JP2008215228A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device which switches "injection stop," "injection without intensifying pressure" and "pressure intensifying injection" and has excellent switching responsiveness. <P>SOLUTION: A first movable valve 61 is provided so as to be independently displaceable with respect to a second movable valve 31, and a first armature 61b and a second armature 31b are magnetically attracted by a common electromagnetic drive part 33 individually. By applying a small first drive current to the electromagnetic drive part 33, only the first movable valve 61 is opened, and the "injection without intensifying pressure" which does not operate a pressure intensifier 17 is performed. By applying a large second drive current to the electromagnetic drive part 33, the first movable valve 61 and the second movable valve 31 are simultaneously opened, and the "pressure intensifying injection" which operates the pressure intensifier 17 is performed. Since the first movable valve 61 and the second movable valve 31 are magnetically attracted by the common electromagnetic drive part 33 individually, responsiveness of the "injection without intensifying pressure" and "pressure intensifying injection" is improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection device capable of increasing a fuel pressure in a fuel reservoir of an injection nozzle.

(Existing technology)
A fuel injection device capable of increasing the fuel pressure in the fuel reservoir of the injection nozzle is known (see, for example, Patent Document 1).
An example of this type of fuel injection device will be described with reference to FIG.
The injector 2 of the fuel injection device includes a differential pressure switching valve 12 having a switching valve back pressure chamber 11 in the upper part of the drawing, an electromagnetic valve 13 for switching the internal pressure of the switching valve back pressure chamber 11, and an injection having a nozzle back pressure chamber 14 in the upper part of the drawing. A nozzle 15 and a pressure intensifier 17 having a differential pressure chamber 16 in the middle are provided.

The differential pressure switching valve 12 is a three-way switching valve, and the switching valve back pressure chamber 11 to which the high pressure fuel is supplied is connected to the low pressure side by the electromagnetic valve 13 so that the switching valve back pressure chamber 11 is switched to the low pressure side. Then, “low pressure switching” is performed to lower the internal pressure of the differential pressure chamber 16 and the nozzle back pressure chamber 14.
On the contrary, when the solenoid valve 13 cuts off the communication between the switching valve back pressure chamber 11 and the low pressure side, the switching valve back pressure chamber 11 is switched to the high pressure side, and the internal pressures of the differential pressure chamber 16 and the nozzle back pressure chamber 14 are increased. "High pressure switching".

The solenoid valve 13 shuts off the communication between the switching valve back pressure chamber 11 and the low pressure side when energization is stopped (OFF), and communicates the switching valve back pressure chamber 11 and the low pressure side when energized (ON). Thus, the differential pressure switching valve 12 is “low pressure switched”, and the differential pressure switching valve 12 is “high pressure switched” when OFF.
The internal pressure of the nozzle back pressure chamber 14 of the injection nozzle 15 is switched by the differential pressure switching valve 12 through the differential pressure chamber 16, and the nozzle is set by “low pressure switching (electromagnetic valve 13 ON)” of the differential pressure switching valve 12. Fuel is injected when the back pressure chamber 14 is switched to the low pressure side, and conversely, injection is performed when the nozzle back pressure chamber 14 is switched to the high pressure side by “high pressure switching (electromagnetic valve 13 OFF)” of the differential pressure switching valve 12. Stop.

The pressure booster 17 is a fuel pressurizing device using a two-stage pressure boosting piston 51, and the differential pressure chamber 16 is switched to the low pressure side by “low pressure switching (electromagnetic valve 13 ON)” of the differential pressure switching valve 12. The pressure-increasing piston 51 is lowered, the fuel in the pressure-increasing chamber 53 formed at the lower part of the pressure-increasing piston 51 is pressurized, and the fuel pressure in the fuel reservoir 44 of the injection nozzle 15 communicating with the pressure-increasing chamber 53 is reduced. Increase from rail pressure. On the contrary, when the differential pressure chamber 16 is switched to the high pressure side by the “high pressure switching (the electromagnetic valve 13 is turned off)” of the differential pressure switching valve 12, the pressure increasing piston 51 is raised by the restoring force of the return spring 52 to the initial position. Return.
The pressure increasing chamber 53 communicates with the common rail 1 through a fuel passage 54 including a one-way valve 54a. While the pressure increasing piston 51 is stopped, the fuel pressure in the pressure increasing chamber 53 and the fuel reservoir 44 is reduced to the rail. Maintained at pressure.

(Problems with existing technology)
In the injector 2 described above, when the differential pressure switching valve 12 is “low pressure switched” by the operation of the electromagnetic valve 13, the injection nozzle 15 and the pressure intensifier 17 are simultaneously operated.
For this reason, since the pressure intensifier 17 operates and the fuel pressure in the fuel reservoir 44 rises even in the short-time injection, a large amount of fuel is injected even in the short-time injection. As a result, it is difficult to control the amount of minute injection at the time of minute injection such as multistage injection and pre-injection. That is, it is difficult to control with high accuracy from a very small injection amount to a very small injection amount. It has also been difficult to control the injection rate pattern by varying the injection rate during the injection period.

As a technique for avoiding the above problems, the nozzle back pressure chamber 14 in the injection nozzle 15 and the switching valve back pressure chamber 11 of the differential pressure switching valve 12 (or the differential pressure switching valve 12 are eliminated, and the pressure booster is directly used. It is conceivable to switch and control the 17 differential pressure chambers 16) independently.
That is, it is conceivable to use a first solenoid valve that switches the operation of the injection nozzle 15 and a second solenoid valve that switches the operation of the pressure intensifier 17.
However, if the first and second electromagnetic valves are mounted on the injector 2, the cost increases and the injector 2 becomes larger.

In view of this, there has been proposed a technique that can switch between two hydraulic chambers by providing a differential by operating one electromagnetic drive unit (see, for example, Patent Document 2). By using this technique, it is possible to switch the nozzle back pressure chamber 14 for switching the operation of the injection nozzle 15 and the differential pressure chamber 16 for switching the operation of the pressure intensifier 17 by providing a differential.
However, the technique disclosed in Patent Document 2 is a technique for switching the hydraulic pressures of two hydraulic chambers by a spool that slides in the axial direction, and this spool is driven by one electromagnetic drive unit (linear solenoid). When switching between “injection stop”, “non-intensified injection”, and “intensified injection” using the technique disclosed in Patent Document 2, “injection stop” by sliding in the axial direction of the spool, Switching between “non-pressure-increasing injection” and “pressure-increasing injection” is performed. As a result, to switch from “injection stop” to “pressure-increasing injection”, the spool needs to be stroked for a long time, resulting in poor responsiveness.
In addition, since the technique disclosed in Patent Document 2 has a structure in which the outer peripheral surface of the spool closes the hydraulic pressure switching port, even if the spool closes the hydraulic pressure switching port, the spool clearance causes There is a problem that the hydraulic pressure change port cannot be completely closed and the amount of leak fuel increases.
JP 2006-161568 A Japanese Patent Laid-Open No. 10-110658

  The present invention has been made in view of the above problems, and its purpose is to enable switching between “injection stop”, “non-pressure-increasing injection” and “pressure-increasing injection”, and further excellent switching responsiveness. A fuel injection device.

[Means of claim 1]
In the fuel injection device employing the means of claim 1, the first movable valve is provided so as to be independently displaceable with respect to the second movable valve, and the first and second armatures are individually provided by a common electromagnetic drive unit. It is magnetically attracted, and the switching state of the first and second movable valves differs depending on the energization amount given to the electromagnetic drive unit.
Thereby, by controlling the energization amount of the electromagnetic drive unit, (1) only the first movable valve is switched to operate only the injection nozzle, and the fuel is injected without operating the pressure intensifier “non-pressure-increasing injection” , And (2) two patterns of injection modes of “pressure-intensifying injection” in which fuel is injected by operating both the injection nozzle and the pressure intensifier by simultaneously switching both the first and second movable valves. Is possible.
In addition, since the first and second armatures of the first and second movable valves are individually magnetically attracted by the electromagnetic drive unit, the responsiveness from the operation stop to the “non-intensified injection” and the operation stop Both responsiveness up to “pressure-injection” can be increased.
That is, by adopting the means of claim 1, it is possible to switch between “injection stop”, “non-pressure-increasing injection” and “pressure-increasing injection”, and to provide a fuel injection device with excellent switching responsiveness. .

[Means of claim 2]
Each function part of the fuel injection device adopting the means of claim 2 adopts the following configuration.
The injection nozzle performs injection and injection stop by changing the oil pressure in the nozzle back pressure chamber to which high-pressure fuel is supplied.
The first movable valve switches the oil pressure in the nozzle back pressure chamber directly or indirectly.
The pressure intensifier performs pressure increase and pressure increase stop by changing the oil pressure in the differential pressure chamber to which high pressure fuel is supplied.
The second movable valve switches the oil pressure in the differential pressure chamber directly or indirectly.

[Means of claim 3]
A fuel injection device employing the means of claim 3 includes a differential pressure switching valve that switches the pressure in the differential pressure chamber to the high pressure fuel side or the low pressure fuel side in accordance with a change in the hydraulic pressure of the switching valve back pressure chamber to which high pressure fuel is supplied. The second movable valve indirectly switches the hydraulic pressure of the differential pressure chamber by switching the hydraulic pressure of the switching valve back pressure chamber.

[Means of claim 4]
The nozzle back pressure chamber in the fuel injection device employing the means of claim 4 communicates with the differential pressure chamber.
Thereby, the pressure control of the differential pressure chamber by switching the second movable valve can be given to the pressure control of the nozzle back pressure chamber by switching the first movable valve, and the pressure control range of the nozzle back pressure chamber is widened. Can do.
This will be described by taking as an example a case where the injection nozzle performs fuel injection when the nozzle back pressure chamber is switched to low pressure, for example, in accordance with Example 1 described later.
When the second movable valve switches the differential pressure chamber to a high pressure and the first movable valve switches the nozzle back pressure chamber to a low pressure, fuel flows into the nozzle back pressure chamber from the differential pressure chamber. The pressure drop in the back pressure chamber is moderate. As a result, the rapid opening of the injection nozzle can be suppressed. That is, the needle lift speed in the injection nozzle can be suppressed, and the controllability of the fine injection can be improved.
In addition, when the first movable valve switches the low pressure of the nozzle back pressure chamber and the second movable valve operates to switch the differential pressure chamber to a low pressure, the nozzle back pressure chamber is switched to the low pressure by the first movable valve. Since the fuel also flows out to the pressure chamber, the pressure in the nozzle back pressure chamber can be quickly switched to a low pressure. Thereby, the injection nozzle can be opened quickly. That is, the needle lift speed in the injection nozzle can be increased, and a large injection (injection with a large injection rate) can be performed in a short time.

[Means of claim 5]
The second movable valve in the fuel injection device adopting the means of claim 5 switches the oil pressure in the differential pressure chamber directly.
As a result, the differential pressure switching valve described in claim 3 can be eliminated, so that the cost can be reduced and the fuel injection device can be downsized.

[Means of claim 6]
The first valve body of the fuel injection device adopting the means of claim 6 opens and closes the first low pressure fuel passage that communicates the nozzle back pressure chamber to the low pressure side, thereby switching the operation between injection of the injection nozzle and injection stop. The second valve body switches between the pressure increase of the pressure booster and the pressure increase stop by opening and closing the second low pressure fuel passage that communicates the switching valve back pressure chamber to the low pressure side. It is.
The first valve body is provided so as to close the first valve port by being pressed and seated around the first valve port provided in the middle of the first low-pressure fuel passage. The valve body is provided so as to close the second valve port by being pressed and seated around the second valve port provided in the middle of the second low-pressure fuel passage.
Thus, the first and second valve bodies are seated around the first and second valve ports that open and close the first and second low pressure fuel passages, and close the first and second valve ports. Therefore, the blocking rate of the first and second valve ports is increased as compared with the conventional technique using a spool. As a result, leakage fuel when the first and second valve ports are closed can be reduced.

[Means of Claim 7]
The first and second movable valves in the fuel injection device employing the means of claim 7 are arranged on both sides of the electromagnetic drive unit, and operate in opposite directions by the operation of the electromagnetic drive unit.

[Means of Claim 8]
The first and second movable valves in the fuel injection device employing the means of claim 8 are arranged on one side of the electromagnetic drive unit and operate in the same direction by the operation of the electromagnetic drive unit.

The fuel injection device in the best mode includes a fuel reservoir to which high-pressure fuel is supplied, an injection nozzle that performs injection and injection stop operations of the fuel in the fuel reservoir, and pressure increase and stop of pressure increase in the fuel reservoir. A first pressure valve that switches between injection and injection stop operation of the injection nozzle, a first movable valve that includes a first armature that moves integrally with the first valve body, A second valve body that switches operation between pressure increase and pressure increase stop; and a second movable valve that includes a second armature that moves integrally with the second valve body.
The first movable valve is provided so as to be independently displaceable with respect to the second movable valve, and the first and second armatures are individually magnetically attracted by a common electromagnetic drive unit. The switching states of the first and second movable valves are different depending on the energization amount given to.

In the first embodiment, a schematic configuration of an existing fuel injection device to which the present invention is not applied will be described as a “reference example” with reference to FIG. 1A, and then FIG. 1B and FIG. The fuel injection device to which the present invention is applied will be described as “characteristics of the first embodiment”.
[Description of Reference Example]
The fuel injection device is a common rail fuel injection device that injects fuel into each cylinder of an engine (for example, a diesel engine: not shown), such as a common rail 1, an injector 2, a supply pump (not shown), a control device (not shown), and the like. Consists of.

  The common rail 1 is a well-known pressure accumulating container that accumulates high-pressure fuel supplied to the injector 2, and the fuel accumulated in the common rail 1 is supplied to the injector 2 via the injector piping. The fuel pressure (rail pressure) accumulated in the common rail 1 is regulated by a pump discharge amount supplied from the supply pump to the common rail 1 and a pressure reducing valve that causes the fuel to overflow from the common rail 1. Further, a pressure limiter is attached to the common rail 1, and the valve is opened when the rail pressure in the common rail 1 exceeds the limit set pressure, so that the rail pressure in the common rail 1 is suppressed below the limit set pressure. The fuel overflowing from the pressure reducing valve or the pressure limiter is returned to the fuel tank 3 through the relief pipe. Note that the pressure reducing valve may not be provided.

The injector 2 is mounted for each cylinder of the engine, is connected to the downstream end of a plurality of injector pipes branched from the common rail 1, and injects and supplies high-pressure fuel accumulated in the common rail 1 into each cylinder. The specific configuration will be described later.
Note that the leaked fuel from the injector 2 is also returned to the fuel tank 3 via the relief pipe.

  The supply pump is a high-pressure fuel pump that pumps high-pressure fuel to the common rail 1. A feed pump that sucks the fuel in the fuel tank 3 into the supply pump, and pressurizes the fuel sucked up by the feed pump and pumps the fuel to the common rail 1. A high-pressure pump. The feed pump and the high-pressure pump are driven by a common cam shaft, and this cam shaft is rotationally driven by the engine.

  In the supply pump, an SCV (suction metering valve) for adjusting the degree of opening of the fuel flow path is mounted on the fuel flow path for guiding fuel from the feed pump to the pressurizing chamber of the high pressure pump. The SCV is a metering valve that adjusts the amount of fuel sucked into the pressurizing chamber and changes the discharge amount of fuel pumped to the common rail 1 by being controlled by a pump drive signal from the control device. The rail pressure is adjusted by adjusting the discharge amount of fuel pumped to the common rail 1. That is, the control device controls the rail pressure to a pressure corresponding to the vehicle running state by controlling the SCV.

(Description of injector 2)
Next, the configuration of the injector 2 of the reference example to which the present invention is not applied will be described with the upper side in FIG. 1 as the upper side and the lower side in FIG. 1 as the lower side. Note that the upper and lower sides are for explanation, and do not relate to the actual mounting direction.
The injector 2 includes a differential pressure switching valve 12 that is switched by an internal pressure change of the switching valve back pressure chamber 11 formed in the upper part, an electromagnetic valve 13 that changes the internal pressure of the switching valve back pressure chamber 11, and a nozzle formed in the upper part. Switching between injection nozzle 15 for switching between injection and injection stop by changing internal pressure of back pressure chamber 14 and pressure increase and stop of pressure increase (including return to initial position) by change of internal pressure of differential pressure chamber 16 formed at intermediate portion And a pressure intensifier 17 to be provided.

(Description of differential pressure switching valve 12)
The differential pressure switching valve 12 is a three-way switching valve and includes a switching movable valve 22 that is slidably supported in the vertical direction of the injector body 21. A sliding piston that is slidably supported in the vertical direction of the injector body 21 is provided at the upper part of the switching movable valve 22, and an upper valve body from the upper side to the lower side is provided at the lower part of the switching movable valve 22. A small diameter portion and a lower valve body are formed.

A switching valve back pressure chamber 11 for generating a downward (high pressure switching direction) force on the switching movable valve 22 by the pressure of the fuel is formed above the switching movable valve 22. The switching valve back pressure chamber 11 is formed by a space surrounded by the upper surface of the sliding piston and the injector body 21.
The switching valve back pressure chamber 11 is connected to a high pressure fuel passage 24 that leads to a constant pressure chamber 23 to which high pressure fuel is supplied from the common rail 1, and the high pressure fuel supplied to the constant pressure chamber 23 is connected to the high pressure fuel passage 24, and The high pressure fuel passage 24 is supplied through an inlet orifice 24a.

The switching valve back pressure chamber 11 is connected to a low pressure fuel passage 25 that leads to a low pressure side (a side that communicates with the fuel tank 3 via a relief pipe), and an outlet orifice 25 a provided in the low pressure fuel passage 25 is connected to the switching valve back pressure chamber 11. The fuel in the switching valve back pressure chamber 11 can be discharged through.
The low pressure fuel passage 25 is opened and closed by the electromagnetic valve 13, and when the electromagnetic valve 13 opens the low pressure fuel passage 25 (exit orifice 25 a), the internal pressure of the switching valve back pressure chamber 11 decreases, and the switching movable valve 22. Rises due to differential pressure. Conversely, when the electromagnetic valve 13 closes the low-pressure fuel passage 25 (exit orifice 25a), the internal pressure of the switching valve back pressure chamber 11 increases, and the switching movable valve 22 decreases due to the differential pressure.

The differential pressure switching valve 12 forms a valve chamber by a space (space around the small diameter portion) sandwiched between the upper valve body and the lower valve body. This valve chamber always communicates with the inside of the differential pressure chamber 16 via the fuel passage 26.
The upper valve body switches between communication and blocking of the fuel passage 26 leading to the differential pressure chamber 16 and the low pressure fuel passage 27 leading to the low pressure side. When the switching movable valve 22 is lowered, the upper valve body is moved to the injector body 21. The communication between the fuel passage 26 and the low pressure fuel passage 27 is cut off, and conversely, when the switching movable valve 22 is raised, the fuel passage 26 and the low pressure fuel passage 27 are connected.
The lower valve body switches between communication and blocking of the fuel passage 26 leading to the differential pressure chamber 16 and the high pressure fuel passage 28 leading to the isobaric chamber 23. When the switching movable valve 22 is lowered, the lower valve body When the high pressure fuel passage 28 is communicated and conversely the switching movable valve 22 is raised, the injector body 21 is seated and the communication between the differential pressure chamber 16 and the high pressure fuel passage 28 is cut off.

By adopting the above-described configuration, the differential pressure switching valve 12 opens the low pressure fuel passage 25 so that the internal pressure of the switching valve back pressure chamber 11 decreases and the switching movable valve 22 rises. By switching the communication destination of the pressure chamber 16 to the low pressure fuel passage 27, “low pressure switching” is performed to lower the internal pressure of the differential pressure chamber 16 of the pressure intensifier 17 and the nozzle back pressure chamber 14 of the injection nozzle 15 communicating with the differential pressure chamber 16. ”Is executed.
On the contrary, when the electromagnetic valve 13 closes the low pressure fuel passage 25, the internal pressure of the switching valve back pressure chamber 11 is increased, the switching movable valve 22 is lowered, and the communication destination of the differential pressure chamber 16 is switched to the high pressure fuel passage 28. Thus, “high pressure switching” is performed to increase the internal pressure of the differential pressure chamber 16 of the pressure intensifier 17 and the nozzle back pressure chamber 14 of the injection nozzle 15 communicating with the differential pressure chamber 16.
It should be noted that a spring force directed in one direction (for example, upward) may be applied to the switching movable valve 22.

(Description of solenoid valve 13)
For example, the electromagnetic valve 13 is fastened and fixed to the upper portion of the injector body 21, and is provided with a movable valve 31 that opens and closes the outlet orifice 25 a in the low-pressure fuel passage 25, and a movable valve 31 in a direction to close the low-pressure fuel passage 25. The return spring 32 is energized, and the electromagnetic drive unit 33 opens the low-pressure fuel passage 25 by magnetically attracting the movable valve 31.
The movable valve 31 is supported so as to be slidable in the vertical direction (axial direction), and has a valve body 31a capable of closing the outlet orifice 25a of the low-pressure fuel passage 25 at the lower end surface, and a substantially fixed upper part of the valve body 31a. It consists of a magnetic armature 31b having a disc shape.
The electromagnetic drive unit 33 includes a coil 34 formed by winding a number of conductive wires on which an insulating coating is formed, and a magnetic stator 35 that accommodates the coil 34.

Then, when the coil 34 is energized (ON), the electromagnetic drive unit 33 magnetically attracts the armature 31b upward to open the outlet orifice 25a of the low pressure fuel passage 25, and communicates the switching valve back pressure chamber 11 to the low pressure side. When the energization of the coil 34 is stopped (OFF), the armature 31b closes the outlet orifice 25a of the low pressure fuel passage 25 by the action of the return spring 32, and disconnects the switching valve back pressure chamber 11 from the low pressure side. .
By this operation, the differential pressure switching valve 12 can be “low pressure switched” when the electromagnetic valve 13 is ON, and the high pressure switching valve 12 can be “high pressure switched” when the electromagnetic valve 13 is OFF.

(Description of injection nozzle 15)
The injection nozzle 15 switches between fuel injection and stop, and includes a needle 42 that is slidably supported in the vertical direction (axial direction) inside a nozzle holder 41 fastened to the lower portion of the injector body 21. The needle 42 is urged downward by the urging force of the spring 42a.
The needle 42 is configured such that a needle sliding portion provided at an upper portion is slidably supported in the nozzle holder 41, and a lower end conical portion of the needle 42 is formed on an annular sheet formed on the lower end inner surface of the nozzle holder 41. Sit or leave. Note that a plurality of nozzle holes 43 that communicate the inside and the outside of the annular sheet are formed at the lower end of the nozzle holder 41.

  A fuel reservoir 44 is formed at a middle portion of the needle 42 by a space surrounded by the needle 42 and the nozzle holder 41. The fuel reservoir 44 communicates with a pressure increasing chamber 53 described later via a fuel passage 45, and the fuel pressure in the pressure increasing chamber 53 is supplied to the fuel reservoir 44. Further, the fuel reservoir 44 communicates with the lower space formed in the gap between the lower side of the needle 42 and the nozzle holder 41, and the fuel supplied to the fuel reservoir 44 when the needle 42 is separated from the lower space. It is injected from the nozzle hole 43 through. The high-pressure fuel supplied to the fuel reservoir 44 and the lower space acts on the diameter difference of the needle 42 and generates an upward force (separating direction) on the needle 42.

A nozzle back pressure chamber 14 for generating a downward force (sitting direction) on the needle 42 by the pressure of the fuel is formed at the upper portion of the needle sliding portion. The nozzle back pressure chamber 14 is formed in a space surrounded by the upper surface of the needle sliding portion, the injector body 21 and the nozzle holder 41. The nozzle back pressure chamber 14 is connected to the differential pressure chamber 16 of the pressure intensifier 17 via the fuel passage 46. The fuel passage 46 is provided with an orifice 46a for reducing the flow passage area and a one-way valve 46b in parallel with the orifice 46a.
This one-way valve 46b stops the flow of fuel from the differential pressure chamber 16 to the nozzle back pressure chamber 14, and conversely stops the flow of fuel from the nozzle back pressure chamber 14 to the differential pressure chamber 16. This is a means for slowing down the speed (pressure reduction speed of the needle back pressure chamber 14) and increasing the descending speed of the needle 42 (pressure increase speed of the needle back pressure chamber 14). In addition, although the example which does not use the one-way valve 46b is shown in FIG.1 (b), the one-way valve 46b may be provided.

As described above, the internal pressure of the differential pressure chamber 16 that communicates with the nozzle back pressure chamber 14 is switched between high pressure and low pressure by the differential pressure switching valve 12. That is, the internal pressure of the nozzle back pressure chamber 14 of the injection nozzle 15 is switched by the differential pressure switching valve 12 via the differential pressure chamber 16.
For this reason, when the internal pressure of the differential pressure chamber 16 decreases due to “low pressure switching (electromagnetic valve 13 ON)” of the differential pressure switching valve 12, the internal pressure of the nozzle back pressure chamber 14 also decreases via the differential pressure chamber 16. When the upward force (seating direction) of the needle 42 exceeds the downward force (seating direction) of the needle 42, the needle 42 is lifted and high pressure fuel supplied to the fuel reservoir 44 is injected from the injection hole 43. .
Conversely, when the internal pressure of the differential pressure chamber 16 rises due to “high pressure switching (electromagnetic valve 13 OFF)” of the differential pressure switching valve 12, the internal pressure of the nozzle back pressure chamber 14 also rises via the differential pressure chamber 16. When the downward force (seating direction) of the needle 42 exceeds the upward force (seating direction) of the needle 42, the needle 42 is lowered. Then, when the needle 42 is seated on the nozzle holder 41, fuel injection from the nozzle hole 43 is stopped.

(Description of pressure booster 17)
The pressure booster 17 includes a pressure increasing piston 51 that is displaced downward due to a pressure drop of the differential pressure chamber 16 with respect to the equal pressure chamber 23, and a return spring 52 that returns the pressure increasing piston 51 to an initial position (upward).
The pressure-increasing piston 51 is slidably supported in the vertical direction inside the injector body 21. The pressure increasing piston 51 is provided with a spring seat, a spring accommodating shaft, a large diameter portion, and a small diameter portion from above to below.
The spring seat and the spring housing shaft are disposed in the isobaric chamber 23 that receives high-pressure fuel from the common rail 1, and the isobaric chamber 23 is always kept at the rail pressure. The high-pressure fuel in the isobaric chamber 23 acts on the diameter difference on the upper side of the pressure-increasing piston 51 to generate a downward force (in the pressure-increasing direction) on the pressure-increasing piston 51.
The spring seat is a seating portion of a return spring 52 that urges the pressure-increasing piston 51 upward (in the initial position return direction). The return spring 52 is a compression coil spring that urges the spring seat upward by a restoring force.

Both the large diameter portion and the small diameter portion are slidably supported by the injector body 21, and a differential pressure chamber 16 is formed between the step between the large diameter portion and the small diameter portion and the injector body 21.
Further, between the lower surface of the small diameter portion and the injector body 21, a pressure increasing chamber 53 is formed in which the volume is changed by the vertical displacement of the pressure increasing piston 51 and fuel is pressurized by the lowering of the pressure increasing piston 51. Has been.
The pressure increasing chamber 53 communicates with the equal pressure chamber 23 via a fuel passage 54 having a one-way valve 54 a that allows fuel to flow from the equal pressure chamber 23 only to the pressure increasing chamber 53. Therefore, the fuel pressure in the pressure increasing chamber 53 and the fuel reservoir 44 of the injection nozzle 15 is maintained at the rail pressure while the pressure increasing piston 51 is in the stopped state and rising to the initial position, and when the pressure increasing piston 51 is lowered, the pressure increasing chamber is increased. The internal pressure of 53 increases, and the fuel pressure in the pressure increasing chamber 53 and the fuel reservoir 44 becomes higher than the rail pressure.

As described above, the internal pressure of the differential pressure chamber 16 is switched between high pressure and low pressure by the differential pressure switching valve 12.
For this reason, when the differential pressure chamber 16 is switched to the low pressure side by “low pressure switching (electromagnetic valve 13 ON)” of the differential pressure switching valve 12, the pressure is increased by the upward force of the pressure increasing piston 51 (initial position return direction). The downward force (pressure increasing direction) of the piston 51 is increased, the pressure increasing piston 51 is lowered, the volume of the pressure increasing chamber 53 is reduced, and the fuel pressure in the fuel reservoir 44 of the pressure increasing chamber 53 and the injection nozzle 15 is the rail pressure. Increase more.
On the other hand, when the differential pressure chamber 16 is switched to the high pressure side by “high pressure switching (electromagnetic valve 13 OFF)” of the differential pressure switching valve 12, the upward force of the pressure increasing piston 51 (initial position return direction) is increased. It exceeds the downward force (pressure increasing direction) of the piston 51, the pressure increasing piston 51 rises, and the pressure increasing piston 51 returns to the initial position (upper side).

[Features of Example 1]
In the fuel injection device shown in the above reference example, when the solenoid valve 13 is turned ON and the differential pressure switching valve 12 is switched to “low pressure switching”, the injection nozzle 15 performs fuel injection and the pressure intensifier 17 is connected to the injection nozzle 15. Increase fuel pressure.
For this reason, the pressure intensifier 17 is activated even in a short time injection, and the fuel pressure in the fuel reservoir 44 is increased, and a large amount of fuel is injected even in the short time injection. As a result, it is difficult to control the amount of minute injection at the time of minute injection such as multistage injection and pre-injection. That is, it is difficult to control with high accuracy from a very small injection amount to a very small injection amount.
It is also difficult to control the injection rate pattern by changing the injection rate during the injection period.

Therefore, in the first embodiment, the present invention is adopted to solve the above problems.
In order to employ the present invention, the injector 2 of the first embodiment includes a fuel reservoir 44 to which high-pressure fuel is supplied, an injection nozzle 15 that performs fuel injection and injection stop operations of the fuel reservoir 44, a fuel reservoir. 44, a pressure intensifier 17 that performs the operation of increasing and stopping the pressure increase of the high-pressure fuel, a first valve body 61a that switches the operation of the injection nozzle 15 between injection and stop, and the first valve body 61a. A first movable valve 61 having a first armature 61b, a second valve body 31a for switching the operation of increasing and stopping the pressure intensifier 17, and a second armature that moves integrally with the second valve body 31a. 2nd movable valve 31 provided with 31b.

The first movable valve 61 is provided so as to be independently displaceable with respect to the second movable valve 31, and the first armature 61 b and the second armature 31 b are individually magnetically attracted by the common electromagnetic drive unit 33. Therefore, the switching state of the first movable valve 61 and the second movable valve 31 differs depending on the energization amount given to the electromagnetic drive unit 33.
The second movable valve 31 (second valve body 31a, second armature 31b) and the second low-pressure fuel passage 25 are the same as the movable valve 31 (valve body 31a, armature 31b) and low-pressure fuel passage 25 shown in the reference example. The same function is performed and will be described with the same reference numerals.

The injector 2 of the first embodiment is different from the above reference example in that the structure of the solenoid valve 13 is different and the back pressure control of the nozzle back pressure chamber 14 can be independently controlled by the solenoid valve 13. The present invention is employed by providing a first low-pressure fuel passage 62 that communicates between the chamber 14 and the low-pressure side.
The electromagnetic valve 13 according to the first embodiment includes the first movable valve 61, the second movable valve 31, the electromagnetic drive unit 33, and the return spring 32 described above.

In the electromagnetic valve 13 of the first embodiment, the first movable valve 61 and the second movable valve 31 are arranged separately on the upper and lower sides of the electromagnetic drive unit 33 and are operated in opposite directions by the operation of the electromagnetic drive unit 33. It is.
The first movable valve 61 is disposed on the lower side of the electromagnetic drive unit 33, and is supported so as to be slidable in the axial direction and can close the first low-pressure fuel passage 62 at the lower end surface. And a first armature 61b made of a magnetic material having a substantially disc shape fixed to the upper portion of the first valve body 61a.
The first valve body 61a opens and closes a first low pressure fuel passage 62 (specifically, an outlet orifice 62a provided in the first low pressure fuel passage 62) that communicates the nozzle back pressure chamber 14 to the low pressure side. The operation of the injection nozzle 15 is switched between injection and injection stop, and is pressed around the first valve port (in this embodiment, the outlet orifice 62a) provided in the middle of the first low-pressure fuel passage 62. The first valve port is closed by sitting.

The second movable valve 31 is arranged on the upper side of the electromagnetic drive unit 33, is supported so as to be slidable in the axial direction, and has a second valve body 31a capable of closing the second low-pressure fuel passage 25 at the upper end surface. The second armature 31b made of a magnetic material having a substantially disk shape fixed to the lower portion of the second valve body 31a.
The second valve body 31a opens and closes the second low pressure fuel passage 25 (specifically, the outlet orifice 25a provided in the second low pressure fuel passage 25) that communicates the switching valve back pressure chamber 11 to the low pressure side. Thus, the differential pressure switching valve 12 is switched to switch the operation of increasing the pressure of the pressure intensifier 17 and stopping the pressure increase. The second valve port provided in the middle of the second low pressure fuel passage 25 (this implementation) In the example, the second valve port is closed by being pressed and seated around the outlet orifice 25a).

  The electromagnetic drive unit 33 has different switching states of the first movable valve 61 and the second movable valve 31 according to the energization amount (drive current value) given from the control device. When a predetermined drive current value (hereinafter referred to as a first drive current) shown in FIG. 2 (b) is given, only the first movable valve 61 is opened, and the controller drives the electromagnetic drive unit 33 from FIG. 2 (a). Both the first movable valve 61 and the second movable valve 31 are opened when a predetermined drive current value (a current value higher than the first drive current, hereinafter referred to as a second drive current) is applied. Is.

Similarly to the reference example, the electromagnetic drive unit 33 is configured by a coil 34 and a stator 35, and the first movable valve 61 and the second movable valve 31 according to the first and second drive currents supplied from the control device. As a means for operating the first movable valve 61, the magnetic attractive force of the first movable valve 61 is made larger than the magnetic attractive force of the second movable valve 31.
Specifically, the electromagnetic drive unit 33 is configured by the coil 34 and the stator 35 as in the reference example, but the magnetic attraction force of the first movable valve 61 is greater than the magnetic attraction force of the second movable valve 31. In order to enlarge the coil 34, the lower coil 34a is divided into upper and lower parts, the lower coil 34a for driving the first movable valve 61 is increased in magnetic force, and the upper coil 34b is decreased in magnetic force. The number of turns of 34a is larger than the number of turns of the upper coil 34b. Here, the lower and upper coils 34a and 34b may be two coils connected in series or may be connected in parallel. Alternatively, one conductive wire may be wound in two parts.

Unlike this embodiment, the coil 34 may be provided as one piece without dividing, and the facing area between the first armature 61b and the stator 35 may be larger than the facing area between the second armature 31b and the stator 35. Alternatively, one coil 34 is provided without being divided, and as shown in Example 2 described later, a return spring that biases the first movable valve 61 in the valve closing direction and the second movable valve 31 in the valve closing direction. A return spring that urges the first movable valve 61 may be provided separately, and the urging force of the return spring that urges the first movable valve 61 may be smaller than the urging force of the return spring that urges the second movable valve 31.
By providing as described above, it is possible to open only the first movable valve 61 by applying the first drive current to the electromagnetic drive unit 33, and to apply the second drive current to the electromagnetic drive unit 33. Both the movable valve 61 and the second movable valve 31 can be opened.

(Effect of Example 1)
In the injector 2 of the first embodiment, as described above, the first movable valve 61 is provided so as to be independently displaceable with respect to the second movable valve 31, and the first armature 61b and the second armature 31b are common. It is magnetically attracted individually by the electromagnetic drive unit 33.
Then, as shown in FIG. 2C, by applying a first drive current (see arrow a in the figure) to the electromagnetic drive unit 33, only the first movable valve 61 is opened and only the injection nozzle 15 is operated. Thus, “non-intensified injection (see arrow a ′ in the figure)” that injects fuel without operating the intensifier 17 can be performed, and a second drive current (see arrow b in the figure) is applied to the electromagnetic drive unit 33. As a result, the first movable valve 61 and the second movable valve 31 are simultaneously opened, and both the injection nozzle 15 and the pressure intensifier 17 are operated to inject fuel. “Pressurized injection (see arrow b ′ in the figure) Can be implemented. That is, two patterns of injection forms of “non-pressure-increasing injection” and “pressure-increasing injection” can be obtained according to the energization amount given to the electromagnetic drive unit 33.

In the “non-pressure-increasing injection”, the pressure intensifier 17 does not operate as described above. Therefore, the fuel pressure in the fuel reservoir 44 is maintained at the rail pressure, and the pressure intensifier 17 operates even during short-time injection to reduce the injection amount. There will be no increase. Thereby, in the “non-pressure-increasing injection”, the control of the minute injection amount becomes easy. That is, the control of the minute injection amount is facilitated at the time of minute injection such as multistage injection and pre-injection indicated by an arrow a ′ in FIG.
Further, in the “pressure increasing injection”, both the injection nozzle 15 and the pressure intensifier 17 are operated, and the fuel whose pressure is increased from the rail pressure can be injected from the injector 2. Thereby, it is possible to increase the pressure of the injected fuel at the time of the main injection indicated by the arrow b ′ in FIG. 2C, and it is possible to purify the exhaust gas such as reducing the CO ₂ emission amount for improving the environment.
Furthermore, by variably controlling the interval between the first drive current and the second drive current, the minute injection and the main injection can be independently performed as shown in FIG. 2C, and FIG. ), An injection rate pattern for starting main injection during micro injection can be obtained.

As described above, the injector 2 according to the first embodiment has a structure in which the first armature 61b of the first movable valve 61 and the second armature 31b of the second movable valve 31 are individually magnetically attracted by the electromagnetic drive unit 33. For this reason, the response from “injection stop (solenoid valve 13 OFF)” to “non-intensified injection” without applying a drive current to the electromagnetic drive unit 33 and the response from “injection stop” to “intensified injection”. Both sexes can be increased.
That is, the injector 2 of the first embodiment can be switched between “injection stop”, “non-intensified injection”, and “intensified injection”, and further has excellent switching responsiveness.

  In the injector 2 of the first embodiment, as described above, the first and second valve ports (exit orifice 62a) in which the first and second valve bodies 61a and 31a open and close the first and second low-pressure fuel passages 62 and 25, respectively. 25a), the first and second valve ports are closed, and the first and second valve ports are closed more efficiently than the conventional technique using a spool. As a result, leakage fuel when the first and second valve ports are closed can be reduced. That is, the static leak amount of the injector 2 (leak amount when the injector 2 is not operated) can be suppressed.

As described above, the injector 2 according to the first embodiment can implement the present invention only by changing the electromagnetic valve 13 and adding the first low-pressure fuel passage 62. For this reason, the cost increase of the injector 2 to which the present invention is applied can be suppressed.
In the injector 2 of the first embodiment, the nozzle back pressure chamber 14 communicates with the differential pressure chamber 16 via a fuel passage 46 having an orifice 46a.
Therefore, when the second movable valve 31 switches the differential pressure chamber 16 to a high pressure and the first movable valve 61 switches the nozzle back pressure chamber 14 to a low pressure, the nozzle back pressure chamber 14 includes a differential pressure chamber. Since the fuel flows from 16 through the fuel passage 46, the pressure drop in the nozzle back pressure chamber 14 is moderated. Thereby, the lift speed of the needle 42 can be suppressed, and the controllability of the fine injection can be improved.
When the first movable valve 61 switches the low pressure of the nozzle back pressure chamber 14 and the second movable valve 31 switches the differential pressure chamber 16 to low pressure, the nozzle back pressure chamber 14 is switched to low pressure by the first movable valve 61. In addition, since the fuel flows out to the differential pressure chamber 16 via the fuel passage 46, the pressure in the nozzle back pressure chamber 14 can be quickly switched to a low pressure. Thereby, the lift speed of the needle 42 can be increased, and large injection (injection with a large injection rate) can be performed in a short time.

The injector 2 according to the second embodiment will be described with reference to FIG. In the second embodiment, the same reference numerals as those in the first embodiment indicate the same functional objects.
The first movable valve 61 and the second movable valve 31 of the second embodiment are disposed on one side of the electromagnetic drive unit 33 and are operated in the same direction by the operation of the electromagnetic drive unit 33.
The first movable valve 61 and the second movable valve 31 are both disposed below the electromagnetic drive unit 33. The first movable valve 61 is coaxially disposed around the second movable valve 31, and the first The movable valve 61 and the second movable valve 31 independently open and close the first low pressure fuel passage 62 and the second low pressure fuel passage 25.

Further, in the second embodiment, the coil 34 of the electromagnetic drive unit 33 is provided in one, the first return spring 32a that biases the first movable valve 61 in the valve closing direction, and the second movable valve 31 is closed. The second return spring 32b that is urged in the direction is provided separately, and the urging force of the first return spring 32a is set smaller than the urging force of the second return spring 32b, whereby the electromagnetic drive unit 33 is provided with the first return spring 32b. Only the first movable valve 61 is opened by giving a driving current, and both the first movable valve 61 and the second movable valve 31 are opened by giving a second driving current to the electromagnetic drive unit 33. It has been.
Even if the second embodiment is adopted, the same effect as the first embodiment can be obtained.

[Modification]
In the above-described embodiment, the example in which the second movable valve 31 switches the hydraulic pressure of the switching valve back pressure chamber 11 has been shown. However, the differential pressure switching valve 12 is eliminated, and the second movable valve 31 directly changes the differential pressure. You may provide so that the oil_pressure | hydraulic switching of the chamber 16 may be performed. Thus, by eliminating the differential pressure switching valve 12, it is possible to reduce the cost and downsize the injector 2.
In the above-described embodiment, an example in which the differential pressure chamber 16 and the nozzle back pressure chamber 14 are provided in communication with each other via the fuel passage 46 has been described. However, by connecting the differential pressure chamber 16 and the nozzle back pressure chamber 14 with each other. The improvement in controllability of micro injection, which is one effect obtained, is obtained by supplying fuel to the nozzle back pressure chamber 14 when only the first movable valve 61 is hydraulically switched. The direct communication between the pressure chamber 16 and the nozzle back pressure chamber 14 may be eliminated, and instead, the nozzle back pressure chamber 14 may be communicated with a high pressure fuel supply unit such as the isobaric chamber 23 through an orifice.

It is the schematic of a fuel-injection apparatus (reference example and Example 1). FIG. 6 is a waveform diagram of a first drive current and a second drive current, and a time chart showing a relationship between a drive current applied to an electromagnetic drive unit and an injection rate (Example 1). (Example 2) which is the schematic of a fuel-injection apparatus.

Explanation of symbols

11 switching valve back pressure chamber 12 differential pressure switching valve 14 nozzle back pressure chamber 15 injection nozzle 16 differential pressure chamber 17 pressure booster 25 second low pressure fuel passage 25a outlet orifice (second valve provided in the middle of the second low pressure fuel passage) mouth)
31 2nd movable valve 31a 2nd valve body 31b 2nd armature 33 Electromagnetic drive part 44 Fuel reservoir 61 1st movable valve 61a 1st valve body 61b 1st armature 62 1st low pressure fuel passage 62a Exit orifice (1st low pressure fuel passage) 1st valve port provided in the middle of

Claims (8)

An injection nozzle that includes a fuel reservoir to which high-pressure fuel is supplied, and injects and stops the fuel in the fuel reservoir;
A pressure intensifier that operates to increase and stop the pressure increase of the high pressure fuel in the fuel reservoir;
A first valve body having a first valve body that switches between injection and injection stop of the injection nozzle, and a first armature that moves integrally with the first valve body;
A second valve body for switching the operation of increasing and stopping the pressure booster, and a second movable valve including a second armature that moves integrally with the second valve body,
The first movable valve is provided to be independently displaceable with respect to the second movable valve, and the first and second armatures are individually magnetically attracted by a common electromagnetic drive unit,
The fuel injection device characterized in that the switching state of the first and second movable valves differs according to the energization amount given to the electromagnetic drive unit. The fuel injection device according to claim 1,
The injection nozzle performs injection and injection stop by a change in hydraulic pressure of a nozzle back pressure chamber to which high-pressure fuel is supplied,
The first movable valve switches the oil pressure of the nozzle back pressure chamber directly or indirectly,
The pressure intensifier performs pressure increase and pressure increase stop by changing the oil pressure in the differential pressure chamber to which high pressure fuel is supplied,
The fuel injector according to claim 1, wherein the second movable valve switches the oil pressure of the differential pressure chamber directly or indirectly. The fuel injection device according to claim 2, wherein
This fuel injection device includes a differential pressure switching valve that switches the pressure in the differential pressure chamber to the high pressure fuel side or the low pressure fuel side by changing the hydraulic pressure of the switching valve back pressure chamber to which high pressure fuel is supplied.
The fuel injection device characterized in that the second movable valve indirectly switches the hydraulic pressure of the differential pressure chamber by switching the hydraulic pressure of the switching valve back pressure chamber. The fuel injection device according to claim 3, wherein
The fuel injection device, wherein the nozzle back pressure chamber communicates with the differential pressure chamber. The fuel injection device according to claim 2, wherein
The fuel injector according to claim 1, wherein the second movable valve directly switches the hydraulic pressure of the differential pressure chamber. The fuel injection device according to claim 3 or 4,
The first valve body performs switching between injection and injection stop of the injection nozzle by opening and closing a first low pressure fuel passage communicating the nozzle back pressure chamber to the low pressure side,
The second valve body is configured to perform switching between pressure increase and pressure increase stop operation by opening and closing a second low pressure fuel passage communicating the switching valve back pressure chamber to the low pressure side,
The first valve body is provided so as to close the first valve port by being pressed and seated around a first valve port provided in the middle of the first low-pressure fuel passage,
The second valve body is provided so as to close the second valve port by being pressed and seated around a second valve port provided in the middle of the second low-pressure fuel passage. Fuel injection device. The fuel injection device according to any one of claims 1 to 6,
The first and second movable valves are arranged on both sides of the electromagnetic drive unit and operate in opposite directions by the operation of the electromagnetic drive unit. The fuel injection device according to any one of claims 1 to 6,
The fuel injector according to claim 1, wherein the first and second movable valves are arranged on one side of the electromagnetic drive unit and operate in the same direction by the operation of the electromagnetic drive unit.

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