CN114872784A - Differential speed variable transmission ratio device and method and automobile steering system applying same - Google Patents
Differential speed variable transmission ratio device and method and automobile steering system applying same Download PDFInfo
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- CN114872784A CN114872784A CN202210700394.6A CN202210700394A CN114872784A CN 114872784 A CN114872784 A CN 114872784A CN 202210700394 A CN202210700394 A CN 202210700394A CN 114872784 A CN114872784 A CN 114872784A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D3/00—Steering gears
- B62D3/02—Steering gears mechanical
- B62D3/04—Steering gears mechanical of worm type
- B62D3/06—Steering gears mechanical of worm type with screw and nut
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D3/00—Steering gears
- B62D3/02—Steering gears mechanical
- B62D3/12—Steering gears mechanical of rack-and-pinion type
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
- B62D5/062—Details, component parts
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
- B62D5/062—Details, component parts
- B62D5/064—Pump driven independently from vehicle engine, e.g. electric driven pump
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
- B62D5/20—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle specially adapted for particular type of steering gear or particular application
- B62D5/22—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle specially adapted for particular type of steering gear or particular application for rack-and-pinion type
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
- B62D5/30—Safety devices, e.g. alternate emergency power supply or transmission means to ensure steering upon failure of the primary steering means
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D7/00—Steering linkage; Stub axles or their mountings
- B62D7/20—Links, e.g. track rods
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
- Y02T10/84—Data processing systems or methods, management, administration
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Steering Control In Accordance With Driving Conditions (AREA)
- Power Steering Mechanism (AREA)
Abstract
The invention relates to an automobile steering system, in particular to a differential speed variable transmission ratio device and method and an automobile steering system using the same. The differential variable transmission ratio device comprises a variable transmission ratio motor and a differential transmission assembly, the differential transmission assembly comprises a first sun wheel, a second sun wheel, a planet wheel and a mounting frame, the first sun wheel is connected with an input shaft, the second sun wheel is connected with an output shaft, the planet wheel is fixedly arranged on the mounting frame, and the first sun wheel and the second sun wheel are respectively meshed with the planet wheel. The automobile steering system comprises a hydraulic power-assisted module, an electric power-assisted module, a differential variable transmission ratio device and a tie rod. The invention ensures that the steering system has smaller transmission ratio at low speed and larger transmission ratio at high speed through the differential variable transmission ratio device, so that the automobile is flexible and stable in steering.
Description
Technical Field
The invention relates to an automobile steering system, in particular to a differential speed variable transmission ratio device and method and an automobile steering system using the same.
Background
With the rapid development of the automobile industry, the energy consumption, the safety and the comfort of the automobile are more and more emphasized, as a key part of an automobile chassis system, a power steering system provides a proper power torque for a driver under a steering working condition, the power steering system is the most direct and effective way for the driver to perform the transverse control of the automobile, and the performance of the power steering system directly influences the driving comfort and the driving safety of the driver. At present, a hydraulic power-assisted steering system and an electric power-assisted steering system are generally adopted by an automobile, hydraulic power assistance can provide larger power-assisted torque, but as a hydraulic pump of the hydraulic power-assisted system is driven by an engine, the hydraulic pump is always in a working state as long as the engine runs, the energy consumption of the system is higher, and the economical efficiency is poorer. The electric power-assisted system has no throttling loss and high energy efficiency, but the power-assisted magnitude is limited due to the limitation of electric power density, so that the electric power-assisted system is difficult to be applied to vehicles with large steering load.
In addition, the variable-gear-ratio steering technology of the automobile can continuously change the gear ratio of a steering system according to the change of the automobile speed, so that the low-speed steering is more flexible, and the high-speed steering is more stable and safer. In the early research of a steering variable transmission mechanism in foreign countries, in 2004, BMW has published a variable transmission ratio active steering system based on a double-row planetary gear reducer, which is developed together with German Caefox company, and then applied to a new generation of BMW cars. The double-planetary gear transmission mechanism has high efficiency and good sensitivity, is widely applied to automobile steering systems, but needs two pairs of planetary gear mechanisms, has more parts, complex structure and more fault points. Patent CN107600173A discloses a hydraulic variable transmission ratio steering system for automobiles, but the variable transmission ratio is realized by a valve-controlled hydraulic cylinder, so that certain throttling loss exists, and the system energy efficiency is low.
In view of the above problems, there is a need for a new vehicle steering transmission ratio varying device and a power assisting system to realize active steering with high energy efficiency, high performance and high reliability.
Disclosure of Invention
In order to solve the defects of the prior art, the invention provides the automobile steering variable transmission ratio device and the electro-hydraulic coupling power-assisted system which are simple in structure, low in energy consumption and high in reliability.
The invention adopts the following technical scheme:
the differential variable transmission ratio device comprises a variable transmission ratio motor, the variable transmission ratio motor drives a differential transmission assembly, the differential transmission assembly comprises a first sun wheel, a second sun wheel, a planet wheel and a mounting frame, the first sun wheel is connected with an input shaft, the second sun wheel is connected with an output shaft, the planet wheel is fixedly installed on the mounting frame, and the first sun wheel and the second sun wheel are respectively meshed with the planet wheel.
The differential speed variable transmission ratio device is characterized in that: the variable transmission ratio motor is characterized in that a driving bevel gear is arranged on an output shaft of the variable transmission ratio motor, a driven bevel gear is arranged on the planet wheel mounting frame, the driving bevel gear and the driven bevel gear are meshed with each other, and the output shaft of the variable transmission ratio motor drives the mounting frame to rotate.
An output shaft of the differential variable transmission ratio device is connected with a connecting rod, and the connecting rod drives the transverse pull rod to transversely displace in a gear and rack transmission mode, so that the steering of an automobile tire is realized.
The automobile steering system is characterized in that: the cross pull rod is provided with a screw transmission pair, the screw transmission pair comprises a nut, the hydraulic power assisting module drives the nut of the screw transmission pair to rotate through a speed reducer, and the nut converts torque into axial force of the cross pull rod through the screw transmission pair to achieve a power assisting function.
The automobile steering system is characterized in that: the hydraulic power assisting module comprises a driving motor, a hydraulic pump, a hydraulic motor and an energy accumulator, the driving motor is coaxially connected with the hydraulic pump, oil ports on two sides of the hydraulic pump are respectively communicated with oil ports on two sides of the hydraulic motor to form a closed loop, the oil ports on two sides of the hydraulic motor are respectively provided with an overflow valve which is communicated with the energy accumulator in a one-way mode, and the oil ports on two sides of the hydraulic motor are respectively provided with a one-way valve which is communicated with the hydraulic motor in a one-way mode through the energy accumulator.
The automobile steering system is characterized in that: the electric power-assisted module comprises a power-assisted motor, the power-assisted motor is used for assisting a steering shaft of an automobile through a first speed reducing mechanism, and the steering shaft of the automobile is connected with an input shaft of the differential variable transmission ratio device through a first clutch.
The automobile steering system is characterized in that: the electric power-assisted steering device is characterized by further comprising a control module, wherein the control module comprises a controller, a vehicle speed sensor, a torque sensor and a corner sensor which are arranged on the steering shaft, the input end of the controller is connected with the torque sensor, the corner sensor and the vehicle speed sensor, and the output end of the controller is connected with a power-assisted motor for controlling the electric power-assisted module, a driving motor for the hydraulic power-assisted module and a variable transmission ratio motor for the differential variable transmission ratio device.
The automobile steering system is characterized in that: and the output shaft of the hydraulic power-assisted module is provided with a second clutch.
The automobile steering system is characterized in that: the clutch is an electromagnetic clutch or a manual clutch.
A differential speed ratio-changing method using the differential speed ratio-changing device according to claim 1 or 2, comprising the steps of:
first, the rotation speed of the steering shaft is defined as omega 1 The rotational speed of the output shaft is omega 3 The rotating speed of the variable transmission ratio motor driving mounting rack is omega 0 The rotational speed of the planet wheel is omega 2 ；r 1 、r 2 、r 3 The radiuses of a first sun wheel, a planet wheel and a second sun wheel are respectively,r 0 for the first sun gear to mesh with the planet gearThe distance from the junction to the rotation axis of the mounting bracket and the distance from the junction of the second sun gear and the planet gear to the rotation axis of the mounting bracketr 0 The first sun gear and the second sun gear have the same number of teeth;
the method comprises the following steps: the control module receives a rotating speed signal of a steering wheel driving a steering shaftw 1 And a vehicle speed signal, and determining a gear ratio based on the vehicle speed signal;
step two: according to the transmission ratio obtained in the step one, the variable transmission ratio motor rotates and is transmitted to the mounting rack through the worm gear, and the mounting rack has a certain rotating speed omega 0 ；
Step three: rotational speed of steering shaftw 1 With the rotational speed omega of the mounting frame 0 And (3) superposing, wherein at the moment, the linear speed of the meshing part of the first sun gear and the planet gear is as follows:
the linear velocity of planet wheel and second sun gear meshing department is:
the angular velocity of rotation of the output shaft is:
thus, the angular velocity ω of rotation of the mounting frame is controlled by adjusting the rotational speed of the variable ratio motor 0 And further, the rotational angular velocity of the steering output shaft is adjusted, and the tire rotational speed is adjusted.
The invention enables the steering system to have a smaller transmission ratio at low speed and a larger transmission ratio at high speed through the differential speed variable transmission ratio device, so that the automobile is flexible and stable in steering. Compared with the existing double-row planetary gear variable transmission ratio mechanism, the structure is simpler. In addition, the electric power-assisted module and the hydraulic power-assisted module are used for assisting the steering shaft together, the hydraulic power-assisted module works only when the steering resistance torque is larger than the rated torque of the electric power-assisted module, and the hydraulic system is a pump control system without throttling loss, so that the power-assisted efficiency is high, and good comprehensive steering performance can be obtained.
Drawings
FIG. 1 is a schematic structural diagram of an electro-hydraulic coupling power-assisted steering system of an automobile according to an embodiment of the present invention;
FIG. 2 is a schematic structural view of the differential variable transmission ratio device of the present invention;
fig. 3 is a schematic structural view of a pure electric power-assisted vehicle steering system in the second embodiment of the invention.
In the figure, 1-the steering wheel; 2-a torque sensor; 3-a rotation angle sensor; 4-a steering shaft; 5, an electric power assisting module; 6-a speed reducing mechanism; 7-a power-assisted motor, 72-a second power-assisted motor; 8-a first clutch; 9-an input shaft; 10-differential variable transmission ratio device; 11-an output shaft; 12-a connecting rod; 13-a rack and pinion; 14-tie rods; 15-a ball bearing; 16-a nut; 17-a reducer; 18-a second clutch; 19-a hydraulic motor; 20-a first one-way valve; 21-a second one-way valve; 22-a first relief valve; 23-a second overflow valve; 24-an accumulator; 25-a hydraulic pump; 26-a drive motor; 27-a hydraulic power assisting module; 28-a tire; 29-a controller; 30-vehicle speed sensor; 31-variable transmission ratio motor; 32-drive bevel gear; 33-a first sun gear; 34-a planet wheel; 35-a second sun gear; 36-driven bevel gear; 37-a mounting frame.
Detailed Description
The first embodiment is as follows:
as shown in fig. 1 and fig. 2, the electro-hydraulic coupling power-assisted automobile variable transmission ratio steering system of the invention comprises: the device comprises a mechanical transmission module, a differential variable transmission ratio device 10, an electric power assisting module 5, a hydraulic power assisting module 27 and a control module.
The mechanical transmission module comprises a steering wheel 1, a steering shaft 4, a clutch 8, a connecting rod 12, a gear rack 13, a tie rod 14, a ball screw pair and a tire 16. The ball screw pair comprises a ball and a nut. One end of the steering shaft 4 is connected with the steering wheel 1, and the other end is connected with an input shaft 9 of the differential variable transmission ratio device through a clutch 8, so that rotation and torque are transmitted to the input shaft 9. The output shaft of the differential variable transmission ratio device further drives the tie rod to move linearly through the connecting rod 12 and the gear rack 13, and the tires 28 are driven to steer.
The differential variable transmission ratio device 10 comprises a variable transmission ratio motor 31 and a differential transmission assembly, wherein the differential transmission assembly comprises a first sun gear 33, a second sun gear 35, a planet gear 34 and a mounting frame 36. The first sun gear 33 is connected to the input shaft 9, the second sun gear 35 is connected to the output shaft 11, and the planet gears 34 are fixed to a mounting bracket 37. The first sun gear 33 meshes with the planet gears 34, and the planet gears 34 mesh with the second sun gear 35. The output shaft of the variable transmission ratio motor 31 is provided with a driving bevel gear 32, a planet wheel mounting frame 37 is provided with a driven bevel gear 36, the driving bevel gear 32 is meshed with the driven bevel gear 36, the output shaft of the variable transmission ratio motor 31 drives the mounting frame 37 to rotate, and the planet wheel 34 is fixed on the mounting frame 37 and can rotate around the axis of the mounting frame 37.
The variable transmission ratio working principle of the differential variable transmission ratio steering system is as follows:
defining the rotational speed of the input shaft 9 as ω 1 The rotational speed of the output shaft 11 is omega 3 The rotation speed of the variable transmission ratio motor 31 driving the mounting frame 37 is omega 0 The rotational speed of the planet wheel 34 is omega 2 ；r 1 、r 2 、r 3 The radii of the first sun gear 33, the planet gears 34, the second sun gear 35,r 0 the distance from the axis of rotation of the mounting at the point where the first sun gear 33 engages with the planet gears 34, and the distance from the point where the second sun gear 35 engages with the planet gears 34 to the axis of rotation of the mountingr 0 . The first sun gear 33 and the second sun gear 35 have the same number of teeth.
When the rotating speed of the variable transmission ratio motor 31 is 0, the rotating speed omega of the mounting rack 37 0 And 0, the planet 34 now only rotates on its axis. The rotation speed of the input shaft 9 is transmitted to the output shaft through the meshing of the first sun gear 33, the planet gears 34 and the second sun gear 35 without change, namely: omega 1 =ω 3 。
When the rotating speed of the variable transmission ratio motor 31 is not 0, the mounting rack 37 has a certain rotating speed omega 0 When the rotation direction of the mounting bracket 37 is the same as the rotation direction of the input shaft 9, the linear speed at the meshing position of the first sun gear 33 and the planet gear 34 is as follows:
the linear speed at the meshing point of the planet wheel 34 and the second sun wheel 35 is:
the rotational angular velocity of the output shaft 11 is:
when the rotation direction of the mounting bracket 37 is opposite to the rotation direction of the steering input shaft 9, the linear speed of the meshing part of the first sun gear 33 and the planet gear 34 is as follows:
the linear speed at the meshing point of the planet wheel 34 and the second sun wheel 35 is:
the angular velocity of rotation of the output shaft 11 is:
therefore, by adjusting the rotation speed of the variable transmission ratio motor 31, the rotation speed of the steering output shaft 11, and thus the tire rotation speed, can be adjusted.
The electric power-assisted module 5 comprises a power-assisted motor 7 and a speed reducing mechanism 6. The power-assisted motor 7 outputs proper torque according to the control module signal, and performs power assistance on the steering shaft 4 after the torque amplification effect of the speed reducing mechanism 6.
The hydraulic power assisting module 27 includes a hydraulic motor 19, a first check valve 20, a second check valve 21, a first relief valve 22, a second relief valve 23, an accumulator 24, a hydraulic pump 25, and a driving motor 26. Specifically, the driving motor 26 drives the hydraulic pump 25 coaxially connected to the driving motor to rotate according to the control module signal, and the hydraulic pump oil inlet and outlet are respectively communicated with the hydraulic motor oil inlet and outlet to form a closed loop, so as to drive the hydraulic motor 19 to rotate. The two cavities of the hydraulic motor are simultaneously communicated with an oil inlet of a first overflow valve 22, an oil inlet of a second overflow valve 23, an oil outlet of a first one-way valve 20 and an oil outlet of a second one-way valve 21. The oil inlets of the first check valve 20 and the second check valve 21 are respectively communicated with the energy accumulator 24 and used for compensating the leakage amount of the pump control motor system, and when the pressure of the two cavities of the hydraulic motor 19 is lower than the pressure of the energy accumulator 24, the energy accumulator 24 supplies oil to the system through the first check valve 20 or the second check valve 21, so that the two cavities of the hydraulic motor 19 are prevented from being vacuumed. When the pressure of the two cavities of the hydraulic motor 19 is greater than the safety pressure, the high-pressure oil of the hydraulic system flows to the energy accumulator 24 through the first overflow valve 22 or the second overflow valve 23, and the safety of the hydraulic power-assisted module is ensured. The hydraulic motor 19 is further connected to a speed reducer 17 through a second clutch 18, the speed reducer 17 is engaged with a nut 16 of a ball screw pair to transmit torque to the nut 16, and the nut 16 further converts the torque into linear motion assistance of the tie rod 14 through the ball screw pair. In the working process of the hydraulic power assisting module 27, the rotating speed of the hydraulic motor 19 is directly controlled by the driving motor 26 and the hydraulic pump 25, the system has no throttling loss and high energy efficiency, the energy supply burden of a vehicle-mounted battery can be reduced, and the cruising ability of the automobile is improved. And the output shaft of the hydraulic power-assisted module is provided with a second clutch.
The control module includes a controller 29, a vehicle speed sensor 30, a torque sensor 2 provided on the steering shaft 4, and a steering angle sensor 3. The input end of the controller is connected with the torque sensor 2, the corner sensor 3 and the vehicle speed sensor 30, and the three signals are calculated by the controller 29 and then output control signals to respectively control the power-assisted motor 7 of the electric power-assisted module, the driving motor 26 of the hydraulic power-assisted module and the variable transmission ratio motor 31 of the differential variable transmission ratio device to work.
The clutch is an electromagnetic clutch or a manual clutch.
The control module can be switched into an electric power-assisted mode, a hydraulic power-assisted mode or an electro-hydraulic coupling power-assisted mode according to the real-time running state of the automobile so as to obtain a proper power-assisted hand feeling, meet the flexibility of steering, reduce the working time of hydraulic power assistance and reduce the energy consumption of the system to the maximum. Meanwhile, the steering transmission ratio is adjusted according to road conditions and driving speed, so that the stability and safety of the automobile at high speed are improved, and better comprehensive steering performance is obtained; meanwhile, according to the driving requirement, the automobile can be switched between a mechanical steering mode and an intelligent steer-by-wire mode, and the burden of a driver is relieved. The method comprises the following specific steps:
the controller judges the working condition mode of the automobile according to the speed signal, the torque signal of the steering wheel and the corner signal. In the starting and low-speed sections of the automobile, the surrounding environment of the automobile is complex, and a driver needs to fully observe the surrounding environment, so a mechanical steering mode is adopted. In addition, because the resistance moment that needs to overcome is great, so adopt the mode of hydraulic pressure helping hand and electronic helping hand jointly, reduce driver's steering load, the requirement of the flexibility of turning when satisfying low-speed, through reasonable control helping hand moment, guarantee driver's good steering road feel.
In the middle speed section of the automobile, the controller 31 continuously adjusts the electric power assisting ratio and the hydraulic power assisting ratio according to the steering resistance moment of the automobile, so that the hydraulic power assisting is reduced as much as possible, and the energy consumption of a hydraulic system is reduced to the maximum extent. When the steering resistance torque of the automobile is smaller than the output torque value of the electric power assisting module 7, the second clutch 21 is disconnected, the driving motor 29 stops working, and the working time of a hydraulic system is shortened by adopting an independent electric power assisting mode. According to the specific speed, the variable transmission ratio motor 31 adjusts the differential variable transmission ratio device, the transmission ratio of the system is improved, the steering becomes indirect, the rollover prevention function of the vehicle is realized through the active variable transmission ratio, and the vehicle operation performance is improved.
Besides a mechanical steering mode, the steering system can also adopt an intelligent drive-by-wire mode to realize an automatic driving function, and the method specifically comprises the following steps: the first clutch 8 is disconnected, the second steering shaft 9 is locked, the controller 31 collects parameters of the automobile in running, a control signal of the variable transmission ratio motor 11 is given out through calculation, and the variable transmission ratio motor 11 controls the tire 16 to steer through the worm and gear mechanism 10, the spiral transmission connecting piece 20, the connecting rod 13, the lifting rod 15, the sector shaft 19, the steering rocker 18 and the tie rod 17 in sequence. Therefore, the installed power of the variable transmission ratio motor 11 needs to meet the power demand of the vehicle for medium-speed steering. The freedom of control to the variable transmission ratio motor 11 enables the force transmission ratio and the angle transmission ratio of the steer-by-wire system to be changed in a large range, and the required steering rotating speed is output directly through internal calculation of the controller 31, so that the low-speed steering is more flexible and the high-speed steering stability is improved. In the drive-by-wire mode, the power-assisted motor 6 is used as a road feel simulation motor, the steering execution mechanism inputs external environment information such as wheel aligning moment and frictional resistance distance with the ground, which are acquired by the sensor, into the controller 31, and the controller 31 controls the power-assisted motor 1 to output corresponding resistance torque to simulate driving road feel according to the provided information and feed back the driving road feel to a driver.
Except adopting mechanical steering mode, the steering system can also adopt intelligent drive-by-wire mode, realizes the autopilot function, specifically is: the clutch 6 is disconnected, the steering shaft 4 is locked, the sensor inputs information such as torque, a corner and rotating speed input to a steering wheel by a driver into the controller, meanwhile, the controller collects parameters of a vehicle in running, a control signal of the motor 7 is given out through calculation, and the motor 7 controls tires to steer through the bevel gear 31, the mounting frame 32, the bevel gear 20, the bevel gear 21, the steering output shaft 8, the rack and pinion 9 and the tie rod 10 in sequence. Therefore, the installed power of the motor 7 needs to meet the power demand for the vehicle to steer at a medium speed. The freedom of control of the motor 7 enables the force transmission ratio and the angle transmission ratio of the steer-by-wire system to be changed in a larger range, and the required steering rotating speed is output directly through the internal calculation of the controller, so that the low-speed steering is more flexible and the high-speed steering stability is improved. In the drive-by-wire mode, the motor 22 is used as a road feel simulation motor, the steering actuator inputs external environment information such as wheel aligning torque and frictional resistance distance with the ground, which are acquired by the sensor, into the controller, and the controller controls the motor 22 to output corresponding resistance torque to simulate driving road feel according to the provided information and feed back the driving road feel to a driver.
The high-speed section of the automobile requires the automobile to have enough operation stability, and the transmission ratio of the steering system is larger at the moment.
When the electric power-assisted module 7 breaks down, the hydraulic power-assisted module 30 continues to provide power assistance for the steering system; when the hydraulic power-assisted module 30 breaks down, the electric power-assisted module 7 continues to provide power assistance for the steering system; when the electric power-assisted module 7 and the hydraulic power-assisted module 30 both have faults, the automobile can still realize emergency steering under the mechanical transmission module, and the safety of a steering system is ensured by the triple-steering redundancy design. In addition, the automobile has two steering redundancy modes of mechanical steering and intelligent steer-by-wire, and the driving reliability of the automobile is further ensured.
Example two:
fig. 3 is a schematic structural diagram of a variable transmission ratio steering system of a pure electric power-assisted vehicle according to the present invention, the power-assisted steering system in the present embodiment has the same structure and working principle as those of the present embodiment, except that the hydraulic power-assisted module 30 is replaced with a second power-assisted motor 72, so that the steering system is a pure electric power-assisted steering system.
Claims (10)
1. Differential becomes drive ratio device, including becoming the drive ratio motor, characterized by: the variable transmission ratio motor drives the differential transmission assembly, the differential transmission assembly comprises a first sun wheel, a second sun wheel, a planet wheel and a mounting frame, the first sun wheel is connected with the input shaft, the second sun wheel is connected with the output shaft, the planet wheel is fixedly arranged on the mounting frame, and the first sun wheel and the second sun wheel are respectively meshed with the planet wheel.
2. The differential variable ratio device of claim 1 wherein: the variable transmission ratio motor is characterized in that a driving bevel gear is arranged on an output shaft of the variable transmission ratio motor, a driven bevel gear is arranged on the planet wheel mounting frame, the driving bevel gear and the driven bevel gear are meshed with each other, and the output shaft of the variable transmission ratio motor drives the mounting frame to rotate.
3. An automobile steering system using the differential variable transmission ratio device of claim 1 or 2, comprising a hydraulic power assisting module, an electric power assisting module, the differential variable transmission ratio device, and a tie rod, wherein: an output shaft of the differential variable transmission ratio device is connected with a connecting rod, and the connecting rod drives the transverse pull rod to transversely displace in a gear and rack transmission mode, so that the steering of an automobile tire is realized.
4. The steering system for a vehicle of claim 3, wherein: the cross pull rod is provided with a screw transmission pair, the screw transmission pair comprises a nut, the hydraulic power assisting module drives the nut of the screw transmission pair to rotate through a speed reducer, and the nut converts torque into axial force of the cross pull rod through the screw transmission pair to achieve a power assisting function.
5. The steering system for a vehicle of claim 3, wherein: the hydraulic power assisting module comprises a driving motor, a hydraulic pump, a hydraulic motor and an energy accumulator, the driving motor is coaxially connected with the hydraulic pump, oil ports on two sides of the hydraulic pump are respectively communicated with oil ports on two sides of the hydraulic motor to form a closed loop, the oil ports on two sides of the hydraulic motor are respectively provided with an overflow valve which is communicated with the energy accumulator in a one-way mode, and the oil ports on two sides of the hydraulic motor are respectively provided with a one-way valve which is communicated with the hydraulic motor in a one-way mode through the energy accumulator.
6. The steering system for a vehicle of claim 3, wherein: the electric power-assisted module comprises a power-assisted motor, the power-assisted motor is used for assisting a steering shaft of an automobile through a first speed reducing mechanism, and the steering shaft of the automobile is connected with an input shaft of the differential variable transmission ratio device through a first clutch.
7. The steering system for a vehicle of claim 3, wherein: the electric power-assisted steering device is characterized by further comprising a control module, wherein the control module comprises a controller, a vehicle speed sensor, a torque sensor and a corner sensor which are arranged on the steering shaft, the input end of the controller is connected with the torque sensor, the corner sensor and the vehicle speed sensor, and the output end of the controller is connected with a power-assisted motor for controlling the electric power-assisted module, a driving motor for the hydraulic power-assisted module and a variable transmission ratio motor for the differential variable transmission ratio device.
8. The steering system for a vehicle of claim 3, wherein: and the output shaft of the hydraulic power-assisted module is provided with a second clutch.
9. The power steering system according to claim 6 or 8, wherein: the clutch is an electromagnetic clutch or a manual clutch.
10. A differential speed ratio-changing method using the differential speed ratio-changing device according to claim 1 or 2, characterized in that: comprises the following steps:
first, the rotation speed of the steering shaft is defined as omega 1 The rotational speed of the output shaft is omega 3 The rotating speed of the variable transmission ratio motor driving mounting rack is omega 0 The rotational speed of the planet wheel is omega 2 ；r 1 、r 2 、r 3 The radiuses of a first sun wheel, a planet wheel and a second sun wheel are respectively,r 0 the distance from the meshing point of the first sun gear and the planet gear to the rotation axis of the mounting frame is also the distance from the meshing point of the second sun gear and the planet gear to the rotation axis of the mounting framer 0 The first sun gear and the second sun gear have the same number of teeth;
the method comprises the following steps: the control module receives a rotating speed signal of a steering wheel driving a steering shaftw 1 And a vehicle speed signal, and determining a transmission ratio according to the vehicle speed signal;
step two: according to the transmission ratio obtained in the step one, the variable transmission ratio motor rotates and is transmitted to the mounting rack through the worm gear, and the mounting rack has a certain rotating speed omega 0 ；
Step three: rotational speed of steering shaftw 1 With the rotational speed omega of the mounting frame 0 And (3) superposing, wherein at the moment, the linear speed of the meshing part of the first sun gear and the planet gear is as follows:
the linear speed of the meshing part of the planet wheel and the second sun wheel is as follows:
the angular velocity of rotation of the output shaft is:
thus, the angular velocity ω of rotation of the mounting bracket is controlled by adjusting the rotational speed of the variable ratio motor 0 And further, the rotational angular velocity of the steering output shaft is adjusted, and the tire rotational speed is adjusted.
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