Patent Application
20230049861
The present invention relates to a brake system for a vehicle having at least two axles. The present invention also relates to a method for braking a vehicle having at least two axles.
The related art, for example, German Patent Application No. DE 10 2016 208 529 A1, describe brake systems for vehicles having two axles, the brake systems each having exactly four wheel brake cylinders, each wheel brake cylinder being hydraulically connected at a master brake cylinder of the respective brake system to a brake pedal upstream of the master brake cylinder.
The present invention provides a brake system for a vehicle having at least two axles, and a method for braking a vehicle having at least two axles.
The present invention provides hybrid brake systems having a first “hydraulic axle” and a second “dry axle”. As will become clear from the following description, all stabilizing functions of a conventional pure hydraulic brake system, both for longitudinal stabilization and for lateral stabilization, as well as all assisted deceleration functions, can also be carried out by means of a brake system according to the present invention. Likewise, advantageous redundancies for an automated driving of the respective vehicle equipped with the brake system according to the present invention and for an automated parking of the respective vehicle, including remote controlled parking, are also realized with the brake system according to the present invention.
The second “dry axle” of the brake system according to the present invention can in particular be a central axle, the rear axle or rearmost axle of the respective vehicle having at least two axles. A conventional parking brake function is also integrable into the second “dry axle.” Another advantage of the second “dry axle” is the reduced need for toxic brake fluid in the brake system produced in this manner according to the present invention, because brake fluid is only needed for the first “hydraulic axle”, preferably the front axle or frontmost axle of the respective two-axle vehicle. Likewise, there is also no longer a need to lay brake lines to the second “dry axle” for guiding brake fluid, which significantly reduces assembly effort during assembly of the brake system according to the present invention.
In addition, the use of the first “hydraulic axle” and the second “dry axle” in the brake system according to the present invention automatically produces a variable braking force distribution for advantageously braking the respective vehicle having at least two axles, in particular if the first “hydraulic axle” is the front axle of the vehicle and the second “dry axle” is the rear axle of the vehicle. In addition, in the case of installation of at least one electric motor on the rear axle, there is the possibility of cooperation/symbiogenesis with an electric motor used for recuperative braking of the respective vehicle, while converting the kinetic energy of the vehicle into electrically storable energy. Furthermore, the brake system according to the present invention has redundancies for a reliable automated driving of the respective vehicle having at least two axles, without increasing a probability of failure of one of the components of the brake system according to the present invention, compared to related prior art.
In an advantageous embodiment of the brake system of the present invention, the hydraulic deceleration unit comprises a brake fluid reservoir to which the first wheel brake cylinder is hydraulically coupled via a first currentlessly closed outlet valve and the second wheel brake cylinder is hydraulically coupled via a second currentlessly closed outlet valve. By contrast to conventionally used check valves, the first currentlessly closed outlet valve and the second currentlessly closed outlet valve realize improved return hydraulics, in particular with a load relief in the direction of the brake fluid reservoir.
Preferably, according to an example embodiment of the present invention, the hydraulic deceleration unit comprises a master brake cylinder, to which a brake actuating element of the vehicle is connectable or connected in such a way that at least one piston of the master brake cylinder limiting at least one chamber of the master brake cylinder is adjustable by way of an actuation of the brake actuating element by a driver of the vehicle, and wherein the first wheel brake cylinder and/or the second wheel brake cylinder are hydraulically connected to the at least one chamber of the master brake cylinder via at least one currentlessly open switch valve. Thus, in the embodiment of the brake system described here, even in the event of a complete failure of all electronics of the vehicle, the driver of the vehicle still has the option of producing by his driver brake force a sufficient brake pressure in the first wheel brake cylinder and/or in the second wheel brake cylinder in order to bring the vehicle to a stop.
For example, the hydraulic deceleration unit comprises a simulator which is hydraulically connected to the at least one chamber of the master brake cylinder via a currentlessly closed switch valve. In this case, after a decoupling of the master brake cylinder from the first wheel brake cylinder and the second wheel brake cylinder, the driver can still brake into the simulator via the open switch valve, such that the driver has a standard braking feel/pedal feel despite the decoupling of the master brake cylinder.
Preferably, according to an example embodiment of the present invention, the single chamber or one of the chambers of the master brake cylinder is hydraulically connected to the brake fluid reservoir via a separator valve. This allows for a “sniffing” via the opened separator valve.
In another advantageous embodiment of the brake system of the present invention, the hydraulic deceleration unit is electrically connectable or connected to a first energy storage unit, while the electromechanical deceleration unit is electrically connectable or connected to a second energy storage unit formed separately from the first energy storage unit. In this case, if one of the two energy storage units fails, the hydraulic deceleration unit or the electromechanical deceleration unit can still be used in order to brake the vehicle. In this way, the vehicle can still be brought to a stop, in particular during autonomous driving, such as driverless driving, despite the failure of one of the two energy storage units.
According to an example embodiment of the present invention, preferably, a first control device of the hydraulic deceleration unit is designed and/or programmed in order to actuate the motorized brake pressure buildup device, the first pressure control valve, and the second pressure control valve, taking into account at least one brake specification signal output by at least one brake actuating element sensor of the vehicle, an automatic speed control of the vehicle, a second control device of the electromechanical deceleration unit, and/or a further stabilizing device of the brake system to the first control device, such that a first brake pressure present in the first wheel brake cylinder can be adjusted and modulated individually for each wheel and a second brake pressure present in the second wheel brake cylinder can be adjusted and modulated individually for each wheel. In this way, a variety of stabilization functions, such as ABS and VDC, are executable by means of the hydraulic deceleration unit.
As an advantageous further development of the present invention, the second control device of the electromechanical deceleration unit may be designed and/or programmed in order to individually actuate the first electromechanical wheel brake cylinder and the second electromechanical wheel brake cylinder, taking into account at least one further brake specification signal output by the at least one brake actuating element sensor, the automatic speed control of the vehicle, the second control device of the hydraulic deceleration unit, and/or the further stabilizing device of the brake system to the second control device. Thus, a variety of standard stabilization functions can also be executed by means of the electromechanical delay unit. In particular, by means of the electromechanical deceleration unit, wheel-individual, active deceleration modulations that may be a component of a vehicle stabilization function, for example VDC and TCS, are possible.
Preferably, according to an example embodiment of the present invention, the hydraulic deceleration unit and the electromechanical deceleration unit are linked at most to one another via at least one signal and/or bus line connected to the first control device and the second control device. It is expressly pointed out here that a link between the hydraulic deceleration unit and the electromechanical deceleration unit via hydraulic lines is not necessary. This results in a significant reduction of the cost of assembly of the brake system according to the present invention.
The advantages described above can also be produced by performing a corresponding method for braking a vehicle having at least two axles. It is expressly noted that the method for braking a vehicle having at least two axles can be further developed according to the example embodiments of the brake system discussed above.
Further features and advantages of the present invention are explained below with reference to the figures.
The brake system schematically depicted in
The brake system comprises a hydraulic deceleration unit 10 with at least one motorized brake pressure buildup device 12, a first wheel brake cylinder 14a which is or can be mounted on a first wheel of a first axle of the vehicle, and a second wheel brake cylinder 14b which is or can be mounted on a second wheel of the first axle. The hydraulic deceleration unit 10 can also be referred to as a decoupled power brake. Preferably, in addition to the two wheel brake cylinders 14a and 14b, the hydraulic deceleration unit 10 does not have any further wheel brake cylinders.
The first wheel brake cylinder 14a and the second wheel brake cylinder 14b can each be referred to as a “hydraulic” wheel brake cylinder that is hydraulically connected to the motorized brake pressure buildup device 12. In addition, the first wheel brake cylinder 14a is hydraulically connected to the motorized brake pressure buildup device 12 via a first pressure control valve 16a. Accordingly, the second wheel brake cylinder 14b is hydraulically connected to the motorized brake pressure buildup device 12 via a second pressure control valve 16b. Thus, a first brake pressure present in the first wheel brake cylinder 14a can be adjusted by way of the motorized brake pressure buildup device 12 with an at least partially open first pressure control valve 16a and a closed second pressure control valve 16b, independently of a second brake pressure present in the second wheel brake cylinder 14b. Accordingly, the second brake pressure in the second wheel brake cylinder 14b can also be adjusted using the motorized brake pressure buildup device 12 with an at least partially open second pressure control valve 16b and a closed first pressure control valve 16a, independently of the first brake pressure in the first wheel brake cylinder 14a. Due to the configuration of the hydraulic deceleration unit 10 with the first pressure control valve 16a and the second pressure control valve 16b, a wheel-individual brake pressure setting is thus possible for both the first wheel brake cylinder 14a and the second wheel brake cylinder 14b. Correspondingly, a wheel-individual pressure modulation is also possible for both the first brake pressure present in the first wheel brake cylinder 14a and the second brake pressure present in the second wheel brake cylinder 14b. To the extent to which a pressure difference between the first brake pressure in the first wheel brake cylinder 14a and the second brake pressure in the second wheel brake cylinder 14b is desired, the higher brake pressure can be built up using the motorized brake pressure buildup device 12, while the lower brake pressure in the respective wheel brake cylinder 14a or 14b is producible/is produced by means of a suitable delta pressure control of the associated pressure control valve 16a or 16b.
The brake system also comprises an electromechanical deceleration unit 18 having a first electromechanical wheel brake cylinder 20a which is or can be mounted on a first wheel of a second axle of the vehicle and a second electromechanical wheel brake cylinder 20b which is or can be mounted on a second wheel of the second axle. The first electromechanical wheel brake cylinder 20a and the second electromechanical wheel brake cylinder 20b can each also be referred to as an electromechanical single-wheel actuator or an electromechanical brake (EMB). Preferably, in addition to the two electromechanical wheel brake cylinders 20a and 20b, the electromechanical deceleration unit 18 does not have any further “hydraulic” wheel brake cylinders. Also, due to the configuration of the electromechanical deceleration unit 18 with first electromechanical wheel brake cylinder 20a and second electromechanical wheel brake cylinder 20b, a braking force applied to the first wheel of the second axle and the second wheel of the second axle can be adjusted or varied on a wheel-individual basis.
The first axle of the vehicle equipped with the hydraulic deceleration unit 10 can be described as a “hydraulic axle,” while the second axle of the vehicle equipped with the electromechanical deceleration unit 18 can be called a “dry axle.” Typical stabilization functions, such as ABS (antiblocking system) and VDC (vehicle dynamic control), can be implemented on the “hydraulic axle.” ABS modulations (electromechanical brake modulations) in particular can be easily implemented on the “dry axle.”
Preferably, the first axle of the vehicle is its front axle, or frontmost axle, while the second axle of the vehicle is a center axle, its rear axle, or its rearmost axle. The first wheel of the first axle and the second wheel of the first axle can thus be front wheels of the vehicle, while the first wheel of the second axle and the second wheel of the second axle can be understood to mean its rear wheels. The allocation of the hydraulic deceleration unit 10 to the front axle or the frontmost axle of the vehicle and the electromechanical deceleration unit 18 to the center axle and/or the rear axle or the rearmost axle of the vehicle takes into account the fact that, for a braking of the rear wheels of the vehicle, often a lower force/clamping force, a smaller dynamic response, and a lower setting accuracy is sufficient in comparison to a braking of the front wheels. Thus, the electromechanical deceleration unit 18 can produce reliable braking of the rear wheels, while the advantages/strengths of the hydraulic deceleration unit 10 compared to the electromechanical deceleration unit 18 for the front wheels can be utilized. Again, it is noted here that the advantages of the hydraulic deceleration unit 10 compared to the electromechanical deceleration unit 18 lie in a higher dynamics and in an increase in the applicable force. Since, due to dynamic axle load distributions, higher dynamics and a greater applicable force is normally desired on the front wheels compared to the rear wheels, the use of the hydraulic deceleration unit 10 is beneficial specifically for the front wheels. For the rear wheels, the more cost-efficiently manufactured electromechanical deceleration unit 18 can instead be used. At the same time, by equipping the brake system with the electromechanical deceleration unit 18, its need for toxic brake fluid is significantly reduced compared to the prior art.
The allocation of the hydraulic deceleration unit 10 to the front axle or frontmost axle of the vehicle and of the electromechanical deceleration unit 18 to the center axle, the rear axle and/or rearmost axle of the vehicle also automatically produces a variable braking force distribution between front and rear wheels, which provides a stable braking of the respective vehicle. Because the function of the parking brake is typically integrated into the rear wheel actuators in the prior art, in the brake system schematically shown by
Additionally, electromechanical deceleration unit 18 can cooperate well with an electric motor utilized in order to recuperatively decelerate the particular vehicle, while converting the kinetic energy of the vehicle into electrically storable energy. In particular, there are possibilities for cooperation/symbiogenesis such that, when the electric motor is not usable for recuperative braking of the vehicle, this can easily be compensated by means of an appropriately adjusted operation of the electromechanical deceleration unit 18. Thus, in the event that the electric motor is not usable for recuperative braking of the vehicle, it is often not necessary to respond with a complex “hydraulic blending process” of the hydraulic deceleration unit 10, i.e., with a variation of the first brake pressure in the first wheel brake cylinder 14a and/or the second brake pressure in the second wheel brake cylinder 14b. Instead, by appropriately controlling the first electromechanical wheel brake cylinder 20a and/or the second electromechanical wheel brake cylinder 20b, an absent usability of the electric motor for recuperative braking of the vehicle can be easily compensated. In addition, recuperation in the vehicle equipped with the brake system is possible without limitations of a recuperation efficiency or affecting a brake actuation feeling/pedal feeling.
Another advantage of the brake system schematically illustrated in
As an advantageous further development, the hydraulic deceleration unit 10 of the brake system of
A further advantageous development of the brake system of
During normal operation of the brake system, the at least one currentlessly open switch valve 30a and 30b, via which the first wheel brake cylinder 14a and/or the second wheel brake cylinder 14b are connected to the at least one chamber of the master brake cylinder 26, is closed and the driver brakes via the currentlessly closed switch valve 34, which is present in its open state, into the simulator 32. In normal operation of the brake system, when outlet valves 22a and 22b are closed, the pressure control valves 16a and 16b, which are present in their open state, can be used in order to set the respectively desired brake pressure in first wheel brake cylinder 14a and second wheel brake cylinder 14b.
A reference chamber of the simulator 32, which is located on a side of a piston of the simulator 32 facing away from the currentlessly closed switch valve 34, can be hydraulically connected to the brake fluid reservoir 24, as shown schematically in
Merely by way of example, in the brake system of
As can be seen in
Preferably, the brake system comprises at least a first control device 40a, by means of which at least the motorized brake pressure buildup device 12, the first pressure control valve 16a, and the second pressure control valve 16b, and possibly at least one further component of the hydraulic deceleration unit 10, are actuated or actuatable. Optionally, the first control device 40a can also be designed and/or programmed in order to actuate the first electromechanical wheel brake cylinder 20a and the second electromechanical wheel brake cylinder 20b. Preferably, however, in addition to the first control device 40a of the hydraulic deceleration unit 10, the brake system also comprises a second control device 40b of the electromechanical deceleration unit 18, which device is designed and/or programmed in order to actuate the first electromechanical wheel brake cylinder 20a and the second electromechanical wheel brake cylinder 20b. Due to the equipping of the brake system with the two control devices 40a and 40b, it can be ensured that, in the event of a failure of one of the two control devices 40a and 40b, at least the hydraulic deceleration unit 10 or the electromechanical deceleration unit 18 can perform its function such that the vehicle can be reliably brought to a stop.
The brake system of
Preferably, at least the motorized brake pressure buildup device 12, the first pressure control valve 16a, and the second pressure control valve 16b, and possibly at least one further component of the hydraulic deceleration unit 10, are actuatable by means of the first control device 40a, such that the first brake pressure present in the first wheel brake cylinder 14a and the second brake pressure present in the second wheel brake cylinder 14b are adjustable and modulatable on a wheel-individual basis. Preferably, the second control device is also designed and/or programmed in order to individually actuate the first electromechanical wheel brake cylinder 20a and the second electromechanical wheel brake cylinder 20b. Further functions, such as TCS (Traction Control System) and VDC (Vehicle Dynamic Control), can also be implemented by means of the hydraulic deceleration unit 10 and/or the electromechanical deceleration unit 18.
The first control device 40a of the hydraulic deceleration unit 10 can in particular be designed and/or programmed in order to actuate at least the motorized brake pressure buildup device 12, first pressure control valve 16a, and second pressure control valve 16b, and possibly at least one further component of the hydraulic deceleration unit 10, taking into account at least one braking specification signal 42 output by at least one brake actuating element sensor 44 of the vehicle, an automatic speed control (not shown) of the vehicle, the second control device 40b of the electromechanical deceleration unit 18, and/or a further stabilizing device (not shown) of the brake system to the first control device 40a. For example, the at least one brake actuating element sensor 44 can be a rod path sensor and/or a differential path sensor. The automatic speed control can be, for example, an intelligent cruise control, specifically an ACC device (Adaptive Cruise Control), or an emergency braking device, such as in particular an AEB device (Autonomous Emergency Braking). The second control device 40b of the electromechanical deceleration unit 18 can also be configured and/or programmed in order to actuate the first electromechanical wheel brake cylinder 20a and the second electromechanical wheel brake cylinder 20b, taking into account at least one further brake specification signal 46 output by the at least one brake actuating element sensor 44, the automatic speed control of the vehicle, the first control device 40a of the hydraulic deceleration unit 10, and/or the further stabilizing device of the brake system to the second control device 40b. Also, at least one pressure signal 48 of at least one pressure sensor 12d and 50 can be considered during the actuation by means of first control device 40a and/or the second control device 40b.
Preferably, the hydraulic deceleration unit 10 and the electromechanical deceleration unit 18 are linked at most to one another via at least one signal and/or bus line 52 connected to the first control device 40a and the second control device 40b. It is expressly noted here that, in the brake system of
The method discussed below can be performed on (nearly) any vehicle having at least two axles. It is expressly noted that a feasibility of the method is not limited to a particular type of the (motor) vehicle.
In a method step S1 of the method, a motorized brake pressure buildup device of a hydraulic deceleration unit is operated, and a first pressure control valve, via which a first wheel brake cylinder of the hydraulic deceleration unit mounted on a first wheel of a first axle of the vehicle is hydraulically connected to the motorized brake pressure buildup device, and a second pressure control valve, via which a second wheel brake cylinder of the hydraulic deceleration unit mounted on a second wheel of the first axle is hydraulically connected to the motorized brake pressure buildup device, are switched in such a way that the first wheel is decelerated by means of the first wheel brake cylinder and the second wheel is decelerated by means of the second wheel brake cylinder.
In a further method step S2, a first wheel of a second axle of the vehicle is decelerated by means of a first electromechanical wheel brake cylinder of an electromechanical deceleration unit mounted thereon and a second wheel of the second axle is decelerated by means of a second electromechanical wheel brake cylinder of the electromechanical deceleration unit mounted thereon. Thus, an execution of the method described herein also provides the advantages discussed above.
The method steps S1 and S2 can be carried out in any order, simultaneously or overlapping in time. In addition to the method steps S1 and S2, the method can also be expanded by the processes explained above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 213 437.5 | Oct 2020 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/071600 | 8/3/2021 | WO |
