CN108275139B - Partially and fully decoupled compound electric power-assisted braking system - Google Patents

Abstract

The invention discloses a partially and completely decoupled compound electric power-assisted braking system, which solves the problems of difficult decoupling, high decoupling cost and poor pedal feel maintenance of a braking system in the prior art, and comprises a braking intention generating unit, an electric power-assisted assembly, a power-assisted motor assembly, a braking pedal and braking force decoupling component, a braking master cylinder assembly, an HCU and an electronic control unit; the brake pedal push rod of the brake intention generating unit is arranged in the power-assisted push rod and is connected with the electric power-assisted assembly, the screw rod of the electric power-assisted assembly is connected with the speed reducing mechanism in a meshed manner and is connected with the power-assisted motor assembly, the decoupling cylinder of the brake pedal and the braking force decoupling component is connected with the coupling push rod and is connected with the electric power-assisted assembly, the master cylinder push rod of the brake master cylinder assembly is connected with the decoupling cylinder and the brake pedal and is connected with the braking force decoupling component, the master cylinder is connected with the HCU, and the electronic control unit and the brake intention generating unit, the power-assisted motor assembly, the brake pedal and the braking force decoupling component are connected with the HCU through wires.

Description

Partially and fully decoupled compound electric power-assisted braking system

technical field

The invention relates to an automobile braking system, in particular to a composite electric power-assisted braking system with partial decoupling and complete decoupling functions.

Background technique

With the development of technology in the automotive field, the traditional hydraulic braking system can no longer meet people's requirements for high safety and high comfort vehicle performance. Especially in recent years, with the development trend of automobile electrification and intelligence, higher requirements are put forward for the automobile braking system. For electric vehicles, in order to increase the cruising range, the braking system must have regenerative braking capability; for intelligent vehicles, it is required that the vehicle must have the function of active braking. Obviously, the traditional hydraulic brake system can no longer meet the above requirements. In this context, brake-by-wire technology and electric power-assisted braking system came into being.

Compared with the traditional braking system, the essence of the brake-by-wire system is to cancel the physical connection between the brake pedal and the actuator, and replace it with sensors and motors. When the driver steps on the pedal, he actually steps on the sensor. The sensor converts the driver's intention into an electrical signal and sends it to the ECU to drive the motor to generate braking force. This essential feature of the brake-by-wire system has attracted the attention of automotive engineers. Taking electric vehicles as an example, for electric vehicles, braking energy recovery is a key technology, and braking energy recovery involves the decoupling of the braking system. For conventional braking systems, decoupling is difficult to achieve due to the physical connection between the brake pedal and the actuator. In other words, when the braking energy is recovered, for the traditional braking system, the driver depresses the brake pedal. At this time, the braking force of the brake depends not only on the pedal force, but also on the braking torque of the motor, which in turn is related to the rotational speed (vehicle speed). In this way, under the same pedal force, the brake braking force produced is not the same, which is extremely unfriendly to the driver. In view of the above-mentioned situation, brake-by-wire came into being. Due to the "flexible" connection between pedal and actuator, the problem of decoupling of the braking system is solved. Brake-by-wire technology currently mainly includes two forms: Electro-hydraulic brake system (EHB) and electro-mechanical brake system (EMB).

Although the brake-by-wire technology solves the problem of decoupling, its own defects restrict its own development. EMB is a form of brake-by-wire technology, which has the advantages of high integration and high electromechanical degree, but there is no real mass production now, and it is only displayed on some concept cars. This is because: EMB needs four sets of independent executive motors, and the cost is very high; the four sets of executive motors of EMB work in the locked-rotor condition for a long time, and the performance requirements of the motors are particularly high. Especially the front axle motor, due to the forward movement of the axle load during braking, requires a large torque, so the voltage requirement for the on-board power supply is relatively high, usually 42V; according to regulations, EMB requires an additional failure backup mechanism, which means that in the brake-by-wire system that does not have any hydraulic system, the hydraulic system needs to be re-arranged, which greatly increases the complexity of the system.

As another form of brake-by-wire system, EHB has been mass-produced, but its own defects are also obvious: the brake pressure of EHB is provided by a high-pressure accumulator, and it takes a certain amount of time to build up the pressure of the accumulator. Under long-term, high-intensity braking conditions, it is prone to insufficient brake pressure; although the failure backup mechanism is slightly simpler than EMB, it is still very complicated overall, which increases the cost of the system.

Compared with the brake-by-wire system, the electric power-assisted braking system occupies the mainstream position in the market. The electric power assist brake systems currently on the market are mainly divided into two categories. One is that it cannot realize the decoupling function by itself and needs to cooperate with other mechanisms to perform decoupling, which is expensive, such as Bosch’s Ibooster; the other is that it can realize decoupling by itself, but the structure is complex, and only partial decoupling can be achieved during decoupling, and complete decoupling cannot be performed, or both partial and complete decoupling can be achieved, such as Hitachi’s E-ACT system.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the problems existing in the prior art that the braking system is difficult to decouple, the cost of decoupling is expensive, and the pedal feel is not maintained well, and to provide a partially and completely decoupled composite electric power-assisted braking system.

In order to solve the above-mentioned technical problems, the present invention is realized by adopting the following technical solutions: the partially and completely decoupled compound electric power-assisted braking system includes a braking intention generation unit, an electric power-assisted assembly, a power-assisted motor assembly, a brake pedal and a braking force decoupling component, a brake master cylinder assembly, an HCU (23) and an electronic control unit (30);

The braking intention generating unit includes a brake pedal push rod;

The electric booster assembly includes a booster push rod, a screw, and a coupling push rod;

The booster motor assembly includes a PMSM motor and a reduction mechanism;

The brake pedal and braking force decoupling components include a decoupling cylinder;

The brake master cylinder assembly includes a master cylinder and a master cylinder push rod;

The braking intention generation unit is loaded into the booster push rod through the brake pedal push rod and connected to the electric power booster assembly. The electric power booster assembly is connected to the lower reduction mechanism through a screw rod and connected to the power booster motor assembly. The output end of the PMSM motor is connected to the input end of the reduction mechanism using a coupling. The master cylinder is connected to the HCU with pipelines, and the electronic control unit, braking intention generation unit, power-assist motor assembly, brake pedal and braking force decoupling components are connected to the HCU with signal lines.

The braking intention generation unit described in the technical solution includes a brake pedal, a pedal stroke sensor and an idle stroke adjusting screw; the pedal stroke sensor is installed on a bracket that adopts a pin shaft to install the brake pedal, the right end of the brake pedal push rod is connected to the upper end of the brake pedal through a hinge, the left end of the brake pedal push rod is machined with an internal thread hole in the axial direction, the right end of the idle stroke adjusting screw is processed with an external thread, the left end of the brake pedal push rod is connected with the right end of the idle stroke adjusting screw through threads, and the connected idle stroke adjusting screw and the brake pedal push rod are inserted into the booster In the push rod blind hole at the right end of the push rod, a gap is reserved between the left end face of the idle travel adjustment screw and the bottom surface of the push rod blind hole of the booster push rod.

The electric booster assembly described in the technical solution also includes a push rod return spring, a lead screw, a booster assembly shell, a buffer plate, a lead screw return spring and a coupled push rod return spring; the booster push rod is installed in the center hole of the lead screw, the push rod return spring is installed in the push rod blind hole at the right end of the booster push rod, the left end of the push rod return spring is fixed on the bottom surface of the push rod blind hole of the booster push rod, and the right end of the push rod return spring is in contact with the left end of the brake pedal push rod in the braking intention generating unit , There is a gap of 5-7mm between the bottom surface of the push rod blind hole of the booster push rod and the right end face of the idle stroke adjustment screw in the braking intention generating unit. The screw is sleeved on the lead screw, and balls are installed in the raceway between the screw and the lead screw. The periphery of the coupling push rod is in contact with the left end face of the lead screw. The buffer plate is fixed in the groove on the right end of the coupling push rod by welding. The right end face of the buffer plate is in contact with the left end face of the booster push rod. The right end surface of the spring is in contact with the left end surface of the lead screw; the stiffness of the return spring of the lead screw is greater than the stiffness of the return spring of the coupling push rod.

The coupling push rod described in the technical solution is composed of the left end decoupling cylinder piston, the middle push rod and the right end push plate. The left end decoupling cylinder piston and the right end push plate are disc-like structural members, the middle push rod is a straight rod structure with equal circular cross section, the left end decoupling cylinder piston, the middle push rod and the right end push plate are sequentially connected into one body. The coupling cylinder piston is put into the decoupling cylinder to form a sliding connection. A cylindrical groove is processed on the right end surface of the right push plate. The cylindrical groove is in line with the rotation axis of the right push plate. The depth of the cylindrical groove is equal to the thickness of the buffer plate in the electric power assist assembly.

The booster push rod described in the technical solution is a cylindrical structural member, the right end of the booster push rod is processed with a push rod blind hole along the axis, the rotation axis of the push rod blind hole is collinear with the rotation axis of the booster push rod, the diameter of the booster push rod is equal to the diameter of the center hole of the screw, and the length of the booster push rod is equal to the length of the center hole of the screw;

The screw is a two-stage stepped shaft structure. A screw through hole is processed at the axis of rotation of the screw. The inner surface of the screw through hole is provided with an inner helical groove that cooperates with the outer helical groove on the lead screw to form a helical raceway for rolling balls; the diameter of the left section of the screw is larger than that of the right section, and the periphery of the left section of the screw is provided with gear teeth that mesh with the speed reduction mechanism.

The brake pedal and braking force decoupling component described in the technical solution also includes a complete decoupling liquid storage chamber, a two-position two-way solenoid valve, a master cylinder push rod return spring, a one-way valve, a proportional pressure control valve, a partial decoupling accumulator and a hydraulic pressure sensor; The left end of the rod return spring is fixed on the inner end surface of the left cylinder wall of the decoupling cylinder, the right end of the push rod return spring of the master cylinder is in contact with the left end face of the decoupling cylinder piston at the right end of the master cylinder push rod, the complete decoupling liquid storage chamber is connected with the upper end of the decoupling cylinder through a hydraulic pipeline, and a two-position two-way solenoid valve is set between the fully decoupling liquid storage chamber and the hydraulic pipeline of the decoupling cylinder; A proportional pressure control valve and a one-way valve are arranged in parallel between the hydraulic pipelines. The liquid inlet of the one-way valve is connected to the liquid inlet and outlet of the partial decoupling accumulator, and the liquid outlet of the proportional pressure control valve is connected to the liquid inlet and outlet of the accumulator when it is partially decoupled.

The brake master cylinder assembly described in the technical solution includes a liquid storage chamber, a second piston return spring, a second piston and a first piston return spring; the second piston is installed in the master cylinder, and the master cylinder is divided into a left cavity and a right cavity. The left end of the second piston is in contact with the left end surface of the second piston, and the left end of the return spring of the second piston acts on the inner end surface of the left cylinder wall of the master cylinder. The left and right chambers of the master cylinder are connected to the liquid storage chamber by hydraulic pipelines, and the lower ends of the left and right chambers of the master cylinder are connected to the hydraulic control unit by hydraulic pipelines.

The master cylinder push rod described in the technical solution is composed of the first piston at the left end, the push rod and the decoupling cylinder piston at the right end. The first piston and the decoupling cylinder piston at the right end are disc-like structural members, and the push rod is a straight rod-like structural member with an equal circular cross section. The decoupling cylinder piston at the right end of the master cylinder push rod is packed into the decoupling cylinder to form a sliding connection, and the first piston of the master cylinder push rod is packed into the right chamber of the master cylinder to form a sliding connection.

The connection between the electronic control unit, the braking intention generating unit, the power assist motor assembly, the brake pedal and the braking force decoupling component and the HCU mentioned in the technical solution means that the electronic control unit is connected to the signal end of the PMSM motor through the wiring harness and the pedal travel sensor, two-position two-way solenoid valve, HCU, proportional pressure control valve, hydraulic pressure sensor.

Compared with prior art, the beneficial effects of the present invention are:

1. The partial and complete decoupling compound electric power-assisted braking system described in the present invention can realize the complete decoupling of the brake pedal and the frictional braking force when the braking force demand is small for electric vehicles. The braking force required by the electric power-assisted braking system is completely provided by the braking force generated by the energy recovery device, thereby recovering energy to the greatest extent and improving the cruising range of electric vehicles;

2. The partly and completely decoupled hybrid electric power-assisted braking system described in the present invention is for an electric vehicle. When the braking force provided by the braking energy recovery device cannot meet the total braking force requirement, the partial decoupling of the brake pedal and the frictional braking force can be realized. Part of the braking force required by the electric power-assisted braking system is provided by the frictional braking force, and the other part is provided by the regenerative braking force, so as to realize the coordination of frictional braking and regenerative braking. While meeting the braking demand, the braking energy is recovered to improve the cruising range of the vehicle;

3. No matter whether the partial and complete decoupling compound electric power-assisted braking system described in the present invention is working in a partially decoupled or completely decoupled state, the total braking force curve generated by the electric power-assisted braking system is completely consistent with the braking force curve generated without decoupling, and the dynamic characteristics of the electric power-assisted braking system are good;

4. The partly and completely decoupled composite electric power-assisted braking system described in the present invention is not directly connected between the decoupling component and the brake pedal. Even if the decoupling component fluctuates slightly in pressure, through the control of the booster motor, it can also ensure that the pedal feeling of the braking system when it is working in the decoupling state is the same as that in the non-decoupling state, so that the road feel of the driver is not affected at all;

5. When the partly and completely decoupled composite electric power-assisted braking system described in the present invention is working in the failure state, the pedal push rod can push the master cylinder push rod only by overcoming the resistance of the coupling push rod return spring, instead of overcoming the resistance of the lead screw return spring to drive all the components including the lead screw pair, deceleration mechanism and PMSM motor to move together, thereby reducing the pedal resistance and to a certain extent reducing the braking burden of the driver when the brake system fails;

6. The partly and completely decoupled composite electric power-assisted braking system described in the present invention can adjust the pedal idle travel, so as to meet the requirements of different vehicles for the braking jump point, or adjust the comfort level of the same model vehicle with different comfort levels, and has good adaptability;

7. The partial and complete decoupling compound electric power-assisted braking system of the present invention can filter out the feedback fluctuation force transmitted to the brake pedal through the booster push rod to a certain extent through the buffer plate provided, thereby improving the comfort during braking.

Description of drawings

Below in conjunction with accompanying drawing, the present invention will be further described:

Fig. 1 is a schematic diagram of the structural composition of a partially and completely decoupled compound electric power-assisted braking system according to the present invention;

In the figure: 1. Brake pedal, 2. Pedal travel sensor, 3. Brake pedal push rod, 4. Idling travel adjustment screw, 5. Push rod return spring, 6. Booster push rod, 7. Screw, 8. Lead screw, 9. Booster assembly shell, 10. Buffer disc, 11. Coupling push rod, 12. Lead screw return spring, 13. Coupling push rod return spring, 14. Complete decoupling liquid storage chamber, 15. Two-position two-way solenoid valve, 16. Decoupling cylinder, 17. Master cylinder push rod return spring, 18. Liquid storage chamber, 19. Master cylinder, 20. Second piston return spring; 21. Second piston; 22. First piston return spring; 23. HCU;

Detailed ways

The present invention is described in detail below in conjunction with accompanying drawing:

The partially and fully decoupled compound electric power-assisted braking system includes a braking intention generating unit, an electric power-assist assembly, a power-assist motor assembly, a brake pedal and a braking force decoupling component, a brake master cylinder assembly, HCU23 and an electronic control unit 30 .

The braking intention generating unit includes a brake pedal 1 , a pedal travel sensor 2 , a brake pedal push rod 3 and an idle travel adjusting screw 4 .

What described pedal travel sensor 2 adopts is Hall type angle sensor, belongs to standard part. The brake pedal push rod 3 is a cylindrical structural member, the left end is provided with an internal thread blind hole along the axial direction, and the right end is provided with a pin shaft through hole radially for installing the pin shaft. The idle stroke adjusting screw 4 is a cylindrical structural member; the pedal stroke sensor 2 is installed on the bracket that adopts the pin shaft to install the brake pedal 1, the right end of the brake pedal push rod 3 is connected with the upper end of the brake pedal 1 through the pin shaft, and the right end of the idle stroke adjusting screw 4 is processed with an external thread, and the brake pedal push rod 3 and the idle stroke adjusting screw 4 are connected by threads.

The electric booster assembly includes a push rod return spring 5, a booster push rod 6, a screw 7, a lead screw 8, a booster assembly housing 9, a buffer plate 10, a coupling push rod 11, a lead screw return spring 12 and a coupling push rod return spring 13.

The push rod return spring 5, lead screw return spring 12 and coupling push rod return spring 13 are all cylindrical springs and belong to standard parts. The booster assembly shell 9 is a cuboid shell with an open lower end, which is a non-standard part. The buffer disc 10 is a cylindrical rubber part, which is a standard part.

The booster assembly casing 9 is the installation base of the electric booster assembly, and the right end surfaces of the booster push rod 6, the screw rod 7, and the lead screw 8 all act on the right inner wall surface of the booster assembly casing 9 in the normal position, and the right limit position is limited by the booster assembly casing 9.

A central through hole is processed on the axis of rotation of the screw 8, and the booster push rod 6 is installed in the center through hole. The booster push rod 6 is collinear with the axis of rotation of the through hole and can move relatively axially; the outer circumference of the screw 8 is provided with an outer helical groove for installing balls, and the outer circumference of the screw 8 is meshed with the inner circumference of the screw 7 to form a screw pair.

The screw 7 is a two-stage stepped shaft structure, the rotation axis of the screw 7 is processed with a screw through hole, and the inner surface of the screw through hole is provided with an inner helical groove for installing balls, and the outer helical groove on the screw 8 and the inner helical groove on the screw 7 cooperate together to form a helical raceway for ball rolling;

The booster push rod 6 is a cylindrical structural member, the right end of the booster push rod 6 is processed with a push rod blind hole, the axis of rotation of the push rod blind hole is collinear with the axis of rotation of the booster push rod 6, the diameter of the booster push rod 6 is equal to the diameter of the center hole of the screw 8, and the length of the booster push rod 6 is equal to the length of the center hole of the lead screw 8; the idle travel adjustment screw 4 and the brake pedal push rod 3 are loaded into the push rod blind hole; There is a gap of 5-7mm reserved between them. By changing the length of the threaded fit between the idle stroke adjustment screw 4 and the brake pedal push rod 3, the size of the reserved gap can be changed, thereby forming different pedal idle strokes to meet the requirements of different vehicles for braking jump points, or to adjust the comfort level of the same model vehicle. The left end of the push rod return spring 5 is fixed on the bottom end face of the push rod blind hole of the booster push rod 6, and the right end abuts against the left end face of the brake pedal push rod 3. When the idle stroke of the pedal changes, the pretightening force of the push rod return spring 5 also changes accordingly.

The coupling push rod 11 is an I-shaped structure. The coupling push rod 11 is composed of a left-end decoupling cylinder piston, a middle push rod and a right-end push plate. The left-end decoupling cylinder piston and the right-end push plate are disc-like structural members. The diameters of the decoupling cylinder 16 are equal, the piston of the left end decoupling cylinder is put into the decoupling cylinder 16 to form a sliding connection, and a cylindrical groove is processed on the right end surface of the right end push plate. The right end face of 10 is contacted and connected with the left end face of booster push rod 6; coupling push rod return spring 13 and lead screw return spring 12 are set inside and outside and coaxially arranged; The stiffness of bar return spring 12 is much larger than the stiffness of coupling push rod return spring 13.

The booster motor assembly includes a PMSM motor 29 and a reduction mechanism 31 .

The PMSM motor 29 is a permanent magnet synchronous DC motor. The deceleration mechanism 31 is a gear-driven deceleration and torque increasing device. The output shaft of the PMSM motor 29 links to each other with the input shaft of the reduction mechanism 31 , and the output end gear of the reduction mechanism 31 meshes with the gear teeth on the left end of the screw rod 7 .

The brake pedal and braking force decoupling components include a complete decoupling liquid storage chamber 14, a two-position two-way solenoid valve 15, a decoupling cylinder 16, a master cylinder push rod return spring 17, a one-way valve 25, a proportional pressure control valve 26, a partially decoupling accumulator 27 and a pressure sensor 28.

The complete decoupling liquid storage chamber 14 and the decoupling cylinder 16 are cylindrical shell parts, which are non-standard parts. The two-position two-way solenoid valve 15, the one-way valve 25 and the proportional pressure control valve 26 belong to valve components and are all standard parts. Master cylinder push rod return spring 17 is a cylindrical spring, which is a standard part. Part of the decoupling accumulator 27 is a capsule-compartment gas accumulator, which is a standard part. The hydraulic pressure sensor 28 is standard.

The right end of the decoupling cylinder 16 is set on the left end of the coupling push rod 11 , and the left end of the decoupling cylinder 16 is set on the right end of the master cylinder push rod 24 . The master cylinder push rod return spring 17 is set on the push rod of the master cylinder push rod 24, the left end of the master cylinder push rod return spring 17 is fixed on the inner end face of the left cylinder wall of the decoupling cylinder 16, and the right end of the master cylinder push rod return spring 17 is in contact with the left end face of the master cylinder push rod 24 right end. The complete decoupling liquid storage chamber 14 is arranged on the upper end of the decoupling cylinder 16 and communicates with the small hole on the upper end surface of the decoupling cylinder 16 through a hydraulic pipeline. A two-position two-way electromagnetic valve 15 is arranged between the hydraulic pipeline of the fully decoupling liquid storage chamber 14 and the decoupling cylinder 16; the partial decoupling accumulator 27 is arranged at the lower end of the decoupling cylinder 16, and the partial decoupling accumulator 27 communicates with the small hole on the lower end surface of the decoupling cylinder 16 through the hydraulic pipeline, and a proportional pressure control valve 26 and a one-way valve 25 are arranged in parallel between the partially decoupling accumulator 27 and the hydraulic pipeline of the decoupling cylinder 16. The liquid inlet is connected to the liquid inlet and outlet of the partial decoupling accumulator 27, the liquid outlet of the check valve 25 is connected to the decoupling cylinder 16 by a hydraulic pipeline, the liquid outlet of the proportional pressure control valve 26 is connected to the liquid inlet and outlet of the partial decoupling accumulator 27 by a hydraulic pipeline, the liquid inlet of the proportional pressure control valve 26 is connected to the decoupling cylinder 16 by a hydraulic pipeline, and the proportional pressure control valve 26 and the one-way valve 25 are respectively used for the liquid inlet and discharge of the partial decoupling accumulator 27. A hydraulic pressure sensor 28 is provided on the hydraulic pipeline between the liquid inlet and outlet of the partial decoupling accumulator 27 and the liquid outlet of the proportional pressure control valve 26 to monitor the pressure of the accumulator 27 in real time during partial decoupling, so as to realize precise control of the braking force during partial decoupling.

The brake master cylinder assembly includes a liquid storage chamber 18 , a master cylinder 19 , a second piston return spring 20 , a second piston 21 , a first piston return spring 22 and a master cylinder push rod 24 .

Although the liquid storage chamber 18 and the master cylinder 19 are not standard parts, they have basically been standardized in the industry, so they can be selected according to needs. The second piston return spring 20 and the first piston return spring 22 are cylindrical springs, which are standard parts. The second piston 21 is a cylindrical structural part, which cooperates with the inner wall of the master cylinder 19 and is a standard part.

The second piston 21 is placed in the master cylinder 19, and the master cylinder is divided into a left chamber and a right chamber. The main cylinder push rod 24 is processed into an I-shaped shape, which is composed of the first piston at the left end, the push rod and the decoupling cylinder piston at the right end. The first piston and the decoupling cylinder piston are disc-like structural members, and the push rod is a straight rod-like structural member with a circular cross section. The first piston, push rod and decoupling cylinder piston are connected in sequence. The right end decoupling cylinder piston of master cylinder push rod 24 is packed in the decoupling cylinder 16 and becomes sliding connection, and the left end of master cylinder push rod 24 is the first piston and is packed into the right chamber of master cylinder 19 and becomes sliding connection. The first piston return spring 22 is in the right cavity, the right end of the first piston return spring 22 acts on the left end face of the first piston in the master cylinder push rod 24, and the left end of the first piston return spring 22 acts on the right end face of the second piston 21. The second piston return spring 20 is in the left cavity, the right end of the second piston return spring 20 acts on the left end face of the second piston 21, and the left end of the second piston return spring 20 acts on the inner left end face of the master cylinder 19. The upper ends of the left and right chambers of the master cylinder 19 are respectively provided with an oil hole, which is connected to the liquid storage chamber 18 through a hydraulic pipeline.

The HCU23 has 2 liquid inlets and 4 liquid outlets. The left chamber liquid inlet of HCU23 is connected with the left chamber liquid outlet of master cylinder 19 through pipelines, the right chamber liquid inlet of HCU23 is connected with the right chamber liquid outlet of master cylinder 19 through pipelines, and the four liquid outlets of HCU23 are respectively connected with the wheel cylinders on the four wheels of the vehicle through pipelines.

The electronic control unit 30 is connected with the pedal travel sensor 2 , the two-position two-way solenoid valve 15 , the HCU 23 , the proportional pressure control valve 26 , the hydraulic pressure sensor 28 , and the signal terminals of the PMSM motor 29 through a wiring harness.

The idling adjustment screw 4 of the braking intention generation unit is loaded into the blind hole at the right end of the booster push rod 6 in the electric power booster assembly, and the idling adjustment screw 4 and the blind hole at the right end of the booster push rod 6 have a gap of 5-7mm reserved on the bottom surface of the hole. The left end gear of the screw rod 7 in the electric booster assembly meshes with the gear in the reduction mechanism 31 of the booster motor assembly; a brake pedal and braking force decoupling component is arranged between the electric booster assembly and the brake master cylinder 19 of the brake master cylinder assembly, and the left end of the coupling push rod 11 of the electric booster assembly is inserted into the decoupling cylinder 16 of the brake pedal and braking force decoupling component. The right end of the master cylinder pushrod 24 of the brake master cylinder assembly is loaded into the left half of the decoupling cylinder 16 of the brake pedal and the braking force decoupling component; the master cylinder 19 of the brake master cylinder assembly is connected to the liquid inlet of the HCU23 through the hydraulic pipeline provided below.

The working principle of the partially and fully decoupled compound electric power-assisted braking system described in the present invention:

1. Electric power assist status

The electric power assist function is the most basic functional requirement of the partially and fully decoupled compound electric power assist braking system described in the present invention. When the partly and completely decoupled compound electric power assist braking system of the present invention is working in the electric power assist state, the two-position two-way solenoid valve 15 in the partly and completely decoupled compound electric power assist braking system of the present invention works in the normally closed position of complete decoupling without power supply, and the solenoid valve 15 is in the cut-off state. At the same time, the proportional pressure control valve 26 used for partial decoupling in the electric power-assisted braking system is also in a cut-off state when it is not energized. At this time, the liquid inside the decoupling cylinder 16 is in a closed state. According to the incompressibility of the liquid, the liquid inside the decoupling cylinder 16 transmits the force between the coupling push rod 11 and the master cylinder push rod 24 like a rigid body. When the brake pedal 1 is just stepped on, the idle travel adjustment screw rod 4 needs to overcome the reserved gap with the booster push rod 6 before contacting the booster push rod 6 . Because the pretightening force of the push rod return spring 5 is less than the pretightening force of the coupling push rod return spring 13, before the idle travel adjustment screw 4 contacts the inner end face of the boost push rod 6, the boost push rod 6 does not move, and the electric power assist system does not work. This stage belongs to the idle travel stage of the brake pedal 1 . By changing the threaded length of the idle stroke adjustment screw 4 and the brake pedal push rod 3, the reserved clearance can be changed to form different pedal idle strokes, which can meet the requirements of different vehicles on the brake jump point, or adjust the comfort level of the same model vehicle. After the idle travel adjustment screw 4 contacts the inner end surface of the booster push rod 6, the brake pedal 1 is continued to be stepped on, and the electric booster stage is entered. In this stage, the pedal stroke sensor 2 transmits the obtained pedal rotation angle signal to the electronic control unit 30, and the electronic control unit 30 senses the driver's braking intention after processing the signal, thereby sending an instruction to the PMSM motor 29 to make it generate a certain torque. parking. In the electric power assist stage, the resultant force formed by the force generated by the driver stepping on the pedal and the force generated by the PMSM motor 29 can be decomposed: the driver's force on the brake pedal 1 is only used to overcome the spring force of the coupling push rod return spring 13, thereby forming a pedal feel; part of the force generated by the PMSM motor 29 is used to overcome the spring force of the lead screw return spring 12, and the other part is used to push the coupling push rod 11 to move to the left to form a braking force. After decomposing like this, the control logic of PMSM motor 29 can be made simple, can not produce influence on the control algorithm of PMSM motor 29 because the force that the driver steps on brake pedal 1 and the force that PMSM motor 29 produces are coupled together;

2. Completely decoupled state

For electric vehicles, when the demand for braking force is small, the braking force required by the partly and completely decoupled compound electric power-assisted braking system described in the present invention is all generated by the braking energy recovery device. At this time, the partly and completely decoupled compound electric power-assisted braking system works in a completely decoupled state. In this state, the two-position two-way solenoid valve 15 for complete decoupling is energized and opened, and the two-position two-way solenoid valve 15 is in the conduction state; the proportional pressure control valve 26 for partial decoupling is in the cut-off state without power supply. When the driver depresses the brake pedal 1, the PMSM motor 29 does not work, and the electric power assist system is in a closed state. Under the action of the force of the driver stepping on the brake pedal, the booster push rod 6 pushes the coupling push rod 11 through the buffer disc 10 to move forward against the spring force of the coupling push rod return spring 13 . Since the two-position two-way solenoid valve 15 is in a conduction state, under the action of the coupling push rod 11 , the liquid in the decoupling cylinder 16 enters the complete decoupling liquid storage chamber 14 through the two-position two-way solenoid valve 15 . At this time, no hydraulic pressure is established in the decoupling cylinder 16, so the master cylinder push rod 24 remains motionless under the action of the master cylinder push rod return spring 17, neither the rear cavity nor the front cavity of the master cylinder 19 builds up braking pressure, and the braking force required by the partially and fully decoupled compound electric power-assisted braking system is completely generated by the braking energy recovery device. Release the brake pedal 1, the brake is released, and the liquid in the completely decoupling liquid storage chamber 14 returns to the decoupling cylinder 16 under the action of gravity, and then the two-position two-way solenoid valve 15 is powered off and cut off.

3. Partial decoupling state

For electric vehicles, when the braking force provided by the braking energy recovery device cannot meet the total braking force requirement, part of the braking force required by the partially and completely decoupled composite electric power-assisted braking system of the present invention is provided by frictional braking force, and the other part is provided by regenerative braking force. At this time, the partially and completely decoupled composite electric power-assisted braking system of the present invention works in a partially decoupled state. In this state, the two-position two-way solenoid valve 15 for complete decoupling is normally closed; the proportional pressure control valve 26 for partial decoupling is energized, and its energized current is adjusted in real time according to the requirements of the electric power-assisted braking system, so that the opening pressure of the proportional pressure control valve 26 meets the requirements of the electric power-assisted braking system. The cracking pressure of the electromagnetic pressure control valve 26 will be specifically described below. Assuming that under a certain pedal stroke, the pedal stroke sensor 2 transmits the detected rotation angle signal to the electronic control unit 30, and the electronic control unit 30 calculates that a total braking force of F should be generated at this time. Since the partial and complete decoupling compound electric power-assisted braking system described in the present invention is working in a partially decoupled state, the braking force required by the electric power-assisted braking system is jointly generated by the regenerative braking force F1 and the frictional braking force F2, namely F1+F2=F. Then the frictional braking force F2=F-F1, convert F2 to the right end surface of the master cylinder push rod 24, and obtain the hydraulic pressure with a pressure P on the right end surface of the master cylinder push rod 24 at this time, that is, the pressure inside the decoupling cylinder 16 should be P. At this time, the electronic control unit 30 controls the PMSM motor 29 to generate a boost torque corresponding to the pressure P. And because the proportional pressure control valve 26 is in the conduction state, the pressure P inside the decoupling cylinder 16 should be equal to the sum of the opening pressure P1 of the proportional pressure control valve 26 and the accumulator pressure P2 (back pressure), that is, P=P1+P2. Then the opening pressure of the proportional pressure control valve 26 is P1=P−P2, and P2 is obtained through the hydraulic pressure sensor 28 . After calculating the cracking pressure of the proportional pressure control valve 26, the energizing current I of the proportional pressure control valve 26 corresponding to the cracking pressure P1 can be obtained according to the current characteristic when the proportional pressure control valve 26 is opened. At the next pedal position, the energizing current of the proportional pressure control valve 26 and the motor assist torque of another pedal position can be obtained through the same algorithm. By analogy, a series of energized currents of the proportional pressure control valve 26 and boosting torque of the motor 29 at different pedal positions in a partially decoupled state can be obtained, so that the total braking force curve generated when the system works in the partially decoupled state is completely consistent with the braking force curve generated when the system is working in the electric power assist state, and the dynamic characteristics of the electric power assist braking system during braking are good. When the driver releases the brake pedal 1, the brake is released, and the proportional pressure control valve 26 is powered off and cut off. Since the partial decoupling accumulator 27 stores a relatively high-pressure liquid, the check valve 25 is opened under the action of the hydraulic pressure, and the liquid in the partial decoupling accumulator 27 returns to the decoupling cylinder 16 through the check valve 25 . If the system is in a fully decoupling state before the partial decoupling state, then when the brake pedal 1 is released, the two-position two-way solenoid valve 15 will be temporarily energized and opened, and the liquid in the completely decoupling liquid storage chamber 14 will return to the decoupling cylinder 16 under the action of gravity, and then the two-position two-way solenoid valve 15 will be powered off and cut off. If the electric power-assisted braking system works in a partially decoupled state from the beginning of braking, the two-position two-way solenoid valve 15 is always in a cut-off state.

4. Active braking status

When it is detected by other on-board sensors (not shown in the figure) that the vehicle needs to be braked and the driver has not stepped on the brake pedal, the electronic control unit 30 sends an instruction to the PMSM motor 29 to generate a certain torque to drive the master cylinder push rod 24 to move to the left, thereby generating frictional braking force to slow down or stop the vehicle. In the active braking state, the 2-position 2-normal solenoid valve 15 used for complete decoupling in the electric power-assisted braking system is normally closed when it is not energized. At the same time, the electromagnetic pressure control valve 26 used for partial decoupling in the electric power-assisted braking system is also in a cut-off state when it is not energized. During active braking, the brake pedal 1 does not move, and the driver can step on the brake pedal 1 so that the pedal travel sensor 2 generates a rotation angle signal and transmits it to the electronic control unit 30, ending the active braking state, and then the electric power-assisted braking system enters the electric power-assisted state.

5. Failed backup status

When the electric booster system fails, the driver can step on the brake pedal 1 to push the booster push rod 6 to drive the coupling push rod 11 to move to the left, and then push the master cylinder push rod 24 to move to the left, thereby establishing oil pressure in the front and rear chambers of the brake master cylinder 19, and the vehicle decelerates or stops when friction braking force is generated. In the fail-back state, the two-position two-way solenoid valve 15 used for complete decoupling in the electric power-assisted braking system is normally closed without power. At the same time, the electromagnetic pressure control valve 26 used for partial decoupling in the electric power-assisted braking system is also in a cut-off state when it is not energized. Because the driver only needs to overcome the spring force of the coupling push rod return spring 13 when pushing the coupling push rod 11 to move forward under the failure backup state, it does not need to overcome the spring force of the lead screw return spring 12 whose stiffness is much larger than the coupling push rod return spring 13.

Claims (4)

1. The combined type electric power-assisted braking system with partial and complete decoupling is characterized by comprising a braking intention generating unit, an electric power-assisted assembly, a power-assisted motor assembly, a brake pedal and braking force decoupling component, a brake master cylinder assembly, an HCU (23) and an electronic control unit (30);

the power-assisted motor assembly comprises a PMSM motor (29) and a speed reducing mechanism (31);

the brake master cylinder assembly comprises a master cylinder (19) and a master cylinder push rod (24);

the braking intention generating unit comprises a braking pedal (1), a pedal stroke sensor (2), a braking pedal push rod (3) and a idle stroke adjusting screw rod (4);

the pedal stroke sensor (2) is arranged on a bracket for installing the brake pedal (1) by adopting a pin shaft, the right end of the brake pedal push rod (3) is connected with the upper end of the brake pedal (1) through a hinge, an internal threaded hole is machined in the left end of the brake pedal push rod (3) along the axial direction, an external thread is machined in the right end of the idle stroke adjusting screw rod (4), the left end of the brake pedal push rod (3) is connected with the right end of the idle stroke adjusting screw rod (4) through threads, the connected idle stroke adjusting screw rod (4) and the brake pedal push rod (3) are arranged in a push rod blind hole in the right end of the power-assisted push rod (6), and a gap is reserved between the left end face of the idle stroke adjusting screw rod (4) and the hole bottom surface of the push rod blind hole of the power-assisted push rod (6);

The electric power-assisted assembly comprises a power-assisted push rod (6), a screw (7), a push rod return spring (5), a screw (8), a power-assisted assembly shell (9), a buffer disc (10), a coupling push rod (11), a screw return spring (12) and a coupling push rod return spring (13);

the power-assisted push rod (6) is arranged in a center hole of the screw rod (8), the push rod return spring (5) is arranged in a push rod blind hole at the right end of the power-assisted push rod (6), the left end of the push rod return spring (5) is fixed on the bottom surface of the push rod blind hole of the power-assisted push rod (6), the right end of the push rod return spring (5) is in contact connection with the left end of a brake pedal push rod (3) in a brake intention generating unit, a gap of 5-7mm is reserved between the bottom surface of the push rod blind hole of the power-assisted push rod (6) and the right end surface of an idle stroke adjusting screw rod (4) in the brake intention generating unit, the screw rod (7) is sleeved on the screw rod (8), balls are arranged in a raceway between the screw rod (7) and the screw rod (8), the coupling push rod (11) is arranged at the left side of the power-assisted push rod (6), the screw rod (8), the right end of the screw rod (7) and the coupling push rod (11) are arranged in a power-assisted assembly shell (9), the left end of the coupling push rod (11) is arranged outside the left side of the left side shell wall of the power-assisted assembly shell (9), the right end of the coupling push rod (11) is positioned outside the left shell wall of the power-assisted assembly shell, the right end face of the coupling push rod (11) is in a manner of the right end face of the coupling push rod (11) is welded with the right end of the push rod disc (10, and the right end of the coupling disc (11) is welded in a contact mode, the right end face of the buffer disc (10) is in contact connection with the left end face of the power-assisted push rod (6); the coupling push rod return spring (13) and the screw rod return spring (12) are sleeved inside and outside and coaxially arranged, the left ends of the coupling push rod return spring (13) and the screw rod return spring (12) are both fixed on the left inner wall surface of the power-assisted assembly shell (9), the right end of the coupling push rod return spring (13) acts on the left end surface of the right end push disc of the coupling push rod (11), and the right end surface of the screw rod return spring (12) is in contact connection with the left end surface of the screw rod (8); the rigidity of the screw rod return spring (12) is larger than that of the coupling push rod return spring (13);

The coupling push rod (11) consists of a left decoupling cylinder piston, a middle push rod and a right push plate, wherein the left decoupling cylinder piston and the right push plate are disc structural members, the middle push rod is a straight rod structural member with an equal circular cross section, the left decoupling cylinder piston, the middle push rod and the right push plate are sequentially connected into a whole, the rotation axes of the left decoupling cylinder piston, the middle push rod and the right push plate are collinear, the diameter of the left decoupling cylinder piston is equal to the inner diameter of the decoupling cylinder (16), the left decoupling cylinder piston is arranged in the decoupling cylinder (16) to be in sliding connection, a cylindrical groove is machined on the right end surface of the right push plate, the cylindrical groove is collinear with the rotation axis of the right push plate, and the depth of the cylindrical groove is equal to the thickness of the buffer plate (10) in the electric power assisting assembly;

the brake pedal and braking force decoupling component comprises a complete decoupling liquid storage chamber (14), a two-position two-way electromagnetic valve (15), a decoupling cylinder (16), a main cylinder push rod return spring (17), a one-way valve (25), a proportional pressure control valve (26), a partial decoupling energy accumulator (27) and a hydraulic pressure sensor (28);

the right end of the decoupling cylinder (16) is sleeved on a left end decoupling cylinder piston of the coupling push rod (11), the left end of the decoupling cylinder (16) is sleeved on a right end decoupling cylinder piston of the main cylinder push rod (24), a main cylinder push rod return spring (17) is sleeved on a push rod of the main cylinder push rod (24), the left end of the main cylinder push rod return spring (17) is fixed on the inner end face of the left cylinder wall of the decoupling cylinder (16), the right end of the main cylinder push rod return spring (17) is in contact connection with the left end face of the right end decoupling cylinder piston of the main cylinder push rod (24), a complete decoupling liquid storage chamber (14) is connected with the upper end of the decoupling cylinder (16) through a hydraulic pipeline, and a two-position two-way electromagnetic valve (15) is arranged between the complete decoupling liquid storage chamber (14) and the hydraulic pipeline of the decoupling cylinder (16); the part of decoupling energy accumulator (27) is connected with the lower end of decoupling cylinder (16) through a hydraulic pipeline, a proportional pressure control valve (26) and a one-way valve (25) are arranged in parallel between the part of decoupling energy accumulator (27) and the hydraulic pipeline of decoupling cylinder (16), the liquid inlet of the one-way valve (25) is connected with the liquid inlet and outlet of the part of decoupling energy accumulator (27), the liquid outlet of the proportional pressure control valve (26) is connected with the liquid inlet and outlet of the part of decoupling energy accumulator (27), and a hydraulic pressure sensor (28) is arranged on the hydraulic pipeline between the liquid inlet and outlet of the part of decoupling energy accumulator (27) and the liquid outlet of the proportional pressure control valve (26);

The main cylinder push rod (24) consists of a first piston at the left end, a push rod and a decoupling cylinder piston at the right end, wherein the first piston and the decoupling cylinder piston at the right end are disc-type structural members, the push rod is a straight rod-type structural member with an equal circular cross section, the first piston, the push rod and the decoupling cylinder piston at the right end are sequentially connected into a whole, the rotation axes of the first piston, the push rod and the decoupling cylinder piston at the right end are collinear, the diameter of the first piston is equal to the inner diameter of the main cylinder (19), and the diameter of the decoupling cylinder piston at the right end is equal to the inner diameter of the decoupling cylinder (16); the right end decoupling cylinder piston of the main cylinder push rod (24) is arranged in the decoupling cylinder (16) to be in sliding connection, and the first piston of the main cylinder push rod (24) is arranged in the right cavity of the main cylinder (19) to be in sliding connection;

the brake intention generating unit is arranged in the power-assisted push rod (6) through the brake pedal push rod (3) and is connected with the electric power-assisted assembly, the electric power-assisted assembly is connected with a speed reducing mechanism (31) below through a screw rod (7) in a meshed manner and is connected with the power-assisted motor assembly, the output end of the PMSM motor (29) is connected with the input end of the speed reducing mechanism (31) through a coupler, the brake pedal and the braking force decoupling component are connected with the coupling push rod (11) through a decoupling cylinder (16) and are connected with the electric power-assisted assembly, the brake master cylinder assembly is connected with the decoupling cylinder (16) through a master cylinder push rod (24) and is connected with the braking force decoupling component through a master cylinder (19), and the electronic control unit (30) and the brake intention generating unit, the power-assisted motor assembly, the braking pedal and the braking force decoupling component are connected with the HCU (23) through signal wires.

2. The partially and completely decoupled composite electric booster brake system according to claim 1, wherein the booster push rod (6) is a cylindrical structural member, a push rod blind hole is machined at the right end of the booster push rod (6) along the axis, the rotation axis of the push rod blind hole is collinear with the rotation axis of the booster push rod (6), the diameter of the booster push rod (6) is equal to the diameter of the central hole of the screw rod (8), and the length of the booster push rod (6) is equal to the length of the central hole of the screw rod (8);

the screw (7) is a two-section stepped shaft structural member, a screw through hole is processed at the rotation axis of the screw (7), and an inner spiral groove which is matched with an outer spiral groove on the screw (8) to form a spiral rolling path for rolling balls is formed in the inner hole surface of the screw through hole; the diameter of the left section of the screw rod (7) is larger than that of the right section, and gear teeth meshed with the speed reducing mechanism (31) are arranged on the periphery of the left section of the screw rod (7).

3. A partially and fully decoupled hybrid electric power brake system according to claim 1, wherein said master cylinder assembly further comprises a reservoir (18), a second piston return spring (20), a second piston (21) and a first piston return spring (22);

The second piston (21) is arranged in the main cylinder (19), the main cylinder is divided into a left cavity and a right cavity, the first piston return spring (22) is arranged in the right cavity, the right end of the first piston return spring (22) is in contact connection with the left end face of the first piston in the main cylinder push rod (24), the left end of the first piston return spring (22) is in contact connection with the right end face of the second piston (21), the second piston return spring (20) is arranged in the left cavity, the right end of the second piston return spring (20) is in contact connection with the left end face of the second piston (21), the left end of the second piston return spring (20) acts on the inner end face of the left cylinder wall of the main cylinder (19), the left and right cavities of the main cylinder (19) are connected with the liquid storage chamber (18) through hydraulic pipelines, and the lower ends of the left and right cavities of the main cylinder (19) are connected with the HCU (23) through hydraulic pipelines.

4. The partially and completely decoupled hybrid electric power-assisted braking system according to claim 1, wherein the connection of the electronic control unit (30) and the intended braking generating unit, the power-assisted motor assembly, the brake pedal and the braking force decoupling member to the HCU (23) using signal lines means:

the electronic control unit (30) is connected with the signal end of the PMSM motor (29) through a wire harness, a pedal stroke sensor (2), a two-position two-way electromagnetic valve (15), an HCU (23), a proportional pressure control valve (26) and a hydraulic pressure sensor (28).