Vehicle control device

Abstract

To optimize control of an internal combustion engine and a motor generator which are mounted as power sources on a vehicle, to further improve a practical fuel economy performance.SOLUTION: A control device of a vehicle, which controls the vehicle that is configured to travel by inputting engine torque outputted by an internal combustion engine to driving wheels and rotating the driving wheels and to be able to assist the internal combustion engine by additionally inputting motor torque outputted by a motor generator to the driving wheels, is configured to determine required driving torque that should be inputted to the driving wheels, on the basis of a stepping-in amount of an accelerator pedal that is operated by a driver, to determine an upper limit of motor torque that the motor generator can output, on the basis of a current electric power storage amount of a power storage device, and to determine whether only the engine torque outputted by the internal combustion engine should supplement the required driving torque or the engine torque outputted by the internal combustion engine and the motor torque outputted by the motor generator should supplement the required driving torque, in accordance with the required driving torque and an upper limit of the motor torque.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to control of an internal combustion engine and a motor generator mounted on a vehicle as a power source. [Background technology]

[0002] Recently, hybrid systems that use both an internal combustion engine and a motor generator as power sources have become popular (see, for example, the following patent documents). Basically, the engine torque output by the internal combustion engine is input to the drive wheels of the vehicle to drive it, but it is also possible to simultaneously input the motor torque output by the motor generator to the drive wheels to assist the internal combustion engine. This makes it possible to operate the internal combustion engine in a range where thermal efficiency is good, and is expected to improve the fuel efficiency of the vehicle.

[0003] The motor generator, which operates as an electric motor, receives power from an on-board power storage device, i.e., a battery such as a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and / or a capacitor, to generate motor torque. The motor generator also operates as a generator when braking the vehicle, and charges the power storage device with regenerated power. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-044643 Summary of the Invention [Problem to be solved by the invention]

[0005] In reality, it is not easy to improve overall practical fuel economy by appropriately controlling both the internal combustion engine and the motor generator.

[0006] When the amount of electricity stored in the power storage device, which serves as the power source, is insufficient, it becomes difficult for the motor generator to provide assistance. This forces the internal combustion engine to operate in an inefficient range and results in increased fuel consumption.

[0007] On the other hand, if a constant limit is placed on the motor torque to prevent the storage capacity of the power storage device from running out, the period during which the power storage device is nearly fully charged will be extended. If the power storage device happens to be nearly fully charged during vehicle braking, the motor generator cannot perform regenerative power generation and charging of the power storage device, and the opportunity to recover the vehicle's kinetic energy as electrical energy will be lost. As a result, improvement in practical fuel economy cannot be expected.

[0008] An intended object of the present invention is to optimize the control of the internal combustion engine and motor generator mounted on a vehicle as a power source, thereby achieving further improvement in practical fuel economy performance. [Means for solving the problem]

[0009] The present invention is a control device for controlling a vehicle that can input engine torque output by an internal combustion engine to drive wheels to rotate them and travel, and also input motor torque output by a motor generator to the drive wheels to assist the internal combustion engine, and the control device calculates a required drive torque to be input to the drive wheels based on the amount of depression of an accelerator pedal operated by a driver, and calculates an upper limit of motor torque that can be output by the motor generator based on the current amount of electricity stored in an electricity storage device, and determines whether the required drive torque will be covered by only the engine torque output by the internal combustion engine, or by combining the engine torque output by the internal combustion engine and the motor torque output by the motor generator, depending on the required drive torque and the upper limit of the motor torque. When the required drive torque is smaller than the torque on the optimum fuel efficiency line of the internal combustion engine, the required drive torque is provided only by the torque output by the internal combustion engine, and when the required drive torque is larger than the torque on the optimum fuel efficiency line of the internal combustion engine, a torque of a magnitude up to the optimum fuel efficiency line of the required drive torque is output from the internal combustion engine, and the shortfall in torque is output from the motor generator. A vehicle control device was configured.

[0010] The upper limit of the motor torque is preferably adjusted to increase or decrease based on at least one of the current vehicle speed, the temperature of the power storage device, and the temperature of an electric circuit or an element on the electric circuit associated with the power storage device. [Effects of the Invention]

[0011] According to the present invention, it is possible to optimize the control of the internal combustion engine and motor generator mounted on a vehicle as a power source, thereby achieving further improvement in practical fuel economy performance. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing a schematic configuration of a vehicle internal combustion engine and a control device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram schematically showing the arrangement of an internal combustion engine and a motor generator in the embodiment. [Figure 3] FIG. 2 is a diagram illustrating an optimum fuel efficiency line of an internal combustion engine. [Figure 4] FIG. 3 is a diagram showing an example of a procedure of a process executed by the control device according to the embodiment in accordance with a program. [Figure 5] 3A and 3B are diagrams illustrating the contents of control performed by the control device according to the embodiment. [Figure 6] 4A and 4B are diagrams illustrating a method for estimating an upper limit of motor torque by the control device of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an overview of an internal combustion engine 100 for a vehicle according to this embodiment. The internal combustion engine 100 is, for example, a spark-ignition four-stroke gasoline engine and is equipped with a plurality of cylinders 1 (one of which is shown in FIG. 1). An injector 11 that injects fuel toward the intake port is provided near the intake port of each cylinder 1 in the intake passage 3. In addition, an ignition plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The ignition plug 12 receives an induced voltage generated by an ignition coil and generates a spark discharge between a center electrode and a ground electrode.

[0014] An intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. An air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from upstream to downstream in the intake passage 3.

[0015] An exhaust passage 4 for discharging exhaust gases guides exhaust gases generated as a result of fuel combustion in the cylinders 1 to the outside from the exhaust ports of each cylinder 1. An exhaust manifold 42 and a three-way catalyst 41 for purifying exhaust gases are arranged on this exhaust passage 4.

[0016] The exhaust gas recirculation device 2 includes, as its elements, an external EGR passage 21 that connects the exhaust passage 4 and the intake passage 3, an EGR cooler 22 provided on the EGR passage 21, and an EGR valve 23 that opens and closes the EGR passage 21 to control the flow rate of EGR gas flowing through the EGR passage 21. The inlet of the EGR passage 21 is connected to a predetermined position downstream of the catalyst 41 in the exhaust passage 4. The outlet of the EGR passage 21 is connected to a predetermined position downstream of the throttle valve 32 in the intake passage 3 (in particular, a surge tank 33 or an intake manifold 34).

[0017] 2 shows an overview of the drive system of the vehicle in this embodiment. The vehicle in this embodiment is equipped with an internal combustion engine 100 and a motor generator 300 as a power source for driving and rotating its drive wheels 500. A known transmission 200 (which may be equipped with a torque converter, a clutch, etc.) and a differential gear 400 are interposed between the crankshaft, which is the output shaft of the internal combustion engine 100, and the drive wheels 500 of the vehicle. The engine torque output by the internal combustion engine 100 is transmitted to the drive wheels 500 via the transmission 200 and the differential gear 400, thereby driving and rotating the drive wheels 500.

[0018] The motor generator 300 is disposed somewhere along the power transmission path from the internal combustion engine 100 to the drive wheels 500, either coaxially with the engine's rotational axis or connected via a gear mechanism, a winding transmission mechanism, or any other mechanism or mechanical element. In the illustrated example, the motor generator 300 is connected to the rotational axis downstream of the transmission 200, but the arrangement of the motor generator 300 is not limited thereto. The motor generator 300 may be connected to the crankshaft of the internal combustion engine 100 or to an axle downstream of the differential 400. When the motor generator 300 operates as an electric motor, the motor torque it outputs is transmitted to the drive wheels 500, driving them to rotate. The required power is supplied from an on-board power storage device. The power storage device may be a battery and / or a capacitor. In this embodiment, a relatively large-capacity lithium-ion secondary battery, nickel-metal hydride secondary battery, or the like is assumed as the power storage device.

[0019] On the other hand, when the motor generator 300 operates as a power generator, torque is input to the motor generator 300 from the drive wheels 500 and / or the internal combustion engine 100, causing the motor generator 300 to rotate and generate electricity. The generated electricity is then charged into the power storage device.

[0020] The ECU0, which is the vehicle control device of this embodiment, is a microcomputer system having a processor, a memory, an input interface, an output interface, etc. The ECU0 may be configured by connecting a plurality of ECUs or controllers to each other so that they can communicate with each other via an electric communication line such as a CAN (Controller Area Network).

[0021] The input interface of the ECU 0 receives a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crankshaft of the internal combustion engine 100 and the engine speed, an accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal operated by the driver as the accelerator opening (i.e., the required driving torque), an intake air temperature / intake pressure signal d output from a temperature / pressure sensor that detects the intake air temperature and intake pressure in the intake passage 3 (particularly, the surge tank 33 or the intake manifold 34) connected to the cylinder 1, a coolant temperature signal e output from a water temperature sensor that detects the coolant temperature of the internal combustion engine 100, an air / fuel ratio signal f output from an air / fuel ratio sensor that detects the air / fuel ratio of the gas discharged from the cylinder 1 and flowing through the exhaust passage 4, a signal g output from a position switch that detects the position of the shift lever or selector lever operated by the driver, and a battery SOC (State Of Charge) signal output from a sensor (particularly, a battery current and / or battery voltage sensor) that detects the amount of charge stored in the power storage device. Charge) signal h etc. are input.

[0022] The output interface of the ECU 0 outputs an ignition signal i to the igniter of the spark plug 12 of the internal combustion engine 100, a fuel injection signal j to the solenoid of the injector 11, an opening operation signal k to the throttle valve 32, an opening operation signal l to the EGR valve 23, a signal m that commands the gear ratio or gear position of the transmission 200, and a signal o that commands the state of the motor generator 300. The control signal o to the motor generator 300 is a signal that commands whether the motor generator 300 should operate as an electric motor or as a generator, or should be in a no-load state where it is neither, the motor torque to be output as an electric motor, the generated power (output current and / or output voltage) to be output as a generator, etc.

[0023] The processor of ECU0 interprets and executes programs stored in memory in advance, calculates operating parameters, and controls the operation of the internal combustion engine 100. ECU0 acquires various pieces of information a, b, c, d, e, f, g, and h required for controlling the operation of the internal combustion engine 100 and the motor generator 300 via an input interface, determines the engine speed, and estimates the amount of air (fresh air) to be drawn into cylinder 1. Then, it determines various operating parameters such as the opening of the throttle valve 32 of the internal combustion engine 100, the required fuel injection amount, ignition timing, the required EGR rate (or EGR gas amount), ignition timing, and the operating state of the motor generator 300. ECU0 applies various control signals i, j, k, l, m, and o corresponding to the operating parameters via an output interface.

[0024] Hereinafter, the control of the output of the internal combustion engine 100 and the motor generator 300 by the ECU0 of this embodiment will be described in detail. First, a supplementary explanation will be given regarding the thermal efficiency of the internal combustion engine 100, which is the premise of the present invention. In FIG. 3, thin dashed lines represent equal power lines along which the output of the internal combustion engine 100 is constant. When the horizontal axis represents engine speed and the vertical axis represents engine torque, the equal power lines along which the engine output, which is the product of the engine speed and the engine torque, is constant, are drawn in the form of a hyperbola. Thin chain lines represent equal fuel consumption rate lines, which are pairs of engine speed and engine torque along which the brake specific fuel consumption of the internal combustion engine 100 is constant. The fuel consumption rate is the amount of fuel [g / kWh] consumed by the internal combustion engine 100 to output a unit amount of mechanical energy, and the fuel consumption rate line is its contour line. Naturally, the smaller the fuel consumption rate, the higher the thermal efficiency of the internal combustion engine 100.

[0025] By combining these equal power output lines and equal fuel consumption curves, it is possible to plot the combination of engine speed and engine torque that results in the smallest fuel consumption (least fuel consumption) when achieving a certain required power output, for various power outputs. This is the optimal fuel economy line, shown by the solid line in Figure 3.

[0026] If we focus solely on the thermal efficiency of the internal combustion engine 100, it is desirable to control the engine speed and engine torque along the optimal fuel efficiency line, i.e., on that line or within a range close to that line. For example, when the vehicle driver strongly depresses the accelerator pedal and requests a large drive torque to be supplied to the drive wheels 500, the internal combustion engine 100 outputs an engine torque on or near the optimal fuel efficiency line, and at the same time, the motor generator 300 operates as an electric motor to output motor torque. The sum of the engine torque and motor torque is input to the drive wheels 500 so that the required drive torque is reached. The power consumed by the motor generator 300 is supplied by electric power generated by regenerative braking and stored in an electric storage device. This motor assist improves the vehicle's practical fuel efficiency.

[0027] However, if the amount of stored electricity in the power storage device is insufficient, it is impossible to perform assistance by the motor generator 300. On the other hand, if the power storage device happens to be nearly fully charged when braking the vehicle, it is impossible to perform regenerative power generation by the motor generator 300 and charge the power storage device. Both of these can be factors that reduce the practical fuel economy performance of the vehicle.

[0028] As shown in FIG. 4, the ECU0 of this embodiment calculates the required drive torque, which is the torque that should currently be input to the drive wheels 500 (step S1), and also calculates the upper limit of the motor torque that can currently be output by the motor generator 300 (step S2). Depending on the required drive torque and the upper limit of the motor torque, it determines whether to cover the required drive torque with engine torque alone, or to cover the required drive torque by combining the engine torque and the motor torque output by the motor generator 300 (step S3).

[0029] In step S1, a required driving torque is calculated based on at least the amount of depression of the accelerator pedal operated by the driver. The required driving torque increases as the amount of depression of the accelerator pedal increases.

[0030] In step S2, an estimate is made of the electric power that can be supplied from the power storage device to motor generator 300. The amount of electric power that can be supplied is calculated based on the SOC indicating the current amount of electric power stored in the power storage device, the current vehicle speed, the current temperature of the power storage device, the current temperature of the electric circuit (which may include an inverter, etc.) associated with the power storage device or the temperature of elements on the electric circuit, etc.

[0031] As shown in FIG. 6, the higher the SOC, i.e., the greater the amount of charge stored in the power storage device, the greater the basic amount of power that can be supplied to motor generator 300. This basic amount is then corrected based on at least one of the following: vehicle speed, temperature of the power storage device, and temperature of the electrical circuit or elements on the electrical circuit associated with the power storage device. Assuming the SOC is the same, the higher the vehicle speed, the greater the power that can be supplied. A high current vehicle speed indicates that there will be an opportunity to perform regenerative braking on the vehicle later, and the higher the vehicle speed, the greater the amount of power that can be generated and charged to the power storage device. The temperature of the power storage device depends on the type and characteristics of the power storage device. However, for a lithium-ion secondary battery, the higher the temperature in an extremely high temperature range above a certain temperature value, the less power can be supplied. Furthermore, the higher the temperature of the electrical circuit or elements on the circuit, the greater the electrical resistance, resulting in less power that can be supplied.

[0032] Thus, the upper limit of the motor torque that can be output by motor generator 300 increases as the electric power that can be supplied to motor generator 300 increases.

[0033] In step S3, the magnitude of the engine torque to be output by the internal combustion engine 100 is determined taking into consideration the current engine speed (or the vehicle speed and the gear ratio of the transmission 200) and the upper limit of the motor torque that can be output by the motor generator 300. Then, if the difference obtained by subtracting the engine torque from the required drive torque is positive, that is, if the engine torque is insufficient for the required drive torque, the shortfall is output from the motor generator 300, which is an electric motor, and the motor generator 300 assists the internal combustion engine 100. Conversely, if the difference obtained by subtracting the engine torque from the required drive torque is negative, that is, if the engine torque exceeds the required drive torque, the excess is input to the motor generator 300, which is an electric generator, and the generated electric power is charged to the power storage device.

[0034] Fig. 5 shows the engine torque output by the internal combustion engine 100. The ECU0 of this embodiment controls the engine speed and engine torque along any one of the α ray, β ray, γ ray, and δ ray shown in Fig. 5, i.e., on the line or within a range close to the line.

[0035] First, gamma rays correspond to the optimum fuel efficiency line of the internal combustion engine 100. However, gamma rays may deviate slightly from the optimum fuel efficiency line of the internal combustion engine 100 alone due to factors such as the location of the motor generator 300 and the resulting power transmission efficiency (loss).

[0036] The δ ray, which produces a lower engine torque than the γ ray, is selected when the SOC of the power storage device is high and close to full charge. Controlling along the δ ray reduces the thermal efficiency of the internal combustion engine 100 more than controlling along the γ ray. However, the δ ray is the lower limit control line where the reduction in thermal efficiency is small and within an acceptable range.

[0037] Beta rays, which produce a higher engine torque than gamma rays, are selected when the SOC of the power storage device is low and the amount of stored electricity is decreasing. Control along beta rays reduces the thermal efficiency of the internal combustion engine 100 more than control along gamma rays. However, beta rays are still the upper limit control line when it is desired to use the internal combustion engine 100 to drive the motor generator 300 to rotate and generate electricity and charge the power storage device.

[0038] Alpha rays are selected when the SOC of the power storage device is even lower than that of beta rays and the amount of stored electricity is insufficient. When it is necessary to charge the power storage device as quickly as possible and the engine torque is increased to rotate and drive the motor generator 300 to generate electricity, alpha rays are selected to control the internal combustion engine 100.

[0039] In step S3, the ECU 0 determines the magnitude of the engine torque to be output by the internal combustion engine 100, roughly depending on whether the current required driving torque is above or below the γ ray.

[0040] <When the required drive torque is smaller than gamma rays> For example, assume that the current engine speed and required drive torque are at point S0 in Figure 5. In this case, the options available to the ECU are as follows: (I) The internal combustion engine 100 outputs an engine torque equivalent to the required driving torque S0. The motor generator 300 is not operated as either an electric motor or a generator, and is placed under no load. (II) The internal combustion engine 100 outputs an engine torque of S1 that exceeds the required drive torque S0. The point S1 is located on or near the efficient gamma line. The surplus torque (S1-S0) is supplied to the motor generator 300, which operates as a generator and charges the generated power to the power storage device. (III) The internal combustion engine 100 outputs an engine torque of S2, which is less than the required drive torque S0. Point S2 is on or near the lower limit line δ. The insufficient torque (S0-S2) is output from the motor generator 300, which is operated as an electric motor, and supplied to the drive wheels 500. (I) and (II) mean that the required drive torque is met only by the engine torque output by the internal combustion engine 100. (III) means that the required drive torque is met by a combination of the engine torque output by the internal combustion engine 100 and the motor torque output by the motor generator 300.

[0041] If the current SOC of the power storage device is high, in other words, if the upper limit of the motor torque that the motor generator 300 can output is greater than the threshold, then (III) is selected and the motor generator 300 assists the internal combustion engine 100 while reducing fuel consumption in the internal combustion engine 100.

[0042] Otherwise, (II) is selected, increasing engine torque to generate electricity and charge the power storage device. Point S1 is on or near the control line γ where efficiency is optimal. However, if the SOC of the power storage device is not close to full charge but is higher than a certain level, in other words, if the upper limit of the motor torque that can be output by motor generator 300 exceeds a certain value (lower than the threshold value of (III) above), then (I) rather than (II) may be selected, and driving wheels 500 may be driven by internal combustion engine 100 alone to allow the vehicle to run. This is because point S0 is closer to control line γ where efficiency is optimal than point S2.

[0043] <When the required driving torque is greater than gamma rays> For example, assume that the current engine speed and required drive torque are at point T0 in Figure 5. In this case, the options available to the ECU are as follows: (IV) The internal combustion engine 100 outputs an engine torque equivalent to the required driving torque T0. The motor generator 300 is not operated as either an electric motor or a generator, and is placed under no load. (V) The internal combustion engine 100 outputs engine torque for T1, which is less than the required drive torque T0. Point T1 is on or near the efficient γ-ray. The insufficient torque (T0-T1) is output from the motor generator 300, which operates as an electric motor, and supplied to the drive wheels 500. (VI) The internal combustion engine 100 outputs an engine torque corresponding to T2, which exceeds the required drive torque T0. Point T2 is on or near the upper limit β line. The surplus torque (T2-T0) is supplied to the motor generator 300, which operates as a generator and charges the generated electric power into the power storage device. (VII) The internal combustion engine 100 outputs engine torque for T3, which exceeds the required drive torque T0. Point T3 is on or near the highest emergency α line. The surplus torque (T3-T0) is supplied to the motor generator 300, which operates as a generator and charges the generated electric power into the power storage device. (IV), (VI), and (VII) mean that the required drive torque is met only by the engine torque output by the internal combustion engine 100. (V) means that the required drive torque is met by a combination of the engine torque output by the internal combustion engine 100 and the motor torque output by the motor generator 300.

[0044] If the current SOC of the power storage device is high, in other words, if the upper limit of the motor torque that can be output by the motor generator 300 is large and exceeds the threshold, (V) is selected to reduce fuel consumption in the internal combustion engine 100 while assisting the internal combustion engine 100 with the motor generator 300. Point T1 is on or near the control line γ where the efficiency is optimal.

[0045] Otherwise, (VI) or (VII) is selected, and engine torque is increased to generate electricity and charge the power storage device. (VII) is selected instead of (VI) when the current SOC of the power storage device is lower than when (VI) is selected; in other words, the upper limit of the motor torque that motor generator 300 can output is even smaller, and the power storage device needs to be charged as quickly as possible. Note that if the SOC of the power storage device is not nearly fully charged but is still relatively high; in other words, the upper limit of the motor torque that motor generator 300 can output exceeds a certain value (lower than the threshold value of (V) above), then (IV) may be selected instead of (VI) or (VII), and the vehicle may run with drive wheels 500 driven solely by internal combustion engine 100. This is because point T0 is closer to control line γ, which provides the best efficiency, than points T2 and T3.

[0046] The ECU 0 operates the opening of the throttle valve 32 to adjust the intake air amount, the fuel injection amount, etc., and controls the motor generator 300 so that the internal combustion engine 100 outputs the engine torque thus determined.

[0047] According to this embodiment, it is possible to further improve practical fuel economy by optimizing the control of the internal combustion engine 100 and the motor generator 300 mounted on the vehicle as a power source. The reduction in fuel consumption also leads to a reduction in the amount of harmful substances emitted to the outside.

[0048] The present invention is not limited to the above-described embodiment, and the specific configuration of each unit and the processing procedure can be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0049] 0...Control unit (ECU) 100...Internal combustion engine 300...Motor generator 500...Drive wheels

Claims

1. A control device for controlling a vehicle that can assist the internal combustion engine by inputting engine torque output by an internal combustion engine to drive wheels to rotate them and running, and by combining this with motor torque output by a motor generator and inputting it to the drive wheels, A required driving torque to be input to the driving wheels is calculated based on the amount of depression of the accelerator pedal operated by the driver. Also, an upper limit of the motor torque that can be output by the motor generator is calculated based on the current amount of stored electricity in the electricity storage device, A determination is made according to the upper limits of the required drive torque and the motor torque as to whether the required drive torque is to be satisfied solely by the engine torque output by the internal combustion engine, or by combining the engine torque output by the internal combustion engine and the motor torque output by the motor generator, When the required drive torque is smaller than the torque on the optimum fuel consumption line of the internal combustion engine, the required drive torque is satisfied only by the torque output by the internal combustion engine, A vehicle control device that, when the required driving torque is greater than the torque on the optimal fuel efficiency line of the internal combustion engine, outputs a torque of the required driving torque up to the optimal fuel efficiency line from the internal combustion engine and outputs the shortfall in torque from the motor generator.

2. 2. The vehicle control device according to claim 1, wherein the upper limit of the motor torque is adjusted to be increased or decreased based on at least one of the current vehicle speed, the temperature of the power storage device, and the temperature of an electric circuit or an element on the electric circuit associated with the power storage device.

Images