Deceleration Support Device

Abstract

To provide a deceleration support device capable of reducing energy consumed by automatic deceleration control, when a travel mode is an eco mode, relative to when a travel mode of a vehicle is a normal mode.SOLUTION: A control unit executes (S130) automatic deceleration control for automatically decelerating a vehicle, until the index value becomes a finish reference value or greater, when an index value obtained by dividing a vehicular gap between a preceding vehicle and an own vehicle by a relative speed of the own vehicle to the preceding vehicle, is a start reference value or lower, and when the vehicular gap becomes a control start reference value Drb or smaller, in a state in which a preset permission condition is established (S10-S30, S70), the control unit sets the start distance reference value Drb to a value for an eco mode which is greater than a standard value for a normal mode (S80, S120) when a travel mode is the eco mode for reducing energy required for travel.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a deceleration assist device for vehicles such as automobiles.

Background Art

[0002] When a deceleration assist device detects a target (referred to as a "deceleration target" in this application) in front of the vehicle (the host vehicle) that needs to decelerate the vehicle, such as a preceding vehicle at a low speed, it executes automatic deceleration control to automatically decelerate the vehicle by controlling the deceleration device.

[0003] For example, as described in Patent Document 1 below, it includes a target detection device that detects at least a deceleration target in front of the vehicle, and a control device that controls the deceleration device. When the control device determines that a preset start condition is satisfied in a situation where no control drive operation is detected by the control drive operation detection device, a deceleration target is detected by the target detection device, and the vehicle is approaching the deceleration target, the control device executes automatic deceleration control to automatically decelerate the host vehicle by controlling the deceleration device until it determines that a preset end condition is satisfied. A deceleration assist device configured as such is known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] 〔Problems to be Solved by the Invention〕 There is known a vehicle equipped with a switch operated by a driver that can switch and set the driving mode of the vehicle between a normal mode and an eco mode that reduces the energy required for the vehicle to travel, so as to reduce the energy consumption of vehicles such as automobiles. According to this type of vehicle, the driver can operate the switch and set the driving mode to the eco mode to reduce the energy required for the vehicle to travel.

[0006] However, in a conventional deceleration assistance device such as the deceleration assistance device described in Patent Document 1, the automatic deceleration control is not changed according to whether the driving mode of the vehicle is the normal mode or the eco mode. Therefore, even if the driving mode of the vehicle is set to the eco mode, the energy consumed by the automatic deceleration control cannot be reduced.

[0007] The present invention provides a deceleration assistance device improved so that when the driving mode of the vehicle is the eco mode, the energy consumed by the automatic deceleration control can be reduced as compared with when the driving mode of the vehicle is the normal mode.

[0008] 〔Means for Solving the Problems and Effects of the Invention〕 According to the present invention, there is provided a target detection device (10) that detects at least a target in front of the host vehicle (50), a control drive operation detection device (pressure sensor 26, accelerator opening sensor 46) that detects a control drive operation by the driver, a deceleration device (20) that decelerates the host vehicle, and a control unit (30) that controls the deceleration device. The control unit performs automatic deceleration control to automatically decelerate the host vehicle by controlling the deceleration device (S138) until it is determined that a preset end condition is satisfied (S132) when it is determined that a preset start condition is satisfied (S135, S136) in a situation where no control drive operation is detected by the control drive operation detection device, a preceding vehicle that requires deceleration of the host vehicle is detected by the target detection device, and the host vehicle is approaching the preceding vehicle (S10 to S30, S70). A deceleration assistance device (100) is provided.

[0009] The control unit (30) calculates an index value (time to collision TTC) obtained by dividing the inter-vehicle distance (Dr) between the preceding vehicle and the host vehicle (50) by the relative speed (Vr) of the host vehicle with respect to the preceding vehicle. When the index value is less than or equal to the start reference value (TTCa) (S135), and when the inter-vehicle distance (Dr) between the preceding vehicle and the host vehicle becomes less than or equal to the control start distance reference value (Drb) (S136), it is determined that a preset start condition is satisfied. When the index value becomes greater than or equal to the end reference value (TTCe) (S132), it is configured to determine that a preset end condition is satisfied. The host vehicle includes a switch (34) operated by the driver to switch and set the driving mode of the host vehicle between a normal mode and an eco mode that reduces the energy required for the host vehicle to travel. When the driving mode is set to the eco mode, the control unit (30) is configured to set the control start distance reference value (Drb) to a value for the eco mode that is larger than the standard value for the normal mode (S80, S110, S120).

[0010] According to the above configuration, an index value obtained by dividing the inter-vehicle distance between the preceding vehicle and the host vehicle by the relative speed of the host vehicle with respect to the preceding vehicle is calculated. When the index value is less than or equal to the start reference value, and when the inter-vehicle distance becomes less than or equal to the control start distance reference value, it is determined that a preset start condition is satisfied. When the index value becomes greater than or equal to the end reference value, it is determined that a preset end condition is satisfied.

[0011] When the driving mode is set to the eco mode, the control start distance reference value is set to a value for the eco mode that is larger than the standard value for the normal mode. Therefore, when the driving mode is the eco mode, the inter-vehicle distance between the preceding vehicle and the host vehicle becomes less than or equal to the control start distance reference value earlier than when the driving mode is the normal mode, and it is determined that a preset start condition is satisfied earlier. Accordingly, the automatic deceleration control is started earlier, and as will be described later, since the index value becomes greater than or equal to the end reference value earlier, it is determined that a preset end condition is satisfied earlier.

[0012] As a result, as will be described later, when the driving mode is the eco mode, the time of the automatic deceleration control can be shortened compared to when the driving mode is the normal mode. Therefore, the energy consumed by the automatic deceleration control can be reduced.

[0013] 〔Aspects of the Invention〕 In one aspect of the present invention, the control unit (30) is configured to variably set a control start distance reference value according to the vehicle speed of the host vehicle so that the control start distance reference value (Drb) increases as the vehicle speed (V) of the host vehicle increases (S110, S120).

[0014] According to the above aspect, the control start distance reference value is variably set according to the vehicle speed so that the control start distance reference value increases as the vehicle speed of the host vehicle increases. Therefore, since the control start distance reference value can be increased as the vehicle speed of the host vehicle increases, the control start distance reference value can be set to an appropriate value according to the vehicle speed. That is, compared with the case where the control start distance reference value is a constant value regardless of the vehicle speed, the risk that the automatic deceleration control is started unnecessarily early due to the control start distance reference value being too large in a situation where the vehicle speed of the host vehicle is low can be reduced. Conversely, the risk that the start of the automatic deceleration control is delayed due to the control start distance reference value being too small in a situation where the vehicle speed of the host vehicle is high can be reduced.

[0017] Furthermore, in another aspect of the present invention, the deceleration device (20) includes a regenerative braking device (28), and the control unit (30) sets the control start distance reference value (Drb) to the standard value for the normal mode when the charging margin rate (Rc) of the battery (28A) of the regenerative braking device is equal to or higher than a preset charging margin reference value (Rcf) even when the driving mode is set to the eco mode (S80, S90, S110).

[0018] According to the above aspect, even when the driving mode is the eco mode, when the charge margin rate of the battery of the regenerative braking device is equal to or higher than a preset charge margin reference value, the control start distance reference value is set to the standard value for the normal mode. Therefore, when there is a margin in regeneration by the regenerative braking device, automatic deceleration control is executed at the control start distance reference value for the normal mode, the host vehicle can be effectively decelerated, and the battery can be efficiently charged by regeneration by the regenerative braking device.

[0019] Furthermore, in another aspect of the present invention, when the control unit (30) determines that the preceding vehicle is stationary (S51), the host vehicle is decelerated so as not to approach the preceding vehicle by more than the minimum distance ( Drs ), and when it is determined that the preceding vehicle has restarted driving (S51, S52), the deceleration of the host vehicle is continued (S59, S60) until it is determined that a preset release condition is satisfied (S54).

[0020] According to the above aspect, when it is determined that the preceding vehicle is stationary, the host vehicle is decelerated so as not to approach the preceding vehicle by more than the minimum distance, and when it is determined that the preceding vehicle has restarted driving, the deceleration of the host vehicle is continued until it is determined that a preset release condition is satisfied.

[0021] Therefore, it is possible to prevent the host vehicle from approaching a stationary preceding vehicle excessively, and even when the preceding vehicle has restarted driving, the deceleration of the host vehicle is continued until it is determined that a preset release condition is satisfied, thereby preventing the host vehicle from approaching the preceding vehicle excessively.

[0022] Furthermore, in another aspect of the present invention, when the control unit (30) determines that the preceding vehicle has restarted driving (S51, S52), the minimum distance ( Drs ) is gradually increased (S53), the relative speed (Vr) is less than a negative relative speed reference value (Vrc), and the inter-vehicle distance (Dr) is the minimum distance ( Drs ) Larger thanIf it is determined that the predetermined release condition is satisfied (S63), it is determined that the predetermined release condition is satisfied (S64).

[0023] According to the above aspect, when the preceding vehicle resumes traveling, the minimum distance is gradually increased, and the relative speed is less than the negative relative speed reference value and the inter-vehicle distance is the minimum distance Larger than When it is determined that the above condition is satisfied, it is determined that the preset release condition is satisfied.

[0024] Therefore, compared to the case where the minimum distance is not gradually increased even when the preceding vehicle resumes driving, the vehicle distance increases excessively quickly to the minimum distance Larger than This reduces the risk of the host vehicle being determined to be too close to the preceding vehicle, thereby reducing the risk of the host vehicle coming too close to the preceding vehicle.

[0025] In the above description, in order to facilitate understanding of the present invention, the names and / or symbols used in the embodiments described below are added in parentheses to the configurations of the invention corresponding to those embodiments. However, each component of the present invention is not limited to the components of the embodiments corresponding to the names and / or symbols added in parentheses. Other objects, other features, and associated advantages of the present invention will be easily understood from the description of the embodiments of the present invention described below with reference to the drawings. [Brief description of the drawings]

[0026]

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Mode for Carrying Out the Invention

[0027] [Embodiment] The deceleration assistance device according to an embodiment of the present invention will be described in detail below with reference to the attached drawings. [Configuration]

[0028] As shown in FIG. 1, the deceleration assistance device 100 according to the embodiment is applied to the vehicle 50 and includes an object detection device 10 that detects at least a front object of the vehicle 50, a deceleration device 20 that decelerates the vehicle, and a deceleration assistance electronic control device 30 that controls the deceleration device. Therefore, the vehicle 50 is provided with the deceleration assistance device 100. A main switch 32 and a control mode switch 34 operated by the driver, a vehicle speed sensor 36, and a longitudinal acceleration sensor 38 are connected to the electronic control device 30. The vehicle speed sensor 36 and the longitudinal acceleration sensor 38 detect the vehicle speed V and the longitudinal acceleration Gx of the vehicle 50, respectively.

[0029] The deceleration support device 100 operates when the main switch 32 is on. The control mode switch 34 is a switch for switching and setting the driving mode of the vehicle 50 between a normal mode and an eco mode. The eco mode is a control mode that reduces the energy required for the vehicle to travel compared to the normal mode. In the present application, "electronic control device" is denoted as "ECU", which is an abbreviation of Electronic Control Unit. Also, the vehicle 50 is referred to as the host vehicle 50 as necessary to distinguish it from a preceding vehicle or the like.

[0030] The target detection device 10 includes a camera sensor 12 and a radar sensor 14 connected to a CAN (Controller Area Network) 52. The camera sensor 12 includes a camera unit and a recognition unit that analyzes the image data obtained by shooting with the camera unit to recognize a target for which deceleration of the vehicle 50 is necessary. The camera unit of the camera sensor 12 shoots at least the scenery in front of the vehicle 50, and the recognition unit of the camera sensor 12 repeatedly supplies information regarding the recognized target for which deceleration of the vehicle is necessary to the deceleration support ECU 30 every time a predetermined calculation cycle elapses.

[0031] In addition to the camera sensor 12 and the radar sensor 14, a navigation device may be used as an auxiliary detection device for detecting a target for which deceleration of the vehicle is necessary. In the following description, "target for which deceleration of the vehicle is necessary" is denoted as "deceleration target". The deceleration target is, for example, a preceding vehicle, a stopped vehicle, a traffic signal, a crosswalk, a road sign such as "slow down", a road surface sign such as "reduce speed", an intersection, a T-junction, a curve in the road, or the like.

[0032] The radar sensor 14 includes a radar transceiver unit and a signal processing unit (not shown). The radar transceiver unit emits millimeter-wave radio waves (hereinafter referred to as "millimeter waves") at least forward of the vehicle 50, and receives the millimeter waves (i.e., reflected waves) reflected by a solid object (e.g., another vehicle, a bicycle, a guardrail, etc.) existing within the radiation range. The signal processing unit acquires information representing the distance between the host vehicle and the solid object, the relative speed between the host vehicle and the solid object, the relative position (direction) of the solid object with respect to the host vehicle, etc. every time a predetermined time elapses based on, for example, the phase difference between the transmitted millimeter wave and the received reflected wave, the attenuation level of the reflected wave, and the time from transmitting the millimeter wave to receiving the reflected wave, and supplies the information to the deceleration support ECU 10. Note that LiDAR (Light Detection And Ranging) may be used instead of or in addition to the radar sensor 14.

[0033] The deceleration device 20 includes a braking device 22 that decelerates the vehicle 50 by applying a braking force to a wheel not shown in FIG. 1, and a deceleration ECU 24 that controls the braking device 22. A pressure sensor 26 that detects the master cylinder pressure Pm is connected to the deceleration ECU 24 as the driver's braking operation amount. The deceleration ECU 24 normally controls the braking device 22 based on the master cylinder pressure Pm, and controls the braking device 22 based on a command signal related to braking when receiving the command signal from the deceleration support ECU 10.

[0034] As shown in FIG. 1, the vehicle 50 includes an acceleration device 40. The acceleration device 40 includes a driving device 42 that accelerates the vehicle 50 by applying a driving force to a driving wheel not shown in FIG. 1, and an acceleration ECU 44 that controls the driving device 42. An accelerator opening sensor 46 is connected to the acceleration ECU 44, and the accelerator opening sensor 46 detects the accelerator opening Acc as the driver's driving operation amount. The acceleration ECU 44 normally controls the driving device 42 based on the accelerator opening Acc, and controls the driving device 42 based on a command signal related to driving when receiving the command signal from the deceleration support ECU 10.

[0035] Since the pressure sensor 26 and the accelerator opening sensor 46 detect the braking operation and the driving operation by the driver respectively, they function as a braking and driving operation detection device that detects the braking and driving operations (braking operation and driving operation) by the driver, and constitute a part of the deceleration assistance device 100. As a braking operation detection device that detects the braking operation by the driver, a brake lamp switch may be adopted instead of the pressure sensor 26.

[0036] Note that the drive device 42 may be any known drive device in the art, such as a combination of an internal combustion engine like a gasoline engine and a transmission, a so-called hybrid system which is a combination of an internal combustion engine and a motor, a so-called plug-in hybrid system, a combination of a fuel cell and a motor, or a motor.

[0037] The deceleration assistance ECU 30, the deceleration ECU 24, and the acceleration ECU 44 are electronic control devices having a microcomputer as a main part, and are connected to be able to transmit and receive information to and from each other via the CAN 52. Each microcomputer includes a CPU, a ROM, a RAM, a non-volatile memory, an interface, and the like. The CPU is configured to realize various functions by executing instructions (programs, routines) stored in the ROM. Some or all of these ECUs may be integrated into one ECU.

[0038] In particular, the ROM of the deceleration assistance ECU 30 stores a deceleration assistance control program corresponding to the flowcharts shown in FIGS. 2 to 4, and the CPU executes deceleration assistance control according to the program.

[0039] As will be described in detail later, when the deceleration target is detected by the detection device 10 and no driving operation by the driver is detected by the pressure sensor 26 and the accelerator opening sensor 46, the deceleration support ECU 30 permits execution of automatic deceleration control for automatically decelerating the vehicle 50. On the other hand, when a braking operation or a driving operation by the driver is detected by the pressure sensor 26 and the accelerator opening sensor 48 even though the deceleration target is detected by the detection device 10, the deceleration support ECU 30 does not permit execution of the automatic deceleration control.

[0040] That is, when no driving operation by the driver is detected, the deceleration target is a preceding vehicle, and the host vehicle 50 is approaching the preceding vehicle, the deceleration support ECU 30 determines that the permission condition for the automatic deceleration control is satisfied. Further, when it is determined that a preset start condition is satisfied, the deceleration support ECU 30 executes the automatic deceleration control.

[0041] In particular, the automatic deceleration control is a control for automatically decelerating the vehicle 50 by controlling the deceleration device 20 to automatically apply a braking force to the wheels without requiring a braking operation by the driver. Further, the automatic deceleration control is executed when an execution command for the automatic deceleration control is output from the deceleration support ECU 30 to the deceleration ECU 24.

[0042] When the deceleration support ECU 30 detects a braking operation by the driver by the pressure sensor 26 or detects a driving operation by the driver by the accelerator opening sensor 46 in a situation where the automatic deceleration control is being executed, the deceleration support ECU 30 stops the automatic deceleration control.

[0043] <Deceleration Support Control Routine> Next, with reference to the flowcharts shown in FIGS. 2 to 4, the deceleration support control routine in the embodiment will be described. The deceleration support control according to the flowcharts shown in FIGS. 2 to 4 is repeatedly executed by the CPU of the deceleration support ECU 30 at a predetermined control cycle when the main switch 32 is on. In the following description, the deceleration support control is simply referred to as "this control".

[0044] First, in step S10, the CPU determines whether a braking operation or a driving operation is being performed by the driver. When the CPU makes an affirmative determination, this control is terminated once. When the CPU makes a negative determination, that is, when it determines that no braking or driving operation is being performed by the driver, this control proceeds to step S20. Note that when the master cylinder pressure Pm detected by the pressure sensor 26 is equal to or higher than a reference value, it may be determined that a braking operation is being performed by the driver. Also, when the accelerator opening Acc detected by the accelerator opening sensor 46 is equal to or higher than a reference value, it may be determined that a driving operation is being performed by the driver.

[0045] In step S20, the CPU determines whether a deceleration target has been detected by the camera sensor 12 and / or the radar sensor 14. When the CPU makes a negative determination, this control is terminated once. When the CPU makes an affirmative determination, this control proceeds to step S30. Note that when a deceleration target has been detected, a display device (not shown in FIG. 1) may display to that effect.

[0046] In step S30, the CPU determines whether the deceleration target is a preceding vehicle. When the CPU makes an affirmative determination, this control proceeds to step S50. When the CPU makes a negative determination, this control proceeds to step S40.

[0047] As shown in FIG. 6, when there are two or more preceding vehicles 100 and 102 in front of the host vehicle 50, the preceding vehicle 100 immediately in front of the host vehicle 50 is determined to be the preceding vehicle. Also, as shown in FIG. 7, even if the immediately preceding vehicle 100 has changed lanes, the immediately preceding vehicle 100 is determined to be the preceding vehicle unless the overlap rate Ro between the host vehicle 50 and the immediately preceding vehicle 100 becomes equal to or less than the reference value Roc. Further, as shown in FIG. 8, when the immediately preceding vehicle 100 has changed lanes and the overlap rate Ro between the host vehicle 50 and the immediately preceding vehicle 100 becomes equal to or less than the reference value Roc, the preceding vehicle 102 is determined to be the preceding vehicle. In this case, the reference value Roc may be a positive constant such as 0.05, or may be 0.

[0048] Note that the overlap ratio Ro may be calculated as follows. As shown in FIG. 7, when the host vehicle 50 is moved along the lane 104 on which the host vehicle is traveling to a position where it contacts the preceding vehicle 100, the length Lo in the vehicle width direction of the region where the host vehicle and the preceding vehicle overlap each other is estimated. Next, the ratio Lo / Lw of the length Lo to the total width Lw (a known value) of the host vehicle 50 is calculated as the overlap ratio Ro.

[0049] In step S40, the CPU executes automatic deceleration control when the deceleration target is a deceleration target other than the preceding vehicle, such as an intersection, a T-junction, or a curve on the road, in a manner known in the art.

[0050] In step S50, the CPU executes control when the preceding vehicle is stationary according to the subroutine shown in FIG. 3.

[0051] In step S70, the CPU determines whether the host vehicle 50 is approaching the preceding vehicle. When the CPU makes a negative determination, the present control is temporarily terminated, and when the CPU makes an affirmative determination, the present control proceeds to step S80. Note that when the inter-vehicle distance Dr between the preceding vehicle and the host vehicle is decreasing, or when the relative speed Vr of the host vehicle with respect to the preceding vehicle is estimated and the relative speed Vr is a positive value, it may be determined that the host vehicle 50 is approaching the preceding vehicle.

[0052] In step S80, the CPU determines whether the control mode switch 34 is set to be switched to the eco mode, that is, whether the control mode is the eco mode. When the CPU makes an affirmative determination, the present control proceeds to step S120, and when the CPU makes a negative determination, the present control proceeds to step S110.

[0053] In step S110, the CPU calculates a control start distance reference value Drb for the normal mode by referring to the map shown by the solid line in FIG. 5 based on the vehicle speed V of the host vehicle 50. As shown in FIG. 5, the control start distance reference value Drb for the normal mode is calculated such that it becomes larger as the vehicle speed V is higher.

[0054] In step S120, the CPU calculates a control start distance reference value Drb for the eco mode by referring to the map shown by the dashed line in FIG. 5 based on the vehicle speed V of the host vehicle 50. As shown in FIG. 5, the control start distance reference value Drb for the eco mode is larger than the control start distance reference value Drb for the normal mode and is calculated such that it becomes larger as the vehicle speed V is higher.

[0055] In step S130, the CPU executes automatic deceleration control according to the subroutine shown in FIG. 4.

[0056] <Subroutine for control when the preceding vehicle is stationary> In step S51 of the flowchart shown in FIG. 3, the CPU determines whether the preceding vehicle is stationary. In this case, when the relative speed Vr of the host vehicle with respect to the preceding vehicle is the same as the vehicle speed V of the host vehicle, it may be determined that the preceding vehicle is stationary. When the CPU makes an affirmative determination, it advances this control to step S55, and when it makes a negative determination, it advances this control to step S52.

[0057] In step S52, the CPU determines whether the flag F is 1, that is, whether the control when the preceding vehicle is stationary is being executed. When the CPU makes a negative determination, it advances this control to step S70, and when it makes an affirmative determination, it advances this control to step S53.

[0058] In step S53, the CPU sets the allowable minimum value Drs of the inter-vehicle distance Dr between the preceding vehicle and the host vehicle when the preceding vehicle is stationary to the sum Drsf + ΔDrs of its previous value Drsf and the increment ΔDrs. As shown in FIG. 9, the allowable minimum value Drs is the minimum value of the inter-vehicle distance Dr that allows the host vehicle approaching the stationary preceding vehicle to stop, and ΔDrs is the increment (positive constant) for each cycle. Note that the initial value of the allowable minimum value Drs may be a preset positive constant.

[0059] In step S54, the CPU determines whether the relative speed Vr of the host vehicle with respect to the preceding vehicle is a positive value, that is, determines whether the host vehicle is approaching the preceding vehicle. When the CPU makes a negative determination, it proceeds with this control to step S61, and when it makes a positive determination, it proceeds with this control to step S57.

[0060] In step S55, the CPU calculates the control start distance reference value Drbs shown by the dashed line in FIG. 5 based on the vehicle speed V of the host vehicle 50. As shown in FIG. 5, the control start distance reference value Drbs is calculated to be a value larger than the control start distance reference value Drb for the eco mode.

[0061] Furthermore, the CPU determines whether the inter-vehicle distance Dr between the preceding vehicle and the host vehicle is less than or equal to the control start distance reference value Drbs, that is, determines whether the host vehicle should start decelerating. When the CPU makes a negative determination, it proceeds with this control to step S70, and when it makes a positive determination, in step S56, it sets the flag F to 1.

[0062] In step S57, the CPU determines whether the inter-vehicle distance Dr between the preceding vehicle and the host vehicle is greater than the allowable minimum value Drs. When the CPU makes a positive determination, it proceeds with this control to step S59, and when it makes a negative determination, it proceeds with this control to step S58.

[0063] In step S58, the CPU outputs a command signal to the deceleration ECU 24 to stop the host vehicle or maintain it in a stopped state.

[0064] In step S59, the CPU calculates a target deceleration Gxbst for decelerating the host vehicle so that the host vehicle stops when the inter-vehicle distance Dr between the preceding vehicle and the host vehicle reaches the allowable minimum value Drs, based on the inter-vehicle distance Dr and the vehicle speed V of the host vehicle.

[0065] In step S60, the CPU outputs a command signal to the deceleration ECU 24 to decelerate the host vehicle so that the deceleration of the host vehicle becomes the target deceleration Gxbst. In this case, the deceleration of the host vehicle may be feedback-controlled based on the longitudinal acceleration Gx of the vehicle 50 detected by the longitudinal acceleration sensor 38.

[0066] In step S61, the CPU determines whether the relative speed Vr of the host vehicle with respect to the preceding vehicle is less than the reference value Vrc (0 or a negative constant), that is, determines whether the preceding vehicle is moving away from the host vehicle. When the CPU makes a negative determination, it proceeds with this control to step S63, and when it makes an affirmative determination, in step S62, it resets the flag F to 0.

[0067] In step S63, similar to step S57, the CPU determines whether the inter-vehicle distance Dr between the preceding vehicle and the host vehicle is greater than the allowable minimum value Drs. When the CPU makes a negative determination, it proceeds with this control to step S59, and when it makes an affirmative determination, it proceeds with this control to step S64.

[0068] In step S64, the CPU outputs a command signal to the deceleration ECU 24 to cancel the automatic deceleration of the host vehicle. In this case, the automatic deceleration of the host vehicle is cancelled, and a command signal may be output to the acceleration ECU 44 to permit the acceleration of the host vehicle.

[0069] Incidentally, when the CPU executes the control when the preceding vehicle in step S50 is stationary, that is, the control from step S521 to S64, it may issue an alarm by activating an alarm device not shown in FIG. 1, and may also display those controls on a display not shown in FIG. 1.

[0070] <Subroutine for Automatic Deceleration Control> In step S131 of the flowchart shown in FIG. 4, the CPU calculates a collision prediction time TTC, which is the predicted time until the host vehicle 50 collides with the preceding vehicle. The collision prediction time TTC is calculated according to the following formula (1) based on the inter-vehicle distance Dr between the host vehicle and the preceding vehicle and the relative speed Vr of the host vehicle with respect to the preceding vehicle. The collision prediction time TTC is an index value representing the likelihood of the host vehicle colliding with the preceding vehicle. The smaller the value, the higher the likelihood (risk) of the host vehicle colliding with the preceding vehicle. TTC = Dr / Vr ···(1)

[0071] In step S132, the CPU determines whether or not automatic deceleration control is being executed. When the CPU makes a negative determination, it advances this control to step S135. When it makes a positive determination, it advances this control to step S133.

[0072] In step S133, the CPU determines whether or not the collision prediction time TTC is equal to or greater than a control end reference value TTCe (a positive constant), that is, determines whether or not the end condition of the automatic deceleration control is satisfied. When the CPU makes a negative determination, it advances this control to step S137. When it makes a positive determination, in step S134, it outputs a command signal for ending the control to the deceleration ECU 24 to end the automatic deceleration control.

[0073] In step S135, the CPU determines whether the time to collision TTC is less than or equal to a control permission reference value TTCa (a positive constant smaller than the control end reference value TTCe), that is, determines whether the first start condition of the automatic deceleration control is satisfied. When the CPU makes a negative determination, this control is terminated once, and when the CPU makes a positive determination, this control proceeds to step S136.

[0074] In step S136, the CPU determines whether the inter-vehicle distance Dr between the host vehicle and the preceding vehicle is less than or equal to a control start distance reference value Drb, that is, determines whether the second start condition of the automatic deceleration control is satisfied. When the CPU makes a negative determination, this control is terminated once, and when the CPU makes a positive determination, this control proceeds to step S137.

[0075] In step S137, the CPU calculates a target deceleration Gxbt for automatically decelerating the host vehicle based on the inter-vehicle distance Dr between the preceding vehicle and the host vehicle, the time to collision TTC, and the vehicle speed V of the host vehicle.

[0076] In this case, the target deceleration Gxbt may be calculated, for example, as follows. First, a target inter-vehicle distance Drt for avoiding the host vehicle approaching the preceding vehicle excessively is calculated so as to be larger as the actual vehicle speed V detected by the vehicle speed sensor 36 is higher, and a target inter-vehicle time Tt is calculated so as to be larger as the vehicle speed V is higher. The target vehicle speed Vt is calculated by dividing the target inter-vehicle distance Drt by the target inter-vehicle time Tt, and the increase amount ΔGxbt of each cycle of the target deceleration Gxbt for making the actual vehicle speed V the target vehicle speed Vt in a predetermined time is calculated, whereby the target deceleration Gxbt is gradually increased. An upper limit value Gxbtmax of the target deceleration Gxbt is calculated so as to be larger as the vehicle speed V of the host vehicle is higher, and when the calculated target deceleration becomes equal to or higher than the upper limit value Gxbtmax, the target deceleration Gxbt is set to the upper limit value Gxbtmax.

[0077] In step S137, the CPU executes automatic deceleration control by outputting a command signal to the deceleration ECU 24 to decelerate the host vehicle so that the deceleration of the host vehicle becomes the target deceleration Gxbt.

[0078] Thus, in a situation where the permission condition for automatic deceleration control is satisfied (S10 to S30, S70), when it is determined that the collision prediction time TTC is equal to or less than the control permission reference value TTCa and the inter-vehicle distance Dr between the host vehicle and the preceding vehicle is equal to or less than the control start distance reference value Drb, it is determined that the start condition for automatic deceleration control is satisfied. When it is determined that the start condition for automatic deceleration control is satisfied, automatic deceleration control is executed until it is determined that the collision prediction time TTC is equal to or greater than the control end reference value TTCe and the end condition for automatic deceleration control is satisfied. The automatic deceleration control is performed by calculating a target deceleration Gxbt for avoiding the host vehicle from approaching the preceding vehicle excessively and automatically decelerating the host vehicle by braking so that the deceleration of the host vehicle becomes the target deceleration Gxbt.

[0079] As described above, the control start distance reference value Drb is calculated as the control start distance reference value Drb for the normal mode when the control mode is the normal mode (S110), and is calculated as the control start distance reference value Drb for the eco mode when the control mode is the eco mode (S120). The control start distance reference value Drb for the eco mode is larger than the control start distance reference value Drb for the normal mode (see FIG. 5). Therefore, the automatic deceleration control is started earlier at a stage where the inter-vehicle distance Dr is larger, that is, when the control mode is the eco mode, compared with when the control mode is the normal mode.

[0080] Moreover, when it is determined that the collision prediction time TTC is equal to or greater than the control end reference value TTCe and the end condition of the automatic deceleration control is satisfied, the automatic deceleration control is ended. Therefore, when the control mode is the eco mode, the automatic deceleration control is ended at a stage where the inter-vehicle distance Dr is large, and the time during which the automatic deceleration control is executed is shortened, compared to when the control mode is the normal mode. Therefore, according to the embodiment, when the control mode is the eco mode, the energy consumed by the automatic deceleration control can be reduced, compared to when the control mode is the normal mode.

[0081] For example, in FIG. 12 and FIG. 13, when the vehicle speed V of the host vehicle is 11 m / sec and the vehicle speed of the preceding vehicle is 5.5 m / sec, the deceleration Gxb changes from 0 to 1.5 m / sec over 1 sec. 2 then increases linearly to 1.5 m / sec 2 In particular, Fig. 12 shows the changes in the inter-vehicle distance Dr and the TTC when the control start distance reference value Drb is 15 m, and Fig. 13 shows the changes in the inter-vehicle distance Dr and the TTC when the control start distance reference value Drb is 20 m.

[0082] As shown by the black circles in Figures 12 and 13, the control end reference value TTCe is 4 seconds. In the case of Figure 12, the automatic deceleration control ends 3.7 seconds after the automatic deceleration control is started. In contrast, in the case of Figure 13, the automatic deceleration control ends 2.6 seconds after the automatic deceleration control is started. Therefore, it can be seen that in the case of Figure 13 where the control start distance reference value Drb is large, the duration of the automatic deceleration control is shorter than in the case of Figure 12.

[0083] Also, according to the embodiment, as shown in FIG. 5, the control initiation distance reference value Drb is variably set according to the vehicle speed so that the higher the vehicle speed V of the host vehicle 50, the larger the control initiation distance reference value Drb is (S110, S120).

[0084] Therefore, since the control start distance reference value can be increased as the vehicle speed of the host vehicle 50 increases, the control start distance reference value Drb can be set to an appropriate value according to the vehicle speed. That is, compared to the case where the control start distance reference value Drb is a constant value regardless of the vehicle speed, it is possible to reduce the risk that the automatic deceleration control is started unnecessarily early due to the control start distance reference value being too large when the vehicle speed of the host vehicle is low. Conversely, it is possible to reduce the risk that the start of the automatic deceleration control is delayed due to the control start distance reference value being too small when the vehicle speed of the host vehicle is high.

[0085] According to the embodiment, when it is determined that the preceding vehicle is stationary (S51), the host vehicle is within the minimum distance Drs The host vehicle is decelerated so as not to approach the preceding vehicle (S59, S60), and when it is determined that the preceding vehicle has resumed traveling (S51, S52), the host vehicle continues to decelerate until it is determined that a preset release condition is satisfied (S54).

[0086] This makes it possible to prevent the host vehicle from approaching excessively close to a stationary vehicle ahead, and even if the vehicle ahead resumes traveling, the host vehicle continues to decelerate until it is determined that a preset release condition is met, thereby preventing the host vehicle from approaching excessively close to the vehicle ahead.

[0087] Furthermore, according to the embodiment, when it is determined that the preceding vehicle has resumed traveling (S51, S52), the minimum distance Drs is gradually increased (S53), and when the relative speed Vr is 0 or less than the negative relative speed reference value Vrc and the inter-vehicle distance Dr is the minimum distance Larger than Drs If it is determined that this is the case (S63), it is determined that a preset release condition is met (S64).

[0088] Therefore, compared to a case where the minimum distance is not gradually increased even when the preceding vehicle resumes traveling, the risk of the inter-vehicle distance being determined to exceed the minimum distance too early can be reduced, and the risk of the vehicle approaching the preceding vehicle excessively can be reduced.

[0089] [Variations] In a modified example, as shown in FIG. 10, the braking device 22 includes a regenerative braking device 28 controlled by a deceleration ECU 24, and performs regenerative braking by the regenerative braking device 28 during braking. The electricity generated by the regenerative braking is recovered by being charged to the battery 28A of the regenerative braking device 28. When a charge margin rate Rc (%) which is a ratio of the current charge margin to the charge capacity of the battery 28A becomes equal to or higher than a reference value Rcf (a positive constant), it is determined that there is a margin for regeneration by the regenerative braking device 28.

[0090] Next, the deceleration assist control routine in the modified example will be described with reference to the flowchart shown in FIG. 11. The deceleration assist control according to the flowchart shown in FIG. 11 is also repeatedly executed by the CPU of the deceleration assist ECU 30 at a predetermined control cycle when the main switch 32 is on.

[0091] The CPU executes steps S10 to S80 and steps S110 to S130 in the same manner as the corresponding steps in the embodiment, and when making a determination in step S80 Affirmative this control proceeds to step S90.

[0092] In step S90, the CPU calculates a relative deceleration Gxr of the preceding vehicle with respect to the host vehicle based on, for example, a time differential value of the relative speed Vr of the host vehicle with respect to the preceding vehicle and the deceleration of the host vehicle. Further, the CPU determines whether the preceding vehicle is suddenly decelerating by determining whether the relative deceleration Gxr is equal to or higher than a reference value Gxrc (a positive constant). When the CPU makes an affirmative determination, this control proceeds to step S 110 and when the CPU makes a negative determination, this control proceeds to step S 100 and proceeds.

[0093] In step S100, the CPU determines whether there is a margin for regeneration by the regenerative braking device 28 by determining whether the remaining charge rate Rc of the battery 28A is equal to or higher than a reference value Rcf (a positive constant). When the CPU makes an affirmative determination, it advances this control to step S110, and when it makes a negative determination, it advances this control to step S120.

[0094] Thus, in a situation where the permission condition for the automatic deceleration control is satisfied (S10 to S30, S70), when the relative deceleration Gxr of the preceding vehicle with respect to the host vehicle is equal to or higher than the reference value Gxrc (S90), the control mode is in the eco mode Yes even if (S80), Normally the control start distance reference value Drb for the mode is calculated. Therefore, when the preceding vehicle is decelerating rapidly, Normally the automatic deceleration control is executed based on the control start distance reference value Drb for the mode, and the host vehicle can be prevented from approaching the preceding vehicle excessively. Effectively decelerated

[0095] Also, in a situation where the permission condition for the automatic deceleration control is satisfied (S10 to S30, S70), when the remaining charge rate Rc of the battery 28A is equal to or higher than the reference value Rcf (S100), even if the control mode is in the eco mode (S80), the control start distance reference value Drb for the normal mode is calculated. Therefore, when there is a margin for regeneration by the regenerative braking device 28, the automatic deceleration control is executed based on the control start distance reference value Drb for the normal mode, the host vehicle can be effectively decelerated, and the battery 28A can be efficiently charged by the regeneration by the regenerative braking device 28.

[0096] Note that steps S90 and S100 are executed in addition to the steps of the embodiment. Therefore, according to this modification example, all the operational effects obtained by the above-described embodiment can be obtained.

[0097] ​In the above, the present invention has been described in detail with respect to specific embodiments and variations. However, the present invention is not limited to the above-described embodiments and variations, and it will be apparent to those skilled in the art that various other embodiments are possible within the scope of the present invention.

[0098] For example, in the above-described embodiments and variations, in step S30, when it is determined that the deceleration target is not the preceding vehicle, in step S40, when the deceleration target is a deceleration target other than the preceding vehicle, such as an intersection, a T-junction, a curve in the road, etc., automatic deceleration control is executed. However, if step S40 is omitted and it is determined that the deceleration target is not the preceding vehicle, the deceleration assistance control shown in FIG. 2 may be modified to end once.

[0099] Also, in the above-described embodiments and variations, in step S50, control is executed when the preceding vehicle is stationary. However, step S50 may be omitted. It may be determined.

[0100] Also, in the above-described embodiments and variations, in step S50, when the inter-vehicle distance Dr between the preceding vehicle and the host vehicle is greater than the allowable minimum value Drs, the host vehicle is decelerated, and when the inter-vehicle distance Dr between the preceding vehicle and the host vehicle is less than or equal to the allowable minimum value Drs, the host vehicle is stopped. However, it may be modified such that when the vehicle speed V of the host vehicle becomes less than or equal to the end reference vehicle speed due to the host vehicle being decelerated, the deceleration assistance control ends and the collision prevention control is shifted to.

[0101] Also, in the above-described embodiments and variations, the increase amount ΔGxbt when calculating the target deceleration Gxbt in step S137 is the same whether the control mode is the eco mode or the normal mode. However, the increase amount ΔGxbt when calculating the target deceleration Gxbt may be made smaller when the control mode is the eco mode than when the control mode is the normal mode.

[0102] Also, in the above-described embodiments and modifications, the control start distance reference value Drbs in the determination of step S55 is the same when the control mode is the eco mode as when the control mode is the normal mode. However, the control start distance reference value Drbs is larger when the control mode is the eco mode than when the control mode is the normal mode. May be

[0103] Furthermore, in the above-described modification, when the determination is made in step S80 Affirmative step S90 is executed, and when the determination is made in step S 90 step S100 is executed. However, either step S90 or S100 may be omitted. Negative

Description of Reference Numerals

[0104] 10... Target detection device, 12... Camera sensor, 14... Radar sensor, 20... Deceleration device, 22... Braking device, 24... Deceleration ECU, 26... Pressure sensor, 30... Deceleration support ECU, 32... Main switch, 34... Control mode switch, 40... Acceleration device, 42... Driving device, 44... Acceleration ECU, 46... Accelerator opening sensor, 50... Vehicle, 100... Deceleration support device​

Claims

1. A deceleration assistance device including a target detection device that detects at least a front target of the host vehicle, a control drive operation detection device that detects a control drive operation by the driver, a deceleration device that decelerates the host vehicle, and a control unit that controls the deceleration device. The control unit performs automatic deceleration control to automatically decelerate the host vehicle by controlling the deceleration device when it is determined that a preset start condition is satisfied in a situation where no control drive operation is detected by the control drive operation detection device, a preceding vehicle that requires deceleration of the host vehicle is detected by the target detection device, and the host vehicle is approaching the preceding vehicle, until it is determined that a preset end condition is satisfied. In the deceleration assistance device, the control unit calculates an index value obtained by dividing the inter-vehicle distance between the preceding vehicle and the host vehicle by the relative speed of the host vehicle with respect to the preceding vehicle, and determines that the preset start condition is satisfied when the inter-vehicle distance becomes equal to or less than a control start distance reference value in a situation where the index value is equal to or less than a start reference value, and is configured to determine that the preset end condition is satisfied when the index value becomes equal to or greater than an end reference value. The host vehicle is provided with a switch operated by the driver for switching and setting the driving mode of the host vehicle between a normal mode and an eco mode for reducing the energy required for the running of the host vehicle. The control unit is configured to set the control start distance reference value to a value for the eco mode that is larger than the standard value for the normal mode when the driving mode is set to the eco mode. The deceleration assistance device.

2. In the deceleration assistance device according to claim 1, the control unit is configured to variably set the control start distance reference value according to the vehicle speed of the host vehicle such that the higher the vehicle speed of the host vehicle, the larger the control start distance reference value. The deceleration assistance device.

3. In the deceleration assistance device according to claim 1, the deceleration device includes a regenerative braking device. The control unit is configured to set the control start distance reference value to the standard value for the normal mode when the driving mode is set to the eco mode and the remaining charge rate of the battery of the regenerative braking device is equal to or higher than a preset remaining charge reference value. The deceleration assistance device.

4. In the deceleration assistance device according to claim 1, when the control unit determines that the preceding vehicle is stationary, the control unit decelerates the host vehicle so that the host vehicle does not approach the preceding vehicle by more than the minimum distance, and when the control unit determines that the preceding vehicle has resumed traveling, the control unit is configured to continue decelerating the host vehicle until it is determined that a preset release condition is satisfied. A deceleration assistance device.

5. In the deceleration assistance device according to claim 4, when the control unit determines that the preceding vehicle has resumed traveling, the control unit gradually increases the minimum distance, and when it is determined that the relative speed is less than a negative relative speed reference value and the inter-vehicle distance is greater than the minimum distance, the control unit is configured to determine that the preset release condition is satisfied. A deceleration assistance device.

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