Control system for internal combustion engines

Abstract

To provide a control system of an internal combustion engine that can complete warming-up of a catalyst more quickly.SOLUTION: A control system of an internal combustion engine comprises: an internal combustion engine; a rotary electric machine that can drive the internal combustion engine; a battery that supplies electric power to the rotary electric machine; and control device that controls the internal combustion engine and the rotary electric machine. The control device switches between first retard operation by which ignition is retarded to first ignition timing and the internal combustion engine is operated by combustion by the internal combustion engine and second retard operation by which ignition is delayed to second ignition timing later than the first ignition timing and the internal combustion engine is rotated by the rotary electric machine, in accordance with a charged state of the battery.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a control system for an internal combustion engine.

Background Art

[0002] Conventionally, a control system for an internal combustion engine having a motor that assists the rotation of the internal combustion engine has been known (see, for example, Patent Document 1). The control system for the internal combustion engine of Patent Document 1 includes a control device. The control device executes control to retard the ignition timing when warming up the catalyst. The control device executes control to supplement the amount by which the torque of the internal combustion engine has decreased due to the retardation of the ignition timing, by the motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, such internal combustion engines have been required to complete catalyst warming up more quickly.

[0005] An object of the present disclosure is to provide a control system for an internal combustion engine that can complete catalyst warming up more quickly.

Means for Solving the Problems

[0006] The control system for an internal combustion engine according to this disclosure comprises an internal combustion engine, a rotating electric machine capable of driving the internal combustion engine, a battery that supplies power to the rotating electric machine, and a control device that controls the internal combustion engine and the rotating electric machine. The control device switches between a first retard operation, in which the ignition timing is retarded to a first ignition timing and the internal combustion engine is operated by combustion by the internal combustion engine, and a second retard operation, in which the ignition timing is retarded to a second ignition timing that is retarded further than the first ignition timing and the internal combustion engine is rotated by the rotating electric machine, depending on the charge state of the battery.

[0007] This internal combustion engine control system performs a second retard operation depending on the battery status. In the second retard operation, the internal combustion engine is rotated by a rotating electric machine, allowing for a second ignition timing that is retarded compared to the first ignition timing. This enables faster catalyst warm-up.

[0008] Furthermore, the control system for this internal combustion engine performs a first retard operation depending on the battery status. This protects the battery. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a control system for an internal combustion engine that can complete catalyst warm-up more quickly. [Brief explanation of the drawing]

[0010] [Figure 1] A system diagram of an electric vehicle according to one embodiment of the present disclosure. [Figure 2] A system diagram of an internal combustion engine according to one embodiment of the present disclosure. [Figure 3] A flowchart illustrating a control procedure performed by a control device according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0011] Hereinafter, one embodiment of this disclosure will be described with reference to the drawings.

[0012] As shown in Figure 1, the control system 3 for the internal combustion engine 1 comprises the internal combustion engine 1, a generator 4, a drive battery 6, and a vehicle control device (an example of a control device) 12. The control system 3 for the internal combustion engine 1 in this embodiment is mounted on an electric vehicle C that drives the wheels C1 using the internal combustion engine 1 and a motor (FrM) 2 as power sources. However, the internal combustion engine 1 may be mounted on a vehicle that uses only the internal combustion engine 1 as a power source, as long as it is an internal combustion engine 1 capable of motoring.

[0013] The electric vehicle C includes an internal combustion engine 1, a motor 2, a generator (GEN: an example of a rotating electric machine) 4, a drive battery (BT: an example of a battery) 6 including a secondary battery such as a lithium-ion battery, and a transaxle 8. The transaxle 8 has multiple gears and a clutch 8a. The internal combustion engine 1 is connected to the generator 4 and the axle 10 via the transaxle 8. When the clutch 8a of the transaxle 8 is open, power transmission between the internal combustion engine 1 and the axle 10 is interrupted, and when the clutch 8a is engaged, power from the internal combustion engine 1 is transmitted to the axle 10. The motor 2 is connected to the axle 10 via the transaxle 8. The electric vehicle C may also include a vehicle control device 12, an engine control device 14 that controls the internal combustion engine 1, an accelerator pedal 16 operated by the user of the electric vehicle C, an inverter 18 that controls the motor 2 and the generator 4, a charging button (not shown), and a power supply button (not shown). Furthermore, in this embodiment, the electric vehicle C is a plug-in hybrid vehicle (PHEV) having a charger 20 that can be connected to an external power source and a power supply device 22 that can supply power from the drive battery 6 to external devices such as home appliances. However, the electric vehicle C may be a hybrid vehicle that does not have such devices.

[0014] The electric vehicle C of this embodiment has various modes, including EV mode, series mode, parallel mode, charging mode, and power supply mode. In EV mode, the electric vehicle C drives the motor 2 with power from the drive battery 6. In series mode, the electric vehicle C drives the generator 4 with the internal combustion engine 1, and uses the power generated by the generator 4 to drive the motor 2. In parallel mode, the electric vehicle C engages the clutch 8a and uses the power from the internal combustion engine 1 to drive the axle 10. In charging mode, the electric vehicle C drives the generator 4 with the internal combustion engine 1, and stores the power generated by the generator 4 in the drive battery 6. Depending on the state in which the accelerator pedal 16 is pressed or the operation state of the charging button or power supply button, the vehicle control device 12 switches between modes, controls the motor 2 and generator 4 via the inverter 18, and causes the engine control device 14 to control the internal combustion engine 1.

[0015] As shown in Figure 2, the internal combustion engine 1 comprises an in-cylinder injection valve 30, a high-pressure pump 32, a spark plug 34, a front catalytic converter 36, an underfloor catalytic converter 38, a throttle 40, a temperature sensor 46, and an air-fuel ratio sensor 48. In this embodiment, the internal combustion engine 1 is a gasoline engine that ignites a fuel-air mixture injected from the in-cylinder injection valve 30 with intake air using a spark plug 34. The front catalytic converter 36 and the underfloor catalytic converter 38 are three-way catalytic converters that purify the exhaust gas of the gasoline engine.

[0016] The in-cylinder injection valve 30 is a device that injects fuel into the cylinder of each cylinder. The in-cylinder injection valve 30 is connected to a high-pressure pump 32, which supplies high-pressure fuel. The high-pressure pump 32 is a device that pressurizes the fuel supplied via the low-pressure pump 42a of the fuel tank 42. In this embodiment, the high-pressure pump 32 is a mechanical pump that drives the plunger 32a with a pump cam 44a which is arranged coaxially with the camshaft 44 of the internal combustion engine 1. The high-pressure pump 32 is not limited to such a mechanical pump, but may also be an electric pump that drives the plunger or impeller with a motor.

[0017] The temperature sensor 46 is a sensor that detects the temperature Tfcc of the front catalyst 36. In the present embodiment, the temperature sensor 46 is disposed on the front catalyst 36. However, the temperature sensor 46 may be disposed, for example, upstream of the underfloor catalyst 38 as long as it can detect the temperature of the front catalyst 36.

[0018] The air-fuel ratio sensor 48 is a sensor that detects the air-fuel ratio in the exhaust gas. In the present embodiment, the air-fuel ratio sensor 48 is disposed between the front catalyst 36 and the underfloor catalyst 38. However, the air-fuel ratio sensor 48 may be disposed, for example, downstream of the underfloor catalyst 38 as long as it can detect the air-fuel ratio in the exhaust gas.

[0019] The generator 4 is connected to the internal combustion engine 1 and can drive the internal combustion engine 1. While the generator 4 is powered by the power from the driving battery 6, it performs motoring to drive the internal combustion engine 1. On the other hand, the generator 4 is driven by the internal combustion engine 1 during the operation of the internal combustion engine 1 to generate electricity. Therefore, the generator 4 is a motor-generator capable of power running and power generation.

[0020] The vehicle control device 12 is electrically connected to the generator 4 via the inverter 18 and controls the generator 4. Further, the vehicle control device 12 transmits instructions such as at least the first retard operation and the second retard operation to the engine control device 14 to cause the engine control device 14 to control the internal combustion engine 1. The vehicle control device 12 is an ECU (Electronic Control Unit) constituted by a microcomputer including an arithmetic device, a memory, an input / output buffer, etc. The vehicle control device 12 executes various controls of the electric vehicle C based on maps and programs stored in the memory.

[0021] Further, the vehicle control device 12 is electrically connected to a control unit (not shown) of the driving battery 6 and can acquire information such as the state of charge SOC and the battery temperature T of the driving battery 6 from the control unit of the driving battery 6.

[0022] The engine control device 14 is a control device that is electrically connected to at least the in-cylinder injection valve 30, the high-pressure pump 32, the ignition plug 34, and the throttle 40, and controls the internal combustion engine 1. The engine control device 14 is actually an ECU (Electronic Control Unit) constituted by a microcomputer including an arithmetic unit, a memory, an input / output buffer, etc. The engine control device 14 executes various controls of the internal combustion engine 1 based on maps and programs stored in the memory. Note that the control of the internal combustion engine 1 may be executed by the vehicle control device 12 in addition to the engine control device 14.

[0023] When the engine control device 14 acquires an instruction for the first retard operation, it executes normal retard control to retard the ignition timing to such an extent that the internal combustion engine 1 can rotate independently. The ignition timing in the normal retard control is from 1° ATDC (After Top Dead Center) or more to 20° ATDC or less (an example of the first ignition timing). Also, at this time, the vehicle control device 12 controls the generator 4 to generate electricity while being driven by the internal combustion engine 1.

[0024] When the engine control device 14 acquires an instruction for the second retard operation, it executes super retard control to retard the ignition timing while performing motoring by the generator 4. The ignition timing in the super retard control is a value from more than 20° ATDC to about 35° ATDC, more preferably a value of 30° ATDC or more, and a value of about 30° ATDC to 35° ATDC (an example of the second ignition timing). When it exceeds 20° ATDC, combustion fluctuations become remarkable and the rotation of the internal combustion engine 1 becomes unstable. Also, at an ignition timing of 30° ATDC to 35° ATDC, the internal combustion engine 1 hardly generates output (torque). Therefore, the rotation of the internal combustion engine 1 is maintained by the generator 4 performing motoring. On the other hand, at an ignition timing of more than 20° ATDC to 35° ATDC, exhaust is likely to afterburn. Therefore, the time required to warm up the catalyst becomes shorter than that in the normal retard control.

[0025] Next, the control procedure performed by the vehicle control device 12 will be explained using the flowchart in Figure 3. The vehicle control device 12 starts the control procedure when an ignition switch (not shown) is turned on.

[0026] In step S1, the vehicle control device 12 obtains the accelerator opening Th, which is the degree of opening of the accelerator pedal 16. The vehicle control device 12 also calculates the vehicle speed V, which is the speed of the electric vehicle C, from the rotation of the wheels C1. Once the vehicle control device 12 has obtained the accelerator opening Th and the vehicle speed V, it proceeds to step S2.

[0027] In step S2, the vehicle control device 12 calculates the requested output PW, which is the output required by the electric vehicle C, from the accelerator opening Th and the vehicle speed V. The vehicle control device 12 then proceeds to step S3.

[0028] In step S3, the vehicle control device 12 determines whether the front catalytic converter 36 or the underfloor catalytic converter 38 needs to be warmed up. Whether warming up is necessary may be determined by whether the temperature of the front catalytic converter 36 or the underfloor catalytic converter 38 has reached its activation temperature (hereinafter referred to as the light-off temperature in this specification). The vehicle control device 12 may also determine whether warming up the front catalytic converter 36 or the underfloor catalytic converter 38 is necessary by detecting the temperature using the temperature sensor 46. The vehicle control device 12 may also determine whether warming up the front catalytic converter 36 or the underfloor catalytic converter 38 is necessary by accumulating the operating time of the internal combustion engine 1, etc. If the vehicle control device determines that warming up the front catalytic converter 36 or the underfloor catalytic converter 38 is necessary (step S3 YES), it proceeds to step S4.

[0029] In step S4, the vehicle control device 12 determines whether the charge level (SOC) of the drive battery 6 is equal to or greater than a predetermined charge level (SOCt). The predetermined charge level (SOCt) is the charge level at which the generator 4 can motor the internal combustion engine 1. If the charge level (SOC) is equal to or greater than the predetermined charge level (SOCt) (step S4 YES), the vehicle control device 12 proceeds to step S5.

[0030] In step S4, the vehicle control device 12 may obtain the battery temperature Tbt in addition to the charge level (SOC), and if the battery temperature Tbt is equal to or greater than a predetermined battery temperature Tbt1, it may proceed to step S5. When the drive battery 6 is in a low temperature state, it may not be able to supply sufficient power to the generator 4. For this reason, the predetermined battery temperature Tbt1 should be a temperature at which the generator 4 can perform motoring.

[0031] In step S5, the vehicle control device 12 performs a second retard operation. More specifically, the vehicle control device 12 sends an instruction for the second retard operation to the engine control device 14. The engine control device 14 performs super retard control. During this time, the vehicle control device 12 powers the generator 4 and performs motoring. By performing super retard control while motoring in this way, the vehicle control device 12 supplies exhaust gas with a higher exhaust temperature Tex than in normal retard control to the front catalytic converter 36 and the underfloor catalytic converter 38. As a result, the vehicle control device 12 heats up the front catalytic converter 36 and the underfloor catalytic converter 38 more quickly.

[0032] The vehicle control device 12 may set the air-fuel ratio during the second retard operation to stoichiometric (stoichiometric air-fuel ratio) for a predetermined period after the start of the second retard operation, and then lean it out. The vehicle control device 12 may lean out the air-fuel ratio (ratio of air to fuel) to about 30 when motoring is being performed. The vehicle control device 12 may have the engine control device 14 perform this control. By leaning out the air-fuel ratio, the vehicle control device 12 can increase the exhaust temperature Tex. This increases the rate of increase in heat quantity Q, allowing the front catalyst 36 and the underfloor catalyst 38 to be heated up earlier. In addition, by setting the air-fuel ratio to stoichiometric at the beginning of the second retard operation, the vehicle control device 12 can promote the release of substances adsorbed on the adsorbent catalyst, for example, if there is an adsorption catalyst between the front catalyst 36 and the underfloor catalyst 38. When the vehicle control device 12 performs the second retard operation, it proceeds to step S6.

[0033] In step S6, the vehicle control device 12 integrates the heat quantity Q of the exhaust from the internal combustion engine 1 during the second retard operation and determines whether the heat quantity Q has reached a predetermined heat quantity Qt. The predetermined heat quantity Qt is the amount of heat required for the front catalyst 36 and the underfloor catalyst 38 to reach the light-off temperature. The predetermined heat quantity Qt is also the amount of heat required to prevent melting of the front catalyst 36 and the underfloor catalyst 38. In this embodiment, the vehicle control device 12 detects the temperature Tfcc of the front catalyst 36 using the temperature sensor 46 and calculates the integrated value of the heat quantity Q from the temperature Tfcc of the front catalyst 36. More specifically, the vehicle control device 12 determines that the integrated value of the heat quantity Q has reached the predetermined heat quantity Qt if the time during which the temperature Tfcc of the front catalyst 36 is at a predetermined catalyst temperature Tfcct continues for a predetermined time Pt ​​or longer. If the vehicle control device 12 determines that the integrated value of the heat quantity Q has reached the predetermined heat quantity Qt (step S6 YES), it proceeds to step S7.

[0034] In addition, in step S6, the vehicle control device 12 may detect the rate of increase ΔTfcc of the temperature Tfcc of the front catalyst 36, and if the rate of increase ΔTfcc is equal to or greater than a predetermined rate of increase ΔTfcct, it may estimate that the integrated value of heat Q has reached a predetermined heat quantity Qt. The predetermined rate of increase ΔTfcct is sufficient if the rate of increase ΔTfcc of the temperature Tfcc of the front catalyst 36 reaches the light-off temperature (approximately 300°C) within a few seconds. When the rate of increase ΔTfcc is equal to or greater than a predetermined rate of increase ΔTfcct, the vehicle control device 12 may determine that the integrated value of heat Q has reached a predetermined heat quantity Qt and proceed to step S7.

[0035] In step S7, the vehicle control device 12 stops the second retard operation. Once the vehicle control device 12 stops the second retard operation, it proceeds to step S8.

[0036] In step S8, the vehicle control device 12 determines whether a first retard operation is necessary. The vehicle control device 12 may determine that a first retard operation is necessary if, after reaching a predetermined heat quantity Qt through a second retard operation, at least one of the front catalyst 36 and the underfloor catalyst 38 has not yet reached the light-off temperature. For example, if the front catalyst 36 and the underfloor catalyst 38 have been exposed to low temperatures, even if the heat quantity Q reaches a predetermined heat quantity Qt, one of the front catalyst 36 and the underfloor catalyst 38 may not reach the light-off temperature. In such cases, it is preferable to continue warming up the engine with a first retard operation while preventing melting damage to the front catalyst 36 and the underfloor catalyst 38.

[0037] If the vehicle control device 12 determines that a first retard operation is necessary (step S8 YES), it proceeds to step S9 to execute the first retard operation. After executing the first retard operation, the vehicle control device 12 proceeds to step S10.

[0038] In step S10, the vehicle control device 12 determines whether the warm-up of the front catalytic converter 36 and the underfloor catalytic converter 38 is complete. The vehicle control device 12 may determine that the warm-up is complete if both the front catalytic converter 36 and the underfloor catalytic converter 38 have reached the light-off temperature. If the warm-up of the front catalytic converter 36 and the underfloor catalytic converter 38 is complete (step S10 YES), the vehicle control device 12 proceeds to step S1.

[0039] If, in step S3, the vehicle control device 12 determines that warming up the front catalytic converter 36 and the underfloor catalytic converter 38 is not necessary (step S3 NO), the vehicle control device 12 proceeds to step S11 and performs normal operation. Normal operation means controlling the internal combustion engine 1, motor 2, and generator 4 based on the requested output obtained in step S2, without performing ignition retard control or the like. Once normal operation is performed, the vehicle control device 12 proceeds to step S1.

[0040] If, in step S4, the vehicle control device 12 determines that the state of charge (SOC) of the drive battery 6 is less than a predetermined charge level (SOCt) (step S4 NO), the vehicle control device 12 proceeds to step S12 and executes the first retard operation. In the first retard operation, the vehicle control device 12 minimizes motoring of the internal combustion engine 1 by the generator 4 and allows the internal combustion engine 1 to operate autonomously. After executing the first retard operation in step S12, the vehicle control device 12 proceeds to step S10.

[0041] If, in step S6, the vehicle control device 12 determines that the heat quantity Q during the second retard operation has not reached the predetermined heat quantity Qt (step S6 NO), the vehicle control device 12 proceeds to step S5 and continues the second retard operation.

[0042] If the vehicle control device 12 determines in step S8 that the first retard operation is not necessary (step S8 NO), the vehicle control device 12 proceeds to step S10.

[0043] If, in step S10, the vehicle control device 12 determines that the warm-up of the front catalytic converter 36 and the underfloor catalytic converter 38 is not complete (step S10 NO), the process proceeds to step S4, and the warm-up is continued by either the first retard operation or the second retard operation.

[0044] As explained above, according to this disclosure, the vehicle control device 12 performs a second retard operation depending on the state of the drive battery 6. In the second retard operation, the vehicle control device 12 can set a second ignition timing that is retarded compared to the first ignition timing while motoring the internal combustion engine 1 with the generator 4. As a result, the control system 3 of the internal combustion engine 1 can supply higher temperature exhaust gas to the catalyst while ensuring exhaust flow rate. This enables the control system 3 of the internal combustion engine 1 to achieve faster catalyst warm-up. Consequently, the control system 3 of the internal combustion engine 1 can complete catalyst warm-up more quickly.

[0045] Furthermore, as shown in Figure 3, the vehicle control device 12 performs a first retard operation if the charge level (SOC) falls below a predetermined charge level (SOCt). That is, even when the vehicle control device 12 is performing a second retard operation, if the charge level (SOC) falls below a predetermined charge level (SOCt), it stops the motoring of the internal combustion engine 1 by the generator 4 and performs the first retard operation (see step S4 in Figure 3). This allows the control system 3 of the internal combustion engine 1 to suppress a decrease in the charge level (SOC). As a result, the control system 3 of the internal combustion engine 1 can protect the drive battery 6 while suppressing an extreme decrease in the charge level (SOC).

[0046] In this embodiment, the electric vehicle C having the power supply device 22 may experience a decrease in its State of Charge (SOC) due to external power supply, such as from household appliances, even when not driving. The vehicle control device 12 switches between second retard operation and second retard operation according to the SOC of the drive battery 6, thereby protecting the drive battery 6 while quickly completing catalyst warm-up. As a result, the control system 3 of the internal combustion engine 1 can achieve both the convenience of the electric vehicle C and its performance (especially exhaust gas purification performance).

[0047] Furthermore, the vehicle control device 12 stops the second retard operation after reaching the heat quantity Qt through the second retard operation. This suppresses melting of the catalyst. The vehicle control device 12 can also estimate the integrated value of the heat quantity Q using the rate of increase ΔTfcc of the temperature Tfcc of the front catalyst 36. This allows for faster calculation of the heat quantity Q. As a result, the control system 3 of the internal combustion engine 1 can quickly decide to stop the second retard operation. Consequently, the control system 3 of the internal combustion engine 1 can suppress melting of the front catalyst 36 and the underfloor catalyst 38.

[0048] <Other Embodiments> Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. In particular, the various modifications described herein can be combined as needed.

[0049] (a) In the above embodiment, the internal combustion engine 1 was described using a gasoline engine using an in-cylinder injection valve 30 as an example, but the disclosure is not limited thereto. The internal combustion engine 1 may also be an internal combustion engine 1 having a port injection valve.

[0050] (b) In the above embodiment, an example of raising the temperature of the front catalyst 36 and the underfloor catalyst 38 was used, but the disclosure is not limited thereto. In addition to the three-way catalyst, various catalysts such as a gasoline particulate filter and a trap catalyst may be used. These catalysts may also be used in the front catalyst 36 and the underfloor catalyst 38. Furthermore, a gasoline particulate filter, a trap catalyst, etc. may be added upstream, downstream, or between the front catalyst 36 and the underfloor catalyst 38. [Explanation of symbols]

[0051] 1: Internal combustion engine 4: Generator (an example of a rotating electric machine) 6: Power battery (an example of a battery) 12: Vehicle control device (an example of a control device) Q: Heat amount Qt: Predetermined amount of heat SOC: Charging rate SOCt: Predetermined charging rate ΔTfcc: Percentage increase ΔTfcct: predetermined rate of increase

Claims

1. Internal combustion engines and A catalyst provided in the exhaust passage of the internal combustion engine, A rotating electric machine capable of driving the aforementioned internal combustion engine, A battery that supplies power to the aforementioned rotating electric machine, A control device for controlling the internal combustion engine and the rotating electric machine, Equipped with, When the control device determines that the catalyst needs to be warmed up, it switches between a first retard operation, in which the ignition timing is retarded to the first ignition timing and the internal combustion engine is operated by combustion, depending on the state of the battery, and a second retard operation, in which the ignition timing is retarded to a second ignition timing, which is retarded further than the first ignition timing so that the combustion fluctuations are greater than those of the internal combustion engine at the first ignition timing, and the internal combustion engine is rotated by the rotating electric machine. The control device performs the second retard operation when the battery is at or above a predetermined charge level, and performs the first retard operation when the battery is below the predetermined charge level. Control system for internal combustion engines.

2. The control device integrates the amount of heat from the exhaust of the internal combustion engine during the second retard operation, When the heat quantity reaches a predetermined amount, the second retard operation is stopped. The control system for an internal combustion engine according to claim 1.

3. The control device detects the rate of increase in the exhaust temperature of the internal combustion engine during the second retard operation, and stops the second retard operation if the rate of increase exceeds a predetermined rate of increase. A control system for an internal combustion engine according to claim 1 or 2.

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