Disc brake with dynamic adjustment of distance between brake disc and pads and related method

Abstract

At least one disc brake (12) having a brake disc (16) with a disc brake caliper (20) and at least one pair of pads (24) on opposite sides along an actuation axis (AA); at least one electric actuator (32) operatively connected to a piston (36) acting as a pusher on at least one of the pads (24); and a piston (36) operatively connected to the electric actuator (32) for bringing the pads (24) into contact with the brake disc (16) upon a braking demand and for moving the piston (36) and the pads (24) to a rest position or a rest position. a processing and control unit (40) programmed to move the pads (24) along an actuation axis (AA) to an forward position or back to a reverse position; a clearance (44) is identified between the pads (24) and the brake disc (16); and the processing and control unit (40) is programmed to implement an algorithm to actuate the electric actuator (32) by varying the clearance (44) in accordance with at least one dynamic parameter of the vehicle (8) defining a prediction of a future demand for braking action in the absence of a braking demand.

Description

[Technical field]

[0001] The present invention relates to a brake-by-wire (BBW) disc brake system with dynamic adjustment of the distance between the brake disc and the pads. Furthermore, the present invention relates to a method for adjusting the distance between the brake disc and the pads in a BBW type brake system. [Background technology]

[0002] In hydraulic disc brake calipers, the distance between the brake disc and the pads is defined at the design stage and cannot be actively changed. The caliper piston is only passively extended or retracted by the elastic deformation of the seal when the brake control, and thus the hydraulic pressure in the brake system, is released. The piston seal and its seat can be designed in such a way that the seal deforms more, so that the piston can achieve a return stroke (rollback) with more force upon release. However, this results in a worsening of the braking requirements (i.e. the pedal working travel is reduced) with less movement / displacement of the brake fluid and a good braking feeling at the pedal. In known solutions, the position of the piston cannot in any case be arbitrarily changed during the use of the vehicle.

[0003] In BBW type braking systems that do not use hydraulic fluid and therefore have electromechanical calipers, the distance between the brake disc and the pads is controlled by software and can be changed at any time, but its value cannot be chosen arbitrarily, since it results from a compromise between the different needs of:

[0004] A large or high clearance reduces the residual braking torque on the brake disc and the associated pad wear, but it also significantly increases brake response time by creating a measurable delay between the user's request for braking and the onset of actual braking action.

[0005] But at the same time, it increases the residual brake torque when there is no braking demand, increases pad wear, increases the vehicle's fuel consumption and therefore reduces the vehicle's range (especially for electric vehicles), and also increases the vehicle's overall pollution in terms of energy consumed and dust and particle emissions due to pad wear.

[0006] The distance between the brake disc and the pads is therefore a compromise between achieving an effective braking action on the one hand and the lowest possible residual torque on the other hand.

[0007] Prior art solutions do not allow the distance between the brake disc and the pads to be changed dynamically, i.e. in real time, and therefore do not allow optimization of the braking action and reduction of the residual torque under all dynamic conditions of vehicle use. Summary of the Invention

[0008] Therefore, a need is felt in the art to provide a braking system that can overcome the technical drawbacks discussed with reference to the prior art.

[0009] This need is met by a brake system according to claim 1 and a method for adjusting the distance between a brake disc and a pad according to claim 19.

[0010] In particular, this need is met by a braking system for a vehicle, the braking system comprising: At least one disc brake including a brake disc having a disc brake caliper arranged to straddle the brake disc, and at least one pair of pads opposed to each other and acting on the brake disc from opposite sides along an actuation axis parallel to the rotation axis of the brake disc; at least one electrically actuated actuator operatively connected to a piston acting as a pusher on at least one of said pads along said actuation direction; a processing and control unit operatively connected to the electric actuator and programmed to move the piston and the opposing pads axially to an advanced position to bring the pads into contact with the brake disc when braking is required, and to move the piston to a rest or retracted position to determine a clearance between the pads and the brake disc; The processing and control unit is programmed to implement an algorithm that operates the electric actuator by varying the clearance in accordance with at least one dynamic parameter of the vehicle defining a prediction of a future braking request, in the absence of a braking request, to increase the clearance when a braking request is imminent and to decrease the clearance when a braking request is not imminent.

[0011] According to one embodiment, the disc brake caliper at said pad is provided with thrust means, such as a spring or spider, which exerts a resilient action to move the pad axially away from the brake disc so as to retract the pad towards the associated piston when no braking action is required.

[0012] According to an embodiment, the pads are constrained to their associated pistons for unified translation therewith along the actuation axis.

[0013] According to an embodiment, the algorithm determines whether to establish the clearance at a maximum or high value corresponding to a defined low residual torque and high response time, or at a low value corresponding to a high residual torque and low response time.

[0014] According to one embodiment, the dynamic parameters of the vehicles comprise a collision time estimated as the time it takes for a collision to occur between the vehicle equipped with the braking system and another vehicle preceding it, without changing the respective speeds and trajectories of the vehicles. If the estimated collision time is reduced, the gap is also reduced and vice versa.

[0015] According to one embodiment, said time to impact is estimated as a function of the coefficient of friction of the road surface on which the vehicle equipped with said braking system is travelling: if the coefficient of friction decreases, the clearance also decreases and vice versa.

[0016] According to one embodiment, the time to collision is estimated as a function of the difference in acceleration between the vehicle equipped with the braking system and another vehicle preceding it: if the difference in acceleration results in the need for braking or the possibility of a collision, the gap is reduced and vice versa.

[0017] According to an embodiment, said dynamic parameter of the vehicles consists of a hazard index, i.e. a dimensionless index defining the collision risk between two vehicles defined as the relationship between the critical braking distance and the critical hazard distance, such that if the critical braking distance is smaller than the critical hazard distance, the gap is reduced and vice versa.

[0018] According to one embodiment, said dynamic parameters of a vehicle consist of a predefined safe distance between the vehicle equipped with said braking system and another vehicle preceding it. Obviously, if said safe distance decreases, the clearance also decreases and vice versa.

[0019] According to one embodiment, said dynamic parameters of a vehicle equipped with said braking system consist of an emergency signal from a leading vehicle to which a following vehicle is connected.

[0020] According to an embodiment, the dynamic parameters consist of information about real-time traffic conditions along the route of the vehicle.

[0021] According to one embodiment, the dynamic parameters of a vehicle equipped with the braking system consist of information about real-time conditions of the vehicle's path, such as speed limits and / or road slopes and / or curves.

[0022] According to an embodiment, the dynamic parameters of the vehicle consist of the comfort requirements by the vehicle's passengers, increasing the clearance when more comfort is required and vice versa.

[0023] According to an embodiment, the gap variation caused by the electric actuator is of discrete type.

[0024] According to one embodiment, the algorithm identifies a minimum crash time value and a maximum crash time value. If the crash time value remains within this range, the gap is maintained in its current state, whereas if the crash time exceeds the threshold defined by the minimum and maximum crash time values, the gap is modified. Obviously, in particular, a low crash time means that it is highly likely that braking will be required in the short term, whereas a high crash time means that it is less likely that braking will be required in the short term. If the crash time exceeds the maximum value, the gap is set to its upper limit value, which corresponds to a lower residual torque and a higher response time, and conversely, if the crash time becomes smaller than the minimum value, the gap is set to its lower limit value, which corresponds to a higher residual torque and a lower response time.

[0025] According to an embodiment, the minimum impact time is 4.5 seconds and the maximum impact time is 5 seconds.

[0026] According to an embodiment, the variation of the gap by the electric actuator is of continuous type, so as to vary the gap between a minimum and a maximum value depending on the dynamic parameters of the vehicle.

[0027] The invention also relates to a vehicle including a braking system as previously described.

[0028] The present invention also relates to a method for controlling a braking system (4) for a vehicle (8), comprising the step of setting the braking system (4). The brake system (4) at least one disc brake comprising a brake disc having a disc brake caliper arranged to straddle the brake disc; At least one pair of pads acting on the brake disc on opposite sides along an operating axis direction parallel to a rotation axis of the brake disc; at least one electric actuator operatively connected to a piston acting as a pusher on at least one of the pads along the actuation axis; a processing and control unit operatively connected to the electric actuator and programmed to axially move a piston and each pad to an advanced position and to move the piston and each pad to a rest or retracted position so as to press the pads into contact with the brake disc upon a braking request, wherein a clearance between the pads and the brake disc is determined; The processing and control unit is programmed to implement an algorithm that operates the electric actuator by varying the clearance as a function of at least one dynamic parameter of the vehicle defining a prediction of a future request for a braking operation, in the absence of a braking request, to increase the clearance when a braking operation is imminent and to decrease the clearance when a braking operation is not imminent. [Brief description of the drawings]

[0029] Further features and advantages of the present invention will become more apparent from the following description of preferred, non-limiting embodiments thereof.

[0030] [Figure 1] FIG. 1 is a schematic diagram of a vehicle including a brake system according to an embodiment of the present invention.

[0031] Elements or parts of elements that are common to the embodiments described below are designated by the same reference numerals. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] With reference to the aforementioned figures, reference numeral 4 globally indicates a braking system for a vehicle 8 .

[0033] The braking system 4 comprises at least one disc brake 12 comprising a brake disc 16 having a disc brake caliper 20 arranged to straddle the brake disc 16 and at least one pair of pads 24, 28 opposing each other and acting on said brake disc 16 on opposite sides along an actuation axis AA parallel to the rotation axis XX of the brake disc 16. It should be noted that the present invention applies to both fixed and floating disc brake calipers 20 known in the art.

[0034] The disc brake 12 further comprises at least one electric actuator 32 operatively connected to a piston 36 acting as a pusher for at least one of the pads 24 along the actuation axis AA. In the case of a fixed disc brake caliper 20, there is at least one piston 36 acting on at least one pad 24 on both sides of the brake disc 16. In the case of a floating type disc brake caliper, there is at least one piston 36 acting on at least one pad 24 on one side of said brake disc 16.

[0035] The brake system 4 further comprises a processing and control unit 40 operatively connected to the electric actuator 32 and programmed to move the piston 36 and each pad 28 along the actuation axis AA to an advanced position so as to bring the pad 28 into contact with the brake disc 16 upon a braking request, and to return the piston 36 and each pad 28 to a rest or retracted position so that a gap 44 between the pad 28 and the brake disc 16 is determined.

[0036] The processing and control unit 40 may be stand-alone, may be physically integrated into the actuator packaging, or may be integrated into other control units already installed in the vehicle to perform various functions.

[0037] The connection between the electric actuator 32 and the piston may be direct or may include intermediate kinematics, in a known manner.

[0038] It is worth noting that the disc brake caliper 20 may include thrust means, such as springs or spiders 48, which act resiliently on the brake pads 24 to axially space the pads 24 away from the brake disc 16 so as to retract the pads 24 towards their respective pistons 36 when no braking action is required.

[0039] According to a further embodiment, the pads 24 may be constrained to their respective pistons 36 so as to translate unitarily therewith.

[0040] Advantageously, the processing and control unit 40 is programmed to implement an algorithm which, in the absence of a braking request from the user of the vehicle 8, operates the electric actuator 32 by varying said gap 44 as a function of at least one dynamic parameter of the vehicle defining a prediction of a future request for a braking operation by the user, increasing the gap 44 when a request for a braking operation is imminent and decreasing the gap 44 when a request for a braking operation is not imminent.

[0041] Specifically, the algorithm maintains the gap 44 in a range between a maximum value (or a very small value or less) at which the residual torque is negligible, i.e., no braking effect is applied to the brake disc 16, and a minimum value at which residual torque or braking effect on the brake disc 16 is tolerated.

[0042] In this way, when a request for braking is deemed unlikely, the gap 44 is increased to ensure there is no braking torque, however, at the expense of the responsiveness of the disc brake to braking requests that are deemed unlikely or unlikely.

[0043] On the other hand, if a braking request is deemed likely, the gap 44 is reduced to allow for a smaller braking torque, as will be seen, to favor the responsiveness of the disc brake to the likely braking request.

[0044] The algorithms implemented by the processing and control unit 40 may be configured with different dynamic parameters of the vehicle.

[0045] The following dynamic parameters are not substitutes for each other and may be combined: In other words, the processing and control unit 40 may take into account one or more dynamic parameters of the vehicle to implement a more or less sophisticated algorithm that takes into account multiple parameters that contribute to the definition of the best and most efficient strategy for adjusting the clearance 44 according to the actual and fortuitous driving conditions of the vehicle 8.

[0046] According to an embodiment of the invention, the dynamic parameter consists of the collision time estimated as the time required for a collision to occur between the vehicle 8 equipped with the braking system 4 and another vehicle preceding it, without changing the respective speeds and trajectories of the vehicles. If the estimated collision time is reduced, the gap 44 is also reduced and vice versa.

[0047] According to a possible embodiment of the invention, the time to crash is estimated as a function of the coefficient of friction of the road surface on which the vehicle 8 equipped with the braking system 4 travels. If the coefficient of friction decreases, the gap 44 decreases and vice versa.

[0048] According to a possible embodiment of the invention, the impact time is estimated as a function of the difference in acceleration between the vehicle 8 equipped with the braking system 4 and an additional vehicle preceding it: if the acceleration difference increases, the gap 44 decreases and vice versa.

[0049] According to a possible embodiment of the invention, the dynamic parameters of the vehicle 8 consist of a hazard index, i.e. a dimensionless index defining the risk of a collision between two vehicles defined as the relationship between the critical braking distance and the critical hazard distance, such that if the critical braking distance is smaller than the critical hazard distance, the gap 44 decreases and vice versa.

[0050] According to a further embodiment of the invention, said dynamic parameter of the vehicle consists of a predefined safety distance between the vehicle 8 equipped with the braking system 4 and a further vehicle preceding it. Obviously, if the safety distance is reduced, the gap 44 is also reduced and vice versa.

[0051] According to a further embodiment, the dynamic parameters of the vehicle with the brake system include an emergency signal from the leading vehicle to which the following vehicle is connected. In other words, if the leading vehicle detects a dangerous situation, it sends a danger signal that is picked up by the processing and control unit 40 which commands the electric actuators to reduce the gap 44. In effect, the presence of a potentially dangerous situation increases the probability of a braking request occurring, thus justifying a reduction in the gap 44.

[0052] According to a further embodiment, the dynamic parameters consist of information about real-time traffic conditions along the vehicle's route, and in this case information about an intensification of traffic or a slowdown or approaching congestion along the route traversed by the vehicle 8 statistically increases the probability of a braking request and thus justifies a reduction of the gap 44 and vice versa.

[0053] According to a possible embodiment, the dynamic parameters of a vehicle 8 equipped with a braking system 4 consist of information about real-time conditions on the path of the vehicle, such as speed limits and / or road slopes and / or curves.

[0054] Indeed, a reduction in the speed limit, a downhill section of road, or the presence of a curve all constitute conditions that statistically increase the probability that the user will request a braking action, thereby resulting in a reduction in gap 44, and vice versa.

[0055] According to a further embodiment of the invention, said dynamic parameters of the vehicle consist of the comfort demands for the passengers of the vehicle 8, increasing the gap 44 when more comfort is required and vice versa. In particular, a higher comfort demand results in less hard braking and conversely a lower comfort demand results in less hard braking.

[0056] According to the present invention, the variation of the gap 44 by the electric actuator 32 may be discrete.

[0057] For example, the algorithm identifies a minimum impact time and a maximum impact time, so that a change in the gap 44 occurs discretely when the impact time exceeds a threshold defined by those minimum and maximum values, respectively.

[0058] According to an embodiment, the minimum impact time value is 4.5 seconds and the maximum impact time value is 5 seconds.

[0059] According to a further embodiment of the invention, the variation of the gap 44 by the electric actuator 32 is of continuous type so as to vary the gap 44 between a minimum and a maximum value depending on said dynamic parameters of the vehicle 8 .

[0060] As can be seen from the foregoing, the present invention overcomes the shortcomings of the prior art.

[0061] In particular, the braking system of the present invention makes it possible to dynamically and in real time adjust the distance between the brake disc and its pads as a function of several dynamic parameters of the vehicle and the actual accidental driving conditions.

[0062] In this way, the responsiveness to braking varies depending on several dynamic parameters of the vehicle, taking into account the likelihood that the user will need to brake depending on traffic conditions, road conditions, hazard situations, comfort situations, etc. Thus, when the likelihood of a braking operation is low, the gap is increased to avoid residual torque at the expense of braking readiness, whereas when a braking operation is judged to be highly likely, the gap is decreased to reduce braking readiness at the expense of residual torque, albeit slightly. Overall, it is clear that the residual torque is usually reduced, which in turn reduces the consumption of the friction material of the pads and also reduces the consumption of the vehicle (fuel and / or electricity).

[0063] In this way, in addition to improving driving safety, it is also possible to reduce pad wear, reduce residual braking torque, improve the overall vehicle range, reduce particulate pollution emissions due to pad wear, and reduce pollutant emissions from the vehicle's internal combustion engine.

[0064] Furthermore, this system makes it possible to reduce as much as possible the gap between the brake disc and the pads and thus the delay between the braking request and its onset, which obviously makes it possible to improve the driving feeling felt by the driver when requesting a braking action.

[0065] As shown, it is also possible to improve the comfort of the driver and thus the passengers of the vehicle, and generally the active dynamic safety conditions of said vehicle.

[0066] Those skilled in the art may make numerous modifications and variations to the above-described system and method to meet their foreseeable and particular needs, all of which are within the scope of the present invention as defined in the following claims.

Claims

1. A brake system (4) for a vehicle (8), comprising: At least one disc brake (12), A brake disc (16) having a disc brake caliper (20) arranged to straddle the brake disc (16); At least one disc brake (12) including a pair of pads (24) opposed to each other across the at least one disc brake (12) and acting on the brake disc (16) from opposite sides along an actuation axis direction (A-A) parallel to the rotation axis (X-X) of the brake disc (16); at least one electrically-operated actuator (32) operatively connected to a piston (36) acting as a pusher for at least one of the pair of pads (24) along the actuation axis direction (A-A); a processing and control unit (40) operatively connected to the electric actuator (32) and programmed to move the piston (36) and the pair of opposing pads (24) along the actuation axis direction (A-A) to an advanced position so that the pair of pads (24) contact and press against the brake disc (16) when braking is required, and to move the piston (36) to a rest position or a retracted position where a gap (44) is specified between the pair of pads (24) and the brake disc (16), The processing and control unit (40) is programmed to execute an algorithm that, when there is no braking request, operates the electric actuator (32) while varying the gap (44) as a function of at least one dynamic parameter of the vehicle (8) that defines a prediction of a braking request, increasing the gap (44) when a braking request is imminent and decreasing the gap (44) when a braking request is not imminent.

2. 2. The brake system (4) for a vehicle (8) according to claim 1, wherein the disc brake caliper (20) is provided with thrust means, such as a spring or spider (48), for exerting a resilient action on the pair of pads (24) to axially move the pair of pads (24) away from the brake disc (16) so as to retract the pair of pads (24) towards the piston (36) when no braking action is required.

3. 2. A brake system (4) for a vehicle (8) as recited in claim 1, wherein the pair of pads (24) are connected to each of the pistons (36) so as to translate together along the operating axis direction (A-A).

4. 2. A brake system (4) for a vehicle (8) as claimed in claim 1, wherein the algorithm determines whether to set the clearance (44) to a maximum or high value corresponding to a defined low residual torque and high response time, or to set the clearance (44) to a low value corresponding to a high residual torque and low response time.

5. the dynamic parameters of the vehicle (8) include a collision time estimated as the time required for a collision to occur between the vehicle (8) equipped with the braking system (4) and another vehicle preceding the vehicle (8) if the vehicle (8) and the other vehicle do not change their speeds and trajectories, respectively; If the estimated impact time is reduced, the gap (44) is reduced, If the estimated impact time increases, the gap (44) increases. A brake system (4) for a vehicle (8) according to claim 1.

6. The time to crash is estimated as a function of a coefficient of friction of a road surface on which a vehicle (8) equipped with the braking system (4) is traveling; If the coefficient of friction is reduced, the gap (44) is reduced.

6. A braking system (4) for a vehicle (8) according to claim 5, characterized in that the clearance (44) is increased if the coefficient of friction increases.

7. the collision time is estimated as a function of the difference in acceleration between the vehicle (8) equipped with the braking system (4) and the other vehicle preceding the vehicle (8); If the difference in acceleration results in the possibility of braking being required or a collision being possible, the gap (44) is reduced; 6. A braking system (4) for a vehicle (8) as claimed in claim 5, wherein the gap (44) is increased if the difference in acceleration does not result in a possible need for braking or a possible collision.

8. said dynamic parameters of said vehicle (8) include a hazard index, i.e. a dimensionless index defining the collision risk between two vehicles defined as the relationship between a critical braking distance and a critical hazard distance, When the critical braking distance is less than the critical hazard distance, the gap (44) is reduced; 2. A braking system (4) for a vehicle (8) as claimed in claim 1, wherein said gap (44) is increased when said critical braking distance is greater than said critical hazard distance.

9. the dynamic parameters of the vehicle (8) include a predetermined safety distance between the vehicle (8) equipped with the braking system (4) and another vehicle preceding the vehicle (8); If the safety distance is decreased, the gap (44) is decreased.

2. A braking system (4) for a vehicle (8) according to claim 1, wherein the gap (44) increases as the safety distance increases.

10. 2. The brake system (4) for a vehicle (8) according to claim 1, wherein the dynamic parameters of the vehicle (8) equipped with the brake system (4) include an emergency signal from a leading vehicle, and the vehicle (8) following the leading vehicle is connected to the leading vehicle.

11. The braking system (4) for a vehicle (8) according to claim 1, wherein the dynamic parameters include information regarding real-time traffic conditions along a route of the vehicle (8).

12. 2. A braking system (4) for a vehicle (8) as claimed in claim 1, wherein the dynamic parameters of the vehicle (8) equipped with the braking system (4) include information about real-time conditions of the path of the vehicle (8), such as speed limits and / or road inclinations and / or curves.

13. said dynamic parameters of said vehicle (8) including passenger comfort requirements, 2. A brake system (4) for a vehicle (8) according to claim 1, characterized in that the gap (44) is increased when more comfort is required and reduced when vice versa.

14. 2. The brake system (4) for a vehicle (8) according to claim 1, wherein the variation of the gap (44) by the electric actuator (32) is discrete.

15. A braking system (4) for a vehicle (8) according to claim 14 in combination with at least claim 4, characterized in that the algorithm identifies a minimum impact time and a maximum impact time, and the variation of the gap (44) is performed discretely when the impact time exceeds a threshold defined by the minimum impact time and the maximum impact time, respectively.

16. 16. A braking system (4) for a vehicle (8) according to claim 15, wherein said minimum crash time is 4.5 seconds and said maximum crash time is 5 seconds.

17. 16. A braking system (4) for a vehicle (8) as claimed in claim 15, wherein the variation of the gap (44) by the electric actuator (32) is continuous so as to vary the gap (44) as a function of the dynamic parameters of the vehicle (8) between a minimum crash time and a maximum crash time.

18. A vehicle (8) comprising a brake system (4) for a vehicle (8) according to claim 1.

19. Providing a braking system (4) for a vehicle (8), comprising the steps of: The brake system (4) comprises: At least one disc brake (12) comprising a brake disc (16) having a disc brake caliper (20) arranged to straddle the brake disc (16), and a pair of pads (24) opposed to each other and acting on the brake disc (16) from opposite sides along an axial direction (A-A) parallel to a rotation axis (X-X) of the brake disc (16); at least one electrically-operated actuator (32) operatively connected to a piston (36) acting as a pusher for at least one of the pair of pads (24) along the actuation axis direction (A-A); a processing and control unit (40) operatively connected to the electric actuator (32) and programmed to move the piston (36) and the pair of opposing pads (24) along the axial actuation direction (A-A) to a forward position so that the pair of pads (24) contact and press against the brake disc (16) when braking is required, and to return the piston (36) and the pair of opposing pads (24) to a rest or retracted position where a gap (44) is specified between the pair of pads (24) and the brake disc (16), The processing and control unit (40) is programmed to implement an algorithm for operating the electric actuator (32) in the absence of a braking request by varying the clearance (44) as a function of at least one dynamic parameter of the vehicle (8) defining a braking request prediction, increasing the clearance (44) when it is determined that a braking operation is not possible and decreasing the clearance (44) when it is determined that a braking operation is possible.

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