JP6497035B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control apparatus for an internal combustion engine, which includes a fuel injection valve that directly injects fuel into a combustion chamber, and a gas flow enhancement device that enhances gas flow in the combustion chamber.

  Patent Document 1 discloses a direct injection internal combustion engine that directly injects fuel into a combustion chamber. In this internal combustion engine, for example, when the engine is decelerated, a fuel cut is performed to temporarily stop fuel injection in order to improve fuel efficiency. Then, after the fuel cut, a fuel cut recovery for restarting the fuel supply is started.

JP 2012-241654 A

  During fuel cut, combustion is not performed in the cylinder, so the temperature in the cylinder gradually decreases. In such a situation, the fuel injected at the time of the fuel cut recovery is not sufficiently vaporized and tends to adhere to the cylinder wall surface and the piston crown surface. Such fuel adhesion is a factor that increases particulate matter (PM) in the exhaust. In recent years, in consideration of extremely small exhaust particulates, the exhaust particulate emission tends to be regulated not by the total weight of particulates but also by the number of particles (PN).

The present invention includes a fuel injection valve that directly injects fuel into a combustion chamber, and a gas flow enhancement device that enhances gas flow in the combustion chamber, and performs fuel cut at a predetermined deceleration of the internal combustion engine, and then The present invention relates to a control device for an internal combustion engine that performs fuel cut recovery when the fuel cut recovery condition is satisfied. This controller repeatedly estimates the estimated piston temperature during the fuel cut, and starts the gas flow enhancement device prior to the fuel cut recovery only when the estimated piston temperature becomes lower than the predetermined temperature. Fuel injection at the time of fuel cut recovery is performed with the gas flow in the chamber intensified.

  Therefore, at the time of fuel cut recovery, the fuel is injected in a state where the gas flow in the cylinder is strengthened, and the vaporization of the injected fuel is promoted.

  According to the present invention, since the gas flow in the cylinder is strengthened in advance before the fuel cut recovery, the vaporization of the fuel injected at the time of the fuel cut recovery is promoted to the cylinder wall surface and the piston crown surface. The adhesion of fuel is reduced. This reduces the number of particles in the exhaust.

It is explanatory drawing of the direct injection type internal combustion engine of one Example of this invention. It is a flowchart about control of the tumble control valve after the fuel cut in one Example. It is a map which shows the characteristic of the combustion frequency criteria at the time of recovery. FIG. 3 is a time chart related to the embodiment of FIG. 2 showing changes in various parameters during fuel cut and recovery. It is a flowchart about control of the tumble control valve after the fuel cut in another Example. FIG. 6 is a time chart related to the embodiment of FIG. 5 showing changes in various parameters during fuel cut and recovery.

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

  FIG. 1 shows a system configuration of a direct injection type internal combustion engine 1 according to an embodiment of the present invention. The internal combustion engine 1 includes a cylinder block 3 that forms a cylinder 2, and a cylinder head 4 that is fixed to the upper surface of the cylinder block 3. An intake port 5 and an exhaust port 6 are formed in the cylinder head 4 and open to, for example, a pent roof type combustion chamber 7 that is recessed in the lower surface of the cylinder head 4. The tip of the intake port 5 is opened and closed by an intake valve 8, and the tip of the exhaust port 6 is opened and closed by an exhaust valve 9. In the drawing, one intake port 5 and one exhaust port 6 are shown opening to the combustion chamber 7, but in reality, a pair of intake ports 5, 5 and a pair of exhaust ports 6, 6 are shown. 6 opens to the combustion chamber 7 and is opened and closed by an intake valve 8 and an exhaust valve 9, respectively. A spark plug 10 is arranged in the center of the combustion chamber 7. A fuel injection valve 11 that directly injects fuel into the combustion chamber 7 is disposed below the intake port 5.

  Further, a tumble control valve 12 is provided in the intake port 5 as a gas flow enhancement device that enhances the gas flow in the combustion chamber 7. In FIG. 1, the tumble control valve 12 in the closed state, that is, the tumble control valve 12 is rotated to the lower surface portion 5A side of the port wall surface of the intake port 5 and the lower half of the intake port 5 is blocked. Has been. In this closed state, the flow velocity of the intake air increases in the intake port 5 and flows into the combustion chamber 7 along the upper surface portion 5B of the port wall surface, so that the tumble flow is strengthened in the combustion chamber 7. Further, the tumble control valve 12 is configured to be able to adjust the opening degree from the position where the tumble control valve 12 is in the closed state to a position which is substantially parallel to the main flow direction of the intake air in the intake port 5. The opening degree of the tumble control valve 12 is controlled according to the operating conditions of the internal combustion engine 1.

  An electronically controlled throttle valve 16 whose opening is controlled by a control signal from an engine control unit (ECU) 15 is interposed upstream of the collector portion 14 of the intake passage 13 connected to the intake port 5. An air flow meter 17 for detecting the amount of intake air is disposed on the upstream side.

  Further, a catalytic converter 19 made of, for example, a three-way catalyst is interposed in the exhaust passage 18 connected to the exhaust port 6, and an air-fuel ratio sensor 20 for detecting the air-fuel ratio is disposed upstream thereof. .

  In addition to the air flow meter 17 and the air-fuel ratio sensor 20, the engine control unit 15 includes a crank angle sensor 21 for detecting the engine speed, a water temperature sensor 22 for detecting the coolant temperature, and an accelerator pedal operated by the driver. Detection signals of sensors such as an accelerator opening sensor 23 for detecting the amount of depression of the vehicle, a vehicle speed sensor 24 for detecting the vehicle speed, and an intake air temperature sensor 25 for detecting the intake air temperature in the intake passage 13, for example, the collector section 14, are input. . Based on these detection signals, the engine control unit 15 optimally controls the fuel injection amount and injection timing by the fuel injection valve 11, the ignition timing by the spark plug 10, the opening of the throttle valve 16, and the like.

  FIG. 2 is a flowchart for explaining the control of the tumble control valve 12 after the fuel cut in this embodiment.

  In step 1, it is determined whether or not the fuel cut has already started, in other words, whether or not the fuel cut is in progress. If the driver fully closes the accelerator pedal opening while the vehicle is running, a predetermined fuel cut condition (for example, that the coolant temperature is after the warm-up is completed, that the vehicle speed is equal to or higher than a predetermined threshold, engine speed) The fuel cut is executed on the condition that the value is equal to or greater than a predetermined threshold.

  If it is determined in step 1 that the fuel is not being cut, the process of this flowchart is terminated.

  If the fuel cut is in progress in step 1, the process proceeds to step 2 to measure the fuel cut period using the counter FCTCNT indicating the fuel cut period. In addition, as a fuel cut period, fuel cut time and the number of fuel cut cycles can be used. In step 3, the fuel cut period (counter FCTCNT) measured in step 2 is compared with a predetermined fuel cut period tumble control valve closing criteria SLFCTCV. If the fuel cut period FCTCNT is equal to or shorter than the predetermined criteria SLFCTCV in step 3, the tumble control valve 12 is opened in step 9 and the process proceeds to step 5. Note that an appropriate intermediate opening degree may be maintained.

  If the fuel cut period FCTCNT is longer than the predetermined criteria SLFCTCV, the process proceeds to step 4 to close the tumble control valve 12 in preparation for fuel cut recovery. This corresponds to a state in which the temperature in the cylinder 2 is lowered due to the fuel cut for a long time. Then, the process proceeds to step 5 to determine whether or not fuel cut recovery control is being performed. That is, it is determined whether or not a predetermined fuel cut recovery condition is satisfied. For example, the fuel cut recovery condition may include that the driver depresses the accelerator pedal, that the vehicle speed has dropped below a predetermined threshold, or that the engine speed has dropped below a predetermined threshold. Based on the establishment of this fuel cut recovery condition, fuel injection from the fuel injection valve 11 is resumed according to a fuel injection control routine (not shown).

  If it is determined in step 5 that fuel cut recovery control is not being performed, the process returns to step 2 and measurement of the fuel cut period FCTCNT is continued.

  If the fuel cut / recover control is being performed in step 5, the process proceeds to step 6 and the recovery combustion number RCMBCNT indicating the number of combustion cycles after the fuel cut recovery is compared with a predetermined recovery time combustion number criterion SLRCCNT. Here, the combustion frequency criterion SLRCCNT at the time of recovery is obtained from a characteristic map as shown in FIG. 3, which is set in advance using the fuel cut period FCTCNT and the load at the time of recovery (the amount of air in the cylinder at the time of recovery) as parameters. Criteria SLRCCNT is set so that the number of combustion increases as the fuel cut period FCTCNT is longer and the load during recovery is lower. That is, if the fuel cut period FCTCNT is long, the temperature in the cylinder 2 decreases, so the number of combustions is increased. Also, if the amount of air in the cylinder is small, the amount of heat generated is small, so the number of times of combustion is also increased.

  In step 6, when the number of times of recovery combustion RCMBCNT exceeds a predetermined criterion SLRCCNT, the routine proceeds to step 7 where the tumble control valve 12 is set to normal control. Thereby, the opening degree of the tumble control valve 12 is controlled to a normal opening degree according to the operating condition of the internal combustion engine 1. Therefore, after the temperature in the cylinder rises due to combustion, the premature combustion is prevented by returning the opening degree of the tumble control valve 12 to the normal opening degree.

  In step 6, when the number of combustion times RCMBCNT during recovery is equal to or less than a predetermined criterion SLRCCNT, the number of times of combustion during recovery is repeated through step 8. In step 8, acceleration determination is performed. Here, the acceleration determination is performed by comparing the change rate of the accelerator opening detected by the accelerator opening sensor 23 with a predetermined threshold. When the detected change rate of the accelerator opening is larger than a predetermined threshold value, the closing operation of the tumble control valve 12 is stopped and normal control is performed. Thereby, the fall of the intake air amount by the tumble control valve 12 can be prevented, and deterioration of the acceleration performance can be prevented.

  FIG. 4 is a time chart for explaining the operation by the control of the above embodiment, and shows changes in various parameters from the start of fuel cut to the recovery of fuel cut. In order from the top of the figure, (a) engine rotational speed, (b) in-cylinder equivalence ratio, (c) counter FCTCNT indicating fuel cut period, (d) opening of tumble control valve, (e) number of combustions during recovery RCMBCNT, (f) Particle number (PN) in the exhaust, respectively.

  In the example of this figure, the tumble control valve 12 is closed until just before time t1. At time t1, the driver performs the fuel cut by fully closing the accelerator pedal opening. As a result, the engine speed gradually decreases. The fuel cut period is measured by the counter FCTCNT. Along with this fuel cut, the tumble control valve 12 is opened.

  At time t2, when the fuel cut period FCTCNT exceeds a predetermined fuel cut period tumble control valve closing criteria SLFCTCV, the tumble control valve 12 is controlled to be closed. Thereby, the gas flow in the cylinder 2 is strengthened.

  At time t3, fuel cut recovery is executed based on a recovery condition such as a reduction to a vehicle speed threshold, and fuel injection is started. At the same time, the count of the number of combustions during recovery RCMBCNT is started.

  Next, at time t4, when the number of combustion times RCMBCNT at the time of recovery exceeds a predetermined criterion SLRCCNT, the tumble control valve 12 is returned from the forced closed state to the normal opening degree control.

  As described above, when the fuel is injected at the time of fuel cut recovery, the tumble control valve 12 is closed in advance to promote the vaporization of the fuel injected at the time of recovery, and the fuel adheres to the cylinder wall surface or the piston crown surface. Reduced. Thereby, the number of particles PN in the exhaust during recovery is suppressed.

  Further, in order to forcibly release the oxygen absorbed excessively by the catalytic converter 19 during the fuel cut, generally during the fuel cut recovery, the fuel injection amount is corrected to be increased to temporarily make the air-fuel ratio of the exhaust rich. The so-called fuel recovery rich injection is performed. If the fuel recovery rich injection is performed without operating the tumble control valve 12 before the start of the fuel cut recovery, a larger amount of fuel adheres to the cylinder wall surface or piston crown surface where the temperature has dropped during the fuel cut. The number of particles PN in the exhaust gas increases compared to the time of fuel injection. However, if fuel recover rich injection is performed after the tumble control valve 12 has been operated in advance before the start of fuel cut recovery, fuel is injected into the combustion chamber 7 in a state where a tumble flow has occurred in the cylinder 2. become. Accordingly, the vaporization of the injected fuel is promoted and it is difficult to adhere to the cylinder wall surface and the piston crown surface. Thereby, the number of particles PN in the exhaust gas is reduced.

  In addition, the broken line of (f) of a figure shows the characteristic of the particle number PN at the time of performing fuel recovery rich injection without operating the tumble control valve 12 before the start of fuel cut recovery, and a continuous line shows the said Example. Thus, the characteristics of the number of particles PN when the fuel recovery rich injection is performed after the tumble control valve 12 is operated in advance before the start of the fuel cut recovery is shown.

  Next, FIG. 5 is a flowchart for explaining the control of the tumble control valve 12 after fuel cut in another embodiment.

  In step 11, it is determined whether or not a fuel cut has already started, in other words, whether or not a fuel cut is in progress. As in step 1 of the flowchart of FIG. 2, when the driver fully closes the accelerator pedal opening degree while the vehicle is traveling, fuel cut is executed on condition that a predetermined fuel cut condition is satisfied.

  If it is determined in step 11 that the fuel is not being cut, the processing of this flowchart is terminated.

  Further, when the fuel is being cut in step 11, the process proceeds to step 12 to calculate the estimated piston temperature ESPSTMP. Here, the estimated piston temperature ESPSTMP is calculated using a load (intake air amount) before the fuel cut, an air amount passing through the cylinder 2 during the fuel cut, and the like. In step 13, the estimated piston temperature ESPSTMP calculated in step 12 is compared with a predetermined estimated piston temperature tumble control valve closing criterion SLPSTMP. If the estimated piston temperature ESPSTMP is equal to or higher than the predetermined criteria SLPSTMP in step 13, the tumble control valve 12 is opened in step 19 and the process proceeds to step 15. Note that an appropriate intermediate opening degree may be maintained.

  If the estimated piston temperature ESPSTMP is lower than the predetermined criteria SLPSTMP, the process proceeds to step 14 where the tumble control valve 12 is closed in preparation for fuel cut recovery. Then, the process proceeds to step 15 to determine whether or not the fuel cut recovery control is being performed. That is, it is determined whether or not a predetermined fuel cut recovery condition is satisfied. The fuel cut recovery condition is the same as step 5 in the flowchart of FIG. Based on the establishment of this fuel cut recovery condition, fuel injection from the fuel injection valve 11 is resumed according to a fuel injection control routine (not shown).

  If it is determined in step 15 that the fuel cut recovery control is not being performed, the process returns to step 12, and the estimation of the piston temperature ESPSTMP and the comparison with the predetermined criteria SLPSTMP are repeated.

  If fuel cut recovery control is being performed in step 15, the process proceeds to step 16 where the estimated piston temperature ESPSTMP is compared with a predetermined estimated piston temperature tumble control valve closing criterion SLPSTMP. When the estimated piston temperature ESPSTMP exceeds the predetermined criteria SLPSTMP, the routine proceeds to step 17 where the tumble control valve 12 is set to normal control. Thereby, the opening degree of the tumble control valve 12 is controlled to a normal opening degree according to the operating condition of the internal combustion engine 1.

  If the estimated piston temperature ESPSTMP is equal to or lower than the predetermined criteria SLPSTMP in step 16, the temperature comparison in step 16 is repeated through step 18. In step 18, acceleration determination is performed. Here, this acceleration determination is performed in the same manner as step 8 in the flowchart of FIG. When the detected change rate of the accelerator opening is larger than a predetermined threshold value, the closing operation of the tumble control valve 12 is stopped and normal control is performed.

  FIG. 6 is a time chart for explaining the operation by the control according to the above embodiment, and shows changes in various parameters from the start of fuel cut to the recovery of fuel cut. In order from the top of the figure, (a) engine rotational speed, (b) in-cylinder equivalence ratio, (c) estimated piston temperature ESPSTMP, (d) tumble control valve opening, (e) number of particles PN in exhaust, Respectively.

  In the example of this figure, the tumble control valve 12 is closed until just before time t1. At time t1, the driver performs the fuel cut by fully closing the accelerator pedal opening. As a result, the engine speed gradually decreases. As described above, the estimated piston temperature ESPSTMP is calculated using the load (intake air amount) before the fuel cut, the air amount passing through the cylinder 2 during the fuel cut, and the like. Along with this fuel cut, the tumble control valve 12 is opened.

  Thereafter, when the estimated piston temperature ESPSTMP falls below a predetermined estimated piston temperature tumble control valve closing criterion SLPSTMP at time t2, the tumble control valve 12 is controlled to be closed.

  At time t3, fuel cut recovery is executed based on a recovery condition such as a reduction to a vehicle speed threshold, and fuel injection is started. As a result, the fuel is combusted again in the combustion chamber 7, and the piston temperature starts to rise.

  Next, when the estimated piston temperature ESPSTMP exceeds the predetermined criteria SLPSTMP at time t4, the tumble control valve 12 is returned from the forced closed state to the normal opening control.

  Therefore, as in the embodiment of FIG. 4, the number of particles PN in the exhaust at the time of recovery is suppressed by previously closing the tumble control valve 12 at the time of fuel injection at the time of fuel cut recovery.

  The fuel recover rich injection is the same as that in the embodiment of FIG.

  In addition, the broken line of (e) of a figure shows the characteristic of the particle number PN at the time of performing fuel recovery rich injection, without operating the tumble control valve 12 before the start of fuel cut recovery, and a continuous line shows the said Example. Thus, the characteristics of the number of particles PN when the fuel recovery rich injection is performed after the tumble control valve 12 is operated in advance before the start of the fuel cut recovery is shown.

  In each of the embodiments described above, an example in which the gas flow in the cylinder 2 is enhanced by the operation of the tumble control valve has been disclosed. You may make it carry out by the lift difference in a pair of intake valves, etc.

  Further, in each of the above flowcharts, in order to start the operation of the tumble control valve 12 before recovery in preparation for fuel injection at the time of fuel cut recovery, the fuel cut period FCTCNT and the estimated piston temperature ESPSTMP are compared with related criteria, An example has been disclosed in which the tumble control valve 12 is actuated with the timing of this comparison as a trigger. However, in the present invention, the operation timing of the tumble control valve 12 does not necessarily coincide with the timing of the comparison, and in consideration of response delay, the tumble control valve 12 is prior to fuel injection at the time of fuel cut recovery. Should be activated.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 5 ... Intake port 11 ... Fuel injection valve 12 ... Tumble control valve 15 ... Engine control unit

Claims (5)

A fuel injection valve that directly injects fuel into the combustion chamber; and a gas flow enhancement device that enhances the gas flow in the combustion chamber. The fuel cut is performed at a predetermined deceleration of the internal combustion engine, and then the predetermined fuel cut is performed. In a control device for an internal combustion engine that performs fuel cut recovery when a recovery condition is satisfied,
The estimated piston temperature is repeatedly estimated during the fuel cut, and only when the estimated piston temperature becomes lower than a predetermined temperature , the operation of the gas flow enhancement device is started prior to the fuel cut recovery, and the combustion is performed. A control device for an internal combustion engine, which performs fuel injection at the time of fuel cut recovery in a state where gas flow in the chamber is enhanced. In a state in which the gas flow is enhanced, when the estimated piston temperature exceeds the predetermined temperature, according to claim 1, characterized in that return the degree of opening of the gas flow strengthening device to the normal opening Control device for internal combustion engine. When the gas flow enhancement device is operating after the fuel cut recovery and the change rate of the accelerator opening is larger than a predetermined threshold, the operation of the gas flow enhancement device is stopped. The control apparatus for an internal combustion engine according to claim 1 or 2 . The gas flow strengthening device tumble control valve, the swirl control valve, claim 1-3, characterized in that the lift difference generation mechanism in the single valve stop mechanism or a pair of intake valves, the pair of intake valves The control apparatus of the internal combustion engine described in 1. The control apparatus for an internal combustion engine according to any one of claims 1 to 4 , wherein the fuel injection amount from the fuel injection valve is corrected to increase during the fuel cut recovery.

Images