JP2003291693A - Braking force controller for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a braking force controller for a vehicle capable of improving the durability and reliability of a braking force providing means while reducing energy consumed by the braking force providing means greatly during automatic stop of an internal combustion engine. <P>SOLUTION: When an engine 1 is in an idle stop which is an automatic stop and the brake pressure PB<SB>2</SB>becomes an idle stop release set pressure of 0.7 MPa or less, the wheel cylinder pressure at the time is held. When the brake pressure PB<SB>3</SB>is less than a holding release set pressure of 0.2 MPa and it is expected that the vehicle starts, brake force control when the engine restarts is performed by the processings for reducing the wheel cylinder pressure (step S20 to Step S30). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a braking force control device for restarting an engine in a vehicle having an idle stop function for the purpose of improving fuel efficiency and reducing exhaust gas.

[0002]

2. Description of the Related Art Conventionally, as a braking force control device for restarting an engine in a vehicle having an idle stop function, for example, one disclosed in Japanese Patent Laid-Open No. 2000-313253 is known.

In this prior art publication, a means for holding the braking force of the vehicle while the engine is automatically stopped with the object of suppressing the feeling of jumping out of the vehicle and preventing the vehicle from moving backward while ensuring good starting performance. And means for detecting the recovery state of the driving force (creep force) of the vehicle when the engine is restarted,
And a technique for reducing the braking force of the vehicle according to the recovery state of the driving force of the vehicle when the engine that has automatically stopped is restarted.

[0004]

However, in the conventional braking force control device for a vehicle, the creep force is eliminated during the idle stop to prevent the vehicle from moving backward (sliding down) on a gentle slope. In addition, it is configured to continuously control the braking force from when the engine is stopped to when the engine is restarted.

Therefore, if the time from the engine stop to the engine restart is long, the solenoid valve of the brake hydraulic unit is continuously energized to maintain the braking force, which results in energy consumption (electric power consumption) of the vehicle. However, there is a problem in that the fuel efficiency improvement effect is impaired.

Further, when the brake fluid pressure is held by using a solenoid valve of a hydraulic unit such as ABS, the time during which the solenoid valve can be continuously turned on is limited and exceeds the limit time (generally 1-2 minutes). There is a problem that the solenoid valve may be deteriorated.

The present invention has been made in view of the above-mentioned problems, and drastically reduces the energy consumed by the braking force applying means during the automatic stop of the internal combustion engine while maintaining the durability reliability of the braking force applying means. It is an object of the present invention to provide a braking force control device for a vehicle that can improve the braking force.

[0008]

In order to achieve the above object, in the present invention, a vehicle that automatically stops an internal combustion engine when a predetermined stop condition is satisfied and automatically starts the internal combustion engine when a predetermined start condition is satisfied. In the braking force control device, when the internal combustion engine stop detection means detects that the internal combustion engine is automatically stopped, and the braking operation amount detected by the braking operation amount detection means becomes less than or equal to the first predetermined amount. , Regardless of the driver's intention, the braking force is applied by the braking force applying means,
A braking force control means for releasing the braking force when the vehicle is expected to start by the vehicle start predicting means is provided.

Here, the "braking operation amount detecting means" is a means for directly or indirectly detecting the amount of braking operation of the driver, such as a brake stroke sensor for detecting the amount of operation of the driver's brake depression, or driving. A brake pressure sensor that detects a brake pressure generated by a person's braking operation, a brake pedal force sensor that detects a brake pedal force generated by a driver's braking operation, and the like.

The "braking force applying means" is a means that can generate a brake fluid pressure without the driver performing a brake operation, and is, for example, an ABS hydraulic unit, a VDC hydraulic unit, a control booster, or the like.

"The detected braking operation amount is equal to or less than the first predetermined amount" means that the vehicle operation stop is lowered to a level at which the braking operation amount cannot be maintained on a gentle slope, for example.

The "vehicle start predicting means" is a means for predicting the start of the vehicle according to the operation based on the driver's intention to start or the state of the vehicle. For example, when the braking operation amount falls to the brake release level, the internal combustion engine When the engine is automatically started, after the internal combustion engine is automatically started, when the rotational speed of the internal combustion engine is stable, the vehicle is expected to start.

[0013]

In the prior art, the control for continuously maintaining the braking force is performed during the automatic stop from the engine stop to the engine restart. On the other hand, in the present invention, for example, when the driver performs the brake release operation with the intention of starting, and the braking operation amount becomes equal to or less than the first predetermined amount, from that time to the time when the vehicle is expected to start. The braking force is automatically applied only during a short period of time, and the duration of energization of the solenoid valve when applying the braking force is significantly shortened as compared with the prior art.

Therefore, according to the braking force control device for a vehicle of the present invention, the energy consumed by the braking force applying means during the automatic stop of the internal combustion engine is greatly reduced, and the durability of the braking force applying means is improved. Can be improved.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment for realizing a vehicle braking force control device of the present invention will be described with reference to a first embodiment corresponding to the invention according to claims 1, 2 and 3, and to claim 4. A description will be given based on a second embodiment corresponding to the invention and a third embodiment corresponding to the invention according to claim 5.

(First Embodiment) First, the structure will be described. FIG. 1 is an overall system diagram showing a braking force control device for a vehicle according to a first embodiment. To explain the configuration of the drive system, in FIG. 1, 1 is an engine (internal combustion engine), 2 is a transmission, 3 is a differential, 4 is a right drive shaft, 5 is a left drive shaft, 6 is a right front wheel, 7 is a left front wheel, 8 is a right rear wheel, and 9 is a left rear wheel. That is, it is a front-wheel drive vehicle in which the left and right front wheels 6, 7 are driven by the engine 1.

To explain the structure of the braking system, in FIG. 1, 10 is a brake pedal, 11 is a brake booster,
Reference numeral 12 is a brake master cylinder, 13 is a master cylinder hydraulic pressure passage, 14 is an ABS hydraulic unit (braking force applying means), 15 is a wheel cylinder hydraulic pressure passage, and 16 is a wheel cylinder. That is, during normal braking in which the ABS hydraulic unit 14 is inoperative, the master cylinder hydraulic pressure generated by the brake master cylinder 12 based on the braking operation on the brake pedal 10 is applied to each wheel cylinder 16 via the ABS hydraulic unit 14. Granted.
The control hydraulic pressure generated by the ABS hydraulic unit 14 is applied to each wheel cylinder 16 regardless of whether or not the brake operation is performed during the ABS operation or the brake control when the engine is restarted.

The structure of the electronic control system will be described. In FIG. 1, 20 is an engine / A / T control unit,
Reference numeral 21 is an engine speed sensor (internal combustion engine rotation speed detecting means), 22 is a power supply voltage sensor, 23 is an accelerator opening sensor, 24 is an engine start alarm lamp, 25 is a brake controller, 26 is a wheel speed sensor, and 27 is a brake stroke. A sensor 28 is a master cylinder pressure sensor (braking operation amount detection means), and the power supply voltage sensor 22 detects a voltage of a battery power supply 31 stored by a motor generator 30 driven by the engine 1 via a belt 29. .

The engine / A / T control unit 20 includes sensor information from an engine speed sensor 21, a power supply voltage sensor 22 and an accelerator opening sensor 23,
Necessary information from the brake controller 25 connected by the bidirectional communication line is input. Then, the engine / A / T control unit 20 outputs a command to automatically stop the engine 1 when the idle stop condition is satisfied, and when the condition to release the idle stop and restart the engine 1 is satisfied. , Outputs a command to automatically start the engine 1. When restarting the engine 1, a command to turn on the engine start warning lamp 24 is output in order to notify the driver of the engine start.

The brake controller 25 includes sensor information from a wheel speed sensor 26, a brake stroke sensor 27, and a master cylinder pressure sensor 28, and an engine / A / T control unit 20 connected by a bidirectional communication line. Required information and are input. And
From the brake controller 25, if the ABS operation condition is satisfied, the pressure increasing / holding / decompressing command is output to the ABS hydraulic unit 14, and if the brake control condition at engine restart is satisfied, the ABS hydraulic unit 14 is output. A command for holding / depressurizing is output to 14.

FIG. 2 is a view showing one wheel of the ABS hydraulic unit 14, wherein the ABS hydraulic unit 14 is the oil pump 1
4a, a pump motor 14b, an IN side solenoid valve 14c, an OUT side solenoid valve 14d, and a reservoir 14e.

During normal braking (OFF), the IN side solenoid valve 14c is opened by the spring force, and the OU
By closing the T-side solenoid valve 14d, the hydraulic pressure generated in the master cylinder 12 is applied to the wheel cylinder 1
6 is supplied.

When the ABS is activated (ON), the open IN side solenoid valve 14c is closed by the solenoid force to maintain the brake fluid pressure (the brake of the portion of the oil passage shown in the figure marked with X). Hydraulic pressure is maintained). Also,
OU from the holding state where both valves 14c and 14d are closed
By opening the T-side solenoid valve 14d by the solenoid force, the brake fluid is drained to the reservoir 14e to reduce the pressure.
Further, the IN side solenoid valve 14c is opened from the holding state where both valves 14c and 14d are closed, and the brake fluid is supplied from the oil pump 14a to increase the pressure. This ABS is used during brake control when the engine is restarted.
A brake fluid pressure retention mode and a brake fluid pressure reduction mode during operation are used.

Next, the operation will be described.

[Idle Stop Control Process] FIG. 3 is a flowchart showing the flow of the idle stop control process executed by the engine / A / T control unit 20. Each step will be described below.

In step S1, the vehicle speed Vcar is detected,
Control goes to step S2. Here, the vehicle speed Vcar is obtained, for example, by an average value of the wheel speed sensor values from the wheel speed sensors 26, 26 of the left and right rear wheels 8, 9.

In step S2, it is determined whether or not the vehicle speed Vcar is less than 0.4 km / h which is the stop determination set vehicle speed. If YES, the process proceeds to step S3, and if NO, the process proceeds to step S12.

In step S3, the accelerator opening sensor 2
Based on the sensor signal from 3, the accelerator opening Acc is detected, and the process proceeds to step S4.

In step S4, it is determined whether or not the accelerator opening Acc is 0, that is, the accelerator is released and there is no driver's start request. If YES, step S5
If NO, the process proceeds to step S12.

In step S5, the battery voltage V is detected based on the sensor signal from the power supply voltage sensor 22, and the process proceeds to step S6.

In step S6, the battery voltage V is set to 39.
It is determined whether or not V is exceeded, that is, whether or not battery charging is not necessary, and if YES, the process proceeds to step S7, N
If it is O, the process proceeds to step S12.

In step S7, the brake pressure P _B is detected based on the sensor signal from the master cylinder pressure sensor 28, and the process proceeds to step S8.

In step S8, it is determined whether or not the brake pressure P _B1 exceeds the idle stop start set pressure 0.8 Mpa. If YES, the process proceeds to step S9, and if NO, the process proceeds to step S15.

Incidentally, this step S7 and step S8
Is a step of determining whether or not the driver has a stop intention and the braking force that can maintain the vehicle stop is secured. Therefore, instead of the determination based on the brake pressure (= master cylinder pressure), the brake stroke BS from the brake stroke sensor 27 is detected, and the determination is made based on whether or not this brake stroke BS is, for example, 15 mm or more. Is also good.

In step S9, a command to stop the engine 1 is output by satisfying all the idle stop conditions of step S2, step S4, step S6, and step S8, and the process proceeds to step S10.

In step S10, the counter N is added to N + 1 every control period (10 msec), and step S11
Move to. That is, the value of the counter N represents the duration time after the idle stop is started.

In step S11, the counter N is set to 18000.
It is determined whether or not the above is true, and if YES, the process proceeds to step S13, and if NO, the process returns to step S1. That is, the maximum idle stop duration is 180 seconds (3 minutes).

In step S12, any of step S2, step S4, or step S6 is performed.
If NO is determined, it is determined whether or not the idle stop is being performed. If YES, the process proceeds to step S13, and if NO, the process proceeds to END.

In step S13, a command to turn on the engine start warning lamp 24 is output to notify the driver of the engine start, and the process proceeds to step S14.

In step S14, starting of the engine 1 is permitted, the engine 1 is restarted, and the process proceeds to END.

In step S15, the brake pressure P _B1 in step S8 is set to the idle stop start set pressure 0.8.
When it is determined that the pressure is equal to or lower than Mpa, the brake pressure P _B is determined based on the sensor signal from the master cylinder pressure sensor 28.
Is detected and the process proceeds to step S16.

In step S16, the brake pressure P _B2
(Detected braking operation amount) is the idle stop release set pressure
Judge whether it exceeds 0.7Mpa (first predetermined amount),
If YES, the process proceeds to step S17, and if NO, the process proceeds to step S18. Here, the idle stop release set pressure of 0.7 Mpa is set to a hydraulic pressure that generates a braking force that keeps the vehicle stopped on a gentle slope.

In step S17, it is determined whether or not the idle stop is being performed. If YES, the process returns to step S1, and if NO, the process proceeds to END.

In step S18, it is determined whether or not the engine is in idle stop. If YES, the process proceeds to step S19, and if NO, the process proceeds to END (internal combustion engine stop detection means).

In step S19, the braking force control by the wheel cylinder pressure control when the engine is restarted is executed according to the flowchart shown in FIG.

[Brake Force Control Processing During Idle Stop] FIG. 4 is a flow chart showing the flow of the brake force control processing executed by the brake controller 25 when the process proceeds to step S19 of the flow chart of FIG. Will be described (braking force control means).

In step S20, the IN side solenoid valve 14c of the ABS hydraulic unit 14 is opened and the OU
The IN side solenoid valve 14c is closed from the normal state in which the T side solenoid valve 14d is closed, and the holding of the wheel cylinder pressure is started. Then, the process proceeds to step S21.

In step S21, the brake pressure P _B is detected based on the sensor signal from the master cylinder pressure sensor 28.
Is detected and the process proceeds to step S22.

In step S22, the brake pressure P _B3
Determines whether the engine start permission constant pressure is less than 0.6Mpa, and
If S, the process proceeds to step S25, and if NO, the process proceeds to step S23.

In step S23, the counter N is added to N + 1 every control cycle (10 msec), and step S24
Move to. That is, the value of the counter N represents the continuation time after the holding of the wheel cylinder pressure is started.

In step S24, it is determined whether or not the counter N is 100 or more. If YES, the process proceeds to step S25, and if NO, the process returns to step S20. That is, the duration of holding the wheel cylinder pressure until the engine start is permitted is 1 second at maximum.

In step S25, when the brake pressure P _B3 is determined to be less than the engine start permission set pressure of 0.6 Mpa in step S22, or the maximum wheel cylinder pressure is maintained until the engine start is permitted in step S24. If the time is exceeded, the engine 1 is allowed to start, the engine 1 is restarted, and the process proceeds to step S26.

In step S26, the brake pressure P _B is detected based on the sensor signal from the master cylinder pressure sensor 28.
Is detected and the process proceeds to step S27.

In step S27, the brake pressure P _B3
Is less than the holding release set pressure 0.2Mpa (second predetermined amount), the process proceeds to step S30 if YES, the process proceeds to step S28 if NO (vehicle start according to claim 3 Equivalent to a predictor).

In step S28, the counter N is added to N + 1 every control cycle (10 msec), and step S29
Move to. That is, the value of the counter N represents the holding duration of the wheel cylinder pressure after the engine start is permitted.

In step S29, it is determined whether or not the counter N is 100 or more. If YES, the process proceeds to step S30, and if NO, the process returns to step S26. That is, the duration of holding the wheel cylinder pressure after permitting the engine start is set to 1 second at maximum.

In step S30, when it is determined in step S27 that the brake pressure P _B4 is less than the holding release set pressure of 0.2 Mpa, or in step S29, the wheel cylinder pressure is kept at the maximum after the engine start is permitted. When the time is exceeded, the wheel cylinder pressure is gradually reduced and the process shifts to END.

Here, the reduction of the wheel cylinder pressure is A
Both solenoid valves 14c, 1 of the BS hydraulic unit 14
When the OUT side solenoid valve 14d is opened from the holding state where 4d is closed, the brake fluid is released from the master cylinder 1.
Depressurize by pulling out to the oil tank attached to 2. When the OUT-side solenoid valve 14d is opened during depressurization, the pressure is not reduced at once, but is reduced with a gradient due to the line resistance. However, since the pressure reduction gradient is steep, when it is desired to control the pressure reduction gradient more gently or to control it with a desired gradient, duty control should be performed so as to gradually increase the valve opening time ratio of the OUT-side solenoid valve 14d. Then, gradually decrease the wheel cylinder pressure.

[Idle Stop Control Operation] The idle stop control automatically stops the engine 1 when the vehicle is stopped by the driver's braking operation and the idle stop condition (see below) is satisfied. This control is intended to suppress air pollution due to exhaust gas and fuel consumption by stopping the engine 1.

An example of the idle stop condition is that the vehicle speed is less than 0.4 km / h (the vehicle is stopped), accelerator opening = 0 (no driver's request to start), master cylinder pressure 0.8 Mpa or more, or brake stroke 15 mm or more (There is an intention to stop and there is a braking force that can maintain the stop.) When the battery voltage is 39 V or higher (there is no need to charge the power supply), the engine 1 is automatically stopped when all of the above conditions are satisfied.

That is, in the flowchart of FIG. 3, steps S1 to S2 → step S3 → step S4 → step S5 → step S6 → step S
7-> Proceeds to step S8, the vehicle stop condition of step S2, the accelerator release condition of step S4, and the step S
When the power supply voltage condition of 6 and the master cylinder pressure condition of step S8 are all satisfied, the process proceeds to step S9, and the idle stop for automatically stopping the engine 1 is started.

During the idle stop, the vehicle speed is 0.4 km / h or more (the vehicle is moving), the accelerator opening is> 0 (the driver has a request to start), the master cylinder pressure is less than 0.7 Mpa, or the brake stroke is 15 mm. Less than (no intention to stop, insufficient braking force to maintain the stop) Battery voltage is less than 39V (need to charge the power supply) One of the conditions that the duration from the start of idle stop is 180 seconds or more When established, the engine 1 is automatically restarted.

That is, in the flowchart of FIG. 3, step S2 or step S4 or step S
6 to step S12 → step S13 → step S1
4 and restart engine 1 automatically (,,
). Further, the process proceeds from step S9 to step S10 → step S11 → step S13 → step S14 to automatically restart the engine 1 (). Further, in the flowcharts of FIGS. 3 and 4, the process proceeds from step S8 to step S15 → step S16 → step S18 (→ step S19) → step S20 → step S21 → step S22 → step S25 and automatically restarts the engine 1. ().

[Brake force control action during idle stop] The brake force control action at the time of engine restart will be described based on the flowchart of FIG. 4 and the time chart of FIG.

First, after the idle stop start time t2 has passed from the vehicle stop time t1, the idle stop cancellation determination time
Until t3, the master cylinder pressure is maintained by the driver depressing the brake, and during this period, the ABS cylinder unit 14 does not control the wheel cylinder pressure.

Then, in step S16 of the flow chart of FIG. 3, it is determined that the brake pressure P _B2 is equal to or less than the idle stop release set pressure 0.7 Mpa, and step S16
If it is determined at 18 that the idle stop is being performed, the process proceeds to step S19, and the wheel cylinder pressure is controlled according to the flowchart shown in FIG.

That is, when the idle stop cancellation is determined
Immediately before t3, when the driver intends to start, and the brake pressure P _B2 becomes equal to or less than the idle stop release set pressure 0.7 Mpa at the idle stop release determination time point t3 by shifting from the brake depression state to the release operation, in step S20. , The wheel cylinder pressure at that time (about 0.7 Mpa) is held based on the brake pressure holding command to the ABS hydraulic unit 14.

After that, when either the time t4 when the brake pressure P _B3 becomes less than the engine start permission setting pressure 0.6 Mpa or the time when the brake pressure holding duration (1 second) is exceeded, whichever comes first, The process proceeds to step S25 of the flowchart, and the start of the engine 1 is permitted. In addition,
As shown in FIG. 5, there is a mechanical time delay from the start permission of the engine 1 to the time t5 of the actual engine start.

After that, when the brake pressure P _B3 reaches the time point t4 at which the holding release set pressure becomes less than 0.2 Mpa, the process proceeds to step S30 in the flowchart of FIG. 4, and the wheel cylinder pressure is gradually reduced. Due to this pressure reduction, the wheel cylinder pressure becomes zero at time t6.

After the driver releases the brake, the driver depresses the accelerator to increase the engine speed and the driving force, and when the time t8 is reached, the vehicle starts moving.

[Comparison of Brake Force Control] In a vehicle in which idle stop control is executed for the purpose of improving fuel efficiency and reducing exhaust gas, the creep force due to the torque converter of the automatic transmission disappears as the engine stops. It is necessary to provide a means for securing the braking force at least between the time when the engine is stopped and the time when the engine is restarted, in order to prevent the vehicle from slipping down a slope and preventing the vehicle from jumping out when the engine is started.

In the case of the prior art, the control is such that the braking force is continuously maintained from the time when the engine is stopped to the time when the engine is restarted. In the time chart of FIG. The brake actuator is operated (ON) for a long time T1 until time t7 immediately before starting.

Therefore, if the time from the engine stop to the engine restart is long, the solenoid valve of the brake actuator is continuously energized to maintain the braking force, and the vehicle energy consumption (power consumption) is increased.
Is increased, and the fuel efficiency improvement effect is impaired. Further, when the wheel cylinder pressure is maintained by using the solenoid valve such as the ABS hydraulic unit as in the first embodiment, the time during which the solenoid valve can be continuously turned on is limited, and the limit time (generally 1-2 minutes). If it exceeds), the solenoid valve may be deteriorated.

On the other hand, in the braking force control device for a vehicle according to the first embodiment, when the driver stops by depressing the brake, the brake depressing state is maintained even if the idle stop is started, and then the driver intends to start. We paid attention to the point that the brake release operation is performed when this is done.

That is, when the brake pressure P _B2 becomes equal to or lower than the idle stop release set pressure of 0.7 Mpa due to the brake release operation, from that time t3, the brake pressure P _B3 becomes less than the hold release set pressure of 0.2 Mpa (time t4 (vehicle start)). The wheel cylinder pressure of about 0.7Mpa is maintained for a short time T3 until the time (at which is expected). That is, the ABS hydraulic unit 14 used as the brake actuator continues to operate (ON) the ABS hydraulic unit 14 for a short time T2 from the idle stop cancellation determination time point t3 to the time point t6.

Therefore, as compared with the prior art, the duration time T2 (<T1) of the braking force control by the ABS hydraulic unit 14 is increased.
Is significantly reduced, and while the electric energy consumed by the ABS hydraulic unit 14 during the idle stop of the engine 1 is significantly reduced, the ABS hydraulic unit 1
The durability reliability of the solenoid valve 14c, which is a component of No. 4, can be improved.

Next, the effect will be described.

In the vehicle braking force control system of the first embodiment, the effects listed below can be obtained.

(1) When the engine 1 is automatically stopped during idle stop and the brake pressure P _B2 becomes equal to or less than the idle stop release set pressure of 0.7 Mpa, the wheel cylinder pressure at that time is held and the brake pressure is maintained. When it is expected that the vehicle will start when P _B3 becomes less than the holding release set pressure of 0.2 Mpa, the wheel cylinder pressure is reduced (steps S20 to S30) to perform braking force control at engine restart. As a result, the ABS hydraulic unit 14 is stopped during idle stop of the engine 1.
While significantly reducing the electric energy consumed by
The durability reliability of the solenoid valve 14c, which is a component of the BS hydraulic unit 14, can be improved.

(2) In the brake control process (steps S20 to S30) at the time of restarting the engine, the engine 1 is in the idle stop during the automatic stop, and the brake pressure P _B2 is the idle stop release set pressure 0.7 Mpa. When the following occurs, the wheel cylinder pressure at which the vehicle can be stopped on a gentle slope is maintained, and when the vehicle is expected to start, the held wheel cylinder hydraulic pressure is gradually weakened, so that the It is possible to reliably maintain the vehicle stop without moving the vehicle even on a slope or a downhill, and it is possible to prevent unintended swaying behavior in the front-rear direction due to sudden release of the braking force in the vehicle stop state.

(3) Since the vehicle is expected to start, when the detected brake pressure P _B becomes less than the holding release setting pressure 0.2 Mpa which is smaller than the idle stop release setting pressure 0.7 Mpa, the vehicle is expected to start. Brake pressure P _B
Following the determination to start holding the wheel cylinder pressure by using the same, the same brake pressure P _B is used as input information, and it is possible to easily predict the start of the vehicle simply by monitoring that the brake pressure P _B has decreased to the brake operation release level. can do.

(Second Embodiment) The second embodiment is the engine 1
Is an example in which when the vehicle is automatically started, it is expected that the vehicle will start and the control for reducing the wheel cylinder pressure is entered.
Since the configuration is the same as that of the first embodiment, illustration and description thereof will be omitted.

Next, the operation will be described.

[Braking Force Control Process During Idle Stop] FIG. 6 is a flowchart showing the flow of the braking force control process executed by the brake controller 25 when the process proceeds to step S19 of the flowchart of FIG. Will be described (braking force control means).

Incidentally, steps S40 to S45
Is the same as step S20 to step S25 in FIG.

In step S46, the engine speed Ne is detected based on the sensor signal from the engine speed sensor 21, and the process proceeds to step S47.

In step S47, it is determined whether the engine speed Ne is less than the engine start determination threshold value 100 rpm,
If YES, the process proceeds to step S50, and if NO, the process proceeds to step S48 (corresponding to the vehicle start prediction means according to claim 4).

Steps S48 to S50 are shown in FIG.
Since it is the same as step S28 to step S30, the description thereof will be omitted.

[Brake Force Control Operation During Idle Stop] The brake force control operation at the time of engine restart will be described based on the flowchart of FIG. 6 and the time chart of FIG. 7.

First, after the idle stop start time t2 has passed from the vehicle stop time t1, the idle stop cancellation determination time
Until t3, the master cylinder pressure is maintained by the driver depressing the brake, and during this period, the braking force control (wheel cylinder pressure control) by the ABS hydraulic unit 14 is not performed.

Then, in step S16 of the flow chart of FIG. 3, it is determined that the brake pressure P _B2 is equal to or less than the idle stop release set pressure 0.7 Mpa, and step S16
If it is determined in 18 that the idle stop is being performed, the process proceeds to step S19, and the braking force control is performed according to the flowchart shown in FIG.

That is, when the idle stop cancellation is determined
Immediately before t3, when the driver intends to start and shifts from the brake depression state to the release operation so that the brake pressure P _B2 becomes equal to or less than the idle stop release set pressure 0.7 Mpa at the idle stop release determination time point t3, in step S40. , The wheel cylinder pressure at that time (about 0.7 Mpa) is held based on the brake pressure holding command to the ABS hydraulic unit 14.

After that, when the brake pressure P _B3 reaches the engine start permission set pressure of less than 0.6 Mpa, the time t4, or the time exceeding the wheel cylinder pressure holding duration (1 second), whichever comes first, The process proceeds to step S45 of the flow chart of No. 1 and the start of the engine 1 is permitted.

Since there is a mechanical time delay from the start permission of the engine 1 to the actual engine start, when the time t5 when the engine speed Ne reaches 100 rpm is reached, the process proceeds to step S50 in the flowchart of FIG. The wheel cylinder pressure is gradually reduced. Due to this decompression, time point t7
At 0, the wheel cylinder pressure is made zero.

Then, after the driver releases the brake, the driver depresses the accelerator to operate the engine speed.
Ne and the driving force increase, and when the time point t8 is reached, the vehicle starts moving.

[Comparison of Brake Force Control] In the vehicle brake force control system of the second embodiment, the brake pressure P _B2 is set to 0.7 Mpa for the idle stop release in accordance with the brake release operation.
When it becomes below, at that time t3 the engine speed Ne will be 100r
The wheel cylinder pressure of about 0.7 Mpa is maintained for a short time T3 'until the time t5 (the time when the vehicle is expected to start) that becomes pm or more. In other words, the ABS hydraulic unit 14 used as the brake actuator continues the ABS for a short time T2 'from the idle stop cancellation determination time point t3 to the time point t7.
The hydraulic unit 14 will be activated (ON).

Therefore, compared with the prior art in which the brake actuator is continuously operated (ON) for a long time T1 from the idle stop start time t2 to the time t7 immediately before starting,
The duration T2 '(<T1) of the braking force control by the ABS hydraulic unit 14 is significantly shortened, and the electric energy consumed by the ABS hydraulic unit 14 during the idle stop of the engine 1 is significantly reduced, ABS
Solenoid valve 1 which is a component of the hydraulic unit 14
The durability reliability of 4c can be improved.

Next, the effect will be described.

In the vehicle braking force control system of the second embodiment, the following effects can be obtained in addition to the effects (1) and (2) of the first embodiment.

(4) When the engine speed Ne becomes 100 rpm or more and the automatic start of the engine 1 is determined, the control for reducing the wheel cylinder pressure is started in anticipation of the vehicle starting. By optimizing the balance between the driving force (creep force) gradually generated by and the braking force gradually reduced by the pressure reduction control, it is possible to ensure a smooth start of the vehicle.

(Third Embodiment) A third embodiment is an engine 1
Is an example in which, when the rotation speed of the engine 1 is stabilized after automatic starting, the vehicle is expected to start and the control for reducing the wheel cylinder pressure is entered. The configuration is the first
Since it is similar to the embodiment, illustration and description thereof are omitted.

Next, the operation will be described.

[Braking Force Control Process During Idle Stop] FIG. 8 is a flowchart showing the flow of the braking force control process executed by the brake controller 25 when the process proceeds to step S19 of the flowchart of FIG. Will be described (braking force control means).

Incidentally, steps S60 to S65.
Is the same as step S20 to step S25 in FIG.

In step S66, the engine rotation speed Ne detected based on the sensor signal from the engine rotation speed sensor 21 is time-differentiated to calculate the engine rotation speed differential value dNe, and the process proceeds to step S67.

In step S67, it is determined whether or not the engine speed differential value dNe shifts to (0 → plus → 0 → minus → 0). If YES, the procedure shifts to step S70, and if NO, the step The process proceeds to S68 (corresponding to the vehicle start prediction means according to claim 5). That is, when the engine speed Ne is about to overshoot, the convergence state of the engine speed Ne is monitored, and when it changes in the convergence direction, it is determined that the rotation speed of the engine 1 is stable.

Steps S68 to S70 are shown in FIG.
Since it is the same as step S28 to step S30, the description will be omitted.

[Brake Force Control Operation During Idle Stop] The brake force control operation at engine restart will be described with reference to the flowchart of FIG. 8 and the time chart of FIG.

First, after the idle stop start time t2 has elapsed from the vehicle stop time t1, the idle stop cancellation determination time
Until t3, the master cylinder pressure is maintained by the driver depressing the brake, and during this period, the braking force control (wheel cylinder pressure control) by the ABS hydraulic unit 14 is not performed.

Then, in step S16 of the flow chart of FIG. 3, it is determined that the brake pressure P _B2 is equal to or less than the idle stop release set pressure 0.7 Mpa, and step S16
If it is determined in 18 that the idle stop is being performed, the process proceeds to step S19, and the braking force control is performed according to the flowchart shown in FIG.

That is, when the idle stop cancellation is determined
Immediately before t3, when the driver intends to start and the brake pressure P _B2 becomes equal to or less than the idle stop release set pressure 0.7 Mpa at the idle stop release determination time point t3 by shifting from the brake depression state to the release operation, in step S60. , The wheel cylinder pressure at that time (about 0.7 Mpa) is held based on the brake pressure holding command to the ABS hydraulic unit 14.

After that, when the brake pressure P _B3 reaches the engine start permission set pressure of less than 0.6 Mpa, the time t4 or the time of exceeding the wheel cylinder pressure holding duration (1 second), whichever comes first, The process proceeds to step S65 of the flow chart of No. 1 and the start of the engine 1 is permitted.

There is a mechanical time delay from the start permission of the engine 1 to the actual engine start. After the time delay elapses, the engine speed Ne becomes as shown in the engine speed characteristic of FIG. , The point at which the engine speed Ne is considered to be stable due to the converging action of rising slightly overshoot, then falling, and then rising.
When t7 is reached, step S7 in the flowchart of FIG.
At 0, the wheel cylinder pressure is gradually reduced.

Then, after the driver releases the brake, the driver depresses the accelerator to operate the engine speed.
When Ne and the driving force increase and reach time point t8, the vehicle starts to move, and then the wheel cylinder pressure is reduced to zero at time point t9 by reducing the wheel cylinder pressure.

[Comparison of Brake Force Control] In the vehicle braking force control system according to the third embodiment, the brake pressure P _B2 is set to 0.7 Mpa for the idle stop release in accordance with the brake release operation.
When it becomes below, the wheel cylinder pressure of about 0.7Mpa is maintained for a short time T3 "from the time t3 to the time t7 when the engine speed Ne stabilizes (the time when the vehicle is expected to start). AB
S hydraulic unit 14 is at the time of idle stop cancellation determination
The ABS hydraulic unit 14 is operated (ON) for a short time T2 "from t3 to time t9.

Therefore, compared with the prior art in which the brake actuator is continuously operated (ON) for a long time T1 from the idle stop start time t2 to the time t7 immediately before starting,
The duration T2 "(<T1) of the braking force control by the ABS hydraulic unit 14 is significantly shortened, and the electric energy consumed by the ABS hydraulic unit 14 during the idle stop of the engine 1 is significantly reduced, ABS
Solenoid valve 1 which is a component of the hydraulic unit 14
The durability reliability of 4c can be improved.

Next, the effect will be described.

In the vehicle braking force control system of the third embodiment, the following effects can be obtained in addition to the effects (1) and (2) of the first embodiment.

(5) When the engine speed differential value dNe shifts to (0 → plus → 0 → minus → 0), the engine 1
When the engine speed is determined to be stable, the vehicle pressure reduction control of the wheel cylinder pressure is started in anticipation of the vehicle starting, so a vehicle equipped with the engine 1 that has a large rotational overshoot when the engine is restarted. In the case of, the feeling of jumping out due to engine restart is suppressed, and a smooth start is possible.

The vehicle braking force control device of the present invention has been described above based on the first to third embodiments, but the specific configuration is not limited to these embodiments, and patents Modifications and additions of the design are allowed without departing from the gist of the invention according to each claim of the claims.

For example, in the first to third embodiments, the ABS hydraulic unit 14 is used as the braking force applying means, but the VDC hydraulic unit 44 (FIG. 10) and the control booster 54 (FIG. 11 and FIG. 11). 12) or the like may be used.

The VDC hydraulic unit 44 is shown in FIG.
As shown in (for one wheel), an oil pump 44a, a pump motor 44b, a first switching valve 44c, a second switching valve 44d, an IN-side solenoid valve 44e, and an O valve.
A UT side solenoid valve 44f, a reservoir 44g,
Is configured. Then, the step of "starting holding of wheel cylinder pressure" (step S20, step S
40, step S60), the first switching valve 4
4c is closed, the second switching valve 44d is opened, and the oil pump 44a is operated to generate the wheel cylinder hydraulic pressure. When the hydraulic pressure reaches an appropriate value, the IN side solenoid valve 44e is closed and the wheel cylinder pressure is changed. Hold. Further, when the process proceeds to the "wheel cylinder pressure reduction" step (step S30, step S50, step S70), the IN side solenoid valve 44e is opened, the first switching valve 44c is opened, and the second switching valve 44d is closed. Releases the wheel cylinder pressure.

As shown in FIG. 11, the control booster 54 is employed in place of the brake booster of the first embodiment. As shown in FIG. 12, the solenoid 54a, armature 54b, armature spring 54c and , Valve body 54d, control piston 54e,
Plunger 54f, poppet seal 54g, poppet spring 54h, atmosphere valve 54i, and vacuum valve 54j.
A lever 54k, a switch rod 54m, an operating pressure chamber 54n, and a vacuum pressure chamber 54p. Then, after proceeding to the step of "starting holding of wheel cylinder pressure" (step S20, step S40, step S60), by supplying a current to the solenoid 54a, the armature 54b and the control piston 54e are moved to open the atmospheric valve 54i, When the solenoid valve 54a reaches an appropriate value, the solenoid valve 54a is kept energized to close the atmospheric valve 54i and hold the master cylinder pressure (= wheel cylinder pressure). In addition, the step of "reducing wheel cylinder pressure" (step S30, step S50, step S70)
When the process proceeds to step S3, the master cylinder pressure (= wheel cylinder pressure) is released by reducing / cutting off the current flowing through the solenoid 54a.

When the control booster 54 is used, the master cylinder pressure is equal to the wheel cylinder pressure. Therefore, when the brake force control is started, the master cylinder pressure (brake pressure) is used as in the first to third embodiments. If so, it becomes impossible to judge the amount of braking operation. Therefore, the brake stroke amount from the stroke sensor 27, not the master cylinder pressure sensor 28, is used to determine the braking operation amount.

In the first to third embodiments, the example in which the master cylinder pressure sensor 13 is used as the braking operation amount detecting means is shown, but the brake stroke sensor 27 may be used or the brake pedal force is detected. A brake pedal force sensor that operates may be used.

As a vehicle start predicting means, when the brake pressure is reduced to the level immediately before the brake is released (first embodiment),
When the engine 1 is automatically started (second embodiment), when the engine 1 is automatically started and then the rotation speed of the engine 1 is stable (third embodiment), an example in which the vehicle is expected to start is shown.
Alternatively, a means for predicting the start of the vehicle may be used by using an operation (accelerator operation) based on the driver's intention to start or a vehicle state (vehicle speed).

[Brief description of drawings]

FIG. 1 is an overall system diagram showing a braking force control device for a vehicle according to a first embodiment.

FIG. 2 is a diagram showing one wheel of an ABS hydraulic unit used in the vehicle braking force control system of the first embodiment.

FIG. 3 is a flowchart showing a flow of an idle stop control process executed by an engine / A / T control unit 20 of the first embodiment device.

FIG. 4 is a flowchart showing a flow of a braking force control process executed by a brake controller 25 of the first embodiment device.

FIG. 5 is a vehicle with an idle stop function equipped with the device of the first embodiment, from start to stop, vehicle speed, engine speed, driving force, brake pedal stroke, master cylinder pressure, wheel cylinder pressure, brake actuator, brake pressure. It is a time chart which shows a holding command value and prior art.

FIG. 6 is a flowchart showing a flow of a braking force control process executed by a brake controller 25 of the second embodiment device.

FIG. 7 is a vehicle with an idle stop function equipped with the device of the second embodiment, vehicle speed from start to stop, engine speed, driving force, brake pedal stroke, master cylinder pressure, wheel cylinder pressure, brake actuator, brake pressure. It is a time chart which shows a holding command value and prior art.

FIG. 8 is a flowchart showing a flow of a braking force control process executed by a brake controller 25 of the third embodiment device.

FIG. 9: Vehicle speed, engine speed, drive force, brake pedal stroke, master cylinder pressure, wheel cylinder pressure, brake actuator, brake pressure from vehicle stop to start in a vehicle with an idle stop function equipped with the third embodiment device It is a time chart which shows a holding command value and prior art.

FIG. 10 shows a VDC hydraulic unit that can be used as a braking force applying means in the vehicle braking force control device of the present invention.
It is a figure showing a circle.

FIG. 11 is a braking system system diagram to which a control booster that can be used as a braking force application means is applied in the vehicle braking force control device of the present invention.

FIG. 12 is a cross-sectional view showing a control booster that can be used as a braking force applying unit in the vehicle braking force control device of the present invention.

[Explanation of symbols]

1 engine (internal combustion engine) 2 transmission 3 differential 4 right drive shaft 5 left drive shaft 6 right front wheel 7 left front wheel 8 right rear wheel 9 left rear wheel 10 brake pedal 11 brake booster 12 brake master cylinder 13 master cylinder hydraulic path 14 ABS Hydraulic unit (braking force applying means) 15 Wheel cylinder hydraulic passage 16 Wheel cylinder 20 Engine / A / T control unit 21 Engine speed sensor (internal combustion engine speed detecting means) 22 Power supply voltage sensor 23 Accelerator opening sensor 24 Engine start Alarm lamp 25 Brake controller 26 Wheel speed sensor 27 Brake stroke sensor 28 Master cylinder pressure sensor (braking operation amount detection means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 29/02 321 F02D 29/02 321A 41/04 301 41/04 301 F term (reference) 3D041 AA21 AA30 AA65 AA66 AB01 AC26 AD02 AD04 AD10 AD41 AD51 AE02 AE41 3D046 BB02 CC02 EE01 GG01 HH02 HH05 HH12 HH16 HH17 HH22 HH36 JJ05 KK09 3G092 AC03 CA01 EA15 EA16 HFZHG20ZZ HG16Z20HA21 HG16ZH20HA02 HA20GA20ZH16HA01 GB01 GA10 HE11 GB02 AA01 BA16 BA17 BA19 BA21 BA22 BA24 BA30 3G301 JA02 JA03 JA15 KA04 KA26 KA28 KB01 ND01 NE03 PA11Z PE01Z PF01Z PF03Z PF05Z PF16Z

Claims (5)

[Claims] 1. A braking force control device for a vehicle, which automatically stops an internal combustion engine when a predetermined stop condition is satisfied, and automatically starts the internal combustion engine when a predetermined start condition is satisfied, wherein the internal combustion engine is automatically stopped. There is an internal combustion engine stoppage detection means that detects the presence, a braking operation amount detection means that detects the braking operation amount of the driver, a braking force application means that applies a braking force regardless of the driver's intention, and a vehicle start is expected. When the vehicle start predicting means and the internal combustion engine are automatically stopped, and the detected braking operation amount is less than the first predetermined amount, the braking force is applied regardless of the driver's intention. A braking force control device for a vehicle, comprising: a braking force control unit that releases the braking force when the vehicle is expected to start. 2. The braking force control device for a vehicle according to claim 1, wherein the braking force control means detects that the internal combustion engine is automatically stopped, and the detected braking operation amount is loose. When the braking force that keeps the vehicle stopped on a slope falls below the first predetermined amount set as the braking operation amount threshold value,
A braking force control device for a vehicle, which holds the braking force at that time as it is by the operation of the braking force applying means and gradually weakens the held braking force when the vehicle is expected to start. 3. The vehicle braking force control device according to claim 1, wherein the vehicle starting anticipation means detects a braking operation amount that is smaller than a first predetermined amount. A braking force control device for a vehicle, characterized in that the vehicle is expected to start when the amount becomes equal to or less than a predetermined amount. 4. The braking force control device for a vehicle according to claim 1, wherein the vehicle start predicting means predicts that the vehicle will start when the internal combustion engine is automatically started. A braking force control device for a vehicle. 5. The braking force control device for a vehicle according to claim 1, further comprising an internal combustion engine rotational speed detecting means for detecting a rotational speed of the internal combustion engine, wherein the vehicle start predicting means is A braking force control device for a vehicle, comprising: anticipating that the vehicle will start when the rotation speed of the internal combustion engine is stabilized after the internal combustion engine is automatically started.