JP2015085897A - Electric parking brake system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric parking brake system capable of outputting wear warning with high accuracy.SOLUTION: An electric parking brake system 1 comprises: an electric parking brake device 10 having a PKB 13 including a friction member 14 for applying brake force to a wheel H and an actuator 11 for actuating the PKB 13 via a brake cable 12; a stroke change amount detection part 31 for detecting a stroke change amount of the brake cable 12; and a warning output part 40 for outputting wear warning based on the stroke change amount. The stroke change amount detection part 31 determines whether initial extension of the brake cable 12 is removed or not based on the actuation state of the electric parking brake device 10, and sets a predetermined position of the brake cable 12 when it is determined that the initial extension of the brake cable 12 is removed as a reference position for detecting the stroke change amount.

Description

  The present invention relates to an electric parking brake system.

  As a technique related to a conventional parking brake system, for example, Patent Document 1 below describes a parking brake device that uses a torque wrench attached to a grip of a brake lever as an attachment. In the parking brake device described in Patent Document 1, when a vehicle is shipped, the brake lever is turned upward with a large operation force of about twice the normal operation force to apply tension to the brake cable. It is intended to provide initial elongation.

Japanese Utility Model Publication No. 7-40328

  Incidentally, in recent years, an electric parking brake system in which a parking brake mechanism is operated by an actuator via a brake cable is known. In such an electric parking brake system, there may be a case where a wear warning related to wear of a friction member that applies braking force to a wheel is output based on a stroke change amount of the brake cable.

  In this regard, in the above-described prior art, there are cases where the stroke change amount of the brake cable still includes not only the wear of the friction member but also the extension of the brake cable. Therefore, there is a possibility that the adverse effect of the extension of the brake cable may reach the output of the wear alarm.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the electric parking brake system which can output a wear warning accurately.

  In order to solve the above-described problem, an electric parking brake system according to the present invention includes an electric parking brake mechanism including a friction member that applies a braking force to wheels, and an actuator that operates the parking brake mechanism via a brake cable. A parking brake device; a stroke change amount detecting means for detecting a stroke change amount of the brake cable; and an alarm means for outputting a wear warning regarding wear of the friction member based on the stroke change amount. Determines whether or not the initial elongation of the brake cable has been removed based on the operating status of the electric parking brake device, and determines the predetermined position of the brake cable when the initial elongation of the brake cable has been removed as the stroke change amount. Set as a reference position for detecting To, characterized in that.

  In this electric parking brake system, the stroke change amount detecting means determines the removal of the initial elongation of the brake cable (hereinafter also simply referred to as “initial elongation”) based on the operating state of the electric parking brake device, and the initial elongation is removed. The predetermined position of the brake cable when it is determined that the stroke has been determined is set as a reference position for detecting the stroke change amount. Here, after the initial elongation is removed, it is found that the influence of the elongation of the brake cable on the wear of the friction member becomes small in the stroke change amount. Therefore, the influence of the extension of the brake cable can be reduced with respect to the stroke change amount detected by the stroke change amount detecting means, so that a wear alarm can be output with high accuracy.

  Further, the stroke change amount detection means may determine whether or not the initial elongation of the brake cable has been removed based on the number of times that the parking brake mechanism is operated by an index load that is equal to or greater than a predetermined load and continues for a predetermined time. . In this case, the load amount and duration of the index load and the number of operations by the index load can be used as the determination condition for removing the initial elongation.

  Specifically, the predetermined load is the maximum index load with which the actuator can drive the parking brake mechanism, the predetermined time is 10 seconds, and the number of times is 250. The structure to do is mentioned.

  Further, the alarm means may not output the wear alarm until it is determined that the initial elongation of the cable has been removed. By preventing the wear warning from being output until the initial elongation is removed as described above, it is possible to suppress a false alarm due to the influence of the initial elongation and to output the wear warning with higher accuracy.

  According to the present invention, a wear alarm can be output with high accuracy.

It is the schematic which shows the structure of the electric parking brake system which concerns on one Embodiment. It is a graph explaining the elongation amount of a brake cable. It is a flowchart explaining operation | movement of the electric parking brake system of FIG. It is a figure which shows an example of the stroke variation | change_quantity of a brake cable.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are used for the same or corresponding elements, and duplicate descriptions are omitted.

  FIG. 1 is a schematic diagram showing the configuration of an electric parking brake system according to an embodiment of the present invention. As shown in FIG. 1, an electric parking brake system 1 according to this embodiment is mounted on a vehicle V and includes an electric parking brake device (Electronic Parking Brake: EPKB) 10, a PKB operation switch 20, and an ECU. (Electronic Control Unit) 30 and an alarm output unit 40 are provided.

  Examples of the vehicle V include large vehicles such as trucks, buses, and heavy machinery, and medium-sized vehicles. The applied vehicle V is not limited to these, and may be a normal passenger car, a small vehicle, a light vehicle, or the like.

  The electric parking brake device 10 is an electric parking brake device for braking the vehicle V, and includes an actuator 11, a brake cable 12, a PKB (Parking Brake) 13, a friction member 14, a load sensor 15, and a cable. A position sensor 16 is provided. In the electric parking brake device 10, the actuator 11 is actuated and the brake cable 12 is pulled with a predetermined index load to drive the PKB 13 and apply a desired braking force to the wheels H of the vehicle V.

  The actuator 11 includes a motor, a cable winding unit (not shown), and the like. The actuator 11 performs the pulling operation of the brake cable 12 by converting the rotational motion of the motor into linear motion at the cable winding portion. The actuator 11 is electrically connected to the ECU 30, and the index load of the brake cable 12 is controlled by the ECU 30.

  The brake cable 12 is a pull cable having an inner cable (not shown) inserted through an outer casing (not shown). The inner cable is made of a material such as hard steel wire (SWRH) or stainless steel (SUS), and is a strand type having a double twist structure. Both end portions of the inner cable are respectively connected to the actuator 11 and the PKB 13, and the index load by the motor of the actuator 11 is transmitted to the PKB 13.

  The outer casing is composed of a liner, a spring, and a coat. The liner is made of a material such as polyethylene (PE), polyacetal (POM), or fluororesin (FEP), and the inner cable is inserted therethrough. The spring is made of a material such as SWRH or SUS and is wound around a liner. The coat is made of a material such as polyvinyl chloride (PVC) or polypropylene (PP), and is formed so as to cover the spring from the outside. The outer casing is fixed to the vehicle V via a bracket.

  In the illustrated example, in the vehicle V, the brake cable 12 extends forward from the actuator 11 between the driver seat D and the passenger seat P in the vehicle V, and then bends so as to pass through the front side and the right side of the driver seat D. And is connected to the PKB 13. Hereinafter, the outer casing or the inner cable is also simply referred to as a brake cable 12.

  The PKB 13 employs a center brake type drum brake or the like, and has a friction member 14 inside. In the present embodiment, the PKB 13 is installed behind the transmission 2. In the PKB 13, for example, the friction member 14 (shoe or the like) is pressed against the drum according to the index of the brake cable 12, thereby restraining the propeller shaft 3. The PKB 13 is not limited in its configuration and method, and may have a common brake mechanism installed on the wheel H as long as the brake cable 12 and the friction member 14 are included. A parking brake mechanism different from the regular brake mechanism may be incorporated in the wheel H.

  The load sensor 15 is a sensor that detects an index load (cable index load) of the brake cable 12 by the actuator 11, and is configured by, for example, a load cell. The load sensor 15 is electrically connected to the ECU 30 and outputs the detected value to the ECU 30.

  The cable position sensor 16 is a sensor that detects the position of the brake cable 12. The position of the brake cable 12 is detected based on the number of rotations of the motor in the actuator 11, for example. The cable position sensor 16 is electrically connected to the ECU 30 and outputs the detected value to the ECU 30. The position of the brake cable 12 may be detected by providing a potentiometer or an encoder in the cable winding portion of the actuator 11.

  The PKB operation switch 20 is for operating the electric parking brake device 10, and is electrically connected to the ECU 30. The PKB operation switch 20 operates the actuator 11 by transmitting a signal to the ECU 30 so that the electric parking brake device 10 is operated or released when the driver is switched ON or OFF by, for example, a driver. Let

  ECU30 is a control part which controls operation | movement of the electric parking brake apparatus 10, for example, is comprised by the computer containing CPU (Central Processing Unit), ROM (Read OnlyMemory), RAM (Random Access Memory). Further, the ECU 30 of the present embodiment includes a stroke change amount detection unit 31.

  The stroke change amount detection unit 31 determines whether or not the initial elongation of the brake cable 12 has been removed based on the operating state of the electric parking brake device 10. The stroke change amount detection unit 31 sets a predetermined position of the brake cable 12 when it is determined that the initial elongation of the brake cable 12 has been removed as a reference position for detecting the stroke change amount.

  FIG. 2 is a graph for explaining the extension amount of the brake cable. In FIG. 2, the horizontal axis represents the number of operations of the PKB 13, and the vertical axis represents the extension amount of the brake cable 12. Note that the index load in the trajectory F1 is larger than the index load in the trajectory F2. Moreover, in the locus | trajectory F1 and the locus | trajectory F2, the continuation time which indexes the brake cable 12 is made into the mutually same predetermined time.

  As shown in FIG. 2, for example, when comparing the respective extension amounts when the number of actuations is N, the extension amount of the brake cable 12 hardly increases after the number of actuations is N times in the trajectory F1. In this state, the initial elongation is removed. On the other hand, in the trajectory F2, it can be said that there is room for the amount of elongation of the brake cable 12 to increase greatly even after the number of actuations is N, and the initial elongation of the brake cable 12 has not yet been removed.

  The initial extension amount of the brake cable 12 includes the extension amount of the inner cable itself and the apparent extension amount of the inner cable. The apparent amount of extension of the inner cable occurs when the length of the routing path of the brake cable 12 in the vehicle V is relatively short with respect to the length of the inner cable.

  For example, the length of the routing path is shortened by eliminating the play of the bracket or the slack of the cable when the brake cable 12 is attached to the vehicle V. The play of the bracket or the slack of the cable is gradually eliminated every time an index load is applied to the inner cable. Therefore, when a constant index load is applied to the inner cable, bracket play or cable slack is almost eliminated, and the apparent amount of extension of the inner cable hardly increases. Thus, the initial elongation of the brake cable 12 is removed.

  The stroke change amount detection unit 31 detects the stroke change amount of the brake cable 12 based on the set reference position and the detection value of the cable position sensor 16. The stroke change amount detection unit 31 outputs a signal related to the stroke change amount to the alarm output unit 40.

  The warning output unit 40 is an output unit that outputs a wear warning of the friction member 14 to the occupant of the vehicle V based on a signal from the stroke change amount detection unit 31. Specifically, the warning output unit 40 outputs a wear warning when the stroke change amount detected by the stroke change amount detection unit 31 exceeds a predetermined amount. The alarm output unit 40 may be, for example, a warning light in a combination meter or a speaker that outputs a warning sound.

  Next, the operation of the electric parking brake system 1 will be described. First, the setting of the reference position of the stroke change amount will be described with reference to FIG. FIG. 3A is a flowchart for explaining a reference position setting process for detecting a stroke change amount.

  As shown in FIG. 3A, when the PKB operation switch 20 is turned ON in step S <b> 1, a signal related to a braking request for operating the electric parking brake device 10 is transmitted to the ECU 30. In the electric parking brake device 10, the actuator 11 is operated and the brake cable 12 is pulled to drive the PKB 13.

  Subsequently, in step S2, the load sensor 15 causes the actuator 11 to detect the index load of the brake cable 12, and the detected value is output to the ECU 30. Subsequently, in step S3, the stroke change amount detection unit 31 determines whether or not the index load is equal to or greater than a predetermined load.

  When it is determined that the index load is equal to or greater than the predetermined load, the process proceeds to step S4. On the other hand, when the index load is less than the predetermined load, the process ends. This predetermined load is a predetermined value stored in the ECU 30 in advance, and is set to the maximum index load that the actuator 11 can drive the PKB 13 here.

  In step S4, the stroke change amount detection unit 31 measures the duration time during which the brake cable 12 is indexed. Subsequently, in step S5, the stroke change amount detection unit 31 determines whether or not the measured duration is equal to or longer than a predetermined time. When it is determined that the duration time is equal to or longer than the predetermined time, the process proceeds to step S6. On the other hand, when the duration is less than the predetermined time, the process ends.

  This predetermined time is a predetermined value stored in the ECU 30 in advance. For example, the predetermined time is set to be equal to or longer than the index holding time that the holding of the index can contribute to the removal of the initial elongation of the brake cable 12. Here, the index holding time is set to 10 seconds.

  Subsequently, in step S6, the stroke change amount detection unit 31 counts the number of times the index load is equal to or greater than the predetermined load and the indexed duration is equal to or greater than the predetermined time (hereinafter referred to as the effective number). In step S7, the stroke change amount detection unit 31 determines whether or not the effective number is equal to or greater than a predetermined number. When it is determined that the effective number is equal to or greater than the predetermined number, the process proceeds to step S8. On the other hand, when the effective number is less than the predetermined number, the process ends.

  This predetermined number of times is a predetermined value stored in the ECU 30 in advance. The predetermined number of times, for example, takes into account differences in the structure of the brake cable 12, differences in the layout of the layout, etc., and can be determined based on the results of the test. Here, this predetermined number is set to 250 times.

  If it is determined in step S8 that the initial elongation of the brake cable 12 has been removed by the stroke change amount detection unit 31, the predetermined value of the brake cable 12 when it is determined in step S9 that the initial elongation of the brake cable 12 has been removed. The position is set as a reference position for detecting the stroke change amount.

  Next, the output of the wear warning based on the stroke change amount will be described with reference to FIG. FIG. 3B is a flowchart for explaining the output processing of the wear warning based on the stroke change amount.

  As shown in FIG. 3B, in step S10, it is determined whether or not the initial elongation of the brake cable 12 has already been removed. If it is determined that the initial elongation of the brake cable 12 has already been removed, the process proceeds to step S11. On the other hand, if not, the process ends without outputting a wear warning of the friction member 14 (stopping the output of the friction warning).

  Subsequently, in step S <b> 11, the stroke change amount detection unit 31 detects the stroke change amount of the brake cable 12. Here, the stroke change amount of the brake cable 12 will be described with reference to FIG.

  FIG. 4 is a diagram illustrating an example of the stroke change amount of the brake cable 12. In FIG. 4, the horizontal direction indicates the number of operations of the PKB 13, and the number n2> the number n1. On the other hand, the vertical direction indicates the position of the brake cable 12 detected by the cable position sensor 16.

  In the example in the figure, the position P0 is a predetermined position of the brake cable 12 when it is determined in step 8 that the initial elongation of the brake cable 12 has been removed. This position P0 becomes the reference position for detecting the stroke change amount after the number of times n1.

  As shown in FIG. 4A, with the position P0 as the reference position, for example, the stroke change amount of the brake cable 12 at the number of times n2 is detected as follows. First, the stroke of the brake cable 12 at the number n1 (that is, the length L1 at which the brake cable 12 is indexed by the actuator 11 to operate the PKB 13) is returned to the brake cable 12 by the actuator 11 to release the operation of the PKB 13. Is equal to the length L1 ′ (the stroke change amount is 0).

  On the other hand, as shown in FIG. 4B, the length L2, which is the stroke of the brake cable 12 at the number n2, is longer than the length L1 ′ at which the brake cable 12 is returned by the actuator 11 to release the operation of the PKB 13. It will be a thing. Therefore, the difference (L2−L1 ′) between the lengths L2 and L1 ′ is detected as the stroke change amount at the number n2.

  Returning to FIG. 3B, in step S12, it is determined whether or not the stroke change amount is equal to or greater than a predetermined amount. If it is determined that the stroke change amount is greater than or equal to the predetermined amount, the process proceeds to step S13. On the other hand, when the stroke change amount is less than the predetermined amount, the process ends.

  The predetermined amount is a predetermined amount stored in advance in the ECU 30 and is, for example, a stroke change amount corresponding to the wear limit of the friction member 14. In step S <b> 13, the warning output unit 40 outputs a wear warning for the friction member 14 based on the signal from the stroke change amount detection unit 31.

  As described above, in the electric parking brake system 1 of the present embodiment, it is determined whether or not the initial elongation of the brake cable 12 has been removed based on the operating state of the electric parking brake device 10. Then, the predetermined position of the brake cable 12 when it is determined that the initial elongation of the brake cable 12 has been removed is set as a reference position for detecting the stroke change amount. After the initial elongation is removed, the influence of the elongation of the brake cable 12 on the amount of wear of the friction member 14 is reduced in the stroke variation (see FIG. 2), so that the stroke variation detected by the stroke variation detector 31 is detected. Regarding the amount, the influence of the elongation of the brake cable 12 can be reduced. As a result, it is possible to output a wear alarm with high accuracy.

  Further, in the present embodiment, it is determined whether or not the initial elongation of the brake cable 12 has been removed based on the number of times that the index load is equal to or greater than the predetermined load and the indexed duration is equal to or greater than the predetermined time (effective number). Thus, the load amount and duration of the index load and the number of operations by the index load can be used as the determination condition for removing the initial elongation.

  In the present embodiment, the warning output unit 40 does not output a wear warning until it is determined that the initial elongation of the brake cable 12 has already been removed. As a result, it is possible to suppress erroneous output of the friction alarm because the initial change is included in the stroke change amount, and it is possible to output the wear alarm with higher accuracy.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. The present invention can be modified without departing from the scope described in the claims or applied to other embodiments. May be.

  For example, each of the predetermined load, the predetermined time, and the predetermined number of times in the above embodiment is not particularly limited, and may be various loads, times, and times as long as it can be determined that the initial elongation has been removed. Further, the determination of the removal of the initial elongation may be based on the operating state of the electric parking brake device 10, and is not limited to the determination of the above embodiment.

  In the above embodiment, the index load of the brake cable 12 may be changed (controlled) depending on whether or not the initial elongation of the brake cable 12 has been removed. For example, until the initial elongation of the brake cable 12 is removed, the brake cable 12 is always indexed with the maximum index load to remove the initial elongation early, while the initial elongation of the brake cable 12 is removed. After being done, the brake cable 12 may be indexed with an index load corresponding to the attitude of the vehicle V.

  DESCRIPTION OF SYMBOLS 1 ... Electric parking brake system, 10 ... Electric parking brake device, 11 ... Actuator, 12 ... Brake cable, 13 ... PKB (parking brake mechanism), 14 ... Friction member, 15 ... Load sensor, 16 ... Cable position sensor (Stroke change) Quantity detection means), 31... Stroke change amount detection section (stroke change amount detection means), 40... Alarm output section (alarm means), V.

Claims (4)

An electric parking brake device comprising: a parking brake mechanism including a friction member for applying a braking force to the wheel; and an actuator for operating the parking brake mechanism via a brake cable;
Stroke change amount detecting means for detecting the stroke change amount of the brake cable;
Warning means for outputting a wear warning related to wear of the friction member based on the stroke change amount,
The stroke change amount detecting means includes
Determining whether the initial extension of the brake cable has been removed based on the operating status of the electric parking brake device;
An electric parking brake system, wherein a predetermined position of the brake cable when it is determined that the initial elongation of the brake cable has been removed is set as a reference position for detecting the stroke change amount. The stroke change amount detecting means includes
2. The method according to claim 1, wherein it is determined whether or not the initial elongation of the brake cable has been removed based on the number of times the parking brake mechanism is operated with an index load that is equal to or greater than a predetermined load and continues for a predetermined time. The described electric parking brake system. The predetermined load is a maximum index load with which the actuator can drive the parking brake mechanism,
The predetermined time is 10 seconds,
The electric parking brake system according to claim 2, wherein the number of times is 250 times.   The electric parking brake system according to any one of claims 1 to 3, wherein the warning means does not output the wear warning until it is determined that the initial elongation of the cable has been removed.

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