Method for controlling disc brake of vehicle

Abstract

A method for controlling a disc (7) brake (2) of a vehicle, suitable for a disc brake, the brake comprising: brake pads (6) each carrying a friction lining (10); and an electromechanical actuator (9) for moving the brake pads such that their respective friction linings clamp the disc, thereby effecting braking. According to the method, the movement of the brake pads is controlled according to the thermal expansion state of the disc and the respective friction linings of the brake pads after the braking is finished, so that after the movement, the stroke length (d1, d2) between the friction linings of each brake pad and the disc remains greater than 0 mm and less than a predetermined stroke length (d1, d2).

Description

Technical Field

[0001] The present invention relates to a method for controlling a disc brake of a vehicle. The present invention also relates to a disc brake capable of implementing the method. Finally, the present invention also relates to a vehicle including at least one disc brake according to the present invention. Background Art

[0002] An electromechanically actuated disc brake for a vehicle (e.g., a motor vehicle) generally includes an electric motor for providing a clamping force to a clamping member (e.g., a piston) to move a brake pad carrying a brake friction lining towards a disc such that the friction lining of the brake pad clamps the disc to effect braking. Friction between the brake disc and the friction lining of the brake pad causes their temperatures to rise and thus causes their respective thermal expansions. This thermal expansion varies according to a plurality of parameters, such as parameters related to previously implemented braking. When braking stops, the brake disc and the friction lining of the brake pad gradually cool, causing their respective thermal expansions to decrease until they return to their normal state at room temperature.

[0003] When braking stops, the brake pads are moved by an electromechanical actuator so as to leave a space between the brake disc and the friction linings of the brake pads located on both sides of the brake disc. If this gap is too small, there is a risk that the friction linings of the brake pads remain in contact with the brake disc for some time due to thermal expansion at the end of braking, thereby generating an undesired residual braking that may affect the dynamic performance of the vehicle. In addition, the residual braking unnecessarily generates braking particles that cause air pollution. In the case where the space between the friction lining of the brake pad and the brake disc is too large, the response time between a braking command and the implementation of braking increases, and thus the braking distance increases, which is undesirable in terms of the use safety of the vehicle.

[0004] Therefore, during the manufacturing process of the disc brake, especially when determining the space left between the friction lining of the brake pad and the disc during a non-braking period, a choice must be made between a shorter response time and a longer response time, where the former may have a greater (significant) risk of residual braking and the latter may have no risk of residual braking. Summary of the Invention

[0005] An object of the present invention is in particular to enable a disc brake for a vehicle to have a very short response time to a braking command and at the same time have a reduced risk of residual braking.

[0006] To this end, the present invention relates to a method for controlling a disc brake of a vehicle, wherein the disc brake comprises brake pads and an electromechanical actuator, each brake pad carrying a friction lining, and the electromechanical actuator is used to move the brake pads so that their respective friction linings clamp (brake) a disc to effect braking, characterized in that at the end of braking, the movement of the brake pads is controlled according to the thermal expansion states of the (brake) disc and the friction linings of the brake pads respectively, such that the stroke length between the friction lining of each brake pad and the (brake) disc after the movement remains between greater than 0 mm and a predetermined stroke length.

[0007] Therefore, during non-braking periods, the position of the brake pads relative to the (brake) disc is not fixed, but varies according to the thermal expansion states of the friction linings of the brake pads and the (brake) disc. By keeping the stroke length between the friction lining of each brake pad and the (brake) disc greater than 0 mm and less than a predetermined stroke length, it is possible to dynamically maintain the gap between the friction lining of the brake pads and the (brake) disc, which gap is large enough not to cause residual braking and is also small enough to have a short response time after obtaining a braking command, thus reducing the braking distance.

[0008] Since the stroke length between the friction lining of each brake pad and the disc is greater than 0 mm, during non-braking periods, the friction lining of the brake pads, whether it is the friction lining on the first side facing the (brake) disc or the friction lining on the second side facing the (brake) disc, does not contact the (brake) disc.

[0009] The predetermined stroke length is selected such that the response time to a braking command is as short as possible.

[0010] The present invention may include one or more of the following optional features employed alone or in combination.

[0011] Advantageously, the predetermined stroke length is between 0.002 mm and 0.100 mm. The stroke length within this range should be long enough to avoid the occurrence of residual braking and at the same time short enough to enable the response time to a braking command to achieve the shortest possible braking distance.

[0012] Advantageously, during or after braking, the thermal expansion states of the (brake) disc and the friction linings of the brake pads are determined by measuring the temperature of the (brake) disc and / or the friction linings of the brake pads. The determination of the temperature of the (brake) disc and / or the friction linings of the brake pads is a reliable indicator of their thermal expansion states.

[0013] Preferably, the determination of the thermal expansion state of the disc and the friction lining of the brake pad is achieved by using a corresponding (control) table or physical model that correlates the temperature of the disc and / or the friction lining of the brake pad with their thermal expansion state. This is a simple, reliable, and economical method for determining the thermal expansion state of the (brake) disc and the friction lining of the brake pad based on their temperature. The corresponding table or physical model is established in advance, for example, according to the characteristics of the brake, such as the composition of the friction lining of the brake pad.

[0014] Advantageously, the temperature of the friction lining of the brake disc and / or the brake friction lining is estimated by using at least one braking duration and / or a braking force. These are reliable indicators for estimating the temperature of the brake disc and / or the brake pad friction lining. Therefore, it is not necessary to use temperature sensors to determine these temperatures, which is economical. It can be understood that the longer the braking duration and the greater the braking force, the greater the temperature increase of the friction lining of the brake disc and the brake friction lining during braking. It should also be understood that the shorter the braking duration and the smaller the braking force, the smaller the temperature increase during braking.

[0015] Preferably, the temperature of the friction lining of the disc and / or the brake pad is also estimated by using at least one parameter selected from vehicle speed, vehicle mass, or brake size. It should be understood that these parameters affect the temperature rise of the friction lining of the disc and the brake pad during braking. Therefore, the use of these parameters enables an improvement in the estimation of the temperature of the disc and the brake pad. It should be understood that the greater the speed of the vehicle during braking, the greater the mass of the vehicle or the size of the brake, the greater the temperature rise of the friction lining of the (brake) disc and the brake pad during braking. According to other embodiments, other parameters are used to improve the estimation of the temperature of the friction lining of the disc and the brake pad.

[0016] Advantageously, if residual braking is detected after the movement of the brake pad ends, the movement of the brake pad is controlled to increase the corresponding stroke length between the friction lining of each brake pad and the disc. This monitoring and detection of residual braking enables ensuring that if residual braking occurs for any reason, the residual braking can be detected and eliminated, thus avoiding defects associated with residual braking. The detection of residual braking is carried out in different ways according to different embodiments. According to a specific embodiment, a force sensor or an observer determines the braking force, and if the sensor or the observer determines that the presence of residual braking exceeds the desired braking time, the movement of the brake pad is controlled to increase the corresponding stroke length between the friction lining of each brake pad and the disc.

[0017] According to one embodiment, if an undesired decrease in the rotational speed of a wheel of a vehicle equipped with a disc brake is detected, the presence of residual braking is considered to be detected. This is a simple and effective method for detecting residual braking. Moreover, this is an economical means since it uses sensors or observers of the rotational speed of the vehicle wheels that are generally already present or are being used.

[0018] The invention also relates to an electro-mechanically actuated disc brake for a vehicle, which includes an electronic control unit capable of controlling the implementation of the method as described above.

[0019] Finally, the invention also relates to a vehicle including at least one disc brake as described above. Description of the Drawings

[0020] The invention will be better understood by reading the following description given by way of non-limiting example only and with reference to the drawings, in which:

[0021] Figure 1 is a view of a vehicle according to the invention;

[0022] Figure 2 is a perspective view of a disc brake according to the invention;

[0023] Figure 3 is a schematic view of a clamping member, brake pads and a disc of a disc brake according to the invention during braking;

[0024] Figure 4 is with Figure 3 a similar schematic view showing the state at the end (after) of braking. Detailed Description

[0025] Figure 1 A vehicle according to the invention is shown, in the illustrated case a motor vehicle 1, which includes at least two disc brakes 2, in the illustrated case four in number, each wheel 3 of the motor vehicle 1 being equipped.

[0026] The invention is applicable to any type of brake, particularly those intended to equip passenger motor vehicles, SUVs (acronym for Sport Utility Vehicle), two-wheel vehicles (particularly motorcycles), aircraft, industrial vehicles selected from vans, "heavy" vehicles (i.e., subways, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles (such as agricultural or civil engineering vehicles)), or other transport or handling vehicles. The invention is also applicable to non-motor vehicles, such as in particular trailers, semi-trailers or caravans.

[0027] Figure 2Shows a brake 2 which, in the present case, is of the floating caliper disc type. Thus, in a conventional manner, it includes a caliper 4 which is mounted to slide relative to a bracket (yoke) 5 which is fixed relative to the motor vehicle 1.

[0028] According to other embodiments, the brake 2 can be of a different type, such as a disc brake 2 with a fixed caliper, as Figure 3 and Figure 4 shown.

[0029] Thus, as Figure 3 and Figure 4 shown, the disc brake 2 includes at least two brake pads 6 which are intended to cooperate by friction with opposite faces of a disc 7 which is integrally and rotationally fixed to a wheel 3 of the motor vehicle 1, respectively, in order to effect braking.

[0030] Figure 3 and Figure 4 shown, the disc brake 2 further includes an electric motor 8 which is used to provide a clamping force to a clamping member 9 which is here formed by a piston, so that the brake pads 6 move in the direction of the disc 7, such that the friction linings 10 of the brake pads 6 contact and clamp the disc 7 in order to effect braking, as Figure 3 shown. During braking, the friction between the friction linings 10 of the brake pads 6 and the disc 7 causes the temperature of the friction linings 10 of the brake pads 6 and the disc 7 to increase and thus causes their respective thermal expansions.

[0031] At the end of braking, the movement of the brake pads 6 is controlled such that their respective friction linings 10 no longer contact the brake disc 7 and thus the wheel 3 of the motor vehicle 1 no longer decelerates. The disc brake 2 includes an electronic control unit (not shown) which is used to control the operation of the disc brake 2, in particular to control the movement of the clamping member 9 and thus the movement of the brake pads 6.

[0032] It should be noted that Figure 2 shown, the floating caliper brake 2 includes elements which are not shown but which are similar to those of the fixed caliper brake schematically shown in Figure 3 and Figure 4 , in particular two brake pads which are intended to cooperate by friction with opposite faces of a disc of a wheel 3 of the motor vehicle 1, respectively. Similarly, Figure 2 shown, the floating caliper brake 2 includes an electric motor which is used to provide a clamping force to a clamping member in order to move the brake pads towards the disc.

[0033] This will be referred to more specifically below with reference to Figure 3 and Figure 4A method for controlling a disc brake 2 according to the present invention is described. The electronic control unit is capable of controlling the various steps described below. Although a fixed caliper brake is shown in Figure 3 and Figure 4 which includes a piston 9 on each side of the disc, it should be understood that the implementation of the method for controlling a floating caliper brake 2 as shown in Figure 2 is not beyond the scope of the present invention, and Figure 2 the control method of the brake 2 in

[0034] is similar to that described below. According to this method, at the end of braking, the movement of the brake pads 6 is carried out according to the thermal expansion states of the brake disc 7 and the corresponding friction linings 10 of the brake pads 6, so that after the movement, the stroke lengths d1, d2 between the friction linings 10 of each brake pad 6 and the brake disc 7 remain greater than 0 mm and less than a predetermined stroke length (see Figure 4 ). By keeping the stroke lengths d1, d2 between the friction linings 10 of each brake pad 6 and the disc 7 greater than 0 mm and less than the predetermined stroke length, the gap (void) between the friction linings 10 of the brake pads 6 and the disc 7 can be dynamically maintained, which is large enough not to cause residual braking and small enough to enable a short response time after a braking command, thereby being able to reduce the braking distance. Since the stroke lengths d1, d2 between the friction linings 10 of each brake pad 6 and the brake disc are greater than 0 mm, during non-braking, the friction linings 10 of the brake pads 6, whether the friction linings on the first side facing the brake disc 7 or the friction linings on the second side facing the brake disc 7, do not contact the brake disc 7 (see Figure 4 ). According to this embodiment, the predetermined stroke length is between 0.002 mm and 0.10 mm.

[0035] It can be understood that in order to satisfy the condition that the stroke lengths d1, d2 between the friction linings 10 of each brake pad 6 and the disc 7 remain greater than 0 mm and less than the predetermined stroke length, the brake pads 6 move as the friction linings 10 of the brake pads 6 and the disc 7 cool. In particular, it can be understood that after the first axial movement in the direction opposite to the disc 7, as it cools and thus as the thermal expansion decreases, the brake pads 6 move axially in the direction towards the disc 7.

[0036] The thermal expansion states of the friction linings 10 of the brake pads 6 and the disc 7 are determined in different ways according to the embodiment. In particular, for example, the thermal expansion state is measured or estimated by using a thermal expansion observer.

[0037] According to this embodiment, the thermal expansion state of the friction linings 10 of the brake disc 7 and / or the brake pads 6 is determined by measuring the temperature of the brake disc 7 and / or the friction linings 10 of the brake pads 6. The temperature of a known element is a reliable method for determining its thermal expansion state. It can be noted that according to the present invention, measuring only the temperature of the disc 7 can simultaneously determine the thermal expansion state of the friction linings 10 of the disc 7 and the brake pads 6. In the same way, measuring only the temperature of the friction linings 10 of the brake pads 6 can simultaneously determine the thermal expansion state of the friction linings 10 of the brake pads 6 and the disc 7. In fact, the temperatures of the disc 7 and the friction linings 10 are usually very close, such that measuring the temperature of one of them allows the temperature of the other to be inferred with an acceptable approximation. Measuring only the temperature of one of these elements can simplify the method.

[0038] The estimated or measured temperature is, for example, used as an input to a look-up table that correlates the temperature of the friction linings 10 of the brake disc 7 and / or the brake pads 6 with their respective thermal expansion states. This is a simple and economical method for determining the thermal expansion state from the temperature.

[0039] According to an embodiment, the temperature of the friction linings 10 of the brake disc 7 and / or the brake pads 6 is measured or estimated. In this case, the temperature of the friction linings 10 of the brake disc 7 and the brake pads 6 is estimated by using the duration or force of the just-occurred braking, the speed of the motor vehicle 1 (especially its variation during braking), the mass of the vehicle, and the dimensions of the brake 2. The use of all these parameters enables an accurate estimate of the temperature of the friction linings 10 of the brake disc 7 and the brake pads 6. According to other embodiments, more or fewer parameters may be used depending on the desired degree of accuracy for determining the temperature and thus the thermal expansion state.

[0040] The method advantageously further includes an additional step according to which, if residual braking is detected at the end of the movement of the brake pads 6 as described above, an additional movement of the brake pads 6 is controlled so as to increase the respective stroke lengths d1, d2 between each friction lining 10 of the brake pads 6 and the disc 7. Thus, if at the end of the movement of the brake pads 6 that occurs after braking, it is detected that this movement is insufficient for any reason to avoid the presence of residual braking, the error is corrected to reduce the time during which residual braking occurs.

[0041] For example, if an undesired decrease in the rotational speed of the wheel 3 of the motor vehicle 1 equipped with the disc brake 2 is detected, the presence of residual braking is detected. For this purpose, for example, a wheel speed sensor is used, which is usually already present on the motor vehicle 1, which is economical.

[0042] The present invention is not limited to the presented embodiments, and other embodiments will be apparent to those skilled in the art.

[0043] List of References

[0044] 1: Motor vehicle

[0045] 2: Disc brake

[0046] 3: Wheel

[0047] 4: Caliper

[0048] 5: Bracket

[0049] 6: Brake pad

[0050] 7: (Brake) disc

[0051] 8: Electric motor

[0052] 9: Clamping member

[0053] 10: Friction lining of the brake pad

[0054] d1, d2: Stroke length between the friction lining of the brake pad and the disc

Claims

1. A control method for a disc (7) brake (2) of a vehicle (1), wherein, The disc (7) type brake (2) includes brake pads (6) and an electromechanical actuator (9). Each brake pad (6) is carried with a friction lining (10). The electromechanical actuator (9) is arranged to move the brake pads (6) so that their respective friction linings (10) clamp the disc (7) to achieve braking. It is characterized in that after braking, the movement of the brake pads (6) is controlled according to the thermal expansion states of the disc (7) and the corresponding friction linings (10) of the brake pads (6), so that after the movement, the stroke lengths (d1, d2) between the friction linings (10) of each brake pad (6) and the disc (7) remain greater than 0 mm and less than a predetermined stroke length.

2. The method according to claim 1, wherein The predetermined stroke length (d1, d2) is between 0.002 mm and 0.10 mm.

3. The method according to claim 1 or 2, wherein The thermal expansion states of the disc (7) and the friction linings (10) of the brake pads (6) during or after braking are determined by measuring the temperatures of the disc (7) and / or the friction linings (10) of the brake pads (6).

4. The method according to claim 3, wherein, The determination of the thermal expansion states of the disc (7) and the friction linings (10) of the brake pads (6) is achieved by using a look-up table that correlates the temperatures of the disc (7) and / or the friction linings (10) of the brake pads (6) with their thermal expansion states.

5. The method according to claim 3 or 4, wherein The temperatures of the disc (7) and / or the friction linings (10) of the brake pads (6) are estimated by using at least one of the braking duration and / or a braking force.

6. The method according to claim 5, wherein The temperatures of the disc (7) and / or the friction linings (10) of the brake pads (6) are also estimated by using at least one parameter selected from the speed of the vehicle (1), the mass of the vehicle (1), or the size of the brake (2).

7. The method according to any one of the preceding claims, wherein, If residual braking is detected after the movement of the brake pads (6) ends, the movement of the brake pads (6) is controlled to increase the corresponding stroke lengths (d1, d2) between each friction lining (10) of the brake pads (6) and the disc (7).

8. The method according to claim 7, wherein, If an undesired decrease in the rotational speed of the wheel (3) of the vehicle (1) equipped with the disc brake (2) is detected, the presence of residual braking is detected.

9. An electromechanically actuated disc brake (2) for a vehicle, which includes an electronic control unit that can control the implementation of the method according to any one of claims 1 to 8.

10. A vehicle (1) that includes at least one disc (7) type brake (2) according to claim 9.

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