DE9320790U1 - Device for ensuring the driving stability of front or all-wheel drive motor vehicles in critical driving situations - Google Patents

Description

Description

Device for ensuring the driving stability of front-wheel or all-wheel drive vehicles in critical driving situations

The invention relates to a device for ensuring the driving stability of front-wheel or all-wheel drive motor vehicles in critical driving situations in which a largely constant reduction in driving speed over a relatively long period of time is necessary, but no deceleration of the vehicle to a standstill is necessary.

In addition to front-wheel drive, four-wheel drive is increasingly being used as a drive principle in modern passenger cars. On unpaved terrain, on poor or dirty roads and on extreme gradients, four-wheel drive vehicles have advantages over vehicles with conventional drive. However, the good traction in such driving situations results in a psychological risk of accident that should not be underestimated: the driver of an four-wheel drive vehicle is often not aware that such a vehicle behaves just as disadvantageously as a vehicle with conventional drive in other driving situations, e.g. it tends to swerve out of the direction of travel when braking hard while driving downhill or on icy roads.

Anti-lock braking systems are generally suitable for ensuring driving stability during braking. These anti-lock braking systems, known as ABS, are activated by pressing the brake pedal, i.e. after the driver has moved his foot from the accelerator pedal to the brake pedal and the drive unit is therefore only running at idle speed. The brake pressure is preferably changed electronically depending on the wheel speed so that the wheels do not lock. This means that the braking force required to bring the vehicle to a standstill is reduced, particularly in the event of emergency braking.

Braking distance minimized.

A disadvantage of the known anti-lock braking systems is the equipment and control technology required, which has a significant impact on the manufacturing costs of the respective motor vehicle. Furthermore, these anti-lock braking systems are only suitable to a limited extent for driving situations in which a largely constant reduction in driving speed over a relatively long period of time is necessary to ensure stable driving behavior, but the vehicle should not be slowed down to a standstill. Such driving situations, for example driving on icy roads or long downhill drives, require the driver to constantly or intermittently press the brake pedal, which causes considerable problems, especially for inexperienced drivers.

The object of the invention is to create a device that is independent of the skills of the driver and that ensures stable driving behavior in a largely constant speed range in critical driving situations in which the traction-specific advantages of motor vehicles with front or all-wheel drive are not relevant.

This object is achieved according to the invention by arranging actuating elements for activating a central control unit in the driver's grip area. The control unit has an evaluation circuit which, depending on the driving speed recorded at the time of activation, derives a control command for dosing the actuating strengths of the drive unit and brake unit. The control unit is connected to the throttle valve shaft and the master brake cylinder as well as to devices for deactivating the control elements for the drive unit and the brake unit that can be actuated by the driver.

A further actuating element for resetting the forcibly initiated control process to normal driving mode is located within the driver's reach.

• *

If the control period is to be divided into sections, a device that can be operated by the driver is assigned to the evaluation circuit of the control unit to determine a driving speed that can be selected in stages.

As an actuating element for activating the central control unit, a circumferential sensor spiral that responds to pressure is arranged in the steering wheel rim. The control unit can also be actuated using two switches arranged diametrically opposite one another on the steering wheel. To deactivate the control elements that can be actuated by the driver, it is proposed that articulated joints or pull magnets be assigned to the accelerator and brake actuating rods. Finally, the brake unit can also be deactivated by having the master brake cylinder with two pistons, one of which is assigned to actuation in normal driving mode and one in forced driving mode, such that the piston that acts alone in normal driving mode is deactivated when control begins.

The invention improves the driving stability of motor vehicles with front or four-wheel drive in critical driving situations in which the good traction of such drive concepts is only partially effective, e.g. when driving downhill or on icy roads. This achieves a significant increase in safety for such vehicles with relatively little equipment and control technology effort.

It is particularly useful to trigger the compulsory control by manual operation by the driver, whereby the psychological reaction of the "twitch" of the hand in fright situations is advantageously used to reduce the driver's reaction time. By applying the invention, the wear of the activated motor vehicle components is slightly increased, although this can be largely neglected in relation to the increase in safety achieved. However, taking the "wear" criterion into account, the application of the solution according to the invention should be limited to extreme driving situations.

An embodiment of the device according to the invention is shown in the drawing and is described below: In a motor vehicle with all-wheel drive or front-wheel drive, actuating elements for activating a central control unit 2 are arranged in the driver's grip area, preferably on the steering wheel 1. In the embodiment shown, a sensor spiral 3 running around the steering wheel rim and responding to pressure is used as the actuating element. Instead of this sensor spiral 3, for example, two switches 4 can be used, which are arranged diametrically opposite one another on the steering wheel 1 and are switched in such a way that the central control unit 2 is only activated when these switches 4 are actuated simultaneously and in combination. Furthermore, a further actuating element 5 is provided in the driver's grip area for resetting the central control unit 2 to normal driving mode. The actuating elements 3, 4, 5 are connected to the central control unit 2, shown in the drawing as a dash-dot line. The control unit 2 has an evaluation circuit 6, to which the instantaneous driving speed "v _moment " of the motor vehicle is applied as an information signal. The evaluation circuit 6 is also assigned a step switch 7 for determining a step-by-step selectable driving speed "v _wa }j2", which can be operated by the driver.

The central control unit 2 is connected to the throttle valve shaft 8 and to the master brake cylinder 9.

The accelerator pedal 10 is connected in the usual way via a rod 11 to the drive unit 12. However, a device 13 for deactivating the accelerator pedal 10 that can be operated by the driver is arranged in the accelerator actuation rod 11. This device 13, e.g. an articulated joint or a pull magnet, is connected to the central control unit 2. The brake pedal 14 is also connected in the usual way via a rod 15 to the brake unit 16. A device 17 for deactivating the brake pedal 14 that can be operated by the driver is also arranged in this brake actuation rod 15. This device 17, preferably an articulated joint or a pull magnet, is also connected to the central control unit 2. The master brake cylinder 9 can, not shown in the drawing

shown in more detail, also have two pistons, one piston of which is assigned to actuation in normal driving mode and one piston in forced driving mode. In this case, the piston assigned to normal driving mode is activated to deactivate the brake pedal 14 that can be actuated by the driver.

When using the device according to the invention, the motor vehicle is initially in normal driving mode. The current driving speed " ^v moment" * ^is determined by the position of the accelerator pedal 10 and brake pedal 14 operated by the driver. When an impending difficult driving situation is recognized, for example before starting a long downhill ride or before driving over an icy section of road, the driver can apply pressure to the sensor spiral 3 by firmly grasping the steering wheel rim with both hands, so that the central control unit 2 is activated. The control unit 2 is also activated if the driver is frightened, and in such dangerous moments the driver's reaction time is advantageously shortened by the psychologically induced reaction of the hands "twitching". The central control unit 2 can also be activated by simultaneously operating the combined switches 4. At the moment of activation of the central control unit 2, the evaluation circuit 6 ^evaluates the driving speed " ^v moment" present as an information signal and determines the actuation strengths for the drive unit 12 and brake unit 16 required for conflict-free continued driving. Subsequently, the central control unit 2 deactivates the accelerator pedal 10 and brake pedal 14 that can be operated by the driver by controlling the devices 13, 17 in the actuating rods 11, 15. At this moment, the central control unit 2 begins a forced and simultaneous actuation of the drive unit 12 and brake unit 16, whereby the throttle valve shaft 8 and the master brake cylinder 9 are actuated with the dosage determined by the evaluation circuit 6. As a result of the already carried out

If the control elements 10;14 that can be operated by the driver are deactivated, the actuation strengths determined by the evaluation circuit cannot be affected by subjective influences from the driver. A further increase in braking force as a result of additional effective actuation of the brake pedal 14 by the driver would, for example, cause the wheels to lock and consequently the motor vehicle to swerve out of the direction of travel.

During the forced control, the drive unit 12 is generally operated at a higher speed than the idling speed. The actuation strengths of the throttle valve shaft 8 and the master brake cylinder 9 remain constant over the entire control period. If the driver, particularly at initially high driving speeds " ^v moment" ^to command ¹¹¹¹ of the forced control or when the road conditions are noticeably becoming more difficult, aims to further reduce the speed, the step switch 7 must be actuated to select a different speed range "v _¥3 £�idiagr;". The control period of the simultaneous actuation of the drive unit 12 and brake unit 16 is thus divided into several control sections, each with a different actuation strength.

If the forced control is finally to be cancelled and normal driving is to be resumed, e.g. after overcoming critical sections of the road or if the vehicle has to be brought to a standstill, the central control unit 2 is reset via the element 5 which can be operated by the driver. At the moment this element 5 is operated, the forced operation of the throttle valve shaft 8 and the master brake cylinder 9 and at the same time the inoperative switching of the accelerator and brake actuating rods 15 are cancelled. The driver can thus independently regulate the driving speed "v _moment " of the vehicle again by operating the accelerator pedal 10 and brake pedal 14.

By using the device, a stable driving behavior of front-wheel or all-wheel drive vehicles is achieved in critical driving situations in which the good traction of front-wheel or all-wheel drive is not sufficient, by largely canceling out the driving and braking forces.

is not relevant. Particularly advantageous in such situations, e.g. during steep downhill rides or on icy roads, is a largely
constant speed is achieved regardless of the driver's skills. The resulting increase in safety justifies the use of the invention despite the slightly increased wear of the vehicle components operated.

Reference symbol position

1 steering wheel

2 central control unit

3 Sensor spiral

4 combined switches

5 Actuator for reset

6 Evaluation circuit

7 step switch driving speed

8 Throttle shaft

9 Master brake cylinder

10 Accelerator pedal

11 Throttle control linkage

12 Drive unit

13 Accelerator pedal function disabled

14 Brake pedal

15 Brake actuation rod

16 Brake unit

17 Brake pedal function disabled ^v moment current driving speed ^v wahl selectable driving speed

Claims (7)

• * *·> «ta Protection claims 1. Device for ensuring the driving stability of front-wheel or all-wheel drive motor vehicles in critical driving situations in which a largely constant reduction in driving speed over a relatively long period of time is necessary, but no deceleration of the vehicle to a standstill is necessary, characterized by that actuating elements (3; 4) for activating a central control unit (2) are arranged in the driver's grip area, the control unit (2) having an evaluation circuit (6) which, depending on the driving speed (iv _moment ) detected at the time of activation, derives a control command for dosing the actuating strengths of the drive unit (12) and brake unit (16), and the control unit (2) is further connected to the throttle valve shaft (8) and the master brake cylinder (9) as well as to devices (13; 17) for deactivating the control elements (10; 14) for the drive unit (12) and the brake unit (16) that can be actuated by the driver, and wherein a further actuating element (5) for resetting the forcibly initiated control process to normal driving mode is arranged in the driver's grip area. 2. Device according to claim 1, characterized in that that the evaluation circuit (6) of the control unit (2) is assigned a device (7) that can be operated by the driver for determining a stepwise selectable driving speed (v·^^). 3. Device according to claim 1, characterized in that that a rotating sensor spiral in the steering wheel rim responds to pressure and activates the central control unit (2) (3) is arranged. 4. Device according to claim 1, characterized in that φφ &phgr; φφ φφ &phgr; &phgr; φφ ·· • ϕ ϕ ΦΦΦ· ϕ ϕ φφ φφ •ϕ &phgr; &phgr; ϕ ϕ &phgr; &phgr; ϕ ϕ 0 ϕ ··· ϕ &phgr; • ϕ·ΦΦΦ ·ΦΦ· &phgr; &phgr; &phgr; • • φφφφ •ΦΦ &phgr; - II - that two diametrically opposed switches (4) are arranged on the steering wheel (1) which, when operated simultaneously and in combination, activate the central control unit (2). 5. Device according to claim 1, characterized in that that the accelerator and brake actuation linkages (11; 15) are assigned articulated joints for deactivating the control elements (10; 14) that can be actuated by the driver. 6. Device according to claim 1, characterized in that that the accelerator and brake actuation linkages (11; 15) are assigned pull magnets for deactivating the control elements (10; 14) that can be actuated by the driver. 7. Device according to claim 1, characterized in that that the master brake cylinder (9) has two pistons, of which one piston is assigned to actuation in normal driving mode and one in forced-controlled driving mode in such a way that the piston acting alone in normal driving mode is switched to non-functional mode at the start of control.