Brake control device

Abstract

To improve the efficiency of driving of an electric pump during anti-lock brake control.SOLUTION: A brake control device 30 comprises: a pressure control reservoir 306 into which brake fluid discharged from wheel cylinders 11L, 11R, 12L, 12R flows during ABS control; an electric pump 304 that draws out the brake fluid from the pressure control reservoir 306; and a controller 35 that controls a pump speed of the electric pump 304. During ABS control, the controller 35 calculates a predicted fluid amount, which is a predicted value of the amount of brake fluid remaining in the pressure control reservoir 306 at the time when the vehicle speed decreases to a predetermined speed under the assumption that the current ABS control continues until the vehicle speed decreases to the predetermined speed, and controls the pump speed on the basis of the predicted fluid amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Some vehicle braking control systems employ anti-lock brake control, which adjusts braking force to prevent wheels from locking. Anti-lock brake control reduces the pressure in the wheel cylinder of a wheel that is about to lock during braking, and then increases the pressure in the wheel cylinder again when the wheel resumes rotation. Brake fluid discharged from the wheel cylinder due to the reduction in pressure flows into a pressure regulating reservoir. If the pressure regulating reservoir becomes full, no more brake fluid can be discharged from the wheel cylinder, resulting in a bottoming condition. Therefore, during anti-lock brake control, an electric pump is used to suck out brake fluid from the pressure regulating reservoir, preventing the wheel from bottoming out.

[0003] A conventional brake control device that performs such antilock brake control is described in Patent Document 1. The brake control device in Patent Document 1 detects or estimates the amount of brake fluid discharged from the wheel cylinder during pressure reduction. The brake control device then drives an electric pump at a rotational speed that allows the detected or estimated amount of brake fluid to be sucked out of a pressure regulating reservoir in a fixed time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-267736 Summary of the Invention [Problem to be solved by the invention]

[0005] The braking control device described in Patent Document 1 can reduce the rotational speed of the electric pump to a level that allows all brake fluid to be sucked out of the pressure regulating cylinder after a certain time has elapsed since the start of wheel cylinder pressure increase. This reduces the electric pump's power consumption and operating noise. However, there is room for further improvement in the efficiency of pump drive during antilock brake control. [Means for solving the problem]

[0006] A brake control device that solves the above problem is a device that performs anti-lock brake control in a vehicle and includes a pressure regulating reservoir into which brake fluid discharged from a wheel cylinder during the anti-lock brake control flows, an electric pump that sucks the brake fluid from the pressure regulating reservoir, and a controller that controls the pump speed, which is the rotational speed of the electric pump, and during execution of the anti-lock brake control, the controller is configured to calculate a predicted fluid volume, which is a predicted value of the amount of brake fluid remaining in the pressure regulating reservoir at the time the vehicle speed decreases to a predetermined speed, assuming that the current anti-lock brake control will continue until the vehicle speed decreases to the predetermined speed, and to perform fluid volume prediction pump control that controls the pump speed based on the predicted fluid volume. [Effects of the Invention]

[0007] The braking control device has the effect of improving the efficiency of driving the electric pump during antilock brake control. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of an embodiment of a braking control device; [Figure 2] 4 is a flowchart of a process executed by a controller of the braking control device for fluid volume prediction pump control. [Figure 3]1 is a time chart showing an example of the control mode of ABS control by the above-mentioned brake control device, in which (A) shows the change in vehicle speed, (B) shows the change in master pressure and wheel pressure, (C) shows the change in pump speed, and (D) shows the change in the amount of brake fluid remaining in the pressure regulating reservoir. [Figure 4] 10 is a time chart showing another example of the control mode of ABS control by the above-mentioned brake control device, in which (A) shows the change in vehicle speed, (B) shows the change in master pressure and wheel pressure, (C) shows the change in pump speed, and (D) shows the change in the amount of brake fluid remaining in the pressure regulating reservoir. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) A first embodiment of the braking control device will be described below with reference to FIGS. <Structure of braking control device> First, the configuration of a brake control device 30 of this embodiment will be described with reference to FIG. 1. The brake control device 30 of this embodiment is mounted on a vehicle having four wheels, front, rear, left and right. The vehicle is equipped with a reserve tank 21 and a master cylinder 22. The reserve tank 21 is a tank that stores brake fluid, which is a liquid that serves as a medium for transmitting hydraulic pressure. The master cylinder 22 is a mechanical pressure device that generates hydraulic pressure in response to depression of the brake pedal 20. The master cylinder 22 is connected to wheel cylinders 11L and 11R of the left and right front wheels through a first fluid path 13. Furthermore, the master cylinder 22 is connected to wheel cylinders 12L and 12R of the left and right rear wheels through a second fluid path 14.

[0010] The brake control device 30 is a device that can individually adjust the hydraulic pressure of the wheel cylinders 11L, 11R, 12L, and 12R of each wheel. In the following description, the hydraulic pressure of the wheel cylinders 11L, 11R, 12L, and 12R of each wheel will be referred to as wheel pressure. The brake control device 30 can perform anti-lock brake control by individually adjusting the wheel pressure of each wheel. In the following description, the anti-lock brake control will be referred to as ABS control. The brake control device 30 includes a first assisting device 31 and a second assisting device 32.

[0011] Next, the configurations of the first assisting device 31 and the second assisting device 32 will be described. First, the configuration of the hydraulic circuit for the wheel cylinder 11L in the first assisting device 31 will be described. This hydraulic circuit includes a differential pressure control valve 301, a holding valve 302, a pressure reducing valve 303, an electric pump 304, a pressure regulating reservoir 306, and a return fluid path 307.

[0012] The first fluid line 13 is connected to a fluid line 308 via a differential pressure control valve 301. The differential pressure control valve 301 is a normally open linear solenoid valve. By controlling the opening degree of the differential pressure control valve 301, a differential pressure can be generated between the first fluid line 13 and the fluid line 308. A check valve 309 is installed in parallel with the differential pressure control valve 301. The check valve 309 is a valve that allows the flow of brake fluid from the first fluid line 13 to the fluid line 308, while preventing the flow of brake fluid in the opposite direction.

[0013] Fluid passage 308 is connected to wheel cylinder 11L via fluid passage 310. A check valve 311 is provided in parallel with fluid passage 302 between fluid passage 308 and fluid passage 310. Check valve 311 is a valve that allows the flow of brake fluid from fluid passage 310 to fluid passage 308, while blocking the flow of brake fluid from fluid passage 308 to fluid passage 310.

[0014] The fluid path 310 is connected to the pressure regulating reservoir 306 via a pressure reducing valve 303. The pressure reducing valve 303 is a normally closed solenoid valve that opens when energized and closes when de-energized. The pressure reducing valve 303 and the pressure regulating reservoir 306 are connected via a fluid path 312.

[0015] Fluid path 312 is connected to fluid path 308 through pump fluid path 313. An electric pump 304 is installed in pump fluid path 313. Electric pump 304 is operated by the rotation of electric motor 305. In response to its operation, electric pump 304 sucks brake fluid from pressure regulating reservoir 306 and discharges it into fluid path 308. A check valve 314 is installed in the portion of pump fluid path 313 between electric pump 304 and fluid path 308. Check valve 314 is a valve that allows brake fluid to flow from electric pump 304 toward fluid path 308, while blocking the flow of brake fluid from fluid path 308 toward electric pump 304.

[0016] The pressure regulating reservoir 306 is connected to the first fluid path 13 through the return fluid path 307. When there is a certain amount of brake fluid inside the pressure regulating reservoir 306, the pressure regulating reservoir 306 is in a state of blocking communication with the return fluid path 307. At this time, the electric pump 304 sucks the brake fluid inside the pressure regulating reservoir 306. On the other hand, when the brake fluid inside the pressure regulating reservoir 306 decreases due to suction by the electric pump 304, the pressure regulating reservoir 306 is in a state of communication with the return fluid path 307. This allows the electric pump 304 to suck brake fluid from the first fluid path 13 via the return fluid path 307.

[0017] The hydraulic circuit for wheel cylinder 11R in first assisting device 31 has the same configuration as the hydraulic circuit for wheel cylinder 11L. The hydraulic circuits for wheel cylinder 11L and wheel cylinder 11R share differential pressure control valve 301, electric pump 304, pressure regulating reservoir 306, return fluid line 307, fluid lines 308 and 312, pump fluid line 313, and check valves 309 and 314. The hydraulic circuit for wheel cylinder 11L and the hydraulic circuit for wheel cylinder 11R each have separate retention valve 302, pressure reducing valve 303, fluid line 310, and check valve 311.

[0018] On the other hand, the hydraulic circuits for the wheel cylinders 12L and 12R in the second assisting device 32 have the same configuration as the hydraulic circuits for the wheel cylinders 11L and 11R in the first assisting device 31. Furthermore, the first assisting device 31 and the second assisting device 32 share an electric motor 305.

[0019] The controller 35 is an electronic control device that includes one or more processors that execute various controls and a memory that stores control programs and data. The controller 35 is controllably connected to the first assisting device 31 and the second assisting device 32. The controller 35 also receives detection signals from a stroke sensor 280, a hydraulic pressure sensor 33, and wheel speed sensors 36 to 39. The stroke sensor 280 is a sensor that detects a pedal stroke S. The pedal stroke S represents the amount of depression of the brake pedal 20. The hydraulic pressure sensor 33 is a sensor that detects a master pressure. The master pressure represents the hydraulic pressure supplied by the master cylinder 22 to the first hydraulic path 13. The wheel speed sensors 36 to 39 are sensors that detect the rotational speeds of the left and right front wheels and the left and right rear wheels, respectively.

[0020] Based on the detection results of each wheel speed sensor 36 - 39, etc., the controller 35 calculates and obtains the vehicle body speed VS, which is the traveling speed of the vehicle, and the acceleration and deceleration of the vehicle. Further, the controller 35 calculates and obtains the hydraulic pressure of each wheel cylinder 11L, 11R, 12L, 12R from the detection result of the hydraulic pressure sensor 33 and the control states of the first booster device 31 and the second booster device 32. In the following description, the wheel cylinders 11L, 11R, 12L, 12R of each wheel are described as wheel hydraulic pressure.

[0021] <Regarding ABS control> Next, the ABS control executed in the braking control device 30 will be described. During braking of the vehicle, the controller 35 checks whether wheel lock has occurred based on the detection results of the wheel speed sensors 36 - 39 of each wheel. When the controller 35 confirms wheel lock, it starts the ABS control. When starting the ABS control, the controller 35 performs a pressure reduction process. The pressure reduction process is a process of controlling the first booster device 31 and the second booster device 32 to reduce the wheel pressure of the wheel where lock has occurred. Specifically, the controller 35 performs the process of closing the holding valve 302 and opening the pressure reduction valve 303 as the pressure reduction process implementation. As a result, the brake fluid of the wheel cylinders 11L, 11R, 12L, 12R of the locked wheel is discharged to the pressure regulating reservoir 306, so the wheel pressure decreases. After that, when the controller 35 confirms that the wheel lock has been released, it performs a pressure increase process. The pressure increase process is a process of controlling the first booster device 31 and the second booster device 32 to increase the wheel pressure of the wheel where the lock has been released again. Specifically, the controller 35 performs the process of closing the pressure reduction valve 303 and opening the holding valve 302 as the pressure increase process. As a result, the discharge of the brake fluid from the wheel cylinders 11L, 11R, 12L, 12R stops, so the wheel pressure of the wheel where the release of the lock has been confirmed increases. During the ABS control, the controller 35 repeatedly executes these pressure reduction processes and pressure increase processes alternately.

[0022] <Regarding the control of the liquid volume prediction pump> During ABS control, the controller 35 in the brake control device 30 of this embodiment drives the electric pump 304 to suck out brake fluid that has flowed into the pressure regulating reservoir 306 from the wheel cylinders 11L, 11R, 12L, and 12R. The controller 35 controls the pump speed when driving the electric pump 304 during ABS control. The pump speed is the discharge speed of the electric pump 304. In this embodiment, the controller 35 controls the pump speed by adjusting the drive current flowing to the electric motor 305. In the following description, the control of the pump speed during ABS control in the brake control device 30 of this embodiment is referred to as fluid volume predictive pump control.

[0023] FIG. 2 shows a flowchart of the process executed by the controller 35 for fluid volume predictive pump control. The controller 35 repeatedly executes the process of FIG. 2 for each predetermined control cycle while ABS control is being executed. In the process of FIG. 2, the controller 35 sets the pump speed. After setting the pump speed in step S120 or step S160 of FIG. 2, the controller 35 ends the process of FIG. 2 for the current control cycle. Then, the controller 35 adjusts the drive current of the electric motor 305 to drive the electric pump 304 at the set pump speed.

[0024] 2 starts, the controller 35 first acquires the current vehicle body speed VS and the vehicle deceleration DVS in step S100. Then, in the following step S110, the controller 35 determines whether the vehicle deceleration DVS is equal to or greater than a predetermined value X. The predetermined value X is set to, for example, a lower limit value of the vehicle deceleration DVS indicating that the vehicle is undergoing sudden braking. If the controller 35 determines that the vehicle deceleration DVS is equal to or greater than the predetermined value X (S110: YES), the controller 35 proceeds to step S120. In step S120, the controller 35 sets the pump speed to a predetermined first speed V1, and then ends the processing of FIG. 2 for the current control cycle. The first speed V1 is set to a value of the pump speed that can maintain the increase in brake fluid remaining in the pressure regulating reservoir 306 during ABS control close to "0." That is, the first speed V1 is set to a pump speed at which the flow rate of brake fluid sucked out of the pressure regulating reservoir 306 is equal to or greater than the maximum flow rate of brake fluid flowing into the pressure regulating reservoir 306 during ABS control.

[0025] On the other hand, if the controller 35 determines that the vehicle deceleration DVS is less than the predetermined value X (S110: NO), the controller 35 proceeds to step S130. In step S130, the controller 35 calculates an expected deceleration time T. The expected deceleration time T represents the time required for the vehicle body speed VS to decrease to a predetermined speed S1 if the vehicle maintains the current deceleration DVS. Specifically, in calculating the expected deceleration time T, the controller 35 first obtains the difference between the vehicle body speed VS and the predetermined speed S1 (= VS - S1). Then, the controller 35 divides this difference by the deceleration DVS and calculates the divided value as the value of the expected deceleration time T. The predetermined speed S1 is set to an upper limit value of the vehicle body speed VS at which the stop of ABS control is permitted. For example, a slow speed of "0" or close to "0" is set to the predetermined speed S1.

[0026] In the next step S140, the controller 35 calculates the predicted fluid volume Q based on the predicted deceleration time T. Specifically, the controller 35 multiplies the predicted deceleration time T by a predetermined fluid volume increase rate A, and calculates the multiplied value as the value of the predicted fluid volume Q. The fluid volume increase rate A represents the amount of increase per unit time of brake fluid in the pressure regulating reservoir 306 when ABS control is executed with the pump speed set to a second speed V2 (described below) and the electric pump 304 driven. The value of this fluid volume increase rate A can be obtained in advance, for example, by experimentation. The second speed V2 is set to a speed lower than the first speed V1.

[0027] Next, in step S150, the controller 35 determines whether the predicted fluid volume Q is less than a predetermined threshold Y. The threshold Y is set to a value slightly smaller than the maximum storage volume MAX, which is the upper limit of the amount of brake fluid that can be stored in the pressure regulating reservoir 306. If the controller 35 determines that the predicted fluid volume Q is equal to or greater than the threshold Y (S150: NO), the controller 35 proceeds to the processing of step S120 described above. In this case, the pump speed is set to the first speed V1. On the other hand, if the controller 35 determines that the predicted fluid volume Q is less than the threshold Y (S150: YES), the controller 35 proceeds to the processing of step S160. In step S160, the controller 35 sets the pump speed to the second speed V2.

[0028] <Operations and Effects of the Embodiments> The operation and effects of this embodiment will be described. When ABS control starts, brake fluid discharged from wheel cylinders 11L, 11R, 12L, and 12R flows into pressure regulating reservoir 306. When pressure regulating reservoir 306 becomes full, brake fluid cannot be discharged from wheel cylinders 11L, 11R, 12L, and 12R any more, and ABS control cannot be continued. During ABS control, controller 35 drives electric pump 304 to discharge brake fluid that has flowed in from wheel cylinders 11L, 11R, 12L, and 12R from pressure regulating reservoir 306.

[0029] Controller 35 sets a first speed V1 and a second speed V2 as the pump speed of electric pump 304 during ABS control. First speed V1 is set to a speed that allows the amount of brake fluid remaining in pressure regulating reservoir 306 during ABS control to be maintained close to zero. In contrast, second speed V2 is set to a speed lower than first speed V1. Therefore, if ABS control is continued while maintaining the pump speed at second speed V2, there is a possibility that the amount of brake fluid remaining in pressure regulating reservoir 306 will gradually increase.

[0030] The controller 35 in the brake control device 30 of this embodiment calculates a predicted fluid volume Q during ABS control. The predicted fluid volume Q is a predicted value of the amount of brake fluid remaining in the pressure regulating reservoir 306 at the time when the vehicle body speed VS decreases to a predetermined speed S1, assuming that the current ABS control will continue until the vehicle body speed VS subsequently decreases to the predetermined speed S1. During ABS control, the controller 35 sets the pump speed to a first speed V1 if the predicted fluid volume Q is equal to or greater than a predetermined threshold Y, and to a second speed V2 if the predicted fluid volume Q is less than the threshold Y.

[0031] FIG. 3 shows an example of an embodiment of ABS control by the brake control device 30 of this embodiment. FIG. 3(A) shows the transition of vehicle speed VS during ABS control. FIG. 3(B) shows the transition of master pressure and wheel pressure during ABS control. FIG. 3(C) shows the transition of pump speed during ABS control. FIG. 3(D) shows the transition of the remaining amount of brake fluid in pressure regulating reservoir 306. Note that FIG. 3(D) also shows the transition of predicted fluid volume Q with a dashed dotted line. FIG. 3(D) also shows the transition of the remaining amount of brake fluid in pressure regulating reservoir 306 when the pump speed during ABS control is fixed at first speed V1 throughout and when it is fixed at second speed V2.

[0032] In the example of Fig. 3, ABS control is initiated at time t1. Then, ABS control ends at time t4 when the vehicle speed VS drops to "0" and the vehicle comes to a stop. In the example of Fig. 3, the vehicle maintains a constant deceleration DVS from the start of ABS control until the vehicle comes to a stop. Furthermore, ABS control is performed so that the same amount of brake fluid flows into the pressure regulating reservoir 306 at a constant cycle.

[0033] In FIG. 3 , the predicted fluid volume Q exceeds the threshold value Y at time t1 when ABS control is started. Therefore, the controller 35 sets the pump speed to the first speed V1 and starts ABS control. At time t2, the predicted fluid volume Q is less than the threshold value Y. At this time t2, the controller 35 switches the pump speed from the first speed V1 to the second speed V2. When the pump speed is switched to the second speed V2, the electric pump 304 is unable to completely pump out the brake fluid that has flowed in from the wheel cylinders 11L, 11R, 12L, and 12R from the pressure regulating reservoir 306. Therefore, after time t2, the remaining amount of brake fluid in the pressure regulating reservoir 306 tends to increase. However, the remaining amount of brake fluid in the pressure regulating reservoir 306 has not yet reached the maximum storage volume MAX until time t3, when the vehicle speed VS decreases to the predetermined speed S1. Therefore, the ABS control continues until time t3.

[0034] When the pump speed during ABS control is fixed at the first speed V1, the residual amount of brake fluid in the pressure regulating reservoir 306 is maintained near zero. However, the higher the pump speed, the greater the operating noise and power consumption of the electric pump 304 and the electric motor 305. Therefore, the brake control device 30 of this embodiment can reduce the operating noise and power consumption of the electric pump 304 and the electric motor 305 compared to when the pump speed is fixed at the first speed V1. On the other hand, when the pump speed during ABS control is fixed at the second speed V2, the residual amount of brake fluid in the pressure regulating reservoir 306 is likely to reach the maximum storage amount MAX before the vehicle speed VS decreases to the predetermined speed S1. When the residual amount reaches the maximum storage amount MAX, the discharge of brake fluid from the wheel cylinders 11L, 11R, 12L, and 12R is restricted, making it impossible to properly perform ABS control.

[0035] FIG. 4 shows another example of ABS control by the brake control device 30 of this embodiment. FIG. 4(A) shows the transition of vehicle speed VS during ABS control. FIG. 4(B) shows the transition of master pressure and wheel pressure during ABS control. FIG. 4(C) shows the transition of pump speed during ABS control. FIG. 4(D) shows the transition of the remaining amount of brake fluid in the pressure regulating reservoir 306. FIG. 4(D) also shows the transition of predicted fluid volume Q with a dashed dotted line. Furthermore, FIG. 4(D) also shows the transition of the remaining amount of brake fluid in the pressure regulating reservoir 306 when the pump speed during ABS control is fixed at first speed V1 throughout.

[0036] In the case of Figure 4, ABS control is initiated at time t5 and continues until the vehicle speed VS becomes "0" and the vehicle stops at time t7. In the case of Figure 4 as well, the vehicle deceleration DVS is constant during ABS control, and ABS control is performed so that the same amount of brake fluid flows into pressure regulating reservoir 306 at regular intervals.

[0037] In the case of Figure 4, at time t5 when ABS control is started, the predicted fluid volume Q is below the threshold value Y. Therefore, the controller 35 starts ABS control with the pump speed set to the second speed V2. The controller 35 then maintains the pump speed at the second speed V2 until time t7 when the ABS control ends. In this case, too, the remaining amount of brake fluid in the pressure regulating reservoir 306 at time t6 when the vehicle speed VS drops to the predetermined speed S1 has not yet reached the maximum storage volume MAX, and ABS control can continue until that time.

[0038] The brake fluid remaining in the pressure regulating reservoir 306 at the end of ABS control is subsequently discharged from the pressure regulating reservoir 306 by driving the electric pump 304 under the control of the controller 35 or by operation by the driver at a predetermined timing.

[0039] The braking control device 30 of this embodiment described above provides the following effects. (1) In the brake control device 30 of this embodiment, during ABS control, the controller 35 calculates a predicted fluid volume Q, which is a predicted value of the amount of brake fluid remaining in the pressure regulating reservoir 306 when the vehicle speed VS decreases to the predetermined speed S1. The controller 35 then performs fluid volume predictive pump control, which controls the pump speed based on the calculated predicted fluid volume Q. If ABS control is to be continued until the vehicle speed VS decreases to the predetermined speed S1, the electric pump 304 needs to be driven so that the amount of brake fluid remaining in the pressure regulating reservoir 306 up to that point does not reach the maximum storage volume MAX. By using the predicted fluid volume Q, it is possible to adjust the pump speed so that the amount of brake fluid remaining in the pressure regulating reservoir 306 does not reach the maximum storage volume MAX when the vehicle speed VS decreases to the predetermined speed S1. For example, it is possible to drive the electric pump 304 at a low pump speed within a range that allows ABS control to be continued until the aforementioned point. Therefore, the braking control device 30 has the effect of improving the efficiency of pump drive during antilock brake control.

[0040] (2) In fluid volume predictive pump control, the controller 35 sets the pump speed to a predetermined first speed V1 when the predicted fluid volume Q is equal to or greater than a threshold Y. Furthermore, when the predicted fluid volume Q is less than the threshold Y, the controller 35 sets the pump speed to a second speed V2, which is lower than the first speed V1. For example, the controller 35 starts ABS control by setting the pump speed to the first speed V1 when the predicted fluid volume Q at the start of ABS control is equal to or greater than the threshold Y, and to the second speed V2 when the predicted fluid volume Q is less than the threshold Y. Furthermore, if the controller 35 sets the first speed V1 as the pump speed at the start of ABS control, the controller 35 switches the pump speed to the second speed V2 when the predicted fluid volume Q falls below the threshold Y after the start of ABS control. During ABS control, the electric pump 304 is driven with the pump speed set to the second speed V2, which is lower than the first speed V1, within a range in which the amount of brake fluid remaining in the pressure regulating reservoir 306 is less than the threshold Y when the vehicle speed VS drops to the predetermined speed S1. Therefore, the operating noise and power consumption of the electric pump 304 during ABS control can be reduced.

[0041] (3) In fluid volume predictive pump control, the controller 35 prohibits switching of the pump speed from the first speed V1 to the second speed V2 when the vehicle deceleration DVS is equal to or greater than the predetermined value X. When the vehicle brakes suddenly, the braking noise is loud, making the operating noise of the electric pump 304 less noticeable. On the other hand, when braking suddenly, the ABS control may adjust the wheel pressure more significantly than when braking gently. In the brake control device 30 of this embodiment, when braking suddenly, priority is given to reducing the amount of brake fluid remaining in the pressure regulating reservoir 306 over reducing the operating noise and power consumption of the electric pump 304, thereby enabling more reliable ABS control.

[0042] (4) The controller 35 calculates the predicted fluid volume Q based on the vehicle speed VS and the vehicle deceleration DVS. Therefore, the predicted fluid volume Q can be calculated easily and with sufficient accuracy. (Other embodiments) This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0043] In step S130 of Fig. 2, the controller 35 sets a constant for the fluid volume increase rate A and calculates the expected deceleration time T. The flow rate of brake fluid flowing into the pressure regulating reservoir 306 during ABS control varies depending on the implementation status of ABS control. Therefore, the fluid volume increase rate A may be variably set to calculate the expected deceleration time T depending on the implementation status of ABS control.

[0044] The predicted fluid volume Q may be calculated using a method different from that of the above embodiment. For example, the predicted fluid volume Q may be calculated as follows. First, the amount of brake fluid flowing into the pressure regulating reservoir 306 during the pressure reduction process and the amount of brake fluid discharged from the pressure regulating reservoir 306 during the pressure increase process are calculated for each process. The current remaining amount of brake fluid in the pressure regulating reservoir 306 is then calculated from these calculation results. Furthermore, the subsequent increase in the remaining amount of brake fluid in the pressure regulating reservoir 306, assuming that ABS control continues until the vehicle speed VS decreases to the predetermined speed S1, is calculated. The value of the predicted fluid volume Q is then calculated by adding the current remaining amount of brake fluid to the subsequent increase in the remaining amount of brake fluid.

[0045] The pump speed may be set by the process in Figure 2 only at the start of ABS control. In this case, the pump speed set at the start of ABS control is maintained until the end of ABS control.

[0046] In the liquid volume predictive pump control, the pump speed may be switched between three or more stages. In the liquid volume predictive pump control, the pump speed may be continuously switched in response to the predicted liquid volume Q. That is, in the liquid volume predictive pump control, the controller 35 may continuously variably set the second speed V2 in accordance with the predicted liquid volume Q.

[0047] In the liquid volume predictive pump control, the pump speed may be feedback controlled in accordance with the difference between the predicted liquid volume Q and the threshold value Y. The controller 35 may be configured as a circuit including one or more processors operating according to a computer program, one or more dedicated hardware circuits such as dedicated hardware for performing at least some of the various processes, or a combination thereof. Dedicated hardware may include, for example, an application-specific integrated circuit (ASIC). The processor includes a CPU and memory such as RAM and ROM, which stores program code or instructions configured to cause the CPU to perform the processes. The memory, i.e., storage medium, includes any available medium accessible by a general-purpose or dedicated computer. [Explanation of symbols]

[0048] 11L, 11R, 12L, 12R...wheel cylinder, 13...first fluid path, 14...second fluid path, 20...brake pedal, 21...reserve tank, 22...master cylinder, 30...braking control device, 31...first assisting device, 32...second assisting device, 33...fluid pressure sensor, 35...controller, 36-39...wheel speed sensors, 280...stroke sensor, 301...differential pressure control valve, 302...holding valve, 303...pressure reducing valve, 304...electric pump, 305...electric motor, 306...pressure regulating reservoir, 307...return fluid path, 308, 310...fluid path, 309, 311, 314...check valve, 313...pump fluid path.

Claims

1. A braking control device that performs antilock brake control in a vehicle, a pressure regulating reservoir into which brake fluid discharged from a wheel cylinder during the antilock brake control flows; an electric pump that sucks the brake fluid from the pressure regulating reservoir; and a controller that controls a pump speed, which is a rotation speed of the electric pump, and during execution of the antilock brake control, the controller Calculating a predicted fluid amount, which is a predicted value of the amount of brake fluid remaining in the pressure regulating reservoir at the time when the vehicle speed decreases to a predetermined speed, assuming that the current antilock brake control will be continued until the vehicle speed decreases to the predetermined speed; performing a fluid volume predictive pump control for controlling the pump speed based on the predicted fluid volume; A braking control device that performs the above.

2. 2. The brake control device according to claim 1, wherein in the fluid volume predictive pump control, the controller sets the pump speed to a predetermined first speed when the predicted fluid volume is equal to or greater than a threshold, and sets the pump speed to a second speed lower than the first speed when the predicted fluid volume is less than the threshold.

3. 2. The brake control device according to claim 1, wherein in the fluid volume predictive pump control, the controller sets the pump speed to a predetermined first speed when the predicted fluid volume at the start of the antilock brake control is equal to or greater than a threshold value, and sets the pump speed to a second speed lower than the first speed when the predicted fluid volume at the start of the antilock brake control is less than the threshold value.

4. 4. The brake control device according to claim 2, wherein the controller variably sets the second speed in a stepless manner in accordance with the predicted fluid amount.

5. 4. The brake control device according to claim 2, wherein in the fluid volume predictive pump control, the controller prohibits switching of the pump speed from the first speed to the second speed in accordance with the deceleration of the vehicle.

6. The brake control device according to claim 1 , wherein the controller calculates the predicted fluid amount based on the vehicle speed and the deceleration of the vehicle.

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