MOTOR VEHICLE

Abstract

A motor vehicle includes a plurality of wheels and a brake system, which has brakes, which can be hydraulically actuated and are each associated with a wheel. The brakes can be actuated by at least one brake circuit which can be operated by a brake booster. The brake booster can be actuated by a brake pedal to be pressed by the driver. At least one pressure-generating and/or pressure-accumulating device, controlled by a control device to modulate the hydraulic pressure within the brake circuit. A second pressure-generating and/or pressure-accumulating device is provided in the brake circuit to automatically increase the pressure within the brake circuit in dependence on demand independently of the first pressure-generating and/or pressure-accumulating device, when a malfunction is detected in the brake system.

Claims

1.-9. (canceled)

10. A motor vehicle, comprising: a plurality of wheels; and a braking system including; hydraulically actuatable brakes operably connected to the wheels in one-to-one correspondence, at least one brake circuit configured for actuation of the brakes, a brake booster operably connected to the brake circuit and actuated by a driver through actuation of a brake pedal, a first member selected from the group consisting of a pressure generating device and a pressure storage device, said first member being configured for modulation of hydraulic pressure within the brake circuit, a control device configured to control the first member, and a second member selected from the group consisting of a pressure generating device and a pressure storage device and disposed in the brake circuit, said second member being configured to automatically increase pressure inside of the brake circuit independently of the first member, when a malfunction is detected in the brake system.

11. The motor vehicle of claim 10, further comprising a switchable valve, said second member being coupled to the brake circuit via the switchable valve and feeding hydraulic fluid under elevated pressure into the brake circuit with the switchable valve being open.

12. The motor vehicle of claim 10, wherein the second member includes a hydraulic pump, or is connected to a hydraulic pump of the first member.

13. The motor vehicle of claim 10, wherein the second member includes a mechanical device which includes a switchable pressure generating element, a piston movable by the pressure generating element and acting on the hydraulic fluid, when the pressure generating element is released.

14. The motor vehicle of claim 13, wherein the pressure generating element includes a releasably locked spring element.

15. The motor vehicle of claim 14, wherein the piston is movable in response to an increase of the hydraulic pressure through operation of a hydraulic pump of the first member in opposition to a recoiling force of the spring element until the spring element is locked again.

16. The motor vehicle of claim 13, wherein the pressure generating element includes a pyrotechnic ignition device.

17. The motor vehicle of claim 10, wherein the brake booster is configured as a vacuum brake booster and represents the second member, and further comprising a switchable valve configured for venting the vacuum brake booster.

18. The motor vehicle of claim 10, further comprising a further control device configured to control the second member.

Description

[0016] Further advantages, features and details of the invention will become apparent from the exemplary embodiment described in the following and from the drawing.

[0017] The FIGURE shows in the form of a schematic representation a motor vehicle 1 according to the invention, wherein only the braking system 2 is shown here, including a brake pedal 3, which is usually actuated by the driver, a brake booster 4 that can be actuated via the brake pedal 3 and via which, in turn, a brake circuit 5 is operated, which, in turn, acts on individual brakes 6 which are associated with wheels 7, respectively. The FIGURE is a purely schematic representation. Of course, provision is normally made for two separate brake circuits, i.e. the braking system 2 is correspondingly configured as redundant. The FIGURE is purely a function diagram which should only represent the basic functionality of the invention.

[0018] Integrated into the braking system 2 is a first pressure generating and/or pressure storage device 8, for example, an ESC block, which includes in a manner known per se a corresponding valve block including a plurality of separately switchable valves, at least one hydraulic pump via which the pressure of the hydraulic fluid present in the brake circuit 5 can be varied, as well as a corresponding control device via which the individual valves as well as the hydraulic pump are controlled. The construction of such an ESC block is well known. The brake pressure within the braking system 2 can be modulated by it so that a respective individual pressure level can be applied to the respective brakes 6 in order to decelerate separately and selectively. Different assistance functions, such as, for example, an ABS function or a slip control etc. can be realized by its use.

[0019] According to the invention, a second pressure generating and/or pressure storage device 9 is now integrated into the braking system 2 and, if need be, is used to increase the brake pressure within the braking system 2 or the brake circuit 4, when a malfunction occurs in the braking system. Such a malfunction may, for example, involve a malfunction within the ESC block 8, for example, in the valve block, i.e. one or more valves can no longer be switched, causing a power failure and control of the ESC block 8 can no longer be realized, etc. In order to ensure fail-operational operation in this case, and to decelerate the motor vehicle without falling back on the driver, and to provide a sufficient transitional period to the driver, within which he may take over control again, the hydraulic pressure within the braking system 2 can temporarily be increased via this second pressure generating and/or pressure storage device 9, i.e. the brakes 6 are actuated to decelerate the motor vehicle in a targeted manner, i.e. initiate an automatic deceleration operation hereby. In the example shown, a separate control device 10 is assigned to the second pressure generating and/or pressure storage device 9 or the device 9 includes such, as an alternative a control could also be implemented via the control device of the ESC block, i.e. the first pressure generating and/or pressure storage device 8 as long as it is ensured that the latter is connected to an uninterruptible power supply and is active at all times.

[0020] When detecting any type of fault within the braking system 2, causing parts thereof or overall to no longer operate properly so that the driver is prompted to take over control of the motor vehicle, corresponding information is transmitted to the control device 10 which then commands an increase in pressure. It then comes to an automatic build-up of sufficiently high brake pressure in order to decelerate the vehicle. An action by the driver, as in only fail-safe configured systems in which the driver must actively actuate the accelerator pedal, for example, despite a malfunction within the brake booster 4, is not needed according to the present invention.

[0021] Different configurations of the second pressure generating and/or pressure storage device 9 are conceivable in order to be able to build up the increased brake pressure. These are shown in the FIGURE here merely by way of examples and alternatives represented with a), b) and c).

[0022] According to the embodiment a), the second pressure generating and/or pressure storage device 9 is integrated via a switchable valve 11 in a respective line 12, which is part of the braking system. It includes a separately controllable pump 13 via which the brake fluid residing in a reservoir 14 is pumped under high pressure. When the valve 11 is switched to open, the pump 13 is also automatically actuated so that hydraulic fluid is pumped under high pressure in the braking system 2 and the brakes 6 are correspondingly actuated. The corresponding activation of the controllable components is, of course, implemented via the control device 10.

[0023] Even though in accordance with configuration a) the pump 13 is part of the second pressure generating and/or pressure storage device 9, it is conceivable to use a corresponding pump, which is part of the first pressure generating and/or pressure storage device 8, instead of the pump 13. That means that, for example, during normal operation of this first pressure generating and/or pressure storage device 8, i.e. when the pump there thus operates flawlessly, the hydraulic fluid residing in the reservoir 14 is stored under high pressure at all times. If a fault is detected, there is only need to activate the valve 11 via the control device 10 so that the reservoir 14, thus the storage, is discharged.

[0024] In the embodiment according to the invention according to variant b), the second pressure generating and/or pressure storage device 9 includes a movable piston 15 in a cylinder 16, wherein piston 15 can be acted upon via a switchable pressure generating element 17. Hydraulic fluid which is received in the cylinder 16 is introduced via the line 12 under high pressure into the braking system 2 via the piston 15.

[0025] In the configuration according to b), the switchable pressure generating element 17 is a spring element 18 which is fixed in a locking position, in which it is compressed. When the switchable locking, which can be controlled via the control device 10, is released, the spring element 18 relaxes and actuates the piston 15, which then pushes the hydraulic fluid from the cylinder 16 under high pressure.

[0026] The embodiment variant c) is an alternative to variant b). Again, the second pressure generating and/or pressure storage device 9 includes a piston 15 which is movable in a cylinder 16. The switchable pressure generating element 17 is configured here as a pyrotechnic ignition device 19. When this is ignited, there is a sudden corresponding increase in pressure, which, in turn, acts on the piston 15, which is moved in the cylinder 16 and pushes the brake fluid into the braking system 2 under high pressure.

[0027] The exemplary embodiments shown in a), b) and c) merely represent examples. Of course, other embodiments may be selected as long as they realize a possible pressure increase in case of need.

[0028] Whereas the embodiment variants b) and c), since ultimately only able to be actuated once, allow a brief and ultimately not variable pressure increase, the embodiment variant a), depending on the encountered fault, even enables an at least rudimentary reproduction of the ABS or ESC functionalities realized during regular operation. In the event, for example, the pump is defective on the part of the ESC block 8 while the valve block is still fully operational, hydraulic fluid could thus be fed under respective pressure via the second pressure generating and/or pressure storage device 9 according to embodiment variant a) with its separate pump 13 and distributed respectively modulated via the valve block of the ESC block 8. The functionalities could be made available at least for a transitional period until either the driver has assumed full control, or until the vehicle is definitely braked to a standstill. Optionally, a possibly existing transmission is also automatically switched to the neutral level, as braking results in the standstill.