JP2009190648A - Brake control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake control device capable of preventing a vehicle from moving backward when driving force disappears when a vehicle is stopped on an uphill road.
In a brake control device capable of automatically controlling a braking force of a vehicle, a road surface gradient detecting means 40 for detecting an uphill road, a stop state detecting means 31 for detecting a stop state of the vehicle, and an action on a drive wheel. Driving force disappearance predicting means 35 for predicting the occurrence of disappearance of the driving force where the driving force is interrupted and when the occurrence of the disappearance of the driving force is predicted when the uphill road is stopped, the vehicle stop state after the disappearance of the driving force is maintained. As described above, a braking force control means 36 that increases the braking force of the vehicle in advance before the driving force disappears is provided.
[Selection] Figure 3

Description

  The present invention belongs to the technical field of a brake control device that prevents a vehicle from moving backward when driving force is interrupted on an uphill road.

  Conventionally, for the purpose of improving fuel efficiency, when the driving range is selected when the vehicle is stopped, the engagement capacity of the forward clutch provided on the driving force transmission path between the output shaft of the automatic transmission and the driving wheels is reduced. A technique for performing neutral control is known. When this neutral control is performed on an uphill road, the driving force decreases, and the vehicle may move backward (slid down). Therefore, the braking force of the vehicle is increased in cooperation with the neutral control.

In Patent Document 1, in order to achieve both the prevention of reverse and the improvement of responsiveness at the time of restart by minimizing the amount of increase in braking force, the road surface gradient and the forward clutch engagement capacity are reduced. Accordingly, a technique for adjusting the amount of increase in braking force during neutral control is disclosed.
JP 2006-31378 A

  However, in the above prior art, for example, immediately after the engine is stopped, when the driving force decreasing gradient of the vehicle is larger than the increasing gradient of the braking force, that is, in a situation where the driving force is suddenly interrupted when the uphill is stopped. There was a problem that the braking force was insufficient and the vehicle moved backward.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a brake control device that can prevent the vehicle from moving backward when the driving force is interrupted when the vehicle is stopped on an uphill road. is there.

  In order to achieve the above object, in the brake control device of the present invention, when it is predicted that the driving force disappears when the driving force acting on the driving wheel is interrupted when the climbing vehicle is stopped, the vehicle stopped state after the driving force disappears. So that the braking force of the vehicle is increased in advance before the driving force disappears.

  Therefore, in the brake control device of the present invention, it is possible to prevent the vehicle from retreating when the driving force is interrupted while the vehicle is stopped on the uphill road.

  Hereinafter, the best mode for realizing a brake control device of the present invention will be described based on each embodiment shown in the drawings.

[Example 1]
First, the configuration will be described.
(Vehicle system configuration)
FIG. 1 is a system configuration diagram of a vehicle to which the brake control device of the first embodiment is applied.
The vehicle according to the first embodiment has an engine ENG as a power source for driving the vehicle, decelerates the engine rotation by the automatic transmission AT, and drives the left and right rear wheels RL and RR that are drive wheels.

The engine control ECU 10 that controls the engine ENG obtains information from the automatic transmission control ECU 20 that controls the automatic transmission AT and the brake control (braking force control means) ECU 30 that controls the braking force, and generates a control command for the engine ENG. To do.
The automatic transmission control ECU 20 acquires information from the engine control ECU 10 and the brake control ECU 30, and generates a control command for the automatic transmission AT.

  The brake control ECU 30 acquires each information from the engine control ECU 10, the automatic transmission control ECU 20, and the road surface gradient detecting means 40, and acquires each information and each wheel speed sensor 53a provided on each wheel FL, FR, RL, RR. , 53b, 53c, and 53d, a control command to the braking force control unit 52 is generated based on each wheel speed signal.

  The road surface gradient detection means 40 detects the road surface gradient and transmits road surface gradient information to the brake control ECU 30. As a method for detecting the road surface gradient, there are a method of calculating from the absolute value of the longitudinal acceleration detected by a longitudinal acceleration sensor (not shown) when the vehicle is stopped, or a method of directly measuring with an inclinometer.

The braking device 50 includes a braking force generation unit (first braking force generation unit) 51 and a braking force control unit (second braking force generation unit) 52.
The braking force generator 51 generates a braking force according to the amount of operation of the brake pedal BP.
The braking force control unit 52, depending on the control command generated by the brake control ECU 30, the braking force generated by the braking force generation unit 51 or the braking force applied to each wheel FL, FR, RL, RR by the braking force generated by itself. To control.
Each wheel speed sensor 53a, 53b, 53c, 53d detects the wheel speed of the corresponding wheel, and transmits the wheel speed information to the brake control ECU 30.

(Brake hydraulic circuit configuration)
FIG. 2 is a hydraulic circuit diagram of the braking device 50 according to the first embodiment.
The braking device 50 has a piping structure called X piping composed of two systems of a P system and an S system. The wheel cylinder of the left front wheel FL and the right rear wheel RR is connected to the P system, and the wheel cylinder of the right front wheel FR and the left rear wheel RL is connected to the S system.

In the following description, what is provided in both the P system and the S system, for example, in the case of a reservoir, the P system reservoir is represented as 16P, and the S system reservoir is represented as 16S. In addition, in the case of a wheel cylinder, for example, a wheel cylinder, the wheel cylinder of the left front wheel FL and the right rear wheel RR connected to the P system is connected to the W / CFL, W / CRR, system. The wheel cylinders of the right front wheel RL and the left rear wheel RL are represented as W / CRL and W / CRL.
Further, since the P system and the S system have the same structure in the braking device 50, only the P system will be described, and the description of the S system will be omitted.

  The braking force generator 51 discharges the brake fluid to the braking force controller 52 according to the operation of the brake pedal BP. The input rod INR is input according to the operation amount of the brake pedal BP of the driver, and the input of the input rod INR is boosted by a booster BO using a negative pressure of the engine ENG, a so-called negative pressure booster. From the input of the boosted input rod INR, the master cylinder M / C discharges the same amount of brake fluid to the P system and the S system.

The braking force control unit 52 is a brake fluid that is discharged from the braking force generation unit 51 and flows into the wheel cylinders W / CFL, W / CRR, or a brake fluid that flows into the wheel cylinders W / CFL, W / CRR to generate braking force by itself. By controlling the brake fluid flowing from the wheel cylinders W / CFL, W / CRR into the reservoir 16P, the brake pressure of the wheel cylinders W / CFL, W / CRR is controlled, and the braking force of the wheels is controlled.
The braking force control unit 52 is provided with a pump PP as means for generating a braking force separately from the braking force generation unit 51, and the pump PP is driven by one motor MT.

  The master cylinder M / C of the braking force generator 51 and the suction side of the pump PP are connected by a pipe line 11P. A gate-in valve 2P, which is a normally closed electromagnetic valve, is provided on the pipe line 11P. A check valve 6P is provided on the pipeline 11P and between the gate-in valve 2P and the pump PP. This check valve 6P allows the flow of brake fluid in the direction from the gate-in valve 2P toward the pump PP, and prohibits the flow in the opposite direction. In addition, a master cylinder pressure sensor PMC is provided upstream of the gate-in valve 2P between the master cylinder M / C and the pipe line 11P. In the first embodiment, the master cylinder pressure sensor PMC is provided only in the P system, but it may be provided in at least one of the P system or the S system.

  The discharge side of the pump PP and the wheel cylinders W / CFL, W / CRR are connected by a pipe line 12P. Solenoid in valves 4FL, 4RR, which are normally open solenoid valves corresponding to the wheel cylinders W / CFL, W / CRR, are provided on the pipe line 12P. Further, a check valve 7P is provided on the pipeline 12P and between the solenoid-in valves 4FL, 4RR and the pump PP. The check valve 7P allows the flow of brake fluid in the direction from the pump PP toward the solenoid-in valves 4FL and 4RR, and prohibits the flow in the determination direction.

  Further, the pipe line 12P is provided with pipe lines 17FL and 17RR that bypass the solenoid-in valves 4FL and 4RR. Check valves 10FL and 10RR are provided in the pipe lines 17FL and 17RR. The check valves 10FL, 10RR allow the brake fluid to flow in the direction from the wheel cylinders W / CFL, W / CRR to the pump PP, and prohibit the flow in the opposite direction.

  In FIG. 2, the master cylinder M / C of the braking force generator 51 and the pipeline 12P are connected by a pipeline 13P. The pipe line 12P and the pipe line 13P merge between the pump PP and the solenoid-in valves 4FL and 4RR. A gate-out valve 3P, which is a normally open solenoid valve, is provided on the pipeline 13P. Further, on the pipeline 13P, a pipeline 18P that bypasses each gate-out valve 3P is provided, and a check valve 9P is provided on the pipeline 18P. This check valve 9P allows the flow of brake fluid in the direction from the master cylinder M / C side toward the wheel cylinders W / CFL, W / CRR, and prohibits the flow in the opposite direction.

  A reservoir 16P is provided on the suction side of the pump PP, and the reservoir 16P and the pump PP are connected by a pipe line 15P. A check valve 8P is provided between the reservoir 16P and the pump PP. The check valve 8P allows the flow of brake fluid in the direction from the reservoir 16P to the pump PP, and prohibits the flow in the opposite direction.

  Wheel cylinders W / CFL, W / CRR and pipe 15P are connected by pipe 14P. The pipeline 14P and the pipeline 15P merge between the check valve 8P and the reservoir 16P. Solenoid out valves 5FL and 5RR, which are normally closed solenoid valves, are provided in the pipe line 14P.

(Brake control ECU configuration)
FIG. 3 is a control block diagram of the brake control ECU 30 according to the first embodiment.
The brake control ECU 30 includes a stop state detection means 31, a hill hold function determination means 32, an idle stop function determination means 33, a hill start assist function determination means 34, a driving force disappearance prediction means 35, and a braking force control means 36. And.

  The stop state detection means 31 detects the stop state of the vehicle. As a detection method of the stop state, for example, based on information from each wheel speed sensor 53 (53a to 53d) and the master cylinder pressure sensor PMC, the wheel speeds of all four wheels are zero, and the master cylinder pressure is lower than the threshold value. If it is larger, it is determined that the vehicle is in a stopped state.

  The determination may be made by adding the open / closed state of the door of the driver's seat to the above two conditions. That is, when all the four wheel speeds are zero and the master cylinder pressure is larger than the threshold value and the driver's seat door is closed, it is determined that the vehicle is stopped. Accordingly, when the driver leaves the vehicle, it is determined that the vehicle is not stopped, so that the brake control without the driver can be prevented.

  The hill hold function determination means 32 determines whether or not the hill hold function is necessary, which is a brake control state that increases or holds the braking force acting on the wheel cylinder W / C while the hill is stopped and prevents the vehicle from moving backward. judge. The necessity of the hill hold function is determined based on information from the road surface gradient judging means 40, the automatic transmission control ECU 20 and the engine control ECU 10, for example, when the road surface gradient is equal to or greater than a threshold and the shift position of the automatic transmission MT is other than the parking range. If the force (estimated from the accelerator opening and shift position) is less than the specified value and the parking brake is all satisfied, it is determined that the hill hold function is necessary. If any of the above four conditions is not satisfied, the hill hold function is satisfied. Is determined to be unnecessary. As another determination method, the above four conditions may include the fact that there is no driver's accelerator operation, no intervention of vehicle behavior control such as ABS, TCS, VDC (vehicle behavior stabilization control system), etc. Good.

  The idle stop function determination means 33 determines whether or not an idle stop function that is a vehicle control state in which the engine ENG is temporarily stopped when the vehicle is stopped. The necessity of the idle stop function is determined based on information from the automatic transmission control ECU 20 and the engine control ECU 10, for example, when the shift position of the automatic transmission AT is in the travel range and the driver does not operate the accelerator. Is determined to be necessary, and if either of the two conditions is not satisfied, it is determined that the idle stop function is unnecessary.

  In addition to the above two conditions, determine that the engine is warmed up sufficiently, the battery voltage and current are sufficient, the negative pressure of the booster is sufficient, the electrical load from the air conditioner etc. is small, etc. Also good. As a result, it is possible to prevent the engine from being restarted after the idling stop, and to secure the braking force by the brake operation by the driver during the idling stop.

  The hill start assist function determination means 34 detects the driver's intention to start while the hill hold function is being executed, and when the driver tries to start while the hill hold function is being executed, the hill start assist function determination means 34 applies the braking force according to the start state of the vehicle. It is determined whether or not the hill start assist function is in the brake control state to be changed (mainly decreased). Here, the driver's intention to start is detected based on information from the automatic transmission control ECU 20 and the engine ECU 10. The shift position is in the driving (drive) range, the driver has an accelerator operation, the parking brake is off, and there is no brake operation. When all of the above conditions are satisfied, it is determined that there is an intention to start, and when any of the four conditions is not satisfied, it is determined that there is no intention to start.

The hill start assist function is necessary, for example, when the driver is willing to start and the wheel cylinder pressure is greater than the threshold value while the hill hold function is being executed or the hill start assist function is being executed. It is determined that the start assist is necessary, and when one of the two conditions is not satisfied, it is determined that the hill start assist is unnecessary.
It may be determined by adding to the above two conditions that there is no intervention of vehicle behavior control such as ABS, TCS, and VDC. Thereby, the hill start assist in the state where the vehicle behavior is unstable can be prevented.

  When the vehicle is stopped, the hill hold function is required, the hill start assist function is not required, and the idle stop function is required. Predict the occurrence of loss of driving force where the applied driving force is interrupted.

The braking force control means 36 sends a control command to obtain a wheel cylinder pressure for realizing each brake control state based on each necessity determination by each function judging means 31, 32, 33, 34. Output to 52.
In addition, when the driving force disappearance predicting unit 35 predicts the occurrence of the driving force disappearance, the driving force control unit 36 is configured to execute the idle stop function in order to maintain the vehicle stop state even after the driving force disappears. A control command for increasing the braking force of the vehicle is output to the braking force control unit 52 in advance.

  FIG. 4 is a state transition diagram showing a brake control state on an uphill road. In FIG. 4, “no brake control” is a state in which normal braking is performed without controlling the brake control device, and “idle stop” “+ Hill hold” is a brake control state in which the idle stop function and the hill hold function are executed simultaneously.

FIG. 5 is a diagram illustrating a transition condition to each brake control state.
The condition A for transitioning from “no brake control” to “idle stop” is that the vehicle stop state is determined by the stop state detection means 31, the hill hold function determination means 32 determines that the hill hold function is unnecessary, and the idle stop This is a case where the function determination means 33 satisfies all the determinations that the idle stop function is unnecessary.

  Condition B for transition from idle stop to no brake control is when one of the vehicle stop state detection means 31 determines that the vehicle is not stopped and the idle stop function determination means 33 determines that the idle stop function is unnecessary. .

  The condition C for transitioning from no brake control to hill hold is as follows: the stop state detection means 31 determines that the vehicle is stopped, the hill hold function determination means 32 determines that the hill hold function is necessary, and the hill start assist function determination means 34 This is a case where the hill start assist function satisfies all the unnecessary determinations.

  The condition D for transitioning from hill hold to no brake control is when the vehicle stop state detection means 31 determines that the vehicle is stopped and the hill hold function determination means 32 determines that the hill hold function is not required. is there.

  The condition E for transitioning from hill start assist to no brake control is when the hill start assist function determining means 34 determines that the hill start assist function is not required.

  The condition F for transition from hill hold to hill start assist is as follows: the stop state detection means 31 determines that the vehicle is stopped, the hill hold function determination means 32 determines that the hill hold function is necessary, and the hill start assist function determination means 34 This is a case where the hill start assist function satisfies all the judgments required.

  The condition G for transition from idle stop to idle stop + hill hold is determined by the stop state detection means 31 when the vehicle is stopped, the hill hold function determination means 32 determines that the hill hold function is necessary, and the idle stop function determination means. This is a case where the idle stop function is determined to be necessary at 33 and the hill start assist function determination means 34 satisfies all the determinations that the hill start assist function is not required.

  The condition H for transition from hill hold to idle stop + hill hold is that the vehicle stop state is determined by the stop state detection means 31, the hill hold function is determined to be necessary by the hill hold function determination means 32, and the idle stop function determination means. This is a case where the idle stop function is determined to be necessary at 33 and the hill start assist function determination means 34 satisfies the determination that the hill start assist function is not required.

  The condition I for transition from idle stop + hill hold to hill hold is that the vehicle stop state is determined by the stop state detection means 31, the hill hold function determination means 32 determines that the hill hold function is unnecessary, and the idle stop function determination means. This is a case in which either the idle stop function is determined to be unnecessary in 33, or the hill start assist function determining means 34 is determined to require hill start assist.

[Braking force control processing]
FIG. 6 is a flowchart showing a flow of a braking force control process executed by the brake control ECU 30 to realize each brake control state described above, and each step will be described below. This control process is repeatedly executed every predetermined calculation cycle. In this flowchart, only a part of communication steps is provided, but the information to be acquired and the information obtained by calculation are stored at any time, and the stored information is read at any time as necessary. To do.

  In step S2a, the state quantity is detected from each sensor, and each state quantity of the vehicle is acquired from the engine control ECU 10, the automatic transmission control ECU 20, and the road surface gradient detecting means 40, and the driving force of the vehicle is estimated. Migrate to

  In step S2b, the brake control state (or vehicle control state) to be executed is determined from each state quantity acquired in step S2a based on the transition condition shown in FIG. 5, and the process proceeds to step S2c.

  In step S2c, a control command for realizing the brake control state determined in step S2b is output to the braking force control unit 52, and this control is terminated.

  FIG. 7 is a flowchart showing the flow of the process in step S2a in FIG. 6, and each step will be described below.

  In step S210, the wheel speeds detected by the wheel speed sensors 53a to 53d and the master cylinder pressure detected by the master cylinder pressure sensor PMC are detected, and the process proceeds to step S211.

  In step S211, the engine speed is acquired from the engine control ECU 10, the shift position is acquired from the automatic transmission control ECU 20, and the road gradient is acquired from the road gradient detecting means 40, and the process proceeds to step S212.

  In step S212, the current driving force of the vehicle is estimated based on the engine speed and shift position acquired in step S211 and the process proceeds to step S2b.

  FIG. 8 is a flowchart showing the flow of processing in step S2c in FIG. 6, and each step will be described below.

  In step S230, it is determined whether or not the brake control state determined in step S2b is only “idle stop” or “no brake control”. If the brake control state is only “idle stop” or “no brake control”, the process proceeds to step S234. If the brake control state is other than “idle stop” only or “no brake control”, the process proceeds to step S234. Control goes to step S231.

  In step S231, it is determined whether or not the brake control state determined in step S2b is only “hill start assist”. When the brake control state is only “hill start assist”, the process proceeds to step S235, and when negative determination, that is, when the brake control state is other than “hill start assist”, the process proceeds to step S232.

  In step S232, it is determined whether or not the brake control state determined in step S2b is “hill hold” only. If the brake control state is “hill hold” only, the process proceeds to step S236. If the determination is negative, that is, if the brake control state is other than “hill hold”, the process proceeds to step S233.

  In step S233, the end of pump pressure increase is determined. “Pump boosting” means that the pump PP is used to prevent the vehicle from moving backward due to the loss of the driving force of the vehicle when the engine is stopped due to the idle stop when performing idle stop during hill hold. The pump pressure increase when driving to increase the wheel cylinder pressure. If the pump pressure increase has been completed, the process proceeds to step S236. If the negative determination, that is, if the pump pressure increase has not been completed, the process proceeds to step S237.

The determination method of the end of pump pressure increase is determined as the end of pump pressure increase when the wheel cylinder pressure is equal to or higher than the pressure capable of generating the “target braking force”.
The “target braking force” is a braking force that is equal to or greater than the absolute value of the component of the gravity direction of the vehicle acting on the vehicle. The pump pressure increase amount for obtaining the target braking force needs to be an amount capable of obtaining a braking force equal to or greater than the absolute value of the difference between the vehicle backward direction component of gravity acting on the vehicle and the current braking force. The current braking force can be estimated from the master cylinder pressure or the like.

  Here, when the absolute value of the vehicle backward direction component of gravity acting on the vehicle is larger than the absolute value of the current driving force of the vehicle, the difference between the vehicle backward direction component of gravity acting on the vehicle and the current braking force is calculated. Since the absolute value matches the absolute value of the current driving force of the vehicle, the pump pressure increase amount can be obtained from the estimated driving force of the vehicle.

  In step S233, whether or not pump pressure increase is necessary may be added as a condition. The necessity of pump pressure increase is determined based on the relationship between road surface gradient, braking force, and driving force when the brake control state changes from “idle stop” to “idle stop + hill hold”. If it is predicted that the pump will move backward, it is determined that pump pressure increase is necessary. Thereby, an excessive pump pressure increase can be suppressed. When it is determined that pump pressure increase is unnecessary, the process proceeds to step S236, and when negative determination, that is, pump pressure increase is determined to be necessary, the process proceeds to step S237.

  In step S234, the braking force control unit 52 is brought into a non-control state, and this control is terminated.

  In step S235, a control command for opening the gate-out valves 3P, 3S is output to the braking force control unit 52 so as to decrease the braking force in accordance with the increase in driving force, and this control is terminated.

  In step S236, in order to maintain the wheel cylinder pressure, a control command for closing the gate-out valves 3P and 3S is output to the braking force control unit 52, and this control is terminated.

  In step S237, in order to increase the wheel cylinder pressure, the gate-out valves 3P and 3S are closed, the gate-in valves 2P and 2S are opened, and a control command for driving the motor MT is sent to the braking force control unit 52. Output and end this control.

Next, the operation of the first embodiment will be described.
[Vehicle retreat prevention action on uphill road]
FIG. 9 is a diagram illustrating a relationship between forces acting in the vehicle traveling direction and the vehicle backward direction when the hill is stopped. (a) shows the case where the vehicle backward direction component of gravity acting on the vehicle is larger than the driving force (creep torque) in the vehicle before the idle stop, and (b) shows the vehicle before the idle stop, The case where the vehicle backward direction component of the gravity acting on the vehicle is smaller than the driving force is shown. And (c) has shown the case where an idle stop function is performed after increasing the braking force of a vehicle, when the necessity determination of an idle stop function is made.

  In (a) and (b), the vehicle backward direction component FG of gravity acting on the vehicle due to the slope of the uphill road is opposite to the driving force FC of the vehicle. In the case of (a), since the absolute value of the vehicle backward direction component FG of gravity is larger than the absolute value of the driving force FC, the direction of the braking force FB of the vehicle by the driver's braking operation is forward in the vehicle The magnitude is the difference between the absolute value of the vehicle backward direction component FG of gravity and the absolute value of the driving force FC of the vehicle. On the other hand, in the case of (b), since the absolute value of the vehicle backward direction component FG of gravity is smaller than the absolute value of the driving force FC of the vehicle, the direction of the braking force FB of the vehicle is the vehicle backward direction. The magnitude is the difference between the absolute value of the vehicle driving force FC and the absolute value of the vehicle backward direction component FG of gravity.

  In (a) and (b) above, when the driving force FC of the vehicle disappears due to the idle stop function, both | FG |> | FB |, so the vehicle will stop unless the driver increases the brake operation amount. The state cannot be maintained, and the vehicle moves backward on the uphill road.

  On the other hand, in the first embodiment, in the stopped vehicle that is idling as in the above (a) or (b), when the necessity determination of the idle stop function is made, the driving force FC of the vehicle disappears. The braking force FB is increased to FB ′ in advance before executing the idle stop function.

  As a result, even when the driving force FC disappears due to the execution of the idle stop function, the relationship between the vehicle backward direction component FG of gravity and the braking force FB ′ after pressure increase is expressed as | FG | ≦ | FB ′ | Therefore, it is possible to prevent the vehicle from retreating on the uphill road.

  Here, the amount of increase in braking force FB necessary to establish | FG | ≦ | FB '| is the amount obtained from | FG−FB | in both (a) and (b). In this case, since | FG−FB | = FC, the pump increase amount can be obtained from the estimated driving force FC without obtaining FB.

[Brake control action]
FIG. 10 is a time chart showing the braking control action of the first embodiment when stopping on an uphill road. The brake control state is “no brake control” → transition C → “hill hold” → transition H → “idle stop + hill”. "Hold"-> Transition I->"HillHold"-> Transition F->"Hill Start Assist"-> Transition E->"No brake control". In addition, the vehicle backward direction component of gravity acting on the vehicle due to the road surface inclination is assumed to be larger than the driving force of the vehicle.

  At time t0, since the stop state detection means 31 determines that the vehicle is in a non-stop state, “no brake control” is selected as the brake control state, and the braking force control unit 52 is not controlled. At this time, in the flowchart of FIG. 8, the flow proceeds from step S230 to step S234.

  At time t1, the wheel speeds of all four wheels become zero due to braking, and it is determined by the stop state detection means 31 that the vehicle is in a stop state, and the hill hold function determination means 32 determines that the hill hold function is necessary. Then, “Hill hold” is selected as the brake control state, and the gate-out valves 3P and 3S are closed to hold the wheel cylinder pressure. At this time, in the flowchart of FIG. 8, the process proceeds from step S230 → step S231 → step S232 → step S236.

  At time t2, the idle stop function determination means 33 determines that the idle stop function is necessary, so “idle stop + hill hold” is selected as the brake control state, and the gate-out valves 3P and 3S are closed and gated. In addition to opening the in-valves 2P and 2S, the motor MT is driven prior to idle stop, and the pump pressure is increased until the wheel cylinder pressure reaches the target value. The target value of the wheel cylinder pressure is a pressure value at which a braking force greater than the current driving force estimated in step S2a is obtained. At this time, in the flowchart of FIG. 8, the process proceeds from step S230 → step S231 → step S232 → step S233 → step S237.

  At time t3, because the wheel cylinder pressure has reached the target value due to the pump pressure increase, the gate-in valves 2P and 2S are opened and the motor MT is stopped to maintain the wheel cylinder pressure. Further, the engine ENG is stopped by the start of the idle stop. At this time, in the flowchart of FIG. 8, the process proceeds from step S230 → step S231 → step S232 → step S233 → step S236.

  In the section from time t3 to t3 ′, the driving force of the vehicle rapidly decreases as the engine stops due to idle stop, and becomes zero at time t3 ′. Therefore, although the driving force disappears, in Example 1, the braking force of the vehicle is increased in advance from time t2 prior to the idling stop at time t3. Therefore, the driving force disappears with the engine stop at time t3. Despite this, the vehicle can be kept stationary.

  At time t4, the idle stop function determination means 32 determines that the idle stop function is not required, so “hill hold” is selected as the brake control state. The engine ENG is restarted upon completion of the idle stop. At this time, in the flowchart of FIG. 8, the process proceeds from step S230 → step S231 → step S232 → step S236.

  Here, since the driving force is generated by the start of idling, the wheel cylinder pressure may be reduced by opening the gate-out valves 3P and 3S in order to reduce the increase in the braking force due to the pump pressure increase. Thereby, at the time of start by “hill start assist” after idling stop, it is possible to prevent the start performance from deteriorating due to the high wheel cylinder pressure.

  At time t5, the hill start assist function determination means 34 determines that hill start assist is necessary, so “hill start assist” is selected as the brake control state, and the gate-out is performed so that the braking force changes according to the driving force. Open valves 3P and 3S. At this time, in the flowchart of FIG. 8, the process proceeds from step S230 to step S231 to step S235.

  At time t6, the hill start assist function determination means 34 determines that hill start assist is not required, so “no brake control” is selected as the brake control state, and the braking force control unit 52 is not controlled. At this time, in the flowchart of FIG. 8, the flow proceeds from step S230 to step S234.

Next, the effect of Example 1 will be described.
The brake control device according to the first embodiment has the following effects.

  (1) In a brake control device that can automatically control the braking force of the vehicle, a road surface gradient detecting means 40 for detecting an uphill road, a stop state detecting means 31 for detecting a stop state of the vehicle, left and right rear wheels RL, Driving force disappearance predicting means 35 for predicting the occurrence of driving force disappearance in which the driving force acting on RR is interrupted, and when the occurrence of driving force disappearance is predicted in the stopping state of the uphill road, the vehicle stopping state after the disappearance of the driving force So that the braking force of the vehicle is increased in advance before the driving force disappears. Thereby, it is possible to prevent the vehicle from moving backward when the driving force is interrupted while the vehicle is stopped on the uphill road.

  (2) The braking force control means 36 increases the braking force to be increased before the driving force disappears to an absolute value of the difference between the braking force and the vehicle backward direction component of gravity acting on the vehicle when the occurrence of the driving force disappearance is predicted. Magnitude. As a result, the braking force of the vehicle when the driving force disappears becomes equal to or greater than the vehicle backward direction component of gravity acting on the vehicle, so that the backward movement of the vehicle can be reliably prevented.

  (3) When the absolute value of the vehicle backward direction component of gravity is larger than the absolute value of the driving force of the vehicle, the braking force control means 36 increases the braking force to be increased before the driving force disappears to be equal to or more than the disappearing driving force. Magnitude. That is, since the braking force to be increased can be set based on the driving force, it is possible to save time and effort for estimating the braking force based on the sensor signal from the master cylinder pressure sensor PMC or the like.

  (4) The driving force disappearance prediction means 35 predicts the occurrence of the disappearance of the driving force when the idling stop start condition for stopping the engine ENG is satisfied when the vehicle stops, so that the vehicle can be prevented from moving backward during the idling stop.

  (5) A braking force generation unit 51 that boosts the driver's brake pedal depression force using the negative pressure of the engine ENG to generate a braking force, and a braking force control unit 52 that generates a braking force using the pump PP The brake control ECU 30 causes the braking force control unit 52 to increase the braking force. In other words, by increasing the braking force by the braking force control unit 52 that does not use the negative pressure of the engine ENG, the boosting action of the brake pedal depression force by the braking force generation unit 51 becomes less effective when the engine is stopped when the engine is stopped. On the other hand, the necessary braking force can be reliably ensured.

  (6) Decrease the braking force by the hill hold function determination means 32 that determines whether or not the hill hold function is required to increase or hold the braking force when the hill is stopped and the driver's intention to start the hill hold function. Hill start assist function determining means 34 for determining whether or not the hill start assist function is necessary, idle stop function determining means 33 for determining whether or not the idle stop function for stopping the engine ENG when the vehicle is stopped, and determining whether the hill hold function is necessary. When the hill start assist function is not required and the idle stop function is required, the driving force disappearance predicting means 35 for predicting the occurrence of the driving force disappearing in which the driving force acting on the left and right rear wheels RL and RR is interrupted, and the driving force When the occurrence of disappearance is predicted, the braking force control means 36 for increasing the braking force of the vehicle in advance before the idle stop function is executed, Is provided. Thereby, it is possible to prevent the vehicle from retreating at the time of idling stop on the uphill road.

  (7) The driving force disappearance predicting means 35 is for stopping the disappearance of the driving force when the shift position of the automatic transmission AT selects the traveling range and the driver does not operate the accelerator when the vehicle is stopped on the uphill road. During idle stop on the uphill road, it is possible to prevent the vehicle from retreating due to the disappearance of the creep torque.

  (8) In the brake control device that can automatically control the braking force of the vehicle, the road surface gradient detecting means 40 for detecting the uphill road, the stop state detecting means 31 for detecting the stop state of the vehicle, and the stop state of the uphill road Therefore, when the shift position of the automatic transmission AT selects the travel range and the driver does not operate the accelerator, the driving force disappearance prediction that predicts the occurrence of the driving force loss that interrupts the driving force acting on the left and right rear wheels RL and RR Means 35 and braking force control means 36 for increasing the braking force of the vehicle in advance before the disappearance of the driving force so that the vehicle stopping state after the disappearance of the driving force is maintained when the occurrence of the disappearance of the driving force is predicted. And comprising. When idling is stopped on an uphill road, it is possible to prevent the vehicle from moving backward due to the disappearance of creep torque.

[Example 2]
Next, Example 2 will be described.
In the second embodiment, an electric booster is used as the booster BO of the braking force generator 51. Since other configurations are the same as those of the first embodiment, illustration and description of the same components are omitted.

  FIG. 11 is a schematic diagram showing the configuration of the braking force generator 51 of the second embodiment. The electric booster of the second embodiment includes an input rod INR that strokes according to the operation of the brake pedal BP, and the input rod. A booster rod BOR arranged in parallel with the INR and an electric actuator EA that strokes the booster rod BOR are provided. The input rod INR and the booster rod BOR are connected via a spring (brake pedal operation suppressing portion) KS.

  An input piston INP is attached to the tip of the input rod INR, and a booster piston BOP is attached to the tip of the booster rod BOR. Both pistons INP and BOP move back and forth in the master cylinder pressure chamber MCR, and the master cylinder M is driven by the input thrust applied from the brake pedal BP to the input piston INP and the booster thrust applied from the electric actuator EA to the booster piston BOP. Generate brake pressure in / C.

  In the second embodiment, the spring constant of the spring KS connecting the input rod INR and the booster rod BOR is set to the hydraulic reaction force that the input piston INP receives as the brake fluid amount changes in the master cylinder pressure chamber MCR when the pump PP is driven. The maximum variation is set.

Next, the operation of the second embodiment will be described.
[Pedal vibration suppression effect]
When the necessity of the idle stop function is determined on the uphill road, in the hydraulic circuit in FIG. 2, the brake fluid is drawn from the master cylinder pressure chamber MCR of the master cylinder M / C by driving the pump PP, and each wheel cylinder W / C Supplied to. Thereafter, when the driver removes his / her foot from the brake pedal BP and determines that the idle stop function is unnecessary, the brake fluid in each wheel cylinder W / C is temporarily stored in the reservoirs 16P and 16S. The brake fluid stored in the reservoirs 16P and 16S is returned to the master cylinder pressure chamber MCR by driving the pump PP at a predetermined timing.

  That is, when the pump PP is driven, the amount of brake fluid in the master cylinder pressure chamber MCR changes regardless of the driver's brake operation, and the hydraulic reaction force acting on the input piston INP fluctuates. If no measures are taken against force fluctuations, the brake pedal BP vibrates, giving the driver a sense of incongruity.

  On the other hand, in the second embodiment, the spring constant of the spring KS is set to the maximum fluctuation amount of the hydraulic reaction force that the input piston INP receives as the brake fluid amount changes in the master cylinder pressure chamber MCR when the pump PP is driven. Therefore, even if the hydraulic reaction force acting on the input piston INP from the master cylinder pressure chamber MCR increases or decreases, the spring KS that biases the input piston INP forward due to the fluctuation and relative displacement of the hydraulic reaction force Is almost equal to the spring force. For this reason, the increase in the hydraulic reaction force is almost completely offset by the spring force of the spring KS, and the influence on the brake pedal BP can be minimized.

Next, the effect of Example 2 will be described.
The brake control device according to the second embodiment has the following effects in addition to the effects (1) to (8) of the first embodiment.
(9) The braking force control unit 52 sucks and pressurizes the brake fluid in the master cylinder M / C, then discharges it to each wheel cylinder W / C, and increases or decreases the brake fluid in the master cylinder M / C. And a spring KS that suppresses the stroke of the brake pedal BP. Thereby, pedal vibration at the time of pump operation can be controlled.

(Other examples)
The best mode for carrying out the present invention has been described based on each embodiment. However, the specific configuration of the present invention is not limited to the configuration shown in each embodiment. Design changes and the like within a range that does not depart from the gist are also included in the present invention.

  For example, the determination method of the end of pump pressure increase is based on the time during which the pump pressure increase execution time can be increased to the wheel cylinder pressure set based on the preset maximum stoptable gradient or the road surface gradient when the vehicle is stopped. When it reaches a time at which the wheel cylinder pressure determined based on the time can be increased, it may be determined that the pump pressure increase has ended.

1 is a system configuration diagram of a vehicle to which a brake control device of Embodiment 1 is applied. 1 is a hydraulic circuit diagram of a braking device 50 according to a first embodiment. FIG. 3 is a control block diagram of a brake control ECU 30 according to the first embodiment. It is a state transition diagram showing a brake control state on an uphill road. It is a figure which shows the transition conditions to each brake control state. 3 is a flowchart showing a flow of a braking force control process executed by a brake control ECU 30 according to the first embodiment. It is a flowchart which shows the flow of a process of step S2a of FIG. It is a flowchart which shows the flow of a process of step S2c of FIG. It is a figure which shows the relationship of the force which acts on a vehicle advancing direction and a vehicle backward direction at the time of an uphill stop. It is a time chart which shows the braking control effect | action of Example 1 at the time of an uphill stop. FIG. 6 is a schematic diagram illustrating a configuration of a braking force generation unit 51 according to a second embodiment.

Explanation of symbols

ENG engine
AT automatic transmission
PP pump
M / C master cylinder
W / C wheel cylinder
KS spring (brake pedal operation suppression part)
31 Stop state detection means
32 Hill hold function judgment means
33 Idle stop function judgment means
34 Hill start assist function judgment means
35 Driving force loss prediction means
36 Braking force control means
40 Road slope detection means
51 Braking force generator (first braking force generator)
52 Braking force control unit (second braking force generator)

Claims (9)

In a brake control device that can automatically control the braking force of a vehicle,
Road surface gradient detecting means for detecting an uphill road,
Stop state detection means for detecting the stop state of the vehicle;
Driving force disappearance predicting means for predicting the occurrence of disappearance of the driving force where the driving force acting on the drive wheel is interrupted;
Braking force that increases the braking force of the vehicle in advance before the driving force disappears so that the vehicle stopping state after the disappearance of the driving force is maintained when the occurrence of the driving force disappears is predicted when the climbing vehicle is stopped Control means;
A brake control device comprising: The brake control device according to claim 1, wherein
The braking force control means increases a braking force to be increased before the driving force disappears to an absolute value greater than an absolute value of a difference between a vehicle backward direction component of gravity acting on the vehicle when the occurrence of the driving force disappearance is predicted. A brake control device characterized by that. In the brake control device according to claim 1 or 2,
When the absolute value of the vehicle backward direction component of gravity is greater than the absolute value of the driving force of the vehicle, the braking force control means increases the braking force to be increased before the driving force disappears to be greater than the disappearing driving force. A brake control device characterized by that. The brake control device according to any one of claims 1 to 3,
The driving force disappearance prediction means predicts the occurrence of the disappearance of the driving force when an idle stop start condition for stopping the engine when the vehicle stops is satisfied. The brake control device according to claim 4, wherein
A first braking force generator for generating a braking force by boosting a driver's brake pedal depression force using the negative pressure of the engine;
A second braking force generator that generates a braking force using means other than the negative pressure of the engine;
With
The brake control device, wherein the braking force control means increases the braking force by the second braking force generator. The brake control device according to claim 5,
The second braking force generator is
A pump that sucks and pressurizes the brake fluid in the master cylinder and then discharges it to the wheel cylinder of each wheel;
A brake pedal operation suppression unit that suppresses the stroke of the brake pedal that accompanies increase / decrease in brake fluid in the master cylinder;
A brake control device comprising: Hill hold function determination means for determining whether or not a hill hold function is required to increase or hold braking force when the climbing road is stopped,
Hill start assist function determination means for determining whether or not a hill start assist function is required to reduce the braking force according to the driver's intention to start the hill hold function.
Idle stop function determination means for determining whether or not an idle stop function is required to stop the engine when the vehicle is stopped;
When the hill hold function is necessary, the hill start assist function is not necessary, and the idle stop function is necessary, the driving force disappearance predicting means for predicting the occurrence of the driving force disappearing in which the driving force acting on the driving wheel is interrupted. When,
Braking force control means for increasing the braking force of the vehicle in advance before the idle stop function is executed when the occurrence of the driving force loss is predicted;
A brake control device comprising: The brake control device according to any one of claims 1 to 7,
The driving force disappearance predicting means predicts the occurrence of the disappearance of the driving force when the shift position of the automatic transmission selects a travel range and there is no driver's accelerator operation in a stopped state on an uphill road. Brake control device. In a brake control device that can automatically control the braking force of a vehicle,
Road surface gradient detecting means for detecting an uphill road,
Stop state detection means for detecting the stop state of the vehicle;
Driving force disappearance prediction that predicts the occurrence of loss of driving force when the driving force acting on the driving wheel is interrupted when the shift position of the automatic transmission selects the driving range and the driver does not operate the accelerator while the uphill is stopped Means,
Braking force control means for increasing the braking force of the vehicle in advance before the disappearance of the driving force so that the vehicle stopping state after the disappearance of the driving force is maintained when the occurrence of the disappearance of the driving force is predicted;
A brake control device comprising:

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