System for controlling a braking device capable of implementing a parking brake function

Abstract

The invention relates to a control system (14) for controlling a braking device (16) which is capable of implementing a parking brake function, the control system (14) being configured to send to the braking device (16) a parking brake command which consists in applying a force of a first predefined amplitude making it possible to keep the vehicle (10) stationary regardless of the current conditions of the vehicle (10), characterised in that the control system (14) is configured to send to the braking device (16) a parking brake command which consists in applying a clamping force of a second amplitude that is less than the first amplitude and large enough to keep the vehicle (10) stationary.

Description

[0001] Description

[0002] Title: CONTROL SYSTEM FOR A BRAKING DEVICE CAPABLE OF IMPLEMENTING AN IMMOBILIZATION BRAKING FUNCTION

[0003] TECHNICAL FIELD

[0004] The invention relates to a system for controlling at least one motor vehicle braking device allowing the implementation of an additional action to keep the vehicle stationary.

[0005] STATE OF THE PRIOR ART

[0006] A motor vehicle has, for each of its wheels, a braking device of the disc brake or drum brake type, which includes a piston intended to set braking shoes in motion and apply them against a disc or a drum.

[0007] The piston is driven in movement by an electromechanical system, itself controlled by a brake control system (Parking Brake Controller in English terminology).

[0008] When the motor vehicle is stationary, according to a known operating mode, the control system implements a parking brake function, which consists of controlling the electromechanical system in order to apply, by the piston, a braking force sufficiently strong to keep the vehicle stationary, whatever the conditions in which the vehicle is located.

[0009] This braking effort is generally set to keep the vehicle stationary when the vehicle is stopped on sloping ground with a steep gradient.

[0010] This braking mode is particularly suitable for parking the vehicle without a driver present, in which case no one is able to intervene in the event of a braking fault. On the other hand, in the case of a vehicle stopping, such as for example when stopping at a traffic light, implementing the parking brake function involves exerting an unnecessarily high braking force.

[0011] Furthermore, due to the significant amplitude of the braking force, the implementation of the parking brake function implies that significant mechanical stresses are also exerted on the components of the braking device, as well as a significant application time.

[0012] The aim of the invention is to provide a control system which is capable of implementing an additional parking brake function.

[0013] STATEMENT OF THE INVENTION

[0014] The invention relates to a system for controlling at least one braking device for a motor vehicle which is capable of implementing a parking brake function, the braking device comprising in particular a piston capable of producing a force for clamping a disc or for clamping a disc brake caliper and electrical means for driving the piston in order to produce said clamping force, the control system being configured to send to said at least one braking device a parking brake command which consists of applying by the piston a clamping force of a first predefined amplitude making it possible to keep the vehicle stationary whatever the conditions in which the vehicle is located,characterized in that the control system is configured to send to said at least one braking device an immobilization braking command which consists of applying by the piston a clamping force of a second amplitude which is less than the first amplitude and which is sufficiently large to keep the vehicle stationary.,

[0015] Preferably, the control system is configured to send to said at least one braking device the parking braking command when at least one of the following operating conditions is met:

[0016] - the presence of a vehicle driver is detected; - the slope of the terrain on which the vehicle is located is less than a predefined value;

[0017] - the vehicle is stationary.

[0018] Preferably, the control system is configured to send to said at least one braking device the immobilization braking command when the operating condition according to which a pressure force on the brake pedal of the vehicle is greater than a predetermined threshold value is met.

[0019] Preferably, the presence of a driver is detected by:

[0020] - detection of pressure on a brake, accelerator and / or clutch pedal;

[0021] - detection of seat belt fastening;

[0022] - detection of a load on the driver's seat while the motor vehicle engine is running.

[0023] Preferably, the control system is configured to send the parking brake command to said at least one braking device when at least one of said operating conditions is not met.

[0024] Preferably, the control system is configured to send to said at least one braking device either the parking brake command or the immobilization braking command after a trigger condition is met.

[0025] Preferably, a trigger condition consists of a vehicle parking brake button being pressed or a vehicle driver pressing a brake pedal with an amplitude greater than a predefined amplitude threshold.

[0026] The invention also relates to a motor vehicle comprising several wheels, several braking devices, each braking device of which is associated with a wheel and a control system according to the invention, which is capable of controlling at least one braking device for the implementation of a parking brake function and the implementation of an immobilization braking function.

[0027] Preferably, the vehicle has four wheels, and the braking devices associated with two or four wheels of the vehicle are capable of being controlled by the control system for implementing a parking brake function and implementing a parking brake function.

[0028] The invention also relates to a method of operating a control system according to the invention for implementing the parking brake function or the immobilization braking function, which comprises:

[0029] - an initial stage in which neither the parking brake function nor the immobilization braking function is implemented,

[0030] - a step of verifying a condition for triggering the implementation or not of the parking brake function or the immobilization braking function;

[0031] - at least one step of verifying at least one operating condition when the trigger condition has been verified;

[0032] - a step of implementing the parking brake function or the immobilization braking function depending on whether said at least one operating condition has been met or not.

[0033] Preferably, when the trigger condition has been met, said at least one step of verifying at least one operating condition is implemented.

[0034] Preferably, if at least one of said at least one operating condition is not met, then the parking brake function is implemented.

[0035] Preferably, if all operating conditions are met then the parking braking function is implemented.

[0036] BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic representation of a motor vehicle comprising a system for controlling the braking devices associated with each wheel of the vehicle. Figure 2 is a diagram showing the relationship between an electric current supplying a braking device and the braking force applied by this braking device when implementing a parking brake function.

[0038] Figure 3 is a diagram similar to that of Figure 2, representing the relationship between an electric current supplied to a braking device and the braking force applied by that braking device when implementing a parking braking function.

[0039] Figure 4 is a flowchart illustrating a method of operation of the control system 14.

[0040] DETAILED DESCRIPTION OF THE INVENTION

[0041] Figure 1 shows a vehicle 10 which is here a motor vehicle. It will be understood that the invention is not limited to a control system for a motor vehicle, and that the invention may also relate to another vehicle such as a motorcycle for example.

[0042] Here, the vehicle 10 comprises four wheels 12, a plurality of braking devices 16, each braking device 16 of which is associated with one of the wheels 12 and a control system 14 for the braking devices 16.

[0043] Each braking device 16 consists of a brake of the disc brake or drum brake type, and comprises a piston driven into movement by an electromechanical actuator under the control of the control system 14 to produce a braking force.

[0044] At least some of the braking devices 16, for example the braking devices 16 associated with the two rear wheels 12 or the four braking devices 16 are capable of implementing a parking brake function.

[0045] In the following description, reference will be made to a braking force exerted by the piston of a single braking device. This embodiment is applicable in the case where only one of the braking devices 16 of the vehicle 10 is capable of implementing the parking brake function. This example may be extrapolated to a braking force exerted by several braking devices 16. In this case, the value of the braking force that will be described will have to be divided by the number of braking devices 16 implementing the function considered, to obtain the value of the braking force that each braking device 16 will have to exert.

[0046] This parking brake function consists of producing a braking force by the piston of the braking device 16, the amplitude of the braking force of which is sufficiently large to keep the vehicle stationary whatever the conditions in which the vehicle is located, that is to say in particular when the engine of the vehicle is not running, when a driver is not present at the vehicle's cockpit, when a parking brake command has been issued, or when a significant slope of the terrain on which the vehicle is located has been measured.

[0047] Thus, depending on the operating conditions, the control system 14 is configured to send to the braking device 16 a command to implement the parking brake function to exert the braking force defined previously.

[0048] The control system 14 is also configured to send to the braking device 16 a command to implement an additional immobilization braking function which consists of applying by the piston a clamping force of a second amplitude which is less than the first amplitude and which is sufficiently large to keep the vehicle stationary for certain operating conditions of the vehicle.

[0049] Triggering conditions

[0050] Trigger conditions are defined as the conditions that must be met for the control system 14 to be activated to implement either the parking brake or the immobilization braking function.

[0051] When one of these triggering conditions is met, the control system 14 performs a check of the operating conditions and, depending on whether the operating conditions are met or not, the control system 14 implements either the parking brake function or the immobilization braking function.

[0052] By way of non-limiting example, a triggering condition consists of pressing a parking brake button on the vehicle or the driver pressing the brake pedal with an amplitude greater than a predefined amplitude threshold.

[0053] Operating conditions

[0054] The parking brake function is preferably implemented when the vehicle is under certain conditions that do not require the application of the full braking force associated with the parking brake function.

[0055] Thus, the control system is configured to detect certain operating conditions of the vehicle and when certain operating conditions are met, it sends the command to implement the immobilization braking function rather than the command to implement the parking brake function.

[0056] Since the braking force exerted by the piston is less when the parking braking function is implemented, this braking force may not be sufficient to keep the vehicle 10 stationary at all times.

[0057] For this, the operating conditions of the vehicle 10 for which the immobilization braking function is implemented are conditions making it possible to guarantee a certain safety of the vehicle 10.

[0058] A first operating condition is the presence of a driver of vehicle 10.

[0059] Indeed, when a driver is present, he can intervene immediately when the application of the immobilization braking function becomes faulty or insufficient to effectively keep the vehicle 10 stationary.

[0060] Non-limiting examples of means for verifying the presence of the driver include checking that the seat belt associated with the driver's seat is fastened, whether the engine of the vehicle 10 is running, whether a brake or accelerator pedal of the vehicle 10 is pressed, or whether a load on the driver's seat is detected.

[0061] Another operating condition is that the vehicle 10 is stationary. This condition is verified by a speedometer of the vehicle 10.

[0062] Without limitation, the vehicle 10 will be considered to be stationary if its speed measured by the speedometer is less than or equal to a predefined value calibrated by the vehicle manufacturer. For example, the predefined speed value is 3km / h.

[0063] Another operating condition is that the vehicle's engine 10 is running.

[0064] This operating condition makes it possible to differentiate whether the vehicle 10 is parked, and therefore may be immobilized for a long time, or whether the vehicle 10 is stopped briefly and may therefore be required to start again shortly.

[0065] Another operating condition is the driver pressing the vehicle's brake pedal. This condition is preferably met when the force value is greater than a predefined threshold value.

[0066] Another operating condition is the slope of the terrain on which the vehicle is located. Preferably, the parking brake function can be implemented when the slope of the terrain is less than a predefined value calibrated by the vehicle manufacturer. For example, the predefined slope value is 10%.

[0067] In the context of an automatic driving function, for example of the automatic cruise control type (ACC in English terminology), braking can be generated from data provided by a sensor, for example an optical sensor, proximity sensor, radar or other.

[0068] Numerical examples

[0069] By way of non-limiting example, for a braking device 16 consisting of a disc brake, the implementation of the parking brake function consists of exerting by the piston a disc clamping force of 14500N for a vehicle weighing approximately 2500Kg. In addition, the time required for the actuator to reach this clamping force is approximately 0.99 seconds and the time required for the actuator to release this clamping force is approximately 1.04 seconds, which consumes a total of 57.01 Joules of energy.

[0070] By way of non-limiting example, for a braking device 16 consisting of a disc brake, the implementation of the immobilization braking function consists of exerting by the piston a disc clamping force of 9500N for a vehicle weighing approximately 2500Kg. In addition, the time required for the actuator to reach this clamping force is approximately 0.82 seconds and the time required for the actuator to release this clamping force is approximately 0.87 seconds, which consumes a total of 33.05 Joules of energy.

[0071] Comparison of diagrams

[0072] Figures 2 and 3 represent diagrams showing the curves representing the variation of the clamping force exerted by the piston as a function of the electric current emitted when the control system 14 implements one of the parking brake function (figure 2) or the immobilization braking function (figure 3).

[0073] In each of figures 2 and 3, a first curve 20 represents the variation of the electric current, the second curve 22 represents the variation of the braking force exerted by the piston of the braking device 16.

[0074] In the first diagram, the first curve 20 includes a peak 24 corresponding to the transmission by the control system 14 of the order to implement the parking brake function. Immediately after this peak 24, the current drops rapidly to reach a low value.

[0075] The first curve 20 comprises a rectilinear section 26 corresponding to a phase during which the value of the electric current remains substantially constant and equal to the low value.

[0076] The first curve 20 comprises an increasing section 28 corresponding to the supply of the braking device 16 to progressively increase the braking force exerted by the piston. The end of the increasing section corresponds to the moment at which the required braking force is reached. This increasing section is followed by a final section 30 for which the value of the electric current becomes zero, that is to say the end of the supply of the braking device 16 to maintain the braking force by the piston.

[0077] The second curve 22 corresponds to the braking force exerted by the braking device 16. It comprises a first flat section 32 for which the braking force is zero. This first flat section 32 is associated with the peak 24 and the straight section 26 of the first curve 20, and corresponds to the period of time during which the braking device 16 performs a play-compensating function between the different elements of the braking device 16. The value of the current supplying the braking device 16 is thus non-zero but is not sufficiently high for the braking device to be able to produce a braking force.

[0078] The second curve 22 comprises a second increasing section 34 which corresponds to the progressive increase in the braking force. This second increasing section 34 corresponds to the increasing section 28 of the first curve 20 and therefore corresponds to the period of time during which the braking device 16 is sufficiently supplied to produce a braking force by the piston.

[0079] The second curve 22 includes a final section 36 corresponding to the braking conservation effort when the braking device is no longer powered.

[0080] Figure 2 shows a first upper line 38 which corresponds to the value of the clamping force exerted by the braking device 16 at the end of the implementation of the parking brake function, the value of which is defined previously.

[0081] Figure 3 shows a second upper line 41 which corresponds to the value of the clamping force exerted by the braking device 16 at the end of the implementation of the immobilization braking function, the value of which is defined previously.

[0082] Finally, each of Figures 2 and 3 shows a second line 40 corresponding to the minimum value of the clamping force that must be exerted by the braking device 16 to hold the vehicle after implementing the parking brake function, the value of which is defined previously. As can be seen in Figure 2, the amplitude of the clamping force is greater when implementing the parking brake function than when implementing the parking brake function.

[0083] Thus, as can be seen in Figure 2, the difference 42 between the amplitude of the clamping force when implementing the parking brake function (line 38) and the value of the force making it possible to hold the vehicle shows the excess part of the force which is exerted by the braking device 16 when implementing the parking brake function while the operating conditions of the vehicle 10 correspond to those of the implementation of the immobilization braking function.

[0084] Similarly, Figure 3 shows the difference between the amplitude of the clamping force when implementing the parking brake function (line 41) and the value of the force used to hold the vehicle.

[0085] By comparing the two diagrams, it can be seen that the excess part of the force which is exerted by the braking device 16 when implementing the parking braking function is significantly less than the excess part of the force which is exerted by the braking device 16 when implementing the parking brake function.

[0086] Also, by comparing the two diagrams, it can be seen that the end of the increasing section 28 of the first curve 20 occurs earlier in the case of the implementation of the immobilization braking function compared to the implementation of the parking brake function.

[0087] Operating method

[0088] Figure 4 is a flowchart illustrating a method of operation of the control system 14 for deciding whether to implement the parking brake function or the immobilizing brake function.

[0089] In a first initial step 44, the braking device 16 is released, that is to say that no braking force is exerted by the braking device

[0090] 16. In a second step 46, the trigger condition is tested.

[0091] If the trigger condition is not met, as can be seen by branch 48, the control system 14 returns to the first step

[0092] 44.

[0093] If the trigger condition is met, as can be seen by junction 50, the control system 14 considers that the vehicle must be kept stationary, whether permanently or not.

[0094] In a third step 52, the control system 14 checks whether a first operating condition is met.

[0095] If the first operating condition is not met, as can be seen by branch 54, a step 56 of implementing the parking brake function follows this third step 52.

[0096] If the first operating condition is met, as can be seen by branch 58, another step 62 of verifying a second operating condition is implemented.

[0097] If the second operating condition is not met, as can be seen by branch 64, and similarly to the third step 52 of verifying compliance with the first operating condition, step 56 of implementing the parking brake function is implemented.

[0098] If the second operating condition is met, as can be seen by branch 66, a step 68 of implementing the immobilization braking function is implemented.

[0099] It will be understood that the flowchart may include a different number of operating condition verification steps arranged in series one after the other. The number of these operating condition verification steps corresponds to the number of operating conditions that must be met.

[0100] It is understood that in this method, if at least one operating condition is not met, step 56 of implementing the parking brake function is implemented. On the contrary, if all of the operating conditions concerned are met then the immobilization braking function is implemented.

[0101] Benefits

[0102] Since the magnitude of the force exerted by the piston when implementing the parking brake function is less than when implementing the parking brake function, the stresses experienced by the components of the braking device are also reduced, which can improve the service life of the braking device.

[0103] This parking brake function is most beneficial when the vehicle is in operation and is temporarily stopped, for example when stopping at a traffic light.

[0104] It is also understood that the implementation of this immobilization braking function allows a lower quantity of energy to be consumed while being quicker to implement.

[0105] Because the braking force exerted by the braking device 16 is less, it is also faster to disengage, i.e. the parking brake function can be deactivated more quickly than the parking brake function, which can add responsiveness to the vehicle when stopped in traffic.

[0106] NOMENCLATURE:

[0107] 10: vehicle

[0108] 12: wheels

[0109] 14: control system

[0110] 16: braking device

[0111] 20: first curve

[0112] 22: second curve

[0113] 24: peak

[0114] 26: straight section

[0115] 28: growing section 30: final section

[0116] 32: flat section

[0117] 34: second growing section

[0118] 36: last section 38: first upper line

[0119] 40: second line

[0120] 41: second upper line

[0121] 42: difference in values

[0122] 44, 46, 52, 56, 62, 68: steps 48, 50, 54, 58, 64, 66: branches

Claims

CLAIMS 1. Control system (14) of at least one braking device (16) for a motor vehicle (10) which is capable of implementing a parking brake function, the braking device (16) comprising in particular a piston capable of producing a force for clamping a disc or for clamping a disc brake caliper and electrical means for driving the piston in order to produce said clamping force, the control system (14) being configured to send to said at least one braking device (16) a parking brake command which consists of applying by the piston a clamping force of a first predefined amplitude making it possible to keep the vehicle (10) stationary whatever the conditions in which the vehicle (10) is located,characterized in that the control system (14) is configured to send to said at least one braking device (16) an immobilization braking command which consists of applying by the piston a clamping force of a second amplitude which is less than the first amplitude and which is sufficiently large to keep the vehicle (10) stationary., 2. Control system (14) according to claim 1, characterized in that it is configured to send to said at least one braking device (16) the immobilization braking command when all of the following operating conditions are met: - the presence of a driver of the vehicle (10) is detected; - the slope of the terrain on which the vehicle (10) is located is less than a predefined value; - the vehicle (10) is stationary.

3. Control system (14) according to claim 2, characterized in that it is configured to send to said at least one braking device (16) the command of immobilization braking when the operating condition according to which a pressure force on the brake pedal of the vehicle (10) is greater than a predetermined threshold value is also respected.

4. Control system (14) according to claim 2, characterized in that the presence of a driver is detected by: - detection of pressure on a brake, accelerator and / or clutch pedal; - detection of seat belt fastening; - the detection of a load on the driver's seat while the engine of the motor vehicle (10) is running.

5. Control system (14) according to one of claims 2 to 4, characterized in that it is configured to send to said at least one braking device (16) the parking brake command when at least one of said operating conditions is not met.

6. Control system (14) according to one of the preceding claims, characterized in that it is configured to send to said at least one braking device (16) one or other of the parking brake command or the immobilization braking command after a triggering condition is met.

7. Control system (14) according to the preceding claim, characterized in that a triggering condition consists of pressing a parking brake button of the vehicle (10) or pressing by a driver of the vehicle (10) on a brake pedal with an amplitude greater than a predefined amplitude threshold.

8. Motor vehicle (10) comprising several wheels (12), several braking devices of which each braking device (16) is associated with a wheel (12) and a control system (14) according to any one of the preceding claims, which is capable of controlling at least one braking device (16) for implementing a parking brake function and implementing a parking brake function.

9. Vehicle (10) according to the preceding claim, which comprises four wheels (12), characterized in that the braking devices associated with two or four wheels (12) of the vehicle (10) are capable of being controlled by the control system (14) for the implementation of a parking brake function and the implementation of an immobilization braking function.

10. Method of operating a control system (14) according to any one of claims 1 to 7 for implementing the parking brake function or the immobilization braking function, which comprises: - an initial stage in which neither the parking brake function nor the immobilization braking function is implemented, - a step of verifying a condition for triggering the implementation or not of the parking brake function or the immobilization braking function; - at least one step of verifying at least one operating condition when the trigger condition has been met; - a step of implementing the parking brake function or the immobilization braking function depending on whether said at least one operating condition has been met or not.

11. Method according to claim 10, characterized in that if at least one of said at least one operating condition is not met, then the parking brake function is implemented.

12. Method according to one of claims 10 or 11, characterized in that if all of the operating conditions are met then the parking braking function is implemented.

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