Automatically controlled braking system for vehicles and method of actuating and controlling a braking system for vehicles

A braking system for vehicles includes a hydraulic actuator unit operatively connected to at least one braking device, so as to control its actuation by a first hydraulic circuit at a first working pressure. The hydraulic actuator unit includes at least one manual actuator for a user to allow the user to supply the braking system with a braking request. A power generation unit is operatively connected to the hydraulic actuator unit by a second hydraulic circuit at a second working pressure. An actuated brake pump is connected in input to the second hydraulic circuit of the power generation unit to be actuated, and operatively connected, in output, to the first hydraulic circuit for actuation of the at least one braking device. The first and the second hydraulic circuits are supplied with different hydraulic fluids fluidically separate from each other.

This application is a National Stage Application of PCT/IB2015/054825, filed 26 Jun. 2015, which claims benefit of Serial No. BG2014A000023, filed 30 Jun. 2014 in Italy and which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications.

FIELD OF APPLICATION

This invention regards an automatically controlled braking system for vehicles and a method of actuating and controlling a braking system for vehicles.

STATE OF THE ART

In particular, the diffusion of kinetic energy recovery systems (KERS), increasingly powerful on racing cars, has necessitated the diffusion of systems able to automatically “mix” regenerative and dissipative braking. Regenerative braking is precisely the one that allows the recovery of energy during braking by converting the kinetic energy lost by the vehicle into electricity energy to be recovered and/or stored; dissipative braking is, instead, that “traditional” one that consists in converting/dissipating the kinetic energy of the vehicle as thermal energy, i.e., the heating of the brakes, which are typically disc brake callipers, pads and brake discs.

These systems actuate the traditional (or dissipative) braking system by means of “Brake By Wire” actuators: in other words, the user does not directly control the braking devices by directly operating a lever or pedal that puts pressure on the system fluidically connected to such braking devices, but the braking requested by the user, exerted by the actuation of a lever or pedal, is read and converted into the corresponding actuation of the braking devices by the related actuators.

The reduced actuation times (0.1-0.2 s to reach maximum pressure in the braking system) mean that these actuators require a high instantaneous power but also a low average power on the lap (when it comes to racing cars).

Moreover, being in a competition environment, the mass of the actuator also plays a crucial role and must be as low as possible.

SUMMARY OF THE INVENTION

In the known solutions, therefore, always in the field of racing cars, the need for high instantaneous powers and low power supply voltages, leads to electrical components of large size and mass, not very suitable for racing applications.

This, therefore, reveals a glaring technical contradiction: to have the performance required, the components are too massive, while, with acceptable masses, the components are able to provide the required actuation powers.

Therefore, there is a need to solve the drawbacks and limitations mentioned in reference to the known art, namely there is a need to provide a braking system that ensures high power, reduced actuation times and, at the same time, components having small masses so as not to affect the performance of the vehicles on which such systems are installed.

In particular, this need is met by a braking system for vehicles comprisinga hydraulic actuator unit operatively connected to at least one braking device, so as to control its actuation by means of a first hydraulic circuit at a first working pressure, wherein the hydraulic actuator unit comprises at least one manual actuator for a user, to allow the user to supply the braking system with a braking request,a power generation unit, operatively connected to the hydraulic actuator unit by means of a second hydraulic circuit at a second working pressure,an actuated brake pump, operatively connected, in input, to the second hydraulic circuit of the power generation unit to be actuated, and operatively connected, in output, to the first hydraulic circuit for the actuation of the at least one braking device,wherein the first and the second hydraulic circuits are supplied with different hydraulic fluids fluidically separate from each other,providing at least one control unit of the system that supervises the operation of the system.

According to a possible embodiment, the system comprises a control valve interacting with the manual actuator and with the output of the actuated brake pump, said control valve being operable in at least a first operating condition or standard condition, in which the control valve fluidically connects an outlet of the actuated brake pump with the at least one braking device and fluidically disconnects an outlet branch of the manual actuator from the at least one braking device.

According to a possible embodiment, the hydraulic actuator unit comprises a hydraulic tank or accumulator that, in the first operating condition, receives and stores the fluid received from an outlet branch of the manual actuator.

According to a possible embodiment, the control valve, in the first operating condition, fluidically connects said hydraulic accumulator or tank to the outlet branch of the manual actuator.

According to a possible embodiment, the control unit is programmed so as to actuate the control valve in the first operating condition if the second working pressure in the second hydraulic circuit is maintained greater than or equal to a threshold value.

According to a possible embodiment, said control valve is operable in a second operating condition or safety condition, in which the control valve fluidically disconnects the outlet of the actuated brake pump from the at least one braking device and fluidically connects the outlet of the manual, actuator to the at ‘least one’ braking device.

According to a possible embodiment, the hydraulic actuator unit comprises a hydraulic tank or accumulator that, in the second operating condition, receives and stores the fluid received from an outlet of the actuated brake pump.

According to a possible embodiment, the control valve, in the second operating condition, fluidically connects said tank to the outlet of the actuated brake pump.

According to a possible embodiment, the control unit is programmed so as to actuate the control valve in the second operating condition if the pressure inside the second hydraulic circuit falls below a threshold value.

According to a possible embodiment, the control valve is actuated by the control unit of the system by means of the second hydraulic circuit.

According to a possible embodiment, the control valve is provided with elastic pre-loading means that push the control valve to function in the second operating or safety condition.

According to a possible embodiment, the actuated brake pump comprises a dual effect actuating cylinder, subjected at opposite chambers to the action of different pressures regulated by a servo-valve that acts in the second hydraulic circuit.

According to a possible embodiment, the power generation unit comprises an auxiliary circuit of the vehicle for the control of the auxiliary devices of the vehicle.

According to a possible embodiment, the power generation unit comprises at least one motor operatively connected to a pump for pressurizing the second hydraulic fluid to the second working pressure.

According to a possible embodiment, the power generation unit is operatively connected to the control unit of the system so as to be controlled by the latter.

According to a possible embodiment, the actuated brake pump is operatively connected, in output, to at least two braking devices arranged on the same axle of a vehicle (in case of a 4-wheel vehicle) or to a single braking device (in the case of a 2-wheel vehicle).

According to a possible embodiment it is possible to provide for the mounting on the vehicle of two actuation units so as to independently control braking on different axles, without the need to use a splitter.

The technical problem of this invention is also solved by a method of actuating and controlling a braking system for vehicles comprising the steps of:providing a hydraulic actuator unit operatively connected to at least one braking device, so as to control its actuation by means of a first hydraulic circuit at a first working pressure, wherein the hydraulic actuator unit comprises at least one manual actuator for a user, to allow the user to supply the braking system with a braking request,providing a power generation unit, operatively connected to the hydraulic actuator unit by means of a second hydraulic circuit at a second working pressure,providing an actuated brake pump, operatively connected, in input, to the second hydraulic circuit of the power generation unit to be actuated, and operatively connected, in output, to the first hydraulic circuit for the actuation of the at least one braking device,supplying the first and the second hydraulic circuits with different hydraulic fluids fluidically separate from each other,providing at least one control unit of the system that supervises the operation of the system.

According to one embodiment, said method for actuating and controlling comprises the step of providing a braking system for vehicles according to any one of the embodiment variants listed above.

The elements, or parts of elements, in common between the embodiments described below will be indicated with the same reference numbers.

DETAILED DESCRIPTION

With reference to the above figures, the reference number4globally indicates a braking system for vehicles.

First, for the purposes of this invention, it is necessary to specify that, by vehicles is meant, in general, motor vehicles, of any type, size and power, with two, three, four or more wheels, as well as two or more related axles; it is then obvious that this invention preferably, although not exclusively, refers to high-performance four-wheel vehicles, as explained in the introductory part.

The braking system comprises a hydraulic actuation unit8operatively connected to at least one braking device12, so as to control it in actuation through a first hydraulic circuit16at a first working pressure P1.

For the purposes of this invention, the type of braking device12used is irrelevant since it can be, preferably but not exclusively, a calliper for a fixed or floating type disc brake in a single piece or two half-callipers connected to each other and so on.

The hydraulic actuation unit8comprises at least one manual actuator20for a user so as to allow the user to provide the braking system a braking request.

The manual actuator20may comprise, for example, an operating lever or pedal that actuates a hydraulic pump that pressurizes the brake fluid.

The manual actuator20is in turn equipped with its own hydraulic circuit comprising an output branch24and a brake fluid tank28to supply brake fluid to the circuit following the consumption of the friction material of the brake pads. The hydraulic circuit of the manual actuator20interacts with the first hydraulic circuit16, as better described below.

The braking system4also comprises a power generation unit32, operatively connected to the hydraulic actuator unit8by means of a second hydraulic circuit36at a second working pressure P2. According to an embodiment of this invention, the power generation unit32comprises an auxiliary circuit of the vehicle for the control of the auxiliary devices of the vehicle. Such auxiliary devices can include both vehicle accessories such as, for example, an actuation system of the distribution of the propulsion unit, power supply systems of the propulsion unit and the like.

For example, in certain categories of “top racing” vehicles (e.g., F1), the cars are equipped with a high-pressure hydraulic system that can be exploited, as the power generation unit, for the actuation of the braking devices.

In other categories, for design or regulatory choices, a high-pressure hydraulic system is not present on the vehicle and actuation can be performed using electrical and, in particular, electro-hydraulic systems.

For example, according to a possible embodiment, the power generation unit32comprises at least one motor40operatively connected to a pump44for pressurizing the hydraulic fluid to the second working pressure P2. The motor40may also be replaced by a power take-off operatively connected, for example, to a drive shaft or auxiliary shaft of the propulsion unit of the associable vehicle on which the braking system4is mounted.

Preferably, said power generation unit32is electro-hydraulic, in which the motor40is an electric motor.

The braking system4also comprises an actuated brake pump48, operatively connected, in input54, to the second hydraulic circuit36of the power generation unit32to be actuated, and operatively connected, in output, to the first hydraulic circuit16for the actuation of the at least one braking device12.

The first and the second hydraulic circuits16,36are supplied with different hydraulic fluids fluidically separate from each other.

For example, the hydraulic fluid of the first hydraulic circuit16is a typical brake fluid known in the art having, preferably, characteristics for use in high-performance systems; this brake fluid is of the synthetic type, characterized by high hygroscopicity and high resistance to bubble formation to prevent fading phenomena. Such fluid ensures high reliability in the actuation of the braking devices12.

The hydraulic fluid of the second hydraulic circuit36is preferably a mineral fluid particularly suitable to working at much higher pressures, on the order of several hundreds of bar.

As seen, the first and the second hydraulic circuits16,36are supplied with different hydraulic fluids fluidically separate from each other: in other words, the two hydraulic fluids, being of different types and working with working pressures P1and P2extremely different from each other, never mix and are never in direct contact with each other; the related first and second hydraulic circuit16,36receive these hydraulic fluids that interact with each other by means of said actuated brake pump48.

For example, the actuated brake pump48comprises a dual effect actuating cylinder49, equipped, for example, with a first separation baffle50subjected, in correspondence of opposite chambers, for example a first and a second chamber51,53, to the pressure action of the first and second hydraulic circuit16,36. For example, the first chamber51is fluidically connected to the first hydraulic circuit16and the second chamber53is fluidically connected to the second hydraulic circuit36; the dual effect actuating cylinder49moves in function of the forces acting from the side of each chamber51,53.

The braking system4also comprises at least one control unit of the system52that supervises the operation of the system.

The power generation unit32is operatively connected to the control unit of the system52so as to be controlled by the latter.

Moreover, it is possible to provide that the control unit of the system52can be connected to a corresponding control unit of the vehicle56(FIG. 4); in this way, under normal operating conditions, control unit of the vehicle56communicates instant by instant to the control unit of the system52which pressure it must implement.

If, instead, the control unit of the vehicle56detects a malfunction of the control unit of the system52, it is able to by-pass the latter by operating the braking system in a conventional manner, namely through direct control of the user, by means of the manual actuator20, without, therefore, actuation by the actuated brake pump48. For example, between the control unit of the vehicle56and the control unit of the system52, there is interposed a switch/relay58with which the control unit of the vehicle56, which acts as “master”, can bypass and/or off at least momentarily switch off the control unit of the system52, which acts as “slave”.

The braking system4comprises a control valve60that interacts with the manual actuator20and with an outlet or output64of the actuated brake pump48.

Said control valve60is operable in at least a first operating condition or safety condition, in which the control valve60fluidically connects the outlet or output64of the actuated brake pump48to the at least one braking device12and fluidically disconnects an outlet branch24of the manual actuator20from the at least one braking device12.

According to an embodiment, the hydraulic actuator unit8comprises a hydraulic tank or accumulator68that, in the first operating condition, receives and stores the fluid received from the outlet branch24of the manual actuator20.

In this condition, the tank or accumulator68has the function of allowing a specific actuating stroke of the manual actuator operated by the user and to return to the latter a sensation of gradually increasing resistance so as to allow him to modulate the desired braking. At the same time, the control unit of the system52reads the braking request from the user and converts it into actuation of the braking devices12by means of said actuated brake pump48, which is connected to the braking device12through the control valve60.

In particular, the control valve60, in the first operating condition, simultaneously, on the one hand, connects the actuated brake pump48to the braking device12, and on the other, fluidically connects said hydraulic tank or accumulator68with the outlet branch24of the manual actuator20.

The control valve60is, for example, a 4-way valve.

Preferably, the control unit of the system52is programmed to actuate the control valve60in the first operating condition if the second working pressure P2in the second hydraulic circuit36is kept above or equal to a threshold value.

In other words, the control unit of the system52is programmed to operate the system always in the first mode, i.e., in the “by-wire” mode, in which the user makes a request for braking torque by acting on the manual actuator20but, in fact, never directly controls the braking devices12, which are always actuated by the actuated brake pump48, obviously depending on the request made manually by the user.

This first operating or functioning condition is always maintained as long as, for safety reasons, the pressure P2in the second hydraulic circuit36is maintained above a predefined threshold value. In the case in which this threshold value is no longer ensured and, therefore, the system is no longer able to ensure the correct and fast actuation of the braking devices12by the actuated brake pump, the system, for safety reasons, passes to the second operating condition.

In particular, the control valve60is operable in a second operating condition or safety condition, in which the control valve60fluidically disconnects the outlet64of the actuated brake pump48from the at least one braking device12and fluidically connects the outlet branch24of the manual actuator20to the at least one braking device12.

In this way, the user has direct control of the actuation of the braking devices12by means of the manual actuator20.

Furthermore, in the second operating condition, said hydraulic tank or accumulator68of hydraulic actuation unit8receives and stores the fluid received from the outlet64of the actuated brake pump48.

In particular, the control valve60, in the second operating condition, fluidically connects said tank or accumulator68to the outlet64of the actuated brake pump48.

The control unit of the system52is programmed so as to actuate the control valve60in the second operating condition if the pressure P2inside the second hydraulic circuit36falls below a threshold value, it detects a malfunction or if the driver decides to pass to manual mode.

According to an embodiment, the control valve60is actuated by the control unit of the system52by means of the second hydraulic circuit36.

According to an embodiment, the control valve60provided with elastic pre-loading means72that push the control valve60to work in the second operating or safety condition.

In other words, in the absence of hydraulic actuation of the control valve60to operate in the first operating condition (standard condition), the system, thanks to the action of the elastic pre-loading means72, automatically brings it to work in the second, safety, operating condition.

For example, a control branch76of said second hydraulic circuit36is fluidically connected to the control valve60via the interposition of an actuation valve80. The actuation valve80provides a first operating condition in which it fluidically connects the control branch76with the control valve60: this fluid connection allows overcoming the action of the elastic pre-loading means72in such a way that also the control valve60can work in the first operating condition. The actuation valve80also provides a second operating condition in which it fluidically disconnects the control branch76from the control valve60: this fluid disconnection makes prevail the action of the elastic pre-loading means72in such a way that also the control valve60can work in the second operating condition.

The control valve60may, for example, comprise a piston84subjected, on the one hand, to the thrust action of the elastic pre-loading means72and, the other, to the thrust action of the fluid coming from the control branch76.

Usually, i.e., in the first operating condition, the hydraulic thrust action coming from the control branch76prevails over the elastic thrust of the elastic pre-loading means72; while, in the second operating condition, the thrust action of the elastic pre-loading means72prevails.

The system also comprises a servo-valve88that receives the fluid coming from the power generation unit32. This servo-valve88is able to adjust the pressure to be sent to the actuated brake pump48. It is, therefore, possible to reduce the pressure of the second hydraulic circuit P2to different values in order to adjust the operation of the actuated brake pump48.

It should be noted that the correct operation of the servo-valve88requires that it operate with highly-filtered fluid absolutely free of impurities. This hydraulic fluid of the second hydraulic circuit36has this high degree of filtration while the hydraulic fluid of the first hydraulic circuit16, which acts on the braking devices12, cannot provide this degree of filtration. It is therefore important, for the purposes of this invention, that the fluids of the first and second hydraulic circuit16,36are always separated from each other and that these hydraulic circuits16,36are fluidically separated from each other. In this way, each hydraulic fluid can work optimally within its circuit in order to fulfil its technical function.

According to a possible embodiment, the actuated brake pump48is operatively connected, in output64, to at least two braking devices12arranged on the same axle of a vehicle (in case of a 4-wheel vehicle) or to a single braking device (in the case of a 2-wheel vehicle).

According to a possible embodiment it is possible to provide for the mounting on the vehicle of two actuation units so as to independently control braking on different axles, without the need to use a splitter.

As can be appreciated from the description, the brake system for vehicles according to the invention allows overcoming the drawbacks presented in the prior art.

In particular, the brake system for vehicles according to this invention allows solving the technical contradiction of the systems of the prior art, which consists in the fact that, to obtain the required performance, the components are too massive while, with acceptable masses, the components are unable to provide the required actuation powers.

Thanks to this invention, it is instead possible to dimension the electrical components to the average power, and not to power peaks and, therefore, these electrical components will have a lighter weight compatible with use on racing cars.

In fact, the energy introduced in the actuator is gradually accumulated in the form of pressure energy of a fluid and from this “tank” the high power peaks are derived that are required in fast actuations.

The proposed solution also allows exploiting the advantage of a hydraulic application even on vehicles not equipped with a high-pressure hydraulic system: in fact, for such vehicles it is possible to use a specific electro-hydraulic unit able to pressurize a fluid pressure suitable to operate the actuators of the braking devices.

The braking system according to this invention ensures safe conditions; in fact, if the pressure in the second hydraulic circuit falls below a threshold value, the system automatically passes to the second, safety, operating condition that provides direct manual control of the braking devices by the user, through the actuation of the manual actuator.

Under standard conditions, i.e., in the first operating condition, the system provides “BBW” or “brake-by-wire” operation in such a way as to obtain fast, powerful and reliable braking that always meets the request for braking torque that the user makes by operating the manual actuator.

Obviously, the system according to this invention can be easily and advantageously supplemented with additional operating functions such as, for example, the automatic management of braking to avoid locking phenomena (ABS).

A person skilled in the art, in order to satisfy contingent and specific needs, may make numerous modifications and variations to the braking systems described above, all however contained within the scope of the invention as defined by the following claims.