Patent Application
20250001992
The present invention relates to a parking brake with improved command.
Modern parking brakes are often electromechanical, controlled by an integrated geared motor, according to predefined strategies and under the control of an electric motor control unit. The commands can be triggered either by the driver of the vehicle or automatically according to driving parameters, if the parking brake is also used as an emergency brake during journeys of the vehicle.
Whilst the vehicle is at a standstill, the driver may trigger a command to apply the parking brake by mistake or may change their mind immediately after, which is all the more plausible given that the controller of such electromechanical parking brakes is often a button that when pressed alternately commands the brake to be applied or released, without it being possible to tell directly what the applied command will be. But when a command has been transmitted to the control unit, it is carried out up to completion before a following command, which cancels the first one, is considered.
The prior art comprises document US2013/096796 A1. The braking method described therein involves replacing an ordinary strategy by a limited brake application strategy in certain circumstances, in particular when a temperature sensor of the brake is faulty. The method then comprises checks for a “crazy mode”, in which the brake control button is constantly pressed. Each time the button is pressed, a count value is decreased in an index. If this value reaches zero, the limited brake application strategy replaces the normal brake application strategy. The function of this part of the method is to ensure safety by preventing excessive brake applications, but not to quickly correct incorrect button commands. Indeed, a brake application strategy in progress during “crazy mode” is not interrupted, but replaced by another strategy, and only when a value in an index has dropped to zero, possibly after a large number of successive commands. Finally, it should be noted that the change of strategy only applies to applying the brake, but not to releasing it, which is still carried out as normal.
The aim of the invention is to avoid the wasted time caused by incorrect or unintentional commands of the parking brake, by enabling the effect of these incorrect commands to be cancelled more quickly when they are corrected immediately.
According to the invention, the brake application strategy is then no longer completed, but is interrupted as soon as the command has been cancelled by pressing the controller again.
Interruptions to electromechanical brake command strategies are unusual, especially if they interrupt an already commanded brake application. The particular case of a parking brake is different, since the vehicle is at a standstill or at low speed when the commands originating from the vehicle are taken into account, and the dangers associated with driving are therefore absent.
According to a general definition, the invention relates to a motor control unit of an electromechanical motor vehicle parking brake, supplying brake application and release commands to an electric motor of an actuator of the brake, said commands being governed by predefined strategies in response to inputs given to a controller by an occupant of the vehicle, characterized in that it is designed, if a second action follows a first action on the controller while a first command, triggered by the first action, is still in progress, to start a second command according to the second action immediately, interrupting the first command.
In particular, the invention is applied if the first action is a command to release the brake.
The controller is advantageously a button (or a similar device with a single actuation state), the commands of which are alternately, by design, brake application and brake release commands.
The invention can be applied in particular to systems where the strategies impose application commands which, uninterrupted, produce a given final brake application force, and release commands which, uninterrupted, produce brake actuator strokes of a given length.
So if the first command is an application command, it is advantageous that the second command has an imposed duration similar to the first command.
Another aspect of the invention is a corresponding motor vehicle braking device; this device comprising the parking brake, the brake actuator, the electric motor controlling the actuator, the motor control unit supplying brake application and release commands to the electric motor, said commands being governed by predefined strategies, and the controller according to the above.
Another aspect is a motor vehicle comprising this braking device, the brake possibly in particular being fitted to a non-driven wheel of the vehicle.
The different aspects, features and advantages of the invention will become apparent from the detailed description of a specific embodiment thereof, provided purely for illustrative purposes, which is now given by means of the following figures:
In various vehicle models, the brakes 7 can also be used as service brakes at the same time as the main brakes 6 when the driver carries out braking, or as emergency brakes to complement the action of the main brakes 6; the motor control unit 9 then uses the indications of sensors 10 mounted on the vehicle which measure various driving parameters, without the driver intervening. However, these additional possibilities for controlling the brakes 7 do not influence the invention, which is applied when the vehicle is stationary, or almost stationary.
When the brake 7 is moved by the actuator 8, the latter is controlled by the motor control unit 9 according to predefined strategies taught to it. If the driver wanting to park or leave switches between the released state and the applied state, standard strategies involve establishing a given brake application force 7 for application, and a given stroke of the actuator 8 or piston 14 for release. In both cases, these strategies are always carried out until the application force has been reached, or the release stroke is completed. This is still true in the document quoted above, even if the application force can be reduced compared to the normal force.
Reference is now made to
The driver gives an initial impulse 25 at a time t1, which triggers a first command 26, in this case applying the brake 7. The motor control unit 9 closes an electrical circuit on which the electric motor and a battery, or another means of supplying electricity are placed, which sets the electric motor 18 in motion. The current in the electrical circuit adjusts as a function of the application force. Three periods can be distinguished in the change in the current I supplied: a first peak period 27, which corresponds to backlash compensation in the actuator 8, during which the current I is high, a second much longer plateau period 28 during which the current I is conversely much lower and approximately constant and which corresponds to an idle stroke of the actuator 8, and a third period of growth 29 during which the current I increases regularly and which corresponds to effective and progressive application of the brake 7. The current I is therefore approximately proportional to the application force. The command stops at a time t3, when a given stopping current threshold I0, corresponding to a desired application force, has been reached. The actuator 8 moves at constant speed during this command 26, as shown by the corresponding part, or first part 30, of the lower diagram 24, the slope of which is uniform.
If a second impulse 31 is given by the driver at the time t2 very shortly after t1, a second command 32, relative to releasing the brake 7, is applied to the electric motor 18. It comprises a first peak period 33, with a gradual decline, which corresponds both to the backlash compensation in the actuator 8 and progressive release of the brake 7, then a second plateau period 34 where the current I is low and uniform, and which corresponds to an idle stroke of the actuator 8, in order to return it approximately to its initial state prior to the first impulse 25, which is shown by the second part 41 of the lower diagram 24, with a uniform downward slope, and more or less symmetrical to the first part 30. The second command 32 starts at a time t4 shortly after t3, and it finishes at a later time t5. As the standard strategy imposes a final force or an invariable stroke length, the duration (t5−t4) of the second command 32 is similar to that (t3−t1) of the first command 26, and the second command 32 only starts when the first command 26 is completed, which means that the starting time t4 is substantially later than that of the second impulse 31. This response time is unpleasantly long for the driver if they have made an unintentional or incorrect command to park the vehicle that they would like to immediately correct.
That is why it is envisaged, in accordance with the invention, to modify the strategy for controlling the brake 7 according to
The first command 37 applied according to the invention at the time t1 of the first impulse 25 starts as with the previous first command 26, but it is now interrupted at the time t2 when the second impulse 26 intended to cancel the previous one is issued. The second command 38 can then start at a time to immediately following, corresponding only to a response time of the system. It is envisaged that it too is curtailed, and stops at a time t7 after a duration (t7−t6) similar to the duration that was itself curtailed (t2−t1) of the first command 37. This ensures that the actuator 8 and brake 7 return to a virtually unchanging release state. The lower diagram 36 again has, as a consequence of this, two symmetrical parts 39 and 40, which show the return of the system to its initial state from the time t7, i.e. a lot quicker than when applying the standard strategy.
If the first command that the conductor interrupts by a second opposite command is a release command, a similar time saving is achieved, as the first command can be interrupted without delay, and the second command, which starts immediately after, is curtailed too as the stopping current threshold I0 is reached more quickly.
One advantage of the invention is therefore an acceleration in the commands of the parking brake 7; other advantages are saving electrical energy, and decreased wear on the brake 7 thanks to the reduced amplitude of movement.
The invention is only applied when circumstances allow, i.e. when the vehicle is stationary or almost stationary, and parking is feasible. The function of the brake 7 is not modified in other circumstances.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2108685 | Aug 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2022/051303 | 6/29/2022 | WO |
