JP3991717B2 - Fuel supply device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel supply device having a function of injecting and supplying a fuel held at a high pressure to a combustion chamber of an internal combustion engine.
[0002]
[Prior art]
Conventionally, this type of fuel supply apparatus includes a pressure accumulation chamber that stores a predetermined amount of fuel in a high pressure state, and a plurality of fuel injection valves that are connected to the pressure accumulation chamber through a predetermined fuel passage. And it has a function which quantitatively injects and supplies the fuel pumped to the pressure accumulating chamber by the high pressure pump to each combustion chamber of the multi-cylinder internal combustion engine through each fuel injection valve.
[0003]
In such a device configuration, the pressure of the fuel that is held in the common rail or the fuel passage that connects the common rail and the individual fuel injection valves is extremely high. Waves (reflected waves) tend to cause pulsation in the fuel in the fuel passage. The fuel pulsation thus generated in the fuel passage propagates not only to the fuel injection valve connected to the passage, but also to other fuel passages through the common rail, and the quantitativeness of fuel injection executed through each fuel injection valve is improved. Will be reduced.
[0004]
In order to solve such a problem, for example, in the fuel supply apparatus described in Japanese Patent Application Laid-Open No. 09-112380, an orifice is provided in a fuel passage that connects the common rail and each fuel injection valve, and the fuel injection valve is operated with an opening / closing valve operation. The generation of fuel pulsations that occur in this way is suppressed.
[0005]
[Problems to be solved by the invention]
By the way, in addition to the main fuel injection for generating the output of the internal combustion engine (hereinafter referred to as main injection), there is known multi-fuel injection control in which a small amount of fuel injection is performed as a sub-injection prior to or subsequent to the main injection. It has been. Multi-fuel injection control has various effects such as stabilization of engine output and improvement of exhaust characteristics. However, since multiple fuel injections must be executed for one engine combustion stroke, high accuracy is required for adjusting the fuel injection amount and the injection timing for each fuel injection.
[0006]
However, in the apparatus described in the above publication, for example, the quantitativeness of the fuel injection performed through each fuel injection can be improved to some extent by the action of damping the pressure pulsation by the orifice, but the fuel injection amount and the injection timing thereof. With respect to this control, it has been difficult to sufficiently secure the accuracy required in the multi-fuel injection control.
[0007]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a function of injecting and supplying fuel stored in a high pressure state to a combustion chamber of an internal combustion engine through a fuel injection valve. To provide a fuel supply device for an internal combustion engine that sufficiently attenuates a reflected wave generated in accordance with an opening / closing operation of a fuel injection valve and can ensure high accuracy in control of fuel injection. It is in.
[0008]
In order to achieve the above object, the present invention provides:
  A first passage communicating with a pressure accumulating chamber for storing fuel at a predetermined pressure;
  A second passage communicating with a fuel injection valve for injecting and supplying the internal combustion engine;
With
  A fuel supply device that pumps high-pressure fuel stored in the pressure accumulation chamber to a fuel injection valve through the first passage and the second passage, and supplies the fuel injection valve to a combustion chamber of an internal combustion engine;
  The first passage and the second passage are interposed between the first passage and the second passage, and according to the difference between the pressure in the first passage and the pressure in the second passage. With a flow path adjustment mechanism that makes the effective flow area of the fuel flowing between,
When the pressure in the first passage exceeds the pressure in the second passage, the flow path adjustment mechanism determines an effective flow area of the fuel flowing from the first passage to the second passage. The pressure in the second passage is larger than the effective flow area of the fuel flowing from the second passage to the first passage when the pressure in the first passage exceeds the pressure in the first passage. Because
The flow path adjusting mechanism includes a pressure chamber that is interposed between the first passage and the second passage and communicates with open ends of both passages,
A valve body provided in the pressure chamber and moving between the open ends in accordance with a difference between the pressure in the first passage and the pressure in the second passage;
A third passage formed through the valve body and communicating the two open ends with each other;
A fourth passage formed to include a part of the wall of the pressure chamber and communicating and closing both the open ends with each other as the valve body moves;
A spring member provided in the pressure chamber and biasing the valve body from the first passage side toward the second passage side;
Have
The fuel pressure in the first passage is equal to the fuel pressure in the second passage, or the fuel pressure in the first passage is higher than the fuel pressure in the second passage. The urging force of the spring member presses the valve body against the open end of the second passage, and the fuel from the first passage toward the second passage passes through the third passage and the fourth passage. Through both the passage and
When the fuel pressure in the second passage exceeds the sum of the fuel pressure in the first passage and the biasing force of the spring member, the valve body moves toward the first passage, Fuel traveling from the second passage toward the first passage passes only through the third passage.This is the gist.
[0009]
In addition, the effective flow path area of a channel | path means the gross total cross-sectional area of the flow path for the fluid which flows through the said channel | path.
[0010]
According to this configuration, the effective flow area of the fuel flowing between the two passages is made variable according to the difference between the pressure in the first passage and the pressure in the second passage, so that fuel injection from the pressure accumulation chamber It becomes possible to easily control the propagation of the pressure wave of the fuel toward the valve and the propagation of the pressure wave of the fuel from the fuel injection valve to the pressure accumulating chamber.
[0011]
In addition, the flow path adjustment mechanism is configured so that the effective flow path of the fuel flowing from the first passage to the second passage when the pressure in the first passage exceeds the pressure in the second passage. The area is larger than the effective flow area of the fuel flowing from the second passage to the first passage when the pressure in the second passage exceeds the pressure in the first passage. It is good to do.
[0012]
According to this configuration, when the pressure in the first passage exceeds the pressure in the second passage, a sufficient flow path in the direction of fuel pressure is secured, and the pressure in both passages is quickly equalized. It becomes. Therefore, high supply efficiency is ensured when high pressure fuel is supplied from the pressure accumulating chamber toward the fuel injection valve. On the other hand, when the pressure in the second passage exceeds the pressure in the first passage, the influence of the reflected wave that goes backward in the pumping direction is suitably suppressed. Therefore, when the fuel injection through the fuel injection valve is performed, the quantitativeness related to the injection amount and the injection timing can be maintained with high accuracy.
[0013]
In addition, the flow path adjustment mechanism includes a third passage that always communicates between the first passage and the second passage, a pressure in the first passage, and a pressure in the second passage. And a fourth passage that communicates and closes between the first passage and the second passage.
[0014]
According to this configuration, the effective flow area of the fuel flowing between the first passage and the second passage can be changed stepwise depending on whether the fourth passage is in communication or closed. .
[0015]
The flow path adjustment mechanism is provided between the first passage and the second passage and is connected to the open ends of both passages, and is provided in the pressure chamber. And a valve body that moves between the two opening ends in accordance with a difference between the pressure in the second passage and the pressure in the second passage, and the third passage is formed through the valve body so as to penetrate the both openings. The fourth passage is a passage that includes a part of the wall of the pressure chamber, and that communicates and closes both the open ends with the movement of the valve body. There should be.
[0016]
According to this configuration, the effective flow area of the fuel flowing between the first passage and the second passage is changed stepwise depending on whether the fourth passage is in communication or closed. This can be realized with a simple configuration. Therefore, the fuel can be efficiently pumped from the pressure accumulating chamber to the fuel injection valve while suppressing the influence of the reflected wave going backward in the fuel pumping direction. For this reason, for example, even when injection supply of high-pressure fuel to an internal combustion engine is performed at a plurality of close timings, the injection amount and injection timing can be controlled with high accuracy.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which an exhaust gas purification apparatus for an internal combustion engine according to the present invention is applied to a diesel engine system will be described.
[0018]
[Basic configuration and functions of engine system]
In FIG. 1, an internal combustion engine (hereinafter referred to as an engine) 1 is an in-line four-cylinder diesel engine system that includes a fuel supply system 10, a combustion chamber 20, an intake system 30, an exhaust system 40, and the like as main parts.
[0019]
First, the fuel supply system 10 includes a supply pump 11, a common rail 12, a fuel injection valve 13, a shutoff valve 14, a metering valve 16, a reducing agent addition valve 17, an engine fuel passage P1, an addition fuel passage P2, and the like. The
[0020]
The supply pump 11 makes the fuel pumped up from a fuel tank (not shown) into a high pressure and supplies it to the common rail 12 via the 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 11 at a predetermined pressure, and distributes the accumulated fuel to each fuel injection valve 13 through the fuel passage unit 80. 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.
[0021]
On the other hand, the supply pump 11 supplies a part of the fuel pumped up from the fuel tank to the reducing agent addition valve 17 through the addition fuel passage P2. In the added fuel passage P2, a shutoff valve 14 and a metering valve 16 are sequentially arranged from the supply pump 11 toward the reducing agent addition valve 17. The shutoff valve 14 shuts off the fuel supply P2 in an emergency and stops the fuel supply. The metering valve 16 controls the pressure (fuel pressure) PG of the fuel supplied to the reducing agent addition valve 17. The reducing agent addition valve 17 is an electromagnetic valve provided with an electromagnetic solenoid (not shown) in the same manner as the fuel injection valve 13, and the exhaust system 40 is supplied with an appropriate amount of fuel that functions as a reducing agent at an appropriate timing. Addition is supplied upstream of the catalyst casing 42.
[0022]
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.
[0023]
The engine 1 is provided with a known supercharger (turbocharger) 50. The turbocharger 50 includes rotating bodies 52 and 53 connected via a shaft 51. One rotating body (turbine wheel) 52 is exposed to exhaust in the exhaust system 40, and the other rotating body (compressor wheel) 53 is exposed to intake air in the intake system 30. The turbocharger 50 having such a configuration performs so-called supercharging in which the compressor wheel 53 is rotated using the exhaust flow (exhaust pressure) received by the turbine wheel 52 to increase the intake pressure.
[0024]
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 steplessly, and changes the flow area of the intake air under predetermined conditions. And the function of adjusting the supply amount (flow rate) of the intake air.
[0025]
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 (EGR gas) flowing through the passage, and exhaust gas that passes (refluxs) the EGR passage 60. An EGR cooler 62 for cooling is provided.
[0026]
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) is provided downstream of the communication part of the exhaust system 40 and the EGR passage 60.
[0027]
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.
[0028]
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) PG of the fuel introduced into the reducing agent addition valve 17 via the metering valve 16 among the fuel flowing through the addition fuel passage P2. The air flow meter 72 outputs a detection signal corresponding to the flow rate (intake amount) GN of air (intake air) introduced into the intake system 30. The air-fuel ratio (A / F) sensor 73 outputs a detection signal that continuously changes in accordance with the oxygen concentration in the exhaust gas upstream of the catalyst casing 42 of the exhaust system 40. The exhaust temperature sensor 74 is attached to an exhaust inflow portion of the catalyst casing 42 in the exhaust system 40, and outputs a detection signal corresponding to the exhaust temperature (exhaust temperature) TEX at the portion. The NOx sensor 75 also outputs a detection signal that continuously changes in accordance with the NOx concentration in the exhaust gas downstream of the catalyst casing 42 of the exhaust system 40.
[0029]
The accelerator position sensor 76 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 77 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 77 is electrically connected to an electronic control unit (ECU) 90.
[0030]
The ECU 90 includes a central processing unit (CPU) 91, a read only memory (ROM) 92, a random access memory (RAM) 93, a backup RAM 94, a timer counter 95, and the like. These units 91 to 95 and an A / D converter are provided. The external input circuit 96 and the external output circuit 97 are connected to each other via a bidirectional bus 98, and a logic operation circuit is provided.
[0031]
The ECU 90 configured as described above inputs the detection signals of the various sensors via an external input circuit, and controls the opening / closing valve operation of the fuel injection valve 13 based on these signals, adjusts the opening of the EGR valve 61, or Various controls relating to the operating state of the engine 1, such as adjusting the opening of the throttle valve 32, are performed.
[0032]
The common rail 12, the fuel injection valve 13, the fuel passage unit 80, etc. together constitute a fuel supply device for the engine 1 according to the present embodiment.
[0033]
[Structure and function of catalyst casing]
Next, among the components of the engine 1 described above, the structure and function of the catalyst casing 42 provided in the exhaust system 40 will be described in detail.
[0034]
The catalyst casing 42 accommodates an NOx storage reduction catalyst (hereinafter referred to as a NOx catalyst).
[0035]
The NOx catalyst is, for example, alumina (Al₂O_ThreeFor example, potassium (K), sodium (Na), lithium (Li) that functions as a NOx occlusion agent on the surface of the particulate filter (carrier). ), An alkali metal such as cesium Cs, an alkaline earth such as barium Ba and calcium Ca, a rare earth such as lanthanum (La) or yttrium (Y), and platinum Pt that functions as an oxidation catalyst (noble metal catalyst), for example. It is comprised by carrying | supporting noble metals like.
[0036]
The NOx storage agent has a characteristic of storing NOx when the oxygen concentration (exhaust air / fuel ratio) in the exhaust gas is high (lean state) and releasing NOx when the oxygen concentration in the exhaust gas is low. Further, when NOx is released into the exhaust gas, if HC, CO, or the like is present in the exhaust gas, the noble metal catalyst promotes an oxidation reaction of these HC and CO, so that NOx is an oxidizing component, and HC and CO is removed. A redox reaction as a reducing component occurs between the two. That is, HC and CO are CO₂And H₂Oxidized to O, NOx is N₂Reduced to
[0037]
On the other hand, if the NOx storage agent absorbs a predetermined limit amount of NOx even when the oxygen concentration in the exhaust gas is high, it will not absorb NOx any more. In the engine 1, before the NOx absorption amount of the NOx catalyst accommodated in the catalyst casing 42 reaches the limit amount, the reducing agent (fuel in this embodiment) is upstream of the catalyst casing 42 in the exhaust passage through the reducing agent addition valve 17. By adding and supplying NO, the control of releasing and reducing and purifying NOx absorbed in the NOx catalyst and restoring the NOx storage capacity of the NOx catalyst is repeated at predetermined intervals.
[0038]
Furthermore, the particulate filter that forms the carrier for the NOx storage agent and the noble metal catalyst purifies particulates such as soot and harmful components such as NOx contained in the exhaust gas based on the following mechanism.
[0039]
As described above, the NOx catalyst repeatedly stores, releases, and purifies NOx in accordance with the oxygen concentration in the exhaust gas and the amount of the reducing component by the cooperation of the NOx storage agent and the noble metal catalyst that are the constituent elements. On the other hand, the NOx catalyst has a characteristic of generating active oxygen as a secondary in the process of purifying NOx. When the exhaust gas passes through the particulate filter, fine particles such as soot contained in the exhaust gas are captured by the structure (porous material). Here, since the active oxygen generated by the NOx catalyst has extremely high reactivity (activity) as an oxidant, fine particles deposited on or near the surface of the NOx catalyst among the captured fine particles are the active oxygen. Reacts quickly (without emitting a luminous flame) and is purified.
[0040]
[Overview of fuel injection control]
The ECU 90 performs fuel injection control based on the operating state of the engine 1 that is grasped from detection signals of various sensors. In the present embodiment, the fuel injection control is related to the fuel injection into each combustion chamber 20 through each fuel injection valve 13 by setting parameters such as the fuel injection amount Q, the injection timing, and the injection pattern. This is a series of processes for executing the opening / closing operation of the individual fuel injection valves 13 based on the set parameters.
[0041]
The ECU 90 repeats such a series of processes every predetermined time during the operation of the engine 1. The fuel injection amount Q and the injection timing are basically set in advance based on the depression amount ACC to the accelerator pedal and the engine speed NE (a parameter that can be calculated based on the pulse signal of the crank angle sensor). The determination is made with reference to a map (not shown).
[0042]
Further, regarding the setting of the fuel injection pattern, the ECU 90 obtains engine output by performing fuel injection in the vicinity of compression top dead center for each cylinder as well as fuel output prior to main injection (hereinafter referred to as pilot injection). ) And fuel injection following the main injection (hereinafter referred to as post-injection) are performed for the selected cylinder at the time appropriately selected as the sub-injection.
[0043]
[Pilot injection]
In a diesel engine, generally, at the end of the compression stroke, the combustion chamber reaches a temperature that induces fuel self-ignition. In particular, when the engine is operating in the middle and high load region, when fuel supplied for combustion is injected into the combustion chamber all at once, the fuel burns explosively with noise. By performing the pilot injection, the fuel supplied prior to the main injection becomes a heat source (or fire type), and the heat source gradually expands in the combustion chamber and reaches combustion. The state becomes relatively slow and the ignition delay time is shortened. For this reason, noise associated with engine operation is reduced, and further, the amount of NOx in the exhaust gas is also reduced.
[0044]
[Post injection]
The fuel supplied into the combustion chamber 20 by the post injection is reformed into light HC in the combustion gas and discharged to the exhaust system 40. That is, light HC that functions as a reducing agent is added to the exhaust system 40 through post injection, and the concentration of reducing components in the exhaust is increased. The reducing component added to the exhaust system 40 reacts with NOx released from the NOx catalyst via the NOx catalyst in the catalyst casing 42 and other oxidizing components contained in the exhaust. The reaction heat generated at this time has an effect of increasing the bed temperature of the NOx catalyst.
[0045]
[Structure and function of fuel passage unit]
FIG. 2A is a side sectional view schematically showing the internal structure of the fuel passage unit 80 for supplying fuel held at a high pressure in the common rail 12 to each fuel injection valve 13.
[0046]
The internal structure of the fuel passage unit 80 flows between the first passage P10 and the second passage P20 according to the difference between the fuel pressure in the first passage P10 and the fuel pressure in the second passage P20. It has a function as a flow path adjustment mechanism that makes the effective flow area of the fuel variable.
[0047]
That is, as shown in FIG. 2A, the fuel passage unit 80 includes a first passage member 81 connected to the common rail 12 and a second passage member 82 connected to the fuel injection valve 13. It is configured by being assembled via G. A substantially cylindrical internal space (pressure chamber) S <b> 1 is formed at a portion where both the passage members 81 and 82 are assembled. Of the open ends of the through-hole (first passage) P10 formed in the first passage member 81, the internal space S1 has one open end in the internal space S1 and the other open end in the common rail 12. Communicate. Of the two open ends of the through hole (second passage) P <b> 20 formed in the second passage member 82, one open end communicates with the internal space S <b> 1 and the other open end of the fuel injection valve 13. It communicates with an internal passage (not shown). Note that the open ends of the passages P10 and P20 communicating with the internal space S1 are in an arrangement relationship facing each other. The open end of the first passage P10 communicating with the internal space S1 protrudes into the internal space S1 to form a cylindrical convex portion 81a. Further, in the internal space S1, a valve body 83 and a coil spring 84 that constantly applies a constant urging force to the valve body 83 are accommodated. The coil spring 84 is attached to the outer periphery of the convex portion 81a so as to urge the valve body 83 from the first passage P10 side toward the second passage P20 side. The arrangement of the valve body 83 in the internal space S1 is determined by a dynamic relationship between the pressure of the fuel received from the first passage P10, the pressure of the fuel received from the second passage P20, and the biasing force of the coil spring 84.
[0048]
FIGS. 2B, 2C, and 2D show the valve element 83 in the state accommodated in the internal space S1 when viewed from the first passage P10 side (front side) (FIG. 2B). It is a top view which each shows the external appearance when it sees from the side (FIG.2 (c)), and the case where it sees from the 2nd channel | path P20 side (back) (FIG.2 (d)).
[0049]
As shown in FIGS. 2B to 2D, the valve body 83 has a bottomed cylindrical shape and has a recess 83a that opens toward the first passage P10 (the common rail 12). Yes. The cylindrical valve body 83 is formed with an orifice P30 as a third passage from the back of the recess 83a to the bottom surface on the opposite side. The center line of the orifice P30 is substantially the same as the center lines of the first passage P10 and the second passage P20. That is, the first passage P10, the orifice P30, and the second passage form one passage space continuously. Further, on the bottom surface 83b of the valve body 83 facing the second passage P10, four grooves 83d are formed radially from the opening 83c of the orifice P30 toward the outer periphery of the valve body 83. .
[0050]
Next, the operation of the fuel passage unit 80 having such a configuration will be described.
[0051]
When the fuel pressure Pf1 in the first passage P10 is equal to the fuel pressure Pf2 in the second passage P20, or when the fuel pressure Pf1 exceeds the fuel pressure Pf2, it is shown in FIG. Thus, the valve body 83 is pressed against the open end of the second passage P20 by the biasing force of the coil spring 84. Under such conditions, the fuel (or pressure wave) from the common rail 12 toward the fuel injection valve 13 is formed along the orifice (third passage) P30, the outer peripheral surface of the valve body 83, and the groove 83d. It can pass through both the passage (fourth passage) (arrows in FIG. 3A).
[0052]
On the other hand, when the fuel pressure Pf2 in the second passage P20 exceeds the sum of the fuel pressure Pf1 in the first passage P10 and the biasing force of the coil spring 84, as shown in FIG. 2 moves toward the passage P20 and is fitted to the convex portion 81a. Then, since the fuel flow path formed in the state of FIG. 3A is closed, the fuel (or pressure wave) from the fuel injection valve 13 toward the common rail 12 passes only through the orifice P30. be able to.
[0053]
That is, in the fuel passage unit 80, when the fuel pressure Pf1 on the common rail 12 side (first passage P10) exceeds the fuel pressure Pf2 on the fuel injection valve 13 side (second passage P20), the fuel from the common rail 12 The flow path area of the fuel toward the injection valve 13 is substantially enlarged. On the other hand, when the fuel pressure Pf2 on the fuel injection valve 13 side exceeds the fuel pressure Pf1 on the common rail 12 side, the flow area of the fuel from the fuel injection valve 13 toward the common rail 12 is substantially reduced. It has become.
[0054]
FIG. 4 shows the transition of the command signal output by the ECU when the pilot injection and the main injection following the pilot injection are performed (when the on-off valve operation of the fuel injection valve is continuously performed twice) (FIG. 4A). FIG. 5 is an example of a time chart showing the transition of the fuel pressure in the common rail (FIG. 4B) on the same time axis. In FIG. 4B, the transition curve indicated by the alternate long and short dash line is a case where a conventional fuel passage structure is applied between the common rail and the fuel injection valve, and the transition curve indicated by the solid line is the present implementation. The fuel passage unit 80 according to the embodiment is applied.
[0055]
As shown in FIGS. 4A and 4A, when a command signal for opening the fuel injection valve (hereinafter simply referred to as a command signal) is output over a predetermined period (Δt1, Δt2), the fuel injection valve Since the valve is opened and the pressure in the common rail temporarily decreases, a negative peak appears on the time axis in FIG. In this respect, the same applies when the conventional fuel passage structure is applied and when the fuel passage unit 80 according to the present embodiment is applied.
[0056]
However, when the structure of the conventional fuel passage is applied, after the first command signal is output (after the period Δt1) and before the second command signal is output (before the period Δt2), FIG. ) A positive peak appears on the middle time axis. When the fuel injection valve opens and closes according to the first command signal, a pressure wave propagating from the common rail to the fuel injection valve is generated, and the pressure wave is reflected by the fuel injection valve and returns to the common rail with a slight delay. Therefore, it is considered that such a peak appears. If the pressure in the common rail or fuel passage fluctuates due to the pressure wave (reflected wave) returning from the fuel injection valve to the common rail, the quantitative performance of the second and subsequent fuel injections will be reduced. Will end up.
[0057]
In this respect, in the fuel passage unit 80 according to the present embodiment, when the fuel (pressure wave) moves (propagates) from the common rail 12 to the fuel injection valve 13, the pressure on the common rail 12 side is changed to the fuel injection valve 13 side. When the pressure is exceeded, the fuel flow path is expanded (see FIG. 3A), and the pressure on the common rail 12 side and the pressure on the fuel injection valve 13 side are quickly equalized from the common rail 12 to the fuel injection valve 13. Fuel moves toward. Accordingly, efficient fuel supply to the fuel injection valve 13 is performed. On the other hand, when the reflected wave propagates from the fuel injection valve 13 side to the common rail 12 side, the pressure of the fuel injection valve 13 side exceeds the pressure of the common rail 12 side, thereby reducing the fuel flow path (FIG. 3 ( b)), the propagation of the reflected wave is suppressed. For this reason, as shown by a solid line in FIG. 4 (b), it is possible to significantly reduce the fluctuation of the fuel pressure generated after the preceding fuel injection execution period Δt1. Therefore, when performing the subsequent fuel injection, the control accuracy of the injection amount and the injection timing can be improved.
[0058]
As described above, according to the fuel supply device of the present embodiment, when performing multiple fuel injections for one engine combustion stroke, the control accuracy of the injection amount and injection timing for each fuel injection And can improve reliability.
[0059]
Furthermore, when performing multiple fuel injections for one engine combustion stroke, each injection time is shortened to increase the number of fuel injections, or each time fuel injection is performed at a closer timing, etc. It is also easy to construct a precise control structure that requires higher accuracy in hardware operation performance.
[0060]
In addition, such a reflection wave attenuation effect can be reliably obtained with a simple configuration.
[0061]
Note that the decrease in the control accuracy of fuel injection caused by the reflected wave becomes more significant as the number of fuel injections continuously performed increases and the execution timing of each fuel injection approaches. For example, as the responsiveness and operation performance of the fuel injection valve with respect to the command signal increases, the number of fuel injections continuously performed is increased, the execution timing of each fuel injection is brought closer, or the control accuracy of the fuel injection amount is increased. This makes it possible to carry out more precise fuel injection control, but on the other hand, the influence of fluctuations in fuel pressure due to the reflected waves on the control system also increases.
[0062]
In other words, the reflected wave suppression function by the fuel passage unit 80 becomes more useful as the responsiveness and operation performance of the fuel injection valve with respect to the command signal increases in the device configuration to which the fuel passage unit 80 is applied.
[0063]
[Other Embodiments]
The internal structure of the fuel passage unit is not limited to that shown in FIG. 2 or 3, and various effects can be applied to achieve the same effects as those in the above embodiment. For example, as shown in FIG. 5, in the internal space S1 ′ that does not have the convex portion 81a (see FIGS. 2 and 3), the fuel pressure in the fuel passage P10 ′ on the common rail connection side and the fuel passage P20 on the fuel injection valve side. ′ Includes a valve body 83 ′ whose arrangement is determined depending on the relationship with the fuel pressure in the ′, and a structure in which the flow path area of the fuel passing through the internal space S 1 ′ changes according to the operation of the valve body 83 ′. The provided fuel passage unit 80 'can also be applied.
[0064]
In short, the passage structure is interposed between the common rail and the fuel injection valve, and flows in the passage structure according to the difference between the fuel pressure in the passage on the common rail side and the pressure in the passage on the fuel injection valve side. As long as the fuel has a function as a flow path adjusting mechanism that makes its substantial flow path area (effective flow path area) variable, at least the same effects as those of the above-described embodiment can be obtained.
[0065]
In the above embodiment, when the fuel supply device provided with the fuel passage unit 80 (80 ') is described, the pilot injection and the main injection are performed once for each engine combustion stroke. The action and effect were illustrated. However, the present invention is not limited to this. For example, when a plurality of pilot injections are performed prior to the main injection, or when post injection is performed subsequent to the main injection, a plurality of fuel injections are performed for one engine combustion stroke. No matter what control method is used, the fuel supply having the same function as the fuel passage unit 80 (80 ') in that the control accuracy of the injection amount and the injection timing for the subsequent fuel injection is improved. An effect equivalent to that of the above embodiment can be obtained using the apparatus.
[0066]
In the present embodiment, an electromagnetic valve provided with an electromagnetic solenoid (not shown) is used as the fuel injection valve 13, but a piezoelectric element that expands and contracts in response to the magnitude of an applied voltage or the like is used. Even if a so-called piezo-drive type fuel injection valve utilizing the characteristics is applied, the same effects as in the present embodiment can be obtained.
[0067]
In the present embodiment, the fuel supply apparatus of the present invention is applied to a so-called common rail type diesel engine. However, in supplying (pressure feeding) high-pressure fuel through a predetermined passage structure, The present invention can also be applied to other systems in which the influence of the backward reflected wave causes a problem in maintaining the quantitative property of the pumped fuel with high accuracy.
[0068]
【The invention's effect】
As described above, according to the present invention, the fuel flowing between the two passages according to the difference between the pressure in the first passage communicating with the pressure accumulating chamber and the pressure in the second passage communicating with the fuel injection valve. Since the effective flow path area is variable, the propagation of the pressure wave from the pressure accumulation chamber to the fuel injection valve and the propagation of the pressure wave from the fuel injection valve to the pressure accumulation chamber can be easily controlled. Become.
[0069]
Further, based on such a configuration, when supplying (pressure feeding) high-pressure fuel from the pressure accumulating chamber to the fuel injection valve, high supply efficiency is ensured while the pressure in the second passage is maintained in the first passage. When the pressure exceeds the pressure, it is possible to suitably suppress the influence of the reflected wave that goes backward in the pumping direction.
[0070]
Therefore, when the fuel injection through the fuel injection valve is performed, the quantitativeness related to the injection amount and the injection timing can be maintained with high accuracy.
[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 showing the structure of a fuel passage unit according to the embodiment.
FIG. 3 is a schematic diagram for explaining the structure and operation of the fuel passage unit according to the embodiment;
FIG. 4 is a time chart showing the correspondence between the command signal of the electronic control unit and the fuel pressure in the fuel passage unit in the embodiment.
FIG. 5 is a schematic diagram for explaining the structure and operation of a fuel passage unit according to another embodiment of the present invention.
[Explanation of symbols]
1 engine (internal combustion engine)
10 Fuel supply system
11 Supply pump
12 Common rail
13 Fuel injection valve
16 Metering valve
17 Reducing agent addition valve
20 Combustion chamber
30 Intake system
31 Intercooler
32 Throttle valve
40 Exhaust system
42 Catalyst casing
50 turbocharger
51 shaft
52 Turbine wheel
53 Compressor wheel
60 EGR passage
61 EGR valve
62 EGR cooler
70 Rail pressure sensor
71 Fuel pressure sensor
72 Air flow meter
73 Air-fuel ratio (A / F) sensor
74 Exhaust temperature sensor
75 NOx sensor
76 Accelerator position sensor
77 Crank angle sensor
80 Fuel passage unit
81, 82 passage member
81a Convex
83 Disc
83a recess
83b Bottom
83c opening
83d groove
84 Coil spring
84 Disc
90 Electronic control unit (ECU)
91 Central processing unit (CPU)
92 Read-only memory (ROM)
93 Random Access Memory (RAM)
94 Backup RAM
95 timer counter
96 External input circuit
97 External output circuit
98 bidirectional bus
P1 Engine fuel passage
P2 added fuel passage
P10 1st passage
P20 second passage
P30 Orifice (third passage)
S1 Internal space (pressure chamber)

Claims (1)

A first passage communicating with a pressure accumulating chamber for storing fuel at a predetermined pressure;
A second passage communicating with a fuel injection valve for injecting and supplying to the internal combustion engine,
A fuel supply device that pumps high-pressure fuel stored in the pressure accumulation chamber to a fuel injection valve through the first passage and the second passage, and supplies the fuel injection valve to a combustion chamber of an internal combustion engine;
The first passage and the second passage are interposed between the first passage and the second passage, and according to the difference between the pressure in the first passage and the pressure in the second passage. With a flow path adjustment mechanism that makes the effective flow area of the fuel flowing between and variable,
Before Kiryuro adjustment mechanism, effective flow area of the fuel flowing from the first passage to the passage of the second when the pressure in the first passage is higher than the pressure in the second passage When the pressure in the second passage exceeds the pressure in the first passage, compared to the effective flow area of the fuel flowing from the second passage to the first passage. And
The flow path adjusting mechanism includes a pressure chamber that is interposed between the first passage and the second passage and communicates with open ends of both passages,
A valve body provided in the pressure chamber and moving between the open ends in accordance with a difference between the pressure in the first passage and the pressure in the second passage;
A third passageway for communicating the both opening ends formed through the valve body to each other,
A fourth passage formed to include a part of the wall of the pressure chamber and communicating and closing both the open ends with each other as the valve body moves ;
A spring member provided in the pressure chamber and biasing the valve body from the first passage side toward the second passage side;
Have
The fuel pressure in the first passage is equal to the fuel pressure in the second passage, or the fuel pressure in the first passage is higher than the fuel pressure in the second passage. The urging force of the spring member presses the valve body against the open end of the second passage, and the fuel from the first passage toward the second passage passes through the third passage and the fourth passage. Through both the passage and
When the fuel pressure in the second passage exceeds the sum of the fuel pressure in the first passage and the biasing force of the spring member, the valve body moves toward the first passage, the fuel supply system of the combustion engine within the fuel toward the first passage from the second passage, characterized in <br/> to pass only the third passage.

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