Vehicle travel control device

Abstract

To appropriately switch a plurality of control modes without requiring a previous assumption of acceleration in each control mode.SOLUTION: A travel control device (70) can switch a pulse mode to a glide mode and vice versa and execute either mode. A inclination calculation unit (63) can calculate, based on an output of an engine (11) calculated by an engine ECU (61), a known weight of an own vehicle (10), and calculated inclination, pulse acceleration when assuming that the pulse mode is executed and glide acceleration when assuming that the glide mode is executed. The travel control device switches from the pulse mode to the glide mode on the condition that when assuming that the glide mode is executed from the current time during execution of the pulse mode, it is determined that an inter-vehicle distance becomes shorter than a target inter-vehicle distance at the point when the speed of a preceding vehicle and the speed of the own vehicle match, based on the acquired own vehicle speed, relative speed, inter-vehicle distance, glide acceleration, and preceding vehicle acceleration.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a driving control device that causes a host vehicle to follow a preceding vehicle.

Background Art

[0002] For example, there is a driving control device that executes a first control mode for controlling the driving force of a host vehicle so that the inter-vehicle distance from a preceding vehicle becomes a predetermined value set in advance, a second control mode for stopping the engine and releasing a clutch mechanism to cause the host vehicle to coast, and a third control mode for operating the engine with an operating point in a region indicating the optimum fuel consumption of the engine (see Patent Document 1). The driving control device described in Patent Document 1 sets a determination boundary line that divides each region of the first to third control modes in a map with the relative speed between the host vehicle and the preceding vehicle based on the host vehicle on the horizontal axis and the relative distance between the host vehicle and the preceding vehicle based on the host vehicle on the vertical axis. Then, when the current driving state of the host vehicle determined by the relative speed and the relative distance exceeds the determination boundary line, the control mode is switched.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the driving control device described in Patent Document 1, in order to appropriately switch between the first to third control modes, it is necessary to appropriately set a determination boundary line in advance. In order to set the determination boundary line, it is necessary to consider the relationship between the accelerations assumed in the second and third control modes respectively and the changes in the relative speed and relative distance. However, since the accelerations in the second and third control modes vary depending on the characteristics of the engine, the characteristics of the transmission, the vehicle weight, the road gradient, the air resistance of the vehicle, etc., it is difficult and time-consuming to assume them in advance. As a result, it is difficult and time-consuming to appropriately set the determination boundary line in advance.

[0005] The present invention has been made to solve the above problems, and its main object is to appropriately switch between a plurality of control modes in a vehicle driving control device without the need to assume in advance the accelerations in each control mode.

Means for Solving the Problems

[0006] The first means for solving the above problems is applied to a host vehicle (10) including an engine (11), drive wheels (21), and a transmission interruption mechanism (12) that transmits and interrupts driving force between the engine and the drive wheels, and is a driving control device (70) that causes the host vehicle to follow and drive a preceding vehicle, The host vehicle includes a host vehicle speed detection unit (23) that detects the host vehicle speed, which is the speed of the host vehicle, a relative speed detection unit (30, 40, 70) that detects the relative speed between the preceding vehicle and the host vehicle, a distance detection unit (30) that detects the inter-vehicle distance, which is the distance between the preceding vehicle and the host vehicle, a gradient calculation unit (63) that calculates the gradient of the road on which the host vehicle travels, and an engine ECU (61) that controls the engine, The driving control device can switch between and execute a pulse mode in which the engine is operated in a predetermined operation region where the thermal efficiency of the engine is maximized to drive the host vehicle, and a glide mode in which the engine is stopped and the driving force is interrupted by the transmission interruption mechanism to cause the host vehicle to coast, The engine ECU calculates the output of the engine based on the known characteristics of the engine and the current operating state of the engine. The gradient calculation unit calculates, based on the output of the engine calculated by the engine ECU, the known weight of the host vehicle, and the calculated gradient, a pulse acceleration which is the acceleration of the host vehicle when it is assumed that the pulse mode is executed, and a coasting acceleration which is the acceleration of the host vehicle when it is assumed that the coasting mode is executed. The driving control device acquires the host vehicle speed detected by the host vehicle speed detection unit, the relative speed detected by the relative speed detection unit, the inter-vehicle distance detected by the distance detection unit, and the pulse acceleration and the coasting acceleration calculated by the gradient calculation unit. When it is assumed that the coasting mode is executed from the current time during the execution of the pulse mode, based on the acquired host vehicle speed, the acquired relative speed, the acquired inter-vehicle distance, the acquired coasting acceleration, and the acceleration of the preceding vehicle which is the acceleration of the preceding vehicle acquired or calculated, when it is determined that the inter-vehicle distance becomes shorter than a predetermined target inter-vehicle distance at the speed matching point which is the point in time when the speed of the preceding vehicle which is the speed of the preceding vehicle and the host vehicle speed match, the driving control device switches from the pulse mode to the coasting mode.

[0007] According to the above configuration, the host vehicle speed detection unit detects the host vehicle speed, the relative speed detection unit detects the relative speed between the preceding vehicle and the host vehicle, the distance detection unit detects the inter-vehicle distance, and the gradient calculation unit calculates the gradient of the road surface. That is, the host vehicle includes a detection unit and a calculation unit that detect the driving state of the host vehicle, the relationship between the driving states of the host vehicle and other vehicles, and the driving environment of the host vehicle. And the engine ECU controls the engine. Note that the relative speed between the preceding vehicle and the host vehicle is the speed obtained by subtracting the host vehicle speed from the speed of the preceding vehicle which is the preceding vehicle speed.

[0008] The above driving control device can be executed by switching between a pulse mode and a glide mode. In the pulse mode, usually the host vehicle approaches another vehicle. In the glide mode, usually the host vehicle moves away from another vehicle. Therefore, by switching between the pulse mode and the glide mode and executing, the host vehicle can be made to follow the preceding vehicle.

[0009] Here, since the engine ECU controls the engine, it grasps the rotational speed and output torque (operating state) of the engine. Therefore, the engine ECU can calculate the output of the engine based on the known characteristics of the engine and the current operating state of the engine. And the gradient calculation unit, based on the output of the engine calculated by the engine ECU, the known weight of the host vehicle, and the calculated gradient, can appropriately calculate the pulse acceleration when it is assumed that the pulse mode is executed and the glide acceleration when it is assumed that the glide mode is executed.

[0010] For example, as a state where the pulse mode is being executed, it is possible to assume a state where the inter-vehicle distance is longer than a predetermined target inter-vehicle distance and the host vehicle speed is higher than the preceding vehicle speed. If the time for continuing the pulse mode from that state is too long, there is a risk that the inter-vehicle distance will become shorter than the target inter-vehicle distance and the host vehicle speed will become too high compared to the preceding vehicle speed. Therefore, it is considered that there is an appropriate timing to switch from the pulse mode to the glide mode before that.

[0011] In this regard, when it is assumed that the grid mode will be executed from now on during the execution of the pulse mode, the travel control device, based on the acquired own vehicle speed, the acquired relative speed, the acquired inter-vehicle distance, the acquired grid acceleration, and the acquired or calculated leading vehicle acceleration, switches from the pulse mode to the grid mode on the condition that it is determined that the inter-vehicle distance becomes shorter than a predetermined target inter-vehicle distance at the speed matching point, which is the point in time when the leading vehicle speed and the own vehicle speed match. That is, since the inter-vehicle distance does not change in the state where the own vehicle speed and the leading vehicle speed match, if the inter-vehicle distance becomes shorter than the target inter-vehicle distance in that state, it should be switched to the grid mode from now on. Therefore, if the switching from the pulse mode to the grid mode is performed on the condition that the above determination is made, the switching from the pulse mode to the grid mode can be appropriately performed at the right time. Furthermore, since the travel control device acquires the pulse acceleration and the grid acceleration calculated by the gradient calculation unit and uses them for the determination of mode switching, it is not necessary to assume the pulse acceleration and the grid acceleration in advance.

[0012] In the second means, representing the predetermined target inter-vehicle time as THt, the own vehicle speed as Vs, the grid acceleration as Ag, the relative speed as Vr, the leading vehicle acceleration as Aa, and the inter-vehicle distance as D, the travel control device switches from the pulse mode to the grid mode on the condition that it is determined that THt * {Vs - Ag * Vr / (Aa - Ag)} > D - (1 / 2) * (Vr^2) / (Aa - Ag) and Aa - Ag > 0.

[0013] According to the above configuration, since the condition can be simply defined by a quadratic inequality of the relative speed Vr, the computational load of the travel control device can be reduced. The predetermined target inter-vehicle time THt corresponds to the time obtained by dividing the target inter-vehicle distance, which is set longer as the own vehicle speed is higher, by the own vehicle speed, and can be set in advance. "*" represents multiplication, " / " represents division, and "Vr^2" represents the square of Vr.

[0014] In the third means, on the condition that it is further determined that THt*Aa > Vr, the travel control device switches from the pulse mode to the glide mode.

[0015] According to the above configuration, as a state in which the above quadratic inequality holds, it is possible to determine that the relative speed obtained by subtracting the own vehicle speed from the preceding vehicle speed is not high, that is, the own vehicle is executing the pulse mode before the mode switch. Therefore, it is possible to appropriately switch from the pulse mode to the glide mode.

[0016] The fourth means is applied to a host vehicle (10) including an engine (11), drive wheels (21), and a transmission cutoff mechanism (12) that transmits and cuts off driving force between the engine and the drive wheels, and is a travel control device (70) that causes the host vehicle to follow the preceding vehicle, The host vehicle includes an own vehicle speed detection unit (23) that detects the own vehicle speed, which is the speed of the host vehicle, a relative speed detection unit (30, 40, 70) that detects the relative speed between the preceding vehicle and the host vehicle, a distance detection unit (30) that detects the inter-vehicle distance, which is the distance between the preceding vehicle and the host vehicle, a gradient calculation unit (63) that calculates the gradient of the road on which the host vehicle travels, and an engine ECU (61) that controls the engine. The travel control device is capable of switching and executing a pulse mode in which the engine is operated in a predetermined operation region where the thermal efficiency of the engine is maximized to cause the host vehicle to travel, and a glide mode in which the engine is stopped and the driving force is cut off by the transmission cutoff mechanism to cause the host vehicle to coast. The engine ECU calculates the output of the engine based on the known characteristics of the engine and the current operating state of the engine, and the gradient calculation unit calculates, based on the output of the engine calculated by the engine ECU, the known weight of the host vehicle, and the calculated gradient, a pulse acceleration, which is the acceleration of the host vehicle when it is assumed that the pulse mode is executed, and a glide acceleration, which is the acceleration of the host vehicle when it is assumed that the glide mode is executed. The driving control device acquires the own vehicle speed detected by the own vehicle speed detection unit, the relative speed detected by the relative speed detection unit, the inter-vehicle distance detected by the inter-vehicle distance detection unit, and the pulse acceleration and the glide acceleration calculated by the gradient calculation unit. When it is assumed that the pulse mode will be executed from the current time during the execution of the glide mode, based on the acquired own vehicle speed, the acquired relative speed, the acquired inter-vehicle distance, the acquired pulse acceleration, and the acceleration of the preceding vehicle, which is the acceleration of the preceding vehicle obtained or calculated, the driving control device switches from the glide mode to the pulse mode on the condition that it is determined that the inter-vehicle distance becomes longer than a predetermined target inter-vehicle distance at the speed matching point, which is the point in time when the speed of the preceding vehicle, which is the speed of the preceding vehicle, matches the own vehicle speed.

[0017] For example, as a state in which the glide mode is being executed, it is possible to assume a state in which the inter-vehicle distance is shorter than a predetermined target inter-vehicle distance and the own vehicle speed is lower than the speed of the preceding vehicle. If the time for continuing the glide mode from that state is too long, there is a risk that the inter-vehicle distance will become longer than the target inter-vehicle distance and the own vehicle speed will become too low compared to the speed of the preceding vehicle. Therefore, it is considered that there is an appropriate point in time to switch from the glide mode to the pulse mode before that.

[0018] In this regard, when the driving control device assumes that the pulse mode will be executed from now on during the execution of the grid mode, based on the acquired vehicle speed of the host vehicle, the acquired relative speed, the acquired inter-vehicle distance, the acquired pulse acceleration, and the acquired or calculated leading vehicle acceleration, on the condition that it is determined that the inter-vehicle distance becomes longer than a predetermined target inter-vehicle distance at the speed matching point, which is the point in time when the leading vehicle speed and the host vehicle speed match, the driving control device switches from the grid mode to the pulse mode. That is, since the inter-vehicle distance does not change when the host vehicle speed and the leading vehicle speed match, if the inter-vehicle distance becomes longer than the target inter-vehicle distance in that state, it should be switched to the pulse mode from now on. Therefore, if the driving control device switches from the grid mode to the pulse mode on the condition that the above determination is made, it can be switched from the grid mode to the pulse mode at an appropriate time. Further, since the driving control device acquires the pulse acceleration and the grid acceleration calculated by the gradient calculation unit and uses them for the determination of mode switching, it is not necessary to assume the pulse acceleration and the grid acceleration in advance.

[0019] In the fifth means, with a predetermined target inter-vehicle time represented as THt, the host vehicle speed as Vs, the pulse acceleration as Ap, the relative speed as Vr, the leading vehicle acceleration as Aa, and the inter-vehicle distance as D, on the condition that it is determined that THt*{Vs - Ap*Vr / (Aa - Ap)} < D - (1 / 2)*(Vr^2) / (Aa - Ap) and Aa - Ap < 0, the driving control device switches from the grid mode to the pulse mode.

[0020] According to the above configuration, since the condition can be simply defined by a quadratic inequality of the relative speed Vr, the computational load of the driving control device can be reduced.

[0021] In the sixth means, on the condition that it is further determined that THt*Aa < Vr, the driving control device switches from the grid mode to the pulse mode.

[0022] According to the above configuration, as a state in which the above quadratic inequality holds, it is possible to determine that the relative speed obtained by subtracting the own vehicle speed from the preceding vehicle speed is not low, that is, the host vehicle is executing the glide mode before mode switching. Therefore, it is possible to appropriately switch from the glide mode to the pulse mode.

[0023] When calculating the acceleration of the preceding vehicle based on the differential value of the inter-vehicle distance detected by the distance detection unit, the accuracy of the acceleration of the preceding vehicle may decrease. In that case, if the mode switching determination is made using the inaccurate acceleration of the preceding vehicle, there is a possibility that the pulse mode and the glide mode cannot be switched at an appropriate timing. On the other hand, generally, in a scenario where the host vehicle follows the preceding vehicle, the preceding vehicle and the host vehicle often travel on an exclusive automobile road or a main road with few traffic signals. In this case, the preceding vehicle often travels at a constant speed, and considering the acceleration of the preceding vehicle as zero may result in higher accuracy of the acceleration of the preceding vehicle than calculating it based on the differential value of the inter-vehicle distance.

[0024] In this regard, in the seventh means, the travel control device makes the determination with the acceleration of the preceding vehicle being zero. Therefore, when there is a possibility that the accuracy of the acceleration of the preceding vehicle may decrease, the acceleration of the preceding vehicle can be appropriately calculated. As a result, the pulse mode and the glide mode can be switched at an appropriate timing.

[0025] Generally, the preceding vehicle is equipped with a vehicle speed sensor that detects the speed of the preceding vehicle, and the acceleration of the preceding vehicle can be calculated with high accuracy based on the vehicle speed of the preceding vehicle detected by the vehicle speed sensor.

[0026] In this regard, in the eighth means, when the traveling control device can acquire the preceding vehicle acceleration from the preceding vehicle through vehicle-to-vehicle communication with the preceding vehicle, the traveling control device acquires the preceding vehicle acceleration from the preceding vehicle and makes the determination. When it is impossible to acquire the preceding vehicle acceleration from the preceding vehicle, the traveling control device makes the determination with the preceding vehicle acceleration set to zero. According to such a configuration, when it is possible to acquire a highly accurate preceding vehicle acceleration, the determination of mode switching can be made using the acquired preceding vehicle acceleration. On the other hand, when there is a possibility that the accuracy of the preceding vehicle acceleration may decrease, by setting the preceding vehicle acceleration to zero, the preceding vehicle acceleration can be appropriately calculated.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0028] Hereinafter, an embodiment embodied in a traveling control device mounted on a vehicle will be described with reference to the drawings. The vehicle is an automobile having an engine as a driving power source, a hybrid automobile having an engine and a motor as driving power sources, or the like. Note that the vehicle targeted in this embodiment is referred to as the own vehicle, and the vehicle preceding the own vehicle is referred to as the preceding vehicle.

[0029] First, with reference to FIG. 1, the configuration of the host vehicle 10 controlled by the traveling control device 70 of the present embodiment will be described. Note that FIG. 1 shows the configuration of a hybrid vehicle equipped with a drive / brake system including an engine 11 (internal combustion engine), a motor 13, a transmission disconnect mechanism 12, and a brake 22.

[0030] The host vehicle 10 has an engine 11 as a driving force source, and a transmission disconnect mechanism 12 is connected to the output side of the engine 11. The transmission disconnect mechanism 12 is constituted by a planetary gear mechanism that changes the gear ratio and transmits and disconnects the driving force, or is constituted by a transmission that changes the gear ratio and a clutch mechanism that transmits and disconnects the driving force.

[0031] The host vehicle 10 has a motor 13 as a driving force source, and a transmission disconnect mechanism 12 is connected to the output side of the motor 13. The motor 13 is, for example, a three-phase motor, and is driven by electric power supplied from a secondary battery (power source), not shown, via an inverter (power converter). The motor ECU (Electronic Control Unit) 62 controls the output torque of the motor 13 by controlling the inverter. The motor ECU 62 is configured as a microcomputer including, for example, a CPU, a ROM, a RAM, and an input / output interface. Note that other ECUs also have a similar configuration.

[0032] The type of the engine 11 may be any driving force source for driving the host vehicle 10, and examples include a port injection type or in-cylinder injection type gasoline engine, a diesel engine, and the like. Further, the structure of the engine 11 may be a vane type rotary engine in addition to a reciprocating engine. The engine 11 has a crankshaft, not shown. The crank angle, which is the rotation angle of the crankshaft, is detected by a crank angle sensor, not shown. Based on the crank angle detected by the crank angle sensor, the engine ECU 61 (engine control device) calculates the rotational speed of the engine 11.

[0033] Although illustration is omitted, an electronically controlled throttle valve is provided in the intake passage of the engine 11. The engine ECU 61 calculates an optimal throttle opening based on signals from an accelerator pedal sensor that detects the amount of depression of the accelerator pedal and signals sent from other various sensors, and outputs it to the throttle valve. As a result, the throttle valve is controlled to an optimal throttle valve opening. The engine 11 burns fuel in the cylinder (combustion chamber) to generate driving force. The driving force of the engine 11 is input to the transmission disconnect mechanism 12. The engine ECU 61 controls the output torque and rotational speed of the engine 11 by controlling the amount of fuel injected into the cylinder of the engine 11 (the amount of air inhaled into the cylinder), the ignition timing of the air-fuel mixture, etc.

[0034] The engine ECU 61 determines an appropriate gear ratio based on engine operation information (engine rotational speed, vehicle speed, throttle opening, etc.) for operating the engine 11 and the range position of a gearshift lever (not shown), and shifts the transmission disconnect mechanism 12. As a result, the transmission disconnect mechanism 12 is controlled to an optimal gear ratio. Note that the host vehicle 10 may be provided with a transmission ECU that controls the transmission disconnect mechanism 12.

[0035] When transmitting the driving force from the engine 11 and / or the motor 13 to the drive wheels 21, the transmission disconnect mechanism 12 is connected, and when it is desired to disconnect the drive wheels 21 from the engine 11 and the motor 13, the transmission disconnect mechanism 12 is disconnected.

[0036] The brake 22 applies a braking force to the drive wheel 21 based on the depressing force from a brake pedal (not shown). The wheel speed sensor 23 (own vehicle speed detection unit) detects the rotation angle of the drive wheel 21, and thus the rotational speed. The acceleration sensor 51 detects the own vehicle acceleration As which is the acceleration of the own vehicle 10. The brake ECU 63 (gradient calculation unit) calculates the own vehicle speed Vs based on the rotational speed detected by the wheel speed sensor 23, and calculates the gradient of the road (travel path) in combination with the own vehicle acceleration As detected by the acceleration sensor 51. The brake ECU 63 executes a hill start assist to suppress the vehicle from slipping down when starting from, for example, an uphill road (a road with an upward gradient), and controls the braking force applied to the drive wheel 21 by the brake 22. Note that the brake ECU 63 may have functions such as an ABS (Anti-lock Braking System) function to prevent tire lock during braking, a TCS (Traction Control System) function to prevent tire spin during acceleration, and an ESC (Electronic Stability Control) function to prevent the vehicle from skidding during turning. In that case, the brake ECU 63 enables the road surface properties of the road (travel path) to realize these functions.

[0037] The external information detection device 30 is composed of a millimeter wave radar device, a lidar device, a camera, etc. The external information detection device 30 (distance detection unit) detects the inter-vehicle distance D which is the distance between the preceding vehicle and the own vehicle 10. The external information detection device 30 (relative speed detection unit) detects (calculates) the relative speed Vr between the preceding vehicle and the own vehicle 10 by dividing the change amount of the detected inter-vehicle distance D by the change time, or by differentiating the inter-vehicle distance D, or directly detects the relative speed Vr by utilizing the Doppler effect. The relative speed Vr between the preceding vehicle and the own vehicle 10 is the speed obtained by subtracting the own vehicle speed Vs which is the speed of the own vehicle 10 from the preceding vehicle speed Va which is the speed of the preceding vehicle (Vr = Va - Vs). The inter-vehicle distance D and the relative speed Vr (external information) detected by the external information detection device 30 are input to the travel control device 70.

[0038] When the vehicle-to-vehicle communication device 40 (communication means) can communicate with a preceding vehicle (another vehicle), it communicates with the preceding vehicle to transmit and receive information to and from each other. This information includes, for example, the preceding vehicle speed Va, the preceding vehicle acceleration Aa which is the acceleration of the preceding vehicle, and the like. The preceding vehicle acceleration Aa is calculated based on, for example, the preceding vehicle speed Va detected by a wheel speed sensor of the preceding vehicle, or detected by an acceleration sensor of the preceding vehicle. The accuracy of the preceding vehicle acceleration Aa calculated or detected in this way is higher than the accuracy of the preceding vehicle acceleration Aa calculated based on the inter-vehicle distance D detected by the external information detection device 30.

[0039] The engine ECU 61, the motor ECU 62, the brake ECU 63, and the vehicle-to-vehicle communication device 40 are connected to each other by a communication line and transmit and receive information to and from each other by communication. The travel control device 70 communicates engine control information and shift control information with the engine ECU 61, and causes the host vehicle 10 to follow the preceding vehicle in combination with the external recognition information from the external information detection device 30. Further, the travel control device 70 causes the host vehicle 10 to travel at a preset set vehicle speed.

[0040] FIG. 2 is a diagram for explaining the operating point of the engine 11, and is a map in which an optimum fuel consumption line and a high-efficiency region are drawn based on an engine characteristic map showing the engine rotational speed on the horizontal axis and the engine torque on the vertical axis.

[0041] The travel control device 70 executes a pulse mode in which the engine 11 is operated in a high-efficiency region where the thermal efficiency of the engine 11 becomes high-efficiency to cause the host vehicle 10 to travel. In the pulse mode, the engine ECU 61 controls the engine rotational speed, the engine torque, the engine output, and the gear ratio so that the operating point enters the high-efficiency region (predetermined operating region where the thermal efficiency is maximized) in FIG. 2.

[0042] Further, the travel control device 70 executes a glide mode in which the host vehicle 10 coasts with the engine 11 stopped and the driving force blocked by the transmission blocking mechanism 12. In the glide mode, since the engine 11 is stopped, the operating point moves to the origin in FIG. 2 and there is no fuel consumption, so the fuel consumption is optimal.

[0043] The travel control device 70 executes by switching between a pulse mode and a glide mode. In the pulse mode, usually the host vehicle 10 approaches other vehicles. In the glide mode, usually the host vehicle 10 moves away from other vehicles. For this reason, by switching between the pulse mode and the glide mode and executing, the travel control device 70 can make the host vehicle 10 follow the preceding vehicle so that the inter-vehicle distance D is within a predetermined range from the predetermined target inter-vehicle distance THd in a state with good fuel efficiency. The target inter-vehicle distance THd is the distance obtained by multiplying the target inter-vehicle time THt by the host vehicle speed Vs (THd = THt * Vs). The target inter-vehicle time THt is set to a fixed value adapted in advance, for example. In other words, the target inter-vehicle time THt is the time obtained by dividing the target inter-vehicle distance THd that is proportional to the host vehicle speed Vs (the higher the host vehicle speed Vs, the longer it becomes) by the host vehicle speed Vs (THt = THd / Vs).

[0044] Note that when the inter-vehicle distance D is outside the predetermined range from the target inter-vehicle distance THd only with the pulse mode and the glide mode, the travel control device 70 executes the normal ACC (Auto Cruise Control) mode. In the normal ACC mode, the engine ECU 61 controls the engine rotation speed, engine torque, engine output, and gear ratio regardless of the thermal efficiency of the engine 11 so that the inter-vehicle distance D becomes the target inter-vehicle distance THd. At the same time, the travel control device 70 causes the braking force applied to the drive wheels 21 to be controlled by the brake ECU 63. Examples of such cases where it is outside the predetermined range include, for example, when going downhill on a steep slope, both the pulse mode and the glide mode cause the host vehicle 10 to accelerate, and when the preceding vehicle is traveling at a constant vehicle speed, there is a possibility of approaching the preceding vehicle or colliding with the preceding vehicle within a range closer to the preceding vehicle than the predetermined range from the target inter-vehicle distance THd.

[0045] The engine ECU 61 controls the rotational speed and output torque of the engine 11 in the pulse mode and the normal ACC mode. Therefore, the engine ECU 61 grasps the current rotational speed and output torque (current operating state) of the engine 11, the current gear ratio (current gear shifting state) in the transmission of the transmission interruption mechanism 12, and the like. Further, in order to appropriately execute the pulse mode, the engine ECU 61 has information such as the characteristics of the engine 11, the characteristics of the transmission interruption mechanism 12 (gear ratio of the transmission), and the vehicle weight of the host vehicle 10. For this reason, the engine ECU 61 can calculate the engine output (power unit: kW) when it is assumed that the pulse mode is executed based on the known characteristics of the engine 11, the known characteristics of the transmission interruption mechanism 12, the current operating state of the engine 11, and the current gear shifting state of the transmission interruption mechanism 12. The calculated engine output is sequentially updated for each control cycle in which the engine ECU 61 executes control. Then, the brake ECU 63 can estimate the current value from the data storing the current vehicle weight, the magnitude gradient of the road surface resistance, etc. considering the occupants and the load based on the way the wheel speed changes with respect to the engine output, the detection value of the acceleration sensor 51, and the pre-input vehicle design weight value in time series, and can calculate the pulse acceleration Ap achieved by the host vehicle 10 in the pulse mode by combining with the engine output in the pulse mode calculated by the engine ECU 61. Also, by assuming the engine output to be 0, the glide acceleration Ag achieved by the host vehicle 10 in the glide mode can be calculated.

[0046] FIG. 3 is a schematic diagram for explaining the glide mode start condition. At time t = 0, it is assumed that the tip of the host vehicle 10 is located at the distance X = 0 of the reference position, the host vehicle speed is Vs, the host vehicle acceleration is As, the preceding vehicle speed is Va, the preceding vehicle acceleration is Aa, and the distance between the tip of the host vehicle 10 and the rear end of the preceding vehicle is the inter-vehicle distance D.

[0047] At time t, the distance Xs from the reference position (X = 0) to the tip of the host vehicle 10 is expressed by the following formula (1). Here, it is assumed that the host vehicle acceleration As (glide acceleration Ag) in the glide mode is constant.

[0048] Xs = 0 + Vs * t+(1 / 2)*As * t^2 ···(1) At time t, the distance Xa from the reference position to the rear end of the preceding vehicle is represented by the following equation (2). Here, it is assumed that the preceding vehicle is traveling with a constant acceleration and the preceding vehicle acceleration Aa is constant.

[0049] Xa = D + Va * t+(1 / 2)*Aa * t^2 ···(2) For example, as a state in which the pulse mode is being executed, it is possible to assume a state in which the inter-vehicle distance D is longer than a predetermined target inter-vehicle distance THd (= THt * Vs) and the own vehicle speed Vs is higher than the preceding vehicle speed Va. If the time for continuing the pulse mode from that state is too long, there is a possibility that the inter-vehicle distance D becomes shorter than the target inter-vehicle distance THd and the own vehicle speed Vs becomes too high compared to the preceding vehicle speed Va. Therefore, it is considered that there exists an appropriate timing for switching from the pulse mode to the glide mode before that.

[0050] Therefore, when the travel control device 70 assumes that the glide mode is being executed from the current time (t = 0) during the execution of the pulse mode, the travel control device 70 sets as a condition for switching from the pulse mode to the glide mode that the inter-vehicle distance D2 becomes shorter than the target inter-vehicle distance THt * Vs2 at the speed matching time (time t) when the preceding vehicle speed Va2 and the own vehicle speed Vs2 match.

[0051] The preceding vehicle speed Va2 at time t is represented by the following equation (3).

[0052] Va2 = Va + Aa * t ···(3) The own vehicle speed Vs at time t is represented by the following equation (4).

[0053] Vs2 = Vs + As * t ···(4) The inter-vehicle distance D2 at time t is represented by the following equation (5).

[0054] D2 = Xa - Xs ···(5) Therefore, the above conditions for switching from the pulse mode to the glide mode are represented by the following inequality (6).

[0055] THt*Vs2>D2 ···(6) At time t, since Va2 = Vs2, the following equation (7) holds from equations (3) and (4).

[0056] Va + Aa*t = Vs + As*t ···(7) From equation (7), the time t is represented by the following equation (8).

[0057] t = (Vs - Va) / (Aa - As) ···(8) Substitute equations (4), (5), (2), and (1) into inequality (6), and use the relative speed Vr = (Va - Vs) at time t = 0 (current) to simplify the inequality, which is represented by the following inequality (9).

[0058] THt*{Vs - As*Vr / (Aa - As)} > D - (1 / 2)*Vr^2 / (Aa - As) ···(9) In inequality (9), let Y = (left side) - (right side) and simplify the inequality, which is represented by the following inequality (10).

[0059] Y = a*Vr^2 + b*Vr + c > 0 ···(10) In inequality (10), a = (1 / 2) / (Aa - As), b = THt*{-Aa / (Aa - As) - 1}, and c = THt*Va - D. Here, assuming that the own vehicle acceleration As and the preceding vehicle acceleration Aa are constant, the target headway time THt is a constant value, and the preceding vehicle speed Va and the headway distance D are the detected values at time t = 0, the coefficients a, b, and c can be regarded as constant values (constants). Therefore, Y in inequality (10) can be considered as a quadratic function of the relative speed Vr at time t = 0 (current). Y is, from equation (6), the difference between the target headway distance THt*Vs2 and the headway distance D2 at time t, representing the future target headway distance difference.

[0060] When a graph of Y is drawn with the relative speed Vr at time t = 0 (now) on the horizontal axis and the future target inter-vehicle distance difference Y on the vertical axis, it is represented as shown in FIG. 4, for example. The graph of Y shows how much the future target inter-vehicle distance difference Y becomes for the current relative speed Vr when the speed of the preceding vehicle Va2 and the speed of the host vehicle Vs2 match after time t. Therefore, if the inequality (10) holds for the current relative speed Vr, it can be said that it is the timing to switch from the pulse mode to the glide mode now. For example, if the current driving state of the host vehicle 10 is at point P1, the inequality (10) does not hold, so the pulse mode is continued. On the other hand, if the current driving state of the host vehicle 10 is at point P2, the inequality (10) holds, so the mode is switched from the pulse mode to the glide mode. That is, when assuming that the glide mode is to be executed from now during the execution of the pulse mode, the driving control device 70, based on the host vehicle speed Vs, the relative speed Vr, the inter-vehicle distance D, the host vehicle acceleration As (glide acceleration Ag), and the acceleration Aa of the preceding vehicle, determines that when the time t (the time point when the speeds match) at which the speed of the preceding vehicle Va2 and the speed of the host vehicle Vs2 match, the inter-vehicle distance D2 becomes shorter than the target inter-vehicle distance THt*Vs2 (future target inter-vehicle distance difference Y>0), and switches from the pulse mode to the glide mode.

[0061] At time t = 0 (now), each parameter is obtained as follows. The host vehicle speed Vs is detected based on the rotation angle of the drive wheel 21 detected by the wheel speed sensor 23. The inter-vehicle distance D is detected by the external information detection device 30. The relative speed Vr is detected (calculated) by the external information detection device 30 by dividing the change amount of the detected inter-vehicle distance D by the change time or differentiating the inter-vehicle distance D. The host vehicle acceleration As (pulse acceleration Ap, glide acceleration Ag) in the pulse mode and the glide mode is calculated by the brake ECU 63. The driving control device 70 receives (obtains) the host vehicle speed Vs, the inter-vehicle distance D, the relative speed Vr, the pulse acceleration Ap, and the glide acceleration Ag by communication. The acceleration Aa of the preceding vehicle is detected or calculated (obtained) by the driving control device 70 by dividing the change amount of the speed of the preceding vehicle Va obtained by adding the relative speed Vr to the host vehicle speed Vs by the change time or differentiating the speed of the preceding vehicle Va.

[0062] In addition, when calculating the leading vehicle acceleration Aa based on the relative speed Vr based on the differential value of the inter-vehicle distance D detected by the external information detection device 30, the accuracy of the leading vehicle acceleration Aa may decrease. In that case, if the determination of mode switching is performed using the leading vehicle acceleration Aa with low accuracy, there is a possibility that the pulse mode and the glide mode cannot be switched at an appropriate time. On the other hand, generally, in a scenario where the host vehicle 10 follows the leading vehicle, the leading vehicle and the host vehicle 10 often travel on an exclusive automobile road or a main road with few traffic signals. In this case, the leading vehicle often travels at a constant speed, and assuming the leading vehicle acceleration Aa to be zero may result in higher accuracy of the leading vehicle acceleration Aa than calculating the leading vehicle acceleration Aa based on the relative speed Vr based on the differential value of the inter-vehicle distance D. Therefore, the travel control device 70 determines whether the inequality (10) holds with the leading vehicle acceleration Aa = 0.

[0063] However, in order to determine whether it is appropriate to use the inequality (10) to determine whether to switch from the pulse mode to the glide mode with respect to the assumed driving states of the host vehicle 10 and the leading vehicle, the following inequalities (11) and (12) are further added as prerequisite conditions for establishment.

[0064] Aa - As > 0 ···(11) Inequality (11) means that the host vehicle acceleration As (glide acceleration Ag) in the glide mode is smaller than the leading vehicle acceleration Aa. If inequality (11) does not hold, the host vehicle speed Vs2 will not approach the leading vehicle speed Va2 (the host vehicle speed Vs2 will not decrease to the leading vehicle speed Va2) even if the glide mode is executed, so it is inappropriate for the assumed driving states of the host vehicle 10 and the leading vehicle. Therefore, in this case, the determination of whether to switch from the pulse mode to the glide mode using the inequality (10) is not performed. Or, it is determined that the condition for switching from the pulse mode to the glide mode is not satisfied. The fact that inequality (11) holds is equivalent to the coefficient a = (1 / 2) / (Aa - As) being positive, which means that the graph in Fig. 4 is convex downward.

[0065] -b / 2a > Vr ···(12) Inequality (12) means that in the graph of the future target inter-vehicle distance difference Y, the relative speed Vr is in the operating range on the left side of the central axis of the graph. If the relative speed Vr is in the range on the right side of the central axis of the graph, then the higher the relative speed Vr (the higher the leading vehicle speed Va is than the own vehicle speed Vs), the larger the future target inter-vehicle distance difference Y will be (the distance D2 will be shorter than the target inter-vehicle distance THt*Vs2), which is inappropriate for the assumed driving states of the own vehicle 10 and the leading vehicle. Therefore, in this case, it is not determined whether to switch from the pulse mode to the glide mode using inequality (10). Alternatively, it is determined that the condition for switching from the pulse mode to the glide mode is not satisfied.

[0066] Substituting the coefficient a = (1 / 2) / (Aa - As) and the coefficient b = THt*{-Aa / (Aa - As) - 1} into inequality (12) and arranging it, it is expressed by the following inequality (13).

[0067] THt*Aa > Vr ···(13) In the state where the pulse mode and the glide mode are executed, the leading vehicle acceleration Aa is often close to zero. For this reason, inequality (13) means that the current relative speed Vr is negative. Assuming that the pulse mode is being executed before switching to the glide mode, if inequality (13) holds, it is appropriate for the assumed driving states of the own vehicle 10 and the leading vehicle. That is, if the pulse mode is being executed before switching to the glide mode, inequality (13) usually holds. Therefore, the prerequisite inequality (12), that is, the prerequisite inequality (13), can also be omitted.

[0068] Note that in order to determine whether it is appropriate to determine whether to switch from the pulse mode to the glide mode using inequality (10) for the assumed driving states of the own vehicle 10 and the leading vehicle, the following inequality (14) may be further added as a prerequisite condition for it to hold.

[0069] -(b^2 - 4ac) / 4a < 0 ···(14) Inequality (14) means that the vertex of the graph of the future target inter-vehicle distance difference Y is negative. When the graph of the future target inter-vehicle distance difference Y is convex downward and the vertex of the graph is positive, regardless of the magnitude of the current relative speed Vr, the future target inter-vehicle distance difference Y is positive (the inter-vehicle distance D2 is shorter than the target inter-vehicle distance THt*Vs2). In this case, the pulse mode should not have been continued until now, and it is inappropriate for the assumed driving states of the host vehicle 10 and the preceding vehicle. In other words, if the pulse mode is being executed before switching to the glide mode, inequality (14) usually holds. Therefore, the prerequisite inequality (14) may be omitted.

[0070] FIG. 5 is a schematic diagram for explaining the pulse mode start condition. It is the same as FIG. 3 except that pulse running is being executed instead of glide running, and the host vehicle acceleration As is the host vehicle acceleration As (pulse acceleration Ap) in the pulse mode. For this reason, the distance Xs is expressed in the same way as in Equation (1), and the distance Xa is expressed in the same way as in Equation (2).

[0071] For example, as a state where the glide mode is being executed, it can be assumed that the inter-vehicle distance D is shorter than a predetermined target inter-vehicle distance THd (=THt*Vs), and the host vehicle speed Vs is lower than the preceding vehicle speed Va. If the time for continuing the glide mode from that state is too long, there is a possibility that the inter-vehicle distance D becomes longer than the target inter-vehicle distance THd and the host vehicle speed Vs becomes too low compared to the preceding vehicle speed Va. For this reason, it is considered that there is an appropriate timing to switch from the glide mode to the pulse mode before that.

[0072] Therefore, when the travel control device 70 assumes that the pulse mode is to be executed from the current time (t = 0) during the execution of the glide mode, the travel control device 70 sets as a condition for switching from the glide mode to the pulse mode that the inter-vehicle distance D2 becomes longer than the target inter-vehicle distance THt*Vs2 at the speed matching point (time t) when the preceding vehicle speed Va2 and the own vehicle speed Vs2 match.

[0073] The preceding vehicle speed Va2 at time t is expressed as in Equation (3), the own vehicle speed Vs at time t is expressed as in Equation (4), and the inter-vehicle distance D2 at time t is expressed as in Equation (5).

[0074] Therefore, the above condition for switching from the glide mode to the pulse mode is expressed by the following inequality (15).

[0075] THt*Vs2 < D2 ···(15) Similar to the case of switching from the glide mode to the pulse mode, Equation (7) holds. Time t is expressed as in Equation (8).

[0076] Substitute Equations (4), (5), (2), and (1) into inequality (15), and use the relative speed Vr = (Va - Vs) at time t = 0 to rearrange the inequality. Then, it is expressed by the following inequality (16).

[0077] THt*{Vs - As*Vr / (Aa - As)} < D - (1 / 2)*Vr^2 / (Aa - As) ···(16) In inequality (16), when Y = (left side) - (right side) and the inequality is rearranged, it is expressed by the following inequality (17).

[0078] Y = a*Vr^2 + b*Vr + c < 0 ···(17) In inequality (17), the future target inter-vehicle distance difference Y and the coefficients a, b, and c are the same as those in the case of switching from the glide mode to the pulse mode.

[0079] When a graph of Y is drawn with the relative speed Vr at time t = 0 (present) on the horizontal axis and the future target inter-vehicle distance difference Y on the vertical axis, it is represented as shown in FIG. 6, for example. The graph of Y shows how much the future target inter-vehicle distance difference Y becomes with respect to the current relative speed Vr when the speed of the preceding vehicle Va2 and the speed of the host vehicle Vs2 match after time t. Therefore, if the inequality (17) holds with respect to the current relative speed Vr, it can be said that the current is the timing at which the vehicle should be switched from the glide mode to the pulse mode. For example, if the current driving state of the host vehicle 10 is at point P1, the inequality (17) does not hold, so the glide mode is continued. On the other hand, if the current driving state of the host vehicle 10 is at point P2, the inequality (17) holds, so the vehicle is switched from the glide mode to the pulse mode. That is, when it is assumed that the pulse mode is to be executed from the current time during the execution of the glide mode, the driving control device 70, based on the host vehicle speed Vs, the relative speed Vr, the inter-vehicle distance D, the host vehicle acceleration As (pulse acceleration Ap), and the preceding vehicle acceleration Aa, switches from the glide mode to the pulse mode on the condition that it is determined that the inter-vehicle distance D2 becomes longer than the target inter-vehicle distance THt*Vs2 (future target inter-vehicle distance difference Y < 0) at the time t (speed matching time point) when the speed of the preceding vehicle Va2 and the speed of the host vehicle Vs2 match. Note that the driving control device 70 determines whether or not the inequality (17) holds assuming that Aa = 0 for the preceding vehicle acceleration Aa.

[0080] However, in order to determine whether or not it is appropriate to determine whether or not to switch from the glide mode to the pulse mode using the inequality (17) with respect to the assumed driving states of the host vehicle 10 and the preceding vehicle, the following inequalities (18) and (19) are further added as preconditions for holding.

[0081] Aa - As < 0 ···(18) Inequality (18) means that the vehicle acceleration As (pulse acceleration Ap) in pulse mode is greater than the leading vehicle acceleration Aa. If inequality (18) does not hold, even if the pulse mode is executed, the vehicle speed Vs2 will not approach the leading vehicle speed Va2 (the vehicle speed Vs2 will not increase up to the leading vehicle speed Va2), which is inappropriate for the assumed driving states of the host vehicle 10 and the leading vehicle. Therefore, in this case, the determination of whether to switch from the glide mode to the pulse mode is not made using inequality (17). Alternatively, it is determined that the condition for switching from the glide mode to the pulse mode is not satisfied. The fact that inequality (18) holds is equivalent to the coefficient a = (1 / 2) / (Aa - As) being negative, which means that the graph in Fig. 6 is convex upward.

[0082] -b / 2a < Vr ···(19) Inequality (19) means that in the graph of the future target inter-vehicle distance difference Y, the relative speed Vr is in the operating range on the right side of the central axis of the graph. If the relative speed Vr is in the range on the left side of the central axis of the graph, the higher the relative speed Vr (the higher the leading vehicle speed Va is compared to the host vehicle speed Vs), the larger the future target inter-vehicle distance difference Y will be (the inter-vehicle distance D2 will be shorter than the target inter-vehicle distance THt*Vs2), which is inappropriate for the assumed driving states of the host vehicle 10 and the leading vehicle. Therefore, in this case, the determination of whether to switch from the glide mode to the pulse mode is not made using inequality (17). Alternatively, it is determined that the condition for switching from the glide mode to the pulse mode is not satisfied.

[0083] Substituting the coefficient a = (1 / 2) / (Aa - As) and the coefficient b = THt*{-Aa / (Aa - As) - 1} into inequality (19) and simplifying, it is represented by the following inequality (20).

[0084] THt*Aa < Vr ···(20) In a state where the pulse mode and the glide mode are executed, the leading vehicle acceleration Aa is often close to zero. Therefore, the inequality (20) means that the current relative speed Vr is positive. Assuming that the glide mode is being executed before switching to the pulse mode, if the inequality (20) holds, it is appropriate for the assumed traveling states of the host vehicle 10 and the leading vehicle. That is, when the glide mode is being executed before switching to the pulse mode, the inequality (20) usually holds. Therefore, the prerequisite inequality (19), that is, the prerequisite inequality (20), can also be omitted.

[0085] Note that in order to determine whether it is appropriate to switch from the glide mode to the pulse mode using the inequality (17) for the assumed traveling states of the host vehicle 10 and the leading vehicle, the following inequality (21) may be further added as a prerequisite.

[0086] -(b^2 - 4a*c) / 4a > 0 ···(21) The inequality (21) means that the vertex of the graph of the future target inter-vehicle distance difference Y is positive. When the graph of the future target inter-vehicle distance difference Y is convex upward and the vertex of the graph is negative, regardless of the magnitude of the current relative speed Vr, the future target inter-vehicle distance difference Y will be negative (the inter-vehicle distance D2 is longer than the target inter-vehicle distance THt*Vs2). In this case, the glide mode should not have been continued until now, and it is inappropriate for the assumed traveling states of the host vehicle 10 and the leading vehicle. In other words, when the glide mode is being executed before switching to the pulse mode, the inequality (21) usually holds. Therefore, the prerequisite inequality (21) may be omitted.

[0087] The embodiment described in detail above has the following advantages.

[0088] · The engine ECU 61 controls the rotational speed and output torque of the engine 11 in the pulse mode and the normal ACC mode. Therefore, the engine ECU 61 grasps the current rotational speed and output torque (current operating state) of the engine 11, the current gear ratio (current gear shifting state) in the transmission of the transmission interruption mechanism 12, etc. Further, the engine ECU 61 has information such as the characteristics of the engine 11, the characteristics of the transmission interruption mechanism 12 (gear ratio of the transmission), and the vehicle weight of the host vehicle 10 in order to appropriately execute the pulse mode. Therefore, the engine ECU 61 can calculate the engine output (power unit: kW) when it is assumed that the pulse mode is executed based on the known characteristics of the engine 11, the known characteristics of the transmission interruption mechanism 12, the current operating state of the engine 11, and the current gear shifting state of the transmission interruption mechanism 12. Then, the brake ECU 63 can estimate the current value from the data storing the current vehicle weight considering the passengers and the load, the magnitude of the road surface resistance gradient, etc. in time series based on the way the wheel speed changes with respect to the engine output, the detected value of the acceleration sensor 51, and the pre-input vehicle design weight value, and can calculate the pulse acceleration Ap achieved by the host vehicle 10 in the pulse mode by combining it with the engine output in the pulse mode calculated by the engine ECU 61. Also, by assuming the engine output to be 0, the glide acceleration Ag achieved by the host vehicle 10 in the glide mode can be calculated.

[0089] · When the traveling control device 70 assumes that the grid mode will be executed from now on during the execution of the pulse mode, based on the received own vehicle speed Vs, the received relative speed Vr, the received inter-vehicle distance D, the received grid acceleration Ag, and the calculated leading vehicle acceleration Aa, when the leading vehicle speed Va2 and the own vehicle speed Vs2 match at time t (the time of speed match), if it is determined that the inter-vehicle distance D2 becomes shorter than the predetermined target inter-vehicle distance THd (= THt * Vs2), the traveling control device 70 switches from the pulse mode to the grid mode. That is, since the inter-vehicle distance D2 does not change in the state where the own vehicle speed Vs2 after time t and the leading vehicle speed Va2 after time t match, if the inter-vehicle distance D2 becomes shorter than the target inter-vehicle distance THt * Vs2 in that state, it should be switched to the grid mode from now on. Therefore, if it is switched from the pulse mode to the grid mode on the condition that the above determination is made, it can be switched from the pulse mode to the grid mode at an appropriate time. Further, since the traveling control device 70 receives the pulse acceleration Ap and the grid acceleration Ag calculated by the engine ECU 61 and uses them for the determination of mode switching, it is not necessary to assume the pulse acceleration Ap and the grid acceleration Ag in advance.

[0090] · The traveling control device 70 switches from the pulse mode to the grid mode on the condition that the inequality (10) holds. According to the above configuration, since the condition can be simply defined by the quadratic inequality of the current relative speed Vr, the calculation load of the traveling control device 70 can be reduced.

[0091] · In addition to the inequality (10) holding, the traveling control device 70 switches from the pulse mode to the grid mode on the condition that it is further determined that THt * Aa > Vr. According to the above configuration, as the state where the inequality (10) holds, it can be determined that the relative speed Vr obtained by subtracting the current own vehicle speed Vs from the current leading vehicle speed Va is not high, that is, the own vehicle 10 is executing the pulse mode before mode switching. Therefore, it can be appropriately switched from the pulse mode to the grid mode.

[0092] · When the traveling control device 70 assumes that the pulse mode will be executed from now on when the glide mode is executed, based on the received own vehicle speed Vs, received relative speed Vr, received inter-vehicle distance D, received pulse acceleration Ap, and calculated leading vehicle acceleration Aa, when the leading vehicle speed Va2 and the own vehicle speed Vs2 match at time t (the time when the speeds match), if it is determined that the inter-vehicle distance D2 becomes longer than a predetermined target inter-vehicle distance THd (= THt * Vs2), the traveling control device 70 switches from the glide mode to the pulse mode. That is, since the inter-vehicle distance D2 does not change in the state where the own vehicle speed Vs2 after time t and the leading vehicle speed Va2 after time t match, if the inter-vehicle distance D2 becomes longer than the target inter-vehicle distance THt * Vs2 in that state, it should be switched to the pulse mode from now on. Therefore, if it is switched from the glide mode to the pulse mode on the condition that the above determination is made, it can be switched from the glide mode to the pulse mode at an appropriate time. Furthermore, since the traveling control device 70 receives the pulse acceleration Ap and the glide acceleration Ag calculated by the brake ECU 63 and uses them for the determination of mode switching, it is not necessary to assume the pulse acceleration Ap and the glide acceleration Ag in advance.

[0093] · The traveling control device 70 switches from the glide mode to the pulse mode on the condition that the inequality (17) holds. According to the above configuration, since the condition can be simply defined by a quadratic inequality of the current relative speed Vr, the computational load of the traveling control device 70 can be reduced.

[0094] · The traveling control device 70 switches from the glide mode to the pulse mode on the condition that in addition to the inequality (17) holding, it is further determined that THt * Aa < Vr. According to the above configuration, as a state where the inequality (17) holds, it can be determined that the relative speed Vr obtained by subtracting the current own vehicle speed Vs from the current leading vehicle speed Va is not low, that is, it can be determined that the own vehicle 10 is executing the glide mode before mode switching. Therefore, it can be appropriately switched from the glide mode to the pulse mode.

[0095] · The external information detection device 30 (distance detection unit) detects the inter-vehicle distance D, which is the distance between the preceding vehicle and the host vehicle 10. The external information detection device 30 (relative speed detection unit) detects (calculates) the relative speed Vr between the preceding vehicle and the host vehicle 10 by dividing the change amount of the detected inter-vehicle distance D by the change time or differentiating the inter-vehicle distance D. When calculating the acceleration Aa of the preceding vehicle based on the relative speed Vr based on the differential value of the inter-vehicle distance D detected by the external information detection device 30, the accuracy of the acceleration Aa of the preceding vehicle may decrease. In this regard, the driving control device 70 determines that the acceleration Aa of the preceding vehicle is zero. Therefore, when there is a possibility that the accuracy of the acceleration Aa of the preceding vehicle decreases, the acceleration Aa of the preceding vehicle can be calculated appropriately. As a result, the pulse mode and the glide mode can be switched at an appropriate time. Note that the acceleration Aa of the preceding vehicle may not be set to zero, and the acceleration Aa of the preceding vehicle can also be calculated based on the relative speed Vr based on the differential value of the inter-vehicle distance D detected by the external information detection device 30.

[0096] · Since the gradient of the road on which the host vehicle 10 travels changes according to the actual driving environment, it is difficult to assume it in advance. In this regard, the driving control device 70 determines whether to switch between the pulse mode and the glide mode using the gradient calculated by the brake ECU 63. Therefore, the driving control device 70 can appropriately switch between the pulse mode and the glide mode according to the actual gradient of the road on which the host vehicle 10 travels. Note that the driving control device 70 can also determine whether to switch between the pulse mode and the glide mode by further using the road surface properties of the road (travel path) received (acquired) from the brake ECU 63.

[0097] Note that the above embodiment can also be implemented with the following modifications. For the parts identical to those in the above embodiment, the same reference numerals are given and the description thereof is incorporated by reference.

[0098] · The target inter-vehicle distance THd can be set to a constant value (fixed value) regardless of the host vehicle speed Vs.

[0099] · The gradient sensor 52 (see FIG. 1) may be mounted on the host vehicle 10, or the gradient may be detected by combining the gradient information embedded in the map information recorded in the navigation system with the position of the host vehicle 10 on the map identified by the positioning satellite (GPS). Further, the gradient information can also be obtained from roadside facilities through vehicle-to-everything (V2X) communication.

[0100] · The vehicle-to-vehicle communication device 40 communicates with the preceding vehicle to transmit and receive information to and from each other. This information includes the acceleration of the preceding vehicle, such as the preceding vehicle acceleration Aa. The preceding vehicle acceleration Aa is calculated based on the preceding vehicle speed Va detected by the wheel speed sensor of the preceding vehicle, or is detected by the acceleration sensor of the preceding vehicle. The accuracy of the thus detected preceding vehicle acceleration Aa is higher than the accuracy of the preceding vehicle acceleration Aa calculated based on the inter-vehicle distance D detected by the external information detection device 30. Therefore, when the running control device 70 can obtain the preceding vehicle acceleration Aa from the preceding vehicle through vehicle-to-vehicle communication with the preceding vehicle, the running control device 70 may obtain the preceding vehicle acceleration Aa from the preceding vehicle and make a determination. When it is impossible to obtain the preceding vehicle acceleration Aa from the preceding vehicle, the running control device 70 may make a determination with the preceding vehicle acceleration Aa set to zero. According to such a configuration, when it is possible to obtain the preceding vehicle acceleration Aa with high accuracy, the obtained preceding vehicle acceleration Aa can be used to make a determination for mode switching. On the other hand, when there is a possibility that the accuracy of the preceding vehicle acceleration Aa decreases, by setting the preceding vehicle acceleration Aa to zero, the preceding vehicle acceleration Aa can be appropriately calculated.

[0101] · When the vehicle-to-vehicle communication device 40 communicates with the preceding vehicle to transmit and receive information to and from each other and this information includes the preceding vehicle speed Va, which is the speed of the preceding vehicle, the relative speed Vr can also be detected (calculated) as follows. That is, the running control device 70 (relative speed detection unit) may calculate the relative speed Vr by subtracting the host vehicle speed Vs from the preceding vehicle speed Va (Vr = Va - Vs).

[0102] · When assuming that the cruise mode will be executed from now on during the execution of the pulse mode, it may be assumed that the own vehicle acceleration As (cruise acceleration Ag) in the cruise mode changes with the own vehicle jerk AAs. The own vehicle jerk AAs is the rate of change of the own vehicle acceleration As, and can be detected (calculated) by dividing the change amount of the own vehicle acceleration As by the change time, or by differentiating the own vehicle acceleration As. When assuming that the preceding vehicle acceleration Aa changes with the preceding vehicle jerk AAa when assuming that the cruise mode will be executed from now on during the execution of the pulse mode. The preceding vehicle jerk AAa is the rate of change of the preceding vehicle acceleration Aa, and can be detected (calculated) by dividing the change amount of the preceding vehicle acceleration Aa by the change time, or by differentiating the preceding vehicle acceleration Aa. Similarly, when assuming that the pulse mode will be executed from now on during the execution of the cruise mode, it may be assumed that the own vehicle acceleration As (pulse acceleration Ap) in the pulse mode changes with the own vehicle jerk AAs. When assuming that the pulse mode will be executed from now on during the execution of the cruise mode, it may be assumed that the preceding vehicle acceleration Aa changes with the preceding vehicle jerk AAa.

[0103] · When the travel control device 70 causes the host vehicle 10 to follow another vehicle, it can also execute a travel mode other than the pulse mode, the cruise mode, and the normal ACC mode. For example, the travel control device 70 can execute a hybrid mode in which the host vehicle 10 travels using the engine 11 and the motor 13 as driving power sources, or an EV mode in which the host vehicle 10 travels using only the motor 13 as a driving power source. Even when the travel mode of the host vehicle 10 includes those travel modes, when the travel control device 70 switches between the pulse mode and the cruise mode to cause the host vehicle 10 to travel, it may execute the switching according to the conditions of the above embodiment.

[0104] · The motor 13 and the motor ECU 62 can also be omitted. That is, the host vehicle 10 may be provided with only the engine 11 as a driving power source.

[0105] Note that the above embodiment and each modification example can also be combined and executed within a combinable range.

Description of Symbols

[0106] 10…Own vehicle, 11…Engine, 12…Transmission cutoff mechanism, 13…Motor, 21…Drive wheel, 22…Brake, 23…Wheel speed sensor, 30…External information detection device, 40…Inter-vehicle communication device, 51…Acceleration sensor, 61…Engine ECU, 62…Motor ECU, 63…Brake ECU, 70…Travel control device.

Claims

1. An on-vehicle controller (70) applied to a vehicle (10) including an engine (11), drive wheels (21), and a power transmission and cut-off mechanism (12) for transmitting and cutting off power between the engine and the drive wheels, the on-vehicle controller causing the vehicle to follow a preceding vehicle, wherein the vehicle includes a vehicle speed detector (23) for detecting the vehicle speed of the vehicle, a relative speed detector (30, 40, 70) for detecting a relative speed between the preceding vehicle and the vehicle, a distance detector (30) for detecting a distance between the preceding vehicle and the vehicle, a gradient calculator (63) for calculating a gradient of a road on which the vehicle travels, and an engine ECU (61) for controlling the engine, the on-vehicle controller is capable of switching between and executing a pulse mode in which the vehicle travels with the engine being operated in a predetermined operation range where the thermal efficiency of the engine is maximized and a glide mode in which the engine is stopped and the power transmission and cut-off mechanism cuts off the power and the vehicle travels by inertia, the engine ECU calculates an output of the engine based on known characteristics of the engine and a current operation state of the engine, and the gradient calculator calculates a pulse acceleration which is an acceleration of the vehicle when it is assumed that the pulse mode is executed and a glide acceleration which is an acceleration of the vehicle when it is assumed that the glide mode is executed, based on the output of the engine calculated by the engine ECU, a known weight of the vehicle, and the calculated gradient, The travel control device acquires the own vehicle speed detected by the own vehicle speed detection unit, the relative speed detected by the relative speed detection unit, the inter-vehicle distance detected by the distance detection unit, and the pulse acceleration and the glide acceleration calculated by the gradient calculation unit, and when it is assumed that the glide mode will be executed from now on during the execution of the pulse mode, based on the acquired own vehicle speed, the acquired relative speed, the acquired inter-vehicle distance, the acquired glide acceleration, and the acceleration of the preceding vehicle, which is the acceleration of the preceding vehicle obtained or calculated, the travel control device for a vehicle that switches from the pulse mode to the glide mode on the condition that it is determined that the inter-vehicle distance becomes shorter than a predetermined target inter-vehicle distance at the speed coincidence point, which is the point in time when the speed of the preceding vehicle, which is the speed of the preceding vehicle, coincides with the own vehicle speed.

2. Representing the predetermined target inter-vehicle time as THt, the own vehicle speed as Vs, the glide acceleration as Ag, the relative speed as Vr, the acceleration of the preceding vehicle as Aa, and the inter-vehicle distance as D, The travel control device switches from the pulse mode to the glide mode on the condition that it is determined that THt * {Vs - Ag * Vr / (Aa - Ag)} > D - (1 / 2) * (Vr^2) / (Aa - Ag) and Aa - Ag > 0, according to the travel control device for a vehicle described in Claim 1.

3. The travel control device switches from the pulse mode to the glide mode on the condition that it is further determined that THt * Aa > Vr, according to the travel control device for a vehicle described in Claim 2.

4. Applied to a host vehicle (10) including an engine (11), drive wheels (21), and a transmission cutoff mechanism (12) that transmits and cuts off the driving force between the engine and the drive wheels, the travel control device (70) that causes the host vehicle to follow the preceding vehicle, The host vehicle includes an own vehicle speed detection unit (23) that detects the own vehicle speed, which is the speed of the host vehicle, a relative speed detection unit (30, 40, 70) that detects the relative speed between the preceding vehicle and the host vehicle, a distance detection unit (30) that detects the inter-vehicle distance, which is the distance between the preceding vehicle and the host vehicle, a gradient calculation unit (63) that calculates the gradient of the road on which the host vehicle travels, and an engine ECU (61) that controls the engine. The traveling control device is capable of switching between a pulse mode in which the vehicle is traveled by operating the engine in a predetermined operation region where the thermal efficiency of the engine is maximized, and a glide mode in which the engine is stopped and the driving force is blocked by the transmission blocking mechanism and the vehicle is coasted, The engine ECU calculates the output of the engine based on the known characteristics of the engine and the current operating state of the engine, and the gradient calculation unit calculates the pulse acceleration, which is the acceleration of the vehicle when it is assumed that the pulse mode is executed, and the glide acceleration, which is the acceleration of the vehicle when it is assumed that the glide mode is executed, based on the output of the engine calculated by the engine ECU, the known weight of the vehicle, and the calculated gradient. The traveling control device acquires the vehicle speed detected by the vehicle speed detection unit, the relative speed detected by the relative speed detection unit, the inter-vehicle distance detected by the distance detection unit, and the pulse acceleration and the glide acceleration calculated by the gradient calculation unit, and when it is assumed that the pulse mode is executed from now on during the execution of the glide mode, based on the acquired vehicle speed, the acquired relative speed, the acquired inter-vehicle distance, the acquired pulse acceleration, and the acceleration of the preceding vehicle, which is the acceleration of the preceding vehicle acquired or calculated, the traveling control device of the vehicle switches from the glide mode to the pulse mode on the condition that it is determined that the inter-vehicle distance becomes longer than a predetermined target inter-vehicle distance at the speed matching point, which is the point in time when the speed of the preceding vehicle, which is the speed of the preceding vehicle, matches the vehicle speed.

5. Let the predetermined target inter-vehicle time be THt, the vehicle speed be Vs, the pulse acceleration be Ap, the relative speed be Vr, the acceleration of the preceding vehicle be Aa, and the inter-vehicle distance be D. The traveling control device switches from the glide mode to the pulse mode on the condition that it is determined that THt * {Vs - Ap * Vr / (Aa - Ap)} < D - (1 / 2) * (Vr ^ 2) / (Aa - Ap) and Aa - Ap < 0. The traveling control device for a vehicle according to claim 4.

6. The travel control device for a vehicle according to claim 5, further using as the condition that it is determined that THt*Aa < Vr, switches from the grid mode to the pulse mode.

7. The travel control device for a vehicle according to any one of claims 1 to 6, makes the determination with the acceleration of the preceding vehicle being zero.

8. When the travel control device can acquire the acceleration of the preceding vehicle from the preceding vehicle by vehicle-to-vehicle communication with the preceding vehicle, it acquires the acceleration of the preceding vehicle from the preceding vehicle and makes the determination, and when it cannot acquire the acceleration of the preceding vehicle from the preceding vehicle, it makes the determination with the acceleration of the preceding vehicle being zero. The travel control device for a vehicle according to any one of claims 1 to 6.

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