JP2020069812A - Control device of four-wheel drive vehicle - Google Patents

Abstract

To provide a control device of a four-wheel drive vehicle which can maintain adequate four-wheel drive state in spite of state of charge of a battery.SOLUTION: The control device of the four-wheel drive vehicle comprises an engine which drives front wheels, a motor generator which drives rear wheels, a battery which supplies electric power to the motor generator, an ISG which electrically generates by drive of the engine, and a VCM which controls torque of the engine and torque of the motor generator. The VCM is configured so as to be capable of setting either of a battery drive mode which supplies the electric power from the battery to the motor generator and an electric power generation drive mode which supplies the electric power generated at the ISG from the ISG to the motor generator in the four-wheel drive state and sets the battery drive mode if an SOC of the battery is SOCth or greater, and sets the electric power generation drive mode if the SOC of the battery is below SOCth.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a control device for a four-wheel drive vehicle.

  Patent Document 1 discloses a drive control device that includes an engine and an electric motor as drive sources when the vehicle is running, and controls the drive state of a four-wheel drive hybrid vehicle that separately drives the front and rear wheels by the engine and the electric motor. There is.

  This drive control device for a four-wheel drive hybrid vehicle switches the drive mode according to the switching pattern A in which the electric motor is frequently used when the power storage device is overcharged, and the fuel consumption amount when the power storage device is normal. The drive mode is switched according to the minimum switching pattern B, and when the power storage device is in the discharging state, the drive mode is switched according to the switching pattern C in which the electric motor is used less frequently.

JP-A-9-284911

  However, in the above-described conventional drive control device for a four-wheel drive hybrid vehicle, when the use frequency of the electric motor is limited according to the switching pattern C due to the discharging state of the power storage device, the drive control device is driven by the engine. Since the driving force of the driven wheels becomes dominant, there is a possibility that an appropriate four-wheel drive state cannot be maintained.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for a four-wheel drive vehicle that can maintain an appropriate four-wheel drive state regardless of the charging state of the battery.

  In order to achieve the above object, the present invention provides an engine that drives one of front wheels and rear wheels, a motor that drives the other one of the front wheels and the rear wheels, and a battery that supplies power to the motor. A generator that generates electric power by driving the engine, and a control unit that controls the torque of the engine and the torque of the motor, wherein the control unit supplies electric power from the battery to the motor in a four-wheel drive state. It is configured to be able to set either a first mode for supplying or a second mode for supplying the electric power generated by the generator from the generator to the motor, and the state of charge of the battery is predetermined. The first mode is set when the value is equal to or more than the value, and the second mode is set when the state of charge of the battery is less than the predetermined value.

  According to the present invention, it is possible to provide a control device for a four-wheel drive vehicle that can maintain an appropriate four-wheel drive state regardless of the state of charge of the battery.

FIG. 1 is a schematic configuration diagram of a four-wheel drive vehicle according to an embodiment of the present invention. FIG. 2 is a diagram showing engine operating points in a four-wheel drive vehicle according to one embodiment of the present invention. FIG. 3 is a flowchart showing the flow of the engine operating point correction processing executed by the VCM mounted on the four-wheel drive vehicle according to the embodiment of the present invention. FIG. 4 is a diagram showing an example of a shift map in the battery drive mode in the four-wheel drive vehicle according to the embodiment of the present invention. FIG. 5 is a transition diagram of the operating point of the engine in the battery drive mode in the four-wheel drive vehicle according to the embodiment of the present invention. FIG. 6 is a diagram showing an example of a shift map in the power generation drive mode in the four-wheel drive vehicle according to the embodiment of the present invention. FIG. 7 is a transition diagram of operating points of the engine in the power generation drive mode in the four-wheel drive vehicle according to the embodiment of the present invention.

  A control device for a four-wheel drive vehicle according to an embodiment of the present invention supplies an engine that drives one of front wheels and rear wheels, a motor that drives the other one of front wheels and rear wheels, and power to the motor. A battery to be supplied, a generator that generates electric power by driving the engine, and a control unit that controls the torque of the engine and the torque of the motor are provided, and the control unit supplies electric power from the battery to the motor in the four-wheel drive state. It is configured to be able to set either the first mode or the second mode in which the electric power generated by the generator is supplied from the generator to the motor, and when the state of charge of the battery is equal to or greater than a predetermined value. Sets the first mode, and sets the second mode when the state of charge of the battery is less than a predetermined value. Accordingly, the control device for a four-wheel drive vehicle according to the embodiment of the present invention can maintain an appropriate four-wheel drive state regardless of the charge state of the battery.

  Hereinafter, a four-wheel drive vehicle equipped with a control device according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a four-wheel drive vehicle 1 includes an engine 2, a transmission 3, a motor generator 4 as a motor, front wheels 5 and rear wheels 6, and an ECM (Engine Control Module) 11 that controls the engine 2. And a TCM (Transmission Control Module) 12 for controlling the transmission 3 and a VCM (Vehicle Control Module) 13 as a control unit.

  In the four-wheel drive vehicle 1 of the present embodiment, the front wheels 5 are driven by the power of the engine 2 and the rear wheels 6 are driven by the power of the motor generator 4, and the distribution of the driving force between the engine 2 and the motor generator 4 is adjusted. Thus, two-wheel drive or four-wheel drive can be switched. In this embodiment, the engine 2 drives the front wheels 5 and the motor generator 4 drives the rear wheels 6, respectively. On the contrary, the engine 2 drives the rear wheels 6 and the motor generator 4 drives the front wheels 5, respectively. It may be configured to.

  The engine 2 is formed with a plurality of cylinders. In this embodiment, the engine 2 is configured to perform a series of four strokes including an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke for each cylinder.

  An ISG (Integrated Starter Generator) 20 is connected to the engine 2. The ISG 20 is connected to the crankshaft of the engine 2 via a power transmission member such as a belt (not shown). The ISG 20 is connected to the battery 8 and the second inverter 41 via the first inverter 21.

  The ISG 20 has a function of an electric motor that rotates the engine 2 by being rotated by being supplied with electric power from the battery 8, and a function of a generator that converts the rotational force input from the crankshaft by driving the engine 2 into electric power. Have and.

  The ISG 20 can supply electric power generated by driving the engine 2 to the battery 8 or the second inverter 41, or to both the battery 8 and the second inverter 41.

  The transmission 3 is configured by an automatic transmission that shifts and outputs the rotation output from the engine 2 at a gear ratio according to any one of a plurality of gear stages. As the automatic transmission, a multistage AT (Automatic Transmission) or CVT (Continuously Variable Transmission) can be used. Further, the automatic transmission includes not only multi-speed AT and CVT but also AMT (Automated Manual Transmission) that automatically performs a shift operation and a clutch operation. The transmission 3 drives the left and right front wheels 5 via the drive shaft 31.

  The gears that can be established by the transmission 3 include, for example, a gear for traveling from the first gear to the fourth gear and a reverse gear. The number of gear stages for traveling differs depending on the specifications of the four-wheel drive vehicle 1, and is not limited to the above-described first to fourth gears.

  The motor generator 4 is connected to the left and right rear wheels 6 via a drive shaft 61. The motor generator 4 is connected to the second inverter 41. The battery 8 is connected to the second inverter 41. The battery 8 supplies electric power to the motor generator 4 via the second inverter 41.

  The motor generator 4 has a function as an electric motor driven by electric power supplied from the battery 8 and a function as a generator that generates electric power by a reverse driving force input from the rear wheels 6.

  The battery 8 is composed of, for example, a secondary battery such as a lithium ion battery. The battery 8 is charged by the power generation of the ISG 20 and the motor generator 4, and is also charged by the external power source 90 via the charger 9. The four-wheel drive vehicle 1 may be configured so that the external power source 90 does not charge the vehicle. In this case, the four-wheel drive vehicle 1 does not have the charger 9.

  The battery 8 is provided with a battery sensor 81. The battery sensor 81 detects the charging / discharging current or voltage of the battery 8 and outputs it to the VCM 13. The VCM 13 calculates the state of charge of the battery 8, that is, SOC (State Of Charge) based on the detection result input from the battery sensor 81. When the four-wheel drive vehicle 1 is provided with a BMS (Battery Management System) that manages the battery 8, the BMS may calculate the SOC, and the calculated SOC may be transmitted from the BMS to the VCM 13. ..

  The ECM 11, TCM 12, and VCM 13 are each a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data, an input port, and an output port. And a computer unit including.

  ROMs of these computer units store various constants, various maps, and the like, as well as programs for causing the computer units to function as the ECM 11, the TCM 12, and the VCM 13, respectively.

  That is, when the CPU executes the program stored in the ROM using the RAM as a work area, these computer units function as the ECM 11, TCM 12, and VCM 13 in this embodiment, respectively.

  In the present embodiment, the ECM 11 is connected to the VCM 13 and controls the engine 2 according to a command from the VCM 13. A crank angle sensor 23 is connected to the ECM 11. The ECM 11 calculates the engine speed based on the detection information from the crank angle sensor 23.

  The TCM 12 is connected to the VCM 13 and controls the transmission 3 according to a command from the VCM 13. A vehicle speed sensor 101 is connected to the TCM 12. The TCM 12 transmits information indicating the vehicle speed input from the vehicle speed sensor 101 to the VCM 13. The vehicle speed sensor 101 detects, for example, the rotation speed of the output shaft of the transmission 3.

  The VCM 13 is connected to the ECM 11, TCM 12 and the second inverter 41. Various switches such as a normal mode switch 103, an EV mode switch 104, and a 4WD mode switch 105 are connected to the VCM 13.

  The normal mode switch 103 is a switch for selecting a normal mode as the traveling mode of the four-wheel drive vehicle 1 while maintaining the two-wheel drive state by driving the engine 2 and switching to the four-wheel drive state as necessary.

  The EV mode switch 104 is a switch for selecting the EV mode as the traveling mode of the four-wheel drive vehicle 1 while maintaining the two-wheel drive state by the motor generator 4 and switching to the four-wheel drive state as necessary.

  The 4WD mode switch 105 is a switch for selecting the 4WD mode in which both the engine 2 and the motor generator 4 are constantly driven and the four-wheel drive state is maintained as the traveling mode of the four-wheel drive vehicle 1.

  Further, various sensors such as an accelerator sensor 106, a wheel speed sensor 107 for the left and right front wheels 5 and a wheel speed sensor 108 for the left and right rear wheels 6 are connected to the VCM 13.

  The accelerator sensor 106 detects the amount of depression of an accelerator pedal (not shown) by the driver as the accelerator opening. The wheel speed sensor 107 and the wheel speed sensor 108 detect the rotational speeds of the left and right front wheels 5 and the left and right rear wheels 6, respectively.

  The VCM 13 refers to the required power calculation map based on the accelerator opening detected by the accelerator sensor 106 and the vehicle speed detected by the vehicle speed sensor 101 to calculate the required power required for the four-wheel drive vehicle 1. It has become. The required power calculation map is a map in which the required power is associated with the accelerator opening and the vehicle speed, and is experimentally obtained in advance and stored in the ROM of the VCM 13. The required power matches the engine required power in the two-wheel drive state of the engine 2, while it is the sum of the engine required power and the motor required power in the four-wheel drive state.

  In the ROM of the VCM 13, the engine operating point map and the shift map shown in FIG. 2 are stored in addition to the required power calculation map described above.

  The engine operating point map is used to calculate the operating point of the engine 2 in which the current engine torque based on the required engine power has the optimum thermal efficiency, and is obtained experimentally in advance.

  As shown in FIG. 2, the VCM 13 calculates, as an operating point of the engine 2 (hereinafter, referred to as “engine operating point”), an intersection of an equal power line indicating the engine required power and an optimum fuel consumption line on the engine operating point map. , The engine 2 is controlled so that the engine speed and the engine torque correspond to this engine operating point. The equal power line in the engine operating point map shifts to the upper right as the engine required power increases, and shifts to the lower left as the engine required power decreases.

  The shift map is set with shift lines that define the timing of shifts based on the vehicle speed and the accelerator opening, and is experimentally obtained in advance and stored in the ROM of the VCM 13. The VCM 13 refers to the shift map on the basis of the vehicle speed and the accelerator opening degree to perform an upshift or a downshift when crossing a shift line set on the shift map. The shift maps shown in FIGS. 4 and 6 are examples of shift maps in upshifting.

  The VCM 13 increases the gear ratio in the transmission 3 when the current engine operating point is higher than the optimum fuel consumption line on the engine operating point map of FIG. 2, that is, when it is higher than the engine operating point where the thermal efficiency is optimum. As a result, the engine speed is increased and the engine operating point is corrected so that the engine operating point is located on the optimum fuel consumption line.

  Further, the VCM 13 changes the gear ratio in the transmission 3 when the current engine operating point is lower than the optimum fuel consumption line on the engine operating point map of FIG. 2, that is, when it is smaller than the engine operating point where the thermal efficiency is optimum. By making it smaller, the engine speed is lowered and the engine operating point is corrected so that the engine operating point is located on the optimum fuel consumption line. As described above, the VCM 13 of this embodiment improves the fuel efficiency of the engine 2 by correcting the engine operating point.

  Next, with reference to FIG. 3, the above-described engine operating point correction processing will be described.

  As shown in FIG. 3, the VCM 13 determines whether the traveling state of the four-wheel drive vehicle 1 is the four-wheel drive state (step S1). Specifically, the VCM 13 determines whether or not the condition for setting the four-wheel drive vehicle 1 in the four-wheel drive state is satisfied. For example, the VCM 13 determines whether the 4WD mode is selected as the traveling mode of the four-wheel drive vehicle 1 or whether the vehicle is in the traveling mode that requires the four-wheel drive state in the normal mode or the EV mode. It is determined whether or not a condition for setting the driven vehicle 1 in the four-wheel drive state is satisfied.

  When the VCM 13 determines that the traveling state of the four-wheel drive vehicle 1 is not the four-wheel drive state, the process proceeds to step S12.

  When determining that the traveling state of the four-wheel drive vehicle 1 is the four-wheel drive state, the VCM 13 drives the engine 2 and the motor generator 4 (step S2). As a result, the four-wheel drive vehicle 1 enters a four-wheel drive state in which the engine 2 drives the left and right front wheels 5 and the motor generator 4 drives the left and right rear wheels 6.

  Next, the VCM 13 determines whether or not the current SOC of the battery 8 is equal to or higher than the predetermined SOCth (step S3). SOCth is a determination value that determines whether or not the motor generator 4 can output a driving force that can satisfy the required power required for the four-wheel drive vehicle 1 by the electric power supplied from the battery 8. The SOCth is experimentally obtained in advance and stored in the ROM of the VCM 13.

  When it is determined that the current SOC of the battery 8 is equal to or higher than SOCth, the VCM 13 sets the battery drive mode as the drive mode of the engine 2 and the motor generator 4 (step S4). The battery drive mode in this embodiment corresponds to the first mode.

  When the battery drive mode is set, the engine 2 outputs the engine torque that drives the left and right front wheels 5, and the motor generator 4 outputs the motor torque that drives the left and right rear wheels 6 by the electric power supplied from the battery 8. .. Thus, in the battery drive mode, electric power is supplied from the battery 8 to the motor generator 4.

  Next, the VCM 13 determines whether or not the current engine torque is larger than the engine torque of the optimum fuel economy (step S5). The engine torque of the optimum fuel consumption is the engine torque corresponding to the engine operating point which is the intersection of the equal power line and the optimum fuel consumption line on the engine operating point map at a certain engine required power. Therefore, in step S5, the VCM 13 determines whether or not the current engine torque is larger than the engine torque of the optimum fuel consumption, so that the current engine operating point is higher than the optimum fuel consumption line on the engine operating point map of FIG. Is also high or not.

  When the VCM 13 determines that the current engine torque is not larger than the engine torque for the optimum fuel consumption, that is, the current engine torque is equal to or less than the engine torque for the optimum fuel consumption, the VCM 13 reduces the gear ratio of the transmission 3 (step S6), the engine operating point correction process ends.

  When it is determined in step S5 that the current engine torque is larger than the engine torque for the optimum fuel consumption, the VCM 13 increases the gear ratio of the transmission 3 (step S7) and ends the engine operating point correction process. ..

  In step S6 and step S7, the VCM 13 can increase or decrease the gear ratio of the transmission 3 by changing the position of the shift line on the shift map. Details of such a method of changing the gear ratio of the transmission 3 will be described later.

  When it is determined in step S3 that the current SOC of the battery 8 is not equal to or higher than SOCth, the VCM 13 sets the power generation drive mode as the drive mode of the engine 2 and the motor generator 4 (step S8). The power generation drive mode in this embodiment corresponds to the second mode.

  When the power generation drive mode is set, the engine 2 outputs the engine torque for driving the left and right front wheels 5 and at the same time outputs the engine required to drive the motor generator 4 by the ISG 20. The torque is added and output. The motor generator 4 outputs the motor torque that drives the left and right rear wheels 6 by being supplied with the electric power generated by the ISG 20. As described above, in the power generation drive mode, the electric power generated by the ISG 20 is supplied to the motor generator 4.

  Next, the VCM 13 determines whether or not the current engine torque is larger than the engine torque of the optimum fuel consumption (step S9).

  When the VCM 13 determines that the current engine torque is not larger than the engine torque for the optimum fuel consumption, that is, the current engine torque is equal to or less than the engine torque for the optimum fuel consumption, the VCM 13 reduces the gear ratio of the transmission 3 (step S10), the engine operating point correction process ends.

  When the VCM 13 determines in step S9 that the current engine torque is larger than the engine torque of the optimum fuel consumption, the VCM 13 increases the gear ratio of the transmission 3 (step S11) and ends the engine operating point correction process. ..

  In step S12, the VCM 13 determines whether the current SOC of the battery 8 is SOCth or more. When determining that the current SOC of the battery 8 is equal to or higher than SOCth, the VCM 13 sets the engine 2 to non-drive and drives the motor generator 4 (step S13). As a result, the four-wheel drive vehicle 1 enters a two-wheel drive state in which the left and right rear wheels 6 are driven by the motor generator 4.

  Next, the VCM 13 sets the battery drive mode as the drive mode of the engine 2 and the motor generator 4 (step S14), and does not correct the engine operating point (step S15), and ends the engine operating point correcting process. ..

  When it is determined in step S12 that the current SOC of the battery 8 is not equal to or higher than SOCth, the VCM 13 drives the engine 2 and deactivates the motor generator 4 (step S16). As a result, the four-wheel drive vehicle 1 enters a two-wheel drive state in which the engine 2 drives the left and right front wheels 5.

  Next, the VCM 13 sets the power generation drive mode as the drive mode of the engine 2 and the motor generator 4 (step S17). In the power generation drive mode in step S17, the engine 2 outputs the engine torque for driving the left and right front wheels 5 and additionally outputs the engine torque for the electric power for charging the battery 8. As a result, the battery 8 is charged with the electric power generated by the ISG 20.

  Next, the VCM 13 determines whether or not the current engine torque is larger than the engine torque of the optimum fuel consumption (step S18).

  When the VCM 13 determines that the current engine torque is not larger than the engine torque for the optimum fuel consumption, that is, the current engine torque is equal to or less than the engine torque for the optimum fuel consumption, the VCM 13 reduces the gear ratio of the transmission 3 (step S19), the engine operating point correction process ends.

  In step S18, when the VCM 13 determines that the current engine torque is larger than the engine torque of the optimum fuel consumption, the VCM 13 increases the gear ratio of the transmission 3 (step S20) and ends the engine operating point correction process. ..

  Next, a method for changing the gear ratio of the transmission 3 will be described with reference to FIGS. 4 to 7. In FIGS. 4 to 7, the motor generator is simply referred to as “motor”.

(In battery drive mode)
4 and 5 are a shift map and a transition diagram of the engine operating point when the gear ratio is changed to correct the engine operating point in the battery drive mode.

  As shown in FIG. 4, when the position on the shift map based on the accelerator opening degree and the vehicle speed is “P3” in the two-wheel drive state in which the engine 2 is driven (engine: motor = 100: 0), the engine operating point is Assume that it is “P40” (see FIG. 5). In this case, the engine 2 has to output all the required power required for the four-wheel drive vehicle 1, so that the required engine power becomes large.

  At this time, as shown in FIG. 4, since each shift line on the shift map is a solid line, the shift stage in the transmission 3 is the second shift stage (indicated by “2nd” in FIG. 4). The engine operating point P40 is an operating point on the optimum fuel consumption line or an operating point close to the optimum fuel consumption line.

  Here, when the traveling state of the four-wheel drive vehicle 1 is switched to the four-wheel drive state and the distribution of the driving force of the engine 2 and the motor generator 4 is switched to "engine: motor = 50: 50", as shown in FIG. Although the engine required power is small, the vehicle speed, the accelerator opening, and the shift line do not change, so the engine operating point transits from P40 to "P41". Since the engine operating point P41 is located away from the optimum fuel consumption line, the thermal efficiency is lowered.

  At this time, in order to bring the engine operating point closer to the optimal fuel consumption line or to match it on the optimal fuel consumption line, the engine operating point may be changed so that the engine speed decreases.

  In the present embodiment, as shown in FIG. 4, by changing each shift line on the shift map from the solid line to the alternate long and short dash line, the shift speed in the transmission 3 is the third speed (indicated by "3rd" in FIG. 4). Can be changed to That is, the gear ratio can be reduced. As a result, as shown in FIG. 5, the engine speed decreases and the engine required power remains unchanged, so that the engine torque increases. As a result, the engine operating point transits to P42 and approaches the optimal fuel consumption line or coincides with the optimal fuel consumption line, and the thermal efficiency is improved compared to before the gear ratio is changed.

  Even when the distribution of the driving forces of the engine 2 and the motor generator 4 is switched to "engine: motor = 20: 80", the engine operating point transits to "P43", which is far from the optimum fuel consumption line, as shown in FIG. ..

  Also in this case, as shown in FIG. 4, by changing each shift line on the shift map from the solid line to the broken line, the shift speed in the transmission 3 is changed to the fourth speed (indicated by “4th” in FIG. 4). can do. That is, the gear ratio can be reduced. As a result, as shown in FIG. 5, the engine speed decreases and the engine required power remains unchanged, so that the engine torque increases. As a result, the engine operating point transits to P44 and approaches the optimum fuel consumption line or coincides with the optimum fuel consumption line, and the thermal efficiency is improved as compared with before changing the gear ratio.

(In power generation drive mode)
6 and 7 are a shift map and a transition diagram of the engine operating point when the gear ratio is changed to correct the engine operating point in the power generation drive mode.

  As shown in FIG. 6, in the two-wheel drive state in which the engine 2 is driven (engine: motor = 100: 0), when the SOC of the battery 8 is sufficiently high (high voltage power generation request = 0 kW), the accelerator opening and the vehicle speed are changed. When the position on the base shift map is "P5", it is assumed that the engine operating point is "P60" (see FIG. 7). In this case, in addition to the required power required for the four-wheel drive vehicle 1, the engine 2 also has power added to generate electric power required for driving the motor generator 4 and electric power for charging the battery 8. Since there is no engine power required is small.

  At this time, as shown in FIG. 6, since each shift line on the shift map is a solid line, the shift stage in the transmission 3 is the fourth shift stage. The engine operating point P60 is an operating point on the optimum fuel consumption line or an operating point close to the optimum fuel consumption line.

  Here, when the battery 8 is requested to be charged (for example, high voltage power generation request = 3 kW), the engine 2 needs to output the power added with the amount of electric power required to charge the battery 8. As shown in FIG. 7, the required engine power increases. At this time, since the vehicle speed, the accelerator opening, and the shift line do not change, the engine operating point transits from P60 to "P61". Since the engine operating point P61 is located away from the optimum fuel consumption line, the thermal efficiency is lowered.

  Here, in order to bring the engine operating point closer to the optimum fuel consumption line or to match it on the optimum fuel consumption line, the engine operating point may be changed so that the engine speed increases.

  In the present embodiment, as shown in FIG. 6, by changing each shift line on the shift map from the solid line to the alternate long and short dash line, the shift speed of the transmission 3 can be changed to the third speed. That is, the gear ratio can be increased. As a result, as shown in FIG. 7, the engine speed increases and the engine required power does not change, so the engine torque decreases. As a result, the engine operating point transits to P62 and approaches the optimal fuel consumption line or coincides with the optimal fuel consumption line, and the thermal efficiency is improved compared to before changing the gear ratio.

  Even when the battery 8 is requested to charge more power (for example, high voltage power generation request = 5 kW), the engine operating point transits to “P63”, which is away from the optimum fuel consumption line, as shown in FIG. 7.

  Also in this case, as shown in FIG. 6, by changing each shift line on the shift map from a solid line to a broken line, the shift stage in the transmission 3 can be changed to the second shift stage. That is, the gear ratio can be increased. As a result, as shown in FIG. 7, the engine speed increases and the engine required power does not change, so the engine torque decreases. As a result, the engine operating point transits to P64 and approaches the optimum fuel consumption line or coincides with the optimum fuel consumption line, and the thermal efficiency is improved compared to before the gear ratio is changed.

  6 and 7, an example in which the engine operating point is corrected when a high-voltage power generation request for battery charging is described, but the present invention is not limited to this. That is, when the distribution of the driving power of the engine 2 and the motor generator 4 is switched in the power generation drive mode, the engine when there is a high-voltage power generation request for generating the electric power required to drive the motor generator 4 according to the distribution. It can also be applied when correcting the operating point. For example, when the distribution of the driving power of the engine 2 and the motor generator 4 is switched to “engine: motor = 50: 50” in the power generation driving mode, a high voltage power generation request = 3 kW is required, or when the driving power There is a case where a high voltage power generation request = 5 kW is required due to the distribution being switched to “engine: motor = 20: 80”.

  As described above, in the present embodiment, the shift map is such that the position of the shift line is changed based on the distribution of the driving force between the engine 2 and the motor generator 4 or the power generation amount based on the high-voltage power generation request. There is. In this embodiment, the position of the shift line is changed by taking the shift map at the time of upshift as an example in FIGS. 4 and 6, but the position of the shift line is similarly changed at the time of downshift. preferable.

  As described above, the control device for a four-wheel drive vehicle according to the present embodiment sets the battery drive mode when the SOC of the battery 8 is SOCth or more in the four-wheel drive state, and the SOC of the battery 8 is If it is less than SOCth, the power generation drive mode is set.

  Therefore, the control device for a four-wheel drive vehicle according to the present embodiment supplies the electric power from the battery 8 to the motor generator 4 in a state where the SOC of the battery 8 is high, thereby suppressing the fuel consumption of the engine 2 and driving the four-wheel drive. You can drive.

  Further, the control device for the four-wheel drive vehicle according to the present embodiment suppresses the power consumption of the battery 8 by supplying the electric power generated by the power of the engine 2 to the motor generator 4 when the SOC of the battery 8 is low. Four-wheel drive can be performed. As described above, the control device for a four-wheel drive vehicle according to the present embodiment can maintain an appropriate four-wheel drive state regardless of the SOC of the battery 8.

  Further, the control device for a four-wheel drive vehicle according to the present embodiment determines that the engine operating point has the optimum thermal efficiency in the four-wheel drive state based on the engine required power based on the vehicle speed and the accelerator opening and the gear ratio of the transmission 3. Therefore, the four-wheel drive state can be maintained while preventing the fuel consumption from deteriorating.

  Further, the control device for a four-wheel drive vehicle according to the present embodiment increases the gear ratio when the current engine torque based on the engine required power is larger than the engine operating point at which the thermal efficiency is optimal, and increases the engine required power. If the current engine torque based on this is smaller than the engine operating point at which the thermal efficiency is optimum, the gear ratio is reduced. As a result, the control device for a four-wheel drive vehicle according to the present embodiment corrects the engine operating point by changing the gear ratio so that the engine operating point is located on or near the optimal fuel consumption line. be able to.

  Further, in the control device for a four-wheel drive vehicle according to the present embodiment, the shift map changes the position of the shift line based on the distribution of the driving force between the engine 2 and the motor generator 4, so that the distribution of the driving force is performed. Accordingly, it is possible to change to an optimum gear ratio for correcting the engine operating point.

  While an embodiment of this invention has been disclosed, it will be apparent to those skilled in the art that changes may be made without departing from the scope of this invention. All such modifications and equivalents are intended to be included in the following claims.

1 four-wheel drive vehicle 2 engine 3 transmission (automatic transmission)
4 Motor generator (motor)
5 front wheel 6 rear wheel 8 battery 11 ECM
12 TCM
13 VCM (control unit)
20 ISG (generator)
23 crank angle sensor 81 battery sensor 101 vehicle speed sensor 106 accelerator sensor

Claims (4)

An engine that drives either one of the front and rear wheels,
A motor that drives the other of the front wheel and the rear wheel,
A battery that supplies power to the motor,
A generator that generates power by driving the engine,
A control unit for controlling the torque of the engine and the torque of the motor,
The control unit is
In the four-wheel drive state, either one of a first mode for supplying electric power from the battery to the motor and a second mode for supplying electric power generated by the generator from the generator to the motor is set. Is configured to be possible,
The first mode is set when the state of charge of the battery is a predetermined value or more, and the second mode is set when the state of charge of the battery is less than the predetermined value. Control device for four-wheel drive vehicle. The engine is connected to one of the front wheels and the rear wheels via an automatic transmission,
In the four-wheel drive state, the control unit corrects the operating point of the engine to an operating point that optimizes thermal efficiency based on the engine required power based on the vehicle speed and the accelerator opening and the gear ratio of the automatic transmission. The control device for a four-wheel drive vehicle according to claim 1, wherein: The control unit is
When the current engine torque based on the required engine power is larger than the operating point of the engine that optimizes thermal efficiency, the gear ratio is increased,
The control of the four-wheel drive vehicle according to claim 2, wherein when the current engine torque based on the required engine power is smaller than the operating point of the engine where the thermal efficiency is optimum, the gear ratio is reduced. apparatus. The control unit is configured to control a shift of the automatic transmission based on a shift map in which a shift line that defines a shift timing based on the vehicle speed and the accelerator opening is set.
The control device for a four-wheel drive vehicle according to claim 2 or 3, wherein the shift map is such that the position of the shift line is changed based on the distribution of the driving force between the engine and the motor. ..

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