Vehicle control device

Abstract

To provide a vehicle control device that is capable of improving fuel economy.SOLUTION: A vehicle control device having an internal combustion engine and an electromotor as driving force sources is equipped with: an acquisition section for acquiring a range of revolving speed of the internal combustion engine, a range of driving force outputted by the internal combustion engine, and a region with respect to fuel consumption, by using a variation method; and a selection section for selecting an operation point of the internal combustion engine, on the basis of the range of the revolving speed, the range of the driving force, and the region with respect to the fuel consumption.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Vehicles equipped with an internal combustion engine and an electric motor are known. The internal combustion engine and the electric motor function as a power source. A battery is charged with the electric power generated by the electric motor. To improve fuel economy, there is a demand for technology to control the power of the internal combustion engine and the generated electric power (for example, Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-032880 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the improvement in fuel economy has been insufficient. Therefore, an object of the present invention is to provide a vehicle control device that can improve fuel economy. [Means for solving the problem]

[0005] The above object can be achieved by a control device for a vehicle having an internal combustion engine and an electric motor as driving force sources, the control device comprising: an acquisition unit that uses a calculus of variations to acquire the range of rotation speeds of the internal combustion engine, the range of driving force output by the internal combustion engine, and a region for fuel efficiency; and a selection unit that selects an operating point of the internal combustion engine based on the range of rotation speeds, the range of driving force, and the region for fuel efficiency. [Effects of the Invention]

[0006] A vehicle control device capable of improving fuel efficiency can be provided. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a vehicle according to this embodiment. [Figure 2] FIG. 2 is a flowchart illustrating the process according to the embodiment. [Figure 3] 3(a) and 3(b) are diagrams illustrating the relationship between rotation speed and torque. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a control device for an internal combustion engine according to this embodiment will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a vehicle 1 according to this embodiment. The vehicle 1 is a hybrid vehicle or a plug-in hybrid vehicle, and includes an ECU (Electronic Control Unit) 40, an engine 10 (internal combustion engine), a first motor generator (hereinafter referred to as "first MG (Motor Generator)") 14 (first electric motor), a second motor generator (hereinafter referred to as "second MG") 15 (second electric motor), a PCU (Power Control Unit) 17, a battery 18, a torsional damper 19, a power split mechanism 20, a reduction mechanism 22, a differential gear 24, and drive wheels 26. The engine 10 may be a gasoline engine or a diesel engine. The engine 10, the first MG 14, and the second MG 15 are power sources for driving the vehicle 1.

[0009] The first MG 14 and the second MG 15 function as an electric motor and a generator. When drive power is supplied to the first MG 14 and the second MG 15, they output torque, and when torque is applied to them, they generate regenerative power. The first MG 14 and the second MG 15 are, for example, AC rotating electric machines.

[0010] The first MG 14 and the second MG 15 are electrically connected to the battery 18 via the PCU 17. The PCU 17 charges the battery 18 using regenerative power generated in the first MG 14 or the second MG 15, and drives the first MG 14 or the second MG 15 using the power charged in the battery 18. The PCU 17 includes a first inverter that exchanges power with the first MG 14, a second inverter that exchanges power with the second MG 15, and a converter. The converter boosts the power of the battery 18 and supplies it to the first and second inverters, and reduces the power supplied from the first and second inverters and supplies it to the battery 18. The first inverter converts DC power from the converter into AC power and supplies it to the first MG 14, and converts AC power from the first MG 14 into DC power and supplies it to the converter. The second inverter converts DC power from the converter into AC power and supplies it to second MG 15, and converts AC power from second MG 15 into DC power and supplies it to the converter.

[0011] The battery 18 is made up of a plurality of stacked cells, which may be secondary batteries such as nickel-metal hydride batteries or lithium-ion batteries.

[0012] The power split mechanism 20 is, for example, a planetary gear mechanism including a sun gear, a planetary carrier, a pinion gear, and a ring gear. The crankshaft 27 of the engine 10 is connected to the power split mechanism 20 via a torsional damper 19. The power split mechanism 20 mechanically connects the crankshaft 27 of the engine 10, the rotating shaft of the first MG 14, and the output shaft of the power split mechanism 20.

[0013] The reduction mechanism 22 is a multi-stage automatic transmission that changes the gear ratio. The reduction mechanism 22 changes the gear ratio and switches between a plurality of power transmission states under the control of the ECU 40. Instead of the reduction mechanism 22, a continuously variable transmission (CVT) that continuously changes the gear ratio may be used.

[0014] The output shaft of the power split mechanism 20 is connected to a reduction mechanism 22. The rotating shaft of the second MG 15 is also connected to the reduction mechanism 22. The reduction mechanism 22 is connected to a differential gear 24. A drive shaft 25 is connected to the differential gear 24. A drive wheel 26 is attached to the tip of the drive shaft 25.

[0015] The engine 10, the first MG 14, and the second MG 15 function as driving force sources that generate driving force. The driving force of the engine 10, the first MG 14, and the second MG 15 is transmitted to drive wheels 26 via a reduction gear mechanism 22 and a differential gear 24.

[0016] The ECU 40 is a control device of the vehicle 1, and includes a calculation device such as a CPU (Central Processing Unit), and storage devices such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The ECU 40 performs various controls by executing programs stored in the ROM and the storage devices.

[0017] The ECU 40 controls the engine 10, the first MG 14, the second MG 15, and the battery 18. The ECU 40 controls the power for charging the battery 18 and the power discharged from the battery 18. The ECU 40 controls the power of the first MG 14 and the second MG 15 based on, for example, a required charge / discharge value of the battery 18.

[0018] The ECU 40 acquires the power required by the driver from, for example, the accelerator opening. The ECU 40 calculates the power (driving force) to be output by the engine 10 as the difference between the power required by the driver and the charge / discharge request value of the battery 18. The ECU 40 determines the operating point of the engine 10 according to the power and controls the rotation speed and torque of the engine 10.

[0019] The ECU 40 functions as an acquisition unit that acquires the range of engine 10 rotation speed, the range of battery 18 charge / discharge requirement values, the range of engine 10 power, and the range for fuel economy. The range of engine 10 output power is determined based on the driver's required power and the range of charge / discharge requirement values. Calculus of variations is used for these processes. The ECU 40 functions as a selection unit that selects an operating point for the engine 10, and selects an operating point with good fuel economy.

[0020] 2 is a flowchart illustrating the process in this embodiment. The ECU 40 determines whether the engine 10 is in a transient state (step S10). If the determination is negative (No), the ECU 40 determines the intersection of the constant power line and the fuel efficiency line as the operating point based on, for example, the power requested by the driver (step S12).

[0021] If the determination in step S10 is affirmative (Yes), the ECU 40 uses the calculus of variations to obtain the range of the rate of change of the engine 10 rotation speed and the range of the required charge / discharge value of the battery 18 (step S14). The ECU 40 determines an operating point based on the above ranges (step S16). The ECU 40 sets the rotation speed and torque of the operating point determined in step S12 or S16 as command values, and controls the engine 10 so that the command values ​​are realized (step S18).

[0022] The ECU 40 selects an operating point using the calculus of variations. The calculus of variations uses a functional I expressed by Equation 1. I includes a function f as a variable. f represents fuel consumption or fuel efficiency, and is a function of the engine 10 rotation speed x and engine 10 torque y.

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[0023] Under the constraints, the stationary condition of the functional I is calculated. In other words, x, y, and z that minimize L expressed in equation 2 are calculated. z is the charge / discharge request value for the battery 18. λ1 to λ5 and α are coefficients. R1 and R2 are the minimum and maximum values ​​of the rate of change of the rotation speed (time derivative of x). R3 and R4 are the minimum and maximum values ​​of the charge / discharge request value z.

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[0024] The constraints are expressed by equations 3 to 15. A solution to the calculus of variations is found by taking into consideration equations 3 to 6 and using constraints divided into cases according to either equations 6 and 7, either equations 8 and 9, either equations 10 and 11, either equations 12 and 13, or either equations 14 and 15.

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[0025] The ECU 40 uses the calculus of variations to obtain the allowable range of the rate of the rotation speed x (time derivatives of x1 and x2) and the allowable range of the charge / discharge request value z (z1, z2) when L is minimized. For example, z1 corresponds to charging the battery 18 and is a negative value. z2 corresponds to discharging the battery 18 and is a positive value. The ECU 40 obtains the range of the rotation speed x (minimum value x1, maximum value x2) by changing the rotation speed at the current operating point within the allowable range of the rotation speed rate. The ECU 40 obtains the allowable range of the power output by the engine 10 from the difference between the power requested by the driver and the range of the charge / discharge request value z.

[0026] 3(a) and 3(b) are diagrams illustrating the relationship between rotation speed and torque. The horizontal axis represents the rotation speed of the engine 10. The vertical axis represents the torque of the engine 10. The ECU 40 stores such a map.

[0027] In the example of Figure 3(a), the elliptical contour line is a line (constant fuel consumption rate line A) where the specific fuel consumption (BSFC) is constant. Of the multiple constant fuel consumption rate lines, the innermost line indicates lower fuel consumption, and the outermost line indicates higher fuel consumption. The curved line is constant power line B. The constant power line moves within the allowable power range. The intersection (triangle in the figure) between the constant power line B moved within that range and the most fuel-efficient constant fuel consumption rate line A is found. By connecting these intersections, the fuel consumption line (area for fuel consumption) described below can be obtained. The vertical line is a line (constant rotation speed line C) that indicates a position where the rotation speed is constant. The intersection (circle in the figure) between constant rotation speed line C and the most fuel-efficient constant fuel consumption rate line A is found. The fuel consumption line can also be obtained by connecting these intersections.

[0028] In Figure 3(b), the equal fuel consumption rate line is shown enlarged. The range of rotation speeds from x1 to x2 is shown with a dashed line. The line representing the power required by the driver is designated as P0. The range of power (minimum value P2, maximum value P1) of the engine 10 is determined according to the range of the charge / discharge request value z (charge side value z1, discharge side value z2). Specifically, this is expressed by the following formula: P1=P0-z1 P2=P0-z2 3(b), the required power changes from line P0 to line P1 in response to z1. The required power changes from line P0 to line P2 in response to z2. The fuel efficiency line F is shown by a dotted line.

[0029] The operating point is selected from within the range of rotation speed and required power. The intersections of rotation speed x2 with required power P1, required power P2, and fuel efficiency line F are designated as D1, D2, and D3. The intersections of rotation speed x1 with required power P1, required power P2, and fuel efficiency line F are designated as D4, D5, and D6. The intersections of fuel efficiency line F with required power P1 and required power P2 are designated as D7 and D8. Points D7 and D8 are outside the range of rotation speed (x1, x2), so they are not candidates for operating points. Of points D1 to D6, point D1 is close to the inner constant fuel efficiency line and has lower fuel efficiency than the other points. ECU 40 selects point D1 as the operating point (step S16).

[0030] According to the embodiment, the ECU 40 uses the calculus of variations to obtain the range (x1, x2) of the rotation speed x, the range (P2, P1) of the driving force (power) output by the engine 10, and the fuel efficiency line F. The ECU 40 selects an operating point for the engine 10 based on these ranges. Specifically, the operating point is set to the point D1 with the lowest fuel efficiency among the intersections of the ranges. This can improve fuel efficiency.

[0031] Specifically, the rate of the rotation speed x and the range of the charge / discharge demand value are determined by the calculus of variations. The ECU 40 obtains the range of the rotation speed x based on the rate range and the rotation speed of the current operating point. The ECU 40 obtains the range of the power output by the engine 10 based on the range of the charge / discharge demand value z and the driver's required power. The ECU 40 obtains a fuel efficiency line by moving the isopower line B in FIG. 3(a) within the power range. The ECU 40 selects an operating point with low fuel consumption based on the range of the rotation speed x, the power range, and the fuel efficiency line. Fuel efficiency can be improved. As shown in FIG. 3(b), fuel efficiency can be improved by selecting the most fuel-efficient point D1 among the intersection points as the operating point. The rotation speed range and the position of the point change depending on the behavior of the engine 10. The most fuel-efficient point among multiple points can be selected as the operating point.

[0032] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0033] 1 vehicle, 10 engine, 14 first motor generator, 15 second motor generator, 17 PCU, 18 battery, 19 torsional damper, 20 power split mechanism, 22 reduction mechanism, 24 differential gear, 25 drive shaft, 26 drive wheels, 27 crankshaft, 40 ECU

Claims

[Claim 1] A control device for a vehicle having an internal combustion engine and an electric motor as driving power sources, an acquisition unit that acquires a range of rotation speeds of the internal combustion engine, a range of driving force output by the internal combustion engine, and a region for fuel efficiency using a calculus of variations; a selection unit that selects an operating point of the internal combustion engine based on the range of the rotation speed, the range of the driving force, and the region for the fuel economy.

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