JP6567900B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

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

In an internal combustion engine (diesel engine, gasoline engine) equipped with a fuel injection valve that directly injects fuel into a cylinder, fuel is supplied to the exhaust purification device by post injection to raise the temperature of the exhaust purification device (for example, Patent Documents) 1-5) .

Further, if the amount of fuel injected by one post injection is large, the fuel reaches the inner wall of the cylinder, and problems such as bore flushing and oil dilution may occur. Therefore, it has also been proposed to supply an amount of fuel that does not reach the inner wall of the cylinder into the cylinder by a plurality of post injections (see, for example, Patent Documents 1 and 2 ).

JP 2001-159363 A JP 2006-104989 A JP-A-3-149315 JP 2014-055551 A JP 2013-019350 A

  If an amount of fuel that does not reach the inner wall of the cylinder is supplied into the cylinder by a plurality of post-injections, the occurrence of bore flushing and oil dilution can be suppressed. However, the number of post injections that can be performed by the fuel injection valve is limited. Therefore, although there is a limit to the amount of fuel that can be supplied to the exhaust purification device by repeating the post fuel of an amount that does not reach the cylinder inner wall, there are cases where it is desired to supply an amount of fuel exceeding the limit to the exhaust purification device. is there.

  Therefore, an object of the present invention is to exhaust more fuel than can be supplied to the exhaust purification device by repeating fuel injection in an amount that does not reach the cylinder inner wall without increasing the amount of fuel adhering to the cylinder inner wall. An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can be supplied to a purification device.

In order to solve the above-described problem, a fuel injection control device for an internal combustion engine having a fuel injection valve for directly injecting fuel into a cylinder according to the present invention is provided with an exhaust purification device provided in an exhaust system of the internal combustion engine. In the case of warming, the first control condition that defines the timing and fuel injection amount of one or more post injections in one combustion cycle, the fuel injected at each post injection does not reach the inner wall of the cylinder Each post-injection is carried out within a period in which the fuel injected from the fuel injection valve does not ignite before the exhaust valve of the cylinder is opened, and the required amount of fuel is obtained by post injection less than the maximum number of post-injections. A first process for determining whether or not the first control condition to be injected is satisfied is performed, and when it is determined by the first process that the first control condition is not satisfied, the gas amount immediately after combustion in the cylinder is determined. To increase After the control, the second process for determining whether or not the first control condition is satisfied is repeated until the first control condition is satisfied or the gas amount reaches a predetermined gas amount upper limit. A first control unit that causes the fuel injection valve to perform one or more post-injections in accordance with the first control condition when the first control condition is satisfied; and the gas amount becomes the predetermined gas amount upper limit. However, if the first control condition is not satisfied by the second process, the second control condition that defines the post-injection execution time and fuel injection amount of the maximum post-injection number in the one combustion cycle. The fuel injected at the time of each post-injection except for the last post-injection performed last does not reach the inner wall, and each post-injection except for the final post-injection is performed before the exhaust valve is opened. The fuel injection valve The final post-injection fuel injection amount is a value obtained by subtracting the sum of the fuel injection amounts of each post-injection excluding the final post-injection from the required amount. A second control condition for starting the opening of the exhaust valve immediately before the fuel injected by the final post-injection arrives at the inner wall is obtained, and post-injection of the maximum number of post-injections to the fuel injector according to the second control condition A second control unit for performing

  According to the fuel injection control device for an internal combustion engine of the present invention, more fuel than the amount that can be supplied to the exhaust purification device by repeating fuel injection in an amount that does not reach the cylinder inner wall is attached to the cylinder inner wall. Without increasing, it can be supplied to the exhaust emission control device.

FIG. 1 is a schematic configuration diagram of an internal combustion engine system to which a fuel injection control device for an internal combustion engine according to an embodiment of the present invention is applied. FIG. 2 is a flowchart of a post-injection condition determination process executed by the ECU as the fuel injection control device for the internal combustion engine according to the embodiment. FIG. 3 is an explanatory diagram of a calculation procedure of the execution timing of each post injection. FIG. 4 is a flowchart of the check process executed in step S107 of the post injection condition determination process. FIG. 5 is a diagram for explaining a modification of the post injection condition determination process.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a schematic configuration of an internal combustion engine system to which a fuel injection control device for an internal combustion engine according to an embodiment of the present invention is applied.

  This internal combustion engine system is a system mounted on a vehicle. As shown in the figure, the internal combustion engine system includes an internal combustion engine 10, an ECU (Electronic Control Unit) 40 as a fuel injection control device for the internal combustion engine according to the present embodiment, and the like.

  The internal combustion engine 10 is a diesel engine having four cylinders 11, and a temperature sensor 31 for detecting the coolant temperature is attached to the internal combustion engine 10.

  Each cylinder 11 of the internal combustion engine 10 is provided with a fuel injection valve 20 that injects high-pressure fuel in the common rail 22 into the cylinder 11. A pressure sensor 21 for detecting the fuel injection rate is attached to the fuel injection valve 20, and a pressure sensor 23 for detecting the fuel pressure in the common rail 22 is attached to the common rail 22.

  An intake passage 12 is connected to each cylinder 11 via an intake manifold (hereinafter referred to as intake manifold) 12a. Further, an exhaust passage 13 is connected to each cylinder 11 via an exhaust manifold (hereinafter referred to as an exhaust manifold) 13a.

  A throttle valve 14 for adjusting the intake air amount is provided in the middle of the intake passage 12. Further, an air flow meter 32 for detecting the intake air amount and a pressure sensor 33 for detecting the intake air pressure are provided on the upstream side of the throttle valve 14 in the intake passage 12.

A pressure sensor 33 for detecting the pressure in the intake manifold 12a is attached to the intake manifold 12a. Further, an exhaust gas recirculation (EGR) passage 15 for returning a part of the exhaust gas of the internal combustion engine 10 to the intake manifold 12a is disposed between the intake manifold 12a and the exhaust manifold 13a. An EGR valve 16 for adjusting the amount of EGR gas flowing through the EGR passage 15 is disposed in the middle of the EGR passage 15.

In the middle of the exhaust passage 13, an oxidation catalyst 25a for oxidizing NOx (nitrogen oxide) or the like in the exhaust, and a DPF (Diesel Particulate Filter) 25b for collecting PM (Particulate Matter) in the exhaust, An exhaust purification device 25 is arranged. Further, a differential pressure sensor (not shown) for measuring the differential pressure across the DPF 25b and a temperature sensor 37 for detecting the exhaust temperature immediately downstream of the DPF 25b are attached to the exhaust passage 13.

  The ECU 40 is a unit including a CPU (Central Processing Unit), a flash ROM (Read Only Memory), a RAM (Random Access Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), various interface circuits, and the like. The flash ROM of the ECU 40 stores a program (firmware) executed by the CPU and various information (maps) referred to by the program.

  In addition to the various sensors described above, an accelerator opening sensor 35, a crank angle sensor 36, and the like are electrically connected to the ECU 40. The ECU 40 functions as a unit that integrally controls each part (the fuel injection valve 20, the throttle valve 14, etc.) of the internal combustion engine system based on signals from various sensors by the CPU executing the above-described program. .

  Hereinafter, the function of the ECU 40 will be described focusing on the function as the fuel injection control device for the internal combustion engine according to the present embodiment.

  When the regeneration of the DPF 25b is not performed, the ECU 40 causes the fuel injection valves 20 to perform one or two pilot injections, main injections, and after injections. This unit causes each fuel injection valve 20 to perform injection. Then, the ECU 40 determines the execution timing and fuel injection amount of one or more post injections to be performed by the fuel injection valve 20 by the post injection condition determination process of the procedure shown in FIG. 2 for each combustion cycle. It is configured (programmed).

  Hereinafter, the contents of the post injection condition determination process will be described. In the following description, the post-injection conditions are the timing of each post injection to be performed by the fuel injection valve 20 (crank angle at which the fuel injection valve 20 starts post injection) and the fuel injection amount. The cylinder to be controlled is the cylinder 11 for which the post injection condition is determined by the post injection condition determination process. The minimum injection amount is the minimum fuel amount that can be injected into the fuel injection valve 20, and the maximum post injection number is the maximum value of the number of post injections that can be performed in the fuel injection valve 20. That is.

  As shown in FIG. 2, the ECU 40 that has started the post injection condition determination process first sets the value of the required post injection amount Qp to the variable Qpr (step S101). Here, the required post injection amount Qp is the amount of fuel to be supplied from the fuel injection valve 20 of the cylinder to be controlled to the exhaust purification device 25. The required post injection amount Qp is calculated based on, for example, the difference between the temperature of the DPF 25b (the exhaust temperature detected by the temperature sensor 37) and the target temperature of the DPF 25b.

  After completing the process in step S101, the ECU 40 sets “1” to the variable n (step S102).

  In subsequent step S103, the ECU 40 calculates an execution timing θn of post injection (hereinafter, referred to as post injection n) to be executed n times.

  In the process of step S103, when n is “1”, the timing set as the most advanced timing at which the fuel injected from the fuel injection valve 20 does not ignite is calculated as the post-injection 1 execution timing θ1. Is done. Further, when n is not “1” (when it is “2” or more), the post-injection n−1 is completed at the completion time of fuel injection (fuel injection from the fuel injection valve 20). A value obtained by adding the minimum fuel injection interval Tmin is calculated as the execution timing θn of the post injection n. That is, as schematically shown in FIG. 3, the execution timing θ2 of the post injection 2 (“p2”) is calculated by adding Tmin to the completion timing of the post injection 1 (“p1”). 3 (“p3”) is calculated by adding Tmin to the completion time of post injection 2 (“p2”).

  The ECU 40 that has finished the process of step S103 (FIG. 2) determines whether or not the calculated execution timing θn is before the opening timing of the exhaust valve of the cylinder to be controlled (step S104). When the execution timing θn is before the exhaust valve opening timing (step S104; YES), the ECU 40 calculates the limit injection amount QpnL (step S105).

  The limit injection amount QpnL calculated in step S105 is “the distance from each injection hole of the fuel injection valve 20 to the inner wall of the cylinder” when the fuel injection valve 20 starts to inject that amount of fuel at the execution time θn. -The amount of fuel that will satisfy the "arrival distance of fuel spray from each nozzle hole ≦ specified value". The process of step S105 may be a process that can calculate such a limit injection amount QpnL. Therefore, the processing in step S105 is performed by obtaining the gas amount at the execution time θn from the execution time θn and the operating state of the internal combustion engine 10 and from a map storing the correspondence between the gas amount in the cylinder and the limit injection amount. Processing for reading the limit injection amount QpnL associated with the gas amount at the execution time θn may be performed. Further, in the process of step S105, the fuel injection amount is changed by a predetermined amount to obtain the fuel spray arrival distance. The fuel injection amount that satisfies “distance to cylinder inner wall−fuel spray arrival distance ≦ specified value” is satisfied. It may be a process that is repeated until is obtained.

  When the execution time θn is not before the opening time of the exhaust valve (step S104; NO), the ECU 40 sets “0” to QpnL without calculating the limit injection amount QpnL (step S106). As will be described later, the post injection condition determination process (the process of FIG. 2) is a process in which the n value does not exceed “the maximum post injection number + 1”. Since the minimum fuel injection interval of the fuel injection valve 20 in recent years is short, the post-injection condition determination process is normally completed without branching to the “NO” side in step S104.

  The ECU 40 that has finished the process of step S105 or S106 performs a check process (step S107).

  When the n value is small, nothing is performed in the check process (the value of any variable is not changed). For this reason, the details of the remaining steps in FIG. 2 will be described before the details of the check process are described.

  After completing the check process, the ECU 40 determines whether “QpnL ≧ Qpr” is established in step S108. When “QpnL ≧ Qpr” is established (step S108; YES), the ECU 40 sets the Qpr value to the variable Qpn (step S109), and then performs the post injection condition determination process (the process of FIG. 2). ) Ends.

On the other hand, when “QpnL ≧ Qpr” is not established (step S108; NO),
The ECU 40 determines whether or not the QpnL value is “0” (step S110). When the QpnL value is “0” (step S110; YES), the ECU 40 ends the post injection condition determination process. If the QpnL value is not “0” (step S110; NO), the ECU 40 determines whether the QpnL value is “−1” (step S111). Then, when the QpnL value is “−1” (step S111; YES), the ECU 40 starts the processing after step S101.

  Note that the above branching based on the QpnL value is performed so that the check process is a process of setting the QpnL value to “0” when the post injection condition is determined, and the post injection condition. This is because the process of setting the QpnL value to “−1” when it becomes necessary to recalculate.

  When the QpnL value is not “−1” (step S111; NO), the ECU 40 reduces the Qpn value from the Qpr value (step S112), and increments the n value by “1” (step S113). I do. That is, when the post-injection condition is not fixed and it is not necessary to recalculate the post-injection condition (step S111; NO), the process of subtracting the Qpn value that is the fuel injection amount of the post-injection n from the Qpr value ( Step S112) and a process (step S113) for making the post injection for calculating the fuel injection amount and the execution timing the next post injection are performed.

  After finishing the process of step S113, the ECU 40 starts the processes after step S103 again.

Hereinafter, the check process (step S107 in FIG. 2) will be described.
The check process is a process of the procedure shown in FIG.

  That is, the ECU 40 that has started this check process first determines whether or not “QpnL <minimum injection amount” is satisfied (step S201).

  In step S201, it is normally determined whether or not “limit injection amount QpnL <minimum injection amount” is established. However, when the execution timing θn comes after the exhaust valve opening timing, the variable QpnL is set to “0” (see steps S104 and S105 in FIG. 2). Therefore, the determination in step S201 may be a determination as to whether QpnL = 0 (the execution timing θn is after the exhaust valve opening timing).

  If “QpnL <minimum injection amount” has not been established (step S201; NO), the ECU 40 determines whether “n> maximum post-injection count” is established (step S202). Then, if “n> maximum post-injection count” has not been established (step S202; NO), the ECU 40 ends this check processing and performs the processing after step S108 (FIG. 2) already described. Start.

  On the other hand, when “n> the maximum number of post injections” is established (step S202; YES), the ECU 40 determines whether or not the gas amount in the control target cylinder is less than a preset gas amount upper limit. Judgment is made (step S203). More specifically, in this step S203, the ECU 40 compares the estimated value of the gas amount immediately after combustion with the upper limit of the gas amount.

  The ECU 40 also makes the determination in step S203 even when “QpnL <minimum injection amount” is established (step S201; NO).

When the gas amount is less than the upper limit of the gas amount (step S203; YES), the ECU 40
The gas amount is increased by controlling the opening degree of the throttle valve 14 (step S204). The process in step S204 may be a process for increasing the gas amount by a predetermined amount or a process for increasing the gas amount to the upper limit of the gas amount.

  After completing the process in step S204, the ECU 40 sets “−1” in QpnL (step S205). Then, the ECU 40 ends the check process.

  As already described, when QpnL = −1 is satisfied after the check process (see step S111 in FIG. 2), the post injection condition determination process is restarted from the beginning. Since the limit injection amount increases as the gas amount increases, if the gas amount is less than the upper limit of gas amount (step S203; YES), post injection conditions in which the fuel injection amount of each post injection is larger are set. It will be required.

  When the gas amount is not less than the gas amount upper limit (step S203; NO), the ECU 40 starts the post injection condition adjustment process. In FIG. 4, a process including steps described in a dotted frame is a post injection condition adjustment process.

  The ECU 40 that has started the post injection condition adjustment process first determines whether or not the Qpr value is less than the first distribution allocatable amount (step S211).

  Here, the first allocation allocatable amount is that the fuel is distributed to the fuel injection amounts Qp1 to Qp (n-1) so that the fuel does not reach the cylinder inner wall during any of the post injections 1 to n-1. This is the amount of fuel that can be produced. Even if this first allocation allocatable amount is a fixed value, a value obtained from the maximum value of the fuel amount that satisfies the above conditions (hereinafter referred to as the first distribution allocatable maximum fuel amount) (for example, “first It may be “maximum amount of fuel that can be allocated / α” (α <1) or “first maximum amount of fuel that can be allocated for allocation−β” (β> 0)).

  Note that the maximum amount of fuel that can be allocated to the first distribution is the fuel amount (hereinafter referred to as spray arrival) in which the limit injection amount of post injections 1 to n-1 and the fuel spray arrival distance of each post injection coincide with the distance to the cylinder inner wall. It can be calculated from the fuel amount). Therefore, when the first allocation allocatable amount is obtained from the first allocatable maximum fuel amount, the spray reaching fuel amount may be calculated when the limit injection amount is calculated in step S105.

  When the Qpr value is less than the first allocation allocatable amount (step S211; YES), the ECU 40 determines whether or not θn is before the exhaust valve is opened (step S212). Although details will be described later, the determination in step S212 may be omitted.

  When θn is before the opening of the exhaust valve (step S212; YES), the ECU 40 does not reach the cylinder inner wall with the fuel for the Qpr value during any of the post injections 1 to n-1. In this way, the distribution is made to Qp1 to Qp (n-1) (step S213).

  In this step S213, usually, a process of distributing more fuel by post-injection with earlier implementation timing is performed. More specifically, when the first distribution allocatable maximum fuel amount · α (α <1) is used as the first distribution allocatable amount, in step S213, for each post injection, (spray reaching fuel amount) -Limit injection amount) · α is calculated, and the calculated value is added to the fuel injection amount of each post injection. However, the process of step S213 may be a process of distributing the same amount of fuel to each post injection (a process of adding the same fuel amount to the fuel injection amount of each post injection).

The ECU 40 that has finished the process of step S213 sets “0” to Qpn and QpnL, respectively.
"Is set (step S214). Then, the ECU 40 ends the post-injection condition adjustment process and the check process (the process of FIG. 4), and starts the processes after step S108 (FIG. 2). When both QpnL values are “0”, a branch to “NO” is performed in step S108, a branch to “NO” is performed in step S110, and a branch to “YES” is performed in step S111. Therefore, when the process of step S213 (and S214) is performed, the post injection condition determination process (the process of FIG. 2) is terminated.

  As shown in FIG. 4, the ECU 40 has a case where the Qpr value is equal to or larger than the first allocation allocatable amount (step S211; NO) and a case where θn is after the exhaust valve opening timing (step S212; NO). ), The fuel corresponding to the second distribution allocatable amount is distributed to Qp1 to Qp (n-2) (step S221). The second allocation allocatable amount used in step S221 can be distributed to Qp1 to Qp (n-2) so that the fuel does not reach the cylinder inner wall during any of the post injections 1 to n-2. The amount of fuel. This second allocatable allocation amount is a maximum value of the fuel amount that satisfies the above conditions (hereinafter referred to as the “second allocatable maximum fuel amount”), even if it is a fixed value, in the same manner as the first allocatable allocation amount described above. (For example, “second distribution allocatable maximum fuel amount · α” (α <1) and “second distribution allocatable maximum fuel amount−β” (β> 0)). good. Further, the process of step S221 is a process of distributing the same amount of fuel to each post-injection, even if the process is a process of distributing more fuel to the post-injection with earlier implementation timing, similar to the process of step S213 described above. It may be.

  After completing the process of step S221, the ECU 40 adds “Qpr−second allocation allocatable amount” to the Qp (n−1) value (step S222). That is, the ECU 40 changes the Qp (n-1) value to a value obtained by subtracting the sum of the Qp1 to Qp (n-2) values from the Qp value.

  Further, the ECU 40 retards the execution timing θ (n−1) until the exhaust valve starts to open immediately before the fuel injected by the post injection n−1 reaches the cylinder inner wall (step S223). That is, in this step S223, the ECU 40 calculates the post-injection n-1 execution timing θ (n−1) at which the exhaust valve starts to open immediately before the injected fuel reaches the cylinder inner wall. In the process of step S223, the amount of gas near the opening timing of the exhaust valve is estimated from the operating state of the internal combustion engine 10, and the fuel injected from the fuel injection valve 20 near the opening timing of the exhaust valve based on the estimation result. It is possible to employ a process of calculating the time of arrival at the cylinder inner wall and calculating the implementation time θ (n−1) using the calculated arrival time. Further, a simpler process (a process that uses a preset time for each operating condition of the internal combustion engine 10 as an arrival time) may be employed as the process of step S223.

  Thereafter, the ECU 40 sets “0” to Qpn and QpnL, respectively (step S224). Then, the ECU 40 ends the post-injection condition adjustment process and the check process, performs the determinations of steps S108, S110, and S111 (FIG. 2) and ends the post-injection condition determination process.

  Hereinafter, the content of the post injection condition determination process will be described more specifically. When the fuel injection valve 20 is a general one, “n> maximum post-injection number” is normally established before “QpnL <minimum injection amount” and “θn> exhaust valve opening timing” are established. . Therefore, in the following, the contents of the post-injection condition determination process are mainly described in the case where “QpnL <minimum injection amount” and “θn> exhaust valve opening timing” are not established before “n> maximum post-injection count” is established. explain.

  As is clear from the above procedure, in the post-injection condition determination process, the post-injection condition is determined without performing the post-injection condition adjustment process, and the post-injection conditions are determined by performing the processes in steps S221 to S224. In some cases, the post-injection condition may be determined by performing the process in step S213.

  The post-injection condition is determined without performing the post-injection condition adjustment process because the required post-injection amount Qp is the sum of Qp1L to QpML (M is the maximum post-injection number) calculated before / after the gas amount increase. This is the case.

  For example, consider a case where the relationship “Qp ≦ Qp1L” is established between the requested post-injection amount Qp and Qp1L calculated during the process of step S105 (FIG. 2). In this case, θ1 and Qp1L are calculated in steps S103 and S105 executed in a state where n = 1. In the check processing in step S107, since “n (= 1)> maximum post-injection count” (and “QpnL (= Qp1L) <minimum injection amount”) is not established, nothing is performed (any variable value). Is also not changed). If the relationship of “Qp ≦ Qp1L” is established, “Qp1L ≧ Qpr (= Qp)” is established, so that the branch to “YES” is performed in step S108 executed in the state of n = 1. Is done. As a result, it is determined that the fuel injection amount and the execution timing of the post injection 1 are Qpn1 (= Qp) and θ1, respectively, and the post injection condition determination process is ended.

  Further, when the relationship “Qp1L <Qp ≦ (Qp1L + Qp2L)” is established between the required post injection amount Qp and Qp1L and Qp2L calculated at the time of the process of step S105, the process is executed in the state of n = 1. In step S108, branching to the “NO” side is performed. Then, branching to “YES” is performed in step S108 executed in the state of n = 2, and the post injection condition determination processing is completed. That is, in this case, the post injection to be performed is twice, the fuel injection amount and execution timing of the post injection 1 are Qpn1 and θ1, respectively, and the fuel injection amount and execution timing of the post injection 2 are respectively Qpn2 (= Qp−Qpn1), θ2 is determined, and the post-injection condition determination process is terminated.

  When the required post-injection amount Qp is equal to or less than the sum of Qp1L to QpML (M is the maximum post-injection number) calculated before increasing the gas amount, each of the steps executed in the state of n = 1 to M−1. In step S108, branching to the “NO” side is performed. Then, in step S108 executed in a state where n = M, a branch to “YES” is performed, and the fuel injection amounts and execution timings of the post injections 1 to M are determined.

  If the required post injection amount Qp is larger than the sum of Qp1L to QpML calculated before the gas amount increase, a branch to the “NO” side is performed in step S108 executed in a state where n = M. Is called. Then, in step S202 of the check process executed after n is incremented by “1”, a branch on the “YES” side is performed to determine whether or not “gas amount <gas amount upper limit” is satisfied. The

  When “gas amount <gas amount upper limit” is not satisfied (step S203; YES), the gas amount is increased, and the post-injection condition determination process is repeated from the beginning. Therefore, when the sum of Qp1L to QpML becomes equal to or greater than the required post injection amount Qp before the gas amount reaches the upper limit of the gas amount, post injection condition adjustment processing (processing after step S211 in FIG. 4) is performed. However, the post injection condition determination process is terminated.

  On the other hand, if the sum of Qp1L to QpML does not exceed the required post injection amount Qp even if the gas amount reaches the upper limit of gas amount (step S203; NO), post injection condition adjustment processing is performed.

When the post injection condition adjustment process is started, “total of Qp1L to QpML = Qp−Qpr” is established. Therefore, in order to supply the fuel of the required post injection amount Qp into the cylinder with M post fuels, the fuel corresponding to the Qpr value is distributed to each post injection (the fuel injection amount of each post injection is increased by the increase amount). It is necessary to increase the sum so that the sum becomes the Qpr value. However, there is a limit to the amount of fuel that can be distributed to each post injection so that the fuel injected by each post injection does not reach the cylinder inner wall. Therefore, in step S211, it is determined whether or not the fuel for the Qpr value can be distributed to Qp1L to QpML in such a manner that the fuel injected by each post injection does not reach the cylinder inner wall.

  When the fuel for the Qpr value can be distributed to Qp1L to QpML in such a manner that the fuel injected by each post injection does not reach the cylinder inner wall, the fuel for the Qpr value is distributed to each fuel injection amount (step S213). Then, the post injection condition adjustment process and the post condition determination process are terminated.

  On the other hand, when the fuel for the Qpr value cannot be distributed to Qp1L to QpML in such a manner that the fuel injected by each post-injection does not reach the cylinder inner wall, the fuel of the second allocation allocatable amount smaller than the Qpr value is Qp1L to Qp (M-1) L is distributed (step S221). Then, the fuel injection amount QpML of the post-injection M is changed to a value obtained by subtracting the sum of Qp1 to Qp (M-2) values from the Qp value (step S222). Further, the post-injection M execution timing θM is retarded until the exhaust valve of the control target cylinder is opened immediately before the fuel injected by the post-injection M reaches the cylinder inner wall (step S223).

  That is, the fuel injection amount QpML calculated in the above procedure is an amount that reaches the cylinder inner wall when the fuel is injected into the fuel injection valve 20 at the time θM calculated in the process of step S105. When the exhaust valve is opened, an air flow toward the exhaust valve is generated in the cylinder. Therefore, the fuel injected by the post injection M can be put on the air flow and discharged out of the cylinder. However, if fuel injection continues even if the airflow is slow, the fuel reaches the cylinder inner wall. Therefore, it is desired that the time from when the exhaust valve is opened until the post injection M is completed is short. Then, if the fuel of the second allocation allocatable amount is distributed to Qp1L to Qp (M-1) L, the fuel injection amount QpML can be reduced, and if the execution timing θM of the post injection M is the above timing, The fuel injection time after the exhaust valve is opened can be shortened. Therefore, post injection conditions are determined by the above procedure.

  Hereinafter, some items will be supplemented regarding the post injection condition determination processing.

  Depending on the specifications of the fuel injection valve 20, “QpnL <minimum injection amount” or “θn> exhaust valve opening timing” may be satisfied before “n> maximum post-injection number” is satisfied.

  When “QpnL <minimum injection amount” is established before “n> maximum post-injection number” is established (step S201; YES), in the post-injection condition determination process, “n> maximum post-injection number” is established. The same processing is performed. In addition, when “θn> exhaust valve opening timing” is established before “n> maximum post-injection count” is established (step S104; NO), in the post-injection condition determination process, the QpnL value is set to “0”. As a result, the same processing as when “n> the maximum number of post injections” is established is performed.

  Therefore, according to the post-injection condition determination process, even when “QpnL <minimum injection amount” or “θn> exhaust valve opening timing” is satisfied before “n> maximum post-injection number” is satisfied, Post injection conditions can be determined.

  In addition, the post injection condition determination process is a process for changing the determination method of the post injection condition depending on whether θn is before the exhaust valve opening timing (step S211 in FIG. 2) for the following reason.

  When θn is after the exhaust valve opening timing, θ (n−1) (the last post-injection execution timing) is near the exhaust valve opening timing. Therefore, the amount of fuel that is injected into the fuel injection valve 20 at time θ (n−1) and does not reach the cylinder inner wall is extremely small. On the other hand, if the execution timing θ (n−1) is retarded to the vicinity of the exhaust valve opening timing, more fuel than the fuel amount can be injected into the fuel injection valve 20 without reaching the cylinder inner wall.

  Then, considering that there is a possibility that the limit injection amount calculated in step S107 and the value added to each fuel injection amount in step S213 may not be accurate, θn is after the exhaust valve opening timing. Therefore, it is better to determine the post-injection conditions by the processes in steps S221 to S223. Therefore, the post-injection condition determination process is a process of changing the post-injection condition determination method depending on whether or not θn is before the exhaust valve opening timing.

  As described above in detail, when the temperature of the exhaust purification device 25 is raised, the ECU 40 as the fuel injection control device of the internal combustion engine according to the present embodiment first performs steps S221 to S224 of the post injection condition determination processing. Is a first control condition for defining the execution timing and the fuel injection amount of one or more post injections by the processing of each step except for the fuel injected at each post injection does not reach the cylinder inner wall, The first control in which the post-injection is performed within a period in which the fuel injected from the fuel injection valve does not ignite before the exhaust valve is opened, and the required amount of fuel is injected by the number of post injections equal to or less than the maximum number of post-injections. Try to identify the condition.

  Then, when the first control condition can be specified, the ECU 40 causes the fuel injection valve 20 to perform one or more post injections according to the first control condition.

  On the other hand, when the first control condition cannot be specified, the ECU 40 is the second control condition that defines the execution timing and the fuel injection amount of each maximum number of times by the processing of steps S221 to S224. The fuel injected at each post-injection except the final post-injection does not reach the cylinder inner wall, and each post-injection excluding the final post-injection was injected from the fuel injection valve before the exhaust valve was opened Cylinder of fuel injected by the final post-injection, which is performed within the period when the fuel is not ignited, and the fuel injection amount of the final post-injection is a value obtained by subtracting the sum of the fuel injection amounts of the other post-injections from the required amount A second control condition is specified in which the exhaust valve starts to open immediately before arrival at the inner wall. Then, the ECU 40 causes the fuel injection valve 20 to perform the maximum number of post injections according to the specified second control condition.

  When the exhaust valve opens, an air flow toward the exhaust valve is generated in the cylinder. Therefore, if the final post-injection is performed at a time when the exhaust valve starts to open immediately before arrival of the fuel injected by the final post-injection on the cylinder inner wall, the exhaust The injected fuel is discharged out of the cylinder on the airflow generated by opening the valve.

  Therefore, according to the control of the above-described procedure of the ECU 40, more fuel than the amount that can be supplied to the exhaust purification device 25 can be supplied to the exhaust purification device 25 by repeating the amount of fuel injection that does not reach the cylinder inner wall. .

<Deformation>
The above-described technique can perform various modifications. For example, the above-described internal combustion engine 10 is a diesel engine in which the exhaust gas purification device 25 in which the oxidation catalyst 25a and the DPF 25b are arranged in the exhaust passage 13 is provided, but the internal combustion engine controlled by the above procedure is a post injection. The engine may be a diesel engine or a gasoline engine as long as it is a direct injection type internal combustion engine equipped with an exhaust purification device that needs to be heated by the above.

In addition, the limit injection amount of the post injection condition determination process described above is “the distance from each injection hole of the fuel injection valve 20 to the inner wall of the cylinder−each injection when the fuel injection valve 20 starts that amount of fuel injection. The amount of fuel that reaches the fuel spray reach distance from the hole ≦ the specified value is satisfied. However, the limit injection amount is that the fuel spray reach distance reaches the cylinder inner wall when injected at the execution timing θn. It may be a value obtained by subtracting a predetermined amount from “amount of fuel matching the distance of” Moreover, after adopting a small value as the specified value or the predetermined amount, the post injection condition determination process (post injection condition adjustment process) may be modified to a process in which the processes of steps S213 and S221 are not performed.

  The post-injection condition determination process may be modified to a process in which the determination in step S104 or the determination in step S201 is not performed. Further, the post-injection condition determination process may be modified to a process in which the processes in steps S203 to S205 are not performed (a process in which the process from step S211 is performed when branching to “YES” in step S202).

  Further, in a four-cylinder internal combustion engine using a common rail 22 such as the internal combustion engine 10, the execution timing of main injection in a certain cylinder and the execution timing of post injection in another cylinder are close to each other. When the main injection is executed, the rail pressure (fuel pressure in the common rail 22) decreases, and if the post injection is performed in a state where the rail pressure is low, the fuel injection pressure decreases, so that more fuel is supplied to the cylinder inner wall. Can be injected into the cylinder in a manner that does not reach the cylinder.

  Therefore, the process of step S223 is not a process in which the final post-injection execution timing θ (n−1) is set to a timing in the vicinity of the exhaust valve opening timing, but as shown schematically in FIG. Processing for determining the final post-injection timing may be performed so that the final post-injection is performed during the period in which the pressure is reduced.

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 11 ... Cylinder 12 ... Intake passage 12a ... Intake manifold 13 ... Exhaust passage 13a ... Exhaust manifold 14 ... Throttle valve 15 ... EGR passage 16 ... -EGR valve 20 ... Fuel injection valve 21, 23, 33 ... Pressure sensor 22 ... Common rail 25 ... Exhaust gas purification device 25a ... Oxidation catalyst 25b ... DPF
31, 37 ... Temperature sensor 32 ... Air flow meter 35 ... Accelerator opening sensor 36 ... Crank angle sensor 40 ... ECU

Claims (1)

In a fuel injection control device for an internal combustion engine having a fuel injection valve for directly injecting fuel into a cylinder,
When the temperature of an exhaust gas purification device provided in the exhaust system of the internal combustion engine is raised, the first control condition defines the execution timing and fuel injection amount of one or more post injections in one combustion cycle, and each post The fuel injected at the time of injection does not reach the inner wall of the cylinder, and each post-injection is performed within a period in which the fuel injected from the fuel injection valve does not ignite before the exhaust valve of the cylinder opens. A first process for determining whether or not a first control condition for injecting a required amount of fuel is performed by post-injection after the number of post-injections is performed, and it is determined by the first process that the first control condition is not satisfied. If the first control condition is satisfied, the second process for determining whether or not the first control condition is satisfied after the control for increasing the gas amount immediately after combustion in the cylinder is performed. The gas amount is predetermined Repeat until the gas volume limit, when the first control condition is satisfied by the second processing, and the first control unit to perform one or more post-injection to the fuel injection valve in accordance with the first control condition ,
When the first control condition is not satisfied by the second processing even when the gas amount reaches the predetermined gas amount upper limit, the post-injection execution time and the fuel injection amount of the maximum post-injection number in the one combustion cycle The fuel injected at the time of each post-injection except the last post-injection performed last does not reach the inner wall, and each post-injection excluding the last post-injection is Each post-injection is performed within a period in which the fuel injected from the fuel injection valve does not ignite before the exhaust valve is opened, and the fuel injection amount of the final post-injection is the required amount excluding the final post-injection. of a value obtained by subtracting the sum of the fuel injection quantity, it obtains a second control condition in which the exhaust valve just before the arrival of the inner wall of the fuel injected by the final post-injection starts to open, the second system A second control unit to perform the post injection of the maximum post injection times in the fuel injection valve according to the conditions,
A fuel injection control device for an internal combustion engine, comprising:

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