WO2006133993A1

WO2006133993A1 - Starting on a slope with the aid of the service brake when the parking brake is engaged

Info

Publication number: WO2006133993A1
Application number: PCT/EP2006/061841
Authority: WO
Inventors: Martin Frotscher
Original assignee: Robert Bosch Gmbh
Priority date: 2005-06-16
Filing date: 2006-04-26
Publication date: 2006-12-21
Also published as: DE102005027843A1

Abstract

The invention relates to a vehicle comprising control means via which the parking brake can be engaged when the vehicle is at a standstill. In order to start driving on a slope, the service brake (2a, 2b, 6, 8, 9) can be actuated first and the parking brake can be released thereafter, whereupon the drive unit can be impinged upon by torque and the service brake (2a, 2b, 6, 8, 9) can subsequently be released again. In order to be able to start driving in a controlled, comfortable manner in all driving conditions, the parking brake is engaged by means of the control device (11) when the vehicle is at a standstill while (1.1) the service brake (2a, 2b, 6, 8, 9) is actuated first, (1.2) whereupon the parking brake (2b, 5, 7, 10) is released, (1.3) the drive unit is impinged upon by torque, and (1.4) the service brake (2a, 2b, 6, 8, 9) is then released again so as to start driving.

Description

Approaching a slope with the parking brake engaged using the service brake

State of the art

The present invention relates to a method for starting a vehicle, in particular at a slope, wherein the vehicle comprises an operating and a parking brake, which are each controlled by an electronic control unit.

For example, WO 92/04213 discloses an arrangement for holding a vehicle on an inclined roadway, in particular as a traction aid on the hill, which offers a so-called hillholder function.

For Stop & Go systems, which perform a cruise control until the vehicle is at a standstill, the standstill is initially held hydraulically. When the standstill lasts longer than an applicable time (for example, 1 minute), a mechanical parking brake is applied to lower the hydraulic load.

Problems of the prior art

When starting with an active parking brake, the motor must be activated at the same time and the parking brake released. Since the parking brake requires about 1 second to open, takes place in this time a start against the brake. On the other hand, a delayed activation of the engine could lead to a rolling back of the vehicle. The problem arises, among other things, that the parking brake can not continuously adjust the braking force, but only knows the two defined states "open" and "closed". The object of the invention is to realize a controlled, comfortable start in all driving conditions. This should neither be approached noticeably against the brake, nor should it come to an unwanted roll back of the vehicle.

Advantages of the invention

This problem is solved by a method for starting a vehicle, in particular at a slope, wherein the vehicle includes an operating and a parking brake, which are each controlled by an electronic control unit, wherein the parking brake by the control unit during standstill of the vehicle is activated or tightened and the service brake is applied to start, then the parking brake is released, the drive is acted upon by a torque and then the service brake is released again. For the purposes of the invention, a slope is understood to mean inclination (the roadway has a positive gradient in the direction of travel) or a gradient (the roadway has a negative gradient in the direction of travel). The service brake is preferably hydraulically actuated and serves to brake the vehicle while driving. The parking brake is preferably operated mechanically and is usually tightened only when the vehicle is stopped (closed) to prevent it from rolling away, for example on a slope. By hydraulically applying the braking force, a controlled, comfortable starting is possible. In this case, on the one hand, the force can be modulated quickly and, on the other hand, assume any amount to be adjusted engine torque and also slope-dependent. It is essential to realize a start-up procedure with a stop-and-go system with a mechanical parking brake through an upstream transition from mechanical to hydraulic holding and then hydraulic release. This differs from a start-up by the driver in that here as fast as possible release of the brake must be done to ensure acceleration of the vehicle and thus can be approached by the driver from the mechanical brake. Another difference to Stop & Go The system is that a possible rolling back of the vehicle, caused by a too early release of the parking brake, by the driver can be easily compensated by further accelerating, while in a Stop & Go system, this situation must be prevented in any case. A possible time delay due to the upstream hydraulic holding prior to the actual start-up plays only a minor role in Stop & Go systems, since the superimposed ACC system can detect a possibly imminent start-up process by lightly rolling up the leading vehicle at an early stage and already at this time to hold hydraulically can go without immediate arrival.

In one embodiment of the invention, it is provided that the service brake is released during startup depending on the drive torque to the drive wheels. The sum of the holding torque of the service brake and the starting torque of the drive thus prevent, especially when starting on a slope, a rolling back of the vehicle. Furthermore, it can be provided that the service brake is acted upon actuation with a slope-dependent hydraulic holding pressure, the hydraulic holding pressure of the service brake is thus gradient-dependent. The greater the slope or the gradient, the greater the holding pressure is selected. An imminent starting of the vehicle can be determined, for example, by a distance sensor for vehicles in front or a vehicle-vehicle communication. Additionally or alternatively, an imminent starting of the vehicle by operation of a control element, in particular an accelerator pedal, is determined.

The parking brake is preferably after a predetermined downtime of the vehicle, e.g. a minute, dressed. If the parking brake is not applied, the start is made by holding the service brake hydraulically.

The above-mentioned problem is also solved by a vehicle with an operating and a parking brake, which can each be controlled by an electronic control unit, wherein the vehicle comprises control means via which during the stoppage of the vehicle, the parking brake can be applied and for starting on a slope first the service brake can be operated, then the parking brake can be solved, then the drive can be acted upon with a torque and then the service brake can be released again. Preferably, it is provided that the service brake can be acted upon actuation with a slope-dependent hydraulic holding pressure. In one development, the vehicle may comprise a distance sensor for vehicles in front, with the aid of which an imminent approach can be determined. When a vehicle in front drives, this is recognized by an increasing distance to it. In the mass of driving situations, eg a traffic jam, a stop in front of a traffic light system, etc., this will result in the vehicle starting up. Preferably, control devices are provided which can tighten the parking brake after a predetermined downtime of the vehicle. When the vehicle is stopped and then held by the service brake, the parking brake is applied after a predetermined time, eg a few seconds, a minute, etc. The starting process then takes place according to the method of the invention.

drawings

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Showing:

Figure 1 is a sketch of a brake system of a motor vehicle;

Figure 2 is a sketch of the procedure.

FIG. 1 shows a sketch of a brake system of a motor vehicle. Shown are only the essential components for understanding the present invention. The steerable front wheels Ia and the non-steerable rear wheels Ib of a vehicle are each equipped with disc brakes 2a for the front axle and 2b for the rear axle. Both front and back tere disc brakes 2 a, 2 b are each provided with a brake caliper and arranged therein hydraulic brake piston, which are assigned to a service brake. The service brake comprises a service brake circuit 6, wherein for the sake of simplicity a common circuit for all wheels is assumed here, in practice these are usually dual-circuit brake systems. The service brake circuit 6 can be pressurized by means of a master cylinder 8, which can be actuated by an electromechanical actuator 9. If the vehicle is to be held at standstill before rolling away, for example, by a slope or against the torque of a converter in an automatic transmission, the service brake circuit 6 is subjected to a holding pressure p_H. The holding pressure p_H generates a static friction of the brake disks which is greater than the moment driving the vehicle. Instead of a hydraulic brake system, an electromechanical brake system, in which brake pads are pressed against the brake disk, for example by means of an electromotively displaceable wedge, as disclosed as a self-intensifying disc brake, eg, in DE 197 42 920, can be used.

In addition to the service brake circuit and the service brake, the brake system comprises a parking brake, which, for example, as outlined in FIG. 1, can be a mechanically actuated braking device which acts via a cable pull 7 on further brake calipers 5 on the rear axle. The cable 7 is actuated for example by an electromechanical actuator 10. Alternatively, a further hydraulic or electromechanical brake circuit may be provided here, e.g. in which the disc brakes of the rear axle are each equipped with independent e- lektromechanischen actuators. The two actuators 9 and 10 are controlled by a control unit 11.

Alternatively, the parking brake may also act directly on the transmission, e.g. as a parking brake in an automated manual transmission.

FIG. 2 shows the method sequence during a starting process. In the initial situation, the parking brake is engaged in step 1 This corresponds to a "hold on the mountain" operating state, irrespective of whether the vehicle is driving in mountain or downhill direction, ie would roll backwards or forwards when the brake is released In step 2, a check is first made as to whether a startup process is imminent For example, by a vehicle-vehicle communication, a distance sensor that can detect the start of the vehicle in front, or by a driver's request, for example by pressing the accelerator pedal or the like done.So, if a startup before, the decision in step 2 is J as Yes, in a third step, the service brake is first actuated, so the service brake circuit 6 is pressurized via the master cylinder 8 by means of the actuator 9, so that the vehicle alone can prevent the vehicle from rolling away via the service brake is pressed, the parking brake is released in step 4. Das Fahr Now the tool is only held by the braking force of the service brake. In a next step, the drive is applied with torque, in an automatic transmission, this is done by inserting a drive speed for forward drive and increasing the engine speed, in an automated transmission by engaging a forward gear and closing the clutch while increasing the engine speed. The torque to be applied depends essentially on the vehicle weight, any loading of the vehicle and the incline. With regard to the gradient, it may be possible for the vehicle to start uphill or downhill. When driving uphill the downgrade force tries to set the vehicle backwards in motion, is corresponding here by the combination operating the service brake and applying the

Counteract drive with a drive torque. The stronger the drive torque acts, the lower the holding force of the service brake can be selected. The starting process is completed when the service brake is completely released. When starting downhill, the downhill torque tries to move the vehicle forward in the direction of the slope. Here, if necessary, it is possible to completely dispense with a loading of the drive with a torque, where appropriate, depending on here desired acceleration, only slowly to release the service brake.

The start-up procedure in a vehicle that is mechanically stopped by a Stop & Go system thus proceeds as follows: First, the ACC system detects an imminent start-up procedure and sends the start-up request to the brake control unit (for example ESP). This builds up a necessary hydraulic holding pressure (for example slope-dependent) and at the same time commands the mechanical parking brake to release it.

Only when the mechanics are completely solved does the ACC system get permission to drive the engine and accelerate the vehicle. The brake control unit then releases the hydraulic brake pressure as a function of the engine torque and the gradient, as would be the case in the case of normal hydraulic holding (hill holder).

This type of start-up is particularly downhill when driving the vehicle. In this case, it may be necessary to ascend so that not all the braking force has to be reduced to start rolling, but the vehicle should roll off at a defined value. Here, a start from the mechanical parking brake would lead to an excessive unintentional acceleration of the vehicle, which would then have to be compensated again by hydraulic pressure build-up. If the way of starting from hydraulic holding is selected here, the vehicle can be accelerated controlled. This behavior is absolutely necessary for Stop & Go traffic.

Claims

claims

1. A method for starting a vehicle, in particular at a slope, wherein the vehicle is a service brake (2a,

2b, 6) and a parking brake (2b, 5, 7, 10), which are each controlled by an electronic control unit (11), characterized in that activated by the control unit (11) during the stoppage of the vehicle, the parking brake is and to start

(1.1) first the service brake (2a, 2b, 6, 8, 9) is actuated,

(1.2) then the parking brake (2b, 5, 7, 10) is released,

(1.3) the drive is subjected to a torque and then

(1.4) the service brake (2a, 2b, 6, 8, 9) is released again.

2. The method according to any one of the preceding claims, characterized in that the service brake (2a, 2b, 6, 8, 9) in step (1.3) is released depending on the drive torque to the drive wheels.

3. The method according to any one of the preceding claims, characterized in that the service brake (2a, 2b, 6, 8, 9) is acted upon actuation in step (1.1) with a slope-dependent hydraulic holding pressure.

4. The method according to any one of the preceding claims, characterized in that an imminent starting of the vehicle is determined by a distance sensor for vehicles in front.

5. The method according to any one of the preceding claims, characterized in that an imminent start of the vehicle by operation of a control element, in particular an accelerator pedal, is determined.

6. The method according to any one of the preceding claims, characterized in that the parking brake (2b, 5, 7, 10) after a predetermined downtime of the vehicle is tightened.

7. brake system control means for a vehicle with an operating brake (2a, 2b, 6, 8, 9) and a parking brake (2b,

5, 7, 10), which can each be controlled by the brake system control means (11), characterized in that the parking brake can be activated via the brake system control means during standstill of the vehicle and for starting at a slope initially the service brake (2a, 2b, 6, 8, 9) can be actuated, then the parking brake (2b, 5, 7, 10) can be solved, then the drive can be acted upon with a torque and then the service brake (2a, 2b, 6, 8, 9) can be solved again.

8. brake system control means according to the preceding claim, characterized in that the service brake (2a, 2b, 6, 8, 9) can be acted upon actuation with a slope-dependent hydraulic holding pressure.

9. Brake system control means according to any one of the preceding claims, characterized in that they comprise a distance sensor for preceding vehicles.

10. Brake system control means according to one of the preceding claims, characterized in that the parking brake (2b, 5, 7, 10) is activated after a predetermined downtime of the vehicle.