JP2010159690A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of early detecting deposit in a needle part and taking measures therefor. <P>SOLUTION: The control device of an internal combustion engine includes an injector for injecting in a cylinder and a control means. When, for example, a fuel injection amount decreases, the control means injects fuel by increasing a fuel injection pressure and acquires a change in an air-fuel ratio before and after the fuel injection. The control means then determines, based on the change in an air-fuel ratio, which decrease takes place: a decrease of a flow rate of injected fuel due to deposit in a head end part of the injector for injecting in a cylinder; or a decrease of a flow rate of injected fuel due to deposit in a needle of the injector for injection in a cylinder. When a flow rate of injected fuel decreases due to deposit in the needle, the control means performs control to suppress the deposit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that includes an in-cylinder injector and controls fuel injection.

  A control device for an internal combustion engine that includes an in-cylinder injector and controls fuel injection is known. For example, Patent Document 1 discloses a technique for removing deposits by performing in-cylinder injection when the amount of deposits (deposits) deposited on the in-cylinder injector increases.

JP 2006-057538 A

  According to the above-described technique, it is possible to remove deposits adhering to the tip portion (injection hole) of the in-cylinder injector. On the other hand, the deposit adheres not only to the tip portion (injection hole) of the in-cylinder injector but also to the needle portion. However, the needle deposit is generally difficult to remove. Therefore, in this case, in the conventional technique, it is not known whether or not the deposit removal is performed reliably, and there is a possibility that the deterioration of the emission, the deterioration of the drivability, etc. may occur due to the deposit accumulation thereafter. In Patent Document 1, the above problem is not studied at all.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a control device for an internal combustion engine that can detect the deposit of the needle portion at an early stage and execute the countermeasure. And

  In one aspect of the present invention, a control apparatus for an internal combustion engine including an in-cylinder injector that injects fuel into a cylinder of an engine, wherein the fuel injection pressure is increased to perform fuel injection, and before and after the fuel injection. On the basis of the change in the air-fuel ratio, the flow rate of the injected fuel caused by deposit accumulation on the tip of the in-cylinder injector and the flow rate of injected fuel caused by deposit accumulation on the needle of the in-cylinder injector Control means is provided for determining which of the reduction occurs, and for controlling the deposit accumulation when the flow rate of the injected fuel is reduced due to the deposit accumulation on the needle.

  The control device for the internal combustion engine is mounted on a diesel vehicle or the like. The control device for an internal combustion engine includes an in-cylinder injector and control means. When the fuel injection amount decreases or the like, the control means increases the fuel injection pressure to execute the fuel injection and acquires the change in the air-fuel ratio before and after the fuel injection. Then, the control means is based on a change in the flow rate of the injected fuel due to deposit accumulation at the tip of the in-cylinder injector and a deposit accumulation on the needle of the in-cylinder injector based on the change in the air-fuel ratio. It is determined which of the injected fuel flow rate drops. For example, when the air-fuel ratio before and after fuel injection is large, the control unit determines that the flow rate of the injected fuel has decreased due to deposit accumulation on the tip of the in-cylinder injector. On the other hand, when the air-fuel ratio before and after fuel injection is small, the control means determines that the flow rate of the injected fuel has decreased due to deposit accumulation on the needle of the in-cylinder injector. And a control means performs control which suppresses deposit accumulation in the case of the flow volume fall of the injection fuel resulting from the deposit accumulation to a needle. That is, the control means determines that it is difficult to remove the deposit, and takes measures according to the deposit accumulated on the needle. By doing in this way, the control apparatus of an internal combustion engine can specify the site | part to which a deposit accumulates, and can perform the countermeasure to the deposit according to a specific location.

It is a figure which shows an example of schematic structure of an internal combustion engine. It is an example of sectional drawing of the injector for cylinder injection. It is an example of the figure which shows transition of the deposit amount before and behind high-pressure fuel injection in the case where a nozzle hole deposit is a main body. It is an example of the figure which shows transition of the deposit amount before and after the high pressure fuel injection in the case where the needle deposit is the main component. It is an example of the flowchart showing the process sequence in this embodiment.

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

[Configuration of internal combustion engine]
FIG. 1 shows an example of a schematic configuration diagram of an internal combustion engine 100 according to an embodiment of the present invention.

  As shown in FIG. 1, the engine 10 includes four cylinders 112, and each cylinder 112 is connected to a common surge tank 30 via a corresponding intake manifold 20. The surge tank 30 is connected to an air cleaner 50 via an intake duct 40, and an air flow meter 42 and a throttle valve 70 are arranged in the intake duct 40. The opening degree of the throttle valve 70 is controlled based on the output signal S70 of the ECU 22. On the other hand, each cylinder 112 is connected to a common exhaust manifold 80, and this exhaust manifold 80 is connected to a three-way catalytic converter 90.

  Each cylinder 112 is provided with an in-cylinder injector 110 for injecting fuel into the cylinder and a port injector 120 for injecting fuel toward an intake port (not shown). . These injectors 110 and 120 are controlled based on output signals S110 and S120 of the ECU 22, respectively. The in-cylinder injectors 110 are connected to a common fuel distribution pipe 130, and the fuel distribution pipe 130 is connected to an engine-driven high-pressure fuel pump 150.

  The discharge side of the high-pressure fuel pump 150 is connected to the suction side of the high-pressure fuel pump 150 via an electromagnetic spill valve 152. The smaller the opening of the electromagnetic spill valve 152, the more the fuel distribution pipe 130 is connected to the high-pressure fuel pump 150. When the amount of fuel supplied to the inside is increased and the electromagnetic spill valve 152 is fully opened, the fuel supply from the high-pressure fuel pump 150 to the fuel distribution pipe 130 is stopped. The electromagnetic spill valve 152 is controlled based on the output signal S152 of the ECU 22.

  On the other hand, each port injection injector 120 is connected to a common low-pressure side fuel distribution pipe 160, and the fuel distribution pipe 160 and the high-pressure fuel pump 150 are connected to an electric motor driven type via a common fuel pressure regulator 170. A low-pressure fuel pump 180 is connected. Further, the low pressure fuel pump 180 is connected to the fuel tank 200 via a fuel filter 190.

  On the other hand, a canister 230, which is a collection container that collects fuel evaporative gas generated in the fuel tank 200, is connected to the fuel tank 200 via a vapor passage 260. Further, the canister 230 is connected to a purge passage 280 for supplying the fuel evaporative gas collected therein to the intake system of the engine 10. The purge passage 280 communicates with the downstream side of the throttle valve 70 of the intake duct 40. As is well known, the canister 230 is filled with an adsorbent (activated carbon) that adsorbs fuel evaporative gas, and an atmospheric passage for introducing the atmosphere into the canister 230 via a check valve during purging. 270 is provided.

  Further, the purge passage 280 is provided with a purge control valve 250 for controlling the purge amount, and the opening degree of the purge control valve 250 is controlled by an output signal S250 of the ECU 22.

  A fuel pressure sensor 400 that generates an output voltage proportional to the fuel pressure in the fuel distribution pipe 130 is attached to the fuel distribution pipe 130. The output voltage of the fuel pressure sensor 400 is supplied to the ECU 22 by a detection signal S400.

  An air-fuel ratio sensor 420 that generates an output voltage proportional to the oxygen concentration in the exhaust gas is attached to the exhaust manifold 80 upstream of the three-way catalytic converter 90. The air-fuel ratio sensor 420 is a global air-fuel ratio sensor (linear air-fuel ratio sensor) that generates an output voltage proportional to the air-fuel ratio of the air-fuel mixture burned by the engine 10. The output voltage of the air-fuel ratio sensor 420 is input to the ECU 22 by the detection signal S420.

  The accelerator opening sensor 440 detects an amount of depression of an accelerator pedal (not shown), that is, an accelerator opening. The accelerator opening sensor 440 supplies the detected value to the ECU 22 by a detection signal S440.

  The rotational speed sensor 460 generates an output pulse indicating the engine rotational speed. The rotation speed sensor 460 supplies the output pulse to the ECU 22 by the detection signal S460.

  The ECU 22 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an A / D converter, and the like (not shown). The ECU 22 refers to the map stored in the ROM, and determines the fuel injection amount and the like based on the load of the engine 10 and the rotational speed of the engine 10 obtained by the accelerator opening sensor 440 and the rotational speed sensor 460 described above. Further, the ECU 22 feedback-controls the timing at which the electromagnetic spill valve 152 is closed during the pressurization stroke based on the detection signal S400 of the fuel pressure sensor 400 provided in the fuel distribution pipe 130, whereby the fuel in the fuel distribution pipe 130 is obtained. The pressure (fuel pressure) and the amount of fuel supplied to the fuel distribution pipe 130 are controlled. Furthermore, as will be described later, the ECU 22 specifies a part of the in-cylinder injector 110 to which deposits are attached, and takes measures according to the specific part. Thus, ECU22 is an example of the control means in the present invention.

  The configuration of the internal combustion engine 100 described above is an example, and the configuration to which the present invention can be applied is not necessarily limited thereto. For example, in the above description, an in-line four-cylinder gasoline engine is shown as the engine 10, but the present invention is not limited to such an engine. Instead of the above-described configuration, the internal combustion engine 100 may have only the in-cylinder injector 110 without the port injector 120. Further, instead of the air-fuel ratio sensor 420, the internal combustion engine 100 detects on-off whether the air-fuel ratio of the air-fuel mixture burned by the engine 10 is rich or lean with respect to the stoichiometric air-fuel ratio. You may have a sensor. Hereinafter, the air-fuel ratio estimated (learned) by the ECU 22 based on the output voltage of the air-fuel ratio sensor 420 is referred to as “air-fuel ratio learned value”.

[In-cylinder injector configuration]
Next, the configuration of the in-cylinder injector 110 will be described with reference to FIG. FIG. 2 is a longitudinal sectional view of the in-cylinder injector 110. As shown in FIG. 2, the in-cylinder injector 110 has a nozzle body 760 fixed to a lower end of a main body 740 by a nozzle holder via a spacer. The nozzle body 760 has a nozzle hole 500 formed at the lower end thereof, and a needle 520 is disposed in the nozzle body 760 so as to be movable up and down. The upper end of the needle 520 is in contact with a core 540 that can slide in the main body 740. The spring 560 applies pressure downward to the needle 520 via the core 540. The needle 520 is disposed on the inner peripheral sheet surface 522 of the nozzle body 760, and as a result, the nozzle hole 500 is normally closed.

  A sleeve 570 is inserted and fixed at the upper end of the main body 740, and a fuel passage 580 is formed in the sleeve 570. The lower end side of the fuel passage 580 communicates with the inside of the nozzle body 760 through a passage in the main body 740. When the needle 520 is lifted, fuel is injected from the injection hole 500. The upper end side of the fuel passage 580 is connected to the fuel inlet 620 via the filter 600. This fuel inlet 620 is connected to the fuel distribution pipe 130 of FIG.

  The electromagnetic solenoid 640 is disposed in the main body 740 so as to surround the lower end portion of the sleeve 570. When the solenoid 640 is energized, the core 540 rises against the spring 560, the fuel pressure pushes up the needle 520, and the injection hole 500 is opened, so that fuel injection is executed. The solenoid 640 is taken out by the wire 660 in the insulating housing 650, and receives a signal S110 for opening the valve from the ECU 22.

[How to identify the deposit]
Next, control executed by the ECU 22 in this embodiment will be described. The ECU 22 increases the fuel pressure of the in-cylinder injector 110 to remove the deposit accumulated in the nozzle hole 500, and whether the deposit has accumulated mainly in the nozzle hole 500 based on the change in the air-fuel ratio learning value before and after that. It is determined mainly whether the needle 520 has accumulated. Thereby, ECU22 specifies the site | part which deposit accumulates and performs the countermeasure of the deposit according to it. Hereinafter, the ratio of the injected fuel that is reduced due to the deposit to the required value of the fuel injection amount is referred to as a “flow rate reduction rate”.

  Hereinafter, the method for specifying the deposit will be described in detail. First, the ECU 22 acquires an air-fuel ratio learning value (hereinafter referred to as “air-fuel ratio learning value Edfirst1”). Then, the ECU 22 determines the difference between the air-fuel ratio learned value Edfirst1 and the air-fuel ratio learned value calculated in the absence of deposit (hereinafter referred to as “initial air-fuel ratio learned value Edfirst0”) (hereinafter referred to as “initial air-fuel ratio”). This is referred to as the difference ΔEdfirst ”. Thereby, the ECU 22 estimates the deposit accumulation amount of the in-cylinder injector 110, that is, the flow rate reduction rate generated due to the deposit.

  Next, the ECU 22 determines whether or not the initial air-fuel ratio difference ΔEdfirst is greater than a predetermined threshold (hereinafter referred to as “air-fuel ratio learning value change upper limit threshold THΔEdfirst”). The air-fuel ratio learning value change upper limit threshold THΔEdfirst is set to an appropriate value, for example, through experiments. Thereby, ECU22 determines whether the flow rate fall rate has generate | occur | produced more than the predetermined rate.

  When the initial air-fuel ratio difference ΔEdfirst is larger than the air-fuel ratio learning value change upper limit threshold THΔEdfirst, the ECU 22 determines that it is necessary to take a deposit countermeasure. Then, the ECU 22 increases the fuel pressure of the in-cylinder injector 110 and performs fuel injection a predetermined number of times (hereinafter referred to as “high-pressure injection frequency threshold THcount”). The high-pressure injection frequency threshold THcount is set to an appropriate value by, for example, experiments.

  Thereafter, the ECU 22 again acquires an air-fuel ratio learning value (hereinafter referred to as “air-fuel ratio learning value Edfirst2”). Then, the ECU 22 obtains a difference (hereinafter referred to as “recovery amount R”) between the air-fuel ratio learned value Edfirst1 before the fuel pressure increase and the air-fuel ratio learned value Edfirst2 after the pressure increase. That is, the ECU 22 calculates the recovery amount R to estimate the improvement rate of the flow rate reduction rate due to the increase in the fuel pressure.

  Next, the ECU 22 determines whether or not the recovery amount R is greater than a predetermined threshold (hereinafter referred to as “designated recovery amount THR”). That is, the ECU 22 determines whether or not the improvement in the flow rate reduction rate due to the fuel injection is equal to or greater than a predetermined rate. The designated recovery amount THR is set in advance based on, for example, experiments.

  When the recovery amount R is larger than the specified recovery amount THR, the ECU 22 determines that the flow rate decrease before the fuel pressure is increased is caused by the deposit accumulated in the nozzle hole 500. Then, the ECU 22 determines that the deposit in the nozzle hole 500 has been peeled and removed by the pressurized fuel injection.

  On the other hand, when the recovery amount R is equal to or less than the specified recovery amount THR, the ECU 22 determines that the flow rate decrease before increasing the fuel pressure has occurred due to deposits accumulated on the needle 520. And ECU22 performs the countermeasure (for example, deposit suppression) of the deposit adhering to the needle 520 separately.

  In this case, for example, the ECU 22 prompts the occupant to input the fuel cleaning agent with a warning light or the like (see, for example, JP-A-09-170524). As another example, the ECU 22 reduces the tip temperature of the in-cylinder injector 110 by retarding the ignition timing (see JP-A-11-30176, etc.). As another example, the ECU 22 increases the injection fuel pressure. As yet another example, the ECU 22 makes the injection amount of the in-cylinder injector 110 larger than the injection amount of the port injector 120. That is, the ECU 22 increases the direct injection spray division ratio. By doing in the above way, ECU22 can reduce the influence of needle deposit and can suppress needle deposit generation.

  Next, the effect by this embodiment is supplemented. Deposits generated in in-cylinder injector 110 may adhere to nozzle hole 500 and needle 520. The deposit deposition ratio on each part varies depending on the operating conditions, fuel, and the like. The deposit accumulated in the nozzle hole 500 (hereinafter referred to as “hole injection deposit”) is easily peeled off by increasing the fuel pressure. On the other hand, the deposit deposited on the needle 520 (hereinafter referred to as “needle deposit”) is difficult to peel off due to fluid energy or the like inside the nozzle. In particular, when potassium or the like is contained in the fuel, the adhesion force of the deposit deposited on the needle 520 becomes strong, and it is difficult to peel off by normal fuel pressure injection.

  Therefore, when the flow rate drop of the injected fuel is mainly caused by the needle deposit, the ECU 22 cannot sufficiently cope with the flow rate drop caused by the accumulated deposit only by the high-pressure fuel injection. This will be further described with reference to FIGS. FIG. 3 shows the accumulation amount of the nozzle hole deposit and the accumulation amount of the needle deposit when the ratio of the nozzle hole deposit is large. FIG. 4 shows the accumulation amount of the nozzle hole deposit and the accumulation amount of the needle deposit when the ratio of the needle deposit is large. 3 (a) and 4 (a) show the state of the deposit before boosting and performing fuel injection, and FIGS. 3 (b) and 4 (b) show boosting and fuel injection. Indicates the deposit status after execution.

  As shown in FIGS. 3A and 3B, when the ratio of the injection hole deposit is large, the injection hole deposit is reduced by increasing the pressure and executing the fuel injection. Accordingly, as a result, the overall deposit amount is improved. On the other hand, as shown in FIGS. 4 (a) and 4 (b), when the ratio of the needle deposit is large, even if the pressure is increased and the fuel injection is executed, the decrease in the total deposit amount is small. That is, the needle deposit is not reduced, and the reduction amount of the entire deposit amount is small due to the small proportion of the nozzle hole deposit.

  On the other hand, by executing the control of the present embodiment, the ECU 22 detects deposits that are difficult to peel off, that is, accumulation of needle deposits at an early stage, and takes measures against them. Thereby, ECU22 can suppress the deterioration of the emission resulting from the flow volume fall of fuel, and the deterioration of drivability to the minimum.

(Processing flow)
Next, a processing procedure in the present embodiment will be described. FIG. 5 is an example of a flowchart showing a procedure of processing executed by the ECU 22 in the present embodiment. The ECU 22 repeatedly executes the process of the flowchart shown in FIG. 5 according to a predetermined cycle, for example.

  First, the ECU 22 acquires the air-fuel ratio learning value Edfirst1 (step S101). For example, the ECU 22 calculates the air-fuel ratio learning value Edfirst1 based on the output voltage of the air-fuel ratio sensor 420.

  Next, the ECU 22 calculates an initial air-fuel ratio difference ΔEdfirst that is a difference from the initial air-fuel ratio learning value Edfirst0 (step S102). That is, the ECU 22 calculates the initial air-fuel ratio difference ΔEdfirst by subtracting the initial air-fuel ratio learned value Edfirst0 from the air-fuel ratio learned value Edfirst1.

  Then, the ECU 22 determines whether or not the initial air-fuel ratio difference ΔEdfirst is larger than the air-fuel ratio learning value change upper limit threshold THΔEdfirst (step S103). Thereby, ECU22 determines whether the flow rate fall rate of the in-cylinder injector 110 is more than a predetermined rate.

  If the initial air-fuel ratio difference ΔEdfirst is greater than the air-fuel ratio learned value change upper limit threshold THΔEdfirst (step S103; Yes), the ECU 22 determines that it is necessary to take a deposit countermeasure, and proceeds to step S104.

  On the other hand, when the initial air-fuel ratio difference ΔEdfirst is equal to or less than the air-fuel ratio learning value change upper limit threshold THΔEdfirst (step S103; No), the ECU 22 determines that the deposit accumulation amount is small and does not affect the fuel injection, and the process returns to step S101. To return.

  Next, the ECU 22 calculates a fuel pressure upper limit value (step S104). That is, the ECU 22 calculates the upper limit value of the fuel pressure that can be injected by the in-cylinder injector 110 based on the detection signal S400 of the fuel pressure sensor 400 and the like.

  Then, the ECU 22 changes the required fuel pressure (step S105). That is, the ECU 22 boosts the fuel pressure based on the fuel pressure upper limit value calculated in step S104. Thereby, ECU22 promotes peeling of a nozzle hole deposit.

  Next, the ECU 22 determines whether or not the number of injections is greater than the high-pressure injection number threshold THcount (step S106). Here, the number of injections refers to the number of injections of the in-cylinder injector 110 after raising the fuel pressure in step S105.

  If the number of injections is greater than the high-pressure injection number threshold THcount (step S106; Yes), the ECU 22 advances the process to step S107. On the other hand, when the number of injections is equal to or less than the high-pressure injection number threshold THcount (step S106; No), the ECU 22 returns the process to step S101 and loops the process until the number of injections becomes larger than the high-pressure injection number threshold THcount.

  Next, the ECU 22 acquires the air-fuel ratio learning value Edfirst2 (step S107). Then, the ECU 22 calculates the difference between the air-fuel ratio learning values before and after the high pressure injection, that is, the recovery amount R (step S108). In other words, the ECU 22 calculates the recovery amount R by subtracting the air-fuel ratio learned value Edfirst1 from the air-fuel ratio learned value Edfirst2.

  Next, the ECU 22 determines whether or not the recovery amount R is larger than the designated recovery amount THR (step S109). Thereby, the ECU 22 determines whether or not a decrease in the fuel injection flow rate of the in-cylinder injector 110 has improved.

  If the recovery amount R is greater than the designated recovery amount THR (step S109; Yes), the ECU 22 specifies that the nozzle hole deposit is the main component (step S110). At the same time, the ECU 22 determines that the injection hole deposit is peeled off by increasing the pressure and performing the fuel injection, and the flow rate decrease due to the deposit is recovered. That is, the ECU 22 determines that the deposit accumulation amount has changed from the state shown in FIG. 3A to the state shown in FIG.

  On the other hand, when the recovery amount R is equal to or less than the designated recovery amount THR (step S109; No), the ECU 22 specifies that the needle deposit is the main component (step S111). At the same time, the ECU 22 determines that only the fuel injection does not recover the reduced fuel injection flow rate caused by the deposit. That is, the ECU 22 determines that the deposit accumulation amount has changed from the state shown in FIG. 4A to the state shown in FIG.

  And ECU22 performs a response | compatibility to a needle deposit (step S112). That is, the ECU 22 reduces the tip temperature of the in-cylinder injector 110 by prompting the occupant to input the cleaning agent or by controlling the ignition timing.

  In this manner, the ECU 22 can specify a site where deposits are accumulated and can perform a response to the deposit according to the specific location.

10 Engine 20 Intake manifold 22 ECU
30 Surge tank 40 Air intake duct 42 Air flow meter 50 Air cleaner 70 Throttle valve 100 Internal combustion engine 110 In-cylinder injector 112 Cylinder 120 Port injector 200 Fuel tank 400 Fuel pressure sensor 420 Air-fuel ratio sensor 440 Accelerator opening sensor 460 Rotational speed sensor 500 Injection hole 520 Needle

Claims (1)

A control device for an internal combustion engine comprising an in-cylinder injector for injecting fuel into a cylinder of an engine,
The fuel injection pressure is increased and fuel injection is performed. Based on the change in the air-fuel ratio before and after the fuel injection, a decrease in the flow rate of the injected fuel due to deposit accumulation on the tip of the in-cylinder injector, and the cylinder It is determined whether the flow rate of the injected fuel is reduced due to deposit accumulation on the needle of the injector for internal injection, and if the flow rate of injected fuel is reduced due to deposit accumulation on the needle, the deposit is deposited. A control device for an internal combustion engine, comprising control means for performing control for suppressing the engine.

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