JP2012011969A - Brake control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake control device for preventing a vehicle from moving when automatically stopping an engine by an idle stop system in response to causing traveling and stopping by a cruise system.SOLUTION: This brake control device is applied to the vehicle including the cruise system for automatically operating a braking brake so as to make one's own vehicle travel and stop in response to travel and stopping of a preceding vehicle, the idle stop system for automatically stopping the engine 20 and an electric parking brake system for automatically operating a parking brake (a parking brake shoe 53) by an electric motor 50, and automatically operates the parking brake by the electric parking brake system when automatically stopping the engine 20 by the idle stop system in response to causing traveling and stopping by the cruse system.

Description

  The present invention relates to a brake control device applied to a vehicle including a cruise system, an idle stop system, and an electric parking brake system.

  Patent Document 1 describes a cruise system in which a braking brake is automatically actuated so that the host vehicle automatically stops traveling when the preceding vehicle stops traveling. When this cruise system is applied to a vehicle equipped with an idle stop system that automatically stops the engine, the engine automatically stops (idle stop) as the cruise system stops traveling.

  Then, when the hydraulic oil pump of the brake brake is driven by the engine, the hydraulic pressure of the brake brake decreases during the idle stop period and the brake force decreases. For example, in the case of an uphill road or a downhill road There is a concern that the vehicle will start to move due to insufficient braking force.

  Further, when the hydraulic oil pump for the brake brake is electric, the power consumption during the idle stop period increases, and there is a concern that the battery will fall into an overdischarged state. And when sufficient electric power is not supplied from a battery, the said problem that a braking force will fall and a vehicle will start will arise.

JP 2006-316644 A

  The present invention has been made in order to solve the above-described problem, and the purpose of the present invention is to prevent the vehicle from moving when the engine is automatically stopped by the idle stop system in association with the traveling stop by the cruise system. An object of the present invention is to provide a brake control device that prevents the above.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  According to the first aspect of the present invention, a cruise system that automatically operates a braking brake so as to stop traveling of the host vehicle when the preceding vehicle stops traveling, an idle stop system that automatically stops the engine, and a parking brake that is automatically operated by an electric motor. And when the engine is automatically stopped by the idle stop system in association with stopping traveling by the cruise system, the parking brake is applied by the electric parking brake system. It is automatically operated.

  Here, with respect to a parking brake for preventing a parked vehicle from starting to move, a parking brake that automatically operates a parking brake with an electric motor has been developed in recent years (for example, JP 2009-90854 A). Therefore, the present inventor has conceived that the above-mentioned problem such as “the braking force decreases and the vehicle starts moving” is solved by using an electric parking brake system.

  That is, according to the above-described invention, when the vehicle is idle-stopped along with the traveling stop by the cruise system, the parking brake is automatically operated by the electric parking brake system. According to this, since the parking brake that mechanically exerts the braking force is automatically operated without using the hydraulic pressure, the above-mentioned problems such as “the braking force decreases and the vehicle starts to move” can be solved. Further, when the brake pump hydraulic oil pump is electrically operated, according to the above-described invention in which the parking brake is automatically operated, the drive time of the oil pump during idle stop can be shortened (or the drive time can be made zero). Therefore, it can avoid that a battery falls into an overdischarge state.

  The invention according to claim 2 is characterized in that the automatic operation of the parking brake is permitted on condition that a predetermined time has elapsed since the engine was automatically stopped.

  Here, when the parking brake is automatically operated, there is a concern that the start of vehicle travel may be delayed by the time required for releasing the parking brake when the engine is automatically started after releasing the idle stop. Accordingly, it is not desirable to automatically activate the parking brake more than necessary in order to quickly start the vehicle travel.

  On the other hand, for example, when the hydraulic pump of the brake brake is driven by the engine, the hydraulic pressure is maintained so that a sufficient braking force can be exerted for a while after the engine is automatically stopped. Further, when the hydraulic oil pump of the brake brake is electric, sufficient braking force can be exerted by the remaining power of the battery for a while after the engine is automatically stopped.

  According to the above invention in view of these points, it is considered that a sufficient braking force cannot be exerted only after a predetermined time has elapsed after the engine is automatically stopped, so that the automatic operation of the parking brake is permitted. It is possible to avoid automatically operating the parking brake. Therefore, it is possible to achieve both the solution of the problem of “the braking force is reduced and the vehicle starts moving” and the solution of the problem of “the vehicle start to be delayed”.

  The invention according to claim 3 is characterized in that the automatic operation of the parking brake is permitted on the condition that the inter-vehicle distance between the preceding vehicle and the host vehicle is less than a predetermined distance.

  Here, as described above, it is not desirable to automatically activate the parking brake more than necessary in order to promptly start the vehicle travel. On the other hand, if the inter-vehicle distance between the preceding vehicle and the host vehicle is long, the vehicle may start to move due to a decrease in braking force. Moreover, if the parking brake is automatically operated after starting to move in such a manner, sufficient safety may be ensured.

  According to the above invention in view of these points, since the automatic operation of the parking brake is permitted on the condition that the inter-vehicle distance between the preceding vehicle and the host vehicle is less than a predetermined distance, the parking brake is automatically operated more than necessary. Can be avoided. Therefore, it is possible to achieve both the solution of the problem of “the braking force is reduced and the vehicle starts moving” and the solution of the problem of “the vehicle start to be delayed”.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the outline | summary of the brake control apparatus (ECU) concerning one Embodiment of this invention, the engine of a vehicle, the brake system, etc. to which the apparatus is applied. The flowchart which shows the control procedure of the electric parking brake by ECU of FIG.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. A vehicle to which the brake control device according to the present embodiment is applied travels using an engine (internal combustion engine) as a driving force. A cruise system, an idle stop system, and an electric parking brake EPB (Electronic Parking Brake) which will be described in detail later. System. The operation of these systems is controlled by the electronic control unit (ECU 10) shown in FIG. The ECU 10 is constituted by a microcomputer that performs calculations, a ROM that stores programs for causing the microcomputer to execute each process, a RAM that stores various data such as calculation results, and the like.

  The driving force output from the engine 20 is transmitted to the automatic transmission 22 via the clutch 21. The driving force transmitted to the automatic transmission 22 is further transmitted to the wheels via a differential, a drive shaft, and the like. And a vehicle drive | works by driving a wheel.

  The ECU 10 includes a stroke sensor 31 that detects an operation amount (accelerator operation amount) of an accelerator pedal 30 (accelerator operation member), a crank angle sensor 11 that detects a rotation speed of the crankshaft of the engine 20 (engine rotation speed), and an intake air amount. (Engine load) Detection signals from various sensors such as an air flow meter 12 to be detected are input. Based on the detected accelerator operation amount, engine speed, engine load, etc., the ECU 10 controls the operation of the fuel injection valve 23, the ignition device 24, and the like. Thereby, the fuel injection amount, the ignition timing, and the like are controlled, and the driving force of the engine 20 is controlled.

  Further, the ECU 10 operates the automatic transmission 22 based on the shift position of the automatic transmission 22 detected by the shift position sensor 13, the vehicle speed detected by the wheel speed sensor 14, the accelerator operation amount detected by the stroke sensor 31, and the like. To control.

  Next, the aforementioned cruise system will be described.

  A cruise switch 17 is provided in the vicinity of the driver's seat in the passenger compartment. When the vehicle driver turns on the cruise switch 17, a cruise system described below is provided on condition that the execution condition for cruise control is satisfied. The cruise system stops when it is activated and operated off. During the operation of the cruise system, the ECU 10 acquires a detection signal of the inter-vehicle distance between the preceding vehicle and the host vehicle from the inter-vehicle distance sensor 15 mounted on the vehicle. Moreover, the video signal which imaged the front situation of the own vehicle is acquired from the camera 16 mounted in the vehicle. Then, based on the detected inter-vehicle distance and the video signal, the traveling state of the vehicle is controlled so that the inter-vehicle distance is constant at the set distance.

  Specifically, when the cruise system is operating, even if the vehicle driver does not operate the accelerator pedal 30, the operation of the fuel injection valve 23, the ignition device 24, etc. is controlled based on the inter-vehicle distance and the front situation. The driving force is automatically controlled and the operation of the automatic transmission 22 is controlled. As a result, the running state is automatically controlled so that the distance between the vehicles is constant. For example, when the vehicle ahead accelerates and the inter-vehicle distance becomes longer than the set distance, automatic control is performed so that the driving force of the engine 20 increases.

  Further, when the cruise system is operated, even if the vehicle driver does not operate the brake pedal 40 (brake operation member), the brake caliper 41 is automatically operated by the ECU 10 based on the inter-vehicle distance and the front situation, so that the braking force is increased. Automatic control to make it work. For example, when the preceding vehicle decelerates and the inter-vehicle distance becomes shorter than the set distance, automatic control is performed to increase the braking force.

  The brake caliper 41 incorporates a brake pad and a wheel cylinder (not shown), and is arranged corresponding to the brake disc 42 attached to each wheel of the vehicle. The wheel cylinder is connected to a hydraulic circuit 44 via a brake pipe 43. The wheel cylinder is also connected to a master cylinder 45 via a brake pipe 43 and a hydraulic circuit 44.

  During normal braking when the vehicle driver depresses the brake pedal 40, the pressure in the master cylinder 45 rises, and this pressure rise is transmitted to the wheel cylinder via the hydraulic circuit 44 and the brake pipe 43, so that the wheel cylinder The pressure inside rises. When the hydraulic pressure in the wheel cylinder is increased, the brake pad is pressed against the brake disc 42, and the wheel connected to the brake disc 42 is braked by the frictional force.

  The hydraulic circuit 44 includes a hydraulic pump, a plurality of electromagnetic valves, and the like, and communicates between the master cylinder 45 and the wheel cylinder in the brake caliper 41 during automatic braking brake control when the braking force is automatically controlled by the cruise system. Is cut off, and the hydraulic pressure in the wheel cylinder during braking is maintained. When the braking force is insufficient, the brake hydraulic pressure increased by the hydraulic pump is transmitted to the wheel cylinder via the electromagnetic valve, and the wheel cylinder pressure is increased. In addition, the wheel cylinder pressure can be reduced by driving another electromagnetic valve. In this way, the braking force of each wheel is automatically controlled by automatically controlling the operation of each brake caliper 41. It should be noted that the hydraulic pump and electromagnetic valve of the hydraulic circuit 44 are controlled by the ECU 10.

  The ECU 10 is input with a signal indicating the depression amount (brake operation amount) of the brake pedal 40 detected by the stroke sensor 47 and a signal indicating the hydraulic pressure in the master cylinder 45 detected by the master cylinder pressure sensor 46. The

  Next, the idle stop system described above will be described.

  When the cruise system is off when the cruise system is not operating, the ECU 10 is conditioned on the condition that the vehicle speed is less than or equal to a predetermined value or zero and the vehicle driver depresses the brake pedal 40 by a predetermined amount or more. Then, the fuel injection from the fuel injection valve 23 is stopped to idle stop. When the cruise system is operating, the ECU 10 performs fuel injection from the fuel injection valve 23 on the condition that the vehicle speed is equal to or less than a predetermined value or zero and the braking force by the brake caliper 41 is equal to or greater than a predetermined value. Stop and idle stop. In addition, you may add that the vehicle driver is not operating the accelerator pedal 30 to the idle stop conditions mentioned above. Moreover, you may add that the parking brake mentioned later is act | operating.

  When the cruise system is off, the vehicle driver releases the brake pedal 40 during idle stop, or the condition that the depression amount is less than the predetermined amount, or the battery capacity is less than the predetermined amount, The ECU 10 generates a signal for requesting idle stop cancellation. As a result, the starter motor 25 is automatically driven and the operation of the fuel injection valve 23 and the ignition device 24 is started to restart the engine 20 automatically. In addition, you may add that the accelerator pedal 30 is stepped on to the idle stop cancellation | release conditions mentioned above. Moreover, you may add that the parking brake mentioned later is not act | operating.

  When the cruise system is in operation, the ECU 10 generates a signal for requesting release of the idle stop on condition that the vehicle driver depresses the accelerator pedal 30 during the idle stop. As a result, the starter motor 25 is automatically driven and the operation of the fuel injection valve 23 and the ignition device 24 is started to restart the engine 20 automatically. After the restart, the operation of the automatic transmission 22 and the hydraulic circuit 44 is controlled by the operation of the cruise system so that the distance between the vehicle ahead and the preceding vehicle becomes constant at the set distance, and the vehicle is automatically driven.

  Next, the EPB system (electric parking brake system) described above will be described.

  A parking switch 18 is provided near the driver's seat in the passenger compartment. When the vehicle driver turns on the parking switch 18, the electric motor 50 is activated and the parking brake is activated. That is, in the EPB system, the parking brake is operated by the electric motor 50 instead of operating the parking brake by the driver's operation force. The driving force of the electric motor 50 is transmitted to the parking brake shoe 53 (parking brake) via the gear mechanism 51 and the cable 52. As a result, the brake shoe 53 is pressed against the brake drum 54 provided on the rear wheel, and the parking brake force is exhibited by the frictional force, and the wheel is locked.

  The gear mechanism 51 includes a holding device such as a latch that holds the cable 52 in a pulled state (wheel lock state). Therefore, after the cable 52 is pulled by the electric motor 50 to lock the wheel, the driving of the electric motor 50 is stopped and the locked state is held by the holding device of the gear mechanism 51. In short, while the braking force by the brake pedal 40 is exerted by hydraulic pressure, the parking brake force is retained by the retaining device of the gear mechanism 51 after being exerted by the driving force of the electric motor 50.

  When the vehicle driver turns off the parking switch 18, the gear mechanism 51 is operated so as to loosen the tension of the cable 52, and the brake shoe 53 is separated from the brake drum 54. Thereby, the parking brake is automatically released. For example, when the electric motor 50 is driven in reverse, the gear mechanism 51 may be configured to operate so as to loosen the tension of the cable 52.

  In addition, when the engine 20 is automatically stopped by the idle stop system when the traveling is stopped by the cruise system, the electric motor 50 of the EPB is driven even if the vehicle driver does not turn on the parking switch 18. The ECU 10 (brake control device) automatically controls. That is, when the cruise system automatically stops running and idles, the EPB is automatically turned on to lock the wheels.

  Note that when the idle stop is canceled by the cruise system, the gear mechanism 51 is operated so as to loosen the tension of the cable 52. As a result, the EPB is automatically turned off to release the wheel lock.

  FIG. 2 is a flowchart showing a procedure for automatically turning on the EPB as described above by the microcomputer of the ECU 10, and the process is repeatedly executed at a predetermined cycle (for example, a calculation cycle of the microcomputer).

  First, in step S10 shown in FIG. 2, it is determined whether or not the cruise control is being performed. In subsequent step S20, it is determined whether or not the vehicle speed is zero. In subsequent step S30, whether the idle stop condition is satisfied. Determine whether or not. When it is determined that the cruise control is being performed, the vehicle speed is zero, and the idle stop condition is satisfied (S10: YES, S20: YES, S30: YES), the process proceeds to the next step S40. Then, it is determined whether or not the elapsed time Tstp after the engine 20 is automatically stopped by the idle stop has exceeded a predetermined time Tth.

  When it is determined that Tstp ≦ Tth (S40: NO), the elapsed time Tstp counted by the timer is counted up and the process returns to step S10. On the other hand, if it is determined that Tstp> Tth (S40: YES), it is determined in step S60 whether the distance between the preceding vehicle and the host vehicle is equal to or greater than a predetermined value. If it is determined that the inter-vehicle distance is less than the predetermined value (S60: NO), the process proceeds to step S70, and it is determined whether or not the accelerator depression amount detected by the stroke sensor 31 is greater than or equal to the predetermined value.

  If it is determined that the accelerator depression amount is less than the predetermined value (S70: NO), in step S80, the electric motor 50 is driven to automatically turn on the EPB. On the other hand, if it is determined that the accelerator depression amount is equal to or greater than the predetermined value (S70: YES), in the subsequent step S90, the gear mechanism 51 is operated to loosen the tension of the cable 52 and the EPB is automatically turned off (unlocked). )

  Here, when the engine 20 is automatically stopped by the idle stop system in association with the traveling stop by the cruise system (S30: YES), the vehicle driver does not operate the brake pedal 40, and therefore the brake caliper 41 is entered. Even if the vehicle starts to move due to the decrease in the hydraulic pressure supplied and the braking force, it is difficult to notice the movement. Therefore, there is a concern that the brake operation by the driver such as depressing the brake pedal 40 to stop the movement of the vehicle may be delayed.

  In response to this concern, according to the embodiment described in detail above, when the cruise system is used to stop traveling and idle stop (S30: YES), the EPB is automatically turned on (S80). Therefore, even when traveling on an uphill or downhill road is stopped by the cruise system and idle stopped, the brake force is mechanically held by the holding device of the gear mechanism 51 without using hydraulic pressure, as described above. The problem that the vehicle starts to move can be solved.

  By the way, when releasing the idle stop and automatically starting the engine 20, the time required for the EPB OFF operation is longer than the time required for releasing the braking force by reducing the hydraulic pressure to the brake caliper 41. . Therefore, it is more advantageous to operate the brake caliper 41 than to operate the EPB during idle stop in order to start traveling quickly when a signal requesting vehicle travel occurs during the idle stop. That is, it is not desirable to automatically operate the EPB more than necessary in order to quickly start the vehicle travel. On the other hand, for a while after the engine 20 is automatically stopped, the hydraulic pressure supplied to the brake caliper 41 is maintained to such an extent that a sufficient braking force can be exerted.

  In the present embodiment in view of these points, the EPB is automatically turned on under the condition that the elapsed time Tstp after the engine 20 has automatically stopped exceeds the predetermined time Tth (S40: YES). It is possible to achieve both the solution of the problem that “the vehicle starts to move due to a decrease in the vehicle” and the solution of the problem that “the vehicle start of driving is delayed”.

  In addition, if the inter-vehicle distance between the preceding vehicle and the host vehicle is long, the supply pressure to the brake caliper 41 may be decreased and the vehicle may be allowed to move on the downhill road. Further, if the EPB is automatically turned on after such movement, safety may be sufficiently secured. In view of these points, in the present embodiment, the EPB is automatically turned on under the condition that the inter-vehicle distance between the preceding vehicle and the host vehicle is less than a predetermined distance (S60: NO). The operation can be avoided. Therefore, it is possible to promote the coexistence of the solution of the problem “the brake force is reduced and the vehicle starts moving” and the solution of the problem “the vehicle start of driving is delayed”.

  Furthermore, according to the present embodiment, paying attention to the point that the ON operation of the EPB is not required when the accelerator pedal 30 is sufficiently depressed and the travel driving force is exerted, the accelerator depression amount is less than a predetermined value. Under the condition (S70: NO), the EPB is automatically turned on. Therefore, it is possible to promote the coexistence of the solution of the problem “the brake force is reduced and the vehicle starts moving” and the solution of the problem “the vehicle start of driving is delayed”.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  In the embodiment shown in FIG. 1, a hydraulic actuator that supplies hydraulic pressure to the brake caliper 41 is driven by the engine 20. On the other hand, the hydraulic actuator may be driven by an electric motor.

  ・ When the EPB is automatically turned on when the cruise system stops running and idles, the operating state of the hydraulic circuit 44 is maintained as it is, and the braking brake force by the brake caliper 41 is also exerted together with the parking brake force. It may be. Alternatively, when the hydraulic actuator is driven by the electric motor as described above, the electric motor may be stopped along with the ON operation of the EPB to suppress a decrease in battery capacity.

  The brake for braking shown in FIG. 1 is a disc brake system that exerts a braking force by friction generated by sandwiching the brake disc 42 between brake pads, but is controlled by friction generated by pressing a brake shoe against a brake drum. A drum brake system that exerts power may be used.

  DESCRIPTION OF SYMBOLS 10 ... ECU (brake control apparatus), 50 ... Electric motor, 53 ... Brake shoes for parking (parking brake).

Claims (3)

A cruise system that automatically activates a braking brake to stop the traveling of the host vehicle when the preceding vehicle stops traveling, an idle stop system that automatically stops the engine, and an electric parking brake system that automatically operates the parking brake with an electric motor. Applied to vehicles equipped with,
A brake control device that automatically activates the parking brake by the electric parking brake system when the engine is automatically stopped by the idle stop system in association with stopping traveling by the cruise system.   The brake control device according to claim 1, wherein automatic operation of the parking brake is permitted on condition that a predetermined time has elapsed since the engine was automatically stopped.   The brake control device according to claim 1 or 2, wherein the automatic operation of the parking brake is permitted on the condition that a distance between the preceding vehicle and the host vehicle is less than a predetermined distance.

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