JP7014842B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

The present invention relates to a fuel supply control device for an internal combustion engine having a fuel injection pressure boosting means for increasing the fuel pressure.

In an internal combustion engine such as a diesel engine mounted on a vehicle, a diesel particulate filter (hereinafter referred to as "DPF") is used to collect and remove particulate matter (hereinafter referred to as "PM") in the exhaust gas. It is provided. The collected PM is accumulated in the DPF. Therefore, while the vehicle is running, unburned fuel is supplied to the exhaust pipe by performing post-injection that injects fuel in the latter half of the combustion stroke of the internal combustion engine, and reacts with the oxidation catalyst arranged on the upstream side of the DPF. A DPF regeneration operation is performed in which a high temperature is generated by the internal combustion engine, thereby burning and removing PM.

Generally, the DPF regeneration operation is executed when it is determined that the accumulated amount of PM estimated based on, for example, the differential pressure between the front and rear of the DPF (the differential pressure between the upstream pressure and the downstream pressure) has reached a predetermined amount. .. The degree of PM accumulation depends on the driving state of the vehicle, and the frequency of DPF regeneration operation also changes accordingly. For example, in an urban area where there is a lot of traffic congestion, the DPF regeneration operation cannot be completed efficiently due to many low rotation and low load operating conditions, PM accumulation progresses, and the frequency of the DPF regeneration operation may increase. be.

As the frequency of the DPF regeneration operation increases, the number of times the post injection is executed also increases. Since post-injection supplies the fuel injected into the combustion chamber to the exhaust pipe without burning, the amount of deposit (carbon-based compound) adhering to the fuel injection valve when the number of post-injection executions increases. There is a problem that the number of fuels increases. The adhesion of the deposit to the fuel injection valve causes a decrease or fluctuation in the fuel injection amount, which may change the mixing ratio of fuel and air, and increases the emission of PM from the internal combustion engine. Therefore, it is necessary to properly remove the deposit. If this is not done, the frequency of DPF regeneration operation will increase due to the increase in PM emission, and problems such as an increase in oil dilution will occur. In addition, it is desirable to remove such a deposit so that the driver does not notice that it is being executed in order to maintain drivability.

To solve these problems, a technique has been conventionally proposed in which a deposit adhering to a fuel injection valve is washed off at the time of fuel injection by adding a cleaning agent to the fuel. For example, in Patent Document 1, a tank for a cleaning agent is provided separately from the fuel tank for storing the fuel, and the cleaning agent is supplied according to the estimated amount of the deposit attached to the fuel injection valve. In addition to suppressing the deterioration of fuel injection performance, the adverse effects of overdose of the cleaning agent are suppressed.

Japanese Unexamined Patent Publication No. 2007-16662

In the technique described in Patent Document 1, a polyisobutene amine-based compound is used as a cleaning agent. Therefore, the fuel to which such a cleaning agent is added may adhere to the piston head and the cylinder wall in the combustion chamber, thereby promoting the generation of deposits in the combustion chamber.

The present invention has been made to solve the above-mentioned problems, and effectively removes the deposit adhering to the fuel injection valve in a congested urban environment and suppresses the generation of the deposit in the combustion chamber. It is an object of the present invention to provide a fuel supply control device for an internal combustion engine capable of providing a fuel supply control device.

In order to achieve this object, the fuel supply control device 1 for the internal combustion engine according to claim 1 of the present invention is a cylinder of an internal combustion engine (engine 3 in the present embodiment (hereinafter, the same applies hereinafter)) mounted on a vehicle. A fuel injection valve (injector 10) that directly injects fuel into 3a, a fuel supply device (high pressure pump 16) that can change the fuel pressure PF while supplying fuel to the fuel injection valve, and rotation of the internal combustion engine. The rotation number acquisition means (crank angle sensor 43) for acquiring the number NE, the load acquisition means (accelerator opening sensor 44) for acquiring the load LE of the internal combustion engine, and the operation for acquiring the operation history parameter representing the operation history of the vehicle. When the history parameter acquisition means (mileage meter 45) and the acquired operation history parameters satisfy predetermined history conditions (FIG. 3), and the acquired internal rotation speed and load of the internal combustion engine are in the predetermined operation area. (Steps 402 and 403 in FIG. 4), the fuel injection pressure boosting means (ECU 2, step 404) that executes fuel injection pressure boosting control to raise the fuel pressure PF in order to remove the deposit adhering to the fuel injection valve. The operation history parameter is the number of executions of the DPF regeneration operation that captures the deposit in the exhaust gas, and the predetermined history condition is that the DPF after the previous fuel injection pressure boost control is executed and completed. It is characterized in that the number of times of reproduction is a predetermined number or more .

According to the fuel supply control device for the internal combustion engine according to the present invention, in the fuel injection pressure boosting means, the acquired operation history parameter satisfies a predetermined history condition, and the acquired rotation speed and load of the internal combustion engine are predetermined. Since the fuel injection pressure boost control that raises the fuel pressure is executed when the fuel is in the operating area of the above, even in a busy urban environment, by injecting the high pressure fuel, the fuel is atomized and highly dispersed. However, since the fuel vapor burns in the vicinity of the fuel injection valve, the deposit adhering to the fuel injection valve can be effectively removed. Further, unlike the conventional device for adding a cleaning agent, it is possible to suppress the generation of a deposit in the combustion chamber.

Further, according to this configuration, the fuel injection pressure boosting means is used when the previous fuel injection pressure boosting control is executed and the number of times the DPF regeneration operation is executed from the time when the previous fuel injection pressure boosting control is completed becomes a predetermined number or more. , Increases the fuel pressure when the acquired internal combustion engine speed and load are in the predetermined operating range. In this way, the fuel injection pressure boost control is executed on condition that the previous fuel injection pressure boost control is executed and the number of executions of the DPF regeneration operation from the time of completion is equal to or more than a predetermined number of times. The fuel injection pressure can be increased only in a situation where it is presumed that the deposit is being adhered to the injection valve, and the deposit can be removed efficiently.

The invention according to claim 2 of the present invention is characterized in that, in the fuel supply control device for an internal combustion engine according to claim 1 , a predetermined operating region is a predetermined medium rotation / medium load region.

Generally, when the internal combustion engine is in a low rotation / low load operating state, the noise of the internal combustion engine and the vehicle itself is small, so that the driver can easily recognize the change in the combustion sound when the fuel pressure is increased, and the driver. It tends to reduce the ability. On the other hand, when the internal combustion engine is in the operating state of medium rotation and medium load, the noise of the internal combustion engine and the vehicle itself becomes relatively loud, so the noise of the fuel pump when the fuel injection pressure is increased is the driver. It is hard to notice. Further, in general, in the high rotation / high load region, the injection pressure is originally set to be high without introducing the fuel injection pressure boost control.

According to the above configuration, the fuel injection pressure boosting means raises the fuel pressure on condition that the acquired internal combustion engine rotation speed and load are in the operation range of a predetermined medium rotation / medium load. The execution of deposit removal due to increased pressure can be obscured by the driver.

It is a figure which shows the structure of the internal combustion engine schematically. It is a block diagram which shows the structure of the fuel supply control device. It is a flowchart which shows the determination process of the deposit adhesion state. It is a flowchart which shows the control process of fuel injection pressure boosting. It is a figure which shows the predetermined operating area which performs the boosting of a fuel injection pressure.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIGS. 1 and 2, the fuel supply control device 1 of the internal combustion engine according to the present embodiment includes an ECU (electronic control unit) 2 and fuel injection of the internal combustion engine (hereinafter referred to as “engine”) 3. Executes various control processes including control.

The engine 3 is, for example, a diesel engine having four cylinders 3a (only one is shown), and is mounted on a vehicle (not shown) as a power source. An intake pipe 4 and an exhaust pipe 5 are connected to each cylinder 3a, and the intake valve 6 and the exhaust valve 7 provided in the intake port and the exhaust port are driven by the intake camshaft 8 and the exhaust camshaft 9, respectively. ..

Further, a fuel injection valve (hereinafter referred to as "injector") 10 is attached to the cylinder head 3b at the center of each cylinder 3a so as to face the combustion chamber 3c. That is, the engine 3 is a direct injection type that directly injects fuel from the injector 10 into the combustion chamber 3c of the cylinder 3a. The operation of the injector 10 is controlled by the ECU 2.

Each injector 10 is connected to the fuel tank 14 via the respective fuel supply short pipe 10a, the delivery pipe 12, and the fuel supply pipe 13. A low-pressure pump 15 is provided at the most upstream position of the fuel supply pipe 13, and a high-pressure pump 16 is provided in the middle of the fuel supply pipe 13.

The low-pressure pump 15 is an electric type, and under the control of the ECU 2, the fuel in the fuel tank 14 is pressurized at a predetermined low pressure and then discharged to the high-pressure pump 16 side via the fuel supply pipe 13.

The high-pressure pump 16 is a mechanical type driven by a pump drive cam (not shown) integrally provided on the exhaust camshaft 9, and supplies fuel after pressurizing the fuel from the low-pressure pump 15 at a higher pressure. It is discharged to the delivery pipe 12 side via the pipe 13. The high-pressure fuel stored in the delivery pipe 12 is supplied to the injector 10 via the fuel supply short pipe 10a, and is injected into the combustion chamber 3c by opening the injector 10.

Further, the high pressure pump 16 includes a spill control valve 16a (see FIG. 2). The spill control valve 16a is composed of a solenoid valve, and controls the spill operation of recirculating the fuel sucked into the high pressure pump 16 to the low pressure side. More specifically, by controlling the valve closing timing of the spill control valve 16a with the ECU 2, the spill amount of the fuel is adjusted, whereby the amount of fuel discharged to the delivery pipe 12 and the fuel in the delivery pipe 12 are adjusted. Pressure (hereinafter referred to as "fuel pressure") PF is controlled.

From the above configuration, the fuel injection amount of the injector 10 is controlled by the valve opening time of the injector 10 and the fuel pressure PF controlled by the ECU 2. The delivery pipe 12 is provided with a fuel pressure sensor 41 for detecting the fuel pressure PF, and the detection signal is input to the ECU 2.

Further, the intake pipe 4 is provided with an air flow sensor 42. The air flow sensor 42 detects the intake air amount GAIR sucked into the cylinder 3a via the intake pipe 4, and outputs the detection signal to the ECU 2.

The exhaust pipe 5 is provided with a NOx catalyst 21 and a DPF (diesel particulate filter) 22 in order from the upstream side.

The NOx catalyst 21 is a NOx adsorber-reduced type and has an oxygen storage capacity. The NOx catalyst 7 stores oxygen in the exhaust gas and captures NOx when the exhaust gas in an oxidizing atmosphere (exhaust gas whose oxygen concentration is higher than the oxygen concentration of the exhaust gas corresponding to the stoichiometric air-fuel ratio (stoichi)) flows in. On the other hand, when exhaust gas in a reducing atmosphere (exhaust gas whose oxygen concentration is lower than the oxygen concentration of the exhaust gas corresponding to the stoichiometric air-fuel ratio) flows in, the stored oxygen is released and the captured NOx is reduced for desorption and purification. do.

The DPF 22 captures PM (particulate matter) in the exhaust gas that has passed through the NOx catalyst 21. Further, the DPF 22 is regenerated by performing a regeneration operation (hereinafter referred to as "DPF regeneration operation") for burning the particulate matter when the trapped amount of the particulate matter reaches a predetermined amount. The execution number DN of the DPF regeneration operation is stored by the ECU 2.

A crank angle sensor 43 is provided on the crankshaft 3d of the engine 3. The crank angle sensor 43 outputs a CRK signal, which is a pulse signal, to the ECU 2 at a predetermined crank angle (for example, 30 degrees) as the crankshaft 3d rotates. The ECU 2 calculates the engine speed (hereinafter referred to as "engine speed") NE based on the CRK signal.

Further, as shown in FIG. 2, a detection signal representing an accelerator opening degree AP, which is an operation amount of the accelerator pedal (not shown) of the vehicle, is input to the ECU 2 from the accelerator opening degree sensor 44. In the present embodiment, the accelerator opening AP is used as it is as the load (hereinafter referred to as “engine load”) LE of the engine 3. Further, a detection signal representing the total mileage TTV of the vehicle is input from the mileage meter 45 to the ECU 2, and the number of executions DN of the DPF regeneration operation is stored.

The ECU 2 is composed of a microcomputer including a CPU, RAM, ROM, and an I / O interface (all not shown). The ECU 2 responds to the detection signals of the various sensors 41 to 45 described above, and according to the control program stored in the ROM, the ECU 2 controls various engines such as fuel injection control by the injector 10 and fuel pressure control by the spill control valve 16a. To execute.

In particular, in the present embodiment, the ECU 2 determines the state of deposit attached to the injector 10 based on the operation history of the vehicle, and executes the fuel injection pressure boosting control for increasing the fuel pressure PF based on the operation state of the vehicle. It functions as an injection pressure boosting means.

FIG. 3 shows a flow of a process for determining a deposit adhesion state. In this determination process, the state of attachment of the deposit to the injector 10 is determined based on the driving history of the vehicle. This process is repeatedly executed at a predetermined cycle. First, in step 301 (shown as "S301"; the same applies hereinafter), the mileage TV of the vehicle is calculated based on the total mileage TTV detected by the mileage meter 45. The mileage TV is reset every time the fuel injection pressure boosting control described later is executed. That is, the mileage TV represents the mileage of the vehicle after the previous fuel injection pressure boost control is executed.

Next, in step 302, it is determined whether or not the calculated mileage TV is equal to or greater than the predetermined distance TREF. The predetermined distance TREF corresponds to the distance at which it is estimated that an amount of deposit that needs to be removed adheres to the injector 10 when the vehicle travels the distance. The predetermined distance TREF can be set for each country or region where the vehicle is used in consideration of traffic conditions, geographical conditions, climate, etc. In the present embodiment, it is set to, for example, 2000 km.

If the answer in step 302 is YES and the mileage TV is equal to or greater than the predetermined distance TREF, it is determined that the injector 10 has an amount of deposit that needs to be removed, and in step 305, the deposit adhesion flag F_DEPO is set to ". Set to "1" and end this process.

If the answer in step 302 is NO and the mileage TV is less than the predetermined distance TREF, the process proceeds to step 303, and the DPF regeneration execution count DN is acquired. The DPF regeneration execution count DN is reset each time the fuel injection pressure boosting control described later is executed. That is, the DPF regeneration execution count DN represents the number of DPF regeneration operations performed after the previous fuel injection pressure boosting control was executed.

Subsequently, in step 304, it is determined whether or not the acquired DPF regeneration execution count DN has reached the predetermined number of DREF. The predetermined number of DREFs corresponds to the number of times that it is estimated that an amount of deposit that needs to be removed adheres to the injector 10 when the DPF regeneration operation is executed the number of times. The predetermined number of times DN can be set for each country or region where the vehicle is used in consideration of traffic conditions, geographical conditions, climate, etc., and in this embodiment, for example, it is set to 5 times. ..

If the answer in step 304 is YES and the DPF regeneration execution count DN has reached the predetermined number of times DREF, it is determined that the injector 10 has an amount of deposit that needs to be removed, and in step 305, the deposit adhesion flag. Set F_DEPO to "1" and end this process.

If the answer in step 304 is NO and the DPF regeneration execution count DN is less than the predetermined number of DREFs, it is determined that the injector 10 does not have an amount of deposit required to be removed, and the deposit adhesion flag is determined in step 306. Set F_DEPO to "0" and end this process.

Next, the control process for increasing the fuel injection pressure shown in FIG. 4 will be described. This process is repeatedly executed at a predetermined cycle. First, in step 401, it is determined whether or not the deposit adhesion flag F_DEPO is "1". If the answer is NO and it is determined that the injector 10 does not have an amount of deposit that needs to be removed, the present process is terminated without boosting the fuel.

If the answer in step 401 is YES and the deposit adhesion flag F_DEPO is "1", it is determined in the following steps 402 to 403 whether the engine 3 is in an operating state suitable for performing fuel pressurization. Will be done.

In step 402, it is determined whether or not the engine rotation speed NE is in a predetermined medium rotation speed region, which is larger than the first predetermined rotation speed NEREF1 and smaller than the second predetermined rotation speed NEREF2 (> NEREF1). This medium rotation region is set to, for example, a rotation speed region of around 2000 rpm.

If the answer in step 402 is NO and the engine speed NE is not in the predetermined medium speed region, this process is terminated as it is. On the other hand, if the answer in step 402 is YES and the engine speed NE is in the predetermined medium speed region, the process proceeds to the next step 403.

In step 403, it is determined whether or not the engine load LE is in a predetermined medium load region, which is larger than the first predetermined load LEREF1 and smaller than the second predetermined load LEREF2 (> LEREF1).

If the answer in step 403 is NO and the engine load LE is not in the predetermined medium load region, this process is terminated as it is. On the other hand, if the answer in step 403 is YES and the engine load LE is in the predetermined medium load region, the process proceeds to the next step 404.

In step 404, fuel injection pressure boost control for increasing the fuel pressure PF of the fuel supplied to the injector 10 is executed by controlling the spill control valve 16a of the high pressure pump 16. That is, in the present embodiment, when the engine speed NE and the engine load LE are in the predetermined medium rotation / medium load region as shown in FIG. 5, the fuel injection pressure boost control is executed. Further, the fuel pressure PF at this time is set to a high pressure at which the deposit adhering to the injector 10 can be blown off and removed by injecting fuel from the injector 10 at the fuel pressure. In this embodiment, for example, 150 MPa. It is set as above.

Normally, such a high fuel pressure is used in the high rotation / high load operating region, but in the present embodiment, by using the high fuel pressure in the medium rotation / medium load region, the high rotation / high load is used. Even in an environment (traffic conditions, geographical conditions, climate, etc.) where it is rare to enter the driving area of the injector 10, the deposit attached to the injector 10 can be removed.

Further, in the present embodiment, when the engine speed NE and the engine load LE are in the low rotation / low load region, the combustion pressure PF is not increased, but this is because the fuel pressure PF is increased by the high pressure pump 16. This is in consideration of the deterioration of the combustion sound caused by the pumping. That is, in the operating state of low rotation and low load, the noise of the engine 3 itself, for example, the rotation noise and the exhaust noise are relatively small, so that the driver notices the deterioration of the combustion noise due to the increase in the fuel pressure PF. You may feel uncomfortable.

Therefore, in the present embodiment, the fuel pressure PF is not increased in such a low rotation / low load operating region, and the fuel pressure PF is increased only in the medium rotation / medium load operating region where the noise of the engine 3 is medium. This makes it difficult for the driver to notice the execution of deposit removal due to the increase in fuel pressure PF.

The completion determination of the fuel injection pressure boosting control executed in step 404 is, for example, that the execution time obtained by integrating the time during which the fuel injection pressure boosting control is executed exceeds a predetermined time, or the fuel injection pressure boosting control is performed. Can be conditioned on the fact that the integrated value of the physical quantity indicating that the medium rotation / medium load area has been used exceeds a predetermined value, and if these conditions are met, the deposit will be removed. It can be determined that the fuel injection has been completed, and the fuel injection pressure boost control can be terminated.

In the high rotation / high load region, it may be originally set to use a high injection pressure without introducing the fuel injection pressure boost control. In such a case, the integrated value of the time during which the high rotation / high load region was used or the integrated value of the physical quantity indicating that the high rotation / high load region was used is used as the fuel injection pressure in step 404 described above. It can also be set to be added to the integrated value of the execution time or the integrated value of the physical quantity used for determining the completion of the boost control.

Returning to FIG. 4, in step 405 following step 404, it is determined that the injector 10 does not have an amount of deposit required to be removed because the fuel pressure PF is increased in step 404 and the fuel is injected at the high fuel pressure PF. Then, the deposit adhesion flag F_DEPO is set to "0". Subsequently, in step 406 and step 407, the mileage TV and the DPF regeneration execution count DN are reset, respectively, and this process is terminated.

As described above, according to the present embodiment, the mileage TV is a predetermined distance TREF or more, and / or the DPF regeneration execution number DN is a predetermined number DREF or more, and the engine rotation speed NE and the engine load LE. Since the fuel pressure PF is increased when the engine is in the predetermined medium rotation / medium load region, the deposit adhering to the injector 10 can be effectively removed by injecting the high pressure fuel even in a busy urban environment. Can be removed. Further, unlike the conventional device for adding a cleaning agent, it is possible to suppress the generation of a deposit in the combustion chamber.

Further, since the fuel injection pressure boost control is executed on condition that the mileage TV is the predetermined distance TREF or more and / or the DPF regeneration execution count DN is the predetermined number of times DREF or more, the deposit is attached to the injector 10. The fuel pressure PF can be increased and the deposit removal can be performed efficiently only in the situation where it is presumed that the fuel pressure PF is in progress.

Further, since the fuel injection pressure boost control is executed on condition that the engine speed NE and the engine load LE are in the predetermined medium rotation / medium load region, the driver notices that the deposit is removed due to the increase in the fuel pressure PF. It can be difficult to do.

The present invention is not limited to the described embodiments, and can be carried out in various embodiments. For example, in the embodiment, the fuel injection pressure boost control is executed only when the engine rotation speed NE and the engine load LE are in the predetermined medium rotation / medium load region, but the pilot injection amount and the injection timing are optimized. If it is possible to suppress the deterioration of the combustion noise when the fuel injection pressure is increased by such means, the fuel injection pressure increase control may be executed in the low rotation / low load region.

Further, in the embodiment, the accelerator opening AP is used as the load of the engine 3, but the present invention is not limited to this, and other appropriate parameters representing the load of the engine 3, such as the required torque, the intake air amount, the intake pressure, and the like, are used. May be used. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

1 Fuel supply control device 2 ECU (fuel injection pressure boosting means)
3 Engine (internal combustion engine)
10 Injector (fuel injection valve)
16 High-pressure pump (fuel supply device)
43 Crank angle sensor (rotation speed acquisition means)
44 Accelerator opening sensor (load acquisition means)
45 Mileage meter (means for acquiring driving history parameters)

Claims (2)

A fuel injection valve that directly injects fuel into the cylinder of an internal combustion engine mounted on a vehicle,
A fuel supply device that can supply fuel to the fuel injection valve and change the fuel pressure,
A rotation speed acquisition means for acquiring the rotation speed of the internal combustion engine, and
A load acquisition means for acquiring the load of the internal combustion engine and
A driving history parameter acquisition means for acquiring a driving history parameter representing the driving history of the vehicle, and a driving history parameter acquisition means.
To remove the deposit adhering to the fuel injection valve when the acquired operation history parameter satisfies a predetermined history condition and the acquired internal combustion engine rotation speed and load are in a predetermined operation region. In addition, the fuel injection pressure boosting means for executing the fuel injection pressure boosting control for raising the fuel pressure, and the fuel injection pressure boosting means.
Equipped with
The operation history parameter is the number of times the DPF regeneration operation for capturing the deposit in the exhaust gas is executed, and the predetermined history condition is the regeneration of the DPF after the previous fuel injection pressure boost control is executed and completed. A fuel supply control device for an internal combustion engine , characterized in that the number of times of execution is equal to or more than a predetermined number of times . The fuel supply control device for an internal combustion engine according to claim 1, wherein the predetermined operating region is a predetermined medium rotation / medium load region.

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