JP5400700B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for a self-ignition internal combustion engine that supplies fuel by a port fuel injection valve that injects fuel into an intake port and an in-cylinder fuel injection valve that injects fuel into a cylinder.

  As a conventional fuel injection control device for an internal combustion engine, for example, one disclosed in Patent Document 1 is known. This internal combustion engine has a port fuel injection valve that injects fuel into an intake port and an in-cylinder fuel injection valve that injects fuel into a cylinder. Further, this internal combustion engine has a plurality of combustion modes, and in the fire type self-ignition combustion mode, which is one of them, by injecting fuel from the port fuel injection valve during the intake stroke of the internal combustion engine, A homogeneous air-fuel mixture is generated, and an air-fuel mixture is generated near the in-cylinder fuel injection valve by injecting a very small amount of fuel from the in-cylinder fuel injection valve during the compression stroke. Then, this air-fuel mixture is burned by spark ignition, the temperature in the cylinder is increased by flame propagation combustion centered on the fire type generated thereby, and the homogeneous air-fuel mixture is burned by self-ignition.

JP 2008-163870 A

  However, in the above-described conventional fuel injection control device, the in-cylinder injection amount injected from the in-cylinder fuel injection valve during the compression stroke is set to a very small amount. For this reason, if the in-cylinder injection amount is too small, the spark type by spark ignition is small, and the temperature in the cylinder does not rise sufficiently due to combustion of the air-fuel mixture, so there is a possibility that combustion by self-ignition cannot be performed stably. In that case, drivability deteriorates. In addition, in order to avoid such problems, when the in-cylinder injection amount is increased, the air-fuel mixture around the fire type becomes overrich, and oxygen in the cylinder becomes insufficient, resulting in a homogeneous air-fuel mixture. There is a risk of remaining unburned and increasing the amount of smoke generated.

  The present invention has been made in order to solve such problems, and appropriately sets the injection amounts respectively injected from the port fuel injection valve and the in-cylinder fuel injection valve, thereby reducing combustion fluctuations and smoke. An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can satisfactorily perform combustion by self-ignition while suppressing the generation amount.

In order to achieve this object, the invention according to claim 1 of the present application includes a port fuel injection valve 8 that injects fuel into the intake port 3f and an in-cylinder fuel injection valve 6 that injects fuel into the cylinder 3a. A fuel injection control device 1 for an internal combustion engine that burns a mixture of fuel and air supplied into the cylinder 3a by self-ignition, wherein the fuel supply amount for each cylinder 3a required for the internal combustion engine 3 is The total required fuel amount calculating means (the ECU 2 in the embodiment (hereinafter, the same applies to this section), step 1 in FIG. 4) and the in-cylinder injection amount injected from the in-cylinder fuel injection valve 6 to calculate as the total required fuel amount GFTOTAL the GFDI, 3% or more and in-cylinder injection quantity setting means for setting to less than 10% of the total required fuel quantity GFTOTAL (ECU2, step 10 to 14 in FIG. 4), the injection from the port fuel injection valve 8 Port injection amount setting means (ECU 2, step 15 in FIG. 4) for setting the port injection amount GFPI to be set to the difference between the total required fuel amount GFTOTAL and the in-cylinder injection amount GFDI, and the port fuel during the intake stroke of the internal combustion engine 3 An injection control means (ECU2) for injecting fuel of the port injection amount GFPI from the injection valve 8 and injecting fuel of the in-cylinder injection amount GFDI from the in-cylinder fuel injection valve 6 during the compression stroke, and an ignition timing CAFM of the mixture Ignition timing acquisition means (in-cylinder pressure sensor 21, crank angle sensor 22, cylinder discrimination sensor 23, ECU 2, step 3 in FIG. 4) for acquiring each cylinder 3 a, and the in-cylinder injection amount setting means is acquired. The in-cylinder injection amount GFDI injected into the cylinder 3a whose ignition timing CAFM is ahead of the predetermined timing CAREF is decreased (steps 8 and 10 in FIG. 4). Together, characterized in that the obtained ignition timing CAFM increases the in-cylinder injection amount GFDI injected into the cylinder 3a in the retard side of the predetermined time CAREF (step 9 in FIG. 4).

According to this fuel injection control device for an internal combustion engine, fuel is injected from the port fuel injection valve during the intake stroke of the internal combustion engine, thereby generating a homogeneous mixture and fuel from the in-cylinder fuel injection valve during the compression stroke. By injecting, a rich air-fuel mixture is generated in the vicinity of the cylinder fuel injection valve. And combustion by self-ignition is performed by burning this rich air-fuel mixture and combusting the homogeneous air-fuel mixture by flame propagation using this as a fire type. Further, the in-cylinder injection amount injected from the in-cylinder fuel injection valve and the port injection amount injected from the port fuel injection valve at this time are set as follows. First, the total required fuel amount for each cylinder required for the internal combustion engine is calculated, the in-cylinder injection amount is set to 3% or more and less than 10% of the total required fuel amount, and the port injection amount is set to the total required fuel amount and the cylinder. Set to the difference from the internal injection amount.

  FIG. 3 shows the relationship between the ratio of the in-cylinder injection amount with respect to the total required fuel amount (hereinafter referred to as the “in-cylinder injection rate”), the combustion fluctuation rate, and the amount of smoke generated for various self-ignition internal combustion engines. It is obtained by the experiment and the result is shown. Almost the same experimental results have been obtained with any internal combustion engine, and FIG. 3 shows one of them. The combustion fluctuation rate is used as a parameter representing the degree of combustion fluctuation, and is the fluctuation rate of the indicated mean effective pressure between different combustion cycles of the same cylinder.

  As shown in FIG. 3, the combustion fluctuation rate has a characteristic that it is substantially constant and low when the in-cylinder injection rate is 3% or more, and rapidly increases when the in-cylinder injection rate is less than 3%. This is because when the in-cylinder injection rate is lower than 3%, since the kind of fire formed by the fuel injected from the in-cylinder fuel injection valve is small, the temperature in the cylinder does not rise sufficiently, and combustion due to self-ignition does not occur. This is thought to be unstable.

  Further, the amount of smoke generated has a characteristic that it is substantially constant and small when the in-cylinder injection rate is 11% or less, and rapidly increases when the in-cylinder injection rate exceeds 11%. This is considered to be because when the in-cylinder injection rate is higher than 11%, the air-fuel mixture around the fire type becomes over-rich and easily burns away due to lack of oxygen.

Based on the above results, according to the present invention, since the in-cylinder injection amount is set to 3% or more and less than 10% of the total required fuel amount, combustion by self-ignition is suppressed while suppressing combustion fluctuation and smoke generation amount. It can be done well. Further, since the port injection amount is set to the difference between the total required fuel amount and the in-cylinder injection amount, it is possible to meet the demand for output to the internal combustion engine. Further, in an internal combustion engine having a plurality of cylinders, even when the in-cylinder injection amount, port injection amount, and each injection timing of each cylinder are the same, the ignition timing varies among cylinders due to the degree of wear of parts and individual differences. Sometimes. According to this configuration, the ignition timing is acquired for each cylinder, the in-cylinder injection amount of the cylinder whose ignition timing is on the advance side with respect to the predetermined time is reduced, and the ignition timing is on the retard side with respect to the predetermined time. Increase the in-cylinder injection amount of the cylinder. As a result, in a cylinder whose ignition timing is more advanced than the predetermined timing, the ignition timing for that cylinder is controlled to be retarded by reducing the type of fire that causes self-ignition and delaying the propagation of combustion. However, in a cylinder where the ignition timing is retarded from the predetermined timing, the ignition timing of the cylinder can be set to the advanced timing by increasing the fire type and accelerating the propagation of combustion. It is possible to control and approach the predetermined time, and therefore it is possible to suppress variations in the ignition timing between the cylinders. Further, since the ignition timing is controlled by changing the in-cylinder injection amount, for example, heat loss can be suppressed and fuel consumption can be improved as compared with the case where the ignition timing is controlled by changing the internal EGR amount. . Further, unlike the case of the internal EGR amount, the in-cylinder injection amount can be directly changed for each cylinder, so that the ignition timing for each cylinder can be controlled with high accuracy.

1 is a diagram schematically showing an internal combustion engine to which a fuel injection control device according to an embodiment is applied. It is a block diagram of a fuel injection control device. It is a figure which shows the relationship between a cylinder injection rate, a combustion fluctuation rate, and the amount of smoke generation. It is a flowchart which shows the control process of fuel injection quantity. It is a flowchart which shows the calculation process of ignition timing.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. An internal combustion engine (hereinafter referred to as “engine”) 3 to which the fuel injection control device 1 according to the present embodiment shown in FIG. 1 is applied is, for example, a 4-cylinder gasoline engine mounted on a vehicle (not shown).

  An intake pipe 4 and an exhaust pipe 5 are connected to the cylinder head 3c of the engine 3 for each cylinder 3a, and the in-cylinder fuel injection valve 6 and the spark plug 7 (see FIG. 2) face the combustion chamber 3d. (Only one is shown). The in-cylinder fuel injection valve 6 injects fuel boosted by a first fuel pump (not shown) in the vicinity of the spark plug 7 in the combustion chamber 3d during the compression stroke when performing self-ignition combustion. The air-fuel mixture is generated. The valve opening time and opening / closing timing of the in-cylinder fuel injection valve 6 are controlled by the ECU 2, thereby controlling the in-cylinder injection amount GFDI, which is the fuel injection amount of the in-cylinder fuel injection valve 6, and the fuel injection timing.

  The spark plug 7 sparks the air-fuel mixture generated by the fuel from the in-cylinder fuel injection valve 6 to generate sparks for causing self-ignition. The ignition timing of the spark plug 7 is controlled by the ECU 2.

  An in-cylinder pressure sensor 21 is integrally attached to the in-cylinder fuel injection valve 6. The in-cylinder pressure sensor 21 is configured by a ring-shaped piezoelectric element, and outputs a detection signal representing a change amount of pressure in the cylinder 3a (hereinafter referred to as “in-cylinder pressure change amount”) DPV to the ECU 2. The ECU 2 calculates a pressure (hereinafter referred to as “cylinder pressure”) PS and an indicated mean effective pressure Pmi in the cylinder 3a based on the pressure change amount DPV.

  On the other hand, a crank angle sensor 22 and a cylinder discrimination sensor 23 are provided on the crankshaft 3 e of the engine 3. The crank angle sensor 22 outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft 3e rotates.

  The CRK signal is output every predetermined crank angle (for example, 30 °). The ECU 2 calculates the engine speed (hereinafter referred to as “engine speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3b in any one of the cylinders 3a is at a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke. Output every 180 °.

  The cylinder discrimination sensor 23 outputs a CYL signal, which is a pulse signal for discriminating the cylinder 3a, to the ECU 2. The ECU 2 calculates the crank angle CA for each cylinder 3a according to the CYL signal, the CRK signal, and the TDC signal.

  In addition, a port fuel injection valve 8 is provided for each cylinder 3 a in the intake manifold of the intake pipe 4. When performing the self-ignition combustion, the port fuel injection valve 8 injects fuel boosted by a second fuel pump (not shown) toward the intake port 3f during the intake stroke. Further, the opening time and the opening / closing timing of the port fuel injection valve 8 are controlled by the ECU 2, thereby controlling the port injection amount GFPI, which is the fuel injection amount of the port fuel injection valve 8, and the fuel injection timing.

  The intake pipe 4 is provided with a throttle valve mechanism 9. The throttle valve mechanism 9 includes a throttle valve 9a and a TH actuator 9b that drives the throttle valve 9a. The opening degree of the throttle valve 9a is controlled by driving the TH actuator 9b in accordance with a control signal from the ECU 2, whereby the amount of intake air taken into the engine 3 is controlled.

  An air flow meter 24 is provided on the upstream side of the throttle valve 9 a of the intake pipe 4. The air flow meter 24 detects the mass of air flowing through the intake pipe 4 (hereinafter referred to as “air mass”) GAIR and outputs a detection signal to the ECU 2.

  The ECU 2 is composed of a microcomputer including an I / O interface, a CPU, a RAM, and a ROM (all not shown). The ECU 2 determines the operating state of the engine 3 according to the detection signals from the various sensors 21 to 24 described above, and executes various control processes of the engine 3 according to the determination result. In the present embodiment, the ECU 2 corresponds to the total required fuel amount calculation means, the in-cylinder injection amount setting means, the port injection amount setting means, the injection control means, and the ignition timing acquisition means.

  FIG. 4 shows a fuel injection amount control process of the engine 3 executed by the ECU 2. This process is executed for each cylinder 3a in synchronization with the generation of the TDC signal. In this process, first, in step 1 (illustrated as “S1”, the same applies hereinafter), a predetermined map (not shown) is searched according to the detected air mass GAIR and the engine speed NE, so that the total required fuel is obtained. The quantity GFTOTAL is calculated. The total required fuel amount GFTOTAL is a fuel supply amount for each cylinder 3 a required for the engine 3. In this map, the total required fuel amount GFTOTAL is set to a larger value as the air mass GAIR is larger and the engine speed NE is higher.

  Next, in step 2, the basic in-cylinder injection amount GFDIBASE is calculated by multiplying the calculated total required fuel amount GFTOTAL by a predetermined ratio RGFREF (for example, 7%).

  Next, in step 3, the ignition timing CAFM is calculated. FIG. 5 shows the subroutine. This process is executed every predetermined time. In this process, first, in step 21, the in-cylinder pressure PS (k) stored at the previous time is shifted to the previous in-cylinder pressure PS (k-1). In step 22, the current in-cylinder pressure PS is changed to the current in-cylinder pressure PS. Store as (k).

  Next, in step 23, it is determined whether or not the current in-cylinder pressure PS (k) is equal to or higher than a predetermined pressure PSREF. When the answer is YES, in step 24, it is determined whether or not the previous in-cylinder pressure PS (k-1) is smaller than a predetermined pressure PSREF. If the answer is YES and the in-cylinder pressure PS exceeds the predetermined pressure PSREF between the previous time and the current time, it is assumed that ignition has occurred, and in step 25, the crank angle CA at that time is calculated as the ignition timing CAFM. On the other hand, when the answer to either of the above steps 23 and 24 is NO, this process is terminated as it is.

  Returning to FIG. 4, in step 4 following step 3, the absolute value (= | CAFM−CAREF |) of the difference between the calculated ignition timing CAFM and the predetermined timing CAREF is calculated as the ignition timing deviation DCA. Then, it is determined whether or not the calculated ignition timing deviation DCA is smaller than a predetermined value DCAREF close to the value 0.

  If the answer is YES and the ignition timing CAFM substantially coincides with the predetermined timing CAREF, in step 6, the current corrected fuel amount GFDICOR is maintained at the previous corrected fuel amount GFDICOR, and the process proceeds to step 10 described later.

  On the other hand, if the answer to step 5 is NO and the ignition timing CAFM is deviated from the predetermined timing CAFMREF, it is determined in step 7 whether the ignition timing CAFM is smaller than the predetermined timing CAREF. If the answer is YES and the ignition timing CAFM is shifted to the advance side, in step 8, the current correction fuel amount GFDICOR is calculated by subtracting the predetermined amount ΔGFDI from the previous correction fuel amount GFDICOR. Proceed to 10.

  On the other hand, when the answer to step 7 is NO and the ignition timing CAFM is shifted to the retarded side, in step 9, the predetermined amount ΔGFDI is added to the previous corrected fuel amount GFDICOR to thereby determine the current corrected fuel amount GFDICOR. And proceed to Step 10.

  In Step 10 following Step 6, 8 or 9, the in-cylinder injection amount GFDI is calculated by adding the calculated corrected fuel amount GFDICOR to the basic in-cylinder injection amount GFDIBASE calculated in Step 2.

  Next, in step 11 and subsequent steps, limit processing of the in-cylinder injection amount GFDI is performed. First, in step 11, it is determined whether or not the in-cylinder injection amount GFDI is smaller than 3% of the total required fuel amount GFTOTAL. When the answer is YES, in step 12, the in-cylinder injection amount GFDI is set to 3% of the total required fuel amount GFTOTAL, and the process proceeds to step 15 described later.

  On the other hand, when the answer to step 11 is NO, it is determined in step 13 whether or not the in-cylinder injection amount GFDI is larger than 11% of the total required fuel amount GFTOTAL. If the answer is YES, in step 14, the in-cylinder injection amount GFDI is set to 11% of the total required fuel amount GFTOTAL, and the process proceeds to step 15. On the other hand, if the answer to step 13 is NO and the in-cylinder injection amount GFDI is 3 to 11% of the total required fuel amount GFTOTAL, step 14 is skipped and the process proceeds to step 15.

  In this step 15, the port injection amount GFPI is calculated by subtracting the in-cylinder injection amount GFDI from the total required fuel amount GFTOTAL, and this processing is terminated.

  As described above, according to the present embodiment, since the in-cylinder injection amount GFDI is set to 3 to 11% of the total required fuel amount GFTOTAL, combustion by self-ignition is good while suppressing combustion fluctuation and smoke generation amount. Can be done. Further, since the port injection amount GFPI is set to the difference between the total required fuel amount GFTOTAL and the in-cylinder injection amount GFDI (= GFTOTAL−GFDI), it is possible to meet the demand for output to the engine 3.

  Further, the ignition timing CAFM is calculated for each cylinder 3a, and the ignition timing CAFM decreases the in-cylinder injection amount GFDI of the cylinder 3a that is on the advance side with respect to the predetermined time CAREF and is on the retard side with respect to the predetermined time CAREF. Since the in-cylinder injection amount GFDI of the cylinder 3a is increased, the ignition timing CAFM of the cylinder 3a can be brought close to the predetermined timing CAREF, and therefore variations in the ignition timing CAFM between the cylinders 3a can be suppressed. Further, since the ignition timing CAFM is controlled by changing the in-cylinder injection amount GFDI, heat loss can be suppressed compared to, for example, controlling the ignition timing CAFM by changing the internal EGR amount, thereby improving fuel efficiency. At the same time, the ignition timing CAFM for each cylinder 3a can be accurately controlled.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the embodiment, by performing limit processing on the in-cylinder injection amount GFDI calculated as the sum of the basic in-cylinder injection amount GFDIBASE and the corrected fuel amount GFDICOR, the final in-cylinder injection amount GFDI is set within a predetermined range. (3 to 11% of the total required fuel amount GFTOTAL), but by performing a limit process on the corrected fuel amount GFDICOR, the in-cylinder injection amount GFDI is held within a predetermined range. Also good.

  Further, when the ignition timing CAFM is deviated from the predetermined timing CAREF, the in-cylinder injection amount GFDI is increased or decreased by increasing or decreasing the corrected fuel amount GFDICOR by the predetermined amount ΔGFDI. The amount GFDI may be increased or decreased by multiplying by a predetermined coefficient.

  In the embodiment, the air mass GAIR and the engine speed NE are used as parameters for calculating the total required fuel amount GFTOTAL. However, instead of or in addition to these, for example, the opening degree of the accelerator pedal and the intake air The pressure in the tube may be used.

  In the embodiment, the in-cylinder pressure PS is used as a parameter for calculating the ignition timing CAFM. Instead, for example, an increase rate of the in-cylinder pressure PS is used, and this increase rate exceeds a predetermined value. The timing may be calculated as the ignition timing CAFM.

  Further, in the embodiment, sparks for spark ignition of the spark plug 7 burn the air-fuel mixture in the vicinity of the in-cylinder fuel injection valve 6 and generate a fire type for causing self-ignition, but without using the spark plug 7, The air-fuel mixture may be combusted by compression by the piston 3b to generate a fire type.

  The embodiment is an example in which the present invention is applied to a gasoline engine mounted on a vehicle, but the present invention is not limited to this, and may be applied to various engines such as a diesel engine other than a gasoline engine. Also, the present invention can be applied to engines other than those for vehicles, for example, engines for marine propulsion devices such as outboard motors having a crankshaft arranged vertically. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Fuel injection control apparatus 2 ECU (Whole required fuel amount setting means, In-cylinder injection amount setting means, Port injection amount setting means
, Injection control means, ignition timing acquisition means)
3 Internal combustion engine
3a Cylinder 3f Intake port 6 In-cylinder fuel injection valve 8 Port fuel injection valve 21 In-cylinder pressure sensor (ignition timing acquisition means)
22 Crank angle sensor (ignition timing acquisition means)
23 cylinder discrimination sensor (ignition timing acquisition means)
GFDI In-cylinder injection amount GFPI Port injection amount GFTOTAL Total required fuel amount CAFM Mixture ignition timing CAREF Predetermined timing

Claims (1)

It has a port fuel injection valve that injects fuel into the intake port and an in-cylinder fuel injection valve that injects fuel into the cylinder, and burns a mixture of fuel and air supplied into the cylinder by self-ignition A fuel injection control device for an internal combustion engine,
A total required fuel amount setting means for setting a fuel supply amount for each cylinder required for the internal combustion engine as a total required fuel amount;
In-cylinder injection amount setting means for setting the in-cylinder injection amount injected from the in-cylinder fuel injection valve to 3% or more and less than 10% of the total required fuel amount;
Port injection amount setting means for setting a port injection amount injected from the port fuel injection valve to a difference between the total required fuel amount and the in-cylinder injection amount;
Injection control means for injecting the port injection amount of fuel from the port fuel injection valve during the intake stroke of the internal combustion engine and for injecting the in-cylinder injection amount of fuel from the in-cylinder fuel injection valve during the compression stroke; ,
Ignition timing acquisition means for acquiring the ignition timing of the air-fuel mixture for each cylinder;
With
The in-cylinder injection amount setting means reduces the in-cylinder injection amount injected into the cylinder in which the acquired ignition timing is more advanced than a predetermined timing, and the acquired ignition timing is the predetermined ignition timing. A fuel injection control device for an internal combustion engine, characterized by increasing the in-cylinder injection amount injected into the cylinder that is retarded from the timing .

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