JP7798007B2 - Control device for internal combustion engine - Google Patents

Description

The present invention relates to a control device for an internal combustion engine.

A catalyst that purifies the exhaust gas from the internal combustion engine is installed in the exhaust passage. The catalyst is warmed up by retarding the ignition timing, etc., to improve purification performance (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2006-070820

After warm-up is complete, the ignition timing is changed from retarded to advanced. This change in the engine speed can cause noise and vibration, which can be uncomfortable for vehicle occupants. Therefore, the objective is to provide an internal combustion engine control device that can suppress the discomfort caused by noise and vibration.

The above objective can be achieved by an internal combustion engine control device that includes an ignition timing control unit that controls the ignition timing of an internal combustion engine, and an engine speed control unit that controls the engine speed, and when the ignition timing is advanced, the engine speed control unit controls the rate of change of the engine speed based on vehicle speed.

When advancing the ignition timing and the vehicle speed is equal to or greater than a predetermined value, the rotation speed control unit may set the rate of change of the rotation speed to a first rate and reduce the rotation speed at the first rate compared to before the ignition timing was advanced; and when advancing the ignition timing and the vehicle speed is less than the predetermined value and the temperature of the cooling water of the internal combustion engine is equal to or greater than a predetermined temperature, the rotation speed control unit may set the rate of change of the rotation speed to a second rate smaller than the first rate and reduce the rotation speed at the second rate.

The engine may include a load factor control unit that controls the load factor of the internal combustion engine, and when the ignition timing is advanced, if the vehicle speed is less than the predetermined value and the temperature of the internal combustion engine coolant is equal to or higher than a predetermined temperature, the engine speed control unit reduces the engine speed at the second rate, and the load factor control unit sets the rate of change of the load factor to a third rate and reduces the load factor at the third rate. When the ignition timing is advanced, if the vehicle speed is less than the predetermined value and the temperature of the internal combustion engine coolant is less than the predetermined temperature, the engine speed control unit maintains the engine speed before the ignition timing was advanced, and the load factor control unit sets the rate of change of the load factor to a fourth rate greater than the third rate and reduces the load factor at the fourth rate.

A catalyst may be provided to purify exhaust gas from the internal combustion engine, and the ignition timing control unit may advance the ignition timing after the catalyst has been warmed up compared to the ignition timing during the warm-up.

It is possible to provide a control device for an internal combustion engine that can suppress discomfort caused by noise and vibration.

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

The internal combustion engine control device of this embodiment will now be described with reference to the drawings. FIG. 1 is a schematic 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 the "first MG (Motor Generator)") 14 (first electric motor), a second motor generator (hereinafter referred to as the "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 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. The AC rotating electric machine is, for example, a permanent magnet synchronous motor with a rotor in which a permanent magnet is embedded.

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 to AC power and supplies it to the first MG 14, and converts AC power from the first MG 14 to DC power and supplies it to the converter. The second inverter converts DC power from the converter into AC power and supplies it to the second MG 15, and converts AC power from the second MG 15 into DC power and supplies it to the converter.

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

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.

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. The multiple power transmission states include N (neutral) range, D (drive) range, R (reverse) range, and P (parking) range. A continuously variable transmission (CVT) that continuously changes the gear ratio may be used instead of the reduction mechanism 22.

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. The differential gear 24 is connected to a drive shaft 25. Drive wheels 26 are attached to the ends of the drive shafts 25.

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

The ECU 40 is a control device for the vehicle 1 and includes a computing device such as a CPU (Central Processing Unit) and storage 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 storage devices.

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

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

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 vehicle speed sensor 31 detects the speed of the vehicle 1 (vehicle speed). The air flow meter 33 detects the intake air volume. The rotation speed sensor 37 detects the rotation speed of the engine 10. The temperature sensor 39 detects the temperature (water temperature) of the coolant for the engine 10. The ECU 40 obtains the vehicle speed from the vehicle speed sensor 31, the flow rate from the air flow meter 33, the rotation speed from the rotation speed sensor 37, and the water temperature from the temperature sensor 39.

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 acquires the charge rate 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. The ECU 40 controls the amount and timing of fuel injection from the fuel injection valve 38. The ECU 40 functions as an ignition timing control unit that controls the timing of ignition by the spark plug 36. The ECU 40 adjusts the opening of the throttle valve 34 to control the amount of air introduced into the engine 10. The ECU 40 functions as a load factor control unit. The load factor is the ratio of the actual intake amount to the maximum intake amount of the engine 10. The ECU 40 functions as a rotation speed control unit that controls the rotation speed of the engine 10 by adjusting the load factor and ignition timing, etc.

The purification performance of the catalyst 35 depends on temperature and is highest at its activation temperature. To improve purification performance, the ECU 40 performs warm-up control, for example, by 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 to increase the air flow rate. The power of the engine 10 is maintained constant.

After warm-up control is completed, the ECU 40 advances the ignition timing and reduces the air flow rate. Compared to when warm-up control was in progress, the torque of the engine 10 increases and the engine 10 rotation speed decreases. By optimizing the torque and rotation speed, fuel economy improves. However, the decrease in rotation speed can cause vibrations and noise, which can be uncomfortable for passengers in the vehicle 1.

When the vehicle speed is high, the noise generated by driving (running noise) is loud. Noise generated by a drop in engine speed blends in with the running noise and becomes difficult to hear. When the vehicle speed is low, the running noise is low. The noise is heard relatively loudly. Therefore, when the vehicle speed is high, the generation of noise and other noise caused by changes in engine speed is tolerated. By changing the engine speed quickly, fuel economy is improved. When the vehicle speed is low, the engine speed is changed slowly so that noise and other noise are less likely to be generated. Specifically, the engine speed is controlled by reducing the amount of air introduced into the engine 10.

If the amount of air is slowly reduced when the engine 10 temperature is low, particulates will be generated by combustion, resulting in poor exhaust quality. To prevent poor exhaust quality, the air flow rate can be changed quickly. In this embodiment, noise and other issues can be reduced while also preventing poor exhaust quality.

Figure 3 is a flowchart illustrating the control executed by the ECU 40. Warm-up control is performed immediately before the processing of Figure 3 is performed. The ECU 40 terminates the warm-up control (step S10). The ECU 40 acquires the vehicle speed V from the vehicle speed sensor 31 (step S12). The ECU 40 acquires the rate of change when the engine 10 rotation speed is reduced based on the vehicle speed V (step S14). The rate is, for example, d1 and d3, which will be described later.

The ECU 40 determines whether the vehicle speed V is equal to or greater than the threshold value Vth (step S16). If the determination is affirmative (Yes), the ECU 40 reduces the rotation speed at rate d1 (first rate) (step S18). At this time, the load factor decreases. After step S18, the processing in FIG. 3 ends.

If the determination in step S16 is negative (No), the ECU 40 obtains the water temperature T from the temperature sensor 39 and determines whether the water temperature T is less than a predetermined temperature Tth (step S20). If the determination is negative, the ECU 40 reduces the rotation speed at rate d2 (second rate) (step S22). Rate d2 is smaller than rate d1. At this time, the load factor is reduced. After step S22, the process ends.

If the determination in step S20 is affirmative, the ECU 40 reduces the amount of air introduced into the engine 10, thereby lowering the load factor (step S24). The ECU 40 maintains the engine 10 speed constant by controlling the ignition timing, etc. (step S26). After step S26, the process ends. If the process is performed again and the water temperature T rises above Tth, step S22 is performed and the engine speed is reduced.

Figure 4 is a diagram illustrating a time chart. From the top, the diagram shows vehicle speed V, water temperature T, catalyst 35 warm-up control flag, engine 10 rotation speed, engine 10 torque, ignition timing, and engine 10 load factor. The horizontal axis represents time.

Vehicle speed V1 is greater than a predetermined value Vth. Vehicle speed V2 is less than a predetermined value Vth. Water temperature T1 is greater than a predetermined temperature Tth. Water temperature T2 is less than a predetermined temperature Tth. In the chart of rotation speed, torque, ignition timing, and load factor, the solid line represents an example where vehicle speed is V1. Water temperature may be greater than or equal to Tth, or less than Tth. The dotted line represents an example where vehicle speed is V2 and water temperature at the end of warm-up is T1. The dashed line represents an example where vehicle speed is V2 and water temperature at the end of warm-up is T2. During warm-up control, the rotation speed is R1 and torque is Tr1. Ignition timing is P1, and the load factor is A1.

At time ta, the warm-up control flag switches from on to off. Warm-up control ends (step S10 in Figure 3). When the vehicle speed is V1, the ECU 40 advances the ignition timing from P1, as shown by the solid line. The ECU 40 reduces the opening of the throttle valve 34, decreasing the amount of air introduced into the engine 10 and lowering the load factor. At time tb, the ignition timing becomes P2 and the load factor decreases to A2. The engine 10 rotation speed decreases from R1 to R2, and torque increases from Tr1 to Tr2. The rate at which the rotation speed changes is the first rate d1 (step S18 in Figure 2). The rotation speed quickly changes to R2.

When the vehicle speed is V2 and the water temperature is T1, as shown by the dotted line, the ECU 40 advances the ignition timing from P1 to P2. The rate of change of the ignition timing is slower than in the example shown by the solid line. The ignition timing advances slowly, reaching P2 after time tb. The ECU 40 controls the opening of the throttle valve 34 to reduce the amount of air. The rate at which the load factor decreases (third rate d3) is slower than in the example shown by the solid line. The load factor changes slowly from A1 to A2. The rate of change of the rotation speed (second rate d2) is slower than the first rate d1 (step S22 in Figure 3). After time tb, the rotation speed becomes R2 and the torque becomes Tr2.

When the vehicle speed is V2 and the water temperature is T2, as shown by the dashed line, the ECU 40 changes the ignition timing to a timing that is more advanced than P1 and more retarded than P2, and maintains that ignition timing. The load factor decreases from A1. The rate at which the load factor changes (fourth rate d4) is greater than the third rate d3 in the dotted line example and is equal to the rate in the solid line example, for example. At time tb, the load factor decreases to A2 (step S24). By controlling the ignition timing and load factor, the engine speed is maintained at the value R1 during warm-up control until time tc (step S26). The torque is maintained at the value Tr1 during warm-up control. The water temperature T is rising and exceeds the threshold value Tth at time tc. At time tc, the ECU 40 advances the ignition timing to P2. The engine speed decreases to R2. The torque increases to Tr2. The rate of change of speed and torque after time tc is greater than the rate in the dotted line example.

According to this embodiment, for example, after warm-up control is completed, the ECU 40 advances the ignition timing. The ECU 40 controls the rate of change in rotation speed based on the vehicle speed. This can reduce discomfort felt by passengers due to noise, etc.

When the vehicle speed is above Vth, the rate of change in rotation speed is set to d1. The rotation speed quickly becomes R2. By setting the rotation speed to R2 and the torque to Tr2, fuel efficiency can be improved. Rapid changes in rotation speed can cause noise, etc. Because the vehicle speed is high at above Vth, the driving noise is loud. The noise blends in with the driving noise and is difficult for passengers to hear. This reduces the discomfort felt by passengers.

When the vehicle speed is below Vth and the water temperature is above Tth, the ECU 40 sets the rate of change of the rotation speed to a second rate d2, which is slower than d1. Because the rotation speed changes slowly, noise and other issues are less likely to occur. This helps to reduce discomfort caused by noise and other issues. The rate of change of the load factor is a third rate d3.

When the vehicle speed is below Vth and the water temperature is below Tth, the ECU 40 maintains the engine speed at the value R1 before the ignition timing was advanced. By suppressing changes in engine speed, noise and other issues are less likely to occur. This reduces discomfort felt by passengers. The ECU 40 sets the rate of change of the load factor to a fourth rate d4, which is greater than d3. When the water temperature is low, such as below Tth, the load factor changes quickly at rate d4. This prevents exhaust deterioration.

The ECU 40 retards the ignition timing and performs warm-up control. Warm-up control raises the temperature of the catalyst 35 to near its activation temperature, improving purification performance. After warm-up control is complete, the ECU 40 controls the ignition timing, engine speed, load factor, etc. This allows for both improved exhaust emissions and reduced discomfort.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims.

REFERENCE SIGNS LIST 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, 31 vehicle speed sensor, 32 exhaust passage, 33 air flow meter, 34 throttle valve, 35 catalyst, 36 spark plug, 37 rotation speed sensor, 38 fuel injection valve, 39 temperature sensor, 40 ECU

Claims (3)

an ignition timing control unit that controls the ignition timing of the internal combustion engine;
a rotation speed control unit that controls the rotation speed of the internal combustion engine,
When the ignition timing is advanced, the rotation speed control unit controls a rate of change of the rotation speed based on a vehicle speed ,
When the ignition timing is advanced and the vehicle speed is equal to or greater than a predetermined value, the rotation speed control unit sets a rate of change of the rotation speed to a first rate, and reduces the rotation speed at the first rate compared to before the ignition timing was advanced,
a control device for an internal combustion engine, wherein when the ignition timing is advanced, the vehicle speed is less than the predetermined value, and the temperature of the cooling water of the internal combustion engine is equal to or higher than a predetermined temperature, the rotation speed control unit sets the rate of change of the rotation speed to a second rate that is smaller than the first rate, and reduces the rotation speed at the second rate . a load factor control unit that controls a load factor of the internal combustion engine,
When the ignition timing is advanced, and when the vehicle speed is less than the predetermined value and the temperature of the cooling water of the internal combustion engine is equal to or higher than a predetermined temperature, the rotation speed control unit reduces the rotation speed at the second rate, and the load factor control unit sets a rate of change of the load factor to a third rate and reduces the load factor at the third rate,
2. The control device for an internal combustion engine according to claim 1, wherein, when the ignition timing is advanced, if the vehicle speed is less than the predetermined value and the temperature of the cooling water of the internal combustion engine is less than the predetermined temperature, the rotation speed control unit maintains the rotation speed before the ignition timing was advanced, and the load factor control unit sets a rate of change of the load factor to a fourth rate that is greater than the third rate, and reduces the load factor at the fourth rate. a catalyst for purifying exhaust gas from the internal combustion engine is provided;
3. The control device for an internal combustion engine according to claim 1 , wherein the ignition timing control unit advances the ignition timing after the catalyst has been warmed up compared to the ignition timing during the warming up of the catalyst.