The present invention belongs to the field of automotive component technology, and specifically relates to an electric push rod type circulating ball electric power steering device for vehicles. Background technology

At present, vehicle steering gears are mainly divided into two types: gear rack and loop ball type. Among them, gear rack type steering gears are mainly used for passenger cars, while loop ball type steering gears are mainly used for commercial vehicles. Traditional power steering is hydraulic power steering, and the magnitude of power assistance is controlled through slide valves or rotary valves. Traditional hydraulic power steering has the following problems: the assist characteristics cannot be adjusted and controlled in real time with the vehicle speed, making it difficult to coordinate the contradiction between low-speed steering lightness and high-speed steering "road feel"; Even without turning, the oil pump continues to operate, resulting in parasitic energy loss; Due to oil leakage and maintenance issues in the hydraulic system itself, maintenance costs are increased, and hydraulic oil can also cause environmental pollution. Components such as oil pumps, pulleys, and hydraulic pipelines occupy space and are difficult to arrange; Poor low-temperature performance.

The electric power steering system (EPS) is directly assisted by an electric motor, eliminating the hydraulic system. The system consists of a steering wheel torque sensor, a vehicle speed sensor, a controller, a power assist motor, and a reduction mechanism. The basic principle is that the controller receives the steering wheel torque signal and the vehicle speed signal, and after judgment and processing, outputs a control signal based on the predetermined assist characteristics to control the electric motor to output assist torque. The electric power steering system can effectively overcome the problems of hydraulic power steering, with many advantages such as energy saving, improved safety, and environmental protection. It has a trend of gradually replacing hydraulic power steering and is one of the development directions of future power steering technology. However, currently the electric power steering systems worldwide are only applied to cars and are all gear rack type steering systems.

At present, there are no products available for electric power steering with circular balls, and it is still in the research and development stage. Circular ball electric power steering is mainly used in commercial vehicles. When the front axle load of the commercial vehicle is large, if the motor and power assist mechanical device are directly installed on the steering gear, it will increase the size of the steering gear, causing a series of problems such as heaviness and inconvenient installation. The present invention is an electric push rod type electric power steering device, which is not integrated into the steering gear, but is an independent device connected to the steering rocker arm. The power is directly applied to the steering rocker arm, and then the wheels of the vehicle are turned through the steering tie rod and the steering knuckle arm to achieve the effect of power steering. The present invention will greatly reduce the size of the steering gear and has advantages such as lightweight and simplicity.

summary of the invention

The purpose of the present invention is to provide an electric push rod type electric power steering device with a compact structure, high efficiency and energy saving, lightweight low-speed steering, strong sense of high-speed steering, and good return ability.

The above objective of the present invention is achieved through a technical solution, namely an electric push rod type electric power steering device, comprising:

（1） A circulating ball steering gear with a torque measuring device, and a torque sensing device for detecting the torque acting on the steering wheel, arranged at the input end of the circulating ball steering gear.

（2） Electric push rod, one end of which is connected to the steering arm in the circulating ball steering system, and the other end is connected to the frame. Electric push rods include power assisted motors, reduction mechanisms, push rods, etc. The power assisted electric motor is used to provide auxiliary steering torque:

The input end of the deceleration mechanism is connected to the power assisted motor, which has the function of increasing takeoff and landing speed and torque. （3） Electronic Control Unit (ECU) is used to control the current of the power assist motor based on collected signals such as steering wheel torque and vehicle speed.

Among them, the assist motor is a permanent magnet brushed DC motor or a permanent magnet brushless DC motor, with a voltage standard of DC24V or DC42V.

In the electric push rod, the input shaft of the deceleration mechanism of the power assisted motor is connected to the output shaft of the power assisted motor, and the output shaft of the deceleration mechanism is connected to the screw in the push rod. The torque output by the power assisted electric motor is transmitted through a reduction mechanism and a screw nut transmission pair to drive the rocker arm shaft to rotate.

The torque sensing device is equipped with a torsion bar, which amplifies the deformation of the torsion bar into angular displacement or linear displacement through a precise mechanical device. The deformation of the torsion bar is indirectly measured by the angular displacement or linear displacement sensor, and the torque can be obtained based on the stiffness of the torsion bar.

The electronic control unit mainly consists of a CPU, signal acquisition and processing circuit, driving circuit, monitoring circuit, etc. The CPU can be an 8-bit or 16 bit microcontroller, or a 16 bit digital signal processor (DSP). An electronic switch is installed in the motor drive circuit to quickly cut off the switch in case of system abnormalities to ensure system safety.

The beneficial effect of the present invention is that the electric motor only provides assistance during steering (unlike hydraulic power steering, where the oil pump runs continuously even when not steering), thus reducing energy consumption; It can provide appropriate assistance in various driving conditions, reduce the disturbance to the steering system caused by uneven road surfaces, improve the steering characteristics of the car, reduce the steering control force when driving at low speeds, improve the steering stability when driving at high speeds, and thereby enhance the active safety of the car. Different steering hand characteristics can be set to meet the needs of different users; The oil pump, belt, pulley, hydraulic hose, hydraulic oil, and sealing components have been eliminated, resulting in significantly fewer parts compared to hydraulic power steering. Therefore, it is lighter in weight, more compact in structure, easier to choose installation location, and can reduce noise; Without hydraulic circuits, it is easier to adjust and detect than hydraulic power steering, with a higher degree of assembly automation. By setting different programs, it can quickly match different vehicle models, thus shortening production and development cycles; There is no oil leakage problem, which can greatly reduce warranty costs and minimize environmental pollution; It has better low-temperature working performance than hydraulic power steering.

4 Specific Implementation Methods

As shown in Figure i, the electronic control unit determines the target current/c/m/of the power assist motor based on the collected steering wheel torque r and vehicle speed r. Then, the power assist motor current is feedback tracked and controlled based on the actual current/and target current/cd of the power assist motor.

As shown in Figure 2, the working principle of the electric push rod electric power steering device is that when the driver rotates the steering wheel (l),

The driver's applied torque is transmitted to the input shaft of the circulating ball steering gear (5) through the steering shaft (2) and the steering transmission shaft (3). A torque measuring device (4) is installed on the input shaft of the circulating ball steering gear (5), and the torque measuring device (4) sends the measured driver's applied torque to the electronic control unit (ECU). Based on the torque signal and combined with the vehicle speed signal, the ECU controls the power assist motor (13) in the electric push rod to output the appropriate power assist torque. The power assist torque output by the power assist motor (13) is transmitted through the reduction mechanism and screw nut transmission pair to push the rocker arm shaft to rotate, thereby achieving the purpose of power assisted steering.

As shown in Figure 3, one end of the torsion bar (5) is connected to the input shaft (4) of the steering gear, and the other end is rigidly connected to the screw (7) through interference fit. The torsional deformation of the torsion bar (5) is transmitted to the sliding sleeve (2) through the steel ball (3), and the transmission pin (1) is rigidly connected to the screw (7) and cooperates with the spiral groove on the sliding sleeve (2) to generate axial movement while the sliding sleeve (2) rotates. The axial movement of the sliding sleeve (2) is measured by the angular displacement sensor (6), and the relative deformation of the torsion bar (5) (i.e., the relative rotation angle between the steering gear input shaft (4) and the screw (7)) is converted into a signal representing torque. Input the number to the electronic control unit (ECU). The screw (7) and nut (8) form a circulating ball transmission pair. The gear rack on nut (8) meshes with the gear fan (9) on the rocker arm shaft to output steering torque.

As shown in Figure 4, the output shaft of the power assisted motor (1) is connected to the helical gear I (2) through a key, and a reduction mechanism is formed by the helical gear II (3) and the helical gear I (2), which plays a role in reducing speed and increasing torque. The screw (4) is connected to the helical gear II (3), and through the transmission pair of the screw (4) and the nut (5), it rotates in the circumferential direction to move horizontally in the axial direction. Finally, the force is transmitted to the push rod (7) through the nut (5).

As shown in Figure 5, the electronic control unit is mainly composed of CPU, signal acquisition and processing circuit, driving circuit, monitoring circuit, etc. The CPU can be an 8-bit or 16 bit microcontroller, or a 16 bit digital signal processor (DSP). The signal acquisition and processing circuit is used to collect electric motor current signals, as well as process torque signals, vehicle speed signals, engine speed signals, etc. The driving circuit includes electronic switches (such as relays), status indicator lights, and the drive of the electric motor. The drive of the electric motor is an H-type PWM power conversion circuit, consisting of MOSFET transistors G2, G3, G4. The switching of MOSFET tubes is controlled by the high and low levels of PWM signals, with a frequency of 20kHz. Electronic switches (such as relays) are also installed in the motor drive circuit to quickly cut off the switch in case of system abnormalities to ensure system safety. Monitoring circuits are used to protect the system and improve its safety and reliability.

4、 Attached image description

Figure 1 is a schematic diagram of the structure of the present utility model.

Figure 2 is a schematic diagram of the top view structure of Figure 1.

5、 Specific implementation method

As shown in the figure, the parallel electro-hydraulic push rod of the present utility model comprises a motor 1, a coupling 2, a gear pump 3, an integrated block 4, an oil tank 5, an oil cylinder 6, a reversing valve 7, and a manual pump 8. Bidirectional gear pump 3 is connected to motor 1 through coupling 2. Bidirectional gear pump 3 supplies oil to hydraulic manifold block 4, which integrates speed control circuit, pressure regulation circuit, and self-locking circuit. Pressure oil is supplied to cylinder 6 through the manifold block to achieve the expansion and contraction of the cylinder piston. When manual operation is required, the reversing device changes direction and the manual pump works, directly supplying oil to the oil cylinder. The cylinder is equipped with high-precision displacement sensors inside, and the movement of the piston rod is directly displayed on the panel, and commands can be directly issued on the panel to control the action of the piston rod.

Oil cylinder 6 is detachably installed at the bottom of the oil tank through support seat 9, and is not on the same main axis as the motor. A bracket 10 is provided between motor 1 and gear pump 3, which is connected to oil tank 5 through a flange. One end of the bracket is connected to motor 1 through a flange, and the other end of the bracket is overlaid with gear pump 3 and integrated block 4. The working oil is connected to the reversing valve 7 through two hard pipes, and then connected to the two ends of the actuator cylinder 6 at the bottom of the oil tank through two hard pipes. The forward and reverse rotation of the gear shaft is changed by changing the forward and reverse rotation of the motor. Manual pump 8 is connected to directional valve 7. Manual pump 8 adopts a radial multi plunger plunger pump structure, which changes the traditional linear reciprocating motion to rotational motion, making the flow continuous and easy to handle. The pump body is made of modified ultra-high molecular weight polyethylene (UHMWPE) material, which has low friction and good wear resistance. The high-precision displacement sensor (with digital display device) inside the oil cylinder can automatically locate and measure the position of the piston, and can be interlocked and converted between manual and automatic without disturbance. It can achieve single operation, simultaneous operation, and group operation, and can accept the current signal output by the adjustment unit.

The component units in the parallel electro-hydraulic push rod mentioned above can all be realized through existing technology.