Method for activation and deactivation of a control device

Abstract

In a method for activating and deactivating a control unit which can be used to control an electrically activatable assembly, the control unit is switched between a waking state, a sleep state and a deactivated state, wherein in the sleep state, the control device is disabled but can be transferred into the waking state by means of a sensor signal.

Claims

1. A method for activation and deactivation of a control unit configured to control an electrically activatable assembly, the method comprising: controlling, with the control unit, the electrically activatable assembly in a waking state of the control unit, the control unit being active in the waking state; switching the control unit from a sleep state of the control unit to the waking state based on a sensor signal of at least one monitoring sensor, the control unit being unable to control the electrically activatable assembly in the sleep state; maintaining the control unit in the sleep state over a specified time interval and automatically switching the control unit from the sleep state to the deactivated state after expiry of the specified time interval; and switching the control unit from a deactivated state of the control unit to the waking state only in response to switching on the control unit, the control unit being disabled and unable to control the electrically activatable assembly in the deactivated state.

2. The method according to claim 1 further comprising: one of (i) actively energizing and (ii) supplying energy to the at least one monitoring sensor in the sleep state.

3. The method according to claim 1 further comprising: automatically switching the control unit from the sleep state to the waking state after expiry of the specified time interval; and monitoring, with the control unit, in the waking state, a condition of one of (i) the electrically activatable assembly and (ii) an environment of the electrically activatable assembly.

4. The method according to claim 3 further comprising one of: controlling an actuator during the monitoring of the condition; and monitoring a behavior of the actuator during the monitoring of the condition.

5. The method according to claim 3 further comprising: automatically switching the control unit into the deactivated state after a completion of the monitoring of the condition.

6. The method according to claim 1, wherein the electrically activatable assembly is an electric brake motor of a vehicle parking brake, the controlling further comprising: controlling, with the control unit, in the waking state, the electric brake motor.

7. The method according to claim 6, wherein the at least one monitoring sensor is at least one of (i) a wheel speed sensor and (ii) an acceleration sensor, the method further comprising: monitoring a sensor signal of the least one of (i) the wheel speed sensor and (ii) the acceleration sensor during the sleep state of the control unit.

8. The method according to claim 6 further comprising: monitoring a hydraulic brake pressure in a vehicle footbrake.

9. A control unit for controlling an electrically activatable assembly, the control unit configured to: control the electrically activatable assembly in a waking state of the control unit, the control unit being active in the waking state; switch from a sleep state of the control unit to the waking state based on a sensor signal of at least one monitoring sensor, the control unit being unable to control the electrically activatable assembly in the sleep state; maintain the control unit in the sleep state over a specified time interval and automatically switch the control unit from the sleep state to the deactivated state after expiry of the specified time interval; and switch from a deactivated state of the control unit to the waking state only in response to switching on the control unit, the control unit being disabled and unable to control the electrically activatable assembly in the deactivated state.

10. The control unit according to claim 9, wherein the control unit executes program code of a computer program product having to control the electrically activatable assembly and to switch between the waking state, the sleep state, and the deactivated state.

11. A parking brake for a vehicle, the parking brake comprising: at least one electro-mechanical braking system on a vehicle wheel, the at least one electro-mechanical braking system having an electric brake motor configured to move a brake piston towards a brake disc to generate a braking force; and a control unit for controlling adjustable components of the parking brake, the control unit configured to: control the adjustable components of the parking brake in a waking state of the control unit, the control unit being active in the waking state; switch from a sleep state of the control unit to the waking state based on a sensor signal of at least one monitoring sensor, the control unit being unable to control the adjustable components of the parking brake in the sleep state; maintain the control unit in the sleep state over a specified time interval and automatically switch the control unit from the sleep state to the deactivated state after expiry of the specified time interval; and switch from a deactivated state of the control unit to the waking state only in response to switching on the control unit, the control unit being disabled and unable to control the adjustable components of the parking brake in the deactivated state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and expedient designs can be derived from the description of the figures and the drawings. Shown are:

(2) FIG. 1 a schematic representation of a hydraulic vehicle footbrake, wherein wheel braking devices of the vehicle footbrake on opposite wheels of the same axle are each equipped with an electro-mechanical braking system with an electric brake motor,

(3) FIG. 2 a section through an electro-mechanical braking system with an electric brake motor,

(4) FIG. 3 a flow diagram with method steps for activating and deactivating a control unit, which controls the electric brake motor of the electro-mechanical braking systems.

DETAILED DESCRIPTION

(5) In the figures, equivalent components are labelled with the same reference numerals.

(6) The brake system for a vehicle shown in FIG. 1 comprises a dual-circuit hydraulic vehicle footbrake 1 with a first hydraulic brake circuit 2 and a second hydraulic brake circuit 3 for supplying and controlling wheel braking devices 9 on each wheel of the vehicle with a brake fluid under hydraulic pressure. The two brake circuits 2 and 3 are connected to a common master brake cylinder 4, which is supplied with brake fluid via a brake fluid reservoir 5. The master cylinder piston in the master cylinder 4 is operated by the driver via the brake pedal 6, and the pedal travel exerted by the driver is measured via a pedal travel sensor 7. Between the brake pedal 6 and the master brake cylinder 4 a brake servo 10 is located, which comprises, for example, an electric motor, which preferably activates the master cylinder 4 via a transmission (iBooster).

(7) In addition to or as an alternative to the iBooster the hydraulic vehicle brake 1 can have an integrated electro-hydraulic braking unit with an electric motor-driven plunger. The vehicle brake 1 is advantageously designed as a Brake-By-wire system, wherein a brake pedal operation leads to a displacement of hydraulic volumes in a pedal travel simulator. The brake pressure is built up according to the brake pedal actuation via an electric motor-driven actuation of the plunger. In the event of a failure of the electro-hydraulic brake unit, isolating valves which connect the brake circuits to the master cylinder 4 are opened, so that when the brake pedal is operated the driver has a direct hydraulic bypass route to the wheel braking devices 9.

(8) The actuating movement of the brake pedal 6 measured by the pedal position sensor 7 is transmitted as a sensor signal to an open-loop or closed-loop control device 11 in which control signals for activating the brake servo 10 are generated. The supply of the wheel braking devices 9 with brake fluid is carried out in each brake circuit 2, 3 via different switching valves, which together with other units are part of a hydraulic braking system 8. The hydraulic braking system 8 additionally comprises a hydraulic pump, which forms part of an electronic stability program (ESP).

(9) The two hydraulic brake circuits 2 and 3 of the vehicle footbrake 1 are distributed diagonally, for example, so that the first brake circuit 2 supplies brake fluid, for example, to the two wheel braking devices 9 on the left front wheel and on the right rear wheel and the second brake circuit 3 supplies the two wheel braking devices 9 on the right front wheel and on the left rear wheel. Alternatively, it is also possible to split both hydraulic brake circuits 2 and 3 of the vehicle footbrake 1 over the wheel braking devices on the front axle and the wheel braking devices on the rear axle.

(10) In FIG. 2 the wheel braking device 9, which is arranged on a wheel on the rear axle of the vehicle, is shown in detail. The wheel braking device 9 is part of the hydraulic vehicle footbrake 1 and is supplied with brake fluid 22 from a brake circuit 2, 3. The wheel brake device 9 also has an electro-mechanical braking system, which can be used as a parking brake to keep the vehicle stationary when stopped, but also for braking when the vehicle is moving. The parking brake comprises two identically designed electro-mechanical braking systems on two laterally opposite vehicle wheels.

(11) The electro-mechanical braking system comprises a brake caliper 12 with a gripper 19, which engages around a brake disc 20. As an actuator element the braking system has a DC electric motor as a brake motor 13, whose rotor shaft drives a rotating spindle 14, on which a spindle nut 15 is mounted in a rotationally fixed manner During a rotation of the spindle 14, the spindle nut 15 is axially displaced. The spindle nut 15 moves within a brake piston 16, which supports a brake lining 17 which is pressed against the brake disc 20 by the brake piston 16. On the opposite side of the brake disc 20 a further brake lining 18 is located, which is fixed to the gripper 19 in a stationary manner. The brake piston 16 is sealed on its outer side against the accommodating housing with a pressure-tight seal using an encompassing sealing ring 23.

(12) Within the brake piston 16, during a rotational motion of the spindle 14 the spindle nut 15 can move axially forwards towards the brake disc 20, or during a rotational movement of the spindle 14 in the opposite direction axially backwards until a stop 21 is reached. To create a clamping force the spindle nut 15 acts upon the inner end face of the brake piston 16, which causes the brake piston 16 with the brake lining 17, mounted in the braking system in an axially displaceable manner, to be pressed against the facing surface of the brake disc 20.

(13) For the hydraulic braking force the hydraulic pressure of the brake fluid 22 from the hydraulic vehicle footbrake 1 is applied to the brake piston 16. The hydraulic pressure can also be used to provide effective support when the electromechanical braking system is operated when the vehicle is stopped, so that the total braking force is composed of the component applied by the electric motor and the hydraulic component. While the vehicle is being driven, to carry out a braking operation either only the vehicle hydraulic footbrake is active or both the hydraulic vehicle footbrake and the electromechanical braking system or only the electromechanical braking system is active to generate braking force. The actuating signals for controlling both the adjustable components of the hydraulic vehicle footbrake 1 and the electromechanical wheel braking device 9 are generated in the open-loop or closed-loop control device 11.

(14) The wheel braking device 9 shown in FIG. 2, which is equipped with the brake motor 13 in addition to the electromechanical braking system, is preferably located on the rear axle of the vehicle. The electrical brake motors 13 in the two wheel braking devices 9 on the two rear wheels on the rear axle can be controlled independently of each other.

(15) FIG. 3 shows a flow diagram with method steps for activating and deactivating a control unit which controls the electric brake motor 13 of the electromechanical braking system of the parking brake. The method starts in the first method step S1 with the operation of a vehicle with the ignition of the engine switched on. In the following method step S2 a query is issued as to whether the ignition in the vehicle has been turned off. If this is not the case, the No branch (“N”) is followed to return to the first step S1 again and the query in accordance with step S2 is carried out again at periodic intervals.

(16) If the result of the query in step S2 is that the ignition has been switched off and the vehicle engine has therefore been turned off, the procedure is continued following the Yes branch (“Y”) to the two branches in accordance with the method steps S3 to S6, and in accordance with the method steps S7 to S9. In the first branch in accordance with the method steps S3 to S6, immediately after turning off the ignition in the vehicle the state of the control unit is transferred from a waking state, which the control unit occupies when the ignition is switched on, into a sleep state, in which the control device is disabled but one or more monitoring sensors are still active. If a sensor signal of the monitoring sensors occupies a value within a defined range of values, then the control unit is transferred back into the waking state.

(17) Firstly, in the method step S3 it is ensured that one or more monitoring sensors are energized and thus able to generate a sensor signal, in spite of a deactivated control unit. In particular, due to the active design of the monitoring sensor it is possible to generate a permanent sensor signal, even if there is no change of state.

(18) In the following method step S4, a query is made as to whether the sensor signal from the previous method step S3 undergoes a change which is greater than a minimum amount. If this is not the case, the No branch is followed to return to the beginning of method step S4 and the query is executed again at periodic intervals. If, on the other hand, the signal change is greater than the threshold value, the Yes branch is followed to advance to the next method step S5, in which the control unit is automatically transferred from the inactive sleep state into the waking state. This then allows measures to be implemented in the following method step S6 to ensure, for example, a desired state of the parking brake, in particular to carry out a re-tensioning operation by controlling the electric brake motor to generate a minimum braking force. In addition or as an alternative, it is also possible to perform any other action, such as activating and monitoring actuators of the hydraulic vehicle footbrake.

(19) In the method steps S3 and S4, for example, wheel speed sensors or acceleration sensors are energized and examined for the presence of a signal change. This allows it to be determined whether the vehicle has been set in motion accidentally despite the parking brake being activated.

(20) In the second branch with the method steps S7 to S9, in parallel and simultaneously with the execution of the steps S3 to S6, a time query is performed. To this end, in method step S7 a clock is started, wherein in the following method step S8 it is checked at regular intervals whether a defined, fixed time interval has elapsed during which the control unit is in the sleep state. If the time interval has not yet elapsed, the procedure returns to the beginning of method step S8 again following the No branch, and again at regular intervals a check is made for the expiry of the time interval. If, on the other hand, the result of the query in step S8 is that the time interval has elapsed, the Yes-branch is followed to step S9, in which the state of the control unit is changed from the sleep state into the powered-off state, in which the control device is disabled. The method is then terminated until the vehicle is restarted by switching on the ignition again.

(21) The above-described method represents a simplified version of the activation and deactivation of the control unit. It may be appropriate to additionally consider another follow-on state that the control unit occupies after the ignition has been switched off in step S2, but before the control unit is transferred into the sleep state. In the follow-on state, which can also be maintained for a specified time interval, the control unit is still in the activated state, wherein the parking brake can only be activated in a limited way. During the follow-on state various sensor signals such as the wheel speeds are evaluated, in order to determine whether the vehicle has been accidentally set in motion within the follow-on period, whereupon the parking brake can be activated again. On the expiry of the follow-on period, the control unit itself is automatically transferred into the sleep state, whereupon the aforementioned method steps in accordance with steps S3 to S9 are carried out.