JP4956473B2 - Fuel injection control device - Google Patents

Description

  The present invention relates to a fuel injection control device, and is suitably applied to, for example, a fuel injection control device in which injected fuel injected from a fuel injection valve in an internal combustion engine control device is mixed with combustion air and burned.

  Conventionally, as a control device for an internal combustion engine, opening and closing of a fuel injection valve that injects fuel to a specific cylinder in accordance with an opening period of an intake valve mounted on each cylinder (hereinafter referred to as an intake valve opening period). 2. Description of the Related Art A fuel injection control device that controls valve operation is known (see Patent Document 1).

  In the device disclosed in Patent Document 1 as a kind of such fuel injection control device, the end timing of fuel injection from the fuel injection valve is determined in accordance with the closing timing of the intake valve opening period of the specific cylinder. is doing.

In addition, in the device disclosed in Patent Document 2 as another type of fuel injection control device, intake air that passes through the intake valve and flows into the combustion chamber of the cylinder (hereinafter simply referred to as “inside the cylinder”) during the intake valve opening period. The injection end timing of the fuel injection valve is determined so that the injected fuel flows into the cylinder within the specific period section corresponding to the first 1/3 of the period in which the flow velocity exceeds the threshold. This technique includes a pressure increasing device that increases the fuel pressure of the injected fuel in order to cause the injected fuel to flow into the cylinder within the specific period section.
JP-A-4-303141 Japanese Patent Laid-Open No. 11-30142

  The torque generated by the internal combustion engine is almost determined by the amount of intake air that is mixed with the injected fuel and becomes combustible air, and the torque generated by the internal combustion engine is increased by the cooling effect of the vaporization latent heat of the fuel. However, the conventional apparatus according to Patent Document 1 and Patent Document 2 has a concern that the torque cannot be improved at high rotation full load. That is, in the above-described device according to Patent Document 1, since the inflow of fuel continues into the cylinder until the closing timing of the intake valve opening period regardless of the conditions, vaporization is not completed even when the intake valve is closed. There is a possibility that the remaining amount of fuel may remain, and the target charging amount of intake air cannot be obtained, and as a result, torque improvement may not be realized.

  Further, in the above-mentioned device according to Patent Document 2, it is possible to increase the fuel flow rate per unit time by the above-described pressure increasing device that increases the fuel pressure of the injected fuel. However, since a large amount of injected fuel is required when aiming for high output such as when using a supercharger, such a pressure booster is further required to considerably increase the fuel pressure. There is a possibility that the fuel injection may not end during the specific period due to insufficient fuel pressure.

  The inventor does not have a pressure intensifier or the above-mentioned special fuel injection valve because a fuel injection apparatus having such a pressure intensifier or a special fuel injection valve that can vary the injection rate becomes an expensive system. We are considering a fuel injection system. When the technology for terminating the fuel injection during the specific period according to Patent Document 2 is applied to such a device, not only the injection does not end during the specific period but also the injection is completed during the intake valve opening period. As a result, there is a problem that the injection period during which the torque can be improved cannot be determined.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel injection control device suitable for improving full load torque.

  In order to achieve the above object, the present invention comprises the following technical means.

That is, in the inventions according to claims 1 to 7, the fuel injection valve disposed in the intake port communicating with the combustion chamber of the internal combustion engine has fuel injection from the fuel injection valve, and the injected fuel is In a fuel injection control device that performs fuel injection so as to flow into the combustion chamber together with intake air flowing through the intake port during an open period of the intake valve that opens and closes between the intake port and the combustion chamber,
Fuel injection for controlling the injection start timing and the injection end timing by the fuel injection valve based on the intake air flow rate detection means for detecting the intake air flow rate passing through the intake valve during the open period and the fuel injection amount injected from the fuel injection valve A control means that specifies a maximum flow area of intake air that passes through the intake valve based on the intake air flow detected by the intake air flow detection means, and corresponds to the specified maximum flow area in the open period fuel injection amount of the fuel inlet is completed so the into the combustion chamber within a certain period, characterized in that it comprises a fuel injection control means for correcting the injection end timing, the.

  According to such a configuration, in the open period of the intake valve that opens and closes between the intake port and the combustion chamber, the flow rate of the intake air that passes through the intake valve is supplied to the combustion chamber according to a specific period in which the maximum flow rate region is reached. The fuel injection control means corrects the injection end timing by the fuel injection valve that injects the fuel injection quantity to be performed, and the fuel injection control means is a timing when the inflow of the fuel injection quantity into the combustion chamber is completed within a specific period Therefore, fuel injection is performed based on the corrected injection start timing and injection end timing.

  As a result, even if a part of the fuel may flow into the combustion chamber without being completely vaporized, the flow rate of the intake air in the maximum flow rate region can be used to promptly promote the vaporization of the fuel that has not been vaporized. In addition, the intake air filling rate due to the cooling effect due to the latent heat of vaporization of the fuel can be effectively increased.

  Since the intake air flow rate is in the maximum flow rate range during the specific period when the inflow of fuel is completed, uncompleted fuel is quickly vaporized by the shearing action with the intake air having such a relatively high flow velocity. is there. Then, the intake air flowing into the combustion chamber is cooled by the cooling effect of the fuel, and the density is increased and the intake air volume is reduced. This is because the filling rate can be effectively increased.

  Moreover, since the fuel injection control means only offsets the injection start timing in accordance with the injection period corresponding to the fuel injection amount with respect to the corrected injection end timing, the pressure intensifier etc. for increasing the fuel pressure, etc. No special equipment is required.

  According to the first aspect of the present invention, in a full load region such as a high rotation full load that requires a large amount of fuel injection, such a fuel injection amount is injected from the fuel injection valve. Since the charging rate of intake air can be effectively increased by the cooling effect, a fuel injection control device suitable for improving the full load torque can be obtained.

  In the invention according to claim 2, the maximum flow rate region is characterized in that the flow rate of the intake air during the open period is in a flow rate range of 85% or more of the magnitude of the maximum flow rate.

  In such an invention, even if the intake valve opens due to the inertial force of the intake air, a flow delay of the intake air occurs. There is a concern that it is not always easy to accurately calculate or estimate the maximum flow rate that is the maximum flow rate in consideration of the flow characteristics of the intake air.

  However, in addition to the above configuration, the maximum flow rate region is set to a flow rate range in which the flow rate of the intake air is 85% or more of the size of the maximum flow rate, so that the calculation means for calculating or estimating the maximum flow rate region Therefore, a relatively simple control device suitable for improving the full load torque can be realized.

  Moreover, the fuel injection control means performs fuel injection by the fuel injection valve based on a specific period related to the maximum flow rate region in the flow rate of intake air. Of the valve opening time and the mechanical opening range of the intake valve, which is the first 1/3 of the open period defined by the threshold of the flow rate that needs to be determined by adaptation, There is no need to execute fuel injection by the fuel injection valve. For example, the present invention can be applied regardless of the rotation region of the internal combustion engine, and the adaptation man-hour associated with the adaptation can be reduced.

Further, in the invention according to claim 3, intake air flow rate detecting means, characterized in that Ru is provided in the intake port.

  According to such a configuration, since the intake air flow rate detecting means for detecting the flow rate of intake air is provided in the intake port, the position between the installation position where the intake air flow rate detection means is installed in the intake port and the intake valve In consideration of the intake air arrival time, the flow rate of the intake air that substantially passes through the intake valve can be detected.

  In the invention according to claim 4, the intake air pressure detection means for detecting the intake port pressure as the intake air pressure provided in the intake port, and the in-cylinder pressure as the pressure in the combustion chamber provided in the combustion chamber In-cylinder pressure detecting means for detecting the intake air flow rate, and calculating the differential pressure between the intake port pressure and the in-cylinder pressure during the intake valve opening period, and calculating the intake air flow rate based on the differential pressure and the intake valve opening amount And an arithmetic means.

  According to such a configuration, the intake port and the combustion chamber are provided with the intake air pressure detection means for detecting the intake port pressure and the in-cylinder pressure detection means for detecting the in-cylinder pressure, respectively. Since the pressure difference between the two is calculated and calculated based on the opening amount of the intake valve, which is the throttle amount when the intake air passes through the intake valve, and the differential pressure, the flow rate of the intake air passing through the intake valve during the open period Can be estimated with high accuracy.

  According to a fifth aspect of the present invention, there is provided an engine model having a model simulating the behavior of intake air until the intake air that has passed through the intake valve flows into the combustion chamber, and the intake air flow rate detected at the intake port And an engine model calculating means for calculating the flow rate of the intake air flowing into the combustion chamber based on at least one of the detected intake air pressures.

  According to such a configuration, in addition to the above configuration, the intake air flowing into the combustion chamber using an engine model having a model that simulates the behavior of the intake air until the intake air that has passed through the intake valve flows into the combustion chamber. Since the engine model calculation means for calculating the air flow rate is provided, the engine model calculation means can determine the specific period during which the flow rate of the intake air passing through the intake valve is in the maximum flow rate region.

  6. The fuel injection control apparatus according to claim 3, wherein the flow characteristic of intake air such as new air (hereinafter simply referred to as “new air”) flowing in the intake port in the combustion cycle of the internal combustion engine is detected. Alternatively, as in the invention according to claim 6, a fluid injection valve for injecting a working fluid different from the fuel injection valve is provided in the intake port, and the fluid injection valve is used as a working fluid. It is good also as a structure which injects at least any one of an inert gas, air, and exhaust gas toward the intake air which flows through an intake port.

  According to the sixth aspect of the present invention, at least one of an inert gas such as nitrogen, air, and exhaust gas can be injected from the fluid injection valve during the open period of the intake valve. . Thereby, the flow characteristic of the intake air passing through the intake valve can be intentionally changed. For example, it is possible to freely change to a flow rate characteristic that a maximum flow rate region exists in any target period section in the open period.

  Further, the fluid injection valve is preferably disposed upstream of the fuel injection valve.

  According to this, the fluid injection valve can inject the said working fluid toward the injection fuel which is arrange | positioned downstream and is injected from a fuel injection valve. Such a working fluid can effectively push the fuel into the combustion chamber while entraining the injected fuel.

  Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. In addition, the overlapping description is abbreviate | omitted by attaching | subjecting the same code | symbol to the component corresponding in each embodiment.

(First embodiment)
1 to 5 show a fuel injection control apparatus according to the present embodiment. 2 and 3 show a characteristic configuration related to fuel injection control by the fuel injection valve 10, and FIG. 2 shows completion of fuel inflow into the cylinder when the flow rate of the intake air passing through the intake valve is in a specific flow rate region. The intake system model for demonstrating the characteristic structure which makes a timing interlock | cooperate to the said area | region is shown. 3 to 5 show a control process executed by a control circuit (ECU) of the fuel injection control device.

  As shown in FIG. 1, in an engine 10 that is an internal combustion engine, an air cleaner 12 is provided at the uppermost stream portion of an intake pipe 11, and an intake air flow rate detecting means is provided downstream of the air cleaner 12 as “intake air flow rate detection means”. A thermal air flow meter 13 for detecting the amount of air is provided.

  This thermal air flow meter 14 has a built-in hot wire (not shown) and an intake air temperature sensor (not shown) arranged in the flow of intake air, and the temperature of the hot wire cooled by the intake air and the intake air temperature. The supply current to the hot wire is controlled so as to keep the temperature difference constant. As a result, the supply current to the heat wire changes according to the heat radiation amount of the heat wire that changes according to the intake air flow rate, and a voltage signal corresponding to this supply current is output as the intake air flow rate signal.

  A throttle valve 14 whose opening degree is adjusted by a throttle actuator 15 such as a DC motor is provided downstream of the thermal air flow meter 13. The opening degree of the throttle valve 14 (throttle opening degree) is detected by a throttle opening degree sensor built in the throttle actuator 15. A surge tank 16 is provided on the downstream side of the throttle valve 14, and an intake pressure sensor 17 for detecting the pressure in the intake pipe 11 is provided in the surge tank 16 as “intake pressure detection means”. Yes.

  Further, an intake manifold 18 for introducing air into each cylinder of the engine 10 is connected to the surge tank 16, and a fuel as “fuel injection means” is provided around the intake port 18 a of each cylinder in the intake manifold 18. An electromagnetically driven fuel injection valve 20 for injecting fuel is attached. An intake valve 21 and an exhaust valve 22 are provided at an intake port and an exhaust port of the engine 10, respectively.

  The cylinder block 23 has a cylindrical cylinder inner wall surface 23a and a crankcase 23b formed below the cylinder inner wall surface 23a. The piston 24 is accommodated in the cylinder inner wall surface 23a so as to be slidable in the vertical direction in the figure. Has been. An oil pan for storing engine oil as “lubricating oil” is formed below the crankcase 23b. A combustion chamber (hereinafter simply referred to as “in-cylinder”) 25 is defined by the cylinder inner wall surface 23 a, the upper end surface of the piston 24, and the inner peripheral surface of the cylinder head 26.

  When the intake valve 21 is opened during the operation of the engine 10, the mixture of the fuel injected by the fuel injection valve 20 and the intake air is introduced into the combustion chamber 25, and the exhaust gas after combustion is generated by the opening operation of the exhaust valve 22. It is discharged to the exhaust pipe 27. Each of the intake valve 21 and the exhaust valve 22 is provided with variable valve timing devices 28 and 29 that change the valve timing (opening / closing timing) of the valves 21 and 22 as “variable drive valve devices”. The variable valve timing devices 28 and 29 make the intake and exhaust camshaft phases variable with respect to the crankshaft. By changing the valve timing accompanying the change of the camshaft phase, for example, FIG. ), The overlap amount OL indicating the period during which both the intake and exhaust valves 21 are open is adjusted. However, in this embodiment, for the sake of convenience, description will be made assuming that only the valve timing of the intake valve 21 is variably controlled. That is, the intake valve 21 describes the advance amount from the most retarded state as the intake valve timing. The variable valve operating device may be one that can individually control the opening timing and closing timing of the intake valve 21.

  An ignition plug 30 as an “igniting means” is attached to the cylinder head 26 of the engine 10 for each cylinder, and the target (desired) is connected to the ignition plug 30 through an ignition device (not shown) including an ignition coil or the like. A high voltage is applied at the ignition timing. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 30, and the air-fuel mixture introduced into the combustion chamber 25 is ignited and used for combustion.

The exhaust pipe 27 is provided with a catalyst 31 such as a three-way catalyst for purifying CO, HC, NOx, etc. in the exhaust gas, and the air-fuel ratio of the air-fuel mixture with exhaust gas as a detection target upstream of the catalyst 31. An air-fuel ratio sensor (such as an O ₂ (oxygen) sensor) 32 for detecting (or oxygen concentration) is provided. Further, the cylinder block 23 of the engine 10 includes a coolant temperature sensor 33 that detects the coolant temperature, and a crank angle sensor 34 that outputs a rectangular crank angle signal at every predetermined crank angle of the engine (for example, at a cycle of 30 ° CA). Is attached.

  Outputs of the various sensors described above are input to a control circuit (hereinafter referred to as ECU) 40 as an engine control device. The ECU 40 is mainly composed of a microcomputer composed of a CPU, ROM, RAM, backup RAM, and the like, and executes various control programs stored in the ROM, whereby the fuel injection of the fuel injection valve 20 is performed according to the engine operating state. And control of various components such as control of the injection start timing θINJst and injection end timing θINJend forming the fuel injection amount Q, control of the ignition timing by the spark plug 30, and control of the valve timing of the intake valve 21 Execute.

  The ECU 40 also functions as a calculation means for calculating the intake air flow rate into the cylinder by the intake system model by executing a cylinder intake air (also referred to as charge air) flow rate calculation program stored in the ROM. Fulfill.

  This intake system model is obtained from the throttle valve 14 in the intake stroke in which a part of the exhaust stroke overlaps in one combustion cycle of the engine 10 (that is, the intake stroke, the compression stroke, the combustion (expansion) stroke, and the exhaust stroke). This is a model that simulates the behavior of intake air flowing through the intake passage to the intake port of the engine 10, and the ECU 40 has a throttle opening that corresponds to, for example, a required amount of a vehicle driver (a throttle operation amount by an accelerator operation not shown). Based on this, the flow rate of air passing through the throttle valve 14 is calculated, and this air flow rate is added to the bypass air flow rate implemented by the ECU 40 for rotational speed control (for example, ISC control) when the load is low. Then, the flow rate of the intake air passing through the intake port 18a of the engine 10, that is, the intake valve 21 in the open state is calculated.

  Further, the ECU 40 has a region (hereinafter referred to as “the maximum flow rate” shown in FIG. 2D among the intake air flow rate passing through the intake valve 21 during the open period T of the intake valve 21 (see FIG. 2E). In the open period T, specific sections (hereinafter referred to as specific periods) Tamax and Tbmax corresponding to the maximum flow area are derived (specified).

  Further, the ECU 40 controls the injection start timing θINJst and the injection end timing θINJend of the fuel injection valve 20 and supplies the target fuel injection amount Q to the cylinder 25, but within the specific periods Tamax, Tbmax. Then, at least the injection end timing θINJend is corrected so that the fuel of the amount corresponding to the fuel injection amount Q flows into the cylinder.

  The injection start timing θINJst is offset as a timing obtained by subtracting the fuel injection period θτ corresponding to the fuel injection amount Q from the corrected injection end timing θINJend. The fuel injection period θτ is determined by the injection characteristics of the fuel injection valve 10 according to the target fuel injection amount Q. For example, the injection hole for injecting fuel (not shown) and the valve member for opening and closing the injection hole are provided. It depends on the opening characteristics of the lift.

  Next, the operation of the fuel injection device having the above-described configuration will be described in accordance with a program control process executed by the ECU 40. FIG. 3 shows a control process for linking the fuel inflow into the cylinder 25 with the maximum flow rate region as the “specific flow rate region” of the intake air, and FIG. 4 is a control for calculating the intake air flow rate in FIG. FIG. 5 shows a basic control routine for fuel injection by the fuel injection valve 20 in FIG.

  As shown in FIG. 1, in S100 (S is a step), the ECU 40 controls the drive of the fuel injection valve 20, and temporarily determines a control value of a control element related to the fuel injection amount as a main basic characteristic of fuel injection. That is, in S110 shown in FIG. 5, the ECU 40 reads the operating state of the engine 10. Specifically, the ECU 40 detects the operating state of the engine 10 based on information from various sensors, and reads various state values indicating the operating state. For example, the engine speed Ne, the engine load L, and the like are read based on the detected operating state.

  In S120, the ECU 40 calculates the optimum fuel injection amount Q for the operating state based on the engine state values such as the engine speed Ne and the engine load L. Further, based on the calculated fuel injection amount Q, a fuel injection period θτ that is a control element for driving and controlling the fuel injection valve 10 is determined, and the injection start timing θINJst and the injection end are corresponding to the fuel injection period θτ. Temporarily determine the timing θINJend. Here, the provisional determination of the injection start timing θINJst and the injection end timing θINJend means that the injection start timing θINJst and the injection end timing θINJend are determined based only on the basic operating state values such as the engine speed Ne and the engine load L. This is because the flow rate is determined without considering the information value calculated later.

  In the following description, in the fuel injection period θτ, the injection start timing θINJst, and the injection end timing θINJend, the operation state is a low rotation full load and a high rotation full load, respectively, “a”, It is distinguished by attaching a subscript “b”. For example, in the case of a high rotation full load, the subscript “b” is inserted to obtain a fuel injection period θbτ, an injection start timing θINJbst, and an injection end timing θINJbend.

  When the control process of S120 described above is executed, the process proceeds to S200 shown in FIG. In S200, the ECU 40 calculates the flow rate of the intake air passing through the intake valve 21 based on the intake system model described above. That is, in S210 shown in FIG. 4, the ECU 40 reads the operating state of the engine 10, and based on the detected operating state, the engine speed Ne, the engine load L, the opening / closing timing of the intake valve 21 by the variable drive valve device 28, and the like. Is read.

  In S220, the flow rate of intake air passing through the throttle valve 14 based on the throttle opening (hereinafter simply referred to as “throttle intake air flow rate”) is calculated, and the intake valve 21 is turned on based on the calculated throttle intake air flow rate. The flow rate of the intake air passing therethrough is calculated in time series at the crank angle indicated by the horizontal axis in FIG.

  Here, when the operation state is a full load such as a low rotation full load and a high rotation full load, the intake air flow rate passing through the intake valve 21 is substantially the same as the throttle intake air flow rate. It becomes. Further, regarding the behavior of the intake air flow rate due to the influence of behavior such as “returning from the cylinder 25 to the intake port 18a via the intake valve 21” locally generated on the intake port 18a side, an engine including an intake system model is included. More accuracy is obtained when the model is used. In the intake air flow rate shown in FIG. 2D, the forward flow refers to the flow in the direction of flowing into the cylinder 25 from the intake port 18a, and the reverse flow refers to the flow in the blow-back direction.

  When the control process of S220 described above is executed, the process proceeds to S300 shown in FIG. In S300, the maximum flow rate region of the intake air passing through the intake valve 21 is derived (specified). Specifically, since the flow rate of the intake air passing through the intake valve 21 is calculated in chronological order with the crank angle in S220, a region where the substantially maximum flow rate including the maximum flow rates Vamax and Vbmax is determined is specified based on the calculation result. To do. Further, the injection end timings θINJend and θINJbend of the fuel injection valve 20 necessary to achieve the completion of the fuel inflow into the cylinder 25 are calculated by the specific periods Tamax and Tbmax corresponding to the maximum flow rate region.

  In the present embodiment, the maximum flow rate region is defined as a flow rate in the flow rate range of 85% or more of the maximum flow rate Vamax and Vbmax.

  In the present embodiment, as shown in FIG. 2D, the completion of fuel inflow into the cylinder 25 is synchronized with the crank angle position corresponding to the maximum flow rates Vamax and Vbmax within the specific periods Tamax and Tbmax. I am doing so.

  In other words, at the time of the low rotation full load indicated by the alternate long and short dash line in FIG. 2 (d), it is on the low rotation side and the influence of the inertia force of the intake air is small. As a result, the intake air flow rate characteristic approximately similar to the valve lift amount characteristic in FIG. In the intake air flow rate characteristic at the time of such a low rotation full load, the maximum flow rate Vamax is generated in the intermediate region shown in the cylinder volume in FIG. 2B and the cylinder pressure in FIG. . The ECU 40 adjusts the fuel inflow completion timing shown in FIG. 2 (fa) to the crank angle at the maximum flow rate Vamax.

  Further, at the high rotation full load indicated by the solid line in FIG. 2 (d), since it is on the high rotation side and is relatively greatly affected by the inertial force of the intake air, even if the intake valve 21 is opened, the valve opening Initially, the intake air is less likely to flow into the cylinder 25. In other words, a flow delay due to gas inertia called intake air occurs in the characteristics of fuel inflow. However, when the intake air begins to flow once, the gas flow rate is high on the high rotation side, so that an extreme value occurs in two stages as shown in FIG. 2 (d), and the second extreme value is the maximum during the open period T. A flow rate Vbmax is formed.

  The crank angle position at which the maximum flow rate Vbmax is generated at the time of the high rotation full load is larger than the crank angle position at the maximum flow rate Vamax at the time of the low rotation full load, but is within the open period T, and The maximum flow rate Vbmax is generated at a predetermined crank angle interval from the closing timing of the intake valve 21.

  The ECU 40 adjusts the fuel inflow completion timing shown in FIG. 2 (fb) to the crank angle at the maximum flow rate Vbmax.

  When the control process of S300 described above is executed, the process proceeds to S400. In S400, the injection start timing θINJst and the injection end timing θINJend, which were provisional decisions related to fuel injection by the fuel injection valve 20, are based on the calculation result of S300. To correct.

  In other words, when the injection end timings θINJend and θINJbend shown in FIGS. 2 (ga) and 2 (gb) are determined as the injection end timings required to synchronize the maximum flow rates Vamax and Vbmax with the fuel inflow completion in S300. In S400, the injection start timing θINJast, θINJbst and the injection end timing θINJend, θINJbend provisionally determined in S100 are set based on the injection end timing θINJend, θINJbend determined in S300, By correcting θINJbst as well, the injection start timings θINJast, θINJbst and the injection end timings θINJend, θINJbend, which are control elements of the fuel injection valve 20, and the fuel injection period θτ corresponding to these are all determined. Than is.

  Thus, since the intake air flow rate in the maximum flow rate region is used, the intake air filling rate due to the cooling effect due to the latent heat of vaporization of the fuel can be effectively increased. Further, even if part of the fuel may flow into the cylinder 25 without being completely vaporized, by using the intake air flow rate in the maximum flow rate region, rapid vaporization promotion of the fuel that has not been vaporized, It is possible to effectively increase the filling rate of the intake air due to the cooling effect by the latent heat of vaporization of the fuel.

  Since the intake air flow rate is in the maximum flow rate region during the specific periods Tamax and Tbmax in which the inflow of fuel is completed, uncompleted fuel is quickly vaporized by the shearing action with the intake air having such a relatively high flow rate. This is because that. Then, the intake air flowing into the cylinder 25 is cooled by the cooling effect of the fuel, and the density is increased and the intake air volume is reduced. However, the intake air having the relatively high flow rate is quickly sucked in. This is because the air filling rate can be effectively increased.

  In addition, in the fuel injection control means for controlling the fuel injection by controlling the fuel injection valve 20, the injection start timing corresponding to the fuel injection amount Q for the corrected injection end timing θINJend, θINJbend. It is only necessary to offset θINJast and θINJbst, and there is no restriction that the injected fuel from the fuel injection valve 10 reaches the intake valve 21 after the intake valve 21 is opened. Therefore, the device of the present invention having such a fuel injection control means does not require a special device such as a pressure increasing device for increasing the fuel pressure.

  According to the above configuration, in a full load region such as a high rotation full load that requires a large amount of fuel injection Q, such a fuel injection amount Q is injected from the fuel injection valve 20, and due to the cooling effect of the fuel Since the intake air filling rate can be increased effectively, a fuel injection control device suitable for improving the full load torque can be obtained.

  In the embodiment described above, the fuel inflow completion timing is substantially synchronized with the maximum flow rates Vamax and Vbmax. However, the following configuration may be used.

  That is, the crank angle position within the specific periods Tamax and Tbmax corresponding to the maximum flow rate region is set as a timing synchronized with the completion timing of the fuel inflow.

  The maximum flow rate region is defined as a flow rate in a flow rate range of 85% or more of the maximum flow rate Vamax and Vbmax. According to this, in the maximum flow rate region, the performance by the intake air flow rate substantially the same as that at the maximum flow rates Vamax and Vbmax can be obtained. In other words, by setting one of the crank angle positions within the specific periods Tamax and Tbmax corresponding to the maximum flow rate region as a timing synchronized with the completion timing of fuel inflow, the intake air flow rate at the crank angle position, that is, the fuel The intake air flow rate at the completion of the inflow is almost the same as the maximum flow rate of 85% or more of the maximum flow rate.

  Now, in such an invention, due to the gas inertia of the intake air, when the intake valve is opened, a flow delay of the intake air in the cylinder occurs. There is a concern that it is not always easy to accurately calculate or estimate the maximum flow rate when the maximum flow rates Vamax and Vbmax are taken into consideration in consideration of the flow characteristics of the intake air.

  However, as described above, the maximum flow rate region is calculated or estimated by adopting a configuration in which “the flow rate of the intake air is set within a flow rate range of 85% or more of the maximum flow rate Vamax and Vbmax”. Since it is possible to relatively easily perform the calculating means, it is possible to realize a relatively simple control device suitable for improving the full load torque.

  Moreover, since the fuel injection control means performs fuel injection by the fuel injection valve 20 based on the specific periods Tamax and Tbmax related to the maximum flow rate region in the flow rate of intake air, the intake valve 21 as in the prior art. Of the intake valve 21, which is the first 1/3 of the open period defined by the closing timing of the open period T and the threshold of the flow rate that needs to be determined by the fit of the open period T It is not necessary to perform fuel injection by the fuel injection valve 20 in any of the open ranges. The apparatus of the present invention having such a fuel injection control means can be applied regardless of the rotation region of the engine 10, and the adaptation man-hours associated with the adaptation can be reduced.

(Second Embodiment)
A second embodiment is shown in FIG. The second embodiment is a modification of the first embodiment. In the second embodiment, the calculation program stored in the ROM of the ECU 40 includes calculation means based on an engine function model (hereinafter simply referred to as “engine model”) such as a fuel system model and a combustion system model in addition to the intake system model. have.

  The fuel system model is a model for simulating the supply of fuel to the engine, and calculates the amount of fuel charged from the amount of fuel flowing into the cylinder 25. In the fuel system model, for example, of the fuel (fuel spray) injected from the fuel injection valve 20, the fuel portion attached to the inner periphery of the intake port 18a (the fuel portion of the first condition) and the fuel portion not attached ( The fuel part of the second condition) is assumed.

  In the fuel portion of the first condition, the ECU 40 calculates the adhesion rate of fuel adhering to the inner periphery of the intake port 18a and the evaporation rate of fuel evaporating from the inner periphery of the intake port 18a based on the temperature of the intake port. Based on the fuel injection amount Q and the fuel adhesion rate to the inner periphery of the intake port 18a, the amount of fuel attached to the inner periphery of the intake port 18a and the amount of fuel not attached to the inner periphery of the intake port 18a are calculated. The amount of fuel evaporated from the inner periphery of the intake port 18a is calculated based on the amount of fuel adhering to the fuel and the evaporation rate, and the amount of evaporation and the amount of fuel not adhering to the inner periphery of the intake port 18a are added. The amount of fuel filled inside is calculated.

  The combustion system model is a model that simulates the combustion state of the engine 10, and the intake air flow rate into the cylinder 25 calculated by the intake system model, the in-cylinder charged fuel amount calculated by the fuel system model, The calorific value is calculated based on the ignition timing calculated by the ECU 40 and the wall temperature of the cylinder inner wall surface 23a.

  According to such a configuration, the engine model having the intake system model that simulates the behavior of the intake air until the intake air that has passed through the intake valve 21 flows into the cylinder 25 is used. Since the calculating means for calculating the flow rate of the intake air flowing into the inner 25 is provided, the same effect as in the first embodiment can be obtained.

  In addition, by using the engine model as described above in the ECU 40, at least the calculation results of the functional models such as the fuel system model and the combustion system model can be linked to the calculation results of the intake system model. Therefore, it is possible to improve the certainty of specifying the specific periods Tamax and Tbmax in which the flow rate of the intake air passing through the intake valve is in the maximum flow rate region by the calculation means of the engine model, thereby accurately determining the specific periods Tamax and Tbmax. be able to.

(Third embodiment)
A third embodiment is shown in FIG. The third embodiment is a modification of the first embodiment. In the third embodiment, the flow rate of the intake air flowing in the intake port 18a is not directly detected, but the differential pressure between the specific portions of the intake air is used and indirectly based on the differential pressure. Fig. 1 shows an example in which the intake air flow rate is detected.

  As shown in FIG. 7, an intake port pressure sensor 60 as “intake pressure detection means” is provided not in the surge tank 16 but in the intake manifold 18. An in-cylinder pressure sensor 50 serving as “in-cylinder pressure detection means” for detecting the pressure in the cylinder (combustion chamber) 25 of the engine 10 is attached to the cylinder 25. The in-cylinder pressure sensor 50 is attached to the cylinder head in the same manner as the ignition plug 30. For example, the in-cylinder pressure sensor 50 is an in-cylinder unit 130 including an in-cylinder pressure sensor 50 and an ignition device having the ignition plug 30 as shown in FIG. The pressure sensor 50 and the ignition device having the ignition plug 30 may be separately attached to the cylinder head.

  The calculation program stored in the ROM of the ECU 40 calculates the differential pressure detected by the calculation means based on the engine model and the sensors 50 and 60, and based on the differential pressure and the opening amount of the intake valve 21 during the open period T. Thus, it plays a role as calculation means for calculating the flow rate of intake air passing through the intake valve (hereinafter referred to as differential pressure type intake air flow rate calculation means).

  Even if comprised in this way, the effect similar to 1st Embodiment can be acquired. Furthermore, in the present embodiment, the intake manifold 18 and the cylinder 25 on the intake port 18a side are respectively provided with an intake air pressure detecting means 60 for detecting the intake port pressure and an in-cylinder pressure detecting means 50 for detecting the in-cylinder pressure. At the same time, the differential pressure between the intake port pressure and the in-cylinder pressure is calculated and calculated based on the opening amount of the intake valve 21 that is the throttle amount when the intake air passes through the intake valve 21 and the differential pressure. It is possible to accurately estimate the intake air flow rate that passes through the intake valve 21 during the period T.

  In addition, the calculation method of the intake air flow rate based on the differential pressure is superior in response to flow rate detection compared to the calculation method of the intake air flow rate directly based on the flow rate state value or flow index value related to the flow rate. Therefore, when applied at high rotation full load, a fuel injection control device particularly suitable for improving torque can be easily obtained.

(Fourth embodiment)
A fourth embodiment is shown in FIG. The fourth embodiment is a modification of the first embodiment. The fourth embodiment shows an example in which the intake manifold 18 is provided with a thermal air flow meter 113 as “intake air flow rate detection means”.

  As shown in FIG. 8, since the thermal air flow meter 113 is provided in the intake manifold 18 on the intake port 18a side, the installation position where the thermal air flow meter 113 is installed in the intake port 18a and the intake valve 21 The intake air flow rate that substantially passes through the intake valve 21 can be accurately detected by considering the intake air arrival time in between.

(Fifth embodiment)
A fifth embodiment is shown in FIG. The fifth embodiment is a modification of the first embodiment. In the fifth embodiment, an example in which a fluid injection valve 70 as an “air injection means” is provided in the intake port 18a separately from the fuel injection valve 20 as a “fuel injection means” is shown.

  As shown in FIG. 9, the fluid injection valve 70 is attached to the intake port 18 a and is arranged on the upstream side of the fuel injection valve 20. The fluid injection valve 70 is connected to an air pump 80 as an air compression source for compressing air, and air pressurized by the air pump 80 is supplied. The fluid injection valve 70 is an electromagnetically driven fluid injection valve that is driven and controlled by the ECU 40. The fluid injection valve 70 is driven and controlled by the ECU 40 to inject a working fluid such as air.

  The working fluid is not limited to air but may be any of an inert gas such as nitrogen and an exhaust gas.

  According to such a configuration, in the open period T of the intake valve 21, at least one of inert gas such as nitrogen, air, and exhaust gas can be injected from the fluid injection valve 70. Since the working fluid such as air is the same gas as air, the intake air is substantially increased. Thereby, the flow rate characteristic of the intake air passing through the intake valve 21 can be changed intentionally. For example, it is possible to freely change the flow rate characteristic that the maximum flow rate region exists in any target period section in the open period T.

  In addition, in the present embodiment, the fluid injection valve 70 is arranged on the upstream side of the fuel injection valve 20, so that the fluid injection valve 70 is disposed on the downstream side and injected fuel injected from the fuel injection valve 20. The working fluid can be ejected toward the head. Such a working fluid can effectively push the fuel into the cylinder 25 while entraining the injected fuel.

(Other embodiments)
As mentioned above, although one Embodiment of this invention was described, this invention is limited to this embodiment and is not interpreted and can be applied to various embodiment in the range which does not deviate from the summary.

1 is a schematic diagram illustrating an overall configuration of a control device for an internal combustion engine to which a fuel injection device according to a first embodiment of the present invention is applied. FIG. 2 is a schematic diagram showing a behavior model of an intake port, an intake valve, and fuel and intake air flowing into a cylinder (combustion chamber) in the control device for the internal combustion engine of FIG. 1, and FIG. 2 (b) is the in-cylinder volume, FIG. 2 (c) is the in-cylinder pressure, FIG. 2 (d) is the flow rate of the intake air passing through the intake valve, FIG. 2 (e) is the intake valve open period, 2 (fa) and (fb) are the inflow timings of fuel into the cylinder at the time of low full load and high load, respectively. FIGS. 2 (ga) and (gb) are at low full load and high rpm, respectively. It is a characteristic view which shows the fuel injection timing by the fuel injection valve at the time of full load. FIG. 2 is a flowchart showing a control method executed by the ECU in FIG. 1, and is a flowchart showing a control process for performing fuel injection control with fuel inflow timing in a cylinder corresponding to a maximum flow rate region of intake air. is there. It is a flowchart which shows the control processing which calculates the flow volume of the intake air in FIG. It is a flowchart which shows the basic control process of the fuel injection by the fuel injection valve in FIG. It is a schematic diagram which shows the fuel-injection apparatus concerning 2nd Embodiment. It is a schematic diagram which shows the fuel-injection apparatus concerning 3rd Embodiment. It is a schematic diagram which shows the fuel-injection apparatus concerning 4th Embodiment. It is a schematic diagram which shows the fuel-injection apparatus concerning 5th Embodiment.

Explanation of symbols

10 Engine (Internal combustion engine)
11 Intake pipe (intake passage)
13 Thermal air flow meter (intake air flow rate detection means)
14 Throttle valve 16 Surge tank (intake passage)
17 Intake pressure sensor (Intake pressure detection means)
18 Intake manifold 18a Intake port 20 Fuel injection valve (fuel injection means)
21 Intake valve 22 Exhaust valve 23 Cylinder block 23a Cylinder inner wall surface 24 Piston 25 Combustion chamber 26 Cylinder head 28, 28 Variable valve timing device (variable valve operating device)
40 ECU (control circuit, engine control device)

Claims (7)

A fuel injection valve disposed in an intake port communicating with a combustion chamber of an internal combustion engine, injecting fuel from the fuel injection valve, and the injected fuel is disposed between the intake port and the combustion chamber; In a fuel injection control device that performs fuel injection so as to flow into the combustion chamber together with intake air flowing through the intake port during an open period of the intake valve that opens and closes
An intake air flow rate detecting means for detecting an intake air flow rate passing through the intake valve in the open period;
Fuel injection control means for controlling an injection start timing and an injection end timing by the fuel injection valve based on a fuel injection amount injected from the fuel injection valve, wherein the intake air detected by the intake air flow rate detection means based on the flow rate, the specified maximum flow area of the intake air passing through the intake valve, the fuel injection amount to the combustion chamber within a certain period corresponding to the maximum flow area specified among the open period the fuel inflow is complete so, the fuel injection control means for correcting the injection end timing,
A fuel injection control device comprising:   2. The fuel injection control device according to claim 1, wherein the maximum flow rate region is in a flow rate range in which the flow rate of the intake air during the open period is 85% or more of the magnitude of the maximum flow rate. The intake air flow rate detecting means, fuel injection control device according to claim 1 or claim 2, characterized in that Ru is provided on the intake port. An intake air pressure detecting means provided at the intake port for detecting an intake port pressure as a pressure of the intake air;
In-cylinder pressure detecting means provided in the combustion chamber for detecting in-cylinder pressure as pressure in the combustion chamber;
An intake air flow rate calculation means for calculating a differential pressure between the intake port pressure and the in-cylinder pressure in the open period of the intake valve, and calculating a flow rate of the intake air based on the differential pressure and an opening amount of the intake valve;
The fuel injection control device according to any one of claims 1 to 3, further comprising:   An engine model having a model simulating the behavior of intake air until the intake air that has passed through the intake valve flows into the combustion chamber, wherein the intake air flow rate detected at the intake port and the detected intake air pressure are The engine model calculating means for calculating the flow rate of the intake air flowing into the combustion chamber based on at least one of the above, and the engine model calculating means according to any one of claims 1 to 4. Fuel injection control device. A fluid injection valve that is provided in the intake port and injects a working fluid different from the fuel injection valve;
6. The fluid injection valve injects at least one of an inert gas, air, and exhaust gas as the working fluid toward intake air flowing through the intake port. The fuel injection control device according to any one of the above.   The fuel injection control device according to claim 6, wherein the fluid injection valve is disposed upstream of the fuel injection valve in the intake port.

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