阅读说明：本技术 用于电动车辆或混合动力车辆的制动系统及其运行方法 (Brake system for an electric or hybrid vehicle and method for operating the same ) 是由 劳耀新 于 2019-11-12 设计创作，主要内容包括：本发明涉及用于电动车辆或混合动力车辆的制动系统及其运行方法。该制动系统包括制动主缸(1)、至少一个车轮制动器(2)、设置在制动回路(I、II)中的进入阀(3)和排出阀(4)、低压蓄能器(5)、液压泵(6)和隔离阀(7),还包括设置在低压蓄能器(5)的入口与隔离阀(7)之间的泄压阀(8)。泄压阀(8)是常闭的电磁阀。在再生制动期间,关闭进入阀(3)并打开泄压阀(8),从而使得制动回路(I、II)中的压力介质流入低压蓄能器(5)中而不是流向车轮制动器(2)。根据本发明的制动系统及其运行方法,确保了在再生制动期间不会在制动卡钳内存在残余压力,从而提高了能量回收效率。(The invention relates to a brake system for an electric or hybrid vehicle and a method for operating the same. The brake system comprises a master cylinder (1), at least one wheel brake (2), an inlet valve (3) and a discharge valve (4) arranged in a brake circuit (I, II), a low-pressure accumulator (5), a hydraulic pump (6) and an isolation valve (7), and further comprises a pressure relief valve (8) arranged between an inlet of the low-pressure accumulator (5) and the isolation valve (7). The pressure relief valve (8) is a normally closed electromagnetic valve. During regenerative braking, the inlet valve (3) is closed and the relief valve (8) is opened, so that the pressure medium in the brake circuit (I, II) flows into the low-pressure accumulator (5) instead of to the wheel brakes (2). According to the brake system and the operation method thereof, residual pressure in the brake caliper is prevented during regenerative braking, so that the energy recovery efficiency is improved.)

1. A braking system for an electric or hybrid vehicle, the braking system comprising:

a master cylinder (1) having at least one master cylinder piston and at least one hydraulic chamber defined by the master cylinder piston, the hydraulic chamber being connected to at least one brake circuit (I, II) via an isolation valve (7);

at least one wheel brake (2) hydraulically connected to a respective brake circuit (I, II);

a pressure modulation valve arranged in the brake circuit (I, II), which pressure modulation valve comprises one inlet valve (3) and one outlet valve (4) for each wheel brake (2) for regulating the brake pressure on the respective wheel brake (2);

a low pressure accumulator (5) having an inlet connected to the discharge valve (4) so as to be able to receive pressure medium discharged from the discharge valve (4); and

a hydraulic pump (6) having its suction side connected to the outlet of the low pressure accumulator (5) and its output side connected to a respective brake circuit (I, II) between the inlet valve (3) and the isolation valve (7),

characterized in that the braking system further comprises a pressure relief valve (8) arranged between the inlet of the low pressure accumulator (5) and the isolation valve (7), the pressure relief valve being a normally closed solenoid valve which is opened during regenerative braking to allow pressure medium in the brake circuit (I, II) to flow into the low pressure accumulator (5).

2. The braking system of claim 1,

the isolation valve (7) is a normally open solenoid valve, the isolation valve (7) remaining open during regenerative braking.

3. A braking system according to claim 1 or 2,

the inlet valve (3) is a normally open solenoid valve, the inlet valve (3) being closed during regenerative braking.

4. A braking system according to claim 1 or 2,

the discharge valve (4) is a normally closed solenoid valve, the discharge valve (4) remaining closed during regenerative braking.

5. A braking system according to claim 1 or 2,

a switching valve (9) is also provided between the suction side of the hydraulic pump (6) and the respective hydraulic chamber of the master cylinder (1), said switching valve being a normally closed solenoid valve.

6. A braking system according to claim 1 or 2,

the hydraulic pump (6) is a plunger pump driven by a direct current motor.

7. A braking system according to claim 1 or 2,

the master brake cylinder (1) is a tandem master cylinder defining two hydraulic chambers.

8. A method for operating a brake system according to any one of claims 1-7, characterized in that during regenerative braking the isolation valve (7) and the pressure relief valve (8) are opened and the inlet valve (3) and the outlet valve (4) are closed, so that pressure medium in the brake circuit (I, II) flows into the low pressure accumulator (5).

9. A method according to claim 8, characterised in that when the energy recovered by regenerative braking reaches a maximum allowed value or the braking deceleration generated by regenerative braking fails to meet the braking demand, the pressure relief valve (8) is closed and the inlet valve (3) is opened so that pressure medium in the brake circuit (I, II) flows to the wheel brakes (2).

10. A method according to claim 9, characterised by activating the hydraulic pump (6) to deliver pressure medium stored in the low pressure accumulator (5) to the brake circuit (I, II) when the energy recovered by regenerative braking reaches a maximum allowed value or the braking deceleration generated by regenerative braking fails to meet the braking demand.

Technical Field

The invention relates to a brake system for an electric or hybrid vehicle and to a method for operating the brake system.

Background

Hybrid or electric vehicles, in which the driving power is provided by an internal combustion engine and one or more electric drive motors, may operate the electric drive motors as generators during braking in order to convert the kinetic energy of the vehicle into electrical energy and store it in a battery. Such braking processes are commonly referred to as regenerative braking or regenerative braking. In order to recover energy to the maximum, it is desirable to apply the braking deceleration by driving the motor as much as possible at the time of braking. However, the battery cannot continue to store energy after being fully charged, and accordingly, the driving motor cannot continue to operate as a generator to provide a braking action, so that the hybrid vehicle or the electric vehicle is still equipped with a conventional hydraulic or electrohydraulic brake system in order to ensure a sufficient braking deceleration at any time.

During regenerative braking, at least one hydraulic valve of a hydraulic or electrohydraulic brake system is usually controlled by an electronic control unit in order to discharge the pressure medium in the brake circuit, for example, into a low-pressure accumulator of the ESC system, in order to provide the driver with a suitable pedal feel at the brake pedal. However, the piston spring in the low pressure accumulator does not allow the pressure in the brake circuit to be fully released, so that there is a residual pressure in the brake caliper, resulting in a light friction between the friction plates and the brake disc, which consumes part of the kinetic energy and thus reduces the energy recovery efficiency.

Disclosure of Invention

The present invention has been made in view of the above background, and aims to provide a brake system capable of avoiding generation of residual pressure in a brake caliper during regenerative braking, and a method of operating the same.

According to an aspect of the present invention, there is provided a brake system for an electric vehicle or a hybrid vehicle, the brake system including: a brake master cylinder having at least one master cylinder piston and at least one hydraulic chamber defined by the master cylinder piston, the hydraulic chamber being connected to at least one brake circuit via an isolation valve; at least one wheel brake hydraulically connected to a respective brake circuit; a pressure modulation valve arranged in the brake circuit, which pressure modulation valve comprises one inlet valve and one outlet valve for each wheel brake for regulating the brake pressure at the respective wheel brake; a low pressure accumulator having an inlet connected to the discharge valve so as to be capable of receiving the pressure medium discharged from the discharge valve; and a hydraulic pump, a suction side of which is connected to an outlet of the low pressure accumulator, an output side of which is connected to a corresponding brake circuit between the intake valve and the isolation valve. The brake system further includes a pressure relief valve disposed between an inlet of the low pressure accumulator and the isolation valve, the pressure relief valve being a normally closed solenoid valve that is opened during regenerative braking to allow pressure medium in the brake circuit to flow into the low pressure accumulator.

In a preferred embodiment, the isolation valve is a normally open solenoid valve that remains open during regenerative braking.

In a preferred embodiment, the inlet valve is a normally open solenoid valve, which is closed during regenerative braking.

In a preferred embodiment, the exhaust valve is a normally closed solenoid valve that remains closed during regenerative braking.

In a preferred embodiment, a switching valve is also provided between the suction side of the hydraulic pump and the respective hydraulic chamber of the master cylinder, which switching valve is a normally closed solenoid valve and remains closed during regenerative braking.

In a preferred embodiment, the hydraulic pump is a plunger pump driven by a dc motor.

In a preferred embodiment, the brake master cylinder is a tandem master cylinder defining two hydraulic chambers.

According to a further aspect of the invention, a method for operating a brake system as described above is provided, wherein during regenerative braking the isolation valve and the pressure relief valve are opened and the inlet valve and the outlet valve are closed, such that pressure medium in the brake circuit flows into the low pressure accumulator.

In a preferred embodiment, the pressure relief valve is closed and the admission valve is opened when the energy recovered by regenerative braking reaches a maximum permissible value or the braking deceleration generated by regenerative braking fails to meet the braking demand. Further, the hydraulic pump may be activated to deliver pressure medium stored in the low pressure accumulator to the brake circuit.

The braking system and the operation method thereof provided by the invention ensure that residual pressure cannot exist in the braking caliper during regenerative braking, thereby improving the energy recovery efficiency.

Drawings

FIG. 1 is a schematic illustration of a braking system according to an embodiment of the present invention in an inoperative state.

FIG. 2 is a schematic illustration of the braking system shown in FIG. 1 in a braking energy recovery state.

FIG. 3 is a schematic diagram of a conventional braking system during a regenerative braking condition.

Detailed Description

Fig. 1 and 2 show schematic views of a brake system for an electric vehicle or a hybrid vehicle according to an embodiment of the present invention. The brake system is provided with a master cylinder 1 as a first pressure source. The master cylinder 1 is connected to a brake pedal (not shown) which is depressed by a driver to request deceleration of the vehicle. The degree of brake pedal operation may be detected by a stroke detector provided on the brake pedal, but in principle other sensors providing a signal proportional to the driver's brake operation may be used. As shown in fig. 1 and 2, the master cylinder 1 is equipped with a vacuum booster 10. In other embodiments, the brake system may not have a vacuum booster. In the illustrated embodiment, the master brake cylinder 1 is a tandem master cylinder that defines two hydraulic chambers in a housing of the master brake cylinder 1 by a primary piston and a secondary piston; however, the present invention is not limited to the use of such tandem master cylinders. The hydraulic chambers of the master cylinder 1 are connected to a pressure medium reservoir in order to receive pressure medium from the pressure medium reservoir.

The brake pressure built up by the brake master cylinder 1 is transmitted to the wheel brakes 2, which are designed as friction brakes, by means of the pressure medium in the brake lines in order to generate a braking torque acting on the respective wheel. In the illustrated embodiment, the brake system includes two brake circuits I, II and four wheel brakes 2, wherein the wheel brakes 2 of the front left wheel FL and the rear right wheel RR are connected to a first brake circuit I, and the wheel brakes 2 of the front right wheel FR and the rear left wheel RL are connected to a second brake circuit II. That is, each brake circuit of the brake system is diagonally distributed. In a further embodiment, the first brake circuit I can be connected to two wheel brakes 2 on the front axle and the second brake circuit II can be connected to two wheel brakes 2 on the rear axle. Since the first brake circuit I and the second brake circuit II are configured substantially identically, only the components of the first brake circuit I are described below.

A pressure sensor (not shown) can be provided on the hydraulic line of the first brake circuit I to the master cylinder 1 for determining the pilot pressure. The brake line of the first brake circuit I branches after the isolating valve 7 into two brake branches, which lead to the wheel brakes 2 of the front left wheel FL and the wheel brakes 2 of the rear right wheel RR, respectively. A normally open inlet valve 3 is provided in each brake branch. A return line is connected between each inlet valve 3 and the respective wheel brake 2, in each of which a discharge valve 4 is arranged. Both return lines are connected to the inlet of the low pressure accumulator 5 via a common brake line section. As shown in fig. 1, the isolation valve 7 and the inlet valve 3 are both solenoid valves which are normally open, i.e. open in the case of no-electrical control, and the outlet valve 4 is a solenoid valve which is normally closed, i.e. closed in the case of no-electrical control.

The first brake circuit I also has a hydraulic pump 6 driven by the direct current motor M, which can build up pressure as a second pressure source independently of the driver's braking operation. The suction side of the hydraulic pump 6 is connected to the outlet of the low pressure accumulator 5. The output side of the hydraulic pump 6 is connected to the brake line between the isolation valve 7 and the inlet valve 3. Between the outlet of the low-pressure accumulator 5 and the suction side of the hydraulic pump 6, the other brake line opens via a changeover valve 9 into the brake line between the brake master cylinder 1 and the isolating valve 7. As shown in fig. 1, the switching valve 9 is a solenoid valve which is normally closed, i.e. closed in the case of electrical non-control.

If a significant drop in the measured wheel speed occurs at one or more wheels during braking, the inlet valves 3 of the respective wheel brakes 2 can be closed and brake slip regulation can be carried out in a manner known per se. In one embodiment, the brake pressure at the wheel brakes 2 can be determined by means of pressure sensors (not shown) which are respectively arranged in the hydraulic lines of the respective wheel brakes 2. Alternatively, the pressure at the wheel brakes 2 can also be estimated by means of a model known per se.

When the electric vehicle or the hybrid vehicle performs regenerative braking, a driving motor (not shown), which is generally used as a driving power source, operates as a generator to recover kinetic energy of the vehicle as electric energy and charge a battery of the vehicle. In order to efficiently recover energy, the operation of the wheel brakes 2 is not performed as much as possible during regenerative braking. However, in order to provide the driver with a suitable pedal feel at the brake pedal, the pressure medium in the brake circuit needs to be conducted out into the low-pressure accumulator 5.

Fig. 3 shows a schematic diagram of a conventional brake system in a brake energy recovery state. During regenerative braking, at least one normally closed exhaust valve 4 in each brake circuit, for example, the exhaust valve 4 for the wheel brake 2 on the front left wheel FL in the first brake circuit I and the exhaust valve 4 for the wheel brake 2 on the front right wheel FR in the second brake circuit II, is opened by the electronic control unit, thereby causing the pressure medium in the brake circuits to flow into the low pressure accumulator 5. However, since the low pressure accumulator 5 is provided with a piston spring, the force of the piston spring cannot fully release the pressure in the brake circuit, so that there is residual pressure in the brake caliper, resulting in light friction between the friction plates and the brake disc. This results in unnecessary consumption of kinetic energy, reducing energy recovery efficiency.

In response to the above-mentioned problems of conventional brake systems during regenerative braking, the invention proposes that a pressure relief valve 8 be provided in each brake circuit between the inlet of the low-pressure accumulator 5 and the isolating valve 7. As shown in fig. 1, the relief valve 8 is a normally closed solenoid valve provided upstream of the intake valve 3. During regenerative braking, as shown in fig. 2, the pressure relief valve 8 is opened by the electronic control unit while the inlet valve 3 and the outlet valve 4 are closed, so that the pressure medium in the brake circuit flows into the low pressure accumulator 5 without flowing to the wheel brakes 2. Therefore, even if the piston spring of the low pressure accumulator 5 makes it impossible to completely discharge the pressure in the brake circuit, there is no residual pressure in the brake caliper, improving the energy recovery efficiency compared to conventional brake systems.

The method of operation of the brake system in the embodiment shown in fig. 1 and 2 is briefly described below. At the start of braking, the drive motor is preferably first operated as a generator to implement regenerative braking. At this time, as shown in fig. 2, the electronic control unit opens all the relief valves 8 and closes all the intake valves 3 while maintaining the open state of all the isolation valves 7 and the closed state of all the exhaust valves 4 and all the switching valves 9, thereby allowing the pressure medium in the first brake circuit I and the second brake circuit II to flow into the low pressure accumulator 5 without generating frictional force in the wheel brakes 2 that causes a reduction in energy recovery efficiency.

When the energy recovered by regenerative braking is such that the battery reaches a maximum state of charge, or when the braking deceleration, which is generated by regenerative braking, for example in an emergency braking situation, cannot meet the braking demand, the electronic control unit closes the pressure relief valve 8 and opens the inlet valve 3, so that the pressure medium in the brake circuit flows into the wheel brakes 2 and builds up brake pressure there. The pressure medium can come from the brake master cylinder 1 or from the low-pressure accumulator 5. For example, the hydraulic pump 6 may be activated to deliver pressure medium stored in the low pressure accumulator 5 into the brake circuit.

By maintaining the closed state of the relief valve 8 except during regenerative braking, the brake system of the present invention can be operated similarly to the conventional brake system. For example, when the system is building up pressure autonomously, the electronic control unit may open the changeover valve 9 to allow pressure medium to flow from the master cylinder 1 to the suction side of the hydraulic pump 6. These modes of operation are well known to those skilled in the art and will not be described in detail herein.

It will be understood that the above-described embodiments of the present invention are merely exemplary embodiments that have been employed to illustrate the principles of the present invention, and that the present invention is not limited thereto. It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. The scope of the invention is to be defined only by the meaning of the language of the following claims and by the equivalents thereof.