Operation support device of electric vehicle

Abstract

To enable an electric vehicle which is running at low speed to be efficiently charged with electricity during deceleration of the vehicle, without giving a feeling of strangeness to a driver.SOLUTION: An operation support device of an electric vehicle is provided with: a motor generator that drives the electric vehicle by electricity supplied from a battery and charges the battery with electricity generated by regenerative braking during deceleration of the electric vehicle; a vehicle speed detecting part that detects an own vehicle speed of the electric vehicle; a running environment information obtaining part that obtains information on a running environment in front of the electric vehicle; and a control part that controls the vehicle speed and the deceleration of the electric vehicle by driving the motor generator and the regenerative braking, on the basis of the own vehicle speed and the information on the running environment. When detecting a wide road and a narrow road subsequent to the wide road and a temporary stop position at the end of the narrow road on the basis of the information on the running environment, the control part makes the electric vehicle decelerate at smaller deceleration by regenerative braking when the vehicle runs on the wide road just before the narrow road.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a driving assistance device for an electric vehicle. [Background technology]

[0002] Known electric vehicles include battery electric vehicles (BEVs) that use an electric motor powered by electricity stored in a battery as a drive source, and range extender EVs that are equipped with an engine dedicated to generating electricity.

[0003] Some of these electric vehicles are equipped with driving assistance devices that perform autonomous driving and adaptive cruise control (ACC). By controlling the driving of the electric vehicle with the driving assistance device, the burden placed on the driver to drive the vehicle is reduced.

[0004] When such electric vehicles are used for commuting or by delivery drivers, they are often driven on residential roads. Many of these roads have intersections without traffic lights. In addition, the corners of intersections are often bordered by walls of houses or hedges, making visibility poor. Furthermore, many of these roads narrow in width midway through the road, making it difficult for vehicles to pass each other (narrow roads). In addition, when entering an intersection that leads from a narrow road to a priority road, the driver must stop temporarily before the intersection.

[0005] Therefore, when an electric vehicle travels on a residential road under the control of a driving assistance device, the driving assistance device frequently performs control to repeatedly decelerate and accelerate. When decelerating the electric vehicle, the driving assistance device causes the electric motor to operate as a generator for regeneration, converting the deceleration energy into regenerative power to charge the battery.

[0006] In an electric vehicle, the battery power is consumed more when the vehicle starts moving. Therefore, when the battery state of charge (SOC) is low, it is necessary to efficiently convert deceleration energy into regenerative power when decelerating before stopping.

[0007] For example, Patent Document 1 (JP 2011-91935 A) discloses a technique in which, when the charge state of the battery is equal to or lower than a threshold value, rapid deceleration by regenerative braking is permitted in order to actively charge the battery. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2011-91935 A Summary of the Invention [Problem to be solved by the invention]

[0009] By the way, electric vehicles traveling on community roads are controlled by driving assistance devices to travel at low speeds. For example, as shown in Figure 8, assume that on a community road, there is a wide road beyond which vehicles can pass each other, and there is a narrow road beyond that, and a stop line for a temporary stop.

[0010] In this case, the driving assistance device first sets a target vehicle speed when the electric vehicle travels along a narrow road. The driving assistance device then sets a deceleration start point P1 for reaching the target vehicle speed at the entrance to the narrow road based on the difference between the current vehicle speed of the electric vehicle and the target vehicle speed. When the electric vehicle reaches the deceleration start point P1, the driving assistance device starts deceleration of the electric vehicle.

[0011] When the electric vehicle reaches the entrance to a narrow road, i.e., when the electric vehicle reaches the target vehicle speed (P2), the driving assistance device drives the electric vehicle along the narrow road with the vehicle speed set to the target vehicle speed. If the driving assistance device subsequently detects a stop line at which the electric vehicle is to be temporarily stopped, it sets a deceleration start point (constant speed end point) P3 for stopping the electric vehicle at the stop line (vehicle speed = 0 [Km / h]). Then, when the electric vehicle reaches the deceleration start point P3, the driving assistance device starts decelerating the electric vehicle and stops it at a target stop point P4 set just before the stop line.

[0012] In an environment where an electric vehicle is driven at low speed, such as on a residential road, if a driving assistance device allows rapid deceleration through regenerative braking when the battery state of charge is low, as disclosed in Cited Document 1, the following problems arise. When driving at low speeds, the gradients of the deceleration sections P1-P2 and P3-P4 in FIG. 8 become steeper, causing the driver to feel uncomfortable due to sudden deceleration. Rapid deceleration at low speeds shortens the charging interval for regenerative energy, which actually worsens charging efficiency. -When stopping an electric vehicle at a stop line by suddenly decelerating before the stop line, it is difficult to stop the vehicle using regenerative braking, and the distribution rate of friction braking is higher than that of regenerative braking. This further worsens the charging efficiency. Also, if the electric vehicle is a range-extended EV, the frequency with which the engine dedicated to generating electricity starts increases relatively to compensate for the decrease in charging efficiency, resulting in worse fuel economy.

[0013] The object of the present invention is to provide a driving assistance device for an electric vehicle that can efficiently charge an electric vehicle traveling at low speed when it decelerates without causing any discomfort to the driver, thereby improving electricity consumption, and in the case of a range extender EV, can improve fuel consumption by reducing the frequency of starting the engine dedicated to power generation. [Means for solving the problem]

[0014] The present invention relates to an electric vehicle driving method and a control method for controlling the vehicle speed and deceleration of the electric vehicle by driving the motor generator and regenerative braking based on the vehicle speed detected by the vehicle speed detection unit and the driving environment information acquired by the driving environment information acquisition unit. In the driving assistance device, the control unit includes a road detection unit that detects a wide road and a narrow road subsequent to the wide road based on the driving environment information acquired by the driving environment information acquisition unit, a stop position detection unit that detects a stop position beyond the narrow road detected by the road detection unit based on the driving environment information acquired by the driving environment information acquisition unit, and a deceleration control unit that decelerates the electric vehicle at a small deceleration by regenerative braking while traveling on the wide road before entering the narrow road when the narrow road is detected by the road detection unit and the stop position detection unit has detected the stop position. Effect of the Invention

[0015] According to the present invention, when the control unit detects a narrow road and detects a temporary stop position ahead, the control unit decelerates the electric vehicle at a small deceleration rate by regenerative braking while traveling on a wide road before entering the narrow road, so that the electric power generated by regenerative braking can be quickly charged into the battery before the vehicle stops at the temporary stop position. Therefore, charging efficiency during deceleration of an electric vehicle traveling at a low speed can be improved without causing discomfort to the driver. In addition, since regenerative braking is performed at a small deceleration rate, it is possible to improve electricity efficiency. In the case of a range extender EV, the improved electricity efficiency reduces the frequency of starting the engine dedicated to generating electricity, improving fuel efficiency. [Brief description of the drawings]

[0016] [Figure 1] Schematic diagram of an electric vehicle [Figure 2A] Flowchart showing driving assistance control routine (part 1) [Figure 2B] Flowchart showing driving assistance control routine (part 2) [Figure 2C] Flowchart showing driving assistance control routine (part 3) [Diagram 3] Conceptual diagram of deceleration setting table for wide road driving [Figure 4] Brake torque distribution ratio map [Diagram 5] FIG. 13 is an explanatory diagram showing the vehicle speed control state of an electric vehicle traveling on a wide road and a narrow road of a community road. [Figure 6] Aerial view of an electric vehicle traveling on a residential road [Figure 7] Camera image showing a driver entering a narrow road from a wide road on a community road [Figure 8] FIG. 1 is an explanatory diagram showing a conventional vehicle speed control state of an electric vehicle traveling on a wide road and a narrow road of a residential road. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] An embodiment of the present invention will be described below with reference to the drawings. Reference symbol M in Fig. 1 is an electric vehicle. In the drawing, as an example of the electric vehicle M, a four-wheel drive range extender EV vehicle is shown.

[0018] The electric vehicle M is equipped with a front motor generator (FM / G) 1 and a rear motor generator (RM / G) 2 as power sources. An output shaft 1a of the FM / G1 is connected to drive shafts 3l, 3r of the front drive wheels Fl, Fr via a front differential (abbreviated as "front diff") Df. An output shaft 2a of the RM / G2 is connected to drive shafts 4l, 4r of the rear drive wheels Rl, Rr via a rear differential (abbreviated as "rear diff") Dr.

[0019] The FM / G1 and RM / G2 are connected to a battery 6 via an inverter 5. The inverter 5 converts DC power from the battery 6 into AC power and supplies it to the FM / G1 and RM / G2. The FM / G1 and RM / G2 drive the front drive wheels Fl, Fr and the rear drive wheels Rl, Rr with the power supplied from the inverter 5, thereby powering the electric vehicle M.

[0020] During deceleration, the inverter 5 operates the FM / G1 and RM / G2 as generators for regenerative operation, converting the generated AC regenerative power into DC power and supplying it to the battery 6. When the FM / G1 operates as a generator, a regenerative braking force is applied to the front drive wheels Fl, Fr. Similarly, when the RM / G2 functions as a generator, a regenerative braking force is applied to the rear drive wheels RI, Rr.

[0021] Furthermore, the electric vehicle M is equipped with a generator 7, which is a component of a range extender, and an engine 8 dedicated to generating electricity (hereinafter simply referred to as an "engine").

[0022] In addition, the generator 7 is connected to the battery 6 via the inverter 5. When the engine 8 drives and rotates the generator 7, AC generated power is output from the generator 7. The AC generated power output from the generator 7 is converted to DC power by the inverter 5 and is supplied to the battery 6. The engine 8 causes the generator 7 to generate power in order to supplement the power consumption of the battery 6.

[0023] Additionally, the front drive wheels Fl, Fr and the rear drive wheels RI, Rr are each provided with a hydraulic brake mechanism 9. Each hydraulic brake mechanism 9 is a well-known friction brake device such as a disc brake or a drum brake, and pistons of wheel cylinders are actuated by brake fluid pressure supplied from a hydraulic control unit (HCU) 10 to apply hydraulic braking (friction braking) force.

[0024] The HCU 10 is equipped with actuators and valves such as a hydraulic pressure generating device consisting of a boost pump, an accumulator, etc., a pressure adjustment control valve that adjusts the hydraulic pressure during braking and supplies it to the wheel cylinders of each hydraulic brake mechanism 9, and an opening / closing control valve that opens and closes the hydraulic circuit that supplies brake hydraulic pressure to each hydraulic brake mechanism 9.

[0025] The inverter 5, engine 8, and HCU 10 are operated by control signals from a control unit 21 as a control section. The control unit 21 is composed of a microcontroller including a CPU, a RAM, a ROM, a rewritable non-volatile memory (flash memory or EEPROM), and peripheral devices. The ROM stores programs and fixed data required for the CPU to execute each process. The RAM is provided as a work area for the CPU, and temporarily stores various data in the CPU. The CPU is also called an MPU (Microprocessor) or a processor. Instead of the CPU, a GPU (Graphics Processing Unit) or a GSP (Graph Streaming Processor) may be used. Alternatively, a CPU, a GPU, and a GSP may be selectively combined.

[0026] An input side of the control unit 21 is connected to a camera unit 22, a map locator unit 23, a vehicle speed sensor 24 serving as a vehicle speed detector, and an SOC sensor 25 serving as a charge state detector.

[0027] The camera unit 22 is installed at the front of the electric vehicle M. The camera unit 22 is equipped with a stereo camera consisting of a main camera 22a and a sub-camera 22b. An image processing unit is provided in the camera unit 22. The image processing unit processes images of the driving environment in front of the electric vehicle M captured by both cameras 22a and 22b, and acquires driving environment information.

[0028] The map locator unit 23 includes a GNSS (Global Navigation Satellite System) sensor and a road map database. The GNSS sensor receives positioning signals transmitted from a plurality of positioning satellites to acquire the position coordinates of the electric vehicle M. Road map information is stored in the road map database. The map locator unit 23 estimates the current position on the road map by map matching on the road map in the road map database based on the vehicle position information acquired by the GNSS sensor. The camera unit 22 and the map locator unit 23 correspond to the driving environment information acquisition unit of the present invention.

[0029] The vehicle speed sensor 24 detects the vehicle speed (host vehicle speed) Vm of the electric vehicle M from the rotation speed of the output shaft 1a of FM / G1 or the output shaft 2a of RM / G2. The SOC sensor 25 detects the voltage value and current value of the battery 6 to detect the state of charge (SOC). Incidentally, the state of charge can be expressed as a charging rate indicating the amount of discharge that the battery 6 can carry out, as follows: Charge rate = [Remaining capacity (Ah) / Full charge capacity (Ah)] · 100 (%) Here, a charging rate of 100(%) = fully charged state, and a charging rate of 0(%) = completely discharged state.

[0030] The control unit 21 checks whether the electric vehicle M, which is the vehicle itself, is traveling on a community road. When the control unit 21 determines that the electric vehicle M is traveling on a community road, the control unit 21 controls the vehicle speed Vm in automatic driving or ACC driving based on the condition of the community road and the state of charge (SOC) of the battery 6.

[0031] The driving assistance control in the control unit 21 is specifically executed according to a driving assistance control routine shown in Figs. 2A to 2C.

[0032] In parallel with this driving assistance control routine, the control unit 21 executes, at every predetermined calculation period, a process of acquiring driving environment information on the travel route of the electric vehicle M. This driving environment information is acquired from the vehicle position on a road map estimated by the map locator unit 23, or from a driving environment image ahead of the vehicle captured by the camera unit 22.

[0033] When the control unit 21 starts the driving assistance control routine, first, based on the driving environment information on the traveling route of the electric vehicle M, it is checked whether the electric vehicle M is about to enter a community road from a main road or has entered a community road (step S1). Here, in this embodiment, a community road is defined as a road without a center line in a residential area off the main road.

[0034] For example, as shown in Fig. 6, when the electric vehicle M is on a main road and the turn signal for right turning is flashing, it is checked whether the road to which the electric vehicle M is to turn right is a community road or not according to the above definition, based on the driving environment information on the vehicle's travel path. Furthermore, it is also checked whether the road after which the electric vehicle M turns right is a community road or not, based on the driving environment information on the vehicle's travel path.

[0035] If it is determined that the road to be entered or the entered road is not a community road (NO), the routine is terminated. If it is determined that the road to be entered or the entered road is a community road (YES), it is checked whether the community road is wide or not (step S2). Whether the community road is wide or not is checked based on the driving environment information on the vehicle's travel path. Here, a wide road refers to a community road that has a road width that allows on-coming traffic with ease. Alternatively, a community road that has a certain amount of width (e.g., 80 cm) or more on the left and right of the electric vehicle M where on-coming traffic is difficult is considered to be a wide road (see FIG. 6).

[0036] If it is determined that the road is not a wide road (NO), the routine is terminated. If it is determined that the road is a wide road (YES), it is checked whether there is a narrow road ahead of the wide road (step S3). Whether there is a narrow road ahead of the wide road is checked based on driving environment information on the vehicle's travel path. Here, a narrow road refers to a residential road whose width is wider than the vehicle width of the electric vehicle M, but on which two-way traffic is not allowed (see Figures 6 and 7). The processing in steps S1 to S3 corresponds to the road detection unit of the present invention.

[0037] If it is determined that the road ahead is not a narrow road (NO), the routine is exited. If it is determined that the road ahead is a narrow road (YES), it is checked whether there is a stop position at the end of the narrow road (step S4). Whether there is a stop position at the end of the narrow road is checked by referring to static information indicating stop positions stored in the road map information of the road map database. Alternatively, it is determined by recognizing a stop line on the road as shown in Fig. 6 and Fig. 7 based on the driving environment image. The process in step S4 corresponds to the stop position detection unit of the present invention.

[0038] If it is determined that the stop position has not been detected, the routine is terminated. If a stop position is detected ahead (YES), a target stop position P4 is set immediately before the stop position (step S5). This target stop position P4 is a position where the front end of the electric vehicle M is to be stopped.

[0039] Thereafter, the state of charge (SOC) of the battery 6 detected by the SOC sensor 25 is read (step S6). Next, the battery state of charge (SOC) is compared with the charging rate determination threshold value Cth (step S7). In this embodiment, the battery state of charge (SOC) is ensured when the electric vehicle M temporarily stops at a stop position and then starts moving. A lot of power is consumed in the battery 6 when the electric vehicle M starts moving after being temporarily stopped.

[0040] The charging rate determination threshold value Cth is set to a battery state of charge (SOC) that allows the electric vehicle M to start from a temporary stop. If the state of charge (SOC) of the battery 6 is in a state in which it is difficult to start the electric vehicle M, the control unit 21 starts the engine 8 of the range extender to cause the generator 7 to generate electricity and supplies the generated electricity to the battery 6.

[0041] If SOC>Cth (NO), it is determined that the battery state of charge (SOC) has margin, and the routine is terminated. If SOC≦Cth (YES), the target vehicle speed (narrow road entry target vehicle speed) Vin when entering a narrow road is set (step S8). The process in step S8 corresponds to the entry target vehicle speed setting unit of the present invention.

[0042] The narrow road entry target vehicle speed Vin is set by reading the vehicle speed limit set for the narrow road from the road map information in the road map database. Alternatively, the narrow road entry target vehicle speed Vin is set based on the vehicle speed limit written on a road sign recognized based on the driving environment image ahead of the vehicle acquired by the camera unit 22. Alternatively, the narrow road entry target vehicle speed Vin is set based on the road width of the narrow road recognized based on the driving environment image ahead of the vehicle acquired by the camera unit 22. When setting the narrow road entry target vehicle speed Vin based on the road width, for example, the relationship between the road width and the target vehicle speed is calculated and set by referring to a table stored in advance.

[0043] Next, a constant speed start point P2 (see FIG. 5) is set at a preset position before the entrance to a narrow road (for example, 2 to 5 m before the narrow road) (step S9).

[0044] Next, the control unit 21 compares the narrow road entry target vehicle speed Vin with the regenerative vehicle speed Vc (step S10). The regenerative vehicle speed Vc is a threshold value for determining whether or not regenerative power generation by FM / G1 and FM / G2 is possible when decelerating the electric vehicle M. This regenerative vehicle speed Vc is a fixed value obtained through experiments, etc. This regenerative vehicle speed Vc is, for example, 40 [Km / h].

[0045] When Vin < Vc (NO), the routine is exited. When Vin ≥ Vc (YES), it is determined that regeneration is possible, and the vehicle speed Vm detected by the vehicle speed sensor 24 is read (step S11). Next, the vehicle speed Vm is compared with the wide road driving threshold vehicle speed Vth [Km / h] (step S12). The wide road driving threshold vehicle speed Vth is a value obtained by adding the regenerative braking possible vehicle speed during wide road driving to the narrow road entry target vehicle speed Vin. This regenerative braking possible vehicle speed is a fixed value obtained in advance for each vehicle type through experiments or the like.

[0046] When Vm < Vth (NO), it is determined that regenerative braking is not possible, and the routine is exited. When Vm ≥ Vth (YES), the narrow road section distance Ln is calculated (step S13). This narrow road section distance Ln is the distance from the narrow road entrance to the target stop point P4, and is determined based on the driving environment information on the vehicle's traveling path.

[0047] Thereafter, based on the narrow road section distance Ln, the deceleration α1 [Km / h 2 during wide road driving is set (step S14). Note that the process in step S14 corresponds to the deceleration setting unit during wide road driving of the present invention.

[0048] This deceleration α1 during wide road driving is set by referring to the deceleration table during wide road driving. Fig. 3 shows the concept of the deceleration setting table during wide road driving. The deceleration α1 during wide road driving is proportional to the narrow road section distance Ln, and as the narrow road section distance Ln becomes shorter, a smaller deceleration (negative acceleration) value is set. This deceleration α1 during wide road driving is set to a value weaker than the normal deceleration set when generally driving on a road. Note that the deceleration α1 during wide road driving may be calculated from a linear equation with a predetermined slope based on the narrow road section distance Ln.

[0049] Next, the speed difference ΔV between the vehicle speed Vm and the narrow road entry target vehicle speed Vin is calculated (step S15). Note that the process in step S15 corresponds to the speed difference calculation unit of the present invention.

[0050] Then, a deceleration start point P1 is calculated based on the constant speed start point P2, the wide road deceleration α1, and the speed difference ΔV (step S16). The deceleration start point P1 is calculated by back-calculating the point at which the narrow road entry target vehicle speed Vin is reached at the constant speed start point P2 by decelerating the electric vehicle M at the wide road deceleration α1 (see FIG. 5).

[0051] The wide road deceleration α1 is set based on the narrow road section distance Ln, and the shorter the narrow road section distance Ln, the smaller the value. Therefore, when the speed difference ΔV is constant, the shorter the narrow road section distance Ln, the longer the distance from the deceleration start point P1 to the constant speed start point P2. In other words, the electric vehicle M is decelerated at a weak wide road deceleration α1.

[0052] Thereafter, the control unit 21 checks whether the current position of the electric vehicle M has reached the deceleration start point P1 (step S17). Whether the current position of the electric vehicle M has reached the deceleration start point P1 is determined by comparing the vehicle position on the road map estimated by the map locator unit 23 with the deceleration start point P1 plotted on the road map. Alternatively, the determination is made based on the time it takes for the electric vehicle M to reach the deceleration start point P1 from the driving environment image in front of the vehicle captured by the camera unit 22.

[0053] Then, the control unit 21 waits until the vehicle position of the electric vehicle M reaches the deceleration start point P1. If the vehicle position of the electric vehicle M reaches the deceleration start point P1 (YES), a braking torque for decelerating the electric vehicle M is set (step S18). This braking torque is applied by cooperative control of friction braking and regenerative braking by the HCU 10. The control unit 21 sets the distribution rate of friction braking and regenerative braking by referring to a braking torque distribution rate map based on the wide road traveling deceleration α1.

[0054] FIG. 4 shows the concept of the braking torque distribution ratio map. As shown in the figure, the braking torque distribution ratio map is set with braking torque corresponding to deceleration. Furthermore, the braking torque distribution ratio map is set with the maximum braking torque obtained by regenerative braking for each deceleration. Furthermore, a distribution ratio is set to compensate for braking torque insufficient by regenerative braking with friction braking. Note that the braking torque by regenerative braking for each deceleration is determined in advance through experiments, etc. As shown in the figure, as the deceleration increases, regenerative braking alone cannot cover the braking torque. Therefore, as the braking torque increases, the distribution ratio of friction braking by regenerative cooperative control increases.

[0055] In other words, in areas where the vehicle travels at low speeds, such as residential roads, if rapid deceleration is not required, the deceleration rate can be reduced, making it possible to decelerate using only regenerative braking. Also, by reducing the deceleration rate, the travel distance using regenerative braking can be extended, and the charging time can be extended accordingly. As a result, deceleration energy can be efficiently converted into regenerative power.

[0056] Thereafter, the control unit 21 outputs a braking torque command according to the distribution rate of the required braking torque to the inverter 5 and the HCU 10. This starts deceleration of the electric vehicle M (step S19). Then, the vehicle waits until the vehicle speed Vm is decelerated to the narrow road entry target vehicle speed Vin (step S20). The processes in steps S19 and S20 correspond to the deceleration control unit of the present invention.

[0057] Then, when the vehicle speed Vm reaches the narrow road entry target vehicle speed Vin (YES: P2 in FIG. 5), the control unit 21 releases the brake. After releasing the brake of the electric vehicle M, the control unit 21 drives the electric vehicle M at a constant speed (Vm=Vin) so that the vehicle speed Vm of the electric vehicle M is maintained at the narrow road entry target vehicle speed Vin. Since the constant speed start point P2, which is the end point of the deceleration during narrow road travel, is set before the narrow road entrance, the constant speed travel section P2-P3 (see FIG. 5) can be set relatively long. As a result, it is possible to provide a margin for switching from the deceleration during wide road travel to the deceleration during narrow road travel. Since there is a margin for switching from the deceleration during wide road travel to the deceleration during narrow road travel, the driver does not feel uncomfortable even if the deceleration changes, and stable driving performance can be obtained.

[0058] Next, the timer starts counting the count value Tim (Tim←Tim+1: step S21). Note that the initial value of this count value Tim is 0.

[0059] The vehicle waits until the timer count value Tim reaches a preset count value (constant speed end section count value) To (equivalent to, for example, 2 to 3 [sec]) (step S22). After the count value Tim reaches the constant speed end section count value To (YES: Tim=To), a target stop point P4 is set (step S23). The position where the timer count value Tim reaches the constant speed end section count value To is set as the constant speed end point (deceleration start point) P3 (see FIG. 5). The target stop point P4 is set before a stop line drawn on the road ahead of the narrow road. This stop line is detected based on the vehicle position on the road map estimated by the map locator unit 23. Alternatively, this stop line is acquired from an image of the driving environment ahead of the vehicle captured by the camera unit 22.

[0060] Next, the stop point arrival distance Ls is calculated (step S24). This stop point arrival distance Ls is the distance from the constant speed end point P3 to the target stop point P4. This stop point arrival distance Ls is calculated from the road distance between the constant speed end point P3 and the target stop point P4 plotted on the road map of the map locator unit 23. Alternatively, it is calculated based on the distance to a stop line detected from the driving environment image in front of the vehicle captured by the camera unit 22 at the constant speed end point P3.

[0061] Thereafter, the narrow road deceleration α2 is calculated (step S25). This narrow road deceleration α2 is set to stop the electric vehicle M (Vm=0 [Km / h]) at the target stop point P4. This narrow road deceleration α2 is calculated based on the vehicle speed Vm (=Vin) and the stop point reach distance Ls (α2=(-Vm 2 / Ls) / 2).

[0062] Since the constant speed start point P2 is set before the narrow road entrance, the constant speed end point P3 can be set on the narrow road entrance side. As a result, the stopping point arrival distance Ls can be secured relatively long, and the narrow road traveling deceleration α2 can be set small accordingly.

[0063] Next, the regenerative cooperative control distribution rate is set (step S26). This regenerative cooperative control distribution rate is set to compensate for the shortage of braking torque due to regenerative braking by friction braking. This regenerative cooperative control distribution rate is set by searching the braking torque distribution rate map shown in Figure 4. Note that the characteristics of this braking torque distribution rate map have been described above, so a description thereof will be omitted here.

[0064] Next, the control unit 21 outputs a braking torque command according to the required braking torque distribution rate to the inverter 5 and the HCU 10. This starts deceleration of the electric vehicle M (step S27). Then, the process waits until the host vehicle speed Vm is decelerated to the vehicle speed Vs just before stopping (for example, 5 [Km / s]) (step S28). When the host vehicle speed Vm reaches the vehicle speed Vs just before stopping (YES), the process proceeds to step S29. The processes in steps S27 and S28 correspond to the deceleration control unit of the present invention.

[0065] In step S29, the control unit 21 stops the regenerative braking by FM / G1 and RM / G2. At the same time, the regenerative braking portion is also switched to friction braking by the HCU 10. Then, the control unit 21 stops the electric vehicle M at the target stopping point P4 (see FIG. 5) by the friction braking by the HCU 10 (step S30), and ends the routine.

[0066] In this manner, in this embodiment, when the electric vehicle M with a low charge level enters a narrow road from a wide road of a residential road through automatic driving or ACC control and the control unit 21 stops the electric vehicle M at a stop line set at the end of the narrow road, the deceleration rate α1 when traveling on a wide road and the deceleration rate α2 when traveling on a narrow road are set separately.

[0067] The deceleration α1 during wide road travel is weaker than the normal deceleration set when traveling on an ordinary road, and is set to a smaller value as the narrow road section distance Ln becomes shorter. The deceleration α2 during narrow road travel is calculated based on the narrow road entry target vehicle speed Vin and the stopping point reach distance Ls.

[0068] Then, based on the decelerations α1 and α2, the braking torque is set by referring to a braking torque distribution ratio map. Furthermore, the maximum braking torque obtained by regenerative braking using FM / G1 and RM / G2 is set from the braking torque distribution ratio map, and the braking torque deficiency is compensated for by friction braking.

[0069] As is clear from the characteristics of the braking torque distribution ratio map shown in Figure 4, in areas where the vehicle travels at low speeds, such as residential roads, reducing the deceleration rate makes it possible to decelerate using only regenerative braking. In addition, reducing the deceleration rate increases the distance traveled using regenerative braking, which in turn increases the charging time.

[0070] That is, the deceleration α1 during wide road travel is set based on the narrow road section distance Ln, and the shorter the narrow road section distance Ln, the smaller the value is set. The shorter the narrow road section distance Ln, the longer the distance from the deceleration start point P1 to the constant speed start point P2 is set. Therefore, sufficient charging is possible before entering the narrow road by deceleration using only regenerative braking.

[0071] As a result, the deceleration energy generated when the electric vehicle M decelerates on a residential road can be efficiently converted into regenerative power and charged into the battery 6. This can improve the power consumption. Furthermore, in a range extender EV, the frequency with which the generator-only engine 8 is started is reduced, improving fuel efficiency. Also, by gently decelerating the electric vehicle M, the driver does not feel uncomfortable. Furthermore, sufficient charging is performed when entering a narrow road, so that insufficient charging when starting from the target stopping point P4 is eliminated.

[0072] In addition, when entering a narrow road from a wide road in a community road, the constant speed start point P2 is set just before the entrance to the narrow road, so the deceleration start point (P3) on the narrow road can be set on the entrance side of the narrow road. As a result, the stopping point arrival distance Ls can be set longer, and the deceleration rate α2 during narrow road travel can be reduced accordingly. This makes it possible to decelerate using only regenerative braking even when traveling on a narrow road, and the regenerative power can be charged to the battery 6.

[0073] The present invention is not limited to the above-described embodiment, and for example, the electric vehicle M may be a hybrid vehicle that combines a motor generator (M / G) and an engine as a drive source. Also, the stop line includes a stop line before a railroad crossing. [Explanation of symbols]

[0074] 1...Front motor generator (FM / G), 1a, 2a...output shaft, 2...Rear motor generator (RM / G), 3l,3r,4l,4r…drive shaft, 4…Generator, 5...Inverter, 6…Battery, 7…Generator, 8…Engine, 9...Hydraulic brake mechanism, 10...Hydraulic control unit (HCU), 21...control unit, 22...Camera unit, 22a…Main camera, 22b…Sub camera, 23...Map locator unit, 24...Vehicle speed sensor, 25…SOC sensor, Df…Front differential, Dr…Rear differential, Fl,Fr…Front drive wheels, Ls… Distance reached at stopping point, M: Electric vehicle, P1...Deceleration start point, P2…constant speed starting point, P3: Constant speed end point, P4…Target stopping point, Rl, Rr: rear drive wheels, Tim: count value, To: constant speed end section count value, Vc...Vehicle speed at which regeneration is possible, Vin…Target vehicle speed when entering a narrow road, Vs: Vehicle speed just before stopping, Vth: Wide road threshold speed, Vm…Vehicle speed, ΔV…speed difference, α1…Deceleration when driving on wide roads, α2…Deceleration when driving on narrow roads

Claims

1. A battery; a motor generator that drives an electric vehicle using electric power supplied from the battery and charges the battery using electric power generated by regenerative braking during deceleration of the electric vehicle; a vehicle speed detection unit that detects a vehicle speed of the electric vehicle; a driving environment information acquisition unit that acquires driving environment information ahead of the electric vehicle; a control unit that controls a vehicle speed and a deceleration of the electric vehicle by driving the motor generator and regenerative braking based on the host vehicle speed detected by the vehicle speed detection unit and the driving environment information acquired by the driving environment information acquisition unit; A driving assistance device for an electric vehicle having The control unit is a road detection unit that detects a wide road and a narrow road adjacent to the wide road based on the driving environment information acquired by the driving environment information acquisition unit; a stop position detection unit that detects a stop position ahead of the narrow road detected by the road detection unit based on the driving environment information acquired by the driving environment information acquisition unit; a deceleration control unit that decelerates the electric vehicle at a small deceleration rate by regenerative braking while the electric vehicle is traveling on the wide road before entering the narrow road when the road detection unit detects the narrow road and the stop position detection unit detects the stop position; A driving assistance device for an electric vehicle comprising:

2. The control unit is a wide road running deceleration setting section which sets a smaller value of the wide road running deceleration as the section distance becomes shorter based on the section distance from the entrance of the narrow road to a target stop position set based on the temporary stop position; and When the road detection unit detects the narrow road and the stop position detection unit detects the stop position, the deceleration control unit decelerates the electric vehicle by regenerative braking based on the wide road traveling deceleration set by the wide road traveling deceleration setting unit when traveling on the wide road before entering the narrow road.

2. The driving assistance device for an electric vehicle according to claim 1.

3. a charge state detection unit for detecting a charge state of the battery; The deceleration control unit decelerates the electric vehicle by regenerative braking based on the wide road traveling deceleration set by the wide road traveling deceleration setting unit when the charged state detected by the charged state detection unit is equal to or lower than a predetermined value.

3. The driving assistance device for an electric vehicle according to claim 2.

4. The control unit is an entry target vehicle speed setting unit that sets a target vehicle speed when entering a narrow road; a speed difference calculation unit that calculates a speed difference between the host vehicle speed detected by the vehicle speed detection unit and the target vehicle speed set by the entry target vehicle speed setting unit; a deceleration start point setting unit that sets a deceleration start point based on the wide road traveling deceleration set by the wide road traveling deceleration setting unit and the speed difference calculated by the speed difference calculation unit; Further comprising: The deceleration control unit starts deceleration of the electric vehicle when the electric vehicle reaches the deceleration start point.

4. The driving assistance device for an electric vehicle according to claim 3.

5. The deceleration control unit starts deceleration of the electric vehicle when the host vehicle speed detected by the vehicle speed detection unit is equal to or higher than a set vehicle speed.

5. The driving assistance device for an electric vehicle according to claim 4.

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