Driving support apparatus

Abstract

PURPOSE: To provide a driving support apparatus that allows a driver to easily recognize that an upper limit value of a vehicle speed of an own vehicle at the time when traffic congestion is cleared has become higher than an upper limit value set before the congestion occurs.SOLUTION: A driving support apparatus 1 includes an operation device that is shared between an operation for requesting an increase in an upper limit value spmax of a vehicle speed sp0 of an own vehicle and an operation for requesting the start of the own vehicle. A processor of the driving support apparatus 1 controls a notification device 50 so that information indicating that the upper limit value has increased is provided to the driver when the upper limit value at the time when the traffic congestion is cleared is higher than the upper limit value before the traffic congestion occurs around the own vehicle.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a driving assistance device having a function of assisting a driving operation to adjust the speed of a vehicle. [Background technology]

[0002] A driving assistance device has been proposed that has a function for assisting a driver in adjusting the speed of a vehicle (see, for example, Patent Document 1 below). This driving assistance device (hereinafter referred to as the "conventional device") controls the drive system, braking system, and other components of the vehicle (hereinafter referred to as the "drive system, etc.") so that the vehicle speed of the vehicle coincides with a predetermined upper limit (a value preset by the driver) when the vehicle is traveling on a highway (constant-speed traveling function). However, if the speed of a preceding vehicle (another vehicle traveling immediately ahead of the vehicle) is slower than the upper limit (preset vehicle speed), the conventional device controls the drive system, etc. so that the inter-vehicle distance between the vehicle and the preceding vehicle is greater than a predetermined value (inter-vehicle distance adjustment function). When the conventional device detects that the preceding vehicle has stopped, it stops the vehicle behind the preceding vehicle. Then, when the conventional device detects that the preceding vehicle has started moving and that a predetermined operating device (switch) has been operated, it controls the drive system, etc. so that the vehicle starts moving after the preceding vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-20495 Summary of the Invention

[0004] In this type of driving assistance device, a single switch may be provided for both operations, rather than providing separate switches for requesting an increase in the upper limit value and for requesting that the host vehicle start following a preceding vehicle that has started. In this case, the driving assistance device starts the host vehicle when it detects that the switch has been operated in a state in which it has determined that the host vehicle is stopped. On the other hand, the driving assistance device increases the upper limit value when it detects that the switch has been operated in a state in which it has determined that the host vehicle is moving (a state in which it has not determined that the host vehicle is stopped). Here, the driving assistance device may be configured to determine that the host vehicle has stopped when the time Δt during which the host vehicle's speed remains at "0 km / h" exceeds a threshold Δtth.

[0005] For example, a scenario may arise in which a preceding vehicle temporarily stops due to a traffic jam on a highway, and the host vehicle stops behind the preceding vehicle and then starts moving immediately after the preceding vehicle stops. In this scenario, the time Δt may be equal to or less than a threshold value Δtth when the driver operates a switch to start the host vehicle to follow the preceding vehicle. Therefore, the driving assistance device does not determine that the host vehicle has stopped at the time the driver operates the switch. In other words, the driving assistance device determines that the host vehicle is still moving. Therefore, in response to the switch operation, the driving assistance device increases the upper limit of the host vehicle's speed rather than starting the host vehicle. The driver is likely to repeatedly operate the switch to start the host vehicle without realizing that the upper limit has increased. For example, the driving assistance device increases the upper limit by a predetermined value each time the switch is operated within a period in which the time Δt is equal to or less than a threshold value Δtth. The driving assistance device then starts the host vehicle when it detects that the switch was operated after the time Δt exceeded the threshold value Δtth. In this way, in a vehicle to which a conventional device is applied, the driver may unintentionally increase the upper limit of the vehicle's speed during a period of traffic congestion, and after the traffic congestion is resolved, the vehicle may travel at a speed faster than the driver intended.

[0006] One of the objects of the present invention is to provide a driving assistance device that allows the driver to easily recognize that the upper limit of the vehicle speed of the vehicle at the time when the traffic jam is resolved is higher than the upper limit that was set before the traffic jam occurred.

[0007] In order to achieve the above object, the driving assistance device (1) of the present invention comprises: an on-vehicle sensor (20) for acquiring information regarding the behavior (sp0) of a host vehicle (V0) and information regarding the behavior (sp1, D) of a preceding vehicle (V1) traveling immediately in front of the host vehicle; a processor (10) capable of executing a process of controlling a host vehicle so that the host vehicle travels at a predetermined upper limit value (spmax) and a process of controlling the host vehicle so that the host vehicle follows the preceding vehicle, the processor being configured to control the host vehicle so that the host vehicle follows the preceding vehicle when it detects that the preceding vehicle has started moving from a state in which the host vehicle and the preceding vehicle are stopped and detects that the driver of the host vehicle has performed a predetermined operation; Equipped with. The driving assistance device also includes an operation device (25) that is used for both an operation to request an increase in the upper limit value and an operation to request starting of the host vehicle. The processor executes a notification process to control the notification device (50) so that, when the upper limit value at the time when the congestion around the vehicle is resolved is higher than the upper limit value before the congestion occurred, the notification process provides the driver with information indicating that the upper limit value has increased.

[0008] According to the driving assistance device of the present invention, even if the driver unintentionally increases the upper limit of the vehicle speed of the vehicle during a traffic jam, information indicating the increase in the upper limit is provided to the driver when the traffic jam is resolved, so that the driver can easily recognize the increase in the upper limit.

[0009] In one aspect of the present invention, there is provided a driving assistance device, The processor stores the upper limit value in a memory device (10c) when it determines that a traffic jam has occurred around the vehicle, and then, when it determines that the traffic jam has been resolved, executes the notification process if the current value (spmax0) of the upper limit value is higher than the value (spmax1) stored in the memory device.

[0010] This allows the processor to relatively easily detect that the upper limit of the vehicle speed at the time when the traffic jam is resolved is higher than before the traffic jam occurred. The processor may also execute the notification process if, at the time when it is determined that the traffic jam has been resolved, the difference (Δsp) between the current value of the upper limit and the value stored in the storage device exceeds a threshold (Δspth). This allows information indicating the increase in the upper limit to be provided to the driver only when the upper limit has increased relatively significantly. In other words, when the change in the upper limit is slight (when the change does not impede the subsequent driving of the vehicle), provision of the information is suppressed.

[0011] In a driving assistance device according to another aspect of the present invention, the notification process includes a process of providing the driver with information used to execute a restoration operation requesting that the current value of the upper limit value be restored to the value stored in the storage device, When the processor detects that the driver has performed the restoration operation, the processor returns the upper limit value to the value stored in the storage device.

[0012] This allows the driver to relatively easily return the upper limit of the vehicle speed to the original value (the value that the driver intentionally set before the traffic jam occurred).

[0013] In a driving assistance device according to another aspect of the present invention, The processor determines that a traffic jam has occurred around the vehicle when the duration (Δta) of the vehicle's speed remaining below a predetermined first vehicle speed (spa) exceeds a first traffic jam determination threshold (Δtath), and determines that the traffic jam has been resolved when the duration (Δtb) of the vehicle's speed remaining above a second vehicle speed (spb) that is faster than the first vehicle speed exceeds a second traffic jam determination threshold (Δtbth).

[0014] This allows the processor to relatively easily detect whether or not there is congestion around the vehicle.

[0015] In a driving assistance device according to another aspect of the present invention, The processor determines that an operation requesting that the upper limit value be increased has been performed when the operating device is operated under conditions in which the vehicle speed of the vehicle is greater than "0" or the duration (Δt) of the vehicle speed being "0" is equal to or less than a stop determination threshold (Δtth), and determines that an operation requesting that the vehicle start following the preceding vehicle has been performed when the operating device is operated under conditions in which the duration of the vehicle speed being "0" exceeds the stop determination threshold.

[0016] According to this, in a scene where the preceding vehicle starts moving immediately after the vehicle speed of the host vehicle becomes "0", the processor does not determine that the host vehicle has stopped. In this case, the host vehicle can start moving so as to follow the preceding vehicle without the driver operating the operating device. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a block diagram of a driving assistance device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a time chart showing changes in the vehicle speed of the subject vehicle and the preceding vehicle, changes in various flags, and the like. [Figure 3] FIG. 3 is a flowchart of a first program executed by the CPU to realize the notification function. [Figure 4]FIG. 4 is a flowchart of a second program executed by the CPU to realize the notification function. DETAILED DESCRIPTION OF THE INVENTION

[0018] (Summary) A driving assistance device 1 according to one embodiment of the present invention is applied to, for example, a vehicle V0 (hereinafter referred to as "host vehicle") equipped with an automatic driving function. The driving assistance device 1 has a function (notification function) of providing predetermined information to the driver when the upper limit value spmax of the host vehicle's vehicle speed sp0 at the time when the traffic congestion is resolved is higher than the upper limit value spmax set before the traffic congestion occurred (the set value immediately before the time when it was determined that the traffic congestion occurred).

[0019] (Specific configuration) As shown in FIG. 1, the driving assistance device 1 includes a driving assistance ECU 10, an on-vehicle sensor 20, a drive device 30, a braking device 40, and a notification device 50.

[0020] The driving assistance ECU 10 includes a microcomputer equipped with a CPU 10a, a ROM 10b, a RAM 10c, a timer 10d (timer 10d_a, timer 10d_b), etc. The driving assistance ECU 10 is connected to other ECUs provided in the host vehicle via a CAN (Controller Area Network).

[0021] The on-board sensor 20 includes a forward sensor for acquiring information about the behavior of the preceding vehicle V1. Specifically, the on-board sensor 20 includes a millimeter wave radar 21, a sonar 22, and a camera 23 as forward sensors.

[0022] The millimeter-wave radar 21 includes a transmitter / receiver and a signal processor (not shown). The transmitter / receiver emits millimeter-wave band radio waves (hereinafter referred to as "millimeter waves") ahead of the vehicle and receives millimeter waves (reflected waves) reflected by a three-dimensional object (leading vehicle V1) located within the emission range. The signal processor calculates the distance between the vehicle and the three-dimensional object, the position (direction) of the three-dimensional object relative to the vehicle, the speed of the three-dimensional object relative to the vehicle, etc. based on the time from when the transmitter / receiver emits the millimeter waves to when the reflected waves are received, the phase difference between the transmitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, etc., and transmits the calculation results to the driving assistance ECU 10.

[0023] The sonar 22 intermittently emits ultrasonic waves into the area surrounding the vehicle and receives the ultrasonic waves (reflected waves) reflected by a three-dimensional object. The sonar 22 calculates the distance between the vehicle and the three-dimensional object, the position (direction) of the three-dimensional object relative to the vehicle, etc. based on the time from when the ultrasonic waves are transmitted until when the reflected waves are received, and transmits the calculation results to the driving assistance ECU 10.

[0024] The camera 23 includes an imaging device and an image analysis device. The imaging device is, for example, a digital camera incorporating an imaging element such as a CCD (charge coupled device) or a CIS (CMOS image sensor). The imaging device is located above the front windshield glass and faces forward. The imaging device captures images of the front view of the vehicle at a predetermined frame rate to acquire image data. The imaging device transmits the image data to the image analysis device. The image analysis device analyzes the acquired image data and acquires information about objects located in front of the vehicle from the images. For example, the image analysis device identifies (recognizes) the type of object located in front of the vehicle (e.g., another vehicle, a lane marking, etc.) and transmits the identification result to the driving assistance ECU 10.

[0025] Furthermore, the on-board sensors 20 include a vehicle speed sensor 24 for acquiring the vehicle speed as information relating to the behavior of the host vehicle.

[0026] The vehicle speed sensor 24 detects the rotation speed (wheel speed) of each wheel and calculates the vehicle speed sp0 (actual vehicle speed) of the host vehicle based on the wheel speed of each wheel. The vehicle speed sensor 24 transmits data representing the vehicle speed sp0 to the driving assistance ECU 10.

[0027] Furthermore, the on-board sensor 20 includes switches 25 and 26 as operating devices of the host vehicle.

[0028] Switches 25, 26 include push-button type switch elements. Switches 25, 26 are incorporated into, for example, the spokes of a steering wheel. Switch 26 is arranged near (for example, below) switch 25. As will be described in detail later, switch 25 is used both for an operation by the driver to request an increase in the upper limit value spmax of the vehicle speed sp0 (to change the setting), and for an operation by the driver to request that the host vehicle start so as to follow a preceding vehicle V1 that has started moving. Switch 26 is used by the driver to request a decrease in the upper limit value spmax. The driving assistance ECU 10 monitors the on / off states of these switches.

[0029] The drive unit 30 applies drive force to the drive wheels. The drive unit 30 includes an engine ECU, an internal combustion engine, a transmission, a drive force transmission mechanism that transmits the drive force to the wheels, and the like. The engine ECU acquires information (target value) that indicates a target drive force from another ECU (the driving assistance ECU 10), and based on that information, drives the throttle valve of the internal combustion engine to adjust the drive force applied to the drive wheels. The drive force generated by the internal combustion engine is transmitted to the drive wheels via the transmission and the drive force transmission mechanism.

[0030] If the vehicle to which the driving assistance device 1 is applied is a hybrid vehicle (HEV), the engine ECU can control the driving force of the vehicle generated by either or both of an internal combustion engine and an electric motor as the vehicle driving source. Also, if the vehicle to which the driving assistance device 1 is applied is an electric vehicle (BEV), an electric motor ECU can be used instead of the engine ECU to control the driving force of the vehicle generated by an electric motor as the vehicle driving source.

[0031] The braking device 40 applies braking force to the wheels (brake discs). The braking device 40 includes a brake ECU, a brake caliper, etc. The brake caliper includes an actuator that presses brake pads against the brake discs. The brake ECU acquires information (target value) indicating a target braking force from another ECU, and based on that information, drives the actuator of the brake caliper to adjust the braking force applied to the wheels (brake discs).

[0032] The notification device 50 includes an audio device and an image display device. The audio device reproduces a predetermined sound (chime) in response to a command transmitted from the driving assistance ECU 10. The image display device displays a predetermined image in response to a command transmitted from the driving assistance ECU 10.

[0033] (Activated) When an ACC switch (not shown) installed in the host vehicle is in the on state, the driving assistance ECU 10 executes a process to assist the driving operation of adjusting the vehicle speed sp0 of the host vehicle, as will be described below. This function is generally called adaptive cruise control (ACC). The ACC includes a constant speed driving function and a following distance adjustment function.

[0034] (Constant speed driving function) The driving assistance ECU 10 determines whether or not a preceding vehicle V1 exists based on information acquired from the forward sensor. If the preceding vehicle V1 does not exist (if the distance between the host vehicle and the preceding vehicle V1 exceeds a threshold), the driving assistance ECU 10 executes a constant speed traveling process that controls the drive device and the like so that the vehicle speed sp0 of the host vehicle coincides with an upper limit value spmax.

[0035] (Following distance adjustment function) When the driving assistance ECU 10 determines that a preceding vehicle V1 is present, it acquires from the forward sensor the inter-vehicle distance D between the preceding vehicle V1 and the subject vehicle, and the vehicle speed (relative speed) of the preceding vehicle V1 relative to the subject vehicle. Furthermore, the driving assistance ECU 10 acquires the vehicle speed sp0 of the subject vehicle from the vehicle speed sensor 24. The driving assistance ECU 10 calculates a target value Dt for the inter-vehicle distance D based on this information.

[0036] When the vehicle speed sp1 of the preceding vehicle V1 relative to the vehicle speed sp0 of the host vehicle (relative speed vr = v0 - vs) is greater than "0", the inter-vehicle distance D increases. When the inter-vehicle distance D is greater than the target value Dt, the driving assistance ECU 10 sets the target value of the acceleration α of the host vehicle to a predetermined value α1 (>0) so that the vehicle speed sp0 of the host vehicle is greater than the vehicle speed sp1 of the preceding vehicle V1. Then, the driving assistance ECU 10 controls the drive system and the like so that the acceleration α (actual measured value) of the host vehicle matches the predetermined value α1 (acceleration control). As a result, the inter-vehicle distance D decreases and approaches the target value Dt. Then, when the inter-vehicle distance D matches the target value Dt, the driving assistance ECU 10 sets the target value of the acceleration α of the host vehicle to "0". In other words, the driving assistance ECU 10 controls the drive system and the like so that the host vehicle travels at the same speed as the preceding vehicle V1.

[0037] On the other hand, when the relative speed vr is smaller than "0", the inter-vehicle distance D decreases. When the inter-vehicle distance D is smaller than the target value Dt, the driving assistance ECU 10 sets the target value of the acceleration α to a predetermined value α2 (<0) so that the vehicle speed sp0 of the host vehicle becomes smaller than the vehicle speed sp1 of the preceding vehicle V1. Then, the driving assistance ECU 10 controls the drive device, etc. so that the acceleration α (actual measured value) of the host vehicle matches the predetermined value α2 (<0) (deceleration control). As a result, the inter-vehicle distance D increases and approaches the target value Dt. Then, when the inter-vehicle distance D matches the target value Dt, the driving assistance ECU 10 sets the target value of the acceleration α of the host vehicle to "0".

[0038] A database showing the relationship between the vehicle speeds sp0, sp1 and the target value Dt or parameters defining an arithmetic expression for calculating the target value Dt are stored in the ROM 10b. The driving assistance ECU 10 determines the target value Dt based on the database or arithmetic expression. In addition, in the control for adjusting the inter-vehicle distance D, the driving assistance ECU 10 controls the drive device, etc. so that the vehicle speed sp0 of the host vehicle is equal to or less than the upper limit value spmax. In other words, when the vehicle speed sp1 of the preceding vehicle V1 is higher than the upper limit value spmax, an increase in the inter-vehicle distance D is permitted.

[0039] Furthermore, when the preceding vehicle V1 stops (sp1=0 km / h) while the ACC is being executed, the driving assistance ECU 10 stops the host vehicle (sp0=0 km / h) behind the preceding vehicle V1. When the driving assistance ECU 10 determines that the host vehicle has stopped, and detects that the preceding vehicle V1 has started moving and that the switch 25 has been pressed (transitioned from the OFF state to the ON state), the driving assistance ECU 10 starts the host vehicle.

[0040] Here, for example, if there is a traffic jam around the host vehicle, there is a high possibility that the host vehicle will repeatedly stop and start. In this situation, there is a high possibility that the switch 25 for restarting the host vehicle will be operated frequently. Therefore, while ACC is being executed, the driving assistance ECU 10 sequentially acquires the vehicle speed sp0 from the vehicle speed sensor 24, and determines that the host vehicle has stopped when the duration Δt of the state in which the vehicle speed sp0 is "0 km / h" exceeds a threshold Δtth (time point t2 in FIG. 2). At this time, the driving assistance ECU 10 sets a stop flag Fstp (a flag indicating whether the host vehicle is stopped or not) to "1" (a value indicating that the host vehicle is stopped). Thereafter, when the vehicle speed sp0 exceeds "0 km / h" (time point t3 in FIG. 2), the driving assistance ECU 10 determines that the host vehicle is traveling (not stopped). At this time, the driving assistance ECU 10 sets the stop flag Fstp to "0" (a value indicating that the host vehicle is not stopped).

[0041] When the driving assistance ECU 10 detects that the preceding vehicle V1 has started moving while the stop flag Fstp is "0" (for example, immediately after the vehicle speed sp0 has decreased to "0 km / h" (Δt≦Δtt)), the driving assistance ECU 10 controls the drive device and the like so that the host vehicle starts moving following the preceding vehicle V1, regardless of the on / off state of the switch 25. On the other hand, when the driving assistance ECU 10 detects that the preceding vehicle V1 has started moving while the stop flag Fstp is "1" (Δt>Δtth) and detects that the switch 25 has transitioned from the off state to the on state (time t3 in FIG. 2), the driving assistance ECU 10 controls the drive device and the like so that the host vehicle starts moving following the preceding vehicle V1. The driving assistance ECU 10 determines whether the preceding vehicle V1 has started moving based on information acquired from a forward sensor. For example, the driving assistance ECU 10 determines that the preceding vehicle V1 has started moving when the vehicle speed sp1 of the preceding vehicle V1 acquired from the millimeter-wave radar 21 increases from "0 km / h" and exceeds a threshold. Alternatively, for example, the driving assistance ECU 10 may determine that the preceding vehicle V1 has started moving when the distance between the preceding vehicle V1 and the subject vehicle exceeds a threshold.

[0042] Furthermore, the driving assistance ECU 10 adds a predetermined value (e.g., 3 km / h) to the upper limit value spmax each time the switch 25 is pressed while the stop flag Fstp is "0." Furthermore, the driving assistance ECU 10 subtracts a predetermined value (e.g., 3 km / h) from the upper limit value spmax each time the switch 26 is pressed while the stop flag Fstp is "0." In this way, the driver can change the upper limit value spmax in a situation where it is not determined that the host vehicle is stopped (Fstp="0").

[0043] As described above, the switch 25 is used by the driver to request that the host vehicle start following the preceding vehicle V1 and to request that the upper limit value spmax be increased. In a situation where traffic congestion occurs around the host vehicle, the driver may recognize that the host vehicle has stopped during a period T from when the vehicle speed sp0 of the host vehicle decreases to 0 km / h (time t1 in FIG. 2 ) until the duration Δt of this state (sp0 = 0 km / h) exceeds the threshold value Δtth (a period before the driving assistance ECU 10 determines that the host vehicle has stopped). If the preceding vehicle V1 starts moving during this period T, the driver may press the switch 25 with the intention of starting the host vehicle following the preceding vehicle V1. However, because the stop flag Fstp is set to 0 during this period T, the driving assistance ECU 10 only increases the upper limit value spmax each time the switch 25 is pressed, and does not start the host vehicle. The driver may not notice the increase in the upper limit value spmax. When the traffic congestion subsequently clears and the constant speed cruise control process is initiated, the host vehicle may travel at a speed higher than the driver intended. Therefore, the driving assistance ECU 10 has a notification function that executes the notification process described below.

[0044] (Alert function) While ACC is being executed, the driving assistance ECU 10 determines whether or not a traffic jam has occurred around the vehicle based on the vehicle speed sp0. Specifically, when the duration Δta during which the vehicle speed sp0 is equal to or less than the threshold value spa exceeds the threshold value Δtath (time t0 in FIG. 2), the driving assistance ECU 10 determines that a traffic jam has occurred around the vehicle. At this time, the driving assistance ECU 10 sets the traffic jam flag Ftjm to "1" (a value indicating that a traffic jam has occurred). Thereafter, when the duration Δtb during which the vehicle speed sp0 exceeds a predetermined threshold value spb (>spa) exceeds the threshold value Δtbth (time t4 in FIG. 2), the driving assistance ECU 10 determines that the traffic jam has been resolved (no traffic jam has occurred). At this time, the driving assistance ECU 10 sets the traffic jam flag Ftjm to "0" (a value indicating that no traffic jam has occurred). At time t0 when the traffic jam flag Ftjm changes from "0" to "1," the driving assistance ECU 10 acquires the upper limit value spmax (current value) and stores the acquired value as the upper limit value spmax1 in the RAM 10c.

[0045] The driving assistance ECU 10 acquires the upper limit value spmax (current value spmax0) at time t4 when the congestion flag Ftjm transitions from "1" to "0." If the current value spmax0 is greater than the upper limit value spmax1 stored in the RAM 10c and the difference Δsp (= spmax0 - spmax1) exceeds the threshold value Δspth, the driving assistance ECU 10 controls the notification device 50 to provide the driver with predetermined information to alert them to the increase in the upper limit value spmax. Specifically, the driving assistance ECU 10 causes the image display device of the notification device 50 to display an image indicating that the upper limit value spmax has increased (the current upper limit value spmax0 is higher than the upper limit value spmax1 immediately before the occurrence of congestion), and causes the audio device of the notification device 50 to play a predetermined sound (beep).

[0046] Next, with reference to FIGS. 3 and 4, a program PR1 and a program PR2 executed by the CPU 10a (hereinafter referred to as "CPU") of the driving assistance ECU 10 to realize the above-described notification function will be described. In addition to the programs PR1 and PR2, the CPU executes a plurality of programs (programs PR3, PR4, ...) not shown. The program PR3 includes a process for setting the stop flag Fstp to "0" or "1" (switching the value of the stop flag Fstp appropriately) based on a change in the vehicle speed sp0 of the host vehicle. The program PR4 includes a process for "raising the upper limit value spmax when the switch 25 is pressed while the stop flag Fstp is "0"" and a process for "controlling the drive device, etc. so that the host vehicle starts to follow the preceding vehicle V1 when the switch 25 is pressed while the stop flag Fstp is "1".

[0047] (Program PR1) The CPU executes the program PR1 at a predetermined interval when the traffic congestion flag Ftjm is "0." In the process of the CPU executing the program PR1 and the program PR2 (described later), the traffic congestion flag Ftjm is set to "0" or "1." The CPU starts execution of the program PR1 from step 100 and proceeds to step 101.

[0048] In step 101, the CPU initializes the timer 10d_a. That is, the CPU resets the output of the timer 10d_a, which measures the duration Δta during which the vehicle speed sp0 of the host vehicle is equal to or less than the threshold value spa, to "0" (the measurement result of the duration Δta), and causes the timer 10d_a to start measuring the duration Δta. Next, the CPU proceeds to step 102.

[0049] In step 102, the CPU determines whether the vehicle speed sp0 is equal to or less than the threshold value spa. If the CPU determines that the vehicle speed sp0 is equal to or less than the threshold value spa (102: Yes), the CPU proceeds to step 103. On the other hand, if the CPU does not determine that the vehicle speed sp0 is equal to or less than the threshold value spa (102: No), the CPU proceeds to step 106, where it ends the execution of the program PR1.

[0050] In step 103, the CPU determines whether the time Δta exceeds the threshold value Δtath. If the CPU determines that the duration Δta exceeds the threshold value Δtath (103: Yes), the CPU proceeds to step 104. On the other hand, if the CPU does not determine that the duration Δta exceeds the threshold value Δtath (103: No), the CPU returns to step 102.

[0051] In step 104, the CPU sets the congestion flag Ftjm to “1.” Next, the CPU proceeds to step 105.

[0052] The CPU stores the current value of the upper limit value spmax in the RAM 10c as the upper limit value spmax1 in step 105. Next, the CPU proceeds to step 106, where it ends the execution of the program PR1.

[0053] (Program PR2) The CPU executes the program PR2 when the congestion flag Ftjm is 1. The CPU starts the execution of the program PR2 from step 200 and proceeds to step 201.

[0054] In step 201, the CPU initializes the timer 10d_b. That is, the CPU resets the output of the timer 10d_b (measurement result of the duration Δtb) that measures the duration Δtb during which the vehicle speed sp0 of the host vehicle exceeds the threshold spb to "0," and causes the timer 10d_b to start measuring the duration Δtb. Next, the CPU proceeds to step 202.

[0055] In step 202, the CPU determines whether the vehicle speed sp0 exceeds the threshold value spb. If the CPU determines that the vehicle speed sp0 exceeds the threshold value spb (202: Yes), the CPU proceeds to step 203. On the other hand, if the CPU does not determine that the vehicle speed sp0 exceeds the threshold value spb (202: No), the CPU proceeds to step 207, where it ends the execution of the program PR2.

[0056] In step 203, the CPU determines whether the duration Δtb exceeds the threshold value Δtbth. If the CPU determines that the duration Δtb exceeds the threshold value Δtbth (203: Yes), the CPU proceeds to step 204. On the other hand, if the CPU does not determine that the time Δtb exceeds the threshold value Δtbth (203: No), the CPU returns to step 202.

[0057] In step 204, the CPU sets the congestion flag Ftjm to “0.” Next, the CPU proceeds to step 205.

[0058] In step 205, the CPU reads the upper limit value spmax1 from the RAM 10c and determines whether the difference Δsp (=sp,ax0-spmax1) between the current value of the upper limit value spmax (upper limit value spmax0) and the upper limit value spmax1 exceeds the threshold value Δspth. If the CPU determines that the difference Δsp exceeds the threshold value Δspth (205: Yes), the CPU proceeds to step 206. On the other hand, if the CPU does not determine that the difference Δsp exceeds the threshold value Δspth (205: No), the CPU proceeds to step 207, where it ends execution of the program PR2.

[0059] The CPU controls the notification device 50 so that predetermined information (alert) is provided to the driver in step 206. Next, the CPU proceeds to step 207, where it ends the execution of the program PR2.

[0060] (effect) According to the driving assistance device 1, even if the driver unintentionally increases the upper limit value spmax of the vehicle speed sp0 of the vehicle during a traffic jam, information indicating the increase in the upper limit value spmax is provided to the driver when the traffic jam is resolved, so the driver can easily recognize the increase in the upper limit value spmax.

[0061] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

[0062] <Modification 1> In the above embodiment, when the difference Δsp exceeds the threshold value Δspth, the driving assistance ECU 10 causes the image display device of the notification device 50 to display an image indicating that "the upper limit value spmax at the time when the traffic congestion is resolved is higher than the upper limit value before the traffic congestion occurred." In addition, the driving assistance ECU 10 may cause the display device to display an image (a message, an execute button, etc.) used to perform an operation (restoration operation) requesting that the upper limit value spmax be restored to the value before the traffic congestion occurred (upper limit value spmax1). When the driver performs the restoration operation, the driving assistance ECU 10 executes the restoration process.

[0063] <Variation 2> The driving assistance ECU 10 may be configured not to increase the upper limit value spmax even if the switch 25 is pressed in a situation where the traffic congestion flag Ftjm is "1" and the stop flag Fstp is "0". [Explanation of symbols]

[0064] 1... driving assistance device, 10... driving assistance ECU, 20... in-vehicle sensor, 50... alarm device

Claims

1. an on-board sensor for acquiring information on the behavior of the host vehicle and information on the behavior of a preceding vehicle traveling immediately in front of the host vehicle; a processor capable of executing a process of controlling the host vehicle so that the vehicle speed of the host vehicle travels at a predetermined upper limit value and a process of controlling the host vehicle so that the host vehicle follows the preceding vehicle, the processor being configured to control the host vehicle so that the host vehicle follows the preceding vehicle when it detects that the preceding vehicle has started moving from a state in which the host vehicle and the preceding vehicle are stopped and detects that the driver of the host vehicle has performed a predetermined operation; A driving assistance device comprising: an operation device that is used for both an operation to request an increase in the upper limit value and an operation to request a start of the host vehicle; The driving assistance device is configured such that, when the upper limit value at the time when the congestion around the vehicle is resolved is higher than the upper limit value before the congestion occurs, the processor controls the notification device to provide the driver with information indicating that the upper limit value has increased.

2. The driving assistance device according to claim 1, The processor stores the upper limit value in a storage device when it is determined that a traffic jam has occurred around the vehicle, and then, when it is determined that the traffic jam has been resolved, if the current value of the upper limit value is greater than the value stored in the storage device, executes the notification process.

3. The driving assistance device according to claim 2, the notification process includes a process of providing the driver with information used to execute a restoration operation requesting that the current value of the upper limit value be restored to the value stored in the storage device, The driving assistance device is configured such that, when the processor detects that the driver has performed the restoration operation, the processor restores the upper limit value to the value stored in the storage device.

4. The driving assistance device according to claim 1, The processor is configured to determine that a traffic jam has occurred around the vehicle when the duration of the state in which the vehicle speed of the vehicle is equal to or less than a predetermined first vehicle speed exceeds a first traffic congestion determination threshold, and to determine that the traffic jam has been resolved when the duration of the state in which the vehicle speed of the vehicle is greater than a second vehicle speed that is faster than the first vehicle speed exceeds a second traffic congestion determination threshold.

5. 5. The driving assistance device according to claim 1, The processor determines that an operation requesting that the upper limit value be increased has been performed when the operating device is operated under conditions in which the vehicle speed of the vehicle is greater than "0" or the duration of the state in which the vehicle speed of the vehicle is "0" is equal to or less than a stop determination threshold, and determines that an operation requesting that the vehicle start following the preceding vehicle has been performed when the operating device is operated under conditions in which the duration of the state in which the vehicle speed of the vehicle is "0" exceeds the stop determination threshold.

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