JP2008019735A - Fuel adding valve and fuel adding device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of restraining a temperature rise in a fuel adding valve. <P>SOLUTION: This fuel adding valve 11 injects fuel into an exhaust passage of an internal combustion engine, and has a fuel inflow port 42 for supplying the fuel to the fuel adding valve 11, and a fuel outflow port 43 for discharging the fuel from the fuel adding valve 11. The fuel adding valve 11 can be cooled by passing the fuel through into the fuel adding valve 11, by making the fuel flow in from the fuel inflow port 42, and making the fuel flow out of the fuel outflow port 43. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel addition valve and a fuel addition device.

A fuel addition valve and a NOx catalyst are provided in the exhaust passage of the internal combustion engine from the upstream side, and NOx in the exhaust gas can be purified by adding fuel from the fuel addition valve to the NOx catalyst. Since this fuel addition valve is provided in the exhaust passage, it is always exposed to the exhaust. Therefore, particulate matter such as soot in the exhaust (hereinafter referred to as PM) adheres to the tip of the fuel addition valve. When the temperature of the fuel addition valve increases, the PM adhering to the tip of the fuel addition valve solidifies, and the amount of fuel injected from the fuel addition valve decreases.

Here, in the case of a fuel injection valve for supplying fuel to the internal combustion engine, since fuel injection is repeatedly performed at very short intervals, even if PM adheres, it is blown off by the injected fuel. However, since the fuel addition valve provided in the exhaust passage injects fuel when reducing NOx or the like, the time during which fuel is not injected is long, and the attached soot and the like are easily solidified.

  On the other hand, a technique is known in which a cooling water passage is provided around a fuel addition valve provided in an exhaust passage to cool the fuel addition valve (see, for example, Patent Document 1). However, since it is necessary to provide a cooling water passage separately, the place which can be arrange | positioned is restricted and the cost will increase.

Further, a technique for performing fuel injection for removing soot and the like is known (see, for example, Patent Document 2). However, since fuel is consumed, fuel consumption is deteriorated.
JP 2005-264756 A JP 2003-328744 A JP-T-2004-514829 JP 2005-201158 A JP-A-2005-351245

  This invention is made | formed in view of the above problems, and it aims at providing the technique which can suppress a temperature rise in a fuel addition valve.

In order to achieve the above object, a fuel addition valve according to the present invention provides:
In a fuel addition valve for injecting fuel into an exhaust passage of an internal combustion engine,
A fuel inlet for supplying fuel to the fuel addition valve;
A fuel outlet for discharging fuel from the fuel addition valve;
It is characterized by providing.

  When fuel flows into the fuel addition valve from the fuel inlet, fuel can be injected from the fuel addition valve, and fuel for cooling the fuel addition valve can be supplied to the fuel addition valve. .

Then, by letting the fuel flow out from the fuel outlet, the fuel whose temperature has increased in the fuel addition valve can be discharged. Further, even when fuel is not injected from the fuel addition valve, a large amount of fuel can always be circulated through the fuel addition valve by allowing the fuel to flow out from the fuel outlet. Thereby, since a fuel addition valve can always be cooled, a temperature rise can be suppressed.

In addition, in order to achieve the above-described problem, a fuel addition device according to the present invention includes:
Comprising the fuel addition valve;
A fuel discharge passage connected to the fuel outlet and through which the fuel passing through the fuel outlet flows;
Pressure adjusting means for adjusting the pressure of fuel in the fuel addition valve in the fuel discharge passage;
Is further provided.

  The pressure adjusting means adjusts the fuel pressure in the fuel addition valve by adjusting the flow rate of the fuel in the fuel discharge passage. Thereby, since the fuel injection pressure can be adjusted, the fuel injection pressure can also be kept constant. In addition, when a large amount of fuel flows out from the fuel addition valve, it is difficult to adjust the pressure in the fuel addition valve in the fuel supply passage, but the pressure in the fuel addition valve in the fuel discharge passage should be adjusted. This makes it easy to adjust the pressure.

In the present invention, fuel addition valve temperature detection means for detecting the temperature of the fuel addition valve;
Fuel supply amount adjusting means for adjusting the amount of fuel flowing in from the fuel inlet;
With
The higher the temperature detected by the fuel addition valve temperature detecting means, the more the fuel supply amount adjusting means can increase the amount of fuel flowing in from the fuel inlet.

  The fuel supply amount adjusting means can adjust the amount of fuel supplied to the fuel addition valve in order to adjust the amount of fuel flowing from the fuel inlet. When the amount of fuel supplied to the fuel addition valve increases, more heat can be taken from the fuel addition valve, and thus the temperature of the fuel addition valve can be further lowered. That is, the amount of fuel flowing into the fuel addition valve can be adjusted according to the temperature of the fuel addition valve.

  The present invention can suppress a temperature rise in a fuel addition valve.

  Hereinafter, specific embodiments of a fuel addition valve and a fuel addition device according to the present invention will be described with reference to the drawings.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. Here, the case where the fuel addition valve and the fuel addition device according to the present invention are applied to a diesel engine for driving a vehicle will be described as an example.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 1 to which a fuel addition valve 11 according to this embodiment is applied and an exhaust system thereof. The internal combustion engine 1 is a four-cycle diesel engine having four cylinders 2.

  The internal combustion engine 1 includes a fuel injection valve 3 that directly injects fuel into each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 that accumulates fuel to a predetermined pressure.

  The common rail 4 is connected to a high-pressure fuel pump 6 through a fuel supply pipe 5. The high-pressure fuel pump 6 is a pump that operates using the rotational torque of the crankshaft of the internal combustion engine 1 as a drive source.

  The internal combustion engine 1 is also provided with a fuel tank 7 for storing fuel, and a low-pressure fuel pump 8 that discharges fuel at a low pressure is provided in the fuel tank 7. The low pressure fuel pump 8 is connected to the high pressure fuel pump 6 through the fuel supply pipe 5.

  The fuel stored in the fuel tank 7 is discharged to the fuel supply pipe 5 by the low-pressure fuel pump 8 and flows through the fuel supply pipe 5. When the fuel passes through the high pressure fuel pump 6 in the middle of the fuel supply pipe 5, the pressure of the fuel downstream from the high pressure fuel pump 6 increases. Then, the fuel discharged from the high pressure fuel pump 6 flows into the common rail 4. The pressure of the fuel in the common rail 4 is also increased by the high pressure fuel pump 6. The high-pressure fuel is supplied to the fuel injection valve 3, and the fuel injection valve 3 is opened to inject fuel into the cylinder 2.

An exhaust passage 9 is connected to the internal combustion engine 1. An occlusion reduction type NOx catalyst 10 (hereinafter referred to as NOx catalyst 10) is provided in the middle of the exhaust passage 9. The NOx catalyst 10 has a function of storing NOx in the exhaust when the oxygen concentration of the inflowing exhaust gas is high, and reducing the stored NOx when the oxygen concentration of the inflowing exhaust gas is low and a reducing agent is present. .

In this embodiment, a fuel addition device 30 is provided to supply the reducing agent to the NOx catalyst 10. The fuel addition device 30 includes a fuel addition valve 11, an added fuel supply pipe 13, a flow rate adjusting valve 14, a fuel addition common rail 15, an added fuel discharge pipe 16, a pressure control valve 17, and an added fuel pressure sensor 18. Yes.

A fuel addition valve 11 is provided in the exhaust passage 9 upstream of the NOx catalyst 10 to add fuel (light oil) as a reducing agent into the exhaust gas flowing through the exhaust passage 9. The fuel addition valve 11 and the common rail 4 are connected via an added fuel supply pipe 13. In the middle of the added fuel supply pipe 13, a flow rate adjusting valve 14 and a fuel added common rail 15 are provided in this order from the common rail 4 side. The flow rate adjustment valve 14 adjusts the amount of fuel supplied to the fuel addition valve 11 by adjusting the amount of fuel flowing through the addition fuel supply pipe 13. In the fuel addition common rail 15, the fuel is accumulated at a predetermined pressure. In this embodiment, the added fuel supply pipe 13 corresponds to the fuel supply passage in the present invention. In this embodiment, the flow rate adjusting valve 14 corresponds to the fuel supply amount adjusting means in the present invention.

  On the other hand, one end of an added fuel discharge pipe 16 is connected to the fuel addition valve 11. The other end of the added fuel discharge pipe 16 is connected to the fuel tank 7. A pressure control valve 17 that adjusts the pressure of fuel injected from the fuel addition valve 11 by adjusting the amount of fuel flowing through the addition fuel discharge pipe 16 is provided in the middle of the addition fuel discharge pipe 16. ing. In this embodiment, the added fuel discharge pipe 16 corresponds to the fuel discharge passage in the present invention. In this embodiment, the pressure control valve 17 corresponds to the pressure adjusting means in the present invention.

  That is, high-pressure fuel flows from the common rail 4 into the added fuel supply pipe 13 and is temporarily stored in the fuel added common rail 15. Thereafter, fuel is supplied from the fuel addition common rail 15 to the fuel addition valve 11. When the fuel addition valve 11 is opened, fuel is injected into the exhaust. The fuel that has been supplied to the fuel addition valve 11 but has not been injected into the exhaust gas from the fuel addition valve 11 flows through the added fuel discharge pipe 16 and is returned to the fuel tank 7.

  The fuel addition common rail 15 is provided with an added fuel pressure sensor 18 for detecting the pressure of the fuel in the fuel addition common rail 15.

The internal combustion engine 1 configured as described above is provided with an ECU 12 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 12 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  In addition to the added fuel pressure sensor 18, the ECU 12 outputs an electric signal corresponding to the amount by which the driver depresses the accelerator pedal 21 to detect an engine load, and an engine speed sensor. The crank position sensor 23 is connected via electric wiring, and the output signals of these various sensors are input to the ECU 12.

  On the other hand, the fuel injection valve 3, the fuel addition valve 11, the flow rate adjustment valve 14, the pressure control valve 17 and the like are connected to the ECU 12 through electrical wiring, and the opening and closing of these valves is controlled by the ECU 12.

  Here, FIG. 2 is a schematic configuration diagram of the fuel addition valve 11. The fuel addition valve 11 includes a case 41. The case 41 is formed with a fuel inlet 42 through which fuel flows into the case 41 and a fuel outlet 43 through which fuel flows out of the case 41. The fuel inflow port 42 and the fuel outflow port 43 are communicated with each other via a fuel inflow passage 48 and a fuel outflow passage 49 formed in the case 41. The fuel inflow passage 48 is a passage formed in the case 41 and extending from the fuel inlet 42 to the fuel injection port 50. Here, the fuel injection port 50 penetrates the case 41 at the tip of the case 41. On the other hand, the fuel outflow passage 49 is a passage from the fuel inflow passage 48 near the tip of the case 41 to the fuel outflow port 43.

  A needle 44 that reciprocates in the case 41 is stored in the case 41. An armature 45 is attached to the needle 44. The case 41 is provided with a solenoid coil 46, and an iron core 47 is provided on the central axis side of the solenoid coil 46.

  In the fuel addition valve 11 configured as described above, when an electric current flows through the solenoid coil 46, the armature 45 is attracted to the iron core 47. As a result, the tip end portion of the needle 44 is separated from the case 41, so that the fuel inflow passage 48 and the fuel injection port 50 communicate with each other. Therefore, the fuel flowing through the fuel inflow passage 48 is injected from the fuel injection port 50.

  On the other hand, the fuel that has not been injected from the fuel injection port 50 flows through the fuel outflow passage 49 and is discharged from the fuel outlet 43.

  The fuel inlet 42 is connected to the added fuel supply pipe 13, and the fuel outlet 43 is connected to the added fuel discharge pipe 16.

  As described above, in the fuel addition valve 11, a part of the fuel flowing in from the fuel inlet 42 passes through the vicinity of the tip of the fuel addition valve 11 and then flows out from the fuel outlet 43. The vicinity of the tip of 11 can be cooled. Therefore, solidification of PM in the exhaust at the tip of the fuel addition valve 11 can be suppressed.

  Moreover, the temperature of the fuel addition valve 11 can be maintained at an appropriate value by changing the fuel supply amount according to the temperature of the fuel addition valve 11. Here, since the temperature of the fuel addition valve 11 changes according to the operating state of the internal combustion engine 1 (for example, the engine speed and the engine load or the accelerator opening), it can be estimated based on these values. Note that the relationship between the operating state of the internal combustion engine 1 and the temperature of the fuel addition valve 11 may be obtained in advance by experiments or the like and stored in the ECU 12. In this embodiment, the ECU 12 for obtaining the temperature of the fuel addition valve 11 corresponds to the fuel addition valve temperature detecting means in the present invention.

  Then, from the temperature of the fuel addition valve 11 and the heat capacity of the fuel addition valve 11, the amount of fuel necessary for setting the temperature of the fuel addition valve 11 to the target value is calculated. This amount of fuel is the amount of fuel that flows into the fuel addition valve 11 from the fuel inlet 42. The relationship between the temperature of the fuel addition valve 11 and the amount of fuel that flows into the fuel addition valve 11 may be obtained in advance by experiments or the like.

  In order to allow the amount of fuel required for this cooling to flow into the fuel addition valve 11, the opening degree of the flow rate adjustment valve 14 and the pressure control valve 17 is adjusted. That is, as the temperature of the fuel addition valve 11 is higher than the target value, the amount of fuel passing through the fuel addition valve 11 is increased. Then, as the amount of fuel passing through the fuel addition valve 11 is increased, the opening degree of the flow control valve 14 is moved to the more open side. At this time, if the amount of fuel passing through the pressure control valve 17 is not increased, the amount of increase in the fuel passing through the fuel addition valve 11 is reduced, so that the opening degree of the pressure control valve 17 is moved to the open side. Further, the opening degree of the pressure control valve 17 is adjusted so that the fuel pressure in the fuel addition valve 11 becomes a predetermined value. Here, it is assumed that the pressure in the fuel addition valve 11 and the fuel pressure detected by the added fuel pressure sensor 18 are equal.

  At this time, the movement amounts of the fuel addition valve 11 and the pressure control valve 17 are determined in advance by experiments or the like and stored in the ECU 12.

  In this way, the temperature of the fuel addition valve 11 can be adjusted by adjusting the amount of fuel passing through the fuel addition valve 11 based on the temperature near the tip of the fuel addition valve 11.

  In this embodiment, the fuel outflow passage 49 is connected to the fuel inflow passage 48 near the tip of the case 41, but it may be connected to the fuel inflow passage 48 near the fuel inlet 42. That is, if even a part of the fuel addition valve 11 can be cooled, the temperature of the entire fuel addition valve 11 can be lowered.

It is a figure which shows schematic structure of the internal combustion engine which applies the fuel addition valve which concerns on an Example, and its exhaust system. It is a schematic block diagram of a fuel addition valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Fuel injection valve 4 Common rail 5 Fuel supply pipe 6 High pressure fuel pump 7 Fuel tank 8 Low pressure fuel pump 9 Exhaust passage 10 Occlusion reduction type NOx catalyst 11 Fuel addition valve 12 ECU
13 Added fuel supply pipe 14 Flow rate adjusting valve 15 Fuel addition common rail 16 Added fuel discharge pipe 17 Pressure control valve 18 Added fuel pressure sensor 21 Accelerator pedal 22 Accelerator opening sensor 23 Crank position sensor 41 Case 42 Fuel inlet 43 Fuel outlet 44 Needle 45 Armature 46 Solenoid coil 47 Iron core 48 Fuel inflow passage 49 Fuel outflow passage 50 Fuel injection port

Claims (3)

In a fuel addition valve for injecting fuel into an exhaust passage of an internal combustion engine,
A fuel inlet for supplying fuel to the fuel addition valve;
A fuel outlet for discharging fuel from the fuel addition valve;
A fuel addition valve comprising: A fuel addition valve according to claim 1,
A fuel discharge passage connected to the fuel outlet and through which fuel flowing out of the fuel addition valve flows from the fuel outlet;
Pressure adjusting means for adjusting the pressure of fuel in the fuel addition valve in the fuel discharge passage;
The fuel addition apparatus further comprising: Fuel addition valve temperature detecting means for detecting the temperature of the fuel addition valve;
A fuel supply passage connected to the fuel inlet and through which fuel flowing into the fuel addition valve flows from the fuel inlet;
Fuel supply amount adjusting means for adjusting the amount of fuel flowing from the fuel inlet into the fuel addition valve in the fuel supply passage;
With
The fuel addition according to claim 2, wherein the fuel supply amount adjusting means increases the amount of fuel flowing in from the fuel inlet as the temperature detected by the fuel addition valve temperature detecting means is higher. apparatus.

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