Control of a hydraulically actuated motor vehicle brake

Abstract

A hydraulically actuated brake device (120) on a motor vehicle (105) comprises a brake cylinder (215) with a brake piston (220) which can be displaced therein and is configured to press a brake lining (225) against a brake disc (205) in accordance with a hydraulic pressure in the brake cylinder (215). A method for controlling such a brake device (120) comprises steps of detecting a predetermined operating state of the motor vehicle (105); the operating state promoting migration of the brake piston (220) away from the brake disc (205); and of temporarily increasing a hydraulic pressure in the brake cylinder (215) in order to move the brake piston (220) in the direction of the brake disc (205).

Description

[0001] Control of a hydraulically operated vehicle brake

[0002] The present invention relates to the control of a hydraulically actuated brake. In particular, the invention relates to the control of a service brake of a motorcycle.

[0003] A motor vehicle, particularly a motorcycle, includes a hydraulically operated service brake. A brake disc is attached to a wheel of the motor vehicle, and a brake caliper is attached to a chassis. The brake caliper contains a brake cylinder in which a brake piston is slidably mounted. The brake cylinder is filled with a hydraulic medium. If hydraulic pressure increases in the brake cylinder, the brake piston is driven toward the brake disc, pressing a brake pad against the brake disc. The motor vehicle is decelerated by friction between the brake disc and the brake pad.

[0004] The hydraulic pressure can be built up using a hand or foot pump operated by the driver of the vehicle. A slack adjuster ensures that fresh hydraulic fluid can flow from a reservoir on the hand or foot pump to compensate for gradual wear of the brake pad.

[0005] It has been shown that a brake piston of such a brake system occasionally migrates into the brake cylinder during operation of the motor vehicle. Hydraulic fluid can be forced back into the reservoir in the process. If a brake intervention now occurs, a pressure point of the brake system can be shifted, and when the hand or foot lever is operated, a certain amount of play must be overcome before braking occurs. Braking can therefore be performed less precisely or less effectively. The present invention is based on the object of improving the control of a hydraulically actuated brake device of a motor vehicle. The invention achieves this object by means of the subject matter of the independent claims. Subclaims specify preferred embodiments.

[0006] A hydraulically actuated braking device on a motor vehicle comprises a brake cylinder with a brake piston slidably received therein, which is configured to press a brake pad against a brake disc as a function of a hydraulic pressure in the brake cylinder. A method for controlling such a braking device comprises the steps of detecting a predetermined operating state of the motor vehicle; the operating state favors a movement of the brake piston away from the brake disc; and temporarily increasing a hydraulic pressure in the brake cylinder to move the brake piston toward the brake disc.

[0007] It was recognized that the brake piston can migrate into the brake cylinder due to external forces that depend on the operating condition of the motor vehicle. Such forces can be caused, for example, by vibrations or strong accelerations in the motor vehicle. The method can prevent a gap that can form between the brake piston and the brake pad or between the brake pad and the brake disc from exceeding a predetermined size. The pressure point of the braking system can thus be kept constant with improved accuracy. The accuracy with which the braking system can be controlled can be increased. The motor vehicle can be decelerated with improved precision as required by a driving situation or a braking request.

[0008] Preferably, the hydraulic pressure is increased without causing a significant braking effect on the motor vehicle. For example, the braking force or deceleration caused by the increase can remain below a predetermined threshold. A driver of the motor vehicle cannot be distracted from their task by increasing the pressure. The method can be performed unobtrusively, so that the braking system always operates as expected.

[0009] The increase in hydraulic pressure cannot exceed a predetermined duration. For example, the hydraulic pressure can only be increased for a period of less than approximately 1 second, preferably less than approximately

[0010] 0.5 seconds, more preferably less than approximately 100 milliseconds. If a braking maneuver is initiated during the increase, the increase can be aborted immediately. The hydraulic pressure in the brake cylinder can then follow a different specification.

[0011] The increase can be controlled such that the increased pressure does not exceed a predetermined hydraulic pressure. For example, the hydraulic pressure in the brake cylinder of a moving motor vehicle may be 0 bar relative to the ambient pressure. According to the method, the pressure can be temporarily increased to approximately 1 bar. The extent to which the hydraulic pressure is increased may depend on a specific design of the braking system.

[0012] The procedure can only be performed when no braking is currently taking place. The hydraulic pressure in the braking system before increasing the pressure cannot exceed a predetermined threshold. This threshold can be at or just above atmospheric ambient pressure.

[0013] In a simple embodiment, the method can be executed periodically to counteract a possible back migration of the brake piston into the brake cylinder. For example, the method can be executed at regular intervals or after a predetermined distance traveled by the motor vehicle. The time interval or distance can be determined based on experiments, so that a good compromise can be found between too frequent and too infrequent execution. This provides a simple way to counteract the formation of play in the brake system.

[0014] Two reasons have been identified that favor the return migration of the brake piston into the brake cylinder. In a first variant, the operating condition is associated with vibrations in the area of ​​the brake piston. These vibrations can cause the brake piston to be driven away from the brake disc. The vibrations can originate primarily from the vehicle's drive motor. The frequency or intensity of the vibrations can depend on the speed and / or torque requirement of the drive motor. The return migration of the brake piston can occur particularly strongly in a predetermined speed range of the drive motor.

[0015] In one embodiment, the hydraulic pressure is increased if the duration of the vibrations exceeds a predetermined time. The vibrations can be counted only over the time during which the drive motor is in a predetermined operating state. For example, it can be determined that the drive motor has a speed of approximately 2800 rpm, and the method can be executed if this state lasts, for example, for approximately 30 minutes.

[0016] In a further embodiment, the intensity of the vibrations is assessed. The hydraulic pressure can be increased if an integral of the intensity over a period of time exceeds a predetermined level. In this way, it can be taken into account that vibrations of different frequencies or amplitudes promote the return migration of the brake piston to varying degrees. By forming the integral, a cumulative effect of the vibrations can be represented. In this way, the method-based contact of the brake pad against the brake disc can be controlled with improved precision. In a second variant, the operating state causes a predetermined force or a predetermined impulse on the brake piston. For example, driving over a threshold or driving through a depression can greatly accelerate a wheel of the motor vehicle to which the braking device is attached. The brake piston can then be driven back into the brake cylinder. The force orThe pulse can be measured. This allows the hydraulic pressure to be temporarily increased if sufficiently strong or frequent forces or pulses act on the braking device or brake piston.

[0017] In one embodiment, the operating state comprises a predetermined driving maneuver of the motor vehicle. It has been shown that certain driving maneuvers favor the described loads on the braking system. For example, if the motor vehicle is a two-wheeler, driving at a steep angle, sharp acceleration, a rear wheel stumbling, or a lifted front wheel returning to the road surface can each cause the aforementioned forces or impulses. The method can be executed when it has been determined that a predetermined operating state has been entered.

[0018] In a further embodiment, an operating state of the motor vehicle is evaluated. The hydraulic pressure can be increased if the sum of evaluations of several detected operating states exceeds a predetermined threshold. Thus, the method can be executed not for every operating state that favors reversion, but only after several predetermined operating states have been reached in succession, which together can have a significant effect on the position of the brake piston.

[0019] In a simple embodiment, several predetermined operating states are evaluated equally. For example, the hydraulic pressure can be increased when approximately 5, approximately 10, or approximately 50 predetermined operating states have been reached. In another embodiment, different operating states can be weighted differently. This allows for a better distinction between a stronger and a weaker influence of the operating state on the brake piston. The application of the brake pad can be better tailored to the actual demand.

[0020] The motor vehicle may comprise a plurality of wheels, each of which is mounted with an associated braking device. In one embodiment, the method may be performed individually for each of the braking devices. In another embodiment, the hydraulic pressure is increased at a plurality of braking devices of different wheels of the motor vehicle if it is determined that a condition for increasing the hydraulic pressure at at least one of the braking devices is met. The braking devices may be actuated by means of different brake circuits, so that hydraulic pressures in the brake cylinders may differ from one another.

[0021] According to a further aspect of the present invention, a device for controlling a hydraulically actuated braking device of the type described herein for a motor vehicle comprises an interface for connection to an actuator, wherein the actuator is configured to increase a hydraulic pressure in the brake cylinder; an interface to a data source for information regarding an operating state of the motor vehicle; and a processing device. The processing device is configured to determine a predetermined operating state of the motor vehicle, wherein the operating state favors a migration of the brake piston away from the brake disc, and to temporarily increase the hydraulic pressure in the brake cylinder in order to move the brake piston toward the brake disc.

[0022] The processing device is preferably configured to partially or completely execute a method described herein. For this purpose, the processing device can be implemented electronically and, for example, comprise an integrated circuit, a programmable logic module, or a programmable microcomputer. The method can be implemented in the form of a configuration or as a computer program product with program code means for the processing device. The configuration or the computer program product can be stored on a computer-readable data carrier. Features or advantages of the method can be transferred to the device, or vice versa.

[0023] A system is further proposed which comprises a device described herein and an active braking system, wherein the actuator is comprised in the active braking system. The active braking system may, for example, comprise an anti-lock braking system (ABS) or an electronic stability program (ESP). The active braking system is configured to modulate a hydraulic pressure in the brake cylinder of a braking device. The hydraulic pressure can be reduced below an external preset or increased above it. To increase the hydraulic pressure, the active braking system may, for example, comprise a pump and / or a pressure accumulator.

[0024] According to yet another aspect of the present invention, a motor vehicle comprises a device or system described herein. Preferably, the motor vehicle comprises a drive motor configured as an internal combustion engine, in particular a reciprocating piston engine. Vibrations of the drive motor can act on the brake piston in the brake cylinder.

[0025] The motor vehicle can generally comprise any vehicle for use in general road traffic. In a particularly preferred embodiment, the motor vehicle comprises a single-track vehicle. In particular, the motor vehicle can comprise a motorcycle or a scooter. A single-track vehicle can also be considered a vehicle with dual wheels on one axle with a predetermined maximum distance between them. The maximum distance can be legally specified and is 460 mm in some countries.

[0026] The invention will now be described in more detail with reference to the accompanying drawings, in which:

[0027] Figure 1 shows a braking system on a motor vehicle;

[0028] Figure 2 is a schematic representation of an extended braking system; and

[0029] Figure 3 illustrates a flow chart of a process.

[0030] Figure 1 shows a braking system 100 on a motor vehicle 105. Motor vehicle 105 is depicted as a motorcycle, for example. Motor vehicle 105 comprises a drive motor 110 and two wheels 115, each of which has an associated braking device 120. Drive motor 110 is preferably designed as a reciprocating piston engine.

[0031] A braking device 120 can be actuated hydraulically. The hydraulic pressure required for this can be generated by a driver of the motor vehicle 105 using a hand pump 125 or a foot pump 130. Different brake circuits can be formed so that the braking devices 120 can be actuated independently of one another. For example, the hand pump 125 can act on the braking device 120 of the front wheel 115, and the foot pump 130 can act on the braking device 120 of the rear wheel 115.

[0032] Furthermore, a control device 135 may be provided, which is configured to actively control the actuation of a braking device 120. The control device 135 may be configured to increase or decrease a hydraulic pressure for actuating a braking device 120.

[0033] Figure 2 shows a schematic representation of an expanded braking system 100. A braking device 120 is schematically depicted in a lower right-hand area. The braking device 120 comprises a brake disc 205, which is rotationally connected to a wheel 115 of the motor vehicle 105. A brake caliper 210 is mounted on the chassis of the motor vehicle 105. A brake cylinder 215 is formed in the brake caliper 210, in which a brake piston 220 is slidably received. A brake pad 225 is also slidably mounted on the brake caliper 210, so that the brake piston 220 presses the brake pad 225 against the brake disc 205 when hydraulic pressure in the brake cylinder 215 increases.

[0034] In the illustrated embodiment, two brake pistons 220 are shown, which are opposite each other with respect to the brake disc 205. However, different embodiments are also possible. In particular, the

[0035] The braking device may have a fixed caliper, a floating caliper, or a pendulum caliper, and the brake disc 205 may be mounted floatingly along its axis of rotation or be fixedly mounted. A gap 230 is shown in Figure 2 between one of the brake pads 225 and the brake disc 205. The gap 230 may form when the brake piston 220 migrates back into the brake cylinder 215. It is proposed to counteract the formation of the gap 230 by increasing a hydraulic pressure in the brake cylinder 215 under predetermined conditions. Such a condition may exist, in particular, when the braking device 120 is not actuated for a prolonged period or over a longer distance while the motor vehicle 105 is traveling.

[0036] A hydraulic supply line for fluid in the brake cylinder 215 leads to the hand pump 125 or the foot pump 130. In the illustrated embodiment, the fluid line leads through a valve 235 of the control device 135. In this case, the control device 135 also comprises a pressure accumulator 240 and / or a pump 245. A hydraulic pressure provided by the pressure accumulator 240 or the pump 245 can be passed on to the braking device 120 through the valve 235. Furthermore, pressure can be maintained in the braking device 120 or released therefrom by means of the valve 235. A connection between the hand pump 125 or the foot pump 130 and the braking device 120 can optionally also be interrupted by means of the valve 235.

[0037] The valve 235 and the pump 245 can be controlled by a dedicated control device. It is proposed to control a control element of the control device 135, in particular the valve 235 or the pump 245, by means of a device 250 configured to counteract the formation of a gap 230. In the illustrated embodiment, the device 250 is connected to the control device 135 or the actuators 235 and 245 by means of two interfaces 255. In another embodiment, the device 250 can be integrated with the control device 135.

[0038] The device 250 further comprises a processing device 260, which is connected by means of one or more interfaces 265 to one or more data sources on board the motor vehicle 105. A data source can, in particular, comprise a sensor or a system on board the motor vehicle 105. For example, the processing device 260 can be connected to an inertial or acceleration sensor, a speed sensor of the drive motor 110, a speed sensor, a temperature sensor, a steering angle sensor, a speed sensor on a wheel 115, a sensor for determining a spring travel of one of the wheels 115, or a pressure sensor in the braking system 100. Furthermore, the processing device 260 can be connected to an ABS or ESP system or an engine control system for the drive motor 110.It is proposed that the processing device 260 be configured to control, by means of at least one actuator 235, 245 of the control device 135 of the braking system 100, a temporary increase in the hydraulic pressure in the brake cylinder 215 of the braking device 120 when the motor vehicle 105 has assumed a predetermined operating state. In particular, the hydraulic pressure should be temporarily increased if, while the motor vehicle 105 is traveling, the braking device 120 has not been actuated for an extended period of time using the hand pump 125 or the foot pump 130 or the control device 135.

[0039] Figure 3 shows a flowchart of a method 300 for controlling a braking system 100. The method 300 can be executed in particular on the processing device 260.

[0040] In a step 305, an operating state of the motor vehicle 105 can be detected. The operating state can be determined based on sensor values ​​or status information from a system on board the motor vehicle 105. In one embodiment, the operating state of the motor vehicle 105 includes an operating state of the drive motor 110. This can be characterized, for example, by a torque request, an engaged gear, and / or a speed.

[0041] In another embodiment, the operating state comprises a driving maneuver of the motor vehicle 105. The driving maneuver can, for example, include a lifting of the front wheel 115 ("wheelie"), driving at an incline, sharp acceleration, high driving speed, a predetermined steering angle, driving through a dip, or driving over a threshold. In general, driving maneuvers in which strong forces or impulses act on a wheel 115 and thus on a braking device 120 or a brake piston 220 can be determined. In a step 310, the operating state can be evaluated. For example, vibrations at different speed ranges can be assigned different weights. Accordingly, a weight can be assigned to a driving maneuver. The greater the weight, the more the operating state can favor a backward migration of the brake piston 220 in the brake cylinder 215.

[0042] In a step 315, certain operating states or evaluations can be cumulated. A continuous operating state can be integrated over its duration; evaluations of discrete operating states can be added together. It should be noted that both continuous and discrete influences on the brake piston 220 can be determined and evaluated together.

[0043] In addition, in step 315, it can be determined whether a braking device 120 is being actuated in another way or whether the hydraulic pressure in the brake cylinder 215 is being increased in another way. If this is the case, previously accumulated evaluations can be reset. A pressure increase by method 300 cannot then occur.

[0044] In a step 320, the cumulative evaluations can be compared with a predetermined threshold. The threshold indicates how many influences that favor the retraction of the brake piston 220 into the brake cylinder 215 can be tolerated.

[0045] If the threshold value is exceeded, the brake pressure in the brake cylinder 215 of the braking device 120 can be temporarily increased. The increase preferably occurs only over a short time and likewise preferably only by or to a predetermined amount. The time and / or the amount are preferably selected such that no significant braking effect occurs on the motor vehicle 105. A time or duration of the increase can be determined depending on the driving state of the motor vehicle 105. For example, when driving straight ahead at a higher speed, such as on a highway, a stronger or longer impulse can be given than when driving at a lower speed. Furthermore, the increase in the brake pressure can be suspended until a predetermined driving maneuver of the motor vehicle 105 is completed. This can prevent an increase in the brake pressure from being controlled, for example, when driving at an incline.

[0046] Reference symbol

[0047] 100 braking system

[0048] 105 Motor vehicle

[0049] 110 drive motor

[0050] 115 bikes

[0051] 120 braking device

[0052] 125 hand pump

[0053] 130 Foot pump

[0054] 135 Control device

[0055] 205 brake disc

[0056] 210 brake caliper

[0057] 215 brake cylinders

[0058] 220 brake pistons

[0059] 225 brake pad

[0060] 230 gap

[0061] 235 Valve

[0062] 240 pressure accumulators

[0063] 245 Pump

[0064] 250 device

[0065] 255 interface

[0066] 260 processing facility

[0067] 265 interface

[0068] 300 procedures

[0069] 305 Record operating status

[0070] 310 Assess operating status

[0071] 315 cumulative ratings

[0072] Compare 320 with threshold

[0073] 325 Temporarily increase brake pressure

Claims

Claims 1 . A method (300) for controlling a hydraulically actuated braking device (120) on a motor vehicle (105), wherein the braking device (120) comprises a brake cylinder (215) with a brake piston (220) displaceable therein, which is configured to press a brake pad (225) against a brake disc (205) as a function of a hydraulic pressure in the brake cylinder (215); wherein the method (300) comprises the following steps: Detecting (305) a predetermined operating state of the motor vehicle (105); wherein the operating state favors a migration of the brake piston (220) away from the brake disc (205); and temporarily increasing (325) a hydraulic pressure in the brake cylinder (215) in order to move the brake piston (220) towards the brake disc (205).

2. Method according to claim 1, wherein the hydraulic pressure is increased (325) without causing a significant braking effect on the motor vehicle (105).

3. The method according to claim 1 or 2, wherein the increase (325) of the hydraulic pressure does not exceed a predetermined duration.

4. Method according to one of the preceding claims, wherein the increased pressure (325) does not exceed a predetermined hydraulic pressure.

5. Method according to one of the preceding claims, wherein the operating state (305) is associated with vibrations in the region of the brake piston (220).

6. The method according to claim 5, wherein the vibrations originate essentially from a drive motor (110) of the motor vehicle (105).

7. The method according to claim 5 or 6, wherein the hydraulic pressure is increased (325) when a duration of the vibrations exceeds a predetermined time.

8. The method of claim 7, wherein a magnitude of the vibrations is evaluated (310); and the hydraulic pressure is increased (325) if an integral of the magnitude over the duration exceeds a predetermined amount.

9. Method according to one of the preceding claims, wherein the operating state (305) causes a predetermined force or a predetermined impulse on the brake piston (220).

10. The method according to claim 9, wherein the operating state (305) comprises a predetermined driving maneuver of the motor vehicle (105).

11. Method according to claim 9 or 10, wherein an operating state (305) is evaluated (310); and the hydraulic pressure is increased (325) if a sum of evaluations of several detected operating states exceeds a predetermined threshold value (320).

12. The method according to any one of the preceding claims, wherein the motor vehicle (105) comprises a plurality of braking devices (120) mounted on different wheels (115) of the motor vehicle (105); wherein the hydraulic pressure at all braking devices (120) is increased.

13. Device (250) for controlling a hydraulically operated braking device (120) on a motor vehicle (105), wherein the braking device (120) comprises a brake cylinder (215) with a brake piston (220) displaceable therein, which is configured to press a brake pad (225) against a brake disc (205) as a function of a hydraulic pressure in the brake cylinder (215); wherein the device (250) comprises the following elements: an interface (255) for connection to an actuator (235, 245) configured to increase a hydraulic pressure in the brake cylinder (215); an interface (265) to a data source for information regarding an operating state of the motor vehicle (105); and a processing device (260) configured to determine a predetermined operating state of the motor vehicle (105); wherein the operating state promotes a migration of the brake piston (220) away from the brake disc (205);and temporarily increase the hydraulic pressure in the brake cylinder (215) to move the brake piston (220) towards the brake disc (205); 14. Motor vehicle (105) comprising a device (250) according to claim 13.

15. Motor vehicle (105) according to claim 14, wherein the motor vehicle (105) comprises a single-track vehicle.

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