JP3416681B2 - Accumulator type fuel injection device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pressure accumulation type fuel injection device.

[0002]

2. Related Background Art There is known a pressure accumulating fuel injection device capable of stably supplying high pressure fuel stored in a pressure accumulator to each cylinder of a diesel engine to improve engine performance in a wide operating range. However, even when such a fuel injection device is used, if the fuel injection rate immediately after the start of fuel injection is too large, not only does engine explosive combustion take place at the beginning of combustion, but not only the engine operating noise increases. NOx in exhaust gas
Will increase.

In order to solve such a problem, a pressure accumulating fuel injection system has been proposed which injects fuel at a low fuel injection rate at the initial stage of each fuel injection cycle. The device according to this proposal, for example, by selectively communicating a low pressure accumulator that stores low pressure fuel, a high pressure accumulator that stores high pressure fuel, and a low pressure accumulator or a high pressure accumulator with an injector (fuel injection nozzle). A switching valve that switches the injection rate,
It is provided with an opening / closing valve that controls the injection start / end timing by connecting / disconnecting the injector control chamber and the fuel tank.

Regarding the fuel pressure formation in the pressure accumulator, for example, there is one which obtains low-pressure and high-pressure fuel by using a low-pressure pump and a high-pressure pump respectively driven by an engine,
Also, there is one that obtains high-pressure fuel by a high-pressure pump and regulates high-pressure fuel introduced into a low-pressure accumulator to obtain low-pressure fuel (Japanese Patent Laid-Open No. 6-93936). Further, in an accumulator fuel injection device of the type disclosed in International Publication WO98 / 09068, which obtains low-pressure fuel of a low-pressure accumulator from high-pressure fuel of a high-pressure accumulator, for example, an on-off valve for injection timing control and injection rate switching By closing both switching valves of
The fuel passage connecting the switching valve and the fuel chamber of the injector is filled with low-pressure fuel, and the low-pressure fuel is supplied to the control chamber of the injector communicating with the fuel passage to keep the injector closed, and the injection start timing has come. At this time, the on-off valve is opened to discharge the low-pressure fuel in the control chamber to the fuel tank, which causes the injector to open and the low-pressure initial injection (hereinafter,
Low-pressure injection) is performed, and when the low-pressure injection period has elapsed, the switching valve is opened, high-pressure fuel from the high-pressure accumulator is injected from the nozzle, and high-pressure main injection (hereinafter referred to as high-pressure injection) is performed. When the time comes, the switching valve is closed. In the low pressure accumulator, the high pressure fuel flowing from the fuel passage is regulated to obtain low pressure fuel.

[0005]

In such a pressure accumulating fuel injection device, when the engine operation is stopped, the fuel in the fuel passage passes through a gap around the plunger of the high pressure pump and a gap around the control chamber of the injector. And gradually flows out, and the fuel pressure in the fuel passage and the low-pressure accumulator drops to the atmospheric pressure.

When cranking is performed at the next engine start, pressurized fuel is supplied from the high-pressure pump to the high-pressure accumulator, and a switching valve for controlling injection rate switching and injection timing for performing low-pressure injection and high-pressure injection. The on-off valve for control is opened and closed. If the pressurized fuel is discharged from the high-pressure accumulator during the high-pressure injection period, the fuel pressure in the high-pressure accumulator decreases by that amount, and the fuel pressure formation in the high-pressure accumulator tends to be delayed immediately after the engine start. In addition, the fuel pressure formation in the low pressure accumulator is delayed accordingly.

Therefore, it is difficult to obtain a low-pressure fuel having a predetermined pressure higher than the valve opening pressure of the injector immediately after starting the engine. Then, the low-pressure injection is not performed until the fuel pressure in the low-pressure accumulator reaches a predetermined pressure, and the fuel injection start timing is delayed, which causes problems such as engine start failure and white smoke emission from the engine. Therefore, it is an object of the present invention to provide a pressure-accumulation type fuel injection device that optimizes the fuel injection start timing at the time of engine start when the fuel pressure formation in the low pressure accumulator is insufficient.

[0008]

According to a first aspect of the present invention, there is provided a pressure-accumulation fuel injection device, which is connected to a fuel passage downstream of a control valve for controlling discharge of high-pressure fuel in a first pressure accumulator to store low-pressure fuel. The fuel pressure in the second pressure accumulator is controlled at the valve opening timing which is the same as or advanced from the target fuel injection start timing set according to the engine operating condition until it reaches a predetermined pressure after the engine is started. It is characterized by comprising fuel control means for opening the valve.

According to this pressure-accumulation type fuel injection device, when the engine is started, the control valve is opened at the same valve opening timing as the target fuel injection start timing or at an advanced timing. Here, if the fuel injection device is configured so that both the fuel injection nozzle and the control valve are opened when the target fuel injection start timing arrives, the first pressure accumulation is performed when the target fuel injection start timing arrives. The pressurized fuel in the container is supplied to the fuel injection nozzle via the control valve in the open valve state and the fuel passage, and is injected from the fuel injection nozzle. Therefore, unlike the case of the device that executes the control to open the control valve at the valve opening timing that is delayed by the low pressure injection period from the target fuel injection start timing, unlike the case of the device that performs the control from the beginning of cranking, the valve opening timing of the control valve is advanced. According to the device of the present invention, there is no delay in the start of fuel injection even when the engine is started. Therefore, the engine startability is improved and the emission of white smoke from the engine is prevented.

In the pressure-accumulation type fuel injection device according to claim 2,
The fuel control means opens the fuel injection nozzle at the target fuel injection start timing, and at the same time opens the control valve at a valve open timing advanced from the target fuel injection start timing. According to this preferred aspect, the state where both the fuel injection nozzle and the control valve are opened is realized at the target fuel injection start timing, and therefore, fuel injection is started at the intended time even when the engine is started,
There is no delay in the start of fuel injection. Further, in the fuel injection control at the time of engine start, the drive control of the fuel injection nozzle can be performed in the same manner as in the normal case, and therefore only the drive control of the control valve needs to be changed compared to the normal case, and the control content is simple. become. Further, the valve opening timing of the control valve precedes the valve opening timing of the fuel injection nozzle, and accordingly, from the first pressure accumulator to the control valve from the opening of the control valve to the opening of the fuel injection nozzle. Pressurized fuel is supplied to the fuel passage on the downstream side, the fuel injection nozzle is opened, and at the same time, fuel injection is performed at a sufficient fuel pressure.

Contrary to the above case, the fuel injection nozzle may be opened at a valve opening timing advanced from the target fuel injection start timing and the control valve may be opened at the target fuel injection start timing. Both the fuel injection nozzle and the control valve can be opened at the target fuel injection start timing. In this case, it is preferable to advance the valve opening timing of the fuel injection nozzle by the low pressure injection period to simplify the control content.

In the pressure-accumulation type fuel injection device according to claim 3,
The predetermined pressure is a set pressure set according to the engine operating state. According to this preferable aspect, in each fuel injection cycle performed after the fuel pressure in the second pressure accumulator reaches a predetermined pressure equal to the set pressure adapted to the engine operating state, at the time of opening the fuel injection nozzle. The control valve is closed, and the pressurized fuel having the set pressure that has already been supplied from the second pressure accumulator to the fuel injection nozzle is injected from the fuel injection nozzle. That is, low pressure injection is performed. Then, when the control valve opens after a predetermined time has elapsed from the valve opening time of the fuel injection nozzle, the fuel in the first pressure accumulator is injected from the fuel injection nozzle. That is, high-pressure injection is performed. In this way, when the predetermined pressure, which is the requirement for the transition to the normal fuel injection mode, is made equal to the set pressure, the low pressure injection is performed in each fuel injection cycle immediately after the fuel pressure in the second pressure accumulator reaches the predetermined pressure. It is possible to carry out a desired fuel injection consisting of high-pressure injection.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A pressure-accumulation type fuel injection device according to a first embodiment of the present invention will be described below. The pressure-accumulation fuel injection device is, for example, an inline 6-cylinder diesel engine (not shown).
And is equipped with a high-pressure pump 1 as shown in FIGS. 1 and 2. The high-pressure pump 1 is driven by an engine and pumps up and pressurizes the fuel in the fuel tank 17, and is composed of, for example, a positive displacement plunger pump, and the fuel discharge pressure can be adjusted by adjusting the effective section of the pressure feeding stroke. ing. The pressure feeding stroke adjustment is performed, for example, by adjusting the closing timing of a solenoid valve (not shown), and the pressure feeding operation is disabled while the solenoid valve is open. The high-pressure pump in the device of the present embodiment relating to the 6-cylinder engine includes, for example, two plungers. Each plunger is associated with three cylinders and is adapted to perform three pumping strokes during one revolution of the high pressure pump shaft.

The controller 8 of the pressure accumulating fuel injection system is
The pumping stroke of the pump 1 is variably adjusted according to the engine speed Ne detected by the engine speed sensor 8a and the accelerator pedal depression amount (accelerator opening) ACC detected by an accelerator opening sensor (not shown). Further, feedback control of the pressure feeding stroke (fuel pressure) according to the actual pressure PHP in the high pressure accumulator (first accumulator) 3 detected by the pressure sensor 3a (FIG. 2) makes it suitable for the engine operating state. It is designed to get high pressure fuel.

The fuel pressurized by the pump 1 is stored in the high pressure accumulator 3. The high pressure accumulator 3 is common to each cylinder and communicates with the fuel passage 10a. A switching valve (control valve) 5 for switching the fuel injection rate, which is, for example, a two-way solenoid valve, is provided in the middle of the fuel passage 10a for each cylinder, and in the fuel passage 10a immediately downstream of the switching valve 5. A check valve 32 is provided.

A low pressure accumulator (second accumulator) 4 common to each cylinder is connected to the fuel passage 10a via a fuel passage 10b branched from the fuel passage 10a downstream of the check valve 32. A check valve 6 is provided in the middle of the fuel passage 10b, and a bypass fuel passage that bypasses the check valve 6 is attached to the fuel passage 10b, and an orifice 6a is provided in this bypass fuel passage. Fuel passage 10a
When the internal fuel pressure is higher than that in the fuel passage 10b, the fuel in the fuel passage 10a flows into the fuel passage 10b through the orifice 6a, and further to the low pressure accumulator 4. A pressure control valve 34 that operates under the control of the controller 8 is provided between the low pressure accumulator 4 and the fuel tank 17. In FIG. 2, reference numeral 4a represents a pressure sensor for detecting the fuel pressure PLP in the low pressure accumulator 4.

The controller 8 determines that the fuel pressure in the low pressure accumulator 4 is the engine speed Ne and the accelerator pedal depression amount AC.
The pressure control valve 34 is controlled on the basis of the actual pressure PLP detected by the pressure sensor 4a so that the pressure is represented by C and the engine operating condition. The injector (fuel injection nozzle) 9 for each cylinder of the engine has a control chamber 11 and a fuel chamber 12 connected to a fuel passage 10a, and the control chamber 11 is connected to a fuel tank 17 via a fuel return passage 10c. Has been done. Reference numerals 15 and 16 represent orifices. Further, reference numeral 7 represents an on-off valve for injection timing control, which is arranged in the middle of the fuel return passage 10c and is composed of, for example, a two-way solenoid valve. The on-off valve 7 may be incorporated in the injector.

The injector 9 has a needle valve 13 for opening and closing its nozzle hole and a hydraulic piston movably arranged in the control chamber 11. The needle valve 13 is biased toward the nozzle hole by a spring (not shown). ing. When fuel is supplied from the fuel passage 10a to the control chamber 11 and the fuel chamber 12 and the opening / closing valve 7 for injection timing control is closed, the resultant force of the spring force of the spring and the fuel pressure causes the hydraulic piston 14 to move. It is added to the needle valve 13 via the needle valve 13, and the needle valve 13 closes the nozzle hole against the fuel pressure in the fuel chamber 12. On the other hand, when the on-off valve 7 is opened and the fuel in the control chamber 11 is discharged to the fuel tank 17 side, the fuel pressure in the fuel chamber 12 causes the needle valve 13 to resist the spring force of the spring to the hydraulic piston 14 side. The nozzle hole is opened by moving, and the fuel in the fuel chamber 12 is injected into the combustion chamber (not shown) of the engine.

The operation of the fuel injection device having the above structure in the normal mode will be described below. Under the control of the controller 8, the fuel pressure in the high pressure accumulator 3 and the fuel pressure in the low pressure accumulator 4 are controlled so as to match the engine operating state, and the engine operating state (engine speed, accelerator pedal depression amount) is controlled. ), The fuel injection period (fuel injection start / end timing) and the low-pressure injection period are set.

As shown in FIG. 3, both the switching valve 5 and the opening / closing valve 7 are closed until the fuel injection start timing arrives, and the low pressure accumulator 4 is provided in the fuel passage 10a downstream of the switching valve 5. Low-pressure fuel is supplied, and this low-pressure fuel is supplied to the control chamber 11
And to the fuel chamber 12. Since the opening / closing valve 7 is closed, the fuel pressure supplied into the control chamber 11 is applied to the needle valve 13 via the hydraulic piston 14, and the needle valve closes the nozzle hole of the injector 9.

At the fuel injection start timing, only the on-off valve 7 is opened, the low pressure fuel in the control chamber 11 is drained through the orifice 16 and the fuel return passage 10c, and is added to the needle valve 13 through the hydraulic piston 14. When the resultant force of the fuel pressure and the spring force of the spring becomes smaller than the fuel pressure in the fuel chamber 12 that acts to push up the needle valve 13, the needle valve 13 rises and the nozzle hole opens, so that the low-pressure fuel is injected into the injector. It is injected from 9. That is, low-pressure initial injection is performed at a relatively low fuel injection rate (fuel injection amount per unit time). Due to this low-pressure injection, the amount of fuel before ignition is reduced and the premixed combustion amount is reduced, so that combustion is performed relatively slowly in the initial stage of the fuel injection period, which contributes to the reduction of the amount of NOx in the exhaust gas.

After a lapse of a predetermined period from the start of low-pressure injection, the switching valve 5 for switching the injection rate is opened while the open / close valve 7 for controlling the injection timing is held in the open state, and the fuel chamber 1
The high-pressure fuel is supplied to 2, and the high-pressure fuel is injected from the injector 9. That is, fuel injection (high-pressure main injection) is performed at an injection rate higher than the fuel injection rate at low-pressure injection.

At the fuel injection end timing, the on-off valve 7 for controlling the injection timing is closed, and the high pressure fuel supplied to the control chamber 11 is passed through the hydraulic piston 14 to the needle valve 1
3, the needle valve 13 closes the nozzle hole of the injector 9. At the end of fuel injection, the fuel injection rate falls sharply, which contributes to the reduction of black smoke (smoke) and particulate (PM) emissions from the engine. The switching valve 5 for switching the injection rate is closed together with the closing of the on-off valve 7 at the fuel injection end timing Te, or when a predetermined time (indicated by ΔTe in FIG. 8) has elapsed from the fuel injection timing end timing. To be closed.

As shown in FIG. 4, the fuel pressure in the fuel passage 10a between the injector 9 and the switching valve 5 for switching the injection rate gradually decreases from the time when the fuel injection in each fuel injection cycle ends. By the time the fuel injection in the next fuel injection cycle is started, the fuel pressure drops to a fuel pressure suitable for low-pressure injection, and the injection rate in the next low-pressure injection becomes the required value.

When the engine operation is stopped, the fuel passage 10
The fuel in a and 10b gradually flows out through the gap around the control chamber 11 of the injector 9 and the gap around the plunger of the high-pressure pump, and the fuel pressure in the fuel passages 10a and 10b and the low pressure accumulator 4 is large. Reduce to atmospheric pressure. As described above, if the fuel injection at the engine start after the engine operation is once stopped is performed in the same manner as in the case of the above-described normal mode, the fuel pressure formation in the low pressure accumulator 4 is delayed, and the injector is injected. It is not possible to immediately obtain the low-pressure fuel having a predetermined pressure higher than the valve opening pressure of No. 9, so that the low-pressure injection is not performed, the fuel injection start timing is delayed, and problems such as engine start failure occur.

Therefore, in the pressure-accumulation fuel injection device of the present invention, when the fuel is injected in the starting mode different from the normal mode at the time of engine start, and the fuel pressure formation in the low-pressure accumulator is not completed. In this case as well, the fuel injection start timing is optimized. In this embodiment, when the power is turned on at the start of engine start, the controller 8
Executes the fuel injection mode determination routine shown in FIG. 5 at a predetermined cycle.

In this determination routine, the target value (instruction value) PLPTAR of the low-pressure fuel suitable for the engine operating condition is set.
Is calculated, for example, from an engine operating state / low pressure fuel instruction value map (not shown) based on the engine speed Ne and the accelerator pedal depression amount ACC. Further, the output PLP of the pressure sensor 4a indicating the fuel pressure in the low pressure accumulator 4 is read and the actual pressure value of the low pressure fuel is detected. Then, it is determined whether or not this actual pressure value PLP has reached the instruction value PLPTAR (step S1).

The determination result in step S1 is affirmative (Yes).
If so, the fuel pressure formation in the low-pressure accumulator 4 has been completed, and therefore the above-described normal mode fuel injection is performed (step S2), and the execution of the determination routine of FIG. 5 ends. On the other hand, if the determination result in step S1 is negative (No),
Fuel formation in the low-pressure accumulator 4 is not completed, and when fuel injection in the normal mode is performed, problems such as engine start failure may occur as described above.
Fuel injection is performed in the start mode (step S
3).

In the starting mode, the injector opening period (valve opening start / end timing) is the same as in the normal mode, and the valve opening start timing of the switching valve 5 for switching the injection rate is faster than in the normal mode. Be horned. As shown in FIG. 6, in the present embodiment, the valve opening start timing of the switching valve 5 is ΔT more than the valve opening start timing of the injector 9 (target fuel injection start timing).
It is advanced by s hours. That is, the valve opening start timing of the switching valve 5 is advanced by a time equal to the sum of ΔTs and the low-pressure injection period ΔTLP as compared with that in the normal mode (shown by the broken line).

In each fuel injection cycle in the starting mode, when the valve opening start timing of the switching valve 5 comes and the switching valve drive signal is applied from the controller 8 to the switching valve 5, the switching valve 5 opens. As a result, the pressurized fuel in the high pressure accumulator 3 is supplied to the control chamber 11 and the fuel chamber 12 of the injector 9 via the fuel passage 10a. Then, when ΔTs time has elapsed from the opening start timing of the switching valve 5 and the target fuel injection start timing comes, an injector drive signal is applied from the controller 8 to the opening / closing valve 7, and the opening / closing valve 7 opens to open the control chamber 1.
The pressurized fuel in 1 is drained and the needle valve 13 of the injector 9 is pushed up. As a result, the nozzle hole is opened, and the pressurized fuel supplied to the fuel chamber 12 is injected. As described above, even in the starting mode, the opening timing of the on-off valve 7 (target fuel injection start timing) is set so as to match the engine operating state. Therefore, the opening timing of the on-off valve 7 is set as described above. At the same time, when the fuel injection is started, the fuel injection start timing becomes suitable for the engine operating state. Therefore, it is possible to prevent the injection delay due to the failure of the low-pressure injection that occurs when the fuel injection is performed in the normal mode, although the fuel pressure formation in the low-pressure accumulator 4 is not sufficient.

When the fuel pressure formation in the low pressure accumulator 4 is completed, it is determined in step S1 of the determination routine in FIG. 5 that the actual pressure value PLP in the low pressure accumulator 4 exceeds the indicated value PLPTAR. In this case, the fuel injection in the starting mode is changed to the fuel injection in the normal mode. When the actual value PLP of the fuel pressure in the low pressure accumulator 4 reaches the instruction value PLPTAR in a certain fuel injection cycle as described above, the next fuel is closed after the switching valve 5 is closed after the end of this fuel injection cycle. By the time the injection cycle is started, the fuel pressure in the fuel passage 10a decreases to a pressure corresponding to the fuel injection pressure in the low pressure injection in the normal mode. Therefore, the low-pressure injection is smoothly performed even in the first fuel injection cycle performed after the shift to the normal mode.

Hereinafter, a pressure accumulation type fuel injection device according to a second embodiment of the present invention will be described. The device of the second embodiment is common to that of the first embodiment in that the fuel injection start delay is prevented at the time of engine startup, while the injector valve opening period (valve opening start / end timing) is set to the normal mode. Compared with the device of the first embodiment that sets the same value as in the case and advances the valve opening start timing of the switching valve 5, both the valve opening period of the injector 9 and the switching valve 5 has the same value as in the normal mode. Is different from the normal mode in that the injector 9 and the switching valve 5 are opened.

In relation to this feature, in the second embodiment,
The determination routine shown in FIG. 7 is executed instead of the fuel injection mode determination routine of FIG. 5 according to the first embodiment. Since the other points are substantially the same as those of the first embodiment, description thereof will be omitted. In the fuel injection mode determination routine of FIG. 7, the injector valve opening pressure (injectable pressure) PINJ obtained from the set load of the spring applied to the hydraulic piston 14 of the injector 9 is read from the memory device of the controller 8 and stored in the low pressure accumulator 4. Actual fuel pressure PLP
Is determined to have reached the valve opening pressure PINJ (step S11), and if the determination result is affirmative, fuel injection in the normal mode is performed (step S12).

On the other hand, when it is determined in step S11 that the actual value of the fuel pressure in the low pressure accumulator 4 has not reached the instructed value, fuel injection in the starting mode is performed (step S13). In the starting mode, as in the case of the normal mode, the valve opening start timing of the injector 9 and the switching valve 5 and the low pressure injection period ΔTLP according to the engine operating state are obtained from a map not shown. Next, each of the injector valve opening start timing and the switching valve valve opening start timing is corrected to the advance side by using the low pressure injection period ΔTLP.

Therefore, in the starting mode, the opening / closing valve 7 for controlling the injection timing is opened when the injector opening start timing advanced by the low pressure injection period ΔTLP has arrived compared to the injector opening start timing in the normal mode. . here,
The fuel pressure formation in the low-pressure accumulator 4 is insufficient and therefore
The fuel pressure supplied to the fuel chamber 12 of the injector 9 is lower than the set load of the spring applied to the hydraulic piston 14. Therefore, the injector 9 is maintained in the valve closed state.

Next, when the switching valve opening start timing which is advanced by the low pressure injection period ΔTLP from the switching valve opening start timing in the normal mode comes, the switching valve 5 for switching the injection rate is opened. It As a result, the pressurized fuel in the high pressure accumulator 3 is supplied to the fuel chamber 12 through the fuel passage 10a,
The fuel pressure inside exceeds the valve opening pressure, and pressurized fuel is injected from the nozzle hole. After all, in the start mode, fuel injection is started at substantially the same time as the low pressure injection start time in the normal mode. In other words, by performing the fuel injection control in the starting mode in which the valve opening start timings of the injector and the switching valve are advanced, the fuel injection in the normal mode is performed despite the insufficient fuel pressure formation in the low pressure accumulator 4. It is possible to prevent the injection delay due to the ineffectiveness of the low-pressure injection that occurs when performing the above-mentioned procedure.

When the fuel pressure formation in the low pressure accumulator 4 progresses sufficiently, it is determined in step S11 of the determination routine of FIG. 7 that the actual value in the low pressure accumulator 4 exceeds the injectable pressure, and the normal mode is set. Transition to fuel injection. The present invention is not limited to the first and second embodiments described above, but can be modified in various ways. For example, in the first and second embodiments,
Pressure sensor 4a attached to low-pressure accumulator (second accumulator) 4
It is determined whether or not the actual value of the fuel pressure in the low pressure accumulator 4 has reached the indicated value (set pressure) PLPTAR or the injectable pressure PINJ based on the sensor output PLP from the engine start. The arrival at the set pressure or the injectable pressure may be determined based on the elapsed time from the time point or the engine speed.

[0038]

According to the first aspect of the present invention, there is provided the pressure accumulating fuel injection device in the second pressure accumulator connected to the fuel passage downstream of the control valve for controlling the discharge of the high pressure fuel in the first pressure accumulator. After the engine starts, until the fuel pressure reaches a predetermined pressure, the control valve is opened at the same valve opening timing as the target fuel injection start timing set according to the engine operating state or at an advanced timing. Therefore, when both the fuel injection nozzle and the control valve are opened, that is, the injection of the pressurized fuel from the fuel injection nozzle can be started at a desired time suitable for the engine operating condition, and thus the second pressure accumulator is obtained. It is possible to prevent a fuel injection start delay due to poor fuel pressure formation inside, and improve engine startability and the like.

In the pressure-accumulation type fuel injection device according to claim 2,
Since the fuel injection nozzle is opened at the target fuel injection start timing and the control valve is opened at a valve opening timing advanced from the target fuel injection start timing, only the control control of the control valve is changed compared to the normal case. By so doing, fuel injection can be started at a desired time even when the engine is started. Further, since the valve opening timing of the control valve precedes the valve opening timing of the fuel injection nozzle, it is possible to perform fuel injection with sufficient fuel pressure at the same time when the fuel injection nozzle opens.

In the pressure-accumulation type fuel injection device according to claim 3,
Since the predetermined pressure is a set pressure set according to the engine operating state, immediately after the fuel pressure in the second pressure accumulator reaches the predetermined pressure, low pressure premix injection and high pressure main injection are performed in each fuel injection cycle. A desired fuel injection consisting of

[Brief description of drawings]

FIG. 1 is a schematic view showing a pressure accumulation type fuel injection device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing connections between main elements of the fuel injection device shown in FIG. 1 and injectors of respective cylinders of the engine.

FIG. 3 shows changes in the injection rate with the passage of time and changes in the open / close state of each of the switching valve for switching the injection rate and the opening / closing valve for controlling the injection timing in one fuel injection cycle executed in the normal mode. It is a figure.

FIG. 4 is a diagram showing a change in fuel pressure in a fuel passage between an injector and a switching valve over time in one fuel injection cycle performed in a normal mode.

FIG. 5 is a flowchart of a fuel injection mode determination routine according to the first embodiment of the present invention.

FIG. 6 is a diagram showing changes in each of an injection waveform, an injector drive signal, and a switching valve drive signal with the passage of time during fuel injection control at engine startup according to the first embodiment.

FIG. 7 is a flowchart of a fuel injection mode determination routine according to a second embodiment of the present invention.

FIG. 8 is a diagram showing changes in each of an injection waveform, an injector drive signal, and a switching valve drive signal with the passage of time during fuel injection control at engine startup according to the second embodiment.

[Explanation of symbols]

1 high pressure pump 8 controller 8a Engine speed sensor 3 High pressure accumulator (first accumulator) 3a, 4a Pressure sensor 4 Low pressure accumulator (second accumulator) 5 Switching valve (control valve) for switching accumulator (injection rate) 9 injectors 10a, 10b Fuel passage

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02M 47/00 F02M 47/00 P 55/02 350 55/02 350E (56) Reference JP 2000-154764 (JP, A) JP 63-90658 (JP, A) JP 11-218066 (JP, A) JP 6-93936 (JP, A) JP 10-103175 (JP, A) International Publication 98/009068 ( WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02D 41/00 F02M 47/00 F02M 55/02

Claims (3)

(57) [Claims] 1. A first pressure accumulator for storing high-pressure fuel pressurized by a pump, a fuel injection nozzle connected to the first pressure accumulator through a fuel passage and injecting fuel into a combustion chamber of an engine, A control valve for controlling discharge of high-pressure fuel in the first pressure accumulator to a downstream side of the fuel passage, and a high pressure in the first pressure accumulator connected to the fuel passage downstream of the control valve via a branch passage. A second pressure accumulator that stores fuel at a pressure lower than that of the fuel, and a predetermined time has elapsed since the fuel injection nozzle was opened after the fuel pressure in the second pressure accumulator reached a predetermined pressure after the engine was started. At the same time, the control valve is opened and the control valve is closed according to the closing of the fuel injection nozzle, and the fuel pressure in the second pressure accumulator reaches the predetermined pressure after the engine is started. Up to the above Accumulator fuel injection apparatus characterized by comprising a fuel control means for opening the opening timing that is advanced from that same or a target fuel injection start timing which is set in accordance with the operating state of the gin. 2. The fuel control means opens the fuel injection nozzle at the target fuel injection start timing, and opens the control valve at a valve open timing advanced from the target fuel injection start timing. The pressure-accumulation type fuel injection device according to claim 1. 3. The pressure-accumulation fuel according to claim 1, wherein the predetermined pressure is a set pressure related to a fuel pressure in the second pressure accumulator set according to an operating state of the engine. Injection device.