WO2012043641A1

WO2012043641A1 - Vehicle control device and control method

Info

Publication number: WO2012043641A1
Application number: PCT/JP2011/072209
Authority: WO
Inventors: 陽介橋本; 陽介大森; 雪生森; 政義武田
Original assignee: 株式会社アドヴィックス
Priority date: 2010-09-29
Filing date: 2011-09-28
Publication date: 2012-04-05
Also published as: JP5621479B2; CN103124661B; DE112011103322T5; CN103124661A; JP2012071790A; DE112011103322B4

Abstract

This vehicle control device, which performs stopping control for automatically stopping the engine (12) of the vehicle and restarting control for automatically restarting the engine (12), has: electric motors (41, 35a, 35b) that, by means of electric power, increase the braking force applied to vehicle wheels (FR, FL, RR, RL) by braking devices (32a-32d); a braking control unit (55, S18, S22) that, by controlling the electric motors (41, 35a, 35b), performs vehicle-stoppage-maintaining control that increases braking force together with the stopping of the vehicle while the engine (12) is in a stopped state; and a determination unit (55, S15) that determines whether or not the driver intends to depart on the basis of the detection results of a detector (SW1) of a driving operation system provided to the vehicle. When the determination unit (55, S15) has determined that there is an intention to depart, the braking control unit (55, S18, S22) controls the electric motors (41, 35a, 35b) in a manner so as to increase braking force within an electrical power range that does not hinder the restarting of the engine (12), and meanwhile, when the determination unit (55, S15) has determined that there is no intention to depart, the braking control unit (55, S18, S22) controls the electric motors (41, 35a, 35b) in a manner so as to increase braking force prioritizing maintenance of vehicle stoppage over restarting of the engine (12).

Description

Vehicle control apparatus and control method

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

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, there has also been proposed a device for stopping an engine during deceleration of a vehicle before stopping.

Conventionally, as described in Patent Document 1, when the brake depression amount is the first predetermined value S1, it is predicted that the driver will stop the vehicle, and a quick stop process of engine rotation is performed, In this process or when the amount of brake depression is reduced to a value equal to or less than the second predetermined value S2 after stopping the rotation, the driver predicts that the vehicle will be accelerated again and restarts the fuel supply, and the starter motor There has been proposed a vehicle control apparatus that operates the engine to rotate the engine at a predetermined rotational speed or more.

JP 2009-63001 A

By the way, in an AT vehicle equipped with an automatic transmission with a torque converter, thrust in the forward direction of the vehicle due to a creep phenomenon is generated even when the engine is idle. Note that the creep phenomenon is a phenomenon in an AT vehicle where the vehicle slowly moves forward even if the accelerator pedal is not depressed when the shift lever is in the traveling position. 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 amount of brake depression. 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 Patent Document 1, when the amount of stepping on the brake is equal to or less than the second predetermined value S2, the engine is allowed to start. Therefore, when the brake is loosened to near zero on the uphill road, the engine may be started. In this case, if the engine cannot be started before the vehicle stops, the vehicle cannot be maintained in a stopped state on the slope with only the reduced braking force (braking force), and the vehicle may slide down.

In this case, it is effective to perform stop maintenance control to pressurize the brake and maintain the vehicle in a stopped state. However, if engine restart and brake pressurization overlap, power consumption increases, so engine restart and brake There is a problem that both pressures cannot function sufficiently.

One of the objects of the present invention is that, in a vehicle that automatically stops and restarts an engine, even when the timing when the stop maintenance control should be performed and the timing when the engine should be restarted overlap at least partially, It is an object of the present invention to provide a control device and a control method for a vehicle that can effectively balance engine restart and increase in braking force while respecting a person's intention to start.

In the first aspect of the present invention, there is provided a vehicle control apparatus that performs stop control for automatically stopping a vehicle engine (12) and restart control for automatically restarting the engine (12). Provided. The control device includes an electric motor (41, 35a, 35b) that increases the braking force applied by the braking device (32a to 32d) to the vehicle wheels (FR, FL, RR, RL) by electric power, and the engine (12 A braking control section (55, S18, S22) for controlling the electric motor (41, 35a, 35b) to perform stop maintenance control for increasing the braking force in accordance with the stopping of the vehicle in the stop state of And a determination unit (55, S15) for determining whether or not the driver has an intention to start based on the detection result of the driving operation system detector (SW1) provided in the braking control unit (55). , S18, S22), when the determination unit (55, S15) determines that there is an intention to start, the braking force is increased so that the braking force is increased within a power range that does not hinder the restart of the engine (12). Electric motor (41, 35a, 5b), on the other hand, if the determination unit (55, S15) determines that there is no intention to start, an increase in braking force giving priority to vehicle stoppage maintenance over restart of the engine (12) is performed. The electric motors (41, 35a, 35b) are controlled to perform.

A second determination unit (55, S12) that determines whether or not the braking force (Apmc) before the increase is less than the force (Ag) corresponding to gravity acting in the front-rear direction of the vehicle according to the road surface gradient (θ). ), And the braking control unit (55, S18, S22) performs the stop maintenance control when the braking force (Apmc) before the increase is less than the force corresponding to the gravity (Ag). However, when the braking force (Apmc) before the increase is equal to or greater than the force corresponding to the gravity (Ag), it is preferable not to perform the stop maintenance control.

When the determination unit (55, S15) determines that there is no intention to start, the braking control unit (55, S18, S22) increases the braking force giving priority to maintaining the stop of the vehicle. , 35a, 35b), and after the braking force by the electric motor (41, 35a, 35b) has increased, it is preferable to allow the engine (12) to restart.

The brake control unit (55, S18, S22) supplies electric power supplied to the electric motor (41, 35a, 35b) for increasing the braking force when the engine (12) is restarted. ) Is preferably set to be equal to or less than the remaining power consumed.

The braking controller (55, S18, S22) increases the braking force at a time at least avoiding a current peak generation time (PT) in the initial driving of the electric motor (72) that restarts the engine (12). It is preferable to supply electric power for the electric motor (41, 35a, 35b).

In the second aspect of the present invention, there is provided a vehicle control method for performing stop control for automatically stopping the engine (12) of the vehicle and restart control for automatically restarting the engine (12). Provided. The method controls the electric motors (41, 35a, 35b) that increase the braking force applied to the vehicle wheels (FR, FL, RR, RL) by the braking devices (32a to 32d) by electric power, and A braking control step (55, S18, S22) for performing stop maintenance control for increasing the braking force in accordance with the stopping of the vehicle in a stopped state of the engine (12), and reactivation while the engine (12) is stopped. A determination step (55, S15) for determining whether or not the driver is willing to start based on a detection result of a driving operation system detector (SW1) provided in the vehicle when the start request is received; The braking control step (55, S18, S22) starts in the determination step (55, S15) when the restart request is accepted when the start condition of the stop maintenance control is satisfied. If it is determined that there is an intention, the electric motor (41, 35a, 35b) is controlled to increase the braking force within a power range that does not hinder the restart of the engine (12), while the determination step ( 55, S15), when it is determined that there is no intention to start, the electric motors (41, 35a, 35b) increase the braking force with priority given to maintaining the stop of the vehicle rather than restarting the engine (12). ) To control.

The block diagram which shows an example of the vehicle carrying the control apparatus of one Embodiment. The block diagram which shows an example of a braking device. The schematic side view which shows the force which acts on the vehicle which stops on an uphill road. The map which shows the relationship between a gradient acceleration and the electric current value with respect to a linear solenoid valve. The flowchart which shows the principal part of a stop maintenance / restart control routine. The flowchart (part) which shows a part of stop maintenance / restart control routine. The flowchart which shows an engine stop control routine. The timing chart explaining normal sliding prevention control. The timing chart explaining the stop maintenance / restart control when there is an intention to start. The timing chart which shows stop maintenance / restart control when there is no start intention. The drive power of a pump motor and a starter motor is shown, (a) a graph when there is an intention to start, (b) a graph when there is no intention to start.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS. In the following description in the present specification, the traveling direction of the vehicle will be described as the front.

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 also has an audio 60 (including a navigation device) as an example of comfort equipment, a temperature adjustment device 61 as an example of comfort equipment, and a braking force according to the amount of operation of the brake pedal 15 by the driver. A braking device 16 is provided for applying to each wheel FR, FL, RR, RL.

The driving force generator 13 includes an intake pipe 70 that extends outward from the engine 12 and a throttle valve 71 that is disposed in the intake pipe 70 and that changes the sectional area of the opening. The throttle valve 71 is operated by a driving force generated by an actuator (not shown). A fuel injection device (not shown) having an injector for injecting fuel is provided near the intake port (not shown) of the engine 12. Further, the driving force generator 13 is provided with a starter motor 72 as an example of an electric motor that operates when the engine 12 is started.

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

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

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

The audio 60 is a device for providing information such as music according to the operation by the vehicle occupant to the occupant. Such audio 60 operates based on electric power supplied from a battery (not shown) mounted on the vehicle.

The temperature adjusting device 61 is an air conditioner for adjusting the temperature inside the vehicle. The temperature adjusting device 61 includes a compressor 62 that operates based on a driving force generated by the engine 12 and a contact / disconnection mechanism 63 that is disposed on a power transmission path between the engine 12 and the compressor 62. The contact / disconnection mechanism 63 is a mechanism that operates to permit transmission or disconnection of the driving force to the compressor 62. That is, the compressor 62 operates when the driving force generated in the engine 12 is transmitted through the contact / disconnection mechanism 63.

The audio 60 and the temperature adjusting device 61 are controlled by an idle stop ECU 65 (also referred to as “idle stop electronic control device”) having a CPU, a ROM, a RAM, and the like (not shown). More specifically, the idle stop ECU 65 controls the amount of power supplied from the battery to the audio 60 and controls the connection / disconnection mechanism 63.

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 cylinder 32b for the left front wheel FL is connected to the second hydraulic circuit 30. The wheel cylinder 32c for the right rear wheel RR is connected.

In the hydraulic pressure generator 28, the booster 26 is connected to an intake manifold 70 a 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 70a and the atmospheric pressure to assist the operating force of the brake pedal 15 by the driver.

The master cylinder 25 generates a master cylinder pressure PMC corresponding 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, 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, 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 master pressure sensor SE8 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. The master pressure sensor SE8 outputs a detection signal having a value corresponding to the master cylinder pressure PMC to the brake ECU 55.

The

pressure increasing valves

37a, 37b, 37c, 37d made of normally open solenoid valves are provided in the middle of the pipes 36a-36d branched from the

pipes

33, 34 connected to the master cylinder 25 and connected to the wheel cylinders 32a-32d. And pressure-reducing

valves

38a, 38b, 38c, and 38d that are normally closed solenoid valves. 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 pump motor 41. , 43 are 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 pump 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

pipelines

44, 45, 46, and 47, and the sucked brake fluid is fed into the

pipelines

48 and 48. It discharges to 49.

Now, in such a vehicle, when the engine 12 is operated when stopping on an uphill road, a torque due to a creep phenomenon, that is, a creep torque acts, so that the creep torque is used to resist the vehicle from descending. be able to. On the other hand, if the engine 12 is stopped at the time of stopping on the uphill road, the creep torque does not act. Therefore, if the brake pedal 15 is not depressed firmly, the vehicle will slide down the slope.

Therefore, in the present embodiment, “sliding prediction determination” is performed to determine (predict) whether or not the vehicle will slide down after stopping when the engine 12 is traveling uphill. When it is determined that the slippage occurs, the brake is applied so that the control target pressure that can resist the slippage is applied within the range of the vehicle slippage distance “0” or “allowable distance Lp”. Start pressure control. For example, when the amount of depression of the brake pedal 15 is small, and it is predicted that the vehicle will slide down due to the road surface gradient after stopping, the brake pressurization is performed before the vehicle slides down.

Of course, when the engine 12 is restarted, the creep torque acts, so that the vehicle can be stopped against the road surface gradient even with a relatively small amount of brake depression. However, the number of engine restarts increases, and the fuel efficiency improvement effect due to idling stop of the engine 12 decreases. Therefore, in this embodiment, even if such engine restart is not performed, a relatively high fuel efficiency improvement effect is expected by preventing “sliding down” by pressurizing the brake. Therefore, in the vehicle control apparatus according to the present embodiment, the vehicle is preferably prevented from sliding down when stopping on an uphill road.

By the way, there is a case in which the brake pressurization performed to prevent the slippage when the vehicle is stopped and the engine restart that is started when the driver sets the depression amount of the brake pedal 15 to less than a predetermined value overlap in timing. . The engine is restarted by driving a starter motor 72 mounted on the vehicle. The brake pressurization is performed by driving the pump motor 41 and the linear

electromagnetic valves

35a and 35b.

When the timings of brake pressurization and engine restart are overlapped, there is a concern that both the starter motor 72 and the pump motor 41 will be short of supply power and neither engine restart nor brake pressurization will be performed properly. Therefore, in the present embodiment, when the engine is stopped, the execution timing of brake pressurization for preventing slip-down and engine restart is suitably adjusted.

Next, the brake ECU 55 (also referred to as “brake electronic control device”) that controls the drive of the brake actuator 31 will be described.

As shown in FIG. 2, wheel speed sensors SE3, SE4, SE5, SE6 for detecting the wheel speed of each wheel FR, FL, RR, RL are provided on the input side interface of the brake ECU 55 as a braking control unit. An acceleration sensor (also referred to as “G sensor”) SE7 for detecting acceleration in the longitudinal direction of the vehicle is electrically connected. Also, a brake switch SW1 and a master pressure sensor SE8 that are disposed in the vicinity of the brake pedal 15 and detect whether or not the brake pedal 15 is operated are electrically connected to the input side interface of the brake ECU 55. Has been. The

valves

35a, 35b, 37a to 37d, 38a to 38d, the pump motor 41, and the like are electrically connected to the output side interface of the brake ECU 55. The acceleration sensor SE7 outputs a signal that takes a positive value when the center of gravity of the vehicle moves backward, and a signal that takes a negative value when the center of gravity of the vehicle moves forward. Is output.

The brake ECU 55 includes a digital computer composed of 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 a pump motor. A motor driver circuit (not shown) for operating 41 is provided. The ROM of the digital computer stores various control processing (such as idle stop processing described later) programs, various maps (such as the map shown in FIG. 4), and various threshold values. The RAM also stores various types of information that can be appropriately rewritten while an ignition switch (not shown) of the vehicle is on.

FIG. 3 shows the relationship of the force 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 component of gravity g acting on the vehicle in the vehicle rearward direction, and changes according to the road surface gradient θ.

Further, as shown in FIG. 3, 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 in a stopped state, the force Fg and the braking force Fpmc are compared, and if Fg> Fpmc, 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. . The gradient acceleration Ag is calculated based on the detection signal from the acceleration sensor SE7.

In addition, when performing vehicle slip-down prevention control, it is necessary to acquire the gradient acceleration Ag used for the determination of the presence or absence of slip-down before stopping (during driving | running | working). In the present embodiment, a vehicle body speed differential value DVS (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 of the acceleration sensor SE7. The gradient acceleration Ag is calculated by subtracting (corresponding to the traveling acceleration).

Also, in the slip prevention control, it is necessary to acquire the braking force of the vehicle before the vehicle stops. 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. Accordingly, in the present embodiment, focusing on 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. Is done. This braking acceleration Apmc corresponds to an acceleration obtained by dividing the braking force Fpmc by the vehicle body weight M when a braking force Fpmc corresponding to the master cylinder pressure PMC is applied to the wheel. Specifically, the braking acceleration Apmc is obtained by removing the creep acceleration Ac, which is an acceleration component corresponding to creep torque, the running resistance acceleration Ar, which is an acceleration component corresponding to running resistance, and the gradient acceleration Ag, from the vehicle body acceleration G. Calculated (Apmc = G−Ac + Ar + 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, brake pressurization is performed to prevent the vehicle from sliding down. The brake pressurization is performed by controlling the current value supplied to the linear

electromagnetic valves

35a and 35b to adjust the wheel cylinder pressure PWC to the control target pressure P1 (see FIGS. 8 to 10) that can prevent the sliding down. Do. For this reason, in order to adjust the wheel cylinder pressure PWC to the control target pressure P1, the current value to be supplied to the linear

electromagnetic valves

35a and 35b needs to be changed to a value corresponding to the road surface gradient θ, that is, the force Fg acting backward of the vehicle. There is. In this example, acceleration toward the rear of the vehicle obtained by dividing the force Fg by the vehicle body weight M is defined as a gradient acceleration Ag. A gradient acceleration Ag is calculated based on a detection signal from the acceleration sensor SE7, and a current value corresponding to the gradient acceleration Ag is given to the linear

electromagnetic valves

35a and 35b.

Next, various maps stored in the ROM of the brake ECU 55 will be described with reference to FIG.

4 shows the relationship between the absolute value of the gradient acceleration Ag and the current value I for the linear

electromagnetic valves

35a and 35b. The “gradient acceleration Ag” is the vehicle acceleration G calculated based on the detection signal of the acceleration sensor SE7 or a value corresponding to the vehicle acceleration G when the vehicle is stopped on a slope with a road surface gradient θ (that is, the traveling acceleration is zero). It is. The “current value I for the

linear solenoid valves

35a and 35b” is the minimum braking force required to maintain the vehicle stopped when the driving force from the engine 12 is not transmitted to the front wheels FR and FL. This is a value obtained by adding an offset value α to the current value Ix necessary for giving to each wheel FR, FL, RR, RL. Therefore, as shown in FIG. 3, the current value I for the linear

electromagnetic valves

35a and 35b is set to a larger value as the absolute value of the gradient acceleration Ag is larger.

In the vehicle of the present embodiment, the ECUs including the engine ECU 17, the brake ECU 55, and the idle stop ECU 65 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. Has been. For example, information related to the accelerator opening of the accelerator pedal 11 and various requests are appropriately transmitted from the engine ECU 17 to the brake ECU 55. On the other hand, from the brake ECU 55, a stop command for permitting automatic stop of the engine 12, a restart command for permitting automatic restart of the engine 12, and the like are transmitted to the engine ECU 17. Further, the idle stop ECU 65 transmits information related to the audio 60 and the temperature adjustment device 61 to the engine ECU 17 and the brake ECU 55. This information includes information on the power being supplied to the audio 60 and the temperature adjustment device 61, that is, power supply information.

Now, the brake ECU 55 executes an idle stop control routine every predetermined period (for example, 0.01 second period) set in advance. In this idle stop control routine, an engine stop control routine (FIG. 7) for automatically stopping the engine 12 and an engine restart control for automatically restarting the engine 12 in anticipation of fuel efficiency improvement and environmental effects. And a vehicle stop maintenance / restart control routine (a part of FIGS. 5 and 6) including a sliding prevention control. The slip-down prevention control is a control for preventing vehicle slip-down by increasing the braking force by applying brake pressure before the vehicle stops in the engine stop state after the engine is automatically stopped. The slip-down prevention includes each control of brake pressurization for increasing the wheel cylinder pressure PWC to the control target pressure P1, and brake holding for maintaining the wheel cylinder pressure PWC at the control target pressure P1 until the engine is restarted.

First, the engine stop control routine will be described with reference to FIG.

In step S101, it is determined whether or not an idle stop condition is satisfied while the vehicle is traveling. In the present embodiment, the idle stop condition is that the vehicle body speed VS is in a low speed range that is equal to or less than the vehicle speed threshold value V1 (for example, 20 km / h) (VS ≦ V1), the brake pedal 15 is operated, and the brake switch SW1 is turned on. And the condition that the master cylinder pressure PMC is equal to or higher than the specified pressure Ps (PMC ≧ Ps).

When the idle stop condition is satisfied because these conditions are satisfied under the AND condition, the brake ECU 55 permits the engine 12 to stop in step S102. That is, the brake ECU 55 sends a stop command to the engine ECU 17. The engine ECU 17 stops the engine 12 when receiving the stop command. On the other hand, if the idle stop condition is not satisfied in step S101, the routine is terminated.

8 to 10 show timing charts when the idle stop control is performed. Each figure shows idle stop control performed when the vehicle is traveling on an uphill road. The vehicle speed VS, the engine rotation speed, the brake system hydraulic pressure, the slip prediction prediction, the current of the pump motor 41, the linear electromagnetic The transition of the current of the valve 35 (35a, 35b) is shown. 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.

8 to 10 perform common engine stop control, and the processes performed after the engine stop are different from those in FIGS. In the present embodiment, it is determined whether or not the vehicle after the vehicle stops slipping during deceleration of the vehicle after the engine is stopped. When it is determined that the vehicle slips, the brake ECU 55 applies the brake pressurization ( The braking force applied to the wheels FR, FL, RR, RL is increased. As a result, the control for preventing the vehicle from sliding down after stopping is performed.

FIG. 8 is a timing chart when normal vehicle sliding control is performed. First, normal sliding prevention control will be described with reference to FIG. In the normal slip prevention control, the engine restart request is not received from the engine ECU 17 during the control period from the start to the end of the slip control, and the engine restart request is received during a period other than the control period. Engine restart control.

On the other hand, FIGS. 9 and 10 are examples in which the execution timings of the brake pressurization in the slip-down prevention control and the permission of the engine restart performed when the engine restart request is received overlap. In particular, FIG. 9 shows an example in which it is determined that the engine restart request is due to the driver's intention to start, and FIG. 10 shows that the engine restart request is due to something other than the driver's intention to start. It is an example when it is determined. Some requests other than the driver's intention to start are for the purpose of securing electric power to be supplied to comfort facilities such as the temperature adjusting device 61.

First, normal sliding prevention control will be described with reference to FIG. In FIG. 8, when the driver depresses the brake pedal 15 at time t1 while traveling on the uphill road, the master cylinder pressure PMC increases, and the idle stop condition (brake switch on, PMC ≦ Ps, VS ≦ V1) is satisfied. The brake ECU 55 permits the engine 12 to stop, and when the engine ECU 17 stops the engine 12, the engine speed decreases from time t1 and eventually becomes zero.

The vehicle decelerates while the engine is stopped by the braking force applied to the wheels FR, FL, RR, and RL due to the increase in the master cylinder pressure PMC by the brake operation. While the vehicle engine is stopped, the brake ECU 55 is configured to prevent the vehicle from sliding down after the vehicle has stopped, and a restart control that permits the engine 12 to restart when an engine restart request is received. I do. However, in the example of the normal slip prevention control shown in FIG. 8, the engine restart request is not received within the execution period of brake pressurization (in the case of “predicted slip down” to be described later).

After transmitting the stop command, the brake ECU 55 receives a stop notification signal from the engine ECU 17 that has stopped the engine 12 and grasps that the engine 12 has stopped. The slip prediction determination is a prediction of whether or not a vehicle will slip after stopping, and whether or not a brake pressurization start condition for starting brake pressurization for preventing the slip is satisfied. This is a determination process including a brake pressurization start condition determination (hereinafter also simply referred to as “start condition determination”).

In the slip prediction, it is determined whether or not the slope generation condition, gradient acceleration Ag> braking acceleration Apmc, is satisfied. If Ag> Apmc is satisfied, it is predicted that a slip will occur, and if Ag> Apmc is not satisfied, it is predicted that no slip will occur.

In the brake pressurization start condition determination, an estimated time T required until the vehicle stops after the engine stops is calculated. The predicted time T is obtained as the time required from the present time to the stop. The predicted time T is obtained by dividing the vehicle body speed VS by the vehicle body speed differential value DVS (T = VS / DVS). The vehicle body speed differential value DVS is a value obtained by differentiating the vehicle body speed VS with respect to time.

* Brake pressurization is started earlier than the time of stopping by the pressurization required time T1 required for brake pressurization. This is to ensure the braking force necessary to suppress the sliding down until the vehicle stops. Therefore, when the predicted time T reaches the pressurization required time T1, the brake pressurization start condition (T ≦ T1) is satisfied. However, in this embodiment, the slip-down prevention control is performed so that the slip-down distance L of the vehicle is suppressed to the allowable distance La or less. In this case, the brake pressurization start timing may be delayed by an amount of the allowable delay time Ta required for the slippage distance L to reach the allowable distance La from the stop point. The allowable delay time Ta is obtained using a map (not shown) showing the correspondence between the road surface gradient θ and the allowable delay time Ta. Then, the set time T2 from the brake start time to the stop time set to start the brake pressurization earlier than the stop time is set to a value obtained by subtracting the delay allowable time Ta from the pressurization required time T1 (T2 = T1-Ta).

When the predicted time T (= VS / DVS) is equal to or shorter than the set time T2, it is determined that the brake pressurization start condition is satisfied. Of course, when the allowable distance La is zero (that is, the allowable delay time Ta = 0) and the predicted time T is equal to or less than the required pressurization time T1 (T ≦ T1), it is determined that the brake pressurization start condition is satisfied. May be.

When the slippage occurrence condition Ag> Apmc is satisfied and the brake pressurization start condition T ≦ T2 is satisfied, the slippage prediction condition is satisfied. The slip prediction judgment flag is turned off while the slip prediction condition is not satisfied, and is turned on when the slip prediction condition is satisfied. In the example shown in FIG. 8, the slippage prediction determination flag is turned on at time t2 that is earlier than the vehicle stop time t3 by a set time T2 (= T1-Ta).

When the slippage prediction determination flag is turned on, the brake ECU 55 supplies current to the pump motor 41 and the linear electromagnetic valve 35 (35a, 35b) to pressurize the brake, thereby driving the pump motor 41 and linear electromagnetic. The wheel cylinder pressure PWC is increased by reducing the opening degree by operating the valve 35 in the valve closing direction.

Here, the current value I1 to be supplied to the linear electromagnetic valve 35 for pressurizing the brake is based on the absolute value of the gradient acceleration Ag determined from the road surface gradient θ, and referring to the map shown in FIG. Asked in advance before. This current value I1 is a value at which the wheel cylinder pressure PWC can be increased (increased) to the control target pressure P1 when supplied to the linear

electromagnetic valves

35a and 35b under the drive state of the

pumps

42 and 43.

Further, as shown in FIG. 8, the current supplied when the pump motor 41 is driven changes so as to converge once to a stable current value after rising significantly at the start of driving. The current characteristic of the pump motor 41 is a general motor current characteristic, and the starter motor 72 has the same current characteristic.

For example, when the pump motor 41 is driven for a drive time sufficient for the wheel cylinder pressure PWC to reach the control target pressure P1, the supply of current to the pump motor 41 is stopped. Since the brake pressurization is completed when the driving of the pump motor 41 is stopped, the slip prediction prediction flag is switched from on to off. The current supplied to the

linear solenoid valves

35a and 35b is changed from the current value I1 to the current value I2 (> I1) at the timing when the slip prediction prediction flag is turned off (that is, when the brake pressurization is finished). Is done. In this example, the current value I2 is obtained by referring to a map created based on the same concept as the map shown in FIG. 4 according to the absolute value of the gradient acceleration Ag.

The wheel cylinder pressure PWC increases to a pressure corresponding to the current value I due to brake pressurization. For this reason, the braking force applied to the wheels FR, FL, RR, RL increases. For example, the wheel cylinder pressure PWC is increased even when the driver decreases the operation amount (stepping amount) of the brake pedal 15 and the master cylinder pressure PMC decreases from time t2 before the vehicle stops. . For this reason, when the vehicle stops, even if the wheel cylinder pressure PWC does not reach the control target pressure P1, the vehicle after stopping stops so that the sliding distance L falls within the allowable distance La.

When the wheel cylinder pressure PWC reaches the control target pressure P1, the current supply to the pump motor 41 is stopped, and the supply current to the linear

electromagnetic valves

35a and 35b increases the wheel cylinder pressure PWC to the control target pressure P1 ( Switching) to a current value I2 for brake pressure holding, which is higher than the current value I1 at the time of increase). As a result, even after the driving of the pump motor 41 is finished, the wheel cylinder pressure PWC is maintained at the control target pressure P1.

In the example of FIG. 8, the driver once depresses the brake pedal 15 whose operating amount was once reduced before and after stopping, and then stepped on again for a while, and then increased to the master cylinder pressure PMC higher than the control target pressure P1. The wheel cylinder pressure PWC also increases following this master cylinder pressure PMC. Even if the driver depresses the brake pedal 15 and the master cylinder pressure PMC decreases, the current of the current value I2 is supplied to the linear

electromagnetic valves

35a and 35b. Therefore, the wheel cylinder pressure PWC is set to the control target pressure P1. Retained. In other words, the brake is held, and the vehicle is stopped and maintained on the slope without falling off the vehicle.

Thereafter, when the driver stops the depression of the brake pedal 15 and starts operating the accelerator pedal 11 (time t4) in order to start the vehicle, the engine ECU 17 detects the operation with the intention to start. An engine restart request is sent to the ECU 55. When receiving the engine restart request, the brake ECU 55 permits the engine 12 to restart. Thus, the engine 12 is restarted by the engine ECU 17, and the engine speed starts to increase from zero at time t4. When the engine speed increases until it reaches a predetermined value, the brake ECU 55 stops supplying current to the linear electromagnetic valve 35. As a result, the brake holding pressure is released. After the brake holding pressure is released, the restart of the engine 12 is completed, and then the depression of the brake pedal 15 is stopped, so that the vehicle starts by creep torque.

Next, the stoppage maintenance / restart control routine shown in FIGS. 5 and 6 executed by the brake ECU 55 will be described with reference to the timing charts shown in FIGS.

First, in step S11, it is determined whether or not the engine is stopped. If the engine is not stopped, the routine ends. On the other hand, if the engine is stopped, the process proceeds to step S12.

In step S12, the sliding prediction is determined. In this slip prediction determination, it is determined (predicted) whether or not a vehicle slip occurs after the vehicle stops. Specifically, the brake ECU 55 calculates the gradient acceleration Ag and the braking acceleration Apmc, and determines whether or not Ag> Apmc is satisfied. When Ag> Apmc is satisfied, it is predicted that a slip will occur, and when Ag> Apmc is not satisfied, it is predicted that no slip will occur. Further, in this slippage prediction determination, the brake ECU 55 acquires the vehicle body speed VS, calculates the time derivative of the vehicle body speed VS, and acquires the vehicle body speed differential value DVS. Then, the vehicle speed VS is divided by the vehicle speed differential value DVS to obtain a predicted time T (= VS / DVS) required until the vehicle stops. Then, it is determined whether or not the predicted time T is equal to or shorter than the set time T2, and if T ≦ T2 is satisfied, it is determined that the brake pressurization start condition is satisfied. It is determined that the pressure start condition is not satisfied. If both the slip generation condition Ag <Apmc and the brake pressurization start condition T ≦ T2 are satisfied, it is determined that the slip prediction condition is satisfied. The prediction determination flag remains off while the falling prediction condition is not satisfied, and the prediction determination flag is switched from off to on when the falling prediction condition is satisfied. In the present embodiment, the brake ECU 55 that determines whether or not Ag> Apmc also functions as the second determination unit. Step S12 corresponds to a second determination step.

In the next step S13, the brake control target pressure P1 is calculated. Specifically, the brake ECU 55 refers to the map shown in FIG. 4 on the basis of the absolute value of the gradient acceleration Ag and obtains a current value I1 corresponding to the gradient acceleration Ag. When the current value I1 is supplied to the linear

electromagnetic valves

35a and 35b in a pressurized state where the

pumps

42 and 43 are driven, the wheel cylinder pressure PWC can be set as the control target pressure P1. Of course, a map showing the correspondence between the gradient acceleration Ag and the control target pressure is stored in the ROM of the brake ECU 55, and is uniquely determined from the control target pressure P1 according to the map acquired based on the gradient acceleration Ag. Alternatively, the current value I that is determined may be acquired.

In step S14, it is determined whether an engine restart request has been made. That is, the brake ECU 55 determines whether an engine restart request has been received from the engine ECU 17. Here, the engine restart request secures a request when the driver intends to start (hereinafter also referred to as “first request”) and power supplied to comfort equipment such as the audio 60 and the temperature control device 61. For requesting (hereinafter also referred to as “second request”).

Here, the engine ECU 17 sequentially determines whether or not a restart condition for restarting the engine 12 is satisfied. When the restart condition is satisfied, an engine restart request is transmitted to the brake ECU 55. To do. The restart condition includes the audio 60, the temperature adjustment device 61, and the like when the detection signals from the driving operation sensors SE1, SW1, SE3 to SE8, such as the accelerator pedal 11 and the brake pedal 15, satisfy a predetermined start condition. In some cases, the driving state of the comfortable equipment satisfies a predetermined restart condition. The engine ECU 17 transmits the engine restart request to the brake ECU 55 without distinguishing between the first request and the second request.

The brake ECU 55 proceeds to step S15 if there is an engine restart request, and proceeds to step S26 (FIG. 6) if there is no engine restart request.

Here, the processing after step S26 shown in FIG. 6 is normal vehicle sliding prevention control. In this normal vehicle sliding prevention control, the processing shown in the timing chart of FIG. 8 is performed.

In addition, the processes in steps S15 to S20 and the processes in steps S15 and S21 to S25 shown in FIG. 5 are executed by engine restart to be performed in response to the engine restart request and brake pressurization in the slip prevention control. The processing when they overlap in terms of timing is shown. Specifically, the processing in steps S15 to S20 is the first processing performed when the engine restart request is the first request based on the driver's intention to start. The control content of this first process is shown in the timing chart of FIG. 9, and engine restart is performed with priority over brake pressurization. The processes in steps S15 and S21 to S25 are the second processes that are performed when the engine restart request is a second request that the driver does not intend to start. The control content of the second process is shown in the timing chart of FIG. 9, and brake pressurization is performed first in preference to engine restart.

First, the first process performed when the engine restart request is based on the driver's intention to start will be described with reference to the timing chart of FIG.

In step S15, it is determined whether or not the driver intends to start. Here, as an example, the driver's intention to start is that the driver stops pressing the brake pedal 15 and the brake switch SW1 is off (brake switch off), and the driver starts operating the accelerator pedal 11 and opens the accelerator. The determination is made when each condition that the degree takes a positive value is satisfied by an AND condition (hereinafter also referred to as “starting intention condition”). Of course, at least one of the conditions, such as checking the value of the master cylinder pressure PMC and the rate of change of the value, or checking whether the value of the accelerator opening is equal to or greater than a specified value, determines whether to start the vehicle. It may be replaced with at least one of the conditions, or may be added to the start intention determination condition. That is, the conditions may be appropriately combined as long as the intention to start can be determined. If it is determined in step S15 that there is an intention to start, the process proceeds to step S16. If it is determined that there is no intention to start, the process proceeds to step S21. In the present embodiment, the brake ECU 55 that determines whether or not the driver intends to start also functions as a determination unit. Step S15 corresponds to a determination step.

If it is determined that the driver intends to start, the engine 12 is first restarted in step S16. That is, the brake ECU 55 permits restart of the engine 12 by sending a restart command to the engine ECU 17.

In the next step S17, it is determined whether or not there is a sliding prediction. That is, the brake ECU 55 determines whether or not the slip prediction prediction flag is on. If there is a sliding prediction (flag on), the process proceeds to step S18, and if there is no sliding prediction (flag off), the process proceeds to step S19.

In step S18, the brake is pressurized to the control target pressure P1 below the available power. Specifically, when the brake is pressurized, the brake ECU 55 supplies the current to the pump motor 41 to drive the pump motor 41, and causes the linear

electromagnetic valves

35a and 35b to have the current value I1 corresponding to the control target pressure P1. A current is supplied (see FIG. 9). As a result, as shown in FIG. 9, the wheel cylinder pressure PWC is increased to the control target pressure P1. By this brake pressurization, the vehicle stops when the sliding distance L after stopping is equal to or less than the allowable distance La. When the brake pressurization up to the control target pressure P1 is achieved, the brake ECU 55 stops the supply current to the pump motor 41 and stops its driving. When the brake pressurization is finished, the brake ECU 55 switches the slip prediction prediction determination flag from on to off. In the present embodiment, the brake ECU 55 that performs brake pressurization also functions as a brake control unit. Step S18 corresponds to a braking control step.

In the next step S19, the brake is held at the control target pressure P1 below the available power. That is, the brake ECU 55 changes the current supplied to the linear

electromagnetic valves

35a and 35b from the current value I1 to the current value I2 (> I1). As a result, even after driving of the

pumps

42 and 43 is stopped, the wheel cylinder pressure PWC is maintained at the control target pressure P1, so that the vehicle is held in a stopped state on the slope. In addition, when there is no slip down prediction, although brake pressurization is not performed, the brake is held by maintaining the wheel cylinder pressure PWC.

In the next step S20, it is determined whether or not the engine restart is completed. If the engine restart has not been completed, the process waits while maintaining the brake below the power that can be used in step S19 until the engine restart is completed. When the engine restart is completed (Yes in S20), the process proceeds to step S32. move on.

In step S32, brake pressure reduction is performed. That is, the brake ECU 55 stops the supply of current to the linear

electromagnetic valves

35a and 35b. As a result, the control target pressure P1 of the wheel cylinder pressure PWC that has been held until then is canceled, and the braking force applied to the wheels FR, FL, RR, RL for maintaining the stop is released. For this reason, when the driver depresses the accelerator pedal 11, the vehicle starts. Even if the driver does not depress the accelerator pedal 11 so much, the creep torque of the engine 12 suppresses the vehicle from sliding down. Even if it slides down, the sliding speed is very slow. Therefore, the driver can depress the brake pedal 15 with a margin to stop the sliding.

Here, as shown in FIG. 8, the current supplied to the pump motor 41 during the brake pressurization process and the current value I1 supplied to the linear

electromagnetic valves

35a and 35b are both kept below the usable power. The electric power that can be used refers to the remaining electric power consumed by the starter motor 72 that is driven when the engine is restarted.

FIG. 11 is a graph showing the driving power of the pump motor and the starter motor. FIG. 11A shows a case where there is no intention to start (that is, a case where priority is given to brake pressurization), and FIG. 11B shows a case where there is a intention to start (ie, a case where priority is given to engine restart). In each figure, the horizontal axis represents time t, and the vertical axis represents motor drive power. In each graph, the electric power value Wb is electric power that can be used for brake pressurization and engine restart among electric power (battery electric power W) that can be supplied by a battery (not shown) mounted on the vehicle. This electric power Wb excludes electric power used for other purposes such as comfort equipment such as the audio 60 and the temperature adjusting device 61, electric power consumed by lamps, and the like.

The idle stop ECU 65 manages the power consumption of the comfort facilities, the lamps, and the electric system such as various motors. The idle stop ECU 65 grasps electric power Wb that can be used for engine restart and brake pressurization out of the battery electric power W, and information on the electric power Wb is periodically or whenever there is a request from the brake ECU 55. , To the brake ECU 55.

Further, in the brake ECU 55, the electric power characteristic (time-dependent change characteristic of electric power) at the time of engine restart of the starter motor 72 driven at the time of engine restart depends on the battery voltage at that time, but is roughly determined by the vehicle type. . 11 shows the power characteristic of the starter motor 72 in which the time-varying characteristic of the power indicated by the one-dot chain line in the graph of FIG. 11 is determined from the battery voltage.

In the graph shown in FIG. 11A, the remaining power shown in the hatched range in the figure, excluding the power used by the starter motor 72 from the power Wb, is the power that can be used for pressurizing the brake ( Hereinafter, it is referred to as “brake pressurization usable electric power W1”.

Here, at the beginning of the start of the starter motor 72, the power consumption increases greatly to form a peak, and after the end of the peak, it falls within the stable power value. As a result, the brake pressurization usable power W1 is reduced during the period in which the peak of the starter motor driving power occurs. In addition, since the pump motor driving power also forms a peak at the beginning of driving of the pump motor 41, it is desirable to avoid the peak generation period of the starter motor driving power and the peak generation period of the pump motor driving power. Therefore, in this embodiment, a peak avoidance period PT including the peak generation period of the starter motor drive power (in this example, the same as the peak generation period) is set, and after the peak avoidance period PT has elapsed, the drive period of the pump motor 41 is set. Is set.

For this reason, when there is an intention to start, the engine restart is prioritized, and the normal power required for restarting the engine 12 is used as the starter motor drive power. The brake ECU 55 that has received the engine restart request sends a restart command for permitting the engine restart to the engine ECU 17, and then after a time corresponding to the peak avoidance period PT has elapsed, the motor driver circuit The electric power (current) is supplied to the pump motor 41 via and the drive is started. In this case, the pump motor 41 and the

linear solenoid valves

35a and 35b are driven within the range of the remaining brake pressurization usable electric power W1 of the electric power used for restarting the engine, but the pump is used in a period avoiding the peak avoidance period PT. Since the motor 41 is driven, a relatively large current can be supplied to the pump motor 41 and the linear

electromagnetic valves

35a and 35b as compared with the case where the peak avoidance period PT is the driving period. As a result, even when engine restart is prioritized, the wheel cylinder pressure PWC can be increased to the control target pressure P1 relatively quickly. In addition, the line shown with a dashed-two dotted line in the graph of FIG. 11 shows the sum of pump motor drive power and the drive power of linear

electromagnetic valve

35a, 35b.

Next, the second processing shown in steps S21 to S25 in FIG. 5 performed when there is no intention to start will be described with reference to the timing chart shown in FIG.

If it is determined in step S15 in FIG. 5 that the driver does not intend to start, it is determined in step S21 whether or not there is a slip prediction. That is, the brake ECU 55 determines whether or not the slip prediction prediction flag is on. If there is a sliding prediction (flag on), the process proceeds to step S22, and if there is no sliding prediction (flag off), the process proceeds to step S23.

In step S22, the brake is pressurized to the control target pressure P1. Specifically, when this brake pressurization is performed, the brake ECU 55 supplies current to the pump motor 41 to drive the pump motor 41 and causes the linear

electromagnetic valves

35a and 35b to have a current value I1 corresponding to the control target pressure P1. (See FIG. 10). As a result, as shown in FIG. 10, the wheel cylinder pressure PWC is increased to the control target pressure P1. For this reason, the vehicle stops when the sliding distance L after stopping is equal to or less than the allowable distance La. When the brake pressurization up to the control target pressure P1 is achieved, the brake ECU 55 stops the supply current to the pump motor 41 and stops its driving. When the brake pressurization is finished, the brake ECU 55 switches the slip prediction prediction determination flag from on to off.

In the next step S23, restart of the engine 12 is started. That is, the brake ECU 55 permits restart of the engine 12 by sending a restart command to the engine ECU 17. As a result, the engine 12 is restarted by the engine ECU 17 that has received this restart command.

In the next step S24, the brake is held at the control target pressure P1. That is, the brake ECU 55 changes the current supplied to the linear

electromagnetic valves

pumps

42 and 43 is stopped, the wheel cylinder pressure PWC is maintained at the control target pressure P1, so that the vehicle is held in a stopped state on the slope.

In the next step S25, it is determined whether or not the engine restart is completed. If the engine restart has not been completed, the process waits while continuing to hold the brake in step S24 until the engine restart is completed. If the engine restart is completed (affirmative determination in S25), the process proceeds to step S32.

electromagnetic valves

35a and 35b. As a result, the control target pressure P1 of the wheel cylinder pressure PWC that has been held until then is canceled, and the braking force applied to the wheels FR, FL, RR, RL for maintaining the stop is released. For this reason, when the driver depresses the accelerator pedal 11, the vehicle starts. Even if the driver does not depress the accelerator pedal 11 so much, the creep torque of the engine 12 suppresses the vehicle from sliding down.

When the driver does not intend to start, as shown in FIG. 10, when an engine restart request is made at approximately the same timing (time t12) when the slip prediction prediction flag is turned on, a normal current is supplied to the pump motor 41. While being supplied, a necessary current value I1 is supplied to the linear

electromagnetic valves

35a and 35b. As a result, the wheel cylinder pressure PWC increases to the control target pressure P1, and the vehicle slip after the vehicle stops (time t13) is suppressed to, for example, the allowable distance La or less. After the brake pressurization is completed, the supply current to the linear

electromagnetic valves

35a and 35b is slightly increased from the current value I1 during pressurization to the current value I2 during holding pressure. As a result, the vehicle on the slope is maintained in a stopped state.

* When the brake pressurization is finished before or after this, the engine restart is started. Until the engine restart is completed, the wheel cylinder pressure PWC is maintained at the control target pressure P1, so that the vehicle on the slope is maintained in a stopped state and does not slide down. Then, after the engine restart is completed, the energization to the linear

electromagnetic valves

35a and 35b is stopped. At this time, since the creep torque is generated, even if the driver loosens the depression of the brake pedal 15, it is difficult for the vehicle to fall down.

Next, normal sliding control shown in steps S26 to S32 in FIG. 6 will be described with reference to the timing chart in FIG.

If there is no engine restart request (in the case of negative determination in S14), it is determined in step S26 whether or not there is a slip prediction (the slip prediction flag is on). If there is a predicted slip down, the brake is pressurized to the control target pressure P1 in step S27. Specifically, the brake ECU 55 supplies current to the pump motor 41 to drive the

pumps

42 and 43, and supplies a current value I1 corresponding to the road surface gradient θ to the linear

electromagnetic valves

35a and 35b, whereby the wheel cylinder The pressure PWC is set as the control target pressure P1.

In addition, after the brake pressurization is finished, the wheel cylinder pressure PWC is maintained at the control target pressure P1 in step S28. In step S29, it is determined whether or not there is an engine restart request. If there is no restart request, the system waits in step S28 while maintaining the brake until there is an engine restart request, and if there is an engine restart request ( (Yes determination in S29), the process proceeds to step S30.

In step S30, restart of the engine 12 is started. That is, the brake ECU 55 permits restart of the engine 12 by sending a restart command to the engine ECU 17. As a result, the engine 12 is restarted by the engine ECU 17 that has received this restart command.

In the next step S31, it is determined whether or not the engine restart is completed. If the engine restart has not been completed, the system waits while holding the brake. If the engine restart has been completed (Yes determination in S31), the process proceeds to step S32.

electromagnetic valves

35a and 35b. As a result, the brake holding is released, and the braking force applied to the wheels FR, FL, RR, RL for maintaining the stop is released. For this reason, when the driver depresses the accelerator pedal 11, the vehicle starts.

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

(1) At least a part of a period during which brake pressurization is performed in the vehicle sliding prevention control (stop maintenance control) (a period with predicted sliding down) and a period during which engine restart is requested in response to an engine restart request Even if they overlap, it is determined whether or not the driver intends to start, and one of restarting of the engine 12 and brake pressurization is executed with priority over the other according to the determination result. Therefore, the restart of the engine 12 and the brake pressurization can be effectively made compatible while respecting the driver's intention to start.

(2) When the driver intends to start, the restart of the engine 12 is prioritized, and the pump motor 41 and the linear electromagnetic valve 35a, so as to perform brake pressurization in a power range that does not interfere with the restart of the engine 12. 35b (electric motor) is controlled. Therefore, if there is an intention to start, the engine restart is prioritized, but the brake pressurization is advanced in parallel with the restart as far as possible, so the shear before the creep torque generated by the completion of the engine restart occurs. The fall can be effectively suppressed.

(3) When the driver does not intend to start, the brake pressurization has priority over the engine restart, and the engine 12 is restarted after the brake pressurization. Therefore, the vehicle can be prevented from slipping down after stopping, and the engine 12 can be restarted more reliably.

(4) If the braking acceleration Apmc before pressurizing the brake is less than the gradient acceleration Ag, which is the acceleration due to the force corresponding to gravity acting in the longitudinal direction of the vehicle in accordance with the road surface gradient θ, the sliding control is performed. However, when the acceleration is greater than or equal to the gradient acceleration Ag, the sliding prevention control is not performed. Therefore, when it is predicted that the braking force depending on the amount of depression of the brake pedal 15 and the road surface gradient will occur, the vehicle is controlled to prevent the vehicle from sliding down by performing the control for preventing the vehicle from sliding down. In the case where it is predicted that no slip-down occurs, unnecessary stop maintenance control is not performed. Therefore, stop maintenance control is suitably performed when necessary, and wasteful power consumption can be reduced.

(5) The power supplied to the pump motor 41 and the linear solenoid valves 35 and 35b for pressurizing the brake is set to be equal to or less than the remaining power consumed by the starter motor 72 when the engine 12 is restarted. Therefore, while giving priority to the restart of the engine 12, the brake pressurization during the restart can be performed within the allowable range of the battery power at that time.

(6) Electric power for pressurizing the brake is applied to the pump motor 41 and the linear electromagnetic valves 35 and 35b at a time when the peak avoidance period PT set so as to include the generation time of the current peak in the initial drive of the starter motor 72 is avoided. Supply. Therefore, relatively large electric power can be supplied to the pump motor 41 when the brake is applied. For this reason, the wheel cylinder pressure PWC can be increased to the control target pressure P1 relatively quickly, and the braking force for preventing the sliding down can be generated relatively early while giving priority to the engine start.

It should be noted that the above-described embodiments can be implemented with the following modifications.

In the above embodiment, when there is an intention to start, the current is supplied to the pump motor 41 while avoiding the peak avoidance period PT, but the current may be supplied in a period including the peak occurrence period. In this case, it is preferable to shift the generation time of the current peak of the starter motor 72 and the current peak of the pump motor 41. For example, the brake ECU 55 is configured so that the current supply to the pump motor 41 is started before the power supply to the starter motor 72 and the current peak of the starter motor 72 appears after the current peak of the pump motor 41 appears. A drive command and a restart command for the pump motor 41 are performed.

In the above embodiment, when there is an intention to start, both the pump motor 41 and the linear

electromagnetic valves

35a and 35b supply current while avoiding the peak avoidance period PT. The current supplied to the

electromagnetic valves

35a and 35b may be supplied also during the peak avoidance period PT.

In the above-described embodiment, the braking acceleration Apmc and the gradient acceleration Ag (threshold) are compared in the determination of the sliding down. 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 the master pressure sensor SE8 that detects the master cylinder pressure PMC, the braking acceleration Apmc may be acquired based on the master cylinder pressure PMC detected by the master pressure sensor SE8. 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 between the braking force Fpmc and the force Fg). It may be configured to determine the presence or absence of sliding down by comparison.

· 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 certain value, and after the road surface gradient θ exceeds the certain value, the allowable distance La is increased according to the increase in the road surface gradient θ. Let

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

When the vehicle has an electric parking brake device, the braking force for the wheels FR, FL, RR, RL may be increased using the electric parking brake device instead of the brake actuator 31 when the brake is applied. In this case, the drive source of the electric parking brake device corresponds to the electric motor.

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

Claims

A vehicle control device that performs stop control for automatically stopping a vehicle engine (12) and restart control for automatically restarting the engine (12),
Electric motors (41, 35a, 35b) for increasing the braking force applied to the vehicle wheels (FR, FL, RR, RL) by the braking devices (32a to 32d) with electric power;
A braking control unit (55, S18, S22) that controls the electric motor (41, 35a, 35b) to perform stop maintenance control for increasing the braking force in accordance with the stopping of the vehicle when the engine (12) is stopped. )When,
A determination unit (55, S15) for determining whether or not the driver has an intention to start based on a detection result of a driving operation system detector (SW1) provided in the vehicle;
The braking control unit (55, S18, S22)
When the determination unit (55, S15) determines that there is an intention to start, the electric motors (41, 35a, 35b) so as to increase the braking force within a power range that does not hinder the restart of the engine (12). ), While
When the determination unit (55, S15) determines that there is no intention to start, the electric motor (41, 35a, 35b) for controlling a vehicle.
A second determination unit (55, S12) that determines whether or not the braking force (Apmc) before the increase is less than the force (Ag) corresponding to gravity acting in the front-rear direction of the vehicle according to the road surface gradient (θ). )
The braking control unit (55, S18, S22) performs the stop maintaining control when the braking force (Apmc) before the increase is less than the force corresponding to the gravity (Ag), and the braking control unit before the increase is controlled. 2. The vehicle control device according to claim 1, wherein when the power (Apmc) is equal to or greater than the force (Ag) corresponding to the gravity, the stop maintenance control is not performed.
When the determination unit (55, S15) determines that there is no intention to start, the braking control unit (55, S18, S22) increases the braking force giving priority to maintaining the stop of the vehicle. 35a, 35b), and restarting the engine (12) is permitted after the braking force by the electric motor (41, 35a, 35b) is increased. Vehicle control device.
The brake control unit (55, S18, S22) supplies electric power supplied to the electric motor (41, 35a, 35b) for increasing the braking force when the engine (12) is restarted. 4) is set to be equal to or lower than the remaining electric power consumed, the vehicle control device according to any one of claims 1 to 3.
The braking controller (55, S18, S22) increases the braking force at a time at least avoiding a current peak generation time (PT) in the initial driving of the electric motor (72) that restarts the engine (12). The vehicle control device according to any one of claims 1 to 4, wherein electric power for power supply is supplied to the electric motor (41, 35a, 35b).
A vehicle control method for performing stop control for automatically stopping a vehicle engine (12) and restart control for automatically restarting the engine (12),
The engine (12) is controlled by controlling the electric motors (41, 35a, 35b) that increase the braking force applied to the wheels (FR, FL, RR, RL) of the vehicle by the braking devices (32a to 32d). A braking control step (55, S18, S22) for performing stop maintenance control for increasing the braking force in accordance with the stop of the vehicle in the stop state;
When a restart request is received while the engine (12) is stopped, a determination is made as to whether or not the driver is willing to start based on a detection result of a driving operation system detector (SW1) provided in the vehicle. Step (55, S15),
In the brake control step (55, S18, S22), when the restart request is received when the start condition of the stop maintenance control is satisfied, it is determined in the determination step (55, S15) that there is an intention to start. In the case where the engine (12) is restarted, the electric motor (41, 35a, 35b) is controlled so as to increase the braking force within an electric power range that does not hinder the restart of the engine (12), while the determination step (55, S15) starts. The motor (41, 35a, 35b) is controlled so as to increase the braking force giving priority to maintaining the stop of the vehicle over the restart of the engine (12). A vehicle control method characterized by the above.