JP4211733B2 - Common rail fuel injection system - Google Patents

Description

  The present invention relates to a common rail fuel injection device equipped with an injector of a type that always leaks a part of high-pressure fuel supplied to an injector to a low-pressure side.

In recent years, demands for improving the fuel consumption of automobiles and demands for reducing the amount of exhaust gas have increased, and idle stop for vehicles equipped with diesel engines (hereinafter referred to as diesel vehicles) is about to be put into practical use. Accordingly, functional requirements for common rail fuel injection devices mounted on diesel vehicles have also become clear.
In order to realize the idle stop of the diesel vehicle, it is necessary to perform the restart smoothly. However, in order to perform the restart smoothly, it is necessary to prevent a phenomenon in which the common rail pressure decreases while the engine is stopped.

However, the injector of the common rail fuel injection device that is currently flowing has a structure that always leaks a part of the high-pressure fuel supplied to the injector to the low-pressure side. For this reason, when the engine is stopped, the high-pressure fuel stored in the common rail always leaks to the low-pressure side via the injector. As a result, the common rail pressure decreases at the time of restart, and it becomes difficult to perform the restart smoothly.
Therefore, an injector of a type that does not always leak is desired. However, a type of injector that does not leak constantly is currently under development, and it takes several years to actually flow.
In other words, although the demand for idle stop in diesel vehicles is increasing, the current flowing injectors cannot always stop idle due to leaks, so it is necessary to wait for the flow of injectors that do not always leak There is a bug.
JP-A-8-121281

  The present invention has been made in view of the above circumstances, and its purpose is to enable a smooth restart after an engine stop by adding a simple structure even to an injector that constantly leaks. A common rail fuel injection device.

[Means of Claim 1]
In the common rail fuel injection device adopting the means of claim 1, the switching valve provided in the return pipe for returning the fuel leaked from the injector to the fuel tank is closed when the engine is stopped, and is opened when the engine is started. Is.
By providing in this way, the fuel leaked from the injector while the engine is stopped is accumulated upstream of the switching valve, and the common rail pressure is prevented from decreasing due to the constant leak of the injector while the engine is stopped. Thus, the common rail pressure during engine stop can be maintained at a high pressure. As a result, the engine can be started quickly and smoothly during restart.

Further, also by use of the injector of the structure leaking into the part constantly low pressure side of the high pressure fuel supplied from the common rail, the switching valve provided in the return pipe, adding a simple structure in which the switching control its switching valve Thus, restart after the engine stops can be performed smoothly. This makes it possible to realize idle stop without waiting for the flow of a type of injector that does not always leak.
Here, the existing injector has a structure in which the switching leak fuel is discharged to the outside through the valve chamber of the electric valve. However, until now, since the valve chamber has never become high pressure, the motorized valve of the injector has not been designed to withstand high common rail pressure.
However, by closing the switching valve, the upstream side of the switching valve becomes high pressure. Then, the pressure becomes high to the valve chamber via the switching leak discharge path, fuel leaks from a member (O-ring, etc.) that seals the valve chamber, or a part of the motorized valve (screw portion, etc.) is damaged by the high pressure. There are concerns about defects.
Accordingly, the common rail fuel injection device according to the first aspect of the present invention is provided with a check valve in the switching leak discharge passage to prevent the fuel from flowing back to the valve chamber of the electric valve.
As a result, even if the switching valve is closed and the upstream side of the switching valve becomes high pressure, the valve chamber does not become high pressure.
As a result, even if the switching valve is closed and the upstream side of the switching valve becomes high pressure, the valve chamber does not become high pressure. Can do.

[Means of claim 2]
In the common rail fuel injection device employing the means of claim 2, when a plurality of injectors are mounted, a switching valve is provided on the common path of the return pipe.
By providing in this way, even if a plurality of injectors are mounted, only one switching valve is required, and the structure can be simplified.

[Means of claim 3 ]
In the common rail fuel injection device employing the means of claim 3 , the timing at which the control device closes the switching valve is immediately before entering the engine stop operation for idling stop, and the control device opens the switching valve. The timing is just before the engine is restarted from the idle stop state.
By providing in this way, idle stop can be realized.

The best mode common rail type fuel injection device includes a high pressure pump that pressurizes and pressurizes fuel stored in a fuel tank, a common rail that accumulates high pressure fuel pumped by the high pressure pump, and a common rail that is stored in the common rail. An injector that injects high-pressure fuel and always leaks part of the high-pressure fuel supplied from the common rail to the low-pressure side, a return pipe that returns the fuel leaked from this injector to the fuel tank, and opens and closes this return pipe And a control device that closes the switching valve when the engine is stopped and opens the switching valve when the engine is started .
The injector includes a control chamber in which high-pressure fuel is supplied through an inflow passage, a motor-operated valve that opens and closes a discharge passage that discharges the pressure in the control chamber to a low-pressure side, and a sliding needle that slides in the injector due to a pressure change in the control chamber Always leaked fuel that is discharged to the low pressure side through the gap including the moving part to the upstream part of the connection port of the return pipe, and is discharged from the discharge passage to the low pressure side through the valve chamber of the motorized valve. There is a switching leak discharge path for guiding the switched leakage fuel to the upstream portion of the connection port of the return pipe.
The switching leak discharge path is provided with a check valve that prevents the fuel from flowing back to the valve chamber of the electric valve.

(Configuration of Example 1)
A first embodiment in which the present invention is applied to a common rail fuel injection device will be described with reference to FIGS. FIG. 5 shows the prior art shown for reference.
First, the configuration of the common rail fuel injection device will be described with reference to FIG.
The common rail fuel injection device is a system that injects fuel into, for example, a diesel engine (hereinafter, engine: not shown), and includes a supply pump 1, a common rail 2, a plurality of injectors 3, and an ECU 4 (abbreviation of engine control unit: control). Equivalent to the device).

(Description of supply pump 1)
The supply pump 1 is a fuel pump that compresses the fuel stored in the fuel tank 11 to a high pressure and pumps the fuel to the common rail 2, and feeds the fuel in the fuel tank 11 to the supply pump 1 via the fuel filter 11a. And a high-pressure pump that compresses the fuel sucked up by the feed pump to a high pressure and pumps the fuel to the common rail 2, and the feed pump and the high-pressure pump are driven by a common camshaft. The camshaft is rotationally driven by an engine crankshaft or the like.
In addition, the supply pump 1 is equipped with an inflow metering valve (hereinafter referred to as SCV) 12 that adjusts the amount of fuel sucked into the high-pressure pump, and the SCV 12 is adjusted by the ECU 4 so that the common rail pressure is reduced. It has come to be adjusted. Note that the SCV 12 uses a normally open type solenoid valve that is fully opened when energization is stopped.

(Description of common rail 2)
The common rail 2 is a pressure accumulating container that accumulates the high-pressure fuel pumped from the supply pump 1 and supplies the accumulated high-pressure fuel to the injector 3, and the common rail pressure pressurized to the high pressure (fuel supply pressure to the injector 3) Is connected to a discharge port of a supply pump 1 that pumps high-pressure fuel through a fuel pipe (high-pressure fuel flow path) 13 so that pressure is accumulated.
A pressure limiter 16 is attached to a return pipe (fuel return path) 14 for returning fuel from the common rail 2 to the fuel tank 11. The pressure limiter 16 is a pressure relief valve, and opens when the common rail pressure exceeds the limit set pressure, and keeps the common rail pressure below the limit set pressure.

In addition, the common rail 2 may be provided with a pressure reducing valve that adjusts the opening degree of a discharge passage (passage that connects the common rail 2 and the return pipe 14) that overflows the fuel accumulated in the common rail 2 (this pressure reducing valve). May not be provided).
This pressure reducing valve rapidly reduces the common rail pressure via the return pipe 14, and the ECU 4 adjusts the opening of the pressure reducing valve to quickly reduce the common rail pressure to a pressure corresponding to the vehicle running state. Can be controlled. As the pressure reducing valve, a normally closed type electromagnetic valve that is fully closed when energization is stopped is used.

(Description of injector 3)
As the injector 3, an existing one that is currently flowing is used. This injector 3 is mounted in each cylinder of the engine and supplies fuel to each cylinder by injection. The injector 3 is connected to the downstream ends of a plurality of high-pressure fuel pipes 15 branched from the common rail 2 and accumulates pressure in the common rail 2. The supplied high-pressure fuel is injected into each cylinder.
Each injector 3 is connected to a return pipe 14 that returns the leaked fuel leaked from the injector 3 (switched leak fuel and always leaked fuel) to the fuel tank 11.
The return pipe 14 joins the pressure limiter 16 and the return pipe 14 that returns the fuel flowing out from the pressure reducing valve to the fuel tank 11.
The return pipe 14 includes a single common path through which all fuel leaked from each injector 3 passes, and a switching valve 55 described later is provided on the common path.

(Description of ECU 4)
The ECU 4 is a well-known structure composed of a CPU that performs control processing and arithmetic processing, a storage device (ROM, standby RAM or EEPROM, memory such as RAM) that stores various programs and data, an input circuit, an output circuit, and a power supply circuit. It is a microcomputer.
FIG. 1 shows an example in which a pump drive circuit (SCV EDU) is mounted in the case of the ECU 4 and an injector drive circuit (EDU for injector) 21 is mounted separately from the ECU 4, but the injector drive circuit 21 is also ECU4. It may be arranged in the case. Of course, the pump drive circuit may be mounted separately from the ECU 4.

The ECU 4 performs injection control of the injector 3 and opening degree control of the SCV 12 based on various programs stored in the storage device and various data (operation state of the engine or the like) read from sensors connected to the ECU 4. Is.
The ECU 4 has various means such as at least sensors necessary for controlling the injector 3, sensors necessary for controlling the SCV 12, and sensors necessary for controlling the idle stop described later, as means for detecting the operating state of the engine or the like. Sensors are connected. Specifically, a key switch position sensor that detects the position of the key switch, a vehicle speed sensor that detects the vehicle speed, a rotation speed sensor that detects the engine speed, an accelerator sensor that detects the accelerator opening, a brake pedal switch, and a shift position A sensor, a common rail pressure sensor 22 for detecting common rail pressure, and other various sensors are connected.

(Structure of injector 3)
The basic structure of the injector 3 will be described with reference to FIG.
The injector 3 injects high-pressure fuel supplied from the common rail 2 into the cylinders of the engine. The common rail pressure is applied via an inflow passage 31 (a fuel passage provided with an in-orifice) and an exhaust passage 32. A control chamber 33 that is exhausted through (a fuel passage provided with an out-orifice) is provided, and the discharge passage 32 is opened and closed by an electromagnetic valve 34 (an example of an electric valve) to control the control chamber pressure (inside the control chamber 33). When the pressure is reduced to the valve opening pressure, the needle 35 rises and has a nozzle 36 for injecting fuel.

A housing 37 (for example, a nozzle holder) of the injector 3 has a cylinder 41 for slidably supporting a command piston 38 in the vertical direction (in the direction of the opening / closing valve of the needle 35), and high-pressure fuel supplied from the common rail 2 on the nozzle 36 side. A high-pressure fuel passage 42 that leads to the inflow passage 31 side, an exhaust pressure fuel passage (a switching leak discharge passage 39, a constant leak discharge passage 40) that discharges the high-pressure fuel to the low-pressure side, and the like are formed.
The command piston 38 is inserted into the cylinder 41 and is connected to the needle 35 via a pressure pin 44.
The pressure pin 44 is interposed between the command piston 38 and the needle 35, and a spring 45 that urges the needle 35 downward (in the valve closing direction) is disposed around the pressure pin 44.

The control chamber 33 is formed on the upper side (on the electromagnetic valve 34 side) of the cylinder 41, and the volume changes according to the vertical movement of the command piston 38.
The inflow passage 31 is a fuel throttle on the inlet side that depressurizes high-pressure fuel supplied from the high-pressure fuel passage 42, and the high-pressure fuel passage 42 and the control chamber 33 communicate with each other through the inflow passage 31.
The discharge passage 32 is formed on the upper side of the control chamber 33, and is a fuel throttle on the outlet side for restricting fuel discharged from the control chamber 33 to the switching leak discharge passage 39 (low pressure side). 39 communicates via the discharge passage 32.

The solenoid valve 34 is a solenoid 46 that generates electromagnetic force when energized (ON), a valve 47 that is attracted upward (in the valve opening direction) by the electromagnetic force generated by the solenoid 46, and the valve 47 downward (closed). And a return spring 48 for urging in the valve direction).
When the solenoid 46 is OFF, the valve 47 is pressed downward by the urging force of the return spring 48, and the valve 47 (for example, a ball valve (not shown) provided at the tip of the valve 47) closes the discharge passage 32. When the solenoid 46 is ON, the valve 47 moves upward against the biasing force of the return spring 48 by the electromagnetic force generated by the solenoid 46 and the discharge passage 32 is opened.
The valve chamber 47a in which the valve 47 is disposed is filled with leaked fuel discharged from the discharge passage 32. That is, the valve 47 is structured to be affected by the leak pressure.

  A housing 37 (for example, a nozzle body) of the injector 3 communicates with a slide hole 51 that supports the needle 35 so as to be slidable in the vertical direction (opening and closing direction) and a high-pressure fuel passage 42. A nozzle chamber 52 provided in an annular shape, a conical valve seat 53 on which the needle 35 is seated when the valve is closed, and a plurality of injection holes 54 for injecting high-pressure fuel are formed. The nozzle hole 54 is formed on the inner side of a seating seat where the needle 35 and the valve seat 53 come into contact with each other when seated, and is closed when the needle 35 is seated on the valve seat 53.

  The needle 35 includes a sliding shaft portion 35a held in the sliding hole 51, a pressure receiving surface 35b formed below the sliding shaft portion 35a, and a small-diameter shaft shaft 35c extending downward from the pressure receiving surface 35b. And a conical valve 35d that opens and closes the nozzle hole 54 by being seated and separated from the valve seat 53, and the sliding shaft portion 35a seals between the nozzle chamber 52 and the low pressure side (around the pressure pin 44). However, it can be reciprocated in the axial direction.

(Operation of injector 3)
When the ECU 4 gives an injection pulse to the injector 3, the injector drive circuit 21 starts energization of the electromagnetic valve 34. Then, when the solenoid 46 sucks the valve 47 and the valve 47 starts to lift up, the discharge passage 32 opens, and the pressure in the control chamber 33 decompressed in the inflow passage 31 starts to decrease.
When the pressure in the control chamber 33 falls below the valve opening pressure, the needle 35 starts to rise. When the needle 35 is separated from the valve seat 53, the nozzle chamber 52 and the injection hole 54 communicate with each other, and the high-pressure fuel supplied to the nozzle chamber 52 is injected from the injection hole 54.
As the needle 35 rises, the injection rate rises. When the rising injection rate reaches the maximum injection rate, the injection rate does not increase any further.

When the injection pulse applied to the injector 3 by the ECU 4 is stopped, the injector drive circuit 21 stops energization of the electromagnetic valve 34. Then, the solenoid 46 stops the suction of the valve 47, and the valve 47 starts to lift down. When the valve 47 of the electromagnetic valve 34 closes the discharge passage 32, the pressure in the control chamber 33 starts to rise. When the pressure in the control chamber 33 rises above the valve closing pressure, the needle 35 starts to descend.
When the needle 35 is lowered and seated on the valve seat 53, the communication between the nozzle chamber 52 and the injection hole 54 is cut off, and fuel injection from the injection hole 54 is stopped.

(Background of Example 1)
The injector 3 described above leaks a part of the high-pressure fuel supplied from the common rail 2 to the low-pressure side.
The injector 3 leak includes a “switching leak (dynamic leak)” and a “always leak (static leak)”.
“Switching leak” is a leak that occurs only when the solenoid valve 34 is in operation (ON), and the valve 47 opens the discharge passage 32 by the operation of the solenoid valve 34, so that the discharge passage 32 → the valve 47 is arranged. The valve chamber 47a is discharged to the outside of the injector 3 through the switching leak discharge passage 39.

“Always leak” is a leak that always occurs through the sliding portion in the injector 3, and even if the valve 47 of the electromagnetic valve 34 closes the discharge passage 32, the sliding portion (command in the injector 3) The gap between the piston 38 and the cylinder 41, the gap between the sliding shaft 35a of the needle 35 and the sliding hole 51) → is always discharged to the outside of the injector 3 through the leak discharge passage 40.
Note that the switching leak discharge path 39 and the constant leak discharge path 40 join inside the injector 3 and communicate with the connection port of the return pipe 14, and switch only the passage between the junction and the valve chamber 47a. The leak discharge path 39 is used.

On the other hand, an idling stop function is provided in a diesel vehicle equipped with the above-described common rail fuel injection device.
The idle stop function is well known. For example, (1) When the ignition switch is ON, the vehicle speed is 0 km, and the brake pedal is depressed, the operation of the injector 3 is stopped to stop the engine. Stop function and (2) When the ignition switch is on, the vehicle speed is 0 km, and the brake pedal is released (or the accelerator pedal is depressed), the starter is activated and the injector 3 is activated. And a restart function for restarting the engine.
For this idle stop function, the ECU 4 described above is provided to control a starter relay for operating the starter according to the operating state, in addition to the injector 3 and the SCV 12 described above.

  However, as described above, since the injector 3 always leaks, the high-pressure fuel stored in the common rail 2 is stored in the injector 3 as shown in FIG. The flow from the sliding part to the constant leak discharge path 40 → the return pipe 14 → the fuel tank 11. Then, at the time of restart, the common rail pressure decreases, and it becomes difficult to perform restart smoothly.

(Characteristics of Example 1)
In order to solve the above-described problem, the common rail fuel injection device according to the first embodiment is switched to a return pipe 14 for returning the fuel leaked from the injector 3 to the fuel tank 11 as shown in FIG. 55 and a switching valve control function for controlling the switching valve 55 is provided in the ECU 4.
The switching valve 55 is provided in one common path through which all leaked fuel leaked from the plurality of injectors 3 passes through the return pipe 14. When turned on by the ECU 4, the switching valve 55 passes through the common path of the return pipe 14. A normally closed type solenoid valve (an example of an electric valve) that opens a common path of the return pipe 14 when closed and turned off is used.

The switching valve control function of the ECU 4 is a program for controlling the switching valve 55 to open and close (ON-OFF). The switching valve 55 is closed (ON) when the engine is stopped (during idle stop), and the engine is restarted. The switching valve 55 is provided to open (OFF) at the time (when restarting from idle stop).
Specifically, the timing at which the switching valve control function of the ECU 4 closes (ON) the switching valve 55 is immediately before entering the engine stop operation for idling stop, and the switching valve control function of the ECU 4 The timing for opening (OFF) is immediately before restarting the engine from the idle stop state.

As described above, the switching valve 55 is provided in the return pipe 14, and the switching valve 55 is closed at the time of idling stop, and opened at the time of restarting the engine, thereby leaking from the injector 3 while the engine at idling stop is stopped. The accumulated fuel is accumulated upstream of the switching valve 55, and the phenomenon that the common rail pressure decreases while the engine is stopped is prevented.
Thus, the common rail pressure is maintained at a high level while the engine is stopped, so that the engine can be started quickly and smoothly at the time of restart.

However, in the above configuration, there are concerns about the following two problems when the switching valve 55 is closed (when the engine is stopped).
(1) Whether the pressure remaining upstream of the switching valve 55, that is, the common rail pressure while the engine is stopped, can be maintained at a sufficiently high level.
(2) Is there any problem caused by the high pressure upstream of the switching valve 55?

The above (1) will be described.
The upstream volume of the switching valve 55 is the sum of the high pressure section volume including the common rail 2 and the low pressure section volume from the low pressure side of the injector 3 to the switching valve 55. Since the high-pressure part volume is more than twice the low-pressure part volume, the pressure remaining upstream of the switching valve 55 (common rail pressure when the engine is stopped) is at least 2/3 or more of the common rail pressure during idling. This pressure is sufficient to restart the engine, and the engine can be restarted smoothly.
Note that when the engine is stopped (switching valve) so that the pressure remaining upstream of the switching valve 55 (common rail pressure when the engine is stopped) becomes a common rail pressure suitable for restarting the engine (for example, common rail pressure when idling). The ECU 4 may control the pressure reducing valve (or the pressure limiter 16 when the pressure limiting valve 16 is opened by energization control without the pressure reducing valve being mounted) before the valve 55 is closed.

The above (2) will be described.
A specific structure of the electromagnetic valve 34 of the injector 3 is shown in FIG. As described above, the injector 3 has a switching leak caused by opening the solenoid valve 34. The switching leak caused by opening the solenoid valve 34 is the valve chamber 47a of the solenoid valve 34 → the switching leak discharge passage 39 → It is structured to be discharged to the return pipe 14. However, in the conventional common rail type fuel injection device, the valve chamber 47a does not become high pressure, so the structure of the electromagnetic valve 34 is not designed to withstand high common rail pressure.
However, by closing the switching valve 55, when the upstream side of the switching valve 55 becomes high pressure, the pressure increases to the valve chamber 47 a via the switching leak discharge path 39. Then, there is a concern that fuel leaks from a member (O-ring or the like) that seals the inside of the valve chamber 47a, or a part (screw portion or the like) of the electromagnetic valve 34 is damaged by high pressure.

In order to eliminate this concern, the injector 3 of the first embodiment is provided with a check valve 56 in the switching leak discharge passage 39 as shown in FIGS. 2, 3 (b), and 4. The check valve 56 is a one-way valve that prevents the fuel from flowing back to the valve chamber 47a even when the section between the leak discharge path 40 and the switching valve 55 becomes high pressure. Open.
Thus, by providing the check valve 56 in the switching leak discharge path 39, even if the switching valve 55 is closed and the upstream side of the switching valve 55 becomes a high pressure, the check valve 56 is connected to the switching leak discharge path 39. In order to prevent backflow, the valve chamber 47a does not become high pressure. As a result, it is possible to eliminate concerns such as fuel leaking from the seal portion of the electromagnetic valve 34 or damage.

(Description of prior art similar to the configuration of the present invention)
Here, a technique similar to the configuration of the present invention is introduced.
It is known that the pressure (leak pressure) on the low pressure side of the injector 3 affects the operation of the injector 3.
Specifically, in the injector 3 that performs injection control by controlling the internal pressure of the control chamber 33 with the electromagnetic valve 34, the valve 47 of the electromagnetic valve 34 is disposed in the low-pressure side valve chamber 47a. 47 movement is affected by leak pressure. When the leak pressure rises, the valve 47 closes at the discharge passage 32 of the control chamber 33 and the valve 47 closes at a slower speed, so that the substantial valve opening period (injection period) is extended and the injector 3 is injected. The actual injection amount increases with respect to the target injection amount. If the actual injection amount increases from the target injection amount, problems such as deterioration of exhaust gas and increase in engine output occur.

Therefore, as shown in FIG. 5, a check valve (check valve) J1 is arranged in the middle of the return pipe 14 for returning the leaked fuel of the injector 3 to the fuel tank 11, so that the pressure on the low pressure side of the injector 3 is stabilized. A technique for stabilizing the influence on the injection amount is known.
However, the check valve J1 shown in FIG. 5 is not for keeping the low pressure side of the injector 3 at a high pressure, but for the purpose of keeping the pressure on the low pressure side of the injector 3 at a stable low pressure. The low pressure side cannot be kept high. In other words, when the idle stop is restarted, the common rail pressure cannot be kept high, and restarting is difficult.
If the opening pressure of the check valve J1 is set to such an extent that restart is possible, the leaked fuel cannot be discharged during the operation of the engine, and the engine operation becomes difficult.
That is, as shown in FIG. 5, if the return pipe 14 is provided with the check valve J1, idle stop cannot be realized.

(Summary of features of Example 1)
The common rail fuel injection device of the first embodiment has the following effects.
(1) A switching valve 55 is provided in the return pipe 14 for returning the fuel leaked from the injector 3 to the fuel tank 11, and the switching valve 55 is closed when the engine is stopped and opened when the engine is started. The always leaked fuel leaked from the injector 3 while the engine is stopped is accumulated upstream of the switching valve 55, and the common rail pressure is maintained at a high level even when the engine is stopped. As a result, the engine can be started quickly and smoothly during restart.

(2) By simply providing the switching valve 55 in the return pipe 14 and switching the switching valve 55, the engine can be restarted smoothly after the engine is stopped.
As a result, idling stop can be realized only by adding a simple configuration to the existing common rail fuel injection device without waiting for the flow of the injector 3 of the type that does not always leak.

(3) By providing the switching valve 55 on the common path of the return pipe 14, the switching valve 55 can be made one even when a plurality of injectors 3 are mounted.

(4) Although the existing injector 3 is not provided with a specification in which the valve chamber 47a can withstand a high common rail pressure, a check valve 56 is provided in the switching leak discharge passage 39 to the valve chamber 47a of the electromagnetic valve 34. In order to prevent the fuel from flowing backward, even if the upstream side of the switching valve 55 becomes high pressure while the engine is stopped, the valve chamber 47a does not become high pressure.
Thus, since the valve chamber 47a does not become a high pressure, concerns such as fuel leaking from the sealing portion of the electromagnetic valve 34 or damage can be solved.

(5) By providing the check valve 56 in the switching leak discharge path 39, the leak pressure in the valve chamber 47a can be stabilized at a substantially predetermined pressure. As a result, it is possible to eliminate the problem that the actual injection amount changes due to the fluctuation of the leak pressure in the valve chamber 47a.

[Modification]
In the above embodiment, an example in which the switching valve 55 is provided by an electromagnetic valve that opens and closes a valve by electromagnetic force is shown. However, the drive source is not limited, and for example, a piezoelectric stack in which piezoelectric elements are stacked is used as a drive source. As long as the switching valve can be opened and closed by the ECU 4, such as a switching valve, a switching valve by another driving source may be used.
In the above-described embodiment, the 2-way valve type injector 3 is shown as an example of the injector 3 that constantly leaks. However, the common rail type fuel that mounts all types of injectors 3 that always leak such as a 3-way valve. The present invention can be applied to an injection device.

1 is a schematic view of a common rail fuel injection device (Example 1). FIG. It is a schematic sectional drawing of an injector (Example 1). (Example 1) which is a fuel flow system diagram from a common rail to a fuel tank. (Example 1) which is sectional drawing of the solenoid valve periphery in an injector. It is the schematic of a common rail type fuel injection device (conventional example).

Explanation of symbols

1 Supply pump (fuel pump with built-in high-pressure pump)
2 Common rail 3 Injector 4 ECU (control device)
11 Fuel tank 14 Return pipe 31 Inflow passage 32 Discharge passage 33 Control chamber 34 Solenoid valve (motorized valve)
35 Needle 38 Command piston 39 Switching leak discharge path 40 Regular leak discharge path 47a Valve chamber 55 Switching valve 56 Check valve provided in the switching leak discharge path

Claims (3)

(A) a high-pressure pump that pressurizes and pressurizes fuel stored in a fuel tank;
(B) a common rail for accumulating high-pressure fuel pumped by the high-pressure pump;
(C) an injector having a structure for injecting high-pressure fuel stored in the common rail and leaking part of the high-pressure fuel supplied from the common rail to the low-pressure side at all times;
(D) a return pipe for returning the fuel leaked from the injector to the fuel tank; (e) a switching valve capable of opening and closing the return pipe;
(F) a control device that closes the switching valve when the engine is stopped and opens the switching valve when the engine is started ,
The injector slides in the injector by a control chamber to which high-pressure fuel is given through an inflow passage, a motor-operated valve that opens and closes a discharge passage for discharging the pressure in the control chamber to a low pressure side, and a pressure change in the control chamber. A constantly leaking fuel path that leads the constantly leaking fuel discharged to the low pressure side through the gap including the sliding part of the needle to the upstream part of the connection port of the return pipe, from the discharging path through the valve chamber of the motor-operated valve A switching leak discharge path for guiding the switching leak fuel discharged to the low pressure side to the upstream portion of the connection port of the return pipe,
A common rail type fuel injection device characterized in that a check valve for preventing fuel from flowing back to the valve chamber of the electric valve is provided in the switching leak discharge path . In the common rail fuel injection device according to claim 1,
A plurality of the injectors are mounted,
The return pipe includes one common path through which all fuel leaked from the plurality of injectors passes.
The common rail fuel injection device, wherein the switching valve is provided in a common path of the return pipe. In the common rail type fuel injection device according to claim 1 or 2 ,
The timing at which the control device closes the switching valve is immediately before entering the engine stop operation for idle stop,
The common rail fuel injection device, wherein the control device opens the switching valve immediately before restarting the engine from an idle stop state.

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