JP7845149B2 - Vehicle control system - Google Patents

Description

This invention relates to a vehicle control device.

Vehicles equipped with an internal combustion engine and an electric motor are known (for example, Patent Document 1). The electric motor is driven by the torque of the internal combustion engine and generates electricity.

Japanese Patent Publication No. 2016-137868

The ignition timing of an internal combustion engine is sometimes altered to warm up the catalytic converter. After warming up, the ignition timing is changed from retarded to advanced to increase the torque of the internal combustion engine. This increased torque also increases the power generated by the electric motor. This increase in power can lead to overcharging and degradation of the battery. Therefore, the objective is to provide a vehicle control device capable of protecting the battery.

The above objective can be achieved by a vehicle control device for a vehicle equipped with an internal combustion engine, an electric motor, and a battery, wherein the battery is charged by the power generated by the electric motor, and the device comprises an ignition timing control unit that controls the ignition timing of the internal combustion engine, and an acquisition unit that acquires the power generated by the electric motor, and the ignition timing control unit controls the rate at which the ignition timing is advanced based on the power and the battery's allowable power.

The greater the absolute value of the difference between the battery's allowable power and the power, the greater the ignition timing control unit may increase the rate; conversely, the smaller the absolute value, the smaller the rate may be.

A catalyst for purifying the exhaust gas of the internal combustion engine is provided, and the ignition timing control unit controls the rate based on the power and the allowable power of the battery, and may advance the ignition timing after the warm-up is completed by the rate compared to the ignition timing during the warm-up of the catalyst.

We can provide a vehicle control system that can protect the battery.

Figure 1 is a schematic diagram of the vehicle according to this embodiment. Figure 2 is a schematic diagram illustrating an engine. Figure 3 is a flowchart illustrating the processes performed by the ECU. Figure 4 is an example of a time chart.

The control device for the internal combustion engine of this embodiment will be described below with reference to the drawings. Figure 1 is a schematic diagram of the 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 the power sources for driving the vehicle 1.

The first MG14 and the second MG15 function as an electric motor and a generator. The first MG14 and the second MG15 output torque when power is supplied, and generate regenerative power when torque is applied. The first MG14 and the second MG15 are, for example, AC rotating electric machines. An AC rotating electric machine is, for example, a permanent magnet synchronous motor equipped with a rotor in which permanent magnets are embedded.

The first MG14 and the second MG15 are electrically connected to the battery 18 via the PCU17. The PCU17 charges the battery 18 using regenerative power generated by the first MG14 or the second MG15, and drives the first MG14 or the second MG15 using the power charged by the battery 18. The PCU17 includes a first inverter that exchanges power with the first MG14, a second inverter that exchanges power with the second MG15, and a converter. The converter boosts the power from the battery 18 and supplies it to the first and second inverters, and steps down the power supplied from the first and second inverters and supplies it to the battery 18. The first inverter converts the DC power from the converter into AC power and supplies it to the first MG14, and converts the AC power from the first MG14 into DC power and supplies it to the converter. The second inverter converts the DC power from the converter into AC power and supplies it to the second MG15, and then converts the AC power from the second MG15 into DC power and supplies it to the converter.

The battery 18 is composed of multiple stacked batteries. These batteries are, for example, rechargeable batteries such as nickel-metal hydride batteries or lithium-ion batteries.

The power split mechanism 20 is a planetary gear mechanism, for example, comprising a sun gear, planetary carrier, pinion gear, and 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.

The reduction mechanism 22 is a multi-stage automatic transmission that changes the gear ratio. Under the control of the ECU 40, the reduction mechanism 22 changes the gear ratio and switches between multiple power transmission states. These multiple power transmission states include N (neutral), D (drive), R (reverse), and P (parking) ranges. Instead of the reduction mechanism 22, a continuously variable transmission (CVT) that continuously changes the gear ratio may be used.

The output shaft of the power split mechanism 20 is connected to the 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 the differential gear 24. A drive shaft 25 is connected to the differential gear 24. A drive wheel 26 is attached to the end of the drive shaft 25.

Engine 10, the first MG14, and the second MG15 function as drive sources that generate driving force. The driving force from each of the engines 10, the first MG14, and the second MG15 is transmitted to the drive wheels 26 via the reduction gear 22 and the differential gear 24.

The ECU 40 is the control unit for vehicle 1 and includes a CPU (Central Processing Unit) and other arithmetic units, as well as memory devices such as RAM (Random Access Memory) and ROM (Read Only Memory). The ECU 40 performs various controls by executing programs stored in the ROM and memory devices.

Figure 2 is a schematic diagram illustrating engine 10. Engine 10 is, for example, a four-cylinder engine. The intake passage 30 and exhaust passage 32 are connected to the four cylinders of engine 10. Air flows through the intake passage 30 and is supplied to the cylinders of engine 10. The intake passage 30 is equipped with a throttle valve 34 and an airflow meter 33. The throttle valve 34 and airflow meter 33 are arranged in this order from upstream to downstream in the direction of airflow. The larger the opening of the throttle valve 34, the greater the airflow (intake volume) to engine 10. The smaller the opening, the smaller the airflow.

Each of the four cylinders of the engine 10 is equipped with a spark plug 36 and a fuel injector 38. The fuel injector 38 directly injects fuel into the cylinder. In the cylinder, fuel and air form a fuel-air mixture. The spark plug 36 ignites the mixture, causing it to burn. The exhaust gas after combustion is discharged to the outside of the vehicle 1 through the exhaust passage 32.

A catalyst 35 is provided in the exhaust passage 32. The catalyst 35 is, for example, a three-way catalyst, and purifies nitrogen oxides (NOx) and carbon monoxide (CO) in the exhaust gas.

The airflow meter 33 detects the intake air volume. The rotational speed sensor 37 detects the rotational speed of the engine 10. The ECU 40 obtains the flow rate from the airflow meter 33 and the rotational speed from the rotational speed sensor 37.

The ECU 40 controls the engine 10, the first MG 14, the second MG 15, the PCU 17, and the battery 18. The ECU 40 functions as a flow control unit, controlling the airflow by adjusting the opening of the throttle valve 34. The ECU 40 controls the fuel injection amount and timing from the fuel injector 38. The ECU 40 functions as an ignition timing control unit, controlling the ignition timing by the spark plug 36 and the rate at which the ignition timing is changed. The ECU 40 functions as an acquisition unit, acquiring the charge level of the battery 18, the power output from the battery 18, and the power generated by the first MG 14 and the second MG 15. Based on the charge level of the battery 18, the ECU 40 acquires the battery 18's acceptable power Win. The acceptable power Win is the upper limit of the power that the battery 18 can accept.

The purification performance of catalyst 35 is temperature-dependent and increases at its activation temperature. To enhance purification performance, the ECU 40 performs warm-up control, for example, retarding the ignition timing compared to when warm-up control is not in effect. During warm-up control, the ECU 40 opens the throttle valve 34, increasing the airflow. The power of engine 10 is maintained at a constant level.

After the warm-up control is complete, the ECU 40 advances the ignition timing. This advancement of the ignition timing increases the torque of the engine 10. Immediately after the warm-up control is complete, a significant amount of air may remain in the cylinders. The advancement of the ignition timing may cause a sudden increase in torque. The first MG 14 rotates in response to the torque of the engine 10 and generates electricity. As the torque of the engine 10 increases, the power generated by the first MG 14 also increases. Excess power is input to the battery 18, causing it to overcharge and deteriorate. In this embodiment, a sudden increase in torque is suppressed to protect the battery 18.

Figure 3 is a flowchart illustrating the control performed by the ECU 40. Immediately before the process shown in Figure 3 takes place, warm-up control is performed. The ECU 40 terminates the warm-up control and reduces the opening of the throttle valve 34 to a smaller value than during the warm-up control (step S10). The ECU 40 obtains the power W generated by the first MG 14 and the allowable power Win of the battery 18 (step S12). The ECU 40 obtains A, which is the difference between the allowable power Win and the generated power W (step S14). Based on A, the ECU 40 determines the rate at which to change the ignition timing (step S16). Based on the rate, the ECU 40 controls the ignition timing, advancing it compared to during the warm-up control (step S18). This completes the process shown in Figure 3.

Figure 4 illustrates a time chart. From top to bottom, it shows the warm-up control flag, engine speed 10, torque output by engine 10, intake air volume, ignition timing, torque output by the first MG 14, and power. The horizontal axis represents time. Of the torque of the first MG 14, the torque used for power is represented by a positive value, and the torque used for charging is represented by a negative value. In the chart showing the torque of the first MG 14 in Figure 4, the lower the value, the greater the torque used for charging the battery 18. In the power chart, the power input to the battery 18 is represented by a negative value, and the power output from the battery 18 is represented by a positive value. The lower the value, the greater the power input to the battery 18.

At time t1, the warm-up control flag switches from on to off. Warm-up control ends (step S10 in Figure 3). Compared to during warm-up control, the throttle valve 34 opening decreases, and the intake air volume decreases. The ECU 40 advances the ignition timing. The ignition timing changes from F1 to F2. The engine speed of 10 decreases to the optimal value R0. The torque of engine 10 and the torque of the first MG 14 change.

Based on the difference A between the allowable power Win and the generated power W before the warm-up control is complete, the ECU 40 controls the rate at which the ignition timing is advanced (step S16 in Figure 3). The larger the absolute value of the difference A, the larger the rate. The smaller the absolute value of the difference A, the smaller the rate. In the example of the solid line in Figure 4, the rate at which the ignition timing is advanced is large. The torque of the engine 10 increases rapidly before reaching the optimal value Tr0. The torque of the first MG 14 changes rapidly to Tr1. The generated power W of the first MG 14 changes significantly before reaching W0. That is, the absolute value of the generated power W increases before reaching W0. As shown in Figure 4, there is a risk that the generated power W may overshoot to a magnitude exceeding the allowable power Win.

In the dotted line example, the rate of change in ignition timing is small. The torque of engine 10 increases gradually, reaching the optimal value Tr0. The torque of the first MG 14 decreases gradually, reaching Tr1. The power generated by the first MG 14, W, changes more gradually compared to the solid line example, reaching W0. That is, the absolute value of the power generated, W, increases slowly to W0. Overshoot of the power generated, W, is suppressed and kept within the allowable power input Win.

According to this embodiment, the ECU 40 controls the rate at which the ignition timing is advanced based on the power W generated by the first MG 14 and the allowable power Win of the battery 18. This suppresses abrupt changes in the torque of the engine 10 and the torque of the first MG 14. It also suppresses overshoot in the power W generated by the first MG 14. Furthermore, it protects the battery 18 by suppressing overcharging.

The larger the absolute value of the difference A between the allowable power Win and the power W, the larger the rate the ECU 40 increases. As shown by the solid line in Figure 4, the engine speed and torque of the engine 10 change rapidly to the optimal values. Fuel efficiency improves. As shown by the dotted line in Figure 4, the smaller the absolute value of the difference A, the smaller the rate the ECU 40 decreases. The ignition timing advance becomes delayed. Because the torque of the engine 10 changes slowly, the torque change of the first MG 14 also becomes slower. The power W generated by the first MG 14 slowly approaches W0, overshoot is suppressed, and it is kept within the allowable power Win. The battery 18 is not overcharged and is protected.

The ECU 40 retards the ignition timing and performs warm-up control. This warm-up control raises the temperature of the catalyst 35 to near its activation temperature, improving its purification performance. After the warm-up control is complete, the ECU 40 advances the ignition timing at a set rate (step S18 in Figure 3). This optimizes the engine speed and torque of the engine 10, improving fuel efficiency. Reducing the ignition timing advance rate suppresses torque overshoot of the first MG 14. Overcharging of the battery 18 is suppressed, protecting the battery 18. This allows for both improved exhaust emissions and protection of the battery 18.

Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims.

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, 30 Intake Passage, 32 Exhaust Passage, 33 Airflow Meter, 34 Throttle Valve, 35 Catalytic Converter, 36 Spark Plug, 37 Rotational Speed Sensor, 38 Fuel Injector, 40 ECU

Claims (1)

A control device for a vehicle equipped with an internal combustion engine, an electric motor, and a battery,
The battery is charged by the electricity generated by the electric motor.
An ignition timing control unit for controlling the ignition timing of the internal combustion engine,
The system comprises an acquisition unit for acquiring the power generated by the aforementioned electric motor,
Based on the aforementioned power and the battery's allowable power, the ignition timing control unit controls the rate at which the ignition timing is advanced .
A catalyst for purifying the exhaust gas of the internal combustion engine is provided.
The ignition timing control unit warms up the catalyst by retarding the ignition timing.
The ignition timing control unit obtains the difference between the battery's allowable power and the power before the warm-up is complete.
The larger the absolute value of the difference between the battery's allowable power and the power, the greater the ignition timing control unit increases the rate.
The smaller the absolute value, the smaller the rate the ignition timing control unit reduces.
The ignition timing control unit is a vehicle control device that advances the ignition timing after the warm-up is completed, compared to the ignition timing during the warm-up of the catalyst, by a rate based on the absolute value of the difference .