An integrated pedal simulator for an electro-hydraulic braking system

Abstract

The present invention discloses an integrated pedal simulator for an electro-hydraulic braking system, which includes a housing, a pedal push rod, a first piston, a second piston, a plug, a master cylinder push rod, a master cylinder push rod return spring, a simulator spring, and a pedal push rod return spring. The present invention adopts an integrated layout mode of the transmission mechanism of the electro-hydraulic braking system and the pedal simulator, exquisitely designs the components of the electro-hydraulic braking system, uses the relative movement of each component of the braking system to realize the opening and closing of the brake fluid oil circuit, and combines the simulator spring to generate a reasonable pedal damping feeling. Compared with the structure of the traditional brake pedal simulator, the present invention replaces the solenoid valve through an exquisite oil circuit design, and has the advantages of small volume, exquisite structure, low cost, simple control, convenient installation and maintenance, etc.

Description

Technical Field

[0001] The present invention relates to the field of vehicle braking systems, and particularly to an integrated pedal simulator for an electro-hydraulic braking system. Background Art

[0002] The braking system is an important part of automobiles and motor vehicles. Most traditional fuel vehicles use a vacuum booster to help enhance the force of the brake pedal, making it easier for the driver to apply braking force.

[0003] In the context of the development of automotive electrification and intelligence, the traditional vacuum booster can no longer meet the braking requirements of intelligent vehicles. With the development of electronic information technology, in recent years, the electro-hydraulic braking system has gradually replaced the traditional vacuum booster. The electro-hydraulic braking system collects the driver's braking intention through a brake pedal sensor and transmits it to the electronic control unit. The control unit controls the actuator to output the corresponding braking pressure according to different driving intentions. The electro-hydraulic braking system can not only output braking force according to the driver's needs, but also achieve wire-controlled braking, while improving the response accuracy and shortening the braking distance.

[0004] At present, the electro-hydraulic braking systems on the market are generally equipped with a brake pedal simulator to simulate the driver's foot brake pedal feeling. The existing pedal simulators mostly adopt an arrangement mode in parallel with the transmission mechanism, independent of the brake pedal and the master cylinder, with a relatively high cost. Compared with the brake pedal force feeling of the traditional vacuum-assisted braking system, there are significant differences in the damping feeling and the hysteresis feeling, and the driver's acceptance of this kind of brake pedal feeling is relatively low.

[0005] Therefore, in order to solve the above problems, there is an urgent need for an integrated brake pedal simulation device with a delicate structure, high reliability and low cost, so as to meet the driver's demand for braking force feeling. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention aims to provide an integrated pedal simulator for an electro-hydraulic braking system.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] An integrated pedal simulator for an electro-hydraulic braking system, comprising a housing, a pedal push rod, a first piston, a second piston, a plug, a master cylinder push rod, a master cylinder push rod return spring, a simulator spring and a pedal push rod return spring;

[0009] The first piston and the plug are respectively arranged at the rear and front parts inside the housing; the first piston is hollow inside, its outer wall fits with the inner wall of the housing, and a pedal push rod return spring, a simulator spring, and a second piston are sequentially arranged inside it from the rear to the front; the front end of the pedal push rod is connected to the rear end of the pedal push rod return spring through a connector; the outer edge of the rear end of the connector fits with the inner wall of the first piston, and the middle part of its front side is connected to the rear end of the pedal push rod return spring; the front end of the pedal push rod return spring and the rear end of the simulator spring are connected in three phases through a connector, and the front end of the simulator spring is connected to the rear end of the second piston;

[0010] The plug seals the front end of the housing, and the front part of the first piston is movably sleeved on the rear part of the plug; the front end of the first piston, the outer wall of the plug, and the inner wall of the front part inside the housing together form a high-pressure chamber, and a compensation hole is provided on the inner wall of the front part inside the housing, and the compensation hole communicates with the high-pressure chamber and the external brake fluid reservoir respectively; a ring-shaped boss is provided in the middle of the first piston internally, the second piston is in a convex shape, including a front convex platform and a rear base, the front convex platform passes through the middle of the ring-shaped boss, and a low-pressure chamber is formed between the front side surface of the rear base and the rear side surface of the ring-shaped boss, and the outer circular surface of the front convex platform and the inner circular surface of the ring-shaped boss are sealed; an oil guide groove one is provided inside the upper wall of the first piston, and both ends of the oil guide groove one communicate with the high-pressure chamber and the low-pressure chamber respectively; the outer circular surface of the front convex platform of the second piston is sleeved inside the main cylinder push rod return spring; the front end of the main cylinder push rod return spring contacts the inner end surface of the plug, and the rear end contacts the front end surface of the ring-shaped boss;

[0011] The front convex platform inside the second piston is hollow, the rear part of the main cylinder push rod passes through the plug and is sleeved inside the front convex platform of the second piston, and the contact surface between the main cylinder push rod and the plug is sealed; there is a decoupling gap between the rear end surface of the main cylinder push rod and the rear side surface inside the front convex platform of the second piston, an oil drain hole and an oil guide groove four are provided inside the upper wall of the front convex platform of the second piston, one end of the oil guide groove four communicates with the oil drain hole, and the other end communicates with the low-pressure chamber; an oil guide groove five is provided inside the rear part of the main cylinder push rod, one end of the oil guide groove five communicates with the outside of the main cylinder push rod, and the other end communicates with the decoupling gap, and one end of the oil guide groove five and the oil drain hole can be docked and communicated through the relative movement between the main cylinder push rod and the front convex platform; a through hole is provided at the center of the rear base of the second piston, and the through hole communicates with the decoupling gap;

[0012] A first hydraulic chamber is formed between the rear part of the first piston and the rear base of the second piston, and a second hydraulic chamber is formed among the front part of the first piston, the front boss of the second piston and the plug; an oil guide groove II is arranged on the lower wall of the second piston, and two ends of the oil guide groove II are respectively communicated with the first hydraulic chamber and the second hydraulic chamber; an oil guide groove III is further arranged on the upper wall of the first piston, one end of the oil guide groove III is communicated with the first hydraulic chamber, and the other end is communicated with an external brake fluid reservoir.

[0013] Further, the connecting member includes a first connecting member and a second connecting member. The front end of the pedal push rod is hinged to the rear side of the second connecting member, and the second connecting member is fixed to the rear side of the first connecting member; the outer edge of the rear end of the first connecting member is attached to the rear end face of the first piston.

[0014] Further, the annular area of the high-pressure chamber is smaller than the annular area of the low-pressure chamber.

[0015] Further, the inner diameter of the pedal push rod return spring is larger than the outer diameter of the simulator spring; the third connecting member is connected to the front end of the pedal push rod return spring, and a recessed portion recessed backward is arranged in the middle thereof. The rear end of the simulator spring is connected to the recessed portion; a rubber spring is arranged at the center of the front side of the first connecting member, and the rubber spring extends into the pedal push rod return spring and corresponds to the rear side position of the recessed portion.

[0016] The invention discloses a working method of the above integrated pedal simulator, and the specific process is as follows:

[0017] When the electro-hydraulic braking system is in the normal boosting mode, during the pressure building process, the driver steps on the brake pedal of the vehicle, and the brake pedal pushes the pedal push rod to move forward. The displacement of the pedal push rod is collected by the pedal stroke sensor and sent to the control unit of the vehicle. The control unit identifies the braking intention and drives the master cylinder push rod to move forward through the motor, pushing the master cylinder piston to generate braking pressure; meanwhile, the pedal push rod pushes the first piston to move forward and closes the compensation hole. Due to the extrusion effect, the braking fluid pressure in the high-pressure chamber increases, and the braking fluid further flows into the low-pressure chamber through the oil guide groove I; the pedal push rod simultaneously pushes the second piston to move forward through the pedal push rod return spring, the third connecting member and the simulator spring. Since the braking fluid flows into the low-pressure chamber, it will hinder the forward movement of the second piston. At the same time, the master cylinder push rod moves forward faster than the second piston under the drive of the motor, causing the oil guide groove V and the oil drain hole to be misaligned and the oil drain hole to be closed; the braking fluid flow damping, combined with the functions of the master cylinder push rod return spring, the simulator spring and the pedal push rod return spring, forms an ideal brake pedal feel; when the driver releases the brake pedal, under the action of the master cylinder push rod return spring, the first piston retracts, the compensation hole opens, and the braking fluid in the low-pressure chamber flows back to the high-pressure chamber through the diversion groove I.

[0018] Further, when the electronic control system of the electro-hydraulic braking system fails, after the driver steps on the brake pedal, due to the failure of the electronic control system, the master cylinder push rod will not act immediately under the drive of the motor. The driver's braking force is transmitted to the first piston through the pedal push rod, causing the first piston to move forward, closing the compensation hole. The pressure of the brake fluid in the high-pressure chamber increases and further flows into the low-pressure chamber through the first oil guiding groove. At the same time, the second piston also moves forward. After overcoming the decoupling gap, the rear side surface inside the front convex platform of the second piston fits with the rear end surface of the master cylinder push rod. At this time, the oil drain hole and the fifth oil guiding groove are exactly opposite and communicate with each other, resulting in the connection between the low-pressure chamber and the first hydraulic chamber, enabling the driver's pedal braking force to act more directly on the master cylinder push rod. When the driver releases the brake pedal, under the action of the master cylinder push rod return spring, the first piston retracts. The brake fluid in the low-pressure chamber flows back to the high-pressure chamber through the first oil guiding groove and further returns to the brake fluid reservoir through the compensation hole.

[0019] The beneficial effects of the present invention are as follows: The present invention adopts an integrated layout method for the transmission mechanism of the electro-hydraulic braking system and the pedal simulator, exquisitely designs the components of the electro-hydraulic braking system, utilizes the relative movement of the components of the braking system to open and close the brake fluid oil circuit, and combines the simulator spring to generate a reasonable pedal damping feeling. Compared with the traditional brake pedal simulator structure, the traditional solenoid valve function is realized through exquisite oil circuit design and the relative movement of moving parts, which has the advantages of small volume, exquisite structure, low cost, simple control, convenient installation and maintenance, etc. Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of the integrated pedal simulator in the embodiment of the present invention.

[0021] Figure 2 It is a partial enlarged view of the integrated pedal simulator in the embodiment of the present invention. Detailed Embodiment

[0022] The following will further describe the present invention with reference to the drawings. It should be noted that this embodiment is based on the present technical solution and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to this embodiment.

[0023] This embodiment provides an integrated pedal simulator for an electro-hydraulic braking system, as Figure 1-2 shown, including a housing 8, a pedal push rod 1, a first piston 2, a third oil guiding groove 3, a second piston 4, a plug 6, a compensation hole 7, a master cylinder push rod 11, an oil drain hole 12, a second oil guiding groove 13, a master cylinder push rod return spring 15, a simulator spring 17, a pedal push rod return spring 19, and a rubber spring 20;

[0024] The first piston 2 and the plug 6 are respectively arranged at the rear and front parts inside the housing; the first piston 2 is hollow inside, its outer wall fits with the inner wall of the housing, and inside it are successively arranged a pedal push rod return spring 19, a simulator spring 17, and a second piston 4 from back to front; the front end of the pedal push rod 1 is hinged to the rear side of the second connecting member 23, and the second connecting member 23 is fixed to the rear end face of the first connecting member 22; the outer edge of the rear end of the first connecting member 22 fits with the inner wall of the first piston 2, and the middle part of its front side is connected to the rear end of the pedal push rod return spring 19; the front end of the pedal push rod return spring 19 is connected to the rear end of the simulator spring 17, and the front end of the simulator spring 17 is connected to the rear end of the second piston 4;

[0025] The plug 6 seals the front end of the housing, and the front part of the first piston 2 is movably sleeved on the rear part of the plug 6; the front end of the first piston 2, the outer wall of the plug 6, and the inner wall of the front part inside the housing together form a high-pressure chamber 10, and the inner wall of the front part inside the housing is provided with a compensation hole 7, and the compensation hole 7 communicates with the high-pressure chamber 10 and the external brake fluid reservoir respectively; a circular boss 25 is arranged in the middle of the first piston 2 inside; the second piston 4 is in a convex shape, including a front convex platform and a rear base, the front convex platform passes through the middle of the circular boss 25, and a low-pressure chamber 5 is formed between the front side face of the rear base and the rear side face of the circular boss, and the contact surface between the outer circular surface of the front convex platform and the inner circular surface of the circular boss is sealed; a first oil guide groove 24 is arranged inside the upper wall of the first piston 2, and both ends of the first oil guide groove 24 communicate with the high-pressure chamber 10 and the low-pressure chamber 5 respectively; the outer circular surface of the front convex platform of the second piston 4 is sleeved inside the master cylinder push rod return spring 15, the front end of the master cylinder push rod return spring 15 contacts the inner end face of the plug 6, and the rear end contacts the front end face of the circular boss 25.

[0026] The front convex platform inside the second piston 4 is hollow, the rear part of the master cylinder push rod 11 passes through the plug 6 and is sleeved inside the front convex platform of the second piston 4, and the contact surface between the master cylinder push rod 11 and the plug 6 is sealed; there is a decoupling gap 27 between the rear end face of the master cylinder push rod 11 and the rear side face inside the front convex platform of the second piston 4, an oil discharge hole 12 and a fourth oil guide groove 26 are arranged inside the upper wall of the front convex platform of the second piston 4, one end of the fourth oil guide groove 26 communicates with the oil discharge hole 12, and the other end communicates with the low-pressure chamber 5; a fifth oil guide groove 9 is arranged inside the rear part of the master cylinder push rod 11, one end of the fifth oil guide groove 9 communicates with the outside of the master cylinder push rod 11, and the other end communicates with the decoupling gap 27, and one end of the fifth oil guide groove 9 and the oil discharge hole 12 can be docked and communicated through the relative movement between the master cylinder push rod 11 and the front convex platform; a through hole is arranged on the rear base of the second piston 4, and the through hole communicates with the decoupling gap 27;

[0027] A first hydraulic chamber 16 is formed between the rear part of the first piston 2 and the rear-side base of the second piston 4, and a second hydraulic chamber 14 is formed between the front part of the first piston 2, the front-side boss of the second piston 4 and the plug 6; an oil guiding groove two 13 is provided on the lower wall of the second piston 4, and two ends of the oil guiding groove two 13 are respectively communicated with the first hydraulic chamber 16 and the second hydraulic chamber 14; an oil guiding groove three 3 is further provided on the upper wall of the first piston 2, one end of the oil guiding groove three 3 is communicated with the first hydraulic chamber 16, and the other end is communicated with an external brake fluid reservoir.

[0028] When one end of the oil guiding groove five 9 and the oil drain hole 12 are butted, the oil drain hole 12 is opened, and the brake fluid in the low-pressure chamber 5 flows to the first hydraulic chamber 16 through the oil guiding groove four 26, the oil drain hole 12, the oil guiding groove five 9, the decoupling gap and the through hole on the rear-side base.

[0029] In this embodiment, the annular area of the high-pressure chamber is smaller than the annular area of the low-pressure chamber.

[0030] In this embodiment, the front end of the pedal push rod return spring 19 is connected to the rear end of the simulator spring 17 through a connecting member three 18.

[0031] Furthermore, in this embodiment, the inner diameter of the pedal push rod return spring 19 is larger than the outer diameter of the simulator spring 17; the connecting member three 18 is connected to the front end of the pedal push rod return spring 19, and a recessed portion recessed backward is provided in the middle thereof, and the rear end of the simulator spring 17 is connected to the recessed portion; a rubber spring 20 is provided at the center of the front side of the connecting member one 22, and the rubber spring 20 extends into the pedal push rod return spring 19 and corresponds to the rear side position of the recessed portion.

[0032] The working principle of the above integrated pedal simulator is as follows:

[0033] When the electro-hydraulic braking system is in the normal boosting mode, during the pressure build-up process, when the driver steps on the vehicle's brake pedal, the brake pedal pushes the pedal push rod 1 forward. The displacement of the pedal push rod 1 is collected by the pedal travel sensor and sent to the vehicle's control unit. The control unit recognizes the braking intention and drives the master cylinder push rod 11 forward through the motor, pushing the master cylinder piston to generate braking pressure. At the same time, the pedal push rod 1 pushes the first piston 2 forward through the second connecting piece and the first connecting piece, and closes the compensation hole 7. Due to the squeezing effect, the pressure of the brake fluid in the high-pressure chamber 10 increases, and the brake fluid further flows into the low-pressure chamber 5 through the first oil guiding groove 24; the pedal push rod 1 also pushes the second piston 4 forward through the second connecting piece, the first connecting piece, the pedal push rod return spring 19, the third connecting piece 18 and the simulator spring 17. Since the brake fluid flows into the low-pressure chamber 5, it will hinder the forward movement. At the same time, the master cylinder push rod 11 moves forward faster than the second piston 4 under the drive of the motor, causing the fifth oil guiding groove 9 and the oil drain hole 12 to be misaligned, and the oil drain hole 12 is closed. The damping of the brake fluid flow, combined with the action of the master cylinder push rod return spring 15, the simulator spring 17, and the pedal push rod return spring 19, forms an ideal brake pedal feel. When the driver releases the brake pedal, under the action of the master cylinder push rod return spring 15, the first piston 2 retracts, the compensation hole 7 opens, and the brake fluid in the low-pressure chamber 5 flows back into the high-pressure chamber 10 through the first diversion groove 24.

[0034] When the electronic control system of the electro-hydraulic braking system fails, when the driver steps on the brake pedal, due to the failure of the electronic control system, the master cylinder push rod 11 will not act immediately under the drive of the motor. The driver's braking force is transmitted to the first piston 2 through the pedal push rod 1, causing the first piston 2 to move forward, closing the compensation hole 7. The pressure of the brake fluid in the high-pressure chamber 10 increases and further flows into the low-pressure chamber 5 through the first oil guiding groove 24. At the same time, the second piston 4 also moves forward; after overcoming the decoupling gap, the rear side of the inner side of the front boss of the second piston 4 fits with the rear end face of the master cylinder push rod 11. At this time, the oil drain hole 12 and the fifth oil guiding groove 9 are exactly opposite and communicate with each other, so that the low-pressure chamber 5 is connected to the first hydraulic chamber 16, making the driver's pedal braking force act more directly on the master cylinder push rod. When the driver releases the brake pedal, under the action of the master cylinder push rod return spring 15, the first piston 2 retracts, and the brake fluid in the low-pressure chamber 5 flows back into the high-pressure chamber 10 through the first oil guiding groove 24 and further returns to the brake fluid reservoir through the compensation hole 7.

[0035] For those skilled in the art, various corresponding changes and deformations can be given according to the above technical solutions and concepts, and all such changes and deformations should be included within the protection scope of the claims of the present invention.

Claims

1. An integrated pedal simulator for an electro-hydraulic braking system, characterized in that, It includes a housing, a pedal push rod, a first piston, a second piston, a plug, a master cylinder push rod, a master cylinder push rod return spring, a simulator spring and a pedal push rod return spring; The first piston and the plug are respectively arranged at the rear and front of the interior of the housing; the interior of the first piston is hollow, its outer wall fits with the inner wall of the housing, and inside it are successively arranged a pedal push rod return spring, a simulator spring and a second piston from the rear to the front; the front end of the pedal push rod is connected to the rear end of the pedal push rod return spring through a connecting piece; the outer edge of the rear end of the connecting piece fits with the inner wall of the first piston, and the middle part of its front side is connected to the rear end of the pedal push rod return spring; the front end of the pedal push rod return spring and the rear end of the simulator spring are connected in three-phase through a connecting piece, and the front end of the simulator spring is connected to the rear end of the second piston; The plug seals the front end of the housing, and the front part of the first piston is movably sleeved on the rear part of the plug; the front end of the first piston, the outer wall of the plug and the inner wall of the front part of the interior of the housing jointly form a high-pressure chamber, and the inner wall of the front part of the interior of the housing is provided with a compensation hole, and the compensation hole communicates with the high-pressure chamber and the external brake fluid reservoir respectively; a ring-shaped boss is arranged in the middle of the interior of the first piston, the second piston is in a convex shape, including a front convex platform and a rear base, the front convex platform passes through the middle of the ring-shaped boss, and a low-pressure chamber is formed between the front side surface of the rear base and the rear side surface of the ring-shaped boss, and the outer cylindrical surface of the front convex platform and the inner cylindrical surface of the ring-shaped boss are sealed; an oil guide groove one is arranged inside the upper wall of the first piston, and both ends of the oil guide groove one communicate with the high-pressure chamber and the low-pressure chamber respectively; the outer cylindrical surface of the front convex platform of the second piston is sleeved inside the master cylinder push rod return spring; the front end of the master cylinder push rod return spring contacts the inner end surface of the plug, and the rear end contacts the front end surface of the ring-shaped boss; The interior of the front convex platform of the second piston is hollow, the rear part of the master cylinder push rod passes through the plug and is sleeved inside the front convex platform of the second piston, and the contact surface between the master cylinder push rod and the plug is sealed; there is a decoupling gap between the rear end surface of the master cylinder push rod and the rear side surface inside the front convex platform of the second piston, and an oil drain hole and an oil guide groove four are arranged inside the upper wall of the front convex platform of the second piston, one end of the oil guide groove four communicates with the oil drain hole, and the other end communicates with the low-pressure chamber; an oil guide groove five is arranged inside the rear part of the master cylinder push rod, one end of the oil guide groove five communicates with the outside of the master cylinder push rod, and the other end communicates with the decoupling gap, and one end of the oil guide groove five and the oil drain hole can be docked and communicated through the relative movement between the master cylinder push rod and the front convex platform; a through hole is arranged at the center of the rear base of the second piston, and the through hole communicates with the decoupling gap; A first hydraulic chamber is formed between the rear part of the first piston and the rear-side base of the second piston, and a second hydraulic chamber is formed among the front part of the first piston, the front-side boss of the second piston and the plug; an oil guiding groove II is arranged on the lower wall of the second piston, and two ends of the oil guiding groove II are respectively communicated with the first hydraulic chamber and the second hydraulic chamber; an oil guiding groove III is further arranged on the upper wall of the first piston, one end of the oil guiding groove III is communicated with the first hydraulic chamber, and the other end is communicated with an external brake fluid reservoir tank.

2. The integrated pedal simulator according to claim 1, characterized in that, The connecting member includes a connecting member I and a connecting member II. The front end of the pedal push rod is hinged to the rear side of the connecting member II, and the connecting member II is fixed to the rear side of the connecting member I; the outer edge of the rear end of the connecting member I is attached to the rear end face of the first piston.

3. The integrated pedal simulator according to claim 1, characterized in that The annular area of the high-pressure chamber is smaller than that of the low-pressure chamber.

4. The integrated pedal simulator according to claim 1, wherein The inner diameter of the pedal push rod return spring is larger than the outer diameter of the simulator spring; the connecting member III is connected to the front end of the pedal push rod return spring, and a recessed part recessed backward is arranged in the middle thereof. The rear end of the simulator spring is connected to the inside of the recessed part; a rubber spring is arranged at the center of the front side of the connecting member I, and the rubber spring extends into the pedal push rod return spring and corresponds to the rear side position of the recessed part.

5. A working method of the integrated pedal simulator according to any one of claims 1-4, characterized in that, The specific process is as follows: When the electro-hydraulic braking system is in the normal boosting mode, during the pressure building process, the driver steps on the brake pedal of the vehicle, and the brake pedal pushes the pedal push rod to move forward. The displacement of the pedal push rod is collected by the pedal stroke sensor and sent to the vehicle control unit. The control unit identifies the braking intention and drives the master cylinder push rod to move forward through the motor, pushing the master cylinder piston to generate braking pressure; meanwhile, the pedal push rod pushes the first piston to move forward and closes the compensation hole. Due to the extrusion effect, the pressure of the brake fluid in the high-pressure chamber increases, and the brake fluid further flows into the low-pressure chamber through the oil guiding groove I. The pedal push rod simultaneously pushes the second piston to move forward through the pedal push rod return spring, the connecting member III and the simulator spring. Since the brake fluid flows into the low-pressure chamber, it will hinder the forward movement of the second piston. At the same time, the master cylinder push rod moves forward faster than the second piston under the drive of the motor, resulting in the dislocation of the oil guiding groove V and the oil drain hole, and the oil drain hole is closed; the damping of the brake fluid flow, combined with the functions of the master cylinder push rod return spring, the simulator spring and the pedal push rod return spring, forms an ideal brake pedal feel; when the driver releases the brake pedal, the first piston retracts under the action of the master cylinder push rod return spring, the compensation hole is opened, and the brake fluid in the low-pressure chamber flows back to the high-pressure chamber through the diversion groove I.

6. The working method according to claim 5, characterized in that, When the electronic control system of the electro-hydraulic braking system fails, after the driver steps on the brake pedal, due to the failure of the electronic control system, the master cylinder push rod will not move immediately under the drive of the motor. The driver's braking force is transmitted to the first piston through the pedal push rod, causing the first piston to move forward, closing the compensation hole. The pressure of the brake fluid in the high-pressure chamber increases and further flows into the low-pressure chamber through the oil guide groove 1. At the same time, the second piston also moves forward. After overcoming the decoupling gap, the rear side of the inner side of the front boss of the second piston fits with the rear end face of the master cylinder push rod. At this time, the oil drain hole and the oil guide groove 5 are exactly opposite and communicate with each other, resulting in the connection between the low-pressure chamber and the first hydraulic chamber, making the driver's pedal braking force act more directly on the master cylinder push rod. When the driver releases the brake pedal, under the action of the master cylinder push rod return spring, the first piston retracts. The brake fluid in the low-pressure chamber flows back to the high-pressure chamber through the oil guide groove 1 and further returns to the brake fluid reservoir through the compensation hole.

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