Engine control device

Abstract

An engine control device (20) for controlling an internal combustion engine (12) comprising a fuel injector (40) configured to supply fuel to a cylinder and a throttle valve (38) disposed in an intake air passage (34), comprising: a processor (26a); an air flow sensor (52) disposed in the intake air passage (34) upstream of the throttle valve (20) and configured to detect an intake air flow rate; and a throttle position sensor (54) configured to detect a throttle opening degree (TA) of the throttle valve (38), wherein the processor (26a) is arranged to execute a fuel injection control comprising: a first fuel injection timing controller (F1) for controlling the fuel injector (40) to inject a fuel amount in accordance with a first intake air amount based on the intake air flow rate detected by the air flow sensor (52); and a second fuel injection timing controller (F2) for controlling the fuel injector (40) to inject an amount of fuel in accordance with a second intake air amount based on the throttle opening degree (TA) detected by the throttle position sensor (54), wherein the processor (26a) is configured to: Selecting the first fuel injection control sequence (F1) when a pulsation rate (Rp), which is a fluctuation rate of a pulsation of the intake air flow rate detected by the air flow sensor (52), is equal to or less than a pulsation rate threshold value (THp); and Selecting the second fuel injection timing control (F2) when the pulsation rate (Rp) is higher than the pulsation rate threshold (THp), wherein the pulsation rate threshold value (THp) is smaller when a temperature correlation value correlating with a temperature (Tw) of the internal combustion engine is low than when the temperature correlation value is high.

Description

Background of the inventionTechnical field

[0001] The present invention relates to an engine control device, and more particularly to an engine control device for controlling a spark-ignition internal combustion engine. State of the art

[0002] JP H06-307273 A discloses a fuel injection control device for an internal combustion engine. The internal combustion engine is provided with a connecting passage and a secondary air supply device. The connecting passage is configured to connect an intake air passage and an exhaust passage while bypassing a cylinder. The secondary air supply device is configured to supply a portion of intake air as secondary air for exhaust gas purification to the exhaust passage through the connecting passage. In addition, when the pulsation of the intake air propagating to an airflow sensor through the intake air passage resonates with the pulsation of the secondary air propagating to the airflow sensor through the connecting passage in conjunction with the supply of the secondary air, and the secondary air is detected, an intake air amount used to calculate a fuel injection amount is switched as follows.That is, switching is performed from an intake air amount based on the output of the air flow sensor to an intake air amount based on a throttle opening degree and an engine speed.

[0003] Furthermore, JP 2017-186965 A discloses the following technique. That is, in order to reduce the number of particulates (PN: particle number) in exhaust gas, the ignition timing during intake stroke injection by a fuel injection valve in the cylinder is retarded by a larger amount when the piston temperature is equal to or lower than a predetermined temperature than when the piston temperature is higher than the predetermined temperature. The ignition timing is also retarded by a larger amount when the piston temperature is equal to or lower than the predetermined temperature and the intake air amount is equal to or lower than a predetermined amount, compared to the MBT (Minimum Ignition Advance for Best Torque) ignition timing.

[0004] In addition, JP 2008 - 202 534 A shows a technique for controlling a drive timing of an in-cylinder fuel injection valve based on an intake air pulsation.

[0005] Furthermore, DE 101 55 744 B4 and DE 10 2004 019 864 B4 describe methods and systems for controlling fuel injection in cylinders of an internal combustion engine. Summary of the invention

[0006] As a method of calculating a fuel injection amount, a method that uses an intake air amount (first intake air amount) based on the output of an airflow sensor arranged upstream of a throttle valve (first calculation method) and a method that uses an intake air amount (second intake air amount) based on a throttle opening degree (second calculation method) are known. According to the first calculation method that uses the first intake air amount, which is more directly detected, under transient operating conditions where engine torque (i.e., actual intake air amount) changes with time, the intake air amount is easily obtained with high accuracy compared to the second calculation method. However, under high engine load conditions where the throttle opening degree is large, intake air pulsation easily reaches the position of the airflow sensor.Therefore, under high engine load conditions, the output of the airflow sensor (i.e., the intake air flow rate) and the first intake air quantity based on the output are easily pulsated due to the influence of intake air pulsation, and as a result, the controllability of an air-fuel ratio may decrease. On the other hand, the second calculation method has an advantage in that the second intake air quantity can be calculated (estimated) without being affected by intake air pulsation.

[0007] Accordingly, for fuel injection control, the first calculation method may be used when the pulsation rate, which is the fluctuation rate of the pulsation of the intake air flow rate detected by the air flow sensor, is equal to or less than a pulsation rate threshold. Also, the second calculation method may be used when the pulsation rate is higher than the pulsation rate threshold. On the other hand, the particulate number PN increases when the temperature of the internal combustion engine (typically an engine water temperature) is low and the engine load is high. Therefore, if the first calculation method is used even under high load conditions at low temperatures, the particulate number PN may increase when the air-fuel ratio fluctuates toward the rich side, where the particulate number PN increases (that is, when the first intake air amount is used for a long time).Therefore, it is necessary that the pulsation rate threshold is set appropriately, taking into account also this type of particle number PN properties.

[0008] The present invention has been made in view of the above-mentioned problem, and it is an object of the present invention to provide an engine control device that can achieve fuel injection control capable of appropriately selecting either the first intake air amount or the second intake air amount based on the pulsation rate while reducing an increase in the particulate number PN.

[0009] An engine control device according to the present invention for controlling an internal combustion engine including a fuel injector configured to supply fuel to a cylinder and a throttle valve disposed in an intake air passage, comprising: a processor; an airflow sensor disposed in the intake air passage upstream of the throttle valve and configured to detect an intake airflow rate; and a throttle position sensor configured to detect a throttle opening degree of the throttle valve.The processor is configured to execute fuel injection control, including: a first fuel injection timing control for controlling the fuel injector to inject an amount of fuel in accordance with a first intake air amount based on the intake air flow rate detected by the air flow sensor; and a second fuel injection timing control for controlling the fuel injector to inject an amount of fuel in accordance with a second intake air amount based on the throttle opening degree detected by the throttle position sensor.The processor is configured to: select the first fuel injection timing when a pulsation rate, which is a fluctuation rate of a pulsation of the intake airflow rate detected by the airflow sensor, is equal to or less than a pulsation rate threshold; and select the second fuel injection timing when the pulsation rate is higher than the pulsation rate threshold. The pulsation rate threshold is lower when a temperature correlation value, which correlates with a temperature of the internal combustion engine, is low than when the temperature correlation value is high.

[0010] The pulsation rate threshold may be corrected to be larger when a torque increase rate, which is a time rate of increase of a torque of the internal combustion engine, is high than when the torque increase rate is low.

[0011] The pulsation rate threshold may be corrected to be smaller when engine torque is high than when the torque is low.

[0012] The engine control device may be mounted on a hybrid vehicle including an internal combustion engine, an electric motor, and a generator, and may have a series hybrid mode in which all of the driving force of the internal combustion engine is used to drive the generator to generate electrical power, and a wheel of the vehicle is driven by the electric motor. The pulsation rate threshold may include a first pulsation rate threshold selected when the temperature correlation value is equal to or greater than a temperature threshold, and a second pulsation rate threshold selected when the temperature correlation value is less than the temperature threshold. The second pulsation rate threshold is less than the first pulsation rate threshold.The processor may be configured to execute the subsequent torque increase rate limiting scheduling while selecting the second pulsation rate threshold. The torque increase rate limiting scheduling limits a torque increase rate, which is a time rate of increase in engine torque, to be lower than during selection of the first pulsation rate threshold during at least a portion of a torque increase period from the time the pulsation rate reaches the second pulsation rate threshold and while switching to the second fuel injection scheduling is performed until the engine torque reaches a target torque.

[0013] The engine control device may include an air-fuel ratio sensor configured to output a signal responsive to an oxygen concentration of an exhaust gas. The processor may be configured to perform air-fuel ratio feedback control to control a fuel injection amount such that an actual air-fuel ratio approaches a target air-fuel ratio based on the output of the air-fuel ratio sensor. In the torque increase rate limiting scheduling, the processor may be configured to limit the torque increase rate to a small value by adjusting the throttle opening degree such that a width of a fluctuation in the actual air-fuel ratio associated with the air-fuel ratio feedback control falls to a fluctuation width threshold during at least a portion of the torque increase period.

[0014] According to the engine control device of the present invention, when the temperature correlation value correlated with the temperature of the internal combustion engine is low, a pulsation rate threshold is used that is smaller than that when the temperature correlation value is high. By lowering the pulsation rate threshold at low temperatures in this way, switching to the second fuel injection timing control that does not use the first intake air amount can be performed before the pulsation of the first intake air amount becomes excessive. This makes it possible to achieve fuel injection control capable of appropriately selecting either the first intake air amount or the second intake air amount based on the pulsation rate while reducing an increase in the particulate number PN. Brief description of the drawings Fig. 1 is a schematic diagram showing an example of a configuration of a powertrain system of a vehicle to which an engine control device according to a first embodiment of the present invention is applied; Fig. 2 is a schematic diagram showing an example of a configuration of an internal combustion engine used in Fig. 1 is shown; Fig. 3 is a graph showing a relationship of a particle number PN with respect to an engine water temperature Tw and an engine torque TQ; Fig. 4 is a timing chart of a reference example for explaining an aspect related to switching of the fuel injection timing; Fig. 5 is a graph showing a relationship between three threshold values ​​THpN, THpL1 and THpL2 used in the first embodiment and the engine water temperature Tw; Fig. Fig. 6 is a graph schematically showing an example of an engine operating characteristic L used in the internal combustion engine shown in Fig. 1 is shown; Fig. 7A is a graph showing an example of a relationship between a torque increase rate ΔTQ and a correction coefficient K ΔTQ shows; Fig. 7B is a graph showing an example of a relationship between the engine torque TQ and a correction coefficient K TQ shows; Fig. 8 is a flowchart showing a routine of processing related to fuel injection control according to the first embodiment; Fig. 9 is a timing chart used to describe the effect of setting a pulsation rate threshold THp according to the first embodiment; Fig. 10 is a timing chart used to describe the effect of setting the pulsation rate threshold THp according to the first embodiment; Fig. 11 is a graph showing another example of setting the pulsation rate threshold THp; Fig. 12 is a time chart used to describe fuel injection control accompanied by torque increase rate limiting processing according to a second embodiment of the present invention; Fig. 13 is a flowchart showing a routine of processing related to fuel injection control accompanied by the torque increase rate limiting processing according to the second embodiment; Fig. 14 is a time chart used to describe fuel injection control accompanied by torque increase rate limiting processing according to a third embodiment of the present invention; and Fig. 15 is a flowchart showing a routine of processing related to the engine injection control accompanied by the torque increase rate limiting processing according to the third embodiment. Detailed description

[0015] In the following embodiments of the present invention, it is to be understood that even if the number, amount, scope, range, or other numerical characteristic of an element is mentioned in the following description of the embodiments, the present invention is not limited to the mentioned numerical characteristic unless explicitly described otherwise, or unless the present invention is explicitly theoretically defined by the numerical characteristic. Furthermore, structures or steps or the like described in connection with the following embodiments are not necessarily essential to the present invention unless explicitly shown otherwise, or unless the present invention is explicitly theoretically defined by the structures, steps, or the like. 1. First embodiment

[0016] A first embodiment according to the present invention and its modified examples will be described with reference to the Fig. 1 to 11 described. 1-1. Powertrain system configuration example

[0017] Fig. 1 is a schematic diagram showing an example of the configuration of a powertrain system 10 of a vehicle using an engine control device according to the first embodiment. The powertrain system 10 shown in Fig. 1 includes an internal combustion engine 12, two motor generators 14 and 16 (hereinafter referred to as "MG1" and "MG2"), a battery (DC power supply) 18 configured to store electrical energy supplied to the MG2, and a control device 20. The internal combustion engine 12 is a power generation engine coupled to the MG1. The MG1 is driven by the motive power of the internal combustion engine 12 to generate electrical energy. The generated electrical energy is supplied to the battery 18. The MG2 uses the electrical energy supplied from the battery 18 to drive the vehicle (wheels 22). The powertrain system 10 is also configured to charge the battery 18 with electrical energy supplied from outside the vehicle via a connector 24.

[0018] The vehicle on which the powertrain system 10 having the above-described configuration is mounted corresponds to a so-called REEV (Range Extended Electric Vehicle). More specifically, the REEV is used as a BEV (Battery Electric Vehicle) that is driven by the MG2 using only the electric power stored in the battery 18 at the start of the vehicle until the remaining amount of the battery (i.e., the state of charge (SOC) indicating the rate of charge of the battery 18) falls below a predetermined lower limit. In addition, when the SOC falls below the lower limit, the battery 18 is charged with the electric power generated using the motive power of the internal combustion engine 12 to increase the driving range.Therefore, an internal combustion engine that has a small engine displacement relative to the vehicle (mainly relative to the size and weight of the vehicle) is generally used as the internal combustion engine mounted on the REEV, such as the internal combustion engine 12. The REEV can also be classified as a type of plug-in hybrid electric vehicle (PHEV).

[0019] The internal combustion engine 12 is operated by the supply of fuel. More specifically, the internal combustion engine 12 is a spark-ignition engine, and is, for example, an inline three-cylinder engine. Fig. 2 is a schematic diagram showing an example of the configuration of the internal combustion engine 12 used in Fig. 1. The internal combustion engine 12 is, for example, a naturally aspirated engine, but may be configured as a supercharged engine. In each cylinder 30, a piston 32 is arranged, which is reciprocated within the corresponding cylinder 30. A combustion chamber 30a of each cylinder 30 is connected to an intake air passage 34 and an exhaust passage 36. An electronically controlled throttle valve 38 is arranged in the intake air passage 34 for intake air quantity control. The internal combustion engine 12 also includes a fuel injector 40 (only a fuel injector is shown) and an ignition device 42 (only a spark plug is shown). In the Fig. 2, the fuel injector 40 includes a port fuel injector for injecting fuel into an intake port 34a, but may include an in-cylinder fuel injector instead of or in addition to the port fuel injector.

[0020] A control device 20 is configured to control the internal combustion engine 12 (including the throttle valve 38, the fuel injector 40, and the ignition device 42), the MG1, and the MG2. The MG1 and the MG2 are, for example, of a three-phase AC type. The control device 20 includes an electronic control unit (ECU) 26 and power control units (PCUs) 28 and 29. The PCUs 28 and 29 each include a power converter (i.e., an inverter) equipped with a plurality of switching elements. The PCU 28 controls the MG1 based on a command from the ECU 26, and the PCU controls the MG2 based on a command from the ECU 26. The MG1 also functions as a starter motor to crank the internal combustion engine 12.

[0021] The ECU 26 includes at least one processor 26a and at least one memory 26b. The memory 26b stores various data, including maps used to control the internal combustion engine 12, the MG1, and the MG2, and also stores various control programs. The processor 26 receives a control program from the memory 26b and executes it, thereby achieving various types of control sequences and control by the control device 20.

[0022] The control device 20 further comprises sensors 50 for controlling the operation of the powertrain system 10. The sensors 50 comprise an air flow sensor 52, a throttle position sensor 54, a crank angle sensor 56, a water temperature sensor 58 and an air-fuel ratio sensor 60, which are Fig. 2 as sensors related to engine control. The air flow sensor 52 is arranged at an inlet (i.e., on the upstream side of the throttle valve 38) of the intake air passage 34 to detect an intake air flow rate. The air flow sensor 52 is, for example, of a hot wire type. However, as long as the output (intake air flow rate) pulsates due to the influence of intake air pulsation, an air flow sensor of a type other than a hot wire type may be used. The throttle position sensor 54 detects an opening degree of the throttle valve 38 (throttle opening degree TA). The crank angle sensor 56 is arranged near a crankshaft 62 and outputs a signal responsive to the crank angle. The ECU 26 calculates an engine speed NE based on the signal from the crank angle sensor 56.The water temperature sensor 58 outputs a signal responsive to an engine cooling water temperature (engine water temperature) Tw. The air-fuel ratio sensor 60 outputs a signal responsive to an oxygen concentration of an exhaust gas flowing through the exhaust passage 36. The ECU 26 obtains (calculates) the air-fuel ratio based on the output of the air-fuel ratio sensor 60.

[0023] Note that, in the example of the powertrain system 10, the control device 20 corresponds to an example of the "engine control device" according to the present invention and is configured to control not only the internal combustion engine 12 but also the MG1 and the MG2. However, instead of this type of example, the engine control device may be configured to control only the internal combustion engine 12. More specifically, the control device provided in the powertrain system 10 may include, for example, an engine control device that includes an engine ECU that controls the internal combustion engine 12 separately from a hybrid ECU, a generator ECU, and a motor ECU. The hybrid ECU controls the powertrain system 10 comprehensively. The generator ECU controls the MG1. The motor ECU controls the MG2. 1-2. Fuel injection control

[0024] The control of the powertrain system 10 performed by the ECU 26 includes fuel injection control of the internal combustion engine 12. The fuel injection control includes a "first fuel injection timing control" and a "second fuel injection timing control." The ECU 26 (the processor 26a) selectively performs the first fuel injection timing control and the second fuel injection timing control, as described below. 1-2-1. First fuel injection timing and second fuel injection timing

[0025] The first fuel injection control schedule uses an intake air amount (hereinafter referred to as a "first intake air amount") [g] calculated based on the intake air flow rate [g / s] detected by the air flow sensor 52, and controls the fuel injector 40 so that a fuel amount is injected in accordance with the first intake air amount. Specifically, the first intake air amount can be calculated based on the above-described intake air flow rate and the engine speed NE. According to the first fuel injection control schedule, the fuel injection amount (basic injection amount) is calculated so that a target air-fuel ratio (for example, a stoichiometric air-fuel ratio) can be obtained according to the first intake air amount.

[0026] On the other hand, the second fuel injection control process uses an intake air amount (hereinafter referred to as a "second intake air amount") based on the throttle opening degree TA detected by the throttle position sensor 54, and controls the fuel injector 40 so that an amount of fuel is injected in accordance with the second intake air amount. The second intake air amount may be calculated based only on the throttle opening degree TA, but here, for example, it is calculated (estimated) based on the throttle opening value TA and the engine speed NE. More specifically, the second intake air amount is calculated, for example, from a map (not shown) that defines the relationship of the second intake air amount with respect to the throttle opening degree TA and the engine speed NE. (Correction sequence control of the second intake air quantity)

[0027] The second intake air amount calculated as described above is an estimated value (a predicted value) of the intake air amount based on the throttle opening degree TA and the engine speed NE. According to the present embodiment, the ECU 26 performs a correction processing of the second intake air amount in order to obtain the second intake air amount with higher accuracy. More specifically, in this correction processing, the second intake air amount calculated from the map as a value in accordance with the throttle opening degree TA and the engine speed NE as described above is used as its base value. Then, this base value is corrected using a correction coefficient K afcorrected depending on the difference or ratio of the "actual air-fuel ratio" to the target air-fuel ratio (e.g., the stoichiometric air-fuel ratio). The actual air-fuel ratio mentioned here is a calculated value of the air-fuel ratio based on the output of the air-fuel ratio sensor 60.

[0028] The following equation (1) corresponds to an example of an equation for calculating the second intake air quantity with a correction by the correction flow control. In equation (1), a value obtained by dividing the actual air-fuel ratio by the target air-fuel ratio (ie, the actual air-fuel ratio / the target air-fuel ratio) is used as the correction coefficient K. af According to this type of correction sequence control, the correction coefficient K afgreater than 1 when the actual air-fuel ratio is smaller than the target air-fuel ratio (i.e., when the actual air-fuel ratio is shifted toward the rich side). Therefore, the second intake air amount is corrected to be larger than the base value. Conversely, when the actual air-fuel ratio is larger than the target air-fuel ratio (i.e., when the air-fuel ratio is shifted toward the lean side), the correction coefficient K af less than 1. Therefore, the second intake air quantity is corrected to be less than the base value. Second intake air quantity=base value×Kaf (Air-fuel ratio control)

[0029] The ECU 26 performs air-fuel ratio control under the condition that a certain execution condition is satisfied during execution of the first or second fuel injection control process. Air-fuel ratio control is generally performed in an internal combustion engine, and its detailed description will be omitted. The brief description of air-fuel ratio control is to adjust the fuel injection amount so that the actual air-fuel ratio obtained using the air-fuel ratio sensor 60 approaches the target air-fuel ratio (e.g., the stoichiometric air-fuel ratio).Accordingly, the fuel injection amount (basic injection amount) calculated by the first or second fuel injection timing control is corrected by the air-fuel ratio control, and the corrected fuel amount is injected by the fuel injector 40. 1-2-2. Switching a fuel injection sequence control based on a pulsation rate Rp

[0030] According to the method of calculating the fuel injection amount (i.e., the first calculation method) using the first intake air amount based on the output of the air flow sensor 52, the intake air amount can be detected more promptly. Therefore, under transient operating conditions where the engine torque (i.e., the actual intake air amount) changes over time, the intake air amount can be obtained with high accuracy compared to the method (second calculation method) using the second intake air amount based on the throttle opening degree TA. However, under high engine load conditions, the first intake air amount pulsates simply due to the influence of intake air pulsation.The reason is that under high engine load conditions, the throttle opening degree TA is large, and as a result, the intake air pulsation easily reaches the air flow sensor 52 located on the upstream side of the throttle valve 38. On the other hand, the second calculation method has an advantage that the intake air amount can be calculated (estimated) without being affected by the intake air pulsation.

[0031] In view of the above, the ECU 26 selects the first fuel injection timing when a pulsation rate Rp, which is the fluctuation rate of the pulsation of the intake air flow rate detected by the air flow sensor 52, is equal to or lower than a predetermined pulsation rate threshold (simply referred to as a "threshold THp"), and selects the second fuel injection timing when the pulsation rate Rp is higher than the threshold THp. The pulsation rate Rp [%] can be calculated, for example, using the following equation (2). The ECU 26 calculates the pulsation rate Rp for each cycle of the internal combustion engine 12. Rp=(Qmax-Qmin) / Qave×100

[0032] In equation (2), Qmax and Qmin are the maximum and minimum amplitude values ​​of the output signal of the airflow sensor 52 (i.e., the airflow rate signal) during the most recent predetermined crank angle period (e.g., a predetermined plurality of cycles). Qave is an average value of the airflow rate signals during the predetermined crank angle period described above. 1-2-3. Aspect of switching a fuel injection sequence control

[0033] Fig. Figure 3 is a graph showing a relationship between the particle number PN and the engine water temperature Tw and the engine torque TQ. As shown in Fig. As shown in FIG. 3, the particulate number PN increases when the temperature of the internal combustion engine 12 (typically, the engine water temperature Tw) is low and the engine torque TQ [Nm] (i.e., the engine load) is high. Specifically, the particulate number PN increases as the engine water temperature Tw is lower, and also increases as the engine load is higher. Specifically, in a water temperature range lower than normal temperature (for example, 20°C), the degree of increase in the particulate number PN with respect to the decrease in the engine water temperature Tw becomes remarkably high.

[0034] Fig. 4 is a time chart of a reference example for explaining an aspect of switching the engine injection timing. Fig. Figure 4 illustrates operation under a transient condition where it is desired to rapidly increase engine torque TQ to a high load range. For the REEV, this type of transient condition corresponds, for example, to the startup of the internal combustion engine 12, as described below. Fig. 6. It should be noted that in the reference example shown in Fig. 4, a fixed value is used as the threshold THp of the pulsation rate Rp.

[0035] When the intake air flow rate detected by the air flow sensor 52 pulsates, the first intake air quantity also pulsates. Specifically, when the engine torque TQ (i.e., the engine load) increases, the amplitude of the pulsation of the intake air flow rate increases. As a result, the amplitude of the pulsation of the first intake air quantity increases, as shown in Fig. 4, and thus the pulsation rate Rp increases. A time point t0 corresponds to the time point at which switching from the first engine injection timing to the second engine injection timing is performed in response to the pulsation rate Rp reaching the threshold value THp.

[0036] It should be noted that the first and second intake air quantities are calculated values ​​used to calculate the fuel injection quantity. On the other hand, the intake air quantity indicated by a dashed line in Fig. 4, an actual intake air quantity. In addition, Fig. 4 that after switching to the second fuel injection timing control, the above-described correction timing of the second intake air amount causes the second intake air amount to converge toward the actual intake air amount (dashed line) and also causes the actual air-fuel ratio based on the output of the air-fuel ratio sensor 60 to approach the stoichiometric air-fuel ratio. Furthermore, Fig. 4, that after switching to the second fuel injection timing control, the air-fuel ratio control causes the actual air-fuel ratio to fluctuate around the stoichiometric air-fuel ratio.

[0037] As described above, the first calculation method is more suitable for the transient operating condition than the second calculation method. Therefore, considering the transient condition in which it is desired to rapidly increase the engine torque TQ to a high load range, as in the case shown in Fig. 4, it is desirable to increase the threshold value THp as much as possible to use the first calculation method as long as possible while the engine torque TQ increases. However, as the engine load increases, the pulsation of the first intake air quantity increases. As a result, the controllability of the actual air-fuel ratio gradually decreases (i.e., the fluctuation range of the actual air-fuel ratio gradually increases), as in a period before time t0 in Fig. 4, in conjunction with an increase in the pulsation of the first intake air quantity. When the actual air-fuel ratio is shifted to the rich side, if the controllability of the actual air-fuel ratio is reduced in this way (that is, after the fluctuation range of the actual air-fuel ratio increases), there is a fear that the particle number PN may increase. Then, as described with reference to Fig. As described in Section 3, the particle number PN is significantly high at low water temperatures. Therefore, the influence of the above-described rich change in the actual air-fuel ratio on the increase in the particle number PN becomes large at low water temperatures.

[0038] In addition, the internal combustion engine 12 for the REEV has a small engine displacement relative to the vehicle (the size of the vehicle) as described above, and high loads are likely to be used frequently. Thus, the internal combustion engine employing the fuel injection control according to the first embodiment cannot always be used for the REEV, but the above-described aspect becomes notable in the REEV. Furthermore, the internal combustion engine 12 is an in-line three-cylinder engine. In internal combustion engines having four or more cylinders in line, the opening angle of the intake valve partially overlaps between the cylinders, which has the effect of reducing intake air pulsation.Conversely, in the inline three-cylinder engine with a large combustion pitch, the effect of reducing intake air pulsation cannot be achieved because the intake valve opening angles do not overlap among the cylinders. Therefore, in the inline three-cylinder engine, the airflow sensor output is more likely to be affected by intake air pulsation than in an engine with four or more inline cylinders. The above-described aspect also becomes noticeable in the internal combustion engine 12 from this perspective. 1-2-4. Setting a pulsation rate threshold taking into account a reduction of an increase in PN

[0039] In view of the above-described aspect, according to the present embodiment, the threshold value THp of the pulsation rate Rp is reduced when the engine water temperature Tw is low than when the engine water temperature Tw is high. Note that, according to the present embodiment, the engine water temperature Tw corresponds to an example of the "temperature correlation value correlated with the temperature of the internal combustion engine" according to the present invention.

[0040] Fig. 5 is a graph showing a relationship between three threshold values ​​THpN, THpL1, and THpL2 used in the first embodiment and the engine water temperature Tw. According to the present embodiment, three threshold values ​​THpN, THpL1, and THpL2 are used as the threshold values ​​THp. The threshold value THpN is used when the engine water temperature Tw is equal to or higher than a temperature threshold value THt1. This temperature threshold value Tht1 is, for example, a normal temperature (about 20-25°C). That is, the threshold value THpN is used when the engine water temperature Tw is in a water temperature range of the normal temperature or higher (i.e., in the normal state). In this type of normal state, as shown in Fig. 3, the particle number PN is comparatively low.

[0041] On the other hand, the remaining thresholds THpL1 and THpL2 are set to be lower than the threshold THpN and are used at low water temperatures lower than the temperature threshold THt1 (i.e., normal temperature). Furthermore, the threshold THpL2 is set to be even lower than the threshold THpL1 and is used at extremely low temperatures where the engine water temperature Tw is lower than the temperature threshold THt2 (< temperature threshold THt1).

[0042] Fig. Fig. 6 is a graph showing an example of an engine operating characteristic L used in the internal combustion engine 12 shown in Fig. 1. The vertical axis of the Fig. 6 is the engine torque TQ, and the horizontal axis is the engine speed NE. The internal combustion engine 12, which is a power generation engine mounted on the REEV, is started intermittently each time a power generation request is made. In addition, the target engine output is increased as the required power generation amount is larger.

[0043] As the engine output increases, the engine operating point moves along the engine operating characteristic curve L, which is shown in Fig. 6. More specifically, the engine operating point moves forward in a direction in which the engine torque TQ increases at a minimum engine speed NE0. Then, the engine operating point moves forward to a high-speed and high-load side and reaches a maximum torque TQ0. The reason why this type of engine operating characteristic L is used is as follows. More specifically, in order to reduce vibration and noise during engine operation for the purpose of power generation, it is necessary for the internal combustion engine 12 to be operated with the engine speed NE reduced as much as possible. Therefore, when realizing a target engine output, it is necessary to increase the engine torque TQ as much as possible on a characteristic of equal engine power L, as shown in Fig. 6 is shown by way of example. It can be said that the internal combustion engine 12 mounted on the REEV is likely to be heavily used in a high-load range, not only for the reason that the engine displacement is small relative to the vehicle as described above, but also for the reason described here.

[0044] The pulsation rate Rp becomes higher as the engine torque TQ (i.e., the engine load) is higher. For this reason, the three threshold values ​​THpN, THpL1, and THpL2 described above can be represented using a straight line with a constant engine torque TQ, as shown in Fig. 6 is shown schematically. Fig. 6 shows an example in which the internal combustion engine 12 is started upon receiving a power generation request and the engine operating point shifts from P1 to P2.

[0045] According to the switching method of the fuel injection timing according to the present embodiment, in the above-described example of the transition of the engine operating point, when the engine water temperature Tw is equal to or higher than the threshold value THt1 equivalent to the normal temperature, switching from the first fuel injection timing (F1) to the second fuel injection timing (F2) is performed when the pulsation rate Rp reaches the threshold value THpN on the highest load side. Also, when the engine water temperature Tw is lower than the threshold value THt1 and higher than or equal to the threshold value THt2, switching of the fuel injection timing is performed at the low temperature threshold value THpL1, which is lower than the threshold value THpN.As a result, switching is performed at a lower engine load than when the engine water temperature Tw is equivalent to or higher than the normal temperature. When the engine water temperature Tw is lower than the threshold THt2, switching of the fuel injection timing is performed at the extremely low temperature threshold THpL2.

[0046] As in Fig. 6, switching of the fuel injection timing according to the present embodiment is performed at a lower pulsation rate Rp as the engine water temperature Tw is lower. (Correction of a pulsation rate threshold based on ΔTQ and TQ)

[0047] Fig. 7A is a graph showing an example of a relationship between a torque increase rate ΔTQ and a correction coefficient K ΔTQ shows. Fig. 7B is a graph showing an example of a relationship between the engine torque TQ and a correction coefficient K TQ The torque increase rate ΔTQ mentioned here is a time rate of increase of the engine torque TQ [Nm / sec]. According to the present embodiment, the pulsation rate threshold value THp (more specifically, each of the values ​​THpN, THpL1, and THpL2) is corrected based on both the torque increase rate ΔTQ and the engine torque TQ.

[0048] Specifically, the pulsation rate threshold THp is corrected in accordance with the torque increase rate ΔTQ as follows. That is, according to the following equation (3), the pulsation rate threshold THp is corrected by multiplying the base value of the pulsation rate threshold THp with a positive correction coefficient K ΔTQIt is assumed here that the base value is the pulsation rate threshold THp (ie, each of THpN, THpL1 and THpI2) which is Fig. 5. As shown in Fig. As shown in Figure 7A, the correction coefficient K ΔTQ 1, if the torque increase rate ΔTQ is equal to a standard value ΔTQ1 associated with the base value. In addition, if the torque increase rate ΔTQ is higher than the standard value ΔTQ1, the correction coefficient K ΔTQ larger the higher the torque increase rate ΔTQ is. On the other hand, if the torque increase rate ΔTQ is lower than the standard value ΔTQ1, the correction coefficient K ΔTQ smaller the smaller the torque increase rate ΔTQ is. THp=base value×correction coefficient KΔTQ

[0049] According to the correction using the correction coefficient K ΔTQthe pulsation rate threshold THp is corrected to be larger when the torque increase rate ΔTQ is high than when the torque increase rate ΔTQ is low. More specifically, in the Fig. In the example shown in Figure 7A, the pulsation rate threshold THp is corrected to be larger as the torque increase rate ΔTQ is higher.

[0050] The pulsation rate threshold THp is corrected in accordance with the engine torque TQ as follows. That is, according to the following equation (4), the pulsation rate threshold THp is corrected by multiplying the above-described basic value of the pulsation rate threshold THp by the positive correction coefficient K TQ As in Fig. As shown in Figure 7B, the correction coefficient K TQ1 when the engine torque TQ is equal to the standard value TQ1 associated with the base value described above. In addition, if the engine torque TQ is higher than the standard value TQ1, the correction coefficient K TQ smaller the higher the engine torque TQ is. On the other hand, if the engine torque TQ is lower than the standard value TQ1, the correction coefficient K TQ larger the lower the engine torque TQ is. THp=base value×correction coefficient KTQ

[0051] According to the correction using the correction coefficient K TQ the pulsation rate threshold THp is corrected to be smaller when the engine torque TQ is high than when the engine torque TQ is low. More specifically, in the Fig. In the example shown in Fig. 7B, the pulsation rate threshold THp is corrected to be smaller as the engine torque TQ is higher.

[0052] It should be noted that, in contrast to the example described above, only one of the corrections using the correction coefficient K ΔTQ and the correction using the correction coefficient K TQ In addition, the correction coefficient K ΔTQ be set to be larger in steps with two or more steps when the torque increase rate ΔTQ is higher, instead of the example where the correction coefficient K ΔTQ becomes continuously larger when the torque increase rate ΔTQ is higher, as in Fig. 7A. This also applies to the correction coefficient K TQ , which in Fig. 7B is shown. 1-2-5. Process control by the ECU

[0053] Fig. 8 is a flowchart showing a routine of the processing related to the fuel injection control according to the first embodiment. Note that the processing of the present routine is repeatedly executed during operation of the internal combustion engine 12. In addition, according to the present routine, the engine water temperature Tw is used as an example of the "temperature correlation value" according to the present invention. However, a temperature correlation value other than the engine water temperature Tw may be used as long as it correlates with the temperature of the internal combustion engine (more specifically, the temperature of the engine body), and may be, for example, an engine lubricating oil temperature.

[0054] According to the Fig. In the routine shown in Figure 8, the ECU 26 (the processor 26a) first determines in step S100 whether the engine water temperature Tw detected by the water temperature sensor 58 is lower than the temperature threshold THt2 described above. The temperature threshold THt2 is a value for determining whether the internal combustion engine 12 is in an extremely low temperature state and is, for example, -7°C or -20°C.

[0055] If the engine water temperature Tw is lower than the temperature threshold THt2 in step S100, the ECU 26 proceeds to step S102. In step S102, the ECU 26 selects the pulsation rate threshold THpL2 for extremely low temperatures. After executing step S102, or if the engine water temperature Tw is equal to or higher than the temperature threshold THt2 in step S100, the ECU 26 proceeds to step S104.

[0056] In step S104, the ECU 26 determines whether the engine water temperature Tw is not lower than the temperature threshold THt2 and lower than the temperature threshold THt1 described above. The temperature threshold THt1 is a value for determining whether the temperature of the internal combustion engine 12 is lower than a normal temperature, and is, for example, 20°C or 25°C.

[0057] If the determination result of step S104 is positive (THt2≤Tw <THt1), fährt die ECU 26 zu Schritt S106 fort. In Schritt S106 wählt die ECU 26 den Pulsationsratenschwellenwert THpL1(> THpL2) for low temperatures. After the execution of step S106, the ECU 26 proceeds to step S110.

[0058] On the other hand, if the determination result of step S104 is negative (Tw≥THt1), the ECU 26 proceeds to step S108. The ECU 26 selects the pulsation rate threshold THpN (>THpL1) for a normal time. After executing step S110, the ECU 26 proceeds to step S110.

[0059] In step S110, the ECU 26 calculates the final pulsation rate Rp using, for example, the method described with reference to equation (2). The ECU 26 then determines whether the calculated pulsation rate Rp is higher than the pulsation rate threshold THp (THpN, THpL1, or THpL2) that is currently selected.

[0060] If the pulsation rate Rp is equal to or lower than the pulsation rate threshold THp in step S110, the ECU 26 proceeds to step S112. In step S112, the ECU 26 selects the first fuel injection timing using the air flow sensor 52.

[0061] On the other hand, if the pulsation rate Rp is higher than the threshold value THp in step S110, the ECU 26 proceeds to step S114. In step S114, the ECU 26 selects the second fuel injection timing using the throttle opening TA. 1-3. Effect

[0062] As described so far, according to the fuel injection control of the present embodiment, the threshold value THp of the pulsation rate Rp is reduced when the engine water temperature Tw (temperature correlation value) is low than when the engine water temperature Tw is high.

[0063] Fig. 9 and Fig. 10 are timing charts used to describe the effect of setting the pulsation rate threshold THp in accordance with the first embodiment. Fig. 9 and Fig. 10 shows the difference caused by the difference in the pulsation rate threshold THp, taking transient operating conditions as examples where the engine torque TQ increases over time, and two thresholds THpN and THpL1. It should be noted that in Fig. 9, only the fluctuation component of the first intake air amount is shown. Additionally, the waveform of the second intake air amount after switching to the second fuel injection timing is omitted.

[0064] First, the effect of the fuel injection control according to the present embodiment will be described with reference to Fig. 9. A time t1 in Fig. 9 corresponds to a time point at which the pulsation rate Rp reaches the threshold value THpL1 on the low temperature side, and a time point t2 corresponds to a time point at which the pulsation rate Rp reaches the threshold value THpN on the high temperature side (for a normal time). As can be seen from Fig. 9, when the threshold THpN is used (dashed line), the pulsation of the first intake air amount at the time of switching of the fuel injection timing becomes larger than when the threshold THpL1 is used (solid line), and the fluctuation range of the actual air-fuel ratio becomes larger in connection therewith.

[0065] If the threshold THpN is exceeded at the low water temperature at which the particle number PN increases (see Fig. 3) is used (that is, when the first intake air amount is used for a long time), the particle number PN increases as the actual air-fuel ratio shifts to the rich side. In contrast, according to the present embodiment, switching to the second fuel injection timing that does not use the first intake air amount is performed before the pulsation of the first intake air amount becomes too large, as shown in Fig. 9 by lowering the threshold value THp at low temperatures. This makes it possible to achieve fuel injection control that can appropriately select, based on the pulsation rate, either the first intake air amount based on the output of the air flow sensor 52 (the first fuel injection timing) or the second intake air amount based on the throttle opening degree TA (the second fuel injection timing), while reducing an increase in the particulate number PN.

[0066] Next, the effect of the fuel injection control according to the present embodiment will be additionally described with reference to Fig. 10. Regarding the waveforms of the intake air quantity, the actual air-fuel ratio and an integrated value PN in Fig. 10, the solid line represents the selection of the threshold THpL1 for low temperatures, the dashed line represents the selection of the threshold THpN for normal operation, and the thin dashed line represents the case where the first fuel injection timing is used continuously without switching the fuel injection timing. The integrated value PN is an integrated value (number of parts) of the particulate matter number PN after engine start-up.

[0067] A time t3 in Fig. 10 corresponds to a time point at which the engine torque TQ of the internal combustion engine 12, which is started by receiving a power generation request, begins to increase. Time point t4 corresponds to a time point at which the pulsation rate Rp reaches the threshold THpL1 on the low temperature side and switches to the second fuel injection timing, and time point t5 corresponds to a time point at which the pulsation rate Rp reaches the threshold THpN on the high temperature side and switches to the second fuel injection timing.

[0068] First, in the example using only the first fuel injection timing shown by the thin dashed line, in conjunction with an increase in the engine torque TQ, the pulsation of the first intake air amount increases, and the controllability of the air-fuel ratio decreases (that is, the fluctuation range of the actual air-fuel ratio increases). As a result, the integrated value PN increases in accordance with the increase in pulsation.

[0069] Next, the switching at the threshold THpN on the high temperature side (dashed line) and the switching at the threshold THpL1 on the low temperature side (solid line) will be described while comparing these two. The second fuel injection timing according to the present embodiment is accompanied by the above-described second intake air amount correction timing. Accordingly, it will first be described that the effect of setting the threshold THp in accordance with the engine water temperature Tw can be obtained regardless of the presence or absence of this type of correction timing.

[0070] The dashed two-dot line in Fig. 10 is connected to the second intake air quantity obtained when the correction flow control is not performed (ie, the base value). The deviation of the base value (map value) of the second intake air quantity from the actual intake air quantity obtained in Fig. 10 is generated when factors such as a manufacturing variation of the internal combustion engine and an error in a characteristic value of the air flow sensor are superimposed. Fig. 10 shows an example in which the deviation of the second intake air amount is generated on the side that increases with respect to the actual intake air amount. The deviation generated as in this example becomes a factor for enriching the actual air-fuel ratio with respect to the stoichiometric air-fuel ratio. However, as in Fig. As shown in Figure 10, the deviation is generally an order of magnitude smaller than the pulsation amplitude, at which the particle number PN becomes a concern. Therefore, even without the correction scheduling control, the effect of reducing the integrated value PN by lowering the threshold value THp is achieved at low water temperatures.

[0071] On the other hand, with the above-described correction flow control, the second intake air amount approaches the actual intake air amount after switching to the second fuel injection flow control as shown in Fig. 10. As a result, the enrichment of the air-fuel ratio can be reduced not only by the air-fuel ratio control but also by the correction flow control, even if the deviation of the base value of the second intake air amount becomes a factor of the enrichment of the air-fuel ratio, as shown in Fig. 10. Due to this, the effect of reducing the integrated value PN by reducing the threshold value THp at low water temperatures is more sufficiently achieved compared to the example without the correction flow control. More specifically, in the range of the integrated value PN indicated by a symbol A shown in Fig. As shown in Figure 10, the effect of reducing the integrated value PN is obtained by reducing the threshold value THp at low water temperatures.

[0072] In addition, the pulsation rate threshold THp (more specifically, each of THpN, THpL1, and THpL2) used in the present embodiment is corrected to be larger when the torque increase rate ΔTQ is high than when it is low. When the engine water temperature Tw (temperature correlation value) is the same, there is a request to use the first calculation method (first fuel injection timing) suitable for the transient operating conditions as described above for a long time. By correcting the threshold THp in accordance with the torque increase rate ΔTQ, it is possible to appropriately set the threshold THp in accordance with the engine water temperature Tw while satisfying this kind of request.

[0073] In addition, the pulsation rate threshold value THp (more specifically, each of THpN, THpL1, and THpL2) used in the present embodiment is corrected to be smaller when the engine torque TQ is high than when it is low. When the engine torque TQ is high, the throttle opening degree TA becomes large because the actual intake air amount is large. Due to this, the pulsation of the first intake air amount becomes large due to the influence of the intake air pulsation. Therefore, when the engine water temperature Tw (temperature correlation value) is the same, there is a request that, under the condition that the pulsation of the first intake air amount increases, switching to the second calculation method (second fuel injection timing control) that is not affected by the intake air pulsation be performed quickly.By correcting the threshold THp in accordance with the engine torque TQ, it is possible to appropriately set the threshold THp in accordance with the engine water temperature Tw while satisfying this kind of request. 1-4. Examples of variations

[0074] In the first embodiment described above, three threshold values ​​THpN, THpL1, and THpL2, which differ depending on the engine water temperature Tw, are used as the pulsation rate threshold THp. Instead of this type of example, two pulsation rate threshold values ​​that differently depend on the "temperature correlation value" such as the engine water temperature may be used. More specifically, for example, a threshold value THpN for a normal time and a threshold value lower than the threshold value THpN for low temperatures may be used. In addition, four or more pulsation rate threshold values ​​that differ depending on the temperature correlation value may be used.

[0075] Fig. 11 is a graph showing another example of setting the pulsation rate threshold THp. As in Fig. 11, the pulsation rate threshold value THp may be set to be (continuously) smaller as the temperature correlation value, such as the engine water temperature Tw, is lower. When this type of setting is used, the ECU 26 may, for example, execute a routine (not shown) obtained by performing steps S100 to S108 of the Fig. 8 can be replaced by the following step. That is, a map defining a relationship between the pulsation rate threshold THp and the engine water temperature Tw as shown in Fig. 11 is stored in the ECU 26. Then, the ECU 26 performs a step of acquiring the engine water temperature Tw and a step of acquiring the pulsation rate threshold THp from the map depending on the acquired engine water temperature Tw. Furthermore, upon acquiring the pulsation rate threshold THp in this manner, the pulsation rate threshold THp can be corrected based on at least one of the torque increase rate ΔTQ and the engine torque TQ, similarly to the first embodiment. 2. Second embodiment

[0076] Next, a second embodiment according to the present invention will be described with reference to Fig. 12 and Fig. 13. The second embodiment is directed to a powertrain system 10 that incorporates the Fig. 1 and Fig. 2. In the second embodiment, the following "torque increase rate limiting processing control" is performed in conjunction with the fuel injection control described in the first embodiment. 2-1. Overview of the torque increase rate limiting sequence control

[0077] The powertrain system 10 mounted on the REEV has a "series hybrid mode" in which the wheels 22 are driven by the MG2, while the entire driving force of the engine 12 is used to drive the MG1 to generate electric power. During the execution of this type of series hybrid mode, it is not always necessary to change the engine torque TQ and the torque increase rate ΔTQ in accordance with the driver's acceleration request. That is, the driver's torque increase rate ΔTQ can be freely set.

[0078] Fig. 12 is a time chart used to describe fuel injection control accompanied by torque increase rate limiting processing according to the second embodiment. Fig. 12 differs from that in Fig. 10 with regard to the points described below.

[0079] In the Fig. In the example shown in FIG. 12, the torque increase rate ΔTQ (dashed line) obtained when the threshold THpN is used on the high temperature side is lower in a period after time t5 when the pulsation rate Rp reaches the threshold THpNt than in a period before time t5. A torque increase rate during a period from time t4 to time t5 in the example where the threshold THpN is selected is referred to herein as ΔTQ2, and a torque increase rate during the period in the example where the threshold THpL1 is selected is referred to as ΔTQ3.

[0080] In the Fig. In the example shown in Figure 12, the torque increase rate limiting process is performed while selecting the temperature threshold THpL1 on the low temperature side. According to the torque increase rate limiting process, the torque increase rate ΔTQ3 obtained when the threshold THpL1 is selected on the low temperature side is limited to be lower than the torque increase rate ΔTQ2 obtained when the threshold THpN is selected on the high temperature side.

[0081] It should be noted that in the Fig. In the example shown in FIG. 12, the threshold value THpN corresponds to an example of the "first pulsation rate threshold value" according to the present invention, and the threshold value THpL1 corresponds to an example of the "second pulsation rate threshold value" according to the present invention. Furthermore, the period from time t4 to time t5 during which the torque increase rate limiting processing is executed corresponds to a part of the "torque increase period" according to the present invention.

[0082] According to the present invention, a fixed value is used as the torque increase rate ΔTQ3. To be more specific, a value at which the change with time of the engine torque TQ is small enough to be considered a steady-state condition in which the engine torque TQ does not change with time (e.g., 10 [Nm / s]) is used as the torque increase rate ΔTQ3. Limiting the torque increase rate ΔTQ to ΔTQ3 can be performed, for example, as follows. That is, according to the torque increase rate limiting processing, the ECU 26 sets the throttle opening degree TA to coincide with a target throttle opening degree TAt required to obtain a target intake air amount in accordance with a target torque TQt, which is limited not to exceed ΔTQ3.Then, as a result of this kind of adjustment of the throttle opening degree TA, the actual intake air amount (thin dashed line) is reduced at or after the time t4, compared with the case where the threshold THpN is selected on the high temperature side.

[0083] In addition, even during the selection of the extremely low temperature threshold THpL2, the torque increase rate limiting processing according to the present embodiment is performed similarly to that shown in Fig. 12. Therefore, the threshold THpL2 corresponds to another example of the "second pulsation rate threshold" according to the present invention.

[0084] In addition, the Fig. 12, the torque increase rate limiting processing is performed in a period corresponding to a part of the torque increase period (e.g., the period from time t4 to time t5) as described above. However, for the entire “torque increase period”, unlike the example shown in Fig. 12, the torque increase rate ΔTQ obtained when a threshold value on the low temperature side (e.g., THpL1) is used may be limited to be lower than the torque increase rate ΔTQ obtained when the threshold value THpN on the high temperature side is used. 2-2. Process control by the ECU

[0085] Fig. Fig. 13 is a flowchart showing a routine of the processing related to the fuel injection control accompanied by the torque increase rate limiting control according to the second embodiment. The processing of steps S100 to S114 in Fig. 13 is as already described in the first embodiment.

[0086] According to the Fig. In the routine shown in Figure 13, the ECU 26 (processor 26a) proceeds to step S200 after step S114. In step S200, the ECU 26 determines whether the currently selected pulsation rate threshold THp is one of the low-temperature side thresholds THpL1 and THpL2. If this determination result is negative, the ECU 26 ends the current processing cycle.

[0087] On the other hand, if the determination result of step S200 is affirmative, the ECU 26 proceeds to step S202. In step S202, the ECU 26 executes the above-described torque increase rate limiting processing. This torque increase rate limiting processing uses the above-described torque increase rate ΔTQ3 (fixed value), which is limited to be lower than the torque increase rate ΔTQ obtained when the threshold value THpN on the high temperature side is used. Note that in the present embodiment, even if one of the threshold values ​​THpL1 or THpL2 is selected on the low temperature side, the torque increase rate ΔTQ3 is used.However, in this kind of example having a plurality of thresholds on the low temperature side, the torque increase rate ΔTQ may be limited to be even lower when the threshold THpL2 on the low temperature side is used than when the threshold THpL1 is used. 2-3. Effect

[0088] As described so far, according to the torque increase rate limiting control associated with the fuel injection control of the present embodiment, after switching from the first fuel injection control to the second fuel injection control, when the pulsation rate threshold THpL1 or THpL2 is selected on the low temperature side, the torque increase rate ΔTQ is limited to be lower than when the threshold THpN is selected on the high temperature side. As a result, it is possible to make the actual air-fuel ratio follow the target air-fuel ratio more closely in the air-fuel ratio feedback control, as shown in Fig. 12 (thick solid line) when the second fuel injection timing control is used in a situation where the engine torque TQ increases at a low water temperature. Thus, as shown in Fig. 12, the integrated value PN can be further reduced compared with the first embodiment (thin solid line) which is not accompanied by the torque increase rate limiting processing control.

[0089] Note that the "torque increase rate limiting processing" according to the second embodiment described above can be similarly applied to a hybrid vehicle having the series hybrid mode, other than the REEV. An example of this type of hybrid vehicle is a series hybrid vehicle (that is, a vehicle equipped with an electric motor for driving the vehicle, an internal combustion engine dedicated to power generation, and a generator, similar to those of the REEV in terms of hardware configuration). In addition, another example is a hybrid vehicle in which an internal combustion engine is not dedicated to power generation but can perform a series hybrid mode. This also applies to the following embodiment. 3. Third embodiment

[0090] Next, a third embodiment according to the present invention will be described with reference to Fig. 14 and Fig. 15. The third embodiment differs from the second embodiment in the details of the "torque increase rate limiting processing control."

[0091] Fig. 14 is a time chart used to describe fuel injection control accompanied by torque increase rate limiting processing according to the third embodiment. Fig. 14 shows a transient operating condition in which the engine torque TQ increases uniformly. Time t6 corresponds to the time at which the throttle valve 38 begins to open after the engine start, and, in conjunction with this, the engine torque TQ begins to increase. Time t7 corresponds to the time at which the pulsation rate Rp reaches the threshold value THpL1 on the low-temperature side, and switching to the second fuel injection timing is performed.

[0092] It should be noted that, regarding the switching of the fuel injection timing during the selection of the threshold THpL1 on the low temperature side, Fig. 14 shows a waveform of the first embodiment without the torque increase rate limiting process by a dashed line, and also shows a waveform of the third embodiment by a solid line. A waveform of the engine torque TQ shown by a dashed line is the same as that at the time of selecting the high-temperature-side threshold THpN.

[0093] In the Fig. In the example shown in FIG. 14, the torque increase rate limiting scheduling is performed during a period from time t7 until the engine torque TQ reaches the target torque (not shown) (ie, the entire "torque increase period") under the low water temperature conditions where the threshold THpL1 is selected. Note that a similar torque increase rate limiting scheduling may also be performed under extremely low temperature conditions where the threshold THpL2 is selected.

[0094] According to the torque increase rate limiting processing of the present embodiment, the ECU 26 (the processor 26a) sets the throttle opening degree TA so that a fluctuation width W of the actual air-fuel ratio that can be performed with the air-fuel ratio control in the torque increase period specified in Fig. 14, falls to a certain fluctuation width threshold THw to limit the torque increase rate ΔTQ to a low value. As a result, as shown in Fig. As shown in FIG. 14, the torque increase rate ΔTQ is limited to be lower in the torque increase period during the selection of the threshold THpL1 on the low temperature side (the second pulsation rate threshold) than when the torque increase rate limiting processing is not accompanied (i.e., during the selection of the threshold THpN on the high temperature side (the first pulsation rate threshold)). The fluctuation width W is a fluctuation range of the actual air-fuel ratio to the target air-fuel ratio (e.g., stoichiometric air-fuel ratio). The fluctuation width threshold THw is, for example, ±2%.

[0095] More specifically, the limitation of the torque increase rate ΔTQ by the torque increase rate limitation process according to the present embodiment can be performed, for example, by the following method. That is, as shown in Fig. As shown in Fig. 14, at the time t7 of switching to the second fuel injection flow control, the throttle opening degree TA is decreased by a predetermined amount. A time t8 corresponds to a time at which the second intake air amount converges to the actual intake air amount by the above-described correction flow control. After decreasing by the predetermined amount at the time t7, the throttle opening degree TA is increased at a low time increase rate compared to a case where the torque increase rate limiting flow control is not accompanied (dashed line). As a result of this type of adjustment of the throttle opening degree TA, as shown in Fig. 14, the torque increase rate ΔTQ is limited to be lower compared with the case where the torque increase rate limiting processing is not accompanied (that is, compared with the case where the selection of the threshold THpN is made on the high temperature side).

[0096] A time t9 after the time t8 corresponds to a time at which the actual air-fuel ratio based on the output of the air-fuel ratio sensor 60 reaches a certain value near the upper limit of the threshold value THw of the fluctuation width W. At this time t9, the ECU 26 decreases the time increase rate of the throttle opening degree TA by a certain amount, as shown in Fig. 14. As a result, the actual air-fuel ratio does not exceed the upper limit of the threshold THw, as shown in Fig. 14. Then, in the Fig. 14, as a result of the adjustment of the throttle opening degree TA described above, the fluctuation width W of the actual air-fuel ratio is also within the fluctuation width threshold value THw for the remaining period of the torque increase period. In addition, as a result of this type of adjustment of the throttle opening TA, the torque increase rate ΔTQ in the torque increase period is also limited at or after time t9, as shown in Fig. 14 to be low compared with the case where the torque increase rate limiting processing is not accompanied (ie, during the selection of the threshold THpN on the high temperature side).

[0097] Fig. Fig. 15 is a flowchart showing a routine of the processing related to the fuel injection control accompanied by the torque increase rate limiting processing according to the third embodiment. The processing of steps S100 to S114 and S200 in Fig. 15 are as already described in the second embodiment.

[0098] According to the Fig. 15, if the determination result of step S200 is affirmative, the ECU 26 (the processor 26a) proceeds to step S300. In step S300, the ECU 26 executes the torque increase rate limiting processing using the method described with reference to Fig. 14 described procedure.

[0099] As described so far, according to the torque increase rate limiting control process of the present embodiment, the throttle opening degree TA is adjusted so that a fluctuation width W of the actual air-fuel ratio associated with the air-fuel ratio feedback control falls to the fluctuation width threshold THw in the torque increase period. As a result, during the selection of the threshold THpL1 or THpL2 on the low temperature side, the torque increase rate ΔTQ is limited to be lower than during the selection of the threshold THpN on the high temperature side. Also, with this type of method, it is possible to make the actual air-fuel ratio appropriately follow the target air-fuel ratio in the air-fuel ratio feedback control, as shown by the solid line in Fig.14 when the second fuel injection control process is used in a situation where the engine torque TQ is increased at a low water temperature. Therefore, even with the present method, the integrated value PN can be further reduced compared to the first embodiment, which does not include the torque increase rate limiting control process.

[0100] An engine control device (20) comprises a processor (26a) configured to execute fuel injection control, comprising: a first fuel injection timing control (F1) for injecting an amount of fuel in accordance with a first intake air amount based on an intake air flow rate detected by an air flow sensor (52); and a second fuel injection timing control (F2) for injecting an amount of fuel in accordance with a second intake air amount based on a throttle opening degree (TA) detected by a throttle position sensor (54).The processor (26a) selects the first fuel injection timing (F1) when a pulsation rate (Rp) of the intake air flow rate is equal to or less than a pulsation rate threshold (THp), and selects the second fuel injection timing (F2) when the pulsation rate (Rp) is higher than the pulsation rate threshold (THp). The pulsation rate threshold (THp) is lower when a temperature correlation value is low than when the temperature correlation value is high.

Claims

[1] An engine control device (20) for controlling an internal combustion engine (12) comprising a fuel injector (40) configured to supply fuel to a cylinder and a throttle valve (38) disposed in an intake air passage (34), comprising: a processor (26a); an air flow sensor (52) disposed in the intake air passage (34) upstream of the throttle valve (20) and configured to detect an intake air flow rate; and a throttle position sensor (54) configured to detect a throttle opening degree (TA) of the throttle valve (38), wherein the processor (26a) is arranged to execute a fuel injection control comprising: a first fuel injection timing controller (F1) for controlling the fuel injector (40) to inject a fuel amount in accordance with a first intake air amount based on the intake air flow rate detected by the air flow sensor (52); and a second fuel injection timing controller (F2) for controlling the fuel injector (40) to inject an amount of fuel in accordance with a second intake air amount based on the throttle opening degree (TA) detected by the throttle position sensor (54), wherein the processor (26a) is configured to: Selecting the first fuel injection control sequence (F1) when a pulsation rate (Rp), which is a fluctuation rate of a pulsation of the intake air flow rate detected by the air flow sensor (52), is equal to or less than a pulsation rate threshold value (THp); and Selecting the second fuel injection timing control (F2) when the pulsation rate (Rp) is higher than the pulsation rate threshold (THp), wherein the pulsation rate threshold value (THp) is smaller when a temperature correlation value correlating with a temperature (Tw) of the internal combustion engine is low than when the temperature correlation value is high. [2] The engine control device (20) according to claim 1, wherein the pulsation rate threshold value (THp) is corrected to be larger when a torque increase rate (ΔTQ), which is a time rate of increase of a torque (TQ) of the internal combustion engine (12), is high than when the torque increase rate (ΔTQ) is low. [3] An engine control device (20) according to claim 1 or 2, wherein the pulsation rate threshold value (THp) is corrected to be smaller when a torque (TQ) of the internal combustion engine (12) is high than when the torque (TQ) is low. [4] Engine control device (20) according to one of claims 1 to 3, wherein: the engine control device (20) is mounted on a hybrid vehicle including the internal combustion engine (12), an electric motor (16) and a generator (14), and has a series hybrid mode in which an entire driving force of the internal combustion engine (12) is used to drive the generator (14) to generate electrical energy, and a wheel (22) of the vehicle is driven by the electric motor (16); the pulsation rate threshold (THp) comprises a first pulsation rate threshold (THpN) selected when the temperature correlation value is equal to or greater than a temperature threshold (THt1), and a second pulsation rate threshold (THpL1, THpL2) selected when the temperature correlation value is less than the temperature threshold (THt1), wherein the second pulsation rate threshold (THpL1, THpL2) is less than the first pulsation rate threshold (THpN); the processor (26a) is configured to execute a torque increase rate limiting scheduling control during a selection of the second pulsation rate threshold (THpL1, THpL2); and the torque increase rate limiting scheduling controls a torque increase rate (ΔTQ), which is a time rate of increase in a torque (TQ) of the internal combustion engine (12), to be smaller than during a selection of the first pulsation rate threshold (THpN) during at least a part of a torque increase period from a time when the pulsation rate (Rp) reaches the second pulsation rate threshold (THpL1, ThpL2) and switching to the second fuel injection scheduling (F2) is performed until the torque (TQ) of the internal combustion engine (12) reaches a target torque. [5] Engine control device (20) according to claim 4, wherein: the engine control device (20) comprises an air-fuel ratio sensor (60) configured to output a signal responsive to an oxygen concentration of an exhaust gas; the processor (26a) is configured to perform air-fuel ratio control to adjust a fuel injection amount so that an actual air-fuel ratio approaches a target air-fuel ratio based on the output of the air-fuel ratio sensor (60); and in the torque increase rate limiting scheduling, the processor (26a) is arranged to limit the torque increase rate (ΔTQ) to a small value by adjusting the throttle opening degree (TA) so that a width (W) of fluctuation in the actual air-fuel ratio associated with the air-fuel ratio control falls to a fluctuation width threshold value (THw) during at least a part of the torque increase period.

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