Brake control system

Abstract

The present invention provides a braking control device that can handle jamming even without a structure to prevent jamming in the parking brake system. [Solution] The braking control device 100 includes a braking control unit 121 that performs a pressurization process to generate hydraulic braking force on the wheels 11 by controlling the brake actuator 40 so that the hydraulic pressure of the brake fluid in the fluid chamber 37 increases; an apply process to generate parking braking force on the wheels 11 by controlling the electric motor 51 so that the linear motion unit 53 moves in the forward direction X1; and a full release process to control the electric motor 51 so that the linear motion unit 53 moves to its limit in the reverse direction X2. When the brake control unit 121 performs the apply process after performing the full release process, it performs the apply process while performing the pressurization process.

Description

Technical Field

[0001] The present invention relates to a braking control device.

Background Art

[0002] Patent Document 1 describes an electric braking device that generates a parking braking force on a wheel. The braking device includes an electric motor, a piston that moves a brake pad, and a direct-acting conversion mechanism that drives the piston based on the power transmitted from the electric motor. The direct-acting conversion mechanism has a rotating part that rotates based on the power transmitted from the electric motor, and a direct-acting part that moves in the forward or backward direction based on the power transmitted from the rotating part. When the direct-acting part moves forward, the piston moves forward together with the direct-acting part, and the brake pad is pressed against the disk rotor. Thus, a parking braking force is generated on the wheel. On the other hand, when the direct-acting part moves backward, the piston moves backward together with the direct-acting part, and the brake pad moves away from the disk rotor. Thus, the parking braking force generated on the wheel is eliminated. "

Prior Art Documents

Patent Documents

[0003] <~

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the braking device described above, the rotating part and the linear part of the linear motion conversion mechanism have protrusions on opposite sides. Therefore, when the linear part retracts toward its retraction limit, the protrusion of the retracting linear part comes into contact with the protrusion of the rotating part. The braking device then detects a change in the current value of the electric motor when the protrusion of the linear part comes into contact with the protrusion of the rotating part, and stops the power supply to the electric motor. In this way, the linear part is prevented from retracting toward its retraction limit. In other words, the braking device prevents the linear part from becoming jammed in the rotating part by preventing the linear part from coming into contact with the rotating part as it retracts toward its retraction limit. Therefore, while the braking device described above can prevent the linear part from becoming jammed in the rotating part, it is necessary to provide a structure in the linear motion conversion mechanism to prevent jamming. [Means for solving the problem]

[0005] A braking control device that solves the above problems is a braking control device applied to a vehicle comprising: a hydraulic braking device having a rotating body that rotates integrally with the wheel, a friction material pressed against the rotating body, a piston that presses the rotating body against the friction material when moving in the forward direction, a cylinder that partitions a liquid chamber together with the piston, and a pressure regulating unit that increases the liquid pressure in the liquid chamber by supplying brake fluid to the liquid chamber and moves the piston in the forward direction; and a parking braking device having an electric motor and a linear motion conversion mechanism that converts the rotational motion of the electric motor into linear motion and transmits it to the piston, the linear motion conversion mechanism including a rotating part that rotates by power transmitted from the electric motor, and a linear motion part that moves in the forward direction and in the reverse direction, which is the opposite direction of the forward direction, by power transmitted from the rotating part, wherein the brake fluid in the liquid chamber The braking control unit performs the following: pressurization process, which controls the pressure regulating unit to increase the hydraulic pressure of the brake fluid and moves the piston in the forward direction to generate hydraulic braking force on the wheel; apply process, which controls the electric motor to move the linear motion unit in the forward direction and moves the piston in the forward direction with the linear motion unit to generate parking braking force on the wheel; and full release process, which controls the electric motor to move the linear motion unit to its limit in the reverse direction. The piston is rotatable around an axis extending in the forward direction relative to the cylinder, but not around an axis extending in the forward direction relative to the linear motion unit. If the brake control unit performs the apply process after performing the full release process, it performs the apply process while performing the pressurization process. [Effects of the Invention]

[0006] The braking control device can handle jamming even without providing a structure to prevent jamming in the parking brake system. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram of a vehicle equipped with a braking control device. [Figure 2]Figure 2 is a timing chart showing when the braking control device in Figure 1 performs the apply process. [Figure 3] Figure 3 is a flowchart showing the processing flow when the braking control device in Figure 1 performs the apply process. [Figure 4] Figure 4 is a timing chart showing when the braking control device in Figure 1 performs the apply process. [Figure 5] Figure 5 is a flowchart showing the processing flow when the modified braking control device performs the apply process. [Modes for carrying out the invention]

[0008] An embodiment of a vehicle equipped with a braking control device will be described. <Configuration of this embodiment> As shown in Figure 1, the vehicle 10 is equipped with multiple wheels 11, a hydraulic braking system 20, a parking brake system 50, a braking control device 100, and a parking brake switch SW1. The vehicle 10 is, for example, a four-wheeled vehicle. Figure 1 shows one of the four wheels 11 of the vehicle 10.

[0009] <Hydraulic braking system> The hydraulic braking system 20 comprises multiple braking mechanisms 30 and a brake actuator 40. Each of the multiple braking mechanisms 30 corresponds to one of the multiple wheels 11. Each braking mechanism 30 includes a rotating body 31, two friction materials 32 and 33, and a caliper 34.

[0010] The rotating body 31 is fixed to the axle 12 so as to rotate together with the wheel 11. The rotating body 31 is disc-shaped. The rotating body 31 is a so-called brake disc. Two friction materials 32 and 33 are assembled to the caliper 34. When the caliper 34 is assembled to the vehicle 10, the two friction materials 32 and 33 are located on both sides of the rotating body 31 in the thickness direction. The two friction materials 32 and 33 are so-called brake pads. The two friction materials 32 and 33 generate braking force on the wheel 11 by being pressed against the rotating body 31.

[0011] The caliper 34 includes a cylinder 35 and a piston 36. The cylinder 35 is composed of a disc-shaped bottom wall 351 and a cylindrical circumferential wall 352. The axis of the cylinder 35 extends in the same direction as the rotation axis of the wheel 11. Hereafter, the direction in which the axis of the cylinder 35 extends will also be referred to as "axial X". The cylinder 35 includes a port 353 that penetrates the circumferential wall 352 of the cylinder 35 radially. The cylinder 35 is also provided with a bearing 354 and a seal 355. The piston 36 is cylindrical in shape. The piston 36 is housed in the cylinder 35. The gap between the piston 36 and the circumferential wall 352 of the cylinder 35 is sealed by the seal 355. The piston 36 faces one of the two friction materials 32, 33 in the axial X direction. The piston 36, together with the cylinder 35, partitions the fluid chamber 37. The fluid chamber 37 is filled with brake fluid. Hereafter, in terms of the axial direction X, the direction in which the piston 36 approaches the friction material 32 will be referred to as the forward direction X1, and the direction in which the piston 36 moves away from the friction material 32 will be referred to as the backward direction X2.

[0012] The brake actuator 40 may be configured to include, for example, an electric cylinder or electric pump driven by an electric motor. The brake actuator 40 is connected to the port 353 of the cylinder 35 of the braking mechanism 30 via a fluid passage. The brake actuator 40 increases the fluid pressure in the fluid chamber 37 of the braking mechanism 30 by supplying brake fluid to the fluid chamber 37. As the fluid pressure in the fluid chamber 37 increases, the piston 36 moves in the forward direction X1. This causes the two friction materials 32 and 33 to press against the rotating body 31, thereby generating a braking force. This braking force generated by the fluid pressure in the fluid chamber 37 is called "hydraulic braking force". On the other hand, the brake actuator 40 decreases the fluid pressure in the fluid chamber 37 of the braking mechanism 30 by discharging brake fluid from the fluid chamber 37. This reduces the force pressing the two friction materials 32 and 33 against the rotating body 31, thus decreasing the hydraulic braking force. In this respect, the brake actuator 40 corresponds to a "pressure regulating unit".

[0013] <Parking Brake System> The parking brake system 50 includes an electric motor 51, a transmission mechanism 52, and a linear motion conversion mechanism 53.

[0014] The electric motor 51 is fixed to the caliper 34, for example. The electric motor 51 has a different configuration from the drive source of the brake actuator 40. The transmission mechanism 52 transmits the power from the output shaft of the electric motor 51 to the linear motion conversion mechanism 53. The transmission mechanism 52 is, for example, a reduction gear composed of multiple gears.

[0015] The linear motion conversion mechanism 53 is a mechanism that converts the rotational motion of the electric motor 51 into linear motion. The linear motion conversion mechanism 53 includes a rotating part 54 that rotates due to power transmitted from the electric motor 51 via a transmission mechanism 52, and a linear motion part 55 that moves in the forward direction X1 and the reverse direction X2 due to power transmitted from the rotating part 54. The linear motion conversion mechanism 53 is a so-called lead screw mechanism.

[0016] The rotating part 54 includes a transmission shaft 541, a regulating wall 542, and a screw shaft 543. The transmission shaft 541 is rod-shaped. The base end of the transmission shaft 541 is connected to the transmission mechanism 52. The regulating wall 542 is flange-shaped. The regulating wall 542 is provided at the tip of the transmission shaft 541. The outer diameter of the regulating wall 542 is larger than the outer diameters of both the transmission shaft 541 and the screw shaft 543. The screw shaft 543 is rod-shaped. A male thread is provided on the outer circumferential surface of the screw shaft 543. The base end of the screw shaft 543 is connected to the regulating wall 542. The axis of the screw shaft 543 coincides with the axes of both the transmission shaft 541 and the regulating wall 542. The rotating part 54 is rotatably supported around the axis of the cylinder 35 with respect to the bearing 354 of the cylinder 35. The rotating part 54 is immovable in the axial direction X relative to the cylinder 35. The space between the rotating part 54 and the cylinder 35 is sealed by a bearing 354 to prevent brake fluid leakage.

[0017] The linear motion part 55 is cylindrical. An internal thread is provided on the inner peripheral surface of the linear motion part 55. The linear motion part 55 is screwed onto the screw shaft 543 of the rotating part 54. Further, the linear motion part 55 is engaged with the piston 36 while being positioned inside the piston 36. At this time, the linear motion part 55 and the piston 36 are relatively movable in the axial direction X. On the other hand, the linear motion part 55 and the piston 36 are relatively non-rotatable about the axis of the cylinder 35. As an example, such an engagement relationship can be realized by providing a key on the linear motion part 55 and providing a key groove corresponding to the key of the linear motion part 55 on the cylinder 35.

[0018] When the rotating part 54 rotates in the first rotation direction, the linear motion part 55 moves in the forward direction X1. In this case, the linear motion part 55 moves in a direction away from the restricting wall 542 of the rotating part 54. When the linear motion part 55 moves in the forward direction X1, the piston 36 is also pushed by the linear motion part 55 and moves in the forward direction X1. As a result, the two friction materials 32, 33 are pressed against the rotating body 31, and thus a braking force is generated. The braking force generated by the movement of the linear motion part 55 in this way is referred to as a "parking braking force".

[0019] On the other hand, when the rotating part 54 rotates in the second rotation direction, which is the reverse direction of the first rotation direction, the linear motion part 55 moves in the backward direction X2. Then, since the force by which the linear motion part 55 pushes the piston 36 becomes smaller, the piston 36 also moves in the backward direction X2. As a result, since the force pressing the two friction materials 32, 33 against the rotating body 31 becomes smaller, the parking braking force decreases.

[0020] When the linear motion part 55 moves in the backward direction X2, the linear motion part 55 approaches the restricting wall 542 of the rotating part 54. In the present embodiment, the state where the linear motion part 55 contacts the restricting wall 542 of the rotating part 54 is the state where the linear motion part 55 moves farthest in the backward direction X2 within the moving range in the axial direction X. That is, the position of the linear motion part 55 when it contacts the restricting wall 542 of the rotating part 54 is the moving limit of the linear motion part 55 in the backward direction X2 (hereinafter also referred to as the "backward limit").

[0021] Furthermore, the linear motion conversion mechanism 53 has a so-called self-locking function. Therefore, while it is possible to move the linear motion part 55 in the axial direction X by applying torque to the rotating part 54, it is not possible to rotate the rotating part 54 by applying a load in the axial direction X to the linear motion part 55.

[0022] <Braking control device> The braking control device 100 is a processing circuit 110 having a CPU 111 and a ROM 112. By executing a control program stored in memory, the CPU 111 causes the processing circuit 110 to function as a braking control unit 121 and a jamming detection unit 122.

[0023] <Braking Control Unit> The braking control unit 121 adjusts the hydraulic braking force by controlling the brake actuator 40 of the hydraulic braking device 20. Specifically, the braking control unit 121 derives a target hydraulic pressure, which is the target value of the hydraulic pressure in the liquid chamber 37. Subsequently, the braking control unit 121 controls the brake actuator 40 so that the hydraulic pressure in the liquid chamber 37 approaches the target hydraulic pressure. Hereafter, the process of increasing the hydraulic pressure in the liquid chamber 37 will be called the pressurization process, and the process of decreasing the hydraulic pressure in the liquid chamber 37 will be called the depressurization process.

[0024] When the braking control unit 121 performs pressurization, the hydraulic pressure in the fluid chamber 37 increases, causing the piston 36 to move in the forward direction X1. In this case, the piston 36 presses the friction materials 32 and 33 toward the rotating body 31, generating a hydraulic braking force on the wheel 11. On the other hand, when the braking control unit 121 performs depressurization, the hydraulic pressure in the fluid chamber 37 decreases, causing the piston 36 to move in the backward direction X2. In this case, the friction materials 32 and 33 move away from the rotating body 31, reducing or eliminating the hydraulic braking force generated on the wheel 11. Thus, the hydraulic braking force generated on the wheel 11 increases as the force with which the piston 36 presses the friction material 32 increases. In other words, the hydraulic braking force increases as the hydraulic pressure in the fluid chamber 37 increases.

[0025] <Apply and release processes of the braking control unit> The braking control unit 121 adjusts the parking braking force by controlling the electric motor 51 of the parking brake device 50. The braking control unit 121 performs an apply process to generate parking braking force on the wheels 11 and a release process to eliminate the parking braking force generated on the wheels 11.

[0026] The braking control unit 121 performs an apply process when the parking brake switch SW1 is operated after the release process has been executed, that is, when no parking braking force has been generated on the wheels 11. In the apply process, the braking control unit 121 drives the electric motor 51 of the parking brake device 50, causing the piston 36 to move in the forward direction X1 with the linear motion unit 55. As a result, the piston 36 moving in the forward direction X1 pushes the friction material 32 in the forward direction X1, causing the friction materials 32 and 33 to come into contact with the rotating body 31. Consequently, parking braking force is generated on the wheels 11.

[0027] In the apply process, before the piston 36 contacts the friction material 32, the load on the electric motor 51 does not change significantly even when the linear motion unit 55 moves in the forward direction X1. On the other hand, after the piston 36 contacts the friction material 32, the load on the electric motor 51 increases as the linear motion unit 55 moves in the forward direction X1. Therefore, the braking control unit 121 terminates the apply process when the magnitude of the current value of the electric motor 51 becomes greater than or equal to a specified current value IthS. Here, the specified current value IthS is the magnitude of the current value of the electric motor 51 when sufficient parking braking force is generated on the wheels 11 to maintain the parking of the vehicle 10. Hereafter, the magnitude of the current value of the electric motor 51 will be referred to as the "current value Im". In other words, regardless of the direction of the current flowing through the electric motor 51, the current value Im will be greater than or equal to "0".

[0028] Referring to Figure 2, the change in the current value Im of the electric motor 51 during the execution of the apply process will be explained. As shown in Figure 2, when the user operates the parking brake switch SW1 at timing t11, the apply process begins. A surge current flows through the electric motor 51, causing the current value Im of the electric motor 51 to increase rapidly and then gradually decrease. Also, from timing t11, the rotation of the rotating part 54 by the electric motor 51 causes the linear motion part 55 to begin moving in the forward direction X1. At timing t12, when the surge current generation period ends, the current value Im of the electric motor 51 converges to a constant value. Subsequently, at timing t13, the friction material 32, pushed in the forward direction X1 by the piston 36, comes into contact with the rotating body 31. Therefore, from timing t13 onward, the current value Im of the electric motor 51 increases as the amount of movement of the piston 36 in the forward direction X1 increases. Then, at timing t14, when the current value Im of the electric motor 51 reaches a specified current value IthS, the apply process is terminated. In other words, when the electric motor 51 is stopped, the current value Im of the electric motor 51 becomes "0".

[0029] The braking control unit 121 performs a release process when the parking brake switch SW1 is operated after the apply process has been executed, that is, while a parking braking force is being generated on the wheels 11. In the release process, the braking control unit 121 drives the electric motor 51 of the parking brake device 50 to move the linear motion unit 55 in the reverse direction X2. In the release process, the linear motion unit 55 moves in the reverse direction X2 together with the piston 36. When the piston 36 separates from the friction material 32, the parking braking force generated on the wheels 11 is released.

[0030] The release process includes both a normal release process and a full release process. The normal release process is performed when a user uses the vehicle 10. In other words, the normal release process aims to eliminate the parking braking force generated on the wheels 11. For this reason, in the normal release process, the braking control unit 121 stops supplying power to the electric motor 51 at the timing when it is expected that the parking braking force has been eliminated. In other words, at the end of the normal release process, the linear motion unit 55 does not reach the reverse limit. On the other hand, the full release process is performed when a mechanic or other person is servicing the vehicle 10, such as replacing the friction materials 32 and 33. In other words, the full release process aims to move the linear motion unit 55 to the reverse limit. For this reason, in the full release process, the braking control unit 121 stops supplying power to the electric motor 51 at the timing when it detects an increase in the load on the electric motor 51 when the linear motion unit 55 moving in the reverse direction X2 contacts the restricting wall 542 of the rotating unit 54. In other words, the braking control unit 121 terminates the full release process based on the current value Im of the electric motor 51. When the full release process is performed, a value indicating that the full release process has been performed is set in a predetermined flag stored in the ROM 112.

[0031] Normal release and full release are different processes. For example, the braking control unit 121 can determine that a normal release process is requested when the parking brake switch SW1 is operated for a short time, and that a full release process is requested when the parking brake switch SW1 is operated for a long time.

[0032] <Basic methods for resolving bite problems> When a full release process is performed, the linear motion unit 55, which moves in the retraction direction X2, contacts the restricting wall 542 of the rotating unit 54. The female thread of the linear motion unit 55 is tightly fastened to the male thread of the rotating unit 54, which may cause the rotating unit 54 and the linear motion unit 55 to become one. Hereafter, this state in which the rotating unit 54 and the linear motion unit 55 become one will be referred to as the linear motion conversion mechanism 53 being jammed.

[0033] When the linear motion conversion mechanism 53 is in a jammed state, the rotating part 54 and the linear motion part 55 are integrated, allowing them to rotate together. Also, the linear motion part 55 cannot rotate relative to the piston 36, while the piston 36 can rotate relative to the cylinder 35. Therefore, when the apply process is executed while the linear motion conversion mechanism 53 is in a jammed state, the rotating part 54, the linear motion part 55, and the piston 36 rotate together. At this time, the linear motion part 55 and the piston 36 become unable to move in the forward direction X1. In other words, even when the apply process is executed, it becomes impossible to generate parking braking force on the wheel 11. However, even if the linear motion conversion mechanism 53 is in a jammed state, the piston 36 can move in the forward direction X1 relative to the linear motion part 55 by increasing the hydraulic pressure in the liquid chamber 37. Therefore, when the brake control unit 121 executes the apply process after executing the full release process, it executes the apply process while performing the pressurization process.

[0034] When the linear motion conversion mechanism 53 is in a jammed state, applying pressure causes the piston 36 to move in the forward direction X1 relative to the linear motion section 55, causing the piston 36 to contact the friction material 32. As a result, the frictional force generated between the piston 36 and the friction material 32 restricts the rotation of both the piston 36 and the linear motion section 55. Therefore, by performing the apply process while applying pressure, the rotating section 54 can be rotated relative to the linear motion section 55. In other words, the linear motion section 55 can be moved away from the restricting wall 542 of the rotating section 54 in the forward direction X1. Taking a jammed bolt and nut as an example, by holding down the nut corresponding to the linear motion section 55 and rotating the bolt corresponding to the rotating section 54, the nut can be loosened from the bolt.

[0035] In this regard, in the pressurization process performed along with the apply process, the target hydraulic pressure in the liquid chamber 37 should be sufficient to restrict the rotation of the piston 36. Hereafter, this hydraulic pressure will be referred to as the set hydraulic pressure Pset. The set hydraulic pressure Pset varies depending on the specifications of the hydraulic braking device 20 and the parking braking device 50, such as the coefficient of friction between the friction material 32 and the piston 36, the shape of the linear motion section 55, the shape of the piston 36, and the distance from the axis of the axle 12 to the axis of the piston 36. For this reason, it is preferable to set the set hydraulic pressure Pset based on experiments or other means.

[0036] <Bite detection unit> If the linear motion conversion mechanism 53 is not jammed, the linear motion unit 55 can move in the forward direction X1 when the apply process is executed. In this respect, the current value Im of the electric motor 51 tends to be small. On the other hand, if the linear motion conversion mechanism 53 is jammed, the rotating unit 54, the linear motion unit 55, and the piston 36 rotate together when the apply process is executed. In this case, the current value Im of the electric motor 51 tends to be large because the piston 36 slides against the seal 355 of the cylinder 35. Therefore, the jamming determination unit 122 determines whether the linear motion conversion mechanism 53 is jammed based on the current value Im of the electric motor 51 when the apply process is executed. Specifically, the jamming determination unit 122 determines that the linear motion conversion mechanism 53 is jammed if, when the apply process is executed, the current value Im of the electric motor 51 after the inrush current generation period ends is greater than or equal to a first current value Ith1 over the determination time Tth. The determination time Tth and the first current value Ith1 are preferably set based on experiments or other similar methods.

[0037] If the jammed state of the linear motion conversion mechanism 53 is resolved by the execution of the pressurizing process and the apply process, the load on the electric motor 51 will increase until the jammed state is resolved, but after the jammed state is resolved, the load on the electric motor 51 will decrease rapidly. On the other hand, if the jammed state of the linear motion conversion mechanism 53 is not resolved even after the pressurizing process and the apply process are executed, the load on the electric motor 51 will continue to increase, or the rotating part 54, the linear motion part 55, and the piston 36 will continue to rotate together. Therefore, the jamming determination unit 122 determines whether or not the jammed state of the linear motion conversion mechanism 53 has been resolved based on the change in the current value Im of the electric motor 51 when the apply process is executed together with the pressurizing process. Specifically, the jamming determination unit 122 determines that the jammed state has been resolved when, when the apply process is executed together with the pressurizing process, the current value Im of the electric motor 51 goes from a state of less than the second current value Ith2 to the second current value Ith2 or more, and then to less than the first current value Ith1. The second current value Ith2 is set to a value greater than the first current value Ith1. It is preferable that the second current value Ith2 is set based on experiments or other relevant data.

[0038] <Detecting bite problems and methods for resolving bite problems> Even when a full release process is performed, the linear motion conversion mechanism 53 does not necessarily become jammed. If the linear motion conversion mechanism 53 is not jammed even when a full release process is performed, it is not necessary to perform the pressurization process along with the apply process.

[0039] Therefore, the braking control unit 121 performs the apply process without performing the pressurizing process after performing the full release process. If the jamming determination unit 122 determines that no jamming has occurred, the braking control unit 121 continues the apply process and does not perform the pressurizing process.

[0040] On the other hand, if the jamming detection unit 122 determines that a jamming condition has occurred, the braking control unit 121 terminates the apply process. Subsequently, the braking control unit 121 performs the apply process while simultaneously performing the pressurizing process. After that, if the jamming detection unit 122 determines that the jamming condition has been resolved, the braking control unit 121 terminates the pressurizing process without waiting for the application process to be completed. On the other hand, if the jamming detection unit 122 continues to determine that the jamming condition has not been resolved, that is, if the current value Im of the electric motor 51 continues to increase, the braking control unit 121 performs abnormal response processing.

[0041] When the braking control unit 121 performs the pressurization process and the apply process together, it performs an abnormality response process if the current value Im of the electric motor 51 becomes greater than or equal to a predetermined upper limit current value IthL. The abnormality response process is performed when the jammed state cannot be resolved even after performing the pressurization process and the apply process together. In the abnormality response process, the braking control unit 121 terminates the pressurization process and the apply process and notifies the vehicle 10 via the display and lamps, etc., that the jammed state cannot be resolved. In another embodiment, when the braking control unit 121 performs the pressurization process and the apply process together, it may perform an abnormality response process if the current value Im of the electric motor 51 does not fall below a first current value Ith1 within a predetermined time after the start of the apply process.

[0042] Furthermore, if the jammed state is not determined to have been resolved, the liquid pressure in the liquid chamber 37 during the pressurizing process may be increased from the point at which the jammed state is determined to have not been resolved, as shown in the modification example described later. In other words, if the jammed state is not determined to have been resolved, the conditions of the pressurizing process may be changed in order to resolve the jammed state.

[0043] <Processing flow executed by the braking control system> Referring to Figure 3, the process flow performed by the braking control device 100 to execute the apply process will be explained. This process is executed when the parking brake switch SW1 is operated after the full release process has been executed.

[0044] As shown in Figure 3, the braking control device 100 starts the apply process (S11). That is, the braking control device 100 drives the electric motor 51 so that the linear motion unit 55 moves in the forward direction X1. Next, the braking control device 100 determines whether or not the linear motion conversion mechanism 53 is in a jammed state based on the current value Im of the electric motor 51 (S12). Immediately after starting the apply process in step S11, an inrush current is generated in the electric motor 51. For this reason, the braking control device 100 executes the determination process in step S12 after the period during which the inrush current is generated has elapsed since the start of the process in step S11.

[0045] If the linear motion conversion mechanism 53 is not jammed (S12:NO), that is, if the apply process can be continued, the braking control device 100 determines whether the current value Im of the electric motor 51 is equal to or greater than the specified current value IthS (S13). If the current value Im of the electric motor 51 is less than the specified current value IthS (S13:NO), that is, if the parking braking force generated on the wheels 11 is insufficient, the braking control device 100 proceeds to step S13. In other words, the braking control device 100 continues the apply process until the current value Im of the electric motor 51 becomes equal to or greater than the specified current value IthS. On the other hand, if in step S13 the current value Im of the electric motor 51 is equal to or greater than the specified current value IthS (S13:YES), that is, if the parking braking force generated on the wheels 11 is sufficient, the braking control device 100 terminates the apply process (S14). After that, the braking control device 100 terminates this process.

[0046] In step S12, if the linear motion conversion mechanism 53 is jammed (S12: YES), that is, if the apply process cannot be continued, the brake control device 100 terminates the apply process (S15). Subsequently, the brake control device 100 starts the pressurization process by driving the brake actuator 40 (S16). After that, the brake control device 100 starts the apply process while the pressurization process is still running (S17). Here, it is preferable that the brake control device 100 starts the apply process on the condition that the hydraulic pressure in the liquid chamber 37 reaches the set hydraulic pressure Pset.

[0047] Next, the braking control device 100 determines whether the current value Im of the electric motor 51 is greater than or equal to the upper limit current value IthL (S18). If the current value Im of the electric motor 51 is greater than or equal to the upper limit current value IthL (S18: YES), the braking control device 100 performs abnormality response processing (S19). In this case, the braking control device 100 determines that it cannot resolve the jamming state of the linear motion conversion mechanism 53 and terminates the pressurization process and the apply process. After that, the braking control device 100 terminates this process.

[0048] In step S18, if the current value Im of the electric motor 51 is less than the upper limit current value IthL (S18:NO), the braking control device 100 determines whether the jamming state of the linear motion conversion mechanism 53 has been resolved based on the change in the current value Im of the electric motor 51 (S20). If it cannot be determined that the jamming state has been resolved (S20:NO), the braking control device 100 proceeds to step S18. In this case, the braking control device 100 continues the pressurizing process and the apply process.

[0049] On the other hand, if it is determined that the jamming condition has been resolved (S20: YES), the braking control device 100 terminates the pressurizing process while continuing to execute the apply process (S21). In this case, the linear motion unit 55, which moves in the forward direction X1 due to the continuation of the apply process, comes into contact with the piston 36, which moves in the reverse direction X2 due to the termination of the pressurizing process. After the linear motion unit 55 comes into contact with the piston 36, the piston 36 moves in the forward direction X1 together with the linear motion unit 55 due to the continuation of the apply process. After the pressurizing process is completed, the braking control device 100 proceeds to step S13.

[0050] <Operation and Effects of This Embodiment> Referring to Figure 4, the operation when the apply process is executed while the linear motion conversion mechanism 53 is in a jammed state will be explained.

[0051] As shown in Figure 4, when the user operates the parking brake switch SW1 at timing t21, the apply process begins. This causes an inrush current to flow through the electric motor 51, resulting in a rapid increase in the electric motor 51's current value Im, followed by a gradual decrease. In the example shown in Figure 4, the linear motion conversion mechanism 53 is engaged, so even when the electric motor 51 is driven, the linear motion unit 55 cannot move in the forward direction X1. In other words, the rotating unit 54, the linear motion unit 55, and the piston 36 rotate together, resulting in a load acting on the electric motor 51 corresponding to the sliding resistance between the piston 36 and the seal 355. As a result, at timing t22, when the inrush current generation period ends, the electric motor 51's current value Im converges to a value greater than or equal to the first current value Ith1.

[0052] At timing t23, when the determination time Tth has elapsed from timing t22, it is determined that the linear motion conversion mechanism 53 is in a jammed state. As a result, at timing t23, the apply process is completed, and the current value Im of the electric motor 51 becomes "0". Also at timing t23, the pressurization process begins, and the hydraulic pressure in the liquid chamber 37 gradually begins to increase. From timing t23 onward, the hydraulic braking force generated on the wheel 11 increases in accordance with the rise in hydraulic pressure in the liquid chamber 37. In other words, the piston 36 presses the friction material 32 against the rotating body 31, preventing the piston 36 from rotating.

[0053] At timing t24, when the hydraulic pressure in the liquid chamber 37 reaches the set hydraulic pressure Pset, the pressurization process continues, that is, the hydraulic pressure in the liquid chamber 37 is maintained at the set hydraulic pressure Pset, and the apply process begins. Therefore, similar to timing t21, an inrush current flows through the electric motor 51, causing the current value Im of the electric motor 51 to increase rapidly and then gradually decrease. After timing t24, the piston 36 is unable to rotate, so even if the electric motor 51 is driven, the rotating part 54, the linear part 55, and the piston 36 cannot rotate together. Therefore, at timing t25, the electric motor 51 can no longer rotate the rotating part 54, and the current value Im of the electric motor 51 begins to rise.

[0054] At timing t26, the current value Im of the electric motor 51 changes from less than the second current value Ith2 to greater than or equal to the second current value Ith2. Subsequently, at timing t27, the increasing trend of the current value Im of the electric motor 51 switches to a decreasing trend. In other words, the jamming state of the linear motion conversion mechanism 53 is resolved, reducing the load on the electric motor 51. Therefore, from timing t27 onward, the linear motion unit 55 moves in the forward direction X1 in accordance with the rotation of the rotating unit 54. In this way, the braking control device 100 can resolve the jamming state of the linear motion conversion mechanism 53 by performing the apply process along with the pressurizing process. That is, the braking control device 100 can deal with the jamming without providing a jamming prevention structure in the parking brake device 50.

[0055] At timing t28, when the current value Im of the electric motor 51 drops from a state of being equal to or greater than the second current value Ith2 to less than the first current value Ith1, it is determined that the jamming state of the linear motion conversion mechanism 53 has been resolved. Therefore, at timing t28, the decrease in the hydraulic pressure in the liquid chamber 37 begins in order to terminate the pressurization process. Subsequently, at timing t29, the hydraulic pressure in the liquid chamber 37 drops to the initial hydraulic pressure. Thus, the pressurization process ends at timing t29, which is the period during which the apply process is being executed. In this way, the braking control device 100 terminates the pressurization process at the timing at which it is determined that the jamming state of the linear motion conversion mechanism 53 has been resolved. In other words, the braking control device 100 terminates the pressurization process at the timing at which it is no longer necessary to make the piston 36 unable to rotate. Therefore, the braking control device 100 can suppress the increase in the operating time of the brake actuator 40 in order to resolve the jamming state of the linear motion conversion mechanism 53.

[0056] At timing t30, the friction materials 32 and 33 come into contact with the rotating body 31 due to the movement of the linear motion unit 55. As a result, the current value Im of the electric motor 51 gradually increases after timing t30. Subsequently, at timing t31, when the current value Im of the electric motor 51 reaches the specified current value IthS, the execution of the apply process is terminated. In other words, the current value Im of the electric motor 51 becomes "0" when the drive of the electric motor 51 is stopped.

[0057] Furthermore, if the linear motion unit 55 is strongly engaged with the rotating unit 54, the jammed state of the linear motion conversion mechanism 53 may not be resolved even if the pressurizing process is performed while the apply process is performed. Figure 4 shows the transition of the current value Im of the electric motor 51 and the hydraulic pressure of the liquid chamber 37 in this case, illustrated by a dashed line. If the linear motion unit 55 is strongly engaged with the rotating unit 54, as shown in Figure 4, the current value Im of the electric motor 51 continues to increase even after timing t27. Subsequently, at timing t40, if the current value Im of the electric motor 51 becomes greater than or equal to the upper limit current value IthL, the abnormal response process is executed. In other words, the pressurizing process and the apply process are terminated. Therefore, at timing t40, the current value Im of the electric motor 51 becomes "0" and the hydraulic pressure of the liquid chamber 37 begins to decrease. In this way, if the braking control device 100 cannot resolve the jammed state of the linear motion conversion mechanism 53, it terminates the pressurizing process and the apply process. As a result, the braking control device 100 can prevent excessive load from being applied to the electric motor 51 and suppress the temperature rise of the electric motor 51.

[0058] The above explanation, with reference to Figure 4, describes the case where the apply process is performed when the linear motion conversion mechanism 53 is in a jammed state. However, when the linear motion conversion mechanism 53 is not in a jammed state, as shown in Figure 3, the first apply process generates parking braking force on the wheels 11. Therefore, when the linear motion conversion mechanism 53 is not in a jammed state, the braking control device 100 can generate parking braking force on the wheels 11 without performing a pressurizing process. As a result, the braking control device 100 can suppress the execution of unnecessary pressurizing processes.

[0059] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0060] If the linear motion part 55 is strongly engaged with the rotating part 54, the jammed state of the linear motion conversion mechanism 53 may not be resolved even if the pressurizing process is performed while the apply process is performed. In this case, the rotating part 54, the linear motion part 55, and the piston 36 rotate together, while the piston 36 slides against the friction material 32. In other words, the torque proportional to the frictional force between the piston 36 and the friction material 32, or in other words, the torque proportional to the force with which the piston 36 pushes the friction material 32, is greater than the torque required to resolve the jammed state of the linear motion conversion mechanism 53. Therefore, it may be possible to resolve the jammed state of the linear motion conversion mechanism 53 by increasing the force with which the piston 36 pushes the friction material 32.

[0061] Therefore, when the braking control device 100 is performing the apply process while simultaneously performing the pressurizing process, if it is determined that the jamming condition has not been resolved, the device increases the liquid pressure in the liquid chamber 37 during the pressurizing process from the point in time when it is determined that the jamming condition has not been resolved.

[0062] Referring to the flowchart shown in Figure 5, the parts of the process performed by the braking control device 100 that differ from the above embodiment will be explained. As shown in Figure 5, if the current value Im of the electric motor 51 is less than the upper limit current value IthL (S18: NO), the braking control device 100 determines whether or not the determination time Tth has elapsed since the start of the apply process in step S17 (S31). Here, the determination time Tth may be the same determination time Tth used in step S12 to determine whether or not there is a jamming condition. In other modified examples, the determination time Tth used in step S31 may be different from the determination time Tth used in step S12. If the determination time Tth has not elapsed since the start of the apply process (S31: NO), the braking control device 100 determines whether or not the jamming condition has been resolved (S20). On the other hand, if the determination time Tth has elapsed since the start of the apply process (S31: YES), the braking control device 100 sets the target hydraulic pressure in the pressurizing process from the set hydraulic pressure Pset to a second set hydraulic pressure Pset2 which is higher than the set hydraulic pressure Pset (S32). In other words, the braking control device 100 increases the hydraulic pressure in the liquid chamber 37 at a time when step S31 is finally judged as negative. After that, the braking control device 100 proceeds to step S20.

[0063] Thus, when the braking control device 100 performs pressurization and application processing, it may be possible to resolve the jamming condition of the linear motion conversion mechanism 53 by increasing the hydraulic pressure in the liquid chamber 37.

[0064] The jamming determination unit 122 of the braking control device 100 may determine whether or not the jamming state of the linear motion conversion mechanism 53 has been resolved in a manner different from that of the above embodiment. For example, the jamming determination unit 122 may determine that the jamming state of the linear motion conversion mechanism 53 has been resolved when the current value Im of the electric motor 51 changes from a state in which it is equal to or greater than a first current value Ith1 to a state in which it is less than the first current value Ith1. Alternatively, the jamming determination unit 122 may determine that the jamming state of the linear motion conversion mechanism 53 has been resolved when the amount of change per unit time of the current value Im of the electric motor 51 changes from a positive value to a negative value.

[0065] The braking control device 100 may perform an apply process when it detects that the shift lever of the vehicle 10 has been operated from another range to the P range. The processing circuit 110 may also perform a normal release process when it detects that the shift lever of the vehicle 10 has been operated from the P range to another range.

[0066] The timing for ending the pressurization process can be any time after the point at which it is determined that the jamming condition has been resolved. For example, the timing for ending the pressurization process may be the same as the timing for ending the apply process.

[0067] In the above embodiment, if the braking control device 100 determines that the linear motion conversion mechanism 53 is jammed during the execution of the first apply process, it terminates the first apply process and performs a pressurizing process. In the modified example, if the braking control device 100 determines that the linear motion conversion mechanism 53 is jammed during the execution of the first apply process, it may perform a pressurizing process without terminating the apply process.

[0068] The braking control device 100 may, during the pressurization process, gradually increase the hydraulic pressure in the liquid chamber 37 over time, or increase it in proportion to the passage of time. In other words, the braking control device 100 does not need to maintain the hydraulic pressure in the liquid chamber 37 at the set hydraulic pressure Pset during the pressurization process.

[0069] The braking control device 100 does not need to perform any processing to determine whether or not the mechanism is jammed. In other words, if the full release process is performed, the braking control device 100 may assume that the linear motion conversion mechanism 53 is jammed and perform the pressurizing process and the apply process.

[0070] The hydraulic braking system 20 only needs to be equipped with a "pressure regulating unit" that can individually adjust the hydraulic braking force of multiple wheels 11. The pressure regulating unit may be, for example, the hydraulic pressure source in the vehicle 10's skid control system, or it may be a brake booster that is the pressurizing source for the service brake.

[0071] The braking control device 100 is not limited to a processing circuit 110 that includes a CPU 111 and a ROM 112 and executes software processing. For example, the braking control device 100 may include a dedicated hardware circuit that executes at least a part of the various processes performed in the above embodiment. An example of a dedicated hardware circuit is an ASIC. ASIC is an abbreviation for "Application Specific Integrated Circuit". In other words, the braking control device 100 may have any of the following configurations (a) to (c).

[0072] (a) A processing circuit comprising a processing unit that executes all of the above processes according to a program, and a program storage device such as a ROM that stores the program. (b) A processing circuit comprising a processing unit and a program storage unit that perform a part of the above processing according to a program, and a dedicated hardware circuit that performs the remaining processing.

[0073] (c) A processing circuit equipped with dedicated hardware circuits to perform all of the above processes. Here, there may be multiple software execution devices equipped with processing units and program storage devices, as well as dedicated hardware circuits. [Explanation of symbols]

[0074] 10... Vehicles 11...Wheel 20... Hydraulic braking system 31…Rotational body 32,33…Friction material 35...Cylinder 36... Piston 37…liquid chamber 40...Brake actuator (pressure regulating unit) 50…Parking brakes 51… Electric motor 53…Linear motion conversion mechanism 54... Rotating part 55…Linear motion section 100... Brake control device 121... Brake Control Unit 122... Bite detection unit

Claims

1. A hydraulic braking device comprising: a rotating body that rotates integrally with the wheel; a friction material pressed against the rotating body; a piston that presses the rotating body against the friction material when moving in the forward direction; a cylinder that partitions a fluid chamber together with the piston; and a pressure regulating unit that increases the fluid pressure in the fluid chamber by supplying brake fluid to the fluid chamber, thereby moving the piston in the forward direction; A parking brake device having an electric motor and a linear motion conversion mechanism that converts the rotational motion of the electric motor into linear motion and transmits it to the piston, the linear motion conversion mechanism including a rotating part that rotates by power transmitted from the electric motor and a linear motion part that moves in the forward direction and the reverse direction of the forward direction by power transmitted from the rotating part, A braking control device applicable to a vehicle equipped with, The brake control unit performs the following: pressurization process, which controls the pressure regulating unit to increase the hydraulic pressure of the brake fluid in the fluid chamber and moves the piston in the forward direction to generate hydraulic braking force on the wheel; apply process, which controls the electric motor to move the linear motion unit in the forward direction and moves the piston in the forward direction with the linear motion unit to generate parking braking force on the wheel; and full release process, which controls the electric motor to move the linear motion unit to its limit in the reverse direction. The piston is rotatable around an axis extending in the forward direction relative to the cylinder, but is not rotatable around an axis extending in the forward direction relative to the linear motion part. If the brake control unit performs the apply process after performing the full release process, it will perform the apply process while performing the pressurizing process. Brake control device.

2. When the full release process is performed, the linear motion part moving in the retraction direction comes into contact with the rotating part, and the state in which the rotating part and the linear motion part become one is called a jammed state. The braking control unit includes a jamming determination unit that determines whether the linear motion conversion mechanism is jammed or not based on the current value of the electric motor when the braking control unit performs the apply process. The braking control unit executes the apply process without performing the pressurizing process after executing the full release process, and if it is determined that the linear motion conversion mechanism is in the jammed state while the apply process is being executed, it executes the apply process while performing the pressurizing process. The braking control device according to claim 1.

3. The jamming determination unit determines whether the jamming condition has been resolved based on the change in the current value of the electric motor when the apply process is executed. The braking control unit terminates the pressurization process if it determines that the jammed state has been resolved while performing the apply process while simultaneously performing the pressurization process. The braking control device according to claim 2.

4. The jamming determination unit determines whether the jamming condition has been resolved based on the change in the current value of the electric motor when the apply process is executed. When the brake control unit is performing the pressurization process and the apply process is being performed, if it is determined that the jammed state has not been resolved, the brake control unit increases the hydraulic pressure of the brake fluid in the fluid chamber during the pressurization process. The braking control device according to claim 2.

5. The braking control unit terminates the apply process if, while performing the pressurizing process, the magnitude of the electric motor's current continues to increase. A braking control device according to any one of claims 1 to 4.

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