Control device for hybrid vehicle

Abstract

To provide a control device for a hybrid vehicle capable of suppressing deterioration of fuel consumption while suppressing NV.SOLUTION: A control device for a hybrid vehicle includes: an engine; a first electric motor; a power distribution mechanism that distributes power output from the engine to the first electric motor and an output-side rotary member; and a second electric motor connected to the output-side rotary member in a power transmittable manner. The control device for a hybrid vehicle determines engine-requiring power on the basis of travel-requiring power and charge-requiring power, determines a torque command value of the second electric motor, and subtracts the charge-requiring power when the torque command value of the second electric motor is equal to or less than a threshold value.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a control device for a hybrid vehicle. [Background technology]

[0002] Patent Document 1 discloses that when the engine required power exceeds the optimum fuel economy range and the driving required power is equal to or lower than the optimum fuel economy range, the driving required power is left unchanged and the charging required power is limited so that the engine required power is within the optimum fuel economy range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5304298 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration described in Patent Document 1, when the required engine power deviates from the optimum fuel economy range, the required charging power is limited, which inevitably leads to a temporary deterioration in fuel economy, and this phenomenon may be repeated. In the configuration described in Patent Document 1, when the required charging power is large and the motor torque is small, it is conceivable to change the engine operating point to one with a high NV reduction effect in order to suppress NV. However, the operating point with a high NV reduction effect deviates from the operating point with the best fuel economy.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a control device for a hybrid vehicle that can suppress NV while suppressing deterioration in fuel economy. [Means for solving the problem]

[0006] The present invention is a control device for a hybrid vehicle having an engine, a first electric motor, a power distribution mechanism that distributes power output from the engine to the first electric motor and an output side rotating member, and a second electric motor connected to the output side rotating member so that power can be transmitted, characterized in that the control device determines engine required power based on running required power and charging required power, and determines a torque command value for the second electric motor, and subtracts the charging required power when the torque command value for the second electric motor is below a threshold value. [Effects of the Invention]

[0007] The present invention can suppress deterioration of fuel economy while suppressing NV. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram schematically illustrating a hybrid vehicle according to an embodiment. [Figure 2] FIG. 2 is a map showing the driving characteristics of the engine. [Figure 3] FIG. 3 is a flowchart showing the drive control. [Figure 4] FIG. 4 is a diagram for explaining the vehicle state when drive control is executed.

[0009] Hereinafter, a control device for a hybrid vehicle according to an embodiment of the present invention will be specifically described, but the present invention is not limited to the embodiment described below.

[0010] 1 is a diagram illustrating a hybrid vehicle according to an embodiment. The hybrid vehicle 1 includes an engine 2, a first motor (MG1) 3, a second motor (MG2) 4, a power distribution mechanism 5, a drive shaft 6, a reduction gear 7, wheels 8, a battery 11, inverters 12 and 13, and a control device 20.

[0011] The hybrid vehicle 1 has an engine 2 and two motors 3 and 4 as power sources. The power output from the engine 2 is transmitted to wheels 8 via a power distribution mechanism 5, a drive shaft 6, and a reduction gear 7. In the hybrid vehicle 1, the torque output from the second motor 4 can be added to the torque transmitted from the engine 2 to the wheels 8. The power of the engine 2 is distributed by the power distribution mechanism 5 to the first motor 3 side and the wheels 8 side.

[0012] The first motor 3 and the second motor 4 are both motor generators that function as a generator and an electric motor. The first motor 3 functions mainly as a generator, and the second motor 4 functions mainly as an electric motor. The first motor 3 is electrically connected to a battery 11 via an inverter 12. The inverter 12 is a power conversion device that drives the first motor 3. The second motor 4 is electrically connected to a battery 11 via an inverter 13. The inverter 13 is a power conversion device that drives the second motor 4. The battery 11 stores power to be supplied to the first motor 3 and the second motor 4. The second motor 4 is driven by power supplied from the battery 11.

[0013] The power distribution mechanism 5 is composed of a planetary gear mechanism. The power distribution mechanism 5 includes a sun gear, a ring gear, and a carrier that holds pinion gears that mesh with the sun gear and ring gear so that they can rotate and revolve around their own axes. A first motor 3 is connected to the sun gear. An engine 2 is connected to the carrier. A drive shaft 6 is connected to the ring gear. The output shaft of the second motor 4 rotates at the same rotation speed as the drive shaft 6. The drive shaft 6 is an output-side rotating member provided on the output side of the power distribution mechanism 5.

[0014] The control device 20 is an electronic control device that controls the hybrid vehicle 1. The control device 20 includes a microcomputer equipped with a CPU, RAM, ROM, and an input / output interface. The control device 20 processes signals according to a program pre-stored in the ROM. The control device 20 receives signals from various sensors mounted on the hybrid vehicle 1. For example, the control device 20 receives a vehicle speed signal from a vehicle speed sensor that detects the vehicle speed, an accelerator position signal from an accelerator position sensor that detects the amount of accelerator pedal operation, an engine speed signal from an engine speed sensor that detects the engine speed of the engine 2, a signal from an MG1 speed sensor that detects the first motor 3, and a signal from an MG2 speed sensor that detects the second motor 4. The second motor 4 has a rotation speed equal to the rotation speed of the drive shaft 6. The control device 20 executes various controls based on the signals received from the various sensors. The control device 20 performs calculations using the input data and pre-stored data and outputs the calculation results as command signals. The control device 20 includes a driving force control unit, an engine speed control unit, and a charge / discharge required power calculation unit. The control device 20 outputs a signal for controlling the engine 2, a signal for controlling the first motor 3, and a signal for controlling the second motor 4.

[0015] The control device 20 sets the required drive torque based on the accelerator opening and vehicle speed. The control device 20 calculates the required driving power by multiplying the required drive torque by the rotational speed of the drive shaft 6. The rotational speed of the drive shaft 6 can be obtained by multiplying the rotational speed of the second motor 4 or the vehicle speed by a conversion coefficient. The control device 20 calculates the required engine power by adding the required charging / discharging power based on the SOC of the battery 11 to the required driving power. The control device 20 sets the target rotational speed and target torque of the engine 2 so that the required engine power is output from the engine 2. The control device 20 controls the intake air amount, fuel injection, and ignition timing of the engine 2 based on the target rotational speed and target torque of the engine 2. The control device 20 also sets a torque command value for the first motor 3 so that the engine 2 rotates at the target rotational speed. The control device 20 also sets a torque command value for the second motor 4 so that the required drive torque is output to the drive shaft 6 within the input / output limits of the battery 11. The control device 20 performs switching control of the switching elements of the inverters 12 and 13 so that the motors 3 and 4 are driven by the torque command.

[0016] FIG. 2 is a map diagram showing the engine driving characteristics. The operating point (engine operating point) P of the engine 2 is defined based on the engine speed and engine torque. The fuel consumption rate contour line L1 is a line connecting engine operating points where the thermal efficiency of the engine 2 is equal. The center of the fuel consumption rate contour line L1 is the high-efficiency region. In particular, the center of the fuel consumption rate contour line L1 is the operating point where the fuel economy is optimal. Conversely, among the multiple fuel consumption rate contour lines L1, the lines located on the outer sides are the fuel consumption rate contour lines L1 where the thermal efficiency is low. The fuel economy operating line L2 is a line (optimum fuel economy line) connecting engine operating points where the fuel economy of the engine 2 is optimal when the same engine power is obtained. The equal engine power line L3 is a curve connecting engine operating points where the engine power is equal. The equal engine power line L3 is a curve connecting engine operating points where the engine power is equal. The higher the line is located on the upper right side of the map in FIG. 2, the higher the output power is. The NV suppression operation line L4, as indicated by the two-dot chain line, is an operation line for suppressing rattle noise, and is a preset operation line.

[0017] In the hybrid vehicle 1 configured in this manner, adding the charging power requirement to the traveling power requirement allows the engine 2 to be controlled so that it operates in the optimum fuel economy range. As engine torque increases with increasing engine power, the motor torque required for traveling decreases. In the low-motor-torque range, there is less backlash in the gears of the power distribution mechanism 5 and other components. Therefore, to suppress NV due to backlash, it is conceivable to shift the engine operating point P to the NV suppression operation line L4 based on the equal engine power line L3 and reduce the engine torque (forcing force). However, this transition would result in a worsening of fuel economy and would defeat the purpose of adding the charging power requirement. Therefore, the control device 20 prevents the transition of the operating line by applying a decreasing correction to the addition of the charging power requirement when the motor torque decreases by a predetermined amount or more. As a result, by not shifting to the NV suppression operation line L4, fuel efficiency can be maintained.

[0018] The control device 20 calculates the amount of subtraction from the required charging power based on the motor torque. The required engine power is calculated by adding the required charging power to the required driving power. The required motor torque decreases as the engine torque increases due to an increase in engine power. When the motor torque decreases and falls below threshold A, the control device 20 performs a subtraction process on the required charging power. By adding as much required charging power as possible while preventing the motor torque from decreasing to around 0 Nm and the operating line from shifting due to rattle suppression control, the maximum improvement in fuel efficiency is achieved.

[0019] 3 is a flowchart showing the drive control. The control shown in FIG.

[0020] When the control device 20 detects a driving force demand (step S1), it calculates a required traveling power (step S2). In step S1, accelerator operation by the driver is detected. In step S2, the required traveling power is calculated based on the accelerator opening and the vehicle speed. The control device 20 also calculates a required charging / discharging power (step S3). The control device 20 adds the required charging / discharging power calculated in step S3 to the required traveling power calculated in step S2.

[0021] The control device 20 calculates the engine required power (step S4). The control device 20 also calculates a motor torque command value (step S5). In step S5, the motor torque command value for the second motor 4 is calculated.

[0022] The control device 20 calculates the target engine speed (step S6).

[0023] The control device 20 determines whether the motor torque is near 0 Nm (step S7).

[0024] If it is determined that the motor torque is near 0 Nm (step S7: Yes), the control device 20 uses the NV suppression operation line L4 (step S8). In step S8, the engine operating point P is controlled to be on the NV suppression operation line L4.

[0025] If it is determined that the motor torque is not near 0 Nm (step S7: No), the control device 20 uses the fuel efficiency operating line L2 (step S9). In step S9, the engine operating point P is controlled to be on the fuel efficiency operating line L2.

[0026] The control device 20 also determines whether the motor torque is equal to or less than threshold value A (step S10). In step S10, it is determined whether the motor torque of the second motor 4 is equal to or less than threshold value A. Threshold value A is a preset value. The control device 20 can calculate the motor torque of the second motor 4 based on the motor torque command value calculated in step S5. The control device 20 may determine whether the motor torque command value calculated in step S5 is equal to or less than threshold value A.

[0027] If it is determined that the motor torque is not equal to or less than threshold value A (step S10: No), this control routine ends.

[0028] If it is determined that the motor torque is equal to or less than threshold A (step S10: Yes), the control device 20 performs a correction to reduce the charge amount due to the motor torque approaching 0 Nm (step S11). In step S11, the amount of subtraction from the required charge / discharge power is calculated based on the motor torque. The control device 20 subtracts the amount of subtraction from the required charge / discharge power calculated in step S11 from the required charge / discharge power calculated in step S3. The control device 20 adds the value obtained by subtracting the amount of subtraction from the required charge / discharge power to the required traveling power calculated in step S2.

[0029] As shown in Figure 4, in state i), the engine 2 is operated at an operating point that provides optimal fuel efficiency. In state ii), engine torque increases as engine power increases, so the motor torque is reduced to achieve the vehicle's required torque. In this case, as shown by the dashed-dot line, if the motor torque drops to near 0 Nm, the gears are not fully engaged, resulting in increased NV, such as rattles and booming noises. Therefore, in conventional control, as shown in Figure 2, the engine operating point P is shifted to the NV suppression operating line L4 based on the equal engine power line L3, and the engine torque (forcing force) is reduced. However, this behavior moves away from the optimal fuel efficiency point, which is opposite to the original goal of increasing the required charging power, which is to improve fuel efficiency. NV also deteriorates as the engine speed increases. Therefore, when the motor torque decreases to threshold A before approaching 0 Nm, as in state iii), the operating line transition is prevented by applying a downward correction to the increase in the required charging power. As a result, fuel efficiency can be maintained by not transitioning to the NV suppression operation line L4.

[0030] As described above, according to the embodiment, it is possible to prevent the motor torque from decreasing to around 0 Nm and the operation line from shifting due to rattle suppression control. As a result, the required charging power is increased as much as possible, thereby achieving maximum fuel efficiency improvement. [Explanation of symbols]

[0031] 1 Hybrid vehicle 2 engines 3. First motor (MG1) 4 Second motor (MG2) 5 Power distribution mechanism 6 drive shaft 7 Reduction gear 8 wheels 20 Control device

Claims

[Claim 1] The engine and A first electric motor; a power distribution mechanism that distributes power output from the engine to the first electric motor and an output side rotary member; a second electric motor connected to the output side rotary member so as to be capable of transmitting power; A control device for a hybrid vehicle comprising: determining a required engine power based on the required running power and the required charging power, and determining a torque command value for the second electric motor; When the torque command value of the second electric motor is equal to or less than a threshold value, the charging request power is subtracted. A control device for a hybrid vehicle.

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