Control device for internal combustion engine

Abstract

To provide a control device of an internal combustion engine which can properly prevent the corrosion of a fuel injection hole which is formed in a combustion chamber with simpler control without adding processing such as plating or the like to a fuel injection valve.SOLUTION: A control device 1 has: a standby time acquisition part 1b for acquiring a preset standby time as a time up until a difference between combustion-chamber inner pressure being pressure in a combustion chamber of an internal combustion engine 11 and injection-valve inner fuel pressure being the pressure of fuel in injectors 2a to 2d reaches prescribed pressure or lower after a stop of the internal combustion engine 11 which has been operated; and an in-injection hole fuel charging part 1c for valve-opening the injectors 2a to 2d at least one time after the lapse of the standby time for a preset fuel charging time at which fuel is injected in injection holes of the injectors 2a to 2d without valve-opening the injectors 2a to 2d up until the standby time has elapsed after the stop of the internal combustion engine 11 which has been operated.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for an internal combustion engine having a fuel injection valve in which an injection hole for injecting fuel is arranged in a combustion chamber of the internal combustion engine. [Background technology]

[0002] In a direct injection internal combustion engine such as a diesel engine, the tip of an injector (fuel injection valve) extends into a combustion chamber, and an injection hole for injecting fuel is disposed within the combustion chamber. Therefore, when an internal combustion engine is stopped after it has been in operation, sulfuric acid generated by condensation of sulfur and water vapor remaining in the combustion chamber may adhere to the tip of the injector and corrode the tip of the injector. If such corrosion by sulfuric acid reaches the injection hole of the injector and the hole diameter of the injection hole becomes large, the atomization of fuel is not performed properly, which is undesirable as it causes deterioration of fuel efficiency, and therefore it is desirable to prevent such corrosion.

[0003] For example, Patent Document 1 discloses a fuel injection nozzle for an internal combustion engine in which the outer peripheral surface of the tip portion of the injector and the inner peripheral surface of the nozzle hole are plated with amorphous chrome plating, which has excellent corrosion resistance against sulfuric acid corrosion.

[0004] For example, Patent Document 2 discloses a fuel injection control device for an internal combustion engine, which executes a push-back drive on the fuel injection valve of a cylinder during the compression stroke from when the internal combustion engine is requested to stop until the internal combustion engine actually stops, and executes a protection drive on the fuel injection valve multiple times after the internal combustion engine stops. In the push-back drive, the fuel injection valve is opened with a valve opening time according to the fuel pressure in the fuel injection valve and the cylinder pressure (fuel pressure>cylinder pressure), so that the fuel pushed into the fuel injection valve in the compression stroke in the injection hole is pushed back to the outlet side of the injection hole (the valve opening time is driven so that the fuel does not drip from the injection hole). In the protection drive, in a state where the fuel pressure is greater than the cylinder pressure, a small amount of fuel is supplied to the injection hole by multiple opening and closing drives (the valve opening time is shortened as the number of executions increases), so that the fuel swelled into a hemisphere due to surface tension adheres to the injection hole opening (the valve opening time is driven so that the fuel does not drip from the injection hole). In other words, after the internal combustion engine is stopped, the injection hole of the fuel injection valve is filled with fuel, thereby preventing corrosion of the injection hole. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 05-209575 [Patent Document 2] JP 2013-189873 A Summary of the Invention [Problem to be solved by the invention]

[0006] To implement the invention described in Patent Document 1, it is necessary to add a plating process for applying amorphous chrome plating to the outer peripheral surface of the tip portion of the fuel injection valve and the inner peripheral surface of the nozzle hole, as well as a quality control process, in the manufacturing process of the fuel injection valve, which is not preferable in that the manufacturing process of the fuel injection valve increases.

[0007] Moreover, it is very difficult to implement the invention described in Patent Document 2 in practice. For example, the valve opening time of the fuel injection valve during push-back drive is set variably based on three parameters, namely, the rail pressure, the intake pressure, and the engine speed, but a specific method for obtaining the valve opening time from each parameter is not disclosed. In the push-back drive, in a state where the fuel pressure is greater than the cylinder pressure, highly accurate fuel pressure and cylinder pressure are required to obtain a valve opening time that fills the injection hole with fuel and prevents fuel from dripping from the injection hole. The fuel pressure can be detected by a pressure sensor that detects the fuel pressure in the common rail, but the cylinder pressure is considered to be estimated from the intake pressure and the engine speed, but a specific method for estimating the cylinder pressure with high accuracy is not disclosed. If the valve opening time of the push-back drive is too short, the injection hole cannot be filled with fuel, and if the valve opening time of the push-back drive is too long, the fuel will drip from the injection hole, which is not preferable.

[0008] The present invention has been devised in consideration of the above points, and has an object to provide a control device for an internal combustion engine that can appropriately prevent corrosion of a fuel injection hole located in a combustion chamber with simpler control, without requiring additional processing such as plating to the fuel injection valve. [Means for solving the problem]

[0009] According to one feature of the present disclosure, a control device for an internal combustion engine is a control device for an internal combustion engine having a fuel injection valve with an injection hole for injecting fuel arranged in a combustion chamber of the internal combustion engine, and the control device has: a waiting time acquisition unit that acquires a waiting time that is set in advance as a time until a difference between a combustion chamber pressure that is the pressure in the combustion chamber of the internal combustion engine and an injection valve fuel pressure that is the pressure of the fuel in the fuel injection valve becomes equal to or less than a predetermined pressure after the internal combustion engine that was in operation is stopped; and an injection hole fuel filling unit that does not open the fuel injection valve until the waiting time has elapsed after the internal combustion engine that was in operation is stopped, and opens the fuel injection valve at least once after the waiting time has elapsed for a fuel filling time that is set in advance as a time for fuel to be filled into the injection hole of the fuel injection valve.

[0010] After the internal combustion engine is stopped, both the fuel pressure in the injection valve and the pressure in the combustion chamber gradually decrease toward atmospheric pressure. Then, the fuel injection valve is opened when the difference between the pressure in the combustion chamber and the fuel pressure in the injection valve is equal to or less than a predetermined pressure (when there is almost no difference). Since the fuel injection valve is opened when the difference between the pressure in the combustion chamber and the fuel pressure in the injection valve is equal to or less than a predetermined pressure (when there is almost no difference), the injection hole is automatically filled with fuel by capillary action. Moreover, the control device only needs to perform control such that the fuel injection valve is opened for a predetermined fuel filling time after a predetermined waiting time has elapsed. Therefore, it is not necessary to obtain the pressure in the combustion chamber and the fuel pressure in the injection valve, and it is possible to fill the injection hole without dripping fuel with very simple control after the internal combustion engine is stopped. Therefore, it is possible to appropriately prevent corrosion of the fuel injection hole arranged in the combustion chamber with simpler control without adding processing such as plating to the fuel injection valve.

[0011] According to another feature of the present invention, in a control device for an internal combustion engine, the waiting time is set based on at least one of the time required for the pressure in the combustion chamber, where the piston of the internal combustion engine stops at top dead center of compression, to decrease to close to atmospheric pressure after the internal combustion engine is stopped from operating, and the time required for the pressure of the fuel in the fuel injection valve to decrease to close to atmospheric pressure after the internal combustion engine is stopped from operating.

[0012] This allows the standby time to be set to a more appropriate value.

[0013] According to another feature of the present invention, in a control device for an internal combustion engine, the fuel filling time is set as a time required for the fuel remaining in the fuel injection valve to reach an outlet of the injection hole when the fuel injection valve is opened after the waiting time has elapsed.

[0014] This allows the fuel filling time to be set to a more appropriate value. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram showing an overall configuration of an internal combustion engine system equipped with a control device of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing the details of the configuration of an internal combustion engine. [Diagram 3] FIG. 2 is a cross-sectional view showing the configuration of the tip side of the injector. [Figure 4] 11 is a flowchart illustrating an example of a process for filling fuel into an injection hole. [Diagram 5] 1 is a cross-sectional view showing a state of an injection hole immediately before an injector is opened after a standby time has elapsed since an internal combustion engine that was in operation was stopped; FIG. [Figure 6] 5A to 5C are cross-sectional views showing the state of a nozzle hole of an injector during a fuel filling time. [Figure 7] FIG. 7 is a cross-sectional view showing the state of the injection hole when the injector is closed after the state shown in FIG. 6 (after the injector is opened for the fuel filling time). [Figure 8] FIG. 8 is an enlarged view of the periphery of the injection hole in FIG. [Figure 9] 4 is a timing chart showing a driving mode of the injector in the present embodiment. [Figure 10] FIG. 13 is a diagram showing an example of rail pressure-standby time characteristics used in a control device according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] [Overall configuration of the internal combustion engine system 10 (Figure 1)] The overall configuration of an internal combustion engine system 10 equipped with a control device 1 according to the present invention will be described with reference to Fig. 1. Fig. 1 is a diagram showing the overall configuration of an internal combustion engine system 10 equipped with a control device 1 according to the present invention. Note that an internal combustion engine 11 in Fig. 1 is, for example, a diesel engine. Below, the internal combustion engine system 10 shown in Fig. 1 will be described in order from the intake side to the exhaust side.

[0017] The intake air flow rate detection device 9a is, for example, an intake air flow rate sensor, and is provided in the intake passage 12 of the internal combustion engine 11 to output a detection signal corresponding to the flow rate of air taken in by the internal combustion engine 11 to the control device 1. The accelerator opening detection device 9b (for example, an accelerator opening sensor) outputs a detection signal corresponding to the opening of the accelerator operated by the driver (i.e., the load required by the driver) to the control device 1. The rotation detection device 9c is, for example, a rotation sensor, and outputs a detection signal corresponding to the rotation speed of the crankshaft of the internal combustion engine 11 to the control device 1.

[0018] The internal combustion engine 11 has a plurality of cylinders 4a-4d, and injectors 2a-2d (corresponding to fuel injection valves) are provided in the cylinders 4a-4d, respectively. Fuel is supplied to the injectors 2a-2d through a common rail 3 and fuel pipes 3a-3d, and the injectors 2a-2d are driven by control signals from the control device 1 to inject fuel into the cylinders 4a-4d, respectively. The common rail 3 is provided with a fuel pressure detection device 3e, and is filled with fuel adjusted to a target fuel pressure by a fuel pump 5a. A portion of the high-pressure fuel supplied from the common rail 3 to the injectors 2a-2d is returned to a fuel tank 5c through a return pipe 3f. The fuel pump 5a pumps up the fuel 5d stored in the fuel tank 5c and pressure-feeds it to the common rail 3. The fuel filter 5b removes foreign matter from the fuel 5d that the fuel pump 5a draws from the fuel tank 5c. The control device 1 controls the fuel pump 5a so that the fuel pressure detected by the fuel pressure detection device 3e approaches the target fuel pressure.

[0019] The common rail 3 is provided with a pressure reducing valve 3g as a pressure reducing means for releasing the high pressure fuel in the common rail 3. The pressure reducing valve 3g is driven to open by a control signal from the control device 1. When the pressure reducing valve 3g opens, the high pressure fuel in the common rail 3 is discharged to the low pressure side return pipe 3f and returned to the fuel tank 5c, and the rail pressure drops. The return pipe 3f is also connected to the fuel pump 5a. For example, when the internal combustion engine 11 is stopped and the fuel pump 5a stops rotating, the high pressure fuel in the common rail 3 is discharged to the return pipe 3f via the fuel pump 5a. As a result, the high pressure fuel in the common rail 3 and the injectors 2a to 2d is discharged to the fuel tank 5c, and the fuel pressure in the injection valve, which is the pressure of the fuel in the injectors 2a to 2d, drops to atmospheric pressure together with the rail pressure.

[0020] Exhaust gas from the internal combustion engine 11 is exhausted to an exhaust pipe 6 connected to the internal combustion engine 11. The exhaust gas flows downstream from the internal combustion engine 11 through the exhaust pipe 6a, the integrated oxidation catalyst 8, the exhaust pipe 6b, the selective reduction catalyst 16, and the exhaust pipe 6c in this order.

[0021] In the exhaust pipe 6, from the upstream side, there are provided a fuel addition valve 13 driven by the control device 1, an exhaust temperature detection device 9d, and an integrated oxidation catalyst 8. The fuel addition valve 13 is connected to a fuel tank 5c via a fuel supply pipe and a pump (not shown), and fuel is supplied from the fuel tank 5c.

[0022] The integrated oxidation catalyst 8 includes an oxidation catalyst 8a (DOC: Diesel Oxidation Catalyst), an exhaust temperature detector 9e, a DPF 8c (Diesel Particulate Filter) which is a particulate matter removal filter, and a differential pressure sensor 9h.

[0023] The oxidation catalyst 8a is made of a ceramic cellular cylinder formed into a cylindrical shape or the like, with many through holes formed in the axial direction, and the inner surface of each through hole is coated with a precious metal catalyst such as platinum (Pt). The oxidation catalyst 8a oxidizes and removes carbon monoxide (CO), hydrocarbons (HC), etc. contained in the exhaust gas by passing the exhaust gas through the many through holes at a predetermined temperature.

[0024] The particulate matter removal filter (hereinafter referred to as "DPF") 8c is formed into a cylindrical shape or the like from a porous member made of a ceramic material or the like. The porous DPF 8c captures particulate matter (PM) by passing the inflowing exhaust gas through it, and removes the PM from the exhaust gas. As particulate matter (PM) accumulates in the DPF 8c, it becomes more difficult for the exhaust gas to pass through the DPF 8c, and the collection function decreases.

[0025] The exhaust gas temperature detection device 9d is, for example, an exhaust gas temperature sensor, and outputs a detection signal corresponding to the temperature of the exhaust gas upstream of the oxidation catalyst 8a to the control device 1. The exhaust gas temperature detection device 9e is, for example, an exhaust gas temperature sensor, and outputs a detection signal corresponding to the temperature of the exhaust gas downstream of the oxidation catalyst 8a (and upstream of the DPF 8c) to the control device 1.

[0026] The differential pressure sensor 9h outputs a detection signal corresponding to the differential pressure (pressure difference) between the exhaust pressure (exhaust pipe pressure) downstream of the oxidation catalyst 8a and upstream of the DPF 8c, and the exhaust pipe pressure downstream of the DPF 8c, to the control device 1. Here, the differential pressure (pressure difference) changes when a large amount of particulate matter (PM) accumulates in the DPF 8c. The control device 1 can estimate, based on the detection signal output by the differential pressure sensor 9h, whether a large amount of particulate matter (PM) has accumulated in the DPF 8c, making it difficult for exhaust gas to pass through the DPF 8c, and whether it is necessary to remove the particulate matter (PM) accumulated in the DPF 8c and restore (regenerate) the DPF 8c.

[0027] When the control device 1 estimates that the DPF 8c needs to be restored (regenerated), it causes the fuel addition valve 13 to inject fuel into the exhaust gas in order to remove particulate matter (PM) accumulated in the DPF 8c. The fuel injected into the exhaust gas becomes a mixture with the exhaust gas and is guided to the inlet end surface 8b of the oxidation catalyst 8a. The mixture of the exhaust gas and the fuel flows into the integrated oxidation catalyst 8 and is guided to the inlet end surface 8b of the oxidation catalyst 8a of the integrated oxidation catalyst 8.

[0028] The fuel is oxidized by the oxygen remaining in the exhaust gas in the oxidation catalyst 8a. The heat generated by the oxidation raises the temperature of the exhaust gas, and the exhaust gas becomes hot. The hot exhaust gas raises the bed temperature of the DPF 8c. When the bed temperature reaches a predetermined temperature or higher (for example, 590°C), the particulate matter (PM) accumulated in the DPF 8c is burned and incinerated, and the collection function of the DPF 8c is restored (regenerated).

[0029] The exhaust pipe 6b is connected to the downstream side of the DPF 8c, and is provided with an exhaust temperature detection device 9f, a NOx sensor 9i, and a urea water addition valve .

[0030] The exhaust temperature detection device 9f is, for example, an exhaust temperature sensor, and outputs a detection signal corresponding to the temperature of the exhaust gas downstream of the DPF 8c to the control device 1. The NOx sensor 9i outputs a detection signal corresponding to the concentration of NOx in the exhaust gas upstream of the catalyst 17 to the control device 1.

[0031] The urea water addition valve 14 is provided in the exhaust pipe 6b upstream of the dispersion plate 15. The urea water addition valve 14 is driven by the control device 1 to inject urea water in the exhaust gas toward the dispersion plate 15 provided upstream of the selective reduction catalyst 16. The urea water addition valve 14 is connected to a urea water tank via a urea water supply pipe and a urea water pump (not shown), and urea water is supplied from the urea water tank to the urea water addition valve 14.

[0032] The dispersion plate 15 atomizes the urea water injected from the urea water addition valve 14, disperses the atomized urea water in the exhaust gas, and mixes the atomized urea water with the exhaust gas.

[0033] The selective reduction catalyst 16 is formed in a cylindrical shape and is provided therein with a cylindrical catalyst 17. The selective reduction catalyst 16 is provided between the exhaust pipe 6b and the exhaust pipe 6c, and a mixture of the urea water injected into the exhaust gas and the exhaust gas flows into the selective reduction catalyst 16.

[0034] The particulate urea water reaches the inlet end surface 18 of the catalyst 17 from the dispersion plate 15, and is reformed into ammonia by the heat of the exhaust gas. The catalyst 17 is a catalyst that purifies the exhaust gas by reacting nitrogen oxides (NOx) in the exhaust gas with ammonia (by reducing the NOx). The exhaust gas purified by the catalyst 17 flows into the exhaust pipe 6c through the selective reduction catalyst 16.

[0035] The exhaust pipe 6c is connected to the downstream side of the selective reduction catalyst 16, and an exhaust temperature detection device 9g and a NOx sensor 9j are provided in the exhaust pipe 6c. The exhaust temperature detection device 9g is, for example, an exhaust temperature sensor, and outputs a detection signal corresponding to the temperature of the exhaust gas downstream of the selective reduction catalyst 16 to the control device 1. The NOx sensor 9j outputs a detection signal corresponding to the concentration of NOx in the exhaust gas downstream of the selective reduction catalyst 16 to the control device 1.

[0036] The control device 1 includes a CPU 1a, a RAM 1d, a storage device 1e, a timer 1f, and the like. The control device 1 receives a control signal from an ignition switch 19, and starts or stops the internal combustion engine 11 and controls various electrical systems. Detection signals from the various detection devices described above are input to the control device 1 (CPU 1a). The control device 1 (CPU 1a) outputs control signals to the various actuators described above. The inputs and outputs of the control device 1 are not limited to the detection devices and actuators described above. The temperature and pressure of each part may be calculated by estimation without mounting a sensor. The control device 1 detects the operating state of the internal combustion engine 11 based on detection signals from various detection devices including the detection devices described above, and controls various actuators including the actuators described above. The storage device 1e is, for example, a storage device such as a Flash-ROM, and stores programs and data for controlling the internal combustion engine, performing self-diagnosis, and the like. The control device 1 (CPU 1a) also includes a standby time acquisition unit 1b, an in-hole fuel filling unit 1c, and the like, but these will be described in detail later.

[0037] [Injector, cylinder and surrounding structures (Figs. 2 and 3)] Next, the injectors 2a-2d, cylinders 4a-4d, and their peripheral structures in the internal combustion engine 11 will be described in detail with reference to Figures 2 and 3. The injector 2a and cylinder 4a will be described below as examples. Figure 2 is a cross-sectional view showing the details of the configuration of the internal combustion engine 11. Also, Figure 3 is a cross-sectional view showing the configuration of the tip side of the injector 2a.

[0038] As shown in FIG. 2, in the internal combustion engine 11, a cylinder 4a is formed in a cylinder block 4. A piston 4j is accommodated in the cylinder 4a. Three grooves are formed on the outer peripheral surface of the piston 4j over the entire circumference, and a C-ring 4k (piston ring) is attached to each groove. The piston 4j is connected to a connecting rod 4n. The connecting rod 4n is connected to a crankshaft (not shown), which is an output shaft of the internal combustion engine 11. A cylinder head 4e is connected to the upper end of the cylinder block 4. The cylinder head 4e is formed with an intake port 4f and an exhaust port 4i, and is provided with an injector 2a, an intake valve 4g, and an exhaust valve 4h. The intake port 4f is connected to an intake passage 12, and the exhaust port 4i is connected to an exhaust pipe 6 (see FIG. 1). High-pressure fuel is supplied to the injector 2a from a common rail 3 (see FIG. 1).

[0039] The intake port 4f and the exhaust port 4i are connected to the cylinder 4a. The intake valve 4g is provided to open and close the communication between the intake port 4f and the cylinder 4a. The exhaust valve 4h is provided to open and close the communication between the exhaust port 4i and the cylinder 4a. A combustion chamber 4m is formed by the cylinder 4a, the cylinder head 4e, the intake valve 4g, the exhaust valve 4h, and the piston 4j. The tip of the injector 2a (the tip including the injection hole) is disposed in the combustion chamber 4m in the cylinder 4a.

[0040] As shown in FIG. 3, the injector 2a has a metallic housing 7b having a substantially cylindrical shape and a needle valve 7a provided inside the housing 7b. The inner circumference of the housing 7b on the tip side is formed as a valve seat 7c on which the tip of the needle valve 7a is seated. A hollow hemispherical suction cup 7f is formed on the inner circumference further on the tip side of the housing 7b. At the tip of the housing 7b, an injection hole 7d, which is a passage communicating with the internal space of the suction cup 7f, is formed. The high-pressure fuel 7g in the injector 2a is subjected to pressure from the common rail 3. When the needle valve 7a moves away from the valve seat 7c, the high-pressure fuel 7g is injected from the injection hole 7d via the suction cup 7f. The injector 2a injects the high-pressure fuel 7g before and after the piston 4j reaches the top dead center of compression. The diameter of the injection hole 7d is very thin, about the diameter of a hair.

[0041] The injected high-pressure fuel 7g spontaneously ignites during the compression stroke because the air in the combustion chamber 4m is at a high temperature. The combustion gas generated in the combustion chamber 4m functions as a working fluid and pushes the piston 4j down to the bottom dead center (see piston 4q shown by the dotted line in Figure 2). The C-ring 4k (piston ring), together with the lubricating oil (oil film) attached to the inner wall of the cylinder 4a, seals the combustion gas generated in the combustion chamber 4m so that it does not leak to the crankshaft side.

[0042] [Processing procedure of the control device 1 in the first embodiment (FIGS. 4 to 8)] Next, the flow of processing by the control device 1 will be described using the flow chart shown in FIG. 4. The movement of fuel inside the injector 2a will also be described using FIG. 5 to FIG. 8. FIG. 5 is a cross-sectional view showing the state of the injection hole after a standby time has elapsed since the internal combustion engine was stopped while in operation and immediately before the injector is opened. FIG. 6 is a cross-sectional view showing the state of the injection hole of the injector during the fuel filling time. FIG. 7 is a cross-sectional view showing the state of the injection hole when the injector is closed after the state shown in FIG. 6 (after the injector is opened during the fuel filling time). FIG. 8 is an enlarged view of the periphery of the injection hole in FIG. 7.

[0043] The control device 1 (CPU 1a) repeatedly starts the [processing for filling fuel into injection hole] shown in FIG. 4 at predetermined time intervals (several [ms] to several tens of [ms]), for example, and advances the process to step S110.

[0044] In step S110, the control device 1 determines whether or not the internal combustion engine 11 is operating based on the rotation state of the crankshaft of the internal combustion engine 11 acquired from the rotation detection device 9c. If the control device 1 determines that the internal combustion engine 11 is operating (Yes), the process proceeds to step S115, and if the control device 1 determines that the internal combustion engine 11 is not operating (No), the process proceeds to step S120.

[0045] When the process proceeds to step S115, the control device 1 sets an operation history flag to ON, and proceeds to step S120. The operation history flag is a flag for determining whether the internal combustion engine 11 was "operating" when determining whether the internal combustion engine 11 was stopped while operating, and is set to OFF when the control device 1 is started.

[0046] When the process proceeds to step S120, the control device 1 determines whether or not the internal combustion engine 11 is stopped based on the rotation state of the crankshaft of the internal combustion engine 11 acquired from the rotation detection device 9c. If the internal combustion engine 11 is stopped (Yes), the control device 1 proceeds to step S125, and if the internal combustion engine 11 is not stopped (No), the control device 1 ends the process shown in FIG.

[0047] When the process proceeds to step S125, the control device 1 determines whether the driving history flag is ON. If the driving history flag is ON (Yes), the control device 1 proceeds to step S130, and if the driving history flag is not ON (No), the control device 1 ends the process shown in FIG.

[0048] When the process proceeds to step S130, the control device 1 determines whether the standby timer is running. If the standby timer is running (Yes), the control device 1 proceeds to step S140, and if the standby timer is not running (No), the control device 1 proceeds to step S135.

[0049] If the process proceeds to step S135, the control device 1 initializes (resets to zero) and starts the wait timer, and the process proceeds to step S140.

[0050] In step S140, the control device 1 acquires a preset waiting time from the storage device 1e, and proceeds to step S145.

[0051] When the process proceeds to step S145, the control device 1 judges whether the time measured by the standby timer is equal to or longer than the standby time. If the time measured by the standby timer is equal to or longer than the standby time (Yes), the control device 1 proceeds to step S150, and if not (No), the process shown in FIG. 4 ends.

[0052] The standby time is set based on at least one of the time required for the pressure in the combustion chamber where the piston of the internal combustion engine 11 stops at the compression top dead center to drop to near atmospheric pressure after the internal combustion engine 11 is stopped while in operation, and the time required for the fuel pressure in the injector (fuel injection valve) 2a-2d, which is the pressure of the fuel, to drop to near atmospheric pressure after the internal combustion engine 11 is stopped while in operation. Then, as shown in Fig. 5, after the standby time has elapsed, the pressure of the fuel 7h in the injector 2a has dropped to atmospheric pressure. In addition, the pressure of the air in the suction port 7f and the injection hole 7d communicating with the cylinders 4a-4d has also dropped to atmospheric pressure.

[0053] When the process proceeds to step S150, the control device 1 determines whether the filling timer is running. If the filling timer is running (Yes), the control device 1 proceeds to step S160, and if the filling timer is not running (No), the control device 1 proceeds to step S155.

[0054] If the process proceeds to step S155, the control device 1 initializes (resets to zero) and starts the refill timer, and the process proceeds to step S160.

[0055] In step S160, the control device 1 acquires a preset fuel filling time from the storage device 1e, and advances the process to step S165.

[0056] When the process proceeds to step S165, the control device 1 determines whether the time measured by the filling timer is equal to or less than the fuel filling time. If the time measured by the filling timer is equal to or less than the fuel filling time (Yes), the control device 1 proceeds to step S170A, and if the time measured by the filling timer is not equal to or less than the fuel filling time (No), the control device 1 proceeds to step S170B.

[0057] When the process proceeds to step S170A, the control device 1 opens the injectors 2a to 2d and ends the process shown in Fig. 4. Since the fuel filling time is a long time, for example, about 1 [sec], there is no problem if the valves are open until the next [process for filling fuel into the injection hole] is started. As shown in Fig. 6, during the fuel filling time, the gap between the needle valve 7a and the valve seat 7c, the sack 7f, and further the injection hole 7d are filled with fuel 7h due to capillary action.

[0058] When the process proceeds to step S170B, the control device 1 closes the injectors 2a to 2d and ends the process shown in FIG. 4. Specifically, as shown in FIGS. 7 and 8, the needle valve 7a is seated on the valve seat 7c. When the needle valve 7a is driven from the open state to the closed state, the fuel 7h is further pushed out from the outlet of the injection hole 7d by the needle valve 7a. As a result, the periphery of the outlet of the injection hole 7d is covered with the fuel 7h that is bulged into a hemispherical shape due to surface tension, as shown by the reference symbol 7z in FIG. 8.

[0059] In this way, after the internal combustion engine 11, which was in operation, is stopped, the control unit 1 waits until the standby time has elapsed. After that, the injectors 2a to 2d are opened in a state where there is almost no difference between the fuel pressure in the injection valves of the injectors 2a to 2d and the pressure in the combustion chamber of the internal combustion engine 11 (a state where the difference is equal to or less than a predetermined pressure). Since the diameter of the injection hole 7d is about the diameter of a hair, the inside of the injection hole 7d is automatically filled with fuel by capillary action. Moreover, the control unit 1 simply controls the injectors 2a to 2d to open at a predetermined timing for a predetermined time, and does not perform any calculations during this process (there is no need to calculate the pressure in the combustion chamber or the fuel pressure in the injection valve).

[0060] Therefore, fuel can be left in the injection hole 7d by performing simple control on the injectors 2a to 2d. Since the injection hole 7d is filled with the fuel 7h, sulfuric acid generated after the internal combustion engine 11 is stopped does not adhere to the inner wall 7e. Similarly, as shown by the reference symbol 7z in FIG. 8, the periphery of the outlet of the injection hole 7d is covered with the fuel 7h that swells into a hemispherical shape due to surface tension, and sulfuric acid does not adhere to the periphery. Therefore, the injection holes 7d of the injectors 2a to 2d can be protected from corrosion by sulfuric acid.

[0061] The control device 1 (CPU 1a) executing the processing of steps S110 to S140 corresponds to a waiting time acquisition unit 1b (see Figure 1) that acquires a waiting time that is preset as the time until the difference between the fuel pressure in the injectors 2a to 2d, which is the pressure of the fuel in the injectors 2a to 2d, and the cylinder pressure, which is the pressure in the cylinders 4a to 4d (combustion chambers) of the internal combustion engine 11, becomes equal to or less than a predetermined pressure after the internal combustion engine 11, which was in operation, is stopped.

[0062] Furthermore, the control device 1 (CPU 1a) executing the processes of steps S145 to S170A and S170B corresponds to an in-hole fuel filling unit 1c (see FIG. 1) that does not open the injectors 2a to 2d until a standby time has elapsed after the internal combustion engine that was in operation is stopped, and opens the injectors 2a to 2d at least once for a predetermined fuel filling time as a time for filling fuel into the injection holes of the injectors 2a to 2d after the standby time has elapsed. In the example of FIG. 4, the injectors are opened only once during the fuel filling time, but the injectors may be opened multiple times.

[0063] ●[Waiting time and fuel filling time (Figure 9)] Next, the standby time and fuel filling time used in the processing of the control device 1 will be described with reference to the timing chart shown in Fig. 9. As shown in "Injector (fuel injection valve)" in Fig. 9, the control device 1 does not open the injectors 2a to 2d until a standby time tx has elapsed, for example, starting from time t1 when the internal combustion engine 11 completely stops, and opens the injectors 2a to 2d, for example, once, at time t4 after the standby time tx has elapsed.

[0064] The "internal combustion engine speed" in Figure 9 indicates the speed of the internal combustion engine 11 over time, and shows that a stop request (such as turning the ignition switch ON->OFF or starting idling stop) is executed at time t0, and that the internal combustion engine 11 comes to a complete stop at time t1.

[0065] "Pressure" in FIG. 9 indicates the pressure within the combustion chamber of the internal combustion engine 11 (solid line) and the fuel pressure within the injector (fuel injection valve) (dotted line), which is the pressure of the fuel within the injector (fuel injection valve), over time.

[0066] First, the "combustion chamber pressure" shown in "Pressure" in Fig. 9 will be described. Pressure P1 indicates the combustion chamber pressure at the top dead center of compression when fuel is not injected (when combustion is not occurring), and while the internal combustion engine 11 is in operation before time t0, fuel is injected from the injectors 2a to 2d and combustion occurs, so the combustion chamber pressure is equal to or higher than pressure P1 during the combustion stroke, but is lower than pressure P1 during the intake stroke, etc. Note that pressure P1 varies depending on the atmospheric pressure, the intake amount, the rotation speed, etc.

[0067] Furthermore, during the period from time t0 when the stop request is executed to time t1 when the internal combustion engine 11 completely stops, the pressure inside the combustion chamber reaches pressure P1 during the compression stroke, but becomes lower than pressure P1 during the intake stroke, etc. The pressure inside the combustion chamber shown in Fig. 9 shows an example of a cylinder whose piston stops at top dead center of compression at time t1 when the internal combustion engine 11 completely stops. After time t1 when the internal combustion engine 11 completely stops, the pressure inside the combustion chamber gradually decreases toward atmospheric pressure, and reaches atmospheric pressure at time t3.

[0068] The reason why the pressure inside the combustion chamber approaches atmospheric pressure is that, as shown in FIG. 2, the outer peripheral surface of the piston 4j and the bore wall surface 4p are not completely sealed by the C-ring 4k (piston ring), and the combustion chamber 4m is in communication with the outside air through the gap between the C-ring 4k and the bore wall surface 4p. The C-ring 4k (piston ring) is a so-called "C-ring", and has a "C"-shaped notch (discontinuous portion) rather than a continuous annular shape. Therefore, even if the piston stops at the top dead center of the compression stroke, the combustion chamber is not completely sealed, and the pressure inside the combustion chamber leaks little by little from the notch (discontinuous portion) of the C-ring 4k to the crankcase side, so that the pressure inside the combustion chamber gradually drops to atmospheric pressure. Therefore, after the internal combustion engine 11 stops, the pressure inside the combustion chamber eventually drops to atmospheric pressure. The piston 4j can stop at a position other than the top dead center of the compression stroke, but no matter which position it stops at, the time t3 is the latest time. In other words, time t3 is the time when the pressures in the combustion chambers of all the cylinders 4a to 4d will reach atmospheric pressure.

[0069] Next, the "fuel pressure in the injector" shown in "Pressure" in Fig. 9 will be described. Pressure P2 is the fuel pressure in the injector while the internal combustion engine 11 is operating, and is a target fuel pressure that is set to a value higher than pressure P1, which is the pressure in the combustion chamber at the top dead center of compression. Note that pressure P2, which is the target fuel pressure, is variable depending on the operating state. Before time t0 when the stop request is executed, the internal combustion engine 11 is operating, so the fuel pressure in the injector is pressure P2.

[0070] During the period from time t0 when the stop request is executed to time t1 when the internal combustion engine 11 completely stops, the fuel pressure in the injection valve decreases toward atmospheric pressure. This is because the request to stop the internal combustion engine 11 causes the fuel pump 5a to stop rotating, and the high-pressure fuel in the common rail 3 is quickly discharged to the return pipe 3f via the fuel pump 5a. Therefore, the fuel pressure in the injection valve in the injector 2a to 2d also decreases to atmospheric pressure after the internal combustion engine 11, which was in operation, stops. For example, as shown in "Fuel Pressure in Injection Valve" in FIG. 9, the pressure P2 at time t0 when the control device 1 receives the stop request for the internal combustion engine 11 reaches atmospheric pressure at time t2.

[0071] In general, the time t3 at which the pressures in the combustion chambers of all the cylinders 4a to 4d reach atmospheric pressure is later than the time t2 at which the fuel pressure in the injector reaches atmospheric pressure.

[0072] As shown in FIG. 9, the waiting time tx includes the time ta from the time t1 when the internal combustion engine 11, which had been operating, completely stops to the time t3 when the difference between the pressure inside the combustion chamber of the internal combustion engine 11, which is steadily decreasing toward atmospheric pressure, and the fuel pressure inside the injector, which is also steadily decreasing toward atmospheric pressure, becomes 0 (almost zero).

[0073] 9, a waiting time tw is set from time t3 until the valve opening for the fuel filling time ty is started, and the waiting time tx=time ta+waiting time tw is set as an example. Note that the waiting time tw may be set to zero, and the waiting time tx may be set to the time ta.

[0074] Also, if the time t21 is the time when the difference between the fuel pressure in the injection valve and the pressure in the combustion chamber becomes equal to or less than the "predetermined pressure Pa," the time tc from the time t1 when the internal combustion engine 11 is completely stopped to the time t21 may be the standby time. In this case, the standby time tx = time tc. The "predetermined pressure Pa" is a relatively small pressure, and is set to an appropriate value through experiments, simulations, etc. using an actual vehicle.

[0075] The time t3 when the pressure in the combustion chamber drops to atmospheric pressure is generally later than the time t2 when the fuel pressure in the injection valve drops to atmospheric pressure. Therefore, the time ta depends on the time when the pressure in the combustion chamber drops to atmospheric pressure. Therefore, the waiting time tx may include the time when the pressure in the combustion chamber 4m (see FIG. 2) where the piston 4j of the internal combustion engine 11 stops at the compression top dead center drops to atmospheric pressure. Note that, for example, when the time t1 when the internal combustion engine 11 completely stops is used as the base point, the waiting time tx may be set to time tb.

[0076] It should be noted that which of time t2 and t3 comes later varies depending on the individual internal combustion engine. For example, time t2, at which the fuel pressure in the injection valve reaches atmospheric pressure, may be later than time t3. In this case, the waiting time tx may include the time at which the fuel pressure in the injection valve in each of the injectors 2a to 2d drops to atmospheric pressure. That is, the waiting time tx is set based on at least one of the time at which the pressure in the combustion chamber where the piston of the internal combustion engine 11 stops at the compression top dead center drops to near atmospheric pressure after the internal combustion engine 11 that was in operation is stopped, and the time at which the fuel pressure in the injector (fuel injection valve) drops to near atmospheric pressure after the internal combustion engine 11 that was in operation is stopped.

[0077] After the waiting time tx has elapsed, the control device 1 opens the injectors 2a to 2d for a fuel filling time ty from time t4, as shown in "Injector (fuel injection valve)" in Fig. 9. The fuel filling time ty is the time (for example, about 1 second) until the gap between the needle valve 7a and the valve seat 7c, the sucking hole 7f, and the injection hole 7d are filled with fuel 7h due to capillary action (see Fig. 6).

[0078] The fuel filling time ty is set as the time required for the fuel remaining in the injectors 2a-2d (in the fuel injection valves) to reach the outlet of the injection hole by capillary action when the injectors 2a-2d are opened at time t4 after the waiting time tx has elapsed. Since the capillary action is utilized in a state where there is almost no pressure difference, the fuel will not drip from the injection hole even if the injectors are opened for a time longer than necessary.

[0079] The control device for an internal combustion engine of the present invention is not limited to the appearance, configuration, structure, etc. described in this embodiment, and various changes, additions, and deletions are possible within the scope of the present invention. Furthermore, the numerical values ​​used in the description of this embodiment are merely examples, and the present invention is not limited to these numerical values. For example, in this embodiment, the injectors 2a to 2d are described as opening only once after the waiting time has elapsed, but as long as the injection hole 7d is filled with fuel 7h by capillary action (see Figures 7 and 8), they may be opened two or more times.

[0080] 9, the standby time tx has been described as including the time ta from the time t1 when the internal combustion engine 11 completely stops to the time t3 when the difference between the pressure in the combustion chamber of the internal combustion engine 11 and the fuel pressure in the injection valve of the injector 2a-2d becomes 0. However, the time ta included in the standby time tx may be based on the time t0 when the stop request for the internal combustion engine 11 is executed, instead of the time t1.

[0081] 7 to 9, the fuel injection hole 7d is filled with fuel 7h by capillary action during the fuel filling time ty, and the fuel 7h is further pushed out from the outlet of the injection hole 7d by closing the injectors 2a to 2d, and the fuel 7h is expanded into a hemispherical shape as indicated by the reference symbol 7z. However, the fuel filling time may be set shorter than the time ty, and the injectors 2a to 2d may be closed before the fuel 7h is filled up to the outlet of the injection hole 7d, so that the fuel 7h is pushed out by the needle valve 7a, so that the injection hole 7d is filled with fuel 7h all the way to the outlet.

[0082] In addition, in the present embodiment, the standby time is described as being determined in advance, but the standby time may be variable and determined based on the operating state of the internal combustion engine 11 immediately before the engine is stopped. For example, the control device 1 stores rail pressure-standby time characteristics as shown in FIG. 10 as a map for each atmospheric pressure. For example, in the map, a curve Px can be referenced as a characteristic of flat land where the atmospheric pressure is close to the standard atmospheric pressure, and a curve Px can be referenced as a characteristic of highland where the atmospheric pressure is low. For example, when the control device 1 receives a request to stop the internal combustion engine 11, the control device 1 acquires the atmospheric pressure from an atmospheric pressure sensor separately provided in the internal combustion engine system 10 and the rail pressure from the fuel pressure detection device 3e. The control device 1 may select a curve Px based on the acquired atmospheric pressure, and then calculate the standby time tz based on the acquired rail pressure P3. [Explanation of symbols]

[0083] 1 Control device 1a CPU 1b Wait time acquisition part 1c Fuel filling part in nozzle hole 1d RAM 1e storage device 1f Timer 2a~2d Injectors 3 Common Rail 3a~3d Fuel piping 3e Fuel pressure detection device 3f Return piping 4 Cylinder block 4a~4d Cylinders 4e Cylinder head 4f Intake port 4g Intake valve 4h Exhaust valve 4i Exhaust port 4j piston 4k piston ring 4m combustion chamber 5a Fuel pump 5b Fuel filter 5c Fuel Tank 5d fuel 6(6a~6c) Exhaust pipe 7a Needle valve 7b Housing 7c valve seat 7d injection hole 7e interior wall 7f Sack 8 Integrated oxidation catalyst 8a Oxidation catalyst 8b Inlet side end face 8c DPF 9a Intake air flow rate detection device 9b Accelerator opening detection device 9c Rotation detection device 9d~9g Exhaust temperature detector 9h Differential Pressure Sensor 10 Internal Combustion Engine System 11 Internal combustion engine 12 Intake passage 13 Fuel addition valve 14 Urea solution addition valve 15 Dispersion plate 16 Selective reduction catalyst 17 Catalyst 18 Inlet side end face 19 Ignition switch

Claims

1. A control device for an internal combustion engine having a fuel injection valve in which an injection hole for injecting fuel is disposed in a combustion chamber of the internal combustion engine, The control device includes: a standby time acquisition unit that acquires a standby time that is set in advance as a time until a difference between a combustion chamber pressure that is a pressure in the combustion chamber of the internal combustion engine and an injector fuel pressure that is a fuel pressure in the fuel injector becomes equal to or less than a predetermined pressure after the internal combustion engine that has been in operation is stopped; an intra-hole fuel filling unit that does not open the fuel injection valve until a standby time has elapsed after the internal combustion engine that has been in operation is stopped, and that opens the fuel injection valve at least once after the standby time has elapsed, for a predetermined fuel filling time that is a time for filling the injection hole of the fuel injection valve with fuel; having A control device for an internal combustion engine.

2. 2. The control device for an internal combustion engine according to claim 1, The waiting time is a time period during which the pressure in the combustion chamber when the piston of the internal combustion engine stops at the compression top dead center after the internal combustion engine that was in operation is stopped, is reduced to near atmospheric pressure; a time period during which the pressure of the fuel in the fuel injection valve decreases to near atmospheric pressure after the internal combustion engine is stopped from operating; is based on at least one of the following: A control device for an internal combustion engine.

3. The control device for an internal combustion engine according to claim 1 or 2, The fuel filling time is the waiting time is set as a time required for the fuel remaining in the fuel injection valve to reach an outlet of the injection hole when the fuel injection valve is opened after the waiting time has elapsed. A control device for an internal combustion engine.

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