JP2018091267A - Controller of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller of an internal combustion engine capable of suppressing occurrence of deposit in a fuel injector and improving control accuracy of fuel injection, in a case of causing the fuel injector of dividedly executing fuel injection into a sub-combustion chamber.SOLUTION: A controller 1 of an internal combustion engine 3 includes an ECU 2. The ECU 2 is configured to control a sub-fuel injection valve 7 so as to, when a sub-injection valve temperature Tinj is not less than a predetermined value α, dividedly execute fuel injection into a sub-combustion chamber 3d two times during one combustion cycle, and execute one-time fuel injection after combustion of air-fuel mixture in the sub-combustion chamber 3d (steps 9-11).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a control device for an internal combustion engine in which a main combustion chamber and a sub-combustion chamber that communicate with each other are provided for each cylinder, and an air-fuel mixture is generated in the sub-combustion chamber by fuel injection into the sub-combustion chamber by the fuel injection device.

  Conventionally, what was described in patent document 1 is known as a control apparatus of an internal combustion engine. In the case of the internal combustion engine shown in FIG. 1 of the same document, a main combustion chamber and a sub-combustion chamber communicating with each other are provided for each cylinder, and gasoline as main fuel is supplied to the main combustion chamber from an intake port. Further, the injection valve is provided so as to face the auxiliary combustion chamber, and by this injection valve, the fuel of the ignition reaction promoting element (gasoline etc.) is injected into the auxiliary combustion chamber, and this is ignited by the ignition plug, Combustion products flow into the main combustion chamber through the connecting holes. Thereby, the main fuel in the main combustion chamber self-ignites.

  In the case of this control device, in the example shown in FIGS. 9A and 9B of the same document, the fuel of the ignition reaction promoting element is injected so as to be injected once between the intake stroke and the compression stroke. The valve is controlled. Further, in the example shown in FIG. 9C of the same document, the injection valve is controlled so that the fuel of the ignition reaction promoting element is injected divided into a plurality of times from the intake stroke to the compression stroke.

JP 2003-286848 A

  According to the control device of Patent Document 1, since the injection valve is provided so as to face the auxiliary combustion chamber, when the fuel of the ignition reaction promoting element burns in the auxiliary combustion chamber, the amount of heat received by the injection valve increases. As a result, as the injection operation is repeated, the amount of deposit generated in the injection valve increases. In this case, the injection amount is reduced, and the control accuracy of fuel injection is reduced, resulting in an air-fuel ratio shift and combustion fluctuations, resulting in a decline in merchantability. In particular, as in the example shown in FIG. 9C of the same document, when the fuel of the ignition reaction promoting element is divided and injected into a plurality of times, the fuel injection amount for one time is reduced, and the fuel for one time is reduced. The above problem becomes more noticeable when the heat radiation amount of the injection valve is reduced due to the injection.

  The present invention was made to solve the above-described problem, and in the case where the fuel injection into the sub-combustion chamber is divided into a plurality of times and executed by the fuel injection device, generation of deposits in the fuel injection device can be suppressed, An object of the present invention is to provide a control device for an internal combustion engine that can improve the control accuracy of fuel injection.

  In order to achieve the above object, according to the first aspect of the present invention, an air-fuel mixture is generated in the auxiliary combustion chamber 3d by fuel injection into the auxiliary combustion chamber 3d and the main combustion chamber 3c and the auxiliary combustion chamber 3d communicating with each other. The fuel injection device (sub fuel injection valve 7) is a control device 1 for the internal combustion engine 3 provided for each cylinder 3a, and the fuel injection to the sub combustion chamber 3d is divided into a plurality of times during one combustion cycle. And a fuel injection control means for controlling the fuel injection device (sub fuel injection valve 7) so that at least one of the plurality of fuel injections is executed after combustion of the air-fuel mixture in the sub combustion chamber 3d. The ECU 2 includes steps 10 and 11).

  According to this control device for an internal combustion engine, fuel injection into the sub-combustion chamber is performed in a plurality of times during one combustion cycle, and at least one of the plurality of fuel injections is mixed in the sub-combustion chamber. Since the fuel injection device is controlled to be executed after the combustion of the gas, the temperature of the fuel injection device can be lowered by one or more fuel injections after the combustion of the air-fuel mixture in the auxiliary combustion chamber, Generation | occurrence | production of the deposit in an injection apparatus can be suppressed. Thereby, the control accuracy of fuel injection can be improved, and the merchantability can be improved.

  According to a second aspect of the present invention, in the control device 1 for the internal combustion engine 3 according to the first aspect of the present invention, a device temperature (sub-injection valve temperature Tinj) that is the temperature of the fuel injection device (sub-fuel injection valve 7) is acquired. The fuel injection control means further includes a temperature acquisition means (sub-injection valve temperature sensor 21), and the fuel injection control means after combustion of the air-fuel mixture in the sub-combustion chamber 3d when the apparatus temperature (sub-injection valve temperature Tinj) is equal to or higher than a predetermined value α. The fuel injection device (sub fuel injection valve 7) is controlled so as to execute one or more fuel injections in (steps 9 to 11).

  According to the control device for an internal combustion engine, the fuel injection device is controlled to execute one or more fuel injections after the combustion of the air-fuel mixture in the auxiliary combustion chamber when the device temperature is equal to or higher than a predetermined value. By appropriately setting this predetermined value, it is possible to reliably suppress the occurrence of deposits in the fuel injection device. As a result, the control accuracy of fuel injection can be further improved, and the merchantability can be further improved (Note that “acquisition” in “acquisition of apparatus temperature” in this specification refers to an apparatus temperature measured by a sensor or the like. Not only directly detecting, but also calculating / estimating the device temperature based on other parameters).

It is a figure showing typically composition of a control device concerning one embodiment of the present invention, and an internal-combustion engine to which this is applied. FIG. 2 is a partially enlarged view of FIG. 1 showing a schematic configuration around the auxiliary combustion chamber of the internal combustion engine. It is a flowchart which shows an engine control process. It is a timing chart which shows transition of gas temperature etc. in a subcombustion chamber when engine control processing is performed. It is a figure which shows the relationship between the crank angle from the combustion end timing of the air-fuel | gaseous mixture in a subcombustion chamber to the execution timing of post-combustion injection, and the temperature of a sub fuel injection valve.

  Hereinafter, an internal combustion engine control apparatus according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the control device 1 according to the present embodiment controls an operating state of an internal combustion engine (hereinafter referred to as “engine”) 3 and includes an ECU 2. The ECU 2 executes an engine control process described later.

  The engine 3 uses gasoline as fuel, and is mounted on a vehicle (not shown) as a power source. The engine 3 is a multi-cylinder type having a plurality of sets of cylinders 3a and pistons 3b (only one set is shown), and an intake valve and an exhaust valve (both not shown) are provided for each cylinder 3a. During operation of the engine 3, an intake operation into the cylinder 3a and an exhaust operation from the cylinder 3a are performed by the intake valve and the exhaust valve, respectively.

  A throttle valve mechanism 5 and a main fuel injection valve 6 are provided in the intake passage 4 of the engine 3 in order from the upstream side. The throttle valve mechanism 5 includes a throttle valve 5a and a TH actuator 5b that opens and closes the throttle valve 5a. The throttle valve 5a is rotatably provided in the middle of the intake passage 4, and changes the flow rate of air passing through the throttle valve 5a by the change in the opening degree accompanying the rotation.

  The TH actuator 5b is a combination of a motor connected to the ECU 2 and a gear mechanism (not shown), and is controlled by the ECU 2 to change the opening of the throttle valve 5a. Thereby, the amount of air sucked into the cylinder 3a is changed during the intake stroke.

  On the other hand, the main fuel injection valve 6 is provided in the intake manifold of the intake passage 4 for each cylinder 3a, is electrically connected to the ECU 2, and is controlled by the ECU 2 so that fuel is introduced into the intake manifold. Spray. The fuel injected from the main fuel injection valve 6 is sucked into the main combustion chamber 3c as the intake valve is opened during the intake stroke, and an air-fuel mixture is generated.

  Further, a main combustion chamber 3c and a sub-combustion chamber 3d are formed between the piston 3b of each cylinder 3a of the engine 3 and the cylinder head. As shown in FIGS. 1 and 2, the auxiliary combustion chamber 3d is provided on the upper side of the main combustion chamber 3c, and the auxiliary fuel injection valve 7 and the spark plug 8 are arranged on the upper side thereof.

  The auxiliary fuel injection valve 7 (fuel injection device) is provided such that the injection port at the tip thereof faces the auxiliary combustion chamber 3d, is electrically connected to the ECU 2, and is controlled by the ECU 2. Thus, the fuel is injected into the auxiliary combustion chamber 3d. Thereby, an air-fuel mixture is generated in the auxiliary combustion chamber 3d.

  The spark plug 8 is provided so that the electrode at the tip thereof faces the subcombustion chamber 3d. The spark plug 8 is discharged by being controlled by the ECU 2 during the combustion stroke, and the mixture in the subcombustion chamber 3d is discharged. Ignite.

  Further, a plurality of communication holes 3f are formed in the bottom wall portion 3e of the auxiliary combustion chamber 3d, and the auxiliary combustion chamber 3d and the main combustion chamber 3c communicate with each other through these communication holes 3f. Thus, as described above, when the air-fuel mixture in the sub-combustion chamber 3d is ignited by the spark plug 8 during the combustion stroke, the ignited air-fuel mixture flows into the main combustion chamber 3c via the communication hole 3f as a fire type. And the air-fuel mixture in the main combustion chamber 3c is combusted.

  In the case of this engine 3, during normal operation, the air-fuel ratio of the entire air-fuel mixture in the cylinder 3 a is controlled to be a value on the lean side of the stoichiometric air-fuel ratio, and lean burn operation is performed, and a high rotation / high load region During the operation, the air-fuel ratio of the entire air-fuel mixture in the cylinder 3a is controlled so as to become the stoichiometric air-fuel ratio, and the stoichiometric operation is performed. In this case, the air-fuel ratio of the entire air-fuel mixture in the cylinder 3a is the ratio between the total intake air amount in the cylinder 3a and the sum of the fuel injection amount by the main fuel injection valve 6 and the fuel injection amount by the sub fuel injection valve 7. Means.

  On the other hand, a catalyst device 10 is provided in the exhaust passage 9. The catalyst device 10 is a combination of a NOx purification catalyst and a three-way catalyst. The NOx purification catalyst captures NOx in exhaust gas under an oxidizing atmosphere and reduces the captured NOx under a reducing atmosphere. The three-way catalyst purifies the exhaust gas by oxidizing HC and CO in the exhaust gas and reducing NOx under a stoichiometric atmosphere.

  In addition, a crank angle sensor 20, a sub injection valve temperature sensor 21 and an accelerator opening sensor 22 are electrically connected to the ECU 2.

  The crank angle sensor 20 includes a magnet rotor and an MRE pickup, and outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft (not shown) rotates.

  The CRK signal is output at one pulse every predetermined crank angle (for example, 30 °), and the ECU 2 calculates the engine speed NE (hereinafter referred to as “engine speed”) NE based on the CRK signal. The TDC signal is a signal indicating that the piston 3b of each cylinder 3a is at a predetermined crank angle position slightly before the TDC position of the intake stroke, and one pulse is output for each predetermined crank angle.

  Further, the sub injection valve temperature sensor 21 detects the temperature of the sub fuel injection valve 7 (hereinafter referred to as “sub injection valve temperature”) Tinj, and outputs a detection signal indicating it to the ECU 2. In the present embodiment, the sub injection valve temperature sensor 21 corresponds to the apparatus temperature acquisition means, and the sub injection valve temperature Tinj corresponds to the apparatus temperature.

  Further, the accelerator opening sensor 22 detects a depression amount (hereinafter referred to as “accelerator opening”) AP of an accelerator pedal (not shown) of the vehicle, and outputs a detection signal indicating it to the ECU 2.

  On the other hand, the ECU 2 (fuel injection control means) is composed of a microcomputer comprising a CPU, RAM, ROM, an I / O interface (all not shown), and the detection signals of the various sensors 20 to 22 described above. In accordance with the above, the operating state of the engine 3 is determined, and an engine control process or the like is executed as described below in accordance with the operating state.

  Next, the engine control process will be described with reference to FIG. This engine control process calculates the fuel injection amount and injection timing of the two fuel injection valves 6 and 7 and the ignition timing of the spark plug 8, and is executed by the ECU 2 in synchronism with the generation timing of the TDC signal. The In the following description, the operation of injecting fuel from the auxiliary fuel injection valve 7 into the auxiliary combustion chamber 3d after combustion of the air-fuel mixture in the auxiliary combustion chamber 3d is referred to as “post-combustion injection”.

  As shown in the figure, first, in step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), the required torque TRQ is calculated. The required torque TRQ is calculated by searching a map (not shown) according to the engine speed NE and the accelerator pedal opening AP.

  Next, the routine proceeds to step 2, and a main injection amount QINJ1 is calculated by searching a map (not shown) according to the engine speed NE and the required torque TRQ. The main injection amount QINJ1 corresponds to the fuel injection amount by the main fuel injection valve 6.

  Next, at step 3, the main injection timing φINJ1 is calculated according to the main injection amount QINJ1 and the engine speed NE. This main injection timing φINJ1 is an injection end timing of the main injection amount QINJ1 by the main fuel injection valve 6, and is set to a timing during the intake stroke. As described above, when the main injection amount QINJ1 and the main injection timing φINJ1 are calculated, the fuel injection by the main fuel injection valve 6 is executed based on these values in a control process (not shown) (see FIG. 4A). Thereby, an air-fuel mixture is generated in the main combustion chamber 3c.

  In step 4 subsequent to step 3, a sub-injection amount QINJ2 is calculated by searching a map (not shown) according to the engine speed NE and the required torque TRQ. This sub injection amount QINJ2 corresponds to the fuel injection amount by the sub fuel injection valve 7.

  Next, the routine proceeds to step 5, where the sub injection timing φINJ2 is calculated according to the sub injection amount QINJ2 and the engine speed NE. This sub injection timing φINJ2 is the injection end timing of the sub injection amount QINJ2 by the sub fuel injection valve 7, and is set to the timing during the compression stroke. As described above, when the auxiliary injection amount QINJ2 and the auxiliary injection timing φINJ2 are calculated, fuel injection by the auxiliary fuel injection valve 7 is executed based on these values in a control process (not shown) (see FIG. 4B). Thereby, an air-fuel mixture is generated in the auxiliary combustion chamber 3d.

  Next, at step 6, the ignition timing IG is calculated as described below. First, the map value IGmap of the ignition timing is calculated by searching a map (not shown) according to the engine speed NE and the required torque TRQ. Next, the ignition timing IG is calculated by calculating the total correction term IGcor according to various parameters such as the engine water temperature and adding it to the map value IGmap. When the ignition timing IG is calculated in this way, in the control process (not shown), the ignition plug 8 ignites the air-fuel mixture in the auxiliary combustion chamber 3d at the ignition timing IG (see FIG. 4C). ).

  In step 7 following step 6, a sub-injection valve temperature threshold value Tref is calculated. This threshold value Tref is calculated according to various operating state parameters such as the engine speed NE and the required torque TRQ.

Next, the process proceeds to step 8 where the temperature deviation DT is calculated by the following equation (1).
DT = Tinj−Tref (1)

  Next, in step 9, it is determined whether or not the temperature deviation DT is equal to or greater than a predetermined value α. The predetermined value α is set to a positive value. When the determination result is YES, it is determined that the sub-injection valve temperature Tinj needs to be decreased, and the process proceeds to step 10 to calculate the post-combustion injection amount QAfter. This post-combustion injection amount QAfter is the amount of fuel injected from the auxiliary fuel injection valve 7 at the time of post-combustion injection in order to reduce the auxiliary injection valve temperature Tinj. Specifically, the temperature deviation DT, the engine speed NE And calculated according to the required torque TRQ.

  Next, the routine proceeds to step 11 where the post-combustion injection timing φafter is calculated according to the post-combustion injection amount QAfter, the engine speed NE, the total correction term IGcor, and the like. This post-combustion injection timing φafter is the injection end timing of the post-combustion injection amount Qafter by the auxiliary fuel injection valve 7, and is from the expansion stroke to the start of the intake stroke after the combustion of the air-fuel mixture in the auxiliary combustion chamber 3d. Is set to the optimal timing. As described above, when the post-combustion injection amount Qafter and the post-combustion injection timing φafter are calculated, the post-combustion injection is executed by the auxiliary fuel injection valve 7 based on these values in a control process (not shown) (FIG. 4 (b)). The effect of suppressing the temperature rise of the auxiliary fuel injection valve 7 due to the post-combustion injection will be described later.

  As described above, after calculating the post-combustion injection timing φafter in step 11, the present process is terminated.

  On the other hand, if the determination result in step 9 is NO and DT <α is established, it is determined that there is no need to decrease the sub-injection valve temperature Tinj, and the routine proceeds to step 12 where the post-combustion injection amount QAfter is set. After setting the value to 0, this process is terminated. Thereby, the post-combustion injection is stopped.

  Next, the effect of suppressing the temperature rise of the sub-injection valve temperature Tinj when the post-combustion injection in the above engine control process is executed will be described with reference to FIG. At the gas temperature in the auxiliary combustion chamber 3d shown in FIG. 4 (e), the data indicated by the solid line is obtained when DT ≧ α is established and the post-combustion injection described above is executed, and the data indicated by the broken line is For comparison, this is the case when post-combustion injection is stopped even though DT ≧ α is established.

  As shown by the broken line in FIG. 4 (e), when the post-combustion injection is stopped, the gas temperature hardly decreases during the combustion stroke, and the amount of heat received from the combustion gas in the auxiliary fuel injection valve 7 increases. Will do. On the other hand, as shown by the solid line in FIG. 4 (e), when the post-combustion injection is executed, along with the fuel injection by the auxiliary fuel injection valve 7 at the timing immediately after the start of the combustion stroke, The gas temperature in the auxiliary combustion chamber 3d is suddenly lowered. As a result, when post-combustion injection is performed, the amount of heat received from the combustion gas in the auxiliary fuel injection valve 7 can be effectively reduced compared to when the injection is stopped, and the temperature rise of the auxiliary fuel injection valve 7 is effective. Can be suppressed. In addition, by performing post-combustion injection, the fuel passes through the auxiliary fuel injection valve 7, and accordingly, the temperature rise of the auxiliary fuel injection valve 7 can be suppressed.

  When the post-combustion injection control process is executed, the relationship between the crank angle CAafter from the combustion end timing of the air-fuel mixture in the sub-combustion chamber 3d to the execution timing of post-combustion injection and the sub injection valve temperature Tinj is shown in FIG. It will be shown in That is, the smaller the crank angle CAafter, the more quickly the combustion gas temperature can be reduced, thereby suppressing the sub injection valve temperature Tinj. For the same reason, as the post-combustion injection amount QAfter is larger, the combustion gas temperature can be lowered more quickly, whereby the sub-injection valve temperature Tinj can be suppressed.

  As described above, according to the control device 1 of the present embodiment, fuel injection by the auxiliary fuel injection valve 7 is executed once during the compression stroke. Further, when the temperature deviation DT is equal to or higher than the predetermined value α, that is, when the sub-injection valve temperature Tinj is higher than the threshold value Tref by the predetermined value α, the post-combustion injection is executed once. Since this post-combustion injection is executed after the combustion of the air-fuel mixture in the sub-combustion chamber 3d, the gas temperature in the sub-combustion chamber 3d can be effectively reduced, and the combustion gas from the combustion gas in the sub-fuel injection valve 7 can be reduced. The amount of heat received can be effectively reduced. In addition, when the post-combustion injection is executed, the fuel passes through the auxiliary fuel injection valve 7, so that the temperature of the auxiliary fuel injection valve 7 can be lowered by heat exchange at that time. Thus, the temperature of the auxiliary fuel injection valve 7 can be effectively reduced, and the generation of deposits in the auxiliary fuel injection valve 7 can be suppressed. Thereby, the control accuracy of fuel injection can be improved, and the merchantability can be improved.

  The embodiment is an example in which the auxiliary fuel injection valve 7 is used as the fuel injection device. However, the fuel injection device of the present invention is not limited to this, and any fuel injection device can be used as long as it can inject fuel into the auxiliary combustion chamber 3d. Good.

  Further, the embodiment is an example in which the post-combustion injection by the auxiliary fuel injection valve 7 is executed only once, but the post-combustion injection may be executed by dividing it into two or more times. Further, the embodiment is an example in which the normal fuel injection other than the post-combustion injection by the auxiliary fuel injection valve 7 is executed only once, but the normal fuel injection may be divided into two or more times and executed. .

  On the other hand, the embodiment is an example in which the sub-injection valve temperature sensor 21 is used as the apparatus temperature acquisition means. However, the apparatus temperature acquisition means of the present invention is not limited to this, and can acquire the temperature of the fuel injection apparatus. That's fine. For example, the ECU 2 may be configured to estimate / calculate the device temperature according to various parameters such as the engine speed NE, the required torque TRQ, and the intake air temperature.

  In addition, the embodiment is an example in which the control device of the present invention is applied to an internal combustion engine for a vehicle. However, the control device of the present invention is not limited to this, and is used for an internal combustion engine for ships or other industrial equipment. It can also be applied to an internal combustion engine.

1 control device 2 ECU (fuel injection control means)
3 Internal combustion engine 3a Cylinder 3c Main combustion chamber 3d Sub combustion chamber 7 Sub fuel injection valve (fuel injection device)
21 Sub-injection valve temperature sensor (device temperature acquisition means)
Tinj Sub-injection valve temperature (equipment temperature)
α Predetermined value

Claims (2)

A control device for an internal combustion engine in which a main combustion chamber and a sub-combustion chamber communicating with each other, and a fuel injection device that generates an air-fuel mixture in the sub-combustion chamber by fuel injection into the sub-combustion chamber are provided for each cylinder. ,
The fuel injection into the sub-combustion chamber is performed in a plurality of times during one combustion cycle, and at least one of the plurality of fuel injections is performed after combustion of the air-fuel mixture in the sub-combustion chamber. And a fuel injection control means for controlling the fuel injection device. A device temperature acquisition means for acquiring a device temperature that is a temperature of the fuel injection device;
The fuel injection control means controls the fuel injection device to execute the one or more fuel injections after combustion of the air-fuel mixture in the auxiliary combustion chamber when the device temperature is equal to or higher than a predetermined value. The control device for an internal combustion engine according to claim 1.

Images