JP2011038447A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit fluctuation of fuel pressure supplied to a fuel injection valve provided in an exhaust passage. <P>SOLUTION: An internal combustion engine 1 includes: the fuel injection valve 21 provided in the exhaust passage 12; a supply pump 4 supplying fuel; and a fuel pressure compensating device 30 arranged between the supply pump 4 and the fuel injection valve 21 and compensating fuel pressure supplied to the fuel injection valve 21. The fuel pressure supplied to the fuel injection valve 21 can be compensated, allowing the fluctuation of the fuel pressure to be inhibited and an amount of the fuel injected from the fuel injection valve to be accurately controlled. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an internal combustion engine, and more particularly, to an internal combustion engine provided with a fuel injection valve provided in an exhaust passage.

  For example, an exhaust purification element such as an NOx storage reduction catalyst is provided in an exhaust passage of an internal combustion engine such as a diesel engine. In order to periodically regenerate the exhaust purification element, fuel is injected and supplied into the exhaust passage from a fuel injection valve provided in the exhaust passage (see, for example, Patent Document 1).

JP 2008-112455 A

  In this case, it is desirable to accurately control the amount of fuel injected from the fuel injection valve, but it is difficult to accurately control the fuel injection amount due to pressure fluctuations of the fuel supplied to the fuel injection valve. There is a case. For example, if the fuel pressure increases and the actual fuel injection amount exceeds the target amount, an excessively rich exhaust gas is supplied to the NOx storage reduction catalyst, and the catalyst temperature is sufficiently high during the sulfur poisoning regeneration. However, there is a risk of inappropriate regeneration processing.

  Accordingly, the present invention has been made in view of such circumstances, and an object of the present invention is to provide an internal combustion engine that can suppress pressure fluctuations of fuel supplied to a fuel injection valve provided in an exhaust passage. .

  According to an aspect of the present invention, a fuel injection valve provided in an exhaust passage, a supply pump that supplies fuel, and a fuel pump provided between the supply pump and the fuel injection valve are supplied to the fuel injection valve. An internal combustion engine comprising: a fuel pressure compensator that compensates for the pressure of the fuel.

  According to this, the fuel pressure supplied to the fuel injection valve can be compensated by the fuel pressure compensator. Therefore, fluctuations in fuel pressure can be suppressed, and the amount of fuel injected from the fuel injection valve can be accurately controlled.

  Preferably, the fuel pressure compensator includes an apparatus main body into which the first pressure fuel supplied from the supply pump is introduced and the second pressure fuel supplied to the fuel injection valve is led out, and the inside of the apparatus main body A compensation piston disposed in a reciprocable manner, and an orifice formed between the apparatus main body and the compensation piston, wherein the compensation piston responds to a differential pressure between the first pressure and the second pressure. The orifice is expanded and contracted to move so as to eliminate the differential pressure.

  Thus, the pressure of the fuel supplied to the fuel injection valve, that is, the second pressure is controlled to be equal to the pressure of the fuel supplied from the supply pump, that is, the first pressure.

Preferably, the fuel pressure compensator includes an apparatus main body and a compensation piston disposed in the apparatus main body so as to be able to reciprocate.
A first chamber, a second chamber, a third chamber, and a fourth chamber are defined in the apparatus body, and the compensation piston includes a first piston that partitions the first and second chambers, and the second and second chambers. A second piston that partitions three chambers, and a third piston that partitions the third and fourth chambers,
A first pressure fuel supplied from the supply pump is introduced to the first and third chambers, and a second pressure supplied to the fuel injection valve is supplied to the second, third, and fourth chambers. Of fuel is stored,
The compensation piston moves at least by a differential pressure between the first pressure and the second pressure received by the first piston,
The third piston located in the third chamber forms an orifice between the inner wall of the third chamber and expands / contracts by the movement of the compensation piston,
The orifice is positioned between the first pressure fuel introduction section in the third chamber and the second pressure fuel introduction section in the third chamber.

  Preferably, when the second pressure becomes lower than the first pressure, the compensation piston moves in a first direction to expand the orifice to increase the second pressure, and the second pressure is increased to the first pressure. When higher than the pressure, the compensating piston moves in a second direction to reduce the orifice to reduce the second pressure.

  Preferably, the fuel pressure compensation device increases or decreases the pressure of the fuel supplied from the supply pump based on the detection means for detecting the position of the compensation piston and the position of the compensation piston detected by the detection means. And pressure adjusting means.

  The present invention exhibits an excellent effect that the pressure fluctuation of the fuel supplied to the fuel injection valve provided in the exhaust passage can be suppressed.

1 is a schematic view showing an internal combustion engine according to an embodiment of the present invention. It is sectional drawing of a fuel pressure compensator.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows an internal combustion engine (engine) according to an embodiment of the present invention. The engine 1 of this embodiment is an automobile and multi-cylinder compression ignition internal combustion engine, that is, a diesel engine. The engine 1 includes a common rail fuel injection device. That is, the fuel stored in the fuel tank 2 is sent to the high-pressure pump 5 by the feed pump 3 and the supply pump 4, and the high-pressure pump 5 pressurizes the sent fuel to a high pressure and pumps it to the common rail 6. The supply pump 4 and the high-pressure pump 5 are driven by a crankshaft 8 of the engine 1 via a power transmission member 7 such as a belt.

  The high pressure fuel stored in the common rail 6 is directly injected and supplied from the injector 9 into the combustion chamber 10 when the fuel injection valve, that is, the injector 9 is opened. The exhaust gas discharged from the combustion chamber 10 passes through the turbine 11t of the turbocharger 11, then flows through the exhaust passage 12 on the downstream side thereof, is purified as described later, and is discharged to the atmosphere. The engine 1 also includes an EGR device 13. The EGR device includes an EGR passage 15 for circulating the exhaust gas in the exhaust passage 12 (particularly in the exhaust manifold on the turbine upstream side) to the intake passage 14, an EGR cooler 16 for cooling the EGR gas flowing in the EGR passage 15, And an EGR valve 17 for adjusting the flow rate of the EGR gas. An electronically controlled intake throttle valve 49 is provided in the intake passage 14.

  The exhaust passage 12 includes an oxidation catalyst 18 that oxidizes and purifies unburned components (hydrocarbon HC and carbon monoxide CO) in the exhaust gas, and an NOx storage reduction catalyst that purifies nitrogen oxide NOx in the exhaust gas. 19 and a particulate filter (hereinafter referred to as DPF) 20 that collects PM in the exhaust gas are provided in series in order from the upstream side. The oxidation catalyst 18, the NOx catalyst 19 and the DPF 20 form first, second and third exhaust purification elements, respectively.

  The exhaust passage 12 is provided with a fuel injection valve 21 that injects fuel into the exhaust passage 12 in order to mainly regenerate the NOx catalyst 19 and the DPF 20. Hereinafter, the fuel injection valve 21 is referred to as an exhaust injector. The exhaust injector 21 is disposed in the exhaust passage 12 upstream of the oxidation catalyst 18 and downstream of the turbine 11t. At the tip of the exhaust injector 21, a nozzle part 21 </ b> A having one or more nozzles (not shown) serving as fuel outlets is formed. The nozzle part 21 </ b> A is disposed in the exhaust channel 12, and the exhaust channel 12. Exposed inside.

  Between the supply pump 4 and the exhaust injector 21, a fuel pressure compensator 30 for compensating the pressure of the fuel supplied to the exhaust injector 21 is interposed. The supply pump 4 and the fuel pressure compensator 30 are connected via a first pipe 31, and the fuel pressure compensator 30 and the exhaust injector 21 are connected via a second pipe 32.

  The engine 1 is provided with an electronic control unit (hereinafter referred to as ECU) 50 as a control means. The ECU 50 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like (not shown). The above-described injector 9, high-pressure pump 5, EGR valve 17 and exhaust injector 21 are controlled by the ECU 50. The ECU 50 receives detection signals for the accelerator opening, the engine rotation speed, and the intake air amount from an accelerator opening sensor, an engine rotation speed sensor, and an air amount sensor (not shown).

  Further, an exhaust temperature sensor 23 is provided in the exhaust passage 12 immediately before the oxidation catalyst 18, and an exhaust temperature detection signal is input from the exhaust temperature sensor 23 to the ECU 50.

  In the middle of the exhaust passage 12, a bent pipe portion 12A is formed as a bent portion that is bent for the convenience of in-vehicle layout, and an exhaust injector 21 is provided in the bent pipe portion 12A. In the present embodiment, the bending angle of the curved pipe portion 12A is about 90 °, but this bending angle can be arbitrarily set.

  A straight pipe portion 12B is connected to the downstream side of the curved pipe portion 12A as a straight portion, and an oxidation catalyst 18, a NOx catalyst 19 and a DPF 20 are provided in the straight pipe portion 12B. The exhaust injector 21 is attached to the outer corner portion of the curved pipe portion 12A substantially parallel to the central axis of the straight pipe portion 12B, and is arranged so that the nozzle portion 21A at the tip of the exhaust injector 21 faces the oxidation catalyst 18. The fuel injected from the injection port of the exhaust injector 21 can reach the oxidation catalyst 18 without hitting the inner wall of the exhaust passage 12 as much as possible.

  Regarding each exhaust purification element, the oxidation catalyst 18 is formed by dispersing a large number of noble metals such as platinum in the coating material on the surface of the base material, and oxidizes and purifies HC and CO in the exhaust. However, in the case of a diesel engine, the air-fuel ratio A / F of the exhaust gas is significantly leaner than the stoichiometric air-fuel ratio (for example, 14.6), and the excess air ratio λ is greater than 1. Therefore, the amount of HC and CO contained in the exhaust is relatively small. In the case of a diesel engine, the exhaust temperature is relatively low, and the main NOx catalyst 19 and DPF 20 catalyst are difficult to activate. Therefore, the exhaust gas is heated by the oxidation heat of HC and CO, the NOx catalyst 19 and the DPF 20 are heated by this exhaust gas, and the oxidation catalyst 18 is provided to promote the activation of both.

Next, the NOx storage reduction catalyst (LNT: Lean NOx Trap) 19 is configured by supporting a noble metal such as platinum Pt and a NOx absorbing component on the surface of a base material made of an oxide such as alumina Al ₂ O _3. ing. The NOx absorption component is composed of at least one selected from alkali metals such as potassium K, sodium Na, lithium Li, and cesium Cs, alkaline earths such as barium Ba and calcium Ca, and rare earths such as lanthanum La and yttrium Y. .

The NOx catalyst 19 has a NOx absorption / release action. That is, when the air-fuel ratio of the exhaust gas supplied to the catalyst is leaner than the stoichiometric air-fuel ratio (when the catalyst is in an oxygen-excess atmosphere and the excess air ratio λ is greater than 1), the catalyst converts NOx in the exhaust gas to the nitrate content. Occlude in shape. On the other hand, when the air-fuel ratio of the exhaust gas supplied to the catalyst is the stoichiometric air-fuel ratio or richer (when the catalyst is in an oxygen-deficient atmosphere and the excess air ratio λ is 1 or less), the catalyst releases the stored NOx. . The released NOx reacts with the reducing agent (mainly HC) contained in the atmospheric gas in the catalyst and is reduced to N ₂ . This prevents NOx from being discharged into the atmosphere.

  When the NOx catalyst 19 occludes NOx until it is saturated (full), it cannot occlude NOx. Therefore, in order to recover or maintain the NOx storage capacity of the NOx catalyst 19, NOx regeneration for releasing the stored NOx from the NOx catalyst is periodically executed. At this time, rich spike is executed by injecting fuel from the exhaust injector 21 to enrich the air-fuel ratio of the exhaust gas (that is, making the air-fuel ratio of the exhaust gas smaller than the stoichiometric air-fuel ratio).

On the other hand, due to the sulfur (S) content contained in the fuel, the NOx catalyst 19 may occlude the sulfur component in the exhaust gas as a sulfate such as BaSO ₄ and poison (S poison). . When S poisoning occurs, the NOx occlusion ability decreases. Therefore, S poisoning regeneration or S purge for desorbing sulfate from the NOx catalyst is performed. Also at this time, fuel is injected from the exhaust injector 21 to enrich the air-fuel ratio of the exhaust gas. However, since sulfate is more stable than nitrate, it is not detached from the catalyst only by enriching the exhaust air-fuel ratio. In order to desorb the sulfate, it is necessary to place the NOx catalyst at a high temperature (for example, 400 ° C. or higher) and then put it in a rich atmosphere. Therefore, a rich spike intended for high temperature enrichment is referred to as a high temperature rich spike. The released sulfate is decomposed into sulfur oxide (SOx) in the catalyst. Since NOx regeneration can be performed at a lower temperature than S poisoning regeneration (for example, about 200 to 300 ° C.), NOx regeneration is simultaneously performed when S poisoning regeneration is performed.

  Next, the DPF 20 collects and removes particulate matter (PM) contained in the exhaust, and is a so-called wall flow type in which both ends of the honeycomb-shaped heat-resistant substrate are alternately closed in a checkered pattern. Any type of filter that physically collects PM can be used, such as a filter having a mesh shape or a foam shape. In the present embodiment, a so-called continuous regeneration type DPF with a catalyst in which a noble metal such as Pt is supported inside the DPF is used. In this case, HC in the exhaust gas supplied to the DPF is oxidized and burned by the catalytic action, and at this time, PM accumulated in the DPF is burned and removed.

  The DPF can operate even at a relatively low temperature. However, when the amount of accumulated PM exceeds a predetermined amount, it is necessary to perform filter regeneration for forcibly removing the PM to recover the PM collecting ability. When performing this filter regeneration, fuel is injected from the exhaust injector 21 to enrich the air-fuel ratio of the exhaust gas. The amount of PM accumulated in the DPF 20 is estimated by the ECU 50 based on the detection value of the differential pressure sensor 32 shown in FIG.

  During NOx regeneration, fuel is injected from the exhaust injector 21 for a relatively short time (for example, about several seconds to several tens of seconds). On the other hand, at the time of S poisoning regeneration, fuel is injected intermittently or continuously from the exhaust injector 21 for a relatively long time (for example, about several tens of minutes). Then, a part of HC in the exhaust is first oxidized and burned by the oxidation catalyst 18, and rich high-temperature exhaust gas containing the remaining HC is discharged from the oxidation catalyst 18. The rich high-temperature exhaust gas heats the NOx catalyst 19 to a high temperature, and the sulfate stored in the NOx catalyst 19 is desorbed and decomposed by HC.

  Also during filter regeneration, the DPF 20 is heated on the same principle as during S poison regeneration, and the deposited PM is combusted simultaneously with the combustion of HC supplied to the DPF 20 in the DPF 20. However, at this time, sufficient oxygen is required for the combustion of the deposited PM, so it is preferable to intermittently inject fuel from the exhaust injector 21. This is because necessary oxygen can be supplied to the DPF 20 when fuel is not injected.

  Next, the fuel pressure compensator 30 will be described with reference to FIG.

  The fuel pressure compensation device 30 includes a device main body 61 and a compensation piston 62 disposed in the device main body 61 so as to be able to reciprocate. The apparatus main body 61 is connected to a first pipe 31 leading to the supply pump 4 and a second pipe 32 leading to the exhaust injector 21. The compensation piston 62 is movable in a first direction A parallel to the axial direction of the compensation piston 62 toward the right side in the figure and a second direction B toward the left side in the figure. The first direction A and the second direction B are opposite to each other. Hereinafter, the left side in the figure is referred to as “front”, and the right side in the figure is referred to as “rear”.

  In the apparatus main body 61, a first chamber 63, a second chamber 64, a third chamber 65, and a fourth chamber 66 are defined. The compensation piston 62 includes a first piston 67 that partitions the first and second chambers 63, 64, a second piston 68 that partitions the second and third chambers 64, 65, and a third and fourth chambers 65, 66. And a third piston 69 for partitioning. These chambers and pistons are all coaxial.

  The first piston 67 and the second piston 68 are adjacent to each other, and the second piston 68 and the third piston 69 are connected via a shaft 70. The first chamber 63 and the second chamber 64 are formed of a common first hole 71 having a constant inner diameter D1, and a first piston 67 is slidably disposed in the first hole 71 so that the first chamber 63 and the second chamber 64 are in contact with each other. A liquid-tight seal is formed between the two chambers 64. The third chamber 65 and the fourth chamber 66 are also formed of a common second hole 72 having an inner diameter D2, and the rear end portion of the second piston 68 is slidably disposed in the second hole 72. And the third chamber 65 are sealed in a liquid-tight manner. The inner diameter D1 of the first hole 71 is larger than the inner diameter D2 of the second hole 72.

  A diameter-enlarged portion 73 is formed in a substantially middle portion of the second hole 72 in the axial direction. The third chamber 65 and the fourth chamber 66 are inserted in a slidable manner, and a liquid-tight seal is provided between them. On the other hand, a relatively small gap is formed between the corner portion positioned at the peripheral edge portion of the front end surface of the third piston 69 and the corner portion positioned at the peripheral edge portion of the front end surface of the enlarged diameter portion 73, An expandable / reducible orifice 74 is formed. The shaft 70 is disposed in a portion of the second hole 72 adjacent to the enlarged diameter portion 73 on the front side.

  The first and third chambers 63 and 65 are introduced with the fuel having the first pressure P1 supplied from the supply pump 4. That is, the outlet portion of the first pipe 31 is branched, and the branch pipes 31A and 31B are communicated with the first and third chambers 63 and 65 via the inlets formed in the apparatus main body 61, respectively.

  From the second, third, and fourth chambers 64, 65, 66, fuel of the second pressure P2 supplied to the exhaust injector 21 is derived. That is, the inlet portion of the second pipe 32 is branched, and the branch pipes 32A, 32B, and 32C are connected to the second, third, and fourth chambers 64, 65, and 66 through the outlets formed in the apparatus main body 61. Each communicates. In each of the chambers 64, 65, and 66, the fuel at the second pressure P2 supplied to the exhaust injector 21 is stored.

  In particular, the branch pipe 31 </ b> B of the first pipe 31 is connected to and communicated with the enlarged diameter portion 73. Further, the branch pipe 32 </ b> B of the second pipe 32 is connected and communicated with a portion of the second hole 72 adjacent to the front side with respect to the enlarged diameter portion 73. Therefore, the orifice 74 is positioned between the fuel introduction portion at the first pressure P1 in the third chamber 65 and the fuel lead-out portion at the second pressure P2 in the third chamber 65.

  Further, the fuel pressure compensation device 30 includes a position sensor 75 for detecting the position of the compensation piston 62 (particularly the relative position with respect to the device main body 61). The position sensor 75 is installed on the front end surface of the apparatus main body 61 and detects the position of the metal rod 76 that extends forward from the compensation piston 62 and protrudes out of the apparatus main body 61. For example, a capacitance type sensor is used as the position sensor 75, and the position of the rod 76 and the compensation piston 62 is detected from the capacitance of the coil that changes in accordance with the position of the rod 76. As the position sensor 75, other configurations can be used. A position detection signal from the position sensor 75 is sent to the ECU 50.

  Further, the fuel pressure compensation device 30 has a pressure adjusting device 77 for increasing or decreasing the pressure P1 of the fuel supplied from the supply pump 4. The pressure adjusting device 77 includes another branch pipe 31C branched from the first pipe 31, a pressure increasing pipe 78 (not shown in FIG. 1) for introducing the fuel supplied from the high-pressure pump 5, and fuel. A return pipe 79 (not shown in FIG. 1) for returning to the fuel tank 2 is connected. The fuel pressure compensation device 30 includes an electromagnetic valve that switches the connection state of these pipes and adjusts the fuel flow rate. The pressure adjusting device 77 is controlled by the ECU 50.

  Normally, the pressure adjustment device 77 is in a stopped state in which fuel pressure adjustment is not performed. On the other hand, when the pressure adjusting device 77 is activated, the pressure adjusting device 77 connects the pressure increasing pipe 78 to the branch pipe 31C when the fuel pressure P1 is increased, and appropriately supplies the high pressure fuel sent from the high pressure pump 5 to the pressure adjusting apparatus 77. Discharge into the branch pipe 31C at a flow rate. Conversely, when the fuel pressure P1 is reduced, the pressure regulator 77 connects the return pipe 79 to the branch pipe 31C, and discharges the fuel of the first pressure P1 sent from the branch pipe 31C to the fuel tank 2 at an appropriate flow rate. . Thereby, the pressure of the fuel supplied to the fuel pressure compensator 30 is appropriately adjusted from P1.

  In particular, the ECU 50 controls the pressure adjustment device 77 based on the position detection signal output from the position sensor 75. This point will be described later.

  Next, the operation of the fuel pressure compensator 30 will be described. Here, it is assumed that the pressure adjusting device 77 is in a stopped state.

  First, the fuel having the first pressure P1 sent from the supply pump 4 is introduced into the first and third chambers 63 and 65. The fuel at the second pressure P2 to be supplied to the exhaust injector 21 is stored in the second, third, and fourth chambers 64, 65, 66. Since the upstream and downstream portions of the orifice 74 in the third chamber 65 are communicated by the orifice 74, the first pressure P1 and the second pressure P2 are equal. The force acting on the front surface of the first piston 67 (= pressure × area) is equal to the force acting on the rear surfaces of the first piston 67 and the second piston, and the force acting on the front and rear surfaces of the third piston 69 is also equal. Therefore, the compensation piston 62 is in a pressure balance state and does not move in either the first direction A or the second direction B.

  It is assumed that the second pressure P2 becomes lower than the first pressure P1 from the pressure balance state, for example, when the exhaust injector 21 starts fuel injection. Then, the pressure in the second chamber 64 becomes lower than the pressure in the first chamber 63, and the compensation piston 62 moves in the first direction A by at least the differential pressure generated before and after the first piston 67.

  Then, the orifice 74 expands, and more fuel of the first pressure P1 in the enlarged diameter portion 73 on the upstream side of the second hole 72 adjacent to the downstream side of the orifice 74, that is, the front side of the enlarged diameter portion 73. It will flow into the part. The inflowed fuel is also supplied to the second and fourth chambers 64 and 66 through the branch pipes 32A to 32C.

  Therefore, the pressure in the third chamber 65 on the downstream side of the orifice 74, and thus the second and fourth chambers 64 and 66, immediately returns to the first pressure P1. And again, a pressure balance state is obtained. Thus, the pressure P2 of the fuel supplied to the exhaust injector 21 is held constant at the first pressure P1 except for a moment when the decrease occurs. During execution of fuel injection, the fuel at a constant pressure P1 continues to be supplied to the exhaust injector 21.

  On the other hand, if the second pressure P2 becomes higher than the first pressure P1 for some reason from the pressure balance state, the operation is reversed. That is, the pressure in the second chamber 64 and the third chamber 65 on the downstream side of the orifice 74 becomes higher than the pressure in the first chamber 63, and the compensation piston 62 moves in the second direction B.

  Then, the orifice 74 is reduced or closed, and the passage of fuel through the orifice 74 is suppressed or stopped. During this time, if fuel is injected from the exhaust injector 21, the second pressure P2 gradually decreases.

  Therefore, the pressure in the third chamber 65 on the downstream side of the orifice 74, and thus the second and fourth chambers 64 and 66, immediately returns to the first pressure P1 and drops. And again, a pressure balance state is obtained. In this way, the pressure of the fuel supplied to the exhaust injector 21 is also kept constant at the first pressure P1 except for the moment when the increase occurs.

  By the way, since the supply pump 4 is driven by the engine, the discharge pressure P1 changes according to the engine speed. The first pressure P1 also increases or decreases according to the increase or decrease of the engine speed. However, since the upstream and downstream sides of the orifice 74 are communicated by the orifice 74 in the third chamber 65, the second pressure P2 increases and decreases according to the increase and decrease of the first pressure P1, and both are equal. That is, the pressure balance state does not collapse even when the engine speed changes, and the second pressure P2 for the exhaust injector 21 is kept constant at the first pressure P1. More specifically, the second pressure P2 is different from the first pressure P1 only at the moment when both pressures are transiently or rapidly shifted, such as when the fuel injection of the exhaust injector 21 is started, and thereafter both pressures are immediately equal. It is considered to be. It is considered that the difference between the two pressures does not substantially occur in a gradual pressure change such as a change in pump discharge pressure caused by a change in engine rotation speed.

  On the other hand, the exhaust injector 21 deteriorates with time as it is used, and may become abnormal due to some cause. The exhaust injector 21 also has original individual differences and variations. Due to such deterioration, abnormality, variation, and the like, the exhaust injector 21 may cause an injection amount deviation. For example, if the injection port expands due to deterioration, even if the ECU 50 sends a drive pulse corresponding to the target amount, the actual injection amount increases from the target amount. Or, conversely, if the nozzle is clogged due to foreign matters such as deposits or the movement of the needle valve becomes sluggish, even if the ECU 50 sends a drive pulse corresponding to the target amount, the actual injection amount decreases from the target amount.

  Therefore, in the present embodiment, such a deviation in the injection amount is corrected by the pressure adjusting device 77. The movement amount or displacement amount of the compensation piston 62 before and after the start of fuel injection by the exhaust injector 21 is detected by the ECU 50 based on the signal of the position sensor 75. For example, when there is an increase deviation in which the actual injection amount increases from the target amount, the decrease amount of the second pressure P2 at the start of fuel injection is larger than when the increase does not occur, and the displacement of the compensation piston 62 The amount is large. Therefore, the ECU 100 controls the pressure adjusting device 77 so as to decrease the first pressure P1 more as the displacement amount becomes larger. Specifically, the return pipe 79 is connected to the branch pipe 31 </ b> C, and the fuel at the first pressure P <b> 1 sent from the supply pump 4 is discharged to the fuel tank 2 as appropriate. At this time, the pressure reduction amount and the discharge amount are adjusted so as to obtain the second pressure P2 such that the actual injection amount becomes equal to the target amount. As a result, the increase in displacement can be corrected and the accuracy of fuel injection control for the exhaust injector 21 can be improved.

  On the other hand, when there is a decrease in amount that causes the actual injection amount to decrease below the target amount, the reverse is true. That is, when there is a decrease in the amount of displacement, the amount of decrease in the second pressure P2 at the start of fuel injection is small and the amount of displacement of the compensation piston 62 is small as compared with the case where it does not occur. Therefore, the ECU 100 controls the pressure adjusting device 77 so as to increase the first pressure P1 more as the displacement amount becomes smaller. Specifically, the pressure increasing pipe 78 is connected to the branch pipe 31 </ b> C, and an appropriate amount of higher-pressure fuel sent from the high-pressure pump 5 is supplied to the fuel at the first pressure P <b> 1 sent from the supply pump 4. At this time, the pressure increase amount and the supply amount are adjusted so as to obtain the second pressure P2 such that the actual injection amount becomes equal to the target amount. This also corrects the amount-of-loss shift and improves the accuracy of fuel injection control for the exhaust injector 21.

  When the actually detected displacement amount of the compensation piston 62 is outside a predetermined appropriate range, the ECU 100 operates the pressure adjustment device 77 as described above to execute the injection amount deviation correction. When the amount of displacement is within the appropriate range, it can be considered that there is substantially no injection amount deviation, so the pressure adjusting device 77 is stopped and the injection amount deviation correction is not executed.

  By the way, the displacement amount increases as the degree of increase in displacement increases, and the displacement amount decreases as the degree of decrease in displacement increases. Therefore, abnormality diagnosis of the exhaust injector 21 can be executed using this characteristic. In this case, the ECU 50 diagnoses the exhaust injector 21 as abnormal when the amount of displacement is not within a predetermined normal range. Then, a warning device such as a warning light is activated to convey this fact to the user.

  As described above, according to the present embodiment, the fuel pressure P2 supplied to the exhaust injector 21 during fuel injection of the exhaust injector 21 is automatically compensated to be equal to the first pressure P1, and Can be held constant. Therefore, it is possible to control the amount of fuel injected from the exhaust injector 21 accurately by suppressing fluctuations in the fuel pressure P2. At the time of regeneration of the exhaust purification element, the temperature and exhaust air / fuel ratio can be controlled as intended, and regeneration can be performed reliably.

  As mentioned above, although embodiment of this invention was described in detail, this invention can also employ | adopt other embodiment. For example, the internal combustion engine may be a spark ignition internal combustion engine, in particular a direct injection lean burn gasoline engine.

1 Internal combustion engine 4 Supply pump 12 Exhaust passage 21 Fuel injection valve (exhaust injector)
30 Fuel pressure compensator 50 Electronic control unit (ECU)
61 Device body 62 Compensation piston 63 First chamber 64 Second chamber 65 Third chamber 66 Fourth chamber 67 First piston 68 Second piston 69 Third piston 74 Orifice 75 Position sensor 77 Pressure adjusting device A First direction B Second Direction P1 First pressure P2 Second pressure

Claims (5)

A fuel injection valve provided in the exhaust passage;
A supply pump for supplying fuel;
A fuel pressure compensation device that is interposed between the supply pump and the fuel injection valve and compensates the pressure of the fuel supplied to the fuel injection valve;
An internal combustion engine comprising: The fuel pressure compensator includes a device main body into which the first pressure fuel supplied from the supply pump is introduced and a second pressure fuel supplied to the fuel injection valve is derived, and reciprocating motion in the device main body A compensatory piston arranged in a possible manner, and an orifice formed between the apparatus body and the compensation piston,
2. The internal combustion engine according to claim 1, wherein the compensation piston moves so as to expand and contract the orifice and eliminate the differential pressure in accordance with a differential pressure between the first pressure and the second pressure. The fuel pressure compensator includes an apparatus main body and a compensation piston disposed in the apparatus main body so as to be capable of reciprocating.
A first chamber, a second chamber, a third chamber, and a fourth chamber are defined in the apparatus body, and the compensation piston includes a first piston that partitions the first and second chambers, and the second and second chambers. A second piston that partitions three chambers, and a third piston that partitions the third and fourth chambers,
A first pressure fuel supplied from the supply pump is introduced to the first and third chambers, and a second pressure supplied to the fuel injection valve is supplied to the second, third, and fourth chambers. Of fuel is stored,
The compensation piston moves at least by a differential pressure between the first pressure and the second pressure received by the first piston,
The third piston located in the third chamber forms an orifice between the inner wall of the third chamber and expands / contracts by the movement of the compensation piston,
The orifice is located between a fuel introduction portion at the first pressure in the third chamber and a fuel lead-out portion at the second pressure in the third chamber. 2. The internal combustion engine according to 2. When the second pressure is lower than the first pressure, the compensating piston moves in a first direction to expand the orifice to increase the second pressure;
4. The method according to claim 2, wherein when the second pressure becomes higher than the first pressure, the compensation piston moves in a second direction for reducing the orifice to reduce the second pressure. 5. Internal combustion engine. The fuel pressure compensator detects the position of the compensation piston, and increases or decreases the pressure of the fuel supplied from the supply pump based on the position of the compensation piston detected by the detection means. Pressure adjusting means;
The internal combustion engine according to any one of claims 1 to 4, further comprising:

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