JP2023056961A - Control device of vehicle - Google Patents

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

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

BACKGROUND ART Recently, a hybrid system having both an internal combustion engine and a motor generator as power sources has been widely used (for example, see the following patent document). Basically, the engine torque output by the internal combustion engine is input to the driving wheels of the vehicle to drive, but the motor torque output by the motor generator can also be input to the driving wheels to assist the internal combustion engine. can. As a result, it becomes possible to operate the internal combustion engine in a region of good thermal efficiency, and an improvement in the fuel efficiency of the vehicle can be expected.

A motor generator that operates as an electric motor receives power supply from a vehicle-mounted power storage device, that is, a battery such as a lithium-ion secondary battery or a nickel-hydrogen secondary battery and/or a capacitor, and generates motor torque. In addition, the motor generator operates as a power generator when the vehicle is braked, and charges the power storage device with regenerated electric power.

JP 2019-044643 A

In fact, it is not easy to properly control both the internal combustion engine and the motor generator to improve overall practical fuel consumption performance.

When the amount of electricity stored in the power storage device, which is the power source, runs short, it becomes difficult for the motor generator to assist. In this case, the engine torque must cover all of the required drive torque, and the internal combustion engine will be operated in an inefficient region, resulting in an increase in fuel consumption.

On the other hand, if the motor torque is constantly limited to a certain limit in order to prevent the storage amount of the power storage device from running out, the period during which the power storage device is almost fully charged becomes longer. If the power storage device is nearly fully charged during braking of the vehicle, regenerative power generation by the motor generator and charging of the power storage device cannot be executed, and the opportunity to recover the kinetic energy of the vehicle as electrical energy is lost. As a result, improvement in practical fuel consumption performance cannot be expected.

SUMMARY OF THE INVENTION An intended object of the present invention is to optimize the control of an internal combustion engine and a motor generator mounted on a vehicle as a power source, thereby further improving practical fuel consumption performance.

The present invention controls a vehicle that can assist the internal combustion engine by inputting the engine torque output by the internal combustion engine to the driving wheels to rotate the driving wheels, and inputting the combined motor torque output by the motor generator to the driving wheels. The control device determines the required driving torque to be input to the drive wheels based on the depression amount of the accelerator pedal operated by the driver, and based on the current storage amount of the power storage device, the motor generator outputs The upper limit of the possible motor torque is obtained, and depending on the upper limit of the required drive torque and motor torque, the required drive torque is covered by the engine torque output by the internal combustion engine alone, or the engine torque output by the internal combustion engine and the motor generator are output. A control device for a vehicle is configured to determine whether the required driving torque is covered by the combined motor torque.

It is preferable that the upper limit of the motor torque is 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 attached to the power storage device or an element on the electric circuit.

According to the present invention, it is possible to optimize the control of an internal combustion engine and a motor generator mounted on a vehicle as a power source, and to achieve further improvement in practical fuel consumption performance.

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; FIG. The figure which shows typically the arrangement|positioning of the internal combustion engine and motor generator in the same embodiment. The figure explaining the optimal fuel consumption line of an internal combustion engine. The figure which shows the procedure example of the process which the control apparatus of the same embodiment performs according to a program. The figure explaining the content of control by the control apparatus of the same embodiment. FIG. 4 is a diagram for explaining a method of estimating the upper limit of motor torque by the control device of the embodiment;

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

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 on the intake passage 3 from upstream.

An exhaust passage 4 for exhausting exhaust guides exhaust gas generated as a result of combustion of fuel in the cylinder 1 from an exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and a three-way catalyst 41 for purifying exhaust gas are arranged on the exhaust passage 4 .

The exhaust gas recirculation device 2 includes an external EGR passage 21 that communicates the exhaust passage 4 and the intake passage 3, an EGR cooler 22 provided on the EGR passage 21, and an EGR passage 21 to open and close the EGR An EGR valve 23 for controlling the flow rate of EGR gas flowing through the passage 21 is included as an element. The inlet of the EGR passage 21 is connected to a predetermined location downstream of the catalyst 41 in the exhaust passage 4 . The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3 (in particular, the surge tank 33 or the intake manifold 34).

FIG. 2 shows an outline of the drive system of the vehicle in this embodiment. The vehicle of this embodiment includes a motor generator 300 as well as an internal combustion engine 100 as a power source for rotationally driving the drive wheels 500 . Between the crankshaft, which is the output shaft of internal combustion engine 100, and drive wheels 500 of the vehicle, known transmission (which may be accompanied by a torque converter, clutch, etc.) 200 and differential gear 400 are interposed. Engine torque output from internal combustion engine 100 is transmitted to driving wheels 500 via transmission 200 and differential gear 400, and drives driving wheels 500 to rotate.

The motor generator 300 is arranged coaxially with the rotation axis at any position on the transmission path from the internal combustion engine 100 to the drive wheels 500, or is a gear mechanism, a winding transmission mechanism, or any other mechanism or mechanical element. connected via In the illustrated example, the motor generator 300 is connected to the rotary shaft downstream of the transmission 200, but the arrangement of the motor generator 300 is not limited to this. may be connected to the downstream axle of the When motor generator 300 operates as an electric motor, the motor torque output by motor generator 300 is transmitted to driving wheels 500 to rotationally drive driving wheels 500 . At that time, the necessary electric power is supplied from the vehicle-mounted power storage device. A power storage device consists of a battery and/or a capacitor. In this embodiment, a relatively large-capacity lithium-ion secondary battery, a nickel-hydrogen secondary battery, or the like is assumed as the power storage device.

On the other hand, when motor generator 300 operates as a power generator, torque is input to motor generator 300 from drive wheels 500 and/or internal combustion engine 100, and motor generator 300 is rotationally driven to generate power. Then, the power storage device is charged with the generated power.

The ECU0, which is the vehicle control device of the present embodiment, is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like. The ECU 0 may be formed by connecting a plurality of ECUs or controllers so as to be able to communicate with each other via electric communication lines such as CAN (Controller Area Network).

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, a crank angle signal output from a crank angle sensor that detects the rotation angle of the crankshaft of the internal combustion engine 100 and the engine speed. b, 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 (in other words, required drive torque); An intake air temperature/pressure signal d output from a temperature/pressure sensor that detects the intake air temperature and pressure in the tank 33 or the intake manifold 34), and a cooling water temperature that is output from a water temperature sensor that detects the cooling water temperature of the internal combustion engine 100. A signal e, an air-fuel ratio signal f output from an air-fuel ratio sensor that detects the air-fuel ratio of gas discharged from the cylinder 1 and flowing through the exhaust passage 4, and 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 h output from a sensor (in particular, a battery current and/or battery voltage sensor) that detects the amount of charge stored in the power storage device.

From the output interface of the ECU 0, an ignition signal i for the igniter of the ignition plug 12 of the internal combustion engine 100, a fuel injection signal j for the solenoid of the injector 11, an opening operation signal k for the throttle valve 32, an EGR valve 23 , a signal m for commanding the transmission gear ratio or gear stage, a signal o for commanding the state of the motor generator 300, and the like. The control signal o for the motor generator 300 is to operate the motor generator 300 as an electric motor or as a generator, or to set the motor generator 300 to an unloaded state that is neither of these, the motor torque to be output as the electric motor, or the power generation to be output as the generator. It is a signal that commands power (output current and/or output voltage) and the like.

The processor of the ECU 0 interprets and executes programs stored in memory in advance, calculates operating parameters, and controls the operation of the internal combustion engine 100 . The ECU 0 acquires various types of information a, b, c, d, e, f, g, and h necessary for controlling the operation of the internal combustion engine 100 and the motor generator 300 through an input interface, and acquires the engine speed and the number of cylinders. Estimate the amount of air (fresh air) sucked into 1. Then, various operating parameters such as the opening of the throttle valve 32 in the internal combustion engine 100, the required fuel injection amount, the ignition timing, the required EGR rate (or EGR gas amount), the ignition timing, and the operating state of the motor generator 300 are determined. . The ECU 0 applies various control signals i, j, k, l, m, and o corresponding to the operating parameters through the output interface.

Hereinafter, the control of the outputs of the internal combustion engine 100 and the motor generator 300 by the ECU 0 of this embodiment will be described in detail. First, the thermal efficiency of the internal combustion engine 100, which is a premise, will be supplemented. In FIG. 3, the thin dashed lines represent iso-output lines where the output of the internal combustion engine 100 is constant. If the engine speed is plotted on the horizontal axis and the engine torque is plotted on the vertical axis, iso-output lines are drawn in the form of hyperbolas where the engine output, which is the product of the engine speed and the engine torque, is constant. The thin dashed line represents an equal fuel consumption rate line, which is a set of engine speed and engine torque at 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 .

By combining these iso-output lines and iso-fuel consumption rate lines, various combinations of engine speed and engine torque that give the lowest fuel consumption rate (lowest fuel consumption) when achieving a certain required output are obtained. Output can be plotted. This is the optimum fuel consumption line represented by the solid line in FIG.

Focusing exclusively on the thermal efficiency of the internal combustion engine 100, it can be said that it is desirable to control the engine speed and the engine torque along the optimum fuel consumption line, that is, within the range on or near the line. For example, when the driver of the vehicle 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 engine torque on or near the optimum fuel consumption line. At the same time, the motor generator 300 is operated as an electric motor to output a motor torque, and the sum of the engine torque and the motor torque is input to the drive wheels 500 so that the torque becomes the required drive torque. Electric power consumed by motor generator 300 is generated by regenerative braking and stored in a power storage device. Such motor assist is intended to improve the practical fuel consumption performance of the vehicle.

However, when the power storage device is depleted of the power storage amount, motor generator 300 cannot provide assistance. On the other hand, if the power storage device is nearly fully charged during braking of the vehicle, regenerative power generation by motor generator 300 and charging of the power storage device cannot be performed. All of these can be factors that reduce the practical fuel consumption performance of the vehicle.

As shown in FIG. 4, the ECU 0 of the present embodiment obtains a required drive torque, which is the torque to be currently input to the drive wheels 500 (step S1), and determines the upper limit of the motor torque that the motor generator 300 can currently output. (step S2), and depending on the upper limits of the required driving torque and motor torque, the required driving torque is covered by the engine torque alone, or the required driving torque is covered by combining the engine torque and the motor torque output by the motor generator 300. is determined (step S3).

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

In step S2, electric power that can be supplied from the power storage device to motor generator 300 is estimated. The amount of electric power that can be supplied includes the SOC indicating the current amount of power stored in the power storage device, the current vehicle speed, the current temperature of the power storage device, and an electric circuit associated with the current power storage device (which may include an inverter, etc.). Alternatively, it is obtained according to the temperature of the elements on the electric circuit, or the like.

As shown in FIG. 6, the higher the SOC, that is, the greater the amount of electric charge stored in the power storage device, the greater the basic amount of electric power that can be supplied to motor generator 300 . Then, the basic amount is corrected according to at least one of the vehicle speed, the temperature of the power storage device, the temperature of an electric circuit attached to the power storage device or the temperature of an element on the electric circuit, and the like. Assuming that the SOCs are the same, the higher the vehicle speed, the greater the power that can be supplied. This is because the fact that the current vehicle speed is high means that there will be an opportunity to apply regenerative braking to the vehicle later, and the higher the vehicle speed, the greater the amount of electric 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, but in the case of a lithium-ion secondary battery, the higher the temperature in an extremely high temperature range above a certain temperature value, the smaller the power that can be supplied. In an extremely low temperature range below a certain temperature value, the lower the temperature, the smaller the power that can be supplied. Also, the higher the temperature of the electric circuit or the elements on the circuit, the higher the electric resistance and the smaller the power that can be supplied.

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.

In step S3, the magnitude of the engine torque to be output by the internal combustion engine 100 is determined in consideration of the current engine speed (or vehicle speed and gear ratio of the transmission 200) and the upper limit of the motor torque that the motor generator 300 can output. decide. Then, when the difference obtained by subtracting the engine torque from the required driving torque is positive, that is, when the engine torque is insufficient with respect to the required driving torque, the motor generator 300, which is an electric motor, outputs the shortage, and the motor generator 300 The internal combustion engine 100 is assisted. Conversely, when the difference obtained by subtracting the engine torque from the required drive torque is negative, that is, when the engine torque exceeds the required drive torque, the excess amount is input to the motor generator 300 as a generator, and the generated electric power is stored in the power storage device. to charge.

FIG. 5 shows the engine torque output by the internal combustion engine 100. As shown in FIG. The ECU 0 of this embodiment adjusts the engine speed and the engine torque along any of the α line, β line, γ line, and δ line shown in FIG. Control.

First, gamma rays correspond to the optimum fuel consumption line of the internal combustion engine 100 described above. However, γ-rays may slightly deviate from the optimum fuel consumption line for internal combustion engine 100 alone due to the position of motor generator 300 and the resulting power transmission efficiency (loss).

The δ line, which gives a lower engine torque than the γ line, is selected when the SOC of the power storage device is high and the battery is nearly fully charged. Control along the δ line lowers the thermal efficiency of the internal combustion engine 100 than control along the γ line. However, the δ line is the lower limit control line at which the decrease in thermal efficiency is small and within an allowable range.

The β-ray, which gives a higher engine torque than the γ-ray, is selected when the SOC of the power storage device is low and the amount of stored electricity is decreasing. Control along the β rays lowers the thermal efficiency of the internal combustion engine 100 than control along the γ rays. However, even so, the β line is the upper limit control line when it is desired to rotate the motor generator 300 by the internal combustion engine 100 to generate power and charge the power storage device.

α-rays are selected when the SOC of the power storage device is lower than that of β-rays and the amount of stored electricity is insufficient. It is desired to charge the power storage device as quickly as possible, and when generating power by increasing the engine torque and rotationally driving the motor generator 300, the α rays are selected to control the internal combustion engine 100.

At step S3, the ECU 0 determines the magnitude of the engine torque to be output from the internal combustion engine 100, roughly speaking, depending on whether the current required drive torque is above or below the γ-ray.

<When the required drive torque is smaller than the γ-ray>
For example, assume that the current engine speed and required drive torque are at point _S0 in FIG. In this case, the options available to the ECU are:
(I) Cause the internal combustion engine 100 to output an engine torque corresponding to the required driving torque _S0 . The motor generator 300 does not operate as an electric motor or as a generator, and (II) causes the internal combustion engine 100 to output an engine torque of _S1 that exceeds the required drive torque _S0 . Point S ₁ is on or near an efficient gamma ray. The surplus torque (S ₁ −S ₀ ) is supplied to the motor generator 300 to operate the motor generator 300 as a power generator, and the power storage device is charged with the generated electric power. The engine torque for _S2 minutes below _S0 is output. The point _S2 is on or near the delta line of the lower limit. The insufficient torque (S ₀ -S ₂ ) is output from the motor generator 300 operated as an electric motor and supplied to the driving wheels 500. It means to cover the torque. (III) means that the engine torque output by the internal combustion engine 100 and the motor torque output by the motor generator 300 are combined to cover the required driving torque.

If the current SOC of the power storage device is high, in other words, if the upper limit of the motor torque that motor generator 300 can output exceeds the threshold, (III) is selected to reduce fuel consumption in internal combustion engine 100, Motor generator 300 assists internal combustion engine 100 .

Otherwise, select (II) to increase the engine torque and generate power to charge the power storage device. Point S ₁ is on or near the control line γ where efficiency is best. However, it cannot be said that the SOC of the power storage device is close to full charge, but it is higher than a certain level. , it is possible to select (I) instead of (II) and drive the drive wheels 500 only with the internal combustion engine 100 for running. This is because the point _S0 is closer to the control line γ at which the efficiency is the best than the point _S2 .

<When the required drive torque is greater than the γ rays>
For example, assume that the current engine speed and required drive torque are at point _T0 in FIG. In this case, the options available to the ECU are:
(IV) The internal combustion engine 100 is caused to output an engine torque corresponding to the required driving torque _T0 . The motor generator 300 does not operate as an electric motor or as a generator, and causes the internal combustion engine 100, which is assumed to be no load (V), to output an engine torque of _T1 , which is lower than the required driving torque _T0 . Point T ₁ is on or near an efficient gamma ray. The insufficient torque (T ₀ −T ₁ ) is output from the motor generator 300 operated as an electric motor and supplied to the driving wheels 500 (VI) from the internal combustion engine 100, the engine torque T ₂ exceeding the required driving torque T ₀ output. Point T ₂ is on or near the β line of the upper limit. The surplus torque (T ₂ −T ₀ ) is supplied to the motor generator 300 to operate the motor generator 300 as a generator, and the power storage device is charged with the generated electric power (VII). The engine torque for _T3 minutes exceeding _T0 is output. Point _T3 is on or near the most urgent alpha line. The surplus torque (T ₃ -T ₀ ) is supplied to the motor generator 300 to operate the motor generator 300 as a generator, and the generated electric power is charged to the power storage device (IV), (VI), (VII) means that the required drive torque is covered only by the engine torque output by the internal combustion engine 100 . (V) means that the engine torque output by the internal combustion engine 100 and the motor torque output by the motor generator 300 are combined to meet the required driving torque.

If the current SOC of the power storage device is high, in other words, if the upper limit of the motor torque that motor generator 300 can output exceeds the threshold, (V) is selected to reduce fuel consumption in internal combustion engine 100, Motor generator 300 assists internal combustion engine 100 . Point T ₁ is on or near the control line γ where efficiency is best.

Otherwise, select (VI) or (VII) to increase engine torque and generate electricity to charge the storage device. The reason why (VII) is selected instead of (VI) is that the current SOC of the power storage device is lower than when (VI) is selected. is even smaller and it is necessary to charge the power storage device as quickly as possible. It cannot be said that the SOC of the power storage device is close to full charge, but it is higher than a certain level. , it is possible to select (IV) instead of (VI) or (VII) and drive the drive wheels 500 only with the internal combustion engine 100 to run. This is because the point T ₀ is closer to the control line γ that maximizes the efficiency than the points T ₂ and T ₃ .

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 as to output the determined engine torque to the internal combustion engine 100 .

According to this embodiment, it is possible to optimize the control of the internal combustion engine 100 and the motor generator 300 mounted on the vehicle as power sources, thereby further improving practical fuel consumption performance. A reduction in fuel consumption also leads to a reduction in the amount of harmful substances emitted to the outside.

The present invention is not limited to the embodiments detailed above. Various modifications can be made to the specific configuration of each part, the procedure of processing, and the like without departing from the scope of the present invention.

0... Control unit (ECU)
100... Internal combustion engine 300... Motor generator 500... Drive wheel

Claims (2)

A control device for controlling a vehicle that can assist the internal combustion engine by inputting the engine torque output by the internal combustion engine to the drive wheels to rotate the wheels for running, and inputting the combined motor torque output by the motor generator to the drive wheels. There is
Based on the amount of depression of the accelerator pedal operated by the driver, the required drive torque to be input to the drive wheels is obtained,
Also, the upper limit of the motor torque that the motor generator can output is determined based on the current amount of electricity stored in the electricity storage device,
Depending on the upper limits of the required drive torque and motor torque, the required drive torque may be covered by the engine torque output by the internal combustion engine alone, or by combining the engine torque output by the internal combustion engine and the motor torque output by the motor generator. The vehicle's controller that determines what torque is covered. 2. The vehicle according to claim 1, wherein the upper limit of the motor torque is 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 attached to the power storage device or an element on the electric circuit. Control device.

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