JP2018053876A - Exhaust pipe injection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust pipe injection system capable of inhibiting stagnant fuel in a fuel supply passage.SOLUTION: An exhaust pipe injection system 100 includes: a fuel tank T; an exhaust pipe injector 1; a pump P1 for supplying fuel to the exhaust pipe injector 1; a fuel supply passage 2 for connecting the pump P1 with the exhaust pipe injector 1; a fuel return passage 3 for connecting the exhaust pipe injector 1 or the fuel supply passage 2 located in front of the exhaust pipe injector with the fuel tank T; an on-off valve 4 for opening/closing the fuel return passage 3; and a control device 5 for controlling the exhaust pipe injector 1 and the on-off valve 4. When fuel injection by using the exhaust pipe injector 1 is not performed, the control device 5 opens the on-off valve 4.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust pipe injection system for injecting fuel into an exhaust pipe.

  Generally, in an exhaust pipe injection system, fuel stored in a fuel tank is supplied to an exhaust pipe injector through a fuel supply passage, and is injected into the exhaust pipe from the exhaust pipe injector. The fuel injected into the exhaust pipe is used, for example, for regeneration of a diesel particulate filter (DPF) or recovery of NOx storage capacity in a NOx storage reduction catalyst (LNT).

JP 2011-220155 A JP 2010-031675 A

  In the above exhaust pipe injection system, when the fuel injection by the exhaust pipe injector is not performed, the fuel stays in the fuel supply passage. This accumulated fuel tends to be oxidized and deteriorated due to heat transmitted from the turbocharger or the exhaust pipe during operation of the internal combustion engine, resulting in a high viscosity.

  As a result, there is a risk that the fuel having increased viscosity may block the fuel supply passage, resulting in a problem that the fuel cannot be injected from the exhaust pipe injector.

  Accordingly, an object of the present invention is to provide an exhaust pipe injection system capable of solving the above-described problems and suppressing fuel from remaining in the fuel supply passage.

  According to one aspect of the present invention, a fuel tank, an exhaust pipe injector that injects fuel into the exhaust pipe, a pump that supplies fuel stored in the fuel tank to the exhaust pipe injector, the pump, and the exhaust pipe A fuel supply passage for connecting an injector, a fuel return passage for connecting the exhaust pipe injector or a fuel supply passage located in front of the injector and the fuel tank, an on-off valve for opening and closing the fuel return passage, and the exhaust pipe injector And an exhaust pipe injection system characterized by opening the open / close valve when fuel injection by the exhaust pipe injector is not performed. Provided.

  Further, it is preferable that the control device closes the on-off valve when fuel injection is performed by the exhaust pipe injector.

  ADVANTAGE OF THE INVENTION According to this invention, the exhaust pipe injection system which can suppress that a fuel retains in a fuel supply path can be provided.

1 is a schematic configuration diagram of an exhaust pipe injection system according to an embodiment of the present invention. In the exhaust pipe injection system of one Embodiment of this invention, it is a time chart with which it uses for description of the state of exhaust pipe injection, and the open / close state of an on-off valve. It is a schematic block diagram which shows the 1st modification of the exhaust pipe injection system which concerns on this invention. It is a schematic block diagram which shows the 2nd modification of the exhaust pipe injection system which concerns on this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of an exhaust pipe injection system according to an embodiment of the present invention.

  As shown in FIG. 1, the exhaust pipe injection system 100 supplies a fuel tank T, an exhaust pipe injector 1 that injects fuel into an exhaust pipe (not shown), and fuel stored in the fuel tank T to the exhaust pipe injector 1. A feed pump P1. Further, the exhaust pipe injection system 100 includes a fuel supply passage 2 that connects the feed pump P1 and the exhaust pipe injector 1, and a fuel return passage that connects the fuel supply passage 2 located in front of the exhaust pipe injector 1 and the fuel tank T. 3. Further, the exhaust pipe injection system 100 includes an opening / closing valve 4 that opens and closes the fuel return passage 3 and a control device 5 that is configured to control the exhaust pipe injector 1 and the opening / closing valve 4.

  The fuel tank T is a container that stores fuel of an internal combustion engine (not shown) inside. In the present embodiment, the internal combustion engine is a multi-cylinder compression ignition internal combustion engine, that is, a diesel engine mounted on a vehicle (not shown), but the type, type, and the like of the internal combustion engine are arbitrary.

  The exhaust pipe injector 1 includes an electronically controlled fuel injection valve, and is electrically connected to the control device 5. The exhaust pipe injector 1 has a fuel passage (not shown) formed therein, and an injection port 1a formed at the tip. The exhaust pipe injector 1 is configured such that when the injection port 1a is opened, fuel in the fuel passage is injected into the exhaust pipe through the injection port 1a, and when the injection port 1a is closed, fuel injection is stopped.

  Moreover, the exhaust pipe injector 1 is provided in the part of the exhaust pipe located in the downstream of the turbine of the turbocharger which is not shown in figure. Further, an exhaust gas purification device (not shown) is provided in a portion of the exhaust pipe located downstream of the exhaust pipe injector 1.

  The exhaust purification device includes a diesel particulate filter (DPF) for collecting particulate matter (PM) in the exhaust, and an oxidation catalyst (DOC) provided on the upstream side of the DPF. Further, the exhaust purification device may include a NOx occlusion reduction type catalyst (LNT) that reduces and purifies nitrogen compounds (NOx) in the exhaust.

  The feed pump P1 corresponds to a pump referred to in the claims. The feed pump P <b> 1 is connected to the fuel tank T located upstream thereof through the fuel suction passage 6. Further, a filter 7 for collecting impurities contained in the fuel is provided in the middle of the fuel suction passage 6.

  The feed pump P1 is connected through the main fuel supply passage 10 to a supply pump P2 located downstream thereof. Further, the feed pump P1 is connected to a fuel passage in the exhaust pipe injector 1 through an exhaust pipe fuel supply passage 20 that is branched in the middle of the main fuel supply passage 10 (position indicated by X in the figure).

  The feed pump P <b> 1 is configured to suck in fuel from the fuel tank T through the fuel suction passage 6, perform primary pressurization, and discharge the fuel to the main fuel supply passage 10 and the exhaust pipe fuel supply passage 20.

  The fuel supply passage 2 includes a portion 10 x from the feed pump P 1 to the branch point X in the main fuel supply passage 10 and an exhaust pipe fuel supply passage 20.

  The supply pump P <b> 2 is connected to the common rail 9 located downstream thereof through the high-pressure supply passage 8. The supply pump P <b> 2 is configured to secondarily pressurize the fuel supplied from the main fuel supply passage 10 and discharge the fuel to the high-pressure supply passage 8. The supply pump P2 is connected to a first fuel return passage 3a for recovering excess fuel to the fuel tank T.

  Although not shown, the common rail 9 is connected to a plurality of in-cylinder injectors that inject fuel into the cylinder of the internal combustion engine, and the common rail 9 supplies fuel to these in-cylinder injectors. The common rail 9 is connected to a second fuel return passage 3b for recovering excess fuel to the fuel tank T.

  On the other hand, a third fuel return passage 3c is connected to the exhaust pipe fuel supply passage 20 at a position in front of the exhaust pipe injector 1 (position indicated by Y in the figure). Here, “front” refers to the end of the exhaust pipe fuel supply passage 20 on the exhaust pipe injector 1 side, or a portion in the vicinity thereof.

  The first fuel return passage 3a, the second fuel return passage 3b, and the third fuel return passage 3c are connected to a tank return passage 30 connected to the fuel tank T, respectively.

  In the present embodiment, the fuel return passage 3 includes a third fuel return passage 3 c and a passage 30 z from the connection point Z of the tank return passage 30 to the third fuel return passage 3 c to the fuel tank T.

  Note that at least one of the third fuel return passage 3c and the on-off valve 4 has a smaller flow rate than the fuel passing through the exhaust pipe fuel supply passage 20 and the main fuel supply passage 10, that is, in the exhaust pipe fuel supply passage 20. It is preferable that the flow path is narrowed so that a small amount of fuel necessary and sufficient to suppress the stagnation in the gas passes.

  The on-off valve 4 is a two-way valve provided in the middle of the third fuel return passage 3c. The on-off valve 4 is an electronically controlled valve and is electrically connected to the control device 5.

  The control device 5 forms an electronic control unit or controller that controls the exhaust pipe injector 1 and the on-off valve 4. Specifically, the control device 5 includes a CPU that executes various arithmetic processes related to electronic control of the vehicle, a ROM that stores programs and data necessary for the control, a RAM that temporarily stores calculation results of the CPU, And an input / output port for inputting / outputting signals between the two.

  Although not shown, the control device 5 includes an exhaust temperature sensor that detects the inlet exhaust temperature of the DPF and DOC, a differential pressure sensor that detects the differential pressure upstream and downstream of the DPF, and NOx that detects the NOx concentration in the exhaust. Various sensors such as sensors are electrically connected.

  In the present embodiment, the control device 5 opens the on-off valve 4 when fuel injection by the exhaust pipe injector 1 (hereinafter referred to as exhaust pipe injection) is not performed, and on-off valve 4 when performing exhaust pipe injection. The on-off valve 4 is controlled so as to be closed.

  In the present embodiment, the control device 5 may control the on-off valve 4 so as to open the on-off valve 4 immediately after controlling the exhaust pipe injector 1 so as not to perform (stop) the exhaust pipe injection. . Further, the control device 5 may control the on-off valve 4 so as to close the on-off valve 4 immediately before controlling the exhaust pipe injector 1 so as to perform (start) the exhaust pipe injection.

  The effects of the exhaust pipe injection system 100 according to this embodiment will be described.

  First, the control of the exhaust pipe injector 1 will be briefly described. In the present embodiment, the control device 5 controls the exhaust pipe injector 1 to perform exhaust pipe injection when regenerating the DPF. That is, by supplying hydrocarbons (HC) to the DOC by exhaust pipe injection and increasing the exhaust temperature by the oxidation heat of HC, PM accumulated in the DPF can be incinerated and removed to regenerate the DPF.

  Further, the control device 5 controls the exhaust pipe injector 1 to perform exhaust pipe injection when recovering the NOx storage capability in the LNT. That is, NOx stored in the LNT can be reduced and purified by making the exhaust gas rich by exhaust pipe injection.

  Next, control of the on-off valve 4 will be described with reference to FIG. FIG. 2 is a time chart showing the control state of the control device 5 in the exhaust pipe injection system 100, where (a) shows the exhaust pipe injection state and (b) shows the open / close state of the on-off valve 4.

As shown in FIGS. 2A and 2B, at time t ₀ , the control device 5 controls the exhaust pipe injector 1 to perform exhaust pipe injection. At this time, the control device 5 controls the on-off valve 4 to be closed. In this state, the fuel in the exhaust pipe fuel supply passage 20 is supplied to the exhaust pipe injector 1 without returning to the fuel tank T through the fuel return passage 3.

Then, at time t _1, the control unit 5 controls the exhaust pipe injector 1 so as not to exhaust pipe injection (to stop). Further, the control device 5 controls the on-off valve 4 to open the on-off valve 4 at time t ₂ immediately after time t ₁ . At time t ₃ , the control device 5 controls the on-off valve 4 so as to close the on-off valve 4, and at time t ₄ immediately after time t ₃ , exhaust pipe injection is performed again (starts). The exhaust pipe injector 1 is controlled.

That is, in the present embodiment, the on-off valve 4 is open at the time when the exhaust pipe injection from time t ₂ to time t ₃ is not performed, and the exhaust pipe from time t ₀ to time t ₁ and after time t _4. The on-off valve 4 is closed at the time of injection.

However, the control device 5 may execute control for opening the on-off valve 4 simultaneously with control for stopping the exhaust pipe injection (time t ₁ ). Further, the control for closing the on-off valve 4 may be executed simultaneously with the control for starting the exhaust pipe injection (time t ₄ ).

  Here, as a comparative example, an exhaust pipe injection system in which the third fuel return passage 3c is not provided in the exhaust pipe fuel supply passage 20 is assumed.

  In this comparative example, when exhaust pipe injection is not performed, fuel stays without being discharged from the exhaust pipe fuel supply passage 20. As described above, since the exhaust pipe injector is provided in the exhaust pipe portion located immediately downstream of the turbine of the turbocharger, this accumulated fuel is oxidized by the heat transmitted from the turbocharger and the exhaust pipe during the operation of the internal combustion engine. It tends to deteriorate. As a result, there is a possibility that the fuel with increased viscosity may block the exhaust pipe fuel supply passage, resulting in a problem that fuel cannot be injected from the exhaust pipe injector.

  On the other hand, the exhaust pipe injection system 100 according to the present embodiment includes the third fuel return passage 3c and the on-off valve 4, and when the exhaust pipe injection is not performed, the exhaust pipe fuel is opened by opening the on-off valve 4. The fuel in the supply passage 20 can be returned to the fuel tank T. The fuel can be prevented from staying in the exhaust pipe fuel supply passage 20 by circulating the fuel between the fuel tank T and the exhaust pipe fuel supply passage 20. As a result, it is possible to effectively suppress the exhaust pipe fuel supply passage 20 from being blocked due to the stagnation of fuel.

  In the present embodiment, the open / close valve 4 of the third fuel return passage 3c is closed when the exhaust pipe injection is performed. Thus, the fuel in the exhaust pipe fuel supply passage 20 does not flow toward the fuel tank T but is supplied to the exhaust pipe injector 1, so that the exhaust pipe injector 1 and the exhaust pipe fuel supply passage 20 located in front of the exhaust pipe fuel supply passage 20 are supplied. The fuel pressure (hereinafter referred to as “fuel pressure”) can be maintained and exhaust pipe injection can be performed efficiently. As a result, the regeneration of the DPF and the recovery of the NOx storage capacity in the LNT can be sufficiently performed.

  In particular, the control device 5 of the present embodiment controls the on-off valve 4 so that the on-off valve 4 opens immediately after the exhaust pipe injection stops. Although not shown, for example, if the on-off valve 4 is opened before the exhaust pipe injection is stopped due to a shift in the calculation cycle in the control device 5, the fuel pressure is lowered before the stop and is necessary for the exhaust pipe injection. There is a risk that it will not be possible to maintain a proper pressure. On the other hand, in the present embodiment, by controlling the on-off valve 4 to open immediately after the stop of the exhaust pipe injection, the fuel pressure is reliably set to a pressure required for the exhaust pipe injection before the stop of the exhaust pipe injection. Can be held.

  Further, the control device 5 controls the on-off valve 4 so that the on-off valve 4 is closed immediately before the start of exhaust pipe injection. Thereby, exhaust pipe injection can be started in a state where the fuel pressure is increased to a pressure necessary for exhaust pipe injection.

  On the other hand, the third fuel return passage 3c in the present embodiment is connected to an exhaust pipe fuel supply passage 20 located in front of the exhaust pipe injector 1. Thus, when exhaust pipe injection is not performed, fuel can be circulated between the connection point Y in the exhaust pipe fuel supply passage 20 and the fuel passage of the exhaust pipe injector 1. It is also possible to suppress stagnation of fuel in the fuel cell.

  When at least one of the third fuel return passage 3c and the on-off valve 4 is throttled, the flow of fuel from the feed pump P1 to the supply pump P2 is unnecessarily inhibited when the exhaust pipe injection is not performed. Without this, the stagnation of fuel in the exhaust pipe fuel supply passage 20 or in the fuel passage of the exhaust pipe injector 1 can be suppressed.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement. For example, the above-described embodiments can be modified as follows. In the following description, the same reference numerals are used for the same components as in the basic embodiment described above, and detailed descriptions thereof are omitted.

(First modification)
In the exhaust pipe injection system 100 described above, the third fuel return passage 3c is connected to the exhaust pipe fuel supply passage 2b located in front of the exhaust pipe injector 1. On the other hand, the third fuel return passage 3c may be connected to the exhaust pipe injector 1 as in the exhaust pipe injection system 200 shown in FIG. Specifically, the third fuel return passage 3c may be connected to the fuel passage in the exhaust pipe injector 1. According to the first modification, it is possible to circulate the fuel between the fuel tank T and the fuel passage in the exhaust pipe injector 1, and it is possible to reliably suppress the fuel from staying in the fuel passage. .

(Second modification)
In the exhaust pipe injection system 100 described above, the on-off valve 4 is composed of a two-way valve provided in the middle of the third fuel return passage 3c. On the other hand, as in the exhaust pipe injection system 300 shown in FIG. 4, a three-way valve 4 ′ as an on-off valve is provided at the connection position between the exhaust pipe fuel supply passage 20 and the third fuel return passage 3c. There may be. Specifically, the three-way valve 4 ′ is an electronically controlled valve, and is configured such that the flow path of the fuel flowing through the exhaust pipe fuel supply passage 20 is switched by the control device 5.

  In the second modification, when the exhaust pipe injection is not performed, the control device 5 causes the three-way valve 4 ′ to flow to the third fuel return passage 3c and not to flow to the exhaust pipe injector 1 side. Control. Further, when the exhaust pipe injection is performed, the control device 5 controls the three-way valve 4 ′ so that the fuel flows to the exhaust pipe injector 1 side and does not flow to the third fuel return passage 3 c side.

DESCRIPTION OF SYMBOLS 1 Exhaust pipe injector 2 Fuel supply path 3 Fuel return path 4 On-off valve 5 Control device P1 Feed pump (pump)
T Fuel tank 100 Exhaust pipe injection system

Claims (2)

A fuel tank,
An exhaust pipe injector for injecting fuel into the exhaust pipe;
A pump for supplying fuel stored in the fuel tank to the exhaust pipe injector;
A fuel supply passage connecting the pump and the exhaust pipe injector;
A fuel return passage connecting the exhaust pipe injector or a fuel supply passage located in front of the injector and the fuel tank;
An on-off valve for opening and closing the fuel return passage;
A control device configured to control the exhaust pipe injector and the on-off valve; and
The exhaust pipe injection system, wherein the control device opens the on-off valve when fuel injection by the exhaust pipe injector is not performed. The exhaust pipe injection system according to claim 1, wherein the control device closes the on-off valve when fuel injection is performed by the exhaust pipe injector.

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