ease at low speeds and handling stability at high speeds. Damping control: Damping control can be performed during high-speed steering and fast steering. By applying a small reaction force to the power assist system, the steering wheel becomes heavy, simulating the damping effect of the electric power steering system in the damping control of the motor short circuit, preventing the vehicle from Occurrence of sideslip and rollover; centering control: After the vehicle turns at low speed, the steering wheels can automatically return to the centering position, so that the vehicle can continue to drive in a straight line, and at the same time, it can suppress the tendency of the vehicle to return to the centering overshoot and oscillation at high speed, thereby Improve the straight-line driving performance of the vehicle;

The specific working process of the recirculating ball magneto-fluid electronically controlled hydraulic power steering device is as follows:

When the system was not energized, the electrode plates in the magnetic fluid hydraulic cylinder were not energized, and the conductive liquid 29 was stored in the piston cavity on both sides of the piston (steering nut rack 3). The magnetic field in the horizontal direction is not affected by the electric field in the vertical direction, so Lorentz force will not be generated. At this time, the piston (steering nut rack 3) in the hydraulic cylinder is in a free and unstressed state. At this time, the magnetic fluid hydraulic pressure The power assist system does not assist the steering system.

When the system is energized, the magnetic fluid hydraulic power assist system begins to assist the mechanical steering gear. When the electrode plate at the upper end of the hydraulic cylinder is positive and the electrode plate at the lower end is negative, a vertical electric field is formed in the hydraulic cylinder, and the direction of the electric field is from top to bottom; the strong magnets arranged horizontally on the inner wall of the magnetic fluid hydraulic cylinder form A strong magnetic field in the horizontal direction perpendicular to the direction of motion of the piston (steering nut rack 3); the conductive liquid 29 will produce a rightward Lorentz force under the joint action of the mutually perpendicular electric field and magnetic field, and under the action of the Lorentz force The lower conductive liquid 29 promotes the piston (steering nut rack 3) to move to the right. The conductive liquid 29 in the right piston chamber A flows into the left piston chamber B through the oil pipe. The steering nut rack 3 moves to the right under the joint action of the steering screw 2 and the conductive liquid 29, the outer rack of the steering nut rack 3 meshes with the sector gear 4 installed on the steering rocker shaft 7, and the sector gear 4 drives The steering rocker arm 40 swings, and the steering rocker arm pulls the steering tie rod 41 to drive the steering wheel 42 to complete the steering action.

When the electrode plate at the upper end of the hydraulic cylinder is negative and the electrode plate at the lower end is positive, a vertical electric field is formed in the hydraulic cylinder, and the direction of the electric field is from bottom to top; The magnet forms a strong magnetic field in the horizontal direction perpendicular to the direction of motion of the piston (steering nut rack 3); the conductive liquid 29 can produce a leftward Lorentz force under the joint action of the mutually perpendicular electric field and magnetic field, and the Lorentz force Conductive liquid 29 promotes piston (steering nut rack 3) to move to the left under the effect of. The conductive liquid 29 in the left piston cavity B flows into the right piston cavity A through the oil pipe. The steering nut rack 3 moves to the left under the joint action of the steering screw 2 and the conductive liquid 29, the outer rack of the steering nut rack 3 meshes with the sector gear 4 installed on the steering rocker shaft 7, and the sector gear 4 drives The steering rocker arm 40 swings, and the steering rocker arm pulls the steering tie rod 41 to drive the steering wheel 42 to complete the steering action.

In the above two working conditions, the strength and direction of the magnetic field received by the conductive liquid 29 in the hydraulic cylinder are fixed, but the direction and strength of the electric field can be changed, so the voltage value at both ends of the electrodes and the polarity of the power supply can be adjusted. The magnitude and direction of the thrust of the conductive liquid 29 on the piston (steering nut rack 3 ) thereby control the magnitude and direction of the power assist of the hydraulic power assist device to the steering system. The voltage value across the electrodes and the polarity of the power supply are controlled and switched by the electronic control unit 43 .

The flow chart of the main program of the controller of the recirculating ball magnetic fluid electronically controlled hydraulic power steering system is shown in Figure 6. After the controller is powered on, it enters the main program. Modules such as PWM and CAN are initialized, and each module is self-inspected. After the system automatically detects successfully, the watchdog function is turned on. After that, the system further detects whether the ignition switch and the engine are started (the ignition switch is not turned on or the engine is not started, and the power assist system is not working). The system enters an interrupt program every 4ms, and completes the selection of the control mode and the refresh of the control quantity in the interrupt program.

The flow chart of the timing interrupt program is shown in Figure 7. After entering the timing interrupt program each time, the system checks whether the ignition switch is turned on and the engine is started. If the system is normal, the main circuit relay is closed to collect torque, rotation angle, voltage and vehicle speed signals. Then judge according to the sensor signal which working mode should be entered, and after calling the corresponding working mode program, exit the timing interrupt program.

The magnetic fluid electronically controlled hydraulic power steering system has three working modes: power assist mode, damping mode and return mode. The system judges which working mode the system enters according to the flow shown in FIG. 8 . If the torque is greater than 2Nm, enter the assist mode; if the torque is less than or equal to 2Nm, judge whether the steering wheel torque is opposite to the steering wheel rotation direction and whether the vehicle speed is less than 60km/h, if the steering wheel torque is opposite to the steering wheel rotation direction and the vehicle speed is not less than 60km/h , to enter the damping control mode; if the steering wheel torque is opposite to the direction of the steering wheel rotation and the vehicle speed is between 5km/h and 60km/h, the system enters the positive control mode.

When the system enters the power assist control mode, as shown in Figure 8, it first performs phase compensation on the torque signal of the steering wheel to solve the phase lag problem, and then enters the basic power assist control module. The control system first finds out the basic power assist voltage value at both ends of the electrode in the basic power assist characteristic chart according to the steering wheel torque signal and the vehicle speed signal, and then calculates the system friction compensation voltage value, and then compares the basic power assist voltage value at both ends of the electrode with the system friction compensation voltage value Values are added to calculate the total target voltage value, and then the following control of the voltage at both ends of the electrode plate is realized according to the power boost characteristic control strategy program, and finally the power boost control mode is exited.

When the system enters the damping control mode, the system first determines the voltage value that needs to be applied to the system according to the vehicle speed. The force applied by the system is small and is opposite to the direction of the steering wheel to increase the driver's sense of road. The system controls the voltage at both ends of the electrodes according to the target voltage value to realize the damping control of the system and help the system to generate damping.

When the system enters the centering control mode, the system first detects the steering wheel angle signal and the vehicle speed signal, and then finds out the target voltage value at both ends of the corresponding electrode according to the values of the steering wheel angle and vehicle speed according to the electrode voltage characteristic table when the system is returning to the centering control, and controls the electrode. The voltage at both ends and the polarity of the power supply, and finally exit the program back to the positive control mode.

Both the traditional hydraulic power steering system and the electronically controlled hydraulic power steering system rely on the positioning parameters of the steering wheel itself to complete the automatic return of the steering system. There is a close relationship between load, road conditions, tire pressure, and vehicle speed. When the car is running at high speed, the centering torque is relatively large, which is prone to "centering overshoot". Returning to positive overshoot will cause the steering wheel to oscillate near the neutral position, which greatly reduces the handling stability of the car. When the car is running at a low speed, the righting moment is small, and "insufficient backing" is likely to occur. When the correction is insufficient, the driver needs to correct the position of the steering wheel, thereby increasing the labor intensity of the driver. Magnetic fluid is an electronically controlled hydraulic power steering system that can adjust the power to the steering system by controlling the voltage at both ends of the electrodes, and can realize the active return function. The research on the centering control strategy includes two parts: one is the control strategy to ensure that the steering wheel returns to the neutral position, which is called "centering control"; Active Damping Control". The function of centering control is to overcome the damping and friction of the steering system to ensure that the steering wheel can quickly and accurately return to the neutral position. The damping control strategy is used to adjust the return speed of the steering wheel.

The theoretical basis of the utility model is that the charged particles will be subjected to the Lorentz action in the magnetic field, which is the theoretical basis of the magnetic fluid. The utility model is a new circulating ball type magnetofluid electric control hydraulic power steering device, which saves the necessary components of steering oil pump, steering control valve and other complex oil circuit control parts on the traditional circulating ball type hydraulic power steering system. A simple hydraulic cylinder with a piston in the middle is adopted, and the conductive liquid filling the hydraulic cavity at both ends of the piston is simply connected together by an oil pipe, which makes the structure of the product simple, the volume of the system small, and easy to maintain. The utility model is a new circulating ball type magneto-fluid electric control hydraulic power steering device. It is determined that the power source of the whole system is directly powered by the vehicle power battery. The system only needs to be powered by the on-board power supply battery when it is working. The electronic control unit ECU can control the power boost and direction. The electronic control unit combines information such as vehicle speed, steering wheel torque and steering wheel angle, and can provide different power assistance to the steering system according to the vehicle speed by separately controlling the voltage value and power polarity at both ends of the two pairs of electrodes, and can realize mechanical hydraulic power steering. The active return function that cannot be realized in the system and the conventional electronically controlled hydraulic power steering system.

Claims (4)

1. A recirculating ball type magnetofluid electronically controlled hydraulic power steering device, characterized in that: it comprises a recirculating ball steering gear housing, and the inside of the recirculating ball steering gear housing includes a straight cavity and a protrudingly arranged underside of the middle part of the straight cavity. The lower protruding cavity, the straight cavity is provided with a steering screw, the two ends of the steering screw are supported on the bearings, the steering nut rack is set on the steering screw, the internal thread of the steering nut rack is connected with the outer There are steel balls and steel ball conduits between the threads to form a steel ball circulation raceway. A sector gear is provided in the lower protrusion cavity to engage with the steering nut rack for transmission. The sector gear drives the steering rocker arm to swing, and the circulation ball turns to Insulated and sealed magnetic fluid chambers are respectively provided on the left and right sides of the steering nut rack in the housing of the device. Conductive liquid is provided in the magnetic fluid chamber, and the magnetic fluid chambers on both sides are connected through a catheter. A pair of electrode plates are arranged in parallel on the upper and lower inner surfaces, and an electric field in the vertical direction is generated between the two electrode plates by electrification. In contrast to the strong magnets, two strong magnets form a horizontal strong magnetic field in the magnetic fluid cavity, and the directions of the strong magnetic field and the electric field are perpendicular to each other. 2. A recirculating ball type magneto-fluid electronically controlled hydraulic power steering device according to claim 1, characterized in that: a conductive liquid reservoir with a one-way valve is connected to the catheter. 3. A recirculating ball type magnetofluid electronically controlled hydraulic power steering device according to claim 1, characterized in that: seal rings are respectively provided at both ends of the magnetofluid chamber, and seal rings are arranged on the inner surface of the recirculating ball steering housing. A layer of insulating layer is provided on the outer surface of the steering nut rack and the steering screw rod. 4 . The recirculating ball type magnetic fluid electric control hydraulic power steering device according to claim 1 , wherein the cross section of the recirculating ball steering housing is rectangular or square.