HYDRAULIC BRAKING SYSTEM

Abstract

Hydraulic braking system for a vehicle that features: a wheel brake device (10) which is provided for a wheel of the vehicle and is configured to generate a braking force based on the pressure of one of the working fluids supplied to the wheel brake device (10); a first braking system (12) comprising a high-pressure source device (26) with a first pump device (22) and an accumulator (24) which accumulates the working fluid ejected by the first pump device (22), wherein the first pump device (22) is configured to be driven intermittently such that the pressure of the working fluid accumulated in the accumulator (24) is not lower than a set lower limit pressure and not higher than a set upper limit pressure, wherein the first braking system (12) is configured to supply the working fluid to the wheel brake device (10), the pressure of which is regulated depending on the high-pressure source device (26); a second brake system (14) comprising a second pump device (58) and configured to supply the working fluid to the wheel brake device (10), the pressure of which is regulated depending on the second pump device (58); and a main power source (80) configured to supply power to the first braking system (12) and the second braking system (14), wherein the hydraulic braking system additionally has an auxiliary power source (82) configured to supply power to the first braking system (12) in the event of a failure of the main power source (80), and wherein the first pump device (22) is continuously driven independently of the pressure of the working fluid accumulated in the accumulator (24) when the main power source (80) fails.

Description

BACKGROUND Technical area

[0001] The following disclosure relates to a hydraulic braking system that is installed in a vehicle. Description of the state of the art

[0002] JP 2020-32962 A discloses a hydraulic braking system for a vehicle, comprising a wheel brake device intended for a wheel of the vehicle and configured to generate a braking force based on the pressure of a working fluid supplied to the wheel brake device; a first braking system comprising a high-pressure source device with a first pump device and an accumulator that accumulates the working fluid ejected by the first pump device, wherein the first pump device is configured to be driven intermittently such that the pressure of the working fluid accumulated in the accumulator is not lower than a set lower limit pressure and not higher than a set upper limit pressure; wherein the first braking system is configured to supply the wheel brake device with the working fluid whose pressure is regulated depending on the high-pressure source device; and a second braking system.which has a second pump device and is configured to supply the working fluid to the wheel brake device, the pressure of which is regulated depending on the second pump device, and has a main power source configured to supply power to the first brake system and the second brake system. Documents DE 11 2018 006 055 T5, DE 101 60 619 A1 and DE 100 36 287 A1 disclose further hydraulic brake systems. SUMMARY

[0003] The hydraulic braking system of JP 2020-32 962 A is powered by the main power source. However, it is conceivable that the main power source could fail. Several measures for dealing with a fault or failure of the main power source improve the efficiency of the hydraulic braking system. In this respect, the hydraulic braking system disclosed in JP 2020-32 962 A comprises two braking systems. Therefore, there remains considerable scope for developing measures to prevent the failure of the main power source. Dealing with the failure of a main power source is important regardless of whether the hydraulic braking system comprises the two braking systems. Based on the prior art, the invention aims to provide a highly efficient hydraulic braking system. This objective is achieved according to the invention with a hydraulic braking system having the features of claim 1. Advantageous embodiments are the subject of the dependent claims.

[0004] In a first aspect of the present disclosure, a hydraulic braking system for a vehicle is provided, which has: a wheel brake device designed for a wheel of the vehicle and configured to generate a braking force based on the pressure of one of the working fluids supplied to the wheel brake device; a first braking system comprising a high-pressure source device with a first pump device and a storage or accumulator that accumulates the working fluid ejected by the first pump device, wherein the first pump device is configured to operate or be driven intermittently such that the pressure of the working fluid accumulated in the accumulator is not lower than a set lower limit pressure and not higher than a set upper limit pressure, wherein the first braking system is configured to supply the wheel brake device with the working fluid whose pressure is regulated depending on the high-pressure source device; a second braking system comprising a second pumping device and configured to supply the wheel brake device with the working fluid, the pressure of which is regulated depending on the second pumping device; and a main power source configured to supply power to the first braking system and the second braking system, wherein the hydraulic braking system additionally has an auxiliary power source configured to supply power to the first braking system in the event of a fault or failure of the main power source, and wherein the first pumping device is continuously driven regardless of the pressure of the working fluid accumulated in the accumulator when the main power source fails.

[0005] A second aspect of the present disclosure provides for a hydraulic braking system for a vehicle which has: a main power source; an auxiliary power source; a wheel brake device intended for a wheel of the vehicle; and a braking system to which current is supplied from the main power source, wherein the braking system is configured to regulate, depending on the drive of a motor, a pressure of one of the working fluids to be supplied to the wheel brake device; wherein the auxiliary power source supplies power to the braking system when a fault occurs in the main power source or when the main power source fails, and the motor is continuously driven in the event of a failure of the main power source.

[0006] The hydraulic braking system according to the first aspect of this disclosure includes an auxiliary power source to cope with the failure of the main power source. The auxiliary power source supplies current not to both the first and second braking systems, but only to the first system. This configuration allows the auxiliary power source to have a relatively small capacity. Hereinafter, the first braking system and the second braking system will be referred to as the first system and the second system, respectively.

[0007] The first pump is activated, or driven, when the pressure of the working fluid accumulated in the accumulator (hereinafter referred to as "accumulator pressure") falls below the set lower limit pressure. Driving the first pump requires a high current; in other words, the inrush current is large. With intermittent operation of the first pump, the starting of the pump is repeated, thus placing a heavy load on the auxiliary power source when current is being supplied. That is to say, if the auxiliary power source includes a secondary battery, capacitor, or the like, a large inrush current flowing when the charge level in the auxiliary power source is low will result in a large voltage drop across the auxiliary power source.This voltage drop can adversely affect the actuation of a control unit of the first system and the actuation of other vehicle systems besides the first and second systems when the auxiliary power source supplies power to these other vehicle systems. In the hydraulic brake system according to the present disclosure, the first pump device, when driven by the auxiliary power source, is driven continuously, independent of the accumulator pressure, instead of being driven intermittently. Thus, the hydraulic brake system according to the present disclosure prevents the adverse effect on the control unit of the first system and the actuation of the other vehicle systems, even if a failure occurs in the main power source.

[0008] In the hydraulic braking system according to the second aspect of this disclosure, in the event of a failure of the main power source, the motor that drives the working fluid in the braking system is continuously driven by the current supplied by the auxiliary power source. This configuration reduces the number of inrush currents to the motor compared to a configuration in which the motor is driven intermittently, thereby reducing the voltage drop of the auxiliary power source. This makes it possible to cope with the failure of the main power source in a suitable manner. VARIOUS FORMS

[0009] The hydraulic braking system according to the present disclosure can use as its main power source a power source that includes a storage battery for storing current generated, for example, by an alternator (a generator). In contrast, the auxiliary power source primarily serves to cope with the failure of the main power source and only needs to supply current for a relatively short time. It is therefore desirable for the auxiliary power source to have a lower capacity than the main power source. To simplify the design of the hydraulic braking system, it is desirable for the auxiliary power source to be charged not by the alternator, but by the main power source via a converter or the like.As explained in detail later, in a case where the auxiliary power source is configured to supply power to a system even when there is no failure of the main power source, it is preferably configured to supply power to a system while being charged by the main power source at all times.

[0010] Consider a case in which the vehicle, in which the hydraulic braking system of the present disclosure is installed, is configured for automated driving. In this case, more suitable measures must be taken when the main power source fails during automated driving than when the main power source fails during manual driving by the driver. From the perspective of quickly and smoothly handling the failure of the main power source during automated driving, the hydraulic braking system of the present disclosure is preferably configured such that, during automated driving, the auxiliary power source supplies power to the first system instead of the main power source, even if no failure occurs in the main power source.

[0011] The hydraulic braking system comprises the pump devices, the electromagnetic valves, etc. The hydraulic braking system is controlled by a control unit, which typically includes a computer, drives for electric motors (each as a drive source) of the pump devices, drives for the electromagnetic valves, etc. Only the first system operates if the main power source in the hydraulic braking system of this disclosure fails. Accordingly, the first system preferably comprises a first control unit configured to control the first system, and the second system preferably comprises a second control unit configured to control the second system. The two control units provide a sufficiently redundant hydraulic braking system. It is desirable that, under normal operating conditions, the two systems jointly control the braking force generated by the wheel brake device.In this case, the first control unit and the second control unit can be configured to perform their respective controls while, for example, sending and receiving information to each other through communication.

[0012] The primary power source is not limited to the one that supplies only the first and second systems. That is, the primary power source can also supply power to other vehicle systems besides the first and second systems. Such a hydraulic braking system can be configured so that in the event of a failure of the primary power source, the auxiliary power source supplies power not only to the first system, but also to at least some of the other vehicle systems.

[0013] In the hydraulic brake system of the present disclosure, the working fluid, the pressure of which is regulated with respect to the first system or the second system depending on the high-pressure source device or the second pump device, can be the working fluid itself supplied by the high-pressure source device or the second pump device and whose pressure is regulated, or it can be another working fluid whose pressure is regulated using the pressure of the working fluid supplied by the high-pressure source device or the second pump device.

[0014] In the hydraulic braking system of the present disclosure, the specific structures of the first and second systems and the interaction of the two systems are not limited to specific structures. For example, the hydraulic braking system of the present invention can be configured such that the working fluid is supplied from the first system to the second system, and that the second system supplies the working fluid to the wheel brake device at a second pressure that is higher than a first pressure, which is the pressure of the working fluid supplied by the first system. The hydraulic braking system configured in this way makes it possible to easily implement joint control of the braking force by the first and second systems.In the hydraulic brake system configured in this way, the second pump device of the second system is driven when the second system supplies the wheel brake device with the working fluid at the second pressure, namely when the second system supplies the wheel brake device with the working fluid whose pressure is higher than the pressure of the working fluid supplied by the first system.

[0015] If the first pump of the first system is continuously driven during a failure of the main power source, the pressure in the accumulator can become too high. Accordingly, the first system preferably has a pressure relief valve that releases the pressure of the working fluid accumulated in the accumulator when the pressure reaches an overpressure higher than the set upper limit pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The functions, features, advantages, and technical and industrial significance of this disclosure will be better understood if one reads the following detailed description of an embodiment when it is considered in conjunction with the accompanying drawings, in which: Fig. 1 a hydraulic circuit diagram of a hydraulic brake system installed in a vehicle according to an embodiment; Fig. 2A is a block diagram illustrating the relationship between power sources and the hydraulic braking system of the embodiment and other vehicle-side systems when the vehicle is driven manually; Fig. 2B is a block diagram illustrating the relationship between the power sources and the hydraulic braking system of the embodiment and the other vehicle-side systems during automated driving of the vehicle; Fig. 2C is a block diagram illustrating the relationship between the power sources and the hydraulic braking system of the embodiment and the other vehicle-side systems in the event of a failure of a main power source; Fig. 3 a flowchart representing a high-pressure source device control program and a flowchart representing a master cylinder pressure control program, both of which are executed in the hydraulic brake system of the embodiment; Fig. 4 is a flowchart representing a wheel cylinder pressure control program that is executed in the hydraulic brake system of the embodiment; Fig. 5A is a diagram illustrating a relationship between the drive of a pump device in the hydraulic brake system of the embodiment and changes in an accumulator pressure, an electric current supplied to a pump motor, and a voltage of a current source supplying the electric current to the pump device, wherein the diagram illustrates a case in which the pump device is driven intermittently; and Fig. 5B is a diagram illustrating the relationship between the drive of the pump device in the hydraulic brake system of the embodiment and the changes in the accumulator pressure, the electric current supplied to the pump motor, and the voltage of the power source supplying the electric current to the pump device, the diagram illustrating a case in which the pump device is driven continuously. DETAILED DESCRIPTION OF THE EXECUTION FORM

[0017] The drawings illustrate in detail a hydraulic braking system according to one embodiment of the present disclosure. It should be noted that the present disclosure is not limited to the details of the following embodiment, but may be based on the forms described in "various forms" and may be modified and altered based on the knowledge of those skilled in the art. A. Configuration of the hydraulic braking system

[0018] Referring to a hydraulic circuit diagram in Fig. 1. A configuration of a hydraulic braking system according to an embodiment of the present disclosure is described. The hydraulic braking system is configured to exert a braking force on each of the four wheels of a vehicle, i.e., on the right and left front wheels and the right and left rear wheels. As shown from Fig. As can be seen from Figure 1, the hydraulic braking system comprises wheel brake devices 10FL, 10FR, 10RL, 10RR (hereinafter each referred to as a “wheel brake device 10”), which are provided for a left front wheel, a right front wheel, a left rear wheel, and a right rear wheel. Each wheel brake device 10 has a conventional structure consisting of a disc rotor that rotates with the corresponding wheel and a brake caliper supported by a carrier that allows the wheel to rotate. The brake caliper comprises brake pads, a wheel cylinder to which the working fluid is supplied, and an actuator configured to move a piston, by pressure from the working fluid supplied to the wheel cylinder, to press the brake pads against the disc rotor. Hereinafter, “supplying the working fluid to the wheel cylinder of the brake caliper of the wheel brake device 10” is, where appropriate, simply expressed as “supplying the working fluid to the wheel brake device 10.”

[0019] The hydraulic braking system according to the present embodiment (hereinafter optionally referred to as "the present braking system") comprises two braking systems, i.e., a first braking system 12 (hereinafter optionally referred to as "first system 12") and a second braking system 14 (hereinafter optionally referred to as "second system 14"). With respect to the flow of the working fluid supplied to the wheel brake devices 10, the first system 12 can be referred to as an upstream system (which can be considered a subsystem) and the second system 14 as a downstream system (which can be considered the main system). As will be explained in detail later, the working fluid supplied by the first system 12 is routed via the second system 14 to the wheel brake devices 10. The hydraulic braking system includes a brake pedal 16 as the brake actuation element.

[0020] The first system 12 comprises: a typical high-pressure source device 26 with a reservoir 20 in which the working fluid is stored at atmospheric pressure; a first pumping device 22 configured to pump the working fluid up into the reservoir 20 and pressurize it; an accumulator 24; a master cylinder 28 to which the brake pedal 16 is connected; a regulator 30 as a control device; and an electromagnetic pressure-boosting linear valve SLA and an electromagnetic pressure-reducing linear valve SLR. The first pumping device 22 comprises a piston pump 22a and a pump motor 22b, which is an electric motor for driving the pump 22a.

[0021] The main cylinder 28 comprises a housing 28a and three pistons arranged in the housing 28a, namely an inlet piston 28b, a first pressure piston 28c, and a second pressure piston 28d. Within the housing 28a, there is an intermediate piston chamber R1 between the inlet piston 28b and the first pressure piston 28c, a first pressure chamber R2 between the first pressure piston 28c and the second pressure piston 28d, and in front of the second pressure piston 28d (in Fig. 1 on the left side) a second pressure chamber R3, an annular servo chamber R4 behind a flange 28e of the first pressure piston 28c (in Fig. 1 on the right side) and an annular counterforce chamber R5 is defined in front of the flange 28e. The input piston 28b is connected to the brake pedal 16 via a rod 32.

[0022] In the first system 12, an inter-chamber connecting passage 34 is provided to establish a connection between the inter-piston chamber R1 and the counterforce chamber R5. An inter-chamber communication valve SGH is arranged in the inter-chamber connecting passage 34. The inter-chamber communication valve SGH is a normally closed electromagnetic open / close valve. The normally closed valve is in a closed state when not energized and in an open state when energized. In the first system 12, a counterforce chamber release passage 36 is provided to establish a connection between the reservoir 20 and a section of the inter-chamber connecting passage 34 located between the inter-chamber communication valve SGH and the counterforce chamber R5. A two-chamber shut-off valve SSA is arranged in the counterforce chamber release passage 36.The two-chamber shut-off valve SSA is a normally open electromagnetic open / close valve. The normally open valve is in an open state when not energized and in a closed state when energized. A stroke simulator 38 is connected to a section of the inter-chamber connecting passage 34, located between the inter-chamber communication valve SGH and the counterforce chamber R5. The stroke simulator 38 enables depressor actuation of the brake pedal 16 while an actuation reaction force is applied to the brake pedal 16.

[0023] In normal operation, the inter-chamber communication valve SGH and the two-chamber shut-off valve SSA are energized, so that the inter-chamber communication valve SGH is in the open state and the two-chamber shut-off valve SSA is in the closed state. That is, the inter-piston chamber R1 and the counter-force chamber R5 are closed while communicating with each other. The pressure-bearing area of ​​the first pressure piston 28c with respect to the inter-piston chamber R1 is equal to the pressure-bearing area of ​​the flange 28e of the first pressure piston 28c with respect to the counter-force chamber R5. Accordingly, the first pressure piston 28c does not move forward in the state in which the inter-chamber communication valve SGH and the two-chamber shut-off valve SSA are energized, even if the working fluid in the inter-piston chamber R1 is pressurized by actuating the brake pedal 16.When the working fluid is supplied to servo chamber R4 in this state, the first pressure piston 28c moves forward by a force corresponding to the pressure of the working fluid, namely a force corresponding to a servo pressure Psrv, and the second pressure piston 28d is moved forward by the forward movement of the first pressure piston 28c. The forward movements of the first pressure piston 28c and the second pressure piston 28d cause the working fluid in the first pressure chamber R2 and the second pressure chamber R3 to be pressurized to a master cylinder pressure Pmc corresponding to the servo pressure Psrv, so that the pressurized working fluid in the first pressure chamber R2 and the second pressure chamber R3 is supplied to the second system 14 via master fluid passages 40f, 40r (hereinafter each referred to as "master fluid passage 40").

[0024] In the event of an electrical fault or failure in the first system 12, the interchamber communication valve SGH and the two-chamber shut-off valve SSA are not energized, so that the counterforce chamber R5 is depressurized to atmospheric pressure, while the inter-piston chamber R1 remains closed. In this state, the first pressure piston 28c and the second pressure piston 28d move forward due to an actuating force exerted by the driver on the brake pedal 16, independent of the servo pressure Psrv, and the working fluid at the master cylinder pressure Pmc corresponding to the actuating force is supplied to the second system 14.

[0025] The regulator 30 is a control device with a slide valve mechanism. That is, the regulator 30 comprises: a housing 30a; and a piston 30b and a slide 30c, which are arranged in the housing 30a. The piston 30b and the slide 30c are moved forward (in Fig. (1 in the direction of the left side). In the housing 30a, a first pilot chamber or control chamber R6 is defined between the piston 30b and the slide 30c, and a second pilot chamber or control chamber R7 is defined in front of the piston 30b. It should be noted that the second control chamber R7 forms part of the main fluid passage 40f.

[0026] The housing 30a is provided with a low-pressure port P1, a high-pressure port P2, and a control pressure port P3. The low-pressure port P1 is connected to the reservoir 20, the high-pressure port P2 is connected to the high-pressure source device 26, and the control pressure port P3 is connected via corresponding fluid passages to the servo chamber R4 of the main cylinder 28. Fig. Figure 1 shows a state in which pressure is not introduced into the first control chamber R6. In this state, the slide 30c is in its forward-end position, the low-pressure port P1 and the control pressure port P3 are connected, and the high-pressure port P2 and the control pressure port P3 are disconnected. The pressure of the working fluid in the first control chamber R6 is referred to as the first pilot pressure or control pressure Pp1. When the working fluid is supplied to the first control chamber R6 with a relatively high first control pressure Pp1, the slide 30c moves to the rear, the low-pressure port P1 and the control pressure port P3 are disconnected, and the high-pressure port P2 and the control pressure port P3 are connected. That is, the governor 30 supplies working fluid from the control pressure port P3 to the servo chamber R4 of the master cylinder 28, with a pressure level corresponding to the first control pressure Pp1.In other words, the controller 30 has the task of regulating the servo pressure Psrv to a pressure level that corresponds to the first control pressure Pp1.

[0027] In the first system 12, a second control pressure Pp2 (equal to the pressure of the main cylinder Pmc), corresponding to the pressure of the working fluid in the second control chamber R7, is slightly lower than the first control pressure Pp1. Thus, the piston 30b does not operate under normal conditions. However, in a situation where the first control pressure Pp1 is not introduced into the first control chamber R6 due to an electrical failure or the like, the working fluid at servo pressure Psrv, whose pressure level corresponds to the second control pressure Pp2, is supplied by the governor 30 to the main cylinder 28 until the pressure of the working fluid supplied by the high-pressure source device 26 (hereinafter optionally referred to as "accumulator pressure Pacc") drops to a certain level.

[0028] The pressure booster linear valve SLA and the pressure reducer linear valve SLR are arranged in series in a fluid passage connecting the high-pressure source device 26 and the reservoir 20. The pressure booster linear valve SLA and the pressure reducer linear valve SLR regulate the pressure of the working fluid between them; that is, the valves SLA and SLR regulate the first control pressure Pp1. The pressure booster linear valve SLA is a normally closed linear valve. The pressure booster linear valve SLA regulates a difference between the pressure of the working fluid on an upstream side and the pressure of the working fluid on a downstream side, i.e., a pressure differential, depending on the excitation flow supplied to it. In particular, the pressure booster linear valve SLA regulates the pressure differential so that it decreases when the excitation flow increases. The pressure reducer linear valve SLR is a normally open linear valve.The pressure-reducing linear valve SLR regulates a difference between the pressure of the working medium on an upstream side and the pressure of the working medium on a downstream side, i.e., a pressure differential, depending on the excitation flow supplied to it. Specifically, the pressure-reducing linear valve SLR regulates the pressure differential so that it increases with an increase in the excitation flow. Although not explained in detail, the initial control pressure Pp1, which is fed into the regulator 30, is controlled by controlling the excitation flow supplied to both the pressure-boosting linear valve SLA and the pressure-reducing linear valve SLR.

[0029] The second system 14 is formed from two systems corresponding to the two main fluid passages 40f and 40r, i.e., a front wheel system 50f and a rear wheel system 50r (hereinafter each referred to as "system 50"). The second system 14 includes an electromagnetic pressure control linear valve SMF, provided in the front wheel system 50f, and an electromagnetic pressure control linear valve SMR, provided in the rear wheel system 50r.The second system 14 additionally comprises in each system 50 two pairs of electromagnetic opening / closing valves corresponding to the right and left wheel brake devices 10, in particular a pair of a pressure holding valve SFLH and a pressure reducing valve SFLR for the wheel brake device 10FL, a pair of a pressure holding valve SFRH and a pressure reducing valve SFRR for the wheel brake device 10FR, a pair of a pressure holding valve SRLH and a pressure reducing valve SRLR for the wheel brake device 10RL and a pair of a pressure holding valve SRRH and a pressure reducing valve SRRR for the wheel brake device 10RR. In the following, the pressure regulating linear valves SMF, SMR will be referred to as "pressure regulating linear valve SM" where applicable, the pressure holding valves SFLH, SFRH, SRLH, SRRH will be referred to as "pressure holding valve SH" where applicable, and the pressure reducing valves SFLR, SFRR, SRLR, SRRR will be referred to as "pressure reducing valve SR" where applicable.

[0030] In the front wheel system 50f and the rear wheel system 50r, the main fluid passage 40 branches into two wheel supply passages 52L, 52R (hereinafter referred to as "wheel supply passage 52") to supply the left and right wheel brake devices 10, respectively, with working fluid. The pressure regulating linear valve SM is located upstream of the branch point. The pressure holding valve SH is located in each wheel supply passage 52. The pressure reducing valve SR is located in a pressure reducing passage 56, which connects a reservoir 54 and a section of each wheel supply passage 52 located between the pressure holding valve SH and the wheel brake device 10.

[0031] Although not described in detail, a second pumping device 58 is provided in both the front wheel system 50f and the rear wheel system 50r. Each second pumping device 58 comprises a pump and a pump motor for driving the pump. The second pumping device 58 is configured to pump the working fluid from the reservoir 54 and pressurize the working fluid. The pressurized working fluid is then fed, via a check valve 60, to a section of the main fluid passage 40 located downstream of the pressure regulating linear valve SM, i.e., upstream of the pressure holding valves SH. A section of the main fluid passage 40 located upstream of the pressure regulating linear valve SM is connected to the reservoir 54 via an inflow permit valve 62, which allows the working fluid to flow into the reservoir 54 when the quantity of working fluid in the reservoir 54 is less than a set quantity.

[0032] Each pressure-holding valve SH is a normally open electromagnetic open / close valve, and each pressure-reducing valve SR is a normally closed electromagnetic open / close valve. Neither the pressure-holding valve SH nor the pressure-reducing valve SR is energized during normal operation. The pressure-holding valve SH and the pressure-reducing valve SR are energized when the wheel cylinder pressures Pwcf, Pwcr (hereafter referred to as "wheel cylinder pressure Pwc") are released in a situation where the hydraulic braking system is performing an anti-lock braking (ABS) operation, traction control (TRC) operation, vehicle stability control (VSC) operation, etc. The wheel cylinder pressure Pwc is a pressure of the working fluid supplied to the wheel cylinder of each wheel brake device 10.

[0033] Each pressure control linear valve SM is a normally open electromagnetic linear valve. The pressure control linear valve SM regulates a pressure differential, i.e., a difference between the master cylinder pressure Pmc and the wheel cylinder pressure Pwc, depending on the excitation flow supplied to it. In particular, the pressure control linear valve SM regulates the pressure differential so that it increases with an increase in the excitation flow. By controlling the supply flow to the pressure control linear valve SM while the second pump device 58 is driven, the working fluid, whose pressure is regulated in accordance with the supply flow so that it is higher than the master cylinder pressure Pmc, is directed to each wheel brake device 10. In other words, the hydraulic brake system is configured such that the working fluid is directed from the first system 12 to the second system 14.Furthermore, in a case where the master cylinder pressure Pmc is defined as a first pressure and the wheel cylinder pressure Pwc is defined as a second pressure, the second system 14 is configured to supply each wheel brake device 10 with the working fluid which has the second pressure higher than the first pressure, which is the pressure of the working fluid supplied by the first system 12.

[0034] The first system 12 has an electronic control unit of the first brake 70 as a first control unit configured to control the first system 12, and the second system 14 has an electronic control unit of the second brake 72 as a second control unit configured to control the second system 14. Hereinafter, the electronic control unit of the first brake 70 and the electronic control unit of the second brake 72 are referred to as "first brake ECU 70" and "second brake ECU 72," respectively. The first brake ECU 70 controls actuations of the pump motor 22b of the first pump device 22, the pressure boosting linear valve SLA, the pressure reducing linear valve SLR, the intermediate chamber communication valve SGH, the dual-chamber shut-off valve SSA, etc.The first brake ECU 70 comprises a computer and drivers (actuator circuits) for the pump motor 22b, the pressure-increasing linear valve SLA, the pressure-reducing linear valve SLR, the interchamber communication valve SGH, the dual-chamber shut-off valve SSA, etc. The second brake ECU 72 controls the actuations of the pump motor of the second pump device 58, the pressure-regulating linear valve SM, the pressure-holding valves SH, the pressure-reducing valves SR, etc., of both the front wheel system 50f and the rear wheel system 50r. The second brake ECU 72 has a computer and drivers (actuator circuits) for the pump motor, the pressure-regulating linear valve SM, the pressure-holding valves SH, the pressure-reducing valves SR, etc., of both the front wheel system 50f and the rear wheel system 50r. The first brake ECU 70 and the second brake ECU 72 transmit and receive information via a CAN (controllable area network) that is not shown.“Controllable Area Network” or “Car Area Network”) to control the first System 12 or the second System 14. B. Relationship between: power sources and hydraulic braking systems and other vehicle systems

[0035] As in the Fig. As shown in Figures 2A to 2C, the vehicle is equipped with a main power source 80 and an auxiliary power source 82, which can be used in the event of a failure of the main power source 80. The main power source 80 stores the current generated by an alternator 84 and has a relatively large capacity. The auxiliary power source 82, on the other hand, is connected to the main power source 80 via a DC-DC converter 86 and is constantly recharged by the main power source 80. The auxiliary power source 82 has a significantly lower capacity than the main power source 80.

[0036] In addition to the hydraulic braking system, other systems are also installed in the vehicle. These systems will be referred to below, where appropriate, as "other vehicle systems". In the Fig. Figures 2A to 2C depict an automated driving system and a steering system. The present hydraulic braking system can be considered a redundant system, comprising the second system 14 as a main system and the first system 12 as a subsystem. Similarly, the automated driving system and the steering system are each also redundant systems. As shown in the Fig. As shown in Figures 2A to 2C, the automated driving system comprises: a main electronic control unit for automated driving (hereinafter referred to as the “main automated driving ECU”) 90m and a sub-electronic control unit for automated driving (hereinafter referred to as the “sub-automated driving ECU”) 90s, configured to control the automated driving of the vehicle; and a main detection sensor 92m and a sub-detection sensor 92s, such as lidars and cameras, the sensors 92m and 92s being sensors related to automated driving. The steering system also operates during automated driving and comprises a main steering system 94m and a sub-steering system 94s.

[0037] When the vehicle is driven by manual operation of the driver (hereinafter referred to as “manual driving”), the current from the main power source 80 is additionally routed to the second system 14 of the hydraulic braking system of the main ECU for automated driving 90m, the main detection sensor 92m and the main steering system 94m, as shown in Fig. 2A is shown. Furthermore, the current from the main power source 80 is also supplied to the first system 12 of the hydraulic brake system of the sub-ECU for automated driving 90s, the under-detection sensor 92s and the under-steering system 94s.

[0038] During automated driving, the current from the main power source 80 is routed to the second system 14 of the hydraulic braking system of the main ECU for automated driving 90m, the main detection sensor 92m and the main steering system 94m, as shown in Fig. Figure 2B shows that the DC-DC converter 86 has a circuit. To ensure suitable operation of the redundant systems in the event of a failure of the main power source 80 during automated driving, current from the auxiliary power source 82 is supplied in addition to the first system 12 of the hydraulic braking system of the sub-ECU for automated driving 90s, the under-detection sensor 92s and the under-steering system 94s.

[0039] Consider a situation where the main power source 80 is not functioning. If the main power source 80 is not functioning during manual driving, none of the systems will receive power from the moment the main power source 80 fails, since the auxiliary power source 82 does not supply power to any of the systems during manual driving. In a case where the main power source 80 is not functioning during automated driving, power from the auxiliary power source 82 will continue to be supplied to the automated driving sub-ECU 90s, the under-detection sensor 92s, the under-steering system 94s, and the first system 12 of the hydraulic brake system, which were previously supplied with power by the auxiliary power source 82. That is, as in Fig. As shown in Figure 2C, the current from the auxiliary power source 82 is supplied to the first system 12 of the hydraulic brake system only to the sub-ECU for automated driving 90s, the under-detection sensor 92s and the under-steering system 94s, until the current stored in the auxiliary power source 82 is depleted. C. Control of the hydraulic braking system(a) Control during normal operation

[0040] Under normal operating conditions, i.e., in a situation where no failure occurs in the hydraulic brake system, the first system 12 and the second system 14 of the present hydraulic system are each controlled independently by the first brake ECU 70 and the second brake ECU 72, respectively. The control of the first system 12 and the control of the second system 14 are explained below in that order. i) Control of the first braking system

[0041] In the control of the first system 12, a control of the high-pressure source device 26 and a control of the pressure of the working fluids led from the first system 12 to the second system 14, i.e. a control of the main cylinder pressure Pmc, are carried out in parallel to each other.

[0042] In the control of the high-pressure source device 26, the actuation of the pump motor 22b is controlled such that the pressure of the working fluid from the high-pressure source device 26, i.e., the accumulator pressure Pacc, which is the pressure of the working fluid accumulated in the accumulator 24, does not fall below a set lower limit pressure PaccL and does not rise above a set upper limit pressure PaccU. The first brake ECU 70 repeatedly executes a high-pressure source device control program at short intervals, e.g., from a few to a few tens of milliseconds (ms), which is defined by a Fig. The flow diagram shown in Figure 3 represents the control of the high-pressure source device 26.

[0043] The high-pressure source device control program begins with step 1, in which the accumulator pressure Pacc is measured by the accumulator pressure sensor 100 ( Fig. 1) is recorded. (Step 1 is abbreviated as "S1" below. The other steps are abbreviated similarly.) In S2, it is determined whether a pump flag Fpump is "1". The pump flag Fpump is a marker or flag whose initial value, i.e., a value when the first pump device 22 is not driven, is "0" and which is set to "1" when the first pump device 22 is driven.

[0044] If the pump flag Fpump is determined to be "0", S3 determines whether the detected accumulator pressure Pacc is lower than the set lower limit pressure PaccL. If the accumulator pressure Pacc is not lower than the set lower limit pressure PaccL, the first pump device 22 remains stopped. If the accumulator pressure Pacc is lower than the set lower limit pressure PaccL, the control flow passes to S4 to start the drive of the first pump device 22. That is, electrical current is supplied to the pump motor 22b, and the pump motor 22b begins to operate. In S5, the pump flag Fpump is set to "1".

[0045] If S2 determines that the pump flag Fpump is "1", S6 determines whether the detected accumulator pressure Pacc is higher than the set upper limit pressure PaccU. If it is determined that the accumulator pressure Pacc is not higher than the set upper limit pressure PaccU, the first pump device 22 continues to be driven. If S6 determines that the accumulator pressure Pacc is higher than the set upper limit pressure PaccU, the drive of the first pump device 22 is terminated in S7. That is, the electrical current is no longer supplied to the pump motor 22b, and the pump motor 22b stops operating. In S8, the pump flag Fpump is set to "0".

[0046] According to the control described above, the first pumping device 22 is driven each time the accumulator pressure Pacc falls below the set lower limit pressure PaccL due to the generation of the braking force, until the accumulator pressure Pacc reaches the set upper limit pressure PaccU. In other words, the first pumping device 22 is driven intermittently to control the accumulator pressure Pacc so that it is neither lower than the set lower limit pressure PaccL nor higher than the set upper limit pressure PaccU.

[0047] In the master cylinder pressure control (Pmc), the electrical current supplied to each of the pressure-increasing linear valve (SLA) and the pressure-reducing linear valve (SLR) is controlled based on a pedal stroke δ, which is the amount of actuation (depression) of the brake pedal 16. The first brake ECU 70 repeatedly executes a master cylinder pressure control program at short intervals, e.g., from a few to several tens of milliseconds (ms), which is determined by a Fig. The flowchart shown in section 3 represents how the main cylinder pressure (PMC) is controlled.

[0048] The master cylinder pressure control program begins with S11, in which a required braking force Fb* is determined. The required braking force Fb* is a target for the braking force Fb to be generated. In manual driving mode, the required braking force Fb* is determined based on the pedal travel δ, i.e., the amount of actuation (depression) of the brake pedal 16, according to the following expression: Fb*=α⋅δ α: Gain (coefficient)

[0049] In this respect, the hydraulic braking system of the present embodiment has two redundant pedal stroke sensors 102a, 102b ( Fig. 1) as sensors for detecting pedal travel δ. The pedal travel δ detected by pedal travel sensor 102a is used to control the master cylinder pressure Pmc, while the pedal travel δ detected by pedal travel sensor 102b is used to control the wheel cylinder pressure Pwc, which will be explained later. During automated driving, the required braking force Fb* is determined based on a command from the automated driving sub-ECU 90s, as explained above.

[0050] In S12, a target servo pressure Psrv* is determined based on the required braking force Fb* according to the following expression. The target servo pressure Psrv* is a target of the servo pressure Psrv, which is the pressure of the working fluid that is supplied by the controller 30 to the servo chamber R4 of the master cylinder 28. Psrv*=β⋅Rp⋅Fb* β:: Gain (coefficient)

[0051] In the above expression, “Rp” is a contribution ratio of the first system 12 with respect to the braking force Fb.

[0052] The contribution ratio Rp is explained. In the present hydraulic brake system, which is constructed as described above, the braking force Fb can be controlled solely by the first system 12, solely by the second system 14, or jointly by the first system 12 and the second system 14. That is, the braking force Fb can be controlled by controlling the pressure of the working fluid supplied by the first system 12, namely the master cylinder pressure Pm, while the pressure control linear valves SM of the second system 14 are held in the open position. Even if the master cylinder pressure Pmc is held at atmospheric pressure, the braking force Fb can also be controlled by controlling the excitation flow to the pressure control linear valves SM while the second pump device 58 of the second system 14 is driven. Furthermore, the braking force Fb can be controlled as follows.The excitation current to the pressure control linear valves SM is controlled while the second pump device 58 is driven to control the pressure difference between the wheel cylinder pressure Pwc and the master cylinder pressure Pmc in a state in which the pressure level of the master cylinder pressure Pmc is made lower than a pressure level at which the required braking force Fb* is generated only by the master cylinder pressure Pmc.

[0053] The control of the braking force Fb by the first system 12 (hereinafter referred to simply as control by the first system 12) and the control of the braking force Fb by the second system 14 (hereinafter referred to simply as control by the second system 14) differ in their characteristics. With control by the second system 14, the braking force Fb increases more rapidly, and the tracking capability in a range where the braking force Fb is relatively small is better than with control by the first system 12. In this case, the good tracking capability means that the actual braking force Fb is less likely to be delayed compared to the required braking force Fb.When controlled by the first system 12, a relatively large braking force Fb, which requires a relatively large amount of supplied working fluid for each wheel brake device 10, is reached earlier than when controlled by the second system 14. Given the difference in their characteristics, the combined control by the first system 12 and the second system 14 in the present hydraulic system is implemented, for example, such that the contribution by the control of the second system 14 is increased when the required braking force Fb* is relatively small, while the contribution by the first system 12 is increased when the required braking force Fb* is relatively large. Although not described in detail, the contribution ratio Rp is therefore set so that it increases with an increase in the required braking force Fb*, falling within a range of 0 to 1.

[0054] After the target servo pressure Psrv* has been determined based on the contribution ratio Rp, a first target control pressure Pp1* is determined in S13 based on the target servo pressure Psrv*. The first target control pressure Pp1* is a target of a first control pressure Pp1, which is the pressure of the working fluid in the first control chamber R6 of the controller 30. (The determination of the first target control pressure Pp1* is not explained here). The control flow continues in S14, in which a pressure boost excitation flow Ia, to be supplied to the pressure boost linear valve SLA, and a pressure reduction excitation flow Ir, to be supplied to the pressure reduction linear valve SLR, are determined based on the first target control pressure Pp1*. In S15, the pressure boosting excitation current Ia and the pressure reducing excitation current Ir, which are determined in S14, are supplied to the pressure boosting linear valve SLA and the pressure reducing linear valve SLR, respectively.According to the procedure explained above, the working fluid is supplied from the first system 12 to the second system 14 at the main cylinder pressure Pmc, which corresponds to the required braking force Fb* and takes into account the contribution ratio Rp.

[0055] The relatively simple control of the master cylinder pressure Pmc was explained above. The first system 12 includes a servo pressure sensor 104 ( Fig. 1) for detecting an actual servo pressure Psrv. The first target servo pressure Pp1* can be determined, for example, according to a control law based on a deviation of the actual servo pressure Psrv from the target servo pressure Psrv*. The first system 12 includes a reaction force pressure sensor 106 for detecting the pressure of the working fluid in the lifting simulator 38 as the reaction force pressure Prct. The required braking force Fb* can be determined based on the reaction force pressure Prct, i.e., based on a braking force applied by the driver to the brake pedal 16. ii) Control of the second braking system

[0056] The control of the second system 14 serves to control the wheel cylinder pressure Pwc to a pressure level corresponding to the required braking force Fb*. The wheel cylinder pressure Pwc is the pressure of the working fluid supplied to the wheel cylinder of each wheel brake device 10. The second brake ECU 72 repeatedly executes a wheel cylinder pressure control program at short intervals, e.g., from a few to several tens of milliseconds (ms), which is controlled by a Fig. The flowchart shown in section 4 represents the control of the wheel cylinder pressure Pwc. The control of the wheel cylinder pressure Pwc is implemented for both the front wheel system 50f and the rear wheel system 50r. Since the control procedures for the front wheel system 50f and the rear wheel system 50r are identical, the controls will be explained with a focus on one of them.

[0057] In the procedure according to the wheel cylinder pressure control program, the required braking force Fb* in S21 is determined as in the procedure according to the master cylinder pressure control program. During manual driving, the required braking force Fb* is determined according to the above expression based on the pedal stroke δ detected by pedal stroke sensor 102b. During automated driving, the required braking force Fb* is determined by the main ECU 90m for automated driving based on the command explained above. A change in the determination of the required braking force Fb* in the first system 12 and the determination of the required braking force Fb* in the second system 14 can be performed based on the value determined in the other of the two determinations and transmitted via CAN.

[0058] In S22, a target wheel cylinder pressure Pwc* is determined based on the specified required braking force Fb* according to the following expression. The target wheel cylinder pressure Pwc* is a setpoint for the wheel cylinder pressure Pwc. Pwc*=γ⋅Fb* Pwc*=γ·Fb* γ: Gain (coefficient)

[0059] In S23, an actual master cylinder pressure PMC is measured by the master cylinder pressure sensor 108 ( Fig. 1) of the second system 14 is recorded. In S24, a pressure difference ΔP, which is a difference between the target wheel cylinder pressure Pwc* and the master cylinder pressure Pmc, is determined based on the recorded master cylinder pressure Pmc and the target wheel cylinder pressure Pwc* according to the following expression: ΔP=Pwc*−Pmc

[0060] Subsequently, in S25, it is determined whether the pressure difference ΔP is greater than 0. If the pressure difference ΔP is greater than 0, the second pump device 58 is driven in S26. That is, the second system 14 is only driven if the working fluid, whose pressure is higher than the master cylinder pressure Pmc, is supplied to each wheel brake device 10. In S27, a pressure control excitation flow Im, which is an excitation flow to be supplied to the pressure control linear valve SM, is determined based on the pressure difference ΔP. In S28, the determined pressure control excitation flow Im is supplied to the pressure control linear valve SM.

[0061] If S25 determines that the pressure difference ΔP is equal to 0, the second pump device 58 is stopped in S29, and the pressure control excitation current Im is determined to be 0 in S30. Accordingly, the excitation current is not supplied to the pressure control linear valves SM.

[0062] The relatively simple control of the wheel cylinder pressure Pwc was explained above. The second system 14 comprises wheel cylinder pressure sensors 110 ( Fig. 1), each of which detects a current wheel cylinder pressure Pwc. The pressure control excitation current Im can be determined according to a control law based on a deviation of the actual wheel cylinder pressure Pwc from the target wheel cylinder pressure Pwc*. As with the control of the master cylinder pressure Pmc in the first system 12, the required braking force Fb* can be determined based on the reaction force pressure Prct. (b) Control in the event of a failure of the main power source i) Control of the braking force

[0063] In a case where the main power source 80 fails during manual driving, as explained above, neither the first system 12 nor the second system 14 receives power. In this case, each wheel brake device 10 generates the braking force Fb depending on the actuation force (pushing force) exerted by the driver on the brake pedal 16, as can be seen from the configuration of the present hydraulic braking system. As explained above, the actuation force is assisted by the accumulator pressure Pacc to generate the braking force Fb until the pressure of the working fluid in the accumulator 24 of the first system 12, i.e., the accumulator pressure Pacc, has decreased to a certain degree.

[0064] In the event of a failure of the main power source 80 during automated driving, the first system 12 continues to receive power from the auxiliary power source 82. In other words, only the first system 12 is powered by the current supplied by the auxiliary power source 82. Accordingly, the contribution ratio Rp is set to 1 at all times, and the procedure according to the master cylinder pressure control program described above is executed. The first system 12 is controlled in such a way that the braking force Fb can be generated sufficiently by the first system 12 alone, based on the command from the automated driving system, but only until the amount of current stored in the auxiliary power source 82 decreases to a certain degree. ii) Problem related to the actuation of the high-pressure source device and measure to avoid the problem

[0065] In the procedure according to the high-pressure source device control program described above, the first pump device 22 is driven intermittently such that the accumulator pressure Pacc is neither lower than the set lower limit pressure PaccL nor higher than the set upper limit pressure PaccU. When the accumulator pressure Pacc falls below the set lower limit pressure PaccL and the first pump device 22 is driven, a relatively large electrical current is required for the pump motor 22b of the first pump device 22. That is, the inrush current at the beginning of the drive of the first pump device 22 is relatively large. Accordingly, the intermittent drive of the first pump device 22 results in a relatively large inrush current being generated each time the first pump device 22 is driven.This places a heavy load on the auxiliary power source 82, which has a relatively small capacity, when the current is supplied to the first system 12 from the auxiliary power source 82 in the event of a failure of the main power source 80.

[0066] Fig. 5A and Fig. Figure 5B shows diagrams that depict changes in the accumulator pressure Pacc, a drive state of the first pump device 22, a pump motor current Ip, and a voltage V of the auxiliary power source 82 over time. The diagram in Fig. Figure 5A illustrates the change in a case where the first pump device 22 is intermittently driven in a state where the main power source 80 is not functioning or has failed. If, after the failure of the main power source 80, the accumulator pressure Pacc drops below the set lower limit pressure PaccL at a failure time td during automated driving, the drive of the first pump device 22 begins. If the accumulator pressure Pacc is increased by the drive of the first pump device 22 and subsequently exceeds the set upper limit pressure PaccU, the drive of the first pump device 22 stops. If, after a further time t, the accumulator pressure Pacc drops again below the set lower limit pressure PaccL, the drive of the first pump device 22 begins again. In the diagram, the time of the start of the drive of the first pump device 22 is represented as "ts".In the line that indicates the change in the accumulator pressure Pacc of the first pumping device 22, a section marked by the solid line represents a state in which the first pumping device 22 is driven, and a section marked by the dashed line represents a state in which the first pumping device 22 is stopped.

[0067] The pump motor current Ip flowing in the pump motor 22b is relatively large at the time of starting the drive of the first pump device 22, as shown in the diagram of Fig. 5A is shown. In other words, a relatively large inrush current flows in the pump motor 22b. On the other hand, the auxiliary power source 82 is not charged, and the voltage V of the auxiliary power source 82 decreases with a decrease in the amount of current stored in the auxiliary power source 82 and changes according to the change in the pump motor current Ip. In particular, the degree of decrease in the voltage V of the auxiliary power source 82 is high when the pump motor current Ip increases. Specifically, when the pump motor current Ip is the inrush current, the auxiliary power source 82 is heavily loaded, and the voltage V of the auxiliary power source 82 drops sharply.

[0068] The intermittent drive of the first pump device 22 causes the inrush current to be generated repeatedly. After the inrush current has been generated several times (twice in the diagram), the voltage V of the auxiliary power source 82 falls below a lower limit voltage Vlim. The lower limit voltage Vlim is set as the voltage V that negatively affects the actuations of the first system 12 and the actuations of other vehicle-side systems powered by the auxiliary power source 82, e.g., the sub-ECU for automated driving 90s, the under-detection sensor 92s, and the under-steering system 94s. That is, in a case where the first pump device 22 is driven intermittently by the current stored in the auxiliary power source 82, it is very likely that the actuations of the first system 12 and the other vehicle-side systems will be negatively affected.

[0069] To avoid the phenomenon described above, which is caused by the intermittent drive of the first pump device 22, the hydraulic braking system of the present embodiment is configured such that the first pump device 22 is continuously driven from the time of failure td when the main power source 80 fails during automatic driving, as shown in the diagram of Fig. Figure 5B shows the continuous drive of the first pump device 22, causing the accumulator pressure Pacc to increase. The first system 12 includes a relief valve 112 ( Fig. 1) which is configured to release the accumulator pressure Pacc when the accumulator pressure Pacc reaches a relief pressure (valve opening pressure) PaccR that is higher than the set upper limit pressure PaccU. The accumulator pressure Pacc is maintained at the relief pressure PaccR.

[0070] As shown in the diagram of Fig.As shown in Figure 5B, the first pump device 22 is only driven once in the event of a failure of the main power source 80. Accordingly, the inrush current is only generated once when the first pump device 22 is driven. Since the amount of current stored in the auxiliary power source 82 is relatively large, the voltage V of the auxiliary power source 82 does not fall below the lower limit voltage Vlim due to the generation of the inrush current. No further inrush current is generated, so the voltage V of the auxiliary power source 82 only falls below the lower limit voltage Vlim after a longer time t. This means that the operation of the first system 12 and the vehicle-side systems is not affected for a long time t. Although not shown in the diagram, in the event of a failure of the main power source 80 during automated driving, a warning (an alarm) is issued to the driver, and the driver is prompted to switch to manual driving.Since the voltage V of the auxiliary power source 82 does not fall below the lower limit voltage Vlim for a long time in this case, there is enough time to switch to manual driving.

[0071] In the hydraulic braking system of the present embodiment, a so-called duty-drive operation is performed when the first pumping device 22 is continuously driven in the event of a failure of the main power source 80. The duty-drive operation allows the time elapsed before the voltage V of the auxiliary power source 82 drops below the lower limit voltage Vlim to be extended compared to an arrangement in which the first pumping device 22 is continuously driven by a 100% ON operation, i.e., by a duty-drive operation where the duty cycle is 100%. modification

[0072] The hydraulic braking system of the illustrated embodiment comprises the two braking systems, i.e., the first system 12 and the second system 14. The present disclosure is applicable to a hydraulic braking system with a single braking system. In particular, the present disclosure is applicable to a hydraulic braking system that comprises an on-demand braking system in which the second system 14 of the illustrated hydraulic braking system is not provided and which includes a return passage through which the working fluid is returned without having the accumulator 24 of the first system 12. In such a hydraulic braking system, in the event of a failure of the main power source, the power source supplying current to the pumping device of the braking system is switched to the auxiliary power source, and the pumping device is continuously driven.

Claims

[1] Hydraulic braking system for a vehicle which has: a wheel brake device (10) which is provided for a wheel of the vehicle and is configured to generate a braking force based on the pressure of one of the working fluids supplied to the wheel brake device (10); a first braking system (12) comprising a high-pressure source device (26) with a first pump device (22) and an accumulator (24) which accumulates the working fluid expelled by the first pump device (22), wherein the first pump device (22) is configured to be driven intermittently such that the pressure of the working fluid accumulated in the accumulator (24) is not lower than a set lower limit pressure and not higher than a set upper limit pressure, wherein the first braking system (12) is configured to supply the working fluid to the wheel brake device (10), the pressure of which is regulated depending on the high-pressure source device (26); a second braking system (14) comprising a second pumping device (58) and configured to supply the working fluid to the wheel brake device (10), the pressure of which is regulated depending on the second pumping device (58); and a main power source (80) configured to supply power to the first braking system (12) and the second braking system (14), wherein the hydraulic braking system additionally has an auxiliary power source (82) configured to supply power to the first braking system (12) in the event of a failure of the main power source (80), and wherein the first pump device (22) is continuously driven independently of the pressure of the working fluid accumulated in the accumulator (24) when the main power source (80) fails. [2] Hydraulic braking system according to claim 1, wherein the auxiliary power source (82) has a lower capacity than the main power source (80), and the auxiliary power source (82) is charged by the main power source (80). [3] Hydraulic braking system according to claim 1 or 2, configured such that when the vehicle is driven automatically, the auxiliary power source (82) supplies power to the first braking system (12) instead of the main power source (80) even when the main power source (80) does not fail. [4] Hydraulic brake system according to any one of claims 1 to 3, wherein the first brake system (12) has a first control unit (70) configured to control the first brake system (12), and the second brake system (14) has a second control unit (72) configured to control the second brake system (14). [5] Hydraulic braking system according to any one of claims 1 to 4, wherein the main power source (80) is configured to supply power to other vehicle systems besides the first brake system (12) and the second brake system (14), and wherein the auxiliary power source (82) is configured to supply power to at least some of the vehicle systems in the event of a failure of the main power source (80). [6] Hydraulic braking system according to any one of claims 1 to 5, wherein the hydraulic brake system is configured such that the working fluid is supplied from the first brake system (12) to the second brake system (14), and wherein the second braking system (14) is configured to supply the working fluid to the wheel braking device (10) at a second pressure which is higher than a first pressure which is a pressure of the working fluid supplied by the first braking system (12). [7] Hydraulic brake system according to claim 6, wherein the second pump device (58) is driven when the second brake system (14) supplies the working fluid to the wheel brake device (10) at the second pressure. [8] Hydraulic brake system according to any one of claims 1 to 7, wherein the first brake system (12) has a pressure relief valve (112) configured to release the pressure of the working fluid accumulated in the accumulator (24) when the pressure reaches an overpressure higher than the set upper limit pressure. [9] Hydraulic braking system for a vehicle which has: a main power source (80); an auxiliary power source (82); a wheel brake device (10) intended for a wheel of the vehicle; and a braking system (12) to which current is supplied from the main power source (80), wherein the braking system (12) is configured to regulate a pressure of one of the working fluids to be supplied to the wheel brake device (10) depending on the drive of a motor (22b), wherein the auxiliary power source (82) supplies power to the braking system (12) when a failure of the main power source (80) occurs, and wherein the motor (22) is continuously driven when the main power source (80) fails.

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