JP5586446B2 - Engine exhaust pipe injector - Google Patents

Description

  The present invention relates to an exhaust pipe injection device that injects fuel into an exhaust pipe of an engine.

  Conventionally, in a diesel engine, an exhaust purification filter (diesel particulate filter: DPF) that collects particulates in exhaust gas is arranged in the middle of the exhaust pipe, and fuel is injected into the exhaust pipe upstream of the exhaust purification filter. A regenerating process for regenerating the exhaust purification filter is performed by burning and removing particulates collected by the exhaust purification filter by the oxidation reaction heat of the fuel injected from the injection nozzle (for example, Patent Document 1).

JP 2010-150941 A

By the way, if fuel remains in the fuel supply pipe that supplies fuel to the injection nozzle after fuel injection from the injection nozzle, the fuel supply pipe may be clogged due to carbonization of the residual fuel.
Here, it is possible to prevent clogging of the fuel supply pipe by pushing out the residual fuel in the fuel supply pipe with air and injecting it from the injection nozzle and reducing the fuel remaining in the fuel supply pipe. In this case, the following problems occur.

  That is, by injecting residual fuel into the exhaust pipe at a time, the catalyst performance of a catalyst (for example, an SCR (Selective catalytic reduction) catalyst) disposed downstream of the exhaust purification filter can be improved by the sulfur content (S) in the fuel gas oil. Injecting residual fuel in the fuel supply pipe after regeneration processing wastes excess fuel, and when trying to start fuel injection from the injection nozzle In addition, since the fuel supply pipe is empty, there is a problem that a delay occurs before the start of fuel injection.

  Therefore, in view of the above-mentioned problems of the prior art, the present invention prevents clogging of fuel piping due to carbonization of the remaining fuel while suppressing temporary deterioration of catalyst performance, wasteful consumption of fuel, and delay in starting injection. An object of the present invention is to provide an exhaust pipe injection device for an engine that can be prevented.

  Therefore, in the present invention, an injection nozzle that injects fuel into the exhaust pipe of an engine, a fuel supply pipe that supplies fuel to the injection nozzle, and a fuel supply pipe that is interposed in the fuel supply pipe and controls the fuel supply to the injection nozzle A fuel supply valve, an accumulator provided in the fuel supply pipe between the injection nozzle and the fuel supply valve, a shutoff valve provided in the fuel supply pipe between the injection nozzle and the accumulator, Air supply means for sending air into the fuel supply pipe between the cutoff valve and the fuel supply valve; after fuel injection by the injection nozzle, the fuel supply valve and cutoff valve are closed, and the air supply means By sending air into the fuel supply pipe between the cutoff valve and the fuel supply valve, the cutoff valve and the fuel supply The fuel remaining in the fuel supply pipe between the lube was so pushed into the accumulator.

  According to the present invention, after the fuel is injected from the injection nozzle, the residual fuel in the fuel supply pipe is accumulated in the accumulator, and the residual fuel is not injected into the exhaust pipe. It is possible to suppress a temporary decrease in catalyst performance and wasteful fuel consumption, and it is possible to suppress a delay in the start of injection by using the fuel accumulated in the accumulator.

The system block diagram of the diesel engine in embodiment of this invention The circuit diagram which shows the structure of the exhaust pipe injection apparatus in embodiment The flowchart which shows control of the exhaust pipe injection device in an embodiment Timing chart showing valve opening / closing characteristics in the exhaust pipe injection device according to the embodiment The figure for demonstrating the effect | action of the accumulator in embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a vehicle diesel engine (internal combustion engine) 10 to which an exhaust pipe injection device according to the present invention is applied.

  The diesel engine 10 sucks air through the intake pipe 14 and the intake manifold 12. The intake pipe 14 includes, in order from the upstream side, an air cleaner 16 that filters dust in the air, a compressor 18A of a turbocharger 18 that performs intake air supercharging, and an intercooler that cools the intake air that has passed the compressor 18A and has become hot. 20 is provided.

  On the other hand, the diesel engine 10 emits exhaust through the exhaust manifold 22 and the exhaust pipe 24. The exhaust pipe 24 includes, in order from the upstream side, an exhaust turbine 18B of the turbocharger 18, an exhaust pipe injection device 25 having an injection nozzle for injecting fuel gas oil into the exhaust pipe 24, a continuously regenerating DPF device 26, a reducing agent precursor. As a reducing agent injection device 28 having an injection nozzle for supplying and supplying urea aqueous solution, SCR catalyst 30 for selectively reducing and purifying NOx using ammonia (reducing agent) generated from urea aqueous solution, and ammonia passing through SCR catalyst 30 An ammonia oxidation catalyst 32 to be oxidized is provided.

The continuous regeneration type DPF device 26 includes a DOC (Diesel Oxidation Catalyst) 26A that oxidizes NO (nitrogen monoxide) to NO ₂ (nitrogen dioxide), and a DPF (capturing and removing PM (Particulate Matter)) in exhaust gas. Diesel Particulate Filter) 26B.
As the exhaust purification filter, a CSF (Catalyzed Soot Filter) in which a catalyst (active component and additive component) is supported on the filter surface can be used instead of the DPF 26B.

The diesel engine 10 also includes an EGR (Exhaust Gas Recirculation) device 34 that lowers the combustion temperature by recirculating a part of the exhaust to the intake side and reduces the NOx concentration in the exhaust.
The EGR device 34 includes an EGR pipe 34A that recirculates a part of the exhaust gas that flows through the exhaust pipe 24 to the intake pipe 14, an EGR cooler 34B that cools the exhaust gas that flows through the EGR pipe 34A, and an exhaust amount that recirculates to the intake pipe 14 (EGR EGR control valve 34C that controls the rate).

A control unit 42 having a built-in computer inputs an output signal of a rotational speed sensor 44 that detects the rotational speed NE of the diesel engine 10 and a load sensor 46 that detects a load Q of the diesel engine 10.
Here, the load sensor 46 is closely related to the torque of the diesel engine 10 such as the intake flow rate, the intake pressure, the supercharging pressure, the accelerator opening, and the intake throttle valve as a state quantity indicating the load Q of the diesel engine 10. Detect related state quantities.

The control unit 42 executes a control program stored in a non-volatile memory such as a built-in ROM (Read Only Memory), thereby controlling the reproduction processing of the DPF 26B based on signals from various sensors.
The control unit 42 determines whether or not there is a regeneration request for the DPF 26B based on, for example, the accumulated operation time of the engine, the accumulated value of the particulate emission estimated from the engine operating conditions, the differential pressure between the upstream and downstream of the DPF 26B, and the like.

  Then, based on the regeneration start signal of the DPF 26B, the control unit 42 causes the exhaust pipe injection device 25 to inject fuel gas oil into the exhaust pipe 24 on the upstream side of the continuous regeneration type DPF device 26. The fuel gas oil injected into the exhaust pipe 24 is oxidized by the DOC 26A (oxidation catalyst), and the oxidation reaction heat burns the fine particles (soot) deposited on the DPF 26B to regenerate the DPF 26B.

FIG. 2 is a circuit diagram showing details of the exhaust pipe injection device 25.
The exhaust pipe injection device 25 joins the injection nozzle 101 for injecting fuel gas oil into the exhaust pipe 24, the fuel supply pipe 102 for introducing pressurized fuel to the injection nozzle 101, and the fuel supply pipe 102 in the middle. And an air supply pipe 103 that guides air into the fuel supply pipe 102.

The fuel supply pipe 102 communicates with a fuel tank via a fuel pump (not shown) and is supplied with pressurized fuel discharged from the fuel pump.
The upstream side fuel supply valve 105, the check valve 106, the pressure sensor 107, and the downstream side fuel supply valve 108 are disposed in the fuel supply line 102 in order from the upstream side, and the bypass line 109 bypasses the downstream side fuel supply valve 108. Check valves 110 are arranged, and these valves control the supply of pressurized fuel to the injection nozzle 101.

In addition, a shutoff valve 111 is disposed in the fuel supply pipe 102 immediately before the injection nozzle 101.
The upstream side fuel supply valve 105, the downstream side fuel supply valve 108, and the shutoff valve 111 are electromagnetic valves that are opened and closed by a drive current sent from the control unit 42.

The check valve 106 and the check valve 110 block the reverse flow of fuel in the fuel supply pipe 21 and the bypass pipe 109.
The pressure sensor 107 detects the fuel pressure in the fuel supply pipe 102 between the check valve 106 and the downstream fuel supply valve 108 and outputs the detection signal to the control unit 42.

Pressurized air discharged from an air pump (not shown) or pressurized air stored in an air reservoir is supplied to the air supply pipe 103.
An air supply valve 112 is interposed in the air supply pipe 103. A check valve for stopping the backflow of pressurized air can be provided on the downstream side of the air supply valve 112.
The air supply valve 112 is an electromagnetic valve, and opens and closes by a drive current sent from the control unit 42.

The pressure sensor 107 is used for failure diagnosis of the upstream fuel supply valve 105, the downstream fuel supply valve 108, and the air supply valve 112, which is performed by the control unit 42.
Specifically, the control unit 42 assumes the upstream fuel supply valve 105, the downstream fuel supply valve 105, the downstream fuel supply valve 108, and the open / closed control state of the air supply valve 112, and the upstream fuel supply valve 105 and the downstream fuel supply. By comparing the pressure between the valve 108 and the pressure actually detected by the pressure sensor 107, the upstream fuel supply valve 105, the downstream fuel supply valve 108, and the air supply valve 112 are closed or stuck open. Diagnose whether there is a failure.

The injection nozzle 101 has an injection hole (throttle) that reduces the passage cross-sectional area at the downstream end of the fuel supply pipe 21, this injection hole faces the exhaust pipe 24, and sprays fuel gas oil into the exhaust flowing in the exhaust pipe 24. And spray.
An accumulator (accumulator) 114 is connected to the fuel supply pipe 21 immediately before the shutoff valve 111 via an accumulator valve 113.

The accumulator 114 is a device that converts the pressure energy of fuel into the pressure energy of gas (nitrogen gas), which is a compressible fluid, and stores it. When the fuel is pushed into the container, the gas is compressed through the partition wall. When an amount of fuel corresponding to the pressure of the fuel enters the container, and then the force for pushing the fuel is released by opening the pressure accumulation valve 113, the fuel contained in the container is exposed to the outside of the container by the force of gas expansion. To erupt.
The accumulator valve 113 is an electromagnetic valve and opens and closes by a drive current sent from the control unit 42.

Next, control of the exhaust pipe injection device 25 by the control unit 42 will be described according to the flowchart of FIG. 3 with reference to the timing chart of FIG.
Note that the routine shown in the flowchart of FIG. 3 shows a control program executed during operation of the diesel engine 10.
First, in step S81, the exhaust pipe injection device 25 is controlled in the normal mode.

The normal mode means that the injection nozzle 101 is clogged by injecting air from the injection nozzle 101 periodically (for example, at regular intervals) during a period in which there is no DPF regeneration request and fuel is not injected from the injection nozzle 101. This mode prevents the
In the normal mode, as shown in FIG. 4, the upstream side fuel supply valve 105, the downstream side fuel supply valve 108 and the pressure accumulating valve 113 are kept closed, while the shutoff valve 111 is kept open, and periodically. By opening the air supply valve 112 for a certain period of time, air is intermittently introduced into the exhaust pipe 24 via the fuel supply pipe 21 after the air supply pipe 103 and the air supply pipe 103 merge, and further through the injection nozzle 101. To spray.

As described above, by periodically injecting air from the injection nozzle 101, the fuel supply pipe 21 (the fuel supply pipe 21 between the cutoff valve 111 and the injection nozzle 101) remains immediately after fuel injection. The fuel gas oil can be discharged, and thereafter, it is possible to prevent the exhaust particulates from adhering to the injection nozzle 101 and causing clogging.
In a state where the exhaust pipe injection device 25 is controlled in the normal mode, it is determined in step S82 whether or not a regeneration start signal for the DPF 26B has been generated.

The regeneration start signal may be output manually by a driver operating a button based on a regeneration request warning in the DPF 26B, or the control unit 42 automatically outputs based on the regeneration request. There may be.
When the regeneration start signal is output, the operation proceeds to the regeneration processing mode in which the DPF 26B is regenerated by injecting the fuel gas oil from the injection nozzle 101.

First, in step S83, as the first stage of the regeneration processing mode, as shown in FIG. 4, the upstream fuel supply valve 105, the downstream fuel supply valve 108 and the air supply valve 112 are closed, and the shutoff valve 111 is opened. The pressure accumulating valve 113 is opened for a predetermined time in a state where the pressure is held in the state.
As will be described later, immediately after the fuel injection for regeneration of the DPF is terminated, the fuel gas oil remaining in the fuel supply pipe 21 is pushed into the accumulator 114. In the normal mode, the pressure accumulation valve 113 is closed. By holding, the state where the fuel gas oil is pushed into the accumulator 114 is held.

  Accordingly, when the pressure accumulation valve 113 is opened in step S83, the gas (nitrogen) in the accumulator 114 expands, so that the fuel gas oil pushed into the accumulator 114 is ejected to the outside of the accumulator 114, and the accumulator 114 The fuel accumulated therein is injected into the exhaust pipe 24 through the fuel supply pipe 21 and the injection nozzle 101.

When the injection of the fuel gas oil that has been pushed into the accumulator 114 is completed, the process proceeds to step S84, and the process proceeds to the second stage of the regeneration process mode.
Specifically, as shown in FIG. 4, the air supply valve 112 and the pressure accumulating valve 113 are kept closed, while the upstream fuel supply valve 105, the downstream fuel supply valve 108 and the shutoff valve 111 are kept open. Thus, the pressurized fuel is injected into the exhaust pipe 24 via the fuel supply pipe 21 and the injection nozzle 101.

The fuel gas oil injected into the exhaust pipe 24 is oxidized by the DOC 26A (oxidation catalyst), and particulates (soot) deposited on the DPF 26B are burned by this oxidation reaction heat, and the DPF 26B is regenerated.
When the fuel gas oil injection is continued for a predetermined time and the DPF regeneration process is completed, the process proceeds to step S85, and a transition is made to a residual fuel processing mode in which the fuel remaining in the fuel supply pipe 21 is processed.

In the residual fuel processing mode, as shown in FIG. 4, first, the upstream fuel supply valve 105, the downstream fuel supply valve 108, the shutoff valve 111 and the pressure accumulating valve 113 are kept closed, and the air supply valve 112 is opened. The pressure in the fuel supply pipe 21 is increased by continuing the state of maintaining the maintained state for a certain period of time.
If the pressure in the fuel supply pipe 21 is increased in advance as described above, it is possible to prevent the fuel from being discharged from the accumulator 114 by the residual pressure in the accumulator 114 when the pressure accumulation valve 113 is opened late.

Thereafter, the upstream fuel supply valve 105, the downstream fuel supply valve 108, and the shutoff valve 111 are held in a closed state, and the air supply valve 112 and the pressure accumulating valve 113 are switched to a state in which they are held in an open state. A process of pushing the fuel remaining in the fuel supply pipe 21 with pressure, specifically, the fuel supply pipe 21 between the downstream fuel supply valve 108 and the shutoff valve 111 into the accumulator 114 is performed for a certain period of time.
Thereby, the residual fuel in the fuel supply pipe 21 is pushed by the pressurized air and pushed into the accumulator 114. When the fuel is pushed into the accumulator 114, the gas (nitrogen) in the accumulator 114 is compressed, and the gas The fuel flows into the vacant volume that is compressed.

Here, the air supply pipe 103 is connected to the upstream side of the fuel supply pipe 102 between the shutoff valve 111 and the downstream fuel supply valve 108, and is supplied via the air supply pipe 103 in the residual fuel processing mode. The pressurized air pushes the fuel remaining downstream from the portion where the air supply pipe 103 joins into the accumulator 114, so that most of the residual fuel can be pushed into the accumulator 114.
When the process of pushing the fuel into the accumulator 114 is performed for a certain time, the normal mode is restored.

  In the normal mode, the pressure accumulation valve 113 is held in the closed state, so that the state where the fuel is pushed into the accumulator 114 is maintained, and the pressure accumulation valve 113 is opened in the first stage of the DPF regeneration mode described above. Thus, the fuel that has been pushed into the accumulator 114 is ejected as the gas expands, and is injected into the exhaust pipe 24.

FIG. 5 shows the state of gas (nitrogen) and fuel in the accumulator 114 in each mode, and the open / close state of the pressure accumulation valve 113.
First, in the normal mode, when the fuel is pushed into the accumulator 114 and the gas is compressed, and the pressure accumulation valve 113 is opened in the first stage of the regeneration processing mode, the compressed gas (nitrogen) expands. Thus, the fuel is ejected to the outside of the accumulator 114 and is injected into the exhaust pipe 24 through the injection nozzle 101.

Since the pressure accumulation valve 113 is closed in the second stage of the regeneration processing mode, the gas (nitrogen) in the accumulator 114 maintains the expanded state.
In the residual fuel processing mode, when the pressure accumulation valve 113 is opened and fuel is pushed into the accumulator 114, the gas (nitrogen) is compressed, and in this state, the pressure accumulation valve 113 is returned to the normal mode to close the next DPF regeneration. In the processing, the apparatus waits in a state where the fuel confined in the accumulator 114 can be injected into the exhaust pipe 24.

According to the exhaust pipe injection device 25 described above, since the fuel in the fuel supply pipe 21 is pushed into the accumulator 114 after fuel injection for DPF regeneration, the amount of fuel remaining in the fuel supply pipe 21 is sufficiently reduced. The clogging of the injection nozzle 101 due to carbonization of residual fuel can be prevented.
Further, since the fuel remaining in the fuel supply pipe 21 is moved into the accumulator 114, a large amount of fuel may be injected into the exhaust pipe 24 at a time in order to reduce the amount of fuel remaining in the fuel supply pipe 21. However, it can be avoided that the catalyst performance of the SCR catalyst 30 is temporarily lowered by injecting a large amount of fuel.

Moreover, after DPF regeneration is complete | finished, the fuel which does not contribute to DPF regeneration is injected in the exhaust pipe 24, and it can suppress that fuel is consumed wastefully.
Further, at the start of DPF regeneration (at the start of fuel injection to the exhaust pipe 24), although no fuel remains in the fuel supply pipe 21, an accumulator 114 connected to the fuel supply pipe 21 near the injection nozzle 101 is provided. Since the stored fuel is injected, it is possible to suppress delay of fuel injection into the exhaust pipe 24.

In the above embodiment, the injection nozzle 101 and the shutoff valve 111 are separated from each other. However, an injection valve provided integrally with the jet nozzle 101 and the shutoff valve 111 can be used.
Further, in the DPF regeneration mode, the fuel and air may be mixed and injected from the injection nozzle 101.

DESCRIPTION OF SYMBOLS 10 Diesel engine 24 Exhaust pipe 25 Exhaust pipe injection device 26 Continuous regeneration type DPF device 26A DOC
26B DPF
28 Reducing Agent Injection Device 30 SCR Catalyst 32 Ammonia Oxidation Catalyst 42 Control Unit 101 Injection Nozzle 102 Fuel Supply Pipe 103 Air Supply Pipe 105 Upstream Fuel Supply Valve 108 Downstream Fuel Supply Valve 111 Shutoff Valve 112 Air Supply Valve 113 Accumulation Valve 114 Accumulator

Claims (5)

An injection nozzle that injects fuel into an exhaust pipe of an engine, a fuel supply pipe that supplies fuel to the injection nozzle, a fuel supply valve that is interposed in the fuel supply pipe and controls fuel supply to the injection nozzle, and An accumulator provided in the fuel supply pipe between the injection nozzle and the fuel supply valve; a cutoff valve provided in the fuel supply pipe between the injection nozzle and the accumulator; the cutoff valve and the fuel supply valve; Air supply means for sending air into the fuel supply pipe between
After the fuel injection by the injection nozzle, the fuel supply valve and the shutoff valve are closed, and the air supply means feeds air into the fuel supply pipe between the shutoff valve and the fuel supply valve, whereby the shutoff valve An exhaust pipe injection device for an engine, wherein the fuel remaining in the fuel supply pipe between the fuel supply valve and the fuel supply valve is pushed into the accumulator.   The exhaust pipe injection device for an engine according to claim 1, wherein the accumulator is opened with a delay from the start of air supply by the air supply means.   3. When fuel is injected from the injection nozzle, the fuel in the accumulator is released, and then the fuel supply valve is opened to start supplying fuel to the injection nozzle. Engine exhaust pipe injector.   4. The air injection unit according to claim 1, wherein air is periodically sent into the fuel supply pipe by the air supply unit and the air is injected from the injection nozzle during a period in which fuel is not injected from the injection nozzle. An exhaust pipe injection device for an engine according to claim 1. An exhaust purification filter is provided in the exhaust pipe of the engine, and the injection nozzle is disposed in an exhaust pipe upstream of the exhaust purification filter,
The engine exhaust pipe injection device according to any one of claims 1 to 4, wherein fuel is injected from the injection nozzle based on a regeneration start signal of the exhaust purification filter.