CN113771811A

CN113771811A - Automobile brake-by-wire system with backup function and pressure control method thereof

Info

Publication number: CN113771811A
Application number: CN202111231745.5A
Authority: CN
Inventors: 初亮; 李会超; 许炎武; 赵迪; 常城; 李世博
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2021-10-22
Filing date: 2021-10-22
Publication date: 2021-12-10
Anticipated expiration: 2041-10-22
Also published as: CN113771811B

Abstract

The invention discloses an automobile brake-by-wire system with a backup function and a pressure control method thereof, wherein the automobile brake-by-wire system comprises the following steps: the brake system comprises a semi-active brake pedal feel simulator, a liquid storage tank, a main brake unit and a backup brake unit, wherein a liquid inlet a of the liquid storage tank is connected with a liquid outlet D of the semi-active brake pedal feel simulator, external interfaces b and C of the liquid storage tank are respectively connected with external interfaces e and f of the main brake unit, an external interface D of the liquid storage tank is connected with an external interface G, H of the backup brake unit, and external interfaces A, B and g of the main brake unit are respectively connected with an external interface E, F of the backup brake unit and a liquid inlet C of the semi-active brake pedal feel simulator. The automobile brake-by-wire system with the backup function can be switched into the backup mode when the main brake unit fails. The invention also provides a pressure control method of the automobile brake-by-wire system with the backup function.

Description

Automobile brake-by-wire system with backup function and pressure control method thereof

Technical Field

The invention relates to a brake-by-wire system in the field of automobile brake systems, in particular to an automobile brake-by-wire system with a backup function and a pressure control method thereof.

Background

With the increasing number of automobiles and the increasing requirements of people on safety and comfort, the problems such as road congestion, frequent accidents and the like become more serious. In order to reduce traffic accidents, improve driving safety, meet driving habits of drivers and improve comfort, line-controlled braking is continuously developed in the field of automobile braking. The brake control of the vehicle is implemented by using the brake-by-wire, and the method has important significance for the brake energy recovery of the electrically driven vehicle, the automatic driving and the unmanned driving brake control of higher level.

The advent of autonomous driving systems has put even greater demands on their development. This requires that the brake system can implement brake-by-wire by command, have high reliability, have a backup function to prevent failure. Likewise, in the event of a failure, still have better braking capability. The conventional vehicle braking system usually comprises a main cylinder, a valve group, a wheel cylinder, a motor, a controller and a main energy supply device, if the main energy supply device of the conventional vehicle braking system can not provide braking pressure, backup braking can be carried out only by the braking pressure generated by driving the main cylinder by a pedal, so that the braking feeling is slightly different, the requirement of emergency braking cannot be met, and a series of problems of inaccurate braking pressure control, poor braking stability and the like are caused.

The backup brake means that when the main brake unit 3 fails, the backup brake unit is connected to a brake system. When the brake-by-wire system enters a backup mode, all key functions including brake-by-wire are redundant and cannot meet the requirements by means of traditional master cylinder mechanical backup.

Several patent applications have been searched for in connection with the present invention:

the invention relates to a brake-by-wire system with backup function and a control method thereof, which is invented under the Chinese patent publication No. CN 112406836A, publication No. 2021.02.26, and application No. 202011454370.4. The brake system designed by the invention comprises a brake control mechanism, an active brake pedal stroke simulator, a main energy supply device and a hydraulic adjusting unit. The invention has the disadvantages that firstly, the main energy supply device of the braking system is directly driven by the motor, the bearing capacity and the efficiency are poor, the operation noise is high, and the reliability is insufficient. Secondly, the backup function needs to rely on the pedal analogue means to realize, and the pedal analogue means will realize both the simulation sensation and the backup pressure and pressure increase, leads to the complicated volume of structure great, arranges inconveniently, in order to compromise pressure and pressure increase and simulation pedal sensation when playing the backup effect moreover, leads to the control degree of difficulty great.

The invention relates to a brake-by-wire system with a backup brake system and a control method thereof, which are published as CN 111731252A (published as 2020.10.02) in China, and the application number is 202010483837.1. The invention provides an electronic brake system which adopts a planetary gear mechanism as a transmission mechanism to drive a ball screw to provide braking force to push a brake block and adopts a magnetostrictive backup brake device as a backup unit. The invention has the disadvantages that the structure of the actuating mechanism of the electronic braking system is complex and the control difficulty is high, and the cost of the braking system is improved because the four wheels adopt repeated actuating mechanisms. The ball screw in the backup braking system has complex manufacturing process, high requirements on manufacturing materials, high working conditions and limited braking capability.

Disclosure of Invention

The invention adopts a semi-active line control brake system pedal feel simulator integrated with the pedal, and eliminates components such as a brake master cylinder connected with the brake pedal, an independent pedal feel simulator and the like; the main energy supply device adopts planetary gear transmission and is integrated with the main cylinder, so that the reliability is improved and the structure is compact; the hydraulic adjusting unit is connected to the backup hydraulic pump. The problems that the prior art can not meet the requirements of a brake-by-wire system, the control difficulty is high, the structure is complex, a backup system is complex and the braking capability is insufficient are solved. An automobile brake-by-wire system with a backup function and a pressure control method thereof are provided.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

an automobile brake-by-wire system with a backup function comprises a semi-active brake pedal feel simulator, a liquid storage tank, a main brake unit and a backup brake unit. The braking force output of the two braking units are mutually backup, and when any unit fails, the braking system can work normally.

In the technical scheme, the semi-active brake pedal feeling simulator mainly comprises a brake pedal, a pedal force and displacement sensor, a simulator cylinder body, a first piston, a first spring, a second piston, a second spring, a third piston, a third spring, a piston limiting ring, a fourth piston, a simulator liquid inlet valve, a simulator liquid inlet one-way valve, a simulator liquid outlet valve and a piston sealing ring.

Furthermore, the brake pedal is arranged below the front part of the driver, the top end of the rotating part in the brake pedal is fixed on the pedal support through a pin shaft, and the pedal support is fixedly connected on the vehicle body through bolts. The force applied to the brake pedal is transmitted to a pedal push rod by a hinge fulcrum, a pedal force sensor is arranged on the brake pedal, a pedal displacement sensor is arranged on the pedal push rod, and the obtained information of the brake pedal force and the pedal displacement is transmitted to an Electronic Control Unit (ECU). The brake pedal passes through the front end cover of the simulator cylinder body through a pedal push rod and is connected with the first piston. The axial line along the simulator cylinder body is processed with the cylindrical shoulder hole of syllogic, and the diameter of syllogic ladder from left to right diminishes, is first shoulder hole, second shoulder hole, third shoulder hole respectively. First piston, second piston, third piston, fourth piston assemble in the simulator cylinder body in proper order, and first piston and second piston are installed in first step hole, are equipped with first spring between the two. The third piston and the fourth piston are located in the second stepped hole, and a second spring is arranged between the second piston and the fourth piston. The third piston cavity is arranged in the second spring between the second piston and the fourth piston, and one end of the third piston cavity is fixed on the fourth piston. The side wall of the third piston cavity is opened for ventilation, and the third piston is arranged in the third piston cavity. Each piston is connected with the inner cylinder wall of the simulator in a sliding mode, and a piston sealing ring is installed on the outer cylindrical surface of each piston. The j port of the simulator cylinder body is connected with the a port of the simulator liquid inlet valve and the p port of the simulator liquid inlet one-way valve, the p port of the simulator liquid inlet valve and the a port of the simulator liquid inlet one-way valve are connected with the C port of the external interface of the semi-active brake pedal feeling simulator, the k port of the simulator is connected with the p port of the simulator liquid outlet valve, and the a port of the simulator liquid outlet valve is connected with the D port of the external interface of the brake pedal feeling simulator.

Furthermore, the left end face and the right end face of the simulator cylinder body are provided with openings with different diameters, a flange plate is arranged on the outer cylindrical surface of the left end cylinder opening, an opening is formed in the flange plate and used for extending out the brake push rod, and the diameter of the opening is slightly larger than that of the push rod and used for air intake and exhaust. And a boss is processed on the right side of the first piston, and after the second piston is in compression contact with the left side face of the second stepped hole, the boss can be pressed into a concave hole of a boss on the left side of the third piston when the first spring is compressed for a certain distance, so that the first spring and the third spring are connected in parallel. The second piston is a circular ring-shaped structural member, a through hole is processed along the central axis, the diameter of the through hole is slightly larger than that of the boss on the right side of the first piston, so that the boss can smoothly pass through, and meanwhile, the ventilation effect is realized. The first spring and the second spring have certain precompression quantity in the initial state, so that the brake misoperation caused by the fact that a driver mistakenly steps on a brake pedal is avoided, and the purpose of discharging brake fluid to the liquid storage tank is achieved under the non-emergency brake condition.

Further, the semi-active brake pedal feeling simulator controls springs with different rigidity to be connected in series or in parallel, so that pedal feeling under the conditions of small, medium and large-intensity braking is simulated when the main brake unit works normally, pedal feeling is supplemented when emergency braking is carried out, and brake pedal feeling under the conditions of small, medium and large intensity is simulated when the main brake unit fails and the backup brake unit works as a passive brake pedal feeling simulator.

In the technical scheme, the bottom of the liquid storage tank is provided with four external interfaces which are respectively an a port, a b port, a c port and a D port and are respectively connected with a D port of a semi-active brake pedal feeling simulator, an e port of a main brake unit, an f port of the main brake unit and an G, H port of a backup brake unit. The liquid storage tank is arranged above the main braking unit.

In the technical scheme, the main brake unit comprises a hydraulic cylinder front cover, a hydraulic cylinder first spring, a hydraulic cylinder first piston, a hydraulic cylinder second spring, a hydraulic cylinder second piston, a hydraulic cylinder push rod, a push rod limiting ring, a first bearing, a ball, a planet carrier positioning sleeve, a hydraulic cylinder rear cover, a gear ring, a planetary gear needle bearing, a planetary gear limiting ring, a sun gear positioning sleeve, a second bearing, a hydraulic cylinder motor control unit, a rear cover connecting screw, an output shaft spline, a third bearing, a front cover connecting rivet, a rear cover connecting rivet, a hydraulic cylinder pressure sensor, a hydraulic cylinder first liquid outlet valve and a hydraulic cylinder second liquid outlet valve.

Furthermore, the front cover and the rear cover of the hydraulic cylinder are riveted into a whole through the connecting rivet, the inner diameter of the front cover of the hydraulic cylinder is sequentially increased from left to right, and the rear cover of the hydraulic cylinder is opposite to the front cover of the hydraulic cylinder. And on the front cover of the hydraulic cylinder, the leftmost side is processed into the hydraulic cylinder. And a first hydraulic cylinder working cavity and a second hydraulic cylinder working cavity are respectively formed between the first hydraulic cylinder piston and the left wall of the brake master cylinder body and between the first hydraulic cylinder piston and the second hydraulic cylinder piston, and a first hydraulic cylinder spring and a second hydraulic cylinder spring are sequentially arranged in the two working cavities.

Furthermore, a hydraulic cylinder push rod connected with the second piston of the hydraulic cylinder is also a screw rod of the ball screw mechanism. The left part and the right part of the push rod of the hydraulic cylinder have different processing methods. The left part is processed into a smooth polished rod, a displacement sensor (not shown) can be installed in a cavity where the polished rod is located, a rolling way for rolling balls is processed on the right side, the rolling way is matched with the rolling balls in the planet carrier, and the push rod limiting ring can limit the movement of the steel balls.

Further, the planet carrier be the triangular prism component, its left side processes out the cylinder boss, acts as ball screw mechanism's nut, the first bearing of boss outer cylindrical surface installation. The center of the boss is provided with a through hole, the left half part of the inner side of the through hole is provided with a raceway matched with the ball, and the right half part is a smooth inner wall so as to limit the movement of the ball. Three bosses are processed at three top angles on the right side of the planet carrier and used as planet gear shafts, needle bearings and straight-tooth planet gears are sequentially arranged on the shafts, and the planet gear limiting rings limit the axial movement of the gears.

Furthermore, the planetary gear is meshed with the gear ring and the sun gear, and the gear ring is fixedly connected to the inner wall of the circular hole with the largest diameter on the left side of the rear cover of the hydraulic cylinder. The hydraulic cylinder rear cover small-diameter inner hole is sequentially provided with a hydraulic cylinder motor control unit and a hydraulic cylinder motor from right to left. And a second bearing, a sun wheel positioning sleeve, a sun wheel and a third bearing are sequentially arranged on the output shaft of the motor. The third bearing ensures the relative positions of the planet carrier and the sun gear, etc., and the rotation axes of the sun gear and the planet carrier are coaxial.

Furthermore, the output shaft of the motor transmits the torque to the sun gear through the spline, transmits the torque to the planet carrier through the planetary gear mechanism, and finally converts the torque into the force for pushing the push rod of the main cylinder to move axially through the ball screw mechanism, and pushes the piston to realize the purpose of accurately increasing and decreasing the pressure.

Furthermore, a first liquid outlet valve of the hydraulic cylinder and a second liquid outlet valve of the hydraulic cylinder control the on-off of an external brake pipeline of the main brake unit.

The backup brake unit comprises a first hydraulic pump, a hydraulic pump motor, a second hydraulic pump and a hydraulic pump liquid inlet one-way valve. The braking force of the backup braking unit is provided by a first hydraulic pump and a second hydraulic pump which are synchronously driven by a motor. The brake fluid of the hydraulic pump comes from the liquid storage tank, and a one-way valve is connected between the hydraulic pump and the liquid storage tank to control the flow direction of the brake fluid. The backup brake unit further comprises a left rear wheel check valve, a left rear wheel liquid inlet valve, a right front wheel check valve, a right front wheel liquid inlet valve, a left front wheel check valve, a left front wheel liquid inlet valve, a right rear wheel check valve, a right rear wheel liquid inlet valve, a left rear wheel liquid outlet valve, a right front wheel liquid outlet valve, a left front wheel liquid outlet valve and a right rear wheel liquid outlet valve.

Furthermore, the m port of the first hydraulic pump, the N port of the second hydraulic pump and the a port of the hydraulic pump liquid inlet check valve are connected, the p port of the hydraulic pump liquid inlet check valve is connected with the G port hydraulic pipeline of the backup brake unit, the a port of the left rear wheel check valve, the p port of the left rear wheel liquid inlet valve, the a port of the right front wheel check valve, the p port of the right front wheel liquid inlet valve and the o port of the first hydraulic pump are all connected with the E port hydraulic pipeline of the backup brake unit, the a port of the left front wheel check valve, the p port of the left front wheel liquid inlet valve, the a port of the right rear wheel check valve, the p port of the right rear wheel liquid inlet valve and the p port of the second hydraulic pump are all connected with the F port hydraulic pipeline of the backup brake unit, the p port of the left rear wheel check valve, the a port of the left rear wheel liquid inlet valve and the p port of the left rear wheel liquid outlet valve are all connected with the N port hydraulic pipeline of the backup brake unit, the p port of the right rear wheel check valve, the N port of the left rear wheel check valve, the right rear wheel check valve, the p port of the backup brake unit, the backup, An a port of the right front wheel liquid inlet valve and a P port of the right front wheel liquid outlet valve are all connected with an O port hydraulic pipeline of the backup braking unit, a P port of the left front wheel one-way valve, an a port of the left front wheel liquid inlet valve and a P port of the left front wheel liquid outlet valve are all connected with a P port hydraulic pipeline of the backup braking unit, a P port of the right rear wheel one-way valve, an a port of the right rear wheel liquid inlet valve and a P port of the right rear wheel liquid outlet valve are all connected with a Q port hydraulic pipeline of the backup braking unit, and an a port of the left rear wheel liquid outlet valve, an a port of the right front wheel liquid outlet valve, an a port of the left front wheel liquid outlet valve and an a port of the right rear wheel liquid outlet valve are all connected with an H port hydraulic pipeline of the backup braking unit; the G port is connected with the inlet of the one-way valve, and the H port is connected with the liquid outlet of the liquid outlet valve, so that the G port is the liquid inlet of the backup braking unit, and the H port is the liquid outlet of the backup braking unit.

Furthermore, a pressure sensor is arranged on each pipeline connected with the brake wheel cylinder, so that the pressure information of the brake wheel cylinder can be provided for the control unit in real time.

In the technical scheme, in the automobile brake-by-wire system with the backup function, a port D of a semi-active brake pedal feel simulator is connected with a port a of an external interface of a liquid storage tank; the external interfaces G, H of the backup brake unit are connected with the d port of the liquid storage tank; an external interface E port and an external interface F port of the main brake unit are respectively connected with an external interface B port and an external interface C port of the liquid storage tank, an external interface A port and an external interface B port of the main brake unit are respectively connected with an external interface E port and an external interface F port of the backup brake unit, and an external interface g port of the main brake unit is connected with a liquid inlet C port of the semi-active brake pedal feeling simulator; and an external interface N port, an external interface O port, an external interface P port and an external interface Q port of the backup brake unit are respectively connected with the left rear wheel, the right front wheel, the left front wheel and the right rear wheel.

The technical scheme is that the automobile brake-by-wire system with the backup function further provides a pressure control method, wherein the pressure control method comprises the following steps: a relief pressure algorithm. Under the relief pressure control, the wheel cylinder pressure is controlled to be near the relief pressure (i.e., the inlet pressure of the normally closed linear valve) by adjusting the duty ratio of the normally closed linear valve using the static relief characteristic of the normally closed linear valve so that the wheel cylinder pressure can be rapidly changed toward the target pressure.

Further, a definite relation exists between the coil current of the normally closed linear valve and the inlet pressure, namely the overflow pressure, of the normally closed linear valve. The coil current is linearly related to the duty cycle, so that the control of the relief pressure is finally the control of the duty cycle of the coil.

Furthermore, firstly, the control software inputs target pressure, then corresponding coil duty ratio is obtained according to the relation between the overflow pressure and the duty ratio, and finally, a duty ratio signal is input to the coil driving circuit, so that the accurate control of the wheel cylinder pressure can be realized.

Compared with the prior art, the invention has the beneficial effects that:

1. according to the automobile brake-by-wire system with the backup function, the brake control mechanism is improved and integrated on the basis of the traditional passive pedal feeling simulator, and different pedal simulation counter forces are provided according to different brake strengths. When the brake is in normal operation, the pedal feelings under different conditions of low-intensity braking, medium-intensity braking, high-intensity braking and emergency braking are simulated respectively, and under the condition of emergency braking, the pedal feelings under the conditions of low-intensity braking, medium-intensity braking and high-intensity braking are simulated, so that the conventional braking and the backup braking respectively have different simulation effects of an active pedal feeling simulator and a passive pedal feeling simulator. The brake control system avoids a complex pipeline and is more suitable for a brake-by-wire system.

2. According to the automobile brake-by-wire system with the backup function, the transmission mechanism assembly of the main brake unit adopts the planetary gear coaxial transmission mechanism, the input and the output run coaxially, the motion is stable, the bearing capacity is high, the work is reliable, and the service life is long. The integration degree of the main brake unit and each unit is high, the complexity of the system is reduced, and the arrangement space of the automobile chassis is increased.

3. The automobile brake-by-wire system with the backup function provided by the invention can close the liquid outlet valve of the hydraulic cylinder when the hydraulic cylinder motor works abnormally or even fails suddenly in the driving process of an automobile, and electrify the hydraulic pump motor in the brake loop, so that the hydraulic pump motor and the hydraulic pump are connected into the brake loop, namely, the backup mode is switched in, the brake function is realized, and the safety and the reliability are improved.

4. The automobile brake-by-wire system with the backup function has the advantages of rapid backup response and high pressure control precision, can be installed in hybrid electric vehicles and electric vehicles, enables hydraulic braking and motor braking to be better matched, and fully exerts the regenerative braking capability of the electric vehicles.

Drawings

The invention is further described with reference to the accompanying drawings in which:

FIG. 1 is a schematic structural diagram of a brake-by-wire system with a backup function for an automobile according to the present invention;

FIG. 2 is a schematic diagram of a semi-active brake pedal feel simulator in a brake-by-wire system with backup function for an automobile according to the present invention;

FIG. 3 is a schematic diagram of a main brake unit in a brake-by-wire system with backup function for a vehicle according to the present invention;

FIG. 4 is a front view of a planetary gear mechanism in a brake-by-wire system for an automobile having a backup function according to the present invention;

FIG. 5 is a schematic diagram of a backup brake unit in a brake-by-wire system for an automobile having a backup function according to the present invention;

FIG. 6 is a flow chart of the brake intention recognition of the brake-by-wire system for an automobile with a backup function according to the present invention;

in the figure: 1. a semi-active brake pedal sense simulator, 2, a liquid storage tank, 3, a main brake unit, 4, a backup brake unit, 5, a left rear wheel pressure sensor, 6, a right front wheel pressure sensor, 7, a left front wheel pressure sensor, 8, a right rear wheel pressure sensor, 9, a left rear wheel, 10, a right front wheel, 11, a left front wheel, 12, a right rear wheel, 13, a brake pedal, 14, a pedal force sensor, 15, a pedal push rod, 16, a pedal displacement sensor, 17, a simulator cylinder, 18, a first piston, 19, a first piston seal ring, 20, a first spring, 21, a second piston, 22, a second piston seal ring, 23, a second spring, 24, a third piston, 25, a third piston cavity, 26, a third piston seal ring, 27, a third spring, 28, a fourth piston seal ring, 29, a piston limit ring, 30, a fourth piston, 31, a simulator liquid inlet valve, 32. the simulator comprises a simulator liquid inlet one-way valve, 33, a simulator liquid outlet valve, 34, a hydraulic cylinder front cover, 35, a hydraulic cylinder first spring, 36, a hydraulic cylinder first working chamber, 37, a hydraulic cylinder first piston, 38, a hydraulic cylinder second spring, 39, a hydraulic cylinder second working chamber, 40, a hydraulic cylinder second piston, 41, a hydraulic cylinder air hole, 42, a hydraulic cylinder push rod, 43, a push rod limiting ring, 44, a first bearing, 45, a ball, 46, a planet carrier, 47, a planet carrier positioning sleeve, 48, a hydraulic cylinder rear cover, 49, a gear ring, 50, a planet gear, 51, a planet gear needle bearing, 52, a planet gear limiting ring, 53, a sun gear, 54, a sun gear positioning sleeve, 55, a second bearing, 56, a hydraulic cylinder motor, 57, a hydraulic cylinder motor control unit, 58, a rear cover connecting screw, 59, an output shaft, 60, an output shaft spline, 61, a third bearing, 62, a front cover connecting rivet, 63. the hydraulic cylinder pressure sensor, 64 hydraulic cylinder first liquid outlet valves, 65 hydraulic cylinder second liquid outlet valves, 66 first hydraulic pumps, 67 hydraulic pump motors, 68 second hydraulic pumps, 69 hydraulic pump liquid inlet one-way valves, 70 left rear wheel one-way valves, 71 left rear wheel liquid inlet valves, 72 right front wheel one-way valves, 73 right front wheel liquid inlet valves, 74 left front wheel one-way valves, 75 left front wheel liquid inlet valves, 76 right rear wheel one-way valves, 77 right rear wheel liquid inlet valves, 78 left rear wheel liquid outlet valves, 79 right front wheel liquid outlet valves, 80 left front wheel liquid outlet valves, 81 right rear wheel liquid outlet valves.

Detailed Description

The invention is described in detail below with reference to the attached drawing figures:

the automobile brake-by-wire system with the backup function comprises a semi-active brake pedal feel simulator 1, a liquid storage tank 2, a main brake unit 3 and a backup brake unit 4.

Referring to fig. 1, the liquid storage tank 2 is made of a rigid plastic material, four liquid outlets, namely, an opening a, an opening b, an opening c and an opening d, are formed in the bottom of the liquid storage tank 2, and the liquid storage tank 2 stores and supplies brake fluid to a hydraulic pipeline and detects the residual amount of the brake fluid.

The left rear wheel pressure sensor 5, the right front wheel pressure sensor 6, the left front wheel pressure sensor 7 and the right rear wheel pressure sensor 8 adopt 303 type active pressure sensors of BOSCH company to obtain the pressure of each wheel cylinder.

Referring to fig. 2, the semi-active brake pedal feel simulator 1 includes a brake pedal 13, a pedal force sensor 14, a pedal push rod 15, a pedal displacement sensor 16, a simulator cylinder 17, a first piston 18, a first piston seal ring 19, a first spring 20, a second piston 21, a second piston seal ring 22, a second spring 23, a third piston 24, a third piston cavity 25, a third piston seal ring 26, a third spring 27, a fourth piston seal ring 28, a piston limit ring 29, a fourth piston 30, a simulator inlet valve 31, a simulator inlet check valve 32, and a simulator outlet valve 33.

The specific specifications and functions are as follows: the semi-active brake pedal feel simulator 1 mainly plays a role of simulating pedal feel under the conditions of small, medium and large intensity braking when the main brake unit 3 normally works and supplementing pedal feel during emergency braking, and plays a role of simulating pedal feel during small, medium and large intensity braking when the main brake unit 3 fails and the backup brake unit 4 works as a passive brake pedal feel simulator.

The brake pedal 13 applies a lever principle, force applied to the brake pedal 13 by a driver is transmitted to the pedal push rod 15 through a hinge fulcrum, and the pedal displacement sensor 16 is arranged on the pedal push rod 15 and used for acquiring displacement information of the brake pedal. The pedal force sensor 14 is disposed on the brake pedal 13 and is configured to obtain information of the force of the driver stepping on the brake pedal. The pedal displacement sensor 16 and the pedal force sensor 14 are respectively connected with the electronic control unit ECU through lines, and the pedal displacement sensor 16 and the pedal force sensor 14 can reflect the braking intention of a driver and transmit force and displacement signals in real time.

The simulator cylinder body 17 is a cylindrical structural member, the left end surface and the right end surface of the simulator cylinder body are provided with openings with different diameters, a flange plate is arranged on the outer cylindrical surface of the left end cylinder opening, an opening is formed in the flange plate and used for extending out the brake push rod 15, and meanwhile, the diameter of the opening is slightly larger than that of the push rod and used for air intake and exhaust. The axle wire along simulator cylinder body 17 processes has the cylindrical shoulder hole of syllogic, and the syllogic ladder decreases progressively from left to right diameter, is first shoulder hole, second shoulder hole, third shoulder hole respectively.

The first piston 18, the second piston 21 and the first spring 20 between the first piston and the second piston are all installed in the first stepped hole, and the first piston 18 is provided with two air holes for air intake and exhaust.

And a boss is processed on the right side of the first piston 18, and when the second piston 21 contacts the left side surface of the second stepped hole and then the first spring 20 is compressed for a certain distance, the boss can be pressed into a concave hole of a boss on the left side of the third piston 24, so that the first spring 20 and the third spring 27 are connected in parallel to improve the rigidity. The first spring 20 stiffness k1 is greater than the second spring 23 stiffness k 2.

The second piston 21 is a circular ring-shaped structural member and is used for mounting the first spring 20. A through hole is processed along the central axis, the diameter of the through hole is slightly larger than that of a boss on the right side of the first piston 18, so that the boss can be smoothly pressed into a concave hole on a boss on the left side of the third piston 24 through the through hole, the first spring 20 and the third spring 27 are connected in parallel, and meanwhile, the ventilation effect is realized.

The first spring 20 and the second spring 23 have a certain pre-compression amount in an initial state, and the pre-compression amount is set to avoid a braking misoperation caused by a driver stepping on the brake pedal 13 by mistake, and simultaneously, the aim of discharging brake fluid to the reservoir tank 2 is fulfilled under the non-emergency braking condition.

The third piston 24 and the third spring 27 are installed in the third piston cavity 25, the third piston cavity 25 is installed in the second spring 23, and the wall of the third piston cavity 25 is provided with air holes for air intake and exhaust.

The fourth piston 30 is installed in the second stepped hole to serve as a mounting base for the third piston 24 and the third piston cavity 25. The piston check ring 29 is used to prevent the fourth piston 30 from shifting to the right, and the chamber on the right side of the fourth piston 30 can store brake fluid to supplement pedal force.

The simulator liquid inlet hole j is a third step hole, the hydraulic cylinder first working chamber 36 can adjust the simulator liquid inlet valve 31, brake liquid is provided for the simulator through the liquid inlet hole j, and pedal force is supplemented.

And the k port of the simulator can adjust the opening of the liquid outlet valve 33 of the simulator when the main brake unit 3 fails or is in a non-emergency brake condition, and the brake liquid is discharged to the liquid storage tank 2 through the k port to supplement the pedal force.

The simulator liquid inlet valve 31 and the simulator liquid outlet valve 33 are both two-position two-way normally-closed linear valves, the simulator liquid inlet valve 31 can control the first working cavity 36 of the hydraulic cylinder to provide the brake fluid oil path for the simulator to be switched on and off, and the simulator liquid outlet valve 33 can control the simulator to discharge the brake fluid oil path from the liquid storage tank 2 to be switched on and off.

The position and the connection mode of the concrete components are as follows: the brake pedal 13 is connected with a pedal push rod 15, a pedal displacement sensor 16 is arranged on the pedal push rod 15, and a pedal force sensor 14 is arranged on the brake pedal 13.

The first piston 18, the second piston 21, the third piston 24 and the fourth piston 30 are sequentially assembled in the simulator cylinder 17, a first spring 20 is arranged between the first piston 18 and the second piston 21, and a second spring 23 is arranged between the second piston 21 and the fourth piston 30; the third piston chamber 25 and the inner third piston 24 are provided inside the second spring 23 between the second piston 21 and the fourth piston 30, and one end is fixed to the fourth piston 30.

The contact parts of the first piston 18, the second piston 21, the third piston 24 and the fourth piston 30 and the cylinder wall are respectively provided with a first piston sealing ring 19, a second piston sealing ring 22, a third piston sealing ring 26 and a fourth piston sealing ring 28, two air holes are processed on two sides of a boss of the first piston 18, and the aperture of a through hole formed in the second piston 21 is slightly larger than the diameter of a push rod of the third piston 24 so as to facilitate air ventilation. When the second piston 21 is compressed to contact with the inner ladder of the cylinder body, the push rod of the third piston 24 can smoothly extend out, and can contact with the right boss of the first piston 18 after being compressed for a certain distance, so that the first spring 20 and the third spring 27 are connected in parallel, and the side wall of the third piston cavity 25 is symmetrically provided with holes for ventilation.

The brake pedal 13 passes through a flange plate on the left side of the simulator cylinder body 17 through a pedal push rod 15 to be connected with the first piston 18, a boss is processed on the right side face of the first piston 18, a concave hole in the end part of a piston push rod of the third piston 24 passes through the third piston cavity 25 to be opposite to the boss on the end part of the first piston 18, and the shapes of the two are mutually matched. The right side surface of the fourth piston 30 is closely contacted and limited with the piston limiting ring 29 through the action of a spring, the piston limiting ring 29 provides supporting force for the fourth piston 30, and a chamber for containing brake fluid is formed between the fourth piston 30 and the right side wall in the cylinder body.

The j port of the liquid inlet of the simulator is connected with the a port of the liquid inlet valve 31 of the simulator and the p port of the liquid inlet one-way valve 32 of the simulator; a port p of the simulator liquid inlet valve 31 and a port a of the simulator liquid inlet one-way valve 32 are connected with a port C of an external interface of the semi-active brake pedal feeling simulator 1; the simulator liquid outlet k is connected with a port p of the simulator liquid outlet valve 33; the port a of the simulator liquid outlet valve 33 is connected with the port D of the external interface of the brake pedal feeling simulator 1, and the ports C and D of the external interface of the simulator are internally threaded holes.

The working principle is as follows: the braking category of the driver stepping on the brake pedal 13 can be divided into conventional braking and emergency braking, and the conventional braking is divided into low-intensity braking, medium-intensity braking and high-intensity braking. Different degrees of reaction force can be provided depending on the rate and intensity of depression of the brake pedal 13 by the driver. The identification process is as follows: firstly, setting a boundary between emergency braking and conventional braking by using a speed signal, setting a speed boundary value of stepping on a brake pedal 13, namely a threshold value 1, comparing the moving speed of the brake pedal 13 with the threshold value 1 according to a signal acquired by a pedal displacement sensor 16 in real time when a driver steps on the brake pedal 13, and if the stepping speed of the driver is greater than or equal to the threshold value 1, judging that the emergency braking is performed, and if the stepping speed of the driver is less than the threshold value 1, the conventional braking is performed; when the brake is judged to be normal brake, small, medium and large intensity brakes are further distinguished according to the force signals collected by the pedal force sensor 14, the pedal force corresponding to the boundary of the small intensity brake and the medium intensity brake is set as a threshold value M, the pedal force corresponding to the boundary of the medium intensity brake and the large intensity brake is set as a threshold value N, and the threshold value N is larger than the threshold value M. If the brake is determined to be normal brake, if the signal value of the pedal force sensor 14 at the moment is less than or equal to M, the brake is low-intensity brake; the signal value is greater than M and less than or equal to N, and medium-intensity braking is performed; a signal value greater than N is a high intensity brake.

Assuming that the stiffness of the first spring 20 is k1, the stiffness of the second spring 23 is k2, the stiffness of the third spring 27 is k3, and k1 is greater than k 2. In the whole process, the moving distance of the pedal push rod 15 is x; the distance when the second piston 21 moves from the initial position to the step inside the simulator cylinder 17 is a (in the case where the second piston 21 moves this stroke, the first piston 18 moves the stroke is smaller than a); then, entering a medium-intensity braking range, the first piston 18 continuously moves for a distance b and then contacts the piston push rod end of the third piston 24; then, the high-intensity braking range is entered, and the first piston 18 and the third piston 24 are compressed together, and the maximum travel distance of the joint movement of the two is c. And the stroke a, the stroke b and the stroke c are not crossed but are arranged in an adjacent relation.

The boundary between the low-strength braking and the medium-strength braking is as follows: the second piston 21 moves from the initial position to a step inside the simulator cylinder 17, before the low-intensity brake and then the medium-intensity brake. The boundary between medium-strength braking and high-strength braking is as follows: the first piston 18 continues to travel the distance b and contacts the piston pusher end of the third piston 24, which is preceded by a medium strength brake and followed by a high strength brake.

When the brake is carried out with small intensity: when a driver steps on the brake pedal 13, the pedal push rod 15 and the first piston 18 connected with the brake pedal 13 are pushed, the first piston 18 compresses the first spring 20, and the first spring 20 pushes the second piston 21 to move inwards so as to compress the second spring 23. The low intensity braking ends until the second piston 21 moves through the stroke a, contacting a step inside the simulator cylinder 17. During low intensity braking, first piston 18 does not touch the piston pushrod end of third piston 24. At this time, the first spring 20 and the second spring 23 are connected in series to provide an elastic reaction force, and the brake pedal feeling of the driver is simulated together. Equivalent spring rate of the system at this time:

reaction force F of pedal push rod 15 at this stage_AThe relationship with the moving distance x is as follows:

when the medium-strength brake is performed: on the basis of a low-intensity brake, the driver continues to step on the brake pedal 13, and the second piston 21 has moved to a step inside the simulator cylinder 17 and is supported by the step to provide a part of the counterforce, and in the process, the first piston 18 still does not touch the piston rod end of the third piston 24, and the first piston 18 can still move for the stroke b until the first piston 18 touches the piston rod end of the third piston 24. At this time, the first spring 20 is compressed to provide an elastic reaction force, thereby simulating the braking feeling of the driver. Equivalent spring rate of the system at this time:

K_B＝k1

reaction force F of pedal push rod 15 at this stage_BThe relationship with the moving distance x is as follows:

when braking with large intensity: on the basis of medium-intensity braking, at the moment, the first piston 18 starts to touch the piston push rod end of the third piston 24, the driver continues to step on the brake pedal 13, the pedal push rod 15 pushes the first piston 18 to move continuously, the first piston 18 contacts the third piston 24 and pushes the third spring 27, the first piston 18 and the third piston 24 can be regarded as a whole, and the first spring 20 and the third spring 27 are compressed together, namely are connected in parallel, so that the brake pedal feeling of the driver is simulated. Equivalent spring rate of the system at this time:

K_c＝k1+k3

reaction force F of pedal push rod 15 at this stage_CThe relationship with the moving distance x is as follows:

therefore, the threshold M is k2 · a, and the threshold M is k2 · a + k1 · b.

During emergency braking: the electronic control unit ECU sends a control signal to the simulator liquid inlet valve 31 according to signals of the pedal displacement sensor 16 and the pedal force sensor 14, the simulator liquid inlet valve 31 is opened to supplement brake liquid to the cavity on the right side of the fourth piston 30, the fourth piston 30 is further pushed to move forwards, the resistance of the brake pedal 13 is actively increased, the feeling of the brake pedal 13 is adjusted, and therefore the simulated pedal force requirement of emergency braking is met. However, when the master brake unit 3 fails, that is, when the hydraulic cylinder is not operated, only the small, medium, and large strength brake pedal feel simulation is performed, in this case, the simulator corresponds to a passive pedal feel simulator, and the brake intention recognition flow is as shown in fig. 6.

Referring to fig. 3, the main brake unit 3 includes a hydraulic cylinder front cover 34, a hydraulic cylinder first spring 35, a hydraulic cylinder first working chamber 36, a hydraulic cylinder first piston 37, a hydraulic cylinder second spring 38, a hydraulic cylinder second working chamber 39, a hydraulic cylinder second piston 40, a hydraulic cylinder air hole 41, a hydraulic cylinder push rod 42, a push rod limit ring 43, a first bearing 44, a ball 45, a planet carrier 46, a planet carrier positioning sleeve 47, a hydraulic cylinder rear cover 48, a gear ring 49, a planetary gear 50, a planetary gear needle bearing 51, a planetary gear limit ring 52, a sun gear 53, a sun gear positioning sleeve 54, a second bearing 55, a hydraulic cylinder motor 56, a hydraulic cylinder motor control unit 57, a rear cover connection screw 58, an output shaft 59, an output shaft spline 60, a third bearing 61, a front and rear cover connection rivet 62, a hydraulic cylinder pressure sensor 63, a hydraulic cylinder first liquid outlet valve 64, and a hydraulic cylinder second liquid outlet valve 65.

The specific specifications and functions are as follows: the main brake unit 3 is mainly used as an energy supply device of a brake system to realize the functions of active pressurization, pressure maintaining and pressure reduction.

The hydraulic cylinder front cover 34 and the hydraulic cylinder rear cover 48 are cylindrical hollow stepped cylinder type structural members, flanges are machined on the outer cylindrical surface of the opening end, six rivet holes are evenly machined in the flanges, and the corresponding rivet holes are concentric.

The diameter of the hydraulic cylinder front cover 34 is gradually increased from left to right, and a liquid outlet g machined at the left end is used for supplying brake liquid to the simulator. The left end of the hydraulic cylinder rear cover 48 is open, the right end of the hydraulic cylinder rear cover 48 is closed, and four uniformly distributed screw holes are processed at the right end of the hydraulic cylinder rear cover 48. The center axis of the hydraulic cylinder rear cover 48 is provided with a stepped hole, the right end of the hydraulic cylinder rear cover is closed and used for installing a hydraulic cylinder motor 56, a hydraulic cylinder motor control unit 57 and a small-diameter round hole of the second bearing 55, the left end of the hydraulic cylinder motor control unit is a large-diameter round hole for installing the gear ring 49, the two round holes are mutually communicated, and the rotating shafts are collinear.

A first hydraulic cylinder working cavity 36 and a second hydraulic cylinder working cavity 39 are respectively formed between the first hydraulic cylinder piston 37 and the left wall of the cylinder body of the brake master cylinder and between the first hydraulic cylinder piston 37 and the second hydraulic cylinder piston 40; the first hydraulic cylinder spring 35 and the second hydraulic cylinder spring 38 are respectively arranged in the first hydraulic cylinder working chamber 36 and the second hydraulic cylinder working chamber 39.

The first piston 37 and the second piston 40 are both cylindrical disc-like structures, and an annular groove (not shown) for placing a sealing ring is formed along the outer cylindrical surface of the piston. The first hydraulic cylinder spring 35 and the second hydraulic cylinder spring 38 are cylindrical coil springs for restoring the piston.

The second piston 40 is connected to one end of the cylinder rod 42. The ball screw (i.e., the cylinder push rod 42), and the cylinder push rod 42 pushes the cylinder secondary piston 40 to adjust the brake master cylinder hydraulic pressure.

The hydraulic cylinder push rod 42 is also a screw rod of the ball screw mechanism. The hydraulic cylinder push rod 42 is composed of two parts, which have different processing methods respectively. The left part has no surface matching requirement, so the left part is processed into a smooth polished rod, and a displacement sensor can be arranged in a cavity (the displacement sensor is not shown) where the hydraulic cylinder push rod 42 is positioned; a raceway for rolling the balls 45 is processed on the right side, and the raceway is matched with the balls 45 in the planet carrier 46; the hydraulic ram 42 functions to convert the rotational action of the carrier 46 into linear motion through the ball screw pair. The push rod stop collar 43 limits the movement of the steel ball.

The planetary carrier 46 is a triangular prism-like structure as shown in fig. 4. As shown in fig. 3, a cylindrical boss is arranged at the center of the left side of the planet carrier 46, a central through hole is processed at the center of the boss, a raceway for mounting the balls 45 is arranged on an inner cylindrical surface of the central through hole at a distance, the length of the raceway is determined according to the number and the moving distance of the balls and meets the requirement of strength, and the other end of the raceway is a smooth inner wall and plays a role in limiting the movement of the balls 45; in order to reduce the moment of inertia of the planet carrier 46, three waist-shaped circular holes which are uniformly distributed along the circumference are processed outside the cylindrical boss; three cylindrical bosses with the same diameter are machined on the right sides of three vertex angles of the planet carrier 46 to serve as planet gear shafts, and are matched with the planet gears 50 and the planet gear needle roller bearings 51 to form circular grooves for installing the planet gear limiting rings 52. Three top corners of the planet carrier 46 are rounded.

A stepped through hole is processed along the axis of the planetary gear 50, a small-diameter hole on the right side is matched with the planetary gear shaft, and a planetary gear needle roller bearing 51 is installed in a large-diameter hole on the left side; the step functions to restrict the axial movement of the planetary needle bearing 51.

The planetary gear needle bearing 51 is a needle bearing and cage assembly, which is used to bear the radial acting force of the planetary gear 50 and ensure the relative rotation between the planetary gear 50 and the planetary gear shaft.

The planetary gear limiting ring 52 is processed by aluminum alloy in order to ensure strength and facilitate installation, and the mass is reduced. The planet gear limiting ring 52 and the planet carrier positioning sleeve 47 both function to limit the axial displacement of the planet carrier 46.

The gear ring 49 is a straight toothed spur gear and is meshed with the planetary gear 50.

The sun gear 53 and the planetary gear 50 are straight-tooth cylindrical gears, and the sun gear 53 is installed at the output stepped shaft of the hydraulic cylinder motor 56 and is matched with the hydraulic cylinder motor through a flat key 60. The sun gear 53 receives an output torque from the hydraulic cylinder motor 56 and transmits the torque to the planetary gear 50. The sun gear positioning sleeve 54 secures the axial position of the sun gear 53.

The hydraulic cylinder motor 56 is a brushless dc motor, and the output shaft 59 is stepped to position and mount the sun gear 53. The rear cover connecting screws 58 are evenly distributed along the circumference, are ordinary fine-thread hexagon bolts, and are used for fixing the hydraulic cylinder motor control unit 57. The output shaft spline 60 adopts an a-type common flat key to transmit the output torque of the hydraulic cylinder motor 56 to the sun gear 53.

The first bearing 44 and the second bearing 55 adopt deep groove ball bearings, wherein the second bearing 55 can bear the radial acting force of the output end of the hydraulic cylinder motor 56 and can limit the axial displacement of the planetary gear 50 and the sun gear 53.

The third bearing 61 is a thrust bearing, and the first bearing 44 and the third bearing 61 ensure the independent rotation of the planet carrier 46 and also ensure the axial position of the planet carrier 46.

The front and rear cover connecting rivets 62 are half-round rivets and are used for connecting the hydraulic cylinder front cover 34 and the hydraulic cylinder rear cover 48. The rivet holes in the flanges of the front cylinder cover 34 and the rear cylinder cover 48 are concentrically aligned.

The hydraulic cylinder pressure sensor 63 adopts a pressure sensor with the model number 303 of BOSCH company, and measures the pressure of the brake master cylinder.

The first liquid outlet valve 64 and the second liquid outlet valve 65 of the hydraulic cylinder are two-position two-way normally closed electromagnetic valves.

The position and the connection mode of the concrete components are as follows: on the hydraulic cylinder front cover 34, a hydraulic cylinder first working chamber 36 and a hydraulic cylinder second working chamber 39 are respectively formed between the hydraulic cylinder first piston 37 and the left wall of the brake master cylinder body and between the hydraulic cylinder first piston 37 and the hydraulic cylinder second piston 40, and the hydraulic cylinder first spring 35 and the hydraulic cylinder second spring 38 are respectively arranged in the hydraulic cylinder first working chamber 36 and the hydraulic cylinder second working chamber 39.

The hydraulic cylinder push rod 42 is installed in a central through hole of the planet carrier 46, the push rod limiting ring 43 is sleeved at a screw rod at the right end of the hydraulic cylinder push rod 42, the right end face of the push rod limiting ring 43 is in contact with the left end face of a boss of the planet carrier 46, a ball 45 is installed between the central through hole of the planet carrier 46 and the screw rod in the hydraulic cylinder push rod 42, the hydraulic cylinder push rod 42 is driven through the ball 45, and the ball 45 can circularly roll through a circulating raceway (not completely drawn in the drawing) in the central through hole of the planet carrier 46.

The first bearing 44 is sleeved on a cylindrical boss on the left side of the planet carrier 46, the first bearing and the cylindrical boss are in clearance fit, the right side of the first bearing 44 is in stepped positioning contact with the boss of the planet carrier 46, and the left side of the first bearing is in contact with the positioning finger of the hydraulic cylinder front cover 34, so that the left axial movement of the planet carrier 46 is prevented. Three planet gear shafts with the same diameter are arranged on the right sides of three vertex angles of the planet carrier 46, the three planet carrier positioning sleeves 47, the three planet gears 50 and the three planet gear needle roller bearings 51 are sequentially sleeved on the planet gear shafts, clearance fit is formed between the planet gear shafts and the planet gears 50 and between the planet gear shafts and the planet gear needle roller bearings 51, circular grooves for installing the planet gear limiting rings 52 are machined at the end parts of the right sides of the planet gear shafts, and the planet gear limiting rings 52 are installed in the circular grooves.

The hydraulic cylinder front cover 34 is connected with the hydraulic cylinder rear cover 48 through six identical front and rear cover connecting rivets 62, the gear ring 49 is fixed in a large-diameter circular hole formed in the left end opening of the hydraulic cylinder rear cover 48, three planetary gears 50 which are meshed with each other and are cylindrical straight-tooth gears are uniformly distributed in the gear ring 49 along the circumference, and the planetary gears 50 are meshed with the sun gear 53 through straight teeth.

The left output shaft 59 of the hydraulic cylinder motor 56 is a stepped shaft, and the second bearing 55, the sun gear positioning sleeve 54, the sun gear 53 and the third bearing 61 are sequentially arranged from right to left. The sun gear 53 is in transition fit with the second-stage output shaft journal of the hydraulic cylinder motor 56 through the flat key 5, and the sun gear 53 and the output shaft of the hydraulic cylinder motor 56 rotate in the same line. The third bearing 61 is a thrust bearing whose left side surface is in contact with the right side surface positioning finger of the carrier 46 and whose right side surface is in contact with the left side surface of the sun gear 53.

The hydraulic cylinder motor 56 is installed on the left end face of the hydraulic cylinder motor control unit 57, and the hydraulic cylinder motor control unit 57 is fixed at the rightmost circular hole of the hydraulic cylinder rear cover 48 through four rear cover connecting screws 58. The input end of the hydraulic cylinder motor 56 is connected to the left output terminal of the hydraulic cylinder motor control unit 57, and the hydraulic cylinder motor control unit 57 is connected to the electronic control unit ECU.

The port e of the first working chamber 36 of the hydraulic cylinder is communicated with the port b of the liquid storage tank 2, and the port f of the second working chamber 39 of the hydraulic cylinder is communicated with the port c of the liquid storage tank 2; the h port of the first working cavity 36 of the hydraulic cylinder is connected with the p port of the first liquid outlet valve 64 of the hydraulic cylinder; the i port of the second working cavity 39 of the hydraulic cylinder is connected with the p port of the second liquid outlet valve 65 of the hydraulic cylinder; the g port of the first working cavity 36 of the hydraulic cylinder is connected with the C port of the semi-active brake pedal feeling simulator 1; the port a of the first hydraulic cylinder outlet valve 64 and the port a of the second hydraulic cylinder outlet valve 65 are respectively communicated with the port A, B of the external interface of the main brake unit 3.

Referring to fig. 5, the backup brake unit 4 includes a first hydraulic pump 66, a hydraulic pump motor 67, a second hydraulic pump 68, a hydraulic pump liquid inlet check valve 69, a left rear wheel check valve 70, a left rear wheel liquid inlet valve 71, a right front wheel check valve 72, a right front wheel liquid inlet valve 73, a left front wheel check valve 74, a left front wheel liquid inlet valve 75, a right rear wheel check valve 76, a right rear wheel liquid inlet valve 77, a left rear wheel liquid outlet valve 78, a right front wheel liquid outlet valve 79, a left front wheel liquid outlet valve 80, and a right rear wheel liquid outlet valve 81.

The specific specifications and functions are as follows: the backup brake unit 4 adjusts the pressure of the brake wheel cylinder and plays a role in backup to realize active pressure increase and reduction and pressure maintaining.

The left rear wheel liquid inlet valve 71, the right front wheel liquid inlet valve 73, the left front wheel liquid inlet valve 75 and the right rear wheel liquid inlet valve 77 are two-position two-way normally open electromagnetic valves which respectively control the pressurization of the left rear wheel 9, the right front wheel 10, the left front wheel 11 and the right rear wheel 12.

The left rear wheel liquid outlet valve 78, the right front wheel liquid outlet valve 79, the left front wheel liquid outlet valve 80 and the right rear wheel liquid outlet valve 81 are two-position two-way normally closed electromagnetic valves and respectively control the decompression of the left rear wheel 9, the right front wheel 10, the left front wheel 11 and the right rear wheel 12.

The left rear wheel check valve 70, the right front wheel check valve 72, the left front wheel check valve 74, and the right rear wheel check valve 76 regulate the brake fluid to flow in one direction.

The hydraulic pump motor 67 can drive the first hydraulic pump 66 and the second hydraulic pump 68 at the same time, the first hydraulic pump 66 and the second hydraulic pump 68 are plunger type hydraulic pumps, and can be matched with a vehicle pressurization process through the hydraulic pump motor 67 to realize rapid pressurization, and the hydraulic pump motor 67 can also be used as a pressure source of a backup brake unit. The ports m of the first hydraulic pump 66 and n of the second hydraulic pump 68 suck low-pressure brake fluid from the reservoir tank 2, and the ports o of the first hydraulic pump 66 and p of the second hydraulic pump 68 output high-pressure brake fluid.

The position and the connection mode of the specific parts are as follows: the m port of the first hydraulic pump 66, the n port of the second hydraulic pump 68 and the a port of the hydraulic pump liquid inlet check valve 69 are connected, and the p port of the hydraulic pump liquid inlet check valve 69 is connected with the G port of the external interface of the backup brake unit 4; the port a of the left rear wheel check valve 70, the port p of the left rear wheel liquid inlet valve 71, the port a of the right front wheel check valve 72, the port p of the right front wheel liquid inlet valve 73 and the port o of the first hydraulic pump 66 are connected with the port E of the external interface of the backup brake unit 4; the port a of the left front wheel check valve 74, the port p of the left front wheel liquid inlet valve 75, the port a of the right rear wheel check valve 76, the port p of the right rear wheel liquid inlet valve 77 and the port p of the second hydraulic pump 68 are connected with the port F of the external interface of the backup brake unit 4; the port p of the left rear wheel check valve 70, the port a of the left rear wheel liquid inlet valve 71 and the port p of the left rear wheel liquid outlet valve 78 are connected with the port N of the external interface of the backup brake unit 4; the port p of the right front wheel check valve 72, the port a of the right front wheel liquid inlet valve 73 and the port p of the right front wheel liquid outlet valve 79 are connected with the port O of the external interface of the backup brake unit 4; the port P of the left front wheel check valve 74, the port a of the left front wheel liquid inlet valve 75 and the port P of the left front wheel liquid outlet valve 80 are all connected with the port P of the external interface of the backup brake unit 4, the port P of the right rear wheel check valve 76, the port a of the right rear wheel liquid inlet valve 77 and the port P of the right rear wheel liquid outlet valve 81 are all connected with the port Q of the external interface of the backup brake unit 4, and the port a of the left rear wheel liquid outlet valve 78, the port a of the right front wheel liquid outlet valve 79, the port a of the left front wheel liquid outlet valve 80 and the port a of the right rear wheel liquid outlet valve 81 are all connected with the port H of the external interface of the backup brake unit 4.

The invention relates to an automobile brake-by-wire system with a backup function, which comprises a pedal mechanism 1, a liquid storage tank 2, a main brake unit 3 and a backup brake unit 4. The connection relationship is as follows: the external interfaces of the main brake unit 3 comprise an E port, an F port, a g port, an A port and a B port, the external interfaces E and F of the main brake unit 3 are respectively connected with the external interfaces B and C of the liquid storage tank 2, the external interfaces A and B of the main brake unit 3 are respectively connected with the external interfaces E and F of the backup brake unit 4, the external interface g of the main brake unit 3 is connected with the liquid inlet C port of the semi-active brake pedal feeling simulator 1, the liquid outlet D port of the semi-active brake pedal feeling simulator 1 is connected with the external interface a port of the liquid storage tank 2, the external interfaces G, H ports of the backup brake unit 4 are respectively connected with the external interface D port of the liquid storage tank 2, and the external interfaces N, O, P and Q of the backup brake unit 4 are respectively connected with the left rear wheel 9, the right front wheel 10, the left front wheel 11 and the right rear wheel 12.

According to the automobile brake-by-wire system with the backup function, provided by the invention, when the main brake unit 3 suddenly works abnormally or even fails, the first liquid outlet valve 64 of the hydraulic cylinder and the second liquid outlet valve 65 of the hydraulic cylinder are powered off and closed, the hydraulic pump motor 67 in the brake loop is powered on, so that the hydraulic pump motor 67 and the hydraulic pump are connected into the brake loop, namely, a backup mode is switched on, and the brake function is realized. Meanwhile, the pedal feeling under the conditions of small, medium and large-intensity braking is simulated during normal work and the pedal feeling is supplemented during emergency braking, and the active small, medium and large-intensity braking is realized as a passive brake pedal feeling simulator when the main braking unit 3 fails, so that the effect of simulating three-stage pedal feeling is realized, and the safety and the reliability of driving the automobile by a driver are improved.

In the working process of the brake system, the control method comprises the following steps:

when the brake system works normally, that is, the main brake unit 3 has no fault, the main brake unit 3 is a source of brake pressure, and at this time, the first hydraulic cylinder outlet valve 64 and the second hydraulic cylinder outlet valve 65 are opened. The left rear wheel liquid inlet valve 71, the right front wheel liquid inlet valve 73, the left front wheel liquid inlet valve 75 and the right rear wheel liquid inlet valve 77 are opened; the hydraulic pump motor 67, the first hydraulic pump 66, and the second hydraulic pump 68 are turned off; the left rear wheel liquid outlet valve 78, the right front wheel liquid outlet valve 79, the left front wheel liquid outlet valve 80 and the right rear wheel liquid outlet valve 81 are closed. If the brake wheel cylinder needs to be pressurized, the hydraulic cylinder motor 56 is electrified to operate in a forward direction, the sun gear 53, the planetary gear 50, the planet carrier 46, the hydraulic cylinder push rod 42 and the like are sequentially driven, and the rotary motion of the hydraulic cylinder motor 56 is converted into the linear motion of the hydraulic cylinder push rod 42. The first piston 37 and the second piston 40 of the hydraulic cylinder compress brake fluid, the brake fluid enters the left rear wheel 9 and the right front wheel 10 wheel cylinders through the left rear wheel fluid inlet valve 71 and the right front wheel fluid inlet valve 73 respectively after passing through the first fluid outlet valve 64 of the hydraulic cylinder from the front cover 34 of the hydraulic cylinder, and enters the left front wheel 11 and the right rear wheel 12 wheel cylinders through the second fluid outlet valve 65 of the hydraulic cylinder and through the left front wheel fluid inlet valve 75 and the right rear wheel fluid inlet valve 77 respectively, so as to complete the pressurization operation. If the brake wheel cylinder needs to be decompressed, the hydraulic cylinder motor 56 is electrified to run reversely, and the brake fluid reversely flows back to the hydraulic cylinder to complete the decompression operation. If the brake wheel cylinders need to maintain pressure, the position of the hydraulic cylinder motor 56 and the opening of each electromagnetic valve are kept unchanged, and each brake wheel cylinder maintains pressure.

When the main brake unit 3 fails, the hydraulic cylinder first liquid outlet valve 64 and the hydraulic cylinder second liquid outlet valve 65 are closed in a power-off mode. The left rear wheel liquid inlet valve 71, the right front wheel liquid inlet valve 73, the left front wheel liquid inlet valve 75 and the right rear wheel liquid inlet valve 77 are opened; the left rear wheel liquid outlet valve 78, the right front wheel liquid outlet valve 79, the left front wheel liquid outlet valve 80 and the right rear wheel liquid outlet valve 81 regulate the opening degree according to the duty ratio signal to control the pressure of the wheel cylinders. If the brake wheel cylinder needs to be pressurized, the hydraulic pump motor 67 is energized to operate, the first hydraulic pump 66 and the second hydraulic pump 68 are opened, and at this time, the low-pressure brake fluid flows to the first hydraulic pump 66 and the second hydraulic pump 68 driven by the hydraulic pump motor 67 through the hydraulic pump inlet check valve 69 and is converted into the high-pressure brake fluid. Brake fluid enters the left rear wheel 9 and the right front wheel 10 wheel cylinders through the left rear wheel fluid inlet valve 71 and the right front wheel fluid inlet valve 73 respectively by the first hydraulic pump 66, and enters the left front wheel 11 and the right rear wheel 12 wheel cylinders through the left front wheel fluid inlet valve 75 and the right rear wheel fluid inlet valve 77 respectively by the second hydraulic pump 68, so that the pressurization operation is completed.

If the brake wheel cylinder needs to be decompressed, the opening degrees of the left rear wheel liquid outlet valve 78, the right front wheel liquid outlet valve 79, the left front wheel liquid outlet valve 80 and the right rear wheel liquid outlet valve 81 are adjusted, and the brake fluid flows back to the liquid storage tank 2 through the liquid outlet valves to complete decompression operation.

If the brake wheel cylinders need to maintain pressure, the opening states of the hydraulic pump motor 67 and the electromagnetic valves are kept unchanged, and the brake wheel cylinders realize pressure maintaining operation.

The pressure control method comprises the following steps:

in order to enable the wheel cylinder pressure to accurately follow the target pressure, the invention provides a pressure control method aiming at the pressure control requirement and combining a hardware scheme of a braking system, wherein the pressure control method comprises the following steps: and (4) controlling the overflow pressure.

Under the control of the overflow pressure, the duty ratio of the normally closed linear valve is adjusted, so that the wheel cylinder pressure can be quickly changed to the target pressure. In this process, the pressure at the inlet of the normally closed linear valve will always fluctuate above and below an approximately constant pressure, and different currents correspond to different inlet pressures. By referring to this pressure as the "relief pressure" at the corresponding current, the inlet pressure of the normally closed linear valve can be ensured by controlling the relief pressure.

The wheel cylinder pressure will be controlled to be in the vicinity of the relief pressure (i.e., the normally closed linear valve inlet pressure) using the static relief characteristic of the normally closed linear valve. If the wheel cylinder pressure is smaller than the overflow pressure, all the brake fluid flowing out of the high-pressure source flows into the brake wheel cylinder to realize pressurization; if the wheel cylinder pressure is equal to the overflow pressure, the brake fluid flowing out of the high-pressure source always closes the linear valve and flows out to the low-pressure source, and pressure maintaining is achieved; if the pressure of the wheel cylinder is larger than the overflow pressure, the brake fluid flows out to a low-pressure source through the wheel cylinder and the normally closed linear valve to realize pressure reduction.

There is a defined relationship between the coil current and the normally closed linear valve inlet pressure, i.e. the relief pressure. The coil current is linearly related to the duty cycle, so that the control of the relief pressure is finally the control of the duty cycle of the coil.

The specific control method comprises the following steps: firstly, the control software inputs target pressure, then the corresponding coil duty ratio is obtained according to the relation between the overflow pressure and the duty ratio, and finally the duty ratio signal is input to the coil driving circuit, so that the accurate control of the wheel cylinder pressure can be realized.

Claims

1. An automobile brake-by-wire system with a backup function is characterized by comprising a semi-active brake pedal feel simulator (1), a liquid storage tank (2), a main brake unit (3) and a backup brake unit (4);

the D port of the semi-active brake pedal feeling simulator (1) is connected with the a port of the liquid storage tank (2), and the external interface G, H ports of the backup brake unit (4) are connected with the D port of the liquid storage tank (2); an e port and an f port of an external interface of the main brake unit (3) are respectively connected with a b port and a c port of the liquid storage tank (2); an external interface A port and an external interface B port of the main brake unit (3) are respectively connected with an external interface E port and an external interface F port of the backup brake unit (4); an external interface g port of the main brake unit (3) is connected with a liquid inlet C port of the semi-active brake pedal feeling simulator (1); an external interface N port, an external interface O port, an external interface P port and an external interface Q port of the backup brake unit (4) are respectively connected with the left rear wheel (9), the right front wheel (10), the left front wheel (11) and the right rear wheel (12).

2. The automotive brake-by-wire system with a backup function according to claim 1, wherein the semi-active brake pedal feel simulator (1) mainly comprises a brake pedal (13), a pedal force sensor (14), a pedal push rod (15), a pedal displacement sensor (16), a simulator cylinder (17), a first piston (18), a first spring (20), a second piston (21), a second spring (23), a third piston (24), a third spring (27), a piston limit ring (29), a fourth piston (30), a simulator inlet valve (31), a simulator inlet check valve (32), and a simulator outlet valve (33);

the brake pedal (13) is arranged below the front part of a driver, the pedal force sensor (14) is arranged on the brake pedal (13), the pedal displacement sensor (16) is arranged on the pedal push rod (15), and information of the obtained brake pedal force and pedal displacement is transmitted to the electronic control unit ECU; the brake pedal passes through the front end cover of the simulator cylinder body (17) through a pedal push rod (15) and is connected with a first piston (18); a three-section cylindrical stepped hole is processed along the central axis of the simulator cylinder body (17), the diameters of the three-section steps are gradually reduced from left to right, and the three-section steps are a first stepped hole, a second stepped hole and a third stepped hole respectively; the first piston (18) and the second piston (21) are arranged in the first stepped hole, and a first spring (20) is arranged between the first piston and the second piston; the third piston (24) and the fourth piston (30) are positioned in the second stepped hole, and a second spring (23) is arranged between the second piston (21) and the fourth piston (30); the third piston cavity (25), the inner third piston (24) and the third spring (27) are arranged in the second spring (23) between the second piston (21) and the fourth piston (30), and one end of the third spring is fixed on the fourth piston (30); each piston is connected with the inner cylinder wall of the simulator in a sliding way, and a piston sealing ring is arranged on the outer cylindrical surface of each piston; a j port of the simulator cylinder body (17) is a third stepped hole, and the j port of the simulator cylinder body (17) is connected with an a port of the simulator liquid inlet valve (31) and a p port of the simulator liquid inlet one-way valve (32); a port p of the simulator liquid inlet valve (31) and a port a of the simulator liquid inlet check valve (32) are connected with a port C of an external interface of the simulator; a k port of a liquid outlet of the simulator is connected with a p port of a liquid outlet valve (33) of the simulator, a port a of the liquid outlet valve (33) of the simulator is connected with a D port of an external interface of the simulator, and the C port and the D port of the external interface of the simulator are internally threaded holes.

3. The brake-by-wire system with backup function for automobile according to claim 1, wherein the left end face and the right end face of the simulator cylinder body (17) are provided with openings with different diameters, a flange plate is arranged on the outer cylindrical surface of the left end cylinder opening, and an opening is formed in the flange plate and used for extending out the brake push rod (15), and the diameter of the opening is slightly larger than that of the push rod and used for air intake and exhaust; a boss is machined on the right side of the first piston (18), and after the second piston (21) is in compression contact with the left side face of the second stepped hole and the first spring (20) is further compressed for a certain distance, the boss can be pressed into a concave hole of a boss on the left side of the third piston (24), so that the first spring (20) and the third spring (27) are connected in parallel; the second piston (21) is a circular structural member, a through hole is processed along the central axis, the diameter of the through hole is slightly larger than that of a boss on the right side of the first piston (18), so that the boss can smoothly pass through the through hole, and meanwhile, the ventilation effect is realized; the first spring (20) and the second spring (23) have a certain precompression amount in an initial state, so that the brake pedal (13) is prevented from being stepped by a driver by mistake to cause brake misoperation, and the aim of discharging brake fluid to the liquid storage tank is fulfilled under the condition of non-emergency braking.

4. The brake-by-wire system with backup function for automobiles according to claim 1, wherein the bottom of the fluid reservoir (2) has four ports, which are respectively port a, port b, port c and port D, and are respectively connected with port D of the semi-active brake pedal feel simulator (1), port e of the main brake unit (3), port f of the main brake unit (3) and port G, H of the backup brake unit (4), and the fluid reservoir (2) is made of hard plastic and is installed above the main brake unit (3).

5. The automobile brake-by-wire system with the backup function according to claim 1, wherein the main brake unit (3) mainly comprises a hydraulic cylinder front cover (34), a hydraulic cylinder first spring (35), a hydraulic cylinder first piston (37), a hydraulic cylinder second spring (38), a hydraulic cylinder second piston (40), a hydraulic cylinder push rod (42), a push rod limit ring (43), a first bearing (44), a planet carrier (46), a hydraulic cylinder rear cover (48), a gear ring (49), a planetary gear (50), a planetary gear needle bearing (51), a planetary gear limit ring (52), a sun gear (53), a sun gear positioning sleeve (54), a second bearing (55), a hydraulic cylinder motor (56), a third bearing (61), a front cover connecting rivet (62), a hydraulic cylinder pressure sensor (63), a hydraulic cylinder first liquid outlet valve (64), A second liquid outlet valve (65) of the hydraulic cylinder;

the front cover and the rear cover of the hydraulic cylinder are riveted into a whole by connecting a front cover and a rear cover with rivets (62), the inner diameters of the front cover (34) of the hydraulic cylinder are sequentially increased from left to right, and the rear cover (48) of the hydraulic cylinder is opposite to the front cover; the left-most side of the hydraulic cylinder front cover (34) is processed into a hydraulic cylinder, the hydraulic cylinder front cover is provided with two working cavities, namely a hydraulic cylinder first working cavity (36) and a hydraulic cylinder second working cavity (39), and a hydraulic cylinder first spring (35) and a hydraulic cylinder second spring (38) are sequentially arranged in the two working cavities; the left side of a hydraulic cylinder push rod (42) is connected with a hydraulic cylinder second piston (40) and is a smooth polished rod, the right side of the hydraulic cylinder push rod is processed into a screw rod of a ball screw mechanism, and a push rod limiting ring (43) can limit the movement of a ball (45).

6. The automotive brake-by-wire system with a backup function according to claim 1, wherein the planet carrier (46) is a regular triangular prism component serving as a nut of the ball screw mechanism, a cylindrical boss is machined on the left side of the planet carrier, a first bearing (44) is installed on the outer cylindrical surface of the boss, a through hole is drilled in the center of the boss, a roller path is machined on the left half part of the inner side of the through hole, and the right half part is a smooth inner wall; bosses are processed at three top corners on the right side of the planet carrier (46) and serve as planet gear shafts, a planet gear needle bearing (51) and a planet gear (50) are arranged on the shafts, the planet gear (50) is meshed with a gear ring (49) and a sun gear (53), and the gear ring (49) is fixedly connected to the inner wall of a circular hole with the largest diameter on the left side of a hydraulic cylinder rear cover (48); a hydraulic cylinder motor control unit (57) and a hydraulic cylinder motor (56) are sequentially arranged in a small-diameter inner hole of the hydraulic cylinder rear cover (48) from right to left; a second bearing (55), a sun wheel positioning sleeve (54), a sun wheel (53) and a third bearing (61) are sequentially arranged on an output shaft (59) of the motor; the third bearing (61) ensures the relative positions of the planet carrier (46) and the sun gear (53) and the like, and the rotation axes of the sun gear (53) and the planet carrier (46) are coaxial;

the port e of the first working cavity (36) of the hydraulic cylinder is communicated with the port b of the liquid storage tank (2), and the port f of the second working cavity (39) of the hydraulic cylinder is communicated with the port c of the liquid storage tank (2); an h port of the first working cavity (36) of the hydraulic cylinder is connected with a p port of a first liquid outlet valve (64) of the hydraulic cylinder; an i port of the second working cavity (39) of the hydraulic cylinder is connected with a p port of a second liquid outlet valve (65) of the hydraulic cylinder; the g port of the first working cavity (36) of the hydraulic cylinder is connected with the C port of the semi-active brake pedal feeling simulator (1); an a port of the first hydraulic cylinder liquid outlet valve (64) and an a port of the second hydraulic cylinder liquid outlet valve (65) are respectively communicated with an external port A, B of the main brake unit (3).

7. The brake-by-wire system according to claim 1, wherein the backup brake unit (4) comprises a first hydraulic pump (66), a hydraulic pump motor (67), a second hydraulic pump (68), and a hydraulic pump inlet check valve (69), and the braking force of the backup brake unit (4) is provided by the first hydraulic pump (66) and the second hydraulic pump (68) which are synchronously driven by the hydraulic pump motor (67).

8. The vehicle brake-by-wire system with backup function according to claim 1, wherein the backup brake unit (4) further comprises a left rear wheel check valve (70), a left rear wheel liquid inlet valve (71), a right front wheel check valve (72), a right front wheel liquid inlet valve (73), a left front wheel check valve (74), a left front wheel liquid inlet valve (75), a right rear wheel check valve (76), a right rear wheel liquid inlet valve (77), a left rear wheel liquid outlet valve (78), a right front wheel liquid outlet valve (79), a left front wheel liquid outlet valve (80), and a right rear wheel liquid outlet valve (81);

the m port of the first hydraulic pump (66), the n port of the second hydraulic pump (68) and the a port of the hydraulic pump liquid inlet check valve (69) are connected, and the p port of the hydraulic pump liquid inlet check valve (69) is connected with the G port hydraulic pipeline of the backup brake unit (4); an opening a of a left rear wheel check valve (70), an opening p of a left rear wheel liquid inlet valve (71), an opening a of a right front wheel check valve (72), an opening p of a right front wheel liquid inlet valve (73) and an opening o of a first hydraulic pump (66) are all connected with an opening E hydraulic pipeline of a backup brake unit (4); an a port of the left front wheel check valve (74), a p port of the left front wheel liquid inlet valve (75), an a port of the right rear wheel check valve (76), a p port of the right rear wheel liquid inlet valve (77) and a p port of the second hydraulic pump (68) are all connected with an F port hydraulic pipeline of the backup brake unit (4); a port p of the left rear wheel check valve (70), a port a of the left rear wheel liquid inlet valve (71) and a port p of the left rear wheel liquid outlet valve (78) are all connected with an N port hydraulic pipeline of the backup braking unit (4); a port p of the right front wheel check valve (72), a port a of the right front wheel liquid inlet valve (73) and a port p of the right front wheel liquid outlet valve (79) are all connected with an O port hydraulic pipeline of the backup braking unit (4); a port P of the left front wheel check valve (74), a port a of the left front wheel liquid inlet valve (75) and a port P of the left front wheel liquid outlet valve (80) are all connected with a port P hydraulic pipeline of the backup brake unit (4); a port p of the right rear wheel check valve (76), a port a of the right rear wheel liquid inlet valve (77) and a port p of the right rear wheel liquid outlet valve (81) are all connected with a port Q hydraulic pipeline of the backup brake unit (4); an a port of the left rear wheel liquid outlet valve (78), an a port of the right front wheel liquid outlet valve (79), an a port of the left front wheel liquid outlet valve (80) and an a port of the right rear wheel liquid outlet valve (81) are all connected with an H port hydraulic pipeline of the backup braking unit (4); the port G is a liquid inlet of the backup brake unit (4), and the port H is a liquid outlet of the backup brake unit (4).

9. The pressure control method of a brake-by-wire system for an automobile having a backup function according to any one of claims 1 to 8, wherein the pressure control method is a relief pressure algorithm; regulating the duty ratio of the normally closed linear valve by utilizing the static overflow characteristic of the normally closed linear valve, so that the wheel cylinder pressure can be quickly changed to the target pressure, and controlling the wheel cylinder pressure to be near the overflow pressure, namely the inlet pressure of the normally closed linear valve; a certain relation exists between the coil current of the normally closed linear valve and the liquid inlet pressure of the normally closed linear valve, namely the overflow pressure, and the coil current is linearly related to the duty ratio, so that the control of the overflow pressure is finally the control of the duty ratio of the coil; firstly, control software inputs target pressure, then corresponding coil duty ratio is obtained according to the relation between overflow pressure and duty ratio, and duty ratio signals are input to a coil driving circuit, so that accurate control of wheel cylinder pressure is realized.