JP4499691B2 - Braking control device - Google Patents

Description

  The present invention relates to a braking control device for a vehicle that includes a mechanical brake device that performs preceding vehicle tracking control including automatic stopping and is driven by an electric actuator.

2. Description of the Related Art A vehicle such as an automobile is known that includes a cruise control device that controls an engine throttle or the like based on the output of a vehicle speed sensor and controls the vehicle so as to maintain a set vehicle speed.
In addition, the cruise control device detects the inter-vehicle distance, relative speed, etc. with the preceding vehicle using a stereo camera, millimeter wave radar, etc., and performs acceleration / deceleration following the preceding vehicle, or when the preceding vehicle stops It is known that the vehicle is automatically stopped by controlling a hydraulic brake. Such control is referred to as “adaptive cruise control (ACC)”.

Vehicles that perform such adaptive cruise control are those that stop the hydraulic brakes with the electric parking brake device in the braking state after stopping to save power to maintain the brake fluid hydraulic pressure of the hydraulic brakes during automatic stopping. Is known (see, for example, Patent Document 1).
JP 2003-34240 A

However, in the above-described prior art, since the electric parking brake is operated after the vehicle stops, it is necessary to maintain the vehicle in a stopped state by a hydraulic brake between the stop and generation of the braking force of the electric parking brake. Therefore, electric power is consumed to maintain the hydraulic pressure during this period, and the frequency of operation of the mechanism that generates and holds the hydraulic pressure increases.
The subject of this invention is providing the braking control apparatus which reduced the burden of the hydraulic brake at the time of automatically stopping by preceding vehicle follow-up control.

The present invention solves the above-described problems by the following means.
According to the first aspect of the present invention, the hydraulic brake is controlled in accordance with the traveling state of the preceding vehicle to automatically stop the vehicle, and the automatic stop of the vehicle by the following traveling control unit is performed on the vehicle. An automatic stop detection unit that detects before stopping, and in response to detection of the automatic stop by the automatic stop detection unit, driving from a mechanical brake release state to a braking state by an electric actuator starts before the vehicle stops and a mechanical brake control unit for the mechanical brake control section is a brake controller you characterized by terminating the drive before the automatic stop of the vehicle.
According to a second aspect of the present invention, the hydraulic brake is controlled in accordance with the traveling state of the preceding vehicle to automatically stop the vehicle, and the automatic stop of the vehicle by the following traveling control unit is performed on the vehicle. An automatic stop detection unit that detects before stopping, and in response to detection of the automatic stop by the automatic stop detection unit, driving from a mechanical brake release state to a braking state by an electric actuator starts before the vehicle stops A brake control device that reduces the braking force of the hydraulic brake as the braking force of the mechanical brake increases.
According to a third aspect of the present invention, in the braking control device according to the second aspect, the follow-up traveling control unit is configured such that the amount of increase in the braking force of the mechanical brake is the same as the amount of decrease in the braking force of the hydraulic brake. A braking control device for setting a braking force of the mechanical brake.

According to a fourth aspect of the present invention, in the braking control device according to any one of the first to third aspects, the mechanical brake control unit is configured so that the mechanical brake applies a braking force before the vehicle stops. The braking control device is characterized in that the driving by the electric actuator is started at the timing of occurrence.
According to a fifth aspect of the present invention, in the braking control device according to any one of the first to fourth aspects, the follow-up traveling control unit is configured to generate the braking force after the mechanical brake has generated the braking force. A braking control device that reduces the hydraulic pressure of the hydraulic brake before the vehicle stops.
A sixth aspect of the present invention is the braking control apparatus according to the fifth aspect , wherein the mechanical brake brakes a rear wheel of the vehicle.
A seventh aspect of the present invention is the braking control device according to any one of the first to sixth aspects, wherein the automatic stop detection unit is configured to estimate the vehicle based on a speed and a deceleration of the vehicle. The stop control time is calculated, and the mechanical brake control unit sets a drive start time of the mechanical brake by the electric actuator according to the estimated stop time.
The invention according to claim 8 is the braking control device according to claim 7 , further comprising an inclination detection unit that detects an inclination of a road surface on which the vehicle is traveling, and the mechanical brake control unit is detected by the inclination detection unit. The braking control device is characterized in that the drive start timing of the mechanical brake is made different according to the slope.
According to a ninth aspect of the present invention, in the brake control device according to any one of the first to eighth aspects, the mechanical brake control unit is configured such that the speed of the vehicle is equal to or lower than a detection lower limit speed of a vehicle speed sensor. The braking control device starts driving the mechanical brake regardless of the output of the automatic stop detection unit in accordance with the time after.

According to the present invention, the following effects can be obtained.
(1) In response to detection of the automatic stop by the automatic stop detection unit, the mechanical brake is actuated by the electric actuator before the vehicle is stopped, thereby generating the braking force of the mechanical brake at an early stage. Since the timing of depressurization and release of the hydraulic brake can be advanced, the usage time and usage frequency of the hydraulic brake can be reduced.
(2) By starting the drive at the timing when the mechanical brake generates a braking force before the vehicle stops, the pressure reduction of the hydraulic brake can be started earlier.
(3) After the braking force of the mechanical brake is generated, the increase in vehicle deceleration due to the braking force of the mechanical brake is suppressed and the braking feeling is improved by reducing the hydraulic pressure of the hydraulic brake before stopping the vehicle. can do. Further, the pressure reduction of the hydraulic brake can be further accelerated.
(4) Since the mechanical brake dynamically brakes only the rear wheels of the vehicle, the nose dive of the vehicle can be suppressed as compared with the case where the front and rear wheels are braked only by the hydraulic brake. Comfort can be improved by suppressing the behavior of the direction.
(5) By setting the mechanical brake drive start timing in accordance with the estimated stop time based on the vehicle speed and deceleration, the braking force generation timing of the mechanical brake can be appropriately controlled.
(6) By varying the mechanical brake drive start timing according to the inclination detected by the inclination detection unit, even if the mechanical brake has a large target braking force and takes a long time to drive, It is possible to prevent the generation delay of the braking force.
(7) Failure of the automatic stop detection unit by starting the driving of the mechanical brake regardless of the output of the automatic stop detection unit according to the time after the vehicle speed becomes equal to or less than the detection lower limit speed of the vehicle speed sensor. It is possible to ensure the fail-safe property of the apparatus against the above.

  An object of the present invention is to provide a braking control device that reduces a load of a hydraulic brake when automatically stopping by preceding vehicle following control, and detects automatic stopping by adaptive cruise control in advance and before the vehicle stops. The solution is to start driving the electric parking brake.

Embodiments of a braking control apparatus to which the present invention is applied will be described below.
FIG. 1 is a block diagram illustrating a configuration of a vehicle including a braking control device according to the present embodiment.
This vehicle is, for example, an automobile such as a passenger car, and includes a hydraulic brake that is operated by the hydraulic pressure of the brake fluid, and an electric parking brake device that is driven by an electric actuator, and has a low-speed tracking (traffic congestion tracking) function. It includes an adaptive cruise control (ACC) function.

  The vehicle includes a parking brake 10, an actuator unit 20, a battery 30, a parking brake controller 40, an operation switch 50, an engine 60, a hydraulic brake 70, a vehicle stability control system (VDC system) 80, an adaptive cruise control system (ACC system). 90).

The parking brake 10 is a braking device that prevents the vehicle from moving when the vehicle is parked or stopped, for example, by braking the wheels of the vehicle. The parking brake 10 cooperates with the actuator unit 20 and the electric parking brake controller 40 to operate the electric parking brake device. It constitutes.
The parking brake 10 also has a function (dynamic braking function) for braking while the vehicle is running when the vehicle is automatically stopped by the ACC system 90. This point will be described in detail later.
The parking brake 10 is provided on each wheel hub portion of left and right rear wheels (not shown) of the vehicle. The parking brake 10 includes a brake drum (not shown) disposed on the inner diameter side of a rotor of a disc brake used in the hydraulic brake 70 and a brake shoe (not shown) that pressurizes and contacts the inner diameter side of the brake drum during braking. This is a so-called drum-in-disk type mechanical brake.

The actuator unit 20 drives the shoe of the parking brake 10 and makes a transition between a braking state in which the parking brake 10 generates a braking force and a released state in which the braking force is not substantially generated. The actuator unit 20 includes a parking brake cable 21 and is fixed to, for example, the lower floor of the vehicle.
For example, the actuator unit 20 reduces the rotational force of a direct current (DC) motor by a reduction gear train, rotates a lead screw, and pulls or relaxes the parking brake cable 21 by an equalizer screwed to the lead screw. is there.

The parking brake cables 21 are provided corresponding to the left and right parking brakes 10, respectively, and have flexibility so as to be deformed according to a stroke of a rear suspension (not shown). The parking brake cable 21 brings the parking brake 10 into a braking state by being pulled, and releases the parking brake 10 by being relaxed. When the parking brake 10 is in the braking state, the braking force of the parking brake 10 is maintained by the frictional force of the internal gears and the like even if the energization of the actuator unit 20 is stopped.
Here, the actuator unit 20 has a function of adjusting the braking force of the parking brake 10 in the braking state by adjusting the traction force applied to the parking brake cable 21. The adjustment of the traction force is performed by changing the stroke with which the actuator unit 20 pulls the parking brake cable 21. For this reason, the actuator unit 20 is provided with a stroke sensor (not shown) that detects this stroke.

The battery 30 is a secondary battery used as a main power source for a vehicle electrical system, and generates a terminal voltage of DC 12V, for example. The battery 30 includes a plus terminal 31 and a minus terminal 32.
The positive terminal 31 is connected to the parking brake controller 40, the engine electronic control unit 63, the vehicle stability control system 80, the ACC system 90, and the like via a wiring (harness) H (harness other than the parking brake controller 40). Is omitted.).
The minus terminal 32 is grounded with respect to the vehicle body.

The parking brake controller 40 is a mechanical brake control device that controls the actuator unit 20 and changes the braking force of the parking brake 10 by changing the traction force of the parking brake cable 21. The parking brake electronic control unit (parking brake electronic control unit) ECU) 41, relay 42, and G sensor 43.
The parking brake controller 40 constitutes a braking control device to which the present invention is applied in cooperation with the VDC system 80 and the ACC system 90.

The parking brake ECU 41 includes a CPU that determines whether or not the parking brake 10 needs to be braked, and performs additional pulling control that increases the braking force when the parking brake 10 is stopped on an inclined road. The parking brake ECU 41 has a function of performing dynamic braking, which will be described later, when the ACC system 90 automatically stops the vehicle.
Furthermore, the parking brake ECU 41 includes an automatic stop detection unit 41a that detects an automatic stop of the vehicle by the ACC control before the vehicle stops. This function will be described in detail later.

  The operation switch 50 is an operation unit for a user such as a driver to input a manual selection operation of the parking brake 10 and a release state of the parking brake 10 and a retraction operation, and is mounted on an instrument panel (not shown) of the vehicle, for example. Equipped with a push button switch. The operation switch 50 transmits the input to the parking brake controller 40, and the parking brake controller 40 supplies the driving power to the actuator unit 20 according to this input and drives the parking brake 10 during the operation in the manual mode. To do.

The engine 60 is, for example, a four-stroke gasoline engine used as a driving power source for the vehicle, and includes a throttle valve 61 that is an electronically controlled throttle, a throttle actuator 62, and an engine electronic control unit (engine ECU) 63.
The throttle valve 61 is provided in a throttle body connected to an intake manifold (not shown) of the engine 60, and controls the output of the engine 60 by limiting the intake air amount of the engine 60.
The throttle actuator 62 includes a motor that drives the throttle valve 61 and is disposed adjacent to the throttle body.
The engine ECU 63 includes a CPU that comprehensively controls the operation of the engine 60 and receives various operation parameters such as the intake air amount, intake air temperature, throttle position, rotation speed, crank position, water temperature, exhaust gas composition of the engine 60. In response to this, a control command signal such as a fuel injection signal and an ignition signal is output. Further, the engine ECU 63 controls the throttle actuator 62 in response to an input from a throttle pedal (not shown) and an adaptive cruise control electronic control unit 91 described later.

The hydraulic brake 70 is a service brake (service brake) provided on each of the front and rear wheels of the vehicle. For example, the hydraulic brake 70 is provided at the hub portion of each wheel, and a disc-shaped rotor that rotates together with the wheel is sandwiched between brake pads by using a piston that is inserted into a wheel cylinder and loaded with brake fluid hydraulic pressure. The braking force is generated by utilizing the friction between them.
Here, the hydraulic pressure of the brake fluid loaded on the piston is generated by a master cylinder (not shown) according to the driver's foot brake operation. Further, a hydraulic control unit 82 of the VDC system 80 described later also generates a hydraulic pressure applied to the piston of each wheel in accordance with the VDC control and the ACC control.

The VDC system 80 includes ABS control for preventing the brake lock of the wheels, and yaw in a direction in which the inner rear wheel is individually braked when the vehicle is in an understeer state, and the outer front and rear wheels are individually braked when the vehicle is in an oversteer state. VDC control for generating a moment is performed.
The VDC system 80 includes a VDC electronic control unit (VDC ECU) 81, a hydraulic control unit (HCU) 82, and a vehicle speed sensor 83.
The VDC ECU 81 includes a CPU that performs each control described above, and outputs a control command to the HCU 82.
The HCU 82 controls the brake fluid hydraulic pressure applied to the piston of the hydraulic brake 70 of each wheel in accordance with a control command input from the VDC ECU 81. The HCU 82 includes a pump unit that increases the hydraulic pressure and a valve unit that maintains or reduces the hydraulic pressure. Further, the HCU 82 includes a hydraulic pressure sensor that detects the brake fluid hydraulic pressure of each wheel cylinder.
The vehicle speed sensor 83 outputs a vehicle speed pulse signal according to the rotation of each wheel, and is incorporated in a hub bearing portion that supports these wheels. The vehicle speed sensor 83 can detect the vehicle speed based on the vehicle speed pulse signal in a region where the vehicle speed is, for example, 2 km / h or more.

The ACC system 90 performs ACC control including preceding vehicle following control.
The ACC system 90 includes an ACC electronic control unit (ACC ECU) 91 and a preceding vehicle detection unit 92.
The ACC ECU 91 includes a CPU that determines whether the vehicle needs to be accelerated or decelerated based on information such as a distance between the preceding vehicle and a relative speed detected by the preceding vehicle detection unit 92. In addition, the ACC ECU 91 has a function of performing low-speed tracking control including an automatic stop that automatically stops the host vehicle when the preceding vehicle stops.

When the ACC ECU 91 determines that acceleration or deceleration of the vehicle is necessary, the ACC ECU 91 outputs a control command to the engine ECU 63, drives the throttle valve 61 by the throttle actuator 62, and adjusts the output of the engine 60. If deceleration is required and the output of the engine 60 is minimized and the vehicle deceleration does not reach the predetermined control target deceleration G, the ACCEUC 91 outputs a control command to the VDC ECU 81, and the HCU 82 A fluid hydraulic pressure is generated to generate a braking force for the hydraulic brake 70. The brake fluid hydraulic pressure is set based on the control target deceleration G described above. The control target deceleration G is set, for example, within a range of about 0.1G to 0.25G.
The preceding vehicle detection unit 92 detects an inter-vehicle distance and a relative speed with respect to the preceding vehicle, and includes, for example, a stereo camera and a millimeter wave radar.

  Further, the electric parking brake controller 40, the engine ECU 63, the VDC ECU 81 of the VDC system 80, and the ACC ECU 91 of the ACC system 90 described above can communicate with each other via a CAN communication system that is a kind of in-vehicle LAN.

Next, the operation of the braking control device when the vehicle of this embodiment automatically stops by ACC will be described.
FIG. 2 is a flowchart showing the operation of the braking control device at this time. Hereinafter, the steps will be described step by step.
<Step S01: Determination during ACC travel>
An automatic stop detection unit 41a provided in the parking brake ECU 41 of the parking brake controller 40 communicates with the ACC ECU 91 to determine whether or not the vehicle is traveling using the ACC control. If the vehicle is traveling using the ACC control, the process proceeds to step S02. Otherwise, the process is repeated from step S01. (return)
<Step S02: Detection lower limit speed determination>
The automatic stop detection unit 41 a communicates with the VDC ECU 81 and detects whether the current vehicle speed (vehicle speed) V is equal to or lower than the detection lower limit speed Vmin of the vehicle speed sensor 83. As described above, the vehicle speed sensor 83 has a detection lower limit speed Vmin of, for example, 2 km / h, and when the vehicle speed V falls below this Vmin, the output of the vehicle speed sensor 83 is substantially zero.
When the vehicle speed V is equal to or lower than the detection lower limit speed Vmin, the process proceeds to step S04, and otherwise, the process proceeds to step S03.

<Step S03: Stop determination timer reset>
The automatic stop detection unit 41a resets the stop determination timer (timer value T = 0), returns to step S01, and repeats the subsequent processing. (return)
Here, the stop determination timer counts the time from when the vehicle speed V becomes equal to or lower than the detection lower limit speed Vmin.
<Step S04: Stop determination timer operation>
When the stop determination timer is reset and stopped, the automatic stop detection unit 41a operates the timer to start counting up the timer value T. When the stop determination timer is operating, the automatic stop detection unit 41a operates the stop determination timer. And the timer value T is counted up. Thereafter, the process proceeds to step S05.

<Step S05: Determination of presence or absence of brake fluid hydraulic pressure>
The automatic stop detection unit 41a communicates with the VDC ECU 81 to determine whether the brake fluid hydraulic pressure is applied to the piston of each wheel cylinder of the hydraulic brake 70 or not substantially applied. When the brake fluid hydraulic pressure is applied (when the vehicle speed is 2 km / h or less and braking is being performed), it is determined that the vehicle is automatically stopped, and the process proceeds to step S07. Advances to step S06.
<Step S06: Timer value T determination>
The automatic stop detection unit 41a determines whether or not the timer value T of the stop determination timer is greater than or equal to a predetermined maximum value Tmax. If it is greater than or equal to Tmax, the process proceeds to step S09. Otherwise, the process proceeds to step S01. Returns and repeats the subsequent processing. (return)

<Step S07: Estimated stop time calculation>
The automatic stop detection unit 41a calculates an estimated stop time that is the timing at which the vehicle completely stops. The estimated stop time is calculated based on the detection lower limit speed Vmin of the vehicle speed sensor 83 and the deceleration of the vehicle.
FIG. 3 is a graph showing an example of a history of vehicle speed sensor output, brake fluid hydraulic pressure, and parking brake braking force when the vehicle automatically stops by ACC control.
For example, as shown in FIG. 3, the estimated stop time is obtained by linearly approximating the timing at which the vehicle decelerates at a predetermined deceleration from the detection lower limit speed Vmin and the vehicle speed becomes zero. Here, the deceleration used for the calculation is the control target deceleration G that the ACC ECU 91 holds for ACC control, the actual deceleration G that is output from the G sensor 43 of the parking brake controller 40, and the vehicle speed sensor 83 that is the detection lower limit speed. The change rate of the detection speed immediately before reaching Vmin can be used alone or in combination.
Then, after the estimated stop time is calculated, the process proceeds to step S08.

<Step S08: Electric parking brake drive timing setting>
The parking brake ECU 41 sets an electric parking brake drive timing for starting driving of the actuator 20 based on the estimated stop time described above, and proceeds to step S09 after reaching this timing.
This electric parking brake drive timing is the time required for the drive from the start of driving of the actuator 20 when the parking brake 10 is released until the parking brake 10 generates the target braking force and the driving of the actuator 20 is stopped. Considering this, it is set so that the driving of the actuator 20 is finished at the same time as the estimated stop time is reached or earlier. The required driving time is, for example, about several hundreds msec although it depends on the configuration of the apparatus.

Here, when the vehicle automatically stops on the ramp, the target braking force of the parking brake 10 necessary for maintaining the vehicle in a stopped state increases, and as a result, the required driving time tends to increase. Accordingly, the electric parking brake drive timing is also advanced.
The detection of the slope of the road surface while the vehicle is traveling can be performed by, for example, comparing the change rate of the detected vehicle speed, which is the output history of the vehicle speed sensor 83, with the acceleration in the longitudinal direction of the vehicle detected by the G sensor 43. it can. Specifically, if the G detected by the G sensor 43 is larger than the deceleration G estimated based on the rate of change of the vehicle speed, it is determined that the vehicle is downhill, and vice versa. The And it can be considered that the amount of deviation of each G correlates with the degree of inclination. Such inclination detection is performed, for example, by the parking brake ECU 41. In this case, the parking brake ECU 41 also functions as an inclination detection unit.
The target braking force of the parking brake 10 is set, for example, by multiplying the braking force necessary for maintaining the vehicle in a stopped state by a predetermined safety factor according to the road surface inclination thus detected. Is done.

<Step S09: Start of electric parking brake drive>
The parking brake ECU 41 of the parking brake controller 40 controls the relay 42 to start energization of the actuator unit 20. As a result, the transition from the released state of the parking brake 10 to the braking state is started, and a braking force is generated as shown in FIG. 3, and the towing stroke of the parking brake cable 21 increases and the braking force also increases almost linearly. To do.
Proceed to step S10.

<Step S10: Start of brake fluid decompression>
The VDC ECU 81 controls the HCU 82 to start reducing the brake fluid hydraulic pressure applied to the hydraulic brake 70. Here, the amount of pressure reduction of the brake fluid is substantially the same as the amount of decrease in the braking force of the hydraulic brake 70 accompanying the pressure reduction and the amount of increase in the braking force of the parking brake 10 described above, and the vehicle maintains a substantially constant deceleration. Is set as follows.
Proceed to step S11.

<Step S11: Electric parking brake target braking force determination>
The parking brake ECU 41 of the parking brake controller 40 determines, based on the output of the stroke sensor of the actuator unit 20, whether or not the parking brake 10 has entered a state that generates a predetermined target braking force. If the parking brake 10 has generated the target braking force, the process proceeds to step S12. If the parking brake 10 has not yet generated the target braking force, the driving of the parking brake 10 by the actuator unit 20 is continued and step S11 is performed again. Repeat.

<Step S12: End of electric parking brake drive>
The parking brake ECU 41 of the parking brake controller 40 controls the relay 42 to stop energization of the actuator unit 20. Here, the timing of stopping energization (stop of driving) is almost the same as the timing of stopping the vehicle by setting the timing of starting driving as described in step S08, or just before stopping the vehicle. .
Proceed to step S13.
<Step S13: Release of hydraulic brake>
The HCU 82 of the VDC system 80 finishes reducing the brake fluid hydraulic pressure started in step S10, and the hydraulic pressure becomes substantially zero. As a result, the hydraulic brake 70 enters a release state in which substantially no braking force is generated.
As a result, a series of processing ends.

Next, the effect of the above-described embodiment will be described in comparison with a braking control device of a comparative example of the present invention described below.
The braking control device of the comparative example operates only the hydraulic brake until the vehicle automatically stops by ACC control, operates the electric parking brake after stopping, and reduces the brake fluid hydraulic pressure of the hydraulic brake after the braking force is generated. To do.
FIG. 4 is a graph showing an example of a history of vehicle speed sensor output, brake fluid hydraulic pressure, and parking brake braking force when a vehicle equipped with a braking control device of a comparative example automatically stops.

The braking control device of the comparative example uses only a hydraulic brake while the vehicle is running, and this hydraulic brake cannot release the hydraulic pressure until the parking brake generates the target braking force even after the vehicle stops. In addition, the usage time and frequency of hydraulic pressure generating / holding mechanisms such as pumps and valves of hydraulic control units increase. For this reason, the durability required for each mechanism portion becomes severe, and the amount of electric power necessary for driving the mechanism portion increases, and the electrical heat generation also increases.
Further, in the braking control device of the comparative example, the vehicle is stopped by braking the front and rear wheels with a hydraulic brake. Therefore, the braking force of the front wheels increases, so the nose dive immediately before the stop increases and the vehicle is compressed immediately after the stop. In addition, the behavior in the pitching direction caused by the restoration of the front suspension may be increased, causing discomfort to the passenger.

On the other hand, according to the present embodiment, the following effects can be obtained.
(1) When the automatic stop detection unit 41a detects an automatic stop by the ACC control of the vehicle, the driving of the parking brake 10 by the actuator unit 20 is started before the vehicle stops, whereby the pressure reduction start timing of the hydraulic brake 70 is started. Since the release time when the hydraulic pressure becomes almost zero can be advanced respectively, the usage time and usage frequency of the hydraulic brake 70 can be reduced, and the pump, valve, etc. of the HCU 82 that generates and maintains the brake fluid hydraulic pressure, etc. The usage conditions can be relaxed. This also reduces the power consumption of the HCU 82 and prevents electrical heat generation.
(2) Since the braking force of the parking brake 10 is generated before the vehicle stops and the brake fluid hydraulic pressure of the hydraulic brake 70 is reduced according to the increase of the braking force, the vehicle accompanying the operation of the parking brake 10 The braking feeling can be improved by suppressing the change in deceleration. Further, the pressure reduction of the hydraulic brake 70 can be accelerated.
(3) Immediately before the vehicle stops, the front wheel is braked by reducing the braking force of the hydraulic brake 70 that brakes the front and rear wheels and increasing the proportion of the braking force applied by the parking brake 10 that brakes only the rear wheels. The nose dive of the vehicle that is likely to occur at the time is suppressed, and the behavior in the pitching direction due to the extension of the front suspension immediately after the stop is suppressed, thereby improving the comfort.
(4) Since the estimated stop time at which the vehicle stops is obtained based on the vehicle speed and deceleration, and the driving start time of the parking brake 10 is set according to the estimated stop time, the braking force generation time is determined. It can be controlled appropriately.
(5) By detecting the inclination of the road surface and varying the driving start timing of the parking brake 10 according to this inclination, the parking brake 10 can be used even on an inclined road having a large target braking force and a long driving time. The generation delay of the braking force can be prevented.
(6) By automatically starting the driving of the parking brake 10 in accordance with the time from when the vehicle speed becomes equal to or lower than the detection lower limit speed of the vehicle speed sensor 83, the automatic stop detection unit 41a may malfunction or be automatically stopped. It is possible to ensure the fail-safe property of the device against detection errors and the like.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
(1) The configuration of the braking control device is not limited to the configuration of the embodiment and can be changed as appropriate. For example, the follow-up running control unit, the automatic stop detection unit, and the mechanical brake control unit may be provided independently or may be configured by integrating a plurality of them. For example, instead of providing the automatic stop detection unit in the mechanical brake control unit as in the embodiment, it may be provided independently or integrated with the follow-up travel control unit.
(2) The embodiment detects the automatic stop of the vehicle based on the fact that the vehicle speed is lower than the detection lower limit speed and the brake fluid hydraulic pressure is generated, but the automatic stop is detected by other methods. Also good. For example, an automatic stop may be detected based on the follow-up travel control unit setting the target speed to zero, and driving of the mechanical brake may be started.
Further, for example, even if the vehicle speed does not reach the detection lower limit speed or less, the estimated stop time can be calculated from the vehicle speed and deceleration at that time, so S02 can be omitted.
(3) The configuration of the electric parking brake device is not limited to that of the embodiment, and can be changed as appropriate.
For example, the parking brake of the embodiment uses a drum arranged on the inner diameter side of a brake disc for a foot brake, but the parking brake may be of other types, for example, for a foot brake. The disc brake or drum brake and its friction material may be shared and integrated with the parking brake.
Further, the parking brake of the embodiment uses an electric actuator fixed on the body side and drives the parking brake via a parking brake cable. However, the present invention is not limited to this, and for example, the electric actuator is a wheel. The present invention can also be applied to a so-called built-in type electric parking brake provided on the hub side and integrated with the parking brake.
(4) In the embodiment, the driving of the mechanical brake is terminated immediately before the vehicle stops. However, the present invention is not limited to this, and the driving starts before the vehicle stops. It may be.
(5) Although the embodiment controls the pressure reduction of the hydraulic brake so that the sum of the braking forces of the hydraulic brake and the mechanical brake becomes substantially constant, the present invention is not limited to this. In order to improve the control, it may be controlled to reduce the deceleration G by reducing the sum of braking forces immediately before stopping.

1 is a block diagram showing a configuration of a vehicle including an embodiment of a braking control device to which the present invention is applied. It is a flowchart which shows operation | movement of the braking control apparatus of FIG. 2 is a graph showing an example of a history of vehicle speed sensor output, brake fluid hydraulic pressure, and parking brake braking force when the vehicle of FIG. 1 automatically stops by ACC control. It is a graph which shows an example of the log | history of the vehicle speed sensor output at the time of the vehicle provided with the braking control apparatus which is a comparative example of this invention stopping automatically, brake fluid hydraulic pressure, and parking brake braking force.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Parking brake 20 Actuator unit 21 Actuator cable 30 Battery 40 Parking brake controller 41 Parking brake electronic control unit 41a Automatic stop detection part 42 Relay 43 G sensor 50 Operation switch 60 Engine 62 Throttle actuator 63 Engine electronic control unit 70 Hydraulic brake 80 Vehicle Stability Control (VDC) System 81 VDC Electronic Control Unit 82 Hydraulic Control Unit 83 Vehicle Speed Sensor 90 Adaptive Cruise Control (ACC) System 91 ACC Electronic Control Unit 92 Leading Vehicle Detection Unit

Claims (9)

A follow-up running control unit that controls the hydraulic brake according to the running state of the preceding vehicle and automatically stops the vehicle;
An automatic stop detection unit that detects the automatic stop of the vehicle by the follow-up travel control unit before the vehicle stops;
A mechanical brake control unit that starts driving from the release state of the mechanical brake by the electric actuator to the braking state in response to detection of the automatic stop by the automatic stop detection unit, before the vehicle stops ;
The mechanical brake control unit finishes the driving before the automatic stop of the vehicle.
Brake control apparatus said.   A follow-up running control unit that controls the hydraulic brake according to the running state of the preceding vehicle and automatically stops the vehicle;
  An automatic stop detection unit that detects the automatic stop of the vehicle by the follow-up travel control unit before the vehicle stops;
  A mechanical brake control unit that starts driving from the release state of the mechanical brake by the electric actuator to the braking state in response to detection of the automatic stop by the automatic stop detection unit;
  With
  The follow-up travel control unit decreases the braking force of the hydraulic brake as the braking force of the mechanical brake increases.
  A braking control device characterized by the above.   The braking control device according to claim 2, wherein
  The follow-up travel control unit sets the braking force of the mechanical brake so that the braking force increase amount of the mechanical brake is the same as the braking force decrease amount of the hydraulic brake.
  A braking control device characterized by the above. In the braking control device according to any one of claims 1 to 3 ,
The braking control device, wherein the mechanical brake control unit starts driving by the electric actuator at a timing at which the mechanical brake generates a braking force before the vehicle stops. In the braking control device according to any one of claims 1 to 4 ,
The following control unit reduces the hydraulic pressure of the hydraulic brake after the mechanical brake generates a braking force and before the vehicle stops. The braking control device according to claim 5 , wherein
The braking control apparatus, wherein the mechanical brake brakes a rear wheel of the vehicle. In the braking control device according to any one of claims 1 to 6 ,
The automatic stop detection unit calculates an estimated stop time of the vehicle based on the speed and deceleration of the vehicle,
The brake control device, wherein the mechanical brake control unit sets a driving start timing of the mechanical brake by the electric actuator according to the estimated stop time. The braking control device according to claim 7 , wherein
An inclination detector for detecting an inclination of a road surface on which the vehicle is running;
The braking control device, wherein the mechanical brake control unit varies the driving start timing of the mechanical brake according to the inclination detected by the inclination detection unit. In the braking control device according to any one of claims 1 to 8 ,
The mechanical brake control unit starts driving the mechanical brake regardless of the output of the automatic stop detection unit according to the time from when the vehicle speed becomes equal to or lower than the detection lower limit speed of the vehicle speed sensor. A braking control device characterized by the above.

Images