JP4306101B2 - Engine fuel supply system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel supply device having a function of purifying exhaust gas by adding it to a catalyst in an exhaust system, in addition to supplying engine fuel.
[0002]
[Prior art]
Conventionally, an engine that obtains engine output by burning an air-fuel mixture with a higher air-fuel ratio than the stoichiometric air-fuel ratio in at least a predetermined operating range, such as a diesel engine or a gasoline engine that performs lean combustion, has oxygen in its exhaust passage. It is common to provide a NOx absorbent (catalyst) that absorbs NOx below.
[0003]
The NOx catalyst has a characteristic of absorbing NOx when the oxygen concentration in the exhaust is high and releasing NOx when the oxygen concentration in the exhaust is low. Incidentally, NOx released into the exhaust reacts quickly with N2 if it has reducing components such as HC and CO in the exhaust and is reduced to N2. Further, even if the NOx catalyst absorbs a predetermined limit amount of NOx even when the oxygen concentration in the exhaust gas is high, the NOx catalyst does not absorb NOx any more.
[0004]
Therefore, before the NOx absorption amount of the NOx catalyst reaches the limit amount, the intake flow rate is reduced by closing the throttle valve of the intake system and a reducing agent is added into the exhaust system, and the NOx catalyst is absorbed by the NOx catalyst. The control of releasing and reducing NOx and recovering the NOx absorption capacity of the NOx catalyst may be repeated at predetermined intervals.
[0005]
By the way, the HC component contained in light oil or gasoline is suitably vaporized (or atomized), and thus suitably acts as a reducing agent that causes the NOx catalyst to function. Therefore, for example, as in an apparatus described in Japanese Patent Laid-Open No. 284647, a feed pump that pumps fuel from a fuel tank and fuel pumped from a feed pump (feed means) are introduced, and the pressure is increased to each combustion chamber (fuel injection). In a fuel supply device equipped with a high-pressure pump (pressure-increasing means) that supplies pressure to the valve), a fuel passage that connects the feed pump and the high-pressure pump is branched from the middle of the passage, and the branch passage is guided to the exhaust system. is doing.
[0006]
When such an apparatus configuration is applied, NOx in the exhaust gas is efficiently purified by a relatively simple apparatus configuration without requiring a separate supply source of the reducing agent and a pump for transferring the reducing agent. Will be able to.
[0007]
[Problems to be solved by the invention]
By the way, the action of the addition of the reducing agent (fuel) on the NOx catalyst varies greatly depending on factors such as the total amount of fuel added, the timing of addition, and the form (for example, vaporization state and average particle size). In the apparatus described in the above publication, the fuel sent from the branch passage is added (injected and supplied) to the upstream side of the catalyst in the exhaust system using an injection valve capable of controlling the internal on-off valve. In the apparatus having the above, it is possible to precisely adjust the injection amount (including the total amount and flow rate) and the injection timing of the added fuel by the injection valve and accurately control the above elements quantitatively and qualitatively. Indispensable for optimizing the purification function.
[0008]
However, due to the functional characteristics of the high-pressure pump that sends the introduced fuel at a high pressure, it is inevitable that pulsation will occur in the fuel that passes through the high-pressure pump. And since the pulsation accompanying the operation of the high-pressure pump propagates to the branch passage, it has been difficult to precisely adjust the injection amount (including the total amount and flow rate) of the added fuel and the injection timing by the injection valve. That is, the exhaust gas purification function by the NOx catalyst cannot be sufficiently optimized through quantitative and qualitative control regarding the injection amount and injection timing of the added fuel.
[0009]
The present invention has been made in view of such a situation, and the object of the present invention is that the pulsation of the fuel caused by the high pressure of the combustion fuel interferes with the supply control of the addition fuel. Accordingly, an object of the present invention is to provide an engine fuel supply device that can avoid this and optimize exhaust purification.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the first invention provides a feed means for pumping fuel from an engine fuel tank, a boosting means for introducing and boosting the fuel pumped by the feed means, and the boosted fuel. Combustion fuel supply means for injecting and supplying the combustion chamber of the engine, catalyst addition fuel supply means for supplying and supplying the pumped fuel upstream of the catalyst provided in the exhaust system of the engine, and the pumped fuel And a second fuel passage for branching from the middle of the passage of the first fuel passage and leading the pumped fuel to the catalyst addition fuel supply means. In the engine fuel supply apparatus, the timing at which the catalyst supply fuel supply means injects and supplies the fuel and the pressure increase means introduces fuel at a different timing. And gist in that it comprises control means.
[0011]
According to this configuration, the fuel addition timing is set in a period in which the fuel intake pulsation by the boosting means does not affect the fuel addition. Reliability can be improved.
[0012]
Accordingly, both NOx and HC in the exhaust can be reduced efficiently.
Since the boosting operation by the boosting means is stabilized, the fuel pressure of the fuel pumped to the combustion fuel supply means is also kept constant. Therefore, the properties of the spray injected by the combustion fuel supply means are stabilized, and a stable combustion state of the engine can be ensured.
[0013]
According to a second aspect of the present invention, there is provided a feed means for pumping fuel from a fuel tank of an engine, a pressure boosting means that operates in synchronism with the driving of the engine, introduces the fuel pumped by the feed means, and boosts the pressure. Combustion fuel supply means for injecting and supplying boosted fuel to the combustion chamber of the engine; and catalyst addition fuel supply means for injecting and supplying the pumped fuel upstream of the catalyst provided in the exhaust system of the engine; A first fuel passage for guiding the pumped fuel to the pressure increasing means, and a second fuel branching from the middle of the first fuel passage to guide the pumped fuel to the fuel supply means for catalyst addition In the engine fuel supply device having a passage, the timing when the fuel supply means for catalyst addition injects and supplies fuel is synchronized with a specific rotational phase of the engine. And summarized in that comprises timing control means that.
[0014]
According to this configuration, it is easy to grasp the timing of occurrence of fuel intake pulsation by the boosting means and to quantify the effect of the pulsation on fuel addition. Therefore, it becomes possible to sufficiently secure the preciseness and reliability of the control.
[0015]
Further, the generation timing of the fuel intake pulsation by the boosting means is surely grasped, and the fuel addition timing is set by selecting the period during which the fuel intake pulsation by the boosting means does not affect the fuel addition. It becomes easy.
[0016]
According to a third aspect of the present invention, there is provided a feed means for pumping fuel from an engine fuel tank, a boosting means for introducing and boosting the fuel pumped by the feed means, and supplying the boosted fuel to a combustion chamber of the engine Combustion fuel supply means, catalyst addition fuel supply means for supplying the pumped fuel to the upstream side of the catalyst provided in the exhaust system of the engine, and first pump for introducing the pumped fuel to the pressure increasing means. And a second fuel passage for branching from the middle of the first fuel passage and guiding the pumped fuel to the catalyst addition fuel supply means. And a timing control means for making the timing at which the catalyst addition fuel supply means injects and supplies the fuel differ from the timing at which the combustion fuel supply means supplies the fuel. The gist of the door.
[0017]
According to this configuration, the combustion pressure fluctuation based on the operation of the catalyst addition fuel supply means and the fuel pressure fluctuation based on the operation of the combustion fuel supply means do not interfere with each other, and the engine combustion and exhaust purification are optimized. Will come together.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a diesel engine system will be described.
[0019]
In FIG. 1, an engine 1 is an in-line four-cylinder diesel engine system having a fuel supply system 10, a combustion chamber 20, an intake system 30, an exhaust system 40, and the like as main parts.
[0020]
First, the fuel supply system 10 includes a supply pump 100, a common rail 12, a fuel injection valve 13, an emergency shutoff valve 14, a metering valve 16, a fuel addition nozzle 17, an engine engine fuel passage P1, an addition fuel passage P2, and the like. Is done.
[0021]
The supply pump 100 raises the fuel pumped from a fuel tank (not shown) and supplies it to the common rail 12 via the engine engine fuel passage P1. The common rail 12 has a function as a pressure accumulation chamber that holds (accumulates) the high-pressure fuel supplied from the supply pump 100 at a predetermined pressure, and distributes the accumulated fuel to each fuel injection valve 13. The fuel injection valve 13 is an electromagnetic valve provided with an electromagnetic solenoid (not shown) therein, and is appropriately opened to inject and supply fuel into the combustion chamber 20.
[0022]
On the other hand, the supply pump 100 supplies a part of the fuel pumped up from the fuel tank to the fuel addition nozzle 17 through the addition fuel passage P2. An emergency shutoff valve 14 and a metering valve 16 are sequentially arranged from the supply pump 100 toward the fuel addition nozzle 17 in the addition fuel passage P2. The emergency shutoff valve 14 shuts off the added fuel passage P2 in an emergency and stops the fuel supply. The metering valve 16 controls the pressure (fuel pressure) of the fuel supplied to the fuel addition nozzle 17. The fuel addition nozzle 17 is a mechanical on-off valve that opens when a fuel pressure (for example, 0.2 MPa) equal to or higher than a predetermined pressure is applied and injects fuel into the exhaust system 40. That is, by controlling the fuel pressure upstream of the fuel addition nozzle 17 by the metering valve 16, desired fuel is injected and supplied (added) from the fuel addition nozzle 17 at an appropriate timing.
[0023]
The intake system 30 forms a passage (intake passage) for intake air supplied into each combustion chamber 20. On the other hand, the exhaust system 40 forms a passage (exhaust passage) for exhaust gas discharged from each combustion chamber 20.
[0024]
The engine 1 is provided with a known supercharger (turbocharger) 50. The turbocharger 50 includes two turbine wheels 52 and 53 that are connected via a shaft 51. One turbine wheel (intake side turbine wheel) 52 is exposed to intake air in the intake system 30, and the other turbine wheel (exhaust side turbine wheel) 53 is exposed to exhaust in the exhaust system 40. The turbocharger 50 having such a configuration performs so-called supercharging in which the intake side turbine wheel 53 is rotated using the exhaust flow (exhaust pressure) received by the exhaust side turbine wheel 52 to increase the intake pressure.
[0025]
In the intake system 30, an intercooler 31 provided in the turbocharger 50 forcibly cools the intake air whose temperature has been raised by supercharging. The throttle valve 32 provided further downstream than the intercooler 31 is an electronically controlled on-off valve whose opening degree can be adjusted in a stepless manner, and restricts the flow area of the intake air under predetermined conditions. The function of adjusting (reducing) the supply amount of the intake air is provided.
[0026]
Further, an exhaust gas recirculation passage (EGR passage) 60 that bypasses the upstream (intake system 30) and the downstream (exhaust system 40) of the combustion chamber 20 is formed in the engine 1. The EGR passage 60 has a function of returning a part of the exhaust to the intake system 30 as appropriate. The EGR passage 60 is opened and closed steplessly by electronic control, and an EGR valve 61 that can freely adjust the flow rate of exhaust gas flowing through the passage, and EGR for cooling the exhaust gas that passes through (recirculates) the EGR passage 60 A cooler 62 is provided.
[0027]
Further, in the exhaust system 40, a catalyst casing 42 that houses an NOx storage reduction catalyst (hereinafter simply referred to as a NOx catalyst) 41 is provided downstream of the communication part of the exhaust system 40 and the EGR passage 60. The NOx catalyst 41 accommodated in the catalyst casing 42 uses, for example, alumina (Al 2 O 3) as a carrier, and an alkali metal such as potassium (K), sodium (Na), lithium (Li), cesium Cs, or barium on the carrier. An alkaline earth such as Ba or calcium Ca, a rare earth such as lanthanum (La) or yttrium (Y), and a noble metal such as platinum Pt are supported.
[0028]
The NOx catalyst 41 absorbs NOx in a state where a large amount of oxygen is present in the exhaust gas, the operating air-fuel ratio is smaller than the stoichiometric air-fuel ratio, the oxygen in the exhaust gas is low, and the reducing component (for example, unreacted fuel) In the state where the fuel component (HC) is present, NOx is reduced to NO2 or NO and released. NOx released as NO2 or NO is further reduced by reacting quickly with HC and CO in the exhaust gas, and becomes N2. Incidentally, HC and CO are oxidized by reducing NO2 and NO to become H2O and CO2. That is, HC, CO, and NOx in the exhaust can be purified by appropriately adjusting the oxygen concentration and HC component in the exhaust introduced into the catalyst casing 42 (NOx catalyst 41).
[0029]
In addition, various sensors are attached to each part of the engine 1, and signals related to the environmental conditions of the part and the operating state of the engine 1 are output.
[0030]
That is, the rail pressure sensor 70 outputs a detection signal corresponding to the fuel pressure stored in the common rail 12. The fuel pressure sensor 71 outputs a detection signal corresponding to the pressure (fuel pressure) of the fuel introduced into the metering valve 16 among the fuel flowing through the added fuel passage P2. The air flow meter 72 outputs a detection signal corresponding to the flow rate Gn of the intake air downstream of the throttle valve 32 in the intake system 30. The A / F sensor 73 outputs a detection signal that continuously changes according to the oxygen concentration in the exhaust gas downstream of the catalyst casing 42 of the exhaust system 40. The exhaust temperature sensor 74 also outputs a detection signal corresponding to the exhaust temperature (exhaust temperature) Tex downstream of the catalyst casing 42 of the exhaust system 40.
[0031]
The accelerator opening sensor 75 is attached to an accelerator pedal (not shown) of the engine 1 and outputs a detection signal corresponding to the depression amount Acc of the pedal. The crank angle sensor 76 outputs a detection signal (pulse) every time the output shaft (crankshaft) of the engine 1 rotates by a certain angle. Each of these sensors 70 to 76 is electrically connected to an electronic control unit (ECU) 80.
[0032]
The ECU 80 includes a central processing unit (CPU) 81, a read only memory (ROM) 82, a random access memory (RAM) 83, a backup RAM 84, a timer counter 85, and the like. These units 81 to 85 and an A / D converter are provided. The external input circuit 86 including the external output circuit 87 includes a logical operation circuit configured by being connected by a bidirectional bus 88.
[0033]
The ECU 80 configured as described above inputs the detection signals of the various sensors via an external input circuit, performs basic control on the fuel injection of the engine 1 based on these signals, and adds the addition of the reducing agent. Various operation controls such as reducing agent addition control relating to determination of timing and supply amount are executed.
[0034]
Next, the fuel supply system 10 among the main components of the engine 1 will be described in more detail with a focus on the supply pump 100.
[0035]
FIG. 2 schematically shows the main internal structure of the supply pump 100.
[0036]
As shown in FIG. 2, the supply pump 100 includes a feed pump 110 and a high-pressure pump 120 therein.
[0037]
The feed pump 110 (developed by 90 ° in the figure) is configured to include a cylindrical housing 111 and an internal rotor 112 provided in the housing 111 and having vanes on the outer peripheral surface thereof. As the internal rotor 112 rotates, the fuel in the fuel tank 200 is pumped up through the fuel passage P3 and sent out to the fuel passage P4.
[0038]
The fuel passage P4 branches into fuel passages P5 and P6. A pressure regulating valve 113 is provided in the middle of the fuel passage P5. The pressure regulating valve 113 is a check valve that opens only when a fuel pressure exceeding a predetermined value is applied in the direction of the arrow α and allows fuel flow in the direction of the arrow α. The fuel passing through the valve 113 is returned to the fuel passage P3 and fed into the feed pump 110 again.
[0039]
The other fuel passage P6 branched from the fuel passage P4 further branches to the added fuel passages P2 and P7. The addition fuel passage P2 communicates with the fuel addition nozzle 17 via the metering valve 16 as described above with reference to FIG. On the other hand, the fuel passage P <b> 7 is connected to the high-pressure pump 120.
[0040]
The high-pressure pump 120 (developed at 90 ° in the figure) includes a ring-shaped outer ring portion 122 and an inner rotor 123 that rotates within the outer ring portion 122. A through hole 123a is formed in the inner rotor 123 along the radial direction, and two plungers 123b and 123c facing each other from each open end of the hole 123a toward the center are formed in the through hole 123a. Is attached. A high pressure chamber 124 is formed by the front end surfaces of the two plungers 123b and 123c facing each other and the inner peripheral surface of the through hole 123a. The high pressure chamber 124 communicates with the fuel passage P8 in addition to the fuel passage P7 described above. On the other hand, the inner peripheral surface of the outer ring portion 122 protrudes at 90 ° intervals to form a total of four cam surfaces 122a. When the internal rotor 123 rotates in the direction of the arrow B and the cam surface 122a pushes the plungers 123b and 123c, the plungers 123b and 123c are pushed in the directions of the arrows C and C ′ so The fuel is boosted. That is, the fuel introduced (withdrawn) from the fuel passage P7 is pressurized in the high-pressure chamber 124 as the internal rotor 123 rotates and is pumped to the fuel passage P8.
[0041]
The fuel passage P8 branches into engine fuel passages P1 and P10. The engine fuel passage P1 is a check valve that opens only when a fuel pressure exceeding a predetermined value is applied in the direction of the arrow β through the pressure regulating valve 125, and allows the fuel flow in the direction of the arrow β. Of the fuel pumped by the high-pressure pump 120, part of the fuel that does not pass through the pressure regulating valve 125 is returned to the fuel tank 200 through the fuel passage P10.
[0042]
Note that the internal rotor 112 of the feed pump 110 and the internal rotor 123 of the high-pressure pump 120 are rotated by the same drive shaft 130. The drive shaft 130 is connected to a crankshaft (not shown) of the engine 1 and obtains a driving force from the crankshaft. For this reason, the rotation of the drive shaft 130 of the high-pressure pump 120 and the rotation of the crankshaft of the engine 1 are accurately synchronized. Incidentally, in the present embodiment, when the crankshaft of the engine 1 rotates twice, the drive shaft 130 of the high-pressure pump 120 rotates exactly once.
[0043]
Here, the outline of the reducing agent (fuel) addition control according to the present embodiment will be described.
[0044]
In general, in a diesel engine, the air supplied to the combustion chamber and the fuel used for combustion, that is, oxygen in the air-fuel mixture are in a high concentration state in most operating regions.
[0045]
The oxygen concentration of the air-fuel mixture supplied for combustion is usually reflected in the oxygen concentration in the exhaust gas by subtracting the oxygen supplied for combustion as it is. If the oxygen concentration (air-fuel ratio) in the air-fuel mixture is high The oxygen concentration (air-fuel ratio) in the exhaust gas basically increases similarly. On the other hand, as described above, the NOx storage reduction catalyst has a characteristic of absorbing NOx when the oxygen concentration in the exhaust gas is high and reducing NOx to NO2 or NO when it is low, so that the oxygen in the exhaust gas is high. As long as it is in the concentration state, it will absorb NOx. However, there is a limit amount in the NOx absorption amount of the NOx storage reduction catalyst. When the catalyst absorbs the limit amount of NOx, NOx in the exhaust gas is not absorbed by the catalyst and passes through the catalyst casing.
[0046]
Therefore, in the internal combustion engine having the fuel addition nozzle 17 such as the engine 1, the NOx catalyst of the exhaust system 40 is further passed through the fuel addition nozzle 17 while closing the throttle valve 32 at an appropriate time to reduce the intake air amount. 41 By adding fuel upstream, the oxygen concentration in the exhaust gas is temporarily reduced, and the amount of reducing components (HC, etc.) is increased. Then, the NOx catalyst 41 reduces and releases the NOx absorbed so far into NO2 or NO, and recovers (regenerates) its own NOx absorption capability. As described above, the released NO 2 or NO reacts with HC or CO and is quickly reduced to N 2.
[0047]
At this time, NOx absorbed by itself is released in the above-described manner, and for the NOx catalyst 41 to be reduced and purified, the amount of reducing component (fuel concentration) in the exhaust gas flowing into the catalyst casing 42 and the oxygen concentration (air-fuel ratio) Thus, the efficiency of reduction and purification is determined.
[0048]
By the way, in the fuel supply system 10, the fuel delivered from the feed pump 110 is transferred through the fuel passages P4, P6, and P2, and the metering valve 16 is controlled to open and close, whereby the exhaust system 40 is discharged from the fuel addition nozzle 17. It will be injected into the inside. At this time, the fuel pressure in the fuel passages P4, P6, P2 is supplied by the feed pump 110 with a predetermined flow rate (predetermined fuel pressure), and the pressure adjusting action by the pressure adjusting valve 113 (the function of adjusting the fuel pressure so as not to exceed a predetermined value) ) Is basically maintained at a predetermined pressure at all times.
[0049]
However, a system that distributes the fuel fed from the integral feed pump 110 to the fuel introduced into the high-pressure pump 120 and the fuel introduced into the fuel addition nozzle 17 as in the fuel supply system 10 requires a plurality of feed pumps. By doing so, a great advantage in terms of mountability and cost is exhibited, but a relatively large pulsation of fuel accompanying the operation of the high-pressure pump 120 propagates to the fuel upstream of the metering valve 16 and interferes with the fuel pressure. There is an aspect that it is easy.
[0050]
Furthermore, there are the following phenomena as elements that promote such pulsation from the high-pressure pump 120.
[0051]
That is, it has been confirmed by the inventor that a temporary pressure drop occurs with the fuel injection (release) operation by the fuel addition nozzle 17.
[0052]
For example, in FIGS. 3A and 3B, when the fuel addition nozzle 17 injects fuel into the exhaust system 40, the distance between the metering valve 16 and the fuel addition nozzle 17 from the start to the end of the injection (regulation) is shown. The fuel pressure transition (downstream of the metering valve 16) (FIG. 3A) and the fuel pressure transition between the feed pump 110 and the metering valve 16 (upstream of the metering valve 16) (FIG. 3B) are the same time. It is a time chart shown on an axis.
[0053]
As shown in FIG. 3A, when the valve opening operation of the metering valve 16 is started based on the command signal of the ECU 80 (time t1), the downstream of the tuning valve 16 is synchronized with the valve opening operation. The fuel pressure rises. When the fuel pressure downstream of the metering valve 16 exceeds a predetermined pressure, the fuel addition nozzle 17 is opened to start fuel injection. Similarly, when the metering valve 16 is opened based on a command signal from the ECU 80 (time t2), the fuel pressure downstream of the tuning valve 16 decreases in synchronization with the valve opening operation. When the fuel pressure downstream of the metering valve 16 becomes equal to or lower than the predetermined pressure, the fuel addition nozzle 17 is closed and the fuel injection is terminated.
[0054]
Here, as shown in FIG. 3B, in synchronism with the start and end (time t1, t2) of the on-off valve operation of the metering valve 16, a temporary decrease in the fuel pressure upstream of the metering valve 16 is observed. It is done.
[0055]
4 and 5 show (i) pulsation propagating from the high-pressure pump 120 to the upstream of the metering valve 16 (FIGS. 4A and 5A), and (ii) described in FIG. The fuel pressure drop upstream of the metering valve 16 in synchronization with the start or end of the valve operation of the metering valve 16 (FIGS. 4B and 5B), (iii) When they occur almost simultaneously 6 is a time chart virtually showing the transition of each of (i) to (iii) on the same time axis for the fuel pressure change upstream of the metering valve 16 in FIG. 4 (FIG. 4C, FIG. 5C).
[0056]
As described above, the high-pressure pump 120 draws fuel into the high-pressure chamber 124 of the pump 120 through the fuel passage P7, boosts the pressure, and pumps it to the fuel passage P8 periodically in synchronization with the rotation of the crankshaft of the engine 1. Repeat.
[0057]
That is, as shown in FIG. 4 (a) or FIG. 5 (a), the fuel pressure upstream of the metering valve 16 decreases and subsequently increases in accordance with the drawing (intake) and pressure increase (pressure feed) operations by the high pressure pump 120. Here, when the fuel pressure drop synchronized with the opening / closing valve operation of the metering valve 16 occurs in synchronization with the fuel pressure rise by the high-pressure pump 120 (FIG. 4B), the respective fuel pressure fluctuations cancel each other, Apparently, only the fuel pressure drop due to the high-pressure pump 120 appears on the time axis (FIG. 4C).
[0058]
On the other hand, as shown in FIG. 5B, when the fuel pressure drop synchronized with the on / off valve operation of the metering valve 16 occurs in synchronization with the fuel pressure drop by the high-pressure pump 120 (FIG. 5B), In addition, the fuel pressure drop of the fuel pressure overlaps at the same time, and the fuel pressure rise by the high-pressure pump 120 also continues, so that a relatively large fuel pressure fluctuation appears on the time axis (FIG. 5C).
[0059]
As described above, the fuel pressure reduction itself associated with the fuel addition is a phenomenon in which the amount of reduction is very small and is highly reproducible both quantitatively and qualitatively. It doesn't matter much. However, as described above with reference to FIGS. 4 and 5, there is a concern that the magnitude and form of pulsation due to the propagation of pulsations caused by the drawing (inhalation) and pressure-up (pressure feeding) operations by the high-pressure pump 120 may be unstable. There is.
[0060]
When such an unstable (irregular) fuel pressure fluctuation occurs particularly at the start timing of the valve opening operation of the metering valve 16, the fuel addition control is performed with the injection amount, the addition timing, and the form (for example, vaporization state and average particle size) of the added fuel. It is difficult to precisely adjust the (diameter) from a quantitative and qualitative viewpoint.
[0061]
Therefore, in the engine 1 according to the present embodiment, when the fuel is added to the exhaust system 40 through the opening and closing of the metering valve 16, the opening timing of the metering valve 16 is determined by the high-pressure pump 120 (to the high-pressure chamber 124). Control so that it does not overlap with the inhalation timing.
[0062]
The specific control procedure will be described below.
[0063]
FIG. 6 shows the processing contents of a “fuel addition control routine” executed to control the amount and timing of addition of fuel to the exhaust system 40. This routine processing is executed through interruption at every constant crank angle through the ECU 80.
[0064]
When the processing shifts to this routine, the ECU 80 first grasps the operation state necessary for the control of the metering valve 16 related to the execution of fuel addition in step S101.
[0065]
For example, the ECU 80 determines the engine speed Ne of the engine 1 based on the output signal of the crank angle sensor 76, and the oxygen concentration in the exhaust (referred to as an exhaust air-fuel ratio for convenience) A / F based on the output signal of the A / F sensor 73. Each F is calculated. Further, the accelerator depression amount Acc, exhaust temperature Tex, and the like are grasped.
[0066]
In a succeeding step S102, it is determined whether or not to add fuel. Fuel addition is performed, for example, when the following conditions (1) to (4) are all satisfied.
(1) It is determined that the operating state of the engine 1 is suitable for fuel addition from the relationship between the engine speed Ne and the accelerator depression amount. This is a condition in which the operating state of the engine 1 is in a region where no trouble such as torque fluctuation occurs even when fuel addition is executed. For example, this condition is satisfied when decelerating.
(2) The exhaust temperature Tex is higher than a predetermined temperature (for example, 250 ° C.). This corresponds to a condition that the NOx catalyst is sufficiently activated.
(3) The NOx absorption amount of the NOx catalyst exceeds a predetermined amount. This means that the amount of NOx absorbed by the NOx catalyst has approached its limit value to some extent. This absorption amount may be estimated based on the elapsed time from the end of the previous fuel addition, the history of the exhaust air-fuel ratio A / F, the exhaust temperature Tex, and the like.
(4) The current time is not in the fuel intake timing (to the high pressure chamber 124) by the high pressure pump 120. The operation of the high-pressure pump 120 is synchronized with the rotation of the crankshaft of the engine 1, and this routine is a control procedure that is executed by interruption every constant crank angle. For this reason, it is easy to accurately grasp the current operation mode of the high-pressure pump 120 in a series of processing procedures in this routine.
[0067]
When all of the above conditions (1) to (4) are satisfied, ECU 80 determines that fuel addition should be executed, and proceeds to step S103. On the other hand, if any one of the above conditions (1) to (4) does not hold, this routine is temporarily exited.
[0068]
In step S103, when the fuel addition is performed, the exhaust air, strictly speaking, it matches the required value (target value) of the air-fuel ratio (oxygen concentration in the exhaust gas) flowing into the catalyst casing 42, and the NOx catalyst 41 An amount of added fuel and an addition pattern for releasing / reducing all NOx are determined.
[0069]
Here, the fuel addition amount is the total amount of fuel injected in one fuel addition. Further, the addition pattern is an energization waveform to the metering valve 16. This addition pattern determines the fuel injection amount distribution (including the waveform and the number of waveforms) seen on the time axis.
[0070]
Then, the ECU 80 performs energization control to the metering valve 16 according to the addition pattern determined in step S103, and adds the fuel addition amount determined in step S103 to the exhaust system 40 (step S104).
[0071]
After the processing in step S104, the ECU 80 once ends the subsequent processing.
[0072]
As described above, according to this routine for performing the fuel addition control in the above-described manner, the timing when the pulsation generated during the fuel intake operation of the high-pressure pump is propagated upstream of the metering valve 16 can be avoided, and the control related to the fuel addition can be precisely performed. The fuel is added to the exhaust system 40 by always selecting an implementation time at which performance can be reliably obtained.
[0073]
Here, in the conventional apparatus, the suction pulsation of fuel drawn into the high-pressure chamber 124 from the fuel passage P7 by the high-pressure pump 120 that operates in synchronization with the rotation of the crankshaft of the engine 1 (the pressure pulsation secondary to the engine rotation). However, the fuel addition control accuracy is lowered by irregularly interfering with the fuel pressure upstream of the metering valve 16.
[0074]
Further, the influence of the suction pulsation accompanying the operation of the high-pressure pump 120 and the decrease in the fuel pressure caused by the fuel addition (see FIG. 3) on the fuel addition control is that the operating state of the engine 1 is in the low rotation range. In some cases it was even more pronounced. This is because when the rotational speed of the engine 1 is low, the average pumping amount (flow rate) by the high-pressure pump 120 is inevitably reduced, and it takes time to recover the fuel pressure once lowered.
[0075]
Furthermore, if fuel addition is performed under such conditions, the influence of a decrease in fuel pressure upstream of the high-pressure pump 120 will spread, and this will adversely affect the boosting operation of the high-pressure pump 120 and thus the stable fuel pressure retention in the common rail 12. There was concern. The decrease in the fuel pressure in the common rail 12 causes variations in the properties of the spray injected by the fuel injection valve 13, which is not preferable for ensuring a stable combustion state of the engine 1.
[0076]
In this regard, according to the fuel addition control according to the present embodiment, the fuel addition timing (particularly the start timing of fuel addition) is set in a period in which the fuel suction pulsation by the high-pressure pump 120 does not affect the fuel addition. As a result, the preciseness and reliability of the control can be improved when fuel is added to the exhaust system.
[0077]
Accordingly, both NOx and HC in the exhaust can be reduced efficiently.
[0078]
Further, since the boosting operation of the high-pressure pump 120 and the fuel pressure in the common rail 12 are kept constant, the properties of the spray injected by the fuel injection valve 13 are also stabilized, and the engine 1 is in a stable combustion state ( Stable output) can be secured.
[0079]
In the above embodiment, control is performed so that the fuel addition start timing does not overlap with the fuel suction start timing of the high-pressure pump 120 (timing at which the plungers 123b and 123c start moving toward the outer circumferential direction of the internal rotor 123). Most preferably. This is because the fuel pressure in the upstream of the metering valve 16 accompanying the valve opening operation of the metering valve 16 (the valve opening operation of the fuel addition nozzle 17) and the upstream of the metering valve 16 (or the fuel addition nozzle in the operation of the high pressure pump 120). 17) The fluctuation of the fuel pressure in the upstream) is prevented from irregularly overlapping or not overlapping on the time axis, so that the control regarding the injection amount (including the total amount and flow rate) of the added fuel and the injection time is precise. This is because the property can be improved most effectively.
[0080]
However, as described above with reference to FIG. 3, the valve closing operation of the metering valve 16 (or the fuel addition nozzle 17) is accompanied by a decrease in the fuel pressure upstream of the metering valve 16. Therefore, an effect similar to that of the above embodiment can also be obtained by controlling the fuel addition end time and the fuel suction start time by the high-pressure pump 120 so as not to overlap.
[0081]
Further, the decrease in the fuel pressure upstream of the metering valve 16 due to the valve opening operation of the metering valve 16 (or the fuel addition nozzle 17) and the fluctuation of the fuel pressure upstream of the metering valve 16 due to the operation of the high-pressure pump 120 are on the time axis. Even if they overlap each other, if the mode has regularity and reproducibility quantitatively and qualitatively, the control of the injection amount (including the total amount and flow rate) of the added fuel and the control over injection time are sufficient. It can be secured. Therefore, even if control is performed such that the fuel addition timing is simply synchronized with the operation of the high-pressure pump 120, for example, in synchronization with a specific crank angle (rotation phase), the same as in the above embodiment. There is an effect. In addition, when applying such a control logic, the fuel addition to the exhaust system 40 is performed so as to be synchronized with the engine operation related to a specific cylinder in particular, thereby further improving the control precision relating to the fuel addition. It becomes possible to raise effectively.
[0082]
In the fuel supply system 10 according to the above-described embodiment, the high-pressure fuel boosted by the high-pressure pump 120 is temporarily held (accumulated) in the common rail 12 and injected and supplied to each combustion chamber 20 by the individual fuel injection valves 13. The configuration to be applied was applied. In contrast, for example, a device configuration having a function of distributing and supplying fuel boosted by the high-pressure pump to a plurality of fuel passages at a predetermined timing, such as a well-known distributed high-pressure pump device or a row-type high-pressure pump device, is applied. May be. In this case, when a fuel pressure exceeding a predetermined value is applied, a fuel injection nozzle that mechanically opens and supplies fuel to the combustion chamber may be connected to each of the fuel passages, and there is no need to use a common rail. Further, in this case, the fuel injection timing of the fuel injection nozzle and the operation timing of the high-pressure pump are necessarily synchronized, so that the fuel addition timing to the exhaust system and the fuel injection timing to the combustion chamber 20 Control may be performed so that they are different.
[0083]
Further, in the present embodiment, the supply pump 100 that includes the feed pump 110 and the high-pressure pump 120 integrally therein is applied. Alternatively, a feed pump and a high-pressure pump may be provided separately, and both pumps may be connected by a fuel passage, and the fuel passage may be branched halfway, and the branch passage may be guided to a fuel addition nozzle. .
[0084]
In the above-described embodiment, a so-called storage reduction type NOx catalyst is applied as the NOx catalyst, but a so-called selective reduction type NOx catalyst may be applied instead. In short, an exhaust gas purification apparatus that purifies NOx in exhaust gas by applying a catalyst having different NOx purification (reduction) action efficiency in accordance with the amount of reducing component in gas or the amount of component related thereto (for example, oxygen concentration). If so, it is possible to obtain an effect equivalent to or equivalent to that of the embodiment by applying a control structure equivalent to that used in the present embodiment.
[0085]
In the present embodiment, when adding fuel to the exhaust system, the pressure of the fuel supplied via the added fuel passage P2 is controlled by the metering valve 16, and the fuel addition nozzle 17 is opened and closed by the pressure control. A configuration for controlling the valve operation is applied. On the other hand, an electromagnetic valve or the like whose direct on / off valve operation is directly controlled through energization by the ECU 80, such as the fuel injection valve 13, may be applied as an injection valve for adding fuel. In this case, the metering valve 16 may be excluded from the device configuration, and the energization control of the ECU 80 applied to the on / off valve of the metering valve 16 in the above embodiment is the energization control applied to the on / off valve of the injection valve that performs the fuel addition. Can be replaced.
[0086]
In the above embodiment, the exhaust purification apparatus of the present invention is applied to the in-line four-cylinder diesel engine 1 as an internal combustion engine. However, the present invention is also preferably applied to a gasoline engine that performs lean combustion. be able to. Further, the invention is not limited to an in-line four-cylinder internal combustion engine.
[0087]
In the above embodiment, both the feed pump 110 and the high-pressure pump 120 provided in the supply pump 100 obtain driving force from the crankshaft of the engine 1. Instead of such a configuration, a driving force may be obtained by an intake or exhaust camshaft, a motor, or the like. In particular, when the present invention is applied to a gasoline engine that performs lean combustion, even if a high-pressure pump that can be driven with a relatively small driving force is applied, an effect equivalent to or equivalent to that of the above embodiment can be obtained. be able to.
[0088]
【The invention's effect】
As described above, according to the first aspect of the invention, the fuel addition timing is set in a period in which the fuel intake pulsation by the boosting means does not affect the fuel addition, and the fuel addition timing to the exhaust system is reduced. In implementation, it becomes possible to improve the precision and reliability of control.
[0089]
Accordingly, both NOx and HC in the exhaust can be reduced efficiently.
Since the boosting operation by the boosting means is stabilized, the fuel pressure of the fuel pumped to the combustion fuel supply means is also kept constant. Therefore, the properties of the spray injected by the combustion fuel supply means are stabilized, and a stable combustion state of the engine can be ensured.
[0090]
Further, according to the second invention, it is easy to reliably grasp the generation timing of the fuel intake pulsation by the boosting means and quantify the influence of the pulsation on the fuel addition. Further, the generation timing of the fuel intake pulsation by the boosting means is surely grasped, and the fuel addition timing is set by selecting the period during which the fuel intake pulsation by the boosting means does not affect the fuel addition. It becomes easy.
[0091]
Therefore, when the fuel is added to the exhaust system, it is possible to sufficiently secure the preciseness and reliability of the control.
[0092]
According to the third aspect of the present invention, the combustion pressure and the exhaust of the engine can be reduced without interfering with the fuel pressure fluctuation based on the operation of the catalyst addition fuel supply means and the fuel pressure fluctuation based on the operation of the combustion fuel supply means. The optimization of the purification is also planned.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a diesel engine system according to an embodiment of the present invention.
FIG. 2 is a schematic diagram schematically showing the main internal structure of the supply pump according to the embodiment;
FIG. 3 is a time chart showing the transition of the fuel pressure between the fuel addition nozzle and the metering valve and the transition of the fuel pressure between the feed pump and the metering valve on the same time axis.
FIG. 4 is a time chart showing fuel pressure changes on the same time axis that occur when the fuel suction operation of the high-pressure pump and the open / close valve operation of the metering valve are executed almost simultaneously.
FIG. 5 is a time chart showing fuel pressure changes on the same time axis that occur when the fuel suction operation of the high-pressure pump and the open / close valve operation of the metering valve are executed almost simultaneously.
FIG. 6 is a flowchart showing a fuel addition control procedure according to the embodiment;
[Explanation of symbols]
1 engine
10 Fuel supply system (fuel supply device)
12 Common rail
13 Fuel injection valve
14 Emergency shut-off valve
16 Metering valve
17 Fuel addition nozzle
20 Combustion chamber
30 Intake system
31 Intercooler
32 Throttle valve
40 Exhaust system
41 NOx catalyst
42 Catalyst casing
50 turbocharger
51 shaft
52 Exhaust side turbine wheel
53 Intake side turbine wheel
60 EGR passage
70 Rail pressure sensor
71 Fuel pressure sensor
72 Air flow meter
74 Exhaust temperature sensor
75 Accelerator position sensor
76 Crank angle sensor
80 Electronic control unit (ECU)
81 Central processing unit (CPU)
82 Dedicated memory (ROM)
86 External input circuit
87 External output circuit
88 bidirectional bus
100 Supply pump
110 Feed pump (feed means)
111 housing
112 Internal rotor
113 Pressure regulator
120 High-pressure pump (pressure increase means)
122 Outer ring part
122a Cam surface
123 Internal rotor
123a Through hole
123b, 123c Plunger
124 High pressure chamber
125 Pressure regulating valve
130 Drive shaft
200 Fuel tank
P1, P3 fuel passage
P2 fuel passage (second fuel passage)
P4, P6, P7 Fuel passage (first fuel passage)
P5, P8, P10 Fuel passage

Claims (3)

Feed means for pumping fuel from the engine fuel tank;
Boosting means for introducing and boosting the fuel pumped up by the feed means;
Combustion fuel supply means for injecting and supplying the boosted fuel to the combustion chamber of the engine;
Catalyst addition fuel supply means for injecting and pumping the pumped fuel upstream of the catalyst provided in the exhaust system of the engine;
A first fuel passage for guiding the pumped fuel to the pressure increasing means;
A fuel supply device for an engine, comprising: a second fuel passage branched from the middle of the first fuel passage and guiding the pumped fuel to the catalyst addition fuel supply means;
A fuel supply device for an engine, comprising: a timing control means for making the timing for injecting and supplying fuel from the catalyst addition fuel supply means and the timing for introducing the fuel by the boosting means differ. Feed means for pumping fuel from the engine fuel tank;
A pressure-increasing unit that operates in synchronization with the driving of the engine, introduces fuel pumped up by the feed unit, and pressurizes the fuel;
Combustion fuel supply means for injecting and supplying the boosted fuel to the combustion chamber of the engine;
Catalyst addition fuel supply means for injecting and pumping the pumped fuel upstream of the catalyst provided in the exhaust system of the engine;
A first fuel passage for guiding the pumped fuel to the pressure increasing means;
A fuel supply device for an engine, comprising: a second fuel passage branched from the middle of the first fuel passage and guiding the pumped fuel to the catalyst addition fuel supply means;
A fuel supply apparatus for an engine, comprising: a timing control means for synchronizing the fuel supply means for injecting and supplying fuel with a specific rotational phase of the engine. Feed means for pumping fuel from the engine fuel tank;
Boosting means for introducing and boosting the fuel pumped up by the feed means;
Combustion fuel supply means for injecting and supplying the boosted fuel to the combustion chamber of the engine;
Catalyst addition fuel supply means for injecting and pumping the pumped fuel upstream of the catalyst provided in the exhaust system of the engine;
A first fuel passage for guiding the pumped fuel to the pressure increasing means;
A fuel supply device for an engine, comprising: a second fuel passage branched from the middle of the first fuel passage and guiding the pumped fuel to the catalyst addition fuel supply means;
A fuel supply device for an engine, comprising: timing control means for making the timing at which the fuel supply means for catalyst addition injects and supplies fuel differs from the timing at which the fuel supply means for combustion supplies fuel.

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