JP5282584B2 - Device for injecting fuel into engine exhaust pipe and method for measuring injection amount - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To promote the atomization of injection fuel and accurately measure a fuel injection amount in a fuel injection device for injecting an addition fuel into the exhaust pipe of an engine having an exhaust gas post treatment device. <P>SOLUTION: A collision plate 4 is provided to the front of a fuel injection valve 2 attached to an exhaust pipe 1. The collision plate is attached to the fuel injection valve 2 with a stay 5. The fuel injected from an injection hole 22 which serves as an addition fuel for the exhaust gas post treatment device is collided with the collision plate, diffused therearound, and atomized, and chemically combined with the residual oxygen in the exhaust gas. Since there is no need to reduce the diameter of the injection hole of the fuel injection valve 2 for atomization, the occurrence of deposit in the injection hole can be avoided. The temperature of the collision plate 4 is lowered since it is cooled by the injected fuel. When a temperature sensor Ts is built in the collision plate 4 and a temperature difference between the collision plate and the exhaust gas is measured, the quantity of the injected fuel can be measured. By using this measuring method, the quantity of the addition fuel injected into the exhaust pipe can be controlled. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an exhaust gas aftertreatment device for reducing harmful components in engine exhaust gas, and more particularly to a fuel injection device that supplies added fuel to the exhaust gas aftertreatment device and a method for measuring the fuel injection amount. is there.

As an important part of environmental measures, regulations for nitrogen oxides (NOx) or hydrocarbons (HC), which are considered harmful components in exhaust gas, are implemented for vehicle engines, while reducing harmful components Various technologies are being developed vigorously. Vehicle engines include gasoline engines and diesel engines, and diesel engines are widespread mainly in commercial vehicles such as trucks. A diesel engine is an engine that compresses air supplied into a cylinder and injects fuel into air that has become high temperature and pressure and burns it, and generally has higher thermal efficiency than a gasoline engine. As a result, the amount of carbon dioxide (CO ₂ ) emissions is reduced by that amount, and although it has excellent characteristics in terms of environmental measures, NOx and particulate matter (particulates: PM) are reduced. Is strongly requested.

  In order to reduce NOx, various devices such as an EGR device that recirculates engine exhaust gas to intake air are known. Among them, there is an exhaust gas aftertreatment device that uses a NOx storage reduction catalyst. In this apparatus, for example, in an engine that basically performs combustion in a state with a large air-fuel ratio (lean) such as a diesel engine, NOx in the exhaust gas is occluded in the catalyst when the exhaust gas atmosphere is excessive in oxygen, The gas in the reducing atmosphere (spike gas) is intermittently passed through the catalyst to reduce and remove NOx. To make the exhaust gas into a reducing atmosphere gas, the amount of fuel injected into the cylinder of the engine is greatly increased, or fuel is added to the exhaust gas from the fuel injection device provided in the exhaust pipe and burned, resulting in excessive air There is a method of setting the rate λ to 1 or less.

  Further, in order to reduce PM in exhaust gas, a technique of attaching a filter called a diesel particulate filter (DPF) to an exhaust pipe of a diesel engine and capturing PM by this DPF is generally employed. . In this DPF, it is necessary to regenerate the DPF so as to recover the function of the DPF by appropriately removing the accumulated PM. At this time as well, fuel is added to the exhaust gas from the fuel injection device provided in the exhaust pipe. In some cases, the exhaust gas is heated to a high temperature and the PM deposited on the DPF is burned and removed.

A fuel injection device that injects such added fuel into exhaust gas is disclosed in Japanese Patent Application Laid-Open No. 2008-19735 as an example. In this additive fuel injection device, as shown in FIG. 6A, a fuel injection valve 103 is installed on the upstream side of the NOx storage reduction catalyst 102 mounted on the exhaust pipe 101 of the diesel engine 100. The fuel injection valve 103 is connected to a common rail 106 that accumulates high-pressure fuel to be injected into the cylinder via a flow rate adjusting valve 104, an added fuel accumulating chamber 105, and the like. Fuel for in-cylinder injection from is branched and supplied.
As shown in FIG. 6B, the fuel injection valve 103 includes a valve body having an injection hole 103A, a needle 103B that opens and closes the injection hole 103A, an armature 103C formed on the needle 103B, and a solenoid coil 103D. In addition, the added fuel is supplied from the fuel inlet 103E around the needle 103B. When the exhaust gas is a reducing atmosphere gas, the solenoid coil 103D is energized to suck the needle 103B, and the fuel is injected into the exhaust pipe 101 through the injection hole 103A. The amount of fuel to be added can be controlled by changing the energizing time of the solenoid coil 103D or the fuel pressure in the pressure accumulation chamber 105 for the added fuel, and the engine control unit ECU provided in the diesel engine is controlled by an added fuel pressure sensor. 108, the pressure control valve 109, etc. are used to control the amount of fuel added. In this fuel injection valve 103, even when the fuel is not injected into the exhaust pipe, the fuel is supplied from the fuel inlet 103E to the fuel outlet 103F to cool the fuel injection valve 103.

JP 2008-19735 A

  The fuel injection valve attached to the exhaust pipe of the engine is constantly exposed to the heat of the exhaust gas and becomes hot, so if unburned components in the fuel and exhaust gas at the end of injection adhere to the injection hole, this causes carbonization. May cause so-called deposits. The blockage of the nozzle hole due to the deposit is more likely to occur as the diameter of the nozzle hole is smaller. In the fuel injection valve of Patent Document 1, although cooling with fuel is performed, when the diameter of the injection hole is reduced so as to facilitate atomization of the injected fuel and promote mixing with the exhaust gas, the injection hole is formed by the deposit. There is a risk of blockage.

In addition, the amount of added fuel to be injected needs to be accurately controlled according to the amount of remaining air in the exhaust gas. For example, when reducing gas is passed through a NOx storage reduction catalyst, the amount of exhaust gas The amount of added fuel must be controlled so that λ becomes an appropriate value for reduction. However, in a normal fuel injection valve, the fuel injection amount varies according to the fuel pressure at the injection valve inlet and the pressure of the engine exhaust gas, and it is difficult to accurately control the fuel injection amount. In particular, when deposits adhere to the injection hole of the fuel injection valve, the area of the injection hole is reduced even if the injection hole is not completely closed, and the fuel injection amount is greatly increased even at the same inlet fuel pressure and valve opening. Because they are different, precise control is virtually impossible.
An object of the present invention is a fuel injection device for injecting added fuel into an exhaust pipe of an engine, which provides a device that does not generate deposits and has excellent fuel atomization characteristics, and further uses this fuel injection device An object of the present invention is to provide an accurate measurement device for the fuel injection amount to solve the above-mentioned problems.

In view of the above-described problems, the present invention has a basic configuration in which a collision plate with which fuel injected into an engine exhaust pipe collides is provided to promote atomization. A temperature sensor is installed at the same time, and an exhaust gas temperature sensor is provided to constitute a fuel injection amount measuring device. That is, the present invention
“ A fuel injection device for injecting fuel into exhaust gas upstream of the NOx storage reduction catalyst of an engine equipped with a NOx storage reduction catalyst,
A fuel injection valve having a single injection hole mounted on the exhaust pipe of the engine, a collision plate on which fuel injected from the fuel injection valve collides, and
The collision plate is provided with a temperature sensor for measuring the temperature thereof, and provided with an exhaust gas temperature sensor for measuring the temperature of the exhaust gas of the engine, and
Detection means for detecting the difference between the temperature of the collision plate and the temperature of the exhaust gas of the engine, which is generated when fuel is injected from the fuel injection valve, and calculates the fuel injection amount based on the output of the detection means And computing means. "
The fuel injection device is characterized by this.

In the present invention, a fuel injection device having a specific structure is applied to an engine in which an exhaust pipe is equipped with a NOx storage reduction catalyst. However, the fuel injection device itself has a diesel particulate, It can also be applied to a diesel engine equipped with a filter.

And the fuel injection device in the present invention comprises a temperature sensor on the collision plate and an exhaust gas temperature sensor to constitute a fuel injection amount measuring device , that is ,
“A fuel amount measuring device for measuring the amount of fuel injected into the exhaust gas of an engine,
An exhaust gas temperature sensor for providing a collision plate for collision of fuel injected from a fuel injection valve mounted on an exhaust pipe of the engine, and for installing a temperature sensor on the collision plate and measuring the temperature of the exhaust gas of the engine. Provided,
Detection means for detecting the difference between the temperature of the collision plate and the temperature of the exhaust gas of the engine, which is generated when fuel is injected from the fuel injection valve, and calculates the fuel injection amount based on the output of the detection means And a fuel amount measuring device characterized by comprising a computing means "
It can also be understood as Such a measuring apparatus substantially constitutes a measuring method .

According to the fuel injection device of the present invention, as described in claim 2 , in an engine in which an exhaust pipe is equipped with a NOx storage reduction catalyst, when reducing gas is supplied to the NOx storage reduction catalyst, It can be used to control the fuel injected and is preferably used in a diesel engine as claimed in claim 3 .

In the present invention, a fuel injection valve mounted on the exhaust pipe of the engine and a collision plate on which the fuel injected from the fuel injection valve collides are provided. When it is necessary to supply the added fuel to the exhaust pipe, the fuel is injected from the fuel injection valve attached to the exhaust pipe, but the injected fuel collides with the collision plate and diffuses in the form of a mist. . The diffused fuel is quickly vaporized by the high-temperature exhaust gas and combined with oxygen remaining in the exhaust gas. For example, the exhaust gas passing through the NOx storage reduction catalyst is used as a reducing atmosphere gas. Thus, in the fuel injection device of the present invention, since the atomization of the fuel is achieved by the collision plate, it is not necessary to reduce the diameter of the injection hole of the fuel injection valve to improve the atomization characteristics. Generation of deposits due to high-temperature exhaust gas can be prevented.

In the present invention, a temperature sensor is installed on the collision plate and an exhaust gas temperature sensor for detecting the temperature of the exhaust gas is provided, and the amount of injected fuel is obtained based on the difference in temperature detected by both temperature sensors. ing. This is based on the following principle .
The temperature of the collision plate coincides with the temperature of the exhaust gas when no fuel is injected. When the added fuel is injected, if the injected fuel collides with the collision plate, it is cooled by the injected fuel and the temperature of the collision plate is lowered. The temperature difference between the collision plate and the exhaust gas increases as the amount of injected fuel increases. That is, similar to the well-known hot-wire anemometer, the temperature difference between the collision plate and the exhaust gas is a function of the amount of fuel injected from the fuel injection valve, so the relationship between this temperature difference and the fuel injection amount. Is previously determined based on experiments or the like, it is possible to detect the temperature difference and calculate the fuel injection amount.

The fuel injection amount measuring apparatus and measuring method according to the present invention directly measure the amount of injected fuel and are not affected by the state of the fuel injection valve mounted on the exhaust pipe. For example, even if the characteristics of the pressure and the injection amount of the fuel injection valve change, it is possible to accurately measure the fuel injection amount without being affected by the change. Even when the operating state of the engine changes and the temperature or pressure of the exhaust gas fluctuates, the fuel injection amount can be accurately detected. Therefore, when this fuel injection amount measuring device is applied to a control device for added fuel in an engine equipped with a NOx storage reduction catalyst as described in claim 2 , the air of exhaust gas passing through the NOx storage reduction catalyst It is possible to accurately control the excess rate λ and efficiently perform the reduction action of the NOx storage reduction catalyst. In addition , when applied to DPF regeneration control of a diesel engine equipped with DPF, necessary and sufficient added fuel can be supplied into the exhaust gas to prevent wasteful fuel consumption and DPF burnout.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the whole fuel-injection apparatus based on this invention, and a partial enlarged view. It is a figure which shows the Example and modification of a collision board of this invention. It is the schematic which shows the other Example of the fuel-injection apparatus based on this invention. It is a flowchart of the fuel injection amount measuring apparatus of this invention. It is an example of the control flow using the fuel injection amount measuring apparatus of this invention. It is the schematic of the conventional fuel injection apparatus.

  The present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment in which the fuel injection device FI of the present invention is provided at a bent portion of an exhaust pipe of a diesel engine. Although omitted in FIG. 1, similarly to the diesel engine shown in FIG. 6, a NOx storage reduction catalyst (or DPF) is provided downstream of the fuel injection device FI in the exhaust pipe, and the fuel injection device FI. The fuel to be injected into the cylinder is branched and supplied. The injection timing and the injection amount of the fuel injected into the exhaust pipe as the added fuel are controlled by the engine control unit ECU according to the operating state of the diesel engine.

  A fuel injection valve 2 is attached to the exhaust pipe 1 of the diesel engine. As shown in the enlarged view of part A, the fuel injection valve 2 is an electromagnetic valve similar to the fuel injection valve in FIG. 6 that opens and closes the needle valve 21 with a solenoid (not shown). However, the nozzle hole 22 at the tip of the fuel injection valve 2 is not provided with a plurality of nozzle holes with a small diameter but with a single nozzle hole with a relatively large diameter. A fuel supply pipe 3 is connected to the fuel injection valve 2, and fuel branched from the fuel injection device of the diesel engine is supplied via the fuel supply pipe 3.

  A collision plate 4 is provided in front of the fuel injection valve 2 inserted into the exhaust pipe 1, and the collision plate 4 is located near the injection hole 22 at a position where the injected fuel collides as a liquid. Installed. As shown in FIG. 2A, the collision plate 4 is a disk-shaped member made of a heat-resistant material such as a heat-resistant alloy or ceramic. On the surface of the collision plate 4, a convex portion 41 is formed at the center and a radial groove 42 is formed around the center so that the fuel that has collided diffuses and flows around. The collision plate 4 is supported by four stays 5 welded to the main body of the fuel injection valve 2, and is integrated with the fuel injection valve 2. In this embodiment, the collision plate has a disk shape, but the collision plate may have a rectangular shape or other shapes.

When the added fuel is injected from the injection hole 22 of the fuel injection valve 2, the injected fuel collides with the collision plate 4 as shown by a two-dot chain line in the enlarged view of the A part in FIG. After flowing, it is scattered around in the form of mist. High-temperature exhaust gas flows around the collision plate 4, and the scattered fuel is caught in the flow of exhaust gas and quickly vaporized and combined with oxygen in the exhaust gas. Thus, since the atomization of the fuel injected by the collision plate 4 and the mixing with the exhaust gas are greatly promoted, the diameter of the injection hole 22 can be made relatively large, and the high-temperature exhaust gas can be made. There is no risk of deposits occurring even in the nozzle holes placed in the gas.
As shown in FIG. 2B, a metal net 5B is installed between the stays 5A so as to promote mixing with the fuel scattered by causing turbulent flow in the exhaust gas flowing around the collision plate 4. A collision plate 4 may be attached. Further, when the fuel injection valve 2 is attached to the straight portion of the exhaust pipe 1, the stay 5C is fixed to the exhaust pipe 1 to support the collision plate 4 as shown in FIG. The collision plate 4 can be inclined with respect to the injected fuel so as to spread uniformly in the exhaust pipe.

Next, the fuel injection amount measuring device of the present invention using a collision plate will be described.
A temperature sensor TS is embedded in the collision plate 4 as shown in the enlarged view of part A of FIGS. In this embodiment, the temperature sensor TS is a resistance temperature detector, and is configured to detect the temperature of the collision plate 4 by measuring an electrical resistance that varies with temperature. The exhaust pipe is provided with an exhaust gas temperature sensor GTS that detects the temperature of the exhaust gas upstream of the fuel injection valve 2. Since the collision plate 4 is a component having a small heat capacity placed in the high-temperature exhaust gas, the temperature thereof coincides with the temperature of the exhaust gas when the fuel is not injected.

When the added fuel is supplied, the injected fuel collides with the collision plate 4 and diffuses and flows from the central portion to the surroundings. Therefore, the collision plate 4 is cooled by the fuel and its temperature drops, and the temperature of the collision plate 4 decreases. And a temperature difference between the exhaust gas and the exhaust gas. The temperature of the collision plate 4 decreases as the amount of fuel to be cooled increases (however, when the temperature of the collision plate decreases, the heat of exhaust gas flowing around the collision plate flows into the collision plate), the collision plate The temperature difference between 4 and the exhaust gas is eventually a function of the amount of fuel injected. The specific relationship between the temperature difference and the amount of injected fuel varies depending on the shape of the collision plate, the distance between the fuel injection valve nozzle and the collision plate, and the like. By experimentally obtaining a specific relationship with the amount in advance, the fuel injection amount can be calculated from the temperature difference between the collision plate 4 and the exhaust gas.
The fuel injection amount measuring apparatus of the present invention directly measures the amount of fuel injected from the fuel injection valve 2 to the collision plate 4. Therefore, even if the characteristics of the pressure and the injection amount of the fuel injection valve change, it is possible to accurately measure the fuel injection amount without being affected by the change.

In FIG. 4, the flowchart of the process which the fuel injection amount measuring apparatus of this invention performs is shown.
In this flowchart, when the supply of the added fuel is started, the exhaust gas temperature GT detected by the exhaust gas temperature sensor GTS and the temperature PT of the collision plate 4 detected by the temperature sensor TS are read (step S1), and the exhaust gas temperature TG is read. And the temperature difference (TG-TS) between the temperature TS of the collision plate 4 is obtained (step S2). These are in the claims 1, has a detecting means for detecting a difference between the temperature of the exhaust gas temperature and the engine of the collision plate. In the fuel injection amount measuring device, a graph experimentally determining the relationship between the temperature difference (GT-PT) and the fuel injection amount is stored as a map M, and the fuel injection corresponding to the detected temperature difference is stored. The amount is determined by the map M (step S3). This is an arithmetic processor in claim 1, it calculates the injection quantity of fuel based on the output of the detection means.

FIG. 5 shows a control flow chart when supplying the reducing gas to the NOx storage reduction catalyst using the fuel injection amount measuring apparatus of the present invention.
When the engine enters an operation state in which reducing gas is supplied to the NOx occlusion reduction catalyst, the engine control unit ECM contains the amount of fuel injected into the cylinder of the engine and the amount of air supplied to the cylinder. The remaining oxygen amount is calculated (B1). Next, a fuel injection amount Q into the exhaust gas necessary for consuming oxygen in the exhaust gas to form a reducing atmosphere gas is calculated (B2). The temperature difference ΔT is converted into a temperature difference ΔTD as a target value. The temperature difference ΔTD of the target value is compared with the actual temperature difference ΔTA at the addition point B3 to obtain the deviation e, and the injection pressure or valve opening of the fuel injection valve is increased or decreased according to the deviation e (B4). . The resulting new temperature difference ΔTA is fed back to the addition point B3. Such control is executed by the engine control device, and even if the excess air ratio λ of the exhaust gas varies, it is possible to quickly follow the variation and accurately control the fuel injection amount. Note that a λ sensor for detecting the excess air ratio λ of the exhaust gas may be installed in the exhaust pipe of the engine to calculate the amount of residual oxygen in the exhaust gas.

  As described above in detail, the present invention is a fuel injection device that injects added fuel into an exhaust pipe of an engine, and provides a collision plate with which the injected fuel collides to promote atomization. The measuring device that measures the amount of injected fuel by using the collision plate is configured. In the above embodiment, the case where the present invention is applied to a diesel engine equipped with an NOx storage reduction catalyst (or DPF) in the exhaust pipe has been described. However, the present invention performs lean combustion so that the exhaust pipe is connected to the NOx storage reduction catalyst. It can also be applied to gasoline engines equipped with Further, the method for measuring the temperature difference between the collision plate and the exhaust gas is not limited to the method for detecting the change in the electric resistance of the resistance temperature detector in the above-described embodiment. For example, the collision plate has the same temperature as the exhaust gas. It is also possible to obtain a temperature difference by passing a current through the resistance temperature detector and detecting the current value. Thus, in carrying out the present invention, the present invention is not limited to the above-described embodiments, and it is obvious that various modifications can be made thereto.

DESCRIPTION OF SYMBOLS 1 Exhaust pipe 2 Fuel injection valve 21 Needle valve 22 Injection hole 3 Fuel supply pipe 4 Collision plate 41 Convex part 42 Groove 5 Stay (for collision plate attachment)
TS temperature sensor GTS exhaust gas temperature sensor

Claims (3)

A fuel injection device that injects fuel into exhaust gas upstream of the NOx storage reduction catalyst of an engine equipped with a NOx storage reduction catalyst,
A fuel injection valve having a single injection hole mounted on the exhaust pipe of the engine, a collision plate on which fuel injected from the fuel injection valve collides, and
The collision plate is provided with a temperature sensor for measuring the temperature thereof, and provided with an exhaust gas temperature sensor for measuring the temperature of the exhaust gas of the engine, and
Detection means for detecting the difference between the temperature of the collision plate and the temperature of the exhaust gas of the engine, which is generated when fuel is injected from the fuel injection valve, and calculates the fuel injection amount based on the output of the detection means A fuel injection device comprising a calculation means . 2. An engine comprising the fuel injection device according to claim 1, wherein when the reducing gas is supplied to the NOx storage reduction catalyst, the fuel to be injected into the exhaust gas is controlled using the arithmetic means . The engine according to claim 2, wherein the engine is a diesel engine .

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