Abstract:
A control system for a vehicle including a brake pedal operable by a driver and an engine includes an electronic control unit. The electronic control unit is configured to: (a) execute cruise control, the cruise control selectively executed and stopped through an operation of the driver, (b) stop the engine upon depression of the brake pedal, when the cruise control is stopped, (c) stop the engine while the vehicle is being decelerated or stopped, even when the brake pedal is not depressed, when the cruise control is executed, and (d) keep the engine stopped even when the operation to stop the cruise control is performed, after the engine is stopped and the cruise control is executed.

Description:
INCORPORATION BY REFERENCE 
       [0001]    The disclosure of Japanese Patent Application No. 2013-061781 filed on Mar. 25, 2013 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a control system for a vehicle, and in particular to a control system that performs control of an engine when automatic cruise control is stopped while the vehicle is stopped. The invention relates to a control method for the vehicle. 
         [0004]    2. Description of Related Art 
         [0005]    A vehicle having an idling stop function is known in which an engine is automatically stopped while the vehicle is stopped, for example, so as to reduce the amount of consumption of fuel. As one example, the engine is automatically stopped upon depression of a brake pedal. In the meantime, when cruise control for automatically following a vehicle ahead is executed, the engine can be automatically stopped even when the brake pedal is not depressed while the vehicle is decelerated or stopped. 
       SUMMARY OF THE INVENTION 
       [0006]    However, in the case where the engine is stopped during automatic cruise control, if the cruise control is stopped, the engine may be started since the brake pedal is not depressed. Since the engine is started even when the driver does not positively perform an operation to start the engine, the driver may feel uneasy. 
         [0007]    The invention provides a control system and a control method for a vehicle, which is able to alleviate the uneasiness of the driver. 
         [0008]    A control system according to a first aspect of the invention includes an electronic control unit. The electronic control unit (a) executes cruise control so as to automatically follow a vehicle ahead, the cruise control being selectively executed and stopped through an operation of a driver, (b) stops the engine upon depression of the brake pedal, when the cruise control is stopped, (c) stops the engine while the vehicle is being decelerated or stopped, even when the brake pedal is not depressed, when the cruise control is executed, and (d) keeps the engine stopped even when the operation to stop the cruise control is performed by the driver, after the engine is stopped and the cruise control is executed. 
         [0009]    The engine is not started even when the operation to stop the cruise control is performed, after the engine is stopped and the cruise control is executed; thus, the engine is not started even when the brake pedal is not depressed by the driver. Accordingly, the engine can be prevented from being started when the driver does not positively perform an operation to start the engine. Thus, uneasiness of the driver can be alleviated. 
         [0010]    In the control system as described above, the electronic control unit may keep the engine stopped, even when the operation to stop the cruise control is performed while the vehicle is being decelerated under the cruise control, after the engine is stopped and the cruise control is executed. 
         [0011]    Since the engine is not started during deceleration, the amount of fuel wastefully consumed can be reduced. 
         [0012]    Further, in the control system as described above, the electronic control unit may keep the engine stopped, even when the operation to stop the cruise control is performed while the vehicle ahead is being decelerated or stopped, after the engine is stopped and the cruise control is executed. 
         [0013]    Since the engine is not started when the vehicle ahead is decelerated or stopped, a sufficiently large distance between the own vehicle and the vehicle ahead can be maintained. 
         [0014]    Further, in the control system as described above, the electronic control unit may keep the engine stopped, and maintain at least a part of braking force provided through the cruise control, even when the operation to stop the cruise control is performed, after the engine is stopped and the cruise control is executed. 
         [0015]    Since the braking force is maintained, the vehicle is prevented from moving backward even when the engine is not started. 
         [0016]    Further, in the control system as described above, the electronic control unit may start the engine, when the accelerator pedal is depressed while the engine is kept stopped. 
         [0017]    Since the driver can start the engine by operating the accelerator pedal, the driver can cause the vehicle to run according to his/her request. 
         [0018]    Further in the control system as described above, the electronic control unit may keep the cruise control executed, even when the operation to stop the cruise control is performed, after the engine is stopped and where the cruise control is executed. 
         [0019]    Since the cruise control is not stopped; malfunction due to an erroneous operation by the driver can be prevented. 
         [0020]    Further, in the control system as described above, the electronic control unit may stop the cruise control, when the brake pedal is depressed while the cruise control is kept executed. 
         [0021]    Since the cruise control is stopped, the vehicle can be prevented from being started against the intension of the driver to stop the vehicle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
           [0023]      FIG. 1  is a schematic view of the configuration of a vehicle; 
           [0024]      FIG. 2  is a view showing ECU; 
           [0025]      FIG. 3  is a view showing operating conditions of an engine, etc. according to the related art; 
           [0026]      FIG. 4  is a view showing operating conditions of an engine, etc. according to one embodiment of the invention; 
           [0027]      FIG. 5  is a view showing operating conditions of an engine, etc. according to the embodiment of the invention; 
           [0028]      FIG. 6  is a view showing operating conditions of an engine, etc. according to the embodiment of the invention; and 
           [0029]      FIG. 7  is a flowchart illustrating a control process executed by the ECU. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0030]    One embodiment of the invention will be described with reference to the drawings. In the following description, the same reference numerals are assigned to the same components. These components have the same names and the same functions. Accordingly, detailed description of these components will not be repeated. 
         [0031]    Referring to  FIG. 1 , the vehicle includes an engine  100  and a transmission  200 . Torque generated in the engine  100  is transmitted to drive wheels  202  via the transmission  200 . 
         [0032]    The engine  100  is controlled by an ECU (Electronic Control Unit)  300 . Signals indicative of detection results are transmitted from a vehicle speed sensor  304 , a position switch  308  that detects the position of a shift lever  306 , an accelerator pedal position sensor  312  that detects the amount of operation (or acceleration stroke) of an accelerator pedal  310 , and a hydraulic sensor  316  that detects a hydraulic pressure supplied from a master cylinder  400 , to the ECU  300 . In this embodiment, it is determined by means of the hydraulic sensor  316  whether the brake pedal  314  is depressed or returned to the original position. In other words, the hydraulic pressure supplied from the master cylinder  400  is detected as the amount of operation of the brake pedal  314 . A stroke sensor that directly detects the amount of operation of the brake pedal  314 , or a pedal force sensor that detects pedal force applied to the brake pedal  314 , may be used in place of the hydraulic sensor  316 . 
         [0033]    The brake pedal  314  is coupled to the master cylinder  400  via a brake booster  315 . A hydraulic circuit  600  that consists of the master cylinder  400  and a brake actuator  500  connected to the master cylinder  400  is filled with a brake fluid (brake oil). The brake fluid (brake oil) is stored in a reservoir tank  402 . 
         [0034]    The hydraulic pressure generated by the master cylinder  400  is led to brake calipers  700 - 706  provided on respective wheels, via the brake actuator  500 . The brake calipers  700 - 706  produce braking force when hydraulic pressures are applied thereto. 
         [0035]    The brake actuator  500  leads hydraulic pressures generated by pumps  502  to the respective brake calipers  700 - 706  by controlling opening/closing of solenoid valves, so as to control brake hydraulic pressures. The brake actuator  500  is controlled by the ECU  300 . 
         [0036]    A negative-pressure tank  800  is connected to the brake booster  315 . A negative pressure developed in the engine  100  is stored in the negative-pressure tank  800 . The brake booster  315  increases the pedal force applied to the brake pedal  314 , and transmits the resulting force to the master cylinder  400 . 
         [0037]    Referring to  FIG. 2 , the ECU  300  will be further described. The ECU  300  includes a cruise control ECU  900 , a brake ECU  910 , an idling stop ECU  920 , and an engine ECU  930 . The cruise control ECU  900 , brake ECU  910 , idling stop ECU  920 , and the engine ECU  930  are connected such that they can communicate with each other via CAN (Controller Area Network) communication lines. 
         [0038]    The cruise control ECU  900  executes cruise control for automatically following a vehicle ahead. As one example, the cruise control ECU  900  measures a following distance as measured from the vehicle ahead, using a millimeter-wave radar, or the like, and controls the vehicle so that the following distance becomes equal to a given value. Namely, the cruise control ECU  900  accelerates the vehicle if the following distance becomes longer than the given value, and decelerates or stops the vehicle if the following distance becomes shorter than the given value. The cruise control ECU  900  determines a target deceleration to be achieved, from the following distance and the current vehicle speed, referring to a map, or the like, and transmits the this determined target deceleration to the brake ECU  910 . Since well-known general technologies may be utilized for the cruise control, detailed description thereof will not be repeated herein. 
         [0039]    In this embodiment, the driver operates a switch  902  so as to cause the cruise control ECU  900  to execute the cruise control or not to execute the cruise control. The cruise control may be executed or stopped by using a touch panel, voice, or any other operating method, in place of the switch  902 . 
         [0040]    The brake ECU  910  receives a detection signal indicative of the hydraulic pressure, directly from the hydraulic sensor  316 . The brake ECU  910  controls the brake actuator  500 , according to the signal transmitted from the hydraulic sensor  316 , etc. 
         [0041]    Also, the brake ECU  910  controls the brake actuator  500  so as to achieve the target deceleration received from the cruise control ECU  900 . Since well-known general technologies may be utilized for brake control during the cruise control, detailed description of the brake control will not be repeated herein. 
         [0042]    In the case where the cruise control is not executed, the idling stop ECU  920  outputs a request for automatically stopping the engine  100 , to the engine ECU  930 , when certain idle-stop conditions including at least a condition that the brake pedal  314  is being depressed are satisfied. As one example, it is determined that the idle-stop conditions are satisfied, when all of the following conditions that the brake pedal  314  is depressed, the vehicle speed is equal to zero, and the steering angle of the steering wheel is equal to zero, are satisfied. 
         [0043]    In the case where the cruise control is executed, on the other hand, a request for automatically stopping the engine  100  is generated to the engine ECU  930 , while the vehicle is being decelerated or stopped, even when the brake pedal  314  is not being depressed. As one example, if the vehicle ahead is decelerated or stopped, and the following distance as measured from the vehicle ahead becomes smaller than a given value, the request for stopping the engine  100  is generated. It is, however, to be understood that the condition under which the request for stopping the engine  100  is generated is not limited to this condition. 
         [0044]    When a certain re-start condition(s) is/are satisfied, the idling stop ECU  920  outputs a request for re-starting the engine  100 , to the engine ECU  930 , and drives a starter  922  so as to crank the engine  100 . 
         [0045]    As one example, in the case where the cruise control is not executed, if the above-described idle-stop conditions cease to be satisfied, the request for re-starting the engine  100  is generated, and the starter  922  is driven. In the case where the cruise control is executed, on the other hand, if the following distance as measured from the vehicle ahead exceeds a given value, due to acceleration of the vehicle ahead, for example, the request for re-starting the engine  100  is generated, and the starter  922  is driven. 
         [0046]    The engine ECU  930  controls the fuel injection amount, throttle opening, ignition timing, and so forth, during operation of the engine  100 , so as to operate the engine  100  in desired conditions. If the engine ECU  930  receives a request for stopping the engine  100  from the idling stop ECU  920 , it stops fuel injection and ignition, for example, so as to stop the engine  100 . 
         [0047]    Also, if the engine ECU  930  receives a request for re-starting the engine  100  from the idling stop ECU  920 , it resumes fuel injection and ignition, for example, so as to start the engine  100 . 
         [0048]    As described above, the driver is able to cause the cruise control ECU  900  to execute or stop cruise control, by operating the switch  902 . Accordingly, after the engine  100  is automatically stopped in a condition where the cruise control is executed, an operation to stop the cruise control may be erroneously performed. 
         [0049]    As shown in  FIG. 3 , when the cruise control is stopped after the engine  100  is automatically stopped in a condition where the cruise control is being executed, the engine  100  may be re-started since the brake pedal  314  is not depressed. However, since the driver does not positively perform an operation to start the engine  100 , he/she may feel uneasy about starting of the engine  100 . 
         [0050]    In this embodiment, in order to alleviate the uneasiness of the driver, the cruise control is kept executed even when an operation to stop the cruise control is performed by the driver, after the engine  100  is automatically stopped and the cruise control is executed, as shown in  FIG. 4 . Accordingly, even when an operation to stop the cruise control is performed, after the engine  100  is automatically stopped in a condition where the cruise control is executed, the engine  100  is kept stopped or at rest. 
         [0051]    More specifically, even when an operation to stop the cruise control is performed while the vehicle is decelerated under cruise control due to deceleration or stop of the vehicle ahead, after the engine  100  is automatically stopped and the cruise control is executed, the cruise control is kept executed, and the engine is kept stopped or at rest. 
         [0052]    If the cruise control is kept executed, the braking force provided through the cruise control is maintained. Accordingly, even when an operation to stop the cruise control is performed after the engine  100  is automatically stopped and the cruise control is executed, the engine  100  is kept stopped, and the braking force provided through the cruise control is maintained. At least a part of the braking force may be retained. Namely, the braking force may be reduced provided that the braking force does not become equal to zero. 
         [0053]    As shown in  FIG. 5 , when the accelerator pedal  310  is depressed while the engine  100  is kept stopped, namely, while the cruise control is kept executed, the engine  100  may be started. As shown in  FIG. 6 , when the brake pedal  314  is depressed while the cruise control is kept executed, the cruise control may be stopped. As one example, when the hydraulic pressure supplied from the master cylinder  400  (the amount of operation of the brake pedal  314 ) exceeds a given threshold value, the cruise control is stopped. More specifically, when the hydraulic pressure (operation amount) increases to a hydraulic pressure (operation amount) with which the vehicle can be kept in a stopped state, the cruise control is stopped. The threshold value used for determining whether the cruise control is stopped is determined in advance by a developer from the result of experiment, or the like. 
         [0054]    Referring to  FIG. 7 , a control process executed by the ECU  300  will be described. The control process as described below is repeatedly executed at given intervals. 
         [0055]    In step S 100 , it is determined whether an operation to stop cruise control is performed by the driver. If the operation to stop the cruise control is performed (YES in step S 100 ), it is determined in step S 102  whether the vehicle is being decelerated or stopped under the cruise control. 
         [0056]    If the vehicle is being decelerated or stopped under the cruise control (YES in step S 102 ), it is determined in step S 104  whether the engine  100  is being stopped or at rest. Namely, it is determined whether the engine  100  has been stopped, because the following distance as measured from the vehicle ahead is smaller than a given value. 
         [0057]    If the engine  100  is stopped (YES in step S 104 ), it is determined in step S 106  whether the braking force corresponding to the amount of operation of the brake pedal  314  is smaller than the braking force provided through the cruise control. The braking force corresponding to the amount of operation of the brake pedal  314  is calculated using a map, or the like. If the braking force corresponding to the amount of operation of the brake pedal  314  is smaller than the braking force provided through the cruise control (YES in step S 106 ), the cruise control is kept executed in step S 108 . As a result, the engine  100  is kept in a stopped state. Also, the braking force provided through the cruise control is maintained. 
         [0058]    If the vehicle is being accelerated under the cruise control (NO in step S 102 ), the cruise control is stopped in step S 110 . Accordingly, if the engine  100  is stopped, and the brake pedal  314  is not depressed, the engine  100  is re-started. 
         [0059]    In other cases, i.e., in the case where the engine  100  is not stopped (NO in step S 104 ), and the case where the braking force corresponding to the amount of operation of the brake pedal  314  is equal to or larger than the braking force provided through the cruise control (NO in step S 106 ), the cruise control is stopped (S 110 ). 
         [0060]    If the accelerator pedal  310  or the brake pedal  314  is depressed while the cruise control is kept executed (YES in step S 109 ), the cruise control is stopped (S 110 ). When the accelerator pedal  310  is depressed, the cruise control is stopped, resulting in start of the engine  100 . 
         [0061]    The embodiment disclosed herein should be considered as being illustrative in all respects and not restrictive. The scope of the invention is not defined by the above description but defined by the appended claims, and is intended to include all changes within the range of the claims and equivalents thereof.