JP2003184691A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of a conventional fuel injection valve that a valve element collides with a stopper to generate bounce at the time of opening the valve and the valve element collides with a nozzle body to generate bounce at the time of closing the valve, resulting in deterioration of injection characteristics. <P>SOLUTION: When a valve is opened, pressure of a nozzle chamber 27 and a second chamber 22 is reduced by injection. However, because the pressure of a first chamber 20 communicated via a restrictor 21 remains high pressure, an armature 18 is energized upwards (in the direction of opening the valve), and bounce of the valve element 11 is restrained when the valve is opened. At that time, the fuel flows upwards through the restrictor 21 to force the armature 18 upwards, so as to restrain bounce of the valve element 11. At the time of closing the valve, when injection is stopped, the pressure of the nozzle chamber 27 and the second chamber 22 is increased by a water hammer action due to rapid cut-off of injection fuel, and the armature 18 is energized downwards (in the direction of closing the valve), so as to restrain the bounce of the valve element 11 when the valve is closed. At that time, the fuel flows downwards through the restrictor 21 to force the armature 18 downwards, so as to restrain the bounce of the valve element 11. <P>COPYRIGHT: (C)2003,JPO

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 to which a pressure-accumulated fuel is supplied, and is used for a fuel injection valve for injecting a low-viscosity fuel (for example, liquefied gas fuel such as LPG or DME). This is a suitable technique.

[0002]

2. Description of the Related Art For example, in a common rail type fuel injection device for a diesel engine, an electromagnetic type using an electromagnetic force is generally used as a fuel injection valve. In this case, the high-pressure fuel is introduced into the pressure control chamber provided on the back surface of the valve body, and the high-pressure fuel in the pressure control chamber is leaked to the low pressure side every injection, thereby realizing the valve opening operation of the valve body. Therefore, high-pressure fuel leaks at each injection.

On the other hand, in recent years, as an alternative fuel to light oil,
Considering the vaporization, ignition and combustion properties of fuel, emission, etc., it is considered to use liquefied gas fuel such as DME (dimethyl ether) or LPG (liquefied petroleum gas) with an additive for improving the cetane number. There is. In the following description, what is referred to as LPG refers to one to which a cetane number improver is added, unless otherwise specified.

When liquefied gas fuel is used, the amount of leakage of injected fuel tends to increase, and a device for recovering the leakage fuel from the fuel injection valve is required. As a specific example, a purge tank for recovering vaporized liquefied fuel, a compression pump for compressing and liquefying gas fuel (gas) in the purge tank, and the like are required. Therefore, the cost of the fuel injection device increases.

Therefore, in order to make the fuel leakless,
It is conceivable to employ a so-called direct drive type fuel injection valve in which the valve element is directly moved by an electromagnetic solenoid (actuator). The structure is shown in FIG.

A valve body 101 of the fuel injection valve 100 shown in FIG.
Has an elongated shape extending in the vertical direction in the figure, and an armature 102 is fixed to the upper end of the valve body 101 by laser welding or the like. Body 103 and nozzle body 104
Through holes 105 and 106 are provided in the
The valve body 101 is housed in 05 and 106. A stator 107 is provided to face the armature 102,
When the coil 108 is energized, the armature 102 moves to the stator 1.
When the valve body 101 is sucked by 07, the valve body 101 moves from the valve closed position shown to the valve open position against the biasing force of the spring 109. As a result, the injection hole 110 is opened and the high-pressure fuel supplied from the common rail or the like is injected. In the fuel injection valve 100 configured as shown in FIG. 5, since no fuel leak occurs, a leaked fuel recovery device (purge tank, compression pump, etc.) is not required, and cost increase can be suppressed.

[0007]

However, in the fuel injection valve 100, the coil 108 is energized, the armature 102 is attracted to the stator 107, and the valve element 101 is removed.
When the valve is opened, the valve body 101 collides with the stopper 111 and bounces. Due to the bounce when the valve is opened, as shown by the broken line in FIG. 3, the injection amount (Q) corrugates with respect to the drive signal width (τ), and there is a problem that the injection control is difficult. Further, when the coil 108 is de-energized and the suction force of the armature 102 by the stator 107 is lost and the valve body 101 is closed by the urging force of the spring 109, the valve body 101 becomes a seat portion of the nozzle body 104. It will hit and bounce. This bounce at the time of valve closing causes re-injection (secondary injection) after the end of injection, resulting in a problem that the injection characteristic deteriorates.

On the other hand, in many cases, due to the layout of the intake valve of the engine head, etc., the valve element 101 must be made long, and as a result, the valve element 101 becomes heavy and the above-mentioned bounce occurs remarkably. I will end up. Especially LPG and DME
Liquefied gas fuels such as,
As the bounce of No. 1 becomes large, the time until the bounce is attenuated becomes long, and the above-mentioned problem remarkably occurs.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a fuel injection valve that suppresses bounce of a valve body due to a differential pressure or a flow of fuel generated in the fuel injection valve. It is in.

[0010]

[Means for Solving the Problems] [Means for Claim 1] The invention employing the means for claim 1 has the following effects. (When the valve is open) When an electric actuator (for example, an electromagnetic solenoid, a piezo actuator, etc.) displaces the armature (driver) in the valve opening direction, the accumulated fuel is injected from the nozzle. Due to this injection, the pressure on the nozzle side is lower than that on the throttle portion, and the pressure in the second chamber becomes lower than that in the first chamber. Since the second chamber, which has a low pressure, is on the side opposite the nozzle (in the valve opening direction),
The pressure receiving portion is biased toward the side opposite to the nozzle (valve opening direction) by the pressure difference. The urging force of the pressure difference suppresses the bounce of the valve body when the valve is opened.

(When the valve is closed) When the electric actuator displaces the armature in the valve closing direction, fuel injection is stopped. When the injection is stopped, the flow of the injected fuel is suddenly cut off, so that the pressure on the nozzle side of the throttle portion rises above the pressure of the accumulated pressure fuel, and the pressure in the second chamber is higher than that in the first chamber. Get higher At this time, since the first chamber having a low pressure is on the nozzle side (valve closing direction), the pressure receiving portion is urged toward the nozzle side (valve closing direction) by the differential pressure. Bounce of the valve body when the valve is closed is suppressed by the biasing force of this differential pressure.

In this way, the bounce at the time of opening and closing the valve is suppressed, so that the injection characteristic is improved. Further, even when the valve body is long and heavy, the occurrence of bounce due to the differential pressure is suppressed, so that the injection characteristics can be improved. Further, even when the fuel has a low viscosity such as liquefied gas fuel such as LPG or DME, the occurrence of bounce due to the differential pressure is suppressed, so that the injection characteristic can be improved.

[Means for Claim 2] The invention employing the means for claim 2 has the following effects. (When the valve is opened) When the electric actuator displaces the armature in the valve opening direction, the accumulated fuel is injected from the nozzle.
By this injection, the fuel flows from the first chamber to the second chamber on the side opposite to the nozzle (in the valve opening direction) through the passage on the side surface of the armature. Due to the flow in the valve opening direction, the armature receives a force toward the side opposite to the nozzle (in the valve opening direction), so that the bounce of the valve body at the time of valve opening is suppressed.

(When the valve is closed) When the electric actuator displaces the armature in the valve closing direction, fuel injection is stopped. When the injection is stopped, the flow of the injected fuel is suddenly cut off, so that the pressure on the nozzle side of the throttle portion rises higher than the accumulated pressure fuel to be supplied, and the pressure of the second chamber becomes higher than that of the first chamber. . Then, the gas flows from the high pressure second chamber to the first chamber on the nozzle side (valve closing direction) through the passage on the side surface of the armature. Since the armature receives a force toward the nozzle side (valve closing direction) due to the flow in the valve closing direction, bounce of the valve body at the time of valve closing is suppressed.

Thus, as in the first aspect of the invention, the bounce at the time of opening and closing the valve is suppressed, so that the injection characteristic is improved. Even when the valve body is long and heavy, the differential pressure suppresses the occurrence of bounce,
It is possible to improve the injection characteristics. Further, even when the fuel has a low viscosity such as liquefied gas fuel such as LPG or DME, the occurrence of bounce due to the differential pressure is suppressed, so that the injection characteristic can be improved.

[Means of Claim 3] By adopting the means of Claim 3, a differential pressure is generated in the passage for guiding the fuel from the nozzle side of the armature (valve closing direction) to the side opposite the nozzle of the armature (valve opening direction). You may provide the diaphragm part for making it. By providing in this way, the function and effect of the invention of claim 1 can be obtained in the invention of claim 2.

[Means of Claim 4] By adopting the means of Claim 4, the throttle portion may be formed by the clearance between the armature and the stator around it.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to two examples and modifications. In the following embodiments, the present invention is applied to a fuel injection valve that injects fuel into a vehicle diesel engine that uses liquid gas such as DME or LPG as fuel. Here, the fuel injection valve is a direct-acting type in which a valve element is directly driven by an electromagnetic solenoid (an example of an electric actuator), high-pressure accumulated fuel accumulated in a common rail is supplied, and the valve opening operation is performed. Liquefied gas fuel is injected and supplied into the engine combustion chamber. In the following embodiments, the nozzle side (valve closing direction) will be described below and the non-nozzle side (valve opening direction) will be described above. Is.

[Structure of First Embodiment] FIG. 1 is a view showing a sectional structure of a fuel injection valve 1 and a structure around fuel injection. In FIG. 1, the liquefied gas fuel (DME or LPG) stored in the fuel tank 2 is supplied from a low-pressure pump (not shown) to the high-pressure pump 3, is compressed to high pressure by the high-pressure pump 3, and then is fed to the common rail 4. Supplied. In the common rail 4, the injection pressure equivalent (for example, 40M
High-pressure fuel of about Pa) is accumulated. The fuel injection valves 1 for the number of cylinders of the engine are connected to the common rail 4, and these fuel injection valves 1 perform injection operation according to a drive signal from an ECU (engine control unit) 5.

The structure of the fuel injection valve 1 will be described in detail below. The casing of the fuel injection valve 1 is a combination of a body 6 and a nozzle body 7, which are integrated by tightening a retaining nut 8.
The body 6 and the nozzle body 7 have coaxial through holes 9,
10 is provided, and a long valve body 11 is housed in the through holes 9 and 10.

The valve body 11 slides in the through holes 9 and 10 in the vertical direction, and has sliding portions 12 at two upper and lower positions.
Have 13. A plurality of injection holes 14 are provided at the tip of the nozzle body 7, and when the tip of the valve body 11 abuts (seats) the nozzle body 7, the injection hole 14 closes and the valve body 1
When the tip of the nozzle 1 is separated (separated) from the nozzle body 7, the injection hole 14 is opened. A compression coil spring 15 is arranged at the upper end of the valve body 11, and the valve body 11 is constantly urged downward by the restoring force of the spring 15.

Further, a fuel hole 16 is formed on the upper side of the valve body 11, and the fuel supplied from the inlet 17 passes through the body 6 → the first chamber 20 formed immediately below the armature 18 → It is guided into the fuel hole 16 at the center of the armature 18 through the narrowed portion 21 formed by the clearance between the armature 18 and the members around it → the second chamber 22 formed immediately above the armature 18. Diaphragm 21
Specifically, the side surface of the armature 18 and the stator 23
Is formed by the clearance with the inner core lower 34 that constitutes the lower part of the above, and this clearance is set within the range of 60 to 300 μm in the radial direction dimension.

A branch hole 26 is formed in the middle of the valve body 11 to guide the fuel introduced from the fuel hole 16 to a fuel passage 25 formed between the through hole 9 of the body 6 and the valve body 11. The fuel introduced to the fuel passage 25 is introduced to the injection hole 14 side via the nozzle chamber 27 formed between the through hole 10 of the nozzle body 7 and the valve body 11.

Next, the inlet 17 will be described. The inlet 17 sandwiches the gasket 30 so that the body 6
It is installed in the and is the entrance from the common rail 4. A bar filter 31 for preventing foreign matter from entering is press-fitted and fixed to the inlet 17.

Next, the electromagnetic solenoid 32 will be described. The armature 18 of the electromagnetic solenoid 32 is fixed to the upper part of the valve body 11 by press fitting or the like, and the stator 23 is arranged so as to face the armature 18 and constitutes a so-called plunger type solenoid.

The stator 23 includes an inner core upper 33 having a suction surface, an inner core lower 34 having a magnetic pole surface on the side surface of the armature 18, and an inner core upper 33.
And a ring-shaped inner core middle 35 sandwiched by the inner core lower 34. The inner core upper 33 and the inner core lower 34 serve as a magnetic path of the electromagnetic solenoid 32, and are therefore made of a soft magnetic material. The inner core / middle 35 is made of a non-magnetic material so that it does not allow magnetic flux to pass through. And, Inner Core Upper 33, Inner Core Lower 3
4. The inner core / middle 35 is integrally fixed in a stacked state by a joining means such as laser welding to form the stator 23.

A coil 36 for generating a magnetic force to attract the armature 18 to the stator 23 is arranged on the outer periphery of the stator 23, and is molded and fixed in a solenoid housing 37 together with a connection terminal 38 by a resin. A stopper 40 is provided between the stator 23 and the body 6.
Are arranged. The stopper 40 plays a role of determining a fully opened position of the valve body 11 and a role of a shim that adjusts a gap (that is, a final gap) between the armature 18 and the stator 23 when fully opened.

[Operation and Effect of First Embodiment] Next, the operation and effect of the fuel injection valve 1 in the present embodiment will be described with reference to FIG. 1 and FIGS. 2 and 3. Here, in FIG.
6 is a time chart showing the pressure behavior of the lower first chamber 20 and the upper second chamber 22. In FIG. 2, the lift and the injection rate in the present embodiment are shown by solid lines, and the lift and the injection rate in the conventional technique are shown by broken lines. Further, FIG. 3 is a τ-Q characteristic diagram showing the injection amount (Q) with respect to the drive signal width (τ).

(When the valve is open) When the drive signal provided from the ECU 5 is turned on and the coil 36 is energized (the energization of FIG. 2 is started), the armature 18 is attracted to the stator 23 and resists the biasing force of the spring 15. Valve body 11 is lifted upward. Then, when the valve element 11 comes into contact with the stopper 40, the valve opening operation ends, and the valve open state is maintained thereafter. As the valve body 11 rises, the tip of the valve body 11 is separated (seated) from the nozzle body 7, the injection hole 14 is opened, and the liquid fuel is injected from the injection hole 14.

Here, the conventional fuel injection valve 1 shown in FIG.
00, the valve body 101 and the stopper 111 when the valve is opened
Due to the collision with, the valve body 101 is bounced several times as shown by the broken line in FIG. As a result, some parts of the injection rate also decrease due to the effect of bounce. Then, as shown by the broken line in FIG. 3, the injection amount (Q) corrugates with respect to the drive signal width (τ), and stable injection control cannot be performed.

Compared with the above-mentioned prior art, the fuel injection valve 1 of the present embodiment has a nozzle chamber 27 and a second chamber 22 (armature 1 communicating with the nozzle chamber 27 as the injection starts.
The pressure on the upper surface of 8 decreases. At this time, the pressure in the first chamber 20 (the lower surface of the armature 18) hardly changes because the pressure propagation by the throttle portion 21 on the side surface of the armature 18 is suppressed. Therefore, a hydraulic pressure difference acts on the upper and lower sides of the armature 18, and the armature 18 (corresponding to the pressure receiving portion) is urged upward (in the valve opening direction) by the hydraulic pressure difference. Bounce of the valve element 11 at the time of opening the valve is suppressed by the biasing force of this differential pressure. During injection, the fuel is in the first chamber 20.
It flows from (the lower side of the armature 18) to the upper second chamber 22 (the upper side of the armature 18) through the passage (throttle portion 21) on the side surface of the armature 18. Since the armature 18 receives a force directed upward (in the valve opening direction) by the upward flow, this action also suppresses the bounce of the valve body 11 when the valve is opened.

As described above, due to the difference in hydraulic pressure between the first chamber 20 and the second chamber 22 and the flow of fuel from the first chamber 20 to the second chamber 22, as shown by the solid line in FIG. The bounce of the valve body 11 at the time is suppressed, and the reduction of the injection rate can be prevented. Further, as shown by the solid line in the τ-Q characteristic diagram of FIG.
The fuel injection amount (Q) monotonically increases with respect to the drive signal width (τ).

(When the valve is closed) When the drive signal given from the ECU 5 is turned off and the energization of the coil 36 is stopped (energization cutoff in FIG. 2), the attraction force of the armature 18 by the stator 23 disappears and the spring 15 is attached. Valve body 1 by power
1 is displaced downward. When the valve body 11 comes into contact with the seat of the nozzle body 7, the valve closing operation ends, and the valve closed state is maintained thereafter. The valve body 11 descends and the tip of the valve body 11 abuts (seats) the nozzle body 7, so that the injection hole 14 is closed and the liquid fuel injection is stopped.

Here, the conventional fuel injection valve 1 shown in FIG.
00, the valve body 101 and the nozzle body 1 at the time of opening the valve
Due to the collision with the valve body 04, as shown by the broken line in FIG.
One bounce occurs several times. As a result, 2 after closing the valve
The next injection will occur.

Compared with the above-mentioned prior art, in the fuel injection valve 1 of the present embodiment, when the injection is stopped, the flow of the injected fuel is suddenly cut off, so that the water hammer action causes the nozzle chamber 27 to move.
Then, the pressure of the second chamber 22 (the upper surface of the armature 18) communicating with the nozzle chamber 27 increases. At this time, the pressure in the first chamber 20 (the lower surface of the armature 18) is
Since the pressure propagation by the throttle portion 21 on the side surface of 8 is suppressed, there is almost no change. Therefore, a hydraulic pressure difference acts on the upper and lower sides of the armature 18, and the hydraulic pressure difference causes the armature 18 to move.
The (pressure receiving portion) is urged downward (in the valve closing direction). The bounce of the valve body 11 when the valve is closed is suppressed by the biasing force of this differential pressure. In addition, the injection hole 14 is blocked and the second chamber 2
When the pressure of 2 rises, the fuel flows from the second chamber 22 (the upper side of the armature 18) to the lower first chamber 20 (the lower side of the armature 18) through the passage (throttle portion 21) on the side surface of the armature 18. The downward flow causes the armature 18 to receive a downward force (valve closing direction), and this action also suppresses the bounce of the valve body 11 when the valve is closed.

As described above, due to the hydraulic pressure difference between the first chamber 20 and the second chamber 22 and the flow of fuel from the second chamber 22 toward the first chamber 20, as shown by the solid line in FIG. The bounce of the valve element 11 in the above is suppressed, and the occurrence of secondary injection is prevented.

On the other hand, since the fuel injection valve 1 shown above adopts the direct-acting structure in which the valve body 11 is directly driven by the electromagnetic solenoid 32, a structure with less fuel leakage can be realized, and the fuel injection valve 1 for liquefied gas fuel can be realized. It is suitable as the fuel injection valve 1.
Further, as in this embodiment, the valve body 11 is long and the valve body 1 is long.
Even when 1 is heavy, the occurrence of bounce of the valve body 11 is suppressed, so that the injection characteristics can be improved.
Further, when the fuel has a low viscosity such as liquefied gas fuel such as LPG or DME, the problem due to the bounce of the valve body 11 is remarkable, but the bounce can be suppressed even when the fuel viscosity is low.

[Second Embodiment] A second embodiment will be described with reference to the sectional structural view of the fuel injection valve 1 shown in FIG. In this second embodiment, different main parts from the first embodiment will be described, but the same reference numerals as in the first embodiment indicate the same functional objects.

In the first embodiment described above, the first chamber 20 and the second chamber 20
Chambers 22 are provided below and above the armature 18 for armature 1
8 is provided so as to receive the differential pressure. In contrast, this second
In the embodiment, a disc body 41 (corresponding to a pressure receiving portion) that receives a differential pressure is provided at the upper end of the valve body 11 extending above the armature 18, and the first chamber 20 and the circle are provided under the disc body 41. The second chamber 22 is provided on the plate 41. Then, the throttle portion 21 is provided between the disc body 41 and a member (body 6) around the disc body 41 by a clearance. By providing in this way, the same effect as that of the first embodiment can be obtained. The disc body 41 that receives the differential pressure is
It does not have to be above the armature 18. Further, the disc body 41 does not have to be disc-shaped.

[Modification] In the above embodiment, DME and L
Although the fuel injection valve 1 for injecting liquefied fuel such as PG is shown as an example, the present invention may be applied to the fuel injection valve 1 for injecting other fuel. That is, the present invention may be applied to the fuel injection valve 1 for injecting light oil or gasoline to prevent the bounce of the valve body 11. In the above embodiment, the electromagnetic solenoid 32 is used as an example of the electric actuator, but other electric actuators such as a piezo actuator in which a large number of piezo elements are stacked may be used. Further, a passage resistance means for increasing the passage resistance of fuel may be provided in the throttle portion 21 so that the force of the fuel flowing through the throttle portion 21 exerts a great effect on the valve body 11.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a fuel injection valve and a structure around fuel injection (first embodiment).

FIG. 2 is a time chart for explaining the operation of the embodiment (first embodiment).

FIG. 3 is a τ-Q characteristic diagram showing the injection amount with respect to the drive signal width (first embodiment).

FIG. 4 is a sectional structural view of a fuel injection valve (second embodiment).

FIG. 5 is a sectional structural view of a fuel injection valve (conventional example).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fuel injection valve 11 Valve body 16 Fuel hole (passage leading to the nozzle side through the center of the valve body) 18 Armature (pressure receiving portion of the first embodiment) 20 First chamber 21 Throttling portion (from nozzle side of armature to non-nozzle side) (Passage for guiding fuel) 22 Second chamber 23 Stator 32 Electromagnetic solenoid (electric actuator) 41 Disc body (pressure receiving portion of the second embodiment)

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02M 61/10 F02M 61/10 Q (72) Inventor Shigeki Enomoto 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Stock companies Japan Automobile Parts Research Institute (72) Inventor Tetsuo Morita 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Stock Company Japan Automobile Parts Research Institute (72) Inventor Masaaki Kato 1-1 Showa-cho, Kariya City, Aichi Stock Company In DENSO (72) Inventor Hisaharu Takeuchi 1-1, Showa-cho, Kariya city, Aichi Stock company F-term in DENSO (reference) 3G066 AB01 AC09 BA06 BA09 BA11 CC05U CC14 CC18 CC70 CE22 CE33 DA01

Claims (4)

[Claims] 1. A fuel injection valve in which a valve element is directly driven by an electric actuator, the fuel injection valve having a first chamber receiving a supply pressure of accumulated fuel and a nozzle opposite to the first chamber. A member that is formed and includes a second chamber that receives fuel pressure on the nozzle side, and a throttle portion that creates a differential pressure between the first chamber and the second chamber, and a member that opens and closes the nozzle and displaces it, A fuel injection valve comprising a pressure receiving portion that receives the differential pressure. 2. A fuel injection valve for directly driving a valve element by an electric actuator, wherein the fuel injection valve supplies the accumulated pressure fuel from a first chamber formed on a nozzle side of the armature to the armature. A fuel injection valve, characterized in that the fuel injection valve is provided with a passage that flows through a side surface into a second chamber formed on the side opposite to the nozzle of the armature and then leads to the nozzle side through the center of the valve body. 3. The fuel injection valve according to claim 2, wherein a differential pressure is provided between the nozzle side and the non-nozzle side of the armature in a passage for guiding fuel from the nozzle side of the armature to the non-nozzle side of the armature. A fuel injection valve, characterized in that a throttle portion for producing the fuel injection valve is provided. 4. The fuel injection valve according to claim 3, wherein the throttle portion is formed by a clearance between the armature and a stator around the armature.