Braking device comprising means for determining the braking force

Abstract

The braking device (4) for a vehicle comprises: - a member of interest (6), - means for determining the braking force, the means for determining the braking force comprising means for determining a deformation of the member of interest, fitted in a housing (10) for receiving the means for determining a deformation of the member of interest, said housing being formed in the member of interest (6).

Description

Braking device including means for determining the braking force Scope of the invention

[0001] The invention relates to the field of vehicle braking devices, as well as to braking systems comprising such braking devices and to vehicles comprising such braking systems. The invention further relates to means for determining the deformation of a component of interest in a braking device. Finally, the invention also relates to a method for regulating braking force and to a method for manufacturing a braking device. Technical background

[0002] A vehicle braking system, particularly for automobiles, generally includes a braking device comprising friction elements, such as brake pads or shoe linings, connected to an actuator capable of bringing a pair of these friction elements closer to a disc or drum attached to a wheel of the vehicle in order to brake the vehicle by friction, or of moving them away from the disc or drum in order to stop braking.

[0003] It is useful to know the precise braking force of the braking system to ensure its proper functioning. In particular, knowing the braking force allows you to verify that a target braking force value has been reached following a braking command and to take corrective action if necessary. Furthermore, knowing the braking force allows you to check for the absence of residual braking force after braking.

[0004] It is known to use a force sensor placed in the force transmission chain to directly measure the braking force of the braking device. However, such sensors are expensive and make the manufacturing of the braking device complex.

[0005] It is also known to determine the braking force indirectly, using charts or mathematical formulas. However, this indirect determination is less precise.

[0006] The invention aims in particular to provide a braking device that allows the braking force to be determined in a simple, economical and reliable manner.

[0007] For this purpose, the invention relates to a braking device for a vehicle, comprising: - an element of interest, - means for determining the braking force, characterized in that the means for determining the braking force include means for determining a deformation of the element of interest brought into a housing for receiving means for determining a deformation of the element of interest provided in the element of interest.

[0008] When a braking force is applied by the braking system, the components of the braking system undergo a corresponding force that causes their respective deformations. This deformation is greater the greater the braking force. Thus, measuring the deformation of the relevant component of the braking system allows for a reliable and cost-effective determination of the braking force of the system.

[0009] The presence of a housing for the means of determining the deformation of the component of interest, integrated within the component itself, offers several advantages. In particular, this housing facilitates the installation of the deformation measurement means on the component of interest by precisely defining the predetermined location where the means must be installed. This reduces the risk of incorrect positioning, thereby increasing the reliability of the deformation measurement and consequently the reliability of the braking force determination. Furthermore, installing the deformation measurement means in the corresponding housing reduces the overall size of the braking system.It can be foreseen that the housing for receiving the means for determining a deformation of the organ of interest is such that it protects the means for determining a deformation of the organ of interest in a simple and effective way from external attacks, such as mechanical attacks (tearing, projections of foreign elements such as gravel...) or chemical attacks (projection of liquids such as water).

[0010] Depending on the embodiment, the braking device is of the disc or drum type.

[0011] Depending on the embodiment, the braking device is electromechanically actuated and / or hydraulically actuated.

[0012] The component of interest is a part of the braking system that undergoes deformation or stress during the application of braking force. The component of interest varies depending on the embodiment. For a disc brake, the component of interest is, for example, the caliper. Depending on the embodiment, the means for determining the deformation of the component of interest are located on the caliper at various points of interest, which correspond to locations where the deformation or stress experienced by the caliper is preferably greatest. For example, the means for determining the deformation of the component of interest may be located on the outer surface of the caliper's arch, in its central part, or on its bearing surface—that is, the surface of the caliper that faces the translated element of a screw-nut mechanism in an electromechanical actuator and serves as a bearing surface for this translated element.For a drum brake, the component of interest is, for example, the fixed point, also called the support point or anchor point, of the shoes carrying the brake linings.

[0013] The invention includes, as an alternative, one or more of the following optional features, taken alone or in combination.

[0014] Advantageously, the means for determining a deformation of the component of interest comprise: - at least one strain gauge for measuring a deformation of the component of interest, preferably unidirectional or multidirectional and / or arranged to stabilize its response according to its environment, particularly thermal, for example in a manner known in the field of strain gauges; - at least one test body to which the strain gauge is attached, the test body being fixed to the housing for receiving the means for determining a deformation of the component of interest and being designed to transmit at least a portion of a deformation of the component of interest to the strain gauge. The fact that the strain gauge is fixed to the test body, which is itself fixed to the component of interest, facilitates the manufacture of the braking device by simplifying the installation of the strain gauge.Specifically, this avoids having to attach the strain gauge directly to the component of interest, for example by gluing. Such an attachment is less robust and the positioning of the strain gauge is less precise. Preferably, the strain gauge is initially attached to the test body and, once the assembly of the other components of the braking device is complete or nearly complete, the assembly comprising the strain gauge and the test body is transferred to the component of interest, more precisely into the housing for receiving the means for determining the deformation of the component of interest. Preferably, the housing has a shape complementary to that of the test body to facilitate the placement of the assembly comprising the strain gauge and the test body onto the component of interest.

[0015] Advantageously, the test specimen is formed by a functional component of the braking system. A "functional component" of the braking system is defined as a component that is directly or indirectly involved in the braking function of the braking system beyond its function as a test specimen. Components indirectly involved in the braking function include, for example, the assembly screws of the braking system. Such screws do not directly participate in the braking function but are essential for maintaining the integrity of the braking system. They therefore participate indirectly in the braking function, in that if they were removed, the braking system could no longer be used.This reduces the size and cost of the braking device since, by using a component already present on the braking device to perform the braking function, it is not necessary to provide a separate test body, forming an additional component to be added to the braking device.

[0016] Alternatively, the test specimen is formed by a non-functional component, from the perspective of braking mechanics, of the braking system. By "non-functional component" of the braking system, we mean a component of the braking system that does not participate in the braking function. Its sole function is to serve as a test specimen for the strain gauge. Using a non-functional component of the braking system as the test specimen allows for greater flexibility in the positioning and dimensioning of the test specimen. For example, it is easier to position the test specimen and the strain gauge at the location of the component of interest, thus enabling the most accurate possible deformation measurement of that component.

[0017] Advantageously, the test specimen is formed by a screw with a recess that provides a housing for the strain gauge, and the housing for the means of determining the strain of the component of interest is formed by a tapped hole in the component of interest of the braking device, with the screw being screwed into the tapped hole. It is clear that the installation of the means for determining the strain of the component of interest is then particularly precise, easy, and reproducible. Indeed, it is sufficient to screw the screw forming the test specimen into the tapped hole in the component of interest to precisely and securely position the strain gauge at the desired location on the component of interest.

[0018] Preferably, the screw is an assembly screw of the braking device. This improves the compactness of the braking device since it is not necessary to introduce an additional component to fulfill the function of the test body. It is understood that the test body in this case is formed by a functional component of the braking device. Indeed, the assembly screw, by participating in the assembly of at least two components of the braking device, indirectly contributes to the braking function of the braking device. In other words, without the assembly screw, the braking function is compromised.

[0019] In one embodiment, the test specimen is formed by a rod comprising a recess that provides a housing for the strain gauge, and the housing for the means for determining the strain of the component of interest is formed by a hole in the component of interest of the braking device, with the rod itself fitted into this hole. It is clear that the installation of the means for determining the strain of the component of interest is then particularly precise, easy, and reproducible. Indeed, it is sufficient to fit the rod forming the test specimen into the complementary hole in the component of interest to precisely and securely position the strain gauge at the desired location on the component.

[0020] In one embodiment, the test specimen is formed by a plate, and the housing for the means of determining a deformation of the component of interest is formed by a recess on an external surface of the component of interest. The plate has a first face on which the deformation gauge is fixed and a second face, opposite the first, fixed to the recess of the component of interest in the braking system. It is clear that the installation of the means for determining a deformation of the component of interest is then particularly precise, easy, and reproducible. Indeed, it is sufficient to fix the plate in the recess forming the housing for the means of determining a deformation of the component of interest to precisely and securely position the deformation gauge at the desired location on the component of interest. Preferably, the surface of the recess has a shape complementary to that of the plate.In particular, according to a preferred embodiment, the surface of the recess is flat.

[0021] Advantageously, the test specimen is made of a material with a coefficient of thermal expansion β measured between 20°C and 100°C that satisfies 0.95α < β < 1.05α, where α is the coefficient of thermal expansion measured between 20°C and 100°C of the material in which the component of interest for the braking device is made. In other words, β = α ± 5%. Alternatively, a difference of ± 10%, or even ± 20%, is considered. The fact that the coefficient of thermal expansion β of the test specimen is close to the coefficient of thermal expansion α of the material in which the component of interest is made ensures that the test specimen and the component of interest react in essentially the same way to temperature variations. Thus, we improve the reliability of the measurement of the deformation of the component of interest and therefore we improve the reliability of the determination of the braking force.Indeed, if the coefficients of thermal expansion of the test specimen and the component of interest are too different, in the event of a temperature change the strain gauge could detect a deformation of the test specimen that does not correspond to a deformation of the component of interest, thus distorting the determination of the braking force. Typically, the coefficient of thermal expansion α of the component of interest is on the order of 10 x 10. - 6 K - 1 for 20°C / 100°C for spheroidal graphite cast iron, used for example for a disc brake caliper; or 12 x 10 - 6 K - 1 for mild steel of type DC04, used for example for a drum brake fixed point; or between 10.5 x 10 - 6 K - 1 and 13.5 x 10 - 6 K - 1for an alloy steel. Thus, it is proposed to use the same material, or one of these materials, for the test specimen.

[0022] Advantageously, the test specimen is made of a material with a greater elongation at break than the material from which the component of interest is made. Thus, the test specimen is not at risk of breaking in the event of excessive deformation of the component of interest and is able to perform its function across the entire range of possible deformation of the component of interest.

[0023] In one embodiment, the component of interest is a caliper of a disc brake system. In another embodiment, the component of interest is a fixed point of a drum brake system. The caliper in the case of the disc brake system and the fixed point in the case of the drum brake system are advantageous choices as components of interest because they deform with a relatively large amplitude when a braking force is applied. A high amplitude of deformation allows for a more precise determination of the braking force using the strain gauge.

[0024] In one embodiment, the braking device is of the electromechanically actuated disc type and includes a device for converting the rotational motion of an output shaft of an electric motor into the translational motion of a clamping element of the braking device. The conversion mechanism comprises a screw-nut type device. The element of interest is a caliper of the disc-type braking device. The housing for the means of determining a deformation of the element of interest extends through a wall of the caliper, forming a bearing surface for a translated element of the screw-nut type device. The wall of the caliper, forming a bearing surface for the translated element of the screw-nut type device, undergoes significant deformations, particularly due to the transmission of the braking force via the translated element. Thus, this location allows the braking force to be determined accurately and reliably.It is understood that, according to the embodiments, the translated element of the screw-nut type device corresponds, for example, to the nut or the screw of the screw-nut type device.

[0025] Advantageously, the means for determining the deformation of the component of interest comprise at least two strain gauges and at least two test specimens, each strain gauge being attached to one of the test specimens. The strain gauges are designed to measure either the deformation of the component of interest of the braking system, or the strain gauges are designed to measure the deformation of a first component of interest of the braking system and a second component of interest of the braking system. Using two strain gauges to measure the deformation of the same component of interest or of two different components of interest improves the reliability of the measurement of the deformation caused by the braking force and thus improves the reliability of the determination of the braking force.

[0026] The invention also relates to a vehicle comprising at least one braking device as described above. Advantageously, the vehicle comprises between two and four braking devices as described above, preferably a vehicle comprising four braking devices as described above.

[0027] The invention also relates to a vehicle braking system, characterized in that it comprises a braking device as described above and a control unit designed to receive, on the one hand, information relating to a deformation of the component of interest of the braking device from the means for determining the deformation of the component of interest and to deduce an effective braking force therefrom, and, on the other hand, a target braking force instruction, the control unit being capable of comparing the target braking force instruction and the effective braking force and of controlling the braking device so as to match the target braking force instruction and the effective braking force. The braking system according to the invention thus makes it possible to obtain more precise and safer braking.

[0028] The invention also relates to a method for regulating the braking force of a braking system, characterized in that, the braking system being as described above, the method comprises the following steps: a) receiving an instruction for a target braking force, b) determining the effective braking force using the braking force determination means of the braking device, c) comparing the effective braking force to the target braking force, d) regulating the braking force by commanding the braking device to increase the braking force if the effective braking force is less than the target braking force and by commanding the braking device to decrease the braking force if the effective braking force is greater than the target braking force.This braking force regulation step is implemented until the effective braking force equals the target braking force.

[0029] The braking force regulation process of a braking system thus allows for a dynamic adaptation of the braking force by checking whether a braking force instruction has been correctly applied and applying corrective measures if necessary.

[0030] The invention also relates to means for determining a deformation of an element of interest of a braking device, characterized in that they comprise: - at least one strain gauge intended to measure a deformation of an element of interest of a braking device, - at least one test body to which the strain gauge is fixed, the test body being intended to be fixed in a housing for receiving the means for determining a deformation of an element of interest of a braking device and being intended to transmit at least a part of a deformation of an element of interest of the braking device to the strain gauge.

[0031] Such means for determining the deformation of a component of interest can be easily mounted on a braking device, particularly in the housing for receiving the means for determining the deformation of the component of interest. As previously mentioned, depending on the embodiment, the test specimen is, for example, a pad, a screw, or a rod. It is understood that any other test specimen can be used to perform this function on a braking device.

[0032] The invention also relates to a method for manufacturing a braking device for a vehicle, characterized in that:

[0033] a) A strain gauge is fixed to a test specimen, intended to measure the deformation of at least one component of interest in the braking system, and

[0034] b) the assembly comprising the strain gauge and the test specimen obtained in step a) is fixed in a housing provided on a component of interest in the braking system

[0035] The installation of the strain gauge is therefore particularly simple during the manufacturing of the braking device. Specifically, it is possible, firstly, to attach the strain gauge to the test specimen and then, secondly, to attach the test specimen to the designated receiving housing. According to one embodiment, the manufacturing process further includes a step (c) of calibrating the strain gauge so that the strain gauge takes into account the specific characteristics of the braking device. Brief description of the figures

[0036] Other features and advantages of the invention will become clear from the description given below, which is by way of example and in no way limiting, with reference to the attached drawings, in which:

[0037] is a schematic top view of an example vehicle in which a braking system comprising a braking device according to the invention is mounted;

[0038] is a perspective view of a braking device according to a first embodiment of the invention;

[0039] is a cross-sectional view of the braking system of the;

[0040] is a schematic representation of the braking device in figures 2 and 3;

[0041] is a perspective view of a rod forming a test body for the means of determining a deformation of the organ of interest;

[0042] is a perspective view of a braking device according to a second embodiment of the invention;

[0043] is a schematic representation of the braking system of the;

[0044] is a perspective view of part of a braking device according to a third embodiment of the invention;

[0045] is a perspective view of the means of determining a deformation of the organ of interest according to the third embodiment;

[0046] is a schematic representation of part of a braking device according to a fourth embodiment of the invention;

[0047] is a perspective view of the organ of interest of the braking device according to the fourth embodiment of the invention. Detailed description

[0048] In the various figures, identical or similar elements bear the same references. Therefore, the description of their structure and function is not systematically repeated.

[0049] A vehicle 1 is shown in which a braking system 2, comprising a braking device according to the invention, is arranged on at least two wheels 3, advantageously on each of the four wheels 3. In the illustrated examples, these are electromechanically operated brakes used as service brakes, and possibly as parking and / or emergency brakes. It should be noted that, in variants not shown, the invention also applies to a hydraulically actuated braking device, particularly as a service brake, possibly with an electromechanical device for parking and / or emergency braking.

[0050] It should be noted that the invention applies to all types of braking systems, particularly those intended for use in passenger cars, SUVs (Sport Utility Vehicles), two-wheeled vehicles (especially motorcycles), aircraft, commercial vehicles (including vans), heavy goods vehicles (i.e., subways, buses, road transport vehicles such as trucks, tractors, and trailers), off-road vehicles such as agricultural or construction equipment, and other transport or handling vehicles. The invention also applies to non-motorized vehicles such as trailers, semi-trailers, and caravans.

[0051] First method of implementation

[0052] Figures 2 to 4 illustrate a braking device 4 according to a first embodiment of the invention. In this case, the braking device 4 is of the floating caliper disc type. It comprises at least two friction elements 5a, 5b intended to cooperate by friction respectively with two opposite faces of a disc 22, which is rotationally fixed to a wheel 3 of the vehicle 1.

[0053] The braking device 4, according to this first embodiment, is of the disc and electromechanical type. By "electromechanical disc braking device 4", we mean all types of braking device 4 comprising at least one electric actuator intended to bring the friction elements 5a, 5b closer together in order to laterally clamp the disc 22 attached to the wheel 3 of the vehicle 1 to brake it.

[0054] The braking device 4 is equipped with a caliper 6, which in this case is floating. It should be noted that, in an alternative (not shown), the invention also applies to a braking device 4 with a fixed caliper. The braking device 4 further comprises a bracket 7 fixed relative to the vehicle 1, the caliper 6 being movable relative to the bracket 7 and arranged to bring the friction element 5b closer once the friction element 5a is in contact with the disc 22. Such a braking device 4 of the floating caliper type allows for the use of fewer electric actuators than a fixed caliper type, and is thus more compact.

[0055] The electric actuator includes an electric motor 8 that provides the braking force to the braking device 4. The electric motor 8 includes a movable output shaft that rotates when the electric motor 8 is actuated. The braking device 4 further includes a mechanism 9 for converting the rotational motion of the output shaft of the electric motor 8 into translational motion in order to allow the relative movement between the friction elements 5a, 5b between a rest position and a braking position in which the friction elements 5a, 5b grip the brake disc. In this case, the rotational motion conversion mechanism 9 is of the screw-nut type. It is understood that other embodiments use different types of conversion mechanisms.

[0056] According to the invention, the braking device 4 comprises a component of interest whose deformation is indicative of the braking force applied by the braking device 4. In the first embodiment, the component of interest is represented by the caliper 6. In other embodiments, another component of the braking device 4 is chosen as the component of interest.

[0057] According to the first embodiment, the stirrup 6 comprises two holes forming housings 10 for receiving the means for determining a deformation of the component of interest (Figures 3 and 4). As shown in Figure 3, a first hole is provided substantially at the level of the arch of the stirrup 6, and a second hole is formed through a wall of the stirrup, forming a bearing surface for the nut of the screw-nut type device (see Figure 4). According to other embodiments, the number of holes varies and is, for example, between one and ten, preferably between two and five, and preferably again between two and four.

[0058] The braking device 4 further includes means for determining the braking force, the means for determining the braking force including means for determining a deformation of the component of interest – i.e. the caliper 6 in the present case.

[0059] According to the first embodiment, the means for determining a deformation of the member of interest comprise two strain gauges 11 each intended to measure a deformation of the stirrup 6, and two test bodies 12, each test body 12 being fixed respectively to one of the strain gauges 11 on the one hand and to one of the two housings 10 of the stirrup 6 on the other hand.

[0060] Figure 12 represents a test specimen according to the first embodiment. In this case, the two test specimens 12 are formed by rods having a shape complementary to that of the recesses 10 formed by holes in the bracket 6. Each rod includes a recess forming a housing 13 for receiving a strain gauge 11. The strain gauges 11 are fixed in their respective receiving recesses 13 by any means known to those skilled in the art. Preferably, the strain gauges 11 are embedded in adhesive within the receiving recess 13 of a strain gauge 11 to secure the strain gauges 11 to the test specimens 12. As shown in Figures 3 and 4, each rod forming one of the test specimens 12 is embedded respectively in one of the recesses 10 formed by holes in the bracket 6.

[0061] According to the first embodiment, it is understood that the test bodies 12 are formed by non-functional components of the braking device 4. In other words, the test bodies 12 according to the first embodiment do not participate in the braking function. If these test bodies 12 were removed, the braking device 4 could continue to function.

[0062] In this case, each test body 12 is made of a material having a coefficient of thermal expansion β measured between 20°C and 100°C that satisfies 0.95α < β < 1.05α, where α is the coefficient of thermal expansion measured between 20°C and 100°C of the material from which the component of interest in the braking system is made – i.e., the caliper 6 in this case. In other words, β = α ± 5%. The materials used to manufacture the caliper 6 and the test bodies 12 may be freely chosen by a person skilled in the art to ensure that this criterion is met. The fact that the coefficient of thermal expansion β of the test body 12 is close to the coefficient of thermal expansion α of the stirrup 6 ensures that the test body 12 and the stirrup 6 react in a very similar way to temperature variations.This improves the reliability of the caliper 6 deformation measurement and therefore the reliability of the braking force determination. The test specimen 12 is fixed to the housing 10 for receiving the means for determining the deformation of the component of interest and is intended to transmit at least a portion of the deformation of the component of interest to the strain gauge 11.

[0063] According to this embodiment, each test body 12 is made of a material having an elongation at break greater than the elongation at break of the material in which the component of interest is made – that is, the stirrup 6 in this case. Thus, none of the test bodies 12 is likely to break in the event of excessive deformation of the component of interest, and each test body 12 is capable of performing its function over the entire range of possible deformation of the component of interest.

[0064] Each strain gauge 11 is equipped with means for connecting to an electronic control unit (not shown) which is housed in the housing 14 of the geared motor 15. As can be seen in the figure, one of the two strain gauges 11 is advantageously partially housed within the housing 14 of the geared motor 15. Thus, the connection of this strain gauge 11 to the electronic control unit can be made directly in the geared motor housing without the need for additional connecting wires 16. The other strain gauge 11 is housed at the arch of the yoke 6. Therefore, connecting wires 16 are essential to allow connection to the electronic control unit. A portion of these connecting wires 16 is shown in the figure.

[0065] The braking system 2 further includes a computer intended to receive, on the one hand, information relating to a deformation of the component of interest of the braking device – i.e. the caliper 6 in the present case – from the means of determining a deformation of the component of interest and to deduce an effective braking force, and, on the other hand, a target braking force instruction, the computer being able to compare the target braking force instruction and the effective braking force and to control the braking device so as to match the target braking force instruction and the effective braking force.

[0066] Advantageously, the means for determining the braking force are expected to include an analog-to-digital converter operating in the effective braking domain to process the information transmitted by the strain gauge 11.

[0067] For the manufacture of the braking device 4, a strain gauge 11 is first fixed to a test body 12 in the form of a rod by embedding the strain gauge 11 in adhesive within the housing 13 for receiving the strain gauge 11. Secondly, the assembly comprising the strain gauge 11 and the test body 12 in the form of a rod is fixed in one of the housings 10 for receiving the means for determining the deformation of the component of interest. Preferably, the step of fixing the assembly comprising the strain gauge 11 and the test body 12 to the caliper 6 is carried out at the end of the manufacturing process of the braking device 4. In this case, the fixing of the test body 12 to the caliper 6 is achieved by inserting the rod forming the test body 12 into the housings 10 formed by holes having a shape complementary to the rod.

[0068] Preferably, once the assembly including the strain gauge 11 and the test body 12 is mounted on the caliper, a calibration step of the strain gauge 11 is provided in order to take into account the particularities of the braking device on which the strain gauge 11 is mounted and thus improve the reliability of the determination of the braking force.

[0069] A method for regulating the braking force of a braking system 2, as described previously, is described below. The method comprises the following steps: a) receiving a target braking force instruction. This step corresponds, for example, to a brake pedal command or a command issued by an advanced driver assistance system. b) determining the effective braking force using the braking force determination means of the braking device 4.As already explained, the measurement of the deformation of the caliper 6 using the deformation gauges 11 allows the braking force to be determined, c) comparison of the effective braking force to the target braking force, d) regulation of the braking force by commanding the braking device 4 to increase the braking force if the effective braking force is less than the target braking force and by commanding the braking device 4 to decrease the braking force if the effective braking force is greater than the target braking force, this step of regulating the braking force being implemented until the effective braking force is equal to the target braking force.

[0070] Second embodiment

[0071] We describe below the second embodiment of the invention by reference to figures 6 and 7, only with regard to the differences compared to the first embodiment.

[0072] According to the second embodiment, the braking device 4 is of the floating caliper and disc type and is composite. The braking device 4 is described as composite, or hybrid, in that the caliper 6 is formed in two parts made of two different materials. For example, the first part of the caliper 6A is made of spheroidal graphite cast steel and the second part of the caliper 6B is made of aluminum alloy. According to other embodiments, other materials may be used.

[0073] As in the first embodiment, the component of interest is formed by the caliper 6A, 6B (which is here formed in several parts). The means for determining the deformation of the caliper 6A, 6B comprise, in this case, a single deformation gauge 11 which is fixed to a test body 12 in the form of a screw having a recess forming a housing 13 for receiving the deformation gauge 11. The housing 10 for receiving the means for determining the deformation of the component of interest is formed by a tapped hole provided in the two parts 6A, 6B of the caliper. The screw here forms a functional component of the braking device since it is an assembly screw used to fasten the two parts 6A, 6B of the caliper together. The screw is therefore screwed into the tapped hole so as to hold the two parts 6A, 6B of the caliper 6 together.

[0074] Third mode of implementation

[0075] We describe below the third embodiment of the invention with reference to Figures 8 and 9 only with regard to the differences with the first embodiment. This example is described for a single-piece caliper, but could also be applied to a composite caliper.

[0076] According to the third embodiment, the means for determining a deformation of the member of interest comprise three strain gauges 11 and three test bodies 12, each strain gauge 11 being respectively fixed to one of the test bodies 12. In this example, a strain gauge 11 is fixed on the outer surface of the arch of the stirrup 6 in its central part (bottom left of the), a second strain gauge 11 is fixed in the extension of the bearing wall of the stirrup (in the middle at the top of the), that is to say at the location where the arch connects to the body of the stirrup 6, and a third strain gauge 11 is fixed on the outer surface of the body of the stirrup (bottom right of the).

[0077] According to the third embodiment, each test specimen 12 is formed by a plate, the housing 10 for receiving the means for determining a deformation of the component of interest being formed by a recess on an external surface of the bracket 6. Each plate has a first face on which the deformation gauge 11 is fixed and a second face, opposite the first face, fixed to the recess on the bracket 6. Advantageously, the surface of the recess is flat and complementary to the plate. According to the present embodiment, the plate includes two through openings 17 for screwing the plate onto the recess in the bracket 6.Depending on the embodiment variants, the plate is fixed differently on the recess, for example by gluing or welding or gluing and screwing, or any other means to prevent the plate from slipping relative to the bracket and to couple its deformation with that of the component of interest.

[0078] Fourth mode of implementation

[0079] We describe below the fourth embodiment of the invention by reference to figures 10 and 11 only with regard to the differences compared to the first embodiment.

[0080] According to the fourth embodiment, the braking device 4 is of the drum type. Thus, the braking device 4 comprises a base plate 20, a drum (not shown), shoes 18 carrying friction linings designed to rub against the drum to brake it, and an electric or hydraulic actuator 21 for moving at least one of the shoes 18 towards the drum to achieve braking. The braking device 4 further comprises a fixed point 19, also called an anchor point or fulcrum.

[0081] According to the fourth embodiment, the means for determining the deformation of the component of interest comprise three strain gauges 11 and three test specimens, each strain gauge 11 being fixed to one of the test specimens 12. In this case, two of the test specimens 12 are formed by rods embedded in complementary shaped holes provided in the fixed point 19. As described previously, these rods include recesses forming a housing 13 for receiving the strain gauge 11. It is understood that these two rod-shaped test specimens 12 constitute non-functional components of the braking device in that they do not participate in the braking function, either directly or indirectly. The third test specimen 12 forms an assembly screw for fixing the fixed point 19 to the base plate 20.It is therefore understood that the test body 12 in the form of an assembly screw forms here a functional component of the braking device 4.

[0082] Because the fixed point 19 receives the tangential support of the jaws 18 during braking, and thus transmits a braking torque to the plate or the fixed part of the brake, it is subjected to forces and deformations which depend directly on the braking force exerted by the actuator 21. This fixed point 19 here forms an element of interest, whose deformations are measured by means of determining a deformation in order to evaluate the intensity of the braking force.

[0083] The invention is not limited to the embodiments shown and other embodiments will be obvious to a person skilled in the art. List of references

[0084] 1: vehicle 2: braking system 3: wheel 4: braking device 5A, 5B: friction element 6: caliper 6A: first part of the caliper 6B: second part of the caliper 7: yoke 8: electric motor 9: mechanism for converting the rotational motion of the electric motor's output shaft into translational motion 10: housing for the means of determining a deformation of the component of interest 11: strain gauge 12: test body 13: housing for the strain gauge 14: geared motor housing 15: geared motor 16: connecting wires between the strain gauge and the electronic control unit 17: through opening 18: jaw 19: fixed point 20: base plate 21: hydraulic or electric actuator 22: disc

Claims

Braking device (4) for a vehicle (1), comprising: - a component of interest (6, 19), - means for determining the braking force, the means for determining the braking force comprising means for determining a deformation of the component of interest (6, 19) housed in a housing (10) for receiving the means for determining a deformation of the component of interest provided in the component of interest (6, 19), the means for determining a deformation of the component of interest comprising: - at least one deformation gauge (11) intended to measure a deformation of the component of interest (6, 19), and - at least one test body (12) to which the deformation gauge (11) is fixed, the test body (12) being fixed to the housing (10) for receiving the means for determining a deformation of the component of interest and being intended to transmit at least a portion of a deformation of the component of interest (6, 19) to the strain gauge (11),characterized in that the test body (12) is made of a material having a coefficient of thermal expansion β measured between 20°C and 100°C which satisfies 0.95α < β < 1.05α, where α is the coefficient of thermal expansion measured between 20°C and 100°C of the material in which the component of interest (6, 19) of the braking device is made. Braking device (4) according to claim 1, wherein the test body (12) is formed by a functional element of the braking device. Braking device (4) according to claim 1, wherein the test body (12) is formed by a non-functional element, from the point of view of braking mechanics, of the braking device. Braking device (4) according to any one of the preceding claims, wherein the test body (12) is formed by a screw comprising a recess forming a housing (13) for receiving the strain gauge (11), and wherein the housing (10) for receiving the means for determining a strain of the member of interest is formed by a tapped hole provided in the member of interest (6, 19) of the braking device (4), the screw being screwed into the tapped hole. Braking device (4) according to claim 4, wherein the screw is an assembly screw of the braking device (4). Braking device (4) according to any one of claims 1 to 3, wherein the test body (12) is formed by a rod comprising a recess forming a housing (13) for receiving the strain gauge (11), and wherein the housing (10) for receiving the means for determining a strain of the member of interest is formed by a hole of complementary shape to the rod provided in the member of interest (6, 19) of the braking device (4), the rod being embedded in the hole of complementary shape to the rod. Braking device (4) according to any one of claims 1 to 3, wherein the test body (12) is formed by a plate, and wherein the housing (10) for receiving the means for determining a deformation of the member of interest (6, 19) is formed by a recess made on an external surface of the member of interest (6, 19), the plate having a first face on which the deformation gauge (11) is fixed and a second face, opposite to the first face, fixed on the recess of the member of interest (6, 19) of the braking device (4). Braking device (4) according to any one of the preceding claims, wherein the test body (12) is made of a material having an elongation at break greater than an elongation at break of the material in which the member of interest (6, 19) is made. Braking device (4) according to any one of the preceding claims, wherein the element of interest (6, 19) is selected from a caliper (6) of a disc braking device (4) or a fixed point (19) of a drum braking device (4). braking device (4) according to the preceding claim, wherein the braking device is of the electromechanically actuated disc type and comprises a mechanism (9) for converting a rotational movement of an output shaft of an electric motor (8) into a translational movement of a clamping member of the braking device (4), the conversion mechanism (9) comprising a screw-nut type device, the member of interest being a caliper (6) of the disc type braking device (4), the housing (10) for receiving the means for determining a deformation of the member of interest (6) extending through a wall of the caliper (6) forming a support plane for the nut of the screw-nut type device. Braking device (4) according to any one of the preceding claims, wherein the means for determining a deformation of the member of interest (6, 19) comprise at least two strain gauges (11) and at least two test bodies (12), each strain gauge (11) being fixed respectively to one of the test bodies (12), the strain gauges (11) being intended to each measure a deformation of the member of interest (6, 19) of the braking device (4) or the strain gauges (11) being intended to each measure respectively a deformation of a first member of interest (6, 19) of the braking device (4) and of a second member of interest (6, 19) of the braking device (4). Vehicle (1), characterized in that it comprises at least one braking device (4) according to any one of the preceding claims. Braking system (2) for vehicle (1), characterized in that it comprises a braking device (4) according to any one of claims 1 to 11 and a computer intended to receive, on the one hand, information relating to a deformation of the component of interest (6, 19) of the braking device (4) from the means for determining a deformation of the component of interest (6, 19) and to deduce an effective braking force therefrom, and, on the other hand, a target braking force instruction, the computer being capable of comparing the target braking force instruction and the effective braking force and of controlling the braking device so as to match the target braking force instruction and the effective braking force. A method for regulating the braking force of a braking system (2), characterized in that, the braking system (2) being according to claim 13, the method comprises the following steps: a) receiving an instruction of a target braking force, b) determining the effective braking force using the braking force determination means of the braking device, c) comparing the effective braking force to the target braking force, d) regulating the braking force by commanding the braking device (4) to increase the braking force if the effective braking force is less than the target braking force and by commanding the braking device (4) to decrease the braking force if the effective braking force is greater than the target braking force, this braking force regulation step being carried out until the effective braking force is equal to the target braking force. Method of manufacturing a braking device (4) for a vehicle (1) according to any one of claims 1 to 11, characterized in that: a) a strain gauge (11) intended to measure a deformation of at least one element of interest (6, 19) of the braking device (4) is fixed on a test body (12), and b) the assembly comprising the strain gauge (11) and the test body (12) obtained in step a) is fixed in a housing (10) provided on an element of interest (6, 19) of the braking device (4). Manufacturing method according to the preceding claim, further comprising a step c) of calibration of the strain gauge (11).

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