JP2016098712A - Internal combustion engine intra-exhaust pipe direct injection system and internal combustion engine intra-exhaust pipe direct injection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine intra-exhaust pipe direct injection system and internal combustion engine intra-exhaust pipe direct injection method, which enable prevention of caulking in the injection hole of a direct injection nozzle that directly injects fuel into an exhaust gas of an internal combustion engine, and in the vicinity of the hole.SOLUTION: A direct injection system performs: opening a first open-close valve 31 disposed in a fuel supply passage 25 to a high-pressure liquid fuel injection valve 24 and injecting fuel Fs into an exhaust pipe 13 by closing a second open-close valve 33 disposed in an air supply pipe 32 connected between the first open-close valve 31 and the high-pressure liquid fuel injection valve 24; then closing the first open-close valve 31 and opening the second open-close valve 33 to supply air Ap from the air supply pipe 32 to a fuel supply valve 254 downstream of the first open-close valve 31 and discharge the fuel Fs inside the high-pressure liquid fuel injection valve 24; and then while keeping the first open-close valve 31 close, closing the second open-close valve 33 to standby until the next fuel injection.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a direct injection system for an internal combustion engine of an internal combustion engine that can prevent coking of a direct injection nozzle that directly injects fuel into the exhaust gas of the internal combustion engine, and a direct injection method for an internal combustion engine. .

  In general, an exhaust gas purification apparatus that purifies components to be purified such as hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), and particulate matter (PM) contained in exhaust gas of an internal combustion engine. In order to perform the purification process, unburnt fuel (light oil) is directly injected into the exhaust pipe, and the injected fuel is joined by an oxidation catalyst or the like to increase the temperature of the exhaust gas. PM regeneration of the particulate matter collection device and NOx regeneration of the NOx storage reduction catalyst are performed.

  In the prior art, this exhaust pipe direct injection system uses a high-pressure liquid fuel injection valve to inject fuel whose pressure has been increased to high pressure from the fuel injection valve. However, fuel injection is performed by PM regeneration or NOx regeneration. The time in the standby state in which the fuel is not injected is overwhelmingly larger than the time in which the fuel is injected.

  For this reason, when fuel is not injected into the exhaust pipe, high-pressure fuel is supplied to the fuel injection valve. When it comes into contact with high exhaust gas, there is a problem that the fuel is sludged to cause coking, and the injection hole is partially or totally closed. There is also a problem that the fuel consumption is slightly deteriorated due to wasteful fuel consumption due to this fuel leakage.

  In this connection, in an exhaust pipe injection device that injects fuel into the exhaust pipe for DPF regeneration of a diesel engine, it suppresses a temporary decrease in catalyst performance, wasteful consumption of fuel, and a delay in the start of injection. On the other hand, in order to prevent clogging of the fuel pipe due to carbonization of the remaining fuel, a shutoff valve is provided in the fuel supply pipe immediately before the injection nozzle, and a pressure accumulating valve is provided in the fuel supply pipe upstream of the shutoff valve. Connect the accumulator, and after fuel injection for DPF regeneration, close the fuel supply valve and shutoff valve, open the accumulator valve and air supply valve, and push the fuel remaining in the fuel supply pipe into the accumulator with pressurized air At the beginning of DPF regeneration, the pressure accumulation valve is opened, and the exhaust pipe injection of the engine that injects the fuel accumulated in the accumulator. Apparatus has been proposed (e.g., see Patent Document 1).

  However, in this exhaust pipe injection device of the engine, it is possible to purge the fuel in the fuel supply pipe upstream from the shutoff valve, but it is not possible to purge the fuel in the fuel nozzle downstream from the shutoff valve. The problem that the problem of coking in the fuel nozzle (the injection hole of the fuel injection valve) cannot be solved is not solved.

JP 2012-127287 A

  The present invention has been made in view of the above, and an object thereof is an internal combustion engine capable of preventing coking in the vicinity of an injection hole of a direct injection nozzle that directly injects fuel into exhaust gas of the internal combustion engine. It is another object of the present invention to provide an internal direct injection system for an internal combustion engine and an internal direct injection method for an internal combustion engine.

  In order to achieve the above object, a direct injection system for an internal combustion engine of an internal combustion engine of the present invention directly injects fuel into the exhaust pipe of the internal combustion engine using a high-pressure liquid fuel injection valve that injects only fuel. In the injection system, a first on-off valve is provided in a fuel supply passage to the high-pressure liquid fuel injection valve, and an air supply is provided with a second on-off valve between the first on-off valve and the high-pressure liquid fuel injection valve. A fuel injection device configured to connect a pipe and control the direct injection system in the exhaust pipe opens the first on-off valve and closes the second on-off valve to inject fuel into the exhaust pipe After the control and the fuel injection control, the first on-off valve is closed and the second on-off valve is opened, and the air is supplied from the air supply pipe to the fuel supply pipe on the downstream side of the first on-off valve. Supply the high pressure liquid fuel injection Fuel discharge control for discharging the fuel in the fuel, and after the fuel discharge control, with the first on-off valve closed, the second on-off valve is closed to wait for the next fuel discharge control Configured to perform control.

  Further, the direct injection method of an internal combustion engine of the present invention for achieving the above object is an exhaust of an internal combustion engine in which fuel is injected into the exhaust pipe of the internal combustion engine using a high-pressure liquid fuel injection valve that injects only fuel. In the direct pipe injection method, the first on-off valve provided in the fuel supply passage to the high-pressure liquid fuel injection valve is opened, and the air connected between the first on-off valve and the high-pressure liquid fuel injection valve The second on-off valve provided in the supply pipe is closed to inject fuel into the exhaust pipe, and after this fuel is injected, the first on-off valve is closed and the second on-off valve is opened to Air is supplied from the supply pipe to the fuel supply pipe on the downstream side of the first on-off valve, the fuel in the high-pressure liquid fuel injection valve is discharged, and after the fuel is discharged, the first on-off valve is closed. With the valve in the valve state, the second on-off valve is closed and the next fuel injection A method characterized in that to wait.

  According to the direct injection system for an exhaust pipe of an internal combustion engine and the direct injection method for an internal combustion engine of the present invention, when the direct injection nozzle that directly injects fuel into the exhaust gas of the internal combustion engine stops the fuel injection, The fuel supply passage is closed to prevent fuel leakage, and air is directly supplied to the injection nozzle, and the fuel in the fuel passage inside the direct injection nozzle is discharged by air. It is possible to prevent coking in the vicinity of the injection hole due to the adhering fuel.

It is a figure showing typically composition of an in-pipe direct injection system of an internal-combustion engine of an embodiment concerning the present invention. It is a figure which shows typically the structure around the high pressure liquid fuel injection valve 24 of FIG.

  Hereinafter, an internal direct injection system for an internal combustion engine and an internal direct injection method for an internal combustion engine according to embodiments of the present invention will be described with reference to the drawings.

  First, an engine (internal combustion engine) 10 including an internal direct injection system 1 for an internal combustion engine according to an embodiment of the present invention will be described with reference to FIG. In this engine 10, fresh air A introduced from the outside is pressurized by the compressor 14 b of the turbocharger 14, and if necessary, exhaust gas (EGR gas) flowing into the intake pipe 12 from an EGR passage (not shown). Is sent to the cylinder 11a of the engine body 11.

  Further, the exhaust gas G generated in the cylinder 11a flows out to the exhaust pipe 13, a part of which flows as EGR gas in the EGR passage, and the remaining exhaust gas G passes through the turbine 14a and is then purified by exhaust gas. After flowing into the apparatus 20 and being purified, it is discharged into the atmosphere as a purified exhaust gas Gc through a muffler (not shown). In the configuration of FIG. 1, the exhaust gas purification device 20 includes an oxidation catalyst device (DOC) 21, a particulate collection device 22, a selective reduction catalyst device (SCR) 23, and the like.

  A high-pressure liquid fuel injection valve (fuel injection nozzle) 24 is disposed upstream of the oxidation catalyst device 21. The high-pressure liquid fuel injection valve 24 is connected to a high-pressure pump (not shown) or a common rail (not shown). A device that injects light oil (unburned fuel) Fs into the exhaust pipe 13 without the assistance of air, and injects the light oil Fs into the exhaust pipe 13 during PM regeneration of the particulate collection device 22 to oxidize it. The exhaust gas G is heated by the oxidation heat of the light oil Fs oxidized by the catalyst device 21 to raise the temperature of the particulate collection device 22 to a temperature range where PM combustion is possible, and the collected PM is burned and removed. ing.

  The urea water injection nozzle 30 disposed on the upstream side of the selective catalytic reduction device 23 is a device that injects urea water U for NOx reduction into the exhaust pipe 13, and the injected urea water U is decomposed. Then, ammonia is generated, and NOx in the exhaust gas G is reduced to water and nitrogen by the selective catalytic reduction device 23 using this ammonia to make it harmless.

  And the direct injection system 1 in the exhaust pipe of the internal combustion engine of the present invention uses the high pressure liquid fuel injection valve 24 that injects only the fuel Fs as a fuel injection nozzle, and injects the fuel Fs into the exhaust pipe 13 of the engine 10. It is. In the direct injection system 1 in the exhaust pipe of the internal combustion engine, a first on-off valve 31 is provided in the fuel supply passage 25 to the high-pressure liquid fuel injection valve 24, and between the first on-off valve 31 and the high-pressure liquid fuel injection valve 24. In addition, an air supply pipe 32 provided with a second on-off valve 33 is connected.

  Moreover, as shown in FIG.1 and FIG.2, the control apparatus 40 which controls the direct injection system 1 in the exhaust pipe of the internal combustion engine of this invention is provided. The control device 40 controls the high-pressure liquid fuel injection valve 24, the first on-off valve 31, the second on-off valve 32, the air pump 34, and the like in accordance with the operating state of the engine 10, so that the high-pressure liquid fuel injection valve 24 is controlled. This is a device for controlling the supply of the fuel Fs and the supply of the air Ap. Instead of providing the air pump 34, when there is an air tank that stores compressed air for braking, the air supply pipe 32 may be connected to the air tank so as to supply the air Ap.

  The control device 40 normally performs general control of the engine 10 and general control of the vehicle based on information of various sensors provided in the engine 10 or various sensors provided in the vehicle on which the engine 10 is mounted. It is built in an engine control unit (ECU).

  The control device 40 for controlling the exhaust pipe direct injection system 1 is configured to perform the following fuel injection control, fuel discharge control, and injection standby control.

  The fuel injection control is a control for injecting fuel into the exhaust pipe 13 by opening the first on-off valve 31 and closing the second on-off valve 33. Further, in the fuel discharge control, after the fuel injection control, the first on-off valve 31 is closed and the second on-off valve 33 is opened to supply fuel from the air supply pipe 32 to the downstream side of the first on-off valve 31. In this control, air Ap is supplied to the pipe 25 and the fuel Fs in the high-pressure liquid fuel injection valve 24 is discharged. The supply of the air Ap is performed during an air supply period which is a preset fixed period. The air supply period is a time during which the fuel Fs in the pipe can be discharged, and is set in advance through experiments or the like.

  Then, the injection standby control is a control after the fuel discharge control, in which the first on-off valve 31 is closed and the second on-off valve 33 is closed to wait for the next fuel discharge control. The standby control ends when the fuel injection control starts, and the injection standby control shifts to the fuel injection control.

  Next, a fuel direct injection method for an internal combustion engine according to an embodiment of the present invention will be described. This direct fuel injection method for an internal combustion engine is a direct injection method in an exhaust pipe of an internal combustion engine in which fuel Fs is injected into the exhaust pipe 13 of the engine 10 using a high-pressure liquid fuel injection valve 24 that injects only the fuel. Then, the first on-off valve 31 provided in the fuel supply passage 25 to the high-pressure liquid fuel injection valve 24 is opened, and the air supply connected between the first on-off valve 31 and the high-pressure liquid fuel injection valve 24 is performed. The second on-off valve 33 provided in the pipe 32 is closed and the fuel Fs is injected into the exhaust pipe 13.

  After the fuel Fs is injected, the first on-off valve 31 is closed and the second on-off valve 33 is opened, and the air Ap is supplied from the air supply pipe 32 to the fuel supply pipe 24 downstream of the first on-off valve 31. After the fuel Fs in the high-pressure liquid fuel injection valve 24 is discharged and purged, and the fuel Fs is discharged, the first on-off valve 31 is kept closed and the second on-off valve 33 is closed. The valve is closed, the supply of the air Ap is stopped, and it waits until the next fuel injection.

  According to the direct injection system 1 for the internal combustion engine of the internal combustion engine and the direct injection method for the internal combustion engine of the internal combustion engine configured as described above, the high pressure liquid fuel injection for directly injecting the fuel Fs into the exhaust gas G of the exhaust pipe 13 of the engine 10. When the valve 24 stops fuel injection, the fuel supply passage 25 is closed to prevent fuel leakage, and air Ap is supplied to the high-pressure liquid fuel injection valve 24 so that the fuel inside the high-pressure liquid fuel injection valve 24 is supplied. Since the fuel Fs in the passage is discharged from the air Ap and purged, the fuel Fs adhering to the periphery of the injection hole can be blown off by the air Ap, and coking of the injection hole by the adhering fuel Fs can be prevented.

DESCRIPTION OF SYMBOLS 1 Direct injection system in exhaust pipe of internal combustion engine 10 Engine (internal combustion engine)
11 Engine body 11a Cylinder 12 Intake pipe 13 Exhaust pipe 14 Turbocharger 14a Turbine 14b Compressor 20 Exhaust gas purification device 21 Oxidation catalyst device (DOC)
22 Particle collection device 23 Selective reduction type catalyst device (SCR)
24 High-pressure liquid fuel injection valve (fuel injection nozzle)
30 Urea water injection nozzle 25 Fuel supply passage 31 First on-off valve 32 Air supply pipe 33 Second on-off valve 34 Air pump 40 Controller A Fresh air Ap Air (compressed air, pressurized air)
Fs diesel oil (unburned fuel)
G Exhaust gas Gc generated Exhaust gas U purified Urea water

Claims (2)

In a direct injection system of an internal combustion engine for injecting fuel into an exhaust pipe of an internal combustion engine using a high-pressure liquid fuel injection valve that injects only fuel,
A first on-off valve is provided in a fuel supply passage to the high-pressure liquid fuel injection valve, and an air supply pipe having a second on-off valve is connected between the first on-off valve and the high-pressure liquid fuel injection valve. And configure
A control device for controlling the exhaust pipe direct injection system,
Fuel injection control for opening the first on-off valve and closing the second on-off valve to inject fuel into the exhaust pipe;
After the fuel injection control, the first on-off valve is closed and the second on-off valve is opened to supply air from the air supply pipe to the fuel supply pipe on the downstream side of the first on-off valve. A fuel discharge control for discharging the fuel in the high-pressure liquid fuel injection valve;
After the fuel discharge control, an internal combustion engine configured to perform injection standby control in which the first on-off valve is closed and the second on-off valve is closed to wait for the next fuel discharge control Direct exhaust pipe injection system. In the direct injection method in an exhaust pipe of an internal combustion engine for injecting fuel into the exhaust pipe of the internal combustion engine using a high-pressure liquid fuel injection valve that injects only fuel,
A first on-off valve provided in a fuel supply passage to the high-pressure liquid fuel injection valve is opened, and an air supply pipe connected between the first on-off valve and the high-pressure liquid fuel injection valve is provided. 2 Close the on-off valve and inject fuel into the exhaust pipe.
After the fuel is injected, the first on-off valve is closed and the second on-off valve is opened to supply air from the air supply pipe to the fuel supply pipe on the downstream side of the first on-off valve. , Discharging the fuel in the high-pressure liquid fuel injection valve,
A direct injection method in an exhaust pipe of an internal combustion engine, wherein after the fuel is discharged, the second on-off valve is closed while the first on-off valve is closed to wait for the next fuel injection.

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