Vehicle control unit

Abstract

Vehicle control device (12), comprising: an electric motor (14) configured to be connected to at least one wheel (21), an energy storage device (24) connected to the electric motor (14), a charging / discharging control device that controls the charging / discharging of the energy storage device (24), a first driving control device (40) that controls the electric motor (14) according to an operating action by a driver, and a second driving control device (41) that controls the electric motor (14) according to a cruise control function that automatically controls a vehicle speed, wherein, when the first drive control device (40) controls the electric motor (14), the charge / discharge control device controls the charge / discharge power of the energy storage device (24) within a first charge / discharge range (Xa), and wherein, when the second driving control device (41) controls the electric motor (14), the charging / discharging control device controls the charging / discharging power of the energy storage device (24) within a second charging / discharging range (Xb) which is wider than the first charging / discharging range (Xa).

Description

[0001] The present invention relates to a vehicle control device provided with an energy storage device.

[0002] As a driving assistance system, a constant-speed cruise system that maintains a prescribed vehicle speed, or a cruise control system, also called a speed control system, has been developed. A cruise control system that uses a millimeter-wave radar, an infrared laser, a stereo camera unit, a monocular camera, or the like to collect information regarding a preceding vehicle, thereby causing the vehicle equipped with the system to follow the preceding vehicle, has also been developed. Such cruise control systems are used in electric vehicles and hybrid vehicles that use one or more electric motors for propulsion.KR 10 2012 0 060 631 A, for example, describes a system that takes over and optimizes drive control and speed regulation in a hybrid vehicle.

[0003] It is desirable for hybrid vehicles to increase their electric motor travel ranges, within which they are capable of running solely on an electric motor, to actively shut off an internal combustion engine for the purpose of improving fuel consumption. To this end, a hybrid vehicle has been proposed that, when approaching a preceding vehicle, predicts that the driver will not request acceleration and removes limitations on electric motor torque to increase the electric motor travel range (see Japanese Unexamined Patent Application Publication JP 2010-111182 A). In other words, under a driving condition where no driver request for acceleration is predicted, the electric motor torque margin reserved for acceleration is reduced while the electric motor output torque is increased, thereby expanding the electric motor travel range.

[0004] Hybrid vehicles and electric vehicles have a regenerative braking system that enables regeneration of the electric motor, as disclosed, for example, in DE 10 2008 030 521 A1. This system presents a system for regenerative braking, for example, when the vehicle is driven by gravity or the actual speed exceeds the target speed. However, the braking force provided by the regenerative braking system is limited by the battery's capacity to store electricity, making it impossible to increase the braking force depending on the battery's state of charge or temperature. Regenerative electrical energy provided in conjunction with regenerative braking is supplied to the battery, which, depending on the battery's state of charge or temperature, may pose a risk of overcharging the battery.To solve this problem, a hybrid vehicle has been proposed which, when there is a risk of battery overcharging, causes the regenerative electrical energy provided in connection with regenerative braking to be consumed by other electric motors to prevent battery overcharging (JP 2010 - 111 182 A).

[0005] Another possibility for utilizing the energy recovered from braking is described in DE 103 03 866 A1. Here, the energy is converted directly into thermal energy to heat components such as lubricants to operating temperature. This also discusses the possibility of first storing the energy in a battery and then using this electrical energy to heat the components, but this would only exacerbate the problem of overcharging.

[0006] Even if an electric motor torque range is reduced, as described in JP 2012-240566 A, the performance of a battery or capacitor as an energy storage device cannot be optimized, which may lead to limitations in an electric motor travel range. In other words, since the charge / discharge range available to the energy storage device may be restricted by temperature conditions and the state of charge, simply increasing the electric motor output torque may limit the electric motor travel range. In addition, when attempting to select the charge / discharge range for the energy storage device, the charge / discharge range must be narrowed in consideration of overshoot or undershoot associated with charge / discharge to prevent the energy storage device from being overcharged or overdischarged.As a result, the performance of the energy storage device cannot be optimized, making it difficult to expand the electric motor's driving range. In hybrid vehicles, as in electric vehicles, optimizing the performance of the energy storage device is essential to reducing the electric vehicle's power consumption.

[0007] In automatic braking control for the aforementioned driving assistance system, which is not part of the present invention, it is important to quickly and strongly increase the braking force when it is determined that there is a risk of a vehicle accident. In other words, it is important to increase the braking force of the regenerative braking in automatic braking control. However, as described above, the performance of the energy storage device cannot be optimized depending on a battery charge level or temperature because the braking force of the regenerative braking is limited by the battery's capacity to store electricity, making it difficult to increase the braking force. From the perspective of automatic braking control, it is also necessary to optimize the performance of the energy storage device.EP 2 387 093 A1 discloses a system that improves the performance of the energy storage device in a vehicle by avoiding the long-term increase in the internal resistance of the battery that is otherwise caused by high charging / discharging power.

[0008] Accordingly, it is an object of the present invention to optimize the performance of an energy storage device.

[0009] According to one aspect of the present invention, there is provided a vehicle control device including an electric motor configured to be connected to at least one wheel, an energy storage device connected to the electric motor, a charge / discharge control device that controls the charge / discharge of the energy storage device, a first travel control device that controls the electric motor according to an operation of a driver, and a second travel control device that controls the electric motor according to a travel control function (hereinafter referred to as a "cruise control function") that automatically controls a vehicle speed.When the first travel control device controls the electric motor, the charge / discharge control device controls the charge / discharge power of the energy storage device within a first charge / discharge range. When the second travel control device controls the electric motor, the charge / discharge control device controls the charge / discharge power of the energy storage device within a second charge / discharge range that is larger or wider than the first charge / discharge range.

[0010] Another aspect provides a vehicle control device not belonging to the present invention that automatically controls the vehicle according to information regarding an object in front of the vehicle. The vehicle control device includes an electric motor connected to at least one wheel, an energy storage device configured to be connected to the electric motor, a determination device that determines, based on the information regarding the object, whether or not a braking situation in which a distance to the object falls below a predetermined distance has occurred, an energy storage device control device that, when the braking situation is determined, extends a current limit for a charging side in the energy storage device, and an electric motor control device that causes electric motor regeneration when the braking situation is determined.

[0011] The invention is described below using an embodiment with reference to the drawings in which Fig. 1 is a diagram showing a vehicle control device according to a first embodiment of the present invention, Fig. 2 is a mode map showing an area in which an electric motor travel mode is set and another area in which a parallel travel mode is set, Fig. 3 is a block diagram showing some functions provided by a control unit, Fig. 4 is a schematic diagram showing a limit value for a loading side and a limit value for a discharging side, Fig. 5A is a schematic diagram showing a charge / discharge range applicable at a normal temperature, Fig. 5B is a schematic diagram showing a charge / discharge range applicable at high and low temperature, Fig. 6 is a schematic diagram showing a change in the charge / discharge performance of a battery on a discharge side, Fig. 7 is a schematic diagram showing a change in the charge / discharge performance of a battery on a charging side, Fig. Fig. 8 is a diagram showing a vehicle control device according to a second embodiment not belonging to the invention, Fig. 9 is a diagram showing part of functions provided by a control unit, Fig. 10 is a diagram showing an automatic braking situation which is no longer part of the amended claims, Fig. 11 is a schematic diagram showing a charging / discharging section of a battery, Fig. 12 is a flowchart showing a process for performing expansion control for a charging limit, Fig. 13 is a schematic view showing a measure of limit extension, Fig. 14 is a schematic view showing a load limit to be extended in an automatic brake control, and which is no longer part of the amended claims Fig. Figure 15 is a timing chart showing the situation in which an automatic braking control, which is no longer part of the amended claims, is performed by a control unit. [First embodiment]

[0012] A first embodiment of the present invention will be described in detail below with reference to the accompanying drawings. Fig. 1 is a diagram showing a vehicle control device 12 according to the first embodiment of the present invention. As shown in Fig. 1, a hybrid vehicle is provided with a drive unit 10 and a control system 11. The vehicle control device 12 according to the first embodiment of the present invention is configured with the drive unit 10 and the control system 11.

[0013] The drive unit 10 includes an internal combustion engine 13 and a motor generator (electric motor) 14 as drive sources. The drive unit 10 is further provided with a continuously variable automatic transmission 17 having a primary pulley 15 and a secondary pulley 16. The primary pulley 15 is connected at one end to the internal combustion engine 13 through a torque converter 18 and is connected at the other end to the motor generator 14. The secondary pulley 16 is connected to wheels 21 via an output shaft 19 and a differential mechanism 20. Furthermore, a stator 22 of the motor generator 14 is connected to a battery (energy storage device) 24 via an inverter 23. In this way, the motor generator 14 is mechanically connected to the wheels 21 and electrically connected to the battery 24.

[0014] A clutch 25, switchable between an engaged state and a disengaged state, is provided between the torque converter 18 and the primary pulley 15. When a cruising mode is set to an electric motor cruising mode, the clutch 25 is switched to the disengaged state in which the primary pulley 15 and the engine 13 are decoupled from each other. In the electric motor cruising mode, the engine 13 is turned off, while the motor generator 14 is activated to use electric motor power to drive the wheels 21. In contrast, when the cruising mode is selected to be a parallel cruising mode, the clutch 25 is switched to the engaged state in which the primary pulley 15 and the engine 13 are coupled to each other. In this parallel cruising mode, the engine 13 and the motor generator 14 are activated to use engine power and electric motor power to drive the wheels 21.

[0015] Fig. 2 is a mode map showing an area where the electric motor travel mode is selected and another area where the parallel travel mode is selected. As shown in Fig. 2, the mode map has a mode limit value α that is set based on a target driving force and a vehicle speed. As indicated by arrow A in Fig. 2, when the target driving force and the vehicle speed exceed the mode threshold α, the engine 13 is activated to switch the traveling mode from the electric motor traveling mode to the parallel traveling mode. In contrast, as indicated by arrow B in Fig. 2, when the target driving force and the vehicle speed fall below the mode limit value α, the internal combustion engine 13 is deactivated to switch the traveling mode from the parallel traveling mode to the electric motor traveling mode.

[0016] As in Fig. 1, the control system 11 includes a hybrid control unit (hereinafter referred to as "control unit") 30 that controls the engine 13, the motor generator 14, the continuously variable transmission 17, the clutch 25, and the like. The control unit 30 outputs a control signal to a peripheral unit 31 including a throttle valve and an injector, so as to control the torque and rotational speed of the engine 13. The control unit 30 also outputs a control signal to a starter motor 32 for controlling the rotation of the engine 13 during engine start-up. The control unit 30 outputs control signals to the inverter 23, so as to control the torque and rotational speed of the motor generator 14.Furthermore, the control unit 30 outputs a control signal to a valve unit 33, which controls the supply of hydraulic fluid to the continuously variable automatic transmission 17 and the clutch 25 to control the operation of the continuously variable automatic transmission 17 and the clutch 25. The control unit 30 is connected to an acceleration sensor 34 that detects the amount of operation of an accelerator pedal (hereinafter referred to as "accelerator pedal operation amount"), a brake sensor 35 that detects the amount of operation of a brake pedal (hereinafter referred to as "brake operation amount"), a vehicle speed sensor 36 that detects a speed at which the vehicle is traveling, and the like. In addition, the control unit 30 receives data on a temperature level and a state of charge (SOC) of the battery 24 from a battery control unit 37.The control unit 30 includes a CPU that calculates control signals, a ROM that stores a control program, arithmetic equations and map data, and a RAM that temporarily stores data.

[0017] The control system 11 further includes a cruise control function (also referred to as a "cruise control function") that provides automatic vehicle speed control. The cruise control function of the control system 11 includes a constant speed control function that maintains a vehicle speed at a constant level and a following control function that maintains a vehicle-to-vehicle distance from a preceding vehicle at a constant level. The control system 11 has a camera unit 38 that captures an image of the area in front of the vehicle and a cruise control switch 39 that can be operated by a vehicle driver. The cruise control switch 39 is used to activate or deactivate the cruise control function and selects a vehicle speed and a vehicle-to-vehicle distance that serve as control targets of the cruise control function.When the cruise control switch 39 is switched to activate the cruise control function, the control unit 30 checks preceding vehicle information based on image information received from the camera unit 38. Elements of the preceding vehicle information include the presence or absence of a preceding vehicle, a vehicle-to-vehicle distance to the preceding vehicle, and a difference in speed with respect to the preceding vehicle. The control unit 30 performs automatic vehicle speed control to maintain the selected vehicle speed when there is no preceding vehicle and to maintain the selected vehicle-to-vehicle distance without exceeding the selected vehicle speed when there is a preceding vehicle.The automatic vehicle speed control is performed by controlling the internal combustion engine 13, the motor generator 14 and the continuously variable automatic transmission 17.

[0018] Fig. Figure 3 is a block diagram showing some of the functions provided by the control unit 30. As described later, the control unit 30 functions as the first travel control device, the second travel control device, and the loading / unloading control device of the present invention in this embodiment. As shown in Fig. 3, the control unit 30 includes a first target driving force setting module 40 that sets a first target driving force. The first target driving force is a target driving force set based on a driver's operation, such as an accelerator or brake operation, and used during a normal driving period when the cruise control function is deactivated. The control unit 30 includes a second target driving force setting module 41 that sets a second target driving force. The second target driving force is a target driving force used during a cruise driving period when the cruise control function is activated. The rate of change in the first target driving force, which changes with the driver's operation, is set to be greater than the rate of change in the second target driving force, which changes according to the cruise control function.In other words, the upper limit of the change rate is set higher during normal driving, thereby allowing the first target driving force to be changed quickly. In contrast, the upper limit of the change rate is set smaller during cruise control driving, thereby allowing the second target driving force to be changed more slowly. The first target driving force setting module 40 sets the first target driving force with reference to a predetermined driving force map based on a vehicle speed and an accelerator pedal operation amount. The second target driving force setting module 41 sets the second target driving force based on the selected vehicle speed, the selected inter-vehicle distance, a current vehicle speed, a current inter-vehicle distance, and the like.During regenerative braking, the first target driving force setting module 40 sets the first target driving force with reference to a predetermined driving force map based on the vehicle speed and the brake operation amount.

[0019] The control unit 30 also includes a cruise control determination device 42 that determines whether the cruise control function is activated or not. The cruise control determination device 42 refers to the operation of the cruise control switch 39 and the brake pedal to determine whether the cruise control function is activated or not, and outputs the determination results to a first drive control device 43 and a second drive control device 44. The cruise control determination device 42 determines, for example, a normal driving state in which the cruise control function is deactivated when the cruise control switch 39 is turned OFF or when the brake pedal is depressed. The first drive control device 43 outputs a control signal to the inverter 23 and the peripheral unit 31, thereby controlling the engine 13 and the motor generator 14 to steer the wheels 21 with the first target driving force.On the other hand, the cruise control determining device 42 determines cruise control travel in which the cruise control function is activated when the cruise control switch 39 is turned ON or when the brake pedal is not depressed. The second drive control device 44 outputs a control signal to the inverter 23 and the peripheral unit 31, thereby controlling the engine 13 and the motor generator 14 to steer the wheels 21 with the second target driving force.

[0020] Furthermore, the control unit 30 includes a charge / discharge range setting module 45 that sets a range within which the battery 24 is charged / discharged. The charge / discharge range setting module 45 sets a charge / discharge range based on the temperature and the state of charge (SOC) of the battery 24. Fig. Figure 4 is a schematic diagram showing a limit value for a loading side and a limit value for a discharging side. As indicated by the white arrows in Fig. As shown in Figure 4, when the temperature of the battery 24 is high and low, the discharge limit value D1 and the charge limit value C1 are set low, while when the temperature of the battery 24 is normal, a discharge limit value D4 and a charge limit value C4 are set high. In other words, when the temperature of the battery 24 is high and low, a narrow charge / discharge range X1 is set by the limit values ​​D1 and C1. As the temperature of the battery 24 rises from low to normal or as the temperature of the battery 24 drops from high to normal, the charge / discharge range gradually increases to a charge / discharge range X2, a charge / discharge range X3, and a charge / discharge range X4, in that order. As the state of charge (SOC) approaches 0%, the discharge limits D1 to D4 are set to lower values ​​approaching 0.On the other hand, as the state of charge (SOC) approaches 100%, the charge limits C1 to C4 are set to lower values, approaching 0. For the battery 24 at lower temperatures, setting the discharge limits D1 to D4 and the charge limits C1 to C4 considers the protection of various electronic components, since the voltage varies significantly in response to changes in the charge / discharge power. For the battery 24 at high temperatures, setting the discharge limits D1 to D4 and the charge limits C1 to C4 considers the protection of the battery 24 from degradation.

[0021] In order to prevent overcharging or over-discharging of the battery 24, the charge / discharge range setting module 45 corrects the size of the charge / discharge range according to the presence or absence of the cruise control by using the above-mentioned charge / discharge ranges X1 to X4 as a reference. Fig. 5A is a schematic view showing a charge / discharge range applicable at a normal temperature. Fig. Figure 5B is a schematic view showing a charge / discharge range applicable at high and low temperatures. As shown in Fig. 5A, in normal control at normal temperature, the first discharge limit value Da4 is set below a discharge limit value D4 with a margin Ma, while a first charge limit value Ca4 is set below a charge limit value C4 with a margin Ma. In other words, in normal control at normal temperature, a first charge / discharge range Xa4, defined by the first discharge limit value Da4 and the first charge limit value Ca4, is set as a charge / discharge range within which the battery 24 is subjected to charge / discharge control. In cruise control at normal temperature, a second discharge limit value Db4 is set lower than the discharge limit value D4 by a margin Mb, while a second charge limit value Cb4 is set lower than the charge limit value C4 by a margin Mb. As described above, the cruise control uses the margin Mb, which is smaller than the margin Ma, for normal control.In other words, in cruise control at normal temperature, a second charge / discharge range Xb4 defined by the second discharge limit value Db4, which is larger than the first discharge limit value Da4, on the discharge side, and the second charge limit value Cb4, which is larger than the first charge limit value Ca4, on the charge side, is set as the charge / discharge range within which the battery 24 is subjected to charge / discharge control.

[0022] As in Fig. 5B, in normal high- and low-temperature control, a first discharge limit value Da1 is set lower than a discharge limit value D1 by a margin Ma, while a first charge limit value Ca1 is set lower than a charge limit value C1 by a margin Ma. In other words, in normal high- and low-temperature control, a first charge / discharge range Xa1, defined by the first discharge limit value Da1 and the first charge limit value Ca1, is set as the charge / discharge range within which the battery 24 is subjected to charge / discharge control. In cruise control at high- and low-temperature, a second discharge limit value Db1 is set lower than the discharge limit value D1 by a margin Mb, while a second charge limit value Cb1 is set lower than a charge limit value C1 by a margin Mb. As described above, the cruise control uses the margin Mb, which is smaller than the margin Ma, for normal control.In other words, in the high-temperature and low-temperature cruise control, a second charge / discharge range Xb1 defined by the second discharge limit value Db1 larger than the first discharge limit value Da1 on the discharge side and a second charge limit value Cb1 larger than the first charge limit value Ca1 on the charge side is set as the charge / discharge range within which the battery 24 is subjected to the charge / discharge control.

[0023] As described above, under normal control in which the cruise control function is deactivated, a charge / discharge output of the battery 24, namely its charge / discharge power, is subjected to control, that is, controlled, in the first charge / discharge ranges Xa1 and Xa4. On the other hand, under cruise control in which the cruise control function is activated, the charge / discharge power of the battery 24 is controlled in the second charge / discharge ranges Xb1 and Xb4, which are wider than the first charge / discharge ranges Xa1 and Xa4. In other words, under normal control, the charge / discharge power is controlled in the first charge / discharge ranges Xa1 and Xa4 in which the larger range Ma is set, while under cruise control, the charge / discharge power is controlled in the second charge / discharge ranges Xb1, Xb4 in which the smaller range Mb is set.As described above, since the charging / discharging performance of the battery 24 is subject to rapid change during normal control in which the torque of the motor generator 14 changes rapidly depending on the driver's operations, the charging / discharging performance is controlled in the first charging / discharging ranges Xa1 and Xa4 in which the larger margin and the larger safety margin Ma are set, respectively. On the other hand, since the charging / discharging performance of the battery 24 is subject to gradual change during cruise control in which the torque of the motor generator 14 changes gradually, the charging / discharging performance is controlled in the second charging / discharging ranges Xb1 and Xb4 in which the smaller margin and the smaller safety margin Mb are set, respectively. As a result, the performance of the battery 24 can be optimized while preventing overcharging or over-discharging of the battery 24.

[0024] Fig. 6 is a schematic view showing a change in the charging / discharging performance of the battery 24 in the discharging side. Fig. 7 is a schematic view showing a change in the charging / discharging performance of the battery 24 in the charging side. Fig. 6 and Fig. 7 show examples of the charging / discharging range at normal temperature. As in Fig. As shown in Figure 6, the first discharge limit value Da4 for the normal control in which the cruise control function is deactivated has the larger margin Ma to the discharge limit value D4. As a result, even if the control target P1 for the charge / discharge power increases sharply on the discharge side after the accelerator pedal is depressed by a large amount, the first discharge limit value Da4 imposes restrictions on the control target P1 at an early stage. In other words, even if the charge / discharge power P2 from the battery 24 increases to levels exceeding the first discharge limit value Da4, resulting in overshoot, the charge / discharge power P2 can be suppressed so as not to reach the discharge limit value D4. This can prevent over-discharging of the battery 24. For the cruise control control in which the cruise control function is activated, the second discharge limit value Db4 has the smaller margin Mb to the discharge limit value D4.In other words, cruise control, in which the charge / discharge power control target P1 undergoes gradual changes, does not cause excessive overshoot of the charge / discharge power P2, allowing the charge / discharge power P2 to be brought close to the discharge limit D4. With this arrangement, the performance of the battery 24 can be optimized, thereby improving the fuel consumption of a hybrid vehicle.

[0025] As in Fig. As shown in Fig. 7, for normal control in which the cruise control function is deactivated, the first charge limit value Ca4 has the larger margin Ma to the charge limit value C4. With this arrangement, the first charge limit value Ca4 imposes restrictions on the control target P1 at an early stage, even if the control target P1 for the charge / discharge power increases sharply on the charge side after the accelerator pedal is depressed by a large amount. In other words, even if a charge / discharge power P2 from the battery 24 falls below a value of the first charge limit value Ca4, resulting in undershoot, the charge / discharge power P2 can be suppressed so as not to reach the charge limit value C4. This can prevent overcharging of the battery 24. In cruise control control in which the cruise control function is activated, the second charge limit value Cb4 has the smaller margin Mb to the charge limit value C4.In other words, cruise control in which the charge / discharge power control target P1 undergoes gradual changes does not cause excessive undershooting of the charge / discharge power P2, allowing the charge / discharge power P2 to be brought closer to the charge limit C4. As a result, the performance of the battery 24 can be optimized, thereby improving the fuel consumption of the hybrid vehicle.

[0026] As described so far, during normal control with the cruise control function deactivated, the charge / discharge performance of the battery 24 is subjected to control within the first charge / discharge range, while during cruise control with the cruise control function activated, the charge / discharge of the battery 24 is subjected to control within the second charge / discharge range, which is wider than the first charge / discharge range. As described above, the performance of the battery 24 can be optimized by changing the control range of the battery 24 according to the driving condition. In other words, the performance of the battery 24 can be optimized while suppressing overcharging or overdischarging of the battery 24.Since the performance of the battery 24 can be optimized as described above, limitations of the electric motor driving mode and limitations of the degree of electric motor regeneration due to temperature conditions can be reduced, thereby making it possible to improve the fuel consumption of the hybrid vehicle.

[0027] More precisely, although, as in Fig. 5B, the battery 24 at high and low temperatures imposes severe restrictions on the motor driving mode and the degree of motor regeneration due to the narrow charge / discharge range X1 as a reference. By expanding the charge / discharge range from Xa1 to Xb1 during cruise control, the motor generator 14 can be used more frequently. Furthermore, since the battery 24 at low temperatures leads to more frequent use of the motor generator 14, the battery 24 can be heated at an earlier stage as a result of more frequent charging and discharging. In other words, since the heat of the battery 24 leads to a wider charge / discharge range, the motor generator 14 can be used more frequently.

[0028] During the process of switching the cruise control to normal control, that is, narrowing the charge / discharge range, the rate of change of the first target driving force is preferably suppressed according to the driver's operation to prevent overcharging or overdischarging of the battery 24. The charge / discharge power P2 may, for example, be as shown in Fig. 6, in some cases, the first target driving force may exceed the first discharge limit value Da4 during cruise control. When this exceedance occurs, the rapid change in the control target P1 causes the charge / discharge power P2 to exceed the discharge limit value D4. For this reason, during the process of narrowing the charge / discharge range, the rate of change of the first target driving force is preferably limited to suppress a rapid change in the control target P1.

[0029] Needless to say, the present invention is not limited to the above example. Various modifications are conceivable within the scope of the present invention. In the above description, the vehicle control device 12 is applied to a hybrid vehicle. However, the present invention is not limited thereto. Alternatively, the vehicle control device 12 may be applied to an electric vehicle equipped with only electric motors as a drive source. When the present invention is applied to the electric vehicle, it can maximize the performance of the battery 24, thereby making it possible to improve fuel efficiency. In addition, the control system 11 is provided with, but not limited to, the cruise control function, the constant speed control function, and the follow-up control function.The control system 11 may be provided with only the constant speed control function or only the follow-up control function as the cruise control function. In the above description, the loading side and the unloading side use the same margins or safety distances Ma and Mb. However, the present invention is not limited to this. Alternatively, the loading side and the unloading side may use different margins or safety distances. Furthermore, although the same margin Ma is applied to the normal control and the same margin Mb is applied to the cruise control control even if the loading / unloading areas X1 and X4 are changed as a reference, the present invention is not limited to this. Alternatively, the margins may be changed according to the loading / unloading area as a reference.

[0030] In the above description, the battery 24 is used as an energy storage device. However, this is not a limitation. A capacitor may also be used as an energy storage device. In addition, information regarding a preceding vehicle is acquired with the camera unit 38 as described above. The camera unit 38 may be a stereo camera system equipped with multiple cameras or a monocular camera equipped with one camera. Alternatively, information regarding the preceding vehicle may be acquired with a millimeter-wave radar or an infrared laser. The drive unit installed in the hybrid vehicle is not limited to the drive unit 10 shown in the figures. For example, the drive unit shown in Fig. The drive unit 10 shown in Figure 1 is a drive unit provided with a motor generator 14. However, the present invention is not limited thereto. A drive unit having two or more motor generators 14 may be used. [Second embodiment]

[0031] The following embodiment is no longer part of the amended claims. A second embodiment, which is not part of the present invention, is described in detail below with reference to the accompanying drawings. Fig. 8 is a diagram showing a vehicle control device 110 according to a second embodiment not belonging to the present invention. As in Fig. 8, the vehicle control device 110 is provided with a drive unit 113 having an internal combustion engine 111 and a motor generator (electric motor) 112. The drive unit 113 includes a continuously variable automatic transmission 116 with a primary pulley 114 and a secondary pulley 115. The primary pulley 114 is connected at one end to the internal combustion engine 111 through a clutch 117 and a torque converter 118, and at the other end to the motor generator 112 through an electric motor shaft 119. The secondary pulley 115 is connected to wheels 122 through an output shaft 120 and a differential mechanism 121. Furthermore, a stator 123 of the motor generator 112 is connected to a battery (energy storage device) 125 through an inverter 124. As previously described, the motor generator 112 is mechanically connected to the wheels 122 and electrically connected to the battery 125.A regenerative brake 126 includes the motor generator 112, and the wheels 122 can be braked with regenerative torque from the motor generator 112.

[0032] The vehicle control device 110 includes a hydraulic brake 130 that brakes the wheels 122. The hydraulic brake 130 includes a brake pedal 131 configured to be operated by a driver of the vehicle, and a master cylinder 132 that generates brake fluid pressure according to the degree of operation of the brake pedal 131. The hydraulic brake 130 also includes brake discs 133, each mounted on the wheels 122, and brake calipers 134 that brake the brake discs 133. The master cylinder 132 and the brake calipers 134 are connected to each other by a brake line 135 through which brake fluid flows. The hydraulic brake 130 also includes a brake actuator 136 that controls brake fluid pressure. The brake actuator 136 includes an electric pump, an accumulator, and an electromagnetic valve, and the like, all of which are not shown.The brake actuator 136 has a function of adjusting brake fluid pressure in automatic brake control, which will be described later.

[0033] The vehicle control device 110 includes a control unit 140 that controls the internal combustion engine 111, the motor generator 112, and the brake actuator 136, among others. The control unit 140 is connected to a camera unit 141 that captures images from the front of the vehicle, a vehicle speed sensor 142 that detects a vehicle speed, an accelerator pedal sensor 143 that detects the amount of operation of an accelerator pedal, and a brake sensor 144 that detects the amount of operation of the brake pedal 131. The control unit 140 also receives temperature values, the state of charge (SOC), current values, and voltage values ​​of the battery 125 from a sensor (not shown) attached to the battery 125. Based on detection signals from various sensors, the control unit 140 determines the state of the vehicle and outputs a control signal to the internal combustion engine 111, the motor generator 112, the brake actuator 136, and the like.The control unit 140 includes a CPU that performs the calculation of control signals, a ROM that stores programs and data, and a RAM that temporarily stores data.

[0034] Next, the automatic brake control, which automatically brakes the vehicle, is described below. Fig. 9 is a diagram showing parts of the functions provided by the control unit 140. As in Fig. As shown in Figure 9, the control unit 140 includes an engine control device 150, an electric motor control device 151, and a battery control device 152. The control unit 140 also includes an image information processing device 153, a pre-crash determination device 154, and an automatic braking control device 155. The control unit 140 provided here serves as the braking determination device, the energy storage device control device, and the electric motor control device 1, as described later.

[0035] The image information processing device 153 processes image information from the camera unit 141 to detect information (object information) regarding a vehicle traveling ahead of the vehicle. Items of information regarding the vehicle traveling ahead are processed by the image information processing device 153, including a vehicle-to-vehicle distance from the vehicle traveling ahead (distance from the object) and a difference in speed with respect to the vehicle traveling ahead (speed difference from the object), and the like.The pre-crash determination means 154 determines, based on the information regarding the inter-vehicle distance and the speed difference with respect to the preceding vehicle, whether or not an automatic braking situation (braking situation) in which the inter-vehicle distance to the preceding vehicle is less than a predetermined distance has occurred, that is, a braking situation in which the automatic braking control is required has occurred.

[0036] Fig. 10 is a diagram showing the automatic braking situation. As indicated by a symbol α in Fig. As shown in Figure 10, when the inter-vehicle distance L between the vehicle and a preceding vehicle is less than a predetermined distance L1, the pre-crash determiner 154 determines that the automatic braking situation requiring automatic braking control has occurred. When there is a large difference in speed between the vehicle and a preceding vehicle, in other words, when the vehicle is approaching the preceding vehicle at a high speed, the predetermined distance L1 is set high. On the other hand, when the difference in speed between the vehicle and a preceding vehicle is small, in other words, when the vehicle is approaching the preceding vehicle at a low speed, the predetermined distance L1 is set to a small value.The predetermined distance L1 may be varied continuously according to a speed difference or may be varied stepwise according to a speed difference.

[0037] As previously described, the pre-crash determination device 154 determines the automatic braking situation, and the automatic braking control device 155 sets a target deceleration based on the inter-vehicle distance and the speed difference. The automatic braking control device 155 then outputs a control signal to the engine control device 150, the electric motor control device 151, and the brake actuator 136 to decelerate the vehicle at the target deceleration. Specifically, to avoid a collision with the preceding vehicle, the engine torque is reduced, the regenerative torque of the motor generator 112 is increased, and the braking force of the hydraulic brake 130 is increased.When the automatic braking situation is thus determined, the electric motor control device 151 of the control unit 140 sets the motor generator 112 in generative mode so that the regenerative brake 126 increases the braking force.

[0038] It is important to initiate a strong braking force quickly, which requires that a very fast-response braking force of the regenerative brake 126 be increased. However, the magnitude of the braking force of the regenerative brake 126, that is, the magnitude of the regenerative torque from the motor generator 112, is limited by a current limit for the charging side set in the battery 125 (hereinafter referred to as the charging limit). This makes it difficult to make the regenerative brake 126 fully functional, depending on the state of charge and the temperature of the battery 125. To overcome this difficulty, the automatic braking controller 155 also outputs a control signal to the battery controller 152 to expand the charging limit in conjunction with the automatic braking control.

[0039] Next, descriptions of a charge / discharge range of the battery 125 and descriptions of an extension control of the charge limit value follow. Fig. 11 is a schematic view showing the charging / discharging section of the battery 125. Fig. Figure 11 shows the discharge side of the battery 125 in its upper half and the charge side in its lower half. In the following description, as in the case of the charge limit, a current limit for the discharge side is referred to as a discharge limit. As indicated by the white arrows in Fig. As shown in Figure 11, the battery 125 has a discharge limit Dx1 and a charge limit Cx1 set low at high and low temperatures, while the battery 125 has a discharge limit Dx4 and a charge limit Cx4 set high at normal temperatures. In other words, the battery 125 has a narrow charge / discharge range at high and low temperatures, while the battery 125 has a wider charge / discharge range at normal temperatures. As the state of charge approaches 0%, the discharge values ​​Dx1 to Dx4 are set to lower values ​​as 0 is approached. Conversely, as the state of charge approaches 100%, the charge limits Cx1 to Cx4 are set to lower values ​​as 0 is approached.

[0040] Since the voltage varies significantly in response to a change in the charge / discharge performance, the discharge limit and charge limit for the battery 125 are set low at low temperature to protect various electronic components. At a high temperature of the battery 24, the discharge limit and charge limit are set low to protect the battery 24 from deterioration. As described above, in a range where the temperature of the battery 125 (hereinafter referred to as battery temperature) is high, the charge limit is set low to protect the battery 125 from deterioration. In order to increase the regenerative torque of the motor generator 112 and thereby increase the automatic brake performance, the vehicle control device 110 according to this embodiment temporarily expands the charge limit set in consideration of protecting the battery 125 from deterioration.

[0041] An extension control for the charging limit in conjunction with the automatic braking control is described below. Fig. 12 is a flowchart showing a process for performing the charge limit expansion control. Based on the information regarding a preceding vehicle, step S10 determines whether or not the automatic braking situation in which the vehicle is approaching a preceding vehicle has occurred. If it is determined that the automatic braking situation has occurred, the program proceeds to step S11 to determine whether or not the vehicle speed is equal to or greater than a predetermined speed. If it is determined that the vehicle speed is equal to or greater than the predetermined speed, the program proceeds to step S12 to determine whether or not the charge capability of the battery 125 is insufficient.Step S12 determines whether the charge limit of the battery 125 is insufficient to achieve the target braking force for the regenerative brake 126 under automatic braking control. Next, a limit extension flag that allows the charge limit to be extended is set in step S13. Then, in step S14, the limit extension amount (extension amount) Xa for the charge limit is calculated based on the battery temperature.

[0042] Fig. Fig. 13 is a schematic view showing a limit extension amount Xa. The figure shows the limit extension amount Xa at a predetermined state of charge of the battery 125. As shown by a dot-dash line in Fig. As shown in Figure 13, the limit extension amount Xa is set low when the battery temperature is low, while the limit extension amount Xa is set high when the battery temperature is high. That is, the limit extension amount Xa is set based on a battery temperature. On the other hand, if it is determined in step S10 that the automatic braking situation has not occurred, or if it is determined in step S12 that the chargeability of the battery 125 is insufficient, the program proceeds to step S15, where the setting of the limit extension flag is cleared. Then, in step S16, a base limit value Xb, which serves as the basis of the charge limit value, is calculated based on the temperature and the state of charge of the battery 125. For example, as shown in Fig. As shown in Fig. 11, when the state of charge of the battery 125 is S1 and the battery temperature is T1, the base limit value Xb is set as the base of the charge limit value.

[0043] Next, step S17 determines whether the limit extension flag is set or not. If it is determined that the limit extension flag is set, the program proceeds to step S18, where the charging limit X is calculated by adding the limit extension amount Xa to the base limit Xb. Then, the program proceeds to step S19, where the motor generator 112, i.e., the regenerative brake 126, is controlled within the range of the extended charging limit X. Fig. Figure 14 is a schematic diagram showing a load limit X to be extended in the automatic braking control. As shown by a solid line in Fig. As shown in Figure 14, the charging limit X is expanded by the limit expansion amount. As previously described, the regenerative torque of the motor generator 112 can be increased by expanding the charging limit X under automatic braking control, thereby enabling the automatic braking performance to be dramatically improved.

[0044] On the other hand, if it is determined in step S17 that the extension flag is not set, the program proceeds to step S20, in which the basic limit value Xb is calculated as the charging limit value X without any change. Subsequently, S21 sets an upper limit speed applicable to narrowing the charging limit value X. The charging limit value X, if narrowed, is changed at a speed not exceeding the upper limit speed. Next, the program proceeds to step S19, in which the motor generator 112, i.e., the regenerative brake 126, is controlled within the range of the charging limit value X. As described above, in normal control in which the automatic braking control is deactivated, deterioration of the battery 125 can be prevented by narrowing the charging limit value X.The reason why the upper limit speed is set for the threshold value in step S21 is to prevent a rapid change in the regenerative torque to maintain stability. Specifically, when a significant amount of regenerative torque is output from the motor generator 112, a rapid narrowing of the charging threshold value X may involve a risk of a sharp drop in the regenerative torque. Since such a sharp drop in the regenerative torque may deteriorate the stability of the vehicle during its travel, the upper limit speed is set to ensure that the charging threshold value X is changed gradually.

[0045] The situation in which automatic braking control is performed by the control unit 140 will be described with reference to a timing chart. Fig. Fig. 15 is a timing chart explaining a situation in which automatic braking control is performed by the control unit 140. In Fig. 15, a situation in which the charging limit X is extended is indicated by a solid line, while a situation in which the charging limit X is not extended is indicated by a dotted line. As shown in Fig. As shown in Figure 15, when the automatic braking situation (A1) is determined, the limit extension flag (A2) is set to extend the charge limit X of the battery 125 (A3). The thus extended charge limit X provides increased braking force from the regenerative brake 126 (A4), thereby enabling a combined total braking force from the regenerative brake 126 plus the hydraulic brake 130 to be increased (A5). Extending the charge limit X during automatic braking control in this way increases the total braking force and accelerates an initial rise in the total braking force. This can increase the braking capability during automatic braking control, thereby enabling vehicle stability to be improved.

[0046] As in Fig. 15, when the vehicle speed falls below a predetermined speed V1 in conjunction with the automatic braking control (A6), the setting of the limit extension flag is cleared (A7), and a limitation of the charging limit X is started (A8). As indicated by symbols α1 and α2 in Fig.As shown in Figure 15, the rate of change in the reduction or narrowing of the charging limit X is set lower than the rate of change in the expansion of the charging limit X. In other words, since, as described above, the reduction of the charging limit X is accompanied by the setting of the upper limit speed for changing the limit, the charging limit X is configured to be gradually reduced. The gradual reduction of the charging limit X results in restrictions on a rapid change in the regenerative torque even when a significant amount of regenerative torque is output from the motor generator. This can prevent a rapid change in the vehicle braking force, thereby making it possible to increase the stability of the vehicle.

[0047] As described so far, under automatic braking control, the charging threshold is temporarily expanded. The performance of the battery 125 can be optimized by changing the control range of the battery 125 depending on the driving condition. In other words, under automatic braking control, temporarily expanding the charging threshold can increase the regenerative torque while minimizing degradation of the battery 125. This can increase the braking capability during automatic braking control, thereby enabling the vehicle's safety to be dramatically improved. In addition, the improved braking capability during automatic braking control can reduce the changes that require automatic braking control to be activated, leading to improved vehicle safety.Furthermore, the braking force of the regenerative brake 126 can be increased, eliminating the need for the hydraulic brake 130 to be larger or more powerful.

[0048] It goes without saying that the present invention is not limited to the above embodiment. Various modifications are conceivable within the scope of the present invention. In this embodiment, the setting of the limit extension amount Xa is based on the battery temperature. However, the present invention is not limited to this. The setting of the limit extension amount Xa may be based on the battery temperature and other information. Furthermore, the basic limit value Xb is set based on the battery temperature and the state of charge. However, the present invention is not limited to this. The basic limit value Xb may be set based on the current, voltage, and other information regarding the battery 125. Furthermore, in the embodiment, the battery 125 is used as an energy storage device. However, the present invention is not limited to this.A capacitor can also be used as an energy storage device.

[0049] In the present embodiment, object information regarding a vehicle traveling ahead of the vehicle is acquired using the camera unit 141. The camera unit 141 may be a stereo camera system with multiple cameras or a monocular camera with a single camera. Alternatively, such object information may be acquired using a millimeter-wave radar or infrared laser. Furthermore, a combination of the camera unit 141, a millimeter-wave radar, and an infrared laser may be used to acquire the object information. A vehicle traveling ahead is used as the object in front of the vehicle. A bicycle or a pedestrian may also be used as an object.

[0050] In the exemplary embodiment, the automatic braking control is performed without the brake pedal 131 being depressed by the driver. For example, even if the brake pedal 131 is operated, i.e., depressed, by the driver, brake assist control can be performed as an automatic braking control that automatically brakes the wheels 122 when the control unit 140 determines the automatic braking situation. The drive unit 113 is illustrated as a series-parallel type drive unit for a hybrid vehicle. The drive unit 113 may be a series type drive unit, a parallel type drive unit for a hybrid vehicle, or a drive unit for an electric vehicle. SUMMARY OF REVELATION

[0051] A vehicle control device is provided. The vehicle control device includes an electric motor connected to wheels, an energy storage device connected to the electric motor, a charge / discharge controller that controls the charge / discharge of the energy storage device, a first travel control device that controls the electric motor according to a driver's operation command, and a second travel control device that controls the electric motor according to a cruise control function that automatically controls a vehicle speed. When the first travel control device controls the electric motor, the charge / discharge controller controls the charge / discharge power of the energy storage device within first charge / discharge ranges Xa1 and Xa4.When the second travel control device controls the electric motor, the charge / discharge control device controls the charge / discharge power of the energy storage device within second charge / discharge ranges Xb1 and Xb4 that are wider than the first charge / discharge ranges Xa1 and Xa4.

Claims

[1] Vehicle control device (12), comprising: an electric motor (14) configured to be connected to at least one wheel (21), an energy storage device (24) connected to the electric motor (14), a charge / discharge control device that controls the charging / discharging of the energy storage device (24), a first travel control device (40) which controls the electric motor (14) in accordance with an operation of a driver, and a second travel control device (41) which controls the electric motor (14) according to a cruise control function which automatically controls a vehicle speed, wherein, when the first travel control device (40) controls the electric motor (14), the charge / discharge control device controls the charge / discharge power of the energy storage device (24) within a first charge / discharge range (Xa), and wherein, when the second travel control means (41) controls the electric motor (14), the charge / discharge control means controls the charge / discharge power of the energy storage device (24) within a second charge / discharge range (Xb) which is wider than the first charge / discharge range (Xa). [2] The vehicle control device according to claim 1, wherein the first charge / discharge range (Xa4; Xa1) is set according to a first discharge limit value (Da4; Da1) and a first charge limit value (Ca4; Ca1), and wherein the second charge / discharge range (Xb4; Xb1) is set according to a second discharge limit value (Db4; Db1) larger than the first discharge limit value (Da4; Da1) on a discharge side and a second charge limit value (Cb4; Cb1) larger than the first charge limit value (Ca4; Ca1) on a charge side.

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