JP2003148276A - Booster type fuel injection device and booster type fuel injection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection device capable of accurately controlling a combustion ratio in response to an engine speed and a load by changing a valve closing force in response to the engine speed and/or the load. SOLUTION: A valve closing force changing means 6 for changing the valve closing force of an elastic body 24 is provided at an injection means 4 having the elastic body 24 for giving the valve closing force against fuel pressure to switch a position from an injection position, in which fuel is injected, to a non-injection position, in which the fuel is not injected, in response to increased fuel pressure. When at least either detection value of an engine speed detecting means and a load detecting means exceeds the predetermined value, a valve closing force control means 5 controls the valve closing force changing means 6 to increase the valve closing force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure boosting type fuel injection device and a pressure boosting type fuel injection method, and more particularly to a fuel injection device and a pressure boosting type fuel injection method with improved injection rate at the end of injection.

[0002]

2. Description of the Related Art This booster type fuel injection system is disclosed in
As disclosed in Japanese Unexamined Patent Publication (Kokai) -256224, etc., a fuel booster chamber to which fuel is supplied, a booster piston for boosting the fuel in the fuel booster chamber, and fuel boosted in the fuel booster chamber are provided. An injection valve body that opens and closes an injection port to be injected, a pressurizing chamber into which a working fluid that drives the pressure boosting piston flows, and an electromagnetic valve that controls supply and discharge of the working fluid to and from the pressurizing chamber. It becomes.

Since this pressure boosting type fuel injection device pressurizes the fuel through the pressure boosting piston at the time of injection, compared with the pressure accumulation type fuel injection device which injects the fuel which has been boosted to a predetermined pressure in advance, The injection rate of fuel during injection tends to rise slowly. Due to the characteristics of the engine, when the fuel injection rate gradually increases during fuel injection, N
Generation of Ox and combustion noise can be suppressed. Also,
At the end of injection, the pressure of the boosted fuel cannot be used, and the injection valve body is closed by the spring force of the pressing spring provided on the injection valve body, so the injection rate tends to decrease gradually. As described above, according to the booster type fuel injection device, the increase and decrease of the injection rate become relatively gentle.

[0004]

However, in the high engine speed range, it is necessary to inject fuel in a short time.
The increase and decrease of the injection rate do not catch up, resulting in a low mountain-shaped injection rate waveform. In particular, in the high rotation and high load regions of the engine, it is necessary to inject as much fuel as possible in a short time, but in the above-described booster type fuel injector, the injection can be completed within an effective injection period. There is a problem that smoke cannot occur because it cannot be done.

The present invention has been made in view of the above-mentioned conventional problems, and changes the valve closing force according to the engine speed or / and the load so that the valve closing force is appropriate according to the engine speed or / and the load. An object of the present invention is to provide a fuel injection device and a fuel injection method capable of controlling the injection rate.

[0006]

A fuel injection system for solving the above-mentioned problems includes (1) a pressure boosting piston having a pressurizing chamber and a fuel booster chamber at both ends, and the working fluid is provided in the pressurizing chamber. And a pressure increasing means for urging the pressure increasing piston to pressurize the fuel in the fuel pressure increasing chamber, and an injection valve that moves from an injection position for injecting the fuel to a non-injection position for not injecting the fuel. Injection means having a body, rotation speed detection means for detecting the rotation speed of the engine, load detection means for detecting the load of the engine, valve closing force changing means for changing the valve closing force of the injection valve body, and A valve closing force control unit that controls the valve closing force changing unit so that the valve closing force becomes high when the detected value of at least one of the rotation speed detecting unit and the load detecting unit exceeds a predetermined value. The main point is to become. With configuration (1) above, the valve closing force control means increases the valve closing force when the detected value of at least one of the rotation speed detecting means and the load detecting means exceeds a predetermined value. Since the valve closing force changing means is controlled, the injection rate rises and falls rapidly, and appropriate combustion control is performed according to at least one of the rotation speed and the load.

In the above (1), (2) the valve closing force control means is configured to increase the valve closing force when the detected values of the rotation speed detection means and the load detection means exceed a predetermined value. It is preferable to control the valve closing force changing means. According to the above configuration (2), appropriate combustion control is performed according to the rotation speed and the load.

In the above (1) or (2), (3)
A valve accumulator for storing the working fluid, wherein the valve closing force changing means changes the valve closing force of the injection valve element by the working fluid stored in the pressure accumulator. The means preferably adjusts the supply of the working fluid used in the valve closing force changing means. According to the above configuration (3), the valve closing force is changed by using the working fluid stored in the pressure accumulator, and the valve closing force is controlled by adjusting the supply of the working fluid.

In any of the above (1) to (3),
(4) The injection means includes an elastic body that biases the injection valve body in a direction to close the injection valve body, and the valve closing force changing means includes:
It is preferable to have a movably provided piston as the receiving portion of the elastic body, and to change the valve closing force of the injection valve body by moving the piston with the working fluid. According to the configuration of (4) above, when the receiving portion of the elastic body that urges the injection valve body in the valve closing direction is moved by the piston, the pressing force of the elastic body increases and the valve closing force can be increased. .

In the above (4), (5) the piston moves from a first position having a low valve closing force to a second position having a high valve closing force when the engine speed and the load exceed predetermined values. Those that move are preferred. According to the configuration of (5) above,
When the engine speed and the load exceed predetermined values, the piston moves from the first position to the second position, increasing the pressing force of the elastic body and increasing the valve closing force.

In any of the above (3) to (5),
(6) A discharge part for discharging the working fluid used for the valve closing force changing means and a passage are provided on a passage communicating the pressure accumulator and the discharge part, and the discharge part controls the valve closing force. Those that can be opened and closed by means are preferable. According to the above configuration (6), the working fluid from the pressure accumulator reaches the working chamber via the throttle, and the supply amount of the working fluid to the working chamber can be adjusted by opening / closing the discharge portion from the working chamber. it can. Also,
The throttle suppresses a change in pressure inside the pressure accumulator.

In the above item (6), (7) the valve closing force control means preferably comprises a two-way switching valve. According to the above configuration (7), the supply amount of the working fluid to the working chamber can be adjusted by the two-way switching valve that opens and closes the discharge passage.

A fuel injection method for solving the above-mentioned problems is
(8) A pressure increasing piston having a pressure increasing chamber and a fuel pressure increasing chamber at both ends is provided, and a working fluid is caused to flow into the pressure increasing chamber to urge the pressure increasing piston, and the fuel in the fuel pressure increasing chamber is Pressure increasing means for pressurizing the fuel, and injection means having an injection valve body that moves from an injection position for injecting the fuel to a non-injection position for not injecting the fuel A fuel injection method, comprising valve closing force changing means for changing the valve closing force of the injection valve element, a detection value by a rotation speed detecting means for detecting an engine speed, and a load detection for detecting an engine load. The gist of the invention is to control the valve closing force changing means so that the valve closing force increases when at least one of the detection values detected by the means exceeds a predetermined value. According to the configuration of (8), when the detection value of at least one of the rotation speed detection means and the load detection means exceeds a predetermined value, the valve closing force control means sets the valve closing force to be high. Since the valve closing force changing means is controlled, the injection rate rises and falls rapidly, and appropriate combustion control is performed according to at least one of the rotation speed and the load.

In the above (8), (9) the valve closing force changing means is controlled so that the valve closing force becomes high when the detected values by the rotation speed detecting means and the load detecting means exceed a predetermined value. Those are preferable. According to the above configuration (9), appropriate combustion control is performed according to the rotation speed and the load.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a fuel injection device for explaining an embodiment of the present invention, in a state in which a valve closing force changing means is not operating. FIG. 2 shows a schematic diagram of the fuel injection system in the present embodiment.

The fuel injection device 1 has an injection port 28 as shown in the drawing.
It can be installed in an engine such as a diesel engine in a downward position with the bottom down. The downward posture is not limited to vertically downward, but includes diagonal downward.

In FIG. 1, a fuel injection device 1 includes a head 1
In the housing 10 having a cylindrical shape with 0a, the solenoid valve 2, the pressure increasing mechanism 3, and the injection mechanism 4 are housed in this order from top to bottom.

The head portion 10a in which the solenoid valve 2 is housed has a working fluid supply port 31 and a working fluid discharge port 32.
And are open. High-pressure fuel is fed under pressure as a working fluid from the common rail (accumulator) 112 to the supply port 31. Fuel as a working fluid flows out from the exhaust port 32 and is recovered by the recovery device 113 (see FIG. 2). Further, an action port 33 is opened on the opposite side of the discharge port 32 with the solenoid valve 2 interposed therebetween. This action port 3
3 communicates with a pressure chamber 11 described later.

The solenoid valve 2 includes a switching valve 36 which is movable in a valve hole 35 provided in the head portion 10a in a lateral direction, and a switching valve 3.
Solenoid portion 37 provided for the yoke 36a of No. 6
And a return spring 39 provided for the yoke 36a of the switching valve 36, the three-way two-position switching valve.

Between the valve hole 35 and the switching valve 36, a disc-shaped yoke 36a is attracted and opened by exciting a solenoid portion 37, and a first poppet type valve A is opened, and a solenoid portion 37.
Demagnetization causes the disk-shaped yoke 36b to return to the return spring 39.
And a poppet-type second valve B that is pushed back to open. The first valve A and the second valve B have a relationship in which when one is closed, the other is opened. As the first valve A opens,
The second valve B is closed, and the working fluid from the supply port 31 flows into the working port 33. When the second valve B is opened, the first valve A is closed and the working fluid is discharged from the action port 33 to the discharge port 32.

The pressure increasing mechanism (pressure increasing means) 3 is a housing 1
It is housed above 0. A pressure boosting piston 12 is slidably housed in a vertical direction in a large diameter cylinder 10b forming a pressure chamber 11 communicating with the action port 33 and a small diameter cylinder 10c forming a fuel pressure boosting chamber 16.
The pressure boosting piston 12 is composed of a guided rod portion 12a and a pressure boosting plunger portion 12b.

The pressure-increasing plunger portion 12b extends coaxially downward from the center of the lower portion of the guided rod portion 12a,
It is accommodated in the fuel booster chamber 16 so as to be vertically slidable. A hollow portion 13 is formed below the guided rod portion 12a of the booster piston 12. A piston spring 15 is interposed in the hollow portion 13 and urges the pressure boosting piston 12 upward. Further, a bypass passage 14 is formed so as to connect the lower end portion of the hollow portion 13 and the discharge port 32.

The diameter of the pressure boosting plunger portion 12b is smaller than the diameter of the guided rod portion 12a. Therefore, the fuel in the fuel booster chamber 16 is boosted to a pressure higher than the pressure of the working fluid introduced into the pressurizing chamber 11. The pressure increase ratio is “pressure receiving area of the guided rod portion 12a / pressure receiving area of the pressure increasing plunger portion 12b”.

The fuel booster chamber 16 formed below the booster piston 12 is connected to the fuel supply section 2 via the fuel supply passage 20.
It communicates with 1. The fuel sent from the fuel supply pump 121 to the fuel supply unit 21 flows into the fuel booster chamber 16. A check valve 22 is interposed between the fuel booster chamber 16 and the fuel supply passage 20. The check valve 22 moves upward when the pressure inside the fuel booster chamber 16 becomes a certain level or higher,
The communication between the fuel booster chamber 16 and the fuel supply passage 20 is cut off.

The injection mechanism (injection means) 4 is a housing 1
Below 0, the injection valve body 23 and the pressing spring (elastic body) 2
It is configured to accommodate four. The injection valve body 23 is accommodated in the housing 10 so as to be vertically slidable, and includes a pressing piston portion 23a, a large diameter portion 23b, and a step portion 23c.
And a small diameter portion 23d. Pressing piston part 23
A pressing spring 24 is interposed above a and urges the injection valve element 23 downward.

Around the step portion 23c of the injection valve body 23,
A fuel filling chamber 25 is formed. The fuel filling chamber 25 communicates with the fuel pressure increasing chamber 16 via a fuel passage 26.
Further, the fuel passage 27 extends downward from the fuel filling chamber 25.
Is extended and the injection port 28 is provided near the tip of the fuel passage 27.
Are formed. When the fuel in the fuel filling chamber 25 reaches a predetermined pressure, the force acting upward on the injection valve body 23 overcomes the urging force of the pressing spring 24, the injection valve body 23 moves upward, and the fuel is injected from the injection port 28. To be done. Fuel is continuously supplied to the fuel filling chamber 25. While the inside of the fuel filling chamber 25 continues to have a pressure equal to or higher than the predetermined pressure, fuel having a predetermined pressure is injected into the injection port 28.
Is jetted from. When the pressure in the fuel pressure increasing chamber 16 decreases and the pressure in the fuel filling chamber 25 decreases, the injection valve body 23 is seated by the pressing spring 24 acting on the injection valve body 23, and the fuel is ejected from the injection port 28. Is stopped.

The injection mechanism 4 is provided with a valve closing force changing means 6 for changing the valve closing force according to the engine speed and the load. This valve closing force changing means 6 is used for the injection valve body 2
3, a pressing spring 24 that is an elastic body that urges the pressing spring 24 in the direction of closing the valve 3, a piston 41 that is slidable with respect to the accommodating chamber 29 of the pressing spring 24, and presses the pressing spring 24; Chamber 42
And a working fluid passage 43 reaching the working chamber 42, and a control valve 44 for the working fluid reaching the passage 43. The control valve 44 is connected to the common rail (accumulator) via the throttle 45.
It is connected to 112.

The working fluid from the common rail 112 flows into the pressurizing chamber 11 through the solenoid valve 2 and the throttle 4
5, the control valve 44, the working fluid passage 43, and the injection mechanism 4
Flows into the working chamber 42 of the piston 41 at the top of the. When the working fluid flows into the working chamber 42 located above the injection mechanism 4, the piston 41 moves from the first position (state of FIG. 1) where the pressing spring 24 is lengthened to the second position (FIG. 1) where the pressing spring 24 is shortened. 3 state). At the second position, the valve closing force of the pressing spring 24 becomes higher than at the first position.

The control valve 44 connects the common rail 112 and the working chamber 42 to each other, and the common rail 112 and the working chamber 42 are connected to each other.
Three-way switching type having a first switching position for disconnecting the working chamber 42 and the recovery device 113 and a second switching position for connecting the working chamber 42 and the recovery device 113 to the common rail 112. Is a solenoid valve. The control unit 5 controls the timing of switching the control valve 44.

The control unit 5 receives inputs of a load signal f1 from a load detector (load detection means) not shown and a rotation speed signal f2 from an engine rotation speed detector (rotation speed detection means) not shown, and receives the engine rotation speed. It has a judging means for judging that the number and the load exceed a predetermined value. When the engine speed and the load exceed predetermined values, this determination means determines that the engine is in the high rotation and high load region, and the control valve 44 is set to the working chamber 4
2 is switched to the first position for supplying working fluid. When it is determined that the determination means is out of the high rotation and high load region, the control valve 44 is switched to the second position where the working fluid in the working chamber 42 is discharged to the recovery device 113. The control unit 5 also controls the injection timing via the solenoid valve 2. The control unit 5 and the control valve 44 control the valve closing force changing unit so that the valve closing force increases when the detection values of the rotation speed detecting unit and the load detecting unit exceed a predetermined value. It constitutes a force control means.

FIG. 2 shows a fuel injection system 100 to which the above-mentioned fuel injection device 1 is applied. In FIG. 2, 1 mounted in each cylinder head of an engine (not shown)
A working fluid circulation system 101 for supplying fuel to the fuel injection device 1 as working fluid and further recovering it, and a fuel supply system for supplying fuel to the fuel injection device 1 102, a control unit 5 including a computer for electronically controlling the opening / closing operation of the electromagnetic valve 2 of the fuel injection device 1, and the like.

The working fluid circulation system 101 is composed of a fuel supply pump 110, a high pressure pump 111, a common rail 112, a recovery device 113 and the like. The fuel supply pump 110 supplies the fuel in the fuel tank 114 to the high pressure pump 1
Pump to 11. The high-pressure pump 111 supplies fuel, for example, 20
The fuel is pressurized to about 0 atm, and the pressurized fuel is pumped to the common rail 112. The fuel as the working fluid stored in the common rail 112 is supplied to the supply port 31 (see FIG. 1) by the operation of the solenoid valve 2. Recovery device 11
3 collects the fuel as the working fluid flowing out from the discharge port 32 (see FIG. 1) of the fuel injection device 1 by the operation of the solenoid valve 2, and collects the collected fuel from the high pressure pump 11
Recycle to 1. The working fluid of the common rail 112 is
Via the control valve 44, the working chamber 42 in the fuel injection device 1 (see FIG.
Refer to). The working fluid discharged from the control valve 44 is
It is recovered by the recovery device 113.

The fuel supply system 102 is composed of a pump 121 and a valve 122. The pump 121 is
The fuel in the fuel tank 114 is pressure-fed to the fuel supply unit 21 (see FIG. 1) of each fuel injection device 1. The valve 122 adjusts the amount of fuel supplied to the fuel injection device 1.

The control unit 5 controls the solenoid valve 2 of each fuel injection device 1.
A control signal is generated to control the opening / closing of the fuel cell, and the pressure of the fuel as the working fluid by the high-pressure pump 111 is adjusted according to the magnitude of the load. When the load on the engine is high, the pressure of the fuel as the working fluid by the high pressure pump 111 is increased, and when the load on the engine is low, the pressure of the fuel as the working fluid by the high pressure pump 111 is lowered.
The control unit 5 controls the switching of the solenoid valve 2 and the control valve 44.
Switching control.

Next, the operation of the fuel injection device 1 having the above-mentioned structure will be described with reference to FIGS. 1 and 3. First, the operation when the engine speed and the load do not reach the predetermined values will be described with reference to FIG. Load signal f1 input to the controller 5
And the rotation speed signal f2, when the control unit 5 determines that the load is not in the high load and high rotation range, the control valve 44 is maintained at the second switching position. The working chamber 42 communicates with the recovery device 113. The piston 41 is stopped at the first position which is the upper limit position,
The pressing spring 24 maintains a long first length L1.

In FIG. 1, the fuel is supplied from the fuel supply section 21, and the fuel booster chamber 16 is filled with the fuel. At the time of injection, the solenoid portion 37 is excited and the yoke 3
6a is sucked, the switching valve 36 moves to the right in the drawing, the first valve A opens, the second valve B closes, the supply port 31 and the action port 33 communicate, and the working fluid is introduced into the pressurizing chamber 11. To be done. Fuel boost chamber 16 with boost ratio determined by boost piston 12
The fuel inside is pressurized. At this time, the check valve 22 is in a closed state, and when the fuel in the fuel filling chamber 25 reaches a predetermined high pressure, the injection valve body 23 has the first length L1 and the valve closing force of the pressing spring 24 becomes. After overcoming, high-pressure fuel is injected from the injection port 28. When it is time to finish the fuel injection, the solenoid portion 37 is demagnetized, the first valve A is closed, and the second valve B is closed.
Opens. The working fluid introduced into the pressurizing chamber 11 is discharged from the discharge port 32, and the pressure boosting piston 12 turns to a rising stroke by the urging force of the piston spring 15 (see FIG. 1).

The injection pattern in this case is shown in FIG. At the time of injection, the working fluid pressurizes the fuel through the pressure boosting piston 12, and the length of the pressing spring 24 is L1, and the valve closing force is relatively weak. Therefore, the fuel is injected like the line a1. At this time, the fuel injection rate rises slowly. At the end of injection,
Since the pressing spring 24 closes the valve with a low valve closing force,
Like the a2 line, the injection rate tends to decrease gradually.

Next, the operation when the engine speed and the load reach predetermined values will be described with reference to FIG. In FIG. 3, when it is determined by the load signal f1 and the rotation speed signal f2 input to the control unit 5 that the control unit 5 is in the high load and high rotation region, the control valve 44 is switched to the first position. The working fluid from the common rail 112 is supplied to the working chamber 42 to push the piston 41 down to the second position and push the pressing spring 24 to the length L2.

As shown in FIG. 3, the piston 41 has a second
An injection pattern when fuel is injected in the position is shown in FIG. The working fluid, which has become high in pressure during injection, pressurizes the fuel through the pressure boosting piston 12 and opposes the high valve closing force by the pressing spring 24 having the length L2. The injection rate rises sharply, and the ceiling approaches a flat line like the b2 line. At the end of injection, the valve is closed with a high valve closing force by the pressing spring 24, so that the injection rate drops sharply as in line b3.

The embodiment described above has the following effects. (1) As shown in FIG. 4A, in a region other than the high engine speed and high load regions, the valve closing force is reduced to moderate the increase in the initial injection rate due to the pressure boosting injection to reduce NOx. The combustion noise can be suppressed. In addition, FIG.
As shown in (b), in a high engine speed and high load region, the valve closing force is increased to increase the fuel injection amount and the injection is finished in a short injection period. The waveform can be formed and the occurrence of smoke can be suppressed. Further, since the fuel injection amount increases in the high rotation and high load regions of the engine, high torque can be received.

(2) Since the working fluid for operating the pressure boosting piston 12 of the pressure boosting type fuel injection device 1 is introduced into the upper portion of the injection mechanism 4 as the valve closing force changing means 6, the valve closing force is changed. It is possible to control the valve closing force with a simple structure without requiring a separate drive source for. In addition, since the inflow of the working fluid is controlled by the control valve 44, the inflow and the outflow of the working fluid can be performed by the control unit 5 that controls the control valve 44, and it is possible to appropriately perform the operation according to the engine speed and the load. The valve closing force can be changed to.

(3) The piston 42 is used as the end plate for the pressing spring 24, which is an elastic body for urging the injection valve body in the direction of closing the valve, and the working fluid is introduced into the piston 42. The mechanism for can have a simple structure. Further, when the control unit 5 determines that the rotation speed and the load are in the high rotation and high load regions exceeding the predetermined values, the working fluid is introduced into the working chamber 42 via the control valve 44, and the piston is operated to close the valve closing force. It moves from a low first position to a second position with a high valve closing force. Therefore, the valve closing force can be changed according to the engine speed and the load with a simple structure.

(4) A common rail (pressure accumulator) for working fluid
Since it is introduced from 112, the working fluids of the same conditions can be supplied to the valve closing force changing means 6 of the plurality of fuel injection devices 1. Also, the common rail (accumulator) 11
Since the working fluid is supplied from 2 to the upper portion of the injection mechanism 4 via the throttle 45, it is possible to reduce the fluctuation due to the pressure loss of the common rail (accumulator) 112.

The embodiment is not limited to the above, and the following modifications may be made, for example. (1) As shown in FIG. 5, a common rail (accumulator) 11
The working fluid from 2 may be supplied to the working chamber 42 via the throttle 45, and the control valve 52 may be provided in the discharge passage 51 from the working chamber 42. The control valve 52 may be a two-way switching valve type that shuts off or opens the discharge passage 51. In this case, when the control valve 52 is opened, the working fluid supplied to the working chamber 42 is discharged to the recovery device 113, and the piston 41 is in the first position where the valve closing force is low. The working fluid discharged to the recovery device 113 is throttled by the throttle 45. This throttle 45 is a common rail (accumulator) 112.
Control the pressure drop. When the control valve 52 is closed, the pressure of the working fluid reaching the working chamber 42 rises, and the piston 41 is in the second position where the valve closing force is high.

(2) As shown in FIG. 6, the control section 5 interlocks the control of the injection by the solenoid section 37 of the solenoid valve 2 with the control of the supply of the working fluid to the upper portion of the injection mechanism 4 by the control valve 44. An interlocking control means 53 can be provided.
Thereby, the injection rate waveform in each injection can be variously controlled. Based on the interlocking control means 53, the control valve 42 is set to the first position to supply the working fluid to the upper portion of the injection mechanism 4, or the control valve is set to the second position to set the working fluid supplied to the injection mechanism 4. It can be discharged. For example, if control is performed to increase the valve closing force only at the end of injection, the injection rate at the end of injection can be rapidly reduced as indicated by line a11, as shown in FIG. 7A. For example, at the beginning of injection, when the valve closing force is very low,
When the injection is started while the valve closing force is gradually increased, as shown in FIG.
As in (b), the rise of the injection rate in the initial stage of injection can be made extremely gentle as in line b11.
For example, when the valve closing force is increased before and after the injection and the valve closing force is weakened and returned to the original value before the injection is started, as shown in FIG. The pilot injection of the line c12 can be added before the injection of.

(3) In the above-described embodiment, the valve closing force is controlled so as to be changed according to both the engine speed and the load. However, the detected value of either the engine speed or the load is detected. The valve closing force control means for changing the valve closing force may be used.

(4) As the valve closing force changing means, instead of the piston 41 for pushing the pressing spring 24, an advancing / retreating driving means like an electromagnetic cylinder is provided to change the pressing length of the pressing spring 24. You can

(5) As shown in FIG. 8, a step portion 29a may be provided in the storage chamber 29 of the piston 41 to restrict the downward movement of the piston 41 so that the second position is fixed. it can. As a result, the valve closing force can be increased by a constant value.

(6) A pressure adjusting valve is used as the control valve 44 to arbitrarily change the pressure of the working fluid acting on the working chamber 42,
It is possible to use the control valve 44 that can arbitrarily change the valve closing force in accordance with it. Further, in FIG. 5, a control valve capable of arbitrarily changing the pressure of the working fluid acting on the working chamber 42 by using a flow rate adjusting valve or a pressure adjusting valve as the control valve 52 and arbitrarily changing the valve closing force accordingly. It can be 52.

(7) The pressure of the working fluid may be directly applied to the upper portion of the injection valve without the pressing spring 24, and the valve opening force of the injection valve may be changed by controlling the pressure of the working fluid. At this time, the control valve can be a flow rate adjusting valve or a pressure adjusting valve, and can be used as both a pressing spring (elastic body) for giving the valve closing force by the piston and a valve closing force changing means for changing the valve closing force. .

[0051]

As described above in detail, according to the fuel injection device and the fuel injection method of the present invention, NOx can be reduced and combustion noise can be suppressed by the gradual increase of the initial injection rate by the boosting type fuel injection. . Further, the valve closing force can be changed according to the rotation speed and / or the load, and appropriate control according to the rotation speed and / or the load can be performed. For example, in the high rotation and high load regions, the valve closing force can be increased to form a square injection rate waveform, and the generation of smoke can be suppressed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a fuel injection device according to an embodiment of the present invention in a state where valve closing force changing means is not operating.

FIG. 2 is a schematic view of a common rail fuel injection system incorporating the fuel injection device according to the above embodiment.

FIG. 3 is a cross-sectional view of the fuel injection device according to the embodiment of the present invention in a state in which the valve closing force changing means is operating.

FIG. 4 is an injection rate pattern diagram showing an example of controlling the injection rate by the valve closing force control means of the embodiment of the present invention.

FIG. 5 is a cross-sectional view of a fuel injection device according to another embodiment.

FIG. 6 is a cross-sectional view of a fuel injection device according to still another embodiment.

FIG. 7 is an injection rate pattern diagram showing a control example of an injection rate by a valve closing force control means of still another embodiment.

FIG. 8 is a partial cross-sectional view showing another example of accommodation of the piston.

[Explanation of symbols]

1 Fuel injection device 2 Solenoid valve 3 Pressure increasing mechanism (pressure increasing means) 4 Injection mechanism (injection means) 5 Control unit (valve closing force control means) 6 Valve closing force changing means 10 head 11 Pressurization chamber 12 Booster piston 16 Fuel booster chamber 23 Injection valve body 24 Pressing spring (elastic body) 41 piston 42 Working chamber 44 Control valve (valve closing force control means) 45 aperture 52 Control valve (valve closing force control means) 54 discharge path

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02M 51/06 F02M 51/06 Z F term (reference) 3G066 AA07 AC09 AD07 BA19 BA51 CC01 CC05T CC08T CC08U CC14 CC53 CC63 CC68U CE13 CE22 CE34 CE35 DA01 DA08 DC01 DC09 3G301 HA02 JA03 JA14 JA24 LB11 LC01 LC08 MA11 NE01 NE17 PA17Z PE01Z

Claims (9)

[Claims] 1. A pressure boosting piston having a pressurizing chamber and a fuel boosting chamber at both ends, wherein a working fluid is caused to flow into the pressurizing chamber to bias the boosting piston, and the fuel boosting chamber is provided. Pressure increasing means for pressurizing the fuel, injection means having an injection valve body that moves from an injection position for injecting the fuel to a non-injection position for not injecting the fuel, and a rotation speed detecting means for detecting the rotation speed of the engine. A load detection means for detecting the load of the engine, a valve closing force changing means for changing the valve closing force of the injection valve body, a detection value of at least one of the rotation speed detecting means and the load detecting means is predetermined. And a valve closing force control means for controlling the valve closing force changing means so that the valve closing force becomes higher when the pressure increasing type fuel injection device is exceeded. 2. The valve closing force control means controls the valve closing force changing means so that the valve closing force increases when the detected values of the rotation speed detecting means and the load detecting means exceed a predetermined value. The booster type fuel injection device according to claim 1. 3. A valve accumulator for storing the working fluid, wherein the valve closing force changing means changes the valve closing force of the injection valve element by the working fluid stored in the pressure accumulator. 3. The booster type fuel injection device according to claim 1, wherein the valve closing force control unit adjusts the supply of the working fluid used in the valve closing force changing unit. 4. The injection means includes an elastic body that biases the injection valve body in a direction of closing the injection valve body, and the valve closing force changing means is movably provided as a receiving portion of the elastic body. The booster type fuel injection device according to any one of claims 1 to 3, further comprising a piston provided with the piston, the valve closing force of the injection valve body being changed by moving the piston with the working fluid. 5. The piston moves from a first position with a low valve closing force to a second position with a high valve closing force when the engine speed and the load exceed a predetermined value. Booster type fuel injection device. 6. A discharge part for discharging the working fluid used in the valve closing force changing means, and a throttle on a passage communicating with the pressure accumulator and the discharge part, wherein the discharge part includes the valve closing valve. The booster type fuel injection device according to any one of claims 3 to 5, which is opened and closed by force control means. 7. The booster type fuel injection device according to claim 6, wherein the valve closing force control means is a two-way switching valve. 8. A pressure boosting piston having a pressure chamber and a fuel pressure boosting chamber at both ends, wherein a working fluid is caused to flow into the pressure chamber to bias the pressure boosting piston, and the fuel pressure boosting chamber is provided. Pressure boosting means for pressurizing the fuel, and injection means having an injection valve body that moves from an injection position for injecting the fuel to a non-injection position for not injecting the fuel. A chamber type fuel injection method, wherein valve closing force changing means for changing the valve closing force of the injection valve body is provided, and a detection value by an engine speed detecting means for detecting an engine speed and an engine load are detected. A pressure intensifying fuel injection method for controlling the valve closing force changing means such that the valve closing force becomes high when at least one of the detected values by the load detecting means exceeds a predetermined value. 9. The increase according to claim 8, wherein the valve closing force changing means is controlled so that the valve closing force becomes high when the detected values by the rotation speed detecting means and the load detecting means exceed a predetermined value. Pressure fuel injection method.