JP2550975B2 - Fuel injector - Google Patents

Description

The present invention relates to a fuel injection device, and more particularly to a fuel injection device that drives a needle valve with a piezoelectric element to open and close a fuel injection nozzle.

[Prior Art] Heretofore, a fuel injection valve in which a piezoelectric element is used as an actuator and which is opened and closed has been known, paying attention to the high responsiveness of the expansion and contraction action of the piezoelectric element (for example, JP-A-59-206668). This type of fuel injection device includes a fuel injection nozzle having a needle valve provided therein, and is configured to pump fuel pressurized by a fuel injection pump to the fuel injection nozzle via a fuel supply pipe. By driving the needle valve with a piezoelectric element, the needle is lifted in the valve opening direction and fuel injection is executed.

[Problems to be Solved by the Invention] However, in such a fuel injection device, when the fuel injection nozzle is opened to perform fuel injection, expansion of the fuel pressure-fed from the fuel supply pipe to the fuel injection nozzle is performed. In some cases, the wave returns to the fuel injection nozzle as a reflected wave, and the pressure wave stays until the subsequent closing of the fuel injection nozzle. Further, when the fuel injection nozzle is suddenly closed and the fuel injection is suddenly stopped, the pressure wave generated by the water hammer action may increase the pressure in the fuel injection nozzle. From these things,
At the end of fuel injection, the pressure in the fuel injection nozzle becomes too large, and the needle valve is lifted again in the opening direction immediately after the needle valve is closed. There was a problem to do.

The present invention has been made in view of the above problems, and an object thereof is to provide a fuel injection device that prevents secondary injection.

Structure of the Invention [Means for Solving Problems] In order to achieve the above object, the present invention has the following structures as means for solving the problems. That is, the fuel pressurized by the fuel supply pump M1 is sent through the fuel supply pipe M2, the fuel injection nozzle M3, the needle valve M4 provided in the fuel injection nozzle M3 to open and close the fuel injection nozzle M3, and A first piezoelectric element having a laminated structure that drives the needle valve M4 to open and close.
A fuel injection valve M6 composed of M5; and a needle valve opening / closing means M7 for opening / closing the needle valve M4 by expanding / contracting the first piezoelectric element M5 by controlling the voltage applied to the first piezoelectric element M5. A fuel injection device including: a fuel injection device provided in the stacking direction of the first piezoelectric element M5;
A voltage is applied independently of the first piezoelectric element M5, and a second piezoelectric element M8 having a laminated structure that applies a driving force to the needle valve M4 in at least the valve closing direction, and the needle valve opening / closing means M7 are After performing the closing operation of the needle valve M4 on the first piezoelectric element M5, the needle valve M4 based on the generated voltage of the second piezoelectric element M8.
To the second piezoelectric element M8 after the completion of the closing of the needle valve M4 by the closing completion judging means M9 for judging that the closing of the needle valve M4 is completed. And a needle valve closing force increasing means M10 for increasing the valve closing force of the needle valve M4 for a predetermined time by applying a voltage in the needle valve closing direction for a predetermined time. That is the configuration of the characteristic fuel injection device.

[Operation] In the fuel injection device of the present invention configured as described above, the needle valve opening / closing means M7 applies a voltage to the first piezoelectric element M5 to expand or contract the needle valve M4 to the open position. Drive to open fuel injection nozzle M3. The high-pressure fuel pressure-fed from the fuel supply pump M1 through the fuel supply pipe M2 comes to the fuel injection nozzle M3, and fuel injection is performed.

Needle valve opening / closing means M7
However, by applying a voltage in the opposite direction to the first piezoelectric element M5, the needle valve M4 is moved to the closed position. At this time,
A voltage corresponding to the moving amount of the needle valve M4 is generated in the second piezoelectric element M8. Based on this voltage, the valve closing completion determining means
When M9 determines that the needle valve M4 has been closed,
The needle valve closing force increasing means M10 is activated, and the second piezoelectric element M
The voltage in the needle valve closing direction is applied to 8 for a predetermined time. As a result, the pressing force of the needle valve M4 in the valve closing direction is increased for a predetermined time after the valve closing is completed. Therefore, the needle valve M4 can withstand the pressure increase in the fuel injection nozzle after the fuel injection is stopped, and can prevent the secondary injection from occurring.

Example In order to further clarify the configuration of the present invention described above,
An embodiment of the present invention will be described.

A fuel injection device as an embodiment of the present invention is adopted in an internal combustion engine and will be described with reference to the drawings. FIG. 2 is a configuration diagram showing a cross-sectional view of a fuel injection device of an embodiment of the present invention together with a block diagram of an electronic control device, and FIG. 3 is a four-cylinder diesel engine configured by adopting the fuel injection device of the present embodiment. 2 is a schematic configuration diagram of FIG.

As shown in FIG. 3, reference numeral 1 denotes a diesel engine, and each cylinder of the diesel engine 1 is provided with a fuel injection valve 8 for direct injection into a combustion chamber. The intake of the diesel engine 1 is performed by the supercharger T via the intake manifold 9.

The fuel injection valve 8 is connected via a fuel supply pipe 10 to a fuel accumulator pipe 11 common to each cylinder. The fuel pressure accumulating tube 11 has a pressure accumulating chamber 12 with a constant volume therein, and the fuel in the pressure accumulating chamber 12 is supplied to the fuel injection valve 8 through the fuel supply pipe 10. on the other hand,
The pressure accumulating chamber 12 is connected via a fuel supply pipe 13 to a discharge port of a fuel supply pump 14 whose discharge pressure can be controlled. Fuel supply pump 14
The suction port of the fuel pump 15 is connected to the discharge port of the fuel pump 15, and the suction port of the fuel pump 15 is connected to the fuel reservoir tank 16. Further, each fuel injection valve 8 is connected to a fuel reservoir tank 16 via a fuel return conduit 17. The fuel pump 15 is provided to feed the fuel in the fuel reservoir tank 16 into the fuel supply pump 14, and if the fuel can be sucked into the fuel supply pump 14 without the fuel pump 15, It is not necessary to provide the pump 15 in particular. On the other hand, the fuel supply pump 14 is provided for discharging high-pressure fuel, and the high-pressure fuel discharged from the fuel supply pump 14 is accumulated in the pressure accumulating chamber 12. This pressure is also called rail pressure.

In addition, the diesel engine 1 has two crank angle sensors 21, 2 for detecting the operating state of the engine 1.
2, a cooling water temperature sensor 24, a supercharging pressure sensor 26, a fuel pressure sensor 28 and the like are provided. The electronic control unit 30 uses the piezoelectric element drive unit 40 and the pump drive unit 45 to drive the diesel engine 1 based on the outputs of the above-described sensors and the amount of depression of the accelerator pedal 32, that is, the output of the accelerator sensor 34 that detects the load. The fuel injection amount and the fuel injection timing of the diesel engine 1 are controlled to control the output of the diesel engine 1.
The configuration of 30 and the processing performed by it will be described later.

Next, the structure of the fuel injection valve 8 will be described. As shown in FIG. 2, the fuel injection valve 8 includes a fuel injection valve main body 50, a fuel injection nozzle 54 fixed to the fuel injection valve main body 50 by a nozzle holder 52, and an actuator 56 using a piezoelectric element.
And so on.

There is a predetermined gap in the fuel injection valve body 50, and there is a throttle passage.
A control rod 60 is inserted so as to form 58 and is slidable in the axial direction, and a needle valve 62 that is also slidably inserted in the axial direction is arranged in series in the fuel injection nozzle 54. Further, a spring chamber 64 formed at the lower end of the fuel injection valve body 50
A spring 66 for urging the needle valve 62 downward in the figure is inserted therein, and the needle valve 62 is pressed downward by the spring 66. A pressure receiving surface 62a having a conical shape is formed in an intermediate portion of the needle valve 62, and an oil pool 68 is provided in the fuel injection nozzle 54 around the pressure receiving surface 62a.

Further, a fuel inlet 70 communicating with the pressure accumulating chamber 12 (FIG. 3) via the fuel supply pipe 10 is formed on the side surface of the fuel injection valve main body 50, and the fuel hole 72 is connected to the fuel inlet 70. Has been drilled. The fuel injection nozzle 54 is provided with a fuel hole 74 that connects the fuel hole 72 and the oil sump 68. Also,
The oil sump 68 communicates with the throttle passage 58 by the annular fuel passage 76 and the spring chamber 64 formed around the upper portion of the needle 62, and the nozzle through the annular fuel passage 78 formed around the lower portion of the needle 62. It communicates with the hole 79.

On the other hand, in the piezoelectric actuator 56, the first piezoelectric element 84 and the second piezoelectric element 84 are connected to the actuator body 82 via the insulating plate 83.
A piezoelectric element 85 is incorporated. The first piezoelectric element 84 has a laminated structure in which a large number of piezoelectric elements are laminated. Two electrodes 86, 88 are drawn out from the first piezoelectric element 84, and the two electrodes 86, 88 are penetrated into the actuator body 82 via hermetic seals 90, 92, respectively. This first piezoelectric element
When strain is applied to 84 from the outside, a voltage is generated between the two electrodes 86 and 88 (piezoelectric positive effect). Conversely, when a positive voltage is applied to the two electrodes 86 and 88, the first piezoelectric element 84 is distorted and expands in the axial direction, and when a negative voltage is applied, it contracts (piezoelectric reverse effect).

The second piezoelectric element 85 is connected to the first piezoelectric element 84 described above via an insulating plate 94. This second piezoelectric element
Two electrodes 98 and 100 are drawn out from 85, and two electrodes 9
The actuators 8 and 100 are mounted on the actuator body 82 via hermetic seals 102 and 104, respectively. This second piezoelectric element 85
Like the first piezoelectric element 84, is a laminated structure of single piezoelectric elements having the same outer diameter as the first piezoelectric element 84. First overall
It has a thickness 3.5 times that of the piezoelectric element 84.

A piston 108 is arranged in contact with the second piezoelectric element 85 via an insulating plate 106. A cylinder body 110 slidably supporting the piston 108 is screwed into an actuator body 82, and a disc spring 112 is inserted between the piston 108 and the cylinder body 110. This disc spring 112 causes the first piezoelectric element 84 and the second piezoelectric element 8 to pass through the piston 108.
5 and 5 are urged upward in the figure.

The piezoelectric actuator 56 configured as described above has one end screwed into the cylinder body 110 and the other end screwed into the fuel injection valve body 50.
It is attached to the fuel injection valve main body 50 by a connection nut 120 screwed into. This connection nut 120, cylinder body
A pressure chamber 122 is formed by 110 and the piston 108, and
A back pressure chamber 124 is formed by the connecting nut 120, the fuel injection valve main body 50, and the control rod 60, and a fuel hole 126 that connects the pressure chamber 122 and the back pressure chamber 124 is formed in the connecting nut 120. The cross-sectional area of the pressure chamber 122 is larger than the cross-sectional area of the back pressure chamber 124. Therefore, the movement amount of the piston 108 is amplified and transmitted to the control rod 60.

The fuel injection valve 8 having the above-described configuration is used in the fuel supply pump 14
As a result, when the fuel pressurized to a predetermined pressure is supplied to the fuel inlet port 70, the fuel flows into the fuel holes 72, 74, the oil sump 68, and the fuel passage 7.
6, the spring chamber 64, and the throttle passage 58 are sequentially passed to flow into the back pressure chamber 124, and further flow into the pressure chamber 122 via the fuel hole 126.

The electrodes 86, 88 and the electrodes 98, 100 of the piezoelectric actuator 56 are the first constituent elements of the piezoelectric element driving device 40.
The piezoelectric element drive circuit 40a and the second piezoelectric element drive circuit 40b are respectively connected, and the first piezoelectric element 84 is connected to the second piezoelectric element drive circuit 40b according to the voltage applied from the first piezoelectric element drive circuit 40a. The second piezoelectric element 8 according to the applied voltage
5 is driven.

Next, the configuration and function of the electronic control unit 30 will be described. As shown in FIG. 2, the ignition switch 15
The electronic control unit 30, which is operated by receiving power from the battery 151 via 0, includes a well-known CPU 160, ROM 161, and RAM 162, a timer 165, an input port 167, an output port 168, etc.
It is configured as a logical operation circuit interconnected by 69. The crank angle sensor 2 described above is connected to the input port 167.
1,22, cooling water temperature sensor 24, boost pressure sensor 26, fuel pressure sensor
28, the electrodes of the accelerator sensor 34 and the piezoelectric actuator 56
86, 88 are connected, and the CPU 110, via this input port 117, the crank angle (hence the rotation speed N of the diesel engine 1), the cylinder discrimination signal, the cooling water temperature Thw, the supercharging pressure B,
The operating state of the diesel engine 1 such as the fuel pressure P and the load L and the strain amount of the first piezoelectric element 84 can be read.
On the other hand, the output port 168 drives the piezoelectric element drive device 40 (first piezoelectric element drive circuit 40a and second piezoelectric element drive circuit 40b) that drives the piezoelectric elements of the four fuel injection valves 8 and the fuel supply pump 14. It is connected to the pump drive unit 45, and the CPU 160 outputs the fuel injection valve 8 via this output port 168.
Controls the opening and closing of and the fuel supply. Since the control of the fuel supply pump 14 is not directly related to the gist of the present invention, the fuel pressure P is controlled in proportion to the rotational speed N of the diesel engine 1, and the description thereof will be omitted. Further, in FIG. 1, other than the circuit for driving the piezoelectric element included in one fuel injection valve 8 of the piezoelectric element driving device 40, the others are omitted. Piezoelectric actuators provided in the fuel injection valves 8 of the other three cylinders are also controlled via the output port 168 with the same circuit configuration.

Next, the processing performed by the electronic control unit 30 will be described with reference to the flowcharts shown in FIGS. 4 and 5, and the opening / closing of the fuel injection valve 8 associated with the operation of the piezoelectric actuator 56 will be described.

The electronic control unit 30 starts its operation when the ignition switch 150 is turned on, and executes the main control routine shown in FIG. First, in step 200, so-called initialization processing is performed. Here, initial settings such as the clear flag of the internal register of the CPU 160 are performed. In the following step 220, a process of reading the operating states of the diesel engine 1 such as the rotation speed N, the load L, the cooling water temperature Thw, the supercharging pressure B and the fuel pressure P from each sensor via the input port 167 is performed. In the following step 230, a process of calculating the fuel injection amount τ based on the load L and taking into consideration other operating states, and further in step 240, a process of calculating the start of fuel injection and the injection time are performed.

Based on these results, the CPU 160, in step 250,
A process of setting the fuel injection start timing in the timer 165 is performed. As a result, the timer 165 starts self-propelled and outputs an interrupt signal to the CPU 16 at the fuel injection start timing.

In the following step 260, the fuel supply pump 14 is controlled from the output port 168 via the pump drive device 45, and the fuel pressure P
Control is performed, but since it is not directly related to the present invention, description of this control is omitted. After the processing of step 260 ends, the processing returns to step 220 and the processing for fuel injection described above is repeated.

When the fuel injection start timing set in the process of step 250 described above is reached, an interrupt is generated from the timer 165, and the CPU 160 executes the fuel injection valve control routine shown in FIG. When the process starts, the first step 30
At 0, a command is output to the second piezoelectric element drive circuit 40b to apply a predetermined negative voltage to the second piezoelectric element 85. This time,
The second piezoelectric element 85 contracts by a predetermined amount in the axial direction according to the applied negative voltage. Then, the piston 108 moves upward in FIG. 1 due to the biasing force of the disc spring 112. This piston 1
The moving amount of 08 is amplified and transmitted to the control rod 60 to move the control rod 60 upward in FIG. This control rod 60
2, the needle valve 62 moves upward in FIG. 2 against the urging force of the spring 66 by the fuel pressure acting on the pressure receiving surface 62a,
Fuel is injected from the nozzle hole 79.

In the following step 310, after the ejection time calculated in step 240 described above is delayed, a command is output to the second piezoelectric element drive circuit 40b to apply a predetermined positive voltage to the second piezoelectric element 85. At this time, the second piezoelectric element 85 expands by a predetermined amount in the axial direction according to the applied positive voltage, and the expanded amount is amplified and transmitted to the control rod 60. Therefore, the control rod 60 moves downward in FIG. 1, and the needle valve 62 is moved to the fuel injection nozzle 54.
And fuel injection is stopped. It should be noted that due to this contact, the pressure in the pressure chamber 122 rapidly rises, and the first piezoelectric element 84
The pressure applied to and the biasing force of the disc spring 32 rapidly increase. Therefore, the voltage V is generated in the first piezoelectric element 84 by the positive piezoelectric effect.

In the following step 320, the voltage generated in the first piezoelectric element 84 is read in via the input port 167. In the following step 330, the moving amount S of the piston 108 is calculated from the detected voltage V. That is, a graph of the relationship between the voltage V and the movement amount S created in consideration of the spring force of the disc spring 112 and the like is stored in advance in the ROM 52, and the movement amount S is calculated by searching this graph. can do. The movement amount S here is set so that the reference value is zero when the fuel injection nozzle 54 is closed.

In the following step 340, it is determined whether the movement amount S calculated in step 330 is zero or less. That is, the fuel injection nozzle
54 determines whether or not the needle valve 62 is in a closed state such that the moving amount of the needle valve 62 becomes zero. If "NO" in step 340, that is, if it is determined that the movement amount S is greater than zero, the process returns to step 320, and the processes of steps 320 to 340 are repeated. On the other hand, if it is determined to be “YES” in step 340, the process proceeds to subsequent step 350.

In step 350, a command is output to the first piezoelectric element drive circuit 40a to apply a predetermined positive voltage to the first piezoelectric element 84. At this time, the first piezoelectric element 84 expands by a predetermined amount in the axial direction according to the applied positive voltage. This extension amount is amplified and transmitted to the control rod 60. Therefore, the control rod 60 is
2, the needle valve 54 is pressed in the direction to close the fuel injection nozzle 54.

In the following step 360, a command is output to the first piezoelectric element drive circuit 40a to apply a predetermined negative voltage to the first piezoelectric element 84 after a predetermined time stored in the ROM 52 in advance. Then, the first piezoelectric element 84 shrinks, and the pressing force of the needle valve 54 disappears. After the execution of step 360, the processing is "RETUR
Exit to "N" to end this routine.

When the above-mentioned fuel injection valve control routine is executed, the outputs of the first and second piezoelectric element drive circuits 40a and 40b, the fuel injection rate τ, the output voltage V of the first piezoelectric element 94, and the pressure chamber 12
The fuel pressure of 2 changes as shown in the timing chart of FIG. That is, as shown in the figure, when a predetermined negative voltage is applied to the second piezoelectric element 85 from the second piezoelectric element drive circuit 40b at the fuel injection start timing, the fuel injection is started as described above ( Figure 6a). When the fuel injection is started, the pressure in the pressure chamber 122 begins to drop once (b in the same figure), and the first
The output voltage V of the piezoelectric element 84 decreases (FIG. 11C). Immediately thereafter, the pressure in the pressure chamber 122 returns (d in the figure), and the first
The output voltage of the piezoelectric element 84 also returns (e in the same figure).

Then, when the positive voltage is applied to the second piezoelectric element 85 from the second piezoelectric element drive circuit 40b after the fuel is injected for a predetermined fuel injection time, the fuel injection rate starts to decrease as described above (see the same figure). f). When the fuel injection rate starts to decrease, the fuel pressure in the pressure chamber rises (g in the figure) and the output voltage V of the first piezoelectric element 84 also starts to rise (h in the figure). Then, when the output voltage V of the first piezoelectric element 84 becomes equal to or higher than a predetermined value, it is determined that the movement amount S of the piston 108 is equal to or less than zero as described above, and the first piezoelectric element drive circuit 40a outputs a predetermined positive voltage to the first piezoelectric element It is applied to the element 85 (i in the same figure). Even when the movement amount S of the piston 108 is calculated to be zero, the needle valve may be delayed due to the time delay.
78 continues to descend, and when a positive voltage is applied to the first piezoelectric element 85, the first piezoelectric element 85 extends and the needle valve 78 descends with a stronger pressing force. Therefore, conventionally, after the fuel injection nozzle is closed, the secondary injection occurs as shown by 390 in the figure, but as described above, in addition to the extension force of the second piezoelectric element 84, the extension of the first piezoelectric element 85 is performed. Force needle valve 78
The secondary injection does not occur because the is pressed.

Further, since the length of each piping system from the fuel pressure accumulating pipe to each fuel injection valve 8 is different for each cylinder, conventionally, secondary injection may or may not occur for each cylinder, resulting in engine vibration or vibration. Although it caused noise, the above-described vibration and noise can be reduced because the occurrence of secondary injection was prevented as described above.

In the present embodiment, the first piezoelectric element 84 is the needle valve 78.
It functions not only as an actuator for pressing, but also as a sensor for detecting the movement amount S of the piston 108.
Therefore, it is possible to detect when the fuel injection nozzle 54 is closed with a simple structure.

Next, a second embodiment of the present invention will be described. This embodiment is different from the above-described first embodiment in the fuel injection valve control routine executed by the electronic control unit 30, and the main control routine and the hardware configuration are exactly the same.

This embodiment detects whether the secondary injection actually occurs, and when the secondary injection is detected, increases the pressing force of the needle valve 78 until the operating state changes suddenly. In order to prevent the secondary injection, description will be given below with reference to the flow chart showing the fuel injection valve control routine of FIG. 7 and the flow chart showing the operating state observation routine of FIG.

In FIG. 7, steps 400,410,420,430,440,450,46
0 indicates steps 300, 310, 320, 330, 340, 3 in FIG. 5 of the first embodiment.
Since the same processing as 50 and 360 is executed, the description is omitted. After performing step 410, the process proceeds to step 415. In step 415, it is judged whether or not the flag FG described later has a value of 0, and "Y
If it is determined that "ES", that is, FG = 0, the process is step 42.
Go to 0. After performing steps 420, 430, and 440, the process proceeds to step 442. In step 442, the elapsed time after applying the positive voltage to the second piezoelectric element 85 in step 410 is the area TX.
Transfer to. In the following step 444, after the voltage V detected in step 420 is switched from the falling state to the rising state,
It is determined whether or not the voltage becomes equal to or higher than the predetermined voltage Vo. That is, it is known that when the secondary injection occurs from the fuel injection nozzle 54, the output voltage V of the first piezoelectric element 84 has two peak values as shown by the dotted line portion in FIG. By executing the above-described determination, it is possible to determine whether the secondary injection has occurred. "YES" in step 444,
That is, when it is determined that the secondary injection has occurred, the value 1 is set in the flag FG in the following step 446. After execution of step 446, or if it is determined to be “NO” in step 444, the process exits to “RETURN” and ends once.

On the other hand, if it is determined in step 415 that the flag FG is not 0, then in step 448, a process of delaying by the time of the area TX obtained in step 442 is executed. After that, after executing the processing of steps 450 and 460, the process exits to "RETURN" and this routine is once terminated.

Further, the electronic control unit 30 of the present embodiment also executes an operating state observation routine shown in the flowchart of FIG.
This routine is executed at predetermined time intervals, and when the process is started, step 500 is executed first. In step 500, it is determined whether the operating state of the diesel engine 1 has suddenly changed, using the rotational speed N, the load L, the cooling water temperature Thw, etc. read in in step 220 described above. If “YES” in the step 500, that is, if it is determined that the change is abrupt, the process proceeds to a step 510, the value 0 is assigned to the flag FG, and then the process “RETURN” is ended and the present routine is once ended. On the other hand, if "NO" is determined in step 500, step 510 is skipped, the process goes to "RETURN", and this routine is once ended.

Therefore, the fuel injection valve control routine of FIG.
By executing the operating state observation routine shown in the figure, when the operating state changes suddenly, it is possible to determine whether or not secondary injection has occurred in the first fuel injection stroke, and thereafter the operating state changes suddenly. Until then, the secondary injection prevention process similar to that of the first embodiment can be executed. Therefore, during the operation in which the secondary injection does not occur, the first piezoelectric element 84 is not expanded, so that it is possible to save power and improve the durability of the first piezoelectric element.

Note that, instead of the first and second embodiments described above, for example, even if the first piezoelectric element 84 is driven immediately after driving the second piezoelectric element 85, the effect of the present invention can be obtained. it can.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such embodiments, and it goes without saying that the present invention can be implemented in various modes without departing from the scope of the present invention. .

Effects of the Invention As described above in detail, according to the fuel injection device of the present invention, the pressing force of the needle valve when the fuel injection nozzle is closed is increased by the second piezoelectric element, so that the secondary injection can be performed with a simple structure. It has an excellent effect that it can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating the basic configuration of the present invention, and FIGS. 2 to 6 show a first embodiment of the present invention, and FIG.
FIG. 4 is a configuration diagram showing a cross-sectional view of the fuel injection device of the first embodiment together with a block diagram of an electronic control device, and FIG. 3 is a schematic configuration diagram of a four-cylinder diesel engine configured by adopting the fuel injection device. FIG. 5 is a flowchart showing a main control routine executed by the electronic control unit, FIG. 5 is a flowchart showing a fuel injection valve control routine, FIG. 6 is a timing chart showing the fuel injection valve control, FIG. FIG. 8 shows a second embodiment of the present invention,
FIG. 8 is a flow chart showing a fuel injection valve control routine executed by the electronic control unit, and FIG. 8 is a flow chart showing the same operating state observation routine. 1 ... Diesel engine 8 ... Fuel injection valve 10 ... Fuel supply pipe 12 ... Accumulation chamber 14 ... Fuel injection pump 30 ... Electronic control device 40 ... Piezoelectric element drive device 50 ... Fuel injection valve body 54 ... ... Fuel injection nozzle 62 ... Needle valve 84 ... First piezoelectric element 85 ... Second piezoelectric element

Claims (1)

(57) [Claims] 1. A fuel injection nozzle in which fuel pressurized by a fuel supply pump is sent through a fuel supply pipe, a needle valve provided in the fuel injection nozzle to open and close the fuel injection nozzle, and the needle valve. Of the laminated structure that drives opening and closing
A fuel injection valve composed of a piezoelectric element; and a needle valve opening / closing means for controlling the voltage applied to the first piezoelectric element to expand / contract the first piezoelectric element to open / close the needle valve. A fuel injection device, which is provided in a stacking direction of the first piezoelectric elements, and is applied with a voltage independently of the first piezoelectric elements, and applies a driving force in at least a valve closing direction to the needle valve. After the second piezoelectric element having a laminated structure and the needle valve opening / closing means perform the valve closing operation of the needle valve on the first piezoelectric element, the needle valve is generated based on the voltage generated by the second piezoelectric element. A valve closing completion determining means for determining that the M4 has completed valve closing, and a predetermined time for the second piezoelectric element after the valve closing completion determining means determines that the closing of the needle valve is completed. Across And a needle valve closing force increasing means for increasing the valve closing force of the needle valve for a predetermined time by applying a voltage in the direction of closing the needle valve.