EP1307373A1

EP1307373A1 - Electronically controlled parking brake for a motor vehicle

Info

Publication number: EP1307373A1
Application number: EP01974143A
Authority: EP
Inventors: Markus Witzler; Kurt Füchtler; Walter Geltermair
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-08-09
Filing date: 2001-08-08
Publication date: 2003-05-07
Also published as: DE10038786A1; US20040011610A1; BR0113174A; MXPA03001132A; WO2002012040A1; JP2004505835A; KR20030036688A; DE10038786C2; PL360078A1; CZ2003608A3

Abstract

The invention relates to an electronically controlled parking brake for a motor vehicle, comprising a switch-on device (35) for generating an electronic activation signal, a release device (35) for generating an electronic deactivation signal, an electronic control device (25) that processes said signal, a pressure fluid source (14, 16, 21) and brake modules (2) that can be optionally linked with the pressure fluid source (14, 16, 21) via on-off valves (11, 12) and that generate braking forces on the wheels of the motor vehicle. Each brake module is provided with a first pressure compartment (34) that is contiguous with a tensioning member of the respective brake module, said pressure compartment being linkable with a main braking cylinder (23) via service brake circuit (22). Each brake module is further provided with a second pressure compartment (9) that is contiguous with a tensioning member of the respective pressure brake module, said pressure compartment being linkable with the pressure fluid source (14, 16, 21) via a separate hydraulic circuit (17, 18, 19, 20). In at least a part of the brake modules (2) the respective tensioning member is provided with two separate coaxially disposed pressure pistons (4, 5), one of which defines the first pressure compartment (34), and between which the second pressure compartment (9) is configured. The pressure fluid source is provided with a pressure accumulator (16) for accumulating the pressure fluid, and with a pressure generator (14) for filling the pressure accumulator (16) and the fluid reservoir (21). The hydraulic circuit comprises valve systems (11, 12) that are controlled by control signals supplied by the control device (25). Said valve systems optionally link the pressure outlet of the pressure accumulator (16) with the respective second pressure compartment (9) of the wheel brake modules (2) and optionally link the respective second pressure compartment (9) of the wheel brake modules (2) with the fluid reservoir (21). Said valve systems (11, 12) are controlled by the control signals of the control device (25).

Description

description

Electronically controlled parking brake for a vehicle

The invention relates to a parking brake system according to the preamble of claim 1.

Parking brakes are installed in almost all motor vehicles, mainly to secure the vehicle against unintentional rolling away. In addition, the parking brake takes over the safety function of bringing the vehicle to a standstill if the conventional brakes fail.

From DE 198 59 804 a parking brake device for a motor vehicle is known, comprising a lever-like adjustable braking device, by means of which at least one vehicle brake can be actuated, the actuating force of the vehicle brake being proportional to the adjusting position of the actuating device and the actuating device comprising a changeable electrical switching element from the position of which a hydraulic brake device can be acted upon by an electrically controllable valve with a pressurized hydraulic fluid. In locking operation, the brakes are applied by means of tension springs, which act on a piston that is operatively connected to the brake pads. By means of an additional hydraulic connection to the second pressure chamber of the brake module, a force acting against the tension springs can be generated, which reduces or eliminates the corresponding braking force of the tension springs.

The disadvantage of such a parking brake arrangement is that if the additional hydraulic circuit fails, the tension springs automatically trigger an uncontrolled braking and that the arrangement requires many components.

The object of the invention is to develop an electrically actuated parking brake arrangement in such a way that variable hydraulic brake pressures can be generated with a simple and safe construction, the parameters of the vehicle condition and the parking space being able to be taken into account.

The object is achieved by the features of claim 1. The valve means can comprise a reusable valve or also a first switching valve and a second switching valve.

It is advantageous to dispense with an otherwise usual operating lever, which requires considerable space in the vehicle compartment, and the separate pressure supply, which makes it possible to bring the vehicle to a standstill even if the conventional brake system fails completely. In a further development, the pressure status of the wheel brake modules is constantly monitored by means of suitable sensors. For this monitoring, the sensor signals of a pressure control device (ABS) that is common today can also be used, wherein the dynamic and static vehicle state can be recognized on the basis of the sensor signals. This can e.g. the detection of the standstill of the vehicle on a slope or the vehicle rolling away. This also makes it easier to start off on the mountain by releasing the parking brake via a motor traction detection after a defined threshold has been exceeded.

The two pressure pistons can be arranged in tandem one behind the other or can also be guided telescopically one inside the other.

The electric actuation of the parking brake offers a number of possibilities that cannot be achieved with a conventional manually operated parking brake. For example, the switch-on device can be connected to a sensor that responds to the state of the door lock of the driver's door and / or a sensor that responds to the state of the ignition lock and / or a sensor that responds to the load state of the driver's seat, with an activation signal depending on a signal of at least one of the Sensors can be generated. For example, the parking brake can be triggered automatically when the driver's door is closed and locked or when the driver's door and ignition key are removed or when the driver's seat is relieved, i.e. the driver has got out. The various sensor signals can also be linked together.

Depending on the condition of the vehicle, variable brake pressure design or reduction can be used to react flexibly. Advantageous embodiments of the invention are specified in the further subclaims.

Further features and advantages are the subject of the following description and the illustration in the drawings. It shows:

1 shows the arrangement according to the invention in the release position,

Fig. 2 shows the arrangement according to the invention while operating the

Parking brake,

Fig. 3 shows the arrangement according to the invention with the parking brake in

Holding position,

4 shows the arrangement according to the invention when releasing the parking brake,

Fig. 5 shows the arrangement according to the invention during actuation of the

Service brake,

Fig. 6 shows the use of the arrangement according to the invention in operative connection with a pressure control device (ABS), and

7 to 9 each show a schematic sketch of a modified embodiment of a brake module suitable for the parking brake according to the invention in three different states.

For the sake of simplicity, the invention is explained on the basis of the application to a brake module 2, since the structure and the method are the same for the further brake module (s).

The parking brake electronically controlled according to the invention has a parking arrangement 1 which is connected to the wheel brake modules 2 via hydraulic pressure lines 18, 19. The brake modules are, for example, the wheel brakes of the rear axle and / or the front axle of a motor vehicle or a suitable combination of these wheel brakes, which is able to lock the vehicle in its respective position.

The housing of the wheel brake module 2 is known in the broadest sense from the prior art or is already installed millions of times as a so-called floating caliper brake in motor vehicles and is designed in such a way that it has a bore which receives a front pressure piston 4 and a rear pressure piston 5, the pressure pistons comprising sealing elements 6, 7 and being sealed against the housing. An intermediate chamber 9 is formed between the front pressure piston 4 and the rear pressure piston 5 by means of a respective spacing extension 8, molded onto the front pressure piston 4 or optionally also molded onto the rear pressure piston 5. This hydraulically insulated intermediate chamber 9 is connected hydraulically via an inlet bore directly to the pressure line 19 of the electronically controlled parking arrangement 1 and can be acted upon by it, while the rear end face of the rear pressure piston 5 delimits a pressure chamber 34 which via the pressure line 22 is connected to a conventional master brake cylinder 23 is in hydraulic operative connection.

Upstream of the pressure piston 4 there is a customary brake pad 10, which acts on the brake disc 3 under pressure or clamps it via the known floating caliper brake in cooperation with the opposite brake pad 10 to generate a frictional force.

For the optional pressurization of the wheel brake modules 2, a locking arrangement 1 is provided, which has a pressure generator. 14, a pressure accumulator 16, a switching valve 11, a switching valve 12 and a liquid reservoir 21. A suction line 13, connected to the pressure generator 14 (e.g. motor / pump unit), allows the pressure generator 14 to remove liquid from the liquid reservoir 21.

The pressure generator 14 fills the pressure accumulator 16 via the pressure line 15, which is in turn hydraulically connected to the switching valve 11 via a pressure line 17. The switching valve 11 controls the pressure output from the pressure accumulator 16 into the pressure line 18 or into the connected pressure line 19 to the respective intermediate chamber 9 of the wheel brake modules 2. The switching valve 11 is designed as an electromagnetically switchable 2/2-way valve. Switching the Switching valve 11 takes place as a function of control signals from a connected electronic control unit 25 which, among other things, converts the driver's switching commands into electrical signals.

^" Also assigned to the pressure line 18 is a further switching valve 12 which can optionally relieve the pressure in the pressure line 18 via the return line 20 to the liquid reservoir 21. The switching valve 12 is also designed as an electromagnetically switchable 2/2-way valve Switching valve 12 takes place as a function of the control signals of a connected electronic control unit 25, which among other things converts the driver's switching commands into electrical signals.

In order to monitor the state of charge of the pressure accumulator 16, the latter has a pressure sensor 26, the signals of which are processed by the electronic control unit 25, whereupon the pressure generator 14 is started to drop the pressure in the pressure accumulator 16 when the pressure level in the pressure accumulator 16 drops below a defined value to bring it back to its nominal value.

Furthermore, a pressure sensor 27 is connected to the pressure line 18, the signals of which represent the pressure state in the intermediate chamber 9 of the wheel brake module 2. This signal can be interpreted by the electronic control unit 25 as the brake quantity actually acting on the wheel. If this brake variable falls below a defined minimum value, an automatic control can be started, which, depending on the pressure in a wheel brake module 2, triggers the opening of the switching valve 11 in order to increase the pressure in the wheel brake module 2 again to a desired value.

If the slope or the gradient of the lane on which the vehicle is to be parked is recognized, then the electronic control device 25 automatically selects a higher or lower pressure setpoint depending on the gradient and initiates the setting of this pressure variable on the wheel brake module 2 via the above-mentioned regulation.

The signals from wheel speed sensors 24 of a pressure control device (ABS) can additionally be used to further safeguard against unintentional rolling away of the vehicle. An increased pressure is automatically generated in the wheel brake module 2 when the vehicle rolls away over the Wheel speed sensors 24 is detected. To rule out false signals, the pressure increase thus initiated is interrupted when a defined maximum value is reached.

In the rest position of the system shown in Fig. 1, the two switching valves 11, 12 are closed, i.e. the connection of the pressure accumulator 16 to the pressure line 18 and the connection of this to the liquid reservoir 21 is interrupted and the intermediate chamber 9 is depressurized.

If the driver now activates the parking brake by actuating a switch 35 (FIG. 2), the switching valve 11 is switched into an open position by the electronic control unit 25 and a connection of the intermediate chamber 9 to the pressure accumulator 16 is established. In order to achieve a controlled pressure build-up, the switching valve 11 can also be opened and closed again in a short time period, following a pulse rate model, until the desired pressure in the intermediate chamber 9 is set. The pressure is determined by means of a pressure sensor 27.

Due to the pressure increase in the intermediate chamber 9, the pressure pistons 4, 5 are pushed apart, the pressure piston 5 necessarily having to be moved up to its stop in the bottom of the bore. This is especially the case if a brake pressure was already generated in the system via the brake pedal before the parking brake was triggered, e.g. Stop on the mountain.

The pressure piston 4 acts in the usual way on the brake pad 10, which clamps a brake disc 3 according to a floating caliper brake.

After reaching a defined pressure in the intermediate chamber 9, measured by means of the pressure sensor 27, the electronic control unit 25 switches the switching valve 11 into a blocking position according to FIG. 3. Since the switching valve 12 is also in a blocking position, the pressure in the wheel brake module 2 is thus chambered. Both switching valves 11, 12 are so-called normally closed solenoid valves, ie that to maintain these switching positions "pressure chambered", no current supply to the switching valves 11, 12 is necessary. The locking arrangement 1 is still active even during this parking position, ie the pressure state can still be checked continuously via the pressure sensor 27. If the pressure falls below a defined setpoint, an increase in pressure can be initiated automatically by opening the switching valve 11.

If the parking brake is now deactivated by the driver (FIG. 4), the electronic control unit 25 switches the switching valve 12 into a passage position, as a result of which the pressure in the intermediate chamber 9 can be relieved via the return line 20 into the liquid reservoir 21. The complete relief is monitored by means of the pressure sensor 27. Only then is the switching valve 12 switched back into its blocking position by the electronic control unit 25. This ensures that the parking brake has been completely relieved.

5 shows the movement of the pressure pistons 4, 5 during normal brake actuation. A brake pressure was fed via the master brake cylinder 23 and the pressure line 22 into the pressure chamber 34 behind the pressure piston 5. By means of the mechanical coupling via an extension of the pressure piston 4, the pressure forces are transmitted to the pressure piston 4, which then transmits its forces in the usual way to the brake linings 10 that clamp the brake disc 3.

If the parking brake is activated from the normal braking position according to FIG. 5, the pressure piston 5 is pushed back against its pressure in the brake circuit against its actuation direction against the pressure in the intermediate chamber 9 until it stops. Normally, this backward movement causes an equivalent return movement of the brake pedal against the driver's foot, which under certain circumstances could be perceived as negative.

To avoid this, e.g. the pressure control system (ABS) that already exists in most vehicles can be used. It is necessary for this system to have at least one changeover valve 30, 32, 33 and an expansion chamber 31.

By switching the changeover valve 30 into a passage position and switching the changeover valves 32, 33 into a blocking position, the above-mentioned brake pressure previously fed into the expansion chamber 31 can be relieved. By the blocking position of the changeover valves 32, 33, the brake pedal hydraulically decoupled and the above-mentioned backward movement of the brake pedal avoided.

FIGS. 7 to 9 schematically show a further embodiment of a brake module, the same or equivalent parts again being provided with the same reference numerals. The solution according to FIGS. 7 to 9 differs from the solution according to FIGS. 1 to 6 in that the pistons 4 and 5 are not arranged in tandem one behind the other, but are guided telescopically one inside the other. The intermediate chamber 9 is thus located between the bottom of the cup-shaped piston 5 and the piston 4 guided telescopically in it. The supply of pressure fluid to the pressure chamber 34 takes place via an opening 36, while the supply of pressure fluid to the intermediate chamber 9 via openings 37 and 38 is made possible.

FIG. 7 shows the brake in the released state, with both pistons 4 and 5 being retracted. FIG. 8 shows the brake arrangement when the service brake is actuated, that is to say when the pressure chamber 34 is pressurized and the piston 5 is displaced. FIG. 9 finally shows the arrangement when the parking brake is actuated, that is to say when the intermediate chamber 9 is pressurized and the piston 4 is displaced.

The above description shows that the solution according to the invention is extremely simple and space-saving in its structure and in its operation. Therefore, the necessary control commands can also be easily integrated into existing controls. Since the parking brake according to the invention largely works with existing brake modules, it is not only inexpensive to manufacture, but can also be designed in a simple manner as a four-wheel brake with an ABS component. The brake pressure can correspond to the conventional pressure of the service brake. This means that the parking brake can be operated at full brake pressure, while the braking force of conventional hand brakes is a maximum of 30% of the service brake. The parking brake according to the invention can therefore be used as a full emergency braking system.

As described above, there is no need to readjust the parking brake, since the parking brake always adjusts itself via the pressure monitor. It can also do not happen that the braking force of the parking brake decreases after the wheels and brakes have cooled. Since the parking brake works electro-hydraulically, the tensioners required for hand brakes working with brake cables are not required. Also, the parking brake according to the invention cannot freeze due to the lack of brake cables.

Since the same brake pressure acts on all braked wheels, the brake cannot pull on one side. If necessary, the parking brake can also be switched on using a backup battery. No power is required to hold the parking brake, as explained above.

All parts required for the construction of the parking brake are known from conventional brake systems, so that large series parts can be used which keep the costs for the parking brake according to the invention low. The brake can be retrofitted at any time. Because of the small number of parts specifically required for the parking brake and the small size of these parts, the unsprung masses are increased only slightly or not at all.

Claims

claims

Electronically controlled parking brake for a motor vehicle, comprising a switch-on device (35) for generating an electronic activation signal, a release device (35) for generating an electronic deactivation signal, an electronic control device (25) processing these signals, a pressure fluid source (14, 16, 21) and Brake modules (2), which can be connected to the pressure fluid source (14, 16, 21) via switch valves (11, 12), for generating the braking forces on the wheels of the motor vehicle, each with a first pressure chamber (34) bordering an application element of the respective brake module an operating brake circuit (22) can be connected to a master brake cylinder (23), and to a second pressure chamber (9) adjoining the respective application element, which pressure chamber (17, 18, 19, 20) connects to the pressure fluid source (14, 16, 21) is connectable, characterized in that on at least part of the brake modules (2) the respective Z Uspannorgan comprises two separate coaxially arranged pressure pistons (4, 5), one of which delimits the first pressure chamber (34) and between which the second pressure chamber (9) is designed so that the pressure fluid source is a pressure accumulator (16) for storing the pressure fluid, a pressure generator (14) for filling the pressure accumulator (16) and a fluid reservoir (21) and that in the hydraulic circuit by means of control signals from the control device (25) controllable valve arrangements (11, 12) for selectively connecting the pressure output of the pressure accumulator (16) with the respective second Pressure chamber (9) of the wheel brake modules (2) and for optionally connecting the respective second pressure chamber (9) of the wheel brake modules (2) to the liquid reservoir (21) are arranged.

Parking brake according to claim 1, characterized in that the two pressure pistons (4, 5) are arranged in tandem one behind the other.

Parking brake according to claim 1, characterized in that the two pressure pistons (4, 5) are telescopically guided one inside the other.

4. Parking brake according to one of claims 1 to 3, characterized in that the valve arrangement comprises a first and a second switching valve (11, 12).

5. Parking brake according to claim 4, characterized in that the switching valves (11, 12) are designed as a 2/2-way valve and a Durchlaßbzw. Can take locked position.

6. Parking brake according to claim 4 or 5, characterized in that the switching valves (11, 12) are designed as solenoid valves,

7. Parking brake according to claim 6, characterized in that the switching valves (11, 12) assume a locked position when de-energized.

8. Parking brake according to one of claims 1 to 7, characterized in that a pressure sensor (27) for monitoring the fed pressure in the second pressure chamber (9) is connected to the hydraulic circuit.

9. Parking brake according to claim 8, characterized in that at least one defined setpoint can be predetermined for the fed pressure.

10. Parking brake according to claim 9, characterized in that the target value is formed as a function of the road gradient and that the control device (25) so _. is designed so that when the value falls below the setpoint, the pressure is automatically raised by opening the first switching valve (11) until the setpoint is at least reached again.

11. Parking brake according to claim 10, characterized in that the setpoint is constantly monitored even when the vehicle is switched off and readjusted if necessary.

12. Parking brake according to claim 10 or 11, characterized in that means are provided by which a warning signal is transmitted to the driver in the event of an unsuccessful restoration of the setpoint pressure.

13. Parking brake according to one of claims 1 to 12, characterized in that when the parking brake arrangement is activated via wheel speed sensors (24) of the pressure control device (ABS), the vehicle wheels are continuously monitored for movement and that upon detection of movement, the pressure in the second pressure chamber (9) a higher pressure value is regulated.

14. Parking brake according to one of claims 1 to 13, characterized in that the switch-on device with a sensor responsive to the state of the door lock of the driver's door and / or a sensor responsive to the state of the ignition lock and / or a sensor responsive to the load condition of the driver's seat is connected and that an activation signal can be generated as a function of a signal of at least one of the sensors.

15. Parking brake according to one of claims 1 to 14, characterized in that a deactivation signal can be generated as a function of an output signal of at least one sensor detecting the operating state of the motor vehicle.

16. A method for controlling an electronically controlled parking brake according to one of claims 1 to 15, characterized in that when the parking brake arrangement is triggered, the master brake cylinder (23) is hydraulically separated from the associated service brake circuit.

17. A method for controlling an electronically controlled parking brake for a motor vehicle according to claim 16, characterized in that the brake circuits associated with the master brake cylinder (23) are separated by means of the switching valves (32, 33) of a pressure control device (ABS).

18. A method for controlling an electronically controlled parking brake for a motor vehicle according to claim 17, characterized in that after separation of the master brake cylinder (23), the pressure which may be present in the first pressure chambers (34) of the wheel brake modules (2), generated by the Master brake cylinder (23) is relieved by opening the switching valve (30) of the pressure control device (ABS) in its expansion chamber.