Electro-hydraulic brake system and method for operating same and motor vehicle

Abstract

The invention relates to an electro-hydraulic brake system, a method for operating the same and a motor vehicle. The electro-hydraulic brake system comprises a brake master cylinder having at least one master cylinder piston and at least one master hydraulic chamber defined by the master cylinder piston, the master hydraulic chamber being connected to at least one brake circuit via an isolation valve; an electrically controllable pressure providing device which is hydraulically connected to the brake circuit via an on valve for actuating the wheel brakes in a brake-by-wire operating mode; a simulation device which is hydraulically connected to the brake master cylinder via a simulator valve for providing a suitable brake pedal feel for the driver in the brake-by-wire operating mode; and an assist circuit comprising an assist hydraulic chamber formed in the brake master cylinder between the master cylinder piston and a brake pedal and an accumulator arranged between the assist hydraulic chamber and the simulation device. The electro-hydraulic brake system is capable of assisting the driver braking in case of a power failure and of actively collapsing the push rod in case of a frontal collision of the vehicle.

Description

Technical Field

[0001] This invention relates to the field of motor vehicle braking, and more specifically, to an electro-hydraulic braking system and its operating method. Background Technology

[0002] Electro-hydraulic braking systems, also known as brake-by-wire systems, offer numerous advantages over traditional braking systems and are therefore widely used in modern motor vehicles. In brake-by-wire operation, an electrically controlled pressure supply device generates the braking pressure required to brake the wheels based on signals detected by pedal travel sensors. To provide the driver with the same pedal feel as with traditional braking systems, electro-hydraulic braking systems typically include a pedal feel simulation device.

[0003] In online control mode, when the driver depresses the brake pedal, the push rod pushes the master cylinder piston, forcing the pressure medium in the master cylinder into the pedal feel simulation device, compressing the springs and rubber components within, and generating feedback force to the brake pedal, giving the driver the feel (foot feel) of a traditional hydraulic brake pedal. The energy generated during this process of the driver depressing the brake pedal and the pressure medium compressing the simulation device is not stored or further utilized; instead, it is wasted as heat and mechanical energy.

[0004] On the other hand, if the brake-by-wire operation mode fails, for example, in the event of a system power failure, braking pressure cannot be generated using an electrically controlled pressure supply device. In this case, brake assist is usually required for the driver. Therefore, a brake booster unit is typically installed on the front bulkhead of the vehicle. In the event of a frontal collision, the rearward movement of the engine can cause components such as the brake booster unit to move into the passenger compartment, raising the associated pedal arm and potentially causing injury to the driver. Summary of the Invention

[0005] The present invention was made in view of the above background, and aims to provide an electro-hydraulic braking system and its operation method that can improve the energy utilization rate of the braking process and enhance the braking assistance effect.

[0006] A first aspect of the present invention provides an electro-hydraulic braking system comprising: a brake master cylinder operable by means of a brake pedal, the brake master cylinder having at least one master cylinder piston and at least one main hydraulic chamber defined by the master cylinder piston, the main hydraulic chamber being connected to at least one brake circuit via an isolation valve; an electrically controllable pressure supply device hydraulically connected to the at least one brake circuit via an on-off valve to operate wheel brakes in an online controlled-drive mode; a simulation device hydraulically connected to the main hydraulic chamber of the brake master cylinder via a simulator valve, the simulation device providing a suitable brake pedal feel to the driver in the online controlled-drive mode; and an assist circuit including an assist hydraulic chamber formed in the brake master cylinder between the master cylinder piston and the brake pedal and an accumulator disposed between the assist hydraulic chamber and the simulation device.

[0007] In a preferred embodiment, the simulation device includes a simulator piston and a hydraulic chamber and a spring chamber separated by the simulator piston. The hydraulic chamber is hydraulically connected to the main hydraulic chamber of the brake master cylinder via the simulator valve and is also hydraulically connected to the accumulator via a check valve that opens toward the accumulator. A pre-tightened elastic element is provided in the spring chamber, and the simulator piston is supported on the simulator housing by the elastic element.

[0008] In a preferred embodiment, the assist circuit is further provided with an accumulator valve located between the accumulator and the assist hydraulic chamber.

[0009] In a preferred embodiment, the accumulator valve is a normally open solenoid valve.

[0010] In a preferred embodiment, the isolation valve is a normally open solenoid valve.

[0011] In a preferred embodiment, the on-state valve and the simulator valve are normally closed solenoid valves.

[0012] A second aspect of the invention provides a method for operating the electro-hydraulic braking system as described above, wherein, in an online control braking mode, the on-off valve is opened and the isolation valve is closed to operate the wheel brakes via the pressure supply device, the simulator valve is opened to provide the driver with a suitable brake pedal feel via the simulation device, and the accumulator valve is closed so that the energy generated by the driver operating the brake pedal is partially stored in the accumulator.

[0013] In a preferred embodiment, in a power-off failure mode, the isolation valve opens and the on valve and the simulator valve close to operate the wheel brakes via the master cylinder, and the accumulator valve opens to release the energy stored in the accumulator to assist the driver's braking via the power-assisted hydraulic chamber.

[0014] In a preferred embodiment, in the event of a frontal vehicle collision, the isolation valve and the accumulator valve are opened to utilize the energy stored in the accumulator and to achieve active collapse of the pushrod via the power-assisted hydraulic chamber.

[0015] A third aspect of the present invention provides a motor vehicle including an electro-hydraulic braking system according to the first aspect described above.

[0016] The electro-hydraulic braking system and its operating method provided by this invention can partially store the energy generated by the driver's operation of the brake pedal in the accumulator during online controlled braking mode, and utilize the energy stored in the accumulator to assist the driver's braking through the assist hydraulic chamber during power failure mode. Therefore, the energy utilization rate of the braking process is improved and the braking assistance effect is enhanced. Since the assist hydraulic chamber is formed in the brake master cylinder, no additional booster components such as a booster cylinder are required. Furthermore, in the event of a frontal collision, active collapse of the pushrod can be achieved by opening the accumulator valve. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a traditional electro-hydraulic braking system.

[0018] Figure 2 This is a schematic diagram of an electro-hydraulic braking system according to an embodiment of the present invention. Detailed Implementation

[0019] Specific embodiments of the present invention are described below with reference to the accompanying drawings.

[0020] Figure 1 This is a schematic diagram of a traditional electro-hydraulic braking system. (Example) Figure 1 As shown, the electro-hydraulic braking system includes: a master cylinder 3 operable via a push rod 2 using a brake pedal 1; a pressure medium reservoir 4 at atmospheric pressure allocated to the master cylinder 3; an electrically controllable pressure supply device 5; a simulation device 6 acting in conjunction with the master cylinder 3; hydraulically operable wheel brakes 7, 8, 9, and 10 located at each wheel; an electrically controllable pressure modulation device for adjusting the braking pressure at each wheel, including a normally open inlet valve 11 and a normally closed outlet valve 12 for each wheel brake; and an electronic control unit (not shown).

[0021] exist Figure 1 In the example shown, wheel brakes 7 and 8 are assigned to the first brake circuit I, and wheel brakes 9 and 10 are assigned to the second brake circuit II. Inlet valve 11 and outlet valve 12 are connected in pairs via hydraulic lines and hydraulically connected to the corresponding wheel brakes via fittings. The outlet fitting of outlet valve 12 is connected to the pressure medium storage container 4 via return line L0. The inlet fittings of inlet valve 11 in the first brake circuit I are interconnected via brake circuit supply line L1. The inlet fittings of inlet valve 11 in the second brake circuit II are interconnected via brake circuit supply line L2. Inlet valve 11 is connected in parallel with check valves that open towards brake circuit supply lines L1 and L2, respectively.

[0022] The master cylinder 3 has two pistons 31 and 32 arranged sequentially within the master cylinder housing, defining two main hydraulic chambers C1 and C2. The main hydraulic chambers C1 and C2 are connected to the pressure medium reservoir 4 via radial holes constructed in the pistons 31 and 32 and corresponding pressure balancing lines L3 and L4. This connection can be interrupted by relative movement of the pistons 31 and 32 within the master cylinder housing. A normally open diagnostic valve 13 is arranged in the pressure balancing line L3 between the first main hydraulic chamber C1 and the pressure medium reservoir 4. Return springs are provided in the main hydraulic chambers C1 and C2, which position the pistons 31 and 32 in their initial positions when the master cylinder 3 is not operated. The push rod 2 couples the oscillating motion of the brake pedal 1 caused by pedal operation with the translational motion of the piston 31, the piston's stroke being detected by a displacement sensor preferably implemented as redundant. Thus, the corresponding piston stroke signal is a measure of the degree of brake pedal operation. This signal reflects the driver's braking intention.

[0023] On the other hand, each main hydraulic chamber C1, C2 is connected to the brake circuit supply line L1 or L2 via corresponding hydraulic line sections L5, L6, wherein an isolation valve 14 is arranged between the main hydraulic chamber C1 or C2 and the corresponding brake circuit supply line L1 or L2. For example, the first main hydraulic chamber C1 of the brake master cylinder 3 is associated with the first brake circuit I and connected to the brake circuit supply line L1, and the second main hydraulic chamber C2 is associated with the second brake circuit II and connected to the brake circuit supply line L2. The isolation valve 14 is configured as an electrically operable, preferably normally open, two-position two-way valve. Through the isolation valve 14, the hydraulic connection between the main hydraulic chamber C1 or C2 of the brake master cylinder 3 and the corresponding brake circuit supply line L1 or L2 can be interrupted in the online control braking operation mode.

[0024] The electrically controllable pressure supply device 5 may include a cylinder-piston assembly with a pressure chamber, the piston of which can be moved by a motor M via a rotary-translational transmission mechanism. A rotor position sensor detects the rotor position of the motor M. The pressure generated by the piston pressurizing the pressure medium in the pressure chamber is input into the system pressure line L7, and this pressure is detected by a pressure sensor preferably implemented in a redundant manner. The system pressure line L7 is connected to two brake circuit supply lines L1 and L2, and normally closed connecting valves 15 are arranged between the system pressure line L7 and each brake circuit supply line L1 and L2. In the online control operation mode, the electronic control unit opens the connecting valves 15, and the pressure medium flows from the pressure chamber of the pressure supply device 5 to the brake circuit supply lines L1 and L2 and then to the wheel brakes. The pressure chamber of the pressure supply device 5 is also connected to the pressure medium storage container 4 via a connecting line L8. A check valve that opens in the direction of the pressure supply device 5 is arranged in the connecting line L8. Therefore, when the connecting valve 15 is closed, the pressure medium can be replenished into the pressure chamber by the return of the piston.

[0025] The simulation device 6 is hydraulically connected to the master cylinder 3 and includes a simulator piston and a hydraulic chamber and a spring chamber separated by the simulator piston. The hydraulic chamber is connected to the first main hydraulic chamber C1 of the master cylinder 3 via a hydraulic line L9. A pre-tightened elastic element is provided in the spring chamber, through which the simulator piston is supported on the simulator housing. A normally closed simulator valve 16 is provided in the hydraulic line L9. A check valve is arranged in parallel with the simulator valve 16, which allows the pressure medium to flow from the hydraulic chamber back to the first main hydraulic chamber C1 of the master cylinder as unobstructed as possible, regardless of the switching state of the simulator valve 16. Other connection schemes between the simulation device 6 and the master cylinder 3 are conceivable.

[0026] In online control mode, simulator valve 16 opens, and when pedal force is input, pressure medium flows from the first main hydraulic chamber C1 of brake master cylinder 3 into the hydraulic chamber of simulator device 6, thereby providing the driver with a suitable brake pedal feel. The energy in this process is not stored and further utilized, but is instead wasted as heat and mechanical energy. Considering this, the present invention proposes a new design scheme that can improve energy utilization.

[0027] Figure 2 This is a schematic diagram of an electro-hydraulic braking system according to an embodiment of the present invention. The electro-hydraulic braking system according to this embodiment is... Figure 1 The difference in the electro-hydraulic braking system shown is the addition of an assist circuit. The following will primarily describe this assist circuit, in contrast to... Figure 1 The same parts will not be described in detail again.

[0028] like Figure 2As shown, the power assist circuit 20 includes a power assist hydraulic chamber 33 formed in the master cylinder 3 between the first piston 31 and the brake pedal 1, an accumulator 21 disposed between the power assist hydraulic chamber 33 and the simulation device 6, and an accumulator valve 22 located between the accumulator 21 and the power assist hydraulic chamber 33. The accumulator valve 22 can be a normally open two-position two-way solenoid valve. The accumulator 21 is hydraulically connected to the hydraulic chamber of the simulation device 6, and a check valve 23 that opens towards the accumulator 21 is provided between them. The accumulator shown in the figure is a spring-loaded accumulator, but other types of accumulators, such as air-filled accumulators, may also be used depending on the situation. The power assist hydraulic chamber 33 is closed by an end cap 34, and the push rod 2 passes through the central through-hole on the end cap 34 and connects to the first piston 31 of the master cylinder 3 in a dynamically sealed manner.

[0029] In online control mode, the electronic control unit opens the on-off valve 15 and the simulator valve 16, and closes the isolation valve 14 and the accumulator valve 22. When the driver depresses the brake pedal 1, the electronic control unit controls the pressure supply device 5 to generate the pressure required for braking based on the signal detected by the pedal travel sensor. Simultaneously, the push rod 2 pushes the first piston 31 of the master cylinder 3, causing the pressure medium in the first main hydraulic chamber C1 of the master cylinder 3 to be forced into the hydraulic chamber of the simulator device 6. This pressure medium, through the simulator piston, compresses the spring and rubber components in the spring chamber, generating a feedback force to the brake pedal. As the pedal travel increases, the pressure medium further pushes the simulator piston, generating a greater feedback force to the brake pedal and the driver, forming a conventional pedal force-displacement curve. Thus, the simulator device 6 provides the driver with a suitable brake pedal feel.

[0030] Furthermore, the pressure medium in the hydraulic chamber of the simulation device 6 also flows to the accumulator 21 via the section of the booster circuit 20 equipped with a check valve 23, thereby converting excess hydraulic energy into the compression energy of the spring or gas and storing it in the accumulator 21. It should be noted that when setting the spring preload in the simulation device 6, it should be considered that the compression of the spring or gas in the accumulator 21 will also generate a feedback force on the brake pedal.

[0031] In failure modes such as power outages, the on valve 15 and simulator valve 16 are closed, while the isolation valve 14 and accumulator valve 22 are open. At this time, the braking pressure required to operate the wheel brakes is established via the master cylinder 3. The energy stored in the accumulator 21 causes the pressure medium to flow through the open accumulator valve 22 into the power-assisted hydraulic chamber 33, pushing the first piston 31 of the master cylinder 3, thereby assisting the driver's braking.

[0032] In the event of a frontal collision, the Automatic Emergency Braking (AEB) function is triggered to mitigate the impact. This is achieved by opening the accumulator valve 22, isolation valve 14, and inlet valve 11 via the electronic control unit. The energy stored in the accumulator 21 causes pressurized medium to flow through the opened accumulator valve 22 into the booster hydraulic chamber 33, pushing the first piston 31 forward. Simultaneously, the pressurized medium in the main hydraulic chambers C1 and C2 flows through the opened isolation valve 14 and inlet valve 11 into the wheel brakes 7, 8, 9, and 10, further assisting the AEB braking system. The push rod 2, driven by the first piston 31, moves forward to its full stroke position, and the pedal arm moves forward accordingly, thereby reducing the risk of engine compartment components intruding into the passenger compartment and causing injury to the driver during a collision.

[0033] The present invention has been described above with reference to an embodiment in which the brake master cylinder has two master cylinder pistons 31 and 32 and two main hydraulic chambers C1 and C2. However, those skilled in the art will understand that the present invention is also applicable to electro-hydraulic braking systems in which the brake master cylinder has only one master cylinder piston and one main hydraulic chamber.

[0034] It is understood that the above embodiments of the present invention are merely exemplary models used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention. The scope of protection of the present invention is defined only by the meaning of the language used in the appended claims and their equivalents.

Claims

1. An electrohydraulic brake system, comprising: a brake master cylinder (3) which is actuatable by means of a brake pedal (1), said brake master cylinder having at least one master cylinder piston (31, 32) and at least one master hydraulic chamber (Cl, C2) which is delimited by the master cylinder piston, said master hydraulic chamber being connected to at least one brake circuit (I, II) via an isolating valve (14); an electrically controllable pressure-providing device (5) which is hydraulically connected to the at least one brake circuit (I, II) via an on valve (15) in order to actuate wheel brakes (7, 8, 9, 10) in a line control braking operating mode, a simulation device (6) which is hydraulically connected to a master hydraulic chamber (Cl) of the brake master cylinder (3) via a simulator valve (16) in order to provide a suitable brake pedal feel for a driver in a line control braking operating mode, characterized in that the electrohydraulic brake system further comprises a boost circuit (20) which comprises a boost hydraulic chamber (33) which is formed in the brake master cylinder (3) between the master cylinder piston (31) and the brake pedal (1) and an accumulator (21) which is arranged between the boost hydraulic chamber (33) and the simulation device (6).

2. The electrohydraulic brake system as claimed in claim 1, characterized in that the simulation device (6) comprises a simulator piston and a hydraulic chamber and a spring chamber which are separated off by the simulator piston, the hydraulic chamber being hydraulically connected to a master hydraulic chamber (Cl) of the brake master cylinder (3) via the simulator valve (16) and further hydraulically connected to the accumulator (21) via a non-return valve (23) which is open in the direction of the accumulator (21), a pre-tensioned elastic element being arranged in the spring chamber, the simulator piston being supported on a simulator housing by means of the elastic element.

3. The electrohydraulic brake system as claimed in claim 1 or 2, characterized in that a further accumulator valve (22) is arranged in the boost circuit (20) between the accumulator (21) and the boost hydraulic chamber (33).

4. The electrohydraulic brake system as claimed in claim 3, characterized in that the accumulator valve (22) is a normally open electromagnetic valve.

5. The electrohydraulic brake system as claimed in claim 1 or 2, characterized in that the isolating valve (14) is a normally open electromagnetic valve.

6. The electrohydraulic brake system as claimed in claim 1 or 2, characterized in that the on valve (15) and the simulator valve (16) are normally closed electromagnetic valves.

7. A method for operating an electrohydraulic brake system, said electrohydraulic brake system comprising: a brake master cylinder (3) which is actuatable by means of a brake pedal (1), said brake master cylinder having at least one master cylinder piston (31, 32) and at least one master hydraulic chamber (Cl, C2) which is delimited by the master cylinder piston, said master hydraulic chamber being connected to at least one brake circuit (I, II) via a normally open isolating valve (14); an electrically controllable pressure providing device (5) hydraulically connected to the at least one brake circuit (I, II) via a normally closed on valve (15); a simulator device (6) hydraulically connected to a master hydraulic chamber (C1) of the brake master cylinder (3) via a normally closed simulator valve (16); and a boost circuit (20) comprising a boost hydraulic chamber (33) formed in the brake master cylinder (3) between a master cylinder piston (31) and a brake pedal (1), an accumulator (21) arranged between the boost hydraulic chamber (33) and the simulator device (6), and a normally open accumulator valve (22) arranged between the accumulator (21) and the boost hydraulic chamber (33), the accumulator (21) being hydraulically connected to the simulator device (6) via a check valve (23) opening in the direction of the accumulator (21), wherein in a brake-by-wire operating mode, the on valve (15) is opened and the isolation valve (14) is closed to operate the wheel brakes by the pressure providing device (5), the simulator valve (16) is opened to provide a suitable brake pedal feel to the driver by the simulator device (6), and the accumulator valve (22) is closed to cause the energy generated by the driver operating the brake pedal to be partially stored in the accumulator (21).

8. The method of claim 7, wherein, In a failure mode with loss of electrical power, the isolation valve (14) is opened and the on valve (15) and the simulator valve (16) are closed to operate the wheel brakes by the brake master cylinder (3), and the accumulator valve (22) is opened to release the energy stored in the accumulator (21) to boost the driver braking by the boost hydraulic chamber (33).

9. The method according to claim 7 or 8, characterized in that, In case of a frontal collision of the vehicle, the isolation valve (14) and the accumulator valve (22) are opened to actively collapse the push rod (2) connected between the brake pedal (1) and the brake master cylinder (3) using the energy stored in the accumulator (21) and by means of the boost hydraulic chamber (33).

10. A motor vehicle characterised in that An electronic hydraulic brake system according to any one of claims 1 to 6. An electronic hydraulic brake system according to any one of claims 1 to 6.

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