Vehicle control device

Abstract

To provide a vehicle control device in a vehicle comprising an engine and an electric motor as power sources for driving, that can enhance traction of the vehicle in accordance with a road surface condition on which the vehicle travels.SOLUTION: A vehicle 10 comprises an engine 12 and an electric motor MG as power sources for driving. An electronic control unit 100 performs at least one of: execution of control to set the engine 12 in a driving state when the vehicle 10 is in a stuck state; and execution of control to set the electric motor MG in a driving state when a vehicle speed V is equal to or lower than a vehicle speed determination value V_jdg and a requested driving torque Trdem is equal to or greater than a torque determination value Trdem_jdg. Thereby, it becomes easier for the vehicle 10 to escape from the stuck state or to transmit a large driving torque to wheels when a large driving torque is required at a start of driving. Thus, traction of the vehicle 10 is increased in accordance with a road surface condition on which the vehicle 10 travels.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a vehicle equipped with an engine and an electric motor as a power source for running. [Background technology]

[0002] There are known vehicle control devices that increase the traction (driving force) of a vehicle by increasing the contact area of ​​the wheels by changing the tire air pressure in accordance with the road surface conditions on which the vehicle is traveling (for example, whether the vehicle is traveling on-road or off-road). For example, the device described in Patent Document 1 is one such device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 00 / 69662 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there are vehicles equipped with an engine and an electric motor as a power source for running. Even in such vehicles, there is a demand for increasing the traction of the vehicle depending on the road surface conditions on which the vehicle is running.

[0005] The present invention has been made against the background of the above circumstances, and its purpose is to provide a vehicle control device that can increase the traction of a vehicle equipped with an engine and an electric motor as a power source for driving, depending on the road conditions on which the vehicle is driving. [Means for solving the problem]

[0006] The gist of the present invention is to provide a control device for a vehicle equipped with an engine and an electric motor as a power source for driving, which performs at least one of the following: control using the engine as a power source when the vehicle is stuck; and control using the electric motor as a power source when the vehicle speed is below a predetermined vehicle speed value and the required drive torque is above a predetermined torque value. [Effects of the Invention]

[0007] According to the present invention, at least one of control using the engine as a power source is executed when the vehicle is stuck, and control using the electric motor as a power source is executed when the vehicle speed is equal to or lower than a predetermined vehicle speed value and the required drive torque is equal to or higher than a predetermined torque value. Compared to control not using the engine as a power source, control using the engine as a power source can maintain high wheel rotation speeds when the vehicle is stuck, making it easier to escape from the stuck state. Compared to control not using the electric motor as a power source, control using the electric motor as a power source can transmit a large drive torque to the wheels when the vehicle speed is equal to or lower than a predetermined vehicle speed value and the required drive torque is equal to or higher than a predetermined torque value (for example, when a large drive torque is required at the start of driving). In this way, the traction of the vehicle is improved according to the road surface conditions on which the vehicle is traveling. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram of a vehicle equipped with an electronic control device according to an embodiment of the present invention. [Figure 2] 4 is an example of a power source switching map used to switch between power sources for traveling. [Figure 3] 3 is a flowchart illustrating a main part of the control operation of the electronic control device. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately. [Example]

[0010] FIG. 1 is a schematic diagram of a vehicle 10 equipped with an electronic control device 100 according to an embodiment of the present invention.

[0011] The vehicle 10 is a hybrid vehicle equipped with an engine 12 and an electric motor MG that function as power sources for traveling. The vehicle 10 is equipped with a power transmission device 18 that transmits power output from at least one of the engine 12 and the electric motor MG to a pair of front wheels 14 and a pair of rear wheels 16. In this specification, unless otherwise specified, the terms torque, driving force, power, and force (power) are synonymous.

[0012] The engine 12 is a well-known internal combustion engine. The electric motor MG is a well-known electric motor having at least a function as an electric motor (electric motor function) and a function as a generator (generator function), and is, for example, a three-phase synchronous motor.

[0013] The power transmission device 18 is a well-known configuration in which a clutch K0, a torque converter 20, an automatic transmission 22, a transfer case 24, a front propeller shaft 26, a rear propeller shaft 28, an electronically controlled coupling device 30, a front differential 32, a rear differential 34, a pair of front drive shafts 36, and a pair of rear drive shafts 38 are connected as shown in Figure 1. The electronically controlled coupling device 30 is a well-known configuration in which the torque transmitted from the transfer case 24 to the rear differential 34 can be adjusted by controlling its transmission torque (also called coupling torque).

[0014] The vehicle 10 is equipped with a hydraulic control circuit 46 and an inverter 48, which are well-known in configuration. The hydraulic control circuit 46 controls each part of the power transmission device 18 by supplying the necessary hydraulic oil to each part of the power transmission device 18 using, for example, hydraulic oil discharged from an oil pump (not shown) as a source pressure. The inverter 48 is a power supply circuit that is provided between the electric motor MG and a chargeable / dischargeable battery (not shown) and converts direct current to alternating current and vice versa.

[0015] The vehicle 10 is equipped with an air pressure supply device 40 that controls the tire air pressures Pw [Pa] of the pair of front wheels 14 and the pair of rear wheels 16 (the tire air pressure Pw represents the tire air pressures Pw1, Pw2, Pw3, and Pw4 of the pair of front wheels 14 and the pair of rear wheels 16, respectively). The air pressure supply device 40 includes an air pump 42, an accumulator 44 consisting of a pressure-resistant container, four supply pipes 50, 52, 54, and 56 that supply air from the accumulator 44 to the pair of front wheels 14 and the pair of rear wheels 16, respectively, and four pressure control valves 60, 62, 64, and 66 that are provided in the four supply pipes 50, 52, 54, and 56, respectively, and that control the tire air pressures Pw of the pair of front wheels 14 and the pair of rear wheels 16, respectively.

[0016] The vehicle 10 can be selectively switched between an engine driving mode that uses only the engine 12 as a power source to realize engine driving, a BEV driving mode that uses only the electric motor MG as a power source to realize BEV (Battery Electric Vehicle) driving, and an HEV driving mode that uses both the engine 12 and the electric motor MG as power sources to realize HEV (Hybrid Electric Vehicle) driving. In the engine driving mode and the HEV driving mode, the clutch K0 is engaged, and in the BEV driving mode, the clutch K0 is released.

[0017] The vehicle 10 can select an on-road driving mode suitable for on-road driving and an off-road driving mode suitable for off-road driving. On-road driving refers to driving on, for example, paved roads, where compared to off-road driving, it is less likely to become stuck and the required drive torque Trdem [N·m] is less likely to be large at the start of driving. Off-road driving refers to driving on, for example, unpaved roads, where compared to on-road driving, it is more likely to become stuck and the required drive torque Trdem is more likely to be large at the start of driving. A situation where it is more likely to become stuck occurs, for example, when driving on sand. A situation where it is more likely to increase the required drive torque Trdem at the start of driving occurs, for example, when driving on rocky ground. Switching between the on-road driving mode and the off-road driving mode is performed, for example, by manually operating the driving mode selection switch 98 by the driver. The required drive torque Trdem is the drive torque requested by the driver for the vehicle 10. For example, the required driving torque Trdem is calculated based on the accelerator opening θacc and the vehicle speed V.

[0018] The vehicle 10 is equipped with an electronic control unit 100. The electronic control unit 100 is configured to include, for example, a so-called microcomputer, and performs various controls of the vehicle 10 by performing signal processing in accordance with pre-stored programs. The electronic control unit 100 corresponds to the "control unit" in the present invention.

[0019] The electronic control device 100 has a function of increasing the traction of the vehicle 10 according to the road surface conditions on which the vehicle 10 is traveling, for example, when traveling off-road.

[0020] The electronic control unit 100 receives various signals based on detected values ​​from various sensors provided in the vehicle 10 (for example, an engine rotation speed sensor 70, an electric motor rotation speed sensor 72, an accelerator opening sensor 74, an acceleration sensor 76, an accumulator pressure sensor 78, air pressure sensors 80, 82, 84, 86, wheel speed sensors 90, 92, 94, 96, a driving mode selection switch 98, etc.) (for example, an engine rotation speed Ne [rpm] that is the rotation speed of the engine 12, an electric motor rotation speed Nmg [rpm] that is the rotation speed of the electric motor MG, an accelerator opening θacc [%] that is the amount of accelerator operation by the driver that indicates the magnitude of the driver's acceleration operation, a longitudinal acceleration Ax [m / s 2 ] and lateral acceleration Ay [m / s 2 ], the accumulated air pressure Pa [Pa] in the accumulator 44, the tire air pressures Pw1, Pw2, Pw3, Pw4 of the pair of front wheels 14 and the pair of rear wheels 16, respectively, the wheel speeds Vw1, Vw2, Vw3, Vw4 [rpm] of the pair of front wheels 14 and the pair of rear wheels 16 (hereinafter referred to as "wheel speeds Vw" unless otherwise specified), and a driving mode selection signal SWoff indicating whether or not the off-road driving mode has been selected, etc.) are input.

[0021] The electronic control device 100 outputs various command signals (such as an engine control signal Se that controls the operating state of the engine 12, an electric motor control signal Smg that controls the operating state of the electric motor MG via the inverter 48, a hydraulic control signal Sp that controls the engagement and disengagement of the clutch K0, the engagement and disengagement of the lock-up clutch LU of the torque converter 20, and the shift control of the automatic transmission 22, a transfer control signal Str that selects between two-wheel drive and four-wheel drive, a torque control signal Sc that controls the transmission torque capacity of the electronically controlled coupling device 30, and pressure control signals Spw1, Spw2, Spw3, and Spw4) to each device of the vehicle 10.

[0022] The electronic control unit 100 determines whether the off-road driving mode is selected. If the on-road driving mode is selected, the operating state (drive state or non-drive state) of the driving power source is controlled based on, for example, a power source switching map.

[0023] FIG. 2 shows an example of a power source switching map used for switching between power sources for driving. The dashed-dotted line in FIG. 2 indicates the boundary between the engine driving range, which is the selection range for the engine driving mode, and the BEV driving range, which is the selection range for the BEV driving mode. The BEV driving range is set to a low vehicle speed range where the vehicle speed V is relatively low or a low load range where the accelerator opening θacc is relatively low, where engine efficiency generally decreases. Note that even if the vehicle state of the vehicle 10 is within the BEV driving range, for example, if the state of charge value SOC [%] of the battery supplying power to the electric motor MG (the ratio of the amount of charge actually stored to a predetermined full charge capacity) is less than a predetermined state determination value SOC_jdg, the engine 12 is driven and the engine driving mode or the HEV driving mode is selected. The predetermined state determination value SOC_jdg is a predetermined determination value for determining that the state of charge value SOC is such that the engine 12 needs to be driven and the battery needs to be charged.

[0024] When the electronic control device 100 determines that the off-road driving mode is selected, it determines whether the vehicle 10 is stuck (i.e., the wheels are slipping). For example, if a vehicle speed difference ΔV (=Vest-V), which is the difference between an estimated vehicle speed Vest [km / h] estimated from the tire diameter and wheel speed Vw, and an actual vehicle speed V [km / h] calculated based on the longitudinal acceleration Ax and the lateral acceleration Ay, is equal to or greater than a vehicle speed difference determination value ΔV_jdg, it is determined that the vehicle is stuck. For example, if a differential rotation ΔVw (=Vw_max-Vw_min) between a maximum wheel speed Vw_max, which is the maximum of the wheel speeds Vw, and a minimum wheel speed Vw_min, which is the minimum of the wheel speeds Vw, is equal to or greater than a differential rotation determination value ΔVw_jdg, it is determined that the vehicle is stuck. The vehicle speed difference determination value ΔV_jdg is a predetermined determination value that is experimentally or design-based, and is used to determine whether the vehicle is stuck. The differential rotation determination value ΔVw_jdg is a predetermined determination value that is determined experimentally or by design in advance in accordance with the steering angle or the steering angle in order to determine whether the vehicle is stuck.

[0025] When the electronic control device 100 determines that the vehicle 10 is stuck, it controls the engine 12 to a driving state, i.e., executes control using the engine 12 as a power source. Preferably, the electric motor MG is controlled to a non-driving state at this time, but it may also be controlled to a driving state. Note that if the engine 12 is in a non-driving state, the engine 12 is started. Preferably, the engine 12 is controlled to a driving state, and the tire air pressure Pw of all of the pair of front wheels 14 and the pair of rear wheels 16 that are in a slipping state is reduced below the normal pressure (= regular air pressure). The "normal pressure" is a predetermined air pressure that is appropriate for on-road driving and off-road driving when the vehicle is not stuck.

[0026] When the electronic control device 100 determines that the vehicle 10 is not stuck, it determines whether the vehicle speed V is equal to or less than a vehicle speed determination value V_jdg and whether the required drive torque Trdem is equal to or greater than a torque determination value Trdem_jdg. The vehicle speed determination value V_jdg and the torque determination value Trdem_jdg are predetermined determination values ​​experimentally or by design in order to determine whether the required drive torque Trdem is large enough to require the electric motor MG to be driven at the start of traveling. The vehicle speed determination value V_jdg and the torque determination value Trdem_jdg correspond to the "predetermined vehicle speed value" and the "predetermined torque value" in this invention, respectively. When the electronic control device 100 determines that the vehicle speed V is equal to or less than the vehicle speed determination value V_jdg and the required drive torque Trdem is equal to or greater than the torque determination value Trdem_jdg, it controls the electric motor MG to be driven, i.e., executes control using the electric motor MG as a power source. Preferably, the engine 12 is controlled to a non-driven state at this time, but it may also be controlled to be driven.

[0027] Fig. 3 is a flowchart illustrating the main control operations of the electronic control unit 100. The flowchart in Fig. 3 is repeatedly executed while the vehicle is running.

[0028] First, in step S10 (hereinafter, step will be omitted), it is determined whether or not the off-road driving mode has been selected. If the determination in S10 is YES, then in S20 it is determined whether or not the vehicle 10 is stuck. If the determination in S20 is YES, then in S30 the tire air pressure Pw is reduced to increase the grip force, and in S40 the engine 12 is controlled to a driving state. If the determination in S20 is NO, then in S50 the tire air pressure Pw is controlled to a normal pressure, and then in S60 it is determined whether or not the vehicle speed V is equal to or less than a vehicle speed determination value V_jdg and the required driving torque Trdem is equal to or greater than a torque determination value Trdem_jdg. If the determination in S60 is YES, then in S70 the electric motor MG is controlled to a driving state. If the determination in S60 is NO, then the operating states of the engine 12 and electric motor MG, which are the driving power sources, are maintained as they are. If the determination in S10 is NO, then in S80 the tire pressure Pw is controlled to normal pressure, and in S90 the operating state of the engine 12 and the operating state of the electric motor MG are controlled based on the power source switching map. After execution of S40, after execution of S70, or after execution of S60 when the determination in S90 is NO, the process returns.

[0029] According to this embodiment, when the vehicle 10 is stuck, control is executed to drive the engine 12, and when the vehicle speed V is equal to or less than the vehicle speed determination value V_jdg and the required drive torque Trdem is equal to or greater than the torque determination value Trdem_jdg, control is executed to drive the electric motor MG. Compared to control that does not drive the engine 12, executing control to drive the engine 12 makes it possible to maintain the wheels that are in a slipping state at high rotation speed when the vehicle 10 is stuck, making it easier to escape from the stuck state. Compared to control that does not drive the electric motor MG, executing control to drive the electric motor MG makes it possible to transmit a large drive torque to the wheels (= drive wheels) when the vehicle speed V is equal to or less than the vehicle speed determination value V_jdg and the required drive torque Trdem is equal to or greater than the torque determination value Trdem_jdg, i.e., when a large drive torque is required at the start of traveling. In this way, the traction of the vehicle 10 is improved according to the road surface conditions on which the vehicle 10 is traveling.

[0030] The above-described embodiments of the present invention are merely examples, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

[0031] In the above-described embodiment, when the vehicle 10 is stuck, the tire air pressure Pw of all wheels that are in a slipping state is reduced below the normal pressure, but the present invention is also applicable to an embodiment in which the tire air pressure Pw is maintained at the normal pressure.

[0032] In the above-described embodiment, both control is executed to put the engine 12 into a driving state when the vehicle 10 is in a stuck state, and control is executed to put the electric motor MG into a driving state when the vehicle speed V is equal to or less than the vehicle speed determination value V_jdg and the required driving torque Trdem is equal to or greater than the torque determination value Trdem_jdg. However, the present invention may be configured so that at least one of these is executed.

[0033] In the above-described embodiment, the vehicle 10 is a four-wheel drive vehicle, but the present invention can also be applied to a two-wheel drive vehicle. Furthermore, the vehicle to which the present invention is applied is not limited to the vehicle 10 according to the above-described embodiment, and may be any vehicle configuration as long as it is equipped with an engine 12 and an electric motor MG as a power source for traveling. [Explanation of symbols]

[0034] 10: vehicle, 12: engine, 100: electronic control unit (control unit), MG: electric motor, Trdem: required driving torque, Trdem_jdg: torque judgment value (predetermined torque value), V: vehicle speed, V_jdg: vehicle speed judgment value (predetermined vehicle speed value)

Claims

[Claim 1] A control device for a vehicle equipped with an engine and an electric motor as a power source for running, When the vehicle is stuck, at least one of the following is performed: control using the engine as a power source; and control using the electric motor as a power source when the vehicle speed is equal to or lower than a predetermined vehicle speed value and the required drive torque is equal to or higher than a predetermined torque value. A vehicle control device characterized by:

Images