JP2001355533A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple and small-size fuel injection valve capable of setting the initial fuel injection rate low in a case of being used for a common rail type fuel injection device. SOLUTION: The fuel injection valve is provided with a control chamber 109 for retaining the hydraulic pressure energizing a needle in the valve opening direction, in the top of its needle 105. The control chamber communicates with a leak chamber 130 via hydraulic pressure return channels 201 and 203, and the leak chamber is connected to a low-pressure leak channel 107 via a control valve 300. The control valve 300 can take either of a first position cutting off the leak chamber from the leak channels, a second position closing the hydraulic return channel 203 and communicating only the hydraulic return channel 201 to the leak channel via the leak chamber, or a third position communicating the both hydraulic return channels to the leak channel via the leak chamber. The changeover between the second position and the third position can change the hydraulic pressure reducing speed of the control chamber so as to change the lifting speed of the needle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a fuel injection valve.

[0002]

2. Description of the Related Art There is known a so-called common rail type fuel injector in which high-pressure fuel is stored in a pressure accumulating chamber (common rail) and fuel is distributed from the pressure accumulating chamber to fuel injection valves of respective cylinders of an internal combustion engine. In the common rail type fuel injection device,
Since high-pressure fuel is always stored in the common rail, the fuel injection pressure can be set high regardless of the engine speed. For this reason, compared with the conventional engine-driven fuel injection pump (so-called jerk type fuel injection pump), the atomization of the fuel injected from the fuel injection valve is improved even at low rotation, and the combustion state of the engine and the exhaust gas are improved. There is an advantage that the properties are improved.

On the other hand, in the jerk type fuel injection pump, the fuel injection pressure repeatedly fluctuates relatively low in the early stage of the fuel injection and increases in the late stage of the injection. Typically fuel injected into the fuel injection initial high degree of contribution to the combustion chamber temperature rises, the amount of NO and the fuel quantity injected fuel injection early often due to the increase of the combustion temperature _X (nitrogen oxides) is increased There is a problem to do. In the jerk pump, as described above, the fuel injection pressure in the early stage of fuel injection is low, and the fuel injection rate is also low, so that the amount of fuel injected in the early stage of fuel injection is relatively small,
And a preferred injection characteristics over of the NO _X suppression.

However, in the common rail type fuel injection device, the fuel injection pressure becomes substantially constant throughout the injection period.
The fuel injection rate also becomes substantially constant. For this reason, the fuel injection amount at the beginning of the fuel injection period becomes relatively large, and NO
There is a problem that it is difficult to suppress generation of _X. For this reason, various fuel injection valves have been proposed, such as a common rail fuel injection device, which can obtain the same injection characteristics as a jerk type fuel injection pump even at a constant fuel injection pressure.

[0005] For example, as this kind of fuel injection valve, there is one disclosed in Japanese Patent Application Laid-Open No. Hei 5-71438. In the fuel injection valve disclosed in the publication, an electromagnetic three-way valve is provided in a back pressure chamber (control chamber) that holds a hydraulic pressure that urges the needle in a direction to close the fuel injection hole, and communicates the high pressure hydraulic passage with the back pressure chamber. By switching the three-way valve to the position, the closed state of the fuel injection valve is maintained. At the time of fuel injection, the three-way valve is
The needle is moved to a position where the fuel injection hole is opened by switching to a position where the back pressure chamber communicates with the low pressure part and releasing the oil pressure in the back pressure chamber to the low pressure part. In addition, the fuel injection valve of the publication includes a control valve on a passage communicating the three-way valve and the low-pressure portion, in addition to the three-way valve, and the control valve is provided with a fuel that flows to the low-pressure portion through the passage. A first position for interrupting the oil flow and a second position for releasing a part of the fuel oil in the back pressure chamber to the low pressure portion.
And a third position in which the fuel oil in the back pressure chamber is completely released to the low pressure portion.

In the fuel injection valve disclosed in the publication, the three-way valve is switched to a position where the back pressure chamber communicates with the low pressure portion during fuel injection, and the control valve is first switched to the second position.
Thereafter, the fuel injection rate from the fuel injection valve is controlled by switching to the third position. That is, at the time of fuel injection, first, the control valve is switched to the second position, whereby a part of the fuel oil in the back pressure chamber is discharged to the low pressure portion, and the pressure in the back pressure chamber slightly decreases. For this reason, the needle slightly rises and the fuel injection hole is slightly opened. Next, the control valve
, The fuel oil in the back pressure chamber completely escapes to the low pressure portion, the needle rises greatly, and the fuel injection hole opens largely. As a result, an injection characteristic is obtained in which the amount of fuel injected from the fuel injection hole is small at the beginning of the fuel injection and large at the latter stage. That is, according to the fuel injection valve of the same publication, even when used in a common rail fuel injection device, it is possible to obtain a fuel injection characteristic in which the injection rate is small in the early stage of the fuel injection and large in the latter period, similarly to the jerk type fuel injection device. Becomes possible.

[0007]

However, in the fuel injection valve disclosed in Japanese Patent Application Laid-Open No. 5-71438, an electromagnetic three-way valve is required to obtain a fuel injection characteristic in which the injection rate is small in the early stage of fuel injection and large in the latter period. Two valves, a control valve and a control valve, are required, and there is a problem that the structure of the injection valve becomes large and complicated. In addition, in the fuel injection valve disclosed in the publication, not only is it necessary to operate two valves, that is, an electromagnetic three-way valve and a control valve, at the same time, but also an individual power supply is required for each valve, but also the operation timing of each valve is precisely controlled. There is a problem that requires complicated control to manage.

In a diesel engine, pilot fuel injection may be performed before main fuel injection. Depending on the operating state of the engine, it may be necessary to change the fuel injection characteristics between pilot fuel injection and main fuel injection. is there. However, although the fuel injection valve disclosed in the above publication can obtain the fuel injection characteristic in which the injection rate is small in the early stage of the fuel injection and large in the latter period, it cannot be changed once the fuel injection characteristic is set, and the fuel injection characteristic cannot be changed according to the operating state of the engine. The fuel injection characteristics of the pilot fuel injection and the main fuel injection cannot be changed.

The present invention has been made in view of the above problems, and has a simple and small structure. For example, even when used in a common rail fuel injection device, a fuel injection system capable of obtaining desired fuel injection characteristics in accordance with the operating state of the engine. It is intended to provide a valve.

[0010]

According to the first aspect of the present invention, a housing, a fuel injection hole opened in the housing, a high-pressure fuel passage connected to the fuel injection hole, and the fuel injection hole are formed. A control chamber formed at the end of the housing opposite to the fuel injection hole of the needle and the needle that opens and closes, connecting the high-pressure fuel passage and the control chamber,
By connecting the control chamber to a low-pressure section outside the housing and reducing the oil pressure in the control chamber, the hydraulic pressure supply passage supplies a hydraulic pressure that urges the needle into the control chamber in a direction to close the fuel injection hole. At least two hydraulic return passages for moving a needle in a direction to open the fuel injection holes, and a control valve for opening and closing the hydraulic return passages, wherein the control valve closes the entire hydraulic return passages. , A second position in which at least one of the hydraulic return passages is closed and at least one is opened, and a third position in which the entire hydraulic return passage is opened. , A fuel injection valve is provided.

That is, in the first aspect of the present invention, the control chamber for holding the hydraulic pressure for urging the needle in the valve closing direction is always connected to the high-pressure fuel passage by the hydraulic supply passage. In addition, a plurality of hydraulic return passages are provided for communicating the control chamber with the low-pressure section, and only one control valve for opening and closing these hydraulic return passages is provided. Control valves are first to third
The fuel injection and the fuel injection characteristics are controlled by switching the position of the control valve.
That is, when the control valve is in the first position, the entire hydraulic return passage is closed, so that the hydraulic pressure in the control chamber connected to the high-pressure fuel passage is maintained at a high pressure, and the needle is closed (in the fuel injection position). (Position to close the hole), and the fuel injection is stopped. Further, when the control valve assumes the second position, a part of the plurality of hydraulic return passages is closed and partially opened, so that the fuel oil in the control chamber passes through only the opened return passage to the low-pressure section. leak. For this reason, even when the fuel is constantly connected to the high-pressure fuel passage, the oil pressure in the control chamber decreases by a relatively small value, and the needle moves at a relatively small speed in the valve opening direction. , And the fuel injection is performed at a low injection rate as a whole. On the other hand, when the control valve assumes the third position, the entire hydraulic return passage is opened, and a relatively large amount of fuel oil flows out of the control chamber to the low pressure section. For this reason, even in a state where the needle is connected to the high-pressure fuel passage, the oil pressure in the control chamber drops by a relatively large value, and the needle moves at a relatively large speed in the valve opening direction. As a result, the injection rate immediately rises, and fuel injection with a relatively large injection rate as a whole is performed. In the present invention, since the injection rate at the time of fuel injection can be changed using only one control valve as described above, the structure of the fuel injection valve becomes small and simple, and the control valve is used at the time of fuel injection. By switching between the second position and the third position, the fuel injection rate can be freely changed.

[0012] According to the second aspect of the invention, at least one of the hydraulic return passages has a throttle portion between the control valve and the control chamber, and the high-pressure fuel passage further includes: 2. The fuel injection valve according to claim 1, wherein the fuel injection valve is connected between the throttle portion of the at least one hydraulic return passage and the control valve. That is, in the invention of claim 2, at least one of the hydraulic return passages has a throttle portion, and the high-pressure fuel passage is connected to the hydraulic return passage. Therefore, when the hydraulic return passage is closed by the control valve, high-pressure fuel flows from the closed return passage into the control chamber via the throttle. Therefore, for example, when all the hydraulic return passages are closed at the end of the fuel injection, fuel flows into the control chamber from the hydraulic return passage in addition to the hydraulic supply passage, and the pressure recovery of the control chamber is reduced. (Up) The speed increases. Therefore, in the present invention, in addition to the first aspect, the needle closing speed at the time of fuel injection is further increased, so that the so-called cut-off of fuel at the time of fuel injection is improved, so that the fuel injection amount is accurately controlled. Become.

According to the third aspect of the present invention, the housing, the fuel injection hole opened in the housing, the high pressure fuel passage connected to the fuel injection hole, the needle for opening and closing the fuel injection hole, and the housing A control chamber formed at an end of the needle opposite to the fuel injection hole, a leak chamber connected to the control chamber by at least two hydraulic return passages, and connecting the leak chamber and the high-pressure fuel passage A hydraulic pressure supply passage for supplying high-pressure fuel into the leak chamber, a leak passage connecting the leak chamber to a low-pressure portion outside the housing, and a control valve provided in the leak chamber and having a valve body for opening and closing the leak passage. Wherein the control valve has a first position in which the valve element closes the leak path and opens all hydraulic return paths, and the valve element opens the leak path; A second position in which at least one of the hydraulic return passages is closed and at least one is opened, and a third position in which the leak passage and all of the hydraulic return passages are opened, By taking the first position, the valve causes the fuel oil flowing from the hydraulic pressure supply passage into the leak chamber to flow into the control chamber through the entire hydraulic return passage, thereby increasing the hydraulic pressure in the control chamber. Then, the needle is urged in the direction to close the fuel injection hole, and the second or third position is taken, so that the fuel oil flowing from the hydraulic pressure supply passage into the leak chamber passes through the leak passage. To the low pressure section,
At the same time, the fuel oil in the control chamber flows into the leak chamber via the hydraulic return passage, and is further discharged from the leak passage to a low pressure section, thereby lowering the oil pressure in the control chamber to open the needle to the fuel injection hole. The fuel injection valve is characterized in that the fuel injection valve is moved in a direction in which the fuel injection valve moves.

That is, according to the third aspect of the present invention, the hydraulic return passage communicates with the leak chamber connected to the leak passage, and the control valve opens and closes the leak passage so that the fuel flows from the control chamber to the leak passage through the leak chamber. Controlling oil. Further, the hydraulic supply passage is not directly connected to the control chamber, but supplies fuel oil to the leak chamber. When the high-pressure fuel passage and the control chamber are directly connected via the fuel supply passage as in the first aspect of the present invention, even when the hydraulic return passage is opened and communicates with the leak passage, fuel remains in the control chamber. Fuel flows in from the supply passage. For this reason, in order to reduce the oil pressure in the control chamber even when the control valve is in the second position and only a part of the hydraulic return passage communicates with the leak passage, for example, the hydraulic supply passage must be located in the throttle control chamber. It is necessary to reduce the amount of incoming oil. However, when the hydraulic supply passage is narrowed, there is no problem when the fuel pressure in the high-pressure fuel passage is high, but when the fuel pressure decreases, the amount of oil flowing into the control chamber when the fuel injection valve is closed becomes insufficient, There is a case where the rise of the oil pressure in the control chamber is delayed, and the valve closing of the needle is delayed.

In the present invention, the hydraulic supply passage is connected not to the control chamber but to the leak chamber. Therefore, when the control valve is opened, fuel flowing from the hydraulic pressure supply passage into the leak chamber is immediately discharged into the leak passage without flowing into the control chamber. For this reason, even when only a part of the hydraulic return passage is opened, the hydraulic pressure in the control chamber is reliably reduced, and the needle is opened. When the control valve closes the leak passage, the fuel oil flowing from the hydraulic supply passage into the leak chamber flows into the control chamber through all the hydraulic return passages. Therefore, even when the fuel pressure is low, the oil pressure in the control chamber rises at a high speed, and the needle is reliably closed.

According to a fourth aspect of the present invention, the fuel injection valve according to the third aspect further includes a second hydraulic pressure supply passage having a throttle portion, which connects the high-pressure fuel passage and the control chamber. Is provided. That is, in the invention of claim 4, in addition to the hydraulic pressure supply passage connecting the leak chamber and the high pressure fuel passage, a second hydraulic pressure supply passage connecting the control chamber and the high pressure fuel passage is provided. Therefore, when the needle is closed, in addition to the fuel oil flowing into the control chamber from the leak chamber through the hydraulic return passage, the fuel oil flows directly from the high-pressure fuel passage into the control chamber through the second hydraulic supply passage. Therefore, the needle can be more reliably closed even when the fuel pressure is low. Further, a throttle portion is provided in the second hydraulic pressure supply passage, and the flow rate of the fuel oil flowing into the control chamber through the second hydraulic pressure supply passage is relatively low. Therefore, even when the fuel pressure is high, the opening of the needle is not affected.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of an embodiment in which the fuel injection valve of the present invention is applied to a common rail type fuel injection device for an automobile diesel engine. In FIG. 1, reference numeral 1 denotes an internal combustion engine (# 1 in this embodiment).
A four-cylinder four-cycle diesel engine having four cylinders # 1 to # 4 is used. Reference numerals 10a to 10d denote fuel injection valves for directly injecting fuel into the cylinders # 1 to # 4 of the engine 1. I have. The fuel injection valves 10a to 10d are connected to a common accumulator (common rail) 3 via high-pressure fuel pipes 11a to 11d, respectively. The common rail 3 stores pressurized fuel supplied from the high-pressure fuel injection pump 5, and transfers the stored high-pressure fuel to the high-pressure fuel pipe 11a from the high-pressure fuel pipe 11a.
It has a function of distributing to each of the fuel injection valves 10a to 10d via 1d.

In this embodiment, the high-pressure fuel injection pump 5
Is a pump of a plunger type having a discharge amount adjusting mechanism, for example, and boosts fuel supplied from a fuel tank (not shown) to a predetermined pressure and supplies the fuel to the common rail 3. The amount of fuel pressure fed from the pump 5 to the common rail 3 is feedback-controlled by the ECU 20 so that the common rail 3 pressure becomes the target pressure. Therefore, the fuel pressure of the common rail 3 (that is, the fuel injection pressure of each fuel injection valve) can be set to a high pressure even when the engine is running at a low speed. When each of the fuel injection valves 10a to 10d is opened, high-pressure fuel is injected from the common rail 3 into each cylinder through each fuel injection valve, but the volume of the common rail 3 is much larger than a single fuel injection amount. Therefore, during the fuel injection period of each fuel injection valve 10, the fuel pressure of the common rail 3 (that is, the fuel injection pressure) is maintained substantially constant.

In FIG. 1, reference numeral 20 denotes an electronic control unit (ECU) for controlling the engine. The ECU 20 is configured as a microcomputer having a known configuration in which a read-only memory (ROM), a random access memory (RAM), a microprocessor (CPU), and an input / output port are connected by a bidirectional bus. In the present embodiment, the ECU 20 controls the discharge amount of the fuel pump 5 to control the pressure of the common rail 3 to a target value determined according to the engine operating conditions.
Basic control of the engine such as fuel injection control for controlling the valve opening operation such as the valve opening timing and time of 0d to control the injection timing and injection amount of the main fuel injection is performed.

In order to perform these controls, in this embodiment, the common rail 3 is provided with a fuel pressure sensor 27 for detecting the fuel pressure in the common rail, and a fuel pressure sensor 27 near the accelerator pedal (not shown) of the engine 1. An accelerator opening sensor 21 for detecting an accelerator opening (a driver's accelerator pedal depression amount) is provided. In FIG. 1, reference numeral 23 denotes a cam angle sensor for detecting the rotation phase of the camshaft of the engine 1, and reference numeral 25 denotes a crank angle sensor for detecting the rotation phase of the crankshaft. The cam angle sensor 23 is disposed in the vicinity of the cam shaft of the engine 1, and is converted to a crank rotation angle of 7 degrees.
A reference pulse is output every 20 degrees. The crank angle sensor 25 is disposed near the crankshaft of the engine 1 and generates a crank angle pulse at every predetermined crank rotation angle (for example, every 15 degrees).

The ECU 20 calculates the engine speed from the frequency of the crank rotation angle pulse signal input from each of the crank sensors 25, and calculates the fuel based on the accelerator opening signal input from the accelerator opening sensor 21 and the engine speed. The fuel injection timing and the fuel injection amount of the injection valves 10a to 10d are calculated. In the present embodiment, any known method can be used for calculating the fuel injection timing and the fuel injection amount from the fuel injection valve.

Next, the structure of the fuel injection valve 10 of the present embodiment (the fuel injection valves 10a to 10d have the same structure, and are collectively denoted by reference numeral 10 in the following description) will be described. FIG. 2 is a longitudinal sectional view of the fuel injection valve 10 of the present embodiment. In FIG. 1, reference numeral 101 denotes a substantially cylindrical fuel injection valve housing, 103 denotes a fuel injection hole provided at the tip of the housing 1, and 105 denotes a needle valve body.

In FIG. 2, reference numeral 123 denotes a common rail 3 (FIG. 1) via the high-pressure fuel pipes 11a to 11d.
Is a high pressure fuel passage connected to High pressure fuel passage 123
Is connected to a hydraulic chamber 107 formed around the lower part of the needle guide portion 105a of the needle 105. When the fuel injection valve is closed, the tip of the needle valve body 105 is in contact with the nozzle seat around the fuel injection hole 103 to close the fuel injection hole 103. In this state, the fuel oil pressure in the lower part of the hydraulic chamber 107 acts on a pressure receiving area corresponding to an annular area of the needle valve body 105 obtained by subtracting the area (105c) of the nozzle seat portion from the cross-sectional area of the nozzle guide portion 105a. The needle valve 105 is urged in a direction to open the fuel injection hole 103 (a valve opening direction, that is, an upward direction in FIG. 2).

The fuel injection hole 1 of the needle valve body 105
A control room 1 is provided in the housing around the end opposite to the side 03.
09 is formed. The control chamber 109 is connected to the high-pressure fuel passage 123 as described later,
The oil pressure inside is the needle valve body end (command piston part) 1
The needle valve body presses the fuel injection hole 05b in a direction to close the fuel injection hole (a valve closing direction, that is, a downward direction in FIG. 1). In the control chamber 109, a spring 111 for urging the needle 105 in the valve closing direction is disposed. When the pressures in the control chamber 109 and the hydraulic chamber 107 are equal, the needle valve body 105 is moved to and held at the valve closing position by the spring 111 and the fuel injection holes 103
This prevents the needle valve body 105 from moving in the valve opening direction due to the in-cylinder combustion pressure acting on the needle valve body 105, thereby causing erroneous injection.

In the housing 101, a control room 1 is provided.
A leak chamber 130 is provided, which is connected to the engine 09 through hydraulic return passages 201 and 203 described later. The leak chamber 130 is connected to a low-pressure section (for example, a fuel tank) outside the fuel injection valve via a leak passage 117. Reference numeral 300 in FIG. 2 denotes a control valve that blocks communication between the leak chamber 130 and the leak passage 117.

The control valve 300 is connected to a piezo actuator 303 via a hydraulic transmission unit 301. The piezo actuator 303 includes a piston 305 facing the hydraulic transmission unit 301. Now, when a voltage is applied to the piezo actuator 303, the piston 305 is displaced by an amount corresponding to the applied voltage. The displacement of the piston 305 is transmitted to the upper portion of the control valve 300 via the fuel oil in the hydraulic pressure transmission unit 301. That is, the control valve 300 is
05 is multiplied by the ratio of the cross-sectional area of the piston 305 to the upper part of the control valve 300. This allows
When a voltage is applied to the piezo actuator 303, the control valve 300 is displaced downward in FIG.
The leak chamber 130 and the leak passage 117 are communicated.

FIG. 3 shows the control room 109 and the leak room 1 of FIG.
FIG. As shown in FIG.
The control room 109 and the leak room 130 are respectively
01a, 203a, the hydraulic return passages 201, 2
03. Further, the high-pressure fuel passage 123
And the control chamber 109 are connected to the throttle unit 209a and the hydraulic pressure supply passage 2
07, 209. As shown in FIG. 3, the hydraulic return passage 203 is opened immediately below the control valve 300, and when the control valve 300 is displaced until it comes into contact with the lower surface of the leak chamber 130 (when the control valve 300 is at the full lift position), the hydraulic return passage 203 is provided. 203 is closed. On the other hand, the hydraulic return passage 201 always has the leak chamber 130
It is opened at a position for maintaining communication between the control room 109 and the control room 109.

In the fuel injection valve of the present embodiment, the control valve 300 is displaced by applying a voltage to the piezo actuator 303, and the hydraulic return passages 201 and 203 are communicated with the leak passage 117 via the leak chamber 130. Thus, the fuel injection operation is performed. As described above, since the displacement of the piezo actuator 303 changes in accordance with the applied voltage, the displacement (lift) of the control valve 300 is changed with extremely high responsiveness by adjusting the voltage applied to the piezo actuator 303. be able to.
Therefore, in the present embodiment, the position of the control valve 300 is changed to a position (a valve closing position) at which communication between the leak chamber 130 and the leak passage 117 is interrupted, and the hydraulic return passage 203 is displaced until the control valve 300 contacts the bottom surface of the leak chamber 130. Position (full lift position) where the communication between the valve and the leak chamber 130 is interrupted, and a position (intermediate lift position) where the hydraulic return passage 203 and the leak chamber 130 are displaced to an intermediate position between the valve closing position and the full lift position. The operation of the fuel injection valve is controlled by switching to the three positions.

The operation of the fuel injection valve 10 at each position of the control valve will be described below with reference to FIGS. Valve closing position (FIG. 3) When the control valve 300 is in the valve closing position, communication between the leak chamber 130 and the leak passage 117 is shut off. On the other hand, since the control chamber 109 communicates with the high-pressure fuel passage 123 via the hydraulic pressure supply passages 207 and 209, the fuel pressure in the control chamber 109 is maintained at the same value as the high-pressure fuel passage 123 pressure.
Therefore, the needle valve body 105 is pressed toward the fuel injection hole 103 by the spring 111 and the oil pressure in the control chamber 109, and closes the fuel injection hole 103. Therefore, no fuel injection occurs at the control valve closing position. Intermediate lift position (FIG. 4) When the control valve 300 is displaced to the intermediate lift position, the leak chamber 130 communicates with the leak passage. In this position, both the hydraulic return passages 201 and 203 communicate the hydraulic leak chamber 130 and the control chamber 109. Therefore, the fuel oil in the control chamber 109 is supplied to the hydraulic return passages 201 and 203
Through the leak chamber 130 and the leak passage 117
Leaked to Therefore, in this state, the hydraulic supply passage 20
Even if there is fuel oil flowing into the control chamber 109 from the pressure 9, the pressure in the control chamber 109 decreases relatively sharply. Control room 109
Control chamber 1 acting on the needle 105 as the hydraulic pressure in the
09 and the urging force of the spring 111
When the force of the needle becomes smaller than the force received by the oil pressure in the lower part of the hydraulic chamber 107, the needle 105 is displaced in the valve opening direction and high-pressure fuel oil in the hydraulic chamber 107 is injected from the fuel injection hole 103. During the intermediate lift of the control valve 300, the control chamber 303
Since the fuel pressure in the inside of the needle 10 decreases relatively sharply, the needle 10
5, the displacement speed in the valve opening direction also increases. Since the injection rate during fuel injection increases as the displacement of the needle 105 (needle lift) increases, the rate of increase of the injection rate increases at the intermediate lift position of the control valve 300. Full Lift Position (FIG. 5) As shown in FIG. 5, when the control valve is at the full lift position, the hydraulic return passage 203 is closed by the control valve 300, and the leak chamber 130 and the control chamber 109 are communicated only by the hydraulic return passage 201. I do. For this reason, the control room 10
The fuel oil in the nozzle 9 flows out into the leak passage 117 only through the hydraulic return passage 201, and the oil pressure decreasing speed in the control chamber 109 decreases. Therefore, at the full lift position of the control valve, the needle rises at a relatively low speed, and the rising speed of the fuel injection rate decreases.

The control valve 300 is closed from the intermediate lift position (FIG. 4) or the full lift position (FIG. 5) (FIG. 3).
, The flow of the fuel oil from the control chamber 109 to the leak passage 117 stops, and the pressure in the control chamber 109 rises due to the high-pressure fuel oil flowing from the hydraulic supply passages 207 and 209. Therefore, the force for urging the needle 105 in the valve closing direction increases, and the needle 105 returns to the position where the fuel injection hole 103 is closed, and the fuel injection stops.

The displacement speed (lift speed) of the needle 105 at the control valve intermediate lift position, the full lift position, and the valve closing position adjusts the size of the throttles 201a, 203a, and 209a of the hydraulic return passages 201, 203 and the hydraulic supply passage 209. By doing so, an appropriate value can be set in advance. After returning the control valve 300 to the valve closing position (FIG. 3), the needle 105 is actually
If the time from when the fuel injection is stopped until the fuel injection is stopped is long, the accuracy of the fuel injection amount control decreases. Therefore, the control valve 30
It is preferable to raise the oil pressure in the control chamber 303 as soon as possible after 0 returns to the valve closing position. Hydraulic supply passage 2
If the aperture 209a of the 09 is set large, the control room 109
Since the flow rate of the fuel oil flowing into the fuel cell increases, it is possible to shorten the time from the return of the control valve 300 to the stop of the fuel injection. However, if the flow rate of the fuel oil flowing into the control chamber 109 is uniformly increased, the control chamber
Also, there is a problem that the speed of lowering the hydraulic pressure in the inside becomes uniformly small, and the needle lift speed during fuel injection becomes small.

FIG. 6 shows a fuel injection valve which solves the above problem and shortens the time from the closing of the control valve 300 to the stop of fuel injection without greatly affecting the needle lift speed during fuel injection. Is shown. In the embodiment of FIG. 6, only the point that a second hydraulic supply passage 211 and a throttle 211a that connect the hydraulic supply passage 207 and a portion of the hydraulic return passage 203 closer to the control valve 300 than the throttle are provided is the same as FIG. The third embodiment is different from the third embodiment.

By providing the hydraulic pressure supply passage 211 and the throttle 211a, fuel always flows from the high pressure fuel passage 123 into the hydraulic pressure return passage 203. However, when the control valve 300 is at the intermediate lift position, the high-pressure fuel oil flowing into the hydraulic return passage 203 from the second hydraulic supply passage 211 is supplied to the control chamber 10 by the throttle 203a.
The flow to the 9 side is suppressed, and most of the flow flows out of the leak chamber 130 to the leak passage 117. Therefore, at the intermediate lift position where the lift speed of the needle 105 is desired to be set to a large value, the lift speed of the needle 105 hardly decreases compared to the embodiment in FIG.

On the other hand, when the control valve 300 is at the full lift or in the closed position, the fuel oil flowing into the hydraulic return passage 203 from the second hydraulic supply passage 211
03a, and flows into the control room 109.
For this reason, at the time of a full lift in which it is desired to set the lift speed of the needle 105 to a small value, the needle lift can be set smaller than in the embodiment of FIG.
After the closing of the valve 00, the pressure increasing speed in the control chamber 109 increases, and the time from the closing of the control valve 300 to the actual stop of the fuel injection is reduced. That is, in the embodiment of FIG. 6, it is possible to further improve the accuracy of the fuel injection amount control.

Although the second hydraulic supply passage 211 is connected to the hydraulic return passage 203 in the embodiment of FIG. 6, the second hydraulic passage 211 is directly connected to the leak chamber 130 as shown in FIG. By doing so, the hydraulic supply passage 21
1 and the aperture 211a are easily machined. As described above, in the fuel injection valve of the embodiment shown in FIGS. 3 to 7, the fuel injection characteristics can be changed only by the control valve 300, and there is no need to provide another control valve in the fuel injection valve. Therefore, the structure of the fuel injection valve is small and simple, the drive control operation of the control valve is simplified, and one fuel supply valve can be driven by a single power supply.

Next, the actual needle lift speed control using the fuel injection valve shown in FIG. 3 or FIGS. 6 and 7 will be described. As described above, in the fuel injection valve 10 of the above embodiment, by changing the voltage applied to the piezo actuator 303, it is possible to arbitrarily switch between the positions shown in FIGS. Further, since the response speed of the piezo actuator 303 is extremely fast, it is possible to switch the position of the control valve 300 during the fuel injection period. For this reason, by using the fuel injection valve of FIG. 3, FIG. 6 or FIG. 7, the degree of freedom of the needle lift speed control is greatly improved, and the engine operating state will be described below with reference to FIG. 8 to FIG. It is possible to control the fuel injection characteristics according to the conditions. (1) FIG. 7 is a view for explaining an embodiment of the fuel injection characteristic control in a case where the pilot fuel injection and the main fuel injection are relatively close to each other. The rates are indicated respectively.

In this embodiment, when the timings of the pilot fuel injection and the main fuel injection are relatively close to each other, the control valve 300 is held at the intermediate lift position during the pilot fuel injection, and the lift speed of the needle 105 is reduced. At the time of main fuel injection, control is performed such that the control valve 300 is maintained at the full lift position and the lift speed of the needle 105 is relatively reduced. As a result, at the start of pilot fuel injection, the actual fuel pressure (actual injection pressure) at the fuel injection holes 103 sharply increases, and a small amount of pilot injection fuel can be injected at a high speed. Since the pilot injection fuel injected at a high speed has a large penetration force, even a small amount of the fuel reaches the vicinity of the outer periphery of the combustion chamber and burns. Therefore, the fuel injected at the time of the main injection starts combustion from the portion that has reached the combustion gas formed by the pilot injection near the outer peripheral portion of the combustion chamber, and the main injected fuel moves from the outer peripheral portion of the combustion chamber to the central portion. It will start burning. Thereby, the combustion temperature of the main injection fuel is relatively low, generation of the NO _X is suppressed.

Further, since the needle lift speed is relatively low in the main fuel injection, the fuel injection rate at the start of the main fuel injection is relatively low. For this reason, even if the fuel injection timing is advanced, the deterioration of the combustion state does not occur, and the fuel injection can be completed at a relatively early timing, and the smoke due to the fuel injection during the expansion stroke in which the temperature of the combustion chamber decreases. It is possible to suppress the increase. (2) FIG. 9 is a view similar to FIG. 8, illustrating a second embodiment of the injection characteristic control.

In this embodiment, the first embodiment (FIG. 8)
As in the case of the pilot fuel injection, the control valve 300 is held at the intermediate lift position to increase the lift speed of the needle 105.
00 is held at the full lift position to make the needle 105 lift speed relatively slow. However, in the latter half of the injection timing, the control valve 300 is switched from the full lift position (FIG. 5) to the intermediate lift position (FIG. 4). As a result, similarly to the jerk pump, the injection rate in the latter stage of the fuel injection increases, and the fuel injection end timing is further advanced than in the first embodiment, so that the generation of smoke is further suppressed. (3) FIG. 10 is a view similar to FIG. 8, illustrating a third embodiment of the fuel injection characteristic control. In the present embodiment, a case is shown in which early pilot fuel injection, in which pilot fuel injection is performed relatively early, is performed. In this case, since the pilot fuel injection is performed relatively early in the cylinder compression stroke, the pressure and temperature in the combustion are not sufficiently increased during the pilot fuel injection. In addition, since the piston is also at a position away from the top dead center, the injected fuel reaches the combustion wall surface in a liquid state and easily adheres to the wall surface, resulting in dilution of lubricating oil by the fuel and deterioration of lubrication of the piston ring. There are cases. For this reason, in this embodiment, at the time of early pilot fuel injection, the control valve 300 is controlled to the full lift position (FIG. 5), and the lift speed of the needle 105 is reduced. As a result, the rising speed of the actual fuel injection pressure becomes slow, and the injected fuel forms a spray having a small penetration force. Therefore, it is difficult for the fuel to reach the cylinder wall surface in a liquid state, and the fuel wall surface is prevented from adhering. (4) FIG. 11 is a view similar to FIG. 8, illustrating a fourth embodiment of the fuel injection characteristic control. In the present embodiment, post fuel injection for injecting fuel again after the main fuel injection amount is performed. The post fuel injection is performed to prevent the occurrence of exhaust smoke due to incomplete combustion of fuel when the main fuel injection amount becomes large. In this case, the post fuel injection is performed during the expansion stroke, and the combustion chamber temperature,
The operation is performed at a position where the pressure decreases and the piston position is away from the top dead center. For this reason, similarly to the case of the early pilot fuel injection, the fuel injected easily adheres to the combustion chamber wall surface. Therefore, in the present embodiment, early pilot fuel injection (FIG. 1)
As in the case of 0), during the post fuel injection, the control valve 30
0 is controlled to a full lift position (FIG. 5) to form fuel spray having a low penetration force, thereby preventing fuel from adhering to the wall surface. (5) FIG. 12 is a view similar to FIG. 8, illustrating a fifth embodiment of the fuel injection characteristic control.

In this embodiment, at the time of main fuel injection, the control valve 300 is temporarily held at the intermediate lift position at the start of main fuel injection, and when the needle starts lifting, the control valve 300 is controlled.
Switch 0 to full lift position. In the first and second embodiments of the fuel injection characteristic control (FIGS. 8 and 9), the control valve 300 is held at the full lift position at the start of the fuel injection, and a state where the fuel injection rate is relatively low at the start of the injection occurs. I was However, as described with reference to FIGS. 3 to 5, when the control valve is at the full lift position, the fuel oil is
01 (FIG. 4), the control room 10
The oil pressure drop speed of No. 9 decreases. For this reason, from the fuel injection command (start of voltage application to the piezo actuator 303), the pressure in the control chamber 109 decreases until the needle 105 actually starts lifting (that is, the fuel injection from the fuel injection hole is actually started). The delay time becomes longer. When the delay time from the fuel injection command to the actual start of the fuel injection increases, the deviation of the fuel injection timing and the fuel injection amount from the target values increases, and there is a problem that the control accuracy of the fuel injection decreases.

Therefore, in this embodiment, in order to reduce the delay time, the control valve 300 is first held at the intermediate lift position (FIG. 4) at the time of fuel injection so that the pressure in the control chamber 109 is decreased relatively sharply. I have to. Thereby, the delay time until the fuel injection is actually started after the fuel injection command (that is, until the needle 105 starts the lift) is greatly reduced. Needle 105
After the lift starts and the actual fuel injection starts,
The control valve 300 is switched to the full lift position (FIG. 5). As a result, once the needle 105 once starts lifting, the lift speed of the needle is reduced, the increase in the fuel injection rate after fuel injection is suppressed, and it is possible to maintain a relatively low fuel injection rate at the beginning of fuel injection. Becomes

When the control valve 300 is held at the intermediate lift position, the time until the needle 105 starts the lift after the fuel injection command depends on, for example, the fuel pressure in the control chamber 109 (common rail 3 pressure). Change. For this reason, in this embodiment, at each common rail pressure,
The fuel injection operation is performed while the control valve 300 is held at the intermediate lift position, the time until the needle 105 actually starts the lift is measured, and the time is measured in the ROM of the ECU 20 in the form of a one-dimensional map using the common rail pressure as a parameter. It is stored.

At the time of fuel injection, the ECU 20 calculates the delay time of the needle lift from the common rail pressure using the above map, and holds the control valve 300 at the intermediate lift position for the delay time from the start of fuel injection. When the delay time has elapsed, the control valve 300 is switched to the full lift position. As a result, highly accurate fuel injection control with a very small fuel injection delay time is possible.

In this embodiment, the time until the start of the needle lift is obtained from the numerical map based on the actual measurement result as described above. For example, a needle lift sensor for detecting the lift amount of the needle at the fuel injection valve, Alternatively, a needle lift timing sensor that detects that the needle has started lifting is provided, and when it is detected that the needle has actually started lifting, the control valve is switched from the intermediate lift position to the full lift position. Accurate fuel injection control becomes possible.

FIGS. 13 and 14 are diagrams for explaining another embodiment of the configuration of the fuel injection valve of the present invention, which is different from FIGS. In the above-described embodiment of FIG.
13 is different from the embodiment of FIG. 3 in that the hydraulic supply passage 209 is connected to the leak chamber 130 in the embodiment of FIG. FIG.
As in the embodiment, the hydraulic supply passage 209 is
9, the control valve 300 is opened and the fuel oil in the control chamber 109 is supplied to the hydraulic return passages 201, 2
The fuel in the high-pressure fuel passage 123 continues to flow from the hydraulic supply passage 209 into the control chamber 109 even when the fuel flows into the control chamber 109 from both the hydraulic passage 03 and the hydraulic return passage 201 to the leak passage 117. Therefore, especially when the fuel pressure of the common rail 3 (that is, the fuel pressure in the high-pressure fuel passage 123) is high, the fuel flows into the control chamber 109 from the hydraulic supply passage 209 at a relatively large flow rate. In this case, especially when the control valve 300 is at the full lift position, the flow rate of the fuel oil that can escape from the control chamber 109 to the leak passage 117 causes the hydraulic supply passage 209 to move from the control chamber 109
The fuel injection valve cannot be opened unless the flow rate of the fuel oil flowing into the fuel injector is reduced. For this reason, in the embodiment of FIG. 3, a throttle portion 209 a is provided in the hydraulic pressure supply passage 209 to restrict the flow of fuel oil into the control chamber 109. However, if the diameter of the throttle portion 209a is set in accordance with the case where the fuel pressure is high, when the fuel pressure decreases, the hydraulic supply passage 2
09, the flow rate of the fuel oil flowing into the control chamber 109 decreases, and when the control valve 300 is closed, the pressure rise in the control chamber 109 is delayed, and the closing of the needle valve 105 is delayed. There is a case where the problem that the accuracy of the image is reduced occurs.

In the embodiment shown in FIG.
9 is connected to the leak chamber 130 to solve this problem. That is, in the embodiment of FIG. 13, when the fuel injection valve is opened (when the control valve 300 is at the intermediate lift position or the full lift position), the fuel flowing from the hydraulic pressure supply passage 209 into the leak chamber 130 is supplied to the control chamber 109. Without flowing into the low pressure part directly from the leak passage 117. Therefore, the valve opening operation of the fuel injection valve is prevented from being affected by the fuel oil flowing from the hydraulic pressure supply passage 209. On the other hand, when the fuel injection valve is closed (when the control valve 300 is at the closed position), the fuel oil flowing from the hydraulic supply passage 209 into the leak chamber 130 is controlled through the two hydraulic return passages 201 and 203. Room 130
It will flow into. For this reason, even when the fuel oil pressure is low when the control valve 300 is closed, the oil pressure in the control chamber 109 increases in a short time, and even when the fuel pressure is low, a decrease in the accuracy of the fuel injection control is prevented. . In this case, the diameter of the hydraulic pressure supply passage 209 can be arbitrarily determined. However, if the diameter of the passage 209 is excessively small, the closing speed of the fuel injection valve is reduced. The amount of the high-pressure fuel discharged into the leak passage 117 at the time of valve opening increases, and the loss of the fuel pump increases. For this reason, it is preferable that the diameter of the hydraulic pressure supply passage 209 is determined by experiments or the like so as to be optimal over the entire operation range of the engine.

FIG. 14 shows a modification of the embodiment shown in FIG. In the present embodiment, in addition to the hydraulic supply passage 209 connected to the leak chamber 130 as in FIG.
A second hydraulic pressure supply passage 213 is provided for directly connecting the high pressure fuel passage 123 to the second hydraulic pressure supply passage 213. Second hydraulic supply passage 21
3 is provided with a throttle portion 213a.
The flow rate of the fuel flowing into the control chamber 109 through the passage is reduced.

In this embodiment, the control valve 300 is in the middle lift or full lift position and the hydraulic return passage 20
Even when the fuel oil flows out of the control chamber 109 through the control chambers 1 and 203, the second hydraulic supply passage 21
Fuel oil flows in from 3. For this reason, the diameter of the throttle portion 213a is set to a small value so that the pressure in the control chamber 109 is reliably reduced even when the fuel pressure is high. In the present embodiment, when the control valve 300 is closed, in addition to the fuel oil flowing from the hydraulic pressure supply passage 209 through the leak chamber 130 and the hydraulic pressure return passages 201 and 203, the control chamber 109 further includes a second hydraulic pressure supply passage. Since the fuel oil flows into the control chamber 213, the pressure in the control chamber 109 increases quickly, and the delay in closing the fuel injection valve is further reduced.

[0049]

According to the invention described in each of the claims, the structure of the fuel injection valve is simple and small, and even when used in a common rail fuel injection device, a desired fuel injection characteristic can be obtained according to the engine operating condition. Has a common effect that it becomes possible to obtain It is needless to say that the fuel injection control shown in FIGS. 8 to 12 can be performed even when the fuel injection valve having the configuration shown in FIGS. 13 and 14 is used.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment in which a fuel injection valve of the present invention is applied to a common rail type fuel injection device of an automobile diesel engine.

FIG. 2 is a longitudinal sectional view illustrating the configuration of one embodiment of the fuel injection valve of the present invention.

FIG. 3 is a partially enlarged sectional view of the fuel injection valve of FIG. 2;

FIG. 4 is a diagram illustrating the operation of a fuel injection valve at an intermediate lift position of a control valve.

FIG. 5 is a diagram illustrating an operation of the fuel injection valve at a full lift position of the control valve.

FIG. 6 is a view similar to FIG. 3, illustrating another embodiment of the fuel injection valve of the present invention.

FIG. 7 is a diagram illustrating a modification of the embodiment of FIG. 6;

FIG. 8 is a timing chart for explaining a first embodiment of the fuel injection characteristic control using the fuel injection valve of the present invention.

FIG. 9 is a timing chart for explaining a second embodiment of the fuel injection characteristic control using the fuel injection valve of the present invention.

FIG. 10 is a timing chart illustrating a third embodiment of the fuel injection characteristic control using the fuel injection valve of the present invention.

FIG. 11 is a timing chart illustrating a fourth embodiment of the fuel injection characteristic control using the fuel injection valve of the present invention.

FIG. 12 is a timing chart illustrating a fifth embodiment of the fuel injection characteristic control using the fuel injection valve of the present invention.

FIG. 13 is a view showing the configuration of the fuel injection valve according to the present invention;
It is a figure explaining another embodiment.

FIG. 14 is a view for explaining an embodiment of the configuration of the fuel injection valve of the present invention which is different from FIGS. 2 to 7 and FIG. 13;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve 103 ... Fuel injection hole 105 ... Needle 109 ... Control chamber 201, 203 ... Hydraulic return passage 201a, 203a ... Restrictor 207, 209 ... Hydraulic supply passage 300 ... Control valve

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) F02M 61/20 F02M 61/20 NF term (reference) 3G066 AA07 AB02 AC09 AD07 BA13 BA67 CC01 CC05T CC05U CC08T CC08U CC14 CC64T CC64U CC67 CC68T CE13 CE22 CE34 CE35 DA09

Claims (4)

[Claims] A housing, a fuel injection hole opened to the housing, a high-pressure fuel passage connected to the fuel injection hole, a needle for opening and closing the fuel injection hole, and the fuel injection hole of the needle of the housing. A control chamber formed at the opposite end, a hydraulic supply passage connecting the high-pressure fuel passage and the control chamber, and supplying a hydraulic pressure for urging the needle into the control chamber in a direction to close the fuel injection hole. Connecting at least two hydraulic return passages for connecting the control chamber to a low-pressure portion outside the housing and reducing the hydraulic pressure in the control chamber to move the needle in a direction to open the fuel injection holes; A control valve for opening and closing a passage, wherein the control valve is configured to close at least one of the hydraulic return passages and at least one of the hydraulic return passages And a third position in which at least one of the hydraulic return passages is opened and a third position in which at least one of the hydraulic return passages is opened. 2. The apparatus of claim 2, wherein at least one of the hydraulic return passages has a throttle between the control valve and the control chamber, and the high-pressure fuel passage further includes a throttle of the at least one hydraulic return passage. The fuel injection valve according to claim 1, wherein the fuel injection valve is connected between a throttle section and the control valve. 3. A housing, a fuel injection hole opened in the housing, a high-pressure fuel passage connected to the fuel injection hole, a needle for opening and closing the fuel injection hole, and the fuel injection hole of the needle of the housing. Is a control chamber formed at the opposite end, a leak chamber connected to the control chamber by at least two hydraulic return passages, and connects the leak chamber and the high-pressure fuel passage to supply high-pressure fuel to the leak chamber. A hydraulic pressure supply passage, a leak passage connecting the leak chamber to a low-pressure section outside the housing, and a control valve provided in the leak chamber and having a valve body that opens and closes the leak passage. A first position in which the valve body closes the leak passage and opens all hydraulic return passages; and a valve body opens the leak passage and opens the hydraulic return passage. A second position in which at least one of the first and second positions is closed and at least one is opened, and a third position in which the leak passage and the entire hydraulic return passage are opened. By taking the position 1, the fuel oil flowing into the leak chamber from the hydraulic pressure supply passage flows into the control chamber through the entire hydraulic return passage, and the needle in the control chamber is raised by raising the hydraulic pressure in the control chamber. By urging the fuel injection holes in the closing direction, and taking the second or third position, the fuel oil flowing into the leak chamber from the hydraulic pressure supply passage to the low-pressure portion via the leak passage. And at the same time, the fuel oil in the control chamber flows into the leak chamber via the hydraulic return passage, and is further discharged from the leak passage to a low-pressure section, and the oil pressure in the control chamber is reduced to reduce the knee pressure. A fuel injection valve for moving a dollar in a direction to open the fuel injection hole. 4. The fuel injection valve according to claim 3, further comprising a second hydraulic pressure supply passage having a throttle portion, which connects the high-pressure fuel passage and the control chamber.