JPS618462A - Electrostriction fuel injection valve - Google Patents

Abstract

PURPOSE:To reduce a passage between a valve body and a needle valve and promptly stop injection of fuel, by providing the valve body, driven by an electostrictive actuator, on the half way of a passge between a jet, opened and closed by the needle valve, and a supply source of fuel. CONSTITUTION:A needle valve 190 for opening and closing a jet 74 is slidably inserted into a needle body 70, and an oil reservoir 72 formed in a cylinder hole 71 of said body 70 communicates through fuel passages 76, 55, 44 with a fuel passage 53 opened and closed by a valve body 170. The fuel passage 53 is connected with a fuel pump 302 through fuel passage 13, 23 and a fuel inlet 22 or the like. An injection valve drives the valve body 170 to be opened and closed by an electrostrictive actuator 100 arranging in its both upper and bottom ends a thermal distortion connection piston 130 and a driving piston 140. And the injection valve, constituting the needle valve 190 by equipping the first sliding part 191 and the second sliding part 192 having a larger control than that of the first sliding part 191, protrudes the first sliding part 191 to the side of a recessed part 51 in a bottom part of the valve body 170.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a fuel injection valve installed in an internal combustion engine, particularly a diesel engine.

Prior art diesel engines require high fuel pressure. On the other hand, recently, electronic control of fuel injection valves has become widespread in order to increase the degree of freedom in controlling fuel injection.
Electrostrictive elements, which are structurally robust, are often used to handle high pressure fuels.

However, conventional fuel injection valves include a needle valve that opens and closes a nozzle for injecting fuel, a spring that biases the needle valve in a direction to close the nozzle, and a passage between the fuel supply source and the nozzle. a valve body provided in the middle to open and close this passage;
An electrostrictive actuator is provided to drive this valve body, and when the valve body opens, the needle valve receives fuel pressure and opens the nozzle against a spring, and when the valve body closes, the needle valve opens. A spring closes the nozzle.

Problems to be Solved by the Invention However, in conventional fuel injection valves, the valve body part and the injection nozzle part provided with the needle valve are separate bodies, and the passage connecting these parts is long. Therefore, the pressure in this passage does not drop immediately when the needle valve is closed. Therefore, it takes a certain amount of time until the needle valve is pressed by the spring to close the injection port, making it difficult to stop fuel injection quickly. The present invention aims to solve the above problems.

Means for Solving the Problems In order to solve the above problems, the fuel injection valve according to the present invention includes a needle valve that opens and closes a nozzle for injecting fuel;
A valve body is provided in the middle of the passage between the fuel supply source and the nozzle to open and close this passage, and an electrostrictive valve is connected to the valve body and expands and contracts according to the applied voltage to drive the valve body to open and close. the needle valve has a first pressure-receiving surface and a second pressure-receiving surface having a larger pressure-receiving area than the pressure-receiving surface, and the first pressure-receiving surface is within the passage and the valve body The second pressure-receiving surface faces further upstream, and the second pressure-receiving surface faces within the passage and downstream from the valve body.

Example The present invention will be explained below with reference to illustrated embodiments.

In FIG. 1, reference numeral 1 indicates an electrostrictive fuel injection valve according to an embodiment of the present invention, in which an upper casing 20 is screwed into the upper part of the center casing 10, and a lower casing 30 is screwed into the lower part. be done.

A cylinder 40 and a distance piece 50 are disposed below the center casing 10, and the cylinder 40 and distance piece 50 are held between the center casing 10 and the lower casing 30. Therefore, the contact surfaces of the end surface of the center casing 10, the cylinder 40, the distance piece 50, and the lower shoulder of the lower casing 30 are in close contact with each other. Lower casing 3
A needle body 70 is fixed to the lower end of the needle body 70 via a beam tensioning hole 60.

An electrostrictive actuator 100 is housed in a space formed by the center casing 10, the upper casing 20, and the cylinder 40. Electrostrictive actuator 100
Electrical insulating plates 110 and 120 are disposed at the upper and lower ends of the piston, respectively, and a thermal distortion correction piston 130 and a driving piston 140 are further disposed above and below these plates.

The electrostrictive actuator 100 is made by laminating a large number of electrostrictive elements. The electrostrictive element is a ceramic whose main component is lead zirconate titanate, and has electrodes on both sides of a thin disc.If a voltage of 500 V is applied between the two sides, the element will elongate by 1μ in the thickness direction. arise. This electrostrictive element is 10
An electrostrictive actuator 100 is formed by laminating 0 layers into a columnar shape, and this actuator 100 is provided with electrical wiring 150 for applying and releasing a voltage in the thickness direction of each element.

Electrical insulating plates 110 at the upper and lower ends of the electrostrictive actuator 100
, 120 are molded from hard resin, and the recesses 111,
The electrostrictive actuator 100 is fitted into the hole 121. The drive piston 140 has a recess 141 that fits into the outer periphery of the electrically insulating plate 120 and a center casing 10.
A cylindrical portion 142 having a smaller diameter than the inner diameter of the cylinder 4 to be described later.
It is composed of a sliding part 143 that slides into the center hole 45 of 0. The sliding portion 143 has a diameter smaller than that of the cylindrical portion 142, and its tip has a spherical shape and comes into contact with a valve body 170, which will be described later. On the other hand, the thermal distortion correction piston 130
10, a cylindrical portion 132 having a smaller diameter than the inner diameter of the center casing 10, and a sliding portion 133.

The sliding portion 133 has a smaller diameter than the cylindrical portion 132 and has a flat end surface. Further, the diameter of this sliding portion 133 is the same as the diameter of the sliding portion 133 on which the driving piston 140 slides. It is molded to be slightly larger than the diameter of the portion 143.

The sliding part 133 of the piston 130 is connected to the upper casing 2
It is slidably fitted into the sleeve 21 that is press-fitted into the hole 0. A fuel port 22, fuel passages 23, 24, and an annular groove 25 are formed in the upper casing 20, and a check valve seat 26 is formed in the middle of the fuel passage 23. The fuel port 22 and the annular groove 25 communicate with each other via a fuel passage 23.

In the central recess of the upper casing 20, a check valve usage method 1 is provided.
60 and a stopper 27 for this ball 160 are inserted. During assembly, the distance between the upper end surface of the thermal distortion correction piston 130 and the lower end surface of the stopper 27 is determined by the thermal expansion of each piston 130° 140 at the upper and lower ends of the upper casing 20, center casing 10, and electrostrictive actuator 100. Considering this, it is set to around 0.5n. Thus, a thermal strain correction pressure chamber 200 is formed between the upper end surface of the thermal strain correction piston 130 and the lower end surface of the stopper 28.

The center housing 10 is a hollow cylinder, and screws 11 for attaching the upper casing 20 and screws 12 for attaching the lower casing 30 are formed on the upper and lower outer peripheries of the thick interior. Furthermore, the center housing 10 has a fuel passage 13 penetrating through it in the axial direction, a drain fuel passage 14 extending perpendicularly to the axial direction, and a drain fuel passage communicating with the drain fuel passage 14 and reaching the lower end surface of the casing 10. 15 are formed, respectively. The fuel passage 13 communicates with an annular groove 25 of the upper casing 20, and the drain fuel passage 15 communicates with a drain fuel passage 41 of a cylinder 40, which will be described later.

A take-out hole 16 for electrical wiring 150 is bored in a side wall at the center of the center housing 10 .

The cylinder 40 has an annular shape, and includes a fuel passage 42 in the thick wall portion that communicates with the fuel passage 13 of the center casing 10;
A drain fuel passage 41 communicating with the drain fuel passage 15 of the center casing 10 is formed to penetrate therethrough. An annular groove 43 having a groove width of approximately Q,3*m is formed in the lower end surface of the cylinder 40, and this annular groove 43 communicates with a fuel passage 44 that opens at the lower end surface of the outer periphery.

The distance piece 50 is formed into a dish shape, and accommodates the valve body 170 and the leaf spring 180 in the recess 51 .

A cylinder hole 52 that slidably supports a needle valve 190, which will be described later, is formed in the center of the distance piece 50. The thick part of the distance piece 50 has a fuel passage 53 that communicates with the fuel passage 42 of the cylinder 40 and communicates with the upper and lower four parts 51 of the valve body 170, and a cylinder hole that communicates with the drain fuel passage 41 of the cylinder 40. A drain fuel passage 54 that opens at the lower part of the distance piece 52 and a fuel passage 55 that communicates with the fuel passage 44 of the cylinder 40 and opens at the lower end surface of the distance piece 50 are bored.

Valve body 1 accommodated in recess 51 of distance piece 50
70 has a substantially disk shape, and a ring-shaped protrusion 171 on the upper end surface closes the annular groove 43 when seated on the lower end surface of the cylinder 40 . The width of the seal portion of the ring-shaped protrusion 171 is approximately twice the width of the annular groove 43 of the cylinder 40. The distance piece 50 is biased by a disc spring 180,
It comes into close contact with the lower end surface of the cylinder 40 when not in operation. Thus, the lower end surface of the distance piece 50 is a support surface for the disc spring 180.

The outer diameter of the valve body 170 is the same as that of the recess 5 of the distance piece 50.
It is determined to provide a gap that allows movement using the circumferential surface of No. 1 as a guide. Further, the valve body 170 has a balance port 172 formed at a position slightly shifted from the center.
Hydraulic pressure is applied above and below.

The needle body 70 has a cylinder hole 71 that slidably supports the needle valve 190 in the center, and an oil reservoir 72.
A seat portion 73 and a nozzle hole are formed below. Further, a ring-shaped fuel passage 75 is formed on the upper end surface of the needle body 70, and this is similar to the fuel passage 5 of the distance piece 50.
Connects with 5.

The ring-shaped fuel passage 75 and the oil reservoir 72 communicate with each other via a fuel passage 76. The upper end surface of the needle body 70 is brought into close contact with the lower end surface of the distance piece 50 by the tening pin 60.

The needle valve 190 includes a first sliding part 191 slidably supported by the cylinder hole 52 of the distance piece 50, a second sliding part 192 slidably supported by the cylinder hole 71 of the needle body 70, It has a distal end seat portion 193 that is seated on the seat portion 73 of the needle body 70. 1st
If the cross-sectional area of the sliding part 191 is 81, the cross-sectional area of the second sliding part 192 is 82, and the cross-sectional area of the seat part 193 on the inner side of the seat diameter is 83, then (S+)<(S2-33)
There is a relationship.

Further, the diameter of the first sliding part 191 is smaller than the diameter of the second sliding part 192, but the stepped part 194 is formed in the distance bead and the seat 50 when the needle valve 190 is seated on the seat part 73 of the needle body 70. It is located approximately 0.5 fl below the lower end surface.

The space 195 formed at this time is the distance piece 50.
It communicates with the drain fuel passage 55 of. Note that 301 is a fuel tank, 302 is a high-pressure fuel pump, and 30
3 is an accumulator, and 304 is a regulator for maintaining constant pressure. These are low pressure pipes 305.30
6.Communicate with each other through high pressure pipes 307, 308, and 309. Further, the drain fuel passage 14 of the center casing 10 is connected to the fuel tank 301 via a low pressure pipe 310.
communicate with. 311 is a drive circuit for driving the electrostrictive actuator 100.

The operation of the apparatus of this embodiment having the above configuration will be explained with reference to FIGS. 1 to 3.
Fuel sucked from 01 flows in the following order: fuel tank 301 - low pressure pipe 305 - fuel pump 302 - high pressure pump 307 → accumulation lake 303 → high pressure pipe 308 → regulator 304, and high pressure pipe 309 = fuel population 22 of atsupaka casing 20 . As a result, the pressure in the fuel line downstream from the fuel pump 302 and up to the regulator 304 is maintained at the high pressure of 200 atmospheres set by the regulator 304. fuel bosib 302
The fuel supplied in excess is returned to the fuel tank 301 from the low pressure pipe 306.

The fuel supplied to the fuel port 22 of the upper casing 20 is transferred from the fuel passage 23 to the annular groove 25 → the fuel passage 13 of the center casing 10 → the fuel passage 42 of the cylinder 40 → the fuel passage 53 of the distance piece 50 to the distance piece 50. It flows into the recesses 51 in order, and they all have 200
maintained at atmospheric pressure.

On the other hand, this fuel
2 → fuel passage 24 → thermal distortion correction pressure chamber 170 in this order, and 200 atmospheres also acts on the thermal distortion correction piston 130.

In this state, the 200 atmospheres in the recess 51 of the distance piece 50 acts to push up the drive piston 140 when the valve body 170 is seated on the lower surface of the cylinder 40, and Acts on the surface. Therefore, the valve body 170 is connected to the leaf spring 180.
In addition to the urging force of
Pressed against the bottom surface of 0. Note that the pressure of 200 atmospheres within the recess 51 also acts on the end surface of the first sliding portion 191 of the needle valve 190.

The driving piston 140 is pushed upward by a force equivalent to 200 atmospheres that acts on the cross-sectional area of the sliding part 143, but the thermal distortion correction piston 130 above the electrostrictive actuator 100 also pushes against the cross-sectional area of the sliding part 133. It receives a force equivalent to 200 atmospheres, which pushes the actuator 100 downward. As described above, the diameter of the sliding portion 133 of the thermal distortion correction piston 130 is the same as that of the sliding portion 143 of the drive piston 140.
Since the diameter of the electrostrictive actuator 100 and the drive piston 140 are larger than the diameter of these sliding parts 133, 143,
The valve body 170 is biased downward in response to the difference in the pressure receiving area of the valve body 170 and attempts to open the valve body 170.

However, since the disc spring 180 supports the valve body 170 from below, the valve body 170 maintains the closed state. Thus, a force equivalent to 200 atmospheres applied to the cross-sectional area of the sliding portion 133 of the thermal distortion correction piston 130 is applied to the electrostrictive actuator 100 as a preset load, while the valve body 170 maintains its seated state. Furthermore, since 200 atm is also acting on the uppermost end surface of the needle valve 190, this needle valve 1
90 also continues to be seated on the seat portion 73.

In this state, a voltage of 500 V is applied to the electrostrictive actuator 100 via the drive circuit 311. Then, the electrostrictive actuator 100 first expands in the axial direction.

As a result, the check valve usage method 16 in the pressure chamber 200 for thermal strain correction
0, this pressure chamber 20 was initially in a free state.
Due to the pressure increase of 0, the upper casing seats on the seat portion 26 of 2 degrees, and the fuel port 24 is closed. Then, since the electrostrictive actuator 100 cannot extend upward, it begins to extend downward, and pushes down the valve body 170 via the drive piston 140 against the disk spring 180 and the hydraulic pressure. As a result, the valve body 170 opens the annular groove 43 having a width of 0.3 fins, and the 200-atmosphere fuel that had been supplied into the recess 51 or the fuel passage 53 flows into the annular groove 43 and the fuel passages 44-55- 75-'76-Oil sump 72 flows in this order.

On the other hand, the surface of the needle valve 190 that receives the fuel pressure is the end surface (cross-sectional area S1) of the first sliding portion 191 that is about to be pushed down once.
and the cross section (cross-sectional area S2) of the second sliding part 192 and the seat part 193 (cross-sectional area S3) which are trying to be pushed up, and the relationship between these areas is (Si) < (S2-33). Therefore, the needle valve 190 is lifted by 200 atm acting on the surface (S2-33). Once lifted, the needle valve 190 remains open and fuel injection continues while 200 atm is being supplied.

Next, when the voltage applied to the electrostrictive actuator 100 is returned to OV, the electrostrictive actuator 100 contracts in the axial direction. Then, the drive piston 140 moves upward, and the valve body 170 is pushed upward by the force of the disc spring 180 and seats on the lower surface of the cylinder 40. As a result, the annular ring 'a43 is closed, and the replenishment of fuel at 200 atmospheres to the oil reservoir 72 is cut off. As a result, the pressure in the oil reservoir 72 continues to decrease due to fuel injection, and the uppermost end surface of the needle valve 190
Since atmospheric pressure is acting on the needle valve 190, the needle valve 190 descends and seats on the seat portion 73, and fuel injection is stopped.

Now, let us consider the receiving and receiving relationship of the needle valve 190 at this time. The diameter of the first sliding part 191 of the needle valve 190 is 4
The diameter of the second sliding part 192 is 5fi, and the diameter of the seat part 193 of the needle valve 190 is 2mm. The force applied to the cross-sectional area S1 of the first sliding portion 191 is
At 00 atmospheres, the force is 25.13 kg, which is the force that pushes the needle valve 190 downward. On the other hand, the needle valve 190
The force pushing upward is the pressure applied to the area that remains after subtracting the cross-sectional area S3 of the seat portion 193 from the cross-sectional area S2 of the second sliding portion 192, so the valve opening pressure Po of the Ni Nidol valve 190 is (S2 S3) X Po = 25.13 kg.

That is, Po = 152.7 atmospheres. Therefore, 1. When the valve body 170 opens and a high pressure of 152.7 atmospheres or more acts upward on the needle valve 190, the needle valve 190
opens the valve.

On the other hand, looking at the valve closing pressure Pc, the valve closing pressure Pc is S
It is determined from 2 X Pc -25,13kg. That is, Pc = 128.2 atmospheres. Therefore, the valve body 170 closes, the high pressure supplied to the oil reservoir 72 is cut off, and when the pressure downstream of the valve body 170 falls below 128.2 atmospheres, the needle valve 190 closes.

For example, if the area of S2 and S3 is maintained at the same value and the area of Sl is changed, if Sl is equivalent to a diameter of 3 dragons, the valve opening pressure will be 85.9 atm and the valve closing pressure will be 72.1 atm. Become. If Sl is equivalent to a diameter of 4.5 cranes, the valve opening pressure will be 193.
The pressure is 2 atm, and the valve closing pressure is 162.3 atm.

Note that the thermal distortion correction piston 130 corrects thermal distortion as follows. Since the electrostrictive actuator 100 is made of ceramic and the casing 10 etc. are made of metal, the amount of thermal strain is larger in the casing 10 etc. Therefore, when the casing 10 or the like expands or contracts due to external heat, the gap between the pressure chambers 200 changes. This change is very gradual, and therefore takes place with the check valve 16-0 free. As a result, the volume of the pressure chamber 200 changes, but it is filled with incompressible fuel and the electrostrictive actuator 100
Since the expansion of the thermal distortion correction piston 130 is very steep, the check valve 160 is closed regardless of a slight change in volume.
is inhibited from moving upward. Thus, thermal distortion is corrected.

The operation pattern of the valve body 170 and the needle valve 190 will be explained with reference to FIG.

(A) is the driving voltage, (B) is the lift of the valve body 170, (C
) indicates the injection rate. When a voltage is applied to the electrostrictive actuator 100 (ON state), the valve body 170 starts to lift after T1 and reaches the maximum lift at T21&.

Fuel injection starts after T3 and reaches the maximum injection rate after T4. Thereafter, when the applied voltage is turned off after T5, the electrostrictive actuator 100 contracts, and the valve body 170 starts to be seated at T6 after the voltage is turned off, and is seated after T7. The injection rate begins to drop after T8 and fuel injection stops after T9. In this way, the injection amount can be controlled by keeping the lift amount of the valve body 170 constant and changing the ON time.

Control of the injection rate will be explained with reference to FIG.

(D) is the driving voltage, in this example V i p V
It is designed to change in two stages. (E) is the lift of the valve body 170, and (F) is the injection rate.

When a voltage of ■1 is applied to the electrostrictive actuator 100 (ON), the valve body 170 begins to lift after TIo, and To
Later, a low lift condition is reached. Injection starts after Ttz,
A low injection rate state is reached after T+a. When a high voltage (2) is applied after T+, the valve body 170 begins to lift further after Tit from the application of this voltage, and reaches the maximum lift after TI6. Then, the injection rate starts to further increase after T+7 and reaches the maximum injection rate after Trg. T+q followed by O
When set to FF, the valve body 170 starts to descend after Tλ0, and after T2r, the valve body 170 is seated. The injection rate begins to decrease after T23, and injection stops after T23. In this way, the injection rate can be controlled by voltage.

The device of this embodiment operates as described above, and its effects are as follows. That is, (1) Since the valve body 170 is directly driven by the electrostrictive actuator 100, the response is fast.

(2) Since the valve body 170 is directly driven, the opening area of the valve body 170 can be changed by voltage, and the injection rate can be easily controlled.

(3) Since the valve body 170 receives the same pressure except for the seal portion, the load on the electrostrictive actuator 100 can be light.

(4) Since the fuel supply pressure is also applied to the upper part of the needle valve 190, there is no need for a spring used conventionally for returning the needle valve.

(5) Furthermore, by applying the supply pressure to the upper part of the needle valve 190, the valve opening pressure and the valve closing pressure can be easily changed by simply changing the pressure receiving area above and below the needle valve 190.

(6) By changing the fuel supply pressure while keeping the upper and lower area ratio of the needle valve 190 constant, the opening pressure and closing pressure of the needle valve 190 can be changed, and the injection rate can be changed. .

(7) The degree of freedom in the lift amount of the needle valve 190 is high.

(8) Since the diameter of the drive piston 140 can be reduced, the force applied to the electrostrictive actuator 100 can be reduced, and it is easy to increase the pressure of the supplied fuel.

(9) Since the thermal strain correction pressure chamber 200 and the piston 130 are provided, even if the entire device is distorted due to thermal expansion, the valve body 170 can be reliably closed when not in operation, and the valve body 170 can be lifted when the valve is opened. The amount can be kept constant.

In the above embodiment, the needle valve 190 has the first sliding portion 191 and the second sliding portion 192 integrally molded, but these may be molded separately. Furthermore, although the pump 302 is one that generates a pressure higher than the set pressure of the regulator 304, this regulator may not be used and a constant pressure supply fuel pump that supplies only a constant pressure may be used.

Effects of the Invention As described above, according to the present invention, since the passage between the valve body and the needle valve can be shortened, the response time when the needle valve is closed can be shortened as much as possible, and fuel injection can be stopped. can be speeded up. Further, since the spring for returning the needle valve is omitted and high fuel pressure is always applied to the end face of the needle valve, the needle valve can be closed more quickly.

Furthermore, since the two pressure-receiving surfaces of the needle valve face the upstream and downstream sides of the valve body, the opening and closing pressures of the needle valve can be adjusted by changing these pressure-receiving surfaces or the fuel supply pressure. Can be easily changed. Furthermore, since the valve body is directly driven by the electrostrictive actuator, the response is fast.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a graph showing the relationship between valve lift and injection rate, and Fig. 3 is a graph showing the relationship between valve lift and injection rate when the drive voltage is changed. It is a graph showing the relationship between rates. 74... Nozzle port, 100... Electrostrictive actuator, 170... Valve body, 190... Needle valve.

Claims (1)

[Claims] 1. A needle valve that opens and closes a nozzle for injecting fuel, a valve body that is provided in the middle of a passage between a fuel supply source and the nozzle and opens and closes this passage, and this valve body is connected,
The needle valve includes an electrostrictive actuator that expands and contracts in response to an applied voltage to open and close the valve body, and the needle valve has a first pressure receiving surface and a second pressure receiving surface having a larger pressure receiving area than the pressure receiving surface. , the first pressure-receiving surface is within the passageway and faces upstream from the valve body, and the second pressure-receiving surface is within the passageway and faces downstream from the valve body. fuel injection valve.