CN113002510A

CN113002510A - Hybrid braking system

Info

Publication number: CN113002510A
Application number: CN202110373844.0A
Authority: CN
Inventors: 史晓波; 邓伟文
Original assignee: Nanjing Jingweida Automobile Technology Co ltd
Current assignee: Nanjing Jingweida Automobile Technology Co ltd
Priority date: 2021-04-07
Filing date: 2021-04-07
Publication date: 2021-06-22

Abstract

The invention provides a hybrid brake system which mainly comprises a brake pedal, a vacuum booster assembly, an auxiliary electro-hydraulic servo brake assembly, a shuttle valve, a hydraulic control unit and a brake set. The vacuum booster assembly is connected with a brake pedal, and the brake pedal is also provided with a corresponding pedal travel sensor. The vacuum booster and the auxiliary electro-hydraulic servo brake assembly are respectively connected with respective brake master cylinders, the main brake master cylinder is directly connected to a left oil inlet of the hydraulic control unit through a first loop and is connected to a right oil inlet of the hydraulic control unit through a second loop and a shuttle valve and a fourth loop; the auxiliary brake master cylinder is connected to a right oil inlet of the hydraulic control unit through a third loop and a shuttle valve and a fourth loop, and an oil outlet of the hydraulic control unit is connected with the brake set. The auxiliary electro-hydraulic servo brake assembly is applied to vehicles with limited arrangement space, and can meet higher brake pressure requirements by adding the auxiliary electro-hydraulic servo brake assembly on the basis of the original vacuum booster.

Description

Hybrid braking system

Technical Field

The invention belongs to the technical field of automobile braking, and particularly relates to a power-assisted braking system in a hydraulic braking system.

Background

The automobile brake system can be classified into mechanical type, hydraulic type, pneumatic type, electromagnetic type, etc. according to the transmission mode of brake energy. The braking energy transmission mode of the hydraulic braking system is hydraulic pressure, namely, the hydraulic pressure is increased by compressing the braking fluid in the braking system during braking, the hydraulic pressure is transmitted to the wheel-side brake and then finally pushes the friction plate to be attached to a brake disc or a brake drum, braking torque for preventing the wheel from rotating is generated, and finally ground braking force opposite to the driving direction of the wheel is reacted by the ground to brake the vehicle.

Compared with a pneumatic braking system, the hydraulic braking system has the advantages that: the transmission pressure and speed of the liquid are higher than those of the gas, so that the size of the energy transmission device of the hydraulic system is smaller, and the arrangement is more convenient; the transmission lag time is short, and the transmission lag time is generally only 1/2 of an air pressure energy transmission device; high transmission efficiency and high transmission ratio; fourthly, the structure is simple, and the system does not need lubrication; no consumption of engine power.

But is limited by the arrangement space and the model selection of the booster, and the hydraulic brake application vehicle model is relatively limited.

In the existing technical scheme, a certain vehicle type is limited by factors such as arrangement space and cost, only a vacuum booster with a proper physical size can be selected in spatial arrangement, but the input-output characteristic curve of the vacuum booster may not completely cover the corresponding system pressure when full-load braking is locked.

The main disadvantages of the prior art are:

after the overall arrangement and the shaping of the space of the whole vehicle, the size selection of the booster part of the vacuum booster is limited by the spatial arrangement, so that the final braking performance can be influenced. In addition, receive the restriction that encloses the sheet metal component change cost before the whole car cabin, the vacuum booster after the lectotype probably has the risk that can't satisfy the braking demand because radial dimension is littleer.

When the vacuum booster scheme of two diaphragms is adopted, even the booster of using less radial dimension, also can realize more ideal braking helping hand performance, but the radial dimension of two diaphragm schemes is longer than the vacuum booster of single diaphragm, and this has not only increased the axial physics and has arranged the degree of difficulty, still can influence the collision security of whole car.

Disclosure of Invention

The invention aims to apply a hybrid brake system to meet braking requirements on a vehicle limited by arrangement space so as to solve the problem that the braking requirements and the arrangement space cannot be met simultaneously by adopting a single vacuum booster in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

a hybrid brake system comprises a brake pedal, a main brake master cylinder directly or indirectly driven by the brake pedal, an auxiliary electro-hydraulic servo brake assembly, an auxiliary brake master cylinder driven by the auxiliary electro-hydraulic servo brake assembly, a shuttle valve, a hydraulic control unit and a brake set; wherein:

the shuttle valve is provided with two oil inlets and one oil outlet; one oil outlet of the main brake master cylinder is connected to one oil inlet of the hydraulic control unit through a first circuit and is connected with a first brake group in the brake groups through the oil outlet of the hydraulic control unit; the other oil outlet of the main brake master cylinder is connected to a first oil inlet of the shuttle valve through a second loop, the oil outlet of the auxiliary brake master cylinder is connected to a second oil inlet of the shuttle valve through a third loop, the oil outlet of the shuttle valve is connected to the other oil inlet of the hydraulic control unit through a fourth loop, and the other oil outlet of the shuttle valve is connected with a second brake group in the brake groups through the oil outlet of the hydraulic control unit;

the hybrid brake system further comprises a pedal stroke sensor for detecting the treading stroke of the brake pedal, and the pedal stroke sensor is in communication connection with the auxiliary electro-hydraulic servo brake assembly.

Furthermore, the auxiliary electro-hydraulic servo brake assembly is connected with the auxiliary brake master cylinder and comprises a mechanical assembly, a master cylinder piston stroke sensor, a control motor, an auxiliary controller and a current sensor; wherein the mechanical assembly is connected with the auxiliary brake master cylinder; the auxiliary controller is used for receiving sensor signals of the master cylinder piston stroke sensor and the current sensor and taking the sensor signals as a control basis; the auxiliary controller is in communication connection with the pedal stroke sensor and is used for receiving a pedal stroke signal detected by the pedal stroke sensor; the control motor acts under the driving of the auxiliary controller to push the piston of the auxiliary brake master cylinder to move for pressure building.

Preferably, in an embodiment, the hybrid brake further includes a vacuum booster assembly, two ends of the vacuum booster assembly are respectively connected to the brake pedal and the main brake master cylinder, and the brake pedal indirectly drives the main brake master cylinder through the vacuum booster assembly.

Furthermore, a brake lamp switch is also installed on the brake pedal.

Wherein the shuttle valve has a first operating state and a second operating state; in a first working state, the first oil inlet is closed under the action of a spring force, and the second oil inlet is communicated with the oil outlet; when the oil pump works in the first working state, the pressure at the first oil inlet is greater than the resultant force of the pressure at the second oil inlet and the spring force, the first oil inlet is opened, the first oil inlet is communicated with the oil outlet, and the second oil inlet is not communicated with the oil outlet.

In some embodiments, the brake set includes a left front wheel brake, a right front wheel brake, a left rear wheel brake, and a right rear wheel brake; the first brake group consists of a left front wheel brake and a right front wheel brake; the second brake group consists of the left rear wheel brake and the right rear wheel brake.

In other specific embodiments, the brake set includes a left front wheel brake, a right front wheel brake, a left rear wheel brake, and a right rear wheel brake; the first brake group consists of a left rear wheel brake and a right rear wheel brake; the second brake group consists of the left front wheel brake and the right front wheel brake.

At this time, the four brakes adopt an H-shaped arrangement mode, and more ideal pressure distribution can be realized on the H-shaped arrangement mode, so that the working frequency of the pressure regulating unit is reduced, and the service life of the pressure regulating unit is prolonged.

In other embodiments, the four brakes may be arranged in other ways, such as an X-type arrangement: the first brake group consists of a left front wheel brake and a right rear wheel brake, and the second brake group consists of a right front wheel brake and a left rear wheel brake; or the first brake group consists of a right front wheel brake and a left rear wheel brake, and the second brake group consists of a left front wheel brake and a right rear wheel brake.

According to the invention, by utilizing the structural principle of the shuttle valve, the second loop and the fourth loop which are connected with the shuttle valve are communicated or disconnected according to the pressure at the first oil inlet and the second oil inlet of the shuttle valve, so that the hybrid braking system is controlled to work in a brake-by-wire mode, an external request braking mode, a braking energy recovery auxiliary mode or a manual backup braking mode.

When the pressure at the first oil inlet of the shuttle valve is larger than the resultant force of the pressure at the second oil inlet and the spring force inside the shuttle valve, the second loop is communicated with the fourth loop; and when the pressure at the first oil inlet of the shuttle valve is smaller than or equal to the magnitude of the resultant force of the pressure at the second oil inlet and the spring force in the shuttle valve, the second loop is not communicated with the fourth loop.

Further, the hybrid brake system further includes a reservoir for supplying brake fluid to the main brake master cylinder and the auxiliary brake master cylinder. In one embodiment, the reservoir is connected to the primary brake master cylinder and is connected to the secondary brake master cylinder via a conduit.

According to the hybrid brake system provided by the invention, the auxiliary power can be provided by utilizing the added auxiliary electro-hydraulic servo brake assembly, the external braking request function can be realized, and the problem that a single vacuum booster cannot simultaneously meet the braking requirement is solved. For the auxiliary electro-hydraulic servo brake assembly, when the auxiliary controller receives an external braking request command request of signals such as a pedal stroke signal, a brake switch signal and the like, the external braking request command request is output to a control motor control target according to a calculation result, and the control motor is driven to push a piston to move forward to build pressure on a brake system. The piston stroke sensor and the current sensor are used for closed-loop control of displacement and current, respectively.

The hybrid braking system provided by the invention can realize the functions of line-controlled braking, external request braking, braking energy recovery assistance, manpower backup braking and redundant braking. The implementation process of each function is as follows:

1. and (4) a brake-by-wire function.

After a driver steps on the brake pedal for a certain stroke, the vacuum booster assembly builds pressure under vacuum boosting; meanwhile, an auxiliary controller of the auxiliary electro-hydraulic servo brake assembly calculates a control target required by the motor by receiving the signal change of the pedal stroke sensor, then drives the control motor to act, and builds pressure on the whole system at the same time, so that the vehicle realizes the brake-by-wire of the auxiliary electro-hydraulic private brake assembly; and the brake pressure output by the auxiliary brake master cylinder is input into the hydraulic control unit through a third circuit and a fourth circuit which are connected with the shuttle valve, and pressure is built for the corresponding second brake.

2. The braking function is requested externally.

In this mode, when other electronic control systems of the vehicle send braking requests, the auxiliary electro-hydraulic servo braking assembly responds to the braking requests to build pressure on the whole braking system; at the moment, the brake pressure output by the auxiliary brake master cylinder is input into the hydraulic control unit through a third loop and a fourth loop which are connected with the shuttle valve, and pressure is built on a corresponding second brake; and realizing external request braking. The vacuum assist assembly does not participate in braking.

3. And a braking energy recovery auxiliary function.

On the premise of meeting the requirement of braking energy recovery, before the pedal stroke of the brake pedal is smaller than the preset stroke, the VCU of the whole vehicle sends a torque request for energy recovery according to the pedal stroke fed back by the pedal stroke sensor, and the driving motor of the whole vehicle responds to the recovery request and applies a reverse torque with a braking effect to the whole vehicle to realize the braking of the whole vehicle; when the stroke of the treaded brake pedal is larger than the preset stroke, the friction brake provided by the auxiliary electro-hydraulic servo assembly starts to intervene, and the friction brake and the reverse torque in the energy recovery process are provided together or only the friction brake provides the deceleration of the whole vehicle; the friction braking process is the same as the brake-by-wire process.

4. And a manual backup braking function.

When the vacuum booster and the electro-hydraulic servo brake assembly both fail, a driver can directly step on a brake pedal, the brake fluid in the main brake master cylinder is pushed to be compressed by pushing a piston of the brake master cylinder, pressure is generated in the first loop and the second loop, the brake pressure is input into the hydraulic control unit through the first loop, and pressure is built on the corresponding first brake; meanwhile, the brake pressure is input into the hydraulic control unit through a second loop and a fourth loop which are connected with the shuttle valve, and pressure is built up on a corresponding second brake; and manual backup braking is realized.

5. Redundant braking mode.

When the vacuum booster assembly and the electro-hydraulic servo brake assembly have faults or sensors of the electro-hydraulic servo brake assembly, the hybrid brake system described by the application can realize multiple redundant brake functions, and brake safety is guaranteed to the maximum extent.

(1) Redundant braking safety strategy for sensor failure handling

When the driver depresses the brake pedal:

if the brake pedal stroke sensor fails and the vacuum booster assembly works normally, the control motor of the auxiliary electro-hydraulic servo brake assembly performs power-assisted braking through 'fixed PWM control', and the vacuum booster performs normal power-assisted braking;

if the brake pedal stroke sensor fails and the vacuum booster assembly also fails, the vehicle brake is realized only through the manual backup brake function;

if the brake pedal stroke sensor works normally and the vacuum booster assembly breaks down, the vehicle brake is realized only through the manual backup brake function;

if brake pedal stroke sensor and vacuum booster assembly all work normally, then vacuum booster carries out normal helping hand braking, this moment: if the master cylinder piston stroke sensor and the current sensor both have faults, the control motor of the auxiliary electro-hydraulic servo brake assembly realizes the pressure build-up of the brake system through PWM control; if the master cylinder piston stroke sensor fails and the current sensor works normally, the control motor realizes the pressure build-up of the brake system through the control of a single current loop; if the master cylinder piston stroke sensor and the current sensor are normal, the control motor realizes the pressure build-up of the brake system through the 'double closed loop' control.

The fixed PWM control (PWM, pulse width modulation) refers to that when a pedal travel sensor is in fault, after a driver steps on a brake pedal (namely a brake switch is triggered), an auxiliary electro-hydraulic servo brake assembly outputs and controls a motor according to fixed PWM, so that the pressure build-up of a brake system and the braking of the whole vehicle are realized; the PWM control refers to the relation between the travel of the brake pedal and the PWM of the motor, and through the one-to-one corresponding relation, after a driver steps on the brake pedal for a certain travel, a brake system can correspondingly establish pressure with corresponding magnitude; the single current loop refers to the relation between the travel of the brake pedal and the control current of the motor, and through the one-to-one correspondence relation, after a driver steps on the brake pedal for a certain travel, the brake system can correspondingly build corresponding pressure; the unit arrangement ring refers to the relation between the travel of the brake pedal and the displacement of a piston mandril of a brake master cylinder, and through the one-to-one correspondence relation, after a driver steps on the brake pedal for a section of travel, a brake system can correspondingly establish pressure with corresponding magnitude; "double closed loop" refers to a closed loop control strategy that combines a single position loop and a single current loop.

(2) Redundant braking safety strategy for motor failure handling

When a driver steps on a brake pedal, if control motors of the vacuum booster assembly and the auxiliary electro-hydraulic servo brake assembly both break down, the manual backup brake is implemented only through the manual backup brake function; if the vacuum booster assembly fails and a control motor of the auxiliary electro-hydraulic servo brake assembly works normally, vehicle braking is implemented through a manual backup brake function and a brake-by-wire function provided by the auxiliary electro-hydraulic servo brake assembly; if the vacuum booster assembly works normally and a control motor of the auxiliary electro-hydraulic servo brake assembly fails, the vacuum booster assembly only brakes; if the control motors of the vacuum booster assembly and the auxiliary electro-hydraulic servo brake assembly work normally, the control motors of the vacuum booster assembly and the auxiliary electro-hydraulic servo brake assembly brake together.

As an expanded technical solution, preferably, in other embodiments, the brake pedal assembly is directly connected with a piston rod of the main brake master cylinder, and the main brake master cylinder is directly driven by the brake pedal assembly; and a spring for feeding back force sense is further arranged on the piston ejector rod, and a section of gap is reserved between the head of the piston ejector rod and the piston of the main brake master cylinder.

Furthermore, the hybrid brake system comprises two shuttle valves, first oil inlets of the two shuttle valves are respectively and correspondingly connected with two oil outlets of the main brake master cylinder through brake pipelines, second oil inlets of the two shuttle valves are respectively and correspondingly connected with two oil outlets of the auxiliary brake master cylinder through brake pipelines, and oil outlets of the two shuttle valves are respectively and correspondingly connected with two oil inlets of the hydraulic control unit through brake pipelines.

When the technical scheme is adopted, the vacuum booster is not involved, so that the vacuum booster is more suitable for vehicles with limited arrangement space of the front engine room and smaller tonnage. The shuttle valve can also be replaced by an electromagnetic reversing valve or a combination of a plurality of electromagnetic valves to realize the same function.

During normal braking, the pedal travel change can be input into a controller of the auxiliary electro-hydraulic servo brake assembly as a wire control signal, and then the auxiliary electro-hydraulic servo brake assembly provides brake system pressure.

When braking is requested externally, the auxiliary electro-hydraulic service brake assembly also provides brake system pressure.

With respect to braking energy recovery assist. After the brake pedal is stepped on, the preset gap needs to be eliminated, and then the piston can be abutted against the primary piston of the main brake master cylinder, and the piston is pushed forwards to compress brake fluid to build pressure. In the brake pedal stroke corresponding to clearance elimination, the brake energy recovery of the whole vehicle is realized, and the brake deceleration is provided. The excess deceleration demand is supplemented by an auxiliary electro-hydraulic servo brake assembly.

With respect to manual backup braking. When the vacuum booster and the electro-hydraulic servo brake assembly both fail, the manual force directly steps on the pedal to push the main brake main cylinder 5 to build pressure, and then the pressure is built on the whole brake system. The pressure build-up process is similar to systems having vacuum booster assemblies when implementing a human backup braking function.

With respect to the redundant braking portion, the vacuum assist portion is less described than what would be equivalent to a redundant braking strategy for a system having a vacuum booster assembly.

In summary, due to the adoption of the technical scheme, compared with the prior art, the hybrid brake system provided by the application has the following advantages:

1) on the premise of not changing the model selection of a single vacuum booster of the originally designed vehicle, the invention can be directly externally connected with an electro-hydraulic servo brake assembly to meet the braking requirement of the whole vehicle;

2) the hybrid braking system can reduce the axial size of the booster of the front engine room part and improve the collision safety of the original vehicle;

3) compared with a single vacuum booster scheme, the invention can realize more redundant braking functions;

4) compared with the single vacuum booster scheme, the invention can improve the original vehicle brake pedal feel to a certain extent, can realize more efficient brake energy recovery on the premise of ensuring the brake pedal feel, can realize external request braking (convenient for function expansion), and is little influenced by factors such as external air pressure and the like;

5) aiming at the cargo vehicle with obvious load transfer during braking, the invention can optimize the braking pressure distribution and reduce the loss of the brake.

Drawings

Fig. 1 is a schematic structural diagram of a hybrid brake system according to an embodiment of the present application.

FIG. 2 is a schematic structural diagram of an auxiliary electro-hydraulic servo brake assembly according to an embodiment of the present application.

FIG. 3 is a flow diagram of a redundant brake safety strategy control for sensor failure handling according to an embodiment of the present application.

FIG. 4 is a flow diagram of a redundant brake safety strategy control for motor failure handling according to one embodiment of the present application.

FIG. 5 is a schematic structural diagram of a hybrid braking system according to another embodiment of the present application.

Detailed Description

In order to make the technical solution of the embodiments of the present invention better understood, the technical solution of the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by equivalent changes and modifications by one skilled in the art based on the embodiments of the present invention, shall fall within the scope of the present invention.

Example one

Referring to fig. 1, the present embodiment provides a hybrid brake system, which includes a vacuum booster assembly 1, an auxiliary electro-hydraulic servo brake assembly 2, a brake pedal 3, a liquid storage tank 4, a main brake master cylinder 5, an auxiliary brake master cylinder 6, a shuttle valve 7, a Hydraulic Control Unit (HCU)8, and a brake set 9. Two ends of the vacuum booster assembly 1 are respectively connected with the main brake master cylinder 5 and the brake pedal 3, the brake pedal 3 in the embodiment is also provided with a pedal stroke sensor for detecting the pedal stepping stroke and a brake lamp switch for detecting the brake operation of the pedal, and the pedal stroke sensor, the brake lamp switch and the auxiliary electro-hydraulic servo brake assembly 2 are in communication connection through a CAN bus. The auxiliary electro-hydraulic servo brake assembly 2 is connected with an auxiliary brake main cylinder 6.

In this embodiment, the reservoir tank 4 is used to supply brake fluid to the main brake master cylinder 5 and the auxiliary brake master cylinder 6. Reservoir 4 is preferably connected to master cylinder 5 and to slave cylinder 6 via a low pressure line 10.

The front cavity oil outlet of the main brake master cylinder 5 is connected to the left side oil inlet of the hydraulic control unit 8 through a first circuit (circuit 1), and is connected with a first brake group in the brake groups 9 through the oil outlet of the hydraulic control unit 8. The oil outlet of the rear cavity of the main brake master cylinder 5 is connected to a first oil inlet a of a shuttle valve 7 through a second loop (loop 2), the oil outlet of the auxiliary brake master cylinder 6 is connected to a second oil inlet b of the shuttle valve 7 through a third loop (loop 3), and the oil outlet c of the shuttle valve 7 is connected to a right oil inlet of a hydraulic control unit 8 through a fourth loop (loop 4) and is connected with a second brake group in the brake group 9 through the oil outlet of the hydraulic control unit 8. In this embodiment, the brake lines in the

circuits

1, 2, 3, and 4 are all high-pressure lines 11.

In the present embodiment, the brake group 9 includes a left front wheel brake LF, a right front wheel brake RF, a left rear wheel brake LR, and a right rear wheel brake RR. The four brakes of the brake group 9 are grouped in pairs, and the first brake group consists of a left front wheel brake LF and a right front wheel brake RF; the second brake group is composed of a left rear wheel brake LR and a right rear wheel brake RR. The oil outlets of the hydraulic control unit 8 are connected with LF, RF, LR and RR respectively. At this time, the four brakes adopt an H-shaped arrangement mode, and more ideal pressure distribution can be realized on the H-shaped arrangement mode, so that the working frequency of the pressure regulating unit is reduced, and the service life of the pressure regulating unit is prolonged.

Referring to fig. 2, the auxiliary electro-hydraulic servo brake assembly 2 includes a mechanical assembly 201, a master cylinder piston stroke sensor 202, a control motor 203, an auxiliary controller 204, and a current sensor 205. Wherein the mechanical assembly 201 is connected to the auxiliary master cylinder 6. Specifically, auxiliary master cylinder 6 is connected to the left side of mechanical assembly 201. The master cylinder piston stroke sensor 202 and the current sensor 205 are respectively used for detecting the piston stroke of the auxiliary brake master cylinder 6 and controlling the current of the motor 203, and the auxiliary controller 204 is used for receiving sensor signals of the master cylinder piston stroke sensor 202 and the current sensor 205 and is used as a control basis. The pedal travel sensor and the brake lamp switch are in communication connection with the auxiliary controller 204 through a CAN bus. The control motor 203 is electrically connected with the auxiliary controller 204, and the control motor 203 is driven by the auxiliary controller 204 to act to push the ejector rod at the leftmost end of the mechanical assembly 201 so as to push the piston of the auxiliary brake master cylinder 6 to move for pressure building.

The shuttle valve 7 in this embodiment has two oil inlets a, b and an oil outlet c, and when the first oil inlet a and the second oil inlet b have no pressure, the valve core closes the first oil inlet a under the spring force of the internal spring. Therefore, in the present embodiment, the shuttle valve 7 has different conduction effects according to the pressure change at the two oil inlets a, b, thereby having the first operation state and the second operation state. In a first working state, the first oil inlet a is closed under the action of a spring force, the second oil inlet b is communicated with the oil outlet c, the second loop is not communicated with the fourth loop at the moment, and the third loop is communicated with the fourth loop; in a second working state, the pressure at the first oil inlet a is greater than the resultant force of the pressure at the second oil inlet b and the spring force, the first oil inlet a is opened, the first oil inlet a is communicated with the oil outlet c, at the moment, the second loop is communicated with the fourth loop, and the second oil inlet b is not communicated with the oil outlet c.

In the hybrid brake system of the present application, the primary function of the auxiliary electro-hydraulic service brake assembly 2 is to externally request braking. For the auxiliary electro-hydraulic servo brake assembly 2, when the auxiliary controller 204 receives an external braking request command such as a pedal stroke signal, a brake light switch signal, and the like, the command is output to the control motor 203 according to a calculation result to control the target, and the motor is driven to push the piston to move forward to build pressure on the brake system. The piston stroke sensor 202 and the current sensor 205 are used for closed loop control of displacement and current, respectively.

The hybrid brake system can realize a brake-by-wire function, an external request brake function, a brake energy recovery auxiliary function, a manual backup brake function, a redundant brake function and the like. Each function implementation process is described in detail below.

1. Brake-by-wire mode.

After a driver steps on the brake pedal 3 for a certain stroke, the vacuum booster assembly 1 builds pressure under vacuum boosting; meanwhile, the auxiliary controller 204 calculates a control target required by the motor by receiving the signal change of the pedal stroke sensor and the signal of the brake lamp switch, and then drives the motor 203 to act, and the two control targets build pressure on the whole brake system.

Regarding the pressure build-up process. When the main brake master cylinder 5 is pressurized, brake fluid is connected to a left circuit of a hydraulic control unit 8 through a circuit 1, and meanwhile, the brake fluid is also connected to an oil inlet a of a shuttle valve 7 through a circuit 2; when the auxiliary brake master cylinder 6 builds pressure, the brake fluid is connected to the oil inlet b of the shuttle valve 7 through the loop 3. Because the valve switch at the center of the shuttle valve is under the action of the leftward spring force, the oil inlet b is communicated with the oil outlet c when no pressure exists in the system; when the pressure at the oil inlet a is greater than the resultant force of the pressure at the oil inlet b and the spring force, the oil inlet a is communicated with the oil outlet c.

When the brake-by-wire is used for braking, the build-up pressure of the two brake master cylinders is basically equal, so that the brake fluid of the main brake master cylinder 5 basically flows into a left circuit of the hydraulic control unit 8 to control the braking of the two wheels of the first brake group; and the brake fluid of the auxiliary brake master cylinder 6 flows into the right loop of the hydraulic control unit 8 to control the braking of the other two wheels of the second brake group.

Regarding the pressure release process. When the brake pedal 3 is released, the compressed brake fluid respectively flows back to the liquid storage tank 4 through the loop 1 and the loop 4-the loop 3.

2. Externally requested braking mode

In this mode, when a braking request (external braking pressure or entire vehicle deceleration request) is issued by another electronic control system of the vehicle, a suitable motor control target is calculated in response to the braking request, and the direct drive control motor 203 is operated to build pressure on the brake system corresponding to the right side of the hydraulic control unit 8. The vacuum booster assembly 1 does not participate in braking.

Regarding the pressure build-up process. The auxiliary brake master cylinder 6 compresses brake fluid in a cavity, the brake fluid is connected to an oil inlet b of the shuttle valve 7 through the loop 3, then flows out of an oil outlet c, is connected to the right side of the hydraulic control unit 8 through the loop 4, and controls the braking of two wheels of the second brake group. When the pressure is released, the compressed brake fluid returns along the original path.

3. And a braking energy recovery auxiliary mode.

On the premise of meeting the braking energy recovery condition, according to a braking target curve, before a certain small section of travel (preset idle travel) is stepped on by a brake pedal 3, a vehicle controller of the whole vehicle sends a torque request for energy recovery according to the pedal travel fed back by a pedal travel sensor, a driving motor of the whole vehicle responds to the recovery request and applies a reverse torque with a braking effect to the whole vehicle, so that the braking of the whole vehicle is realized; according to the braking target curve, when the brake pedal 3 is larger than a certain stroke (idle stroke), the friction brake provided by the auxiliary electro-hydraulic servo brake assembly 2 starts to intervene, and the energy recovery is provided together or only the friction brake provides the deceleration of the whole vehicle. The friction braking process is the same as the brake-by-wire process.

4. Manual backup brake mode.

When all the vacuum boosters and the electro-hydraulic servo brake assemblies are in failure, a driver can directly step on the brake pedal 3, the piston of the main brake master cylinder 5 is pushed, brake fluid in the main brake master cylinder 5 is pushed to be compressed, pressure is generated in the loop 1 and the loop 2, and the pressure is transmitted to the brake group to brake wheels, so that manual backup braking is realized.

Regarding the pressure build-up process. The circuit 1 corresponding to the brake master cylinder 5 is directly connected to the left circuit of the hydraulic control unit 8 to control the braking of two wheels of the first brake group; the corresponding loop 2 is connected with an oil inlet a of the shuttle valve 7, and because no pressure exists in the loop 3, the valve can be opened after the pressure in the loop 2 is larger than the spring force of the shuttle valve 7, and the loop 2 is connected with the loop 4 through the oil inlet a and the oil outlet c of the shuttle valve 7 and finally connected to a right loop of the hydraulic control unit 8 to brake the other two wheels of the second brake set.

Regarding the pressure release process. When the brake pedal 3 is released, the pressure of the

circuits

1 and 2 is rapidly reduced, at the same time the valve of the shuttle valve 7 is closed, and the brake fluid flows from the circuit 1 back to the main brake master cylinder 5, from the circuit 4 to the oil outlet c and the oil inlet b of the shuttle valve 7, then flows back to the auxiliary brake master cylinder 6 through the circuit 3, and finally returns to the liquid storage tank 4.

5. Redundant braking mode.

When the vacuum booster assembly 1 and the auxiliary electro-hydraulic servo brake assembly 2 have faults or sensors of the vacuum booster assembly and the auxiliary electro-hydraulic servo brake assembly, the hybrid brake system described in the application can realize multiple redundant brake functions, and brake safety is guaranteed to the maximum extent.

(1) Redundant braking safety strategy for sensor failure handling

Referring to fig. 3, when the driver depresses the brake pedal 3:

if the brake pedal stroke sensor fails and the vacuum booster assembly 1 works normally, the control motor 203 of the auxiliary electro-hydraulic servo brake assembly 2 performs power-assisted braking through 'fixed PWM control', and the vacuum booster assembly 1 performs normal power-assisted braking;

if the brake pedal stroke sensor fails and the vacuum booster assembly 1 also fails, the vehicle brake is realized only through the manual backup brake function;

if the brake pedal stroke sensor works normally and the vacuum booster assembly 1 breaks down, the vehicle brake is realized only through the manual backup brake function;

if brake pedal stroke sensor and vacuum booster assembly 1 all work normally, then vacuum booster assembly 1 carries out normal helping hand braking, this moment: if the master cylinder piston stroke sensor 202 and the current sensor 205 both have faults, the control motor 203 of the auxiliary electro-hydraulic servo brake assembly 2 realizes the pressure build-up of the brake system through PWM control; if the master cylinder piston stroke sensor 202 fails and the current sensor 205 works normally, the control motor 203 realizes the pressure build-up of the brake system through the control of a single current loop; if the master cylinder piston stroke sensor 202 and the current sensor 205 are normal, the control motor 203 realizes the pressure build-up of the brake system through the 'double closed loop' control.

The 'fixed PWM control' (PWM, pulse width modulation) means that when a pedal stroke sensor is in fault, when a driver steps on a brake pedal 3 and triggers a brake lamp switch, an auxiliary electro-hydraulic servo brake assembly 2 outputs and controls a motor 203 according to fixed PWM to realize the pressure build of a brake system and the braking of the whole vehicle; the PWM control refers to the relation between the travel of the brake pedal and the PWM of the motor, and through the one-to-one corresponding relation, after a driver steps on the brake pedal 3 for a section of travel, a brake system can correspondingly build corresponding pressure; the single current loop refers to the relationship between the travel of the brake pedal and the control current of the motor, and through the one-to-one correspondence relationship, after the driver steps on the brake pedal 3 for a certain travel, the brake system can correspondingly build corresponding pressure; the unit position ring refers to the relation between the stroke of the brake pedal and the displacement of a piston mandril of a brake main cylinder, and through the one-to-one corresponding relation, after a driver steps on the brake pedal 3 for a section of stroke, a brake system can correspondingly establish pressure with corresponding magnitude; "double closed loop" refers to a closed loop control strategy that combines a single position loop and a single current loop.

(2) Redundant braking safety strategy for motor failure handling

Referring to fig. 4, when the driver steps on the brake pedal 3, if the control motors 203 of the vacuum booster assembly 1 and the auxiliary electro-hydraulic servo brake assembly 2 both fail, the manual backup brake is implemented only through the manual backup brake function; if the vacuum booster assembly 1 fails and the control motor 203 of the auxiliary electro-hydraulic servo brake assembly 2 works normally, vehicle braking is implemented through a manpower backup brake function and an auxiliary brake function provided by the auxiliary electro-hydraulic servo brake assembly 2; if the vacuum booster assembly 1 works normally and the control motor 203 of the auxiliary electro-hydraulic servo brake assembly 2 breaks down, the vacuum booster assembly 1 only performs power-assisted braking; if the control motors 203 of the vacuum booster assembly 1 and the auxiliary electro-hydraulic servo brake assembly 2 work normally, the control motors 203 of the vacuum booster assembly 1 and the auxiliary electro-hydraulic servo brake assembly 2 jointly brake.

Example two

The structure of the hybrid brake system in this embodiment is substantially the same as that in the first embodiment, except that: the first brake group in this embodiment is composed of a left rear wheel brake LR and a right rear wheel brake RR; the second brake group is composed of a left front wheel brake LF and a right front wheel brake RF. Four oil outlets of the hydraulic control unit 8 are respectively connected with LR, RR, LF and RF. At this time, the brake system is in an H-type arrangement.

EXAMPLE III

The structure of the hybrid brake system in this embodiment is substantially the same as that in the first embodiment, except that: the first brake group in this embodiment is composed of a left front wheel brake LF and a right rear wheel brake RR, and the second brake group is composed of a right front wheel brake RF and a left rear wheel brake LR. Four oil outlets of the hydraulic control unit 8 are respectively connected with LF, RR, RF and LR. At this time, the brake system is in an X-type arrangement.

Example four

The structure of the hybrid brake system in this embodiment is substantially the same as that in the first embodiment, except that: the first brake group in this embodiment is composed of a right front wheel brake RF and a left rear wheel brake LR, and the second brake group is composed of a left front wheel brake LF and a right rear wheel brake RR. Four oil outlets of the hydraulic control unit 8 are respectively connected with RF, LR, LF and RR. At this time, the brake system is in an X-type arrangement.

EXAMPLE five

The structure of the hybrid brake system in this embodiment is substantially the same as that in the first embodiment, except that: the vacuum booster assembly 1 is eliminated, the brake pedal 3 is directly connected with the piston ejector rod 1 of the main brake main cylinder 5, and the main brake main cylinder 5 is directly driven by the brake pedal 3; the piston mandril 1 is also provided with a spring for feeding back force feeling, and the spring is preferably a conical spring; a section of gap is reserved between the head of the piston ejector rod 1 and the piston of the main brake master cylinder 5; the hybrid brake system of the embodiment further includes two shuttle valves 71, 72, first oil inlets a of the two shuttle valves 71, 72 are respectively and correspondingly connected with two oil outlets of the front and rear chambers of the main brake master cylinder 5 through brake pipelines (loop 1 and loop 2), second oil inlets b of the two shuttle valves 71, 72 are respectively and correspondingly connected with two oil outlets of the front and rear chambers of the auxiliary brake master cylinder 6 through brake pipelines (loop 4 and loop 5), and oil outlets c of the two shuttle valves 71, 72 are respectively and correspondingly connected with two oil inlets on the left and right sides of the hydraulic control unit 8 through brake pipelines (loop 3 and loop 6).

The two

shuttle valves

71, 72 are constructed as in the first embodiment. Both have a first operating state and a second operating state; in a first working state, the first oil inlet a of the shuttle valve 71 is closed under the action of the spring force, the second oil inlet b is communicated with the oil outlet c, at the moment, the loop 4 is not communicated with the loop 3, and the loop 1 is communicated with the loop 3; the first oil inlet a of the shuttle valve 72 is closed under the action of the spring force, the second oil inlet b is communicated with the oil outlet c, at the moment, the loop 2 is not communicated with the loop 6, and the loop 5 is communicated with the loop 6. In the second working state, the pressure at the first oil inlet a of the shuttle valve 71 is greater than the resultant force of the pressure at the second oil inlet b and the spring force, the first oil inlet a is opened, the first oil inlet a is communicated with the oil outlet c, and the loop 1 is communicated with the loop 3; the second oil inlet b is not communicated with the oil outlet c. The pressure at the first oil inlet a of the shuttle valve 72 is greater than the resultant force of the pressure at the second oil inlet b and the spring force, the first oil inlet a is opened, the first oil inlet a is communicated with the oil outlet c, and at this time, the loop 2 is communicated with the loop 6. The second oil inlet b is not communicated with the oil outlet c.

When the technical scheme is adopted, the vacuum booster is not involved, so that the vacuum booster is more suitable for vehicles with limited arrangement space of the front engine room and smaller tonnage.

During normal brake-by-wire, the pedal stroke change may be input as an external request brake signal to the controller 203 of the auxiliary electro-hydraulic servo brake assembly 2, and then the brake system pressure is provided by the auxiliary electro-hydraulic servo brake assembly 2.

When braking is requested externally, the auxiliary electro-hydraulic service brake assembly 2 also provides brake system pressure.

With respect to braking energy recovery assist. Since the brake pedal 3 is pressed down and then the primary piston of the master cylinder 5 is pressed against after the preset gap is eliminated, the piston is pushed forward and then the brake fluid is compressed to build pressure. In the brake pedal stroke corresponding to clearance elimination, the brake energy recovery of the whole vehicle is realized, and the brake deceleration is provided. The excess deceleration demand is supplemented by the auxiliary electro-hydraulic service brake assembly 2.

With respect to manual backup braking. When the electro-hydraulic servo brake assemblies are all out of work, the pedals are directly stepped on by manpower to push the main brake cylinder 5 to build pressure, and then the pressure is built for the whole brake system. The pressure build-up process is similar to systems having vacuum booster assemblies when implementing a human backup braking function.

It should be noted that, in this embodiment, two shuttle valves may also be replaced by a solenoid directional valve or a combination of a plurality of solenoid valves, so as to achieve the same function.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention; while the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A hybrid brake system is characterized by comprising a brake pedal assembly (3), a main brake master cylinder (5) directly or indirectly driven by the brake pedal assembly (3), an auxiliary electro-hydraulic servo brake assembly (2), an auxiliary brake master cylinder (6) driven by the auxiliary electro-hydraulic servo brake assembly (2), a shuttle valve (7), a hydraulic control unit (8) and a brake set (9); wherein:

the shuttle valve (7) has two oil inlets (a, b) and one oil outlet (c); one of the oil outlets of the main brake master cylinder (5) is connected to one of the oil inlets of the hydraulic control unit (8) through a first circuit, and is connected with a first brake group in the brake groups (9) through the oil outlet of the hydraulic control unit (8); the other oil outlet of the main brake master cylinder (5) is connected to a first oil inlet (a) of the shuttle valve (7) through a second loop, the oil outlet of the auxiliary brake master cylinder (6) is connected to a second oil inlet (b) of the shuttle valve (7) through a third loop, the oil outlet (c) of the shuttle valve (7) is connected to the other oil inlet of the hydraulic control unit (8) through a fourth loop, and is connected with a second brake group in the brake group (9) through the oil outlet of the hydraulic control unit (8);

the hybrid brake system further comprises a pedal stroke sensor for detecting the treading stroke of the brake pedal assembly (3), and the pedal stroke sensor is in communication connection with the auxiliary electro-hydraulic servo brake assembly (2).

2. A hybrid braking system according to claim 1, characterized in that the auxiliary electro-hydraulic servo brake assembly (2) is connected to the auxiliary brake master cylinder (6), the auxiliary electro-hydraulic servo brake assembly (2) comprising a mechanical assembly (201), a master cylinder piston stroke sensor (202), a control motor (203), an auxiliary controller (204), a current sensor (205); wherein the mechanical assembly (201) is connected with the auxiliary brake master cylinder (6); the master cylinder piston stroke sensor (202) and the current sensor (205) are respectively used for detecting the piston stroke of the auxiliary brake master cylinder (6) and controlling the current of the motor (203), and the auxiliary controller (204) is used for receiving sensor signals of the master cylinder piston stroke sensor (202) and the current sensor (205) and is used as a control basis; the auxiliary controller (204) is in communication connection with the pedal stroke sensor and is used for receiving a pedal stroke signal detected by the pedal stroke sensor; the control motor (203) acts under the drive of the auxiliary controller (204) to push the piston of the auxiliary brake master cylinder (6) to move for pressure building.

3. A hybrid brake system according to claim 1, further comprising a vacuum booster assembly (1), both ends of the vacuum booster assembly (1) being connected to the brake pedal assembly (3) and the master cylinder (5), respectively, the brake pedal assembly (3) indirectly driving the master cylinder (5) through the vacuum booster assembly (1).

4. A hybrid braking system according to claim 1, characterized in that it further comprises a reservoir (4) for supplying brake fluid to the primary master cylinder (5) and to the secondary master cylinder (6).

5. A hybrid brake system according to claim 1, characterized in that a brake light switch is also mounted on the brake pedal assembly (3).

6. A hybrid brake system according to claim 1, characterized in that the brake pedal assembly (3) is directly connected with the piston ram (1) of the main brake master cylinder (5), the main brake master cylinder (5) being directly driven by the brake pedal assembly (3); the piston ejector rod (1) is further provided with a spring for feeding back force sense, and a gap is reserved between the head of the piston ejector rod (1) and the piston of the main brake master cylinder (5).

7. The hybrid brake system as claimed in claim 6, wherein the hybrid brake system comprises two shuttle valves, first oil inlets (a) of the two shuttle valves are correspondingly connected with two oil outlets of the main brake master cylinder through brake lines, respectively, second oil inlets (b) of the two shuttle valves are correspondingly connected with two oil outlets of the auxiliary brake master cylinder through brake lines, respectively, and oil outlets (c) of the two shuttle valves are correspondingly connected with two oil inlets of the hydraulic control unit through brake lines, respectively.

8. Hybrid braking system according to claim 1 or 6, characterized in that the shuttle valve (7) has a first operating condition and a second operating condition; in a first working state, the first oil inlet (a) is closed under the action of a spring force, and the second oil inlet (b) is communicated with the oil outlet (c); when the oil pump works in the first working state, the pressure at the first oil inlet (a) is greater than the resultant force of the pressure at the second oil inlet (b) and the spring force, the first oil inlet (a) is opened, the first oil inlet (a) is communicated with the oil outlet (c), and the second oil inlet (b) is not communicated with the oil outlet (c).

9. A hybrid braking system according to claim 1 or 6, characterized in that the brake group (9) comprises a left front wheel brake, a right front wheel brake, a left rear wheel brake and a right rear wheel brake;

the first brake group consists of a left front wheel brake and a right front wheel brake; the second brake group consists of the left rear wheel brake and the right rear wheel brake.

10. A hybrid braking system according to claim 1 or 6, characterized in that the brake group (9) comprises a left front wheel brake, a right front wheel brake, a left rear wheel brake and a right rear wheel brake;

the first brake group consists of a left rear wheel brake and a right rear wheel brake; the second brake group consists of the left front wheel brake and the right front wheel brake.