JP5672917B2 - Vehicle control device - Google Patents

Description

The present invention relates to the control equipment of the vehicle performing automatic stop of the engine, the automatic restart.

  As is well known, the engine is automatically stopped while the vehicle is stopped, such as waiting for a signal, and the engine is automatically restarted according to the driver's starting operation, thereby saving fuel consumption and improving exhaust emission. Stop / restart devices are in practical use. In recent years, a device for stopping the engine while the vehicle is decelerating before stopping has been proposed.

  Conventionally, as described in Patent Document 1, the engine is automatically stopped on the condition that the brake depression amount is equal to or greater than the first threshold value X, and the engine is operated on the condition that the brake depression amount is equal to or less than the second threshold value Y. A vehicle control device has been proposed that automatically restarts and makes the first and second threshold values variable according to the vehicle speed.

JP 2003-35175 A

  By the way, in an AT vehicle (automatic vehicle) equipped with an automatic transmission with a torque converter, thrust in the vehicle front direction due to a creep phenomenon is generated even when the engine is idle. The creep phenomenon is a phenomenon in an AT vehicle in which the vehicle slowly moves forward even if the accelerator pedal is not depressed when the shift lever is in the traveling position. This phenomenon is caused by a slight torque converter even when the engine is idle. The power is transmitted to the drive wheel side.

  Even when the vehicle is stopped on an uphill road, if the engine is operated, torque (creep torque) due to a creep phenomenon is applied, so that the vehicle can be prevented from sliding down with a relatively small brake depression amount. However, if the engine at this time is automatically stopped, creep torque does not act. Therefore, if the amount of brake depression is small, the vehicle may slide down the slope without resisting gravity. In addition, since a relatively large amount of fuel is consumed when the engine is restarted, it is desirable to avoid unnecessary stopping of the engine as much as possible from the viewpoint of fuel saving (improvement of fuel consumption).

The present invention has been made in view of such circumstances, and its purpose is to avoid unnecessary stopping of the engine that cannot contribute to fuel saving in a vehicle that automatically stops and restarts the engine as much as possible. to provide a control equipment for a vehicle capable of suitably preventing sliding down of the vehicle when the vehicle is stopped at the uphill road.

In order to solve the above-described problems, in the present invention, stop control for automatically stopping the engine (12) of the vehicle and control of the vehicle for performing restart control for automatically restarting the engine (12). A first determination means (55, S11) for determining whether or not the stop control execution condition is satisfied; and when it is determined that the stop control execution condition is satisfied, the engine (12 And a second stop control means (55, S15) for permitting the stop of the vehicle (2) to determine whether or not the vehicle will slide down after the vehicle stops when traveling on a slope with the engine (12) stopped. When the determination means (55, S21) and when it is determined that the sliding occurs, the restart of the engine (12) is completed before the vehicle sliding distance (L) exceeds the allowable distance (La). Same engine And restart control means for permitting the start of the automatic restart (12) (55), when the execution condition of the stop control in the middle deceleration of the vehicle is allowed to stop the engine (12) in order to satisfied, stop Under the assumption that the engine (12) is automatically restarted later to suppress the sliding, the time point when the execution condition of the stop control is satisfied is defined as a first time point, and the vehicle body speed at the first time point is determined. An engine stop period that is a period between the first time point and the second time point before the engine (12) is stopped is a vehicle stop time point calculated based on (VS). The amount of fuel saved (Tes) that can be saved in the vehicle is predicted, and the amount of fuel saved (Tes) is not less than the set value (T1) set according to the fuel consumption required for the restart of the engine (12). 3rd judgment to determine whether or not Means (55, S12, S13), and when it is determined that the fuel saving amount (Tes) is less than the set value (T1), the stop control means (55) performs the stop control. The gist is that stop of the engine (12) is not permitted even if the execution condition is satisfied.

According to the above configuration, the fuel saving amount to be saved in the expected engine stop period from the engine stop to the restart is predicted before the engine is stopped, and the predicted fuel saving amount is the fuel required for the engine restart. If it is determined that the value is less than the set value set according to the consumption, the engine stop is not permitted even if the stop control execution condition is satisfied. Therefore, it is possible to suitably prevent the vehicle from sliding down when stopping on an uphill road while avoiding unnecessary stopping of the engine that cannot contribute to fuel saving as much as possible.
Further, in the present invention, there is provided a vehicle control device that performs stop control for automatically stopping the engine (12) of the vehicle and restart control for automatically restarting the engine (12), First determination means (55, S11) for determining whether or not the stop control execution condition is satisfied, and if it is determined that the stop control execution condition is satisfied, the engine (12) is allowed to stop. Stop control means (55, S15), and second determination means (55, S15) for determining whether or not the vehicle is lowered after stopping when traveling on a slope with the engine (12) stopped. S21), and when it is determined that the slipping occurs, the engine (12) is restarted so that the restarting of the engine (12) is completed before the vehicle slipping distance (L) exceeds the allowable distance (La). Automatically When the engine (12) is stopped because the restart control means (55) permitting the start of restart and the execution condition of the stop control are satisfied during the deceleration of the vehicle, the sliding is suppressed after the vehicle stops. Therefore, under the assumption that the engine (12) is automatically restarted, the time point when the execution condition of the stop control is satisfied is set as the first time point, and the calculation is made based on the vehicle body speed (VS) at the first time point. The second time point is a time point before the engine (12) needs to be restarted (Teng) before the vehicle stop point, and the first time point and the second time point before the engine (12) stop. A fuel saving amount (Tes) that can be saved in an engine stop period, which is a period between the time points, is predicted, and the fuel saving amount (Tes) depends on a fuel consumption amount required for the restart of the engine (12). Configured settings (T1) and a third determination means (55, S12, S13) for determining whether or not it is greater than or equal to, the stop control means (55), wherein the fuel saving (Tes) is the set value ( When it is determined that it is less than T1), the gist is that the engine (12) is not allowed to stop even if the stop control execution condition is satisfied.

  Further, in the vehicle control apparatus according to the present invention, it is determined whether or not the braking force (Apmc) corresponding to the operation amount of the brake operation means (15) is secured to a threshold value (Ag) or more that can prevent the sliding after the vehicle stops. When it is determined that the braking force (Apmc) is more than the threshold (Ag), the stop control unit (55) further includes a fourth determination unit (55, S14) for determining. Even when it is determined that the fuel saving amount (Tes) is less than the set value (T1), it is preferable to permit the engine (12) to be stopped.

  According to the above configuration, when it is determined that the braking force according to the operation amount of the brake operation means is secured to a threshold value that can prevent the sliding after the vehicle stops, the braking force that can suppress the sliding when the vehicle is stopped is secured. Means that In this case, since the engine is not restarted to suppress the sliding down, the engine is allowed to stop even when the fuel saving amount is determined to be less than the set value. For this reason, the engine stop frequency can be increased and the further fuel-consumption improvement effect can be acquired.

In the control apparatus for a vehicle according to the present invention, the third judging means (55, S12, S13), the time to the second time point and the engine stop predictable time (Tes) from the first time point, The determination as to whether or not the fuel saving amount is equal to or greater than the set value is based on whether or not the expected engine stoppage possible time (Tes) is equal to or greater than a set time (T1) obtained by converting the set value to an idle time of the engine (12). It is preferable to carry out by determining whether or not there is.

According to the above-described configuration, it is determined whether or not the expected expected engine stop time from the engine stop to the restart is equal to or longer than the set time calculated in terms of idle time. For this reason, for example, without obtaining the fuel injection amount of a fuel injection device that injects fuel into the fuel chamber of the engine, the detection value of an existing sensor (such as a vehicle speed sensor) provided in the vehicle is used. Determination values necessary for determination can be acquired relatively easily. For this reason, the processing necessary for the determination is not complicated.

Furthermore, in the vehicle control apparatus according to the present invention, the third determination means (55) determines the vehicle speed (VS) detected by the vehicle speed detection means (SE3 to SE6) and the vehicle speed (VS) as time. The vehicle body speed differential value (DVS) differentiated by the above is acquired, and the expected engine stoppage possible time (Tes) is the engine torque component that disappears from the vehicle body speed differential value (DVS) when the engine is stopped. It is preferable that the value corresponds to the calculated value obtained by dividing by the value excluding the acceleration (Aet).

According to the above configuration, the estimated engine stoppage possible time is a calculated value obtained by dividing the vehicle body speed VS by a value obtained by dividing the vehicle body speed differential value by the value obtained by removing the acceleration corresponding to the engine torque that disappears due to the engine stop , or It becomes a value according to the calculated value . That is, the expected engine stoppage time is obtained in consideration of the disappearance of the engine torque. Therefore, the third determination unit can make a determination with relatively high accuracy.

  According to the present invention, in a vehicle that automatically stops and restarts an engine, it is preferable to prevent the vehicle from slipping when stopping on an uphill road while avoiding unnecessary stopping of the engine that cannot contribute to fuel saving as much as possible. Can be prevented.

The block diagram which shows an example of the vehicle carrying the control apparatus of one Embodiment. The circuit diagram which shows an example of a braking device. The flowchart which shows an engine stop control routine. The flowchart which shows an engine restart control routine. The schematic side view which shows the force which acts on the vehicle which stops on an uphill road. The timing chart when stopping an engine (Tes> = T1). Timing chart when braking acceleration is larger than gradient acceleration. Timing chart when the engine is not stopped.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS. In the following description of 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 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 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.

  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.

  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 (stepping force) of the brake pedal 15 by the driver.

  The master cylinder 25 generates a master cylinder pressure PMC according to the operation of the brake pedal 15 (hereinafter also referred to as “brake operation”) by the driver. As a result, brake fluid is supplied from the master cylinder 25 into the wheel cylinders 32a to 32d via the hydraulic circuits 29 and 30. Then, braking force according 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, each hydraulic circuit 29, 30 is connected to the master cylinder 25 through pipes 33, 34, and a normally open type linear electromagnetic valve (regulating valve) is provided in the middle of each pipe 33, 34. ) 35a and 35b are provided. The linear solenoid 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. The ECU 55 is displaced according to the current value supplied to the electromagnetic coil from the ECU 55. That is, the wheel cylinder pressure PWC 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.

  Further, a pressure sensor SE2 for detecting the master cylinder pressure PMC is provided at a position closer to the master cylinder 25 than the linear electromagnetic valve 35a in the pipe line 33. A detection signal having a value corresponding to the master cylinder pressure PMC is output from the pressure sensor SE2 to the brake ECU 55.

  In the middle of the pipes 36a to 36d branched from the pipes 33 and 34 connected to the master cylinder 25 and connected to the wheel cylinders 32a to 32d, the pressure increasing valves 37a, 37b, 37c, which are normally open electromagnetic valves, are provided. 37d and pressure-reducing valves 38a, 38b, 38c, 38d made of normally-closed solenoid valves are provided. The pressure increasing valves 37a, 37b, 37c, and 37d are operated when restricting the pressure increase of each wheel cylinder pressure PWC, and the pressure reducing valves 38a, 38b, 38c, and 38d are operated when decreasing the wheel cylinder pressure PWC.

  The hydraulic circuits 29 and 30 include reservoirs 39 and 40 for temporarily storing brake fluid that has flowed out of the wheel cylinders 32a to 32d through the pressure reducing valves 38a to 38d, and a pump 42 that operates based on the rotation of the motor 41, 43 is connected. The reservoirs 39 and 40 are connected to the pumps 42 and 43 through the pipes 44 and 45, and are connected to the pipes 33 and 34 at positions closer to the master cylinder 25 than the linear electromagnetic valves 35a and 35b. , 47, etc., are connected to the master cylinder 25, respectively. The pipes 48 and 49 extending from the discharge ports of the pumps 42 and 43 are connected to connection portions 50 and 51 on the communication path connecting the pressure increasing valves 37a to 37d and the linear electromagnetic valves 35a and 35b. When the motor 41 rotates, the pumps 42 and 43 suck in the brake fluid from the reservoirs 39 and 40 and the master cylinder 25 through the conduits 44, 45, 46 and 47, and the sucked brake fluid is in the conduit 48. , 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, the brake ECU 55 has, as an input system, a pressure sensor SE2, wheel speed sensors SE3, SE4, SE5, SE6 for detecting the wheel speed of each wheel FR, FL, RR, RL, An acceleration sensor (also referred to as “G sensor”) SE7 for detecting acceleration in the front-rear direction is electrically connected. The brake ECU 55 is electrically connected to a brake switch SW1 for detecting whether or not the brake pedal 15 is operated. Further, the brake ECU 55 is electrically connected to the valves 35a, 35b, 37a to 37d, 38a to 38d, the motor 41, and the like as an output system. The acceleration sensor SE7 outputs a signal that takes a positive value when the vehicle stops on an uphill road, while outputting a signal that takes a negative value when the vehicle stops on a downhill road. Is done.

  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. The ROM of the digital computer stores in advance various control processing (idle stop processing (engine stop control, engine restart control, etc.) routines, various threshold values, set values, etc., which will be described later. While the ignition switch (not shown) is on, various information that can be appropriately rewritten is stored.

  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, information related to the accelerator pedal 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 permits the engine 12 to be automatically stopped. A control command (also referred to as “stop command”), a control command for permitting the engine 12 to be automatically restarted (also referred to as “restart command”), and the like are transmitted to the engine ECU 17. .

  FIG. 5 shows the relationship between the forces acting on the vehicle stopped on the uphill road. Here, when the slope (inclination angle) of the uphill road is “θ” and the gravity acting on the vehicle is “g”, the vehicle is pulled backward by the force Fg of “g · sin θ” by the action of the gravity g. become. This force Fg is a vehicle rear direction component (road surface direction component) of gravity g acting on the vehicle, and changes according to 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 is stopped on a slope, the force Fg and the braking force Fpmc are compared, and if Fpmc <Fg, there is a possibility that the vehicle will slip down.

  In this example, the vehicle rearward acceleration obtained by dividing the force Fg by the vehicle body weight M is defined as a gradient acceleration Ag, and the acceleration obtained by dividing the braking force Fpmc by the vehicle body weight M is defined as a braking acceleration Apmc. . Then, when Apmc <Ag is established, it is determined that there is a possibility that the sliding may occur.

  Here, when the slip prevention control is performed, it is necessary to acquire the gradient acceleration Ag used for the determination of the presence or absence of the slip during the traveling before the vehicle stops. In the present embodiment, the vehicle body speed differential value obtained by time-differentiating the vehicle body speed VS calculated based on the detection signals of the wheel speed sensors SE3 to SE6 from the vehicle body acceleration G calculated based on the detection signal from the acceleration sensor SE7. The gradient acceleration Ag is calculated by subtracting DVS. The vehicle body acceleration G calculated based on the detection signal of the acceleration sensor SE7 includes a gradient acceleration Ag that is a vehicle longitudinal component of gravity acceleration acting on the vehicle, whereas the vehicle body speed VS is time-differentiated. The vehicle body speed differential value DVS obtained in this way 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 acquired.

  In the slip prevention control, it is necessary to acquire the braking acceleration Apmc used for determining whether or not there is a slip while traveling before stopping. The vehicle body acceleration G calculated based on the detection signal from the acceleration sensor SE7 varies with the variation of the master cylinder pressure PMC, that is, the variation of the braking force with respect to the wheels FR, FL, RR, and RL. Therefore, in this embodiment, paying attention to the fact that there is a correspondence relationship between the master cylinder pressure (that is, braking force) and the vehicle body acceleration G, the braking acceleration Apmc is acquired as a value corresponding to the master cylinder pressure PMC based on the vehicle body acceleration G. The The braking acceleration Apmc corresponds to an acceleration obtained by dividing the braking force Fpmc by the vehicle body weight M when the braking force Fpmc corresponding to the master cylinder pressure PMC is applied to the wheels FR, FL, RR, and RL. Specifically, the braking acceleration is obtained by removing the creep acceleration Ac, which is an acceleration component corresponding to the creep torque, and the acceleration Ad and the gradient acceleration Ag, which are acceleration components corresponding to a drag component (travel resistance, etc.), from the vehicle body acceleration G. Apmc is calculated (Apmc = G-Ac + Ad + Ag). Then, the gradient acceleration Ag and the braking acceleration Apmc are compared, and if Apmc <Ag, it is determined that there is a possibility that the sliding may occur. In this embodiment, when it is predicted that Apmc <Ag is established and the vehicle may possibly fall after the vehicle stops, the engine 12 is restarted before the vehicle stops in order to prevent the vehicle from falling. Let By restarting the engine 12, creep torque is applied to the vehicle to prevent the vehicle from sliding down.

  By the way, when the idle stop time from the stop to restart of the engine 12 is short and 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 that, the idle stop is performed. On the other hand, fuel consumption increases and fuel consumption deteriorates. For this reason, in this embodiment, when the engine stop control execution condition is satisfied, the fuel saving amount Fd that can be further reduced by the idle stop by the automatic stop of the engine 12 and the fuel consumption amount Fst when the engine 12 is restarted are calculated. In comparison, when the fuel saving amount Fd is equal to or greater than the fuel consumption amount Fst, the engine 12 is stopped to perform the idle stop.

  Specifically, instead of comparing the fuel saving amount Fd and the fuel consumption amount Fst, the estimated idle stop time from the stop of the engine 12 to the restart is calculated as the expected engine stop possible time Tes. The expected stoppage time Tes is compared with the set time T1 obtained by converting the fuel consumption Fc when the engine 12 is restarted into the idle time. The fuel consumption Fid per unit time when the engine 12 is idling is determined approximately uniquely by the vehicle type. However, the idle rotation speed of the engine 12 changes depending on whether the air conditioner installed in the vehicle is driven or not. Therefore, the set time T1 is set by adopting the fuel consumption amount Fid per unit time when the idle rotation speed is the upper limit idle rotation speed (that is, the idle rotation speed when the air conditioner is driven) in the change range of the idle rotation speed. ing. Of course, it is possible to adopt a configuration in which it is determined whether the air conditioner is driven or not and the set time T1 is switched according to the determination result.

Further, the fuel consumption amount Fst at the time of restarting the engine is roughly determined uniquely by the vehicle type. Of course, when the fuel consumption amount Fst at the time of engine restart changes according to the engine operation mode, the fuel consumption amount Fst according to the operation mode may be adopted. In the present embodiment, a value obtained by converting the fuel consumption amount Fst at the time of engine restart into an idle time is obtained as a time T1 (hereinafter, also referred to as “set time T1”) that has an effect of improving fuel efficiency. This set time T1 is given by the following equation.
T1 = Fst / Fid (1)
Further, the expected engine stop possible time Tes is an expected time (predicted time) during which the engine 12 can be held in a stopped state from the stop point of the engine 12 to the restart point of the engine 12, and is given by the following equation.
Tes = VS / (DVS + Aet) (2)
Here, VS is a vehicle body speed, DVS is a vehicle body speed differential value, and Aet is an engine torque acceleration. However, in this example, the vehicle body speed differential value DVS takes a positive value in the deceleration process of the vehicle (that is, the process in which the acceleration in the vehicle rearward direction increases). Further, the engine torque acceleration Aet takes a positive value in the engine operating state. The engine torque acceleration Aet will be described later.

  The engine 12 is stopped when the estimated engine stop possible time Tes is equal to or longer than the set time T1 (when Tes ≧ T1 is established). When the expected engine stop possible time Tes is less than the set time T1, the automatic stop (idle stop) of the engine 12 is worsened and the fuel consumption is worsened. Therefore, the automatic stop of the engine 12 itself is not performed.

  However, when the slippage determination condition (Apmc <Ag) is not satisfied, that is, the braking force condition (where the braking acceleration Apmc is equal to or greater than the gradient acceleration Ag) and the braking force that can suppress the vehicle sliding down is secured ( When (Apmc ≧ Ag) is established, the engine 12 is not restarted to prevent the sliding down. For this reason, in the present embodiment, it is determined whether or not Apmc ≧ Ag is established, whether or not a braking force sufficient to suppress the vehicle sliding down is ensured when the vehicle stops. Even if the condition for the expected engine stop time Tes (Tes ≧ T1) is not satisfied, the stop of the engine 12 is permitted if the braking force condition (Apmc ≧ Ag) is satisfied.

  In the present embodiment, as an execution condition for engine stop control, other idle stop conditions (hereinafter referred to as “IS conditions”) except for the condition of the expected engine stop time Tes (Tes ≧ T1) and the braking force condition (Apmc ≧ Ag). Is also set.). Specifically, the other IS conditions are that the brake switch SW1 is on (brake switch on), the master cylinder pressure PMC exceeds the specified pressure P1 (PMC> P1), and the vehicle body speed VS is Each condition that a specified speed V1 (for example, 20 km / h) or less (VS ≦ V1) is satisfied under the AND condition. Of course, other IS conditions may be changed to appropriate conditions such as eliminating one of the brake switch-on condition and the master cylinder pressure condition.

  6 to 8 show timing charts of the control mode of this embodiment. Each figure shows the signal of the brake switch SW1, the master cylinder pressure PMC, the vehicle body acceleration G output from the acceleration sensor SE7, the engine rotation speed, the vehicle body speed VS, and the vehicle body speed differential value DVS before the vehicle stops on the uphill road. It shows the transition. In the present embodiment, the wheel speed is used as the vehicle body speed VS. The vehicle body speed VS is obtained by adding an integrated value obtained by integrating the wheel acceleration, which is a time differential value of the wheel speed, per unit time to the previous wheel speed. 6-8, the vehicle body acceleration G and the vehicle body speed differential value DVS are different from the vehicle body acceleration G detected by the acceleration sensor SE7 and the calculated vehicle body speed differential value DVS in positive and negative directions, respectively. Is shown to take a negative value.

  The idle stop process will be described with reference to FIG. FIG. 6 is a timing chart when the engine 12 is stopped because the condition that the expected engine stop time Tes is equal to or longer than the set time T1 is satisfied. In FIG. 6, at time t0, the vehicle is running with the engine 12 being operated.

  Here, as shown in FIG. 6, the vehicle body acceleration G during traveling of the vehicle includes acceleration components Ag for gradient, acceleration Aet for engine torque (corresponding to creep torque acceleration), and acceleration Ad for drag. included. Assuming that the acceleration acting on the front side of the vehicle is “positive” and the acceleration acting on the rear side of the vehicle is “negative”, the gradient acceleration Ag is negative, the engine torque acceleration Aet is positive, and the acceleration Ad for dragging is negative. As a result of the addition, the vehicle body acceleration G is detected by the acceleration sensor SE7. However, the acceleration sensor SE7 of the present embodiment outputs the acceleration in the rearward direction of the vehicle as a positive value for convenience of calculation, unlike the actual positive / negative acceleration in FIG. Note that the acceleration Ad for the drag indicates a negative acceleration due to a running resistance between the wheel and the road surface.

  While the vehicle is running, when the driver operates the brake pedal 15 (depresses) at time t1, the brake switch SW1 is turned on, and the master cylinder pressure PMC is increased by this brake operation, and braking force is applied to the wheels. Is done. As a result, the vehicle body speed VS starts to decrease from time t1. At this time, the braking acceleration Apmc corresponding to the master cylinder pressure PMC is applied as a negative acceleration in the direction opposite to the traveling direction (rearward direction) with respect to the vehicle, so that the vehicle body acceleration G is the acceleration corresponding to the master cylinder pressure PMC at that time. It becomes smaller by Apmc and takes a negative value. Further, the master cylinder pressure PMC reaches the specified pressure P1 by the brake operation.

The vehicle body speed VS is decelerated at a rate of change equal to the vehicle body acceleration G (G <0 in FIG. 6) which is reduced by the addition of the braking acceleration Apmc. Eventually, the vehicle body speed VS becomes equal to or less than the specified speed V1.
Then, when other IS conditions are satisfied at the time t2 when the vehicle is traveling and decelerating, an expected engine stop possible time Tes is subsequently calculated. The expected engine stop time Tes assumes that the engine 12 is restarted to prevent the vehicle from sliding down after the engine 12 is stopped, and the engine 12 is restarted from the stop point (current time). Is calculated as the estimated time of the time until the engine 12 is started, that is, the time during which the engine 12 can be held in the stopped state.

  Since the vehicle speed VS obtained from at least one detection signal of the wheel speed sensors SE3 to SE6 at time t2 is before the engine is stopped, it corresponds to the vehicle speed when the vehicle is decelerated at the vehicle acceleration G with the acceleration Aet corresponding to the engine torque. . A two-dot chain line in FIG. 6 indicates a speed profile when the vehicle is decelerated at the vehicle body acceleration G to which the acceleration Aet for the engine torque is added. In the present embodiment, the expected engine stop possible time Tes is calculated assuming a deceleration process in the engine stop state. Therefore, with respect to the speed profile indicated by the two-dot chain line in FIG. 6, it is possible to stop the engine assuming that the vehicle is decelerated at the vehicle body acceleration (= DVS + Aet) excluding the acceleration Aet corresponding to the engine torque that disappears in the engine stop state Time Tes is calculated.

  For this reason, the acceleration Aet corresponding to the disappearing engine torque is excluded from the vehicle body speed differential value DVS, which is the time derivative of the vehicle body speed VS, and the expected engine stop possible time Tes is calculated by the equation shown in the equation (2) Tes = VS / (DVS + Aet). However, in this calculation formula, DVS> 0 and Aet> 0 in the vehicle deceleration process.

  Then, the expected engine stop possible time Tes and the set time T1 are compared, and if Tes> T1 is satisfied, the fuel efficiency improvement effect is obtained, so the engine 12 is stopped from time t2. As a result, the engine speed decreases from time t2 and eventually becomes zero. Then, when the engine rotation speed becomes zero, the amount of engine torque disappears, and thus the actual vehicle speed VS decreases along the solid line in FIG. 6 in the same manner as the predicted vehicle speed. Note that, during the period from time t2 to t3, the expected engine stop possible time Tes may be calculated using a variable acceleration Aet corresponding to the gradually decreasing engine torque.

  Further, as shown in the timing chart of FIG. 7, when the operation amount of the brake pedal 15 is large, the braking acceleration Apmc is larger than the gradient acceleration Ag, and the braking force sufficient to prevent the vehicle from sliding down after stopping is secured. Even if the expected engine stop possible time Tes is shorter than the set time T1 (Tes <T1), the engine 12 is stopped. This is because it is not necessary to restart the engine 12 for the purpose of preventing sliding down after the vehicle stops. As described above, the engine 12 is also stopped when the engine is not restarted when the vehicle is stopped.

  In this embodiment, the engine restart start timing is determined so that the sliding distance L can be suppressed to the allowable distance La or less. The estimated time T2 required for the sliding distance L after the stop to reach the allowable distance La is the time Ta required from the current time to the stop and the time Tb required for the vehicle falling distance L to reach the allowable distance La after the stop. (T2 = Ta + Tb). The time Ta is obtained by dividing the vehicle body speed VS by the vehicle body speed differential value DVS (Ta = VS / DVS). Further, the time Tb is obtained by using a map (not shown) showing the correspondence between the road surface gradient θ and the time Tb. In the present embodiment, the allowable distance La is set to zero (La = 0) as an example. For this reason, the prediction time T2 is calculated by T2 = VS / DVS.

  Then, the predicted time T2 calculated sequentially in the deceleration process of the vehicle after the engine stops reaches the time Teng required from the start to the end of the restart of the engine 12 (hereinafter referred to as “restart required time Teng”). At this point, the start of restart of the engine 12 is permitted. Specifically, the predicted time T2 until the vehicle stops decreases as the vehicle body speed VS decreases. When the restart required time Teng predetermined for each vehicle is reduced, restart of the engine 12 is started. For this reason, in this embodiment, the restart of the engine 12 is completed before the sliding distance L reaches the allowable distance La. As described above, in this embodiment, by waiting for the engine restart start timing until the vehicle body speed VS becomes as small as possible within the allowable range, it is possible to appropriately prevent the vehicle from sliding down while maintaining the fuel efficiency improvement effect. It is.

In the present embodiment, the expected engine stop possible time Tes is calculated using the above equation (2), but the following equation that takes the restart required time Teng into consideration can also be adopted.
Tes = VS / (DVS-Aet) -Teng (3)
Now, the brake ECU 55 executes an idle stop control routine every predetermined period (for example, 0.01 second period) set in advance. The idle stop control routine is shown in FIG. 3 for automatically stopping the engine 12 and FIG. 4 for restarting the engine 12 in order to automatically improve the fuel efficiency and environmental effects. An engine restart control routine. In the engine restart control in the idle stop control routine, when the operation amount of the brake pedal 15 is returned to a prescribed amount or less and the master cylinder pressure PMC becomes the prescribed pressure Px or less, the accelerator opening AP> 0 or the like. The engine 12 is restarted when a predetermined restart condition is satisfied. The engine restart control in the present embodiment further includes a slip-down prevention control that prevents the vehicle from slipping down after the vehicle stops. The engine restart control routine shown in FIG. 4 shows a control part of the engine stop control that restarts the engine 12 for slip prevention control.

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

  First, in step S11, the brake ECU 55 determines whether other idle stop conditions (IS conditions) are satisfied. If the other IS conditions are satisfied, the process proceeds to step S12. If the other IS conditions are not satisfied, the routine ends. In the present embodiment, the other IS conditions correspond to the stop control execution conditions, and the brake ECU 55 that determines whether the other IS conditions are satisfied also functions as the first determination unit. Step S11 corresponds to a first determination step.

  In step S12, the expected engine stop possible time Tes is calculated. The expected engine stop possible time Tes is calculated by the calculation formula Tes = vehicle speed VS / (DVS + Aet) shown in the equation (2).

  In the next step S13, it is determined whether or not the expected engine stop possible time Tes is equal to or longer than a set time T1 having an effect of improving fuel efficiency (that is, Tes ≧ T1). If Tes ≧ T1 is established, the process proceeds to step S15. If Tes ≧ T1 is not established, the process proceeds to step S14. In the present embodiment, the brake ECU 55 that determines the expected engine stop possible time Tes and determines whether or not Tes ≧ T1 also functions as a third determination unit. 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 stop of the engine 12 also functions as a stop control means. Step S15 corresponds to a stop control step.

  On the other hand, if Tes ≧ T1 is not established, it is determined in step S14 whether the braking acceleration Apmc is equal to or higher than the gradient acceleration Ag (Apmc ≧ Ag (threshold)). If Apmc ≧ Ag is established, it means that a braking force sufficient to prevent the sliding down without securing the engine 12 is ensured. For this reason, if Apmc ≧ Ag is established, the process proceeds to step S15 to permit the engine 12 to be stopped. 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 or not Apmc ≧ Ag also functions as a fourth determination unit. Step S14 corresponds to a fourth determination step.

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

  Next, processing when the engine 12 is stopped (Tes ≧ T1) will be described with reference to a timing chart shown in FIG. When the vehicle is running in the engine operating state, when the driver operates the brake pedal 15 at time t1, the brake switch SW1 is turned on, and the master cylinder pressure PMC increases to reach the specified pressure P1. A braking force corresponding to the master cylinder pressure PMC is applied to the wheels FR, FL, RR, RL, the vehicle decelerates, and the vehicle body speed VS becomes equal to or less than the specified speed V1. As a result, at time t2, other IS conditions are satisfied. That is, the brake switch on, master cylinder pressure PMC> specified pressure P1, and vehicle body speed VS ≦ specified speed V1 are satisfied under the AND condition.

  If the other IS conditions are satisfied, next, an expected engine stop possible time Tes is obtained, and it is determined whether or not Tes ≧ T1 is satisfied. And if Tes> = T1 is materialized, the engine 12 will be stopped from the time t2. As a result, the amount of engine torque disappears by time t3, and the vehicle body speed VS decreases along the solid line in FIG. Then, at time t4, the vehicle stops.

  During traveling of the vehicle after the engine is stopped, the brake ECU 55 executes an engine restart control routine shown in FIG. This engine restart control routine permits automatic restart of the engine 12 for the purpose of suppressing the vehicle's sliding after stopping within an allowable range when a predetermined restart condition is satisfied. It is processing of.

  The engine restart control routine shown in FIG. 4 is repeatedly executed by the brake ECU 55 at regular control cycles (for example, 0.01 seconds) during the uphill running with the engine 12 stopped.

  When this routine is started, first, in step S21, it is determined whether or not the vehicle slips after stopping (Apmc <Ag is established) by comparing the braking acceleration Apmc and the gradient acceleration Ag. . Here, when the braking acceleration Apmc is equal to or greater than the gradient acceleration Ag (Apmc ≧ Ag) and it is determined that no slippage occurs after the vehicle stops (No determination in S21), the processing of this routine is terminated as it is. In the present embodiment, the brake ECU 55 that determines whether Apmc <Ag is satisfied also functions as a second determination unit. Step S21 corresponds to a second determination step.

  On the other hand, when the braking acceleration Apmc is less than the gradient acceleration Ag (Apmc <Ag), and it is determined that the vehicle will drop after the vehicle stops (affirmative determination in S21), in the following step S22, the predicted time T2 until the vehicle stops (= VS / DVS) is calculated. In the subsequent step S23, it is determined whether or not the calculated predicted time T2 is equal to or shorter than the restart required time Teng.

  Here, if the predicted time T2 exceeds the restart required time Teng (negative determination in S23), it is not necessary to start restarting the engine 12 yet, and the current process is terminated. On the other hand, if the predicted time T2 is equal to or shorter than the restart required time Teng (Yes in S23), the restart of the engine 12 is permitted in step S24. That is, 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.

  In FIG. 6, it is determined that the master cylinder pressure PMC is relatively small as about the specified pressure P1, Apmc <Ag is established, and the vehicle is lowered after the vehicle stops. For this reason, the restart of the engine 12 is started at a time before the stop time t4 by the restart required time Teng, and the restart is completed by the stop. As a result, the vehicle does not slide down when the vehicle stops. This restart required time Teng is determined by a predetermined method so that the sliding distance L of the vehicle does not exceed a predetermined allowable distance La.

  Further, FIG. 7 shows the case where the expected engine stop possible time Tes is smaller than the set time T1 (Tes <T1), but the braking acceleration Apmc is larger than the gradient acceleration Ag, and a braking force capable of suppressing the sliding is secured. The timing chart in is shown.

  While the vehicle is running in the engine operating state, the brake pedal 15 is operated relatively strongly at time t11, the brake switch SW1 is turned on, and the master cylinder pressure PMC rises to exceed the specified pressure P1 to the predetermined pressure P2. Reach. As a result, the vehicle decelerates, and at time t12, when other IS conditions are satisfied, the next expected engine stoppage time Tes (= VS / (DVS + Aet) is calculated, and it is determined whether or not Tes> T1 is satisfied. In the example of Fig. 7, the expected engine stop possible time Tes is shorter than the set time T1, and Tes> T1 is not established.

  However, since the braking acceleration Apmc is larger than the gradient acceleration Ag and a braking force sufficient to prevent the sliding is ensured, it is not necessary to restart the engine 12 for the purpose of preventing the sliding. For this reason, the stop of the engine 12 is permitted at the time t13 when Apmc> Ag is established. As a result, the engine rotation speed is gradually reduced to zero from time t13. When the engine speed becomes zero (time 14), the engine torque is lost. For this reason, the actual vehicle speed VS decreases along the solid line in FIG. 7 as expected. Since the relatively strong braking force is ensured when the vehicle stops at time t15, the vehicle does not slip down even if the engine 12 is not restarted.

  Further, 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 running in the engine operating state, the brake switch SW1 is turned on and the master cylinder pressure PMC rises to reach the specified pressure P1. As a result, when other IS conditions are satisfied at time t22 when the vehicle decelerates and the vehicle body speed VS becomes equal to or less than the specified speed V1, the next expected engine stoppage time Tes (= VS / (DVS + Aet)) is calculated. , Tes> T1 is determined. In the example of FIG. 8, the estimated engine stop possible time Tes assuming that the vehicle body speed VS decreases along the speed profile indicated by the two-dot chain line where the acceleration Aet corresponding to the engine torque disappears and stops at time t24 is used. Thus, it is determined whether Tes> T1 is satisfied. In the example of FIG. 8, since Tes> T1 is not established, the fuel efficiency improvement effect cannot be obtained even when the engine 12 is stopped.

  Further, since the master cylinder pressure PMC is relatively small as about the specified pressure P1, and the braking acceleration Apmc is smaller than the gradient acceleration Ag, the braking force that can suppress the sliding is not ensured. For this reason, creep torque is required to prevent the vehicle from sliding down after stopping. Therefore, the engine 12 is not stopped. Since the acceleration Aet corresponding to the engine torque does not disappear, the actual vehicle speed VS decreases along the solid line in FIG. And since creep torque is given by the engine 12 which has continued driving | running | working after a stop, the fall of a vehicle does not generate | occur | produce. However, if the road slope θ of the uphill road is quite large and the force Fg of the gravity gradient component acting on the vehicle exceeds the sum of the creep torque and the braking force by the brake operation, the vehicle may slowly fall after stopping. It can happen. In this case, since the sliding speed is slow, the driver further depresses the brake pedal 15 with a comparative margin to prevent the vehicle from further sliding down.

According to the vehicle control apparatus of the present embodiment described above, the following effects can be obtained.
(1) The brake ECU 55 that automatically stops and restarts the engine 12 until other IS conditions are satisfied, until the engine 12 is restarted for the purpose of preventing slippage after the engine stops. It is determined whether the fuel saving amount Fd that can be saved in the engine stop period (idle stop time) is equal to or greater than the fuel consumption amount Fst required for restarting the engine 12. If the fuel saving amount Fd is equal to or greater than the fuel consumption amount Fst, the brake ECU 55 permits the engine 12 to stop. For this reason, when only the engine stop period in which the fuel consumption amount Fst is larger than the fuel saving amount Fd can be ensured, the engine 12 is not allowed to stop. it can.

  (2) When the other IS conditions are satisfied, the brake ECU 55 stops the engine, which is an expected value of the engine stop period from the time when the engine is stopped to the restart of the engine 12 for the purpose of preventing the sliding after the vehicle stops. The possible expected time Tes is calculated, and it is determined whether or not the expected engine stop possible time Tes is equal to or longer than the set time T1. That is, instead of directly comparing the fuel saving amount Fd and the fuel consumption amount Fst, these values Fd and Fst are used as the time corresponding to the idle time using the fuel consumption amount Fid per unit time in the idle state of the engine 12. The estimated engine stop possible time Tes and the set time T1 respectively converted into the above are compared. Therefore, without obtaining the fuel saving amount Fd and the fuel consumption amount Fst, the fuel saving amount Fd is equal to or greater than the fuel consumption amount Fst by using the estimated time Tes that can be stopped and the set time T1 as these time converted values. This can be determined indirectly. Therefore, it is possible to make a determination by a relatively simple process using the expected engine stop possible time Tes that can be obtained by calculation 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 master cylinder pressure corresponding to the gradient acceleration Ag corresponding to the force Fg of the gradient component of gravity acting on the vehicle and the operation amount (stepping amount) of the brake pedal 15 The braking acceleration Apmc determined from the PMC is compared, and if Apmc ≧ Ag is established, it is determined that no sliding occurs after the vehicle stops, and the engine 12 is allowed to stop. That is, the engine 12 is allowed to stop when a braking force that can resist the force Fg of the gravity gradient component acting on the vehicle when the vehicle is stopped is obtained. Therefore, it is possible to increase the frequency of idle stop and obtain further fuel efficiency improvement effect.

  (4) If the expected engine stop possible time Tes is less than the set time T1 and a braking force sufficient to prevent the vehicle from slipping down after stopping is not secured (Apmc ≧ Ag is not established), the engine 12 is not allowed to stop. Therefore, the fuel consumption Fst for restarting the engine 12 is larger than the fuel saving amount Fd that can be saved in the idle stop time just after the engine 12 is stopped. Aggravate and avoid the situation as much as possible.

  (5) When it is determined that there is a possibility of slippage (Apmc <Ag), the engine 12 is restarted to be completed before the vehicle stops. More specifically, when it is predicted that the vehicle will slide down, the engine 12 is restarted when the predicted time T2 until the vehicle stops reaches the restart required time Teng. For this reason, the vehicle does not slide down after the vehicle stops, and the vehicle can be suitably prevented from sliding down on the uphill road.

  (6) The determination as to whether or not a slip occurs after the vehicle stops is made by determining whether the braking acceleration Apmc is determined from the master cylinder pressure PMC corresponding to the operation amount (stepping amount) of the brake pedal 15, the vehicle acceleration G, and the vehicle speed differential value DVS. The gradient acceleration Ag determined from the difference between the two is used. When the gradient acceleration Ag exceeds the braking acceleration Apmc, it is determined that the vehicle slips. Therefore, it is possible to accurately determine whether or not it is necessary to restart the engine 12 for the purpose of preventing the vehicle from sliding down.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the fuel saving amount Fd and the set value F1 corresponding to the fuel consumption amount Fc are respectively compared with the estimated engine stop possible time Tes converted into the idle time and the set time T1, but the fuel saving amount Fd And the set value F1 may be compared to determine whether or not Fd ≧ F1 is satisfied. In this case, the amount of fuel consumed per unit time by the fuel injection device having an injector for injecting fuel into the combustion chamber of the engine 12 is multiplied by the engine stop time from the stop of the engine 12 to the restart thereof. Thus, the fuel saving amount Fd is calculated. Further, a set value F1 corresponding to the actual fuel consumption Fc acquired at the time of starting the engine is stored in the memory of the brake ECU 55. Then, the brake ECU 55 functioning as the third determination unit is configured to determine whether or not the fuel saving amount Fd acquired 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 (in the above embodiment, when Tes = T1), the engine 12 is allowed to stop, but the engine may not be allowed to stop. Good. That is, it is sufficient if the engine 12 is not permitted to stop at least when the fuel consumption is deteriorated. Further, an allowable amount α is set for the fuel consumption amount Fc, or an allowable time Tα corresponding to the allowable amount α is set for the expected engine stoppage time Tes, and the third determination means is Fd ≧ Fc + Fα or Tes ≧ It is good also as a structure which determines establishment of T1 + T (alpha). 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 means may be Fd ≧ Fc−Fα or Tes ≧ T1−Tα. In short, the set value may be a value set in accordance with the fuel consumption at the time of restarting the engine, and may be a value in consideration of a predetermined allowable value for the fuel consumption and its conversion time.

  In the above-described embodiment, the braking acceleration Apmc and the gradient acceleration Ag (threshold) are compared in the determination of the sliding down, but the force Fg (the vehicle front-rear direction component (road surface direction component)) of the braking force and the gravity acting on the vehicle. Threshold value) or a master cylinder pressure conversion value (threshold value) of the master cylinder pressure PMC and the force Fg may be compared.

  In a vehicle including a 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. In the memory of the brake ECU 55, for example, a map (not shown) indicating a correspondence relationship between the master cylinder pressure PMC and the braking acceleration Apmc (or the braking force Fpmc) is stored. The brake ECU 55 obtains the braking acceleration Apmc (or braking force Fpmc) with reference to the map based on the master cylinder pressure PMC, and compares the braking acceleration Apmc with the gradient acceleration Ag (or the braking force Fpmc and the force Fg). It may be configured to determine the presence or absence of sliding down by comparison.

-If the vehicle is stopped on an uphill road, the vehicle may be allowed to slip slightly. That is, the allowable distance La is set to La ≧ 0, and the engine 12 is restarted while the sliding distance L is within the allowable distance La. It is determined whether or not the vehicle after the vehicle stops slipping during climbing while the engine 12 is stopped, and when it is predicted that the vehicle will slip down, the vehicle slipping distance L is the allowable distance La (≧ 0). The engine 12 is restarted so as to be completed by the time of exceeding. More specifically, the time Ta until the vehicle stops when traveling uphill while the engine is stopped, and the time Tb from when the vehicle stops until the vehicle sliding distance L becomes the allowable distance La are obtained. Then, the brake ECU 55 permits the restart of the engine 12 when the predicted time T2 represented by the sum of the time Ta and the time Tb reaches the restart required time Teng. Further, a larger value may be set for the allowable distance La as the road surface gradient θ increases. For example, the allowable distance La is set to “0” until the road surface gradient θ reaches a constant value, and after the road surface gradient θ exceeds the predetermined value, the allowable distance La increases as the road surface gradient θ increases. (Allowable distance La in the embodiment). In addition, when these structures are employ | adopted, it is preferable to calculate the engine stop possibility estimated time Tes by following Formula.
Tes = VS / (DVS + Aet) + Tb−Teng (4)
In the present embodiment, the engine 12 is restarted to apply creep torque to the braking force, thereby preventing the vehicle from sliding down. In this case, when the road surface gradient θ is large and the gradient acceleration Ag is larger than the sum of the creep acceleration Ac and the braking acceleration Apmc due to the creep torque (Ac + Apmc <Ag), a slip occurs. Therefore, when Ac + Apmc <Ag is established, a configuration in which brake pressurization is performed to prevent sliding down can be employed. Specifically, when Ac + Apmc <Ag is established, the motor 41 is driven to drive the pumps 42 and 43, and the linear electromagnetic valves 35a and 35b are supplied with current at a current value corresponding to the magnitude of the gradient acceleration Ag. The brake pressure is applied by increasing the wheel cylinder pressure PWC to the control target value. Thereafter, a current value that can maintain the brake pressure at the control target pressure is supplied to the linear electromagnetic valves 35a and 35b. According to this configuration, even when the road surface gradient θ is large and the creep torque cannot be prevented simply by applying the creep torque, the vehicle can be stopped without sliding down the uphill road.

  In the above-described embodiment, when the rearward acceleration Ag generated by gravity exceeds the braking acceleration Apmc of the vehicle, it is determined whether or not the vehicle slips down. Such a determination can be made on the assumption that the vehicle slips down when the force Fg, which is the component of gravity behind the vehicle acting on the vehicle, exceeds the braking force Fpmc of the vehicle.

  In the above-described embodiment, whether or not the vehicle slips after stopping based on the braking acceleration Apmc determined from the master cylinder pressure PMC corresponding to the operating force (depressing force) of the brake pedal 15 and the detection result of the vehicle body acceleration G is determined. I was going to judge. Similar determinations can be made based on other detection values. For example, it is possible to check the braking force or braking acceleration of the vehicle by using the detected value of the operation amount (depressing amount) of the brake pedal 15 instead of the detected value of the master cylinder pressure PMC. In this case, a sensor for detecting the depression amount of the brake pedal 15 is provided in the vehicle. Further, the acceleration due to the brake can be confirmed by removing the acceleration generated by the engine due to the vehicle body acceleration G, the acceleration due to the rolling resistance, the acceleration due to the road surface gradient, the air resistance, and the like. It is also possible to provide a sensor for detecting the pitch of the vehicle body and grasp the road surface gradient θ from the sensor to make the above determination.

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

  In the above-described embodiment, the case where the control device of the present invention is applied to a vehicle in which a disc brake device is provided on each wheel has been described. However, in the present invention, a drum brake device is provided on some or all of the wheels. The same applies to vehicles.

  The vehicle is not limited to a two-wheel drive vehicle, and the control device of the present invention can be similarly applied to a vehicle of another drive system such as a four-wheel drive vehicle.

  DESCRIPTION OF SYMBOLS 12 ... Engine, 15 ... Brake pedal which is an example of brake operation means, 17 Engine ECU, 18 ... Automatic transmission, 20a ... Torque converter, 25 ... Master cylinder, 26 ... Booster, 31 ... Brake actuator, 32a-32d ... Wheel cylinder, 55... First determination means, second determination means, third determination means, fourth determination means, brake ECU as an example of stop control means and restart control means, 60. Audio as an example, 61 ... Temperature adjustment device as an example of a comfort device, FR, FL, RR, RL ... Wheel, SE1 ... Accelerator opening sensor, SW1 ... Brake switch, SE2 ... Pressure sensor, SE3-SE6 ... Vehicle speed detection Wheel speed sensor, which is an example of means, SE7 ... acceleration sensor, Tes ... engine expected stop time, DESCRIPTION OF SYMBOLS 1 ... Setting time which is an example of setting value, (theta) ... Road surface gradient, L ... Slipping distance, La ... Allowable distance, VS ... Vehicle body speed, DVS ... Vehicle body speed differential value, Ag ... Gradient acceleration, Fpmc ... Braking force, Apmc ... braking acceleration, Aet ... engine torque acceleration, Fd ... fuel saving, Fst ... fuel consumption, F1 ... set value, Teng ... time required for restart.

Claims (5)

A vehicle control device that performs stop control for automatically stopping a vehicle engine (12) and restart control for automatically restarting the engine (12),
First determination means (55, S11) for determining whether or not an execution condition for the stop control is satisfied;
A stop control means (55, S15) that permits the engine (12) to stop when it is determined that the execution condition of the stop control is satisfied;
Second judging means (55, S21) for judging whether or not the vehicle slips after stopping when traveling on a slope with the engine (12) stopped;
When it is determined that the slip occurs, the engine (12) is automatically restarted so that the restart of the engine (12) is completed before the vehicle slip distance (L) exceeds the allowable distance (La). Restart control means (55) for allowing start of restart;
It is assumed that when the engine (12) is stopped because the execution condition of the stop control is satisfied during the deceleration of the vehicle, the engine (12) is automatically restarted in order to suppress the sliding after the vehicle stops. The time point when the execution condition of the stop control is satisfied is defined as a first time point, the vehicle stop time calculated based on the vehicle body speed (VS) at the first time point is defined as a second time point, and the engine (12 ) Is stopped , a fuel saving amount (Tes) that can be saved in an engine stop period that is a period between the first time point and the second time point is predicted, and the fuel saving amount (Tes) is Third determining means (55, S12, S13) for determining whether or not the fuel consumption amount required for restarting the engine (12) is equal to or greater than a set value (T1).
When it is determined that the fuel saving amount (Tes) is less than the set value (T1), the stop control means (55) stops the engine (12) even if the stop control execution condition is satisfied. The vehicle control device is characterized by not permitting. A vehicle control device that performs stop control for automatically stopping a vehicle engine (12) and restart control for automatically restarting the engine (12),
First determination means (55, S11) for determining whether or not an execution condition for the stop control is satisfied;
A stop control means (55, S15) that permits the engine (12) to stop when it is determined that the execution condition of the stop control is satisfied;
Second judging means (55, S21) for judging whether or not the vehicle slips after stopping when traveling on a slope with the engine (12) stopped;
When it is determined that the slip occurs, the engine (12) is automatically restarted so that the restart of the engine (12) is completed before the vehicle slip distance (L) exceeds the allowable distance (La). Restart control means (55) for allowing start of restart;
It is assumed that when the engine (12) is stopped because the execution condition of the stop control is satisfied during the deceleration of the vehicle, the engine (12) is automatically restarted in order to suppress the sliding after the vehicle stops. The time point when the execution condition of the stop control is satisfied is a first time point, and the engine (12) needs to be restarted more than the vehicle stop time calculated based on the vehicle body speed (VS) at the first time point. A fuel that can be saved in an engine stop period that is a period between the first time point and the second time point before the engine (12) is stopped , with a time point before time (Teng) as the second time point. A saving amount (Tes) is predicted, and it is determined whether or not the fuel saving amount (Tes) is equal to or greater than a set value (T1) set according to the fuel consumption required for the restart of the engine (12). Third determining means 55, S12, S13 and) comprises,
When it is determined that the fuel saving amount (Tes) is less than the set value (T1), the stop control means (55) stops the engine (12) even if the stop control execution condition is satisfied. The vehicle control device is characterized by not permitting. Fourth determination means (55, S14) for determining whether or not the braking force (Apmc) corresponding to the operation amount of the brake operation means (15) is secured to a threshold (Ag) or more that can suppress the slippage after stopping. Further comprising
The stop control means (55) determines that the fuel saving amount (Tes) is less than the set value (T1) when it is determined that the braking force (Apmc) is secured to the threshold value (Ag) or more. 3. The vehicle control device according to claim 1, wherein the engine is allowed to stop even if the engine is stopped. 4. The third determination means (55, S12, S13)
The time until the second time and the engine stop predictable time (Tes) from the first time point,
The determination as to whether or not the fuel saving amount is equal to or greater than the set value is based on whether or not the expected engine stoppage possible time (Tes) is equal to or greater than a set time (T1) obtained by converting the set value to an idle time of the engine (12). The vehicle control device according to any one of claims 1 to 3, wherein the vehicle control device is performed by determining whether or not there is. The third determination means (55) calculates the vehicle body speed (VS) detected by the vehicle speed detection means (SE3 to SE6) and the vehicle body speed differential value (DVS) obtained by differentiating the vehicle body speed (VS) with respect to time. Acquired,
The expected engine stoppage time (Tes) is obtained by dividing the vehicle body speed ( VS ) by a value obtained by subtracting the acceleration (Aet) corresponding to the engine torque that disappears due to the engine stop from the vehicle body speed differential value (DVS). The vehicle control device according to claim 4 , wherein the vehicle control device is a value corresponding to a calculated value obtained by the following.

Images