JP2007016746A - Fuel injection control device for variable cylinder engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase a degree of freedom in a timing when supplying fuel which does not contribute to combustion. <P>SOLUTION: Sub-injection is allowed in a predetermined first crank angle range A which includes a compression TDC of a piston in a resting cylinder. The first crank angle range A is such that oil dilution due to the deposition of fuel on a bore wall does not occur in the range A or it is in an allowable range if occurring. In a predetermined second crank angle range B which is smaller than the first crank angle range A and includes the compression TDC of the piston in the resting cylinder, the sub-injection is prohibited to suppress unnecessary torque fluctuation and a smoke increase due to natural ignition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an engine having a fuel injection valve in each of a plurality of cylinders, and a cylinder reduction process in which main injection of fuel to some cylinders is stopped and operation is continued in the remaining cylinders under a predetermined cylinder reduction condition. The present invention relates to a fuel injection control device for a variable cylinder engine that can be operated.

  Various variable cylinder engines have been proposed in which the operation of a specific cylinder is suspended in order to reduce fuel consumption when there is little need for engine output, such as during idling or deceleration.

  In such a variable cylinder engine, a method of activating a catalyst provided in an exhaust system of the engine with unburned components such as HC in the fuel by supplying fuel to the idle cylinder has been attempted (for example, Patent Document 1). In this apparatus, in the idle cylinder, fuel is supplied (post injection) immediately after exhaust top dead center, and then the main injection of the cylinder is paused, so that the cylinders that pause this main injection are not continuous. It is changed sequentially every predetermined cycle.

JP 2003-27996 A

  By the way, in the apparatus disclosed in Patent Document 1, since the fuel is supplied only near the exhaust top dead center, the amount of fuel supply is limited.

  Accordingly, an object of the present invention is to expand the degree of freedom of timing when fuel supply that does not contribute to combustion is performed.

  According to a first aspect of the present invention, in an engine having a fuel injection valve in each of a plurality of cylinders, main fuel injection to some cylinders is stopped under a predetermined cylinder reduction condition and operation is continued in the remaining cylinders. A variable cylinder engine fuel injection control apparatus capable of performing a reduced-cylinder operation, wherein, during the reduced-cylinder operation, sub-injection is performed on the fuel injection valve in the some cylinders under a predetermined sub-injection condition And a sub-injecting means for causing the sub-injection to be executed within a predetermined first crank angle range including a compression top dead center of the pistons of the cylinders. It is a fuel injection control device of a variable cylinder engine.

  In the first aspect of the present invention, the sub-injecting means executes the sub-injection within a predetermined first crank angle range including the compression top dead center of the piston of the idle cylinder. Therefore, according to the first aspect of the present invention, it is possible to extend the degree of freedom of timing when supplying fuel that does not contribute to combustion to the vicinity of the compression top dead center.

  The first crank angle range is particularly preferably set to a range that does not cause oil dilution due to fuel adhering to the bore wall.

  A second aspect of the present invention is the fuel injection control device for a variable cylinder engine according to claim 1, wherein the sub-injection means is more than the first crank angle range even under the sub-injection condition. The variable cylinder engine fuel injection control device is characterized in that the sub-injection is not executed within a predetermined second crank angle range that is narrow and includes a compression top dead center of the pistons of some of the cylinders.

  If fuel is supplied in the vicinity of the compression top dead center, there is a risk of irregular torque fluctuations due to spontaneous ignition. However, in the second aspect of the present invention, the sub-injection means is within the predetermined second crank angle range narrower than the first crank angle range and including the compression top dead center of the piston of the idle cylinder. Do not perform injection. Therefore, irregular torque fluctuations due to spontaneous ignition can be suppressed.

  As in the third aspect of the present invention, the sub-injection means in the present invention preferably performs the sub-injection both before and after the compression top dead center, thereby adjusting the fuel supply amount. The degree of freedom can be further promoted.

  Further, as in the fourth aspect of the present invention, by further including a variable means for varying at least one of the first and second crank angle ranges in accordance with the engine temperature, it is suitable for the engine temperature. Control can be realized.

  In the present invention, as in the fifth aspect of the present invention, the catalyst is disposed in the exhaust passage of the engine, and the sub-injection means is within a predetermined third crank angle range before the compression top dead center of the piston of the idle cylinder. It is particularly preferable to execute the sub-injection.

  Further, in the configuration of the fifth aspect of the present invention, as in the sixth aspect of the present invention, the engine is a diesel engine and is narrower than the third crank angle range and the compression top dead center of the pistons of the some cylinders. If the sub-injection is not executed within the fourth crank angle range including the above, the present invention can be suitably applied to a diesel engine having a high compression ratio and high fuel ignitability. Consumption due to ignition can be suppressed.

  In this case, as in the seventh aspect of the present invention, if the sub-injection is to inject a small amount of fuel that does not cause spontaneous ignition, natural ignition can be effectively suppressed.

  A preferred embodiment of the present invention will be described below. FIG. 1 shows a fuel injection control device 1 for a variable cylinder engine according to a first embodiment of the present invention. The engine 10 is an in-cylinder fuel injection type diesel engine, and includes an intake passage 11, an exhaust passage 12, a combustion chamber 16, and the like. A piston 14 is disposed in each cylinder 13 of the engine 10 so as to be movable up and down. In the center of the top surface 14 a of the piston 14, a concave portion (cavity) 15 constituting the combustion chamber 16 is formed. An injector 17 that injects fuel is provided above the combustion chamber 16.

  The injector 17 is connected to a common rail 18 which is a common fuel pressure accumulation chamber for each cylinder 13. In operation, the fuel stored in the fuel tank 18 a is pumped out by the fuel pump 18 b, pressurized to a high pressure, and stored in the common rail 18. The pressure of the fuel accumulated in this way is applied to the injector 17 of each cylinder 13 connected to the common rail 18. A nozzle (not shown) is provided at the tip of the injector 17 for opening the valve when its back pressure becomes a predetermined high pressure and injecting fuel. The start and end of fuel injection are determined by controlling the back pressure of the nozzle by a solenoid valve (not shown) provided in the injector 17. Therefore, in such a common rail system, highly accurate fuel injection control that does not depend on the rotational speed of the engine 10 can be performed.

  On the other hand, on the upstream side of the intake passage 11, an intake throttle valve 22 that is driven to open and close by a step motor 23 and makes the flow passage area of the intake passage 11 variable is provided. Further upstream, an air flow meter 21 for detecting the amount of intake air flowing through the intake passage 11 and an air cleaner 20 for purifying the intake air are provided.

  A catalyst device 27 is connected to the exhaust passage 12, and a DPF (Diesel Particulate Filter) 28 is connected to the exhaust side of the catalyst device 27. The exhaust side of the DPF 28 is opened to the outside through a silencer (not shown). As the catalyst material accommodated in the catalyst device 27, it is preferable to use a Pt three-way catalyst or a Pd three-way catalyst. The DPF 28 captures and removes PM (Particulate Matter) from the exhaust gas discharged from the combustion chamber 16 of the engine 10. For example, a porous ceramic honeycomb filter is preferably used.

  On the other hand, in the engine 10, the outputs of various sensors including the air flow meter 21 are input to an electronic control unit (ECU) 26 that serves as a control system of the engine 10 and a diagnosis system thereof. The ECU 26 controls driving of the step motor 23 that opens and closes the intake throttle valve 22 and the injector 17 that performs fuel injection. The ECU 26 is configured as a well-known one-chip microprocessor, and details thereof are not shown, but a CPU for performing various arithmetic processing, a ROM storing control programs, initial values of control variables, and the like, temporary control programs and data are temporarily stored. RAM, an input / output port, an A / D and D / A converter, a storage device, and the like.

  In addition to the air flow meter 21, the ECU 26 includes an NE sensor 24 that detects the rotational phase of the crankshaft 24a that is the output shaft of the engine 10, and further an accelerator that detects the amount of depression of the accelerator pedal 25a. Sensor 25, fuel pressure sensor 19 for detecting the pressure of the fuel accumulated in the common rail 18, vehicle speed sensor 37 provided in the vicinity of a drive wheel (not shown), intake air temperature sensor 38 provided in the intake passage, engine coolant passage The outputs of various sensors for detecting the operating state of the engine 10 such as the water temperature sensor 39 provided in the are input. The ECU 26 grasps the operating state of the engine 10 based on the output results of these sensors, and drives and controls various actuators including the injector 17 and the step motor 23 to execute various controls of the engine 10.

  As part of such engine control, the ECU 26 controls the fuel injection amount and the fuel injection timing based on the drive control of the injector 17. This fuel injection control is repeatedly executed in the ECU 26 when a predetermined start condition is satisfied, for example, when an ignition switch in the passenger compartment is turned on.

  First, the ECU 26 determines whether a predetermined cylinder reduction condition is satisfied (S10). This cylinder reduction condition is, for example, that the amount of PM trapped in the DPF 28 provided in the exhaust system has reached a predetermined amount, and that the catalyst substance in the catalyst device 27 has reached a predetermined activatable temperature. can do. Such determination of the reduced cylinder condition can be performed based on the PM accumulation amount or the estimated value of the catalyst temperature calculated by the estimation calculation based on the intake air temperature, the engine water temperature, the operation time, the travel distance, and the like.

  When the cylinder reduction condition is not satisfied, the ECU 26 sets the main injection amount of each cylinder according to the normal operation mode (S50). In this normal operation mode, normal operation using all cylinders is performed. Therefore, the main injection amounts of the respective cylinders are made the same with each other except for various elements for correcting variations among the cylinders.

  When the reduced cylinder condition is satisfied, the ECU 26 sets the main injection amount of each cylinder in the reduced cylinder operation mode (S20). In this reduced-cylinder operation mode, a reduced-cylinder operation is performed in which the main injection of fuel into some cylinders is stopped and the operation is continued with the remaining cylinders. Therefore, the main injection amount of the idle cylinder is set to zero, and the main injection amounts of the other cylinders are set to values that allow the operation to be continued.

  Next, the ECU 26 sets a sub-injection amount for the deactivated cylinder (S30). The sub injection amount here refers to the pilot injection amount and the post injection amount. The pilot injection in the present embodiment is a fuel injection performed on the advance side from the compression top dead center, and refers to a small amount that does not cause spontaneous ignition by itself, post-injection here is Fuel injection that is performed at a retarded angle side from the compression top dead center, which is a small amount that does not cause spontaneous ignition by itself. It does not matter whether the sub-injection in the present invention overlaps the crank angle region of the main injection when the main injection is performed.

  Here, as shown in FIG. 3, the sub-injection amount in the idle cylinder, that is, the pilot injection amount and the post-injection amount has an injection period determined according to the pilot injection amount and the post-injection amount. It is set to be within a predetermined first crank angle range A including the top dead center (compression TDC), that is, between t1 and t4. In other words, the supply of fuel for catalyst activation is prohibited outside the first crank angle range A (t1 to t4). The first crank angle range A is a range in which oil dilution does not occur due to the fuel adhering to the bore wall of the cylinder 13 or even if it occurs within the range A. The first crank angle range A is geometrically determined as a crank angle range in which the fuel injected from the injector 17 does not directly hit the bore wall from the injection angle by the injector 17 and the diameter of the cylinder 13 or the piston 14. Or may be determined experimentally.

  The values (crank angles) of t1 and t4 that are the start and end of the first crank angle range A may be fixed values, and at least one of them may be used as information on engine temperature such as engine water temperature. It may be variable (ie, corrected or dynamically set) based on the parameters it contains. When t1 and / or t4 are made variable, it is possible to realize suitable control according to the engine temperature. When the value of t1 and / or t4 is varied, for example, as shown in FIG. 4, it is preferable that the value of t1 and / or t4 is set closer to the compression TDC as the temperature decreases. For example, t1 and t4 are preferably set within a range of −45 <t1 <t4 <45 [° ATDC].

  Further, as shown in FIG. 3, the sub-injection amount in the idle cylinder, that is, the pilot injection amount and the post injection amount, has an injection period determined according to the pilot injection amount and the post injection amount. The sub-injection is set not to be executed within a predetermined second crank angle range B that is narrower than (t1 to t4) and includes the compression TDC of the piston of the cylinder, that is, between t2 and t3. In other words, in the second crank angle range B (t2 to t3), the supply of fuel for catalyst activation is prohibited. The crank angle range B from t2 to t3 is a range in which spontaneous ignition does not occur in this range, or even if it occurs, unnecessary torque fluctuation and smoke increase due to this are within an allowable range.

  The values (crank angle) of t2 and t3 may be fixed values, and at least one of them may be varied based on a parameter including engine temperature information such as engine water temperature (ie, corrected or dynamically set). May be. When t2 and / or t3 are variable, it is possible to realize suitable control according to the engine temperature. When the value of t2 and / or t3 is varied, for example, as shown in FIG. 4, it is preferable that the value of t2 and / or t3 is set so as to be farther from the compression TDC as the temperature becomes higher.

  In this way, fuel injection for catalyst activation in the idle cylinder is allowed only between t1 and t2 and between t3 and t4. A predetermined map is used to determine how much injection amount is allocated to a period between t1 and t2 and a period between t3 and t4 for a certain injection amount (supply amount) so as to reduce the possibility of spontaneous ignition. Can be arbitrarily determined.

  Finally, fuel injection is executed according to the fuel injection amount set in step S30 or S50 (S40).

  As a result of the above processing, in the idle cylinder, as shown in FIG. 3, the fuel injection command to the injector 17 by the ECU 26 at a timing within the first crank angle range A and outside the second crank angle range B. Is output, and fuel injection for catalyst activation is performed. The fuel in this case is not spontaneously ignited, and therefore passes through the cylinder 13 and is supplied to the catalyst device 27 in an unburned state. As a result, the catalytic substance in the catalytic device 27 is activated by the HC component in the unburned fuel, and the combustion or oxidation of PM deposited on the DPF is promoted by the increase in the catalyst temperature. In addition, the fuel is lightened by the action of the heat remaining in the combustion chamber due to the combustion before stopping, so that the temperature rise performance of the catalyst can be expected.

  As described above, in the present embodiment, the sub-injection is permitted within the predetermined first crank angle range A including the compression TDC of the piston of the idle cylinder. Therefore, the fuel supply that does not contribute to the combustion can be expanded to the vicinity of the compression TDC, and the degree of freedom in the timing of fuel supply can be promoted.

  In addition, if fuel is supplied in the vicinity of the compressed TDC, there is a possibility that unnecessary torque fluctuations and smoke increase may occur due to spontaneous ignition. However, in this embodiment, the ECU 26 prohibits the sub-injection within a predetermined second crank angle range B that is narrower than the first crank angle range A and includes the compression TDC of the piston of the idle cylinder. Therefore, unnecessary torque fluctuation and smoke increase due to spontaneous ignition can be suppressed.

  Further, in the present embodiment, the ECU 26 executes the sub-injection both before and after the compression TDC, so that the degree of freedom when adjusting the fuel supply amount can be further promoted. That is, when the amount of fuel supplied to the intended catalyst is small, the sub-injection is performed only near the exhaust top dead center (exhaust TDC), before and after the compression TDC, or only before the compression TDC. The timing for supplying the fuel can be selected with a degree of freedom. On the other hand, if the sub-injection is executed before and after the compression TDC and in the vicinity of the exhaust TDC, the amount of fuel supplied to the catalyst can be increased as compared with the conventional case.

  In the above embodiments, the present invention has been described with a certain degree of concreteness, but various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention described in the claims. It must be understood that it is possible. That is, the present invention includes modifications and changes that fall within the scope and spirit of the appended claims and their equivalents. For example, in the above embodiment, both pilot injection and post injection are executed. However, in the present invention, only pilot injection or only post injection may be executed. In the configuration in which only pilot injection is performed, instead of the first crank angle range A, the third crank angle range consisting only of the region before compression top dead center in the range A is used, and the second crank angle Instead of the range B, it is possible to use a fourth crank angle range that is not formed in the region before the compression top dead center in the range B.

  In the present embodiment, an example in which the present invention is applied to a diesel engine that is a self-igniting internal combustion engine has been described. However, the present invention relates to various sparks such as a gasoline engine and a gaseous fuel engine using LPG or hydrogen as fuel. The present invention can also be applied to an ignition internal combustion engine, and any configuration belongs to the category of the present invention.

It is a schematic structure figure showing a 1st embodiment of the present invention. It is a flowchart which shows operation | movement of 1st Embodiment. It is a timing diagram which shows the fuel-injection timing in 1st Embodiment. It is a graph which shows the example of a setting of t1, t2, t3, and t4 in 1st Embodiment.

Explanation of symbols

1 Fuel Injection Control Device for Variable Cylinder Engine 10 Engine 17 Injector 21 Air Flow Meter 22 Intake Throttle Valve 26 ECU
27 Catalyst unit 28 DPF
37 Vehicle speed sensor 38 Intake air temperature sensor 39 Water temperature sensor

Claims (7)

Engines with fuel injection valves in each of multiple cylinders can perform reduced-cylinder operation in which the main fuel injection to some cylinders is stopped and operation is continued in the remaining cylinders under specified reduced-cylinder conditions. A fuel injection control device for a variable cylinder engine,
A sub-injection means for causing the fuel injection valve to perform sub-injection in the partial cylinders under predetermined sub-injection conditions during the reduced-cylinder operation;
The fuel injection control device for a variable cylinder engine, wherein the sub-injection means causes the sub-injection to be executed within a predetermined first crank angle range including a compression top dead center of the pistons of the some cylinders. . A fuel injection control device for a variable cylinder engine according to claim 1,
The sub-injecting means is within a predetermined second crank angle range that is narrower than the first crank angle range and includes the compression top dead center of the pistons of the some cylinders even under the sub-injection condition. Then, the fuel injection control device for a variable cylinder engine, wherein the sub-injection is not executed. A fuel injection control device for a variable cylinder engine according to claim 1 or 2,
The fuel injection control device for a variable cylinder engine, wherein the sub-injection means performs the sub-injection both before and after the compression top dead center. A fuel injection control device for a variable cylinder engine according to any one of claims 1 to 3,
A fuel injection control device for a variable cylinder engine, further comprising variable means for varying at least one of the first and second crank angle ranges in accordance with the temperature of the engine. In an engine in which a fuel injection valve is provided in each of the plurality of cylinders and a catalyst is disposed in the exhaust path, the main fuel injection to some cylinders is stopped under a predetermined reduction cylinder condition and the remaining cylinders are operated. A variable cylinder engine fuel injection control device capable of continuing a reduced-cylinder operation,
A sub-injection means for causing the fuel injection valve to perform sub-injection in the partial cylinders under predetermined sub-injection conditions during the reduced-cylinder operation;
The sub-injection means causes the sub-injection to be executed within a predetermined third crank angle range before compression top dead center of the pistons of the some cylinders. . A fuel injection control device for a variable cylinder engine according to claim 5,
The engine is a diesel engine;
The sub-injection means is within a predetermined fourth crank angle range that is narrower than the third crank angle range and includes the compression top dead center of the pistons of the some cylinders even under the sub-injection condition. Then, the fuel injection control device for a variable cylinder engine, wherein the sub-injection is not executed. A fuel injection control device for a variable cylinder engine according to claim 6,
A fuel injection control device for a variable cylinder engine, wherein the sub-injection is for injecting a small amount of fuel that does not cause spontaneous ignition.

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