JP2007024033A - Fuel injection device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an highly reliable fuel injection device of an internal combustion engine in which the distribution of a fuel in a combustion chamber can be changed without using a movable member. <P>SOLUTION: A nozzle injection valve 20 comprises a nozzle plate 30 having a plurality of jetting holes 32. The jetting holes are classified into groups A, B, C, and heaters Ha, Hb, Hc heated by energization are installed in the jetting holes for each group. No heater is energized, the distribution of the jetted fuel is concentrated to the cavity 4a of a piston. When the heater Ha is heated by energization within a temperature range in which the fuel is not boiled in the jetting hole, the fuel is passed through the jetting holes in group A, and the flow of the fuel toward an area near a spark plug 6 is increased over a flow from the jetting holes in the other groups. When the heaters Hb, Hc are heated by energization to more than a temperature at which the fuel is boiled in the jetting holes, a pressure loss in the jetting holes is increased to reduce the amount of the fuel passed through the jetting holes in groups B, C. Consequently, since the fuel distribution is changed, the fuel near the spark plug can be enriched so that the fuel is adaptive to stratified combustion when the engine is cooled. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection device for an internal combustion engine that directly injects fuel into a combustion chamber using a fuel injection valve.

In a direct-injection spark-ignition internal combustion engine that directly injects fuel into a combustion chamber, two combustion modes, homogeneous combustion and stratified combustion, are used properly according to the operating state.
The homogeneous combustion mode is a mode in which the fuel is burned in a state where it is distributed as evenly as possible throughout the combustion chamber, and is a mode when the internal combustion engine is required to output, and consumes a relatively large amount of fuel.
On the other hand, the stratified combustion mode is a mode in which the combustion state varies depending on the combustion chamber part by forming a fuel rich region and a thin region in the combustion chamber. Less fuel is consumed than the mode.

However, the mode of the internal combustion engine is not determined only by the required output, and the amount of fuel consumed, that is, the amount of fuel injected from the fuel injection valve is also different. For example, if the temperature of the members constituting the combustion chamber is low, the fuel adheres to the wall and does not vaporize. Since the fuel that does not evaporate does not contribute to the operation of the internal combustion engine, it is necessary to inject extra fuel adhering to the wall.
The fuel that has not vaporized and contributed to the combustion deteriorates the fuel consumption, and the portion that is burned only incompletely causes the exhaust gas to deteriorate as an unburned gas.
As described above, the optimal fuel injection amount or the optimal distribution of injected fuel differs depending on the operating state of the internal combustion engine.

As a device for changing the distribution of the fuel injected from the fuel injection valve in accordance with the operating state of the internal combustion engine, there is a device disclosed in Japanese Patent Laid-Open No. 7-151039.
In this case, a control plate that forms a curved surface is arranged along the vicinity of the passage of fuel injected from the fuel injection valve, and the control plate can approach and retract toward the passage. When the control plate is brought closer to the passage path, the injection direction bends closer to the control plate due to the Coanda effect, so the fuel injection direction is changed using this, and when necessary, the fuel is focused close to the spark part of the spark plug. Concentrate.
JP-A-7-1551039

However, in the conventional example disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 7-151039, the control plate is a movable plate that approaches and retracts toward the passage path, so it is arranged outside the opening (outer diameter side) of the fuel injection valve. There is a problem in the feasibility in terms of size that must be done, and there is a concern about reliability.
Therefore, an object of the present invention is to provide a highly reliable fuel injection device for an internal combustion engine that can change the fuel distribution in the combustion chamber without using a movable member.

  For this reason, the fuel injection device of the present invention is provided with a nozzle plate having injection holes divided into a plurality of groups at the injection port of the fuel injection valve that injects fuel into the combustion chamber, and at least one group is provided with a heater. Thus, by operating the heater, the temperature of the fuel passing through the injection holes can be increased for each group.

  According to the present invention, when the heater attached to each group is operated, the fuel passing through the injection hole is heated and the temperature rises, so that the viscosity of the fuel decreases, and as the viscosity decreases, the group The fuel flow rate in the injection hole increases. Further, when the heater is further heated and the fuel begins to boil in the injection hole, the pressure loss in the injection hole increases rapidly, and the fuel flow rate in the injection hole of the group decreases. Accordingly, it is possible to increase or decrease the fuel flow rate in a direction toward a specific region of the combustion chamber without using a movable member, which is suitable for stratified combustion, for example.

Next, embodiments of the present invention will be described by way of examples.
First, the first embodiment will be described.
FIG. 1 is a diagram showing a configuration around a combustion chamber of an internal combustion engine to which this embodiment is applied, and a control system for a spark plug and a fuel injection valve.
A cylinder head 3 is fixed to the upper end of the cylinder block 1, and a combustion chamber R is formed between the piston 4 and the cylinder head 3 that move up and down in the cylinder 2.
A spark plug 6 with a spark portion 6 a facing the combustion chamber R is attached to the center top of the cylinder head 3. An intake valve 8 that opens and closes the opening of the intake passage 7 and an exhaust valve 10 that opens and closes the opening of the exhaust passage 9 are provided on both sides of the ignition plug 6 of the cylinder head 3.
The cylinder head 3 is also provided with a fuel injection valve 20 adjacent to the opening of the intake passage 7 and in the vicinity of the coupling portion with the cylinder block 1. The fuel injection valve 20 is supplied with fuel pressurized by a fuel pump (not shown).

A cavity 4a that is biased toward the fuel injection valve 20 is formed on the upper end surface of the piston 4, and the axis L of the fuel injection valve 20 is directed to the cavity 4a when the piston 4 is just before top dead center. .
The control unit 100 that controls the spark plug 6 and the fuel injection valve 20 includes an air flow meter 101 provided in the intake passage 7, a throttle opening sensor 102 attached to a throttle valve (not shown) of the intake passage 7, and a crank angle sensor. 103 and each detection signal from the cooling water temperature sensor 104 are input.
The control unit 100 determines the operating state of the internal combustion engine based on detection signals from the sensors, controls the ignition timing of the spark plug 6 and the injection amount of the fuel injection valve 20 according to the operating state, and also controls the fuel injection valve. The injection quantity from 20 and the distribution of the injected fuel are controlled to obtain the homogeneous combustion mode or the stratified combustion mode.

Next, FIG. 2 shows the detailed structure of the front end of the fuel injection valve 20 on the combustion chamber R side.
The fuel injection valve 20 includes a hydraulic chamber F that temporarily stores fuel inside the housing 21. A flow rate adjusting hole 22 is formed in the bottom wall (lower side in FIG. 2) of the casing 21 as a jet port communicating with the hydraulic chamber F. The fuel injection valve 20 is attached with its flow rate adjusting hole 22 facing the combustion chamber R.
The hydraulic chamber F is provided with a needle valve 25 that can be moved in the axial direction (vertical direction in FIG. 1) by a solenoid (not shown), and a conical valve seat 23 is formed surrounding the flow rate adjusting hole 22. The needle valve 25 has a conical surface 26 that aligns with the valve seat 23 at its tip, and can be seated on the valve seat. The solenoid is turned on and off to move up and down to open and close the flow rate adjusting hole 22.

A nozzle plate 30 is provided in the flow rate adjusting hole 22 portion.
Specifically, a plate holding member 27 is attached to the tip of the housing 21 so as to cover the flow rate adjusting hole 22, and the plate holding member 27 faces the opening of the flow rate adjusting hole 22 so that the nozzle plate 30 is moved. keeping.
When the flow rate adjusting hole 22 is opened, pressurized fuel is jetted into the combustion chamber R through a nozzle plate 30 described later.
The plate holding member 27 holds the nozzle plate 30 via an insulator 28 having a low thermal conductivity such as ceramics or quartz.
From the nozzle plate 30, lead electrodes 50 and 51 extend to the outside through the inside of the insulator 28 and the plate holding member 27.

FIG. 3 shows details of the nozzle plate 30, (a) is an enlarged top view as seen from the flow rate adjusting hole 22 side of the housing 21, and (b) is a sectional view taken along the line XX in (a).
The nozzle plate 30 is configured with a silicon substrate 31 as a base.
In FIG. 3A, a nozzle plate cut out in a quadrilateral shape is shown as the silicon substrate 31, but other polygonal or circular shapes may be used.
A plurality of injection holes 32 arranged in a circular shape as a whole are formed in the silicon substrate 31. In particular, as shown in FIG. 3B, the inner wall surface over the entire length of the injection hole 32 is formed of a metal layer 33, and the metal layer 33 extends to around the opening on the front and back surfaces of the injection hole 32.
The metal layer 33 is made of nickel or gold that does not corrode by high-temperature fuel.

It is preferable that the injection hole 32 has a diameter of about 10 μm or less and a large number of aspect ratios, that is, a larger ratio of length to diameter, are formed to increase the contact area with the passing fuel.
These injection holes 32 are grouped into three groups adjacent to each other. Group B includes a large number of injection holes 32 along the diameter line of the circle, and groups A and C include a relatively small number of injection holes 32 on both sides of the group B.
In FIG. 3, the number of injection holes 32 is small in order to simplify the display.

As shown in FIG. 3A, the metal layer 33 around the opening of the injection hole 32 is connected to each group, and on the surface of the silicon substrate 31, from the metal layer region of each group toward one side 31a of the silicon substrate 31. The electrode portions 34a, 34b, and 34c extend in parallel with each other. The metal layer 33 around the opening of the injection hole 32 is also connected to each group on the back surface of the silicon substrate 31, and the electrodes are parallel to each other from the metal layer region of each group toward the other side 31b opposite to the one side 31a. The portions 35a, 35b, and 35c extend.
Lead electrodes 50 and 51 are connected to the electrode portions 34a to 34c and 35a to 35c formed on the front and back surfaces of the silicon substrate 31, respectively. In FIG. 2, the lead electrodes 50 and 51 are simply shown one by one, but each lead electrode is composed of a plurality of pieces corresponding to each group.

Next, a method for manufacturing the nozzle plate 30 will be described with reference to FIG. FIG. 4 shows a process of forming a YY section cross section in FIG.
First, a silicon substrate 31 as shown in FIG. 4A is cut out from a silicon wafer, and a mask material 40 is formed on the main surface (front surface) as shown in FIG. 4B and patterned. As the mask material 40, for example, a SiO ₂ film is formed by thermal oxidation or CVD.
Next, according to the pattern of the mask material 40, the silicon substrate 31 is etched in a direction perpendicular to the main surface to form a through hole 37 reaching the other main surface (back surface) as shown in FIG. To do.
At this time, when the through-hole 37 to be formed has a large aspect ratio, for example, a Bosch process in which etching and protective film formation on the substrate are alternately repeated can be employed.

After forming the through holes 37, the mask material 40 is removed, and as shown in FIG. 4D, new mask materials 42 are formed on both main surfaces of the silicon substrate 31, and patterned to form the mask holes 43. Form. Here, the mask holes 43 are patterned so as to connect the through holes 37 to be in the same group.
Next, as shown in (e), the metal layer 33 is formed on the inner wall of the through-hole 37 connecting the unmasked region and the two regions on the front and back surfaces of the silicon substrate 31 by electrolytic plating.
Thereafter, the mask material 42 is removed, and the nozzle plate 30 having a plurality of injection holes 32 having the metal layer 33 as the wall surface is completed as shown in FIG. The grouped metal layers 33 constitute heaters Ha, Hb, and Hc described later.

In the nozzle plate 30 configured as described above, when a voltage is applied between the electrode portions formed on the front and back surfaces of the silicon substrate 31 by the extraction electrodes 50 and 51, a current is parallel to the metal layer 33 of each injection hole 32 for each group. Since Joule heat is generated by flowing, the metal layers 33 for each group constitute heaters H (Ha, Hb, Hc), respectively.
Therefore, the injection hole 32 is heated by applying a voltage for each group, and thereby the fuel passing through the injection hole 32 can be selected and heated for each group. The temperature rise is caused by the amount of heat generated by the heater H by energization, the fuel pressure in the hydraulic chamber F of the fuel injection valve 20, the atmospheric pressure outside the flow rate adjusting hole 22, the length and diameter of the injection hole 32, the wall surface of the injection hole 32, Although it is determined by the heat transfer coefficient between fuels, the temperature can be instantaneously increased by energization.

  When the temperature of the fuel rises due to heating, the viscosity first decreases, and the frictional force between the wall surface of the injection hole 32 and the fuel decreases. As a result, the fuel easily passes through the injection hole 32, so The amount of fuel that passes through and is injected increases. Further, when the energization amount is further increased to raise the temperature of the heater, the fuel starts to boil in the injection hole, and as a result, the amount of fuel passing through the injection hole decreases rapidly. Accordingly, if the heater H is energized only for a specific group and the temperature of the heater is adjusted, the flow rate is increased or decreased by the amount of fuel passing through the injection hole 32 of the group, so that the fuel injected through the nozzle plate 30 is injected. The distribution in the combustion chamber R can be changed.

As described above, the nozzle plate 30 is provided at the front end of the fuel injection valve 20 at the opening portion of the flow rate adjusting hole 22.
That is, as shown in FIG. 5, the nozzle plate 30 is set so that the direction in which the three groups A, B, and C of the injection holes 32 are aligned faces the spark portion 6 a of the spark plug 6 facing the combustion chamber R. Has been.
FIG. 6 shows a change in the fuel injection amount due to the energization of the heater.
When none of the groups A, B, and C drives the heater H, the distribution of the injected fuel that has passed through the nozzle plate 30 is Z1, whereas the heater Ha of the group A that is closer to the spark plug 6 is turned on. When the fuel is energized in a temperature range in which the fuel does not boil in the injection holes, and the heaters Hb and Hc of the group B and group C are driven by energizing at a temperature higher than the temperature at which the fuel boils in the injection holes, the injection holes 32 of the group A The flow rate of the fuel passing through the region near the spark plug 6 increases more than the flow rate passing through the injection holes of the other groups B and C, resulting in the distribution of Z2. Accordingly, the fuel in the vicinity of the spark plug 6 can be enriched by the group A heater energization.

  Therefore, when the control unit 100 enters the stratified combustion mode when the temperature detected by the coolant temperature sensor 104 is lower than a predetermined value, the control unit 100 heats the group Ha heater Ha within a range in which the fuel does not boil in the injection hole. In addition, the heaters Hb and Hc of the group B and group C are heated to a temperature equal to or higher than the temperature at which the fuel boils in the injection hole. Further, when the homogeneous combustion mode is set, for example, after warming up when the temperature exceeds a predetermined value, control is performed so that the heater is not driven.

  When the engine is in the stratified combustion mode, since the wall surface temperature of the combustion chamber R of the internal combustion engine is low, as described above, when the injected fuel adheres to the wall surface, heat is taken away and the gas phase changes to the liquid phase, and droplets are formed on the wall surface. Easy to remain. In addition, when high-pressure fuel is injected from the fuel injection valve 20 into the low-pressure combustion chamber R and suddenly adiabatically expands, there is a possibility that the temperature of the fuel may decrease and change from the gas phase to the liquid phase, or combustion. When mixing with the low-temperature air in the chamber R, heat may be lost and the gas phase may change to the liquid phase. When the fuel injected from the fuel injection valve 20 adheres to the spark plug 6 in a liquid phase state, the spark plug smolders and impairs the ignition function.

  For this reason, the heater H of the nozzle plate 30 heats and raises the temperature of the fuel so that the fuel injected into the combustion chamber R maintains a gas phase. The temperature at which the fuel boils in the injection hole and the temperature at which the fuel is kept in the gas phase are generally higher than the temperature at which the fuel boils in the injection hole. This is because the boiling point of the fuel varies depending on the applied pressure, and the pressure in the injection hole is higher than the pressure in the combustion chamber. In other words, the fuel does not boil in the injection hole, but there is a temperature at which it boils in the combustion chamber, so if you want to inject a large amount of fuel, the fuel will not boil in the injection hole, but the ignition plug In the vicinity, the energization amount to the heater is adjusted to a temperature that maintains the vaporized state.

In order to prevent the fuel injected into the combustion chamber R from changing to the liquid phase and maintain the gas phase state, the internal energy of the fuel may be sufficiently increased. Therefore, the control unit 100 raises the temperature of at least the group A heater Ha that injects fuel in the vicinity of the spark plug 6 until the fuel passing through the injection holes 32 is in the supercritical fluid phase or the subcritical fluid phase. Control. For example, it is said that the supercritical state of gasoline is generally generated under conditions of a temperature of 300 ° C. and 4 MPa.
Since the supercritical fluid phase or subcritical fluid phase fuel has higher internal energy than the simple vapor phase fuel, it is prevented from being deprived of heat and changing into the liquid phase. Therefore, even when there are the above-mentioned various factors that take the heat of the fuel and lower the temperature, the fuel is held in the gas phase, so that the spark portion of the spark plug 6 is not wetted and is easily vaporized and has high combustion. Efficiency can be obtained.

The driving timing of the heater H is performed by energizing the lead electrodes 50 and 51 in synchronism with the driving signal of the needle valve 25 that opens and closes the flow rate adjusting hole 22, and when the needle valve 25 is on (open). Is energized to cause the heater H to generate heat, and the energization is cut when the needle valve 25 is off (closed). The energization of the heater H is performed slightly earlier than the ON signal of the needle valve 25 so that the temperature of the heater is sufficiently raised before fuel injection.
As a result, when the needle valve 25 is off and there is no fuel injection and there is no heat exchange between the fuel and the heater H, the temperature of the heater H may be excessively increased and the metal layer 33 of the heater may be melted. It is lost.
Although FIG. 6 shows an example in which only the heater Ha of the group A is driven, the heaters Hb and Hc of other groups can be driven by being energized depending on the operating state.
According to the above configuration, by selectively driving the plurality of heaters H provided on the nozzle plate 30, the fuel distribution in the combustion chamber can be changed, and the combustion mode can be set according to the operating state.

As described above, the control for switching between the stratified combustion mode and the homogeneous combustion mode according to the operation state has been described. However, in the present embodiment, the heater H is provided for each group of the injection holes 32. It is also possible to control the maximum fuel injection amount at the time.
As the background, for example, there is a case where a large amount of fuel is desired to be injected into the combustion chamber R when the vehicle is suddenly accelerated.
The fuel injection amount of the fuel injection valve 20 is determined mainly by three factors: the pressure of the fuel pressurized by the fuel pump, the opening area of the flow rate adjusting hole 22, and the ON time of the needle valve 25. Since the opening area of the flow rate adjusting hole 22 is fixed in the manufacturing stage, either the fuel pressure or the on-time of the needle valve 25 is changed in order to switch the fuel injection amount depending on the operation state.

Of these two means, the switching of the fuel injection amount according to the on-time of the needle valve 25 is more responsive and can be configured at a lower cost than the fuel pressure increase / decrease. Since there is an appropriate injection amount and timing according to the operating state, there is a limit to the time during which the needle valve 25 can be turned on.
The fuel injection valve 20 does not instantaneously inject fuel when voltage is applied to the solenoid of the needle valve 25, but there is a delay time. Except for this delay time, the fuel injection amount is approximately proportional to the ON time of the needle 25 valve. To do. Therefore, there is a maximum injection amount that is limited to the ON time of the needle valve 25.

In this embodiment, when it is desired to inject a large amount of fuel into the combustion chamber R, such as during rapid acceleration of the vehicle, the heater H of the nozzle plate 30 is driven within a range in which the fuel does not boil within the injection hole to generate heat.
This lowers the viscosity of the fuel, reduces the frictional force between the wall surface of the injection hole 32 and the fuel, and makes it easier for the fuel to pass through the injection hole 32. Therefore, the on-time of the needle valve 25 can be increased to the limit. A large amount of fuel exceeding the injection amount is injected into the combustion chamber R.
At this time, the maximum injection amount can be increased stepwise by driving the heaters Ha, Hb, and Hc of the groups A, B, and C as appropriate according to the required fuel injection amount.
As described above, according to this control, there is no restriction on the opening area that is determined in the manufacturing stage of the flow rate adjusting hole 22, and no expensive fuel pump for high pressure is required. The maximum injection amount can be increased.

As described above, in this embodiment, the fuel injection valve 20 that injects the fuel into the combustion chamber R is the fuel outlet of the nozzle plate 30 having the injection holes 32 divided into a plurality of groups A, B, and C. The heaters Ha, Hb, and Hc for each group are attached to the injection holes 32 of each group, and the fuel passing through the injection holes 32 for each group is supplied by energizing these heaters. The temperature could be increased. The injection holes 32 of the group A are closer to the spark plug 6 than the injection holes of the other groups, and the fuel injected from the injection holes 32 is directed toward the vicinity of the ignition plug 6. Therefore, when the heater Ha of the group A is energized and heated to a temperature in a range where the fuel does not boil in the injection hole, the viscosity of the fuel passing through the injection hole 32 of the group A is reduced, and the region close to the spark plug 6 is obtained. By increasing the flow rate of the fuel to be directed, the fuel in the vicinity of the spark plug 6 can be concentrated, and the heaters Hb and Hc of the group B and group C are energized and heated above the temperature at which the fuel boils in the injection holes. Since the pressure loss in the injection hole of the group increases and the amount of fuel injected through the injection hole decreases, the same function can be obtained as when the fuel injection direction is changed substantially. Therefore, a suitable fuel distribution can be obtained when the cooling water temperature of the internal combustion engine is cold or below, particularly when stratified combustion is required.
And since it does not change a fuel-injection direction using a movable member, high reliability is acquired.

  Even in the homogeneous combustion mode of the internal combustion engine, one or more groups of heaters H are energized according to the required injection amount of fuel, and the fuel passing through the injection holes 32 of the group energized by the heaters is injected into the injection holes. When the temperature is raised to a temperature that does not boil, the viscosity decreases and the flow rate increases, so the dynamic range of the fuel injection valve 20 is expanded. For example, when a large amount of fuel is required, such as during rapid acceleration of the vehicle It is effective for.

Since the heater H raises the temperature of the fuel passing through the injection holes 32 to a gas phase state, it can be easily ignited and high combustion efficiency can be obtained.
In particular, by heating the fuel passing through the injection holes 32 until it reaches a supercritical state or a subcritical state, the internal energy of the fuel increases, so there is a factor that lowers the temperature of the fuel around the combustion chamber R. However, there is no fear that the fuel changes from the gas phase to the liquid phase and wets the spark plug 6 or adheres as droplets to the wall surface of the combustion chamber R, resulting in incomplete combustion. .

Further, since the heater H is energized in synchronization with the on / off of the needle valve 25 that ejects fuel from the hydraulic chamber F, the heater temperature is excessively raised when there is no heat exchange between the fuel and the heater H, and the heater H There is no risk of melting or degrading the H metal layer 33.
Similarly, since the heater H is not energized when it is not necessary, extra power consumption can be reduced.

In the embodiment, the injection holes 32 of the nozzle plate 30 are arranged in a circular shape as a whole, and the injection holes 32 are grouped into three groups of a group A and groups B and C sandwiching the injection holes 32. The overall arrangement and grouping of 32 are not limited to this, and can be arbitrarily set according to the shape of the combustion chamber R, the position of the spark plug 6, and the like.
The injection holes 32 are all formed in parallel with each other. However, for example, by inclining by a group, the fuel injection direction from the injection hole of the group can be further directed toward the spark plug 6.

Further, although silicon is used as the substrate material of the nozzle plate 30, the present invention is not limited to this. When ceramic or metal is used as the substrate material, the through hole 37 may be formed by using electric discharge machining or the like.
In particular, when the substrate material of the nozzle plate 30 is a metal, in order to prevent a current from flowing through the substrate material when the heater H is driven, an oxide film or the like is provided between the metal layer 33 forming the heater H and the substrate. It is preferable to form and insulate both. Alternatively, when insulation by an oxide film or the like is difficult, the metal layer 33 forming the heater H is made of a material having high electrical conductivity such as gold, silver, copper, or an alloy thereof, and the substrate material is iron, nickel, A material having low electrical conductivity such as zinc or an alloy thereof can be used so that almost no current flows in the substrate material.
In addition, about the attachment of the heater H with respect to each group, although the metal layer 33 shall extend over the front and back surfaces of a board | substrate including the inner wall of the injection hole 32, not only this but the fuel which passes through the injection hole of a group is enough It may be arranged in the vicinity of the injection hole as long as the temperature can be increased.

Next, a second embodiment will be described.
This embodiment uses a fuel injection valve 20A having a configuration different from that of the fuel injection valve 20 in the first embodiment, and the mounting position and control system of the fuel injection valve 20A are the same as those of the first embodiment shown in FIG. Since the configuration is the same as that described with reference to FIG.
FIG. 7 shows the detailed structure of the front end portion of the fuel injection valve 20A on the combustion chamber R side.
The plate holding member 27 holds the nozzle plate 200 at a position facing the opening of the flow rate adjusting hole 22.
The nozzle plate 200 is provided with a plurality of injection holes 250 penetrating the front and back surfaces.
From the nozzle plate 200, an extraction electrode group 50 </ b> A constituted by a plurality of electrodes extends to the outside through the inside of the insulator 28 and the plate holding member 27.
Other configurations are the same as those described with reference to FIG. 2 in the first embodiment.

Next, details of the nozzle plate 200 will be described.
FIG. 8 shows an exploded perspective view of the nozzle plate, and FIG. 9 shows an upper surface of the heater portion.
The nozzle plate 200 includes a heater part 210, an upper part 220 joined to the upper side of the heater part 210, and a lower part 230 joined to the lower side of the heater part 210.
The upper part 220 and the lower part 230 are made of a nonmetal having electrical insulation, and the heater part 210 is made of a conductive metal or Si.

The heater unit 210 includes a cylindrical outer peripheral heater 211, a central heater 212, and an inner peripheral heater 213. The inner peripheral heater 213 is provided on the inner peripheral side of the central heater 212, and the outer peripheral heater 211 is provided on the outer peripheral side of the central heater 212. Has been placed.
A gap is provided between the central heater 212 and the outer peripheral heater 211, and between the central heater 212 and the inner peripheral heater 213, and the gap constitutes a heat separation region 215.
The thermal separation region 215 thermally isolates and electrically insulates between the outer peripheral heater 211 and the central heater 212 and between the inner peripheral heater 213 and the central heater 212.
The outer peripheral heater 211, the central heater 212, and the inner peripheral heater 213 are each formed with a plurality of injection holes 250A along the cylindrical axial direction.

In particular, as shown in FIG. 9, the inner peripheral heater 213 is provided with a cut in the axial direction of the cylinder, and lead-out portions 213a and 213b extend outward from both ends where the cut is provided.
In the lead portions 213a and 213b, electrodes 213c and 213d are formed on the upper side of the outer end portion (the side to which the upper portion 220 is joined), respectively.
The lead portions 213a and 213b are formed in the vicinity of the upper end portion (the end portion on the side joined to the upper portion 220) of the inner heater 213 as shown in FIG.

  Similarly to the inner peripheral heater 213, the central heater 212 and the outer peripheral heater 211 are provided with cuts, and the central heater 212 has outwardly extending lead portions 212a and 212b, and electrodes 212c at the ends of the lead portions 212a and 212b, respectively. 212d are formed, and the outer peripheral heater 211 has outwardly extending lead portions 211a and 211b, and electrodes 211c and 211d are formed at the ends of the lead portions 211a and 211b, respectively.

As a result, by applying a voltage to the electrodes 213c and 213d, a current flows over the entire surface of the inner peripheral heater 213 to heat it.
Similarly, when a voltage is applied between the electrodes 212c and 212d or between the electrodes 211c and 211d, current flows over the entire surfaces of the central heater 212 and the outer peripheral heater 211, respectively, to heat them.

The upper portion 220 has a through hole 221 formed at a position facing the electrodes 211c, 211d, 212c, 212d, 213c, and 213d when joined to the heater section 210.
The upper part 220 is formed with an injection hole 250B at a position facing the injection hole 250A of the heater section 210, and guides the fuel flowing from above the upper part 220 to the injection hole 250A.

An injection hole 250C is also formed in the lower portion 230 at a position facing the injection hole 250A of the heater section 210, and the fuel that has passed through the injection hole 250A is injected to the combustion chamber side (the lower side in FIG. 8).
The injection holes 250A to 250C are collectively referred to as the injection holes 250.
The lower portion 230 prevents the heat capacity of the heater unit 210 from increasing due to the fuel injected into the combustion chamber side being bounced back and adhering to the heater unit 210.

FIG. 10 shows a W1-W1 cross section in FIG.
The outer peripheral portion of the nozzle plate 200 is fitted with an insulator 28 having a U-shaped cross section.
A thermal separation region 215 formed between the outer peripheral heater 211 and the central heater 212 and between the central heater 212 and the inner peripheral heater 213 is surrounded by the upper part 220 and the lower part 230, and has a thermal resistance higher than that of the heaters 211, 212, and 213. Filled with high-rate materials or vacuumed and sealed.
In the outer peripheral portion of the heater unit 210, the space surrounded by the heater unit 210, the upper part 220, the lower part 230, and the insulator 28 also becomes a heat separation region 215 in the same manner as described above, and has a thermal resistivity higher than that of each heater 211, 212, 213 High material or air is filled or sealed in a vacuum state.

A through hole 28a is formed in the insulator 28 at a position facing the electrodes 211c, 211d, 212c, 212d, 213c, and 213d provided in the heater unit 210 in a state where the nozzle plate 200 is fitted.
Electrode terminals 29 (total of 6 in this embodiment) are inserted into the through holes 28a, respectively, and the electrode terminals 29 and the electrodes 211c, 211d, 212c, 212d, 213c, and 213d are in contact with each other.
A lead electrode group 50 </ b> A is connected to each electrode terminal 29.
In FIG. 7, the extraction electrode group 50A is simply shown as three, but the extraction electrodes are each composed of a number corresponding to the number of electrode terminals 29 (six in this embodiment). .
Therefore, a desired heater (211 212, 213) can be heated by applying a voltage between predetermined electrodes of the extraction electrode group 50A.
As described above, the fuel sent from the needle valve 25 to the nozzle plate 200 is supplied to the heater unit 210 through the injection hole 250B of the upper part 220, and a predetermined heater (211 212, 213) to which a voltage is applied. Is rapidly heated in the injection hole 250A and injected toward the combustion chamber through the injection hole 250C in the lower part 230.

Next, a method for manufacturing the nozzle plate 200 will be described.
The nozzle plate 200 includes a method of forming the injection holes 250A to 250C in each part in advance before assembling and assembling them to form the injection holes 250, and a method of forming the injection holes 250 after assembling.
First, a method for manufacturing the nozzle plate 200 by providing the injection holes 250A to 250C in each part in advance before assembly will be described with reference to FIG.
The injection holes 250B and 250C are previously formed in the upper part 220 and the lower part 230 by drilling.
This drilling can be performed by a method such as drilling, electric discharge machining, etching, or punching.

A gap that becomes the injection hole 250 </ b> A and the heat separation region 215 is also opened in the heater unit 210.
Here, when the heater unit 210 is Si, a gap that becomes the injection hole 250A or the heat separation region 215 can be formed by using Deep RIE.
Leads 211a, 212a, 213a extending outward from the inner peripheral heater 213, the central heater 212, the outer peripheral heater 211, and leading ends of the unillustrated lead portions 211b, 212b, 213b, W, Ni, Pt, etc. Metal is deposited and patterned to form electrodes 211c, 212c, and 213c for applying power, and electrodes 211d, 212d, and 213d (not shown).
In the upper part 220, through holes 221 are formed by machining or the like at positions facing the electrodes 211c, 211d, 212c, 212d, 213c, and 213d.

Positioning is performed so that the injection holes 250B formed in the upper part 220, the injection holes 250A formed in the heater part 210, and the injection holes 250C formed in the lower part 230 communicate with each other, and the upper part 220, the heater part 210, The lower part 230 is joined and the outer peripheral part is surrounded by the insulator 28.
This joining is performed using diffusion welding or friction welding.
Here, the constituent material of the upper part 220 and the lower part 230 is made of ceramic, quartz or the like having high thermal resistance, and the heater part 210 is made of metal having low thermal resistance.
In the case of diffusion bonding, a vacuum atmosphere, an argon gas atmosphere, or an N2 atmosphere is used to increase the temperature and pressure as much as possible to improve the adhesion.
Here, by performing diffusion bonding in a vacuum atmosphere, the heat separation region 215 of the heater unit 210 is thermally separated, and heat loss can be reduced.

Next, as another method, a method of forming the injection hole 250 after assembly will be described with reference to FIG.
The upper part 220, the heater part 210 in which the heat separation region 215 is formed, and the lower part 230 are joined by diffusion bonding or the like, and the outer peripheral part is surrounded by the insulator 28.
In addition, each part shall not be provided with the injection holes 250A, 250B, 250C.
The thermal separation region 215 joins each part so as to be in a vacuum state.

In a state where the upper part 220, the heater part 210, and the lower part 230 are joined, the injection hole 250 is formed by drilling with a drill 290.
In addition to drilling with a drill, methods such as electric discharge machining, etching, and punching can be used for this drilling.
Thereby, there is no problem of the deviation of the injection holes in the case where the injection holes are previously formed in the upper part 220 and the heater part 210 and then joined.

The present embodiment is configured as described above, and the heat separation region 215 is provided in the heater unit 210 so that the outer peripheral heater 211, the central heater 212, and the inner peripheral heater 213 constituting the heater unit 210 can be heated independently. Thus, the temperature of the fuel passing through the injection hole 250A can be raised for each of the heaters 211, 212, and 213, and the viscosity of the fuel can be controlled.
In this way, the fuel viscosity can be controlled for each of the heaters 211, 212, and 213, so that the fuel injection amount and the spray shape can be controlled. As a result, an ideal fuel distribution according to the operating state of the engine is created. be able to.
Further, by making the space between the heaters 211, 212, and 213 as the heat separation region 215, heat transfer between the heaters can be suppressed, and a temperature gradient can be formed between the heaters.

Next, a third embodiment will be described.
In this embodiment, a nozzle plate 300 having a configuration different from that of the nozzle plate 200 in the second embodiment is used.
FIG. 12 shows an upper surface of the nozzle plate 300, and FIG. 13 shows an enlarged view of the W2-W2 cross section of FIG. FIG. 14 shows an upper surface of the heater unit 310.
The nozzle plate 300 includes a heater part 310, an upper part 320 connected to the upper side of the heater part 310, and a lower part 330 joined to the lower side of the heater part 310.

The heater unit 310 includes a cylindrical outer peripheral heater 311, a central heater 312, and an inner peripheral heater 313 that are provided with cuts in the axial direction, and both ends of the cut portions of the outer peripheral heater 311, the central heater 312, and the inner peripheral heater 313. Electrodes 340 (see FIG. 13) are respectively provided on the upper side surfaces.
Clearances are formed between the outer peripheral heater 311 and the central heater 312 and between the central heater 312 and the inner peripheral heater 313 to form a heat separation region 315.
The outer peripheral heater 311, the central heater 312, and the inner peripheral heater 313 are each provided with an injection hole 350A.
The configurations of the outer peripheral heater 311, the central heater 312, and the inner peripheral heater 313 are the same as the configurations of the outer peripheral heater 211, the central heater 212, and the inner peripheral heater 213 in the second embodiment.

In the upper part 320, an injection hole 350B is provided at a position facing the injection hole 350A when joined to the heater unit 310.
A through hole 321 is formed in the upper part 320 at a position facing the electrode 340 of the heater unit 310.
Similarly to the upper part 320, the lower part 330 is provided with an injection hole 350C at a position facing the injection hole 350A of the heater section 310.
These injection holes 350A, 350B, and 350C are collectively referred to as an injection hole 350.

In a state where the heater unit 310, the upper part 320, and the lower part 330 are overlapped, a lead wiring 343 extends from the electrode 340 exposed from the through hole 321 toward the outer peripheral part of the upper part 320 on the upper surface of the upper part 320. (In FIG. 12, a lead-out wiring 343 is disposed below an insulator 341 described later.)
The lead wiring 343 is formed at a position where it does not overlap the injection hole 350.

The nozzle plate 300 is fitted with an insulator 328 having a U-shaped cross section at the outer periphery thereof.
A through hole 328a is formed in the insulator 328, and the electrode terminal 329 is inserted into the through hole 328a as in the second embodiment, and the electrode terminal 329 and the lead wiring 343 are connected.
By applying a voltage through the electrode terminal 329, the outer peripheral heater 311, the central heater 312, and the inner peripheral heater 313 can be heated independently.
In addition, the lead wiring 343 formed on the upper surface of the upper portion 320 is covered with an insulator 341 to be electrically insulated from the fuel.

Next, a method for manufacturing the nozzle plate 300 will be described.
The lead wiring 343, the through hole 321, and the injection hole 350B through which fuel passes are formed in advance on the upper surface of the upper part 320.
The heater portion 310 is also formed with a gap serving as the heat separation region 315, an injection hole 350 </ b> A through which fuel passes, and an electrode 340, and an injection hole 350 </ b> C through which fuel passes also in the lower portion 330.
The heater part 310, the upper part 320, and the lower part 330 are joined by aligning the positions of the injection holes 350A, 350B, and 350C, and at the same time, the electrode 340 of the heater part 310 and the lead wiring 343 of the upper part 320 are connected.
In addition, after joining the heater part 310, the upper part 320, and the lower part 330, the injection hole 350 which a fuel passes can also be formed by drilling processes, such as a drill process.

Since the present embodiment is configured as described above and the temperature can be controlled for each of the heaters 311, 312, and 313 as in the second embodiment, the viscosity of the fuel can be controlled for each heater. Therefore, by controlling the fuel injection amount and spray shape for each of the heaters 311, 312, and 313, an ideal fuel distribution according to the operating state of the engine can be created.
In particular, by forming the lead-out wiring 343 on the upper surface of the upper portion 320, electrode extraction portions (portions where the electrode terminals 329 are formed) can be dispersed, and the size of the nozzle plate 300 in the radial direction can be reduced. Moreover, weight reduction can be achieved by reducing the size.

In the second and third embodiments, the heater portions 210 and 310 of the nozzle plate are cylindrical. However, as shown in FIGS. 15A and 15B, a plurality of injection holes 450 are provided. The heater unit 410 can also be configured by arranging a predetermined number of flat plate heater units 411 provided.
Also in this case, as shown in FIG. 15B, the viscosity of the fuel can be controlled for each flat plate heater 411 by allowing the voltage to be applied independently for each flat plate heater portion 411.
In addition to the flat plate shape of the heater portion, as shown in FIG. 16, an L-shaped heater portion 511 having an L-shaped cross section is used, and an L-shape of another L-shaped heater portion 511 is formed inside the L-shape. The heater unit 510 can also be configured by sequentially arranging a predetermined gap so that the outer sides face each other and combining them.
In these cases, the shapes of the heater portions 411 and 511 are simple, and the same pattern is gathered, so that the efficiency of removing from one metal plate is good when the heater portions 411 and 511 are manufactured.

1 is a diagram showing a configuration around a combustion chamber and a control system of an internal combustion engine to which the present invention is applied. FIG. It is a figure which shows the detailed structure of the combustion chamber side front-end | tip part of a fuel injection valve. It is a figure which shows the detail of a nozzle plate. It is a figure which shows the manufacturing process of a nozzle plate. It is a figure which shows arrangement | positioning of the nozzle plate with respect to a combustion chamber. It is a figure which shows the change of the fuel injection amount by electricity supply of a heater. It is a figure which shows the detailed structure of the combustion chamber side front-end | tip part of a fuel injection valve. It is a disassembled perspective view which shows a nozzle plate. It is a figure which shows the heater part in a 2nd Example. It is a figure which shows the cross section of the nozzle plate in a 2nd Example. It is a figure which shows the manufacturing method of a nozzle plate. It is a figure which shows the nozzle plate in a 3rd Example. It is an enlarged view which shows the W2-W2 part cross section in FIG. It is a figure which shows a heater part. It is a figure which shows the modification of a heater part. It is a figure which shows the modification of a heater part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder 3 Cylinder head 4 Piston 4a Cavity 6 Spark plug 6a Spark part 8 Intake valve 10 Exhaust valve 20 Fuel injection valve 21 Housing 22 Flow rate adjustment hole 23 Valve seat 25 Needle valve (Valve)
26 Conical surface 27 Plate holding member 28, 328 Insulator 30, 200, 300 Nozzle plate 31 Silicon substrate 32, 250, 250A, 250B, 250C, 350, 350A, 350B, 350C, 450, injection hole 33 Metal layer 34a, 34b , 34c, 35a, 35b, 35c Electrode portion 37 Through hole 40, 42 Mask material 43 Mask hole 50, 51 Lead electrode 100 Control unit 101 Air flow meter 102 Throttle opening sensor 103 Crank angle sensor 104 Cooling water temperature sensor 210, 310, 410, 510 Heaters 211, 311 Outer heaters 212, 312 Central heaters 213, 313 Inner heaters 215, 315 Thermal separation regions 220, 320 Upper 230, 330 Lower 411 Flat heater 511 L Type heater unit F hydraulic chamber Ha, Hb, Hc heater R combustion chamber

Claims (17)

A fuel injection valve for injecting fuel into the combustion chamber;
The fuel injection valve includes a nozzle plate that ejects pressurized fuel by the operation of the valve and has a plurality of injection holes at a fuel ejection port,
The injection holes of the nozzle plate are divided into a plurality of groups, and at least one group is provided with a heater,
A fuel injection device for an internal combustion engine, wherein the temperature of the fuel passing through the injection holes can be increased in units of groups by operating the heater. The injection hole of at least one group among the groups provided with the heater is set so that the injection direction of the fuel that has passed through the injection hole is directed toward the spark plug in the combustion chamber. A fuel injection device for an internal combustion engine according to claim 1. In the stratified combustion mode of the internal combustion engine, the heater of the injection hole group set so that the injection direction of the fuel faces the spark plug in the combustion chamber is heated up to a temperature at which the fuel does not boil in the injection hole. The fuel injection device for an internal combustion engine according to claim 2, wherein the fuel injection device is an internal combustion engine. When the internal combustion engine is in the stratified combustion mode, the group heaters of the injection holes other than the injection hole group set so that the injection direction of the fuel faces the spark plug in the combustion chamber is equal to or higher than the temperature at which the fuel boils in the injection holes. The fuel injection device for an internal combustion engine according to claim 2 or 3, wherein the fuel injection device is heated by the internal combustion engine. A temperature at which the heater of the injection hole group set so that the injection direction of the fuel faces the spark plug in the combustion chamber when the cooling water temperature of the internal combustion engine is equal to or lower than a predetermined value does not cause the fuel to boil in the injection hole The fuel injection device for an internal combustion engine according to any one of claims 2 to 4, wherein the fuel injection device is heated up to an upper limit. When the cooling water temperature of the internal combustion engine is equal to or lower than a predetermined value, the heaters in the injection hole groups other than the injection hole group set so that the injection direction of the fuel faces the spark plug in the combustion chamber The fuel injection device for an internal combustion engine according to any one of claims 2 to 5, wherein the fuel injection device is heated to a temperature equal to or higher than a boiling temperature in the hole. The fuel injection device for an internal combustion engine according to any one of claims 1 to 6, wherein one or more of the heaters are operated in accordance with a required fuel injection amount when the internal combustion engine is in a homogeneous combustion mode. . The fuel injection device for an internal combustion engine according to any one of claims 1 to 7, wherein the heater is operated in synchronization with the operation of the valve. The fuel injection device for an internal combustion engine according to any one of claims 1 to 8, wherein a heat separation region is formed around the heater, and the heater is thermally separated. 10. The fuel injection device for an internal combustion engine according to claim 9, wherein the heat separation region is filled with a material having high thermal resistivity or air, or is in a vacuum. The fuel injection device for an internal combustion engine according to any one of claims 1 to 10, wherein the heater is made of a metal capable of Joule heating. Having injection holes divided into a plurality of groups;
At least one group has a heater,
A nozzle plate for a fuel injection device for an internal combustion engine, wherein the temperature of the fuel passing through the injection holes can be raised in groups by operating the heater. 13. The nozzle plate for a fuel injection device for an internal combustion engine according to claim 12, wherein a heat separation region is formed around the heater, and the heater is thermally separated. 14. The nozzle plate for a fuel injection device for an internal combustion engine according to claim 13, wherein the heat separation region is filled with a material having high thermal resistivity, air, or vacuum. The nozzle plate for a fuel injection device for an internal combustion engine according to any one of claims 12 to 14, wherein the heater is made of a metal capable of Joule heating. The injection hole is a hole provided in the heater,
16. The nozzle plate for a fuel injection device for an internal combustion engine according to claim 12, wherein the heater has a multilayer structure in a direction perpendicular to a fuel injection direction. In an internal combustion engine that injects fuel into a combustion chamber with a fuel injection valve having a nozzle plate having injection holes divided into a plurality of groups and a heater attached to each group at a fuel injection port, depending on the operating condition A fuel injection method for an internal combustion engine, wherein the heater is selectively operated to raise the temperature of the fuel that passes through the injection holes independently for each of the groups to change the amount of each fuel injection .

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