JPH11200981A - Fuel injection valve and driving method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve which can control a fuel injection rate during one injection period and enables highly accurate control to make fuel injection at the optimum injection rate corresponding to engine conditions by constituting the injection valve which is opened by pressurizing a control pressure chamber. SOLUTION: A first downward pressure receiving face 130 formed with a difference in steps between a first guide shaft 30 and a second guide shaft 32 of a needle 20 is communicated or exposed to a control pressure chamber 14 of which pressure is changed in accordance with the displacement of an electrostrictive actuator, and a voltage applied on the electrostrictive actuator 1 is changed arbitrarily or at several stages during one injection period. Consequently, a fuel injection rate determined by a lift amount of the needle 20 can be controlled arbitrarily or at several stages during one injection period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device used for a direct injection type diesel engine or a gasoline engine which injects high-pressure fuel and requires high injection quantity adjustment accuracy.

[0002]

2. Description of the Related Art As a fuel injection valve for injecting high-pressure fuel, there are an electrostrictive actuator and a known fuel injection valve using a solenoid as an actuator. FIG.
Is a well-known fuel injection valve using an electrostrictive actuator as an actuator.
It is a cross-sectional view of the fuel injection valve shown by 065.

A back pressure chamber 103 and an oil sump 104 are separated by a guide portion 102 of the needle 101, and a downward load is applied to the needle 101 by a spring 105 in contact with the top surface and a downward load corresponding to the diameter of the guide portion 102. A back pressure load, an upward load due to the pressure of the sack portion 107 corresponding to the inside of the annular seat portion, and a guide portion 102
The difference between the diameter of the seat portion 106 and the diameter of the seat portion 106 causes an upward load due to the application of the fuel pressure of the oil pool to the area formed by the gap. When the back pressure is the specified pressure, the valve is closed because the total of the loads is downward, and the needle 101 is pushed down due to a decrease in the hydraulic pressure of the back pressure chamber 103 due to the operation of the actuator such as expansion and contraction of the electrostrictive actuator 109. When the pressure load decreases and the load becomes upward, the needle 101 rises.

[0004]

In order to purify exhaust gas and improve fuel efficiency of an internal combustion engine, an injection valve capable of performing high-precision control such as controlling an injection rate during one injection period is required. In such a case, high-precision control such as the amount of displacement of the needle and the operation response is required. In the known fuel injection valve, the valve is opened by increasing the upward load of the needle by reducing the back pressure, but the fuel in the back pressure chamber corresponding to the control pressure chamber of the present invention has a reduced pressure. At the same time, the compression ratio decreases (the ratio of the pressure change amount to the volume change amount decreases), and the back pressure hardly changes due to the minute displacement of the needle, so that the needle fluctuates greatly during valve opening.

[0005] Further, when the electrostrictive actuator is suddenly largely displaced, a pressure pulsation having a large amplitude is generated in the back pressure chamber, so that the load of the needle also fluctuates and the displacement is affected. For these reasons, a conventionally known injection valve that opens by reducing the pressure in the back pressure chamber cannot achieve high-accuracy injection amount control.

[0006] In order to solve the above-mentioned problems, the present invention provides an injection valve configured to open by pressurizing a control pressure chamber,
A fuel injection valve that can perform high-precision control such as controlling the fuel injection rate during one injection period, and enables fuel injection at an optimum injection rate according to engine conditions, thereby improving fuel consumption and exhaust gas. It is an object of the present invention to provide a method of driving a fuel injection valve that can realize purification of fuel.

[0007]

The present invention employs the technical means described in claims 1 to 8 to solve the above-mentioned problems. In the fuel injection valve according to the first aspect, a first downward pressure receiving surface formed by a step between the first guide shaft and the second guide shaft is communicated with or exposed to the control pressure chamber. The pressure in the control pressure chamber can be controlled with high precision by controlling the amount of displacement by the applied voltage value. The needle rises when the control pressure chamber is pressurized, and the lift amount is determined by the spring force of the needle spring and the load due to the pressure of the control pressure chamber. Therefore, the lift amount of the needle is applied to the electrostrictive actuator. It can be controlled with high accuracy by the voltage value.

In the fuel injection valve according to a second aspect of the present invention, a fuel pressure transmission path for introducing high-pressure injection fuel supplied to the fuel injection valve to the fuel chamber around the top surface of the third guide shaft of the needle is provided. Therefore, a downward load due to fuel pressure can be applied to the upper part of the needle, and therefore, the load of the needle spring against the rise of the needle can be reduced by the amount corresponding to the above load, and the needle spring is downsized and the spring constant is reduced. Since the downward load increase when the needle is raised can be small with a low spring constant, the displacement of the electrostrictive actuator can be small, and the size of the electrostrictive actuator can be reduced.

[0009] In the fuel injection valve according to the third aspect, further,
The oil reservoir is isolated from the drain hole, and a second downward pressure receiving surface formed by a step between the first guide shaft and the fourth guide shaft is exposed to the drain hole. A guide shaft is provided. Therefore, no load acts on the area corresponding to the step between the fourth guide shaft and the first guide shaft, and the upward load is further reduced. Since the upward load is reduced, the downward load to be opposed can be reduced, and the needle spring force can be further reduced.

As the spring force is smaller, the smaller the set load, the smaller the spring, the easier it is to lower the spring constant.
The amount of displacement of the electrostrictive actuator can be further reduced, and the size of the electrostrictive actuator can be further reduced. In the fuel injection valve according to the fourth aspect, the rod is further divided from the needle, but since the needle and the rod are in close contact with each other, the operation and effect are the same as those of the third aspect.

In the fuel injection valve according to the fifth aspect, a regulator is provided upstream of the check valve to supply fuel to the downstream check valve at a constant pressure lower than the injection fuel pressure. If the injected fuel pressure is high and the load applied to the electrostrictive actuator exceeds the allowable load when the injection pressure is equal to the control pressure chamber, a regulator is installed to reduce the internal pressure of the control pressure chamber to the allowable level of the electrostrictive actuator. Since the load is controlled so as not to exceed the load, and the load of the electrostrictive actuator is kept within an allowable range, proper operation of the electrostrictive actuator can be obtained regardless of the injected fuel pressure.

In the method for driving a fuel injection valve according to the sixth or seventh aspect, the voltage applied to the electrostrictive actuator is changed arbitrarily or in several steps within one injection period, and the displacement amount of the electrostrictive actuator is changed. Is changed arbitrarily or in several stages within one injection period, so that the soft amount of the needle is changed arbitrarily or in several stages within the one injection period, and the fuel injection determined according to the soft amount of the needle The rate can be changed arbitrarily or in several steps within one injection period. This makes it possible to inject fuel at an optimal injection rate according to the engine conditions such as the engine speed and the load condition, thereby improving fuel consumption and purifying exhaust gas.

[0013] In the driving method of the fuel injection valve according to the present invention, the amount of pressure rise in the control pressure chamber due to the extension of the electrostrictive actuator is slightly lower than the amount of pressure rise required for valve opening. Since the voltage applied to the electrostrictive actuator is gradually increased so as to perform the pre-step-up, the fuel injection delay is eliminated, and the improvement of fuel consumption and purification of exhaust gas can be realized.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment according to the first aspect of the present invention, which corresponds to the first aspect.
It is a system diagram of an embodiment. In FIG. 1, an electrostrictive actuator 1 has an upper end surface 3 in contact with a casing wall surface 4 and a lower end surface 5 in contact with a piston upper end surface 6 in an injection valve casing 2. A lead wire 7 protrudes from the upper side surface of the actuator 1 and is connected to a drive circuit 9 outside the injection valve through a hole 8 in the injection valve casing 2. Piston 10
Is pushed upward by a spring 11 and moves up and down due to expansion and contraction of the electrostrictive actuator 1 when it comes into close contact with the electrostrictive actuator 1. The piston side surface 12 has a slight clearance with respect to the guide surface 13 of the injection valve casing 2 and is slidable while isolating the control pressure chamber 14 and the actuator chamber 15 from each other.

The needle 20 is seated on the nozzle casing 22 at the lower seat portion 21, so that a sack portion 24 that opens to the outside through a nozzle hole 23 and a nozzle casing 22 are formed.
The communication with the oil sump 25 inside is shut off. Needle 2
The first guide shaft 30 has a slight clearance with respect to the first first guide hole 31 of the nozzle casing 22 and is slidably supported in the vertical direction.
Has a slight clearance with respect to the second guide hole 33 of the injection valve casing 2 and is slidably supported in the vertical direction. Spring seat surface 34 above second guide shaft 32
Has one end in contact with a needle spring 35 housed in a needle spring housing chamber 100 formed in the injection valve casing 2.

The first guide hole 31 and the second guide hole 3
The annular control pressure chamber needle portion 40 corresponding to the difference of 3
The control pressure communication passage 41 communicates with the control pressure chamber 14 formed by a minute gap between the bottom surface of the piston 10 and the inner wall surface of the injection valve casing 2. That is, the first downward pressure receiving surface 130 formed by the step between the first guide shaft 30 and the second guide shaft 32 has the same configuration as that exposed to the control pressure chamber 14. The control pressure chamber 14 communicates with the injection fuel passage 45 through a control fuel introduction passage 42, and an orifice 43 is provided near the control pressure chamber 14 in the control fuel introduction passage 42.
And a check valve 44.

The injection fuel passage 45 communicates from the high-pressure pump to the oil sump 25 through the common rail and the inlet 47 of the nozzle casing 22. FIG. 2 shows a first embodiment of the first invention.
FIG. 4 is an operation explanatory diagram illustrating the operation of the fuel injection valve shown in the embodiment. At the time of no injection, the voltage applied to the electrostrictive actuator 1 is low, and the electrostrictive actuator 1 is at the reference length. The control pressure chamber 14 is at a regulated supply pressure via a regulator, and the fuel pressure of the sump 25 is at a direct supply pressure from the common rail. In this state, the pressure of the sack portion 24 applied to the cross-sectional area of the seat portion 21 and the injected fuel pressure applied to ((cross-sectional area of the diameter of the first guide shaft 30) − (cross-sectional area of the diameter of the seat portion 21)) , First downward pressure receiving surface 13
The needle 20 is seated on the seat 21 because the downward load by the needle spring 35 is superior to the upward load by the control fuel pressure applied to zero.

When the voltage applied to the electrostrictive actuator 1 is increased at a desired valve opening timing, the pressure in the control pressure chamber 14 increases due to a decrease in volume, and the pressure in the control pressure chamber 14 exceeds the needle opening pressure. 20 rises immediately.
After the valve is opened, by maintaining the applied voltage after the valve is opened until a desired valve closing timing, the pressure of the control pressure chamber 14 is maintained at a high level, and the lift amount of the needle is maintained.

At the desired valve closing timing, the applied voltage is reduced to the reference voltage, the pressure in the control pressure chamber 14 is reduced by contracting the electrostrictive actuator 1, and the needle 20 Lowers, and the injection ends when seated. FIG. 3 shows a first embodiment of the first embodiment in which the first guide shaft 30 and the second guide shaft 32 are provided with O-rings 201 and 202 for maintaining oil tightness, respectively, in the first embodiment of the first invention. It is a system diagram of a second embodiment corresponding to claim 1.

The operation is the same as in the first embodiment. FIG. 4 is a system diagram of a third embodiment corresponding to the first aspect of the first invention described in the first to fourth aspects. The electrostrictive actuator 1 has an upper end surface 3 in contact with the casing wall surface 4 and a lower end surface 5 in contact with the piston upper end surface 6 in the injection valve casing 2. A lead wire 7 protrudes from the upper side of the electrostrictive actuator 1,
It is connected to a drive circuit 9 outside the injection valve through a hole 8 in the injection valve casing 2. The piston 10 is a spring 1
1 and moves up and down due to the expansion and contraction of the electrostrictive actuator 1 when it comes into close contact with the electrostrictive actuator 1. The piston side surface 12 has a slight clearance with respect to the guide surface 13 of the injection valve casing 2 and is slidable while isolating the control pressure chamber 14 and the actuator chamber 15 from each other.

In the third embodiment, the nozzle casing 22 comprises an upper nozzle casing 220 and a lower nozzle casing 221. The needle 20 is seated on the lower nozzle casing 221 at the lower seat portion 21 to cut off communication between the sack portion 24 that opens to the outside through the injection hole 23 and the oil sump 25 in the lower nozzle casing 221. doing. The first guide shaft 30 has a slight clearance with respect to the inner diameter of the guide hole 31 of the upper nozzle casing 220 and is slidably supported in the vertical direction. The spring seating surface 34 above the second guide shaft 32 has a slight clearance, and one end thereof is in contact with a needle spring 35 which is in contact with the bottom end surface 5 of the electrostrictive actuator 1. ing.

The control pressure chamber 14 is formed by an annular gap corresponding to the difference between the first guide shaft 30 and the second guide shaft 32 and a minute gap between the bottom surface of the piston 10 and the inner wall surface of the injection valve casing 2. You. The control pressure chamber 14 communicates with an injection fuel flow path 45 through a control fuel introduction path 42, and has an orifice 43 and a check valve 44 near the control pressure chamber 14 in the control fuel introduction path 42.

The injection fuel flow path 45 communicates from the high pressure pump to the oil sump 25 via the common rail and the inlet 47 of the injection valve casing 2. The operation of the third embodiment is as follows.
The description is omitted because it is similar to the first embodiment. FIG. 5 is a system diagram of a fourth embodiment corresponding to claim 2 of the first invention described in claims 1 to 4.

The electrostrictive actuator 1 has an upper end surface 3 in contact with a casing wall surface 4 in the injection valve casing 2.
The lower end surface 5 contacts the piston upper end surface 6. A lead wire 7 protrudes from the upper side surface of the electrostrictive actuator 1 and is connected to a drive circuit 9 outside the injection valve through a hole 8 in the injection valve casing 2. The electrostrictive actuator 1 is formed in a cylindrical shape by stacking a plurality of piezo elements having a cross section having a circular hole at the center.

The piston 10 has a second guide hole 33 at its center axis, is pushed upward by a spring 11, and moves up and down due to expansion and contraction of the electrostrictive actuator 1 when it comes into close contact with the electrostrictive actuator 1. The piston sliding surface 12
It has a slight clearance with respect to the guide surface 13 of the injection valve casing 2 and can slide with the control pressure chamber 14 and the actuator chamber 15 separated.

Also in the fourth embodiment, the nozzle casing 22 comprises an upper nozzle casing 220 and a lower nozzle casing 221. Needle 20
By sitting on the lower nozzle casing 221 at the lower seat portion 21, the sack portion 24 that opens to the outside through the injection hole 23 and the oil sump 25 inside the lower nozzle casing 221 are provided.
The communication with is interrupted. The first guide hole 30 has a slight clearance with respect to the first guide hole 31 of the upper nozzle casing 220 and is supported so as to be slidable in the vertical direction, and the second guide shaft 32 is connected to the second guide hole 3 of the piston 10.
3 has a slight clearance and is slidably supported in the vertical direction. The spring seat surface 36 above the second guide shaft 32 is in contact with the needle spring 35 in the needle spring storage chamber 100. The third guide shaft 50 has a slight clearance with respect to the third guide hole 51 of the injection valve body 240 forming a part of the injection valve casing 2 and is slidably supported in the vertical direction.

A control pressure chamber 14 is formed by an annular gap corresponding to the difference between the first guide shaft 30 and the second guide shaft 32 and a gap between the bottom surface of the piston 10 and the injection valve casing 2. An orifice 43 and a check valve 44 are provided in the control fuel introduction passage 42 in communication with the injection fuel flow passage 45 near the control pressure chamber 14 in the control fuel introduction passage 42.

An injection fuel flow path 45 communicates from the high pressure pump to the oil sump 25 through a common rail and an inlet 47 of the injection valve casing 2, and a fuel pressure transmission path 48 branching from the middle thereof provides a fuel pressure around the top surface of the needle 20. It communicates with the room 49. As in the second embodiment, the first guide shaft 30, the second guide shaft 32, the third
When an O-ring for maintaining oil tightness is provided on the guide shaft 50, the operation thereof is the same as the operation of the above-described fourth embodiment described later.

The operation of the fuel injection valve according to the fourth embodiment of the first invention will be described in comparison with the first embodiment. Figure 1,
2 and 5, when no injection is performed, the voltage applied to the electrostrictive actuator 1 is low, and the electrostrictive actuator 1 is at the reference length. Further, the fuel pressure injected into the control pressure chamber 14 and the oil sump 25 is also at the supply pressure. In this state, the seat portion 2
1, the injection fuel pressure applied to ((cross-sectional area of the diameter of the first guide shaft 30)-(the cross-sectional area of the diameter of the seat 21)), and the received pressure of the control pressure chamber 14. Since the fuel pressure applied to the top surface of the needle 20 and the downward load applied by the needle spring 35 are superior to the upward load applied by the control fuel pressure applied to the
0 is seated on the seat 21. Since the downward load due to the injected fuel pressure is increased compared to the first embodiment, the load on the needle spring 35 is set lower.

When the voltage applied to the electrostrictive actuator 1 is increased at a desired valve opening timing, the pressure in the control pressure chamber 14 increases due to the decrease in volume, and the pressure in the control pressure chamber 14 exceeds the needle valve opening pressure. 20 rises immediately.
After the valve is opened, by maintaining the applied voltage after the valve is opened until a desired valve closing timing, the pressure in the control pressure chamber 14 is maintained at a high level, so that the lift amount of the needle 20 is maintained.

At a desired valve closing timing, the applied voltage is reduced to the reference voltage, the pressure in the control pressure chamber 14 is reduced by contracting the electrostrictive actuator 1, and the needle 20 Lowers, and the injection ends when seated. FIG. 6 shows claims 1 to 4.
FIG. 13 is a system diagram of a fifth embodiment corresponding to claim 3 of the first invention described in FIG.

The electrostrictive actuator 1 has the upper end surface 3 in contact with the casing wall surface 4 in the injection valve casing 2.
The lower end surface 5 contacts the piston upper end surface 6. A lead wire 7 protrudes from the upper side surface of the electrostrictive actuator 1 and is connected to a drive circuit 9 outside the injection valve through a hole 8 in the injection valve casing 2. The electrostrictive actuator 1 is formed in a cylindrical shape by stacking a plurality of piezo elements having a cross section having a circular hole at the center.

The piston 10 has a second guide hole 33 at its center axis, and is pushed upward by the spring 11.
When the electrostrictive actuator 1 comes into close contact with the electrostrictive actuator 1, the electrostrictive actuator 1 moves up and down. Piston sliding surface 12
Has a slight clearance with respect to the guide surface 13 of the injection valve casing 2 and can slide in an oil-tight manner while isolating the control pressure chamber 14 and the actuator chamber 15 from each other.

The needle 20 is seated on the lower nozzle casing 221 at the lower seat portion 21 so that the injection hole 2
The communication between the sack portion 24 that opens to the outside via 3 and the oil sump 25 in the lower nozzle casing 221 is blocked. The first guide shaft 30 has a slight clearance with respect to the first guide hole 31 of the upper nozzle casing 220,
The second guide shaft 32 has a slight clearance with respect to the second guide hole 33 of the upper nozzle casing 220 and is oil-tightly slidable in the vertical direction. Supported, the second guide shaft 32 has a larger diameter than the first guide shaft 30, the second guide shaft 32 has a slight clearance with respect to the second guide hole 33 of the piston 10, and slides vertically. It is movably supported oil-tight. The spring seat surface 36 above the second guide shaft 32 is
It is in contact with the needle spring 35. Third guide shaft 5
Numeral 0 has a slight clearance with respect to the third guide hole 51 of the injection valve body 240 and is supported in an oil-tight manner so as to be slidable in the vertical direction.

The fourth guide shaft 91 has a slight clearance with respect to the fourth guide hole 90 of the upper nozzle casing 220, and is slidably supported in an oil-tight manner. An annular gap corresponding to the difference between the first guide shaft 30 and the second guide shaft 32, the bottom surface of the piston 10 and the injection valve casing 2
A control pressure chamber is formed by the gap between the control pressure chamber. Control pressure chamber 1
Reference numeral 4 denotes a control fuel introduction passage 42 which communicates with the injection fuel flow passage 45. An orifice 43 and a check valve 44 are provided near the control pressure chamber 14 in the control fuel introduction passage 42.

The fuel injection passage 45 communicates from the high-pressure pump to the oil sump 25 through the common rail and the inlet 47 of the injection valve casing 2, and a fuel pressure transmission passage 48 branched from the middle thereof forms a fuel chamber around the top surface of the needle 20. Communicates up to 49. A second downward pressure receiving surface 111 formed by a step between the first guide shaft 30 and the fourth guide shaft 91 is exposed to the drain hole 110. The drain hole 110 communicates with a drain passage outside the injection valve via a drain passage inside the injection valve casing 2 (not shown).

As in the above-described embodiment, the first guide shaft 30, the second guide shaft 32,
When the third guide shaft 50 and the fourth guide shaft 91 are provided with O-rings for maintaining oil tightness, the operation thereof is the same as that of the fifth embodiment. In the fifth embodiment, the operation is the same as that of the above-described fourth embodiment, and a description thereof will be omitted.

FIG. 7 is a system diagram showing a sixth embodiment corresponding to the fourth aspect of the first invention described in the first to fourth aspects. This sixth embodiment is similar to the fifth embodiment.
Spring guide part 3 of needle 20 in the embodiment
The upper part of the needle 20 is provided with a rod 52 which can be slid up and down with a slight clearance with respect to the third guide hole 51 and whose lower end surface is in contact with the top surface of the needle 20.

The operation is the same as in the fifth embodiment.
A first embodiment of the second invention described in claim 5 will be described. The configuration of the first embodiment is an injection fuel introduction path in which high-pressure fuel is pumped at a specified injection fuel pressure by the fuel injection valve described in the first embodiment of the first invention shown in FIG. In the control fuel introduction passage branching from the control pressure chamber 14 to the control pressure chamber 14, a check valve 4
A regulator that supplies fuel to the check valve 44 downstream at a constant pressure lower than the injection fuel pressure is provided upstream of the fuel injection valve 4.

FIG. 8 is a diagram for explaining the operation of the regulator used in the first embodiment of the second invention. The operation is shown in FIG.
As shown in the figure, the regulator reduces the supply pressure to the control pressure chamber 14 to the check valve 44 side with respect to the pressure of the injection fuel introduction passage controlled to the specified injection fuel pressure, and The pressure in the chamber 14 is maintained below a certain value.

The effects are as follows. Generally, the electrostrictive actuator 1 has a limit in the load allowed in terms of strength, and in that state, the displacement performance is significantly deteriorated. Therefore, it is necessary to avoid using the load beyond that. Even if the injection fuel pressure is equal to the pressure of the control fuel chamber 14, if the load applied to the electrostrictive actuator does not exceed the allowable load, the effect of the regulator is not obtained. However, if the load applied to the electrostrictive actuator 1 exceeds the allowable load when the injected fuel pressure is high and the control pressure chamber 14 and the injected fuel pressure are equalized, the internal pressure of the control pressure chamber 14 is increased by providing a regulator. Is controlled so as not to exceed the allowable load of the electrostrictive actuator, and the load of the electrostrictive actuator 1 is kept within the allowable range. Thus, an appropriate operation of the electrostrictive actuator 1 can be obtained regardless of the injection fuel pressure.

FIG. 9 is an operation explanatory diagram illustrating a method of driving an electrostrictive actuator as a first embodiment corresponding to claim 6 of the third invention described in claims 6 and 7. . The operation when the present invention is applied when the fuel injection valve according to the first embodiment of the first invention is operated will be described with reference to FIG.

In FIG. 2, which is a driving method according to the first embodiment of the first invention, the time for changing the applied voltage is shortened to realize a sharp change in the needle lift. In the first embodiment of the invention, the needle lift within one injection period is changed according to the load condition and the number of revolutions of the engine by arbitrarily changing the applied voltage after the valve is opened.

When no injection is performed, the voltage applied to the electrostrictive actuator 1 is low and the actuator is at the reference length. The injection fuel pressure of the control pressure chamber 14 and the oil sump 25 is also at the specified pressure. In this state, the pressure of the sack portion 24 applied to the area inside the seat portion 21 and ((cross-sectional area of the first guide shaft 30) −
The fuel pressure applied to the top surface of the needle 20 and the spring 35 respond to an upward load caused by the injected fuel pressure applied to the (cross-sectional area of the seat portion 21) and the control fuel pressure applied to the pressure receiving surface 130 of the control pressure chamber 14. The needle 20 is seated on the seat portion 21 because the downward load is superior.

When the voltage applied to the electrostrictive actuator 1 is increased at a desired valve opening timing, the control pressure exceeds the needle valve opening pressure, and the needle 20 immediately increases. After the valve is opened, when the applied voltage is gradually increased, the electrostrictive actuator 1 expands in accordance with the voltage change of the electrostrictive actuator 1. At this time, the needle 20 rises to a position where the load in the vertical direction becomes equal, while increasing the load on the needle spring 35 in response to the increase in the pressure in the control pressure chamber 14.

At the desired valve closing timing, the applied voltage is reduced to the reference voltage, and the pressure in the control pressure chamber 14 is reduced by contracting the electrostrictive actuator 1, and the downward load of the needle 20 overcomes the needle 20. Lowers, and the injection ends when seated. By this operation, the amount of needle lift can be controlled in accordance with a change in the voltage applied to the electrostrictive actuator 1.

FIG. 10 is an operation explanatory view illustrating a method of driving an electrostrictive actuator as a second embodiment corresponding to claim 7 of the third invention described in claims 6 and 7. is there. The operation when applying the present invention when operating the fuel injection valve according to the first embodiment of the first invention will be described with reference to FIG.

When no injection is performed, the voltage applied to the electrostrictive actuator 1 is low and the electrostrictive actuator 1 is at the reference length.
The injection fuel pressure of the control pressure chamber 14 and the oil sump 25 is also at the specified pressure. In this state, the pressure of the sack portion 24 applied to the inner area of the seat portion 21 and ((cross-sectional area of the first guide shaft 30) −
The fuel pressure applied to the top surface of the needle 20 and the needle spring in response to the upward load caused by the injected fuel pressure applied to (the cross-sectional area of the seat portion 21) and the control fuel pressure applied to the pressure receiving surface 130 of the control pressure chamber 14. The needle 20 is seated on the seat portion 21 because the downward load by 35 is superior.

When the voltage applied to the electrostrictive actuator 1 is increased at a desired valve opening timing, the control pressure exceeds the needle valve opening pressure, and the needle immediately rises. After the valve is opened, the applied voltage after the valve is opened is maintained for a period up to a desired injection rate change timing (initial injection rate period), and the lift amount of the needle 20 is maintained. Next, when the voltage applied to the electrostrictive actuator 1 is increased again at a desired injection rate change timing, the electrostrictive actuator 1 further extends. At this time, the pressure in the control pressure chamber 14 increases, but the needle 20 which has been stationary until the load in the vertical direction has become equal until then increases the load on the needle spring 35 in response to the increase in the pressure in the control pressure chamber 14. Then, when the vertical load becomes equal, it stops again.

At the desired valve closing timing, the applied voltage is reduced to the reference voltage, and the pressure in the control pressure chamber 14 is reduced by contracting the electrostrictive actuator 1, and the downward load of the needle 20 overcomes the needle 20. Lowers, and the injection ends when seated. FIG. 11 shows claims 6 and 7.
FIG. 9 is an operation explanatory diagram illustrating a driving method of an electrostrictive actuator as a third embodiment corresponding to claim 7 of the third invention described in the above. The operation when the present invention is applied when operating the fuel injection valve according to the first embodiment of the first invention will be described with reference to FIG.

When no injection is performed, the voltage applied to the electrostrictive actuator 1 is low and the electrostrictive actuator 1 is at the reference length.
Further, the injection fuel pressure of the control pressure chamber 14 and the oil sump 25 is also at the specified pressure. In this state, the pressure of the sack portion 24 applied to the area inside the seat portion 21, the injected fuel pressure applied to ((cross-sectional area of the first guide shaft 30)-(cross-sectional area of the seat portion 21)), and the control pressure chamber 14 The needle 20 is seated on the seat portion 21 because the fuel pressure applied to the top surface of the needle 20 and the downward load applied by the needle spring 35 are superior to the upward load caused by the control fuel pressure applied to the pressure receiving surface 130. ing.

When the voltage applied to the electrostrictive actuator 1 is increased at a desired valve opening timing, the control pressure exceeds the needle opening pressure, and the needle 20 immediately increases. After the valve is opened, the voltage applied after the valve is opened is maintained until a desired time.
The lift amount of 0 is maintained. Next, when the voltage applied to the electrostrictive actuator 1 is reduced at a desired injection rate change timing, the electrostrictive actuator 1 contracts. At this time, the pressure in the control pressure chamber 14 is reduced, but the needle 20 which has been stationary until the load in the vertical direction becomes equal until then decreases the load on the needle spring 35 in response to the pressure decrease in the control pressure chamber 14. Then, when the vertical load becomes equal, it stops again.

At the desired valve closing timing, the applied voltage is reduced to the reference voltage, the pressure in the control pressure chamber 14 is reduced by contracting the electrostrictive actuator 1, and the downward load of the needle 20 overcomes the Lowers, and the injection ends when seated. FIG. 12 is an operation explanatory diagram illustrating a method of driving an electrostrictive actuator according to a first embodiment of the fourth aspect of the present invention.

The operation when the present invention is applied when operating the fuel injection valve according to the first embodiment of the first invention will be described with reference to FIG. At the time of no injection, the voltage applied to the electrostrictive actuator 1 is low and the electrostrictive actuator 1 is at the reference length.
Are at the specified pressure.

In this state, the pressure of the sack portion 24 applied to the inner area of the seat portion 21, the injected fuel pressure applied to ((cross-sectional area of the first guide shaft 30)-(cross-sectional area of the seat portion 21)), and control The needle pressure of the needle 20 and the downward load of the needle spring 35 are superior to the upward load caused by the control fuel pressure applied to the pressure receiving surface 130 of the pressure chamber 14. Sitting.

A desired injection start timing of several tens μs to several tens m
During the period from the time before s to the time immediately before the start of injection, the voltage applied to the electrostrictive actuator 1 is gradually increased, and the pressure in the control pressure chamber 14 is increased by extending the electrostrictive actuator 1. The amount of increase in the applied voltage at this time is smaller than the required pressure increase amount of the control pressure chamber 14 for opening the needle 20.
In addition, the needle 20 does not open due to a gradual voltage increase that does not cause valve opening due to pressure pulsation. This operation is called pre-valve pressure increase.

After the pressure increase before valve opening, the voltage is maintained until a desired valve opening timing. When the voltage is further increased at the desired valve opening timing, the needle 20 immediately rises because the control pressure chamber pressure exceeds the valve opening pressure of the needle 20. After the valve is opened, the applied voltage after the valve is opened is maintained until a desired valve closing timing, and the lift amount of the needle 20 is maintained.

At the desired valve closing timing, the applied voltage is reduced to the reference voltage, the pressure in the control pressure chamber 14 is reduced by contracting the electrostrictive actuator 1, and the needle 20 Lowers, and the injection ends when seated. As described above, by using the fuel injection valve and the driving method thereof described using the various embodiments of the above-described invention, it becomes possible to change the injection rate within the period of one injection. This makes it possible to inject fuel at an optimal injection rate according to engine conditions such as the engine speed and the load condition, thereby improving fuel consumption and purifying exhaust gas.

[Brief description of the drawings]

FIG. 1 is a system diagram of a first embodiment corresponding to claim 1 of the first invention described in claims 1 to 4;

FIG. 2 is an operation explanatory diagram illustrating an operation of the fuel injection valve shown in the first embodiment of the first invention.

FIG. 3 shows a first embodiment in which O-rings 201 and 202 for holding oil tightness are provided on a first guide shaft 30 and a second guide shaft 32, respectively, in the first embodiment of the first invention.
It is a system diagram of a second embodiment corresponding to claim 1.

FIG. 4 is a system diagram of a third embodiment corresponding to claim 1 of the first invention described in claims 1 to 4;

FIG. 5 is a system diagram of a fourth embodiment corresponding to claim 2 of the first invention described in claims 1 to 4;

FIG. 6 is a system diagram of a fifth embodiment corresponding to claim 3 of the first invention described in claims 1 to 4;

FIG. 7 is a system diagram showing a sixth embodiment corresponding to claim 4 of the first invention described in claims 1 to 4;

FIG. 8 is an operation explanatory diagram of a regulator used in the first embodiment in the second invention.

FIG. 9 is an operation explanatory diagram illustrating a driving method of an electrostrictive actuator as a first embodiment corresponding to claim 6 of the third invention described in claim 6 and claim 7;

FIG. 10 is an operation explanatory diagram illustrating a driving method of an electrostrictive actuator as a second embodiment corresponding to claim 7 of the third invention described in claim 6 and claim 7;

FIG. 11 is an operation explanatory diagram illustrating a method for driving an electrostrictive actuator as a third embodiment corresponding to claim 7 of the third invention described in claim 6 and claim 7;

FIG. 12 is an operation explanatory diagram illustrating a method for driving an electrostrictive actuator as a first embodiment of the fourth invention described in claim 8;

FIG. 13 is a cross-sectional view of a fuel injection valve disclosed in Japanese Patent Publication No. 4-54065, which is a known fuel injection valve using an electrostrictive actuator as an actuator.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electrostrictive actuator 2 injection valve casing 10 piston 14 control pressure chamber 20 needle 22 nozzle casing 25 oil sump 30 first guide shaft 31 first guide hole 32 second guide shaft 33 second guide hole 42 control fuel introduction path 43 orifice 44 Check valve 45 Injected fuel flow path 48 Fuel pressure transmission path 49 Fuel chamber 50 Third guide shaft 51 Third guide hole 52 Rod 90 Fourth guide hole 91 Fourth guide shaft 100 Needle spring storage chamber 110 Drain hole 111 Second Downward pressure receiving surface 130 First downward pressure receiving surface

Claims (8)

[Claims] In a fuel injection valve which opens and closes by receiving a pressure change corresponding to a volume change of a control pressure chamber accompanying expansion and contraction of an electrostrictive actuator, a minute clearance is maintained with respect to a first guide hole of a nozzle casing. The first guide shaft slidable in an oil-tight manner and the second guide hole of the injection valve casing or the piston having a through-hole in the center shaft can be slid in an oil-tight manner while maintaining a small clearance. A second guide shaft formed above one guide shaft and having a larger diameter than the first guide shaft; and a first downward pressure-receiving surface formed by a step between the first guide shaft and the second guide shaft. A needle communicating with or exposing to the control pressure chamber, and a non-return valve for suppressing fuel flow from the control pressure chamber to the injection fuel flow path in the middle of a control fuel introduction path connecting the control pressure chamber and the injection fuel flow path. A valve, An orifice for suppressing rapid fuel flow is provided in series, and the control pressure chamber is pressurized by the electrostrictive actuator to open the valve and inject fuel. 2. A fuel injection valve which opens and closes in response to a pressure change corresponding to a change in volume of a control pressure chamber accompanying expansion and contraction of an electrostrictive actuator while maintaining a minute clearance with respect to a first guide hole of a nozzle casing. A first guide shaft that slides oil-tightly and separates the oil reservoir from the control pressure chamber, and a second guide hole of a piston that slides with respect to the injection valve casing, while maintaining a small clearance for oil-tightness. A second guide shaft formed above the first guide shaft and having a diameter larger than that of the first guide shaft, the second guide shaft being separated from the control pressure chamber and the needle spring storage chamber; A third guide shaft which keeps a slight clearance above a second guide shaft with respect to a third guide hole of the injection valve casing and slides in an oil-tight manner; the first guide shaft and the second guide shaft Shaped by the step A needle for exposing a first downward pressure receiving surface formed to the control pressure chamber and a high-pressure injected fuel supplied to a fuel injection valve to a fuel chamber around a top surface of the third guide shaft of the needle. A non-return valve for suppressing fuel flow from the control pressure chamber to the injection fuel flow path in the middle of a control fuel introduction path connecting the control pressure chamber and the injection fuel flow path; A fuel injection valve which is provided in series with an orifice for suppressing a fuel flow, and which opens the valve by pressurizing the control pressure chamber by the electrostrictive actuator to inject fuel. 3. A fuel injection valve which opens and closes in response to a pressure change corresponding to a change in volume of a control pressure chamber accompanying expansion and contraction of an electrostrictive actuator while maintaining a minute clearance with respect to a first guide hole of a nozzle casing. A first guide shaft which slides in an oil-tight manner to isolate a drain hole from the control pressure chamber; and a second guide hole of a piston slides in an oil-tight manner while maintaining a small clearance between the control pressure chamber and the control pressure chamber. A second guide shaft formed above the first guide shaft and having a diameter larger than that of the first guide shaft;
A third guide shaft that slides up and down oil-tightly while maintaining a slight clearance with respect to the third guide hole of the injection valve casing above the second guide shaft, and a fourth guide hole of the nozzle casing. The fourth guide shaft has a small clearance and slides oil-tightly to isolate an oil reservoir from the drain hole, and has a fourth guide shaft smaller in diameter than the first guide shaft. A first downward pressure receiving surface formed by a step of the second guide shaft is exposed to the control pressure chamber, and a second downward pressure receiving surface formed by a step of the first guide shaft and the fourth guide shaft. A needle for exposing the fuel to a drain hole, a fuel pressure transmission passage for introducing injection fuel supplied to a fuel injection valve into a fuel chamber near a top surface of the third guide shaft, and a control pressure chamber and an injection fuel flow path. In the middle of the fuel introduction path, the control A check valve for suppressing fuel flow from the power chamber to the injection fuel flow path and an orifice for suppressing rapid fuel flow are provided in series, and the control pressure chamber is opened by pressurizing the electrostrictive actuator. A fuel injection valve for injecting fuel. 4. A fuel injection valve which opens and closes in response to a pressure change corresponding to a volume change of a control pressure chamber accompanying expansion and contraction of an electrostrictive actuator, while maintaining a minute clearance with respect to a first guide hole of a nozzle casing. A first guide shaft that slides oil-tightly to isolate the drain hole from the control pressure chamber; and a control pressure chamber and a needle spring storage chamber that slide while maintaining a small clearance with respect to the second guide hole of the piston. And a second guide shaft formed above the first guide shaft and having a diameter larger than that of the first guide shaft, and a fourth guide hole of the nozzle casing, which is kept oil-tight with a small clearance. To separate the oil reservoir from the drain hole,
And a fourth guide shaft having a diameter smaller than that of the first guide shaft is provided, and a first downward pressure receiving surface formed by a step between the first guide shaft and the second guide shaft is exposed to the control pressure chamber. A needle for exposing a second downward pressure receiving surface formed by a step between the first guide shaft and the fourth guide shaft to a drain hole, and a fuel injection valve in a fuel chamber above the third guide hole of the injection valve casing. A fuel pressure transmission path for introducing the injected fuel supplied to the fuel injection valve, and a small clearance with respect to the third guide hole of the injection valve casing. The rod is pushed down by receiving the pressure, and the lower end is in contact with the needle upper surface, and the control fuel chamber is connected to the injection fuel flow path. Restrict fuel flow to A check valve, provided a rapid flow of fuel and an orifice in series to suppress, the control pressure chamber is opened by pressurizing by the electrostrictive actuator fuel injection valve, characterized in that to inject fuel. 5. A regulator is provided between the injection fuel flow path and the check valve in the control fuel introduction path connecting the control pressure chamber and the injection fuel flow path, and the control pressure chamber is connected to the injection fuel pressure. The fuel injection valve according to any one of claims 1 to 4, wherein the pressure is lower than that of (1). 6. A method of driving a fuel injection valve for opening and closing a fuel injection valve by controlling a voltage applied to an electrostriction actuator, wherein the fuel valve is opened by an increase in pressure of a control pressure chamber due to extension of the electrostriction actuator. For an injection valve, a temporal change of a voltage applied to the electrostrictive actuator is arbitrarily changed within one injection period, and a displacement amount of the electrostrictive actuator is arbitrarily changed within one injection period. A method for driving a fuel injection valve using an electrostrictive actuator. 7. A method for driving a fuel injection valve for opening and closing a fuel injection valve by controlling a voltage applied to an electrostriction actuator, wherein the fuel valve is opened by an increase in pressure of a control pressure chamber due to extension of the electrostriction actuator. The electrostriction is characterized in that the voltage applied to the electrostrictive actuator is changed in several steps within one injection period for the injection valve, and the displacement of the electrostrictive actuator is changed stepwise within one injection period. A method for driving a fuel injection valve using an actuator. 8. A method of driving a fuel injection valve for opening and closing a fuel injection valve by controlling a voltage applied to an electrostriction actuator, wherein the fuel valve is opened by an increase in pressure of a control pressure chamber due to extension of the electrostriction actuator. During the non-injection period from the end of the previous injection to immediately before the injection start time desired this time, the amount of pressure increase in the control pressure chamber due to the extension of the electrostrictive actuator causes the pressure increase required to open the valve to the injection valve. By gradually increasing the voltage applied to the electrostrictive actuator so as to be slightly lower than the amount, the seating is maintained until the required valve opening timing, while the vertical load difference acting on the needle is small. A method for driving a fuel injection valve using an electrostrictive actuator, characterized by applying pressure to a state.