Engine control device

Abstract

To provide an engine control device suppressing progression of deterioration of a catalyst.SOLUTION: An engine control device includes: a reference temperature calculation part calculating a reference temperature of a catalyst; a delay angle amount calculation part calculating a delay angle amount of a requested ignition timing when a delay angle request is issued; a rise temperature calculation part calculating a rise temperature of the catalyst assumed when making the ignition timing delay angle with the calculated delay angle amount; a temperature calculation part for determining excessive temperature rise calculating excessive temperature rise of the catalyst used for determination whether or not the temperature of the catalyst excessively rises, on the basis of the reference temperature and the risen temperature; a prediction part predicting whether or not the temperature of the catalyst excessively rises on the basis of a temperature for determination of excessively risen temperature; an increase amount calculation part calculating an increase amount of fuel jetting for suppressing temperature rise of the catalyst due to delay angle of the ignition timing in the delay angle amount without depending on a clank angle just after delay angle request; and a control part executing fuel jetting with a fuel jetting amount reflecting the increase amount, and executing ignition to an air fuel mixture at the ignition timing reflecting the delay angle amount.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an engine control device. [Background technology]

[0002] When it is predicted that the catalyst will overheat due to a retarded ignition timing of the engine, the fuel injection amount is increased. By increasing the fuel injection amount, the temperature of the exhaust gas decreases due to the heat of vaporization of the fuel, and the overheating of the catalyst is suppressed. The calculation of such an increase in the fuel injection amount is performed when the crank angle is 90° CA BTDC (Before Top Dead Center) (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-048720 Summary of the Invention [Problem to be solved by the invention]

[0004] A request to retard the ignition timing can be made at any timing. However, the calculation of the fuel injection increase is performed when the crank angle reaches 90° CA BTDC after the retard request is made. Therefore, the period during which fuel injection is possible may end between the time the retard request is made and the time the crank angle reaches 90° CA BTDC. In this case, the calculation of the fuel injection increase may not be completed in time for the fuel injection, and only the ignition timing may be retarded, potentially causing the catalyst to temporarily overheat. Repeated occurrences of such temporary overheating may accelerate catalyst deterioration.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an engine control device that suppresses the progression of catalyst deterioration. [Means for solving the problem]

[0006] The object is to provide a control device for an engine in which exhaust gas is purified by a catalyst, the control device including: a reference temperature calculation unit that calculates, before a request for retarding the ignition timing, a reference temperature of the catalyst that is assumed when the retard amount of the ignition timing is zero; a retard amount calculation unit that calculates a required retard amount of the ignition timing when the retard request is made; a rise temperature calculation unit that calculates a rise temperature of the catalyst that is assumed when the ignition timing is retarded by the calculated retard amount; and an overheating determination temperature calculation unit that calculates, based on the reference temperature and the rise temperature, a temperature for overheating determination of the catalyst that is used to determine whether or not the catalyst will overheat when the ignition timing is retarded by the retard amount. a prediction unit that predicts whether the catalyst will overheat based on the overheat determination temperature; an increase calculation unit that, if it is predicted that the catalyst will overheat, calculates an increase in fuel injection amount to suppress a temperature rise in the catalyst due to retarding of the ignition timing by the retard amount, after the retard request but before the end timing of a period in which fuel injection is possible immediately after the retard request, without depending on the crank angle; and a control unit that executes fuel injection with a fuel injection amount that reflects the increase during the period in which fuel injection is possible, and ignites the air-fuel mixture at an ignition timing that reflects the retard amount.

[0007] The overheating determination temperature calculation unit may calculate the overheating determination temperature assuming that the catalyst is in a brand new state.

[0008] The present invention may include a warm-up determination temperature calculation unit that calculates a warm-up determination temperature of the catalyst used to determine whether warm-up of the catalyst has been completed, and the warm-up determination temperature calculation unit may calculate the warm-up determination temperature assuming that the catalyst is in a deteriorated state.

[0009] the reference temperature calculation unit calculates the reference temperature based on a temperature of exhaust gas flowing into the catalyst that is assumed when the retard amount is zero; The rising temperature calculation unit may calculate the rising temperature based on a temperature of exhaust gas flowing into the catalyst that is expected when the ignition timing is retarded by the calculated retard amount.

[0010] When the engine is temporarily stopped, the reference temperature calculation unit may calculate the reference temperature taking into consideration the temperature of an exhaust passage downstream of the catalyst. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an engine control device that suppresses the progression of catalyst deterioration. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing the general configuration of a vehicle. [Figure 2] FIG. 2 is a flowchart illustrating an example of the overheating suppression control executed by the ECU. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Vehicle outline] FIG. 1 is a schematic diagram of a vehicle 1. The vehicle 1 includes an engine 10, an ECU (Electronic Control Unit) 30, and drive wheels 40. The engine 10 is a gasoline engine that provides the driving power for the vehicle 1. The engine 10 is an in-line cylinder engine, and in this embodiment, has four cylinders #1 to #4. Air is drawn into a combustion chamber 11 of the engine 10 through an intake passage 12, and fuel injected from an in-cylinder injection valve 13 is supplied to the combustion chamber 11. The in-cylinder injection valve 13 is a fuel injection valve that injects fuel directly into the combustion chamber 11. A port injection valve that injects fuel into an intake port may be provided instead of or in addition to the in-cylinder injection valve 13. When an ignition plug 14 ignites a mixture of intake air and injected fuel, the mixture burns, causing a piston 15 to reciprocate, and rotating a crankshaft 16 of the engine 10. The rotational power of the crankshaft 16 is transmitted to the drive wheels 40 via a transmission (not shown). After combustion, the mixture is discharged as exhaust gas from the combustion chamber 11 of the engine 10 to an exhaust passage 17 .

[0014] A catalyst 17a that purifies exhaust gas is provided in the exhaust passage 17. The catalyst 17a is a three-way catalyst that contains catalytic metals, platinum (Pt), palladium (Pd), and rhodium (Rh), and has oxygen storage capacity. The three-way catalyst has catalytic action and oxygen storage capacity, and therefore has the ability to purify NOx and HC according to the amount of oxygen stored.

[0015] The ECU 30 executes various controls for driving the vehicle 1. The ECU 30 includes a central processing unit that executes various arithmetic processes related to the various controls, a non-volatile memory that stores programs and data required for the calculations, a volatile memory that temporarily stores the calculation results of the central processing unit, an input port and an output port for inputting and outputting signals to and from the outside, and the like.

[0016] Various sensors are connected to the ECU 30. These sensors include an accelerator position sensor 31, a throttle position sensor 32, an air flow meter 34, a crank angle sensor 35, and an ignition switch 36. The accelerator position sensor 31 detects the accelerator position, which is the amount of depression of the accelerator pedal 18. The throttle position sensor 32 detects the opening of the throttle valve 19 provided in the intake passage 12. The air flow meter 34 detects the amount of intake air passing through the intake passage 12. The crank angle sensor 35 detects the rotation speed of the crankshaft 16, i.e., the rotation speed of the engine 10. The ignition switch 36 is operated to start or stop operation of the engine 10.

[0017] The ECU 30 grasps the operating conditions of the engine 10, such as the rotation speed and load, based on output signals from various sensors. The ECU 30 controls the opening of the throttle valve 19, the amount of fuel injected from the in-cylinder injection valve 13, the ignition timing of the air-fuel mixture by the spark plug 14, and the like, according to the grasped operating conditions. The ECU 30 functionally realizes a reference temperature calculation unit, a retard amount calculation unit, a rise temperature calculation unit, an overheating determination temperature calculation unit, a prediction unit, an increase calculation unit, a control unit, and a warm-up determination temperature calculation unit, which will be described in detail later. The ECU 30 is an example of an engine control device.

[0018] [Overheating prevention control] FIG. 2 is a flowchart illustrating the excessive temperature rise suppression control executed by the ECU 30. The ECU 30 calculates a warm-up determination temperature of the catalyst 17a (step S1). The warm-up determination temperature is a predicted temperature of the catalyst 17a used to determine whether warm-up of the catalyst 17a has been completed. When the warm-up determination temperature is equal to or greater than a warm-up determination threshold, it is determined that warm-up of the catalyst 17a has been completed. The warm-up determination temperature is calculated using a warm-up physics model. The warm-up physics model refers to, for example, the current operating state, such as the current ignition timing, target equivalence ratio, fuel injection amount, intake air amount, engine speed, and EGR rate. Based on these reference values, the warm-up physics model calculates the temperature of the exhaust gas flowing into the catalyst 17a, the balance of heat due to heat exchange with the engine block and the exhaust passage 17, the heat of reaction of the catalyst 17a, etc. The warm-up physics model calculates the warm-up determination temperature based on these calculated values.

[0019] The warm-up physical model assumes that the catalyst 17a is in a deteriorated state. In other words, the reaction coefficients, maps, and the like used in the warm-up physical model are set assuming that the catalyst 17a is in a deteriorated state. When the catalyst 17a is in a deteriorated state, the heat of reaction is lower than when it is new. Therefore, when the catalyst 17a is not actually in a deteriorated state, the warm-up determination temperature is calculated to be lower than the actual temperature. As a result, when the warm-up determination temperature becomes the warm-up determination threshold, it is considered that the actual temperature is higher than the warm-up determination threshold. In this way, the warm-up determination temperature is calculated to be higher. As a result, it is avoided to determine that warm-up is complete when the actual temperature is below the warm-up determination threshold, and the effectiveness of the warm-up is ensured.

[0020] Next, the ECU 30 calculates a reference temperature of the catalyst 17a, which is used to calculate an overheating determination temperature, which will be described later (step S2). The reference temperature is a predicted temperature of the catalyst 17a when the ignition timing is assumed to be retarded by zero from the MBT (Minimum Advance for the Best Torque) ignition timing. In other words, the reference temperature is a predicted temperature of the catalyst 17a when the ignition timing is assumed to be the MBT ignition timing. The reference temperature is calculated using a reference physical model. The reference physical model refers to, for example, the MBT ignition timing, the current target equivalence ratio, the fuel injection amount, the intake air amount, the engine speed, the EGR rate, and the like. Based on these reference values, the reference physical model calculates the temperature of the exhaust gas flowing into the catalyst 17a when the ignition timing advance amount is zero, the heat balance due to heat exchange with the engine block and the exhaust passage 17, the heat of reaction of the catalyst 17a, and the like. The reference physical model calculates the reference temperature based on these calculated values.

[0021] The reference physical model assumes that the catalyst 17a is in a brand new state. That is, the reaction coefficients, maps, etc. used in the reference physical model are set assuming that the catalyst 17a is in a brand new state. When the catalyst 17a is in a brand new state, the heat of reaction is higher than when the catalyst 17a is in a deteriorated state. Step S2 is an example of processing executed by the reference temperature calculation unit.

[0022] Next, the ECU 30 determines whether or not there is a request to retard the ignition timing (step S3). A request to retard the ignition timing may be made, for example, when upshifting the transmission, but is not limited to this.

[0023] If the answer to step S3 is Yes, the ECU 30 calculates the amount of retardation of the ignition timing (step S4). The amount of retardation is the amount of retardation of the ignition timing based on the MBT ignition timing, as described above. Step S4 is an example of processing executed by the retardation amount calculation unit.

[0024] Next, ECU 30 calculates the temperature rise of catalyst 17a when the ignition timing is retarded by the calculated retard amount (step S5). The temperature rise of catalyst 17a reflects the expected increase in temperature of exhaust gas flowing into catalyst 17a when the ignition timing is retarded by the calculated retard amount, and the temperature rise due to the combustion reaction of unburned gas in catalyst 17a. Specifically, the temperature rise of catalyst 17a is calculated using a map or an arithmetic formula that defines the temperature rise of catalyst 17a according to the retard amount of ignition timing, the intake air amount, and the engine speed. The greater the retard amount, the greater the intake air amount, and the higher the engine speed, the higher the calculated temperature rise.

[0025] The calculation formula for the temperature rise is based on the assumption that the catalyst 17a is in a brand new state. When the catalyst 17a is in a brand new state, the temperature rise is higher than when the catalyst 17a is in a deteriorated state. The calculation of the temperature rise is performed immediately after the calculation of the retard amount, regardless of the crank angle. Step S5 is an example of processing performed by the temperature rise calculation unit.

[0026] Next, the ECU 30 calculates the temperature for determining whether the catalyst 17a is overheating by adding the calculated rising temperature to the calculated reference temperature (step S6). As described above, the reference temperature and the rising temperature are calculated assuming that the catalyst 17a is in a brand new condition. Therefore, the temperature for determining whether the catalyst 17a is overheating is calculated to be higher than the temperature of the catalyst 17a that would be obtained if the ignition timing were retarded by the actually calculated retard amount. The calculation of the temperature for determining whether the catalyst 17a is overheating is performed immediately after the calculation of the rising temperature, regardless of the crank angle. Step S6 is an example of processing performed by the temperature calculation unit for determining whether the catalyst 17a is overheating.

[0027] Next, the ECU 30 predicts whether the catalyst 17a will overheat based on the overheat determination temperature (step S7). Specifically, if the overheat determination temperature is equal to or higher than the overheat determination threshold, it is predicted that the catalyst 17a will overheat. As described above, the overheat determination temperature is calculated to be higher than the temperature of the catalyst 17a when the ignition timing is actually retarded by the calculated retard amount. As a result, if the catalyst 17a is not in a brand new condition, the overheat determination temperature is calculated to be lower than the temperature of the catalyst 17a when the ignition timing is actually retarded. As a result, it is possible to avoid predicting that overheating will not occur when there is actually a risk of overheating.

[0028] The prediction of whether the catalyst 17a will overheat is performed immediately after the calculation of the overheat determination temperature, regardless of the crank angle. Step S7 is an example of processing performed by the prediction unit. When the overheat determination temperature and the above-mentioned warm-up determination temperature are calculated under the same operating conditions of the engine 10, the overheat determination temperature is calculated to be higher than the warm-up determination temperature.

[0029] If the answer to step S7 is Yes, the ECU 30 calculates an increase in the fuel injection amount to suppress excessive temperature rise of the catalyst 17a based on the calculated temperature rise (step S8). The larger the temperature rise, the larger the calculated increase in the fuel injection amount. The increase in the fuel injection amount is calculated immediately after it is predicted that the catalyst 17a will excessively rise in temperature, regardless of the crank angle. The calculation of the increase is performed before the end timing of the period in which fuel injection is possible immediately after a request to retard the ignition timing is made, and without depending on the crank angle. This allows the increase to be reflected in the fuel injection immediately after the retard request, as will be described later. Step S8 is an example of processing performed by the increase calculation unit.

[0030] Next, ECU 30 executes fuel injection with a fuel injection amount that reflects the increase (step S9). For example, if the fuel injection start timing occurs immediately after the calculation of the increase, the fuel injection that reflects the increase is realized from that fuel injection. Furthermore, if the calculation of the increase occurs during fuel injection, the fuel injection that reflects the increase may be realized by extending the valve opening time of the in-cylinder injection valve 13 during injection by a predetermined time corresponding to the increase. Furthermore, if multiple fuel injections are possible during one cycle, the fuel injection that reflects the increase may be realized by an additional injection corresponding to the increase after the end of regular injection. For example, regular injection may be started at 300° CA BTDC, and the additional injection may be started between 150° and 120° CA BTDC. Step S9 is an example of processing executed by the control unit.

[0031] Next, the ECU 30 ignites the air-fuel mixture at an ignition timing that reflects the calculated retard amount (step S10). Step S10 is an example of processing that the control unit executes. As described above, the increase in the fuel injection amount is calculated immediately after a retard request is made, and fuel injection that reflects the increase is executed. This prevents the catalyst 17a from overheating, thereby suppressing the progression of deterioration. Note that if the answer is No in step S3 or S7, fuel injection and ignition are executed without calculating the increase amount (steps S9 and S10).

[0032] As described above, the overheating determination temperature is calculated (step S6) by adding the rising temperature calculated based on the amount of retard after the retard request (step S5) to the reference temperature (step S2) already calculated before the retard request. That is, after the retard request, the overheating determination temperature can be calculated by calculating only the rising temperature. For example, the overheating determination temperature is calculated earlier than when both the reference temperature and the rising temperature are calculated after the retard request. As a result, the increase in the fuel injection amount is also calculated earlier, and fuel injection that reflects the increase can be easily achieved after the retard amount is calculated.

[0033] The calculation of the reference temperature when the rotation of the engine 10 is temporarily stopped will be described. For example, when the rotation of the engine 10 is temporarily stopped due to the idling stop function, air in the exhaust passage 17 flows backward. As a result, the temperature of the portion of the exhaust passage 17 downstream of the catalyst 17a affects the temperature of the portion of the exhaust passage 17 upstream of the catalyst 17a. The temperature of the portion of the exhaust passage 17 upstream of the catalyst 17a affects the temperature of the catalyst 17a. Therefore, when the rotation of the engine 10 is temporarily stopped, the physical model that calculates the reference temperature calculates the reference temperature taking into account the temperature of the portion of the exhaust passage 17 downstream of the catalyst 17a. As a result, the reference temperature is calculated accurately even while the rotation of the engine 10 is temporarily stopped, and the reference temperature is also calculated accurately after the engine 10 is restarted.

[0034] The vehicle 1 is an engine vehicle equipped with only the engine 10 as a power source for running, but is not limited to this. The vehicle 1 may also be, for example, a hybrid vehicle equipped with a motor in addition to the engine 10 as a power source for running. In a hybrid vehicle, the reference temperature may be calculated taking into account the temperature of the exhaust passage 17 downstream of the catalyst 17a while the rotation of the engine 10 is temporarily stopped and the vehicle is running on the motor.

[0035] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0036] 1 vehicle 10 Engine 17a Catalyst 30 ECU (control device, reference temperature calculation unit, retardation amount calculation unit, rising temperature calculation unit, overheating determination temperature calculation unit, prediction unit, increase calculation unit, control unit, warm-up determination temperature calculation unit)

Claims

1. A control device for an engine in which exhaust gas is purified by a catalyst, a reference temperature calculation unit that calculates a reference temperature of the catalyst that is assumed when the amount of retardation of the ignition timing is zero before a request for retardation of the ignition timing is received; a delay amount calculation unit that calculates a required amount of delay of the ignition timing when the delay request is made; a temperature rise calculation unit that calculates an expected temperature rise of the catalyst when the ignition timing is retarded by the calculated retard amount; an overheating determination temperature calculation unit that calculates, based on the reference temperature and the increased temperature, a temperature for determining whether the catalyst will overheat when the ignition timing is retarded by the retard amount; and a prediction unit that predicts whether the catalyst will overheat based on the overheat determination temperature; an increase calculation unit that calculates, when it is predicted that the catalyst will overheat, an increase in fuel injection amount for suppressing a temperature rise of the catalyst due to retarding the ignition timing by the retard amount after the retard request and before the end timing of a period in which fuel injection is possible immediately after the retard request, without depending on a crank angle; a control unit that executes fuel injection with a fuel injection amount that reflects the increased amount during the fuel injection possible period, and ignites the air-fuel mixture with an ignition timing that reflects the retard amount; An engine control device comprising:

2. 2. The engine control device according to claim 1, wherein the overheating determination temperature calculation unit calculates the overheating determination temperature assuming that the catalyst is in a brand new state.

3. a warm-up determination temperature calculation unit that calculates a warm-up determination temperature of the catalyst used to determine whether warm-up of the catalyst has been completed; 3. The engine control device according to claim 2, wherein the warm-up determination temperature calculation unit calculates the warm-up determination temperature assuming that the catalyst is in a deteriorated state.

4. the reference temperature calculation unit calculates the reference temperature based on a temperature of exhaust gas flowing into the catalyst that is assumed when the retard amount is zero; 4. The engine control device according to claim 3, wherein the rising temperature calculation unit calculates the rising temperature based on an estimated temperature of exhaust gas flowing into the catalyst when the ignition timing is retarded by the calculated retard amount.

5. 5. The engine control device according to claim 4, wherein the reference temperature calculation unit calculates the reference temperature taking into account the temperature of the exhaust passage downstream of the catalyst when the engine is temporarily stopped.

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