JP2015137626A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove deposit adhering to an injection valve, and to reduce a variation of an air-fuel ratio accompanied by the removal.SOLUTION: A fuel injection control device comprises a fuel injection valve which injects fuel contained in an air-fuel mixture which is burnt in a combustion chamber of an internal combustion engine by moving a needle valve, and a control part which can selectively perform high-lift injection and low-lift injection. When a specified condition that deposit DP adhering in the fuel injection valve should be removed is not established, the control part performs the high-lift injection, and moves the needle valve so that an air-fuel ratio of an air-fuel mixture reaches a target air-fuel ratio at that time. On the other hand, when the specified condition is established, the control part continuously performs the low-lift injection a plurality of times, and moves the needle valve so that the air-fuel ratio of the air-fuel mixture reaches an air-fuel ratio which is smaller than the target air-fuel ratio at that time. By this constitution, a torque variation amount at the low-lift injection and a degree of the deterioration of emission can be reduced.

Description

  The present invention relates to a fuel injection control device for an internal combustion engine that includes a fuel injection valve that injects fuel by moving a needle valve.

  Deposits are deposited inside the fuel injection valve used in the internal combustion engine, particularly in the vicinity of the tip of the needle (such as a sack wall surface, a nozzle sheet wall surface, and a needle seat wall surface). In order to remove this deposit, the fuel injection control device disclosed in Patent Document 1 supplies fuel in a state in which the lift amount from the nozzle seat of the needle valve (that is, the needle lift amount) is less than the maximum lift amount. Spray. During this low lift injection, the flow path area between the needle sheet and the nozzle sheet is smaller than the flow path area of the nozzle hole. As a result, the fuel flow velocity in the vicinity of the needle valve tip is increased, so that the above-described deposit is effectively removed.

JP 2013-185514 A

  By the way, in the low lift injection, the flow path area between the needle seat and the nozzle seat is small, so the rate of flow reduction due to deposits deposited and deposited inside the tip of the fuel injection valve (and hence the rate of reduction of the injected fuel amount) ) Becomes larger. As a result, when the low lift injection for removing the deposit is performed, the air-fuel ratio of the air-fuel mixture greatly deviates from the target air-fuel ratio (for example, the stoichiometric air-fuel ratio) to the lean side, so that torque fluctuations and emissions are reduced. There is a risk of deterioration.

  An object of the present invention is to perform low lift injection in order to remove deposits deposited and accumulated in the tip of the fuel injection valve, and at the time of the low lift injection, “the lean side of the air-fuel ratio from the target air-fuel ratio It is an object of the present invention to provide a fuel injection control device capable of reducing the “degree of deviation to”.

  The fuel injection control device of the present invention includes a fuel injection valve and a control unit. The fuel injection valve includes a needle valve. The fuel injection valve injects “fuel contained in the air-fuel mixture combusted in the combustion chamber of the internal combustion engine” by moving the needle valve. The control unit can selectively execute high lift injection and low lift injection. High lift injection is an injection method in which fuel is injected by changing the lift amount of the needle valve within a range up to the first lift amount. The low lift injection is an injection method in which fuel is injected by changing the lift amount of the needle valve in a range up to “a second lift amount smaller than the first lift amount”.

  Further, the control unit performs the high lift injection when a specific condition indicating that the deposit adhered in the fuel injection valve should be removed is not satisfied. When performing the high lift injection, the control unit moves the needle valve so that the air-fuel ratio of the air-fuel mixture becomes a target air-fuel ratio determined by the engine operating state. In addition, the control unit continuously performs the low lift injection a plurality of times when the specific condition is satisfied. The control unit moves the needle valve so that the air-fuel ratio of the air-fuel mixture becomes “the air-fuel ratio smaller than the target air-fuel ratio” when the low lift injection is continuously performed a plurality of times.

  According to the present invention, when a specific condition indicating that the deposit adhered in the fuel injection valve should be removed is satisfied (for example, a correction amount for setting the air-fuel ratio of the air-fuel mixture in the combustion chamber to the target air-fuel ratio is a predetermined amount). ), The low lift injection is continuously performed a plurality of times instead of the high lift injection. Therefore, the deposit is effectively removed. In addition, in that case, the needle valve is moved so that the air-fuel ratio of the air-fuel mixture becomes smaller than the target air-fuel ratio (that is, richer than the target air-fuel ratio). In other words, the needle valve is moved so as to reduce the amount of decrease in the fuel injection amount caused by deposits deposited in the fuel injection valve. This movement of the needle valve includes increasing the number of executions of the low lift injection and increasing the injection time in one low lift injection. As a result, the actual fuel injection amount does not become excessively small with respect to the target fuel injection amount to be injected (that is, the fuel injection amount necessary for realizing the target air-fuel ratio). Therefore, it is possible to reduce the torque fluctuation amount, the degree of deterioration of emission, and the like.

FIG. 1 is a diagram showing an internal combustion engine to which a fuel injection control device according to a first embodiment of the present invention is applied. FIG. 2 is a cross-sectional view of the fuel injection valve shown in FIG. FIG. 3 is a cross-sectional view of the tip portion of the fuel injection valve when the fuel injection valve shown in FIG. 2 stops injection. 4 is a cross-sectional view of the tip of the fuel injection valve when the fuel injection valve shown in FIG. 2 is performing high lift injection. FIG. 5 is a cross-sectional view of the tip of the fuel injection valve when the fuel injection valve shown in FIG. 2 is performing low lift injection. FIG. 6A is a diagram showing temporal changes in the needle lift amount and the injection valve drive signal in the maximum lift injection, and FIG. 6B is the time of the needle lift amount and the injection valve drive signal in the low lift injection. It is the figure which showed the change. FIG. 7 is a flowchart showing a fuel injection control routine executed by the CPU of the ECU shown in FIG.

<First Embodiment>
A fuel injection control device according to a first embodiment of the present invention (hereinafter simply referred to as “first device”) is applied to the internal combustion engine 10 shown in FIG. The engine 10 is a well-known gasoline fuel spark ignition direct injection engine. The engine 10 includes a cylinder head 11, a cylinder block 12, a crankcase 13, an ignition device 14 including a spark plug, an intake valve 15, an exhaust valve 16, a piston 17, a connecting rod 18, a crankshaft 19, and the like. A combustion chamber 20 is formed by the lower wall surface of the cylinder head 11, the wall surface of the cylinder bore formed in the cylinder block 12, and the crown surface of the piston 17.

  The ignition device 14 is disposed in the cylinder head 11 so that the spark generating portion 14 a of the ignition plug is exposed to the combustion chamber 20. The intake valve 15 is disposed in the cylinder head 11 so as to open and close the “communication portion between the combustion chamber 20 and the intake port 22 formed in the cylinder head 11” by being driven by the intake cam 21. . The exhaust valve 16 is disposed in the cylinder head 11 so as to open and close the “communication portion between the combustion chamber 20 and the exhaust port 24 formed in the cylinder head 11” by being driven by the exhaust cam 23. .

  Further, the engine 10 includes a fuel injection valve (in-cylinder injection valve, first fuel injection valve) 30 and a high-pressure fuel pump 40. The fuel injection valve 30 is disposed in the “region between the intake port 22 and the cylinder block 12” of the cylinder head 11 so as to inject fuel into the combustion chamber 20. The high-pressure fuel pump 40 increases the pressure of fuel supplied from a fuel tank (not shown) to a “predetermined fuel pressure PF that changes according to a drive (instruction) signal”, and passes the pressurized fuel through the fuel pipe 41. The fuel injection valve 30 is supplied. Note that the first device may further include a fuel injection valve (second fuel injection valve) 45. The fuel injection valve 45 is a port injection valve disposed in the cylinder head 11 so as to inject fuel into the intake port 22.

  The first device includes an ECU (electronic control unit) 50 including a known microcomputer having a CPU, ROM, RAM, backup RAM, and the like. The ECU 50 is electrically connected to the ignition device 14, the fuel injection valve 30, the high-pressure fuel pump 40, and the like, and sends drive signals to them. In addition, the ECU 50 is electrically connected to the crank position sensor 51, the air flow meter 52, the accelerator pedal depression amount sensor 53, the air-fuel ratio sensor 54, and the like, and receives signals from these.

  The crank position sensor 51 generates a pulse signal according to the rotational position of the crankshaft 19. The ECU 50 calculates the engine speed NE based on the signal from the crank position sensor 51. The air flow meter 52 generates a signal representing the flow rate of the intake air of the engine 10. The accelerator pedal depression amount sensor 53 generates a signal indicating the depression amount of the accelerator pedal Ap. The air / fuel ratio sensor 54 generates a signal representing the air / fuel ratio of the exhaust gas. The ECU 50 acquires the absolute crank angle of the engine 10 (the crank angle with reference to the intake top dead center of a certain cylinder) based on a signal from the crank position sensor 51 and a signal from a cam position sensor (not shown). It has become.

(Details of fuel injection valve)
Next, the fuel injection valve 30 will be described in detail. The fuel injection valve 45 has a structure substantially similar to that of the fuel injection valve 30. The fuel injection valve 30 is a so-called inner valve type injection valve. As shown in FIG. 2, the fuel injection valve 30 includes a nozzle main body 31, a needle valve 32, a spring 33, and a solenoid 34.

  In the nozzle main body 31, a cylindrical space A1, a cylindrical space A2, and a cylindrical space A3 are formed in order from the distal end to the proximal end. These spaces are all formed coaxially and communicate with each other. A nozzle hole 31 a that connects the cylindrical space A <b> 1 and the outside is formed at the tip of the nozzle body 31. A fuel intake hole 31b that connects the cylindrical space A3 and a fuel pipe (not shown) is formed at the base end of the nozzle body 31.

  The needle valve 32 has a cylindrical portion 32a having a small-diameter cylindrical shape and a flange portion 32b having a large-diameter cylindrical shape. The tip of the cylindrical portion 32a has a substantially conical shape. The front end side of the columnar part 32a is accommodated in the cylindrical space A1. As a result, a fuel passage FP is formed between the inner peripheral wall surface at the front end side portion of the nozzle body 31 and the outer peripheral wall surface at the front end side portion of the cylindrical portion 32a. The collar portion 32b is accommodated in the cylindrical space A2. The needle valve 32 moves along the needle valve axis CL. Further, in the needle valve 32, “a fuel passage that connects the base end portion of the needle valve 32 and the outer peripheral wall surface of the tip side portion of the cylindrical portion 32 a” is formed. As a result, the fuel flowing into the cylindrical space A3 from the fuel intake hole 31b passes through the fuel passage in the needle valve 32 and is supplied to the fuel passage FP.

The spring 33 is disposed in the cylindrical space A3. The spring 33 biases the needle valve 32 toward the nozzle hole 31a.
The solenoid 34 is a base end side portion of the nozzle main body 31 and is disposed around the cylindrical space A2. The solenoid 34 is energized by a drive signal (injection valve drive signal) from the ECU 50. In this case, the solenoid 34 generates a magnetic force that moves the needle valve 32 toward the fuel intake hole 31b against the urging force of the spring 33. It has become.

  When the solenoid 34 is in a non-energized state, the amount of movement of the needle valve 32 (referred to as “needle lift amount” or simply “lift amount”) is “0”. Not done. When the solenoid 34 is energized and the needle lift amount is greater than “0”, fuel injection is performed. When the needle lift amount reaches a predetermined size, the flange portion 32b comes into contact with the wall portion forming the cylindrical space A2 of the nozzle body portion 31. As a result, the movement of the needle valve 32 is restricted. The needle lift amount at this time is referred to as “maximum lift amount” or “full lift amount”. That is, the needle lift amount can vary in a range from “0” to “maximum lift amount”.

  Here, the operation of the fuel injection valve 30 will be described in detail with reference to “a cross-sectional view of the vicinity of the tip of the fuel injection valve 30, FIGS. 3 to 5”.

  As described above, when the solenoid 34 is in a non-energized state, the needle valve 32 is urged toward the nozzle hole 31 a by the spring 33. As a result, as shown in FIG. 3, the needle seat wall surface 32 c of the needle valve 32 abuts (sits) on the nozzle seat wall surface 31 c that is the inner wall surface of the tip portion of the nozzle body 31. As a result, the flow between the sac S communicating with the nozzle hole 31a and the fuel passage FP described above is blocked, so that fuel is not injected from the nozzle hole 31a. The needle lift amount in this state is “0”. Note that the tip position of the needle valve 32 (position in the needle valve axis CL direction) at this time is defined as a reference position KJ of the tip of the needle valve 32.

  As described above, when the solenoid 34 is energized, the needle valve 32 is moved to the fuel intake hole 31b side. That is, when the solenoid 34 is energized, for example, as shown in FIG. 4, the needle lift amount L (distance from the reference position KJ) is a value L1 larger than “0” (L1 in the example shown in FIG. 4). = Maximum lift amount Lmax). Alternatively, when the solenoid 34 is energized, as shown in FIG. 5, the needle lift amount L becomes a value L2 larger than “0” (however, the value L2 is smaller than the value L1). As a result, the sac S communicating with the injection hole 31a and the fuel passage FP described above communicate with each other, so that fuel flows into the sac S from the fuel passage FP, and then injected to the outside through the injection hole 31a. Is done.

  The fuel injection performed by lifting (moving) the needle valve 32 to the maximum lift amount is referred to as “full lift injection” (see FIG. 4). FIG. 6A shows a change over time of the needle lift amount in one full lift injection. On the other hand, fuel injection performed by lifting (moving) the needle valve 32 within a range up to “a partial lift amount (partial lift amount) smaller than the maximum lift amount” is referred to as “partial lift injection” (FIG. See 5). FIG. 6B shows a time change of the needle lift amount in the partial lift injection that is continuously executed three times.

  In addition, as will be described later, the first device selectively performs high lift injection and low lift injection. The high lift injection is a fuel injection that changes the needle lift amount in a range up to the “first lift amount”. In this example, the first lift amount is the maximum lift amount, but may be a lift amount smaller than the maximum lift amount. That is, the high lift injection is a full lift injection or a partial lift injection. On the other hand, the low lift injection is a partial lift injection in which the needle lift amount is changed in a range up to “a second lift amount smaller than the first lift amount”.

(Outline of the operation of the first device)
As shown in FIG. 1, the tip of the fuel injection valve 30 is exposed in the combustion chamber 20 and is therefore exposed to a high temperature. Therefore, as shown in FIGS. 4 and 5, the deposit DP is likely to be generated and attached inside the tip of the fuel injection valve 30 (particularly, the tip of the needle valve 32). More specifically, metal components (zinc, calcium, etc.) may be mixed in the fuel, and the metal components are ionized when heat is applied to the fuel. The deposit DP is generated by the reaction between the ionized metal component and the combustion gas. The generated deposit DP is applied to the wall surface of the sac S, the nozzle sheet wall surface 31c and the needle sheet wall surface 32c (hereinafter referred to as “needle tip space wall surface”), or the inner wall of the injection hole 31a and the inlet of the injection hole 31a. It adheres to the inner edge of IN and the inner edge of the outlet OUT of the nozzle hole 31a (hereinafter referred to as the “wall surface of the nozzle hole”) and gradually accumulates.

  If the deposit DP is deposited in large amounts on the “needle tip space wall surface and injection hole wall surface” in the fuel injection valve 30 or the like, the injection characteristics of the fuel injection valve 30 greatly deviate from the injection characteristics of the new fuel injection valve 30. That is, the fuel injection valve 30 on which the deposit DP is deposited is less than the new fuel injection valve 30 even if the same drive signal as that of the new fuel injection valve 30 is given (even if the same voltage signal is given to the solenoid 34). Inject an amount of fuel. As a result, the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber 20 (engine air-fuel ratio) deviates greatly toward the lean side with respect to the target air-fuel ratio (for example, the theoretical air-fuel ratio: about 14.6). There is a risk of fluctuations and deterioration of emissions.

Therefore, the first device performs fuel injection control described below.
The first device has a specific condition indicating that the deposit DP deposited / deposited in the fuel injection valve 30 should be removed (the amount of deposit DP deposited / deposited in the fuel injection valve 30 may be equal to or greater than a predetermined value). It is monitored whether or not a specific condition indicating high is satisfied.
The first device supplies fuel into the combustion chamber 20 by executing high lift injection using the fuel injection valve 30 when the specific condition is not satisfied. That is, the first device injects fuel in the normal injection control mode.

  The first device injects fuel in the preliminary removal control (first deposit removal control) mode when the specific condition is satisfied. That is, the first device supplies the fuel into the combustion chamber 20 by increasing the fuel pressure PF to “a value higher than the fuel pressure in the normal injection control mode (for example, the highest value)” and performing high lift injection. To do. By increasing the fuel pressure, the flow velocity of the fuel flowing through the nozzle hole 31a increases. As a result, when fuel injection is performed in the preliminary removal control mode, the deposit DP is separated from the “hole surface” and discharged from the fuel injection valve 30 through the injection hole 31a.

  Furthermore, even if fuel injection is performed in the preliminary removal control mode, if the specific condition is still satisfied, the first device injects fuel in the deposit removal control (second deposit removal control) mode. That is, the first device increases the fuel pressure PF to “a value higher than the fuel pressure in the normal injection control mode (for example, the highest value)” and continuously performs low lift injection a plurality of times. Supply fuel inside. As a result, the deposit DP is separated from the “needle tip space wall surface” and discharged from the fuel injection valve 30 through the injection hole 31a.

  Here, the reason why the deposit DP on the wall surface of the needle tip space is effectively removed when performing the low lift injection as compared with when performing the high lift injection will be described. The area Sap of the “flow path formed between the needle seat wall surface 32c and the nozzle sheet wall surface 31c (hereinafter referred to as“ throttle portion ”)” in the low lift injection shown in FIG. 5 is shown in FIG. It is smaller than the area Saf of the throttle portion in high lift injection. On the other hand, the flow passage area Sb of the nozzle hole 31a is larger than the area Sap and smaller than the area Saf. Therefore, in the case of performing the low lift injection and the case of performing the high lift injection, if the fuel pressure in the fuel passage FP and the pressure in the combustion chamber 20 are constant, the fuel flowing through the throttle portion during the low lift injection The flow velocity Vap is larger than the flow velocity Vaf of the fuel flowing through the throttle portion during high lift injection. As a result, when the low lift injection is performed, the deposit DP is separated from the “needle tip space wall surface” by the fuel having a high flow velocity, and is discharged from the fuel injection valve 30 through the injection hole 31a.

  By the way, if low lift injection is performed in a state where the deposit DP is deposited on the wall surface of the needle tip space, the rate at which the deposit DP reduces the flow passage area of the throttle portion becomes very large. As a result, the rate of decrease in the flow rate of the injected fuel due to the deposit DP (thus, the rate of decrease in the injected fuel amount) increases. For this reason, if low lift injection is performed in order to remove the deposit DP, the air-fuel ratio of the engine greatly deviates from the target air-fuel ratio toward the lean side, resulting in torque fluctuations and emission deterioration.

  Therefore, when the first device performs fuel injection in the deposit removal control mode in which low lift injection is continuously performed a plurality of times, the air / fuel ratio of the engine is “an air / fuel ratio smaller than the target air / fuel ratio determined by the engine operating state”. The needle valve 32 is moved so as to become (the energization state of the solenoid 34, that is, the injection valve drive signal is controlled). More specifically, for example, in order to realize the target air-fuel ratio when the maximum value of the lift amount in the low lift injection is maintained at the constant value Llow and the deposit DP is not adhered, When the fuel injection is performed in the deposit removal control mode in the situation where the injection needs to be performed only the first number of times, the needle is so configured that the low lift injection is performed “the second number greater than the first number”. The valve 32 is moved. Thereby, the first device can effectively remove the deposit DP attached to the wall surface of the needle tip space in the fuel injection valve 30 while reducing the possibility of torque fluctuation and emission deterioration.

<Actual operation of the first device>
Next, the actual operation of the ECU 50 will be described. The CPU of the ECU 50 starts processing of the routine shown by the flowchart of FIG. 7 from step 700 every time a predetermined time elapses, and proceeds to step 705.

  In step 705, the CPU determines whether or not the current fuel injection mode is the normal injection control mode. In the normal injection control mode, the target air-fuel ratio AFtgt is set to “normal air-fuel ratio (in this example, stoichiometric air-fuel ratio) Rst which is the first air-fuel ratio”, the fuel pressure PF is maintained at the normal pressure PF0, and This is a mode in which high lift injection is performed only once in one cycle. The CPU sets the fuel injection mode to the normal injection control mode when the operation of the engine 10 is started. Further, the CPU may change the target air-fuel ratio AFtgt (that is, the normal air-fuel ratio Rst) based on the engine operation state (engine speed NE, intake air amount, etc.).

  Therefore, after the operation of the engine 10 is started, the fuel injection mode is the normal injection control mode, so the CPU makes a “Yes” determination at step 705 to proceed to step 710. In step 710, the CPU determines whether or not the deviation D of the air-fuel ratio learned value KG from the initial value KG0 (air-fuel ratio learned value deviation D = KG−KG0) is equal to or greater than the threshold value Dth. It is determined whether or not there is a high possibility that the deposit DP is attached inside the valve 30. That is, in step 710, the CPU determines whether or not the “specific condition indicating that the deposit DP should be removed” is satisfied.

  The air-fuel ratio learning value KG is a learning value of “the air-fuel ratio correction amount Kfaf for correcting the fuel injection amount Fi so that the air-fuel ratio abyfs of the exhaust gas detected by the air-fuel ratio sensor 54 matches the target air-fuel ratio AFtgt”. More specifically, the air-fuel ratio correction amount Kfaf is increased when the air-fuel ratio abyfs of the exhaust gas is leaner than the target air-fuel ratio AFtgt, and when the air-fuel ratio abyfs of the exhaust gas is richer than the target air-fuel ratio AFtgt Reduced. The air-fuel ratio learning value KG is increased by a certain amount when the average value of the air-fuel ratio correction amount Kfaf in a predetermined period is larger than the first predetermined value, and the average value of the air-fuel ratio correction amount Kfaf in the predetermined period is greater than the second predetermined value. When it is small, it is decreased by a certain amount. Therefore, when the air-fuel ratio abyfs of the exhaust gas is steadily shifted to the lean side of the target air-fuel ratio AFtgt, the air-fuel ratio learning value KG increases the fuel injection amount Fi as the deviation amount increases. It is a value that increases. Therefore, the air-fuel ratio learning value KG increases as the deposit DP deposited and deposited inside the fuel injection valve 30 increases, and as a result, the deviation D increases.

  If the deviation D is less than the threshold value Dth at the time of the determination in step 710, the CPU determines “No” in step 710 and proceeds to step 715 to set the fuel injection mode to the normal injection control mode. That is, as described above, the CPU sets the target air-fuel ratio AFtgt to the normal air-fuel ratio (theoretical air-fuel ratio in this example) Rst, sets the fuel pressure PF to the normal pressure PF0, and increases in one cycle. The fuel injection valve 30 and the high-pressure fuel pump 40 are controlled so that lift injection is performed only once. Since the current fuel injection mode is the normal injection control mode, the process of step 715 is executed for confirmation. Thereafter, the CPU proceeds to step 795 to end the present routine tentatively.

  Next, it is assumed that the deviation D has changed to the threshold value Dth or more in such a state. As described above, when a large amount of deposit DP adheres and accumulates in the fuel injection valve 30, the deviation D changes to the threshold value Dth or more, but other factors (that is, the engine air-fuel ratio is biased to the lean side). Depending on factors other than the deposit to be transferred, the threshold value Dth may be exceeded. Other factors include, for example, the occurrence of detection error of the air flow meter 52 and the deposit on the intake valve 15.

  If the deviation D is equal to or greater than the threshold value Dth, the CPU makes a “Yes” determination at step 705 and step 710 to proceed to step 720 to set the fuel injection mode to the preliminary removal control mode. As described above, the preliminary removal control mode is a mode in which fuel injection is performed with the aim of removing the deposit DP attached to the wall surface of the injection hole of the fuel injection valve 30.

  More specifically, in step 720, the CPU sets the target air-fuel ratio AFtgt to “normal air-fuel ratio (theoretical air-fuel ratio) Rst” and the fuel pressure PF to “pressure PFhigh1 higher than the normal pressure PF0”. In addition, the fuel injection valve 30 and the high-pressure fuel pump 40 are controlled so that the high lift injection is performed only once in one cycle. Thereafter, the CPU proceeds to step 795 to end the present routine tentatively.

  In this preliminary removal control mode, although high lift injection is performed, the fuel pressure PF is set to a pressure PFhigh1 higher than the normal pressure PF0. Therefore, the fuel flow velocity Vb in the injection hole 31a increases as compared with the normal injection control mode. Therefore, when the deposit DP is attached to the wall surface of the injection hole of the fuel injection valve 30, the deposit DP is effectively removed.

  Thereafter, when the CPU restarts the process from step 700, the CPU makes a “No” determination at step 705 to proceed to step 725 to determine whether the current fuel injection mode is the preliminary removal control mode.

  Since the current fuel injection mode is the preliminary removal control mode, the CPU makes a “Yes” determination at step 725 to proceed to step 730 where the duration from the start of the preliminary removal control mode is equal to or longer than the predetermined time. It is determined whether or not. At this time, if the preliminary removal control mode does not continue for a predetermined time, the CPU makes a “No” determination at step 730 to directly proceed to step 795 to end the present routine tentatively. As a result, the preliminary removal control mode is continued.

  Thereafter, when the preliminary removal control mode continues for a predetermined time, the CPU determines “Yes” in step 730 when performing the process of step 730, and proceeds to step 735, where the air-fuel ratio learning value deviation D (= KG−KG0 ) Is greater than or equal to the threshold value Dth.

  By the way, up to this point, the preliminary removal control mode is continued for a predetermined time. Therefore, “the deposit DP attached to the wall surface of the injection hole in the fuel injection valve 30” should be removed by the preliminary removal control mode. In addition, the deposit DP does not adhere to the “needle tip space wall surface inside the fuel injection valve 30”, and there is no “factor other than the deposit that shifts the air-fuel ratio of the engine to the lean side” The deviation D should be small.

  Therefore, it can be said that step 735 is a step for confirming the effect of executing the fuel injection in the preliminary removal control mode. Further, it can be said that step 735 is a step of determining whether or not there is a high possibility that the deposit DP is attached to the “needle tip space wall surface inside the fuel injection valve 30”. That is, “(the preliminary removal control mode is continued for a predetermined time and the air-fuel ratio learned value deviation D (= KG−KG0) is equal to or greater than the threshold Dth” means that the deposit DP should be removed (the deposit DP is a needle). It can be said that this is a specific condition indicating that there is a high possibility of adhering to the tip space wall.

  If the deviation D is less than the threshold value Dth when the CPU executes the process of step 735, it can be determined that a large amount of deposit DP is no longer attached to the fuel injection valve 30. Therefore, in this case, the CPU makes a “No” determination at step 735 to proceed to step 715 to return the fuel injection mode to the normal injection control mode.

  On the other hand, if the deviation D is equal to or greater than the threshold value Dth when the CPU executes the process of step 735, a large amount of deposit DP is attached to the needle tip space wall surface inside the fuel injection valve 30. It can be determined that there is a high possibility of being. Therefore, in this case, the CPU makes a “Yes” determination at step 735 to proceed to step 740 to set the fuel injection mode to the deposit removal control mode (second deposit removal control mode). As described above, the deposit removal control mode is a mode in which the fuel injection control is performed with the aim of removing the deposit DP attached to the needle tip space wall surface of the fuel injection valve 30.

  More specifically, in step 740, the CPU sets the target air-fuel ratio AFtgt to “the air-fuel ratio Rrich that is smaller than the normal air-fuel ratio Rst (ie, the rich side)”, and the fuel pressure PF is set to “from the normal pressure PF0”. The fuel injection valve 30 and the high-pressure fuel pump 40 are controlled so that the low lift injection is continuously performed a plurality of times in one cycle (for example, one intake stroke). Thereafter, the CPU proceeds to step 795 to end the present routine tentatively. The rich air-fuel ratio Rrich is preferably an air-fuel ratio between 10 and 14.6, for example. Further, the pressure PFhigh2 may be the same as or different from the pressure PFhigh1.

  In the deposit removal control mode, the low lift injection is continuously performed a plurality of times. The term “continuous injection” means that, for one cylinder, for example, there is a predetermined interval (Toff) at which the fuel injection is short within a period during which the crank angle rotates 180 degrees (for example, one intake stroke). This means that it is repeated (see FIG. 6B). As a result, as described with reference to FIG. 5, the flow velocity Vap of the fuel flowing through the throttle portion becomes extremely large. In addition, since the fuel pressure PF is set to a pressure PFhigh2 higher than the normal pressure PF0, the flow velocity Vap of the fuel flowing through the throttle portion is further increased. Therefore, when the deposit DP is attached to the wall surface of the needle tip space in the fuel injection valve 30, the deposit DP is effectively removed. The CPU may set the fuel pressure PF in the deposit removal control mode to the normal pressure PF0.

  Thereafter, when the CPU restarts the process from step 700, the CPU makes a “No” determination at both steps 705 and 725 to proceed to step 745, where the duration from when the deposit removal control mode is started is predetermined. It is determined whether or not it is over time. At this time, if the deposit removal control mode does not continue for a predetermined time, the CPU makes a “No” determination at step 745 to directly proceed to step 795 to end the present routine tentatively. As a result, the deposit removal control mode is continued.

  After that, when the deposit removal control mode continues for a predetermined time, the CPU determines “Yes” in step 745 and proceeds to step 750 when performing the process of step 745, and proceeds to step 750, where the air-fuel ratio learned value deviation D (= KG−KG0). ) Is greater than or equal to the threshold value Dth. That is, the CPU confirms the effect of executing the fuel injection in the deposit removal control mode.

  By the way, up to this point, the deposit removal control mode has been executed for a predetermined time. Accordingly, “the deposit DP attached to the wall surface of the needle tip space in the fuel injection valve 30” should be removed by the deposit removal control mode. In addition, since the preliminary removal control mode has already been executed for a predetermined time, the “deposit DP attached to the wall surface of the injection hole in the fuel injection valve 30” is removed by the preliminary removal control mode. It is a spear. That is, the deposit DP attached to the inside of the fuel injection valve 30 up to the present time should be removed. Therefore, when there is no “factor other than the deposit that shifts the air-fuel ratio of the engine to the lean side”, the deviation D should be small. Therefore, when the deviation D is greater than or equal to the threshold value Dth, it can be determined that “a factor other than the deposit that shifts the air-fuel ratio of the engine to the lean side” has occurred, or that the deposit removal has failed. In other words, it can be determined that some abnormality has occurred in the engine 10.

  Therefore, when the deviation D is equal to or greater than the threshold value Dth at the time of executing the processing of step 750, the CPU determines “Yes” in step 750 and proceeds to step 755 to notify the abnormality. Processing (for example, turning on a warning light or generating an alarm from a buzzer) is performed. Furthermore, the CPU stores in the backup RAM that an abnormality has occurred. Next, the CPU proceeds to step 760 to set the fuel injection mode to the failure time control mode.

  The failure time control mode is a mode for performing fuel injection control aiming to ensure that the engine 10 is operated to a repair shop or the like. More specifically, in step 760, the CPU sets the target air-fuel ratio to a fail-time air-fuel ratio (third air-fuel ratio) Rfail smaller than the normal air-fuel ratio Rst, and sets the fuel pressure PF to a pressure PFhigh3 higher than the normal pressure PF0. And the fuel injection valve 30 and the high-pressure fuel pump 40 are controlled so that the high lift injection is performed only once in one cycle. Thereafter, the CPU proceeds to step 795 to end the present routine tentatively. When the fail time control mode is started, the CPU maintains the fail time control mode until a predetermined process is performed in the repair shop.

  On the other hand, if the deviation D is less than the threshold value Dth when the CPU executes the process of step 750, it can be determined that a large amount of deposit DP is no longer adhering to the fuel injection valve 30. Therefore, in this case, the CPU makes a “No” determination at step 750 to proceed to step 715 to return the fuel injection mode to the normal injection control mode.

<Supplementary explanation about fuel injection (movement amount of needle valve and energization time of solenoid)>
The CPU calculates “a fuel injection amount Fi for one cycle of one cylinder” according to the following equation (1). In the equation (1), Mc is “the amount of air taken by one cylinder in one intake stroke (ie, the amount of intake air in the cylinder)”. Mc / AFtgt is also referred to as a basic fuel injection amount TP, and is a feedforward fuel injection amount for making the air / fuel ratio of the engine coincide with the target air / fuel ratio AFtgt.

Fi = KG · Kfaf · (Mc / AFtgt) (1)

1. High lift injection When the CPU injects fuel of the fuel injection amount Fi by one high lift injection, the energization time to the fuel injection valve 30 according to the following formula (2) (for applying the high voltage Hi to the solenoid 34) This is the time during which the signal, that is, the injection valve drive signal is generated, and is also simply referred to as “injection time” hereinafter.) TAUH is determined. In this example, the maximum value of the lift amount in the high lift injection is set to a constant value Lhigh (that is, Lmax) (see FIG. 6A). In addition, when the fuel injection amount Fi is injected by one high lift injection, the fuel injection is performed in each of the above-described “normal injection control mode, preliminary removal control mode, and failure control mode”.

TAUH = KHi · KHiPF · Fi (2)

  In the equation (2), KHi is a predetermined coefficient for converting the fuel injection amount into the injection time at the time of high lift injection. KHiPF is a correction coefficient that changes according to the fuel pressure PF during high lift injection and the in-cylinder pressure during fuel injection. The correction coefficient KHiPF decreases as the fuel pressure PF increases, and increases as the in-cylinder pressure during fuel injection increases. The in-cylinder pressure is estimated from the accelerator pedal Ap operation amount, the intake air amount, the engine rotation speed, and the like, or is acquired by an in-cylinder pressure sensor (not shown). In the present specification, the invalid injection time is ignored.

2. Low lift injection The CPU determines a value n (number of injections n) according to the following equation (3) when injecting fuel of the fuel injection amount Fi by a plurality of consecutive low lift injections (n times). Injecting the fuel of the fuel injection amount Fi by a plurality of consecutive (n times) low lift injections is a case of performing fuel injection in the deposit removal control mode described above (see FIG. 6B). . In the equation (3), FbLо is a fuel injection amount determined in advance for one low lift injection. In this example, the maximum value of the lift amount in the low lift injection is set to a constant value Llow (see FIG. 6B). Of course, the constant value Llow is smaller than the maximum lift amount Lmax.

n = Fi / FbLо (3)

Since the value n is a natural number, if there is a remainder in the calculation result of equation (3), n is calculated so that “1” is added to the quotient value. And CPU determines the energization time (injection time) TAUL to the fuel injection valve 30 according to following (4) Formula. Further, in the deposit removal control mode, the CPU provides a fixed injection interval (non-energization time) Toff between the end of energization for one fuel injection and the start of energization for the next fuel injection (FIG. 6). (See (B) of).

TAUL = KLо, KLоPF, FbLо (4)

  In the equation (4), KLо is a predetermined coefficient for converting the fuel injection amount into the injection time at the time of low lift injection. KLоPF is a correction coefficient that changes according to the fuel pressure PF during low lift injection and the in-cylinder pressure during fuel injection. The correction coefficient KLоPF decreases as the fuel pressure PF increases, and increases as the cylinder pressure during fuel injection increases.

  As will be understood from the above description, in the deposit removal control mode, when the target air-fuel ratio AFtgt is set to “a rich air-fuel ratio Rrich smaller than the normal air-fuel ratio (theoretical air-fuel ratio in this example) Rst”, The fuel injection amount Fi is increased according to the equation (1). As a result, the number of injections n increases as understood from the equation (3).

As described above, the first device includes the control unit (ECU 50) that can selectively execute high lift injection and low lift injection.
Further, the control unit performs high lift injection (step 710 and step 715 in FIG. 7) when a specific condition indicating that the deposit DP adhered in the fuel injection valve 30 should be removed is not satisfied, At this time, the needle valve 32 is moved so that the air-fuel ratio of the engine becomes “target air-fuel ratio AFtgt determined by the engine operating state = normal air-fuel ratio Rst”.
Further, when the specific condition is satisfied, the control unit 50 continuously performs the low lift injection a plurality of times (steps 735 and 740 in FIG. 7), and at that time, the air-fuel ratio of the engine becomes “the target value”. The needle valve 32 is moved so that the air-fuel ratio (Rrich) is smaller than the air-fuel ratio.

  As a result, the first device can effectively remove the deposit DP adhering to the inside of the fuel injection valve 30 (particularly, the wall surface of the needle tip space) while reducing the amount of torque fluctuation and the degree of deterioration of emission. it can.

  The first device may be configured to shift to the deposit removal control mode without passing through the preliminary removal control mode when the above-described specific condition is satisfied in the normal injection control mode. Furthermore, the first device may appropriately change the maximum value of the lift amount in the low lift injection in the deposit removal control mode.

Second Embodiment
The fuel injection control device (hereinafter simply referred to as “second device”) according to the second embodiment of the present invention detects a target empty state when a misfire condition is detected during execution of fuel injection in the deposit removal control mode. It differs from the first device only in that the fuel ratio AFtgt is set to "a misfire prevention air-fuel ratio Rrmf that is further smaller (rich side) than the rich air-fuel ratio Rrich". Therefore, hereinafter, this difference will be mainly described.

  When starting the deposit removal control mode, the second device determines (monitors) whether or not a misfire condition has occurred. More specifically, the CPU of the second device acquires a time T180 when the crank angle elapses 180 degrees when each cylinder is in an explosion stroke, and a predetermined value with respect to the average value of all the cylinders at the time T180. It is determined whether or not there is a cylinder having a longer time T180. And when it determines with such a cylinder existing, CPU determines with the misfire state having generate | occur | produced. Alternatively, the CPU acquires a time T60a in which the crank angle elapses 60 degrees in the latter half of the compression stroke of a certain cylinder, and acquires a time T60b in which the crank angle elapses 60 degrees in the middle of the explosion stroke of the cylinder. Then, the CPU determines that a misfire state has occurred when the ratio of the time T60b to the time T60a is equal to or greater than a predetermined value. In addition, when it is determined that a misfire condition has occurred, the CPU sets the target air-fuel ratio AFtgt to “a misfire-preventing air-fuel ratio Rrmf that is smaller (rich side) than the rich air-fuel ratio Rrich”, and performs deposit removal control. Continue. For example, if the rich air-fuel ratio Rrich is an air-fuel ratio between 10 and 14.6, the misfire prevention air-fuel ratio Rrmf is an air-fuel ratio between 9 and 10, for example. Note that the CPU may be configured to determine whether or not a misfire state has occurred based on a known method other than the method described above.

  According to the second device, when the misfire state is detected during the deposit removal control mode, the target air-fuel ratio AFtgt is set to a smaller value, so that the amount of fuel supplied in the deposit removal control (actually The number of low lift injections) is increased. As a result, the occurrence frequency of the misfire state (lean misfire) in the deposit removal control mode can be reduced.

<Third Embodiment>
The fuel injection control apparatus according to the third embodiment of the present invention (hereinafter simply referred to as “third apparatus”) detects the misfire state during the deposit removal control mode, and thus the target air-fuel ratio AFtgt is set to the misfire prevention sky. In the case where the misfire state continues to be detected when the fuel ratio Rrmf is set, the second device is only set at the point where the maximum value of the lift amount in the low lift injection is set to “a constant value Llow1 larger than the constant value Llow”. Is different. The constant value Llow1 is smaller than the maximum lift amount Lmax.

  According to the third device, when the target air-fuel ratio AFtgt is set to the misfire prevention air-fuel ratio Rrmf during the deposit removal control mode, when the misfire state is still detected, the maximum value of the lift amount in the low lift injection is growing. Therefore, in the deposit removal control, the influence of the deposit DP on the fuel injection amount is reduced, and as a result, the amount of supplied fuel is increased. As a result, the occurrence frequency of the misfire state (lean misfire) in the deposit removal control mode can be reduced.

<Fourth embodiment>
A fuel injection control device (hereinafter simply referred to as “fourth device”) according to a fourth embodiment of the present invention replaces a fuel injection valve (port injection valve) 45 shown in FIG. This is applied to an internal combustion engine used with an injection valve 30.

  By the way, as compared with the in-cylinder injection valve 30, deposits are less likely to accumulate in the port injection valve 45 where the injection hole is exposed in a relatively low temperature environment. Therefore, the port injection valve 45 can inject an amount of fuel closer to the target than the in-cylinder injection valve 30.

  Therefore, the fourth device, when injecting fuel from the in-cylinder injection valve 30 at least in the deposit removal control mode, has a predetermined ratio α of the fuel injection amount Fi required to realize the target air-fuel ratio AFtgt. (Ie, fuel of α · Fi) is injected from the port injection valve 45, and the remaining amount (ie, (1-α) · Fi) is injected from the in-cylinder injection valve 30. The ratio α is preferably between 50 and 75%. The CPU always sets the injection mode of the port injection valve 45 to full lift injection.

  According to this, the fuel of α · Fi is supplied from the port injection valve 45 to the combustion chamber 20. In addition, even if the in-cylinder injection valve 30 performs the low lift injection, even if the fuel can be injected only at the “predetermined amount β of the planned amount”, the amount of fuel that is insufficient as a result is (1−β) · (1− α) · Fi. If α = 0, that is, if the fuel is not injected from the port injection valve 45, the fuel amount that is insufficient in the above case is (1−β) · Fi. Therefore, compared with the case where all of the fuel is injected from the in-cylinder injection valve 30 in the deposit removal control mode, the shortage of fuel can be reduced.

  As a result, the fourth device, like the first device, effectively removes the deposit DP attached to the needle tip space wall in the fuel injection valve 30 while reducing the possibility of torque fluctuations and worsening of emissions. can do. The fourth device maintains the target air-fuel ratio AFtgt in the deposit removal control mode at the normal air-fuel ratio Rst, but sets it to “a rich air-fuel ratio (second air-fuel ratio) Rrich smaller than the normal air-fuel ratio Rst”. May be.

  As described above, the fuel injection control device according to each embodiment of the present invention effectively deposits and deposits DP deposited inside the fuel injection valve 30 while reducing the frequency of occurrence of torque fluctuation and emission deterioration. Can be removed.

  In addition, this invention is not limited to the said embodiment, A various modification can be employ | adopted within the scope of the present invention.

DESCRIPTION OF SYMBOLS 20 ... Combustion chamber (inside cylinder), 30 ... Fuel injection valve, 31 ... Nozzle body part, 31a ... Injection hole, 31b ... Nozzle seat wall surface, 32 ... Needle valve, 32c ... Needle seat wall surface, 33 ... Spring, 34 ... Solenoid 40 ... High pressure fuel pump, 50 ... ECU (electronic control unit), 51 ... Crank position sensor, 52 ... Air flow meter, 53 ... Accelerator pedal depression sensor, 54 ... Air fuel ratio sensor, FP ... Fuel passage, S ... Sack.

Claims (1)

A fuel injection valve that injects fuel contained in the air-fuel mixture burned in the combustion chamber of the internal combustion engine by moving the needle valve;
High lift injection for injecting fuel by changing the lift amount of the needle valve in the range up to the first lift amount, and the range of the lift amount of the needle valve to the second lift amount smaller than the first lift amount A low lift injection that injects fuel by changing in, and a control unit that can selectively execute,
In a fuel injection control device comprising:
The controller is
When a specific condition indicating that deposits adhering to the fuel injection valve should be removed is not satisfied, the high lift injection is performed, and the air-fuel ratio of the air-fuel mixture at that time is determined by the engine operating state. Move the needle valve so that the fuel ratio is the same,
When the specific condition is satisfied, the low lift injection is continuously performed a plurality of times, and at that time, the needle valve is moved so that the air-fuel ratio of the air-fuel mixture becomes smaller than the target air-fuel ratio. ,
Fuel injection control device.

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