JP2000154750A - Accumulator type fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To justify fuel injection starting timing at the time of starting an engine when fuel pressure formation in a low pressure accumulator of an accumulator fuel injection device is insufficient. SOLUTION: A controller 8 of a fuel injection device advances angle opening starting timing of a change-over valve 5 in each of fuel injection cycles more than injector valve opening starting timing until fuel pressure in a low pressure accumulator 4 connected to a fuel passage 10a on the downstream of the change- over valve 5 for injection rate changing reaches set pressure or advances angle respective valve opening starting timing of an injector and the change-over valve 5 more than that of a normal mode after starting an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accumulator type fuel injection device.

[0002]

2. Description of the Related Art There is known a pressure-accumulation type fuel injection device capable of stably supplying high-pressure fuel stored in an 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 excessive, rapid explosion combustion occurs at the beginning of combustion, which not only increases engine operation noise but also increases engine operation noise. NOx in exhaust gas
Increase.

In order to solve such a problem, a pressure-accumulation type fuel injection device which injects fuel at a low fuel injection rate in an initial stage of each fuel injection cycle has been proposed. The device according to this proposal selectively communicates, for example, a low-pressure accumulator for storing low-pressure fuel, a high-pressure accumulator for storing high-pressure fuel, and a low-pressure accumulator or a high-pressure accumulator to an injector (fuel injection nozzle). A switching valve for switching the injection rate,
An on-off valve is provided for controlling the start and end timings of the injection by connecting and disconnecting the control chamber of the injector and the fuel tank.

[0004] With respect to fuel pressure formation in an accumulator, for example, there is one that obtains low-pressure and high-pressure fuel by using a low-pressure pump and a high-pressure pump driven by an engine, respectively.
Further, there is a method in which high-pressure fuel is obtained by a high-pressure pump and low-pressure fuel is obtained by regulating high-pressure fuel introduced into a low-pressure accumulator (Japanese Patent Application Laid-Open No. Hei 6-93936). In a pressure-accumulation type fuel injection device disclosed in International Publication WO98 / 09068 for obtaining low-pressure fuel of a low-pressure accumulator from high-pressure fuel of a high-pressure accumulator, for example, an on-off valve for controlling an injection timing and an injection rate switching device 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 times, the on-off valve is opened to discharge low-pressure fuel in the control chamber to the fuel tank, thereby opening the injector and performing low-pressure initial injection (hereinafter, referred to as “injection”).
When the low-pressure injection period elapses, the switching valve is opened, high-pressure fuel from the high-pressure accumulator is injected from the nozzle to perform high-pressure main injection (hereinafter, referred to as high-pressure injection), and the injection ends. When the time comes, the switching valve is closed. In the low-pressure accumulator, low-pressure fuel is obtained by regulating the high-pressure fuel flowing from the fuel passage.

[0005]

In such a pressure accumulating fuel injection device, when the operation of the engine 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 decreases 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, a switching valve for controlling the injection rate and an injection timing for performing low-pressure injection and high-pressure injection. An 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 correspondingly, and the fuel pressure formation in the high-pressure accumulator tends to be delayed immediately after the start of the engine. In addition, the fuel pressure in the low-pressure accumulator is delayed.

Therefore, it is difficult to obtain a low-pressure fuel having a predetermined pressure exceeding the valve opening pressure of the injector immediately after the start of the engine. Then, the low-pressure injection is not performed until the fuel pressure in the low-pressure accumulator reaches the predetermined pressure, and the fuel injection start timing is delayed, which causes a malfunction such as a poor engine start or a discharge of white smoke from the engine. Therefore, an object of the present invention is 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 in the low-pressure accumulator is insufficient.

[0008]

According to a first aspect of the present invention, there is provided a pressure-accumulation type 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 and stores low-pressure fuel. Until the fuel pressure in the second accumulator reaches a predetermined pressure after the engine is started, the valve opening timing is controlled to be equal to or advanced from the target fuel injection start timing set in accordance with the engine operating state. It is characterized by including fuel control means for opening the valve.

According to this pressure accumulating type fuel injection device, when the engine is started, the control valve opens at the same valve opening timing as the target fuel injection start timing or at an advanced angle. 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 comes, the first pressure accumulation is performed when the target fuel injection start timing comes. The pressurized fuel in the chamber is supplied to the fuel injection nozzle via the control valve and the fuel passage in an open state, and is injected from the fuel injection nozzle. Therefore, unlike the case where the control valve is opened from the beginning of the cranking control to open the control valve at the valve opening timing delayed by the low pressure injection period from the target fuel injection start timing, the valve opening timing of the control valve is advanced. According to the device of the present invention, there is no delay in starting the fuel injection even when the engine is started, so that the engine startability is improved and the emission of white smoke from the engine is prevented.

[0010] In the pressure accumulating fuel injection device according to claim 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 opening 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, the fuel injection is started at the intended timing even when the engine is started,
There is no delay in starting fuel injection. In addition, in the fuel injection control at the time of starting the engine, the drive control of the fuel injection nozzle can be performed in the same manner as in a normal case. become. In addition, the opening timing of the control valve precedes the opening timing of the fuel injection nozzle, and therefore, from the first pressure accumulator to the control valve during the period from when the control valve opens to when the fuel injection nozzle opens. Pressurized fuel is supplied to the fuel passage on the downstream side, and fuel injection with sufficient fuel pressure is performed simultaneously with opening of the fuel injection nozzle.

Contrary to the above case, it is also possible to open the fuel injection nozzle at a valve opening timing advanced from the target fuel injection start timing and to open the control valve at the target fuel injection start timing. At the target fuel injection start timing, both the fuel injection nozzle and the control valve can be opened. In this case, it is preferable to simplify the control contents by advancing the valve opening timing of the fuel injection nozzle only during the low pressure injection period.

[0012] In the pressure accumulating fuel injection device according to claim 3,
The predetermined pressure is a set pressure set according to the operating state of the engine. According to this preferred aspect, in each fuel injection cycle performed after the fuel pressure in the second accumulator reaches the predetermined pressure equal to the set pressure suitable for the engine operating state, at the time of opening the fuel injection nozzle, The control valve is closed, and pressurized fuel at a set pressure already 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. When the control valve opens after a predetermined time has elapsed from the time when the fuel injection nozzle is opened, the fuel in the first accumulator is injected from the fuel injection nozzle. That is, high-pressure injection is performed. As described above, when the predetermined pressure, which is a requirement for shifting to the normal fuel injection mode, is equal to the set pressure, the low-pressure injection is performed in each fuel injection cycle immediately after the fuel pressure in the second accumulator reaches the predetermined pressure. It is possible to perform desired fuel injection including high-pressure injection.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a pressure accumulating fuel injection device according to a first embodiment of the present invention will be described. The accumulator type fuel injection device is, for example, an in-line six-cylinder diesel engine (not shown).
The high pressure pump 1 is provided as shown in FIGS. The high-pressure pump 1 is driven by the engine to pump up and pressurize 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 pumping stroke adjustment is performed, for example, by adjusting the closing timing of a solenoid valve (not shown), and the pumping operation is disabled while the solenoid valve is open. The high-pressure pump in the device of the present embodiment relating to a six-cylinder engine includes, for example, two plungers. Each plunger is associated with three cylinders and performs three pumping strokes during one revolution of the high pressure pump shaft.

The controller 8 of the accumulator type fuel injection device includes:
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, the pumping stroke (fuel pressure) is feedback-controlled according to the actual pressure PHP in the high-pressure accumulator (first accumulator) 3 detected by the pressure sensor 3a (FIG. 2), thereby adapting to the engine operating condition. High pressure fuel is obtained.

The fuel pressurized by the pump 1 is stored in the high-pressure accumulator 3. This high-pressure accumulator 3 is common to each cylinder and communicates with the fuel passage 10a. In the middle of the fuel passage 10a, a switching valve (control valve) 5 for switching the fuel injection rate, for example, comprising a two-way solenoid valve is provided 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) 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 for bypassing the check valve 6 is provided in the fuel passage 10b, and an orifice 6a is provided in the bypass fuel passage. Fuel passage 10a
When the fuel pressure in the fuel passage 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 flows into 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 denotes a pressure sensor for detecting the fuel pressure PLP in the low-pressure accumulator 4.

The controller 8 determines whether the fuel pressure in the low-pressure accumulator 4 is equal to the engine speed Ne and the accelerator pedal depression amount AC.
The pressure control valve 34 is controlled based on the actual pressure PLP detected by the pressure sensor 4a so that the pressure becomes suitable for the engine operating state represented by C. An 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. Have been. Reference numerals 15 and 16 represent orifices. Reference numeral 7 denotes an on-off valve for controlling the injection timing, which is arranged in the middle of the fuel return passage 10c and includes, for example, a two-way solenoid valve. Note that the on-off valve 7 may be incorporated in the injector.

The injector 9 has a needle valve 13 for opening and closing the nozzle hole, and a hydraulic piston movably disposed in the control chamber 11. The needle valve 13 is urged 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 on-off valve 7 for controlling the injection timing is closed, the resultant force of the spring force of the spring and the fuel pressure causes the hydraulic piston 14 to move. The needle valve 13 is configured to close 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 needle pressure 13 moves toward the hydraulic piston 14 against the spring force of the spring due to the fuel pressure in the fuel chamber 12. The nozzle moves to open the nozzle hole, and the fuel in the fuel chamber 12 is injected into a combustion chamber (not shown) of the engine.

The operation of the fuel injection device having the above configuration 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 be compatible with the engine operating state, and the engine operating state (engine speed, accelerator pedal depression amount) is controlled. ), A fuel injection period (fuel injection start / end timing) and a low-pressure injection period are set.

As shown in FIG. 3, the switching valve 5 and the on-off valve 7 are both closed until the fuel injection start timing comes, and the fuel passage 10a downstream of the switching valve 5 is supplied from the low-pressure accumulator 4 to the fuel passage 10a. Low-pressure fuel is supplied, and this low-pressure fuel is supplied to the control room 11.
And the fuel chamber 12. Since the on-off 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 nozzle valve of the injector 9 is closed by the needle valve.

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 applied to the needle valve 13 through the hydraulic piston 14. When the combined force of the fuel pressure and the spring force of the spring becomes smaller than the fuel pressure in the fuel chamber 12 acting to push up the needle valve 13, the needle valve 13 rises to open the nozzle hole, and the low-pressure fuel is injected. It is injected from 9. That is, low-pressure initial injection is performed at a relatively small fuel injection rate (fuel injection amount per unit time). Due to this low-pressure injection, the amount of fuel before ignition decreases and the amount of premixed combustion decreases, so that combustion in the initial stage of the fuel injection period is performed relatively slowly, contributing to the reduction of the amount of NOx in the exhaust gas.

When a predetermined period has elapsed since the start of the low-pressure injection, the switching valve 5 for switching the injection rate is opened while the on-off valve 7 for controlling the injection timing is kept open, and the fuel chamber 1 is opened.
2 is supplied with high-pressure fuel, and the injector 9 injects high-pressure fuel. That is, fuel injection (high-pressure main injection) is performed at an injection rate larger than the fuel injection rate in low-pressure injection.

When the fuel injection ends, the on-off valve 7 for controlling the injection timing is closed, and the high-pressure fuel supplied to the control chamber 11 is supplied to the needle valve 1 via the hydraulic piston 14.
Acting on 3, the needle valve 13 closes the nozzle hole of the injector 9. At the end of fuel injection, the fuel injection rate drops rapidly, contributing to a reduction in the amount of black smoke (smoke) and particulate rate (PM) emitted 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 end time. 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. Then, the fuel pressure is reduced to the fuel pressure suitable for the low-pressure injection before the fuel injection in the next fuel injection cycle is started, and the injection rate in the next low-pressure injection becomes required.

When the operation of the engine is stopped, the fuel passage 10
The fuel in the fuel passages 10a 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 becomes large. It falls to the atmospheric pressure. As described above, if the fuel injection at the time of starting the engine after the engine operation is temporarily stopped is performed in the same manner as in the above-described normal mode, the fuel pressure formation in the low-pressure accumulator 4 is particularly delayed, and the injector It is not possible to immediately obtain a low-pressure fuel having a predetermined pressure exceeding the valve opening pressure of No. 9; therefore, low-pressure injection is not performed, and the fuel injection start timing is delayed, causing a problem such as a poor engine start.

Therefore, in the pressure accumulating fuel injection device of the present invention, when the engine is started, fuel injection is performed in a start mode different from the above-described normal mode, and the fuel pressure formation in the low-pressure accumulator is not completed. In this case, the fuel injection start timing is optimized. In the present embodiment, when the power is turned on at the start of engine start, the controller 8
Performs 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 state
Is obtained, 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, for example. Further, the output PLP of the pressure sensor 4a representing 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 the actual pressure value PLP has reached the designated value PLPTAR (step S1).

The determination result in step S1 is affirmative (Yes).
If so, since the fuel pressure formation in the low-pressure accumulator 4 has been completed, the flow shifts to the fuel injection in the normal mode described above (step S2), and the execution of the determination routine in FIG. 5 ends. On the other hand, if the determination result in step S1 is negative (No),
The fuel formation in the low-pressure accumulator 4 is not completed, and if the fuel injection is performed in the normal mode, there is a possibility that a malfunction such as a poor engine start occurs as described above.
Fuel injection in the start mode is performed (step S
3).

In the start mode, the injector valve open period (start / end timing of valve opening) is made the same as in the normal mode, and the valve opening start timing of the switching valve 5 for switching the injection rate is advanced as compared with 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 longer than the valve opening start timing of the injector 9 (target fuel injection start timing).
It is advanced by s time. 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 a broken line).

In each fuel injection cycle in the start-up mode, when the opening timing of the switching valve 5 arrives and a 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. When the time ΔTs elapses from the opening timing of the switching valve 5 and the target fuel injection starting timing is reached, an injector drive signal is applied from the controller 8 to the on-off valve 7, and the on-off 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 start mode, the valve opening timing (target fuel injection start timing) of the on-off valve 7 is set so as to be compatible with the engine operating state. Therefore, as described above, the on-off valve 7 is opened. At the same time, when fuel injection is started, the fuel injection start timing is adapted to the engine operating state. For this reason, the injection delay caused by the non-execution of the low-pressure injection that occurs when the fuel injection is performed in the normal mode even when the fuel pressure in the low-pressure accumulator 4 is not sufficient is prevented.

When the formation of the fuel pressure 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 has exceeded the designated value PLPTAR. In this case, the fuel injection in the start mode shifts to the fuel injection in the normal mode. As described above, when the actual value PLP of the fuel pressure in the low-pressure accumulator 4 reaches the command value PLPTAR in a certain fuel injection cycle, the switching valve 5 is closed after the end of the fuel injection cycle, and then the next fuel injection is performed. Before the start of the injection cycle, 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. For this reason, the low-pressure injection is smoothly performed also in the first fuel injection cycle after the shift to the normal mode.

Hereinafter, an accumulator 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 the device of the first embodiment in that the start of the fuel injection at the time of engine start is prevented, and the injector valve opening period (valve opening start / end timing) is set to the normal mode. Compared to the device of the first embodiment in which the same value is set as in the case and the valve opening start timing of the switching valve 5 is advanced, both the valve opening periods of the injector 9 and the switching valve 5 have the same value as in the normal mode. And the valve opening start timing of the injector 9 and the switching valve 5 is advanced in comparison with the case of the normal mode.

In connection with this feature, in the second embodiment,
A determination routine shown in FIG. 7 is executed instead of the fuel injection mode determination routine of FIG. 5 according to the first embodiment. The other points are substantially the same as those of the first embodiment, and the description is omitted. In the fuel injection mode determination routine shown in 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 storage device of the controller 8 and stored in the low-pressure accumulator 4. Actual value of fuel pressure PLP
Is determined to have reached the valve opening pressure PINJ (step S11). If the determination result is affirmative, fuel injection in the normal mode is performed (step S12).

On the other hand, if it is determined in step S11 that the actual value of the fuel pressure in the low-pressure accumulator 4 has not reached the designated value, the fuel injection in the starting mode is performed (step S13). In the start mode, as in the case of the normal mode, the 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 opening start timing is corrected to the advance side using the low pressure injection period ΔTLP.

Accordingly, in the start mode, when the injector valve opening start timing which is advanced by the low pressure injection period ΔTLP from the injector valve opening start timing in the normal mode comes, the on-off valve 7 for controlling the injection timing is opened. . here,
The fuel pressure formation in the low-pressure accumulator 4 is insufficient,
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. For this reason, the injector 9 is maintained in the valve closed state.

Next, when the switching valve opening start timing advanced by the low pressure injection period .DELTA.TLP from the switching valve opening start timing in the normal mode comes, the switching valve 5 for switching the injection rate is opened. You. 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 internal fuel pressure exceeds the valve opening pressure, and pressurized fuel is injected from the nozzle holes. After all, in the start mode, the 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 start mode in which the valve opening start timing of the injector and the switching valve is advanced, the fuel injection is performed in the normal mode even though the fuel pressure in the low-pressure accumulator 4 is not sufficient. Injection delay caused by non-implementation of low-pressure injection which occurs when performing the above is prevented.

When the fuel pressure in the low-pressure accumulator 4 is sufficiently advanced, it is determined in step S11 of the determination routine in FIG. 7 that the actual value in the low-pressure accumulator 4 exceeds the injectable pressure. Shift to fuel injection. The present invention is not limited to the first and second embodiments, but can be variously modified. 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 designated value (set pressure) PLPTAR or the injectable pressure PINJ based on the sensor output PLP from the engine. The arrival at the set pressure or the injectable pressure may be determined based on the elapsed time from the time or the engine speed.

[0038]

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

In the pressure accumulating 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 an advanced timing from the target fuel injection start timing, only the drive control of the control valve is changed compared to the normal case By doing so, 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, fuel injection can be performed at a sufficient fuel pressure at the same time as the fuel injection nozzle opens.

[0040] In the pressure accumulating 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 accumulator reaches the predetermined pressure, the low-pressure premix injection and the high-pressure main injection are performed in each fuel injection cycle. Can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a pressure accumulating fuel injection device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing connection between main elements of the fuel injection device shown in FIG. 1 and injectors of each cylinder of the engine.

FIG. 3 shows changes in the injection rate and changes in the open / close states of the switching valve for switching the injection rate and the on-off valve for controlling the injection timing over time in one fuel injection cycle performed in the normal mode. FIG.

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 an injection waveform, an injector drive signal, and a switching valve drive signal over time during fuel injection control at the time of engine start 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 respective changes of an injection waveform, an injector drive signal, and a switching valve drive signal with time during fuel injection control at the time of engine start according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION 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) Injector 10a, 10b Fuel passage

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 47/00 F02M 47/00 M 55/02 350 55/02 350E F-term (Reference) 3G066 AA07 AB02 AC01 AC09 AD12 BA00 BA08 BA14 CB07U CB09 CB11 CB12 CC06T CC08T CC14 CC64T CC66 CC67 CC68U CC70 CD26 CE13 CE22 DA04 DA06 DA12 DA14 DB01 DC04 DC09 DC18 3G301 HA02 JA21 KA01 MA18 MA27 NC02 ND01 NE11 PB05A PB08Z PB08Z

Claims (3)

[Claims] A first pressure accumulator for storing high-pressure fuel pressurized by a pump; a fuel injection nozzle connected to the first pressure accumulator via a fuel passage for injecting fuel into a combustion chamber of the engine; A control valve for controlling discharge of the 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 for storing fuel at a lower pressure than the fuel; and a predetermined time elapses after the fuel pressure in the second pressure accumulator reaches a predetermined pressure after the engine is started. Then, the control valve is opened and the control valve is closed in accordance with the closing of the fuel injection nozzle, and after the engine is started, the fuel pressure in the second accumulator reaches the predetermined pressure. Until the above control valve, 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 advance timing advanced from the target fuel injection start timing. The pressure accumulating fuel injection device according to claim 1, wherein: 3. The accumulator fuel according to claim 1, wherein the predetermined pressure is a set pressure related to a fuel pressure in the second accumulator set according to an operation state of the engine. Injection device.