JP2005291074A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device capable of effectively utilizing fuel discharged from a back pressure chamber of an injector. <P>SOLUTION: A booster unit 70 is provided to an injector 13 of a fuel injection device 10. The booster unit 70 is equipped with a boost piston 101 accommodated in a pressure chamber 100 and a discharge valve 111 capable of discharging fuel in a back pressure chamber 102. An exhaust treating device such as DPF is provided to an exhaust passage 30. A fuel adding part 35 is provided to the upstream side of the exhaust treating device. The fuel adding part 35 and the discharge valve 111 are connected through the medium of an added fuel passage 123. An opening/closing valve 131 is provided to the added fuel passage 123. By opening the opening/closing valve 131 when the exhaust treating device requires fuel, the fuel in the back pressure chamber 102 is supplied to the fuel adding part 35 to add the fuel to the exhaust passage 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection device including a pressure increasing unit used in a fuel injection system of an internal combustion engine such as a diesel engine.

In an exhaust system of a diesel engine, as the exhaust gas treatment apparatus (post-processing apparatus), DPF (diesel particulate filter) or oxidation catalyst, the exhaust gas purifying apparatus using the NO _X catalyst and the like are equipped. In addition, HC (hydrocarbon) is also supplied to the exhaust purification device by adding fuel to the exhaust. (For example, see Patent Document 1 below)
For example, in an engine equipped with a DPF, collected particulate matter, that is, PM (particulate matter), is combusted. As a means for combusting PM when the exhaust temperature is relatively low, an upstream side of the DPF An oxidation catalyst is disposed in the exhaust passage. NO in the exhaust is changed to NO ₂ by this oxidation catalyst, and the PM trapped in the DPF so as to burn at a relatively low temperature by NO _2.

  In addition, when the oxidation catalyst has not reached the activation temperature, a part of the fuel is added to the exhaust to oxidize the HC of the fuel, and the oxidation catalyst is heated by heat generated by the oxidation action of the oxidation catalyst. It is done.

As another example of the exhaust treatment apparatus, a NO _x storage catalyst may be used to remove NO _x in the exhaust. In the case of using the NO _X storage catalyst, fuel (HC) is required as a reducing agent for reducing and removing NO _X , and therefore, fuel is added to the exhaust passage. When fuel is added to the exhaust, the fuel is generally supplied to the fuel addition part of the exhaust passage by a fuel pump. (See Patent Document 1 below)
On the other hand, in a diesel engine, a fuel injection device using a pressure-increase type common rail system (CRS) is known. In this type of fuel injection device, high flow rate and high pressure fuel is used as hydraulic fluid for operating the pressure boosting piston. The booster piston is provided between the pressure chamber inside the injector and the back pressure chamber. When the fuel in the back pressure chamber is discharged, the booster piston is driven based on the pressure difference between the pressure chamber and the back pressure chamber. The pressure is increased and sent to the nozzle portion of the injector. The fuel discharged from the back pressure chamber is returned to the fuel tank as it is. (For example, see Patent Document 2 below)
US Pat. No. 6,293,096 JP 2002-539372 A

  In the configuration in which the fuel added to the exhaust passage is supplied to the fuel addition portion of the exhaust passage by the fuel pump as in Patent Document 1, there is a problem that the load of the fuel pump increases. In addition, the configuration in which the dedicated fuel pump is arranged has a problem that not only the number of parts increases, but also the fuel supply system becomes complicated.

  In the fuel injection device described in Patent Document 2, when the pressure-increasing piston is driven, part of the fuel functioning as hydraulic fluid is directly returned to the fuel tank from the back pressure chamber, The pressurized fuel cannot be used more effectively.

  Accordingly, an object of the present invention is to provide a fuel injection device that can more effectively utilize the fuel discharged from the back pressure chamber of the injector.

  A fuel injection device according to the present invention is a fuel injection device including a common rail that stores pressurized fuel, and an injector that includes a pressure increasing unit that increases the pressure of fuel supplied from the common rail and sends the pressure to a needle valve mechanism. The pressure increasing unit is partitioned from the pressure chamber by the pressure chamber for introducing the fuel sent from the common rail, the pressure increasing piston provided in the pressure chamber, and the pressure increasing piston, and is sent from the common rail. A back pressure chamber into which fuel is introduced; a discharge valve that opens when the fuel in the back pressure chamber is discharged; and a portion that moves integrally with the pressure-increasing piston when the fuel in the back pressure chamber is discharged. A pressure increasing chamber that boosts the fuel and sends it to the needle valve mechanism, and further includes a fuel addition portion provided upstream of an exhaust treatment device installed in an exhaust passage of the engine, and the fuel addition portion; When the exhaust treatment device needs fuel, the fuel that is discharged from the back pressure chamber through the discharge valve to the fuel addition section through the addition fuel passage. It is equipped with the additional fuel supply means to supply.

In a preferred embodiment of the present invention, in a state where the injector does not require pressure increase of fuel, the discharge valve is opened while an injector drive signal for opening the needle valve mechanism is in an OFF state, The fuel in the back pressure chamber is supplied to the fuel addition section by the added fuel supply means. An example of the exhaust treatment device is a DPF or NO _X storage catalyst provided in the exhaust passage.

  According to the present invention, since the fuel discharged from the back pressure chamber of the injector having the pressure increasing unit can be added to the exhaust passage, the fuel can be supplied to the exhaust treatment device as needed, and the back The fuel discharged from the pressure chamber can be used effectively.

An embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 shows a diesel engine 11 provided with a fuel injection device 10. The fuel injection device 10 includes a common rail 12 that stores pressurized fuel, an injector 13 that is provided for each cylinder of the engine 11, a fuel pump 14 that pressurizes and supplies fuel to the common rail 12, and the like. . The common rail 12 and the fuel pump 14 are connected by a fuel supply pipe 15. The discharge amount of the fuel pump 14 is controlled by a control unit 16 (shown in FIG. 2) described later so that the fuel pressure of the common rail 12 becomes a desired value.

  In the intake passage 20 of the engine 11, a compressor 22 of the turbocharger 21, an intercooler 23, an intake throttle valve 24, and the like are provided. The exhaust passage 30 is provided with a turbine 31 of the turbocharger 21 and a DPF (diesel particulate filter) 34 having an oxidation catalyst 33 as an example of the exhaust treatment device 32. A fuel addition unit 35 and an exhaust throttle valve 36 are provided on the upstream side of the exhaust treatment device 32.

The DPF 34 has a function of collecting particulate matter (particulate matter) such as soot in the exhaust gas. The oxidation catalyst 33, the NO in the exhaust is oxidized and is changed to NO _2, particulate matter such as soot trapped in the DPF 34, plays the functions of burning by NO _2.

  When the particulate matter is combusted in the DPF 34, for example, when the exhaust temperature is lower than the activation temperature of the oxidation catalyst 33, in order to heat the oxidation catalyst 33, fuel (HC) is contained in the exhaust as necessary. Is supplied. For this reason, the exhaust passage 30 of the present embodiment has a fuel addition section 35 provided with a valve for adding fuel to the exhaust passage 30 when the exhaust treatment device 32 needs fuel upstream of the exhaust treatment device 32. Is provided.

  FIG. 2 shows details of the fuel injection device 10. The fuel injection device 10 includes a common rail 12 that stores fuel pressurized by the fuel pump 14 and an injector 13 that is provided in a cylinder head of the engine 11. The common rail 12 is formed with a plurality of discharge ports 40 for supplying fuel to the injectors 13 of each cylinder. Although only one injector 13 is shown in FIG. 2, the injector 13 of each cylinder is actually connected to each discharge port 40 of the common rail 12 via the fuel supply path 41, and fuel is supplied to each injector 13. It comes to be supplied.

  The injector 13 shown in FIG. 2 is driven in a direction to open and close the needle valve 52, a body 51 having a nozzle portion 50, a needle valve mechanism 54 including a needle valve 52 and a fuel chamber 53 provided in the vicinity of the nozzle portion 50. And the pressure increasing unit 70 that increases the pressure of the fuel supplied from the common rail 12 and sends the pressure to the needle valve mechanism 54.

  A fuel flow part 72 having a check valve 71 is formed inside the injector 13. The fuel circulation part 72 is connected to the common rail 12 via the fuel supply path 41, and the fuel supplied from the common rail 12 is directed to the fuel chamber 53 via the check valve 71 and the fuel circulation part 73 on the nozzle part 50 side. Can be supplied. A fuel injection hole 74 is formed at the tip of the nozzle portion 50.

  The needle valve drive unit 60 includes a fuel passage 80 formed in the body 51, a pressure receiving piston 82 having a drive shaft 81 that moves integrally with the needle valve 52 in the axial direction, and a spring that biases the needle valve 52 in the valve closing direction. 83, a pressurizing chamber 85 communicating with the fuel passage 80 via the throttle 84, an open / close valve 87 driven by a solenoid 86, a return fuel outlet 88 communicating with the discharge side of the open / close valve 87, and a throttle 89 Etc. The return fuel outlet 88 communicates with the fuel tank 91 via the return flow path 90. The fuel tank 91 communicates with the suction port 14 a of the fuel pump 14 via the fuel supply pipe 92.

  The pressure increasing unit 70 includes a pressure chamber 100 communicating with the fuel supply path 41, a pressure increasing piston 101 accommodated in the pressure chamber 100, and a back pressure chamber 102 partitioned from the pressure chamber 100 by the pressure increasing piston 101. I have. The back pressure chamber 102 communicates with the fuel circulation part 72 through the throttle part 103. High-pressure fuel sent from the common rail 12 through the fuel supply path 41 is introduced into the pressure chamber 100 and the back pressure chamber 102.

  The pressure increasing unit 70 is integrated with a discharge valve 111 that is opened by a solenoid 110 when the fuel in the back pressure chamber 102 is discharged, and the pressure increasing piston 101 when the fuel in the back pressure chamber 102 is discharged. A plunger portion 112 that is a part that moves in a straight line, and a pressure-increasing chamber 113 that pressurizes fuel by the plunger portion 112. The pressure increasing chamber 113 communicates with the fuel circulation part 73.

  A fuel discharge passage 120 is connected to the outlet side of the discharge valve 111. The fuel discharge channel 120 branches into a return fuel channel 122 and an added fuel channel 123 at a branching part 121. The return fuel flow path 122 includes an open / close valve 126 driven by a solenoid 125 and communicates with the suction side 14 b of the fuel pump 14. The added fuel passage 123 is connected to the fuel adding unit 35 via an on-off valve 131 driven by a solenoid 130.

  The solenoid 86 of the on-off valve 87 and the solenoid 110 of the discharge valve 111 are controlled to open and close by the control unit 16 that functions as a controller. The opening / closing valve 126 and the solenoid 130 of the opening / closing valve 131 are also controlled to be opened / closed by the control unit 16.

  The control unit 16 uses an in-vehicle computer such as an ECU, for example, and controls the opening degree of the opening / closing valve 126 of the return fuel passage 122 and the opening / closing valve of the added fuel passage 123 when the exhaust treatment device 32 needs fuel. By opening the valve 131, the fuel discharged from the back pressure chamber 102 is supplied to the fuel addition portion 35 of the exhaust passage 30 through the discharge valve 111 and the addition fuel passage 123.

  The on-off valves 126 and 131, the solenoids 125 and 130, and the control unit 16 function as added fuel supply means in the present invention. Instead of using the on-off valves 126 and 131, a distribution valve capable of adjusting the flow distribution to the return fuel passage 122 and the added fuel passage 123 may be provided in the branch portion 121.

Next, the operation of the fuel injection device 10 of the present embodiment will be described with reference to FIGS.
When the engine 11 rotates and the fuel pump 14 is driven, the fuel sucked into the fuel pump 14 from the fuel tank 91 is pressurized and supplied to the common rail 12. The pressure of the fuel discharged from the fuel pump 14 is adjusted by the control unit 16 according to the operating state of the engine 11, and the fuel pressurized to a predetermined pressure is stored in the common rail 12.

  Fuel is injected into the combustion chamber of each cylinder of the engine 11 from the fuel injection hole 74 of each injector 13. Depending on the operating state of the engine 11, the injector 13 is driven in a mode in which the pressure of fuel is increased (a mode in which the pressure increase unit 70 operates) or a mode in which the pressure of the fuel is not increased (a mode in which the pressure increase unit 70 does not operate). The For example, when the engine 11 is operated at a high load, the injector 13 is in a mode for increasing the pressure of fuel. During low load operation such as when the engine 11 is idling, the injector 13 is in a mode that does not require fuel pressure increase.

  In the mode for increasing the fuel pressure, for example, at time T1 shown on the horizontal axis in FIG. 3, the solenoid 110 of the pressure increasing unit 70 is turned on by the pressure increasing piston drive signal, and the discharge valve 111 is opened. As a result, the pressure increasing piston 101 moves toward the pressure increasing chamber 113 in accordance with the pressure receiving area ratio between the pressure increasing piston 101 and the plunger portion 112, and the fuel in the back pressure chamber 102 passes through the discharge valve 111. It is discharged to the fuel discharge channel 120. For this reason, the fuel in the pressure increasing chamber 113 is increased in pressure and sent to the fuel circulation part 73.

  Further, at time T2 shown in FIG. 3, the solenoid 86 of the needle valve drive unit 60 is turned on by the injector drive signal, and the on-off valve 87 is opened. As a result, the fuel in the pressurizing chamber 85 passes through the on-off valve 87 and is discharged from the return fuel outlet 88 to the return flow path 90, and the pressure receiving piston 82 moves in the direction opposite to the needle valve 52, thereby The valve 52 opens. As a result, the fuel in the fuel chamber 53 is ejected from the fuel injection hole 74 into the combustion chamber of the engine 11.

  As described above, when the exhaust treatment device 32 needs fuel when the pressure increasing unit 70 is functioning during fuel injection, that is, when the exhaust valve 111 of the back pressure chamber 102 is open. Then, the solenoid 130 of the added fuel passage 123 is driven to open the on-off valve 131 by a predetermined amount. As a result, the fuel in the back pressure chamber 102 is sent to the fuel addition section 35 of the exhaust passage 30 via the discharge valve 111, the added fuel passage 123 and the on-off valve 131. By adding this fuel to the exhaust passage 30 from the fuel addition section 35, fuel HC is supplied to the oxidation catalyst 33 of the exhaust treatment device 32, and the oxidation catalyst 33 can be heated to the activation temperature.

  Of the fuel discharged from the back pressure chamber 102 to the fuel discharge passage 120, surplus fuel that exceeds the amount consumed by the fuel addition unit 35 is controlled by the on-off valve 126 of the return fuel passage 122, whereby the fuel pump 14 is supplied to the suction side 14 b and returned to the common rail 12. In this way, by returning a part of the fuel discharged from the back pressure chamber 102 to the suction side 14b of the fuel pump 14, part of the work of the fuel pump 14 can be assisted.

  On the other hand, when the exhaust processing device 32 requires fuel when the injector 13 is in an operation mode that does not require pressure increase, as shown in FIG. 4, while the injector drive signal is off, that is, the needle valve drive. While the solenoid 86 of the part 60 is off and the needle valve 52 is closed, the discharge valve 111 is opened by turning on the booster piston drive signal (turning on the solenoid 110 of the booster unit 70). . Then, the on-off valve 131 of the added fuel passage 123 is opened, and the fuel discharged from the back pressure chamber 102 is supplied to the fuel addition portion 35, whereby the fuel is added to the exhaust passage 30.

  As described above, according to the fuel injection device 10 of the present embodiment, when the exhaust treatment device 32 needs fuel according to the operating state of the engine 11, the fuel is discharged from the back pressure chamber 102 of the injector 13. Fuel can be added to the exhaust passage 30. Since the fuel in the back pressure chamber 102 is pressurized and has a high temperature, vaporization is promoted when it is added from the fuel addition portion 35 to the exhaust passage 30. Further, since the temperature of the fuel supplied to the exhaust passage 30 is high, it is advantageous for keeping the temperature of the oxidation catalyst 33 high.

  In carrying out the present invention, in addition to the above-described embodiment, the constituent elements of the present invention including the injector, the exhaust treatment device, the fuel addition unit, and the added fuel supply means are appropriately modified without departing from the spirit of the invention. Needless to say, this can be done.

The top view which shows typically the engine provided with the fuel-injection apparatus of one Embodiment of this invention. Sectional drawing which shows the fuel-injection apparatus shown by FIG. The figure which shows the relationship between the drive signal of the fuel-injection apparatus shown by FIG. 1, a needle valve lift, and return fuel. The figure which shows the relationship between the injector drive signal and pressure increase piston drive signal of the fuel-injection apparatus shown by FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel injection apparatus 11 ... Engine 12 ... Common rail 13 ... Injector 14 ... Fuel pump 16 ... Control part 30 ... Exhaust passage 32 ... Exhaust treatment device 35 ... Fuel addition part 54 ... Needle valve mechanism 70 ... Pressure increase unit 102 ... Back pressure Chamber 111 ... Drain valve 123 ... Addition fuel passage

Claims (3)

A common rail that stores pressurized fuel,
An injector having a pressure increasing unit for increasing the pressure of the fuel supplied from the common rail and sending it to the needle valve mechanism;
A fuel injection device comprising:
The pressure increasing unit is
A pressure chamber for introducing fuel sent from the common rail;
A pressure increasing piston provided in the pressure chamber;
A back pressure chamber that is partitioned from the pressure chamber by the pressure increasing piston and into which fuel sent from the common rail is introduced;
A discharge valve that opens when the fuel in the back pressure chamber is discharged;
A pressure-increasing chamber that boosts fuel by a portion that moves integrally with the pressure-intensifying piston when the fuel in the back-pressure chamber is discharged, and sends the fuel to the needle valve mechanism;
further,
A fuel addition section provided on the upstream side of the exhaust treatment device installed in the exhaust passage of the engine;
An additional fuel passage connecting the fuel addition portion and the discharge valve;
Added fuel supply means for supplying fuel discharged from the back pressure chamber through the discharge valve to the fuel addition section through the added fuel passage when the exhaust treatment device requires fuel;
A fuel injection device comprising: In a state where the injector does not require fuel pressure increase,
While the injector drive signal for opening the needle valve mechanism is in an OFF state, the discharge valve is opened, and the fuel in the back pressure chamber is supplied to the fuel addition unit by the added fuel supply means. The fuel injection device according to claim 1. 3. The fuel injection device according to claim 1, wherein the exhaust treatment device is a DPF or NO _X storage catalyst provided in the exhaust passage.

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