JPH11200984A - Fuel injection valve of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase degree of freedom in the control of a fuel injection rate in a fuel injection valve. SOLUTION: A pressure receiving face constituted by a difference in steps of a first needle 1 which opens and closes an injection hole receives pressure of a control pressure chamber 40, and the control pressure chamber 40 is pressurized by a piston 50 operated by an electrostrictive actuator 110, thereby giving a lift amount in a former half period of an injection period. This lift amount is stepwise changed when an applied voltage of the electrostrictive actuator 110 is changed. When a top face of the needle 1 rises up to a position where it comes into contact with a lower face of a second needle 120, two needles can move integrally. When an armature part 121 of the second needle 120 is attracted and raised by a solenoid 130 in this condition, the first needle 1 also rises to give a lift amount in a latter half period of the injection period. In this way, it is possible to control the lift amount and fuel injection rate over the wide range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve for an internal combustion engine, and more particularly to a fuel injection valve for a diesel direct injection engine and a gasoline direct injection engine for directly injecting fuel into each cylinder, and a driving method thereof. About.

[0002]

2. Description of the Related Art An example of a conventional fuel injection valve capable of controlling an initial injection rate of an injection rate effective for exhaust gas purification of an internal combustion engine is disclosed in Japanese Patent Application Laid-Open No. 5-71438. Can be mentioned.

[0003]

The conventional fuel injector uses an electromagnetic three-way valve and a spool valve formed by a piezo element to reduce the back pressure acting on the needle by changing the volume of the back pressure chamber. By switching between the three stages, three types of operations, that is, valve closing, injection at a low injection rate, and injection at a high injection rate, can be performed.

Generally, the required initial injection rate time, height, and the response speed of the change in the injection rate are different depending on the operating conditions of the engine. It is necessary to change the injection rate in multiple stages or to freely change the height of the injection rate according to the load state and the number of revolutions.

However, since the degree of change in volume in the fuel injection device is always constant, the change in back pressure is limited to three pressure values corresponding to the amount of change in volume, and the lift amount of the needle during injection is also two. Although it changes in steps, its height cannot be changed.

[0006] Therefore, an object of the present invention is to realize a control of the injection rate which is wider and has a higher degree of freedom than in the past by changing the pressure acting on the needle more variously.

[0007]

In the fuel injection valve according to the first aspect, the control needle pressure is controlled by changing the control pressure chamber volume by expansion and contraction of the electrostrictive actuator to thereby control the first needle. Controls the displacement,
Since the displacement of the second needle is controlled by energizing the solenoid, the controllable lift of the first needle is increased.

According to the driving method of the fuel injection valve according to the second aspect, the displacement of the first needle is controlled by expanding and contracting the electrostrictive actuator in the first half of the injection period, and the solenoid is operated in the second half of the injection period. Actuation displaces the second needle and further displaces the first needle in contact therewith.

In the fuel injection valve and the driving method described in any of the claims, each of the electrostrictive actuator and the solenoid can be operated independently by the supply of electric power from an external driving circuit. Is controlled by an external control circuit. Therefore, by adjusting the operation timing of the electrostrictive actuator and the solenoid, different needle lift amounts can be changed and different injection rates can be obtained. Therefore, the operation for changing the manner of increasing the injection rate will be described in some detail in the following.

First, in the injection stop state, when the solenoid is not energized, the second needle is lowered and seated by receiving the pressure of high-pressure fuel from above. The electrostrictive actuator is in a contracted state with a low applied voltage, and the first needle is in the valve closed position. When the voltage applied to the electrostrictive actuator is increased at a desired injection start timing, the electrostrictive actuator expands and lowers the integrated piston, so that the volume of the control pressure chamber decreases and the internal pressure increases. As a result, the upward load acting on the pressure receiving surface of the first needle increases, and the upward movement starts from the point in time when the total load acting on the needle becomes upward.

When the first needle rises and its top surface collides with the lower contact surface of the second needle, the first needle receiving an upward load and the second needle receiving a downward load. Since the needles are in close contact with each other and the pressure of the control pressure chamber is reduced and the spring load changes with the movement of the first needle, the lift in which the vertical load difference becomes zero while the two needles are integrated is maintained. Rest in position. Since the amount of expansion and contraction of the electrostrictive actuator can be controlled within a range of several tens of μm by controlling the applied voltage, the resting height of the two integrated needles can also be controlled by the applied voltage of the electrostrictive actuator. .

When the solenoid is energized at the desired injection rate increase time after the two needles have come to a standstill together, the second needle, which comes to a standstill together with the first needle, sucks the solenoid. Immediately rises upon receiving power from the armature. Since the first needle receives the fuel pressure from below, it rises with the rise of the second needle and reaches a full lift.

Here, the position where the two needles come together and stand still corresponds to the amount of pressure change in the control pressure chamber.
By changing the voltage applied to the electrostrictive actuator, it is possible to control the height of the injection rate before the injection. Further, the timing at which the needle reaches the full lift can be controlled by controlling the timing of energizing the solenoid. Furthermore, by increasing the voltage applied to the electrostrictive actuator stepwise by the time the solenoid is energized as in the driving method according to the third aspect, it is possible to change the region with a low injection rate stepwise. .

According to the present invention, it is possible to not only lower the initial injection rate but also change the height of the injection rate, in contrast to the control of the initial injection rate which is generally considered to have a large effect on exhaust gas purification. As a result, it is possible to always perform injection at an appropriate injection rate according to the operating conditions of the engine, and as a result, it is possible to purify exhaust to a greater extent than in the past.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of a fuel injection valve according to a first embodiment of the present invention is shown in FIGS. The first needle 1 can be oil-tightly slid by the first sliding portion 10 while maintaining a small clearance with respect to the first guide portion 21 of the injection valve casing 20. And the control pressure chamber 40 are isolated. Also, the second
The sliding portion 11 can maintain a small clearance with respect to the guide portion 51 formed on the piston 50 and can slide in an oil-tight manner, thereby isolating the control pressure chamber 40 and the spring chamber 60. The step between the first sliding portion 10 and the second sliding portion 11 faces a control pressure chamber 40 described later,
The pressure receiving surface 12 is formed. Further, the first needle 1
The second guide portion 7 of the injection valve casing at the sliding portion 13
The oil reservoir 80 and the drain chamber 30 can be slid oil-tightly while maintaining a small clearance with respect to zero.
The first spring 90 is in a flexed state and the first needle 1
The first needle 1 is installed so as to be in contact with the seat surface 14 of the first needle 1.
Is seated on the seat surface 101 of the nozzle casing 100 at the seat portion 15.

The piston 50 is connected to the second needle 1
The second spring 91, which is slidable in an oil-tight manner while maintaining a small clearance with respect to the sliding portion 11 and the third guide portion 22 of the injection valve casing, is provided by a bent second spring 91. By being pushed upward, the top surface 5
2 closely adheres to the bottom surface 111 of the electrostrictive actuator 110. In addition, the bottom surface 53 of the piston 50 maintains a gap between the bottom surface 53 of the piston 50 and the opposing inner surface 23 of the injection valve casing, and the control pressure chamber 40 including the gap portion below the pressure receiving surface 12 of the needle is formed. Form.

The second needle 120 has an armature 12 which is sucked upward by a solenoid 130 in the middle thereof.
1 and slides in an oil-tight manner while maintaining a small clearance with respect to the fourth guide portion 140 of the injection valve casing at a sliding portion 122 equivalent to the diameter of the seat portion 15 of the first needle 1. It is possible to isolate the armature chamber 150 and the pressure chamber 151. In a state where the lower surface 123 of the armature portion 121 contacts the stopper 25 and the second needle 120 is at the lowest position, the lower contact surface 124 maintains a slight gap with the top surface 16 of the first needle 1. .

The electrostrictive actuator 110 is supported by the upper surface 112 thereof being in contact with the wall surface in the actuator chamber 160 and being pushed from below by the piston 50 described above. Lead wire 17 from the side of electrostrictive actuator 110
0 is output and connected to an external electrostrictive actuator drive circuit 180 via a lead hole 171.

The solenoid 130 is fixed in the injection valve casing, and the second needle 120 passes through the center. A lead wire 132 extends from the bottom surface 131 and is connected to an external solenoid drive circuit 181.

The electrostrictive actuator drive circuit 180 and the solenoid drive circuit 181 change the state of energization to the electrostrictive actuator 110 and the solenoid 130 by receiving a signal from the control circuit 182.

High pressure fuel supply line 2 from high pressure pump 200
01 is connected to the common rail 202 and the common rail 2
Injection fuel passages 203 and 204 are connected to the oil sump 80 and the upper pressure chamber 151 from 02. Common rail 20
By the pressure control of 2, the fuel pressure in the injection fuel flow paths 203 and 204 is maintained at a high injection fuel pressure. Further, from the high-pressure pump 200, a control fuel path 205 is connected to the upstream side of the check valve 210 via a regulator 206. Control pressure chamber 4
Numeral 0 denotes a flow path 211 having a small diameter, which is connected to the downstream side of the check valve 210. By controlling the pressure by the regulator 206, the fuel pressure in the control pressure chamber 40 is set so that the load applied to the electrostrictive actuator 110 does not exceed an allowable range. The drain chamber 30 is connected to an external fuel drain path via a groove (not shown) in the injection valve.

In this case, the moving distance from the seating position of the first needle 1 to the contact with the stopper 55 is a full lift, and at the time when the first needle 1 is in contact with the stopper 55, The stepped portion 125 of the second needle 120, which is in contact with the lower contact surface 124 with the top surface 16 of the needle 1, does not contact the stopper surface 126, and even after the first needle 1 reaches the full lift, the second needle 1
20 can be raised until it contacts the stopper surface 126.

The operation of the fuel injection valve according to the first embodiment shown in FIGS. 1 and 2 will be described. FIG. 3 shows the time lapse of the operation of the needle, FIG. 4 shows the time lapse of the operation at the time of valve opening, and FIGS. 5, 6, and 7 show the internal positional relationship. In FIG. 4, the upward load from the sack portion 85 (the cross-sectional area of the seat 15) ×
The (in-cylinder pressure) is the upward load from the oil sump 80 (the cross-sectional area of the third guide 13-the cross-sectional area of the sheet 15) x (injected fuel pressure), and the upward load (the first fuel pressure) of the control pressure chamber 40.
Area of pressure receiving section 12 of needle 1) × (control pressure chamber pressure)
, The downward load of the force of the spring 90, the load increase due to the needle rise (cross-sectional area of the seat 15) × (injection fuel pressure-in-cylinder pressure), and the load increase due to needle contact (the second needle receiving pressure area, That is, (cross sectional area of the fourth guide 140) × (injected fuel pressure) is shown.

When fuel is not being injected, the solenoid 1
30 is not energized, the second needle 120 is lowered by receiving a load of high-pressure fuel from above, and the second needle 120 is lowered.
1 is seated in contact with the stopper 25. As shown in FIG. 5A, the control pressure chamber 40 is stably pressurized by the supply pressure of the regulator 206, the applied voltage of the electrostrictive actuator 110 is low, and the first needle 1 is Sitting by force (state 1).

When the voltage applied to the electrostrictive actuator 110 is increased at a desired injection start timing, the electrostrictive actuator 110 is extended, and the piston 50 is lowered integrally, as shown in FIG. 5 (b). The volume of the pressure chamber 40 decreases and the internal pressure increases. The first needle 1 rises from the point in time at which the upward load acting on the pressure receiving surface 12 increases due to the increase in the pressure of the control pressure chamber 40, and the sum of the loads acting on the needles becomes upward (state 2).

When the first needle 1 rises and its top surface 16 collides with the lower contact surface 124 of the second needle (state 3) as shown in FIG. As shown in FIG. 1, a first needle 1 receiving an upward load,
The second needle 120 receiving a downward load is in close contact, and the pressure of the control pressure chamber 40, which decreases with the movement of the first needle, is balanced with the load of the spring 90.
The two needles move to a lift position where the load difference in the vertical direction becomes zero while being integrated, and stand still (state 4).

After the two needles come to a standstill together, at the desired injection rate increase timing, the solenoid 130
When the power is supplied to the first needle 1, the second needle 120, which is stationary together with the first needle 1, immediately rises when the armature 121 receives the suction force of the solenoid 130. Since the first needle 1 is receiving the fuel pressure from below, as shown in FIG.
(State 5). Then, before the second needle 120 reaches the full lift, the first needle 1 comes into contact with the stopper 55 and stops, and FIG.
As shown in (b), a full lift state is established (state 6).

Thereafter, at a desired fuel injection stop timing, the voltage applied to the electrostrictive actuator 110 is reduced and the energization of the solenoid 130 is stopped, so that both the first needle 1 and the second needle 120 are connected. When the first needle 1 is seated on the seat portion 15, the injection is finished when the downward load increases and the first needle 1 is seated on the seat portion 15.

FIG. 8 shows the operation when the voltage applied to the electrostrictive actuator 110 is changed in a stepwise manner until the solenoid is energized.

In the above-described state 4 (see FIG. 6B), that is, during a period from when the voltage applied to the electrostrictive actuator 110 is increased to open the valve, to when the solenoid 130 is energized to obtain the full lift, a relatively large amount is obtained. During the period when the injection rate is extremely low, the first needle 1 and the second needle 120 are integrated, and the needle lift is determined by the pressure change of the control pressure chamber 40 by the electrostrictive actuator 110.

During this period, the electrostrictive actuator 1
When the applied voltage is changed stepwise, the control pressure chamber 4
The pressure of 0 also changes stepwise. At this time, the load acting on the second needle 120 does not change, so that the load remains downward and keeps in contact with the first needle 1.
In this state, the upward load applied to the pressure receiving surface of the first needle 1 increases, but as the first needle 1 rises, the load of the downward spring 90 increases. The needle stops at the point where the increases in are equal. Subsequent operations are the same as those described above.

FIGS. 9 and 10 show the configuration of the second embodiment of the present invention. FIG. 9 shows one longitudinal section of the injection valve of the second embodiment, and FIG. 10 shows another longitudinal section orthogonal to the longitudinal section shown in FIG.

In the second embodiment, the needle 1 is provided with a first guide portion 21, a second guide portion 300,
The fourth guide portion 70 can slide in an oil-tight manner while maintaining a small clearance with respect to each guide portion. The laterally movable piston 310 can be oil-tightly slid while maintaining a small clearance with respect to the third guide portion 320 of the injection valve casing. Actuator 110 housed in an actuator casing 330 fixed to the side of
Further, when pressed in the direction of the electrostrictive actuator 110 by the spring 340, it can slide in close contact with one end of the electrostrictive actuator 110.

The control pressure chamber 40 has a piston gap 351 formed by the bottom surface of the piston 310 and the wall surface of the injection valve casing, and a needle gap portion 3 formed by the pressure receiving surface which is a step portion of the needle and the wall surface of the injection valve casing.
52, a piston gap 351 and a needle gap 352
And a communication groove 353 that communicates the Other configurations are the same as those of the first embodiment shown in FIGS.

The second embodiment differs from the first embodiment in that the vertical movement directions of the needles 1 and 120 and the movement direction of the piston 310 are different. In the first embodiment, they are all coaxial and the movement directions are the same. Is different. Also, the second
The operation of the injection valve of the embodiment is the same as the operation of the first embodiment except that the movement directions of the needles 1 and 120 and the piston 310 are different, and therefore the second embodiment is described in detail. Is omitted.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing a fuel injection valve as a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional front view showing a part of FIG. 1 in an enlarged manner.

FIG. 3 is a time chart showing a lapse of time of the operation of the needle.

FIG. 4 is a time chart showing a lapse of time of an operation at the time of valve opening.

FIGS. 5A and 5B are vertical sectional front views showing an internal positional relationship for each operation state, wherein FIG. 5A is a state 1 in which a valve is closed and injection is stopped, and FIG. This shows a valve open state when the injection is started by the operation.

FIGS. 6A and 6B are longitudinal front views showing an internal positional relationship for each operation state, wherein FIG. 6A is a state 3 in which the valve is opened when two needles are in contact, and FIG. Shows a valve-open state when they move together to a position where the forces balance.

FIGS. 7A and 7B are longitudinal front views showing the internal positional relationship for each operation state, wherein FIG. 7A is a state 5 and a valve open state in which a solenoid is operated to increase the injection rate, and FIG.
Shows the valve open state when the full lift is reached.

FIG. 8 is a time chart showing an operation in a case where the voltage applied to the electrostrictive actuator is changed stepwise until the energization of the solenoid is started.

FIG. 9 is a vertical sectional front view showing a fuel injection valve as a second embodiment of the present invention.

FIG. 10 is a vertical sectional side view of the fuel injection valve shown in FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st needle 12 ... Pressure receiving surface of 1st needle 16 ... Top surface of 1st needle 20 ... Casing of fuel injection valve 30 ... Drain chamber 40 ... Control pressure chamber 50 ... Piston 55 ... Stopper 80 ... Oil sump 85 ... Suck portion 86 ... Injection hole 90 ... First spring 91 ... Second spring 110 ... Electrostrictive actuator 120 ... Second needle 121 ... Armature 124 ... Lower needle contact surface of second needle 130 ... Solenoid 151 ... Pressure Chamber 210 ... check valve

Claims (3)

[Claims] In a fuel injection valve of an internal combustion engine that injects high-pressure fuel by moving a needle up and down by controlling the pressure of a control pressure chamber by an actuator, a piston moves by an operation of an electrostrictive actuator to change pressure. A pressure receiving surface facing downward with respect to the control pressure chamber is formed in the middle of the control pressure chamber, and as the load acting on the pressure receiving surface increases or decreases due to a change in the pressure of the control pressure chamber, it rises and descends, and the lower seat portion A first needle that communicates and shuts off the oil reservoir with the injection hole, and a lower contact surface that contacts the top surface of the first needle when the first needle rises by a small amount. The pressure is pushed downward by receiving the injected fuel pressure on the upper pressure receiving surface corresponding to the seat area of the fuel injection valve, and the pressure is constantly reduced by the solenoid provided in the injection valve casing. A second needle having an armature portion for maintaining a small gap, and a second needle that moves up and down by increasing and decreasing the attraction force of the solenoid, and changing the volume of the control pressure chamber by expansion and contraction of the electrostrictive actuator; A fuel injection valve for an internal combustion engine, wherein the displacement of the first needle is controlled by controlling the pressure of the first needle, and the displacement of the second needle is controlled by energizing the solenoid. 2. A driving circuit for controlling an applied voltage of an electrostrictive actuator, and a driving circuit for controlling a current of a solenoid, wherein an applied voltage and a voltage maintaining time of the electrostrictive actuator are adjusted in the first half of an injection period. By controlling the displacement of the first needle by expanding and contracting the electrostrictive actuator,
2. The method according to claim 1, further comprising controlling a timing of displacing the second needle by adjusting an energization timing of the solenoid in a later stage of the injection period. 3. The injection rate is changed stepwise by increasing the voltage applied to the electrostrictive actuator stepwise in the first half of the injection period before energization of the solenoid is started. 3. The method for driving a fuel injection valve according to claim 1.