JP2010095219A - Device for controlling vehicle speed, method for controlling vehicle speed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for controlling a vehicle speed and a method for controlling a vehicle speed, preventing a vehicle from abnormally approaching a preceding vehicle due to an accelerator operation after ACC cancellation. <P>SOLUTION: The device 100 for controlling the vehicle speed includes following means 24, 25 for following a captured preceding vehicle, and upper limit vehicle speed limiting means 23 for limiting a vehicle speed by a preset upper limit vehicle speed even when an accelerator pedal 14 is depressed. The device 100 includes: a relative speed detection means 12 for detecting a relative speed to the preceding vehicle; an vehicle speed detection means 11 for detecting the vehicle speed of the vehicle; and an upper limit vehicle speed changing means 21 for setting the upper limit vehicle speed to the vehicle speed of the preceding vehicle or lower if the vehicle speed of the preceding vehicle is faster than that of the vehicle when the function of the following means is released by a driver's operation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle speed control device and a vehicle speed control method that limit a vehicle speed by a preset upper limit vehicle speed even when an accelerator pedal is depressed, and more particularly to a vehicle speed control device and a vehicle speed control method that can change an upper limit vehicle speed.

  There are known cruise control that keeps the vehicle speed of the vehicle at the set vehicle speed set by the driver and adaptive cruise control that follows the vehicle while adjusting the distance between the vehicle and the preceding vehicle according to the vehicle speed. ACC). In ACC, the set vehicle speed can be set, and while the preceding vehicle is supplemented by radar, etc., the vehicle follows the preceding vehicle within the range not exceeding the set vehicle speed, and the preceding vehicle is accelerated when the preceding vehicle is not supplemented. When the set vehicle speed is exceeded, the follow-up running is terminated and the set vehicle speed is constant and the vehicle runs at a constant speed.

  On the other hand, a speed limiter that prevents the vehicle speed from becoming higher than the preset upper limit vehicle speed may be integrated with the ACC so that the vehicle speed does not increase too much due to the accelerator operation by the driver. By setting the upper limit vehicle speed according to the limit vehicle speed and preference, the vehicle can be accelerated on a highway without worrying about the vehicle speed.

  Techniques for making this upper limit vehicle speed variable have been proposed (see, for example, Patent Documents 1 and 2). Patent Document 1 discloses a speed limiter that increases the upper limit vehicle speed when the preceding vehicle accelerates and the inter-vehicle distance increases. As the upper limit vehicle speed increases, the vehicle speeds up and the distance between the preceding vehicle and the preceding vehicle is easily reduced. In Patent Document 2, the upper limit vehicle speed set in advance is set when the vehicle is stopped, the upper limit vehicle speed is prohibited at the dead zone speed, and in other cases, the vehicle speed when the setting means is operated is set as the upper limit vehicle speed. A speed limiter that is set to 1 is disclosed.

  By the way, even when following the ACC, the driver's accelerator operation is prioritized and operations such as closing the distance between the vehicles are possible, but the driver is concerned about the inter-vehicle distance and relative speed with the preceding vehicle. Adjust the accelerator work. In this regard, a technique for supporting the driver's accelerator operation has been proposed (see, for example, Patent Document 3). Patent Document 3 discloses a vehicle speed control device that corrects responsiveness to a driver's operation in accordance with a relative traveling situation such as an inter-vehicle distance and a relative speed with respect to a preceding vehicle.

With this control, the vehicle speed control device described in Patent Document 3 can prevent an abnormal approach to the preceding vehicle due to a driver's operation error, for example, by lowering the response characteristics as the inter-vehicle distance is shorter.
JP 2006-248295 A JP 2007-153147 A JP 2006-291870 A

  However, since the vehicle speed control device described in Patent Document 3 only lowers the responsiveness, there is a problem that when the driving vehicle erroneously continues the accelerator operation, the vehicle will eventually be abnormally approached.

  In many cases, the ACC can be canceled by the driver's brake operation. For example, if the driver determines that the driver has approached too much after the accelerator operation to reduce the distance from the preceding vehicle and the brake operation is performed, the ACC Will be cancelled. However, if the driver is unaware that the ACC has been canceled and misunderstood that the inter-vehicle distance is automatically maintained by the ACC, there is a possibility that the vehicle may abnormally approach the preceding vehicle due to the previous acceleration. is there.

  In view of the above problems, an object of the present invention is to provide a vehicle speed control device and a vehicle speed control method for preventing the host vehicle from abnormally approaching a preceding vehicle due to an accelerator operation after ACC cancellation.

  In view of the above-described problems, the present invention provides vehicle speed control that includes follow-up traveling means that follows a supplemented preceding vehicle and upper-limit vehicle speed limiting means that restricts the vehicle speed by a preset upper-limit vehicle speed even when the accelerator pedal is depressed. A device that detects a relative speed with respect to a preceding vehicle, a host vehicle speed detecting unit that detects a vehicle speed of the host vehicle, and a function of the follower traveling unit that is canceled by a driver's operation. When the vehicle speed of the preceding vehicle is faster than the vehicle speed of the host vehicle, the vehicle has an upper limit vehicle speed changing means for setting the upper limit vehicle speed to be equal to or lower than the vehicle speed of the preceding vehicle.

  It is possible to provide a vehicle speed control device and a vehicle speed control method that prevent the host vehicle from abnormally approaching a preceding vehicle due to an accelerator operation after ACC cancellation.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is an example of a diagram for schematically explaining the change of the upper limit vehicle speed by the vehicle speed control device 100 of the present embodiment.
(1) The host vehicle supplements the preceding vehicle, and the vehicle travels following the set vehicle speed set by the driver to the upper limit (hereinafter referred to as ACC (Adaptive Cruise Control)). The vehicle speed control device 100 includes a variable speed limiter (hereinafter referred to as ASL (Adaptive Speed Limiter)), and an upper limit vehicle speed set by the driver is set. Generally, an upper limit vehicle speed larger than the set vehicle speed is set. Then, for some reason (for example, when the driver depresses the accelerator pedal and accelerates, when the preceding vehicle decelerates, or when another preceding vehicle interrupts from the other person's line), the inter-vehicle distance from the preceding vehicle is the target The distance between the cars became shorter and the driver operated the brake pedal.
(2) The ACC is temporarily canceled by the brake operation. Note that ACC is automatically canceled when the driver's intention to decelerate is detected, and if the vehicle continues to follow or drive at a constant speed, it will be abnormally close to the preceding vehicle, etc. against the driver's will. It is because there is a possibility of doing.

  Since ASL is still valid even if ACC is canceled, when the vehicle speed reaches the upper limit vehicle speed of ASL, the vehicle speed is limited so as not to exceed the upper limit vehicle speed. The upper limit vehicle speed immediately after the ACC is canceled is a value set in advance by the driver.

Here, it is considered that the preferable upper limit vehicle speed differs depending on the magnitude relationship between the vehicle speed of the host vehicle and the vehicle speed of the preceding vehicle. In addition, when the vehicle speed of the own vehicle and the vehicle speed of the preceding vehicle are equal, it is treated that the vehicle speed of the own vehicle is lower than the vehicle speed of the preceding vehicle.
(3) -1 Vehicle speed of own vehicle <Vehicle speed of preceding vehicle The case where the vehicle speed of the own vehicle is lower than the vehicle speed of the preceding vehicle is a case where the vehicle is sufficiently decelerated by the driver's brake operation. Accordingly, although the inter-vehicle distance tends to increase, the driver may depress the accelerator to accelerate the vehicle so as to close the inter-vehicle distance, and depending on the accelerator operation, there is a risk of abnormally approaching the preceding vehicle. Therefore, the vehicle speed control device 100 sets the upper limit vehicle speed of ASL to be equal to or lower than the vehicle speed of the preceding vehicle. As a result, even if the driver depresses the accelerator pedal even if the vehicle is decelerated after the brake operation, the vehicle cannot be accelerated beyond the vehicle speed of the preceding vehicle. In addition, since it is possible to follow the preceding vehicle only by setting the accelerator opening to 100%, for example, without a delicate accelerator work by the driver, the operability is improved. In addition, if the vehicle travels following the preceding vehicle and then returns to ACC, the vehicle can start traveling at the set vehicle speed as it is.
(3) -2 Vehicle speed of the host vehicle> Vehicle speed of the preceding vehicle The vehicle speed of the host vehicle is greater than the vehicle speed of the preceding vehicle. It is. In this case, since the ACC is cancelled, there is a possibility that the vehicle approaches the preceding vehicle as it is. Further, if the upper limit vehicle speed is set to be approximately the same as the vehicle speed of the preceding vehicle, the inter-vehicle distance may be further shortened before the vehicle speed of the host vehicle decreases to the upper limit vehicle speed (vehicle speed of the preceding vehicle). For this reason, when the vehicle speed of the own vehicle is larger than the vehicle speed of the preceding vehicle, the upper limit vehicle speed is set to a value smaller than the vehicle speed of the preceding vehicle. Thereby, the abnormal approach with a preceding vehicle can be prevented reliably.

  When the vehicle speed of the host vehicle becomes smaller than that of the preceding vehicle, the vehicle speed of the preceding vehicle is set as the upper limit vehicle speed, so that the vehicle can follow the preceding vehicle without delicate accelerator work by the driver.

  Therefore, when the ACC is canceled, the vehicle speed control device 100 of the present embodiment can prevent abnormal approach to the preceding vehicle and improve the operability of the driver.

  FIG. 2 shows an example of a block diagram of the vehicle speed control device 100. The vehicle speed control device 100 is mainly controlled by an engine ECU (Electronic Control Unit) 15, and the engine ECU 15 includes an inter-vehicle distance control ECU 13, a meter via an in-vehicle LAN such as CAN (Controller Area Network) and FlexRay and a dedicated line. An ECU 16, an electronic throttle 17, and an accelerator pedal stroke sensor 19 are connected. Each ECU communicates necessary information with each other using the multiplex communication function of the in-vehicle LAN.

  The inter-vehicle distance control ECU 13 detects the preceding vehicle based on the detection signal of the radar sensor 12, and detects the relative speed and the inter-vehicle distance with the preceding vehicle. The radar sensor 12 includes, for example, a millimeter-wave band radar transmission / reception device disposed in the front grille. The radar sensor 12 changes the inter-vehicle distance according to the time until the transmission wave is reflected by the preceding vehicle and received, and the temporal change in the inter-vehicle distance. The relative speed is detected from (differential value etc.). A preceding vehicle can be identified by grouping a series of reflected waves detected as the same inter-vehicle distance. The direction of the preceding vehicle is detected by scanning the transmission direction of the transmission wave, for example. The transmission wave is irradiated in a pulsed manner while scanning a predetermined angle range in the left-right direction centering on the vehicle length direction (for example, a range of 30 degrees left and right). If a vehicle ahead is present in the irradiation direction, a reflected wave is received. The inter-vehicle distance and the relative speed are transmitted to the engine ECU 15 via the CAN.

  Each wheel is provided with wheel speed sensors 11a to 11d (hereinafter simply referred to as wheel speed sensor 11), and the wheel speed sensor 11 is pulsed per unit time detected according to the rotation of the wheel. The vehicle speed information obtained by multiplying this signal by a constant such as the radius of the wheel is obtained. For example, the vehicle speed information is sent to the CAN via the brake ECU and received by the engine ECU 15 or the like.

  The meter ECU 16 displays the ACC set vehicle speed 31 and the upper limit vehicle speed 32 on the meter panel, and provides the current value to the occupant. The input of the ACC set vehicle speed 31 and the ASL upper limit vehicle speed 32 is received by operating the operation lever 18. An example of a method of setting the set vehicle speed 31 is, for example, by operating the operation lever 18. The vehicle speed when the operation lever 18 is operated downward in the predetermined vehicle speed range and returned to the neutral position is acquired, and this is used as the engine speed. This is transmitted to the ECU 15. Further, since the meter ECU 16 transmits the operation time when the operation lever 18 is operated downward to the engine ECU 15, the set vehicle speed 31 can be reduced according to the operation time downward. Similarly, when the operation lever 18 is operated upward, the engine ECU 15 increases the set vehicle speed 31 according to the operation time.

  An example of a method for setting the upper limit vehicle speed 32 is to operate the operation lever 18 in the same manner. When the operation lever 18 is shared, for example, a switch button for switching the setting of the ACC set vehicle speed 31 and the ASL upper limit vehicle speed 32 is pressed. If the operating lever 18 is operated downward while returning to the neutral position, the vehicle speed at that time is set to the upper limit vehicle speed 32. Further, the engine ECU 15 reduces the upper limit vehicle speed 32 according to the operation time during which the operation lever 18 is operated downward while the switch button is pressed. When the operation lever 18 is operated upward while the switch button is pressed, the engine ECU 15 increases the upper limit vehicle speed 32 according to the operation time. Since the upper limit vehicle speed 32 is a vehicle speed that is not desired to be accelerated further, the method of setting the actual vehicle speed to the upper limit vehicle speed 32 needs to accelerate to the vehicle speed once. For this reason, the upper limit vehicle speed 32 may be set by, for example, inputting a numerical value from the touch panel or operating the operation lever 18 up and down in a stopped state.

  The ACC is turned on / off by a switch provided at the end of the operation lever 18, and the speed limiting function is turned on / off by a predetermined button of the ASL. In ACC, the operation lever 18 is moved to the near side or is temporarily canceled by the operation of the brake pedal. In addition, the ACC has a button for setting an inter-vehicle distance at the time of follow-up traveling, and each time the button is pressed, the inter-vehicle distance can be selected from three stages, for example, “large distance”, “medium distance”, and “small distance”. The inter-vehicle distance is variable according to the vehicle speed of the host vehicle.

  The engine ECU 15 is connected to a CPU that executes a program stored in the ROM using the RAM as a working memory, an ASIC (Application Specific Integrated Circuit) that is mounted with a predetermined logic circuit, a nonvolatile memory, a CAN communication unit, a sensor, and an actuator. A computer equipped with an input / output interface, a clock and the like is an entity. An electronic throttle 17 is connected to the engine ECU 15. The electronic throttle 17 is a throttle valve that adjusts the amount of intake air introduced into the combustion chamber of the engine, and controls the actuator in accordance with the required opening of the electronic throttle 17 calculated by the engine ECU 15 to control the opening of the throttle valve. adjust. The electronic throttle 17 is provided with a sensor (for example, a potentiometer) that detects the opening of the throttle valve, and the electronic throttle 17 performs feedback control so that the opening detected by the sensor becomes equal to the required opening.

  When the opening degree of the electronic throttle 17 is increased, the amount of intake air introduced into the combustion chamber of the engine is increased and the vehicle is accelerated. When the opening degree of the electronic throttle 17 is reduced, the amount of intake air introduced into the combustion chamber of the engine is reduced and the vehicle is decelerated. Therefore, the acceleration / deceleration of the vehicle can be controlled by the opening degree of the electronic throttle 17.

  The engine ECU 15 detects the intake air amount by an air flow sensor and controls the opening / closing time of the fuel injection valve in accordance with the intake air amount (throttle opening) into the combustion chamber of the engine. This optimizes the air-fuel ratio in the combustion chamber, specifically, the optimal air-fuel ratio for engine startup, idling, constant speed running, acceleration, accelerator opening fully open, etc. To do.

  The required opening of the electronic throttle 17 may be determined according to the amount of operation of the accelerator pedal 14 by the driver, or may be determined by ACC or ASL. The driver's accelerator pedal 14 is given priority during the follow-up running by the ACC, and the vehicle speed is limited for the ASL in preference to the operation of the accelerator pedal 14. The operation amount of the accelerator pedal 14 is detected by an accelerator pedal stroke sensor 19.

  FIG. 3 shows an example of a functional block diagram of the engine ECU 15. The engine ECU 15 has various functional blocks that are executed by a CPU or implemented by hardware such as an ASIC. That is, the target inter-vehicle distance determining unit 24 that determines the target inter-vehicle distance, the required opening determining unit 25 that determines the required opening of the electronic throttle 17, and the throttle opening that controls the throttle opening of the electronic throttle according to the required opening A control unit 26; a constant speed traveling unit 22 that causes the vehicle to travel at a constant vehicle speed 31; an acceleration prohibiting unit 23 that prohibits the vehicle speed from becoming higher than the upper limit vehicle speed 32; and an upper limit vehicle speed changing unit 21 that changes the upper limit vehicle speed 32 Have. Each will be described in detail below. The set vehicle speed 31 or the upper limit vehicle speed 32 is stored in the RAM or nonvolatile memory of the engine ECU 15.

[About ACC]
The ACC performed by the engine ECU 15 will be described. The target inter-vehicle distance determining unit 24 determines the target inter-vehicle distance according to the vehicle speed of the preceding vehicle that has been followed. FIG. 4A is an example of a map for determining the target inter-vehicle distance. A sufficient braking distance can be ensured by increasing the inter-vehicle distance as the preceding vehicle speed increases, so that the target inter-vehicle distance gradually increases as the preceding vehicle speed increases. Further, when the driver's favorite inter-vehicle distance can be set as described above, the target inter-vehicle distances “large distance”, “medium distance”, and “small distance” are registered as shown in the figure. In the steady state, the vehicle speed of the preceding vehicle is equal to the vehicle speed of the own vehicle, and therefore the vehicle speed of the preceding vehicle in FIG. 4A may be regarded as the vehicle speed of the own vehicle.

  The target inter-vehicle distance is determined so that the inter-vehicle time is constant, for example, in each of “large distance”, “medium distance”, and “small distance”. The inter-vehicle time is the time required to reach the preceding vehicle when the preceding vehicle stops (“target inter-vehicle distance / vehicle speed of the preceding vehicle”), so this value is constant on each line in FIG. Become. For example, it is about 7 seconds in the case of “large distance”, about 5 seconds in the case of “medium distance”, and about 3 seconds in the case of “small distance”.

The required opening determination unit 25 determines the required opening of the electronic throttle 17. The required opening degree of the electronic throttle 17 for following the preceding vehicle is determined from the control for maintaining the target inter-vehicle distance. If the inter-vehicle distance detected by the radar sensor 12 is larger than the target inter-vehicle distance, the inter-vehicle distance should be accelerated and the inter-vehicle distance should be shortened. If the inter-vehicle distance is smaller than the target inter-vehicle distance, the vehicle should be decelerated to widen the inter-vehicle distance. Therefore, the required opening of the electronic throttle 17 in the control for maintaining the inter-vehicle distance is calculated from the following equation, for example.
Required opening degree Md = M (original) + Gd (target inter-vehicle distance−inter-vehicle distance) (1)
Gd is a gain, and M (original) is a required opening degree of the electronic throttle 17 immediately before control at every cycle time. Therefore, if the target inter-vehicle distance> the inter-vehicle distance, the required opening degree Md increases, and if the target inter-vehicle distance <the inter-vehicle distance, Md decreases.

  And it is preferable to add the control which makes a relative speed constant (for example, zero) in addition to inter-vehicle distance control. This can be expected to shift to constant speed control and improve the responsiveness of maintaining the distance between vehicles. The target acceleration / deceleration is used for the control to make the relative speed zero. FIG. 4B is an example of a map in which the relationship between the relative speed and the target acceleration / deceleration is registered. The target acceleration / deceleration is zero when the relative speed is zero (when the vehicle is constantly following), and the target acceleration / deceleration is negative (deceleration) when the relative speed is positive (approaching side). When is negative (separate side), the target acceleration / deceleration is associated with positive (acceleration).

The required opening of the electronic throttle 17 is determined from the target acceleration / deceleration and the acceleration / deceleration of the host vehicle. The acceleration / deceleration of the vehicle can be obtained by, for example, differentiating the speed of the host vehicle detected by the wheel speed sensor 11. From the above, in the control for keeping the relative speed at zero, the required opening degree of the electronic throttle 17 is calculated from the following equation. Gs is a gain.
Required opening Ms = M (original) + Gs (target acceleration / deceleration-acceleration / deceleration of own vehicle) (2)
Therefore, from the expressions (1) and (2), the required opening degree determination unit 25 determines the final required opening degree M based on the following expression. It should be noted that the target vehicle speed and the vehicle speed (that is, the relative speed) of the host vehicle may be used instead of the target acceleration / deceleration and the host vehicle acceleration / deceleration in Equation (2).
Required opening M = M (original) + Gd (target inter-vehicle distance−inter-vehicle distance) + Gs (target acceleration / deceleration—acceleration / deceleration of own vehicle) (3)
The required opening determined in this way is sent to the throttle opening control unit 26, and the throttle opening control unit 26 feedback-controls the throttle opening of the electronic throttle 17 every cycle time. As will be described below, the constant speed traveling unit 22 travels at a constant speed at the set vehicle speed 31 when the vehicle speed of the host vehicle becomes approximately the same as the set vehicle speed 31 even when following the preceding vehicle. Even when the preceding vehicle is not supplemented, the vehicle is driven at a constant speed at the set vehicle speed 31.

In the case of acceleration An example of control in the case of acceleration will be described with reference to FIG. 5 (a) and 5 (b) schematically show the inter-vehicle distance between the host vehicle and the preceding vehicle, and FIGS. 5 (c) and 5 (d) show temporal changes in the vehicle speed of the host vehicle and the preceding vehicle. ) Indicates the change over time in the inter-vehicle distance. The host vehicle was following the preceding vehicle while maintaining the target inter-vehicle distance and the relative speed was zero. However, because the preceding vehicle accelerated, the inter-vehicle distance became larger than the target inter-vehicle distance. Since the inter-vehicle distance becomes larger than the target inter-vehicle distance due to acceleration of the preceding vehicle, the second term of the expression (3) is positive. In addition, since the relative speed becomes negative when the preceding vehicle accelerates, the target acceleration / deceleration in FIG. 4B becomes positive (becomes the acceleration side), which is larger than the acceleration (for example, zero) of the immediately preceding own vehicle. The third term of equation (3) is also positive. Therefore, the required opening degree M of the electronic throttle 17 increases and the host vehicle can be accelerated.

  As the inter-vehicle distance approaches the target inter-vehicle distance, the second term of equation (3) becomes smaller, and the target acceleration / deceleration becomes smaller as the relative speed approaches zero due to acceleration of the host vehicle, so the third term becomes smaller. Accordingly, the target inter-vehicle distance and the inter-vehicle distance eventually become equal, and the preceding vehicle and the host vehicle travel at a constant speed at the same vehicle speed V2.

The constant speed traveling at the set vehicle speed 31 will be described. FIG. 5 (f) shows the limitation of acceleration by the set vehicle speed 31, and FIG. 5 (g) shows the temporal change of the inter-vehicle distance. When accelerating, the constant speed traveling unit 22 monitors the vehicle speed of the host vehicle. When the vehicle speed becomes approximately the same as the set vehicle speed 31, further acceleration is prohibited, and the required opening degree determining unit 25 is configured to travel at a constant set vehicle speed. To request. In this case, since the set vehicle speed 31 is replaced with the vehicle speed of the preceding vehicle, the required opening may be determined according to the vehicle speed of the host vehicle and the relative speed of the set vehicle speed 31. In addition, it is not necessary to perform control to maintain the inter-vehicle distance according to the vehicle speed. Therefore, when the vehicle speed of the host vehicle and the set vehicle speed 31 are substantially equal, the required opening degree determination unit 25 determines the required opening degree M from the following equation.
Required opening M = M (original) + Gs (target acceleration / deceleration determined from set vehicle speed 31 and host vehicle speed−acceleration / deceleration of host vehicle) (4)
Since the relative speed between the set vehicle speed 31 and the vehicle speed of the host vehicle is almost zero, the required opening gradually decreases as the acceleration / deceleration of the host vehicle is positive (when accelerating), and the acceleration / deceleration of the host vehicle approaches zero. The vehicle travels at a constant speed at the set vehicle speed 31. In order to reduce the shock of vehicle speed adjustment due to the set vehicle speed 31, it is preferable to gradually adjust the acceleration from a vehicle speed lower than the set vehicle speed 31.

In the case of deceleration On the other hand, when the preceding vehicle decelerates or there is an interrupt from another lane, the own vehicle decelerates, but the required opening of the electronic throttle 17 is the same in the follow-up traveling in the case of deceleration. Can be determined. Since the inter-vehicle distance becomes shorter than the target inter-vehicle distance due to the deceleration of the preceding vehicle, the second term of Expression (3) is negative. Moreover, since the relative speed becomes positive when the preceding vehicle decelerates, the target acceleration / deceleration in FIG. 4B is negative (decelerates), which is smaller than the acceleration (for example, zero) of the host vehicle immediately before, The second term of equation (3) is also negative. Therefore, the required opening degree M of the electronic throttle 17 decreases and the host vehicle can decelerate.

  When the target acceleration / deceleration determined by the relative speed is equal to or greater than a predetermined value (when greatly decelerating), automatic braking is performed in addition to deceleration by reducing the throttle opening. Further, when TTC (Time To Collision) becomes equal to or less than a predetermined value, a series of pre-crash safety control including seat belt hoisting, warning, and automatic braking is executed.

[Vehicle speed limit by upper limit vehicle speed 32]
For example, when the accelerator pedal 14 is operated, the acceleration prohibition unit 23 prohibits further acceleration when the vehicle speed of the host vehicle becomes approximately equal to the upper limit vehicle speed 32. Therefore, the control of the acceleration prohibition unit 23 can prevent the vehicle speed of the host vehicle from exceeding the upper limit vehicle speed 32 even when the accelerator opening is 100% (fully open). The upper limit vehicle speed 32 is not only variable by the driver, but can be changed by the upper limit vehicle speed changing unit 21 according to the vehicle speed of the preceding vehicle.

The limitation of the vehicle speed by the upper limit vehicle speed 32 is the same as that by the set vehicle speed 31, and can be handled as if the set vehicle speed 31 was replaced by the upper limit vehicle speed 32. When accelerating with the accelerator pedal 14 depressed, the acceleration prohibition unit 23 monitors the vehicle speed of the host vehicle, prohibits further acceleration when the vehicle speed reaches approximately the upper limit vehicle speed 32, and travels at a constant speed at a constant upper limit vehicle speed. The requested opening degree determination unit 25 is requested to do this. In other words, the required opening may be determined according to the relative speed of the host vehicle speed and the upper limit vehicle speed 32. In addition, it is not necessary to perform control to maintain the inter-vehicle distance according to the vehicle speed. Therefore, when the vehicle speed of the host vehicle and the upper limit vehicle speed 32 are substantially equal, the required opening degree determination unit 25 determines the required opening degree M from the following equation.
Requested opening degree M = M (original) + Gs (target acceleration / deceleration determined from upper limit vehicle speed 32 and host vehicle speed−acceleration / deceleration of host vehicle) (5)
[Change of upper limit vehicle speed 32]
The upper limit vehicle speed changing unit 21 changes the upper limit vehicle speed 32 according to the magnitude relationship between the vehicle speed of the preceding vehicle and the vehicle speed of the host vehicle after the ACC is canceled. In addition, since it is preferable to return to the original state after the change, the change includes increasing the upper limit vehicle speed 32.

-Vehicle speed of own vehicle <If the vehicle speed driver of the preceding vehicle is considered to have approached the preceding vehicle by the accelerator operation, the upper limit vehicle speed 32 is considered to be greater than the vehicle speed of the preceding vehicle. FIG. 6A is an example of a diagram for schematically explaining the change of the upper limit vehicle speed 32. The driver of the host vehicle decelerated by operating the brake pedal after depressing the accelerator pedal 14 during ACC to accelerate. ACC is canceled by deceleration. However, if the driver depresses the accelerator pedal 14 again from this state, there is a risk of abnormally approaching the preceding vehicle. Therefore, the upper limit vehicle speed changing unit 21 reduces the upper limit vehicle speed 32 to be lower than the vehicle speed of the preceding vehicle.

  The upper limit vehicle speed 32 is similarly controlled not only when the ACC is canceled by the brake operation but also when the ACC is canceled by the driver's operation.

  FIG. 6B is a diagram illustrating an example of the upper limit vehicle speed 32 after the change. In order to avoid an abnormal approach with the preceding vehicle, the upper limit vehicle speed 32 only needs to be equal to or lower than the vehicle speed of the preceding vehicle. Therefore, the upper limit vehicle speed changing unit 21 changes the upper limit vehicle speed 32 to be equal to or lower than the vehicle speed of the preceding vehicle. The vehicle speed of the preceding vehicle is known from the relative speed of the radar sensor 12 and the vehicle speed of the host vehicle.

  The upper limit vehicle speed 32 does not necessarily have to be lower than the vehicle speed of the preceding vehicle, and includes an upper limit vehicle speed 32 in which the relative speed is extremely reduced.

  As a result, even if the driver depresses the accelerator pedal 14 because the vehicle is decelerated too much after the braking operation, the vehicle cannot be accelerated beyond the vehicle speed of the preceding vehicle, so there is no possibility of abnormal approach. Further, the driver does not need to perform delicate accelerator work, and can follow the preceding vehicle only by setting the accelerator opening to 100%, for example. If the vehicle speed of the preceding vehicle is equal to or lower than the set vehicle speed, it is possible to shift to constant speed traveling by ACC without changing the vehicle speed by resuming ACC.

-Vehicle speed of the host vehicle> Vehicle speed of the preceding vehicle The vehicle speed of the host vehicle exceeds the vehicle speed of the preceding vehicle due to the driver's accelerator operation, and that state may be maintained even if the brake is operated. FIG. 6C is an example of a diagram for schematically explaining the change of the upper limit vehicle speed 32. Although the vehicle is decelerated by operating the brake pedal, the vehicle speed of the host vehicle remains higher than the vehicle speed of the preceding vehicle due to insufficient braking operation or deceleration of the preceding vehicle. If the driver is unaware of canceling the ACC and misunderstood that it will shift to the follow-up running, there is a risk of abnormally approaching the preceding vehicle. Accordingly, it is preferable to forcibly reduce the vehicle speed. However, since the vehicle speed of the host vehicle is higher than that of the preceding vehicle, the vehicle speed decreases to the upper limit vehicle speed 32 only by matching the upper limit vehicle speed 32 with the vehicle speed of the preceding vehicle. There is a risk of abnormally approaching the preceding vehicle in the process. Therefore, the upper limit vehicle speed changing unit 21 reduces the upper limit vehicle speed 32 to be less than the vehicle speed of the preceding vehicle.

  FIG. 6D is a diagram illustrating an example of the upper limit vehicle speed 32 after the change. As shown in the figure, the upper limit vehicle speed changing unit 21 changes the upper limit vehicle speed 32 to be lower than the vehicle speed of the preceding vehicle, so that the vehicle speed of the host vehicle is lowered at an early stage, and abnormal approach to the preceding vehicle can be prevented. The value of the upper limit vehicle speed 32 in this case may be determined in advance such as what percentage of the vehicle speed of the preceding vehicle (for example, 95% to 70%), or the difference between the vehicle speed of the preceding vehicle and the vehicle speed of the host vehicle You may decide at any time according to the distance between vehicles.

  A method for determining the upper limit vehicle speed 32 in the latter case will be described. TTC is obtained by dividing the inter-vehicle distance by the difference between the vehicle speed of the preceding vehicle and the vehicle speed of the host vehicle. Before the TTC elapses, it is necessary to reduce the vehicle speed of the host vehicle to be lower than the vehicle speed of the preceding vehicle. Accordingly, the minimum required deceleration can be determined from “(difference between the vehicle speed of the preceding vehicle and the vehicle speed of the host vehicle) / TTC”. That is, since there is a possibility of contact at the deceleration, the upper limit vehicle speed 32 may be set so that the target deceleration (a positive value) is about 1.5 to 2 times the deceleration. That is, the upper limit vehicle speed 32 = “vehicle speed of the host vehicle−target deceleration × TTC”.

Return of the upper limit vehicle speed 32 after the change The upper limit vehicle speed 32 after the change is determined according to the relationship with the vehicle speed of the preceding vehicle, and thus is not necessarily the upper limit vehicle speed 32 preferred by the driver. For this reason, it is preferable to return the upper limit vehicle speed 32 after the change to the upper limit vehicle speed 32 set by the driver. The condition for returning the upper limit vehicle speed 32 is at least that the accelerator pedal 14 is not being operated, more preferably that the preceding vehicle is not supplemented. If the condition is that the accelerator pedal 14 is not being operated, the distance between the preceding vehicle and the preceding vehicle can be reduced, and the preceding vehicle is not supplemented. There is no abnormal approach to the vehicle. Thus, by returning the upper limit vehicle speed 32 to the original value, the driver does not need to reset the upper limit vehicle speed 32 and the convenience can be improved.

[Operation Procedure of Vehicle Speed Control Device 100]
Based on the above configuration, the operation procedure of the vehicle speed control device 100 will be described with reference to the flowchart of FIG. The flowchart of FIG. 7 is repeatedly executed at predetermined cycle times when ACC is on and ASL is on.

  If the preceding vehicle is supplemented, the vehicle follows the ACC, and if not, the vehicle travels at a constant speed 31 (S10).

  The upper limit vehicle speed changing unit 21 determines whether or not the ACC is canceled by the driver's brake operation (S20). If not canceled (No in S20), follow-up running or constant speed running is continued. When ACC is canceled (Yes in S20), the ASL waits for operation (S30).

  The upper limit vehicle speed changing unit 21 determines whether the vehicle speed of the preceding vehicle supplemented by the radar sensor 12 is faster than the vehicle speed of the host vehicle (S40). The timing of this determination is, for example, immediately after ACC is canceled. By setting immediately after, the upper limit vehicle speed 32 can be changed early.

  When the vehicle speed of the preceding vehicle is faster than the vehicle speed of the host vehicle (Yes in S40), the upper limit vehicle speed changing unit 21 sets the upper limit vehicle speed 32 to approximately the vehicle speed of the preceding vehicle (S50). Accordingly, even if the driver depresses the accelerator pedal 14 again, the vehicle speed of the host vehicle is suppressed to be equal to or lower than the vehicle speed of the preceding vehicle, and the vehicle can travel following the preceding vehicle even when the accelerator pedal 14 is depressed.

  When the vehicle speed of the preceding vehicle is not faster than the vehicle speed of the host vehicle (No in S40), the upper limit vehicle speed changing unit 21 sets the upper limit vehicle speed 32 to be less than the vehicle speed of the preceding vehicle (S60). Thereby, even if the driver misunderstands that the vehicle is following by ACC, abnormal approach can be reliably prevented.

  As described above, according to the vehicle speed control device 100 of the present embodiment, when the ACC is canceled from the follow-up traveling by the ACC, the upper vehicle speed 32 is reduced, thereby making it easy to secure the space between the vehicles. The operability can be improved, such as eliminating the need for.

It is an example of the figure which illustrates vehicle speed control by a vehicle speed control device typically. It is an example of the block diagram of a vehicle speed control apparatus. It is an example of a functional block diagram of an engine ECU. It is an example of the map for determining a target inter-vehicle distance and a target deceleration. It is an example of the figure which illustrates typically the relation between the own vehicle and a preceding vehicle. It is an example of the figure explaining change of an upper limit vehicle speed typically. It is an example of the flowchart figure which shows the operation | movement procedure of a vehicle speed control apparatus.

Explanation of symbols

11 Wheel speed sensor 12 Radar sensor 13 Inter-vehicle distance control ECU
14 Accelerator pedal 15 Engine ECU
17 Electronic throttle 21 Upper limit vehicle speed changing unit 22 Constant speed traveling unit 23 Acceleration prohibiting unit 31 Set vehicle speed 32 Upper limit vehicle speed 100 Vehicle speed control device

Claims (3)

A vehicle speed control device having following traveling means for following the supplemented preceding vehicle, and upper limit vehicle speed limiting means for limiting the vehicle speed by a preset upper limit vehicle speed even when the accelerator pedal is depressed,
A relative speed detecting means for detecting a relative speed with the preceding vehicle;
Own vehicle speed detecting means for detecting the vehicle speed of the own vehicle;
Upper limit vehicle speed changing means for setting the upper limit vehicle speed to be equal to or lower than the vehicle speed of the preceding vehicle when the vehicle speed of the preceding vehicle when the function of the following traveling means is canceled by the driver's operation is faster than the vehicle speed of the host vehicle;
A vehicle speed control device comprising: The upper limit vehicle speed changing means sets the upper limit vehicle speed to a value smaller than the vehicle speed of the preceding vehicle when the vehicle speed of the host vehicle is equal to or lower than the vehicle speed of the preceding vehicle.
The vehicle speed control device according to claim 1. In a vehicle speed control method for limiting the vehicle speed by a preset upper limit vehicle speed even when the accelerator pedal is depressed,
Detecting the speed of the vehicle,
Detecting the relative speed by supplementing the preceding vehicle;
Whether the vehicle speed of the preceding vehicle is higher than the vehicle speed of the own vehicle based on the relative speed when the function of the following running means is released by the driver's operation and the vehicle speed of the own vehicle. Determining whether or not
If the vehicle speed of the preceding vehicle is faster than the vehicle speed of the host vehicle, the step of setting the upper limit vehicle speed below the vehicle speed of the preceding vehicle;
A vehicle speed control method comprising:

Images