JP5659580B2 - Vehicle control apparatus and vehicle control method - Google Patents

Description

  The present invention relates to a vehicle control device and a vehicle control method for performing stop control for automatically stopping a vehicle engine and restart control for automatically restarting the engine.

  In recent years, for the purpose of improving the fuel efficiency of a vehicle, the engine is automatically stopped while the vehicle is stopped or just before the stop, and a so-called idle stop function that automatically restarts the engine upon the start operation by the driver is provided. Development of vehicle control devices is underway. For example, in the vehicle control device described in Patent Document 1, the start timing for automatically stopping the vehicle engine is set based on the depression force (operation amount) of the brake pedal by the driver.

  Further, in the vehicle control device described in Patent Document 2, the internal pressure of the booster that assists the brake operation by the driver using the negative pressure of the engine is detected based on the detection signal from the booster pressure sensor. An intake pressure corresponding to the throttle opening of the engine is detected based on a detection signal from an accelerator opening sensor. When the difference between the detected internal pressure of the booster and the intake pressure is less than a predetermined value, the engine is automatically stopped.

JP-A-11-324755 Japanese Patent No. 3536717

  By the way, in recent years, not only the improvement of the fuel consumption of the vehicle but also the cost reduction of the vehicle is strongly desired. One method for reducing the cost of a vehicle having an idle stop function is to reduce the number of sensors mounted on the vehicle.

  However, in the control device described in Patent Document 1, when a sensor for detecting a pedaling force (for example, a pressure sensor for detecting a fluid pressure (fluid pressure) in the master cylinder) is not mounted on a vehicle, a brake is applied. The pedaling force cannot be detected, and the timing for automatically stopping the engine cannot be set. Further, in the control device described in Patent Document 2, when the booster pressure sensor and the pressure sensor for detecting the hydraulic pressure in the master cylinder are not mounted on the vehicle, the internal pressure of the booster cannot be detected and the engine is automatically activated. The control to stop can not be started. Therefore, even when the vehicle is not provided with a sensor for detecting the depression force of the brake pedal by the driver or the hydraulic pressure in the master cylinder, or even when the sensor is not used, the stop control is started at an appropriate timing. There was a need for technology that could do this.

  The present invention has been made in view of such circumstances. An object of the present invention is to provide a vehicle control device capable of setting a timing for automatically stopping a vehicle engine without using a sensor for detecting a brake operation amount by a driver or a fluid pressure in a master cylinder, and The object is to provide a vehicle control method.

In order to achieve the above object, a vehicle control apparatus according to the present invention communicates with a master cylinder (25) that generates fluid pressure in accordance with a brake operation by a driver, and the master cylinder (25) via a flow path. A wheel cylinder (32a, 32b, 32c, 32d) for applying to the wheels (FR, FL, RR, RL) a braking force corresponding to the fluid pressure generated inside, Acceleration acquisition means (55, S10) for acquiring acceleration (G) in the longitudinal direction of the vehicle based on a signal output from an acceleration sensor (SE7) provided in the vehicle, and the acquired acceleration (G) in the longitudinal direction based on the master cylinder (25) fluid pressure corresponding value corresponding to the fluid pressure in the fluid pressure equivalent value acquisition means for acquiring (Amc) (55, S13), the acceleration acquisition means 55, on the basis of the acceleration (G) wherein in the longitudinal direction obtained by S10), the road gradient corresponding value that corresponds to the gradient of the road surface (the slope acquisition means for acquiring Ag) (55, S14), the vehicle engine (12 Control means (55) for performing stop control for automatically stopping the engine (12) and restart control for automatically restarting the engine (12), and the control means (55, S30, S31). ), The fluid pressure equivalent value (Amc) acquired by the fluid pressure equivalent value acquisition means (55, S13) is larger than the road surface gradient equivalent value (Ag) acquired by the gradient acquisition means (55, S14). In this case, the gist is to perform the stop control.

  The fluid pressure in the master cylinder is a pressure corresponding to the amount of operation of the brake pedal by the driver, that is, a pressure corresponding to the braking force applied to the vehicle wheel. And the acceleration in the front-back direction of the vehicle acquired based on an acceleration sensor fluctuates according to the change of the operation amount of the brake pedal by a driver. That is, the fluid pressure in the master cylinder (that is, the braking force applied to the wheels) and the acceleration in the longitudinal direction of the vehicle acquired based on the acceleration sensor are in a corresponding relationship. Therefore, in the present invention, a fluid pressure equivalent value corresponding to the fluid pressure in the master cylinder is acquired based on the acceleration in the longitudinal direction of the vehicle acquired based on the acceleration sensor. If the obtained fluid pressure equivalent value is larger than the road surface slope equivalent value corresponding to the road surface slope, even if the engine is stopped when the vehicle travels on the uphill road, The possibility of backward movement, that is, sliding down is low. Then, even when the engine is stopped and the creep torque disappears, stop control for stopping the engine is performed at a timing when it is determined that the vehicle located on the uphill road does not slide down. Therefore, the timing for automatically stopping the engine of the vehicle can be set without using a sensor for detecting the amount of brake operation by the driver or the fluid pressure in the master cylinder.

  Note that the creep phenomenon is a phenomenon in which a vehicle has an automatic transmission and the vehicle slowly moves forward even if the accelerator pedal is not depressed when the shift lever is in the traveling position. This occurs because the fluid coupling provided in the automatic transmission transmits some power to the wheel side. The slight amount of power transmitted to the wheels is called “creep torque”.

  In the vehicle control apparatus of the present invention, the fluid pressure equivalent value acquisition means (55, S13) is generated in the vehicle by the acceleration (G) in the longitudinal direction acquired by the acceleration acquisition means (55, S10). It is preferable to obtain the fluid pressure equivalent value (Amc) based on the creep equivalent value (Ac) corresponding to the creep torque and the running resistance equivalent value (Ar) corresponding to the running resistance applied to the vehicle.

  The vehicle that decelerates is given a braking force applied to the wheels, a creep torque generated by the vehicle, and a force corresponding to the running resistance. The acceleration in the longitudinal direction of the vehicle acquired based on the acceleration sensor is an acceleration corresponding to the resultant force of the braking force, the creep torque, and the driving resistance. Therefore, in the present invention, the fluid pressure equivalent value is the acceleration in the longitudinal direction of the vehicle acquired based on the acceleration sensor, the creep equivalent value equivalent to the creep torque, and the running resistance equivalent value equivalent to the running resistance applied to the vehicle. Obtained based on Therefore, the correspondence between the fluid pressure in the master cylinder and the fluid pressure equivalent value is better than when the fluid pressure equivalent value is obtained without considering the creep equivalent value and the running resistance equivalent value. It can be. Therefore, when the engine is automatically stopped based on the fluid pressure equivalent value acquired in this way, it is possible to further reduce the possibility that the vehicle located on the uphill road will slip down.

  In the vehicle control apparatus according to the present invention, the control means (55, S41, S42, S43) is configured such that the fluid pressure acquired by the fluid pressure equivalent value acquisition means (55, S13) while the engine (12) is stopped. When it is determined that the fluid pressure in the master cylinder (25) is being reduced based on the equivalent value (Amc), the restart control is preferably performed.

  When the fluid pressure in the master cylinder is reduced while the engine is stopped, it can be determined that the driver may have the intention to start the vehicle. Therefore, in the present invention, when a change in the fluid pressure equivalent value that can be determined to reduce the fluid pressure in the master cylinder is detected, restart control for restarting the engine is performed. Therefore, the vehicle can be started according to the will of the driver.

  The vehicle control apparatus of the present invention further includes vehicle body speed acquisition means (55, S11) for acquiring the vehicle body speed (VS) of the vehicle, and the control means (55, S40, S41, S42, S43) is the engine. Speed reference value (KVS) set to determine whether or not the vehicle body speed (VS) acquired by the vehicle body speed acquisition means (55, S11) during the stop of (12) is a very low speed region. When it is determined that the fluid pressure in the master cylinder (25) is decreasing based on the fluid pressure equivalent value (Amc) acquired by the fluid pressure equivalent value acquisition means (55, S13). While the restart control is performed, the vehicle body speed (VS) acquired by the vehicle body speed acquisition means (55, S11) while the engine (12) is stopped is the speed reference value (KVS). If it is lower, it is preferable not to determine whether or not to perform the restart control on the basis of the fluid pressure equivalent value obtaining means (55, S13) fluid pressure equivalent value obtained by (Amc).

  When the vehicle body speed is less than the speed reference value, the acceleration in the longitudinal direction of the vehicle obtained based on the signal from the acceleration sensor changes regardless of the fluid pressure in the master cylinder. Therefore, there is no correspondence between the fluid pressure in the master cylinder and the acceleration in the longitudinal direction, and the fluid pressure in the master cylinder, that is, the magnitude of the braking force applied to the wheel is estimated based on the acceleration in the longitudinal direction. It becomes difficult. Therefore, in the present invention, when the vehicle body speed is equal to or higher than the speed reference value, it is determined that there is a correspondence between the fluid pressure in the master cylinder and the acceleration in the front-rear direction, and restart control is performed based on the fluid pressure equivalent value. It is determined whether or not to do so. On the other hand, if the vehicle body speed is less than the speed reference value, it is determined that there is no correspondence between the fluid pressure in the master cylinder and the acceleration in the front-rear direction, and restart control is performed based on the fluid pressure equivalent value. It is not determined whether or not. Therefore, it is possible to reduce the possibility that the engine is restarted against the intention of the driver or the start of the engine restart is delayed.

  In the control device for a vehicle of the present invention, the control means (55, S44, S45, S46) is arranged so that when the engine (12) is stopped in response to the stop control, A reduction suppression control for suppressing a decrease in braking force on the wheels (FR, FL, RR, RL) by operating the provided braking force decrease suppression means (35a, 35b, 37a, 37b, 37c, 37d) is started. Is preferred.

  According to the above configuration, when the engine is stopped in response to the stop control, a decrease in braking force on the wheels is suppressed. Therefore, even when the operation of the brake pedal by the driver is canceled to restart the engine, or even when the operation amount is reduced, a decrease in the braking force on the wheel is suppressed. Therefore, it is possible to suppress the occurrence of unintended vehicle movement (for example, sliding down) during the restart of the engine.

  In the vehicle control apparatus according to the present invention, the braking force reduction suppressing means is disposed in a flow path that connects the master cylinder (25) and the wheel cylinders (32a, 32b, 32c, 32d), and the wheel cylinder. (32a, 32b, 32c, 32d) having control valves (35a, 35b, 37a, 37b, 37c, 37d) that operate to adjust the fluid pressure in the control means (55, S44, S45, S46). When the engine (12) is stopped in response to the stop control, the reduction suppression control for operating the adjustment valve (35a, 35b, 37a, 37b, 37c, 37d) while the vehicle is running is performed. It is preferable to start.

  According to the above configuration, in the reduction suppression control, by controlling the supply of electric power to the regulating valve, it is possible to easily suppress a decrease in fluid pressure in the wheel cylinder, that is, it is possible to easily suppress a decrease in braking force on the wheels.

The vehicle control method of the present invention includes a stop step (S31) for automatically stopping the engine (12) of the vehicle, and a restart step (S43) for automatically restarting the engine (12). A method for controlling a vehicle, which is based on a signal from an acceleration sensor (SE7) provided on the vehicle and acquires an acceleration (G) in the longitudinal direction of the vehicle, and an acquired acceleration direction in the longitudinal direction. A braking force equivalent value acquisition step (S13) for acquiring a braking force equivalent value (Amc) corresponding to the braking force applied to the vehicle based on the acceleration (G), and the front and rear acquired in the acceleration acquisition step (S10) based on the acceleration (G) in the direction, the road gradient corresponding value that corresponds to the gradient of the road surface to the position of the vehicle and the gradient acquisition step of acquiring the (Ag) (S14) Further comprising a, wherein when the braking force corresponding value acquisition braking force corresponding value obtained in step (S13) (Amc) is the acquired road gradient value corresponding with a gradient obtaining step (S14) (Ag) above, wherein The gist of performing the stop step (S31).

  The acceleration in the front-rear direction of the vehicle acquired based on the acceleration sensor varies in accordance with the variation of the braking force applied to the vehicle based on the operation of the brake pedal by the driver. That is, the braking force and the acceleration in the longitudinal direction of the vehicle acquired based on the acceleration sensor have a correspondence relationship with each other. Therefore, in the present invention, the braking force equivalent value corresponding to the braking force is acquired based on the acceleration in the longitudinal direction of the vehicle acquired based on the acceleration sensor. If the acquired braking force equivalent value is larger than the road surface slope equivalent value corresponding to the road surface slope, even if the engine is stopped when the vehicle travels on the uphill road, The possibility of backward movement, that is, sliding down is low. Then, even when the engine is stopped and the creep torque disappears, stop control for stopping the engine is performed at a timing when it is determined that the vehicle located on the uphill road does not slide down. Therefore, the timing for automatically stopping the engine of the vehicle can be set without using a sensor for detecting the amount of brake operation by the driver or the fluid pressure in the master cylinder.

The block diagram which shows an example of the vehicle carrying the control apparatus of this embodiment. The block diagram which shows an example of a braking device. The flowchart explaining an idle stop process routine. The flowchart explaining an engine stop process routine. The flowchart explaining an engine restart process routine. The action figure which shows the relationship of the force added to a vehicle. The timing chart explaining the change of the electric current value with respect to MC pressure, vehicle body acceleration, engine rotation speed, vehicle body speed, and a linear solenoid valve at the time of stopping and restarting an engine automatically. 6 is a timing chart for explaining changes in MC pressure, vehicle body acceleration, engine speed, vehicle body speed, and current value with respect to the linear solenoid valve when the engine is automatically restarted.

  Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS. In the following description of the present specification, the traveling direction (forward direction) of the vehicle is assumed to be the front (front of the vehicle).

  The vehicle according to the present embodiment automatically stops the engine in accordance with the establishment of a predetermined stop condition while the vehicle is running, and then improves the fuel efficiency performance and the emission performance. Has a so-called idle stop function for automatically restarting. Therefore, in this vehicle, the engine is automatically stopped while the vehicle is decelerated or stopped by the brake operation by the driver.

Next, an example of a vehicle having an idle stop function will be described.
As shown in FIG. 1, the vehicle has a plurality of (four in this embodiment) wheels (the right front wheel FR, the left front wheel FL, the right rear wheel RR, and the left rear wheel RL). It is a so-called front wheel drive vehicle that functions as a vehicle. Such a vehicle includes a driving force generator 13 having an engine 12 that generates a driving force corresponding to the amount of operation of the accelerator pedal 11 by the driver, and the driving force generated by the driving force generator 13 is applied to the front wheels FR and FL. And a driving force transmission device 14 for transmission. The vehicle is also provided with a braking device 16 for applying a braking force corresponding to the amount of operation of the brake pedal 15 by the driver to each wheel FR, FL, RR, RL.

  The driving force generator 13 includes a fuel injection device (not shown) that is disposed in the vicinity of an intake port (not shown) of the engine 12 and has an injector that injects fuel into the engine 12. The driving force generator 13 is driven based on control of an engine ECU 17 (also referred to as “engine electronic control device”) having a CPU, a ROM, a RAM, and the like (not shown). The engine ECU 17 is electrically connected to an accelerator opening sensor SE1 that is disposed in the vicinity of the accelerator pedal 11 and that detects an operation amount of the accelerator pedal 11 by the driver, that is, an accelerator opening. The engine ECU 17 calculates the accelerator opening based on the detection signal from the accelerator opening sensor SE1, and controls the driving force generator 13 based on the calculated accelerator opening.

  The driving force transmission device 14 controls the automatic transmission 18, the differential gear 19 that appropriately distributes the driving force transmitted from the output shaft of the automatic transmission 18, and transmits it to the front wheels FR and FL, and the automatic transmission 18. And an AT ECU (not shown). The automatic transmission 18 includes a fluid driving force transmission mechanism 20 having a torque converter 20a as an example of a fluid coupling, and a transmission mechanism 21.

  In the vehicle of this embodiment, a creep phenomenon occurs because the torque converter 20a is provided in the torque transmission path from the engine 12 to the drive wheels (front wheels FR, FL). This creep phenomenon is a phenomenon in which the vehicle slowly moves forward without depression of the accelerator pedal 11 when the shift lever is in the traveling position in a vehicle having the automatic transmission 18. Occasionally, this occurs because the torque converter 20a transmits some power to the front wheels FR, FL. The slight power transmitted to the front wheels FR and FL is referred to as “creep torque”.

  As shown in FIGS. 1 and 2, the braking device 16 includes a hydraulic pressure generating device 28 having a master cylinder 25, a booster 26 and a reservoir 27, and a brake actuator 31 having two hydraulic pressure circuits 29 and 30 (in FIG. 2). 2). The hydraulic circuits 29 and 30 are connected to the master cylinder 25 of the hydraulic pressure generator 28, respectively. A wheel cylinder 32a for the right front wheel FR and a wheel cylinder 32d for the left rear wheel RL are connected to the first hydraulic circuit 29, and a wheel for the left front wheel FL is connected to the second hydraulic circuit 30. A cylinder 32b and a wheel cylinder 32c for the right rear wheel RR are connected.

  In the hydraulic pressure generator 28, the booster 26 is connected to an intake manifold (not shown) that generates a negative pressure when the engine 12 is driven. The booster 26 uses the pressure difference between the negative pressure generated in the intake manifold and the atmospheric pressure to boost the operating force of the brake pedal 15 by the driver.

  The master cylinder 25 generates a master cylinder pressure (hereinafter also referred to as “MC pressure”) as a fluid pressure in accordance with the operation of the brake pedal 15 (hereinafter also referred to as “brake operation”) by the driver. As a result, brake fluid as a fluid is supplied from the master cylinder 25 into the wheel cylinders 32 a to 32 d via the hydraulic circuits 29 and 30. Then, braking force according to the wheel cylinder pressure (also referred to as “WC pressure”) in the wheel cylinders 32a to 32d is applied to the wheels FR, FL, RR, and RL.

  In the brake actuator 31, the hydraulic circuits 29 and 30 are connected to the master cylinder 25 via connection paths 33 and 34, respectively. The connection paths 33 and 34 include normally open linear solenoid valves (adjustments). Valves) 35a and 35b are provided. The linear electromagnetic valves 35a and 35b include a valve seat, a valve body, an electromagnetic coil, and a biasing member (for example, a coil spring) that biases the valve body in a direction away from the valve seat. It is displaced according to the current value supplied from the brake ECU 55 to the electromagnetic coil. That is, the WC pressure in the wheel cylinders 32a to 32d is maintained at a hydraulic pressure corresponding to the current value supplied to the linear electromagnetic valves 35a and 35b.

  The first hydraulic circuit 29 includes a right front wheel path 36a connected to the wheel cylinder 32a and a left rear wheel path 36d connected to the wheel cylinder 32d. The second hydraulic circuit 30 includes a left front wheel path 36b connected to the wheel cylinder 32b and a right rear wheel path 36c connected to the wheel cylinder 32c. Therefore, in the present embodiment, a flow path that connects the master cylinder 25 and the wheel cylinders 32a to 32d is configured by the connection paths 33 and 34 and the paths 36a to 36d. Further, in the paths 36a to 36d, pressure increasing valves 37a, 37b, 37c, and 37d that are normally open electromagnetic valves that operate when restricting the increase in the WC pressure in the wheel cylinders 32a to 32d, and the WC pressure are supplied. Pressure reducing valves 38a, 38b, 38c, and 38d, which are normally closed electromagnetic valves that operate when the pressure is reduced, are provided.

  Further, the hydraulic pressure circuits 29 and 30 include reservoirs 39 and 40 for temporarily storing brake fluid flowing out from the wheel cylinders 32a to 32d via the pressure reducing valves 38a to 38d, and a pump that operates based on the rotation of the motor 41. 42 and 43 are connected. The reservoirs 39 and 40 are connected to the pumps 42 and 43 via the suction flow paths 44 and 45 and are connected to the connection paths 33 and 34 via the master side flow paths 46 and 47 rather than the linear electromagnetic valves 35a and 35b. It is connected to the master cylinder 25 side. Further, the pumps 42 and 43 are connected to connection portions 50 and 51 between the pressure increasing valves 37a to 37d and the linear electromagnetic valves 35a and 35b in the hydraulic pressure circuits 29 and 30 through supply channels 48 and 49, respectively. Yes. When the motor 41 rotates, the pumps 42 and 43 suck the brake fluid from the reservoirs 39 and 40 and the master cylinder 25 side through the suction channels 44 and 45 and the master side channels 46 and 47, The brake fluid is discharged into the supply channels 48 and 49.

Next, the brake ECU 55 (also referred to as “brake electronic control device”) that controls the drive of the brake actuator 31 will be described.
As shown in FIG. 2, wheel speed sensors SE3, SE4, SE5, SE6 for detecting the wheel speed of each wheel FR, FL, RR, RL are provided on the input side interface of the brake ECU 55 as a control means, and An acceleration sensor (also referred to as “G sensor”) SE7 for detecting acceleration in the longitudinal direction of the vehicle is electrically connected. Further, a brake switch SW1 that is disposed in the vicinity of the brake pedal 15 and detects whether or not the brake pedal 15 is operated is electrically connected to the input side interface of the brake ECU 55. The valves 35a, 35b, 37a to 37d, 38a to 38d, the motor 41, and the like are electrically connected to the output side interface of the brake ECU 55. The acceleration sensor SE7 outputs a signal that takes a positive value when the center of gravity of the vehicle moves backward, and a signal that takes a negative value when the center of gravity of the vehicle moves forward. Is output.

  The brake ECU 55 includes a digital computer including a CPU, ROM and RAM (not shown), a valve driver circuit (not shown) for operating the valves 35a, 35b, 37a to 37d, and 38a to 38d, and the motor 41. A motor driver circuit (not shown) for operating the motor. Various control processes (such as an idle stop process described later), various threshold values, and the like are stored in advance in the ROM of the digital computer. The RAM also stores various types of information that can be appropriately rewritten while an ignition switch (not shown) of the vehicle is on.

  In the vehicle of this embodiment, ECUs including the engine ECU 17 and the brake ECU 55 are connected to each other via a bus 56 so that various information and various control commands can be transmitted and received as shown in FIG. For example, the information related to the accelerator opening of the accelerator pedal 11 is appropriately transmitted from the engine ECU 17 to the brake ECU 55, while the brake ECU 55 sends a control command (“stop” to automatically stop the engine 12). A control command (also referred to as a “restart command”) for automatically restarting the engine 12 is transmitted to the engine ECU 17.

  Next, the idle stop processing routine executed by the brake ECU 55 of the present embodiment will be described based on the flowcharts shown in FIGS. 3 to 5, the operation diagram shown in FIG. 6, and the timing charts shown in FIGS. 7 and 8. To do. This idle stop processing routine is a processing routine for setting a timing for permitting automatic stop of the engine 12 and a timing for permitting automatic restart of the engine 12. 7 and 8 are timing charts when the vehicle travels on an uphill road.

  Now, the brake ECU 55 executes an idle stop processing routine every predetermined period (for example, 0.01 second period) set in advance. In this idle stop processing routine, the brake ECU 55 acquires acceleration in the longitudinal direction of the vehicle (hereinafter simply referred to as “vehicle acceleration”) G based on the detection signal from the acceleration sensor SE7 (step S10). Therefore, in this embodiment, the brake ECU 55 also functions as an acceleration acquisition unit. Step S10 corresponds to an acceleration acquisition step.

  Subsequently, the brake ECU 55 acquires the vehicle body speed VS of the vehicle (step S11). Specifically, the brake ECU 55 calculates the wheel speed of each wheel FL, FR, RL, RR based on the detection signal from each wheel speed sensor SE3 to SE6, and the wheel FL, FR, RL, RR of each wheel FL, FR, RL, RR is calculated. The wheel acceleration is obtained by time-differentiating at least one of the wheel speeds. Then, the brake ECU 55 integrates the wheel acceleration with respect to the vehicle body speed acquired at the previous timing, and sets the integration result as the vehicle body speed VS. Therefore, in the present embodiment, the brake ECU 55 also functions as a vehicle body speed acquisition unit. Then, the brake ECU 55 obtains a vehicle body speed differential value DVS by differentiating the vehicle body speed VS acquired in step S11 with respect to time (step S12). The brake ECU 55 may use the wheel acceleration acquired during the processing in step S11 as the vehicle body speed differential value DVS.

  Subsequently, the brake ECU 55 calculates MC pressure acceleration (fluid pressure equivalent value, braking force equivalent value) Amc, which is an acceleration component corresponding to the MC pressure Pmc in the master cylinder 25 (step S13). Here, as shown in FIG. 6, when a vehicle in which the accelerator pedal 11 is not operated travels, the vehicle includes creep torque transmitted to the drive wheels (front wheels FR, FL) and gravity applied to the vehicle body. A component (hereinafter also referred to as “gravity equivalent force”) acting in a direction along the road surface is applied. Further, the vehicle is given a braking force applied to the wheels FR, FL, RR, RL and a force based on a running resistance applied to the vehicle.

  Note that the “gravity equivalent force” is substantially “0 (zero)” when the road surface on which the vehicle is located is a horizontal road, whereas the higher the slope is, the steeper the slope is when the road surface is a slope. It becomes. Therefore, it can be said that the gravity equivalent force is a force having a correspondence relationship with the gradient of the road surface. In the present embodiment, “running resistance” means a resistance component generated by friction between the vehicle body surface of the vehicle and air, and a friction resistance of a bearing portion (not shown) when the wheels FR, FL, RR, RL roll. And a rolling resistance component including a resistance generated by energy loss between the road surface and the tire.

  When the vehicle travels on an uphill road, creep torque is a propulsive force for moving the vehicle forward, while gravity equivalent force, braking force, and running resistance are forces for restricting forward movement of the vehicle. Acts as However, when the vehicle stops with the engine 12 stopped, creep torque and travel resistance are not applied to the vehicle. At this time, the gravity equivalent force acts as a force for moving the vehicle rearward, that is, a sliding down, while the braking force acts as a force for suppressing the sliding down of the vehicle. Therefore, when the gravity equivalent force is larger than the braking force, the vehicle slides down. That is, in order to set the timing for performing stop control for stopping the engine 12, the braking force or a value corresponding to the braking force, that is, the braking force equivalent value and the gravity equivalent force or the gravity equivalent force are equivalent. Need to get the value and.

  By the way, the vehicle body acceleration G calculated based on the detection signal from the acceleration sensor SE7 fluctuates with fluctuations in MC pressure in the master cylinder 25, that is, fluctuations in braking force with respect to the wheels FR, FL, RR, and RL. Therefore, in the present embodiment, it is noted that there is a correspondence relationship between the MC pressure (that is, braking force) and the vehicle body acceleration G, and the MC pressure acceleration Amc is acquired as a value corresponding to the MC pressure Pmc based on the vehicle body acceleration G. The

  Here, the vehicle body speed differential value DVS acquired in step S12 is a value in consideration of braking force, creep torque, running resistance, and gravity equivalent force. Therefore, the vehicle body speed differential value DVS becomes a negative value when the vehicle decelerates and becomes “0 (zero)” when the vehicle stops. On the other hand, the vehicle body acceleration G is a value that does not consider gravity equivalent force. Therefore, the vehicle body acceleration G is not “0 (zero)” but a positive value when the vehicle stops on an uphill road. Therefore, MC pressure acceleration Amc is calculated by removing creep acceleration Ac, which is an acceleration component corresponding to creep torque, and running resistance acceleration Ar, which is an acceleration component corresponding to running resistance, from vehicle body acceleration G.

  Returning to the flowchart of FIG. 3, the brake ECU 55 sets the creep acceleration Ac as a creep equivalent value corresponding to the creep torque generated in the vehicle and the running resistance acceleration Ar as a running resistance equivalent value corresponding to the running resistance applied to the vehicle. get. Then, the brake ECU 55 subtracts the creep acceleration Ac from the vehicle body acceleration G calculated in step S10, adds the running resistance acceleration Ar to the subtraction result (= G−Ac), and uses the addition result as the MC pressure acceleration Amc ( = G-Ac + Ar). Therefore, in the present embodiment, the brake ECU 55 also functions as a fluid pressure equivalent value acquisition unit. Step S13 corresponds to a braking force equivalent value acquisition step.

  The creep acceleration Ac is a value obtained by dividing the creep torque by the weight of the vehicle, and is larger when the air conditioner is used than when it is not used. The running resistance acceleration Ar is a value that can be uniquely set as long as the running resistance can be acquired.

  Then, the brake ECU 55 subtracts the vehicle body speed differential value DVS acquired in step S12 from the vehicle body acceleration G calculated in step S10, and sets the subtraction result as a gradient acceleration (road surface gradient equivalent value) Ag (step S14). When the vehicle travels on a slope, a difference corresponding to the road surface gradient is generated between the vehicle body acceleration G and the vehicle body speed differential value DVS as described above. Therefore, in the present embodiment, the brake ECU 55 also functions as a gradient acquisition unit. Step S14 corresponds to a gradient acquisition step. Subsequently, the brake ECU 55 determines whether or not the engine 12 is being driven based on the information received from the engine ECU 17 (step S15).

  If the determination result is affirmative, the brake ECU 55 performs the engine stop process described in detail in FIG. 4 because the engine 12 is being driven (step S16). This engine stop process is a process for performing stop control for permitting automatic stop of the engine 12 when a predetermined stop condition is satisfied. Thereafter, the brake ECU 55 once ends the idle stop processing routine. On the other hand, if the determination result in step S15 is negative, the brake ECU 55 performs the engine restart process described in detail in FIG. 5 because the engine 12 is stopped (step S17). This engine restart process is a process of performing a restart process that permits automatic restart of the engine 12 when a predetermined restart condition is satisfied. Thereafter, the brake ECU 55 once ends the idle stop processing routine.

Next, the engine stop processing routine in step S16 will be described based on the flowchart shown in FIG.
In the engine stop processing routine, the brake ECU 55 determines whether or not the absolute value of the MC pressure acceleration Amc calculated in step S13 exceeds the absolute value of the gradient acceleration Ag calculated in step S14 (step S30). ). Here, the MC pressure acceleration Amc is a value corresponding to the braking force applied to the wheels FR, FL, RR, RL in order to stop the vehicle. On the other hand, the gradient acceleration Ag is a value corresponding to the gravity equivalent force (see FIG. 6) applied to the vehicle. That is, as the value of the gradient acceleration Ag is larger, it means that the gradient of the road surface is steeper, and the force that causes the vehicle to slide backward is larger.

  When the absolute value of the MC pressure acceleration Amc exceeds the absolute value of the gradient acceleration Ag, even if creep torque is not transmitted to the wheels FR, FL, RR, and RL, that is, the engine 12 is stopped. In this state, the braking force applied to the wheels FR, FL, RR, RL is larger than the gravity equivalent force. Therefore, even if the engine 12 is stopped in this state, the possibility that the vehicle located on the uphill road moves backward, that is, slides down is extremely low.

  If the determination result in step S30 is negative (Amc absolute value ≦ Ag absolute value), the brake ECU 55 causes the vehicle to move unintentionally when the engine 12 is stopped in this state. Then, the engine stop processing routine is terminated. That is, the stop control that permits the automatic stop of the engine 12 is not performed.

  On the other hand, if the determination result in step S30 is affirmative (Amc absolute value> Ag absolute value), the brake ECU 55 does not move the vehicle unintended by the driver even if the engine 12 is stopped in this state. It determines that it does not occur, and performs stop control that permits automatic stop of the engine 12 (step S31), and ends the engine stop processing routine. Therefore, in this embodiment, step S31 corresponds to a stop step. Thereafter, the brake ECU 55 transmits a stop command to the engine ECU 17. When the engine ECU 17 receives the stop command, the engine ECU 17 stops the driving of the engine 12 and transmits a signal indicating that the stop process is completed to the brake ECU 55. The brake ECU 55 that has received the signal from the engine ECU 17 determines that the stop of the engine 12 has been completed.

  That is, as shown in the timing chart of FIG. 7, the MC pressure Pmc in the master cylinder 25 (indicated by the alternate long and short dash line in FIG. 7) at the first timing t <b> 11 when the brake operation by the driver is not performed. “0 (zero) MPa”. At this time, since the vehicle is traveling on the uphill road, the vehicle body speed VS of the vehicle gradually decreases even if no braking force is applied to the wheels FR, FL, RR, and RL. When the driver performs a brake operation, the MC pressure Pmc in the master cylinder 25 increases as the amount of operation of the brake pedal 15 by the driver increases. As a result, the vehicle body acceleration G of the vehicle gradually decreases from the second timing when the brake switch SW1 is turned on. Then, the absolute value of the MC pressure acceleration Amc gradually increases. At this time, when the estimated value Pmcs of MC pressure (shown by a solid line in FIG. 7) is calculated based on the MC pressure acceleration Amc, the estimated value Pmcs of the MC pressure is substantially the same value as the MC pressure Pmc in the master cylinder 25. It becomes.

  At the third timing t13, the absolute value of the MC pressure acceleration Amc exceeds the absolute value of the gradient acceleration Ag, and the braking force for the wheels FR, FL, RR, RL becomes larger than the gravity equivalent force. As a result, stop control is started. Then, the rotational speed of the engine 12 decreases rapidly, and the creep torque decreases with the decrease in the rotational speed of the engine 12 from the fourth timing t14. Then, at the fifth timing t15 when the rotational speed of the engine 12 becomes “0 (zero)”, the creep torque completely disappears. Note that, during the period from the fourth timing t14 to the fifth timing t15, the creep acceleration Ac decreases as the creep torque decreases.

Next, the engine restart processing routine in step S17 will be described based on the flowchart shown in FIG.
In the engine restart process routine, the brake ECU 55 determines whether or not the vehicle body speed VS calculated in step S11 exceeds a preset extremely low speed reference value KVS (step S40). When the vehicle body speed VS is less than or equal to the extremely low speed reference value KVS, the error components of the detection signals from the wheel speed sensors SE3 to SE6 become large, and the accuracy of the wheel speed and the vehicle body speed VS calculated based on the detection signals is abrupt. Worse. Further, when the vehicle body speed VS enters the extremely low speed region, the value of the vehicle body acceleration G varies regardless of the MC pressure Pmc in the master cylinder 25 (see FIG. 8). Specifically, the vehicle body acceleration G approaches the gradient acceleration Ag. Therefore, there is almost no correspondence between the MC pressure acceleration Amc acquired using the vehicle body acceleration G and the MC pressure Pmc. Therefore, the extremely low speed reference value KVS is set in advance as a reference value for determining whether or not the vehicle body speed VS is not within the extremely low speed region.

  When the determination result in step S40 is affirmative (VS> KVS), the brake ECU 55 determines that the vehicle body speed VS is not within the extremely low speed region, and determines whether the engine 12 can be restarted. A restart reference value KAmc, which is a reference value, is set (step S41). This restart reference value KAmc is a reference value for determining whether or not restart of the engine 12 is permitted based on a decrease in the MC pressure acceleration Amc. In the present embodiment, the restart reference value KAmc is set to a larger value as the absolute value of the gradient acceleration Ag calculated in step S14 is larger, that is, as the road surface gradient is larger.

  Then, the brake ECU 55 determines whether or not the absolute value of the MC pressure acceleration Amc calculated in step S13 is equal to or less than the restart reference value KAmc set in step S41 (step S42). If this determination result is a negative determination (absolute value of Amc> KAmc), the brake ECU 55 ends the engine restart processing routine.

  On the other hand, if the determination result in step S42 is affirmative (Amc absolute value ≦ KAmc), the brake ECU 55 performs restart control that permits automatic restart of the engine 12 (step S43). The start processing routine is temporarily terminated. Therefore, in this embodiment, step S43 corresponds to a restart step. Thereafter, the brake ECU 55 transmits a restart command to the engine ECU 17. When the restart command is received, the engine ECU 17 restarts the engine 12 and transmits a signal indicating that the restart process is completed to the brake ECU 55. The brake ECU 55 that has received the signal from the engine ECU 17 determines that the restart of the engine 12 has been completed.

  That is, as shown in the timing chart of FIG. 7, when the vehicle with the engine 12 stopped travels on an uphill road by inertia, if the amount of operation of the brake pedal 15 by the driver decreases, the MC pressure Pmc in the master cylinder 25 Is reduced in pressure (sixth timing t16). Then, after the sixth timing t16, the absolute value of the MC pressure acceleration Amc gradually becomes smaller. Then, at the seventh timing t17, when the absolute value of the MC pressure acceleration Amc becomes equal to or less than the restart reference value KAmc, the braking force applied to the wheels FR, FL, RR, and RL at this time slides down after the vehicle stops. Is determined to occur. As a result, restart control is performed, and the engine 12 is restarted. Thereafter, at the eighth timing t18, the creep torque is transmitted to the front wheels FR, FL.

  Returning to the flowchart of FIG. 5, if the determination result in step S40 is negative (VS ≦ KVS), the brake ECU 55 determines that the vehicle body speed VS is in the extremely low speed region, and has the vehicle stopped? It is determined whether or not (step S44). Immediately before the vehicle stops, the vehicle body acceleration G may fluctuate greatly (second timing t22 shown in FIG. 8). This is because the center of gravity of the vehicle swings back and forth when the vehicle is stopped. This phenomenon is also called “swing back”. Therefore, in the present embodiment, the brake ECU 55 determines that the vehicle has stopped when it detects a swing back.

  If the determination result in step S44 is negative, the brake ECU 55 determines that the vehicle has not yet stopped, and as an example of a decrease suppression control that suppresses a decrease in braking force with respect to the wheels FR, FL, RR, RL. First valve control is performed (step S45). Specifically, the brake ECU 55 sets the current value I for the linear electromagnetic valves 35a and 35b to the first current value Ia (see FIG. 8), and suppresses the reduction of the WC pressure in the wheel cylinders 32a to 32d. The first current value Ia is set in advance to a value sufficiently smaller than the second current value Ib (see FIG. 8) necessary for completely restricting the reduction of the WC pressure in the wheel cylinders 32a to 32d. Therefore, during execution of the first valve control, the magnitude of the braking force for the wheels FR, FL, RR, RL can be adjusted by a brake operation by the driver. Therefore, in the present embodiment, the linear electromagnetic valves 35a and 35b function as braking force reduction suppressing means. Thereafter, the brake ECU 55 proceeds to step S47, which will be described later.

  On the other hand, if the determination result in step S44 is affirmative, the brake ECU 55 determines that the vehicle has stopped, and is a first example of a decrease suppression control that suppresses a decrease in braking force with respect to the wheels FR, FL, RR, and RL. Two-valve control is performed (step S46). Specifically, the brake ECU 55 sets the current value I for the linear electromagnetic valves 35a and 35b to the second current value Ib (see FIG. 8), and maintains the WC pressure in the wheel cylinders 32a to 32d. Thereafter, the brake ECU 55 proceeds to the next step S47.

  In step S47, the brake ECU 55 determines whether or not the brake switch SW1 is off. If this determination result is affirmative (SW1 = off), the brake ECU 55 determines that the brake operation by the driver has been eliminated, and the process proceeds to step S43 described above. That is, in the present embodiment, when the vehicle body speed VS is equal to or less than the extremely low speed reference value KVS, when the braking force is no longer applied to the wheels FR, FL, RR, RL, the restart control is performed. On the other hand, if the determination result in step S47 is negative (SW1 = on), the brake ECU 55 does not cancel the brake operation by the driver, so the engine restart processing routine is not performed without restart control. Exit.

  That is, as shown in the timing chart of FIG. 8, when the vehicle body speed VS is equal to or lower than the extremely low speed reference value KVS with the engine 12 stopped, the first valve control is started (first timing t21). . At the first timing t21, since the current value I for the linear electromagnetic valves 35a and 35b changes from “0 (zero)” to the first current value Ia, the linear electromagnetic valves 35a and 35b operate. As a result, even if the braking operation by the driver is canceled between the first timing t21 and the second timing t22, the braking force for the wheels FR, FL, RR, RL becomes “0 (zero)”. Is avoided.

  Further, after the first timing t21, the correspondence between the MC pressure acceleration Amc and the MC pressure Pmc in the master cylinder 25 is lost. As a result, the estimated value Pmcs of the MC pressure estimated based on the MC pressure acceleration Amc gradually deviates from the actual MC pressure Pmc in the master cylinder 25. For this reason, even if the MC pressure acceleration Amc is used, it is difficult to start the restart control at an appropriate timing.

  In addition, at the second timing t22 when the vehicle stops, the current value I flowing through the linear electromagnetic valves 35a and 35b is changed from the first current value Ia to the second current value Ib (second valve control). As a result, even if the brake operation by the driver is canceled after the second timing t22, the braking force for the wheels FR, FL, RR, RL is maintained. Thereafter, when the brake switch SW1 is turned off, the brake operation by the driver is canceled, and the engine 12 is restarted (third timing t23). In addition, when the engine 12 is restarted, the current value I supplied to the linear electromagnetic valves 35a and 35b is gradually reduced.

Therefore, in this embodiment, the following effects can be obtained.
(1) The MC pressure Pmc in the master cylinder 25 is a pressure corresponding to the amount of operation of the brake pedal 15 by the driver. The vehicle acceleration G calculated based on the detection signal from the acceleration sensor SE7 includes an acceleration component corresponding to the braking force applied to the wheels FR, FL, RR, RL when the driver performs a brake operation. It becomes. That is, the MC pressure Pmc and the vehicle body acceleration G have a correspondence relationship with each other. Therefore, in the present embodiment, the MC pressure acceleration Amc corresponding to the MC pressure Pmc is acquired based on the vehicle body acceleration G. If the absolute value of the acquired MC pressure acceleration Amc is greater than or equal to the absolute value of the gradient acceleration Ag, the driver can stop even if the engine 12 is stopped and the creep torque disappears while the vehicle is traveling on a slope. It is determined that no unintended vehicle movement occurs. Therefore, stop control that permits automatic stop of the engine 12 is performed, and the engine 12 is stopped. That is, the engine 12 is automatically stopped after the timing when it can be determined that the vehicle does not move unintentionally. Therefore, the timing for automatically stopping the engine 12 of the vehicle can be set without using a sensor for detecting the amount of brake operation by the driver or the MC pressure Pmc.

  (2) A braking force applied to the wheels FR, FL, RR, and RL, a creep torque generated in the vehicle, and a force corresponding to running resistance are applied to the vehicle that decelerates. The vehicle body acceleration G calculated based on the acceleration sensor SE7 is an acceleration corresponding to the resultant force of the braking force, the creep torque, and the driving resistance. Therefore, in this embodiment, the MC pressure acceleration Amc is a value obtained by subtracting the creep acceleration Ac from the vehicle body acceleration G and adding the running resistance acceleration Ar to the subtraction result. Therefore, the correspondence between the MC pressure Pmc in the master cylinder 25 and the MC pressure acceleration Amc is better than that in the case where the MC pressure acceleration Amc is acquired without considering the creep acceleration Ac and the running resistance acceleration Ar. Can be. Therefore, when the engine 12 is automatically stopped based on the MC pressure acceleration Amc acquired in this way, it is possible to further reduce the possibility of unintended vehicle movement.

  (3) When the MC pressure Pmc in the master cylinder 25 is reduced while the engine 12 is stopped, there is a possibility that the driver has decreased the operation amount of the brake pedal 15 to start the vehicle. is there. Therefore, in the present embodiment, when a change in the MC pressure acceleration Amc that can be determined to reduce the MC pressure Pmc is detected, restart of the engine 12 is permitted. Therefore, the vehicle can be started quickly according to the will of the driver.

  (4) When the vehicle body speed VS is equal to or lower than the extremely low speed reference value KVS, the vehicle body acceleration G changes regardless of the MC pressure Pmc in the master cylinder 25. Therefore, there is no correspondence between the MC pressure Pmc and the vehicle body acceleration G, and the MC pressure acceleration Amc is a value corresponding to the MC pressure Pmc, that is, the braking force applied to the wheels FR, FL, RR, and RL. It's hard to say. Accordingly, in the present embodiment, when the vehicle body speed VS exceeds the extremely low speed reference value KVS, it is determined that there is a correspondence between the MC pressure acceleration Amc and the MC pressure Pmc, and restart is performed based on the MC pressure acceleration Amc. It is determined whether or not to perform control. On the other hand, when the vehicle body speed VS is equal to or lower than the extremely low speed reference value KVS, it is determined that there is no correspondence between the MC pressure acceleration Amc and the MC pressure Pmc, and restart control is performed using the MC pressure acceleration Amc. It is not determined whether or not. Therefore, it is possible to reduce the possibility that the engine 12 is restarted against the intention of the driver or the start of restart of the engine 12 is delayed.

  (5) When the engine 12 is stopped in response to the stop control, the reduction of the braking force with respect to the wheels FR, FL, RR, RL is suppressed by the operation of the linear electromagnetic valves 35a, 35b. Therefore, even when the operation of the brake pedal 15 by the driver is canceled to restart the engine 12, or even when the operation amount is reduced, a decrease in the braking force on the wheels FR, FL, RR, RL is suppressed. . Therefore, it is possible to suppress the occurrence of unintended vehicle movement while the engine 12 is restarting.

  (6) In this embodiment, the linear electromagnetic valves 35a and 35b serving as adjusting valves for reducing the braking force on the wheels FR, FL, RR, and RL are the MC pressure Pmc in the master cylinder 25 and the wheel cylinders 32a to 32c. This is a differential pressure control valve that adjusts the differential pressure with the WC pressure in 32d. Therefore, by adjusting the magnitude of the current value I with respect to the linear solenoid valves 35a and 35b, the WC pressure, that is, the fluctuation of the braking force can be easily allowed (first timing t21 to second timing t22), or WC. The fluctuation of the pressure, that is, the braking force can be easily regulated (second timing t22 to third timing t23).

  (7) The linear solenoid valves 35a and 35b are generally provided in a brake actuator such as a vehicle stability control device or antilock brake control. Therefore, it is possible to suppress the occurrence of unintended movement of the vehicle during restart of the engine 12 without providing new components in the brake actuator.

  (8) In the present embodiment, the first valve control is performed at the timing when the vehicle body speed VS becomes less than the extremely low speed reference value KVS. Therefore, unlike the case where the second valve control is performed from the timing when the vehicle body speed VS becomes less than the extremely low speed reference value KVS, the wheels FR, FL, RR are changed according to the change in the operation amount of the brake pedal 15 of the driver. , RL can be changed in magnitude. Therefore, the behavior of the vehicle can be in line with the driver's intention.

(9) In addition, current flows through the linear electromagnetic valves 35a and 35b even when the engine 12 is restarted. Therefore, the rapid start of the vehicle accompanying the restart of the engine 12 can be suppressed.
The embodiment may be changed to another embodiment as described below.

In the embodiment, the first valve control may be started at an arbitrary timing from when the engine 12 is stopped until the vehicle body speed VS becomes equal to or lower than the extremely low speed reference value KVS.
Further, the first valve control may be started at an arbitrary timing between the first timing t21 and the second timing t22.

In the embodiment, in the first valve control, the current value I supplied to the linear electromagnetic valves 35a and 35b may be gradually increased, or the current value I may be increased stepwise.
In the embodiment, each process of steps S44 and S45 may be omitted. In this case, the second valve control may be performed at a timing when the vehicle body speed VS becomes less than the extremely low speed reference value KVS. In this case, pressure-increasing valves 37a to 37d may be used as the braking force reduction suppressing means instead of the linear electromagnetic valves 35a and 35b.

  In the embodiment, when the vehicle includes an electric parking brake device, a braking force may be applied to the wheels using the electric parking brake device instead of the first valve control and the second valve control. Even when the reduction suppression control for operating the electric parking brake device as the braking force reduction suppression means is executed, it is possible to suppress the reduction of the braking force applied to the wheels when the driver releases the brake operation.

In the embodiment, when the engine 12 is stopped, the restart control may be performed at the timing when the brake operation is canceled regardless of the value of the vehicle body speed VS.
When the creep torque and running resistance are sufficiently smaller than the braking force applied to the wheels FR, FL, RR, RL, the MC pressure is taken into account without considering the creep acceleration Ac and the running resistance acceleration Ar. The acceleration Amc may be calculated. In this case, the vehicle body acceleration G coincides with the MC pressure acceleration Amc.

  In the embodiment, the difference between the vehicle body acceleration G immediately before the brake switch SW1 is turned on (hereinafter also referred to as “reference acceleration”) and the current vehicle body acceleration G is calculated, and the fluid pressure equivalent value is calculated based on the difference. May be obtained. This focuses on the fact that the fluctuation amount of the vehicle body acceleration G accompanying the brake operation corresponds to the fluctuation amount of the braking force with respect to the wheels FR, FL, RR, and RL. Even if comprised in this way, the effect equivalent to the effect (1) of the said embodiment can be acquired.

-In embodiment, you may acquire the vehicle body speed VS from the navigation apparatus mounted in a vehicle.
In the embodiment, the engine ECU 17 may execute an idle stop processing routine. In this case, various types of information (such as vehicle body speed VS and vehicle body acceleration G) acquired by the brake ECU 55 may be transmitted to the engine ECU 17.

Further, the idle stop processing routine may be executed by an idle stop ECU that exclusively performs control related to the idle stop function.
In the embodiment, in step S31, a control command for releasing a clutch (not shown) of the transmission mechanism 21 of the automatic transmission 18 may be transmitted to the AT ECU. In this case, since the automatic transmission 18 is in a neutral state, creep torque is not transmitted to the drive wheels. Further, in step S43, a control command may be transmitted to the AT ECU to cause the clutch released in step S31 to be engaged.

In the embodiment, the fluid supplied from the master cylinder 25 into the wheel cylinders 32a to 32d is not limited to a liquid but may be a gas such as nitrogen.
Next, the technical idea that can be grasped from the above embodiment and another embodiment will be added below.

  (A) The fluid pressure equivalent value acquisition means (55) is based on the acceleration (G) in the front-rear direction acquired by the acceleration acquisition means (55, S10) before the brake operation by the driver is started. A vehicle control apparatus that obtains a fluid pressure equivalent value (Amc) based on the acceleration change amount.

  DESCRIPTION OF SYMBOLS 12 ... Engine, 25 ... Master cylinder, 32a-32d ... Wheel cylinder, 35a, 35b ... Adjustment valve, linear solenoid valve as braking force reduction suppression means, 37a-37d ... Adjustment valve, pressure increase valve as braking force reduction suppression means 55 ... Control means, acceleration acquisition means, fluid pressure equivalent value acquisition means, gradient acquisition means, brake ECU as vehicle body speed acquisition means, Ac ... creep acceleration as creep equivalent value, Ag ... gradient acceleration as gradient equivalent value , Amc ... MC pressure acceleration as fluid pressure equivalent value, Ar ... running resistance acceleration as running resistance equivalent value, FR, FL, RR, RL ... wheel, G ... vehicle body acceleration, KVS ... very low speed reference as speed reference value Value, SE7: acceleration sensor, VS: body speed.

Claims (7)

A master cylinder (25) that generates fluid pressure according to the brake operation by the driver, and a braking force that is communicated with the master cylinder (25) via a flow path and that generates fluid pressure according to the fluid pressure generated inside the wheel (FR , FL, RR, RL), and a vehicle control device provided with wheel cylinders (32a, 32b, 32c, 32d),
Acceleration acquisition means (55, S10) for acquiring acceleration (G) in the longitudinal direction of the vehicle based on a signal output from an acceleration sensor (SE7) provided in the vehicle;
Fluid pressure equivalent value acquisition means (55, S13) for acquiring a fluid pressure equivalent value (Amc) corresponding to the fluid pressure in the master cylinder (25) based on the acquired acceleration (G) in the longitudinal direction;
Gradient acquisition means (55, S14) for acquiring a road surface gradient equivalent value (Ag) corresponding to the gradient of the road surface based on the acceleration (G) in the front-rear direction acquired by the acceleration acquisition means (55, S10) ;
Control means (55) for performing stop control for automatically stopping the engine (12) of the vehicle and restart control for automatically restarting the engine (12),
The control means (55, S30, S31) is a road surface in which the fluid pressure equivalent value (Amc) acquired by the fluid pressure equivalent value acquisition means (55, S13) is acquired by the gradient acquisition means (55, S14). The vehicle control device characterized in that the stop control is performed when the value is larger than a gradient equivalent value (Ag). The fluid pressure equivalent value acquisition means (55, S13) is a creep equivalent value corresponding to the acceleration (G) in the longitudinal direction acquired by the acceleration acquisition means (55, S10) and a creep torque generated in the vehicle. 2. The vehicle control device according to claim 1, wherein a fluid pressure equivalent value (Amc) is acquired based on (Ac) and a running resistance equivalent value (Ar) corresponding to a running resistance applied to the vehicle. The control means (55, S41, S42, S43) is based on the fluid pressure equivalent value (Amc) acquired by the fluid pressure equivalent value acquisition means (55, S13) while the engine (12) is stopped. The vehicle control apparatus according to claim 1 or 2, wherein the restart control is performed when it is determined that the fluid pressure in the master cylinder (25) is being reduced. Vehicle body speed acquisition means (55, S11) for acquiring the vehicle body speed (VS) of the vehicle;
The control means (55, S40, S41, S42, S43)
A speed reference value (set) for determining whether or not the vehicle body speed (VS) acquired by the vehicle body speed acquisition means (55, S11) while the engine (12) is stopped is in a very low speed region. In the case of exceeding KVS), it is determined that the fluid pressure in the master cylinder (25) is decreasing based on the fluid pressure equivalent value (Amc) acquired by the fluid pressure equivalent value acquisition means (55, S13). When doing, while performing the restart control,
When the vehicle body speed (VS) acquired by the vehicle body speed acquisition means (55, S11) while the engine (12) is stopped is equal to or less than the speed reference value (KVS), the fluid pressure equivalent value acquisition means 4. The vehicle control device according to claim 3, wherein whether or not to perform the restart control is not determined based on the fluid pressure equivalent value (Amc) acquired in (55, S <b> 13). The control means (55, S44, S45, S46) is a braking force reduction suppression means (provided on the vehicle) while the vehicle is running when the engine (12) is stopped in response to the stop control. 35a, 35b, 37a, 37b, 37c, 37d) are actuated to start a reduction suppressing control for suppressing a reduction in braking force on the wheels (FR, FL, RR, RL). Item 5. The vehicle control device according to any one of Items 4 to 4. The braking force reduction suppressing means is disposed in a flow path that connects the master cylinder (25) and the wheel cylinders (32a, 32b, 32c, 32d), and the wheel cylinders (32a, 32b, 32c, 32d). An adjustment valve (35a, 35b, 37a, 37b, 37c, 37d) that operates to adjust the fluid pressure inside
The control means (55, S44, S45, S46)
When the engine (12) is stopped triggered by the stop control,
6. The vehicle control device according to claim 5, wherein the reduction suppression control for operating the adjustment valve (35a, 35b, 37a, 37b, 37c, 37d) is started while the vehicle is running. A vehicle control method comprising: a stop step (S31) for automatically stopping the engine (12) of the vehicle; and a restart step (S43) for automatically restarting the engine (12),
An acceleration acquisition step (S10) for acquiring an acceleration (G) in the longitudinal direction of the vehicle based on a signal from an acceleration sensor (SE7) provided in the vehicle;
A braking force equivalent value acquisition step (S13) for acquiring a braking force equivalent value (Amc) corresponding to the braking force applied to the vehicle based on the acquired acceleration (G) in the front-rear direction;
Based on the acceleration (G) in the longitudinal direction acquired by the acceleration acquiring step (S10), the road gradient corresponding value that corresponds to the gradient of the road surface to the position of the vehicle and the gradient acquisition step of acquiring the (Ag) (S14), the In addition,
When the braking force equivalent value (Amc) acquired in the braking force equivalent value acquisition step (S13) is greater than or equal to the road surface gradient equivalent value (Ag) acquired in the gradient acquisition step (S14), the stopping step (S31) The vehicle control method characterized by performing.

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