WO2012043530A1

WO2012043530A1 - Vehicle control device and vehicle control method

Info

Publication number: WO2012043530A1
Application number: PCT/JP2011/071995
Authority: WO
Inventors: 陽介大森; 陽介橋本; 政義武田; 雪生森
Original assignee: 株式会社アドヴィックス
Priority date: 2010-09-30
Filing date: 2011-09-27
Publication date: 2012-04-05
Also published as: DE112011103318B4; DE112011103318T5; CN103124838B; CN103124838A; JP5672917B2; JP2012077650A

Abstract

In the present invention, a first determination unit determines whether or not the conditions are met for execution of automatic stopping control of a vehicle engine. If it is determined that the conditions are met for execution of stopping control, a stopping control unit permits engine stopping. A second determination unit determines whether or not slipping down of the vehicle will occur after stopping during sloped-road driving by a vehicle with the engine in a stopped state. If it is determined that slipping down will occur, a restarting control unit permits initiation of engine restarting so that engine restarting finishes before the slip-down distance of the vehicle exceeds a permissible distance. Before engine stopping, a third determination unit predicts the amount of fuel savings that it is possible to save in the period of engine stoppage from engine stopping to restarting, and determines whether or not the amount of fuel savings is at least a set value set in accordance with the amount of fuel consumption required for engine restarting. If it is determined that the amount of fuel savings is less than the set value, the stopping control unit does not permit engine stopping even if the conditions for execution of stopping control are met.

Description

Vehicle control apparatus and vehicle control method

The present application relates to a vehicle control device and a vehicle control method for automatically stopping and automatically restarting an engine.

As is well known, fuel consumption is reduced and exhaust emissions are improved by automatically stopping the engine while the vehicle is stopped, such as waiting for a signal, or automatically restarting the engine according to the driver's start operation. Automatic engine stop and restart devices have been put to practical use. In recent years, a device for stopping the engine while the vehicle is decelerating before stopping is also proposed.

The vehicle control device described in Patent Document 1 automatically stops the engine on condition that the brake depression amount is equal to or greater than the first threshold X, and automatically operates the engine on condition that the brake depression amount is equal to or smaller than the second threshold Y. To restart. Furthermore, the vehicle control device of Patent Document 1 is proposed to make the first threshold and the second threshold variable according to the vehicle speed.

JP 2003-35175 A

By the way, an AT car (automatic car) equipped with an automatic transmission with a torque converter generates a thrust in the forward direction of the vehicle due to a creep phenomenon even when the engine is idle. The creep phenomenon is a phenomenon in which, in an AT car, when the shift lever is in the traveling position, the vehicle advances slowly even without depressing the accelerator pedal. The creep phenomenon occurs because the torque converter transmits some power to the drive wheels even when the engine is idle.

If the engine is operated while the vehicle is stopped on the uphill, torque due to the creep phenomenon, that is, creep torque is acting, so it is possible to prevent the vehicle from slipping down with a relatively small amount of brake depression. However, creep torque does not work if the engine on a hill slope is stopped automatically, so if the brake stepping amount is small, it is thought that the vehicle may slip down the slope without resisting gravity. Be In addition, since a relatively large amount of fuel is consumed at the time of engine restart, it is desirable that unnecessary stop of the engine be avoided as much as possible from the viewpoint of fuel saving, that is, improvement of fuel consumption.

The object of the present application is to preferably avoid slipping of the vehicle at the time of stopping on a slope while avoiding unnecessary stopping of the engine which can not contribute to fuel saving as much as possible in a vehicle performing automatic stop and restart of the engine. It is providing a vehicle control device and a vehicle control method that can be prevented.

In order to solve the above problems, the vehicle control device of the present application includes stop control for automatically stopping an engine (12) of the vehicle, and restart control for automatically restarting the engine (12). I do. The first control unit (55, S11) configured to determine whether or not the vehicle control device determines that "the execution condition of the stop control is satisfied"; and "the execution condition of the stop control is satisfied" And a stop control unit (55, S15) configured to permit the stop of the engine (12) when determined. Furthermore, the vehicle control device is configured to determine whether or not “the slippage of the vehicle after stopping occurs is generated” when traveling on a slope with the vehicle in a state where the engine (12) is stopped. Judgment unit (55, S21); when it is determined that "slipping occurs", restart of the engine (12) by the time the sloping lowering distance (L) of the vehicle exceeds the allowable distance (La) And a restart control (55) configured to allow initiation of restart of the engine (12) such that The vehicle control device is further configured to predict fuel savings (Tes) that can be saved in the engine stop period from the stop of the engine (12) to the restart before the stop of the engine (12). A third determination unit (55, S12, S13) is provided. The third determination unit (55, S12, S13) determines that “the fuel saving amount (Tes) is not less than the set value (T1) set according to the fuel consumption amount required for the restart of the engine (12) It is comprised so that it may determine whether it is. If it is determined that "the fuel saving amount (Tes) is less than the set value (T1)", the stop control unit (55) determines that the engine (12) does not meet the condition for executing the stop control. ) Is configured not to allow the suspension of.

According to the above configuration, it is possible to predict the fuel saving amount saved in the engine stop period from the engine stop to the restart before the engine stop. If it is determined that "the predicted fuel saving amount is less than the set value set according to the fuel consumption amount required to restart the engine", the engine will be stopped even if the condition for executing the stop control is satisfied. Stop is not allowed. For this reason, it is possible to preferably prevent the slippage of the vehicle at the time of stopping on the uphill road while avoiding unnecessary stop of the engine which can not contribute to the fuel saving as much as possible.

In one aspect of the present application, the vehicle includes a brake operating unit (15). The vehicle control device further includes a fourth determination unit (55, S14). The fourth determination unit (55, S14) sets “the braking force (Apmc according to the operation amount of the brake operation unit (15) is equal to or more than a threshold (Ag) that can suppress the slippage of the vehicle after It is configured to determine whether or not "secured". When it is determined that "the braking force (Apmc) is secured above the threshold (Ag)", the stop control unit (55) determines that "the fuel saving amount (Tes) is the setting value (T1)". Even if it is determined that “less than or equal to,” the engine (12) is configured to be permitted to stop.

According to the above configuration, the determination that "the braking force corresponding to the amount of operation of the brake operation unit is secured at or above the threshold that can suppress slippage after stopping the vehicle" can suppress slippage when stopping. It means that the braking force is secured. In this case, the engine is not restarted to suppress slippage. Therefore, even if it is determined that "the fuel saving amount is less than the set value", the engine stop is permitted. For this reason, the frequency of stopping the engine increases, so it is possible to obtain a further improvement in fuel consumption.

In one aspect of the present application, the third determination unit (55, S12, S13) is configured to obtain an estimated engine stoppable time (Tes) as a time from a stop of the engine (12) to a restart. . The third determination unit (55, S12, S13) determines whether or not the “fuel saving amount is equal to or more than the set value”, the engine stoppable estimated time (Tes) indicates the set value, and It is comprised so that it may carry out by judging whether it is more than the setting time (T1) converted into the idle time of the engine (12).

According to the above configuration, it is determined whether or not "the estimated engine stoppable time from the stop of the engine to the restart is equal to or longer than the set time of idle time conversion". Therefore, for example, it is not necessary to acquire the fuel injection amount of the fuel injection device that injects the fuel into the fuel chamber of the engine. That is, by using the detection value of an existing sensor such as a vehicle speed sensor provided in the vehicle, the determination value necessary for the determination can be acquired relatively easily. For this reason, the processing required for the determination does not have to be complicated.

In one aspect of the present application, the vehicle includes vehicle speed detection units (SE3 to SE6). The third determination unit (55) generates the vehicle body speed (VS) detected by the vehicle speed detection unit (SE3 to SE6) by time differentiation of the vehicle body speed (VS). It is configured to obtain a vehicle body speed differential value (DVS). The third determination unit (55) divides the vehicle speed by a value obtained by removing the acceleration (Aet) corresponding to the engine torque which disappears due to the stop of the engine from the vehicle speed differential value (DVS), It is comprised so that the said engine stop possibility estimated time (Tes) may be calculated.

According to the above-described configuration, the engine stop estimated expected time can be obtained by dividing the vehicle speed by a value obtained by subtracting the acceleration for the engine torque which disappears from the stop of the engine from the vehicle speed differential value. That is, the expected engine stoppable time can be obtained by considering the disappearance of the engine torque. Therefore, the third determination unit can perform determination with relatively high accuracy.

The vehicle control method according to the present application performs stop control for automatically stopping the engine (12) of the vehicle and restart control for automatically restarting the engine (12). In the vehicle control method, it is determined whether "the execution condition of the stop control is satisfied" and "when the execution condition of the stop control is satisfied", the engine (12) is selected. And allowing the suspension. The vehicle control method further determines whether or not "slipping of the vehicle after stopping occurs" (55, S21) when traveling on a slope with the vehicle in a state where the engine (12) is stopped. When it is determined that "slipping occurs", the restart of the engine (12) is completed by the time the sling lowering distance (L) of the vehicle exceeds the allowable distance (La); And (12) initiating a restart. The method further comprises predicting, before stopping the engine (12), the fuel savings that can be saved in the stopping period between the stopping of the engine (12) and the restarting; Determining whether or not Tes) is equal to or greater than a set value (T1) set in accordance with the fuel consumption required for the restart of the engine (12). In the vehicle control method, when it is determined that "the fuel saving amount (Tes) is less than the set value (T1)", even if the execution condition of the stop control is satisfied, the vehicle control method of Have to not allow the stop. According to the above configuration, it is possible to obtain the same function and effect as the vehicle control device.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows an example of the vehicle carrying the control apparatus of one Embodiment. The hydraulic-circuit figure which shows an example of the damping device shown in FIG. The flowchart which shows an engine stop control routine. The flowchart which shows an engine restart control routine. The model side view which shows the force which acts on the vehicle which stops on a slope. The timing chart in the case of stopping an engine, ie, in the case of Tes> = T1, is shown. The timing chart when braking acceleration is larger than gradient acceleration. Timing chart when not stopping the engine.

Figures 1-8 illustrate one embodiment. In the following description in the present specification, the forward direction of the vehicle will be described as the front of the vehicle.

The vehicle according to the present embodiment has a so-called idle stop function in order to improve the fuel efficiency and the emission performance. That is, the idle stop function automatically stops the engine in response to the establishment of the predetermined stop condition while the vehicle is traveling, and then automatically restarts the engine in response to the establishment of the predetermined start condition. Therefore, in this vehicle, the engine is automatically stopped during deceleration or stop by the driver's brake operation.

Next, an example of a vehicle having an idle stop function will be described.

As shown in FIG. 1, the vehicle is a front wheel drive vehicle, and in the present embodiment, four wheels, that is, the right front wheel FR, the left front wheel FL, the right rear wheel RR, and the front wheels FR and FL of the left rear wheel RL. Acts as a drive wheel. Such a vehicle transmits a driving force generated by the driving force generator 13 to the front wheels FR and FL, and a driving force generator 13 having an engine 12 that generates a driving force according to the amount of operation of the accelerator pedal 11 by the driver. And a driving force transmission device 14. 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 of the wheels FR, FL, RR, and RL.

The driving force generation device 13 is provided with a fuel injection device (not shown) which is disposed in the vicinity of an intake port (not shown) of the engine 12 and has an injector for injecting fuel to the engine 12. The driving force generator 13 is driven based on the control of the engine ECU 17 having a CPU, a ROM, a RAM, and the like (not shown). The engine ECU means an electronic control unit for an engine. The engine ECU 17 is electrically connected to an accelerator opening sensor SE1 disposed in the vicinity of the accelerator pedal 11 and for detecting an operation amount of the accelerator pedal 11 by the driver, that is, an accelerator opening AP. 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 and the like.

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 hydraulic drive power transmission mechanism 20 having a torque converter 20 a as an example of a fluid coupling, and a transmission mechanism 21.

As shown in FIGS. 1 and 2, the braking device 16 comprises a hydraulic pressure generator 28 and a brake actuator 31 having two

hydraulic circuits

29 and 30. FIG. 2 shows the brake actuator 31 by a two-dot chain line. The hydraulic pressure generator 28 has a master cylinder 25, a booster 26 and a reservoir 27. The respective

hydraulic circuits

29, 30 are connected to the master cylinder 25 of the hydraulic pressure generating device 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 cylinder 32b for the left front wheel FL is connected to the second hydraulic circuit 30. And a wheel cylinder 32c for the right rear wheel RR are connected.

In the fluid pressure generating device 28, the booster 26 is connected to an intake manifold (not shown) that generates 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 operation force of the brake pedal 15 by the driver, that is, the depression force.

Master cylinder 25 generates a master cylinder pressure PMC according to the operation of brake pedal 15 by the driver, that is, the brake operation. As a result, the brake fluid is supplied from the master cylinder 25 through the

hydraulic circuits

29, 30 into the wheel cylinders 32a to 32d. Then, a braking force corresponding to the wheel cylinder pressure PWC 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, 30 are connected to the master cylinder 25 through the

conduits

33, 34, respectively, and in the middle of the

conduits

33, 34, normally open

linear solenoid valves

35a, 35b. Are provided respectively. That is, the

linear solenoid valves

35a and 35b are adjusting valves. The

linear solenoid valves

35a, 35b include a valve seat, a valve body, an electromagnetic coil, and an urging member such as a coil spring. The biasing member biases the valve body away from the valve seat. The valve body is displaced in accordance with the current value supplied from the brake ECU 55 described later to the electromagnetic coil. That is, the wheel cylinder pressure PWC in the wheel cylinders 32a to 32d is maintained at a hydraulic pressure corresponding to the value of the current supplied to the

linear solenoid valves

35a, 35b.

A pressure sensor SE2 for detecting a master cylinder pressure PMC is provided at a position closer to the master cylinder 25 than the linear solenoid valve 35a in the pipe line 33. The pressure sensor SE2 outputs a detection signal of a value corresponding to the master cylinder pressure PMC to the brake ECU 55.

The pressure increasing valves 37a, 37b, 37c, which are normally open solenoid valves, are branched from the

conduits

33, 34 connected to the master cylinder 25 and are connected to the wheel cylinders 32a to 32d in the middle of the conduits 36a to 36d. There are provided 37d and

pressure reducing valves

38a, 38b, 38c and 38d consisting of normally closed solenoid valves. The

pressure increasing valves

37a, 37b, 37c and 37d are activated when the pressure increase of each wheel cylinder pressure PWC is restricted, and the

pressure reducing valves

38a, 38b, 38c and 38d are activated when the wheel cylinder pressure PWC is decreased.

In the

hydraulic circuits

29, 30,

reservoirs

39, 40 for temporarily storing the brake fluid that has flowed out from the wheel cylinders 32a-32d through the pressure reducing valves 38a-38d, and pumps 42, 43 operated based on the rotation of the motor 41. And are connected. The

reservoirs

39 and 40 are connected to the

pumps

42 and 43 through the

conduits

44 and 45, and are connected to the master cylinder 25 through the

conduits

46 and 47, respectively. The

conduits

46 and 47 are connected to the

conduits

33 and 34 at a position closer to the master cylinder 25 than the

linear solenoid valves

35a and 35b. The

pipelines

48, 49 extending from the discharge ports of the

pumps

42, 43 are connected to

connection portions

50, 51 on a communication path connecting the pressure increase valves 37a to 37d and the

linear solenoid valves

35a, 35b. The

pumps

42 and 43 suck the brake fluid from the

reservoirs

39 and 40 and the master cylinder 25 through the

pipelines

44, 45, 46 and 47 when the motor 41 rotates, and the brake fluid sucked is

pipelines

48 and 49. To discharge.

Next, the brake ECU 55 that controls the drive of the brake actuator 31 will be described. The brake ECU 55 means a brake electronic control unit.

As shown in FIG. 2, the pressure sensor SE2 and wheel speed sensors SE3, SE4, SE5, SE6 for detecting the wheel speeds of the respective wheels FR, FL, RR, RL as input systems to the brake ECU 55, front and rear of the vehicle An acceleration sensor SE7 for detecting an acceleration in a direction is electrically connected. The acceleration sensor is also referred to as a G sensor. The brake ECU 55 is electrically connected to a brake switch SW1 for detecting whether the brake pedal 15 is operated. Further, the

valves

35a, 35b, 37a to 37d, 38a to 38d, and the motor 41 are electrically connected to the brake ECU 55 as an output system. The acceleration sensor SE7 outputs a signal that gives a positive value when the vehicle stops on an uphill road, and outputs a signal that gives a negative value when the vehicle stops on a downhill road Be done.

The brake ECU 55 is a digital computer comprising a CPU, a ROM, a RAM, etc. (not shown); a driver circuit (not shown) for operating the

valves

35a, 35b, 37a to 37d, 38a to 38d; It has a motor driver circuit (not shown) for operation. In the ROM of the digital computer, various control processes, for example, routines for engine stop control and engine restart control as idle stop processes to be described later, various threshold values, setting values and the like are stored in advance. The RAM also stores various types of information that can be appropriately rewritten while the ignition switch (not shown) of the vehicle is on.

In the vehicle of the present embodiment, ECUs including the engine ECU 17 and the brake ECU 55 are connected to each other via a bus 56 so as to transmit and receive various information and various control commands as shown in FIG. For example, information related to the accelerator opening AP of the accelerator pedal 11 is appropriately transmitted from the engine ECU 17 to the brake ECU 55, while the brake ECU 55 is a control command for permitting the engine 12 to be automatically stopped. A stop command, a restart command as a control command to permit automatic restart of the engine 12, and the like are transmitted to the engine ECU 17.

FIG. 5 shows the relationship of the force acting on the vehicle stopping on the uphill road. Here, assuming that the slope of the uphill road, ie, the inclination angle, is “θ” and the gravity acting on the vehicle is “g”, the vehicle is pulled backward by the force “g · sin θ” by the action of gravity g. Become. The force Fg is a component in the vehicle backward direction of the gravity g acting on the vehicle, that is, a component in the road surface direction, and changes in accordance with the road surface gradient θ.

Further, as shown in FIG. 5, a braking force Fpmc corresponding to the master cylinder pressure PMC acts on the vehicle as a force against the force Fg. When the vehicle stops on a slope, the force Fg and the braking force Fpmc are compared, and if Fpmc <Fg, the vehicle may be slipped down.

In the present embodiment, the acceleration to the rear of the vehicle obtained by dividing the force Fg by the vehicle body weight M is defined as a gradient acceleration Ag. That is, M means a vehicle body mass as a unit system. An acceleration obtained by dividing the braking force Fpmc by the vehicle body weight M is defined as a braking acceleration Apmc. If Apmc <Ag holds, it is determined that there is a possibility that slippage may occur.

Here, when the slippage fall prevention control is performed, it is necessary to acquire the gradient acceleration Ag used to determine the presence or absence of the slippage fall during traveling before the vehicle is stopped. In this embodiment, the gradient acceleration Ag is calculated by subtracting the vehicle body speed differential value DVS from the vehicle body acceleration G calculated based on the detection signal from the acceleration sensor SE7. The vehicle speed differential value DVS is obtained by temporally differentiating the vehicle speed VS calculated based on the detection signals of the wheel speed sensors SE3 to SE6. The vehicle body acceleration G calculated based on the detection signal of the acceleration sensor SE7 includes a gradient acceleration Ag which is a vehicle longitudinal direction component of the gravitational acceleration acting on the vehicle. On the other hand, the vehicle speed differential value DVS obtained by time differentiating the vehicle speed VS of the vehicle does not include the gradient acceleration Ag. Therefore, by subtracting the vehicle body speed differential value DVS from the vehicle body acceleration G, the gradient acceleration Ag is obtained.

Further, in the slippage fall prevention control, it is necessary to acquire the braking acceleration Apmc used to determine the presence or absence of the slippage during traveling before the vehicle is stopped. The vehicle body acceleration G calculated based on the detection signal from the acceleration sensor SE7 fluctuates with the fluctuation of the master cylinder pressure PMC, that is, the fluctuation of the braking force on the wheels FR, FL, RR, and RL. Therefore, in the present embodiment, by focusing on the correspondence between the master cylinder pressure and the vehicle body acceleration G, the braking acceleration Apmc as a value corresponding to the master cylinder pressure PMC is acquired based on the vehicle body acceleration G. Be done. That is, master cylinder pressure PMC means a braking force. The braking acceleration Apmc corresponds to an acceleration obtained by dividing the braking force Fpmc applied to the wheels FR, FL, RR, and RL according to the master cylinder pressure PMC by the vehicle body weight M. More specifically, the braking acceleration Apmc is eliminated by removing from the vehicle body acceleration G the creep acceleration Ac, which is an acceleration component corresponding to the creep torque, and the resistance acceleration Ad, which is an acceleration component corresponding to a drag amount, that is, a traveling resistance. Is calculated. As a calculation formula, Apmc = G-Ac + Ad + Ag. The gradient acceleration Ag is compared with the braking acceleration Apmc. If Apmc <Ag, it is determined that there is a possibility that the vehicle will slip down. In the present embodiment, by satisfying Apmc <Ag, when it is predicted that “a slip of the vehicle may occur after stopping” is predicted, the engine 12 is stopped before the vehicle stops to prevent the slip of the vehicle. Restart in advance. The restart of the engine 12 applies creep torque to the vehicle to prevent the vehicle from slipping down.

By the way, when the idle stop time from stop to restart of the engine 12 is short, the following problems may occur. That is, when the fuel saving amount Fd saved by the idle stop is smaller than the fuel consumption amount Fst consumed by the restart of the engine 12 after the idle stop, the fuel consumption amount is increased by stopping the idle. Fuel consumption will deteriorate. Therefore, in the present embodiment, when the execution condition of the engine stop control is satisfied, the fuel saving amount Fd which can be saved by the idle stop by the automatic stop of the engine 12 and the fuel consumption amount Fst at the restart of the engine 12 are calculated. Compare. When the fuel saving amount Fd is equal to or more than the fuel consumption amount Fst, the engine 12 is stopped to implement idle stop.

Specifically, the present embodiment does not compare the fuel saving amount Fd with the fuel consumption amount Fst, but the predicted idle stop time from the stop to the restart of the engine 12 is assumed as the estimated engine stoppable time Tes. calculate. Then, in the present embodiment, the set time T1 obtained by converting the fuel consumption amount Fc at the time of restart of the engine 12 into the idle time is compared with the estimated engine stoppable time Tes. The fuel consumption Fid per unit time when the engine 12 is idle is approximately uniquely determined by the type of vehicle. However, the idle rotation speed of the engine 12 changes between when the air conditioner mounted on the vehicle is driven and when it is not driven. Therefore, in the present embodiment, the setting time T1 is set based on the upper limit value in the change range of the idle rotation speed, that is, the fuel consumption Fid per unit time at the idle rotation speed at the time of driving the air conditioner. Of course, this embodiment can adopt a configuration in which it is determined whether the air conditioner is driven or not driven, and the value of the set time T1 is switched according to the determination result.

In addition, the fuel consumption Fst at engine restart is also uniquely determined by the vehicle type. Of course, in the present embodiment, when the fuel consumption amount Fst at engine restart changes according to the engine operation mode, the fuel consumption amount Fst according to the operation mode may be adopted. However, in the present embodiment, a value obtained by converting the fuel consumption amount Fst at engine restart into the idle time is calculated as the set time T1 as the time having the fuel efficiency improvement effect. The set time T1 is given by the following equation.
T1 = Fst / Fid (1)
Further, the engine stoppable estimated time Tes is an estimated time or predicted time in which the engine 12 can be kept stopped from the stop time of the engine 12 to the restart time, and is given by the following equation.
Tes = VS / (DVS + Aet) (2)
Here, VS is a vehicle speed, DVS is a vehicle speed differential value, and Aet is an engine torque acceleration. However, in the present embodiment, the vehicle speed derivative value DVS takes a positive value in the process of deceleration of the vehicle, that is, in the process of increasing the acceleration in the backward direction of the vehicle, in calculation. Further, the engine torque acceleration Aet takes a positive value in the engine operating state. The engine torque acceleration Aet will be described later.

In this embodiment, the engine 12 is stopped when the engine stoppable estimated time Tes is equal to or longer than the set time T1, that is, when TesesT1 is satisfied. When the engine stoppable predicted time Tes is less than the set time T1, the automatic stop of the engine 12, that is, the idle stop, rather deteriorates the fuel efficiency, so the automatic stop of the engine 12 itself is not performed.

However, when the slippage lowering determination condition, that is, Apmc <Ag, does not hold, that is, the braking force Apmc is equal to or higher than the gradient acceleration Ag, and the braking force condition by which the braking force sufficient to suppress the slippage of the vehicle is secured If Ag Ag is established, the engine 12 is not restarted to prevent slippage. For this reason, in the present embodiment, it is determined whether or not Apmc ≧ Ag is established whether a braking force sufficient to suppress slippage of the vehicle can be secured when the vehicle is stopped. In this embodiment, the engine 12 is allowed to stop if the braking force condition, that is, ApmcmcAg, is satisfied even if the condition for the engine stoppable estimated time Tes, that is, TesTT1 is not satisfied.

In the present embodiment, as the execution condition of the engine stop control, “other idle stop condition” excluding the condition of the engine stoppable predicted time Tes, that is, Tes ≧ T1 and the braking force condition, that is, ApmcAgAg, is set. Specifically, the "other IS condition", that is, the "other idle stop condition", is that "the brake switch SW1 is on", that is, the brake switch is on; "master cylinder pressure PMC exceeds the specified pressure P1 That is, that each condition that PMC> P1 is satisfied; and that the vehicle speed VS is less than the prescribed speed V1, for example, 20 km / h is satisfied that each condition that VS ≦ V1 is satisfied is AND condition. It is. Of course, the "other idle stop condition" may be changed to an appropriate condition such as eliminating one of the brake switch on condition and the master cylinder pressure condition.

6 to 8 show timing charts of control modes of the present embodiment. In each figure, the signal of the brake switch SW1 before stopping the vehicle on the uphill, the master cylinder pressure PMC, the vehicle acceleration G output from the acceleration sensor SE7, the engine rotation speed, the vehicle speed VS, and the vehicle speed differential value DVS Shows the transition of In the present embodiment, the wheel speed is used as the vehicle speed VS. The vehicle body speed VS can be obtained by adding an integrated value obtained by integrating wheel acceleration, which is a time differential value of the wheel speed, for each unit time to the previous wheel speed. In FIGS. 6 to 8, the vehicle acceleration G and the vehicle speed differential value DVS are shown to be different in positive and negative states from the vehicle acceleration G detected by the acceleration sensor SE7 and the calculated vehicle speed differential value DVS. That is, in FIG. 6 to FIG. 8, the vehicle body acceleration G and the vehicle body speed differential value DVS are shown such that the rear direction of the vehicle takes a negative value.

The idle stop processing will be described with reference to FIG. FIG. 6 is a timing chart in the case where the engine 12 is stopped because the condition for the estimated engine stoppable time Tes to be the set time T1 or more is satisfied. In FIG. 6, at time t0, the vehicle is traveling with the engine 12 being driven.

As shown in FIG. 6, the vehicle acceleration G during traveling of the vehicle includes acceleration components such as acceleration Ag corresponding to the gradient; acceleration Aet corresponding to the engine torque, ie, creep torque acceleration; and acceleration Ad corresponding to the drag. Including. Assuming that the acceleration acting on the front of the vehicle is "positive" and the acceleration acting on the rear of the vehicle is "negative", the gradient acceleration Ag is negative, the engine torque acceleration Aet is positive, and the acceleration Ad is a negative value. As a result of these accelerations being applied to the vehicle, the vehicle acceleration G is detected by the acceleration sensor SE7. However, the acceleration sensor SE7 according to the present embodiment outputs the acceleration in the backward direction of the vehicle as a positive value for the sake of convenience of calculation, unlike the positive / negative of the actual acceleration in FIG. The acceleration Ad corresponding to the drag means a negative acceleration due to running resistance between the wheel and the road surface.

When the driver operates the brake pedal 15 at time t1 while the vehicle is traveling, that is, the brake switch SW1 is turned on when the driver depresses the brake pedal 15, the master cylinder pressure PMC is increased by this brake operation, and the braking force is applied to the wheels. Be done. As a result, the vehicle speed VS starts to decrease from time t1. At this time, the braking acceleration Apmc for the master cylinder pressure PMC is applied to the vehicle as a negative acceleration in the direction opposite to the traveling direction, that is, in the backward direction, so the vehicle body acceleration G is an acceleration for the respective master cylinder pressure PMC. Apmc decreases and takes a negative value. Further, the master cylinder pressure PMC reaches the defined pressure P1 by the brake operation.

The vehicle speed VS is decelerated at a change rate equal to the vehicle acceleration G reduced by the application of the braking acceleration Apmc. In FIG. 6, G <0. Eventually, the vehicle speed VS becomes less than or equal to the specified speed V1.

When the "other idle stop condition" is satisfied at time t2 while the vehicle is decelerating, the engine stoppable estimated time Tes is calculated. The engine stoppable estimated time Tes is a stop time of the engine 12, that is, from the present time when it is assumed that the engine 12 is restarted to prevent a slip of the vehicle after stopping when the engine 12 is stopped. Calculated as the time between the start of restart. That is, the engine stoppable estimated time Tes is calculated as the time that is expected to be capable of holding the engine 12 in the stop state.

Since the vehicle speed VS obtained from the detection signal of at least one of the wheel speed sensors SE3 to SE6 at time t2 is before the stop of the engine, the vehicle body when decelerating with the vehicle acceleration G to which the acceleration Aet corresponding to the engine torque is added It corresponds to the speed. The dashed-two dotted line in FIG. 6 shows the speed profile in the case of decelerating by the vehicle body acceleration G to which the acceleration Aet for engine torque was added. In the present embodiment, the engine stoppable estimated time Tes is calculated on the assumption of the deceleration process in the engine stop state. For this reason, it is possible to predict that the engine can be stopped by decelerating the vehicle speed obtained by excluding the acceleration Aet corresponding to the engine torque which disappears in the engine stop state with respect to the two-dot chain line speed profile of FIG. Calculate time Tes.

For this reason, the acceleration Aet corresponding to the disappearing engine torque is eliminated from the vehicle body velocity derivative value DVS which is a time derivative of the vehicle body velocity VS, and the calculation formula Tes = VS / Calculated by (DVS + Aet). However, in this formula, DVS> 0 and Aet> 0 in the vehicle deceleration process.

The engine stoppable expected time Tes and the set time T1 are compared, and if Tes> T1 holds, the fuel efficiency improvement effect is obtained, so the engine 12 is stopped from time t2. As a result, the engine rotational speed decreases from time t2 and eventually becomes zero. When the engine rotation speed becomes zero, the engine torque component disappears, so the actual vehicle speed VS decreases along the solid line in FIG. 6 in the same manner as the expected vehicle speed. In the period from time t2 to time t3, the engine stoppable estimated time Tes may be calculated using the variable acceleration Aet according to the gradually decreasing engine torque.

As shown in the timing chart of FIG. 7, since the operation amount of the brake pedal 15 is large, the braking acceleration Apmc is larger than the gradient acceleration Ag, that is, the braking force sufficient to prevent slippage of the vehicle after stopping is secured. In the present embodiment, the engine 12 is stopped even if the estimated engine stoppable time Tes is shorter than the set time T1, that is, Tes <T1. This is because it is not necessary to restart the engine 12 for the purpose of preventing slippage after stopping. In the present embodiment, the engine 12 is also stopped even when it is not necessary to restart the engine when the vehicle is stopped.

In the present embodiment, the engine restart start time is determined so that the slippage lowering distance L can be suppressed to the allowable distance La or less. From the present time, the estimated time T2 required for the slippage lowering distance L after the stop to reach the allowable distance La is the time Ta required from the current point to the stop and the slippage lowering distance L of the vehicle after the stop to the allowable distance La It is obtained as the sum of the required time Tb. That is, T2 = Ta + Tb. The time Ta can be obtained by dividing the vehicle speed VS by the vehicle speed differential value DVS. That is, Ta = VS / DVS. Further, the time Tb can be obtained using a map (not shown) that indicates the correspondence between the road surface gradient θ and the time Tb. In the present embodiment, the allowable distance La is zero as an example. That is, La = 0. Therefore, the predicted time T2 is calculated by T2 = VS / DVS.

In this embodiment, when the predicted time T2 sequentially calculated in the deceleration process of the vehicle after the engine stop reaches the restart required time Teng as the time required from the restart start of the engine 12 to the restart end. , To allow the start of the restart of the engine 12. More specifically, the predicted time T2 until the vehicle stops is reduced as the vehicle speed VS decreases. When the required time for restart Teng, which is predetermined for each vehicle, decreases, restart of the engine 12 is started. Thus, in the present embodiment, the restart of the engine 12 is completed before the slippage lowering distance L reaches the allowable distance La. As described above, according to the present embodiment, by waiting for the engine restart start timing until the vehicle speed VS becomes as small as possible within the allowable range, it is possible to appropriately prevent the vehicle from slipping down while maintaining the fuel efficiency improvement effect. It is.

In the present embodiment, the engine stoppable expected time Tes is calculated using the above-mentioned equation (2), but the following equation can also be adopted in consideration of the restart required time Teng.
Tes = VS / (DVS-Aet) -Teng (3)
The brake ECU 55 executes the idle stop control routine at predetermined intervals, for example, every 0.01 second. In this idle stop control routine, an engine stop control routine shown in FIG. 3 for automatically stopping the engine 12 and an engine stop control shown in FIG. And an engine restart control routine. The engine restart control in the idle stop control routine is performed when the master cylinder pressure PMC becomes lower than the specified pressure Px when the operation amount of the brake pedal 15 returns below the specified amount, or the accelerator opening AP> 0. The engine 12 is restarted when a predetermined restart condition such as time is satisfied. The engine restart control in the present embodiment includes slip reduction prevention control that prevents slippage of the vehicle after stopping. The engine restart control routine shown in FIG. 4 shows a part of the engine stop control that restarts the engine 12 for slippage prevention control.

First, engine stop control will be described with reference to FIG. The brake ECU 55 executes an engine stop control routine shown in FIG. 3 while the vehicle is traveling in the engine operating state. The engine stop control routine is a process for stop control that permits the automatic stop of the engine 12 when a predetermined stop condition is satisfied.

In step S11, the brake ECU 55 first determines whether "other idle stop conditions" (other IS conditions) are satisfied. If the "other idle stop condition" is satisfied, the process proceeds to step S12. If the "other idle stop condition" is not satisfied, the routine is ended. In the present embodiment, the “other idle stop condition” corresponds to the execution condition of the stop control, and the brake ECU 55 that determines whether the “other idle stop condition” is satisfied also functions as a first determination unit. . Step S11 corresponds to a first determination step.

In step S12, the brake ECU 55 calculates an estimated engine stoppable time Tes. The estimated engine stoppable time Tes is calculated by the equation Tes = body speed VS / (DVS + Aet) shown in the equation (2).

In the next step S13, the brake ECU 55 determines whether or not "the estimated engine stoppable time Tes is equal to or longer than a set time T1 at which the fuel efficiency improvement effect is achieved", that is, Tes T T1. If Tes ≧ T1 is established, the process proceeds to step S15, and if Tes ≧ T1 is not established, the process proceeds to step S14. In the present embodiment, the brake ECU 55 also functions as a third determination unit by determining the engine stoppable estimated time Tes and determining whether Tes ≧ T1 holds. Steps S12 and S13 correspond to a third determination step.

In step S15, the stop of the engine 12 is permitted. That is, the brake ECU 55 transmits a stop command to the engine ECU 17. As a result, the engine ECU 17 stops the engine 12. In the present embodiment, the brake ECU 55 that permits the engine 12 to stop also functions as a stop control unit. Step S15 corresponds to the stop control step.

On the other hand, when Tes 成立 T1 is not established, the brake ECU 55 determines whether or not "the braking acceleration Apmc is equal to or higher than the gradient acceleration Ag as a threshold value" in step S14. That is, it is determined whether Apmc ≧ Ag holds. The establishment of Apmc ≧ Ag means that a braking force sufficient to prevent slippage without restarting the engine 12 is secured. Therefore, if Apmc ≧ Ag, the brake ECU 55 proceeds to step S15 and permits the engine 12 to stop. That is, the brake ECU 55 transmits a stop command to the engine ECU 17. As a result, the engine ECU 17 stops the engine 12. In the present embodiment, the brake ECU 55 that determines whether Apmc ≧ Ag holds also functions as a fourth determination unit. Step S14 corresponds to a fourth determination step.

On the other hand, when it is determined in step S14 that Apmc ≧ Ag is not established, the routine ends. In this case, stopping of the engine 12 is not permitted. That is, since the fuel efficiency improvement effect by idle stop can not be obtained, the stop of the engine 12 is not permitted.

The timing chart shown in FIG. 6 describes the process when TesTT1 as the process when stopping the engine 12. If the driver operates the brake pedal 15 at time t1 while the vehicle is traveling with the engine operating condition, the brake switch SW1 is turned on and the master cylinder pressure PMC rises to reach the specified pressure P1. By applying a braking force corresponding to master cylinder pressure PMC to wheels FR, FL, RR, and RL, the vehicle decelerates, and the vehicle speed VS becomes equal to or less than a specified speed V1. As a result, at time t2, "other idle stop conditions" are satisfied. That is, each condition of brake switch ON; master cylinder pressure PMC> prescribed pressure P1; and vehicle body speed VS ≦ prescribed speed V1 is satisfied under the AND condition.

When the "other idle stop condition" is satisfied, an engine stoppable estimated time Tes is next obtained, and it is determined whether Tes ≧ T1 is satisfied. If Tes ≧ T1 holds, the engine 12 is stopped from time t2. As a result, the engine torque component disappears by time t3, and the vehicle speed VS decreases along the solid line in FIG. At time t4, the vehicle stops.

During traveling of the vehicle after the engine stop, the brake ECU 55 executes an engine restart control routine shown in FIG. This engine restart control routine is for permitting automatic restart of the engine 12 for the purpose of suppressing slippage of the vehicle after stopping within the allowable range when a predetermined restart condition is satisfied. Processing.

The engine restart control routine shown in FIG. 4 is repeatedly executed by the brake ECU 55 at a constant control cycle, for example, every 0.01 seconds, while traveling uphill with the engine 12 stopped.

When the routine of FIG. 4 is started, first, in step S21, the brake ECU 55 determines whether “slipping of the vehicle occurs after stopping” by comparing the braking acceleration Apmc and the gradient acceleration Ag. That is, it is determined whether Apmc <Ag holds. Here, when it is determined that the braking acceleration Apmc is equal to or higher than the gradient acceleration Ag, that is, Apmc ≧ Ag, that is, when it is determined that "slipping after stopping does not occur", specifically, in the case of a negative determination in S21. The process of this routine ends as it is. In the present embodiment, the brake ECU 55 that determines whether Apmc <Ag holds or not also functions as a second determination unit. Step S21 corresponds to a second determination step.

On the other hand, when it is determined that the braking acceleration Apmc is less than the gradient acceleration Ag, that is, Apmc <Ag, that is, when it is determined that "the vehicle slips down after stopping," specifically, in the case of an affirmative determination in S21. In step S22, the brake ECU 55 calculates the predicted time T2 until the vehicle stops. T2 is calculated by the calculation formula T2 = VS / DVS. In the following step S23, the brake ECU 55 determines whether "the calculated predicted time T2 is equal to or less than the required restart time Teng".

Here, if the predicted time T2 exceeds the restart required time Teng, that is, if the determination in S23 is negative, it is not necessary to start the restart of the engine 12 yet, and the current process is ended as it is. On the other hand, if the predicted time T2 is equal to or less than the required restart time Teng, that is, if the determination in S23 is affirmative, the brake ECU 55 permits the restart of the engine 12 in step S24. That is, the brake ECU 55 transmits a restart command to the engine ECU 17.

When the engine ECU 17 receives the restart command, the engine ECU 17 restarts the engine 12 and transmits a signal to the effect that the restart processing has been 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 is completed.

In FIG. 6, since the master cylinder pressure PMC is relatively small at about the specified pressure P1 and Apmc <Ag is established, it is determined that "slipping of the vehicle occurs after stopping." Therefore, the restart of the engine 12 is started at a time before the stop time t4 by the required restart time Teng, and the restart is completed before the stop. As a result, slipping of the vehicle does not occur when the vehicle is stopped. The required restart time Teng is determined by a predetermined method so that the slippage lowering distance L of the vehicle does not exceed the predetermined allowable distance La.

In FIG. 7, the estimated engine stoppable time Tes is smaller than the set time T1, that is, Tes <T1. However, the timing chart in the case where the braking force capable of suppressing the slippage drop is secured is shown as the braking acceleration Apmc is larger than the gradient acceleration Ag.

When the brake pedal 15 is operated relatively strongly at time t11 while the vehicle is traveling in the engine operating state, the brake switch SW1 is turned on, and the master cylinder pressure PMC rises to exceed the specified pressure P1 to a predetermined pressure It reaches P2. As a result, the vehicle decelerates, and at time t12, when the “other idle stop condition” is satisfied, next, the engine stoppable estimated time Tes is calculated, and it is determined whether Tes> T1 is satisfied. Tes = VS / (DVS + Aet). In the example of FIG. 7, the engine stoppable estimated time Tes is shorter than the set time T1, and Tes> T1 is not satisfied.

However, since the braking acceleration Apmc is larger than the gradient acceleration Ag, a braking force sufficient to prevent slippage is secured. Therefore, there is no need to restart the engine 12 for the purpose of preventing slippage. Therefore, at time t13 when Apmc> Ag is established, the stop of the engine 12 is permitted. As a result, from time t13, the engine rotational speed decreases and eventually becomes zero. When the engine rotational speed becomes zero at time 14, the engine torque disappears. Therefore, the actual vehicle speed VS decreases along the solid line in FIG. 7 as expected. Since a relatively strong braking force is secured when the vehicle is stopped at time t15, the vehicle does not slip down even if the engine 12 is not restarted.

FIG. 8 shows a timing chart when the engine is not stopped. When the brake pedal 15 is operated at time t21 while the vehicle is traveling in the engine operating state, the brake switch SW1 is turned on, and the master cylinder pressure PMC rises to reach the defined pressure P1. As a result, when the "other idle stop condition" is satisfied at time t22 when the vehicle decelerates and the vehicle speed VS becomes equal to or less than the specified speed V1, then the engine stoppable predicted time Tes is calculated, and Tes> T1 It is determined whether or not it is established. Tes = VS / (DVS + Aet). In the example of FIG. 8, the vehicle speed VS decreases along the speed profile indicated by the two-dot chain line where the acceleration Aet for the engine torque has disappeared. Therefore, it is determined whether or not Tes> T1 is established by using the engine stoppable estimated time Tes assumed to stop at time t24. In the example of FIG. 8, since Tes> T1 is not established, the fuel consumption improvement effect can not be obtained even if the engine 12 is stopped.

In FIG. 8, the master cylinder pressure PMC is relatively small at about the prescribed pressure P1, that is, the braking acceleration Apmc is smaller than the gradient acceleration Ag, so that the braking force that can suppress the slippage is not secured. For this reason, in order to prevent slippage of the vehicle after stopping, a creep torque is required. Thus, the engine 12 is not stopped. The actual vehicle speed VS decreases along the solid line in FIG. 8 because the acceleration Aet corresponding to the engine torque does not disappear. Since the creep torque is given by the engine 12 continuing the driving after the stop, the slippage of the vehicle does not occur. However, when the road surface slope θ on the uphill road is quite large, and the force Fg of the gradient component of gravity acting on the vehicle exceeds the sum of the creep torque and the braking force by the brake operation, the vehicle slowly slips after stopping. It can happen. In this case, since the slippage lowering speed is slow, the driver depresses the brake pedal 15 with a relatively large margin to prevent the further slippage of the vehicle.

According to the vehicle control device of the present embodiment described above, the following effects can be obtained.

(1) The brake ECU 55 for automatically stopping the engine 12 and automatically restarting the fuel consumption Fd is equal to or more than the fuel consumption Fst required to restart the engine 12 when the “other idle stop condition” is satisfied. It is determined whether or not. The fuel saving amount Fd means the amount of fuel that can be saved in the engine stop period, that is, the idle stop time from the engine stop to the restart of the engine 12 performed for the purpose of preventing slippage after stopping. If the fuel saving amount Fd is the fuel consumption amount Fst or more, the brake ECU 55 permits the engine 12 to stop. Therefore, for example, when it is possible to secure only the engine stop period in which the fuel consumption Fst is larger than the fuel saving amount Fd, the engine 12 can not be stopped. Therefore, the fuel consumption improvement effect can be further obtained as compared with the conventional case.

(2) The brake ECU 55 is an estimated value of the engine stop period from the engine stop to the restart of the engine 12 performed for the purpose of preventing slippage after stopping when the "other idle stop conditions" are satisfied. An engine stoppable estimated time Tes is calculated. Then, the brake ECU 55 determines whether the estimated engine stoppable time Tes is equal to or longer than the set time T1. That is, the brake ECU 55 does not directly compare the fuel saving amount Fd with the fuel consumption amount Fst. The brake ECU 55 according to the present embodiment uses the fuel consumption amount Fid per unit time in the idle state of the engine 12 to convert the fuel amounts Fd and Fst into time corresponding to the idle time, respectively, to obtain the estimated engine stoppable time Tes. The set time T1 is obtained. The brake ECU 55 compares the estimated engine stoppable time Tes with the set time T1. Therefore, the brake ECU 55 does not obtain the fuel saving amount Fd and the fuel consumption amount Fst, but uses the estimated engine stoppable time Tes, which is a time conversion value thereof, and the setting time T1 to obtain the fuel saving amount Fd It can be determined indirectly that it is Fst or more. Therefore, in the present embodiment, the determination can be made by a relatively simple process using the engine stoppable estimated time Tes which can be acquired by calculating from the detection results of the existing wheel speed sensors SE3 to SE6.

(3) When the fuel saving amount is less than the fuel consumption amount, the brake ECU 55 generates a gradient acceleration Ag corresponding to the force Fg of the gradient component of gravity acting on the vehicle according to the operation amount of the brake pedal 15, that is, the stepping amount. The braking acceleration Apmc is determined from the master cylinder pressure PMC. If Apmc ≧ Ag, it is determined that slipping does not occur after the vehicle is stopped, and the engine 12 is permitted to stop. That is, when the braking force capable of resisting the force Fg of the gradient component of gravity acting on the vehicle when the vehicle is stopped, the stop of the engine 12 is permitted. Therefore, the fuel consumption improvement effect can be obtained by increasing the implementation frequency of the idle stop.

(4) In the case where the engine stoppable expected time Tes is less than the set time T1 and the braking force sufficient to prevent slippage after stopping can not be secured, that is, Apmc 不 Ag is not established, the engine 12 can be stopped. I will not. Therefore, the situation where the fuel consumption Fst for restarting the engine 12 becomes larger than the fuel saving Fd which can be saved in the idle stop time can be avoided as much as possible. That is, it is possible to avoid, as much as possible, a situation where the implementation of the idle stop rather deteriorates the fuel consumption.

(5) When it is determined that slippage may occur, that is, when it is determined that Apmc <Ag, restart of the engine 12 is started so as to be completed by the time the vehicle is stopped. More specifically, when a slippage of the vehicle is predicted to occur, restart of the engine 12 is started when the predicted time T2 until the vehicle stops reaches the required restart time Teng. For this reason, slippage of the vehicle does not occur after stopping, and slippage after stopping of the vehicle on the uphill road can be suitably prevented.

(6) The brake ECU 55 determines whether or not a slippage occurs after the vehicle is stopped, a braking acceleration Apmc determined from the master cylinder pressure PMC according to the operation amount of the brake pedal 15, ie, the depression amount, the vehicle acceleration G and the vehicle speed This is performed using gradient acceleration Ag determined from the difference with the differential value DVS. When the gradient acceleration Ag exceeds the braking acceleration Apmc, the brake ECU 55 determines that "a slip of the vehicle occurs". Therefore, it is possible to accurately determine the necessity of restarting the engine 12 for the purpose of preventing slippage of the vehicle.

The above embodiment can be modified as follows.

In the above embodiment, the estimated engine stoppable time Tes obtained by converting the fuel saving amount Fd and the set value F1 corresponding to the fuel consumption Fc into idle time is compared with the set time T1. Instead of this, by comparing the fuel saving amount Fd with the set value F1, it may be determined whether Fd d F1 holds. For example, the fuel injection device has an injector for injecting fuel into the combustion chamber of the engine 12. In this case, the fuel saving amount Fd is calculated by multiplying the amount of fuel consumed per unit time under the engine idle condition by the fuel injection device by the engine stop time from the stop of the engine 12 to the restart. The memory of the brake ECU 55 stores a set value F1 corresponding to the actual fuel consumption amount Fc acquired at engine start. The brake ECU 55 functioning as the third determination unit is configured to determine whether the fuel reduction amount Fd obtained by the above calculation is equal to or greater than the set value F1.

When the fuel saving amount Fd is the same as the fuel consumption amount Fc, that is, when Tes = T1 in the above embodiment, the engine 12 is allowed to stop. Instead of this, the engine may not be stopped. That is, at least when the fuel consumption is to be deteriorated, the engine 12 may not be stopped. Furthermore, the allowable amount α may be set with respect to the fuel consumption Fc. Alternatively, an allowable time Tα corresponding to the allowable amount α may be set with respect to the estimated engine stoppable time Tes. Then, the third determination unit may be configured to determine that FdFFc + Fα or Tes ≧ T1 + Tα. According to this configuration, even if there is an error between the calculated or set value and the actual value, the engine 12 can be stopped only when there is a fuel saving effect. Of course, the determination condition of the third determination unit may be Fd ≧ Fc−Fα or Tes ≧ T1−Tα. In short, the set value may be a value set according to the fuel consumption at the time of engine restart, and may be a value in which a predetermined allowable value is considered with respect to the fuel consumption and the conversion time of the fuel consumption. .

In the above embodiment, the braking acceleration Apmc is compared with the gradient acceleration Ag, that is, the threshold value, at the time of the slip down determination. Instead of this, the braking force may be compared with the threshold value as the force Fg of the vehicle longitudinal direction component of the gravity acting on the vehicle, that is, the road surface direction component. Alternatively, master cylinder pressure PMC may be compared with a threshold as a force equivalent to master cylinder pressure of force Fg.

In a vehicle including the pressure sensor SE2 that detects the master cylinder pressure PMC, the braking acceleration Apmc may be acquired based on the master cylinder pressure PMC detected by the pressure sensor SE2. The memory of the brake ECU 55 stores, for example, a map (not shown) indicating the correspondence between the master cylinder pressure PMC and the braking acceleration Apmc or the braking force Fpmc. The brake ECU 55 acquires the braking acceleration Apmc or the braking force Fpmc by referring to the map based on the master cylinder pressure PMC. Then, the brake ECU 55 may be configured to determine the presence or absence of slippage by comparing the braking acceleration Apmc with the gradient acceleration Ag, or by comparing the braking force Fpmc with the force Fg.

The slippage of the vehicle at the time of stopping on the uphill may be allowed if it is small. That is, the allowable distance La is set to La ≧ 0, and the engine 12 is restarted while the slippage lowering distance L is within the allowable distance La. It is determined whether or not a slippage of the vehicle after the stoppage occurs while traveling uphill while the engine 12 is stopping. When it is predicted that "slipping occurs", restart of the engine 12 is started so as to be completed by the time the sling lowering distance L of the vehicle exceeds the allowable distance La. The allowable distance La ≧ 0. More specifically, the time Ta until the stop and the time Tb until the slippage distance L of the vehicle from the stop time becomes the allowable distance La are determined at the time of uphill traveling while the engine is stopped. The brake ECU 55 permits start of restart of the engine 12 when the predicted time T2 represented by the sum of the time Ta and the time Tb reaches the required restart time Teng. Further, the larger the road surface gradient θ, the larger the value of the allowable distance La may be set. For example, the allowable distance La is set to “0” until the road surface gradient θ reaches a constant value, and the allowable distance La is increased according to the increase of the road surface gradient θ after the road surface gradient θ exceeds a constant value. . The allowable distance La is the one described in the above embodiment. When these configurations are adopted, it is preferable to calculate the estimated engine stoppable time Tes by the following equation.
Tes = VS / (DVS + Aet) + Tb-Teng (4)
In the embodiment, the engine 12 is restarted to add creep torque to the braking force to prevent the vehicle from slipping down. In this case, if the gradient acceleration Ag is larger than the sum of the creep acceleration Ac due to creep torque and the braking acceleration Apmc, that is, if Ac + Apmc <Ag, then a slippage occurs. Therefore, when Ac + Apmc <Ag holds, a configuration may be adopted in which brake pressure is applied to prevent slippage. Specifically, when Ac + Apmc <Ag holds, the motor 41 is driven to drive the

pumps

42 and 43. Further, current is supplied to the

linear solenoid valves

35a, 35b at a current value according to the magnitude of the gradient acceleration Ag to pressurize the wheel cylinder pressure PWC to a control target value to perform brake pressurization. Thereafter, current values capable of holding the brake pressure at the control target pressure are supplied to the

linear solenoid valves

35a and 35b. According to this configuration, for example, even when slippage can not be prevented only by adding the creep torque because the road surface gradient θ is large, the vehicle can be stopped without slipping down the slope.

In the above-described embodiment, when the acceleration Ag in the rearward direction of the vehicle generated by gravity exceeds the braking acceleration Apmc of the vehicle, it is determined that "the slippage of the vehicle occurs". By changing this, it may be determined that "slipping of the vehicle occurs" when the force Fg, which is a component of the gravity in the backward direction acting on the vehicle, exceeds the braking force Fpmc of the vehicle.

In the embodiment described above, it is determined whether or not the vehicle slips down after stopping based on the braking acceleration Apmc determined from the master cylinder pressure PMC according to the operation force of the brake pedal 15, ie, the pedaling force, and the detection result of the vehicle body acceleration G. It was like that. It is also possible to change this and make the same determination based on other detected values. For example, it is possible to confirm the braking force and the braking acceleration of the vehicle by using the operation amount of the brake pedal 15, that is, the detection value of the depression amount instead of the detection value of the master cylinder pressure PMC. In this case, a sensor for detecting the amount of depression of the brake pedal 15 is provided to the vehicle. Further, the acceleration by the brake can also be confirmed by removing the acceleration generated by the engine by the vehicle acceleration G, the acceleration by the rolling resistance, the road surface gradient acceleration, the acceleration by the air resistance or the like from the vehicle acceleration G. Further, it is also possible to perform the above determination by providing a sensor for detecting the pitch of the vehicle body and grasping the road surface gradient θ by a signal from the sensor.

In the above embodiment, the vehicle speed VS and the vehicle speed differential value DVS are used. This may be modified to use wheel speed and wheel acceleration. As the vehicle body speed, it is possible to use one calculated using at least one of the wheel speed sensors SE3 to SE6 or a value acquired by a car navigation system.

In the said embodiment, the case where the control apparatus of this application was applied to the vehicle in which the disk brake apparatus was provided in each wheel was demonstrated. Changing this, the present application is equally applicable to vehicles in which a drum brake device is provided on part or all of the wheels.

Vehicles are not limited to two-wheel drive vehicles. The vehicle control device of the present invention can be similarly applied to vehicles of other drive systems such as four-wheel drive vehicles.

12 ... engine. 15: A brake pedal which is an example of a brake operation unit. 17 engine ECUs. 18: Automatic transmission. 20a ... torque converter. 25: Master cylinder. 26 ... booster. 31 ... brake actuator. 32a-32d: Wheel cylinder. 55: A brake ECU as an example of a first determination unit, a second determination unit, a third determination unit, a fourth determination unit, a stop control unit, and a restart control unit. FR, FL, RR, RL ... wheels. SE1 ... accelerator opening sensor. SW1 ... brake switch. SE2 ... pressure sensor. SE3 to SE6: wheel speed sensors which are an example of a vehicle speed detection unit. SE7 ... acceleration sensor. Tes: Expected time to stop the engine. T1 ... setting time which is an example of setting value. θ: Road surface gradient. L ... slip down distance. La ... allowable distance. VS ... body speed. DVS ... body speed derivative value. Ag ... gradient acceleration. Fpmc ... braking force. Apmc ... braking acceleration. Aet ... engine torque acceleration. Fd: Fuel savings. Fst: Fuel consumption. F1 ... setting value. Teng ... required time to restart.

Claims

A vehicle control apparatus that performs stop control for automatically stopping an engine of a vehicle and restart control for automatically restarting the engine, the vehicle control apparatus comprising:
A first determination unit configured to determine whether "the execution condition of the stop control is satisfied";
A stop control unit configured to permit stopping of the engine when it is determined that "the execution condition of the stop control is satisfied";
A second determination unit configured to determine whether or not “slipping of the vehicle after stopping occurs” when traveling on a slope with the vehicle in a state where the engine is stopped;
When it is determined that "the slip is occurring", the restart of the engine is permitted to be started so that the restart of the engine is completed before the slip distance of the vehicle exceeds the allowable distance. Configured restart control;
A third determination unit configured to predict a fuel saving amount that can be saved in the engine stop period from the stop of the engine to the restart before the stop of the engine, wherein the third determination unit is And a third determination unit configured to determine whether “the fuel saving amount is equal to or more than a set value set according to the fuel consumption amount required for the restart of the engine”.
When it is determined that "the fuel saving amount is less than the set value", the stop control unit is configured not to permit the stop of the engine even if the execution condition of the stop control is satisfied. ,
Vehicle control device.
The vehicle includes a brake operating unit.
The vehicle control device further includes a fourth determination unit,
The fourth determination unit is configured to determine whether or not "the braking force corresponding to the operation amount of the brake operation unit is secured at or above a threshold that can suppress slippage of the vehicle after stopping." ,
When it is determined that "the braking force is secured above the threshold value", the stop control unit may determine that the amount of fuel saved is less than the set value, even if it is determined that Configured to allow outages,
The vehicle control device according to claim 1.
The third determination unit is configured to obtain an estimated engine stoppable time as a time from stop to restart of the engine,
The third determination unit determines whether or not “the fuel saving amount is equal to or more than the set value”, or more than the set time obtained by converting the set value to the idle time of the engine. Configured to determine whether or not
The vehicle control device according to claim 1.
The vehicle has a vehicle speed detector.
The third determination unit is configured to obtain a vehicle speed detected by the vehicle speed detection unit, and to obtain a vehicle speed derivative value generated by time-differentiating the vehicle speed.
The third determination unit calculates the estimated engine stoppable time by dividing the vehicle body speed by a value obtained by removing an acceleration for an engine torque which disappears due to a stop of the engine from the vehicle body speed differential value. Is configured as
The vehicle control device according to claim 3.
A vehicle control method for performing stop control for automatically stopping an engine of a vehicle and restart control for automatically restarting the engine, the vehicle control method comprising:
Determining whether "the execution condition of the stop control is satisfied";
Allowing the engine to stop when it is determined that "the execution condition of the stop control is satisfied";
Determining whether or not "slipping of said vehicle after stopping occurs" when traveling on a slope road with said vehicle in a state where said engine is stopped;
When it is determined that "the slip is occurring", restart of the engine is started so that the restart of the engine is completed before the slip distance of the vehicle exceeds the allowable distance;
Predicting the fuel savings that can be saved in the stop period between the stop of the engine and the restart before the stop of the engine;
Determining whether "the amount of fuel savings is equal to or greater than a set value set according to the amount of fuel consumption required for the restart of the engine";
The vehicle control method according to any one of the preceding claims, wherein, when it is determined that "the fuel saving amount is less than the set value", stopping of the engine is not permitted even if the execution condition of the stop control is satisfied.