Patent Publication Number: US-2016244056-A1

Title: Vehicle control apparatus

Description:
TECHNICAL FIELD 
     The disclosure is related to a vehicle control apparatus. 
     BACKGROUND ART 
     A vehicle control apparatus that prevents an automatic stop process for an engine when a steering angle exceeds an automatic stop determination steering angle in a decelerated state is known (Patent Literature 1) in which the automatic stop determination steering angle is set such that the automatic stop determination steering angle becomes greater as the vehicle speed becomes lower. 
     CITATION LIST 
     Patent Literature 1 
     [PTL 1] 
     Japanese Laid-open Patent Publication No. 2013-064345 
     SUMMARY 
     Technical Problem 
     However, with respect to a vehicle in which idling stop control is performed, performing lane keeping assist control to generate a steering force with an actuator according to a detection result of a lane boundary sign (a white line, for example) may causes the following problem. In a configuration in which the lane keeping assist control is performed, the steering angle is generated not only due to an operation of a driver but also due to the lane keeping assist control driving an actuator. Preventing the automatic stop process for the engine in the case where the steering angle is generated due to the lane keeping assist control driving an actuator, as is the case with the steering angle being generated due to the operation of the driver, may cause the driver to feel strange. Specifically, when the engine is not stopped due to the lane keeping assist control, the driver may feel strange because the engine is not stopped regardless of the steering operation not being performed by the driver. Further, this means that the engine is not stopped even in a situation where the engine can be appropriately stopped, which prevents the improved fuel economy. Such a problem also holds true with respect to a time of restarting the engine. Specifically, in the case of restarting the engine, the engine may be restarted at an earlier timing due to the lane keeping assist control. 
     Therefore, it is an object of the present disclosure to provide a vehicle control apparatus that can appropriately perform idling stop control as well as lane keeping assist control. 
     Solution to Problem 
     According to one aspect of the present disclosure, a vehicle control apparatus is provided, which includes:
         an idling stop control apparatus configured to operate in a situation where a vehicle speed is less than or equal to a predetermined vehicle speed to stop or restart an engine when a predetermined parameter related to steering meets a predetermined condition; and   a lane keeping assist control apparatus configured to operate even in the situation where the vehicle speed is less than or equal to the predetermined vehicle speed to generate a steering force with an actuator according to at least one of a detection result of a lane boundary sign and a detection result of an object having a predetermined positional relationship with respect to the lane boundary sign, wherein   the predetermined condition is set such that the engine is easier to be stopped or more difficult to be restarted in a case where the lane keeping assist control apparatus is in a predetermined operation state than the engine is in a case where the lane keeping assist control apparatus is in another state.       

     With this arrangement, it becomes possible to appropriately perform the idling stop control as well as the lane keeping assist control, because the engine is easier to be stopped or more difficult to be restarted in a case where the lane keeping assist control apparatus is in a predetermined operation state than the engine is in a case where the lane keeping assist control apparatus is in another state. 
     Advantageous Effects of Invention 
     According to the present disclosure, a vehicle control apparatus that can appropriately perform the idling stop control as well as the lane keeping assist control can be obtained. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram schematically illustrating a configuration of a vehicle control apparatus  1  according to an embodiment. 
         FIG. 2  is a diagram illustrating an example of a steering system. 
         FIG. 3  is a flowchart illustrating an example of a process executed by a LKA ECU  20 . 
         FIG. 4  is a flowchart illustrating an example of a process executed by an idling stop ECU  10 . 
         FIG. 5  is a flowchart illustrating another example of a process executed by the idling stop ECU  10 . 
         FIG. 6  is a flowchart illustrating yet another example of a process executed by the idling stop ECU  10 . 
         FIG. 7  is a diagram illustrating an example of a relationship between thresholds, etc., used in the example illustrated in  FIG. 6 . 
         FIG. 8  is a flowchart illustrating yet another example of a process executed by the idling stop ECU  10 . 
         FIG. 9  is a flowchart illustrating yet another example of a process executed by the idling stop ECU  10 . 
         FIG. 10  is a flowchart illustrating yet another example of a process executed by the idling stop ECU  10 . 
         FIG. 11  is a flowchart illustrating yet another example of a process executed by the idling stop ECU  10 . 
         FIG. 12  is a flowchart illustrating yet another example of a process executed by the idling stop ECU  10 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the following, embodiments are described in detail with reference to appended drawings. 
       FIG. 1  is a diagram schematically illustrating a configuration of a vehicle control apparatus  1  according to an embodiment.  FIG. 2  is a diagram illustrating an example of a steering system, in which (A) illustrates an example of a configuration in which a steering actuator  26  is installed in a steering column, and (B) illustrates an example of a configuration in which the steering actuator  26  is installed for a rack (bar). It is noted that connections between elements in  FIG. 1  are arbitrary. For example, the connection ways may include a connection via a bus such as a CAN (controller area network), etc., an indirect connection via another ECU, etc., a direct connection, or a connection that enables wireless communication. It is noted that, in  FIG. 2 , a mechanical connection is expressed with a double line and an electric connection is expressed with a single line. 
     The vehicle control apparatus  1  includes an idling stop ECU (Electronic Control Unit)  10 , and a LKA (Lane Keeping Assist) ECU  20 . The idling stop ECU  10  and the LKA ECU  20  may be embodied by microcomputers, etc., respectively. It is noted that a distribution of functions among the ECUs (including an EPS ECU  22 , etc.) is arbitrary. For example, a part or all of the functions of the idling stop ECU  10  may be implemented by the LKA ECU  20  and/or the an engine ECU  40 , or reversely a part or all of the functions of the LKA ECU  20  may be implemented by the idling stop ECU  10 . 
     The idling stop ECU  10  is coupled to the EPS ECU  22 . The EPS ECU  22  is coupled to a torque sensor  23  that detects a steering torque applied to a steering shaft  92 , and a steering sensor  24  that detects a steering angle of the steering shaft  92  (or a steering wheel). 
     The EPS ECU  22  supplies the idling stop ECU  10  with the steering torque detected by the torque sensor  23  and the steering angle detected by the steering sensor  24 . Further, the EPS ECU  22  calculates, based on a history of the steering angle detected by the steering sensor  24 , a steering angular velocity (a change amount of the steering angle per an unit time or a predetermined time), and supplies the idling stop ECU  10  with the calculated steering angular velocity. 
     Further, the EPS ECU  22  is connected to a steering actuator  26 . The EPS ECU  22  controls the steering actuator  26  in response to a steering assist demand torque from the LKA ECU  20 . For example, in the example illustrated in  FIG. 2 , the EPS ECU  22  determines, based on a steering assist demand torque from the LKA ECU  20  and the steering torque detected by the torque sensor  23 , an instruction torque (control value) to implement, with feedback control, for example, the steering assist demand torque. In this way, a steering torque according to the steering assist demand torque from the LKA ECU  20  is generated. The steering actuator  26  may include arbitrary configurations for generating the steering torque (steering force). For example, the steering actuator  26  may be an assist motor that is used for an assist control for adding an assist torque in the steering direction of the driver. It is noted that the steering actuator  26  is typically an electric motor; however, the steering actuator  26  may be a hydraulic actuator. 
     It is noted that, in the following, as a premise, it is assumed that the steering actuator  26 , the torque sensor  23 , and the steering sensor  24  are installed in such a positional relationship that the operation of the steering actuator  26  has an influence on the detection values of the torque sensor  23  and the steering sensor  24  (see  FIG. 2  (A)). For example, in the example illustrated in  FIG. 2  (A), the steering actuator  26  is installed to act on the steering shaft  92  (or a shaft that substantially rotates together with the steering shaft  92 ), and the torque sensor  23  and steering sensor  24  are provided for the steering shaft  92  on which the steering actuator  26  acts. In such a configuration, the steering torque detected by the torque sensor  23  substantially corresponds to a total of a torque (i.e., a driver operation torque) generated by the driver operating the input rotary shaft  90  and an operation torque (nearly equal to an instruction torque) generated by the steering actuator  26 . 
     The LKA ECU  20  is coupled to a forward camera  32 , a LKA switch  34 , etc. 
     The forward camera  32  may be a single camera or a stereo camera that captures a scene around the vehicle that mainly includes a predetermined region in front of the vehicle. Photoelectric conversion elements of the forward camera  32  may be CCDs (charge-coupled devices), CMOSs (complementary metal oxide semiconductors), etc. 
     The LKA switch  34  is to be operated by a user. The main switch  34  may be provided at any location in a cabin. The LKA switch  34  may be a mechanical switch or a touch switch. The LKA switch  34  is an interface for the user to input his/her intention whether to perform a lane keeping assist control described hereinafter. As an example, it is assumed hereinafter that the LKA switch  34  is turned on when the user expresses his/her intention to perform the lane keeping assist control. It is noted that a display for indicating an ON/OFF status of the LKA switch  34  (i.e., an ON/OFF status of the lane keeping assist control) may be output in a meter (not illustrated). 
     The LKA ECU  20  may recognize a lane boundary sign from the image data of the forward camera  32  to generate road information. The lane boundary sign represents a road surface sign for delimiting (defining) a traveling lane. For example, the lane boundary sign is a line-shaped sign formed by applying paint which can be recognized from a road surface, such as white paint, in line shape along the road. Further, there is a line formed in a chromatic color such as yellow or orange, depending on a road rule or a nation. Further, the lane boundary sign includes, in addition to a line-shaped sign, a dotted line or a broken line which has portions in which paint is not applied at a predetermined interval. Further, when the traveling lane is delimited by a three-dimensional object such as a bots dots such as in United State of America, instead of the paint, such a three-dimensional object is also included in the lane boundary sign. Further, when the traveling lane is delimited by arranging light emitting objects such as lamps or cat&#39;s eyes along the road, these objects are also included in the lane boundary sign. 
     The LKA ECU  20  performs, in cooperation with the EPS ECU  22 , the lane keeping assist control based on the road information. The lane keeping assist control may include an alert control via an information output device such as a buzzer or the meter, and an intervention control for changing an orientation of the vehicle via the steering actuator  26 . Alternatively, the lane keeping assist control may include the intervention control. It is noted that it is assumed that the intervention control is a LKA (Lane Keeping Assist) that supports a driver&#39;s steering operation such that the vehicle travels to stay in the traveling lane; however, the intervention control may be a LDW (Lane Departure Warning) that is operated when the departure from the traveling lane is detected or the like. According to the LKA, the steering torque is constantly assisted according to the lateral displacement with respect to the target traveling line (traveling lane center), the yaw angle, etc., and, when the departure tendency is detected, the steering assist demand torque for the departure reduction may be calculated. According to the LDW, when the departure tendency is detected, the steering assist demand torque for the departure reduction may be calculated. It is noted that at the time of performing the intervention control the steering torque and a yaw moment with a brake actuator (not illustrated) may be generated or only the steering torque may be generated. 
     The idling stop ECU  10  is coupled to the engine ECU  40 , a brake ECU  50 , and a meter ECU  52 . The brake ECU  50  may supply the idling stop ECU  10  with brake operation information by the driver, vehicle speed information, etc. The meter ECU  52  may output on/off states of the LKA switch  34  and an idling stop cancel switch  70 , alarms, etc. in the meter, according to instructions from the idling stop ECU  10 . 
     The idling stop ECU  10  is coupled to a starter  42 . The starter  42  starts the engine under control by the idling stop ECU  10 . 
     The idling stop ECU  10  is coupled to the idling stop cancel switch  70 . The idling stop cancel switch  70  is to be operated by the user. The idling stop cancel switch  70  may be provided at any location in the cabin. The idling stop cancel switch  70  may be a mechanical switch or a touch switch. The idling stop cancel switch  70  is an interface for the user to input his/her intention whether to perform an idling stop control. Here, as an example, the idling stop cancel switch  70  is turned on when the user does not desire the idling stop control. 
     The idling stop ECU  10  may have various items of vehicle information (signals) input from other ECUs, sensors, etc., if necessary. The various items of vehicle information may include a signal representing a state (current, voltage) of a battery, a signal related to a comfort degree of an air conditioner (a room temperature, etc., for example), a signal representing a brake booster pressure value, an air bag signal, a food lock close signal, a door close signal, a seat belt buckle signal, etc., for example. 
       FIG. 3  is a flowchart illustrating an example of a process executed by the LKA ECU  20 . The process illustrated in  FIG. 3  may be performed at a predetermined cycle during an ON state of an ignition switch (not illustrated), for example. 
     In step S 304 , it is determined whether the LKA switch  34  is in its ON state. When it is determined that the LKA switch  34  is in its ON state, the process routine goes to step S 302 , otherwise the process routine directly ends to start from step S 300  at the next process cycle. 
     In step  302 , it is determined whether a lane keeping assist control operation condition is met. The lane keeping assist control operation condition is arbitrary. Here, as an example, the lane keeping assist control operation condition does not include a condition related to the vehicle speed. In other words, the lane keeping assist control is performed over a whole vehicle speed range. The lane keeping assist control operation condition may include the steering torque by the steering operation of the driver being not greater than or equal to a predetermined value Th1, the lane boundary sign being detected (recognized) by the forward camera  32 , a state of a wiper apparatus being not a “Hi” state, systems (the LKA ECU  20 , the forward camera  32 , etc.) being normal, etc. When it is determined that the lane keeping assist control operation condition is met, the process routine goes to step S 304 , otherwise the process routine directly ends to start from step S 300  at the next process cycle. 
     In step S 304 , the operation of the lane keeping assist control is started. 
     In step  306 , it is determined whether the lane keeping assist control operation condition is met. The lane keeping assist control operation condition may be the same as described above in relation to step S 302 . Alternatively, an element “the steering torque by the steering operation of the driver being not greater than or equal to a predetermined value Th1” may be omitted in step S 302 , but may be included only in step S 306 . If it is determined that the lane keeping assist control operation condition is met, the process routine goes to step  310 , otherwise the process routine goes to step  308 . 
     In step S 308 , the lane keeping assist control is interrupted. In this case, the process routine starts from step S 306  at the next process cycle. 
     In step S 310 , the lane keeping assist control is continued. It is noted that in a situation where the lane keeping assist control has been interrupted, the lane keeping assist control is restored to the operation state (i.e., the operation of the lane keeping assist control is restarted). It is noted that, even in the operation of the lane keeping assist control, there may be a case where the steering actuator  26  does not generate the steering torque when the departure tendency is not detected, as described above. In other words, “in operation of the lane keeping assist control” is not equal to “in operation of the steering actuator  26 ”. When the process in step S 310  is terminated, the process routine goes to step  312 . 
     In step S 312 , it is determined whether the LKA switch  34  is in its OFF state or the system (the LKA ECU  20 , the forward camera  32 , etc.) is abnormal. When it is determined that any one of the conditions is met, the process routine goes to step S 314 , otherwise the process routine directly ends to start from step S 310  at the next process cycle. It is noted that when it is determined that none of the conditions is met, the process routine may directly end to start from step S 306  at the next process cycle. 
     In step S 314 , the lane keeping assist control is terminated. 
     It is noted that, in the process illustrated in  FIG. 3 , in step S 308 , the LKA switch  34  may be turned off (automatically). In this case, in step S 306 , the LKA switch  34  is turned on and it is determined whether the lane keeping assist control operation condition is met. In such a configuration, restarting the lane keeping assist control requires the LKA switch  34  to be turned on by the user again. 
       FIG. 4  is a flowchart illustrating an example of a process executed by the idling stop ECU  10 . The process illustrated in  FIG. 4  may be performed at a predetermined cycle during the ON state of an ignition switch and the OFF state of the idling stop cancel switch  70 . 
     In step S 400 , it is determined, based on the vehicle speed information, whether the vehicle has stopped after traveling at the vehicle speed greater than a predetermined vehicle speed V1. The predetermined vehicle speed V1 is arbitrary, and may be 0 for example. 
     In step S 402 , it is determined whether the LKA switch  34  is in its ON state. Instead of determining whether the LKA switch  34  is in its ON state, it may be determined whether the lane keeping assist control is being operated (i.e., the process of step S 310  in  FIG. 3  is being performed). If it is determined that the LKA switch  34  is in its ON state, the process routine goes to step  406 , otherwise the process routine goes to step  404 . 
     In step S 404 , it is determined, based on the latest information from the EPS ECU  22 , whether any one of the steering torque, the steering angle, and the steering angular velocity is less than or equal to corresponding first idling stop start thresholds (α1, α2, α3). The first idling stop start thresholds are prepared for three parameters including the steering torque, the steering angle, and the steering angular velocity, respectively. In the example, the first idling stop start threshold related to the steering torque is α1, the first idling stop start threshold related to the steering angle is α2, and the first idling stop start threshold related to the steering angular velocity is α3. The first idling stop start thresholds α1, α2, α3 may be set according to lower limit values of ranges in which the parameters could take at the time of the steering operation, in the vehicle stopped state, by the driver who intends to start to accelerate the vehicle immediately after the vehicle stop event, respectively. Specifically, performing the idling stop control, in the case where the vehicle is started to travel immediately after the vehicle stop event, causes the fuel economy to be reduced on the contrary. In scenes where the vehicle is started to travel immediately after the vehicle stop event, the drivers may stop the vehicle while performing the steering operation or perform the steering operation even in the vehicle stopped state. Thus, in such a short stop can be predicted on the parameters, it is better not to start the idling stop control. The first idling stop start thresholds α1, α2, α3 may be determined from such a viewpoint. The first idling stop start thresholds α1, α2, α3 may be adapted based on experimental data, etc. Any one of the steering torque, the steering angle, and the steering angular velocity is less than or equal to the corresponding first idling stop start threshold, the process routine goes to step S 408 , otherwise the process routine directly ends to start from step S 400  at the next process cycle. 
     It is noted that, in step S 404 , it may be determined whether any two of the steering torque, the steering angle, and the steering angular velocity are less than or equal to the corresponding first idling stop start thresholds, or it may be determined whether all the steering torque, the steering angle, and the steering angular velocity are less than or equal to the corresponding first idling stop start thresholds. 
     In step S 406 , it is determined, based on the latest information from the EPS ECU  22 , whether any one of the steering torque, the steering angle, and the steering angular velocity is less than or equal to corresponding second idling stop start thresholds (β1, β2, β3). The second idling stop start thresholds are prepared for three parameters including the steering torque, the steering angle, and the steering angular velocity, respectively. In the example, the second idling stop start threshold related to the steering torque is β1, the second idling stop start threshold related to the steering angle is β2, and the second idling stop start threshold related to the steering angular velocity is β3. The second idling stop start thresholds β1, β2, β3 are substantially greater than the first idling stop start thresholds α1, α2, α3, respectively. With this arrangement, it becomes possible to reduce a probability that the idling stop control, which otherwise could be performed appropriately, is prevented due to the lane keeping assist control. 
     In step S 406 , if it is determined that any one of the steering torque, the steering angle, and the steering angular velocity is less than or equal to the corresponding second idling stop start threshold, the process routine goes to step S 408 . Otherwise, the process routine directly ends to start from step S 402  at the next process cycle. Thus, in this case, there is a probability that the determination result in step S 406  at the next process cycle becomes affirmative. In this way, during a period in which the determination result in step S 402  is affirmative, the determination of step S 406  is performed repeatedly. With this arrangement, it becomes possible to reduce a probability that the idling stop control, which otherwise could be performed appropriately, is prevented due to the lane keeping assist control. Such repeated determinations in step S 406  is in contrast with the determination in step S 404  that is performed only once for a single vehicle stop event (i.e., the affirmative determination event in step S 400 ). This is because, with respect to the determination in step S 404 , only one negative determination result suffices to confirm the intention of the driver to start to drive the vehicle immediately after the vehicle stop event. However, the determination in step S 404  may also be performed repeatedly for a single vehicle stop event, as is the case with the determination in step S 406 . It is noted that the determination in step S 406  may be repeated endlessly for a single vehicle stop event during the period in which the determination result in step S 402  is affirmative; however, the determination in step S 406  may be repeated at predetermined times (or for a predetermined time). 
     In step S 408 , the idling stop control is started on the premise that other start conditions (i.e., predetermined conditions other than the start condition related to the steering described above) are met. Specifically, the engine is stopped. Other start conditions may be related to the state of the battery, the brake operation state, the air conditioner state, etc. 
     In step S 410 , it is determined, based on the latest information from the EPS ECU  22 , whether there is some change in any one of the steering torque, the steering angle, and the steering angular velocity. If it is determined that there is some change in any one of the steering torque, the steering angle, and the steering angular velocity, the process routine goes to step S 412 . Otherwise, the process routine directly ends to start from step S 410  at the next process cycle. However, even if the determination result in step S 410  is negative, the process routine may go to step S 418  when another start condition (i.e., a predetermined start condition other than the start condition related to the steering described hereinafter) is met. Another start condition may be related to the state of the battery, the brake operation state, the air conditioner state, the vehicle speed, etc. 
     It is noted that the determination process of step  410  may be omitted. In this case, the process routine directly goes to step S 412  after the process of step  408 . 
     In step S 412 , it is determined whether the LKA switch  34  is in its ON state. Instead of determining whether the LKA switch  34  is in its ON state, it may be determined whether the lane keeping assist control is being operated (i.e., the process of step S 310  in  FIG. 3  is being performed). If it is determined that the LKA switch  34  is in its ON state, the process routine goes to step  416 , otherwise the process routine goes to step  414 . 
     In step S 414 , it is determined, based on the latest information from the EPS ECU  22 , whether any one of the steering torque, the steering angle, and the steering angular velocity exceeds corresponding first idling stop end thresholds (γ1, γ2, γ3). The first idling stop end thresholds are prepared for three parameters including the steering torque, the steering angle, and the steering angular velocity, respectively. In the example, the first idling stop end threshold related to the steering torque is γ1, the first idling stop end threshold related to the steering angle is γ2, and the first idling stop end threshold related to the steering angular velocity is γ3. The second idling stop start thresholds γ1, γ2, γ3 are greater than the first idling stop start thresholds α1, α2, α3, respectively. The first idling stop end thresholds γ1, γ2, γ3 may be set according to lower limit values of ranges in which the parameters could take at the time of the steering operation, in the vehicle stopped state, by the driver who intends to start to accelerate the vehicle, respectively. Specifically, the driver who intends to start to accelerate the vehicle may perform the steering operation prior to the release operation of the brake pedal, etc. Thus, in such a driver&#39;s intention to start to drive the vehicle can be predicted on the parameters, it is better not to end the idling stop control. The first idling stop end thresholds γ1, γ2, γ3 may be determined from such a viewpoint. The first idling stop end thresholds γ1, γ2, γ3 may be adapted based on experimental data, etc. 
     In step S 414 , if it is determined that any one of the steering torque, the steering angle, and the steering angular velocity exceeds the corresponding first idling stop end threshold, the process routine goes to step S 418 . Otherwise, the process routine directly ends to start from step S 412  at the next process cycle. Alternatively, otherwise, the process routine may directly end to start from step S 410  at the next process cycle. 
     It is noted that, similarly, in step S 414 , it may be determined whether any two of the steering torque, the steering angle, and the steering angular velocity exceed the corresponding first idling stop end thresholds, or it may be determined whether all the steering torque, the steering angle, and the steering angular velocity exceed the corresponding first idling stop end thresholds. 
     In step S 416 , it is determined, based on the latest information from the EPS ECU  22 , whether any one of the steering torque, the steering angle, and the steering angular velocity exceeds corresponding second idling stop end thresholds (η1, η2, η3). The second idling stop end thresholds are prepared for three parameters including the steering torque, the steering angle, and the steering angular velocity, respectively. In the example, the second idling stop end threshold related to the steering torque is η1, the second idling stop end threshold related to the steering angle is η2, and the second idling stop end threshold related to the steering angular velocity is η3. The second idling stop end thresholds η1, η2, η3 are greater than the second idling stop start thresholds β1, β2, β3, respectively. Further, the second idling stop end thresholds η1, η2, η3 are substantially greater than the first idling stop end thresholds γ1, γ2, γ3, respectively. With this arrangement, it becomes possible to reduce a probability that the idling stop control, which otherwise could be continued appropriately, is ended due to the lane keeping assist control. 
     In step S 416 , if it is determined that any one of the steering torque, the steering angle, and the steering angular velocity exceeds the corresponding second idling stop end threshold, the process routine goes to step S 418 . Otherwise, the process routine directly ends to start from step S 412  at the next process cycle. Alternatively, otherwise, the process routine may directly end to start from step S 410  at the next process cycle. It is noted that, during a period in which the determination result in step S 416  (the same holds true for step S 414 ) is repeatedly negative, the process routine may go to step S 418  when another start condition (i.e., the predetermined start condition other than the start condition related to the steering) is met. 
     In step  418 , the engine is restarted. Specifically, the idling stop control is ended. It is noted that restarting the engine may be permitted on the premise that another start condition (i.e., the predetermined start condition other than the start condition related to the steering) is also met. Alternatively, the start condition related to the steering described above may be used solely as one of OR conditions to be met to restart the engine. 
     According to the process illustrated in  FIG. 4 , if the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated), whether to start the idling stop control is determined based on the second idling stop start thresholds β1, β2, β3. Otherwise, whether to start the idling stop control is determined based on the first idling stop start thresholds α1, α2, α3. The second idling stop start thresholds β1, β2, β3 are substantially greater than the first idling stop start thresholds α1, α2, α3, respectively, as described above. Thus, the idling stop control is easier to be started in a case where the LKA switch is in its ON state (or the lane keeping assist control is being operated) than the idling stop control is in another case. With this arrangement, it becomes possible to reduce a probability that the idling stop control, which otherwise could be performed appropriately, is prevented due to the lane keeping assist control. 
     Specifically, the first idling stop start thresholds α1, α2, α3 are set from a viewpoint of detecting the driver&#39;s intention to start to drive the vehicle, as described above. However, the lane keeping assist control is performed, regardless of the presence or absence of the driver&#39;s intention to start to drive the vehicle. When the steering actuator  26  is operated due to the lane keeping assist control at the time of the vehicle stop event after the traveling of the vehicle, there may be a case where the steering torque, the steering angle, and/or the steering angular velocity exceed the first idling stop start thresholds α1, α2, and/or α3 at that time. In such a case, the idling stop control is not started (i.e. the idling stop control is prevented) even without the driver&#39;s intention to start to drive the vehicle, which causes the driver to feel strange. For example, such a message “idling stop control cannot be performed due to steering wheel operation” is displayed, the driver who does not perform the steering operation may feel strange. Further, the idling stop control, which otherwise could be performed, is not performed, which is not preferable in terms of the fuel economy. In contrast, according to the embodiment, as described above, when the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated), whether to start the idling stop control is determined based on the second idling stop start thresholds β1, β2, β3. Thus, it becomes possible to cause the idling stop control to be started easily even when the steering actuator  26  is operated due to the lane keeping assist control at the vehicle stop event after traveling of the vehicle. With this arrangement, it become possible to reduce the probability that the driver feels strange, and improve the fuel economy due to the idling stop control without reducing convenience of the lane keeping assist control. 
     Further, according to the process illustrated in  FIG. 4 , when the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated), whether to end the idling stop control is determined based on the second idling stop end thresholds η1, η2, η3. Otherwise, whether to end the idling stop control is determined based on the first idling stop end thresholds γ1, γ2, γ3. As described above, the second idling stop end thresholds η1, η2, η3 are substantially greater than the first idling stop end thresholds γ1, γ2, γ3, respectively. Thus, the idling stop control is more difficult to be ended in a case where the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated) than the idling stop control is in another case. With this arrangement, it becomes possible to reduce a probability that the idling stop control, which otherwise could be continued appropriately, is ended earlier due to the lane keeping assist control. 
     Specifically, the first idling stop end thresholds γ1, γ2, γ3 are set from a viewpoint of detecting the driver&#39;s intention to start to drive the vehicle, as described above. However, the lane keeping assist control is performed, regardless of the presence or absence of the driver&#39;s intention to start to drive the vehicle. When the steering actuator  26  is operated due to the lane keeping assist control in the vehicle stopped state, there may be a case where the steering torque, the steering angle, and/or the steering angular velocity exceed the first idling stop end thresholds γ1, γ2, and/or γ3 at that time. In such a case, the idling stop control is not ended even without the driver&#39;s intention to start to drive the vehicle, which causes the driver to feel strange. Further, the idling stop control, which otherwise could be continued, is not continued (i.e., ended earlier), which is not preferable in terms of the fuel economy. In contrast, according to the embodiment, as described above, when the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated), whether to end the idling stop control is determined based on the second idling stop end thresholds η1, η2, η3. Thus, it becomes possible to make it more difficult to end the idling stop control even when the steering actuator  26  is operated due to the lane keeping assist control in the vehicle stopped state. With this arrangement, it become possible to reduce the probability that the driver feels strange, and improve the fuel economy due to the idling stop control without reducing convenience of the lane keeping assist control. 
     It is noted that, in the example illustrated in  FIG. 4 , as a preferred embodiment, whether the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated) is considered with respect to both of the start condition and the end condition for the idling stop control; however, it may be considered with respect to only one of them. For example, if whether the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated) is considered with respect to only the start condition for the idling stop control, processes in step S 412  and step S 416  in  FIG. 4  may be omitted. 
     Further, in the example illustrated in  FIG. 4 , in step S 400 , whether the vehicle has stopped after traveling with the vehicle speed greater than the predetermined vehicle speed V1; however, whether the vehicle speed is less than or equal to a predetermined vehicle speed V2 may be determined instead. In other words, a configuration in which the idling stop control is performed even in a low vehicle speed range other than in the vehicle stopped state may be implemented. The predetermined vehicle speed V2 is greater than 0, and corresponds to a lower limit vehicle speed in a range in which the idling stop control can be performed. In this case, when it is determined that the vehicle speed is less than or equal to the predetermined vehicle speed V2, the process routine goes to step S 402 , otherwise the process routine directly ends to start from step S 400  at the next process cycle. Further, from the same viewpoint, in step S 400 , it may be determined whether the vehicle is in a decelerated state and the vehicle speed is less than or equal to the predetermined vehicle speed V2. 
     Further, in the example illustrated in  FIG. 4 , in step S 400 , whether the vehicle has stopped after traveling with the vehicle speed greater than the predetermined vehicle speed V1; however, whether the vehicle is in the stopped state may be determined instead. In this case, when the vehicle is still in the stopped state even after the end of the idling stop control (i.e., after the engine restart), for example, the determination result in step S 400  is affirmative. In this case, if the start condition is met again, the idling stop control can be started. For example, the idling stop control is ended due to the air conditioner state (i.e., the reduction in the comfort degree of the air conditioner), the battery state (i.e., the reduction in the state of charge), etc., to restart the engine. Then, the vehicle is still in the stopped state, and if the comfort degree due to the air conditioner is improved and the state of charge of the battery is increased due to the engine restart, the idling stop control can be started. 
       FIG. 5  is a flowchart illustrating another example of a process executed by the idling stop ECU  10 . The process illustrated in  FIG. 5  may be performed at a predetermined cycle during the ON state of an ignition switch and the OFF state of the idling stop cancel switch  70 . 
     The process routine illustrated in  FIG. 5  differs from the process routine illustrated in  FIG. 4  in that a process of step S 503  is added. The processes in step S 500 , step S 502 , step S 504  through step S 518  may be the same as those in step S 400 , step S 402 , step S 404  through step S 418  illustrated in  FIG. 4 , respectively. 
     If the determination result in step S 502  is affirmative, the process goes to step S 503 . In step S 503 , it is determined, based on the latest information from the EPS ECU  22 , whether the steering torque (i.e., the driver steering torque) due to the steering operation by the driver is greater than or equal to a predetermined value Th2. When the steering actuator  26  is in non-operated state, the steering torque itself detected by the torque sensor  23  may be used as the steering torque due to the steering operation by the driver. On the other hand, when the steering actuator  26  is in the operated state, the steering torque due to the steering operation by the driver may be derived by subtracting the steering torque (i.e., the instruction torque) due to the operation of the steering actuator  26  from the steering torque detected by the torque sensor  23 . The steering torque due to the operation of the steering actuator  26  may be calculated based on a current (or control values such as an instruction torque, etc.) applied to the steering actuator  26 . The predetermined value Th2 is used to detect the steering operation of the driver, and thus may be relatively small. The predetermined value Th2 is smaller than the predetermined value Th1 which may be included in “the steering operation of the driver being not greater than or equal to the predetermined value Th1” of the lane keeping assist control operation condition. If it is determined that the steering torque due to the steering operation by the driver is greater than or equal to the predetermined value Th2, the process goes to step  504 , otherwise the process goes to step  506 . 
     According to the process illustrated in  FIG. 5 , the same effects as the process illustrated in  FIG. 4  can be obtained. Further, according to the process illustrated in  FIG. 5 , the idling stop start threshold is changed according to whether the steering torque due to the steering operation by the driver is greater than or equal to the predetermined value Th2. With this arrangement, it is possible to precisely reduce the probability that the idling stop control, which is better to not be started, is started. 
     Specifically, as described above, even if the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated), there may be a case where the steering actuator  26  does not generate the steering torque when the departure tendency is not detected. In other words, “in operation of the lane keeping assist control” is not equal to “in operation of the steering actuator  26 ”. Thus, according to the process illustrated in  FIG. 4 , the idling stop control may be started when the steering torque, the steering angle, and/or the steering angular velocity that exceed the first idling stop start thresholds α1, α2, and/or α3 but are less than or equal to the second idling stop start thresholds β1, β2, and/or β3 due to the steering operation by the driver in the situation where the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated). In contrast, according to the process illustrated in  FIG. 5 , even such a case, the idling stop control is not started when the steering torque due to the steering operation by the driver is greater than or equal to the predetermined value Th2. With this arrangement, it is possible to precisely reduce the probability that the idling stop control, which is better not to be started, is started. 
     It is noted that, in the example illustrated in  FIG. 5 , in step S 503 , it is determined whether the steering torque due to the steering operation by the driver is greater than or equal to the predetermined value Th2; however, it may be determined whether a change amount of the steering angle or the steering angular velocity due to the steering operation by the driver is greater than or equal to a predetermined value, instead of or in addition to the steering torque due to the steering operation by the driver is greater than or equal to the predetermined value Th2. 
       FIG. 6  is a flowchart illustrating yet another example of a process executed by the idling stop ECU  10 . The process illustrated in  FIG. 6  may be performed at a predetermined cycle during the ON state of an ignition switch and the OFF state of the idling stop cancel switch  70 . 
     The process routine illustrated in  FIG. 6  differs from the process routine illustrated in  FIG. 5  in that a process of step S 513  is added. 
     If the determination result in step S 512  is affirmative, the process goes to step S 513 . In step S 503 , it is determined, based on the latest information from the EPS ECU  22 , whether the steering torque due to the steering operation by the driver is greater than or equal to a predetermined value Th3. A way of obtaining the steering torque due to the steering operation by the driver may be as described above. The predetermined value Th3 is used to detect the steering operation of the driver, and thus may be relatively small. However, preferably, the predetermined value Th3 is set such that the predetermined value Th3 is greater than the predetermined value Th2. However, the predetermined value Th3 may be smaller than the predetermined value Th1 which may be included in “the steering operation of the driver being not greater than or equal to the predetermined value Th1” of the lane keeping assist control operation condition. If it is determined that the steering torque due to the steering operation by the driver is greater than or equal to the predetermined value Th3, the process goes to step  514 , otherwise the process goes to step  516 . 
     According to the process illustrated in  FIG. 6 , the same effects as the process illustrated in  FIG. 5  can be obtained. Further, according to the process illustrated in  FIG. 6 , the idling stop end threshold is changed according to whether the steering torque due to the steering operation by the driver is greater than or equal to the predetermined value Th3. With this arrangement, it is possible to precisely reduce the probability that the idling stop control, which is better to be ended, is not ended. 
     Specifically, as described above, even if the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated), there may be a case where the steering actuator  26  does not generate the steering torque when the departure tendency is not detected. Thus, according to the process illustrated in  FIG. 5 , the idling stop control may not be ended when the steering torque, the steering angle, and/or the steering angular velocity that exceed the first idling stop end thresholds γ1, γ2, and/or γ3 but are less than or equal to the second idling stop end thresholds η1, η2, and/or η3 due to the steering operation by the driver in the engine stopped state in the situation where the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated). In contrast, according to the process illustrated in  FIG. 6 , even such a case, the idling stop control is ended when the steering torque due to the steering operation by the driver is greater than or equal to the predetermined value Th3. With this arrangement, it is possible to precisely reduce the probability that the idling stop control, which is better to be ended, is not ended. 
     It is noted that, in the example illustrated in  FIG. 6 , the process of step S 513  is added with respect to the process routine illustrated in  FIG. 5 ; however, in the example illustrated in  FIG. 6 , the process of step S 513  may be added and the process of step S 503  may be omitted. 
       FIG. 7  is a diagram illustrating an example of a relationship between the thresholds, etc., used in the example illustrated in  FIG. 6  (or  FIG. 5 ). In  FIG. 7 , as an example, the relationship between the thresholds, etc., related to the steering torque is illustrated. This may hold true for the steering angle and/or the steering angular velocity. 
     In the example illustrated in  FIG. 7 , the first idling stop start threshold α1, the second idling stop start threshold β1, the first idling stop end threshold γ1, and the second idling stop end threshold η1 have a relationship of “η1&gt;γ1&gt;β1&gt;α1”. Further, the relationship including the predetermined values Th1, Th2, and Th3 is Th1&gt;η1&gt;Th3&gt;γ1&gt;β1&gt;Th2&gt;α1. In this case, in the example illustrated in  FIG. 6 , for example, when the determination result in step S 503  is affirmative, the determination result in step S 504  automatically becomes negative. Thus, in this case, in the example illustrated in  FIG. 6 , when the determination result in step S 503  is affirmative, the process routine at this cycle may directly end to start from step S 500  at the next process cycle. Similarly, in this case, in the example illustrated in  FIG. 6 , for example, when the determination result in step S 513  is affirmative, the determination result in step S 514  automatically becomes affirmative. Thus, in this case, in the example illustrated in  FIG. 6 , when the determination result in step S 513  is affirmative, the process routine may go to step S 518 . 
     It is noted that the example illustrated in  FIG. 7  is just an example, and other relationships may be used. For example, such a relationship Th1&gt;η1&gt;γ1&gt;Th3&gt;β1&gt;α1&gt;Th2 may be used. 
       FIG. 8  is a flowchart illustrating yet another example of a process executed by the idling stop ECU  10 . The process illustrated in  FIG. 8  may be performed at a predetermined cycle during the ON state of an ignition switch and the OFF state of the idling stop cancel switch  70 . 
     The process routine illustrated in  FIG. 8  differs from the process routine illustrated in  FIG. 5  in that a process of step S 506  is omitted. Specifically, according to the process routine illustrated in  FIG. 8 , when the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated), and the steering torque due to the steering operation by the driver is not greater than or equal to the predetermined value Th2, the idling stop control is started, regardless of the values of the steering torque, the steering angle, and/or the steering angular velocity. With this arrangement, it becomes possible to reduce a probability that the idling stop control, which otherwise could be performed appropriately, is prevented due to the lane keeping assist control. It is noted that the process routine illustrated in  FIG. 8  is substantially equivalent to a configuration in which the second idling stop start thresholds β1, β2, β3 in the process routine illustrated in  FIG. 5  are changed to very great values. 
     It is noted that, in the example illustrated in  FIG. 8 , the process of step S 506  is omitted with respect to the start condition of the idling stop control; however, instead of or in addition to this, the same idea may be applied with respect to the end condition of the idling stop control. Specifically, the process of step S 516  is omitted, and if the determination result of step S 512  is affirmative, the same determination process as that in step S 513  (see  FIG. 6 ) may be performed. As the result of the same determination process as that in step S 513 , if the determination result is affirmative, the process routine may go to step S 514 , otherwise the process routine at this cycle may directly end to start from step S 512  at the next process cycle. In this case, when the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated), and the steering torque due to the steering operation by the driver is not greater than or equal to the predetermined value Th3, the idling stop control is not ended, regardless of the values of the steering torque, the steering angle, and/or the steering angular velocity. It is noted that, even in this case, the idling stop control may be ended when another start condition (i.e., the predetermined start condition other than the start condition related to the steering described above) is met. 
       FIG. 9  is a flowchart illustrating yet another example of a process executed by the idling stop ECU  10 . The process illustrated in  FIG. 9  may be performed at a predetermined cycle during the ON state of the ignition switch and the OFF state of the idling stop cancel switch  70 . 
     The process routine illustrated in  FIG. 9  differs from the process routine illustrated in  FIG. 5  in that the process of step S 503  is replaced with a process of step S 903 . The processes in step S 900 , step S 902 , step S 904  through step S 918  may be the same as those in step S 500 , step S 502 , step S 504  through step S 518  illustrated in  FIG. 5 , respectively. 
     In step S 903 , it is determined whether the steering actuator  26  is being operated. Whether the steering actuator  26  is being operated may be determined based on whether a current (or the control value) applied to the steering actuator  26  is greater than a predetermined value. The predetermined value is arbitrary, and may be 0. If it is determined that the steering actuator  26  is being operated, the process routine goes to step  906 , otherwise the process routine goes to step  904 . 
     According to the process illustrated in  FIG. 9 , the same effects as the process illustrated in  FIG. 4  can be obtained. Further, according to the process illustrated in  FIG. 9 , the idling stop start threshold is changed according to whether the steering actuator  26  is being operated. With this arrangement, it is possible to precisely reduce the probability that the idling stop control, which is better not to be started, is started. 
     Specifically, as described above, even if the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated), there may be a case where the steering actuator  26  does not generate the steering torque when the departure tendency is not detected. Thus, according to the process illustrated in  FIG. 4 , the idling stop control may be started when the steering torque, the steering angle, and/or the steering angular velocity that exceed the first idling stop start thresholds α1, α2, and/or α3 but are less than or equal to the second idling stop start thresholds β1, β2, and/or β3 due to the steering operation by the driver in the situation where the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated). In contrast, according to the process illustrated in  FIG. 9 , even in such a case, the idling stop control is not started when the steering actuator  26  is not being operated. With this arrangement, it is possible to precisely reduce the probability that the idling stop control, which is better not to be started, is started. 
     It is noted that, in the example illustrated in  FIG. 9 , in step S 903 , it may be determined whether the steering actuator  26  is being operated and the steering torque due to the steering operation by the driver is greater than or equal to a predetermined value Th4. Alternatively, it may be determined whether the steering torque of the steering actuator  26  is greater than the steering torque due to the steering operation by the driver. Further, in the example illustrated in  FIG. 9 , the process of step S 903  is performed with respect to the start condition of the idling stop control; however, instead of or in addition to this, the same process as that in step S 903  may be performed with respect to the end condition of the idling stop control. In this case, if the determination result of step S 912  is affirmative, the same determination process as that in step S 903  may be performed, and as a result of this, if the determination result is affirmative, the process routine may go to step S 916 , otherwise the process routine may go to step S 914 . 
       FIG. 10  is a flowchart illustrating yet another example of a process executed by the idling stop ECU  10 . The process illustrated in  FIG. 10  may be performed at a predetermined cycle during the ON state of the ignition switch and the OFF state of the idling stop cancel switch  70 . 
     The process routine illustrated in  FIG. 10  differs from the process routine illustrated in  FIG. 9  in that a process of step S 906  is omitted. Specifically, according to the process routine illustrated in  FIG. 10 , when the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated), and the steering actuator  26  is being operated, the idling stop control is started, regardless of the values of the steering torque, the steering angle, and/or the steering angular velocity. With this arrangement, it becomes possible to reduce a probability that the idling stop control, which otherwise could be performed appropriately, is prevented due to the lane keeping assist control. It is noted that the process routine illustrated in  FIG. 10  is substantially equivalent to a configuration in which the second idling stop start thresholds β1, β2, β3 in the process routine illustrated in  FIG. 9  are changed to very great values. 
     It is noted that, in the example illustrated in  FIG. 10 , the process of step S 906  is omitted with respect to the start condition of the idling stop control; however, instead of or in addition to this, the same idea may be applied with respect to the end condition of the idling stop control. Specifically, the process of step S 916  is omitted, and if the determination result of step S 912  is affirmative, the same determination process as that in step S 903  may be performed. As the result of the same determination process as that in step S 903 , if the determination result is negative, the process routine may go to step S 914 , otherwise the process routine at this cycle may directly end to start from step S 912  at the next process cycle. In this case, when the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated), and the steering actuator  26  is being operated, the idling stop control is not ended, regardless of the values of the steering torque, the steering angle, and/or the steering angular velocity. It is noted that, even in this case, the idling stop control may be ended when another start condition (i.e., the predetermined start condition other than the start condition related to the steering described above) is met. 
     Here, according to the embodiments described above, the engine is made easier to be started or more difficult to be restarted by changing the idling stop start threshold and/or the idling stop end threshold between the case where the LKA switch  34  is in its ON state (or the lane keeping assist control is being operated) and another case; however, substantially the same effect can be obtained by calculating/detecting the steering torque, the steering angle, and/or the steering angular velocity due to the steering operation by the driver (see  FIG. 11 , for example). 
       FIG. 11  is a flowchart illustrating yet another example of a process executed by the idling stop ECU  10 . The process illustrated in  FIG. 11  may be performed at a predetermined cycle during the ON state of the ignition switch and the OFF state of the idling stop cancel switch  70 . 
     In  FIG. 11 , the processes in step S 1100 , step S 1108 , and step S 1118  may be the same as those in step S 400 , step S 408 , and step S 418  illustrated in  FIG. 4 , respectively. 
     If the determination result in step S 1100  is affirmative, the process goes to step S 1104 . In step S 1104 , it is determined, based on the latest information from the EPS ECU  22 , whether the steering torque due to the steering operation by the driver is less than or equal to a predetermined idling stop start threshold. A way of calculating the steering torque due to the steering operation by the driver may be as described above. The predetermined idling stop start threshold is the same as the first idling stop start threshold α1 described above. When it is determined that the steering torque due to the steering operation by the driver is less than or equal to the predetermined idling stop start threshold, the process routine goes to step S 1108 . Otherwise, the process routine directly ends to start from step S 1100  at the next process cycle. Alternatively, otherwise, the process routine may directly end to start from step S 1104  at the next process cycle. Specifically, the determination of step S 1104  may be repeated in the vehicle stopped state. 
     When the process in step S 1108  is terminated, the process routine goes to step  1114 . In step S 1104 , it is determined, based on the latest information from the EPS ECU  22 , whether the steering torque due to the steering operation by the driver exceeds a predetermined idling stop end threshold. The predetermined idling stop end threshold is the same as the first idling stop end threshold γ1 described above. When it is determined that the steering torque due to the steering operation by the driver exceeds the predetermined idling stop end threshold, the process routine goes to step S 1118 . Otherwise, the process routine directly ends to start from step S 1114  at the next process cycle. Specifically, the determination of step S 1104  is repeated in the vehicle stopped state. However, similarly, the process routine may go to step S 1118  during this period, when another start condition (i.e., the predetermined start condition other than the start condition related to the steering) is met. 
     It is noted that, in the example illustrated in  FIG. 11 , the steering torque is compared with the predetermined idling stop start and end thresholds; however, instead of or in addition to this, other parameters (the steering angle and/or the steering angular velocity, for example) may be compared with corresponding thresholds. It is noted that, similarly, when the steering actuator  26  is in non-operated state, the steering angle itself detected by the steering sensor  24  may be used as the steering angle due to the steering operation by the driver. On the other hand, when the steering actuator  26  is in the operated state, the steering angle due to the steering operation by the driver may be derived by subtracting the steering angle due to the operation of the steering actuator  26  from the steering angle detected by the steering sensor  24 . The steering angle due to the operation of the steering actuator may be calculated based on the current, etc., applied to the steering actuator  26 . 
       FIG. 12  is a flowchart illustrating yet another example of a process executed by the idling stop ECU  10 . The process illustrated in  FIG. 12  may be performed at a predetermined cycle during the ON state of the ignition switch and the OFF state of the idling stop cancel switch  70 . 
     The process routine illustrated in  FIG. 12  differs from the process routine illustrated in  FIG. 11  in that processes of step S 1106  and step S 1116  are added. 
     When the determination result in step S 1104  is negative, the process routine directly ends to start from step S 1100  at the next process cycle. If the determination result in step S 1104  is affirmative, the process goes to step S 1106 . In step S 1106 , it is determined, based on the latest information from the EPS ECU  22 , whether the steering torque due to the operation of the steering actuator  26  is less than or equal to a predetermined third idling stop start threshold. The steering torque due to the operation of the steering actuator  26  may be calculated based on a current (or control values such as an instruction torque, etc.) applied to the steering actuator  26 . The predetermined third idling stop start threshold may be the same as the second idling stop start threshold β1 described above; however, the predetermined third idling stop start threshold may be smaller than the second idling stop start threshold β1 as long as the predetermined third idling stop start threshold is greater than the first idling stop start threshold α1. When it is determined that the steering torque due to the steering operation of the steering actuator  26  is less than or equal to the predetermined third idling stop start threshold, the process routine goes to step S 1108 . Otherwise, the process routine directly ends to start from step S 1106  at the next process cycle. Specifically, the determination of step S 1106  may be repeated in the vehicle stopped state. Alternatively, otherwise, the process routine may directly end to start from step S 1100  at the next process cycle. 
     When the determination result of step S 1114  is negative, the process routine goes to step S 1116 . In step S 1116 , it is determined, based on the latest information from the EPS ECU  22 , whether the steering torque due to the operation of the steering actuator  26  exceeds a predetermined third idling stop end threshold. The predetermined third idling stop end threshold may be the same as the second idling stop end threshold described above; however, the predetermined third idling stop end threshold may be smaller than the second idling stop end threshold η1 as long as the predetermined third idling stop end threshold is greater than the second idling stop start threshold β1. When it is determined that the steering torque due to the steering operation of the steering actuator  26  exceeds the predetermined third idling stop end threshold, the process routine goes to step S 1118 . Otherwise, the process routine directly ends to start from step S 1114  at the next process cycle. Specifically, the determinations of step S 1104 , etc., are repeated in the vehicle stopped state. However, similarly, the process routine may go to step S 1118  during this period, when another start condition (i.e., the predetermined start condition other than the start condition related to the steering) is met. 
     It is noted that, similarly, in the example illustrated in  FIG. 12 , the steering torque is compared with the predetermined idling stop start and end thresholds; however, instead of or in addition to this, other parameters (the steering angle and/or the steering angular velocity, for example) may be compared with corresponding thresholds. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment(s) of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention. Further, all or part of the components of the embodiments described above can be combined. 
     For example, in the embodiments described above, there parameters, that is to say, the steering torque, the steering angle, and the steering angular velocity are used to determine the start condition, etc., related to the steering; however, any two of or only any one of the steering torque, the steering angle, and the steering angular velocity may be used. 
     Further, in the embodiments described above, the lane keeping assist control is performed over a whole vehicle speed range; however, the lane keeping assist control may be prevented in a part of the vehicle speed range. Even in this case, the embodiments described above may be effective when the vehicle speed range in which the lane keeping assist control can be performed is at least partially overlapped with the vehicle speed range in which the idling stop control can be performed. For example, the idling stop control may be executable when the vehicle speed is less than or equal to the predetermined vehicle speed V2, described above. In this case, it suffices if the lane keeping assist control is executable even when vehicle speed is less than or equal to the predetermined vehicle speed V2. 
     Further, in the embodiments described above, it is assumed that the steering actuator  26 , the torque sensor  23 , and the steering sensor  24  are installed in such a positional relationship that the operation of the steering actuator  26  has an influence on the detection values of the torque sensor  23  and the steering sensor  24 ; however, other configurations may be used. For example, there may be such a configuration (see  FIG. 2  (B)) in which the detection values of the torque sensor  23  and the steering sensor  24  do not change even if the steering actuator  26  is operated as long as there is no steering operation of the driver. In this case, in the example illustrated in  FIG. 4  (the same holds true for  FIG. 5  through  FIG. 10 ), the three parameters, that is to say, the steering torque, the steering angle, and the steering angular velocity used for the determinations in step S 406  and step S 416  may be calculated (converted) based on the current (or the control value) applied to the steering actuator  26 . It is noted that, in the example illustrated in  FIG. 2  (B), the steering actuator  26  is provided to act on the rack  94  (act on the rack  94  via a ball screw nut mechanism, for example) and the torque sensor  23  and the steering sensor  24  are provided on the steering shaft  92 . According to such a configuration, the steering torque detected by the torque sensor  23  substantially corresponds to the torque (i.e., the driver steering torque) generated the driver operating the steering wheel  90 . Thus, in step S 503  in  FIG. 5  (the same holds true for  FIG. 6 , etc.), for example, the steering torque itself detected by the torque sensor  23  may be constantly used as the steering torque due to the steering operation by the driver. Similarly, in step S 1104  and step S 1114  in  FIG. 11 , the steering torque itself detected by the torque sensor  23  may be constantly used as the steering torque due to the steering operation by the driver. 
     Further, in the embodiments described above, the lane keeping assist control is performed based on the detection result of the lane boundary sign; however, in addition to or instead of the lane boundary sign, an object that has a predetermined positional relationship with respect to the lane boundary sign, such as a guard rail, a surrounding building, etc., may be detected to perform the lane keeping assist control. In this case, suitable lane keeping assist control may be maintained even in a situation where the lane boundary sign cannot be recognized or the recognition rate of the lane boundary sign is reduced due to rain, snow, dirt, etc. 
     The present application is based on and claims the benefit of priority of Japanese Priority Application No. 2013-232477, filed on Nov. 8, 2013, the entire contents of which are hereby incorporated by reference. 
     DESCRIPTION OF REFERENCE SYMBOLS 
     
         
         
           
               1  vehicle control apparatus 
               10  idling stop ECU 
               20  LKA ECU 
               22  EPS ECU 
               23  torque sensor 
               24  steering sensor 
               26  steering actuator 
               32  forward camera 
               34  LKA switch 
               40  engine ECU 
               50  brake ECU 
               70  idling stop cancel switch 
               92  steering shaft 
               94  rack