JP2020026740A - Control device of internal combustion engine - Google Patents

Abstract

To provide a control device of an internal combustion engine which can stabilize stratified charge combustion.SOLUTION: A CPU 42 generates a homogeneous air-fuel mixture by injecting fuel from a port injection valve 16 and an in-cylinder injection valve 20 one time at a time before the valve-closing of an intake valve for the purpose of the rapid warmup treatment of a catalyst 26, and after that, injects the fuel from the in-cylinder injection valve 20 for further and locally enriching the air-fuel mixture in the vicinity of an ignitor 22 at timing at a retardance side with respect to a compression top dead point TDC. Here, when alcohol concentrations of the fuel differs from each other between those of the port injection valve 16 and the in-cylinder injection valve 20, the CPU 42 generates the homogeneous air-fuel mixture by using only the in-cylinder injection valve 20.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for an internal combustion engine applied to an internal combustion engine including a port injection valve for injecting fuel into an intake passage and a direct injection valve for injecting fuel into a combustion chamber.

  For example, Patent Literature 1 below describes a control device for an internal combustion engine that executes stratified combustion control using both a port injection valve and an in-cylinder injection valve.

JP 2009-299569 A

  The inventor of the present invention has found that, in an internal combustion engine mounted on a so-called FFV (Flexible Fuel Vehicle), a homogeneous air-fuel mixture having a high air-fuel ratio is generated using both the port injection valve and the in-cylinder injection valve, and then the vicinity of the ignition plug Injecting fuel by in-cylinder injection valve to generate a rich air-fuel mixture was studied. In this case, if the alcohol concentration in the fuel injected from the port injection valve after the refueling is different from the alcohol concentration in the fuel injected from the in-cylinder injection valve, the homogeneity of the homogeneous mixture decreases. , Found that combustion was not stable.

  In order to solve the above-mentioned problem, the present invention is applied to an internal combustion engine including a port injection valve that injects fuel into an intake passage and an in-cylinder injection valve that injects fuel into a combustion chamber. A determination process for determining whether or not a difference between the alcohol concentration and the alcohol concentration in the fuel supplied to the in-cylinder injection valve is equal to or greater than a predetermined value; The stratified combustion is realized by injecting fuel from both the injection valve and the in-cylinder injection valve. And a stratification process for realizing combustion.

  When the process of generating a homogeneous air-fuel mixture in stratified charge combustion is performed only by the in-cylinder injection valve, the homogeneity tends to be lower than in the case of using the port injection valve. On the other hand, when only the port injection valve is used, there is a possibility that the fuel cannot be completely injected within a period on the advance side that is appropriate for generating a homogeneous air-fuel mixture, and that the amount of fuel adhering to the intake passage may be unstable. is there. Therefore, in the above configuration, a homogeneous air-fuel mixture is generated using the port injection valve and the in-cylinder injection valve. However, if the alcohol concentration in the fuel supplied to the port injection valve is different from the alcohol concentration in the fuel supplied to the in-cylinder injection valve, the homogeneity of the homogeneous mixture is reduced, and the stratified combustion may not be stabilized. is there. Therefore, in the above configuration, when the difference between the alcohol concentration in the fuel supplied to the port injection valve and the alcohol concentration in the fuel supplied to the in-cylinder injection valve is equal to or greater than a predetermined value, only the in-cylinder injection valve is used. To achieve stratified combustion. This makes it possible to stabilize stratified combustion as compared with the case where both the port injection valve and the in-cylinder injection valve are used.

FIG. 1 is a diagram showing a control device and an internal combustion engine according to one embodiment. 5 is a flowchart showing a procedure of a process executed by the control device according to the embodiment. 3A to 3C are time charts showing fuel injection control according to the embodiment.

Hereinafter, an embodiment of a control device for an internal combustion engine will be described with reference to the drawings.
The internal combustion engine 10 shown in FIG. 1 is mounted on a vehicle. The intake passage 12 of the internal combustion engine 10 is provided with a throttle valve 14 and a port injection valve 16 in order from the upstream side. The air sucked into the intake passage 12 and the fuel injected from the port injection valve 16 are supplied to the combustion chamber 18. The combustion chamber 18 is provided with a direct injection valve 20 and an ignition device 22. The mixture in the combustion chamber 18 is used for combustion by spark discharge from the ignition device 22, and the mixture used for combustion is discharged to the exhaust passage 24 as exhaust gas. A catalyst 26 is provided in the exhaust passage 24.

  Fuel is supplied to the port injection valve 16 from the low pressure side delivery pipe 30. Fuel is supplied to the in-cylinder injection valve 20 from the high pressure side delivery pipe 32. The fuel in the fuel tank 34 is supplied to the low-pressure delivery pipe 30, and the fuel in the fuel tank 34 is supplied to the high-pressure delivery pipe 32 by being pressurized by a pump 38.

  The control device 40 controls the internal combustion engine 10 and controls the internal combustion engine 10 such as the throttle valve 14, the port injection valve 16, the in-cylinder injection valve 20, and the ignition device 22 in order to control a torque, an exhaust component ratio, or the like as a control amount. The operation unit of the engine 10 is operated. When operating the operation unit, the control device 40 refers to the intake air amount Ga detected by the air flow meter 50 and the alcohol concentration Da in the fuel passage 36 detected by the alcohol concentration sensor 52. Further, the control device 40 refers to the temperature of the cooling water of the internal combustion engine 10 (water temperature THW) detected by the water temperature sensor 54 and the depression amount of the accelerator pedal (accelerator operation amount ACCP) detected by the accelerator sensor 56. The control device 40 includes a CPU 42 and a ROM 44.

  FIG. 2 shows a procedure of processing executed by the control device 40. The process shown in FIG. 2 is realized by the CPU 42 repeatedly executing the program stored in the ROM 44 at a predetermined cycle, for example. In the following, a step number of each process is represented by a number preceded by “S”.

  In the series of processes shown in FIG. 2, the CPU 42 first calculates the alcohol concentration (port-side concentration Dap) in the fuel injected from the port injection valve 16 (S10). Here, the CPU 42 first branches the fuel passage 36 into a low-pressure passage 36a connected to the low-pressure delivery pipe 30 and a high-pressure passage 36b connected to the high-pressure delivery pipe 32 (see FIG. 1). ) Is calculated. That is, the CPU 42 is provided with the alcohol concentration sensor 52 in the fuel passage 36 in which the integrated value of the sum of the fuel amount injected from the port injection valve 16 and the fuel amount injected from the in-cylinder injection valve 20 is provided. The alcohol concentration Da at the time when the volume from the location to the branch portion B is small is defined as the concentration Dab at the branch portion B. Then, the CPU 42 determines the concentration Dab of the branch portion B at the time when the integrated value of the amount of fuel injected from the port injection valve 16 is smaller by the volume of the low-pressure passage 36 a, the alcohol concentration of the fuel flowing into the low-pressure delivery pipe 30. And The CPU 42 determines that the same amount of fuel as the injected fuel flows into the low-pressure delivery pipe 30 with the injection of the fuel from the port injection valve 16, and determines the alcohol concentration in the low-pressure delivery pipe 30. The density Dap is calculated.

  Next, the CPU 42 calculates the alcohol concentration (in-cylinder concentration Dad) in the fuel injected from the in-cylinder injection valve 20 (S12). More specifically, the CPU 42 determines the concentration Dab of the branch portion B at the time when the integrated value of the amount of fuel injected from the in-cylinder injection valve 20 is smaller by the volume of the high-pressure side passage 36b and the fuel flowing into the high-pressure side delivery pipe 32. Alcohol concentration. Then, the CPU 42 determines that the same amount of fuel as the injected fuel flows into the high-pressure side delivery pipe 32 with the injection of the fuel from the in-cylinder injection valve 20, and determines the alcohol concentration in the high-pressure side delivery pipe 32. The inside density Dad is calculated.

  Next, the CPU 42 determines whether or not the catalyst rapid warm-up flag F is "1" (S14). The catalyst rapid warm-up flag F indicates that the catalyst rapid warm-up process is executed when it is “1”, and indicates that the catalyst rapid warm-up process is not executed when it is “0”. Note that the initial value of the catalyst rapid warm-up flag F is set to “0”.

  When the CPU 42 determines that the catalyst rapid warm-up flag F is “0” (14: NO), the condition (A) that the start of the internal combustion engine 10 is completed, and the water temperature THW is equal to or lower than the predetermined temperature Tth. It is determined whether the logical product of the condition (a) and the condition (1) is true (S16). The processing in S16 is for determining whether or not the conditions for executing the catalyst rapid warm-up processing are satisfied. The condition (a) is a condition that the temperature of the catalyst 26 is low. When determining that the logical product is true (S16: YES), the CPU 42 substitutes “1” for the catalyst rapid warm-up flag F (S18).

  On the other hand, when determining that the catalyst rapid warm-up flag F is “1” (S14: YES), the CPU 42 adds the intake air amount Ga to the integrated value InG of the intake air amount Ga to thereby obtain the integrated value InG. Is updated (S20). The integrated value InG has an initial value of “0” and is a parameter indicating the total amount of combustion energy after the start of the internal combustion engine 10. Next, the CPU 42 determines whether or not the logical sum of the condition (c) that the accelerator is depressed and the condition (d) that the integrated value InG is equal to or more than the predetermined value Inth is true ( S22). Here, when the accelerator operation amount ACCP is equal to or more than the predetermined value, the CPU 42 determines that the condition (C) is satisfied. Further, the CPU 42 calculates the predetermined value Inth to be smaller when the water temperature THW is higher than when the water temperature THW is lower. This process is for determining whether or not a condition for stopping the catalyst rapid warm-up process is satisfied. Here, when the condition (c) is satisfied, when the condition is not satisfied, and when the temperature of the exhaust gas increases as compared with the case where the catalyst rapid warm-up process is not executed, the catalyst rapid warm-up process is stopped. If the condition (d) is satisfied, it can be considered that the warm-up of the catalyst 26 has been completed, so the catalyst rapid warm-up process is stopped.

  When determining that the logical sum is false (S22: NO), the CPU 42 determines whether the absolute value of the difference between the port-side concentration Dap and the alcohol concentration Da is equal to or less than the specified value Dth (E), It is determined whether the logical product of the absolute value of the difference between the inner concentration Dad and the alcohol concentration Da is equal to or less than the specified value Dth is true (S24). This process is a process for determining whether or not the alcohol concentration in the fuel injected from the port injection valve 16 and the alcohol concentration in the fuel injected from the in-cylinder injection valve 20 have both converged. That is, when refueling is performed, the alcohol concentration in the fuel in the fuel tank 34 may change. Even in this case, the fuel in the low-pressure side delivery pipe 30, the low-pressure side passage 36a, the high-pressure side delivery pipe 32, the high-pressure side passage 36b, and the fuel in the fuel passage 36 remains at the alcohol concentration before refueling. Then, fuel is injected from the port injection valve 16 and the in-cylinder injection valve 20, so that the fuel in the fuel tank 34 reaches the low pressure side delivery pipe 30 and the high pressure side delivery pipe 32, and the low pressure side delivery pipe 30 The fuel in the side delivery pipe 32 is gradually replaced. Thereby, when the alcohol concentration Da detected by the alcohol concentration sensor 52 becomes equal to the alcohol concentration in the fuel in the low-pressure side delivery pipe 30 or the high-pressure side delivery pipe 32, the fuel in the fuel injected from the port injection valve 16 The alcohol concentration and the alcohol concentration in the fuel injected from the in-cylinder injection valve 20 have converged.

  When determining that the logical product is true (S24: YES), the CPU 42 executes a normal catalyst rapid warm-up process (S26). That is, the CPU 42 injects the fuel once from each of the port injection valve 16 and the in-cylinder injection valve 20 to generate a homogeneous mixture before closing the intake valve, and thereafter generates a homogeneous mixture. At the timing on the retard side, fuel is injected from the in-cylinder injection valve 20 in order to locally make the mixture near the ignition device 22 richer. Thus, stratified combustion can be performed, and the temperature of exhaust gas can be increased.

  Here, the reason that not only the port injection valve 16 but also the in-cylinder injection valve 20 is used to generate the homogeneous mixture is that, depending on only the port injection valve 16, before the spark ignition by the ignition device 22, This is because it is difficult to inject all the fuel within a period in which the fuel can be sufficiently atomized. Secondly, when the alcohol concentration Da is high to some extent, if the amount of fuel injected from the port injection valve 16 is large, the amount of fuel adhering to the intake passage 12 becomes excessively large. This is because the amount of fuel adhering in the intake passage 12 fluctuates greatly. For this reason, it is difficult to generate a target homogeneous mixture using only the port injection valve 16, so the in-cylinder injection valve 20 is also used. By the way, when generating a homogeneous mixture using only the in-cylinder injection valve 20, compared with the case of using the port injection valve 16 together, the fuel is sufficiently atomized before spark ignition by the ignition device 22. It is difficult to atomize the fuel within the period in which the fuel injection is possible, and as a result, it is difficult to homogenize the fuel as compared with the case where the port injection valve 16 is used together.

  On the other hand, when determining that the logical product is false (S24: NO), the CPU 42 executes the catalyst rapid warm-up process at the time of transition when the alcohol concentration changes (S28). Specifically, the CPU 42 injects fuel from the in-cylinder injection valve 20 to generate a homogeneous mixture before closing the intake valve, and thereafter, near the ignition device 22 at a timing retarded from the compression top dead center TDC. The fuel is injected from the in-cylinder injection valve 20 in order to locally make the air-fuel mixture richer.

  On the other hand, when the CPU 42 makes an affirmative determination in the processing of S22, it sets the catalyst rapid warm-up flag F to “0” (S30). Note that the CPU 42 temporarily ends the series of processing illustrated in FIG. 2 when the processing of S18, S26, S28, and S30 is completed, or when a negative determination is made in the processing of S16.

Here, the operation and effect of the present embodiment will be described.
FIG. 3A shows a state transition of whether or not the replacement of the fuel in both the low-pressure side delivery pipe 30 and the high-pressure side delivery pipe 32 has been completed after refueling, and FIG. FIG. 3C shows the transition of the rotational speed NE of the crankshaft, and FIG. 3C shows the transition of the proportion of the fuel injected from the port injection valve 16 in the fuel injected in one combustion cycle.

  As shown in FIG. 3, after refueling is performed at time t1 with the vehicle stopped, the internal combustion engine 10 is started by the CPU 42 at time t2. In the present embodiment, since the CPU 42 executes the start process using the port injection valve 16, the rate of injection from the port injection valve 16 is "1" until time t3 when the start is completed. However, after time t3 when the start is completed, the CPU 42 executes the catalyst rapid warm-up process using only the in-cylinder injection valve 20.

  After the refueling, the alcohol concentration in the fuel injected from the port injection valve 16 and the injection from the in-cylinder injection valve 20 are performed until the fuel is replaced with the fuel after the refueling in both the low pressure side delivery pipe 30 and the high pressure side delivery pipe 32. And the alcohol concentration in the fuel tends to be different. In this case, when the homogeneous mixture is generated by the process of S26, the alcohol concentration in the fuel injected from the port injection valve 16 and the alcohol concentration in the fuel injected from the in-cylinder injection valve 20 are different. As a result, the homogeneity may be reduced. If the homogeneity of the homogeneous mixture is reduced, it is difficult for the flame propagation to occur continuously, and the stratified combustion is not stabilized. Therefore, in the present embodiment, the CPU 42 executes the stratified combustion using only the in-cylinder injection valve 20 during a period in which the fuel is not replaced by the one after the refueling in both the low-pressure side delivery pipe 30 and the high-pressure side delivery pipe 32. . For this reason, compared with the case where the homogeneous mixture is generated by the cooperation of the port injection valve 16 and the in-cylinder injection valve 20 during the same period, the homogeneity of the homogeneous mixture can be improved. It is possible to stabilize stratified combustion as compared with the case where air is generated.

<Correspondence>
The correspondence between the items in the above embodiment and the items described in the section of “Means for Solving the Problem” is as follows. The determination processing corresponds to the processing of S24, and the stratification processing corresponds to the processing of S26 and S28.

<Other embodiments>
The present embodiment can be modified and implemented as follows. This embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.

In the above-described embodiment, the fuel injection from the in-cylinder injection valve 20 for locally enriching the air-fuel mixture near the ignition device 22 is retarded from the compression top dead center, but is not limited to this. .
-The stratified combustion is not limited to the catalyst rapid warm-up treatment.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 12 ... Intake passage, 14 ... Throttle valve, 16 ... Port injection valve, 18 ... Combustion chamber, 20 ... In-cylinder injection valve, 22 ... Ignition device, 24 ... Exhaust passage, 26 ... Catalyst, 30 ... Low pressure Side delivery pipe, 32 ... High pressure side delivery pipe, 34 ... Fuel tank, 36 ... Fuel passage, 36a ... Low pressure side passage, 36b ... High pressure side passage, 38 ... Pump, 40 ... Control device, 42 ... CPU, 44 ... ROM, 50: air flow meter, 52: alcohol concentration sensor, 54: water temperature sensor, 56: accelerator sensor.

Claims (1)

Applied to an internal combustion engine including a port injection valve that injects fuel into an intake passage and an in-cylinder injection valve that injects fuel into a combustion chamber,
A determination process of determining whether a difference between an alcohol concentration in fuel supplied to the port injection valve and an alcohol concentration in fuel supplied to the in-cylinder injection valve is equal to or greater than a predetermined value;
When it is not determined that the predetermined value or more by the determination process, stratified combustion is realized by injecting fuel from both the port injection valve and the in-cylinder injection valve, and when it is determined that the predetermined value or more by the determination process Is a control device for an internal combustion engine that executes a stratification process of injecting fuel only from the in-cylinder injection valve to realize stratified combustion.