Automobile drum brake and control method thereof

Abstract

The application discloses a kind of automobile drum brake and its control method, including brake bottom plate, first brake shoe, second brake shoe, drive assembly and reset component, first brake shoe and second brake shoe are oppositely installed on brake bottom plate along brake bottom plate longitudinal axis, reset component is installed between first brake shoe and second brake shoe, drive assembly is symmetrically installed along brake bottom plate transverse axis, drive assembly includes interconnection cam device and drive motor, cam device is equipped with self-locking component, and the both ends of first brake shoe and second brake shoe contact point are respectively contacted with cam device. Through the control of positive and negative rotation of cam device by double motor common braking, cooperate with self-locking component, improve the reliability of parking lock, when one motor fails, temporary emergency braking can be completed by single motor, improve the fault tolerance and safety of system, equipped with force sensor and displacement sensor to collect parameters during braking, and then judge fault and wear condition, feedback in time.

Description

Technical Field

[0001] This invention relates to an automotive drum brake and its control method, belonging to the field of brake technology. Background Technology

[0002] With the rapid development of electric vehicle technology, electronically controlled intelligent vehicle technologies are increasingly being applied to automobiles. Drive-by-wire technology is a new type of control system based on information interaction systems and real-time control. Drive-by-wire braking technology includes EHB and EMB. EHB is a braking system that combines traditional hydraulic control and electronic control, while EMB uses an ECU to control the solenoid valves of the brake, causing the brake pads to contact the brake disc and achieve braking. However, with the widespread application of electronic control technology, EMB is the main development direction of drive-by-wire braking technology due to its ease of installation, more precise control, and suitability for the development of intelligent electric vehicles. EMB abandons traditional hydraulic and pneumatic control and related components, using electrical signals to control related mechanical structures to complete braking.

[0003] Drum brakes utilize a brake transmission mechanism to press the brake shoes against the brake friction pads inside the brake drum, thereby generating braking force and enabling the vehicle to brake as required. Traditional drum brakes often perform braking operations through hydraulic transmission, with the brake drum as the rotating element and the brake shoes as the stationary element. However, traditional hydraulic drum brakes are no longer suitable for the current trend of electromechanical braking. To further respond to the development of drive-by-wire chassis, drum brakes need to be electronically controlled.

[0004] However, electronic drive-by-wire technology also has certain problems. When the motor or circuit fails, the braking requirement cannot be completed smoothly, and the system has insufficient fault tolerance. Patent CN107725638A discloses a method to improve the structure of brake shoes and friction pads to compensate for the short replacement cycle of friction pads and the short service life of brakes. However, in the parking lock condition, it only relies on the cam mechanism to open the brake shoes for braking, which cannot guarantee the reliability of parking lock. At the same time, due to the unreliable braking effect, it will lead to inaccurate judgment of brake wear. Although it can improve the replacement cycle of friction pads, it cannot accurately judge the wear degree of brake shoes, thus making timely maintenance impossible. Summary of the Invention

[0005] Purpose of the invention: To address the shortcomings of existing technologies, this invention provides an automotive drum brake and its control method. By setting a self-locking component on the cam device and controlling the forward and reverse rotation of the cam device through a drive motor, and by using displacement sensors and force sensors to jointly detect the degree of wear, this invention solves the problems of unreliable parking locks and inability to determine the degree of wear.

[0006] Technical solution: A drum brake for automobiles includes a brake base plate, a first brake shoe, a second brake shoe, a drive assembly, and a reset assembly. The first and second brake shoes are mounted opposite each other on the brake base plate along its longitudinal axis. A reset assembly is installed between the first and second brake shoes. The drive assembly is symmetrically mounted along the transverse axis of the brake base plate. The drive assembly includes a cam device and a drive motor connected to each other. The cam device is equipped with a self-locking component. The two end contacts of the first and second brake shoes respectively contact the cam device.

[0007] This invention improves the reliability of parking lock by using dual motors to control the forward and reverse rotation of the cam device and installing a self-locking component on the cam device. The parking lock function can be realized without an additional system, reducing production costs. The overall structure is simple, and because dual motor control is used, it is equivalent to having a redundant system. If one motor fails, emergency temporary braking can still be completed by a single motor through the original structure, thus handling the fault situation and improving the fault tolerance and safety of the system.

[0008] In a preferred embodiment, in order to simultaneously drive the first brake shoe and the second brake shoe, the cam device includes a first cam mechanism and a second cam mechanism, which are symmetrically installed along the transverse axis of the brake base plate.

[0009] In a preferred embodiment, in order to simultaneously lock the first cam mechanism and the second cam mechanism, at least two sets of self-locking components are provided on the first cam mechanism and the second cam mechanism, and the self-locking components on the first cam mechanism and the second cam mechanism are respectively centrally symmetrical.

[0010] In a preferred embodiment, to improve the reliability of parking lock, the self-locking assembly includes a protrusion and a recess, the recess contacting the two end contacts of the first and second brake shoes respectively. When the vehicle is braked, the two end contacts of the first and second brake shoes move along the outer surfaces of the first and second cam mechanisms respectively, with the displacement not exceeding the protrusion. When parking lock is engaged, a reversing motor causes the two end contacts of the first and second brake shoes to enter the recess and contact the protrusion. At this point, the first cam mechanism and the second cam mechanism cannot continue to reverse in the parking state via the motor, thereby achieving the purpose of parking lock and improving the reliability of parking lock.

[0011] In a preferred embodiment, to reset the first and second brake shoes, a fixed seat is installed on the brake base plate. The reset assembly includes a reset groove, a limiting rod, and a reset spring. One end of the limiting rod is fixedly connected to the first brake shoe, and the other end slides within the reset groove. One end of the reset spring is connected to the fixed seat, and the other end is connected to the first brake shoe. An identical reset assembly is provided between the second brake shoe and the fixed seat, and at least two sets of reset assemblies are provided between the first and second brake shoes. When braking, the drive motor controls the first and second cam mechanisms to rotate, causing the first and second brake shoes to expand outwards. At this time, the limiting rod slides outwards within the reset groove, and the reset spring is in an extended state. When the vehicle resumes operation, the drive motor resets, and the first and second brake shoes are pulled back to their initial positions by the reset spring. The reset groove acts as a guide, allowing the limiting rod to move outwards horizontally, preventing displacement deviation of the first and second brake shoes during movement, thereby ensuring the stability of the braking process.

[0012] In a preferred embodiment, to determine the degree of brake wear during braking, a force sensor is installed on the fixed base, and the other end of the return spring is connected to the force sensor installed on the fixed base. The force sensor records the magnitude of the received tension in real time during braking, compares the recorded data with pre-calibrated data, and calculates the current wear state of the brake.

[0013] In a preferred embodiment, to determine the degree of brake wear during braking, a displacement sensor is installed on the brake base plate near the reset groove. The displacement sensor records the horizontal displacement of the limit rod in real time during braking, thereby determining the current wear state of the brake.

[0014] In a preferred embodiment, to ensure the stability of braking under single-motor drive, the end of the reset groove near the fixed base is provided with an enlarged groove extending longitudinally. In the event of a fault, to ensure sufficient space for the limit rod to complete longitudinal displacement when only a single motor is operating, the stability and safety of the braking process are guaranteed, thereby completing temporary emergency braking of the single motor.

[0015] A control method for an automotive drum brake includes a service braking condition, a parking lock condition, and a fault condition; the specific steps for the service braking condition, the parking lock condition, and the fault condition are as follows:

[0016] Service braking condition: When the driver applies the service brake, the drive motor drives the first cam mechanism to rotate clockwise and simultaneously drives the second cam mechanism to rotate counterclockwise. The first cam mechanism and the second cam mechanism respectively push the first brake shoe and the second brake shoe to expand outward in the horizontal direction and contact the brake drum to generate braking force to stop the vehicle. If the braking force is not generated in time, the output signal of the drive motor needs to be adjusted in time to generate braking force to stop the vehicle. The displacement sensor and force sensor record the displacement of the limit rod and the tension of the return spring in real time.

[0017] Parking lock operation: When the driver locks the vehicle, the drive motor drives the first cam mechanism and the second cam mechanism to rotate counterclockwise and clockwise respectively, so that the two end contacts of the first brake shoe and the second brake shoe contact the groove. At the same time, the first cam mechanism and the second cam mechanism push the first brake shoe and the second brake shoe to expand outward in the horizontal direction and contact the brake drum to generate braking force to stop the vehicle. If the braking force is not generated in time, the output signal of the drive motor needs to be adjusted in time to generate braking force to stop the vehicle. The displacement sensor and the force sensor record the displacement of the limit rod and the tension of the return spring in real time.

[0018] Fault condition: When the second cam mechanism fails, a single motor is used for braking. At this time, the first cam mechanism rotates clockwise under the drive of the drive motor, thereby pushing the first and second brake shoes to expand outward and contact the brake drum, generating braking force to stop the vehicle, and sending a fault signal to the driver.

[0019] The preferred option, in order to accurately determine the wear level of the brake shoes and thus carry out timely maintenance, also includes wear feedback, the specific steps of which are as follows:

[0020] During braking, the wear condition of the brakes is determined by feedback data from displacement sensors and force sensors. The displacement sensors record the displacement amounts L1 and L2 of the first and second brake shoes, and L1 and L2 are compared. The larger displacement amount is recorded as L. b The smaller displacement is denoted as L. s Determine L b Is it less than the maximum displacement threshold L? max If so, then determine L. s Is it greater than the minimum displacement threshold L? min If not, it means that the brake is malfunctioning at this time; if L s Greater than the minimum displacement threshold L min If the value is 0, it means the brake is in good condition; otherwise, it means the brake is malfunctioning.

[0021] Set a tolerance value x, define the maximum value of the tension value received by the force sensor on the return spring as N, compare the tension value on the return spring with the tension threshold Nx, if it is less than the tension threshold Nx, it means that the brake shoe corresponding to the return spring is worn, and feed the wear signal back to the driver.

[0022] Beneficial effects: This invention controls the forward and reverse rotation of the cam device through dual-motor joint braking, and, in conjunction with a self-locking component, improves the reliability of parking lock. Parking lock functionality can be achieved without an additional system, reducing production costs. The overall structure is simple. Due to the use of dual-motor control, temporary emergency braking can be completed using a single motor if one motor fails, improving the system's fault tolerance and safety. Once the system braking is stable and the fault has been resolved, force and displacement sensors collect parameters during braking to determine the fault and wear condition, adjust the motor output signal, achieve precise braking, and provide timely feedback on faults and wear conditions, facilitating subsequent maintenance. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of the present invention;

[0025] Figure 2 This is a diagram of the internal structure of the present invention;

[0026] Figure 3 This is a schematic diagram of the vehicle braking operation of the present invention;

[0027] Figure 4 This is a schematic diagram of the parking lock working condition of the present invention;

[0028] Figure 5 This is a schematic diagram of the fault conditions of the present invention;

[0029] Figure 6 This is a flowchart of the method of the present invention. Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] like Figure 1 As shown, an automotive drum brake includes a brake base plate 1, a first brake shoe 2, a second brake shoe 3, a drive assembly 4, and a reset assembly 5. The first brake shoe 2 and the second brake shoe 3 are mounted opposite each other on the brake base plate 1 along the longitudinal axis of the brake base plate 1. The reset assembly 5 is installed between the first brake shoe 2 and the second brake shoe 3. The drive assembly 4 is symmetrically mounted along the transverse axis of the brake base plate 1. The drive assembly 4 includes a cam device 41 and a drive motor 42 connected to each other. The cam device 41 is provided with a self-locking component 6. The two end contacts of the first brake shoe 2 and the second brake shoe 3 respectively contact the cam device 41.

[0034] By employing dual motors to control the forward and reverse rotation of the cam mechanism and installing a self-locking component on the cam mechanism, the reliability of parking lock is improved. The parking lock function can be achieved without an additional system, reducing production costs. The overall structure is simple, and because dual motor control is used, it is equivalent to having a redundant system. If one motor fails, emergency temporary braking can still be completed through the original structure using a single motor to handle the fault situation, thus improving the system's fault tolerance and safety.

[0035] like Figure 2 As shown, in order to simultaneously drive the first brake shoe and the second brake shoe, the cam device 41 includes a first cam mechanism 411 and a second cam mechanism 412, which are symmetrically installed along the transverse axis of the brake base plate 1.

[0036] In order to lock the first cam mechanism 411 and the second cam mechanism 412 simultaneously, at least two sets of self-locking components 6 are provided on the first cam mechanism 411 and the second cam mechanism 412 respectively, and the self-locking components 6 on the first cam mechanism 411 and the second cam mechanism 412 are respectively centrally symmetrical.

[0037] To improve the reliability of parking lock, the self-locking assembly 6 includes a protrusion 61 and a recess 62, with the recess 62 contacting the two end contacts of the first brake shoe 2 and the second brake shoe 3, respectively. During service braking, the two end contacts of the first and second brake shoes move along the outer surfaces of the first cam mechanism 411 and the second cam mechanism 412, with the displacement not exceeding the protrusion. When parking lock is engaged, a reversing motor causes the two end contacts of the first and second brake shoes to enter the recess and contact the protrusion. At this point, the first cam mechanism and the second cam mechanism cannot continue to reverse via the motor in the parking state, thus achieving the purpose of parking lock and improving the reliability of parking lock.

[0038] To reset the first and second brake shoes, a fixed seat 12 is installed on the brake base plate 1. The reset assembly 5 includes a reset groove 51, a limiting rod 52, and a reset spring 53. One end of the limiting rod 52 is fixedly connected to the first brake shoe 2, and the other end slides within the reset groove 51. One end of the reset spring 53 is connected to the fixed seat 12, and the other end is connected to the first brake shoe 2. The second brake shoe 3 is connected to the fixed seat 12, and at least two sets of reset assemblies 5 are provided between the first brake shoe 2 and the second brake shoe 3. When braking, the drive motor controls the first cam mechanism and the second cam mechanism to rotate, causing the first and second brake shoes to expand outwards. At this time, the limiting rod slides outwards within the reset groove, and the reset spring is in an extended state. When the vehicle resumes operation, the drive motor resets, and the first and second brake shoes are pulled back to their initial positions by the reset spring. The reset groove acts as a guide, allowing the limiting rod to move outwards horizontally, preventing displacement deviation of the first and second brake shoes during movement, thus ensuring the stability of the braking process. This embodiment uses four sets of reset components for control.

[0039] To determine the wear level of the brake during braking, a force sensor 7 is installed on the fixed base 12, and the other end of the return spring 53 is connected to the force sensor 7 installed on the fixed base 12. The force sensor records the received tension in real time during braking, compares the recorded data with pre-calibrated data, and calculates the current wear state of the brake.

[0040] To determine the wear level of the brake during braking, a displacement sensor 8 is installed on the brake base plate 1 near the reset groove 51. The displacement sensor records the horizontal displacement of the limit rod in real time during braking, thereby determining the current wear state of the brake.

[0041] To ensure the stability of braking under single-motor drive, the reset groove 51 is provided with an enlarged groove 54 extending longitudinally at one end near the fixed base 12. In the event of a fault, to ensure that only a single motor is working, there is sufficient space for the limit rod to complete longitudinal displacement, thus ensuring the stability and safety of the braking process and completing the temporary emergency braking of the single motor.

[0042] like Figures 3-6 As shown, a control method for an automotive drum brake includes a service braking condition, a parking lock condition, and a fault condition; the specific steps for the service braking condition, the parking lock condition, and the fault condition are as follows:

[0043] Service braking condition: When the driver applies the service brake, the drive motor 42 drives the first cam mechanism 411 to rotate clockwise and simultaneously drives the second cam mechanism 412 to rotate counterclockwise. The first cam mechanism 411 and the second cam mechanism 412 respectively push the first brake shoe 2 and the second brake shoe 3 to expand outward in the horizontal direction and contact the brake drum to generate braking force to stop the vehicle. If the braking force is not generated in time, the output signal of the drive motor 42 needs to be adjusted in time to generate braking force to stop the vehicle. The displacement sensor 8 and the force sensor 7 record the displacement of the limit rod 52 and the tension of the return spring 53 in real time.

[0044] Parking lock operation: When the driver locks the vehicle, the drive motor 42 drives the first cam mechanism 411 and the second cam mechanism 412 to rotate counterclockwise and clockwise respectively, so that the two end contacts of the first brake shoe 2 and the second brake shoe 3 contact the groove 62 respectively. At the same time, the first cam mechanism 411 and the second cam mechanism 412 push the first brake shoe 2 and the second brake shoe 3 to expand outward in the horizontal direction and contact the brake drum to generate braking force to stop the vehicle. If the braking force is not generated in time, the output signal of the drive motor 42 needs to be adjusted in time to generate braking force to stop the vehicle. The displacement sensor 8 and the force sensor 7 record the displacement of the limit rod 52 and the tension of the return spring 53 in real time.

[0045] Fault condition: When the second cam mechanism 412 fails, a single motor is used for braking. At this time, the first cam mechanism 411 rotates clockwise under the drive of the drive motor 42, thereby pushing the first brake shoe 2 and the second brake shoe 3 to expand outward and contact the brake drum, generating braking force to stop the vehicle, and sending a fault signal to the driver.

[0046] To accurately determine the wear level of the brake shoes and thus perform timely maintenance, wear feedback is also included. The specific steps are as follows:

[0047] During braking, the wear condition of the brake is determined by feedback data from displacement sensor 8 and force sensor 7. Displacement sensor 8 records the displacement amounts L1 and L2 of the first brake shoe 2 and the second brake shoe 3, and compares L1 and L2, recording the larger displacement amount as L. b The smaller displacement is denoted as L. s Determine L b Is it less than the maximum displacement threshold L? max If so, then determine L. s Is it greater than the minimum displacement threshold L? min If not, it means that the brake is malfunctioning at this time; if L s Greater than the minimum displacement threshold L min If the value is 0, it means the brake is in good condition; otherwise, it means the brake is malfunctioning.

[0048] Set a tolerance value x, define the maximum value of the tension value received by the return spring 53 through the force sensor 7 as N, compare the tension value received by the return spring 53 with the tension threshold Nx, if it is less than the tension threshold Nx, it means that the brake shoe corresponding to the return spring 53 is worn, and feed the wear signal back to the driver.

[0049] When the friction pads on the first and second brake shoes wear out, the first and second brake shoes need a greater displacement to contact the brake drum. This requires the cam device to rotate a larger angle. If the required displacement is greater than the maximum displacement threshold, it indicates that the wear is more serious and the brake clearance is too large. The driver should be warned to avoid braking safety problems.

[0050] When the cam mechanism and the first and second brake shoes wear down, this wear will cause the cam mechanism to have a smaller displacement when rotating to the same angle compared to when there is no wear. In cases of particularly severe wear, the displacement when either brake shoe applies brakes will be less than the preset minimum displacement threshold L. min If this happens, the brake pad is close to failure and needs to be repaired.

[0051] Since this wear is generally not symmetrical, meaning that the left and right sides of the cam mechanism may have different levels of wear, the brake pad return spring may exhibit different deformations. When asymmetrical wear prevents the brake pad from moving smoothly, the force sensor can be used to pinpoint which part of the brake pad has experienced more severe wear.

[0052] When mixed wear occurs, meaning the friction pads, cam mechanism, and first and second brake shoes are all worn, the condition is judged by the displacement on both sides. When wear exists in both the brake shoes and their internal components, the rotation angle of the cam mechanism will also be larger. In this case, it is necessary to consider whether the displacement is less than the maximum displacement threshold L. max Since the maximum displacement threshold is a calibration value that takes into account a certain amount of wear, the system will only issue a danger warning and adjust L after relatively severe wear occurs. s and L min Comparison, if less than L min This indicates that the internal wear is also quite severe. At the same time, the data obtained by the force sensor is used in conjunction with the displacement sensor to locate the wear position.

[0053] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0054] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An automobile drum brake, comprising a brake base plate (1), a first brake shoe (2), a second brake shoe (3), a drive assembly (4), and a reset assembly (5), wherein the first brake shoe (2) and the second brake shoe (3) are mounted opposite to each other on the brake base plate (1) along the longitudinal axis of the brake base plate (1), and a reset assembly (5) is installed between the first brake shoe (2) and the second brake shoe (3), wherein the drive assembly (4) is symmetrically mounted along the transverse axis of the brake base plate (1), and the drive assembly (4) comprises a cam device (41) and a drive motor (42) connected to each other, wherein a self-locking assembly (6) is provided on the cam device (41), and the two end contacts of the first brake shoe (2) and the second brake shoe (3) respectively contact the cam device (41); The cam device (41) includes a first cam mechanism (411) and a second cam mechanism (412), which are symmetrically installed along the transverse axis of the brake base plate (1). At least two sets of self-locking components (6) are provided on the first cam mechanism (411) and the second cam mechanism (412), and the self-locking components (6) on the first cam mechanism (411) and the second cam mechanism (412) are respectively centrally symmetrical; The self-locking assembly (6) includes a protrusion (61) and a groove (62), the groove (62) contacting the two end contacts of the first brake shoe (2) and the second brake shoe (3), respectively; characterized in that: A fixed seat (12) is installed on the brake base plate (1). The reset assembly (5) includes a reset groove (51), a limiting rod (52), and a reset spring (53). One end of the limiting rod (52) is fixedly connected to the first brake shoe (2), and the other end is set in the reset groove (51) for sliding. A force sensor (7) is installed on the fixed seat (12). One end of the reset spring (53) is connected to the force sensor (7) installed on the fixed seat (12), and the other end is connected to the first brake shoe (2). The second brake shoe (3) and the fixed seat (12) are provided with the same reset assembly (5), and at least two sets of reset assemblies (5) are provided between the first brake shoe (2) and the second brake shoe (3). A displacement sensor (8) is installed on the brake base plate (1) near the reset groove (51).

2. The automotive drum brake according to claim 1, characterized in that: The reset groove (51) has an expansion groove (54) extending longitudinally at one end near the fixed base (12).

3. The control method for an automotive drum brake according to claim 2, characterized in that: This includes the driving braking condition, the parking lock condition, and the fault condition; the specific steps for the driving braking condition, the parking lock condition, and the fault condition are as follows: Service braking condition: When the driver applies the service brake, the drive motor (42) drives the first cam mechanism (411) to rotate clockwise and at the same time drives the second cam mechanism (412) to rotate counterclockwise. The first cam mechanism (411) and the second cam mechanism (412) respectively push the first brake shoe (2) and the second brake shoe (3) to expand outward in the horizontal direction and contact the brake drum to generate braking force to stop. If the braking force is not generated in time, the output signal of the drive motor (42) needs to be adjusted in time to generate braking force to stop. The displacement sensor (8) and the force sensor (7) record the displacement of the limit rod (52) and the tension of the return spring (53) in real time. Parking lock operation: When the driver locks the vehicle, the drive motor (42) drives the first cam mechanism (411) and the second cam mechanism (412) to rotate counterclockwise and clockwise respectively, so that the two end contacts of the first brake shoe (2) and the second brake shoe (3) contact the groove (62) respectively. At the same time, the first cam mechanism (411) and the second cam mechanism (412) push the first brake shoe (2) and the second brake shoe (3) to expand outward in the horizontal direction and contact the brake drum to generate braking force to stop. If the braking force is not generated in time, the output signal of the drive motor (42) needs to be adjusted in time to generate braking force to stop. The displacement sensor (8) and the force sensor (7) record the displacement of the limit rod (52) and the tension of the reset spring (53) in real time. Fault condition: When the second cam mechanism (412) fails, a single motor is used for braking. At this time, the first cam mechanism (411) rotates clockwise under the drive of the drive motor (42), thereby pushing the first brake shoe (2) and the second brake shoe (3) to expand outward and contact the brake drum, generating braking force to stop the vehicle, and sending a fault signal to the driver.

4. The control method for an automotive drum brake according to claim 3, characterized in that: It also includes wear feedback, the specific steps of which are as follows: During braking, the wear condition of the brake is determined by the feedback data from the displacement sensor (8) and the force sensor (7). The displacement sensor (8) records the displacement amounts L1 and L2 of the first brake shoe (2) and the second brake shoe (3). L1 and L2 are compared, and the larger displacement amount is recorded as L. b The smaller displacement is denoted as L. s Determine L b Is it less than the maximum displacement threshold L? max If so, then determine L. s Is it greater than the minimum displacement threshold L? min If not, it means that the brake is malfunctioning at this time; if L s Greater than the minimum displacement threshold L min If the value is 0, it means the brake is in good condition; otherwise, it means the brake is malfunctioning. Set the tolerance value x, define the maximum value of the tension value received by the reset spring (53) through the force sensor (7) as N, compare the tension value received by the reset spring (53) with the tension threshold Nx respectively, if it is less than the tension threshold Nx, it means that the brake shoe corresponding to the reset spring (53) is worn, and feed the wear signal back to the driver.

Images