JP2000161175A - Injector and fuel injection system - Google Patents

Abstract

(57) [Problem] To provide an injector which can exhibit the high-speed response of a piezoelectric element and is advantageous in terms of space. A plunger for opening and closing a fuel passage, a piezoelectric element for driving the plunger, a spring for driving the plunger,
In an injector composed of a jig for fixing them, a housing (the outermost structural member of the injector), and the like, around the piezoelectric element and a member supporting the piezoelectric element, a structure (partition) for isolating these from fuel is provided. And the fuel is passed between the housing and the partition wall to supply the fuel to the tip of the injector, and the joint (fuel introduction portion) between the fuel supply line and the injector is disposed behind the piezoelectric element when viewed from the plunger. Injector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an injector and a fuel injection system, and more particularly to a system using a piezoelectric element.

[0002]

2. Description of the Related Art As an injector using a piezoelectric element, for example, Japanese Unexamined Patent Publication No. Hei 7-189853 (hereinafter referred to as Conventional Example 1) discloses that an intervening fluid is interposed between a piezoelectric element and a plunger. A pilot injector that indirectly applies a force to a plunger to open and close a valve is described. Further, for example, JP-A-62-191662 (hereinafter referred to as Conventional Example 2) describes an injector using a cylindrical piezoelectric element (hollow piezoelectric element). Further, for example, JP-A-62-199963 (hereinafter referred to as Conventional Example 3) and JP-A-8-97980 (hereinafter referred to as Conventional Example 4) describe an injector that directly drives a plunger by a piezoelectric element. Have been.

[0003]

SUMMARY OF THE INVENTION There is a strong demand for improved fuel efficiency of automobile engines or purification of exhaust gas.
The development of injectors with high responsiveness is an urgent issue. Since the responsiveness of the conventional electromagnetic injector has almost reached its limit, an injector using a piezoelectric element capable of high-speed operation is expected.

[0004] Piezoelectric injectors can be broadly classified into a pilot type in which the plunger is driven indirectly with a fluid as an intervening body and a direct-acting type in which the plunger is driven directly by a piezoelectric element. The former has the advantage that if the fluid flow path is devised, the stroke of the plunger can be made larger than the stroke of the piezoelectric element, but the response is affected by the sliding resistance between the piston and cylinder or the elastic characteristics of the fluid. It is considered that a direct-acting injector is more advantageous in terms of characteristics.

As a direct-acting injector, an injector using a hollow piezoelectric element (cylindrical piezoelectric element) has been studied. However, the injector becomes thicker, the plunger becomes longer, and the weight increases. Poor responsiveness, furthermore, the production yield of cylindrical elements is poor,
Alternatively, since the element cross-sectional area becomes large, there is a problem that the element becomes expensive.

In considering a piezoelectric injector,
The size of the injector cannot be avoided. In particular, in the case of a direct injection type engine, it is strongly required that the outer shape be thin from the tip of the injector to the central portion and that the members do not protrude. For example, in the case of Conventional Example 4, the fuel is introduced from the side of the tip of the injector (side feed type), which has a space problem.

The operating temperature of the injector is -40.degree.
Wide, ~ 150 ° C. Since the piezoelectric element usually has a significantly different coefficient of thermal expansion from the material constituting the injector, when a direct acting injector is configured, the valve opens due to the difference in thermal expansion, or conversely, excessive compressive stress is applied to the piezoelectric element,
There is a possibility that the element will be damaged.

Further, there is an urgent need to develop a concrete solution to the purification of exhaust gas, but the prior art does not mention this point.

An object of the present invention is to provide an injector for supplying fuel suitable for an internal combustion engine.

[0010] Another object of the present invention is to provide a method for producing NOx in exhaust gas.
To provide a fuel injection system capable of reducing the fuel consumption.

[0011]

SUMMARY OF THE INVENTION A feature of the present invention is that a solid-state (actual) piezoelectric element is used in a piezoelectric injector. This is because the function required of the piezoelectric injector is firstly high-speed response.

Another feature of the present invention is that a plunger for opening and closing the fuel passage, a piezoelectric element having a solid structure for driving the plunger, a partition for separating the piezoelectric element from the fuel, and a housing for holding these elements are provided. Wherein the fuel is passed between the housing and the partition wall to supply the fuel to the tip of the injector, and a fuel introduction portion to the injector is disposed behind the piezoelectric element when viewed from the plunger. Another feature of the present invention is that a member having an electrode for mounting a lead wire of the piezoelectric element is provided, and a flow path through which fuel passes is provided at a position away from the electrode.

Another feature of the present invention is that the injector includes a plunger for opening and closing the fuel passage, a solid-state piezoelectric element for driving the plunger via a solid or elastic body, and a housing for holding the same. A fuel is passed between a housing and a piezoelectric element having a protective film for protecting the fuel, or a hole serving as a flow path is provided in a part of the housing, and the fuel is supplied to the tip of the injector. Is to have a fuel introduction portion to the rear of the piezoelectric element as viewed from the plunger. Another feature of the present invention is that the injector has a plunger that opens and closes a fuel passage, a solid piezoelectric element that drives the plunger, and a movable member that supports the piezoelectric element. 0.1 μm / s or more during injector operation
It is within the range of 500 μm / s.

Another feature of the present invention is that the injector has a plunger for opening and closing the fuel passage, a solid piezoelectric element for driving the plunger, and a movable member for supporting the piezoelectric element. The movable member to be moved is at least −150 μm to 4
That is, it can move by 0 μm.

Still another feature of the present invention is that the piezoelectric element is supported by a movable member connected to a spring attached to the fixed member, a fluid is filled around the movable member, and a part of the partition can be deformed. Is provided.

Another feature of the present invention is that a supporting member for the piezoelectric element is further provided at the center of the deformable member, and the pressure receiving area of a surface of the supporting member perpendicular to the longitudinal center axis of the injector is reduced. Wherein the area of the cross section (the cross section perpendicular to the central axis of the injector) of the region surrounded by the partition is not more than 1/3.

Still another feature of the present invention is that the axial component of the plunger of the pressure received by the deformable member from the fuel is made smaller than the force of the spring attached to the movable member. .

Still another feature of the present invention is that a deformable member is provided in the fluid on the opposite side to the piezoelectric element as viewed from the movable member.

Still another feature of the present invention is that a flow path through which a fluid can pass is formed inside the movable member.

Further, another feature of the present invention is that the movable range of the movable member supporting the piezoelectric element is limited by a part of the partition wall or a member attached thereto.

Still another feature of the present invention is that an elastic member is provided inside a structure provided around the piezoelectric element and separating the fuel and the element.

Another feature of the present invention is that a fuel injection system for an automobile has the above-described injector.

Another feature of the present invention is that the fuel is injected in both the intake stroke and the compression stroke by using a piezoelectric injector so that the injection amount in the compression stroke is smaller than the injection amount in the intake stroke. That is.

Another feature of the present invention is that the ratio of the injection amount in the intake stroke is set to 0.7 to 0.9.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an injector and a fuel injection system according to the present invention will be described below with reference to FIGS. Note that the same parts, arrows, and the like are denoted by the same reference numerals, and duplicate description may be omitted.

FIG. 1 is a view showing a sectional structure of a piezoelectric injector according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a fuel injection system using the piezoelectric injector according to the embodiment of the present invention. In FIG. 1A, a laminated solid element of 5 mm × 5 mm × 40 mm was used as the piezoelectric element 11. The piezoelectric element 11 is supported by a movable member 16 having a diameter of φ10 mm × 15 mm. The piezoelectric element 11 and the movable member 16 are arranged in a region surrounded by the inner tube 12, the inner tube 31, the diaphragm 15 and the like. This was filled with a highly viscous silicone oil. The inner pipe 12 and the inner pipe 31 are arranged inside a housing (corresponding to the outer pipe 13 and the outer pipe 32 in the figure), and fuel is supplied from the fuel introduction portion 33 to the housing and the inner pipe 1.
The configuration is such that the electrode can be supplied to the tip of the injector through the fuel through hole 19 in the electrode take-out section 20 through the space between the electrodes 2 and 31. The housing has an outer diameter of 19 mm except for the electrode take-out portion, and has inner tubes 12, 31 and outer tubes 13, 31.
32, movable member 16 (damper) and diaphragm 15
Is made of stainless steel, and the packing 27 is made of fluorine rubber. The spring 26 has a pressure of 10 kgf and the spring 25 has a pressure of 6 kgf. With this configuration, when the piezoelectric element 11 is extended, the plunger 14 is pressed against the tip of the injector to close the valve. On the other hand, when the piezoelectric element 11 contracted, the movable member 16 did not move abruptly due to the viscosity of the silicon oil, so only the force of the spring 25 acted on the plunger 14 to open the valve. The response time of the on-off valve is about 100 μs, which is about 1
It was found that the valve moved in the time of / 3. Plunger 14
Is supported by the member 28 and is regulated so as to move in the expansion and contraction direction of the piezoelectric element 11. The plunger 14 acts as a valve element that reciprocates with the distortion operation of the piezoelectric element.
A force is transmitted between the piezoelectric element and the valve via a solid member and / or an elastic member without intervening a fluid.

FIG. 1B shows that a fuel through hole 59 serving as a fuel flow path is provided in a part of the housing 60.
And a role of separating the piezoelectric element 11 from the fuel. Here, the fuel introduction section 3 is viewed from the piezoelectric element 11.
The members located on the third side are the same as those in FIG.
It operates on exactly the same principle.

In the injector according to the embodiment (embodiment) of the present invention, the fuel introduction section 33 is located behind or behind the piezoelectric element as viewed from the plunger 14. Therefore,
There is no member requiring a large space, such as a fuel introduction part, at the portion from the tip to the center of the injector, and the diameter is small. Therefore, if the injector according to the embodiment of the present invention is used, a space-saving injector suitable for mounting on an engine can be configured. Lead 11 of piezoelectric element 11
7 is the outside of the injector (the outer tube 1) via the electrode 17.
Out of 3, 32).

Here, the diameter of the injector according to the embodiment of the present invention and the diameter of the injector using the hollow piezoelectric element as a comparative example are compared as follows.

In the embodiment of the present invention, the inner pipe 12 has an outer diameter of 1 mm.
It was 2.5 mm (inner diameter 8.5 mm), and the piezoelectric element 11 was housed inside. The outer tube 13 had an inner diameter of 13 mm and an outer diameter of 19 mm. Since there is room for mechanical force,
If a device such as digging a shallow groove outside the inner tube 12 is used, the diameter can be further reduced.

On the other hand, in the case of a hollow piezoelectric element (cylindrical),
It is necessary to arrange a plunger in the fuel pipe passing through the hollow part. In addition, in the case of a hollow piezoelectric element, it is necessary to prevent the fuel pressure of gasoline from being applied to the hollow piezoelectric element because the piezoelectric element is weak against a radial force from inside to outside. Considering these facts, the inner diameter of the piezoelectric element is required to be about 11 mm in order to secure a space for disposing a pipe, a plunger and the like passing through the hollow portion. Also, hollow elements (hollow piezoelectric elements) are vulnerable to unbalanced loads, and when trying to ensure soundness,
The outer diameter of the element must be at least 19 mm to 20 mm.
In addition, considering that the lead wire of the piezoelectric element is wired to the electrode lead-out part and that the piezoelectric element is fixed inside the injector, the bore diameter (outer diameter) of the injector becomes 25 mm or more, which is a limitation when mounting it on the engine. Occurs.

FIG. 2 is a schematic view showing the configuration of a fuel injection system using a piezoelectric injector according to an embodiment of the present invention. The injector portion has the same structure as that of FIG. Electrode 17
An electric signal 205 for driving the piezoelectric element 11 is applied from the drive circuit 204 via the. The drive circuit 204 is controlled by a control signal 203 from the control circuit 202. The control circuit 202 generates a control signal 203 based on information 201 from various sensors and the like. Further, the fuel is supplied to the fuel introduction unit 33 from the fuel pump 207 via the pipe 206. Fuel is supplied from a fuel tank 209 to the fuel pump 207 via a pipe 208.

FIG. 3 is a view showing in detail an electrode take-out part according to the embodiment of the present invention. FIG. 4 shows a cross-sectional structure of the electrode extraction portion. The electrode take-out part 20 was welded to the inner tube 12 or used as a cutout from the integral body together with the inner tube 12. The electrode take-out part 20 was provided with a fuel through-hole 19 (flow path) through which fuel passed. As shown in FIG. 4, the electrode 17 and the electrode 1 are located at positions away from the fuel through hole 19 (flow path).
7 is provided with an electrical insulating portion 18 that electrically insulates 7 from the outside (for example, the electrode take-out portion 20). As shown in FIG. 3, packings 27 are provided on the outer tube side and the inner tube side, respectively, to prevent fuel leakage. With this configuration, the top feed of the fuel has become possible.

The configuration shown in FIG. 3 has high safety because the current path to the piezoelectric element 11 is completely isolated from the fuel.
In particular, since the joint between the electrode 17 and the lead wire (not shown) of the piezoelectric element 11, which is liable to cause a joint failure, is immersed in the silicone oil filled in the inner tube 12, spark is less likely to occur. Even if it happens, there is little chance of igniting the fuel.

Further, the lead wire of the piezoelectric element 11 and the electrode 1
If the joint with the cover 7 is covered with an electrically insulating member, double measures to prevent ignition can be achieved, and the safety is further improved.

In general, gasoline contains moisture and acid, and when the piezoelectric element is immersed in the gasoline, the piezoelectric element may be deteriorated. In the case of the injector having the structure shown in FIGS. 1, 3 and 4, since the piezoelectric element 11 is not in contact with gasoline, it is not necessary to overcoat the piezoelectric element with a special insulating substance.

FIG. 5 shows a sectional structure of a modification of the present invention. The injector shown in FIG. 5 is obtained by joining a part of the inner pipes 12, 31 and a part of the outer pipes 13, 32 by welding. As compared with the injector using the rubber packing 27 as shown in FIG. 1, a thinner injector can be configured. Other than welding, for example, if the number of joints by caulking is increased, the same effect as in welding can be obtained. Other configurations are the same as those in FIG.

FIG. 6 shows a sectional structure of a piezoelectric injector according to another embodiment of the present invention. The injector shown in FIG. 6 is also basically a direct-acting type (for example, a method in which a liquid is not interposed in driving the plunger 14 by the piezoelectric element 11) and a top feed type (for example, the fuel supply from the fuel tank to the injector is performed by the plunger). 14, the back side of the piezoelectric element 11 (high (head) side in the usage of the injector)
). As in the configuration of FIG. 1, a 5 mm × 5 mm × 40 mm laminated element was used as the piezoelectric element 11. The piezoelectric element 11 was supported by a movable member 16 of φ10 mm × 15 mm via a bellows 29, and the movable member 16 was disposed in an inner tube 31 filled with silicone oil. The inner pipe 31 is arranged inside the outer pipe 32, and the fuel is supplied from the fuel introduction section 33 to the tip of the injector through the space between the outer pipe 32 and the inner pipe 31. Other components of the injector were the same as those of the injector of FIG. With the structure of FIG. 6, the valve can be opened and closed at a high speed, and a space-saving injector can be configured. The bellows 29 (or diaphragm) between the movable member 16 and the piezoelectric element 11 shown in FIG. 6 is deformed by a driving force when a difference in thermal expansion between the piezoelectric element 11 and the injector component occurs. On the other hand, in the configuration of FIG. 1, the bellows 29 or the diaphragm is deformed as the valve is opened and closed. When the deformation due to the difference in thermal expansion is compared with the deformation due to the opening and closing of the valve, the former is overwhelmingly less in number of times. Therefore, the structure shown in FIG. 6 can easily secure the reliability of the deformable member as compared with the structure shown in FIG.

Here, before concretely describing the method of alleviating the difference in thermal expansion, the thermal expansion of the piezoelectric element will be described. Table 1
Is an example of the measurement result of the thermal expansion coefficient of the piezoelectric element 11.

[0040]

[Table 1]

The measurement was performed in three ways: the lead wire of the piezoelectric element 11 was opened, short-circuited, and applied with 250 V. As a result, the average thermal expansion coefficients at a temperature of −40 ° C. to 20 ° C. are 7.0 ppm / ° C., −2.0 ppm / ° C., and −2.0 ppm, respectively.
The average thermal expansion coefficients at 2 ppm / ° C and 20 ° C to 150 ° C are 4.3 ppm / ° C, 0 ppm / ° C, and -2.5 ppm / ° C, respectively.
° C, and the thermal expansion characteristics of the piezoelectric element greatly changed depending on the electrical conditions. It has also been found that these values are affected by the temperature and electrical history of the piezoelectric element.

In the case of an injector, since the temperature condition or electrical condition of the piezoelectric element changes every moment, a method used for a normal structural material, for example, a structural member having a different thermal expansion coefficient from that of the piezoelectric element is attached to the piezoelectric element. Although a method of compensating for thermal expansion with peripheral members is also possible, further contrivance is desirable.

Also, since the thermal expansion characteristics of the piezoelectric element are extremely complicated, it is possible to prepare some database and compensate for the difference in thermal expansion by active control (control of the electric field applied to the piezoelectric element). Further improvement is desirable. A mechanism for reducing the difference in thermal expansion manufactured in consideration of these points will be described with reference to FIG.

FIG. 7 is a diagram showing the operation principle of the damper according to the embodiment of the present invention. As described above, the movable member 34 as a damper and the spring 35 are disposed inside the inner tube 31 and the inner tube 3
1 was filled with silicone oil 36. Piezoelectric element 1
One of them is connected to the movable member 34 via the support member 57. Silicon oil is used for the deformable diaphragm 1
1 can be reduced by the expansion and contraction operation of the spring 35. By the way, the piezoelectric element is connected to the plunger 14 in a state of receiving the elastic force. These members are connected to the housing 56
Covered by The movable member 34 is configured to be pressed by a spring 35 with a constant spring pressure. Thus, a difference in thermal expansion of the piezoelectric element 11 caused by a change in the temperature of the injector can be reduced by the expansion and contraction operation of the spring 35. By the way, when the movable member 34 moves in accordance with the expansion and contraction operation of the piezoelectric element 11 by the electric signal, there is a problem that the plunger does not separate from the tip of the injector and does not open. In this sense, the movable member 34 does not want to move. Although this is a contradictory request to relaxation of thermal expansion, thermal expansion of the piezoelectric element 11 is a phenomenon on the order of one second, and expansion and contraction of the piezoelectric element 11 by an electric signal is a phenomenon on the order of 10 ^-4 seconds. is there.
Therefore, using this point, it is possible to satisfy conflicting demands.

First, the movable member 34 is required to move in accordance with the difference in thermal expansion when the temperature changes, and the movable member 34 needs to have the ability to follow the difference in thermal expansion in a state where the temperature of the injector is the most severe. . This value was obtained from the temperature change rate of the injector (piezoelectric element), the difference in the coefficient of thermal expansion between the piezoelectric element and the constituent members of the injector, and the element length of the piezoelectric element. Then, the damper moving speed for following the difference in thermal expansion became about 0.1 μm / s or more. On the other hand, when the element expands and contracts due to opening and closing of the valve, it is necessary to act as a fixed end, and the moving speed allowed for the movable member was obtained from the change in stroke allowed during fuel injection. as a result,
It has been found that the moving speed of the damper to act as an acceptable fixed wall is less than about 500 μm / s. From the above examination results, the condition that both the relaxation of the thermal expansion and the function as the fixed end can be satisfied is that the moving speed of the damper is in the range of 0.1 μm / s to 500 μm / s as shown in FIG. desirable.

Next, regarding the movable range of the movable member, the operating temperature range of the injector is -40 ° C. or more and 150 ° C. or less, the thermal expansion coefficient of the piezoelectric element and the injector structural member, Taking into account the contraction of the piezoelectric element, expansion of the housing, contraction of the piezoelectric element due to spring pressure, and depolarization, the movable range of at least -150 μm or more and 40 μm or less when the stationary point of the movable member at room temperature is taken as the origin. Is necessary.

With the above in mind, some ideas for creating an injector will now be described.

First, when the movable portion structure shown in FIG. 7 was prototyped and fuel was supplied, the load applied to the piezoelectric element 11 was small with the large injector of the support member 57, and the valve was not completely closed. This is for the following reason. 7 ~ at fuel supply
Since a pressure of 12 MPa is applied to the silicone oil 36,
The silicone oil 36 causes a volume reduction of about 1%.
It is considered that when the size of the support member 57 of the diaphragm 15 increases, the deformation area of the diaphragm 15 decreases, and the deformation cannot follow the volume change of the silicone oil. As a result, the fuel pressure and the internal pressure of the silicone oil 36 do not match, and the fuel pressure, the internal pressure of the silicone oil, and the stress generated in the diaphragm 15 are applied to the plunger 14 to the drag from the springs 25, 35, and the housing 56. Is considered to have stopped at a position shifted from the position at which it originally stopped. Further, since the compression rate of the silicone oil 36 or the elastic constant of the diaphragm changes due to the change in temperature, the piezoelectric element 11
It has also been found that the force applied to has a temperature dependence. Considering the above-mentioned causes, as a solution, it is desirable to increase the amplitude of the irregularities of the diaphragm as much as possible and enlarge the deformation area. In reality, the dimensions and shape of the diaphragm are limited due to space problems or diaphragm strength problems.

Using a substantially flat diaphragm 15 made of fluorine rubber, the diameter of the support member 57 was changed, and a condition under which a predetermined force (about 10 kgf) was applied to the piezoelectric element 11 was searched. Cross-sectional area of the area where the pressure-receiving area is surrounded by the partition wall (cross-section perpendicular to the central axis direction of the injector)
It has been found that it is better to set the value to 1/3 or less.

As a similar solution, as shown in FIG. 9, a spring 35 is attached to the piezoelectric element 11 via a bellows 41 which is smaller than the housing 56 (at least enough to cover the piezoelectric element 11). It was also found that a configuration for applying force from was effective. Table 2 shows the diameter (mm) of the bellows when the fuel pressure is 7 MPa (in Table 2, it is indicated as the pressure receiving portion dimension).
And the force applied to the movable member 34 by the fuel (see Table 2).
Then, the fuel pressure load (kgf) is displayed. ). When the bellows diameter is 2 mm, the fuel pressure load is 2.2 kgf. When the bellows diameter is 3 mm, the fuel pressure load is 4.9 kgf.
When the bellows diameter is 4 mm, the fuel pressure load is 8.8 kgf. When the bellows diameter is 6mm, the fuel pressure load is 19.7kgf
It is. As can be seen from Table 2, when the diameter of the bellows is reduced, the load from the fuel side to the movable member 34 side is reduced. It has been found that if this value is made sufficiently smaller than the force of the spring 35, the force for pushing the piezoelectric element 11 toward the plunger 14 can be kept substantially constant.

[0051]

[Table 2]

FIG. 10 shows an elastic member 42 (for example, a fluorine-based rubber) in a silicone oil 36 in order to reduce a change (a difference depending on a place) of a load generated by a damper (a structure including the movable member 34 in the figure). An example in which is arranged is shown. 7 to 10 omit fuel flow paths and the like for illustration.

FIG. 11 is a diagram showing the relationship between the position of the diaphragm (movable member 34) and the drag according to the embodiment of the present invention. As shown by the curve 111 in FIG. 11, when the elastic member 42 is not provided, the internal pressure (drag) generated in the silicon oil 36 with respect to the fuel pressure is compared with the case where the elastic member 42 shown by the curve 112 is provided. Then, it rapidly changes depending on the position of the movable member 34 (ΔX in the figure is smaller in the case of the curve 111 than in the case of the curve 112). Strictly speaking, the force received by the piezoelectric element 11 is the fuel pressure, the internal pressure of the silicon oil 36, the spring 25, the spring 35, and the plunger 14.
6 is determined by the balance of the drag received from 6, the pulling force of the diaphragm, etc., and under the condition that the piezoelectric element is at rest,
These resultant forces are zero. Therefore, if any one of them has a characteristic that greatly changes depending on the position of the movable member 34, the force received by the piezoelectric element 11 also decreases.
It changes depending on the position.

When the elastic member 42 is arranged as shown in FIG. 10, the rate of change of the drag generated by the position of the movable member 34 is reduced as shown by the curve 112 in FIG. 11, and the load on the piezoelectric element 11 is also movable. It is less affected by the position of the member 34. As a result, a predetermined force could always be applied to the piezoelectric element 11 side.

In the above-described embodiment, the deformable member such as the diaphragm or the bellows is provided at one place, but the same object can be achieved by providing two or more deformable members.

For example, FIG. 12 shows that the bellows 41 and the bellows 43 are provided as deformable members, so that the fuel pressure and the inner pipe 3 can be reduced.
1 shows a structure in which a force is balanced with the silicone oil 36 in 1 and a load is applied to a piezoelectric element (not shown) by a spring 35 fixed to the inner tube 31.

When it is intended to secure a large movable range with one diaphragm, the diameter tends to be large. However, as shown in FIG. 13, two or more deformable members (bellows 41 and bellows 43) are provided. . Movable member 34
Is formed with a flow channel 45 for the silicone oil 36. If a piezoelectric element such as bellows 41 and 43 (not shown, but the positional relationship is the same as in FIG. 1 and the like) extending in the axial direction is used, a damper having a small diameter is obtained.
It is easy to reduce the diameter of the injector.

In the above embodiment, the damping effect is basically realized by the sliding resistance when the silicone oil 36 passes between the movable member 34 and the inner tube 31. On the other hand, it has been found that the same function can be realized by allowing the silicone oil to pass through the flow path 45 inside the movable member as shown in FIG. Next, considering the responsiveness of the injector, in order to achieve high responsiveness with the injector having the structure shown in FIG. 1, the diaphragm 15 is formed into a thin-walled shape so that the diaphragm 15 does not affect the movement of the plunger 14. Need to be something. In this case, at the time of assembling the injector, a load exceeding an allowable value is applied to the diaphragm or the bellows by the spring 25, which may be damaged.

The embodiment shown in FIG. 14 shows a countermeasure against this possibility. The stopper 46 prevents the diaphragm 15 from being excessively displaced, thereby improving the soundness of the diaphragm 15.

Further, as in the embodiment shown in FIG.
A stopper 47 can also be provided at the tip of the second. The stopper 47 has an opening through which the plunger 14 passes. This prevents the diaphragm 15 from being excessively displaced. Therefore, when assembling the injector, the spring 2
By using No. 5, a load exceeding the allowable value was not applied to the diaphragm 15 or the bellows, and the damage of the diaphragm 15 and the like could be further prevented.

In the case of the injector shown in FIG. 1, a pressure distribution is generated in the inner tube 12 with the movement of the diaphragm 15, and the flow of the sealed silicone oil occurs, which may act as a resistance to the movement of the diaphragm. sell. Therefore, in order to solve this problem, an elastic member 48 made of a fluorine-based rubber shown in FIG. 16 is provided near the diaphragm. As a result, the elastic member 48 absorbs minute pressure fluctuations and suppresses oil flow, so that a decrease in responsiveness can be suppressed.

FIGS. 17 and 18 are views showing a sectional structure of an injector using a ball joint according to an embodiment of the present invention. In FIG. 17, a ball joint 50 is provided between the plunger 14 and the diaphragm 15 on the long axis of the piezoelectric element 11 (in a direction showing large expansion and contraction). Since the unbalanced load applied to the piezoelectric element 11 can be reduced, the piezoelectric element 1
1 can be prevented. In FIG. 18, the diaphragm 15
A ball joint 50 was placed between the piezoelectric element 11 and the long axis of the piezoelectric element 11 (a direction showing large expansion and contraction). Also in this case, since the unbalanced load applied to the piezoelectric element 11 can be reduced, the breakage of the piezoelectric element 11 can be prevented.

FIG. 19 is a view showing a cross-sectional structure of the nozzle portion of the injector according to the embodiment of the present invention. FIG. 20 is a diagram showing the relationship between the stroke and the flow rate of the injector according to the embodiment of the present invention. In general, the stroke of a piezoelectric element is temperature-dependent, and in practice, each of the manufactured elements has a slight difference in stroke. If the difference in stroke is directly reflected in the flow rate, a difference occurs in the flow rate characteristics of each injector. Therefore, the cross-sectional area A of the flow path between the ball valve 51 at the tip of the plunger and the injector nozzle section 52 (at the time of maximum displacement) shown in FIG. If the area is smaller than the flow path cross-sectional area B (orifice flow rate control type in FIG. 20), the relationship between the flow rate and the stroke is as shown in FIG. It shows the characteristic that saturates, and by using this characteristic,
The effects of temperature dependence and variation of the stroke of the piezoelectric element can be reduced. In the stroke dependent type in FIG. 20, the cross-sectional area A of the flow path between the ball valve 51 at the tip of the plunger 14 and the injector nozzle portion 52 (at the time of maximum displacement) is determined by changing the cross-sectional area A of the tip of the injector nozzle portion. That is, it is larger than the flow path cross-sectional area B which is the cross-sectional area of the flow path.

FIG. 21 is a diagram showing a cross-sectional structure of an injector using a fixing member according to an embodiment of the present invention. In piezoelectric injectors, even if the partial load on the piezoelectric element is small, the piezoelectric element is driven at a high speed.
In some cases, the piezoelectric element caused a rotational movement and the lead wire of the element was disconnected. FIG. 21 shows an example of a countermeasure for this problem, in which a fixing member 58 in which a rectangular groove slightly larger than the piezoelectric element 11 is dug between the diaphragm 15 and the piezoelectric element 11 is provided. 11 could be prevented from rotating. The groove of the fixing member 58 is inserted into the piezoelectric element 1 such that one end of the piezoelectric element 11 having a generally rectangular cross-section is fitted.
It is a square groove slightly larger than 1. Therefore, the groove shape of the fixing member is determined according to the cross-sectional shape of the piezoelectric element 11 whose rotation is to be prevented.

FIGS. 22 and 23 are views showing the cross-sectional structure of the injector nozzle portion according to the embodiment of the present invention. It is also conceivable to provide a stopper on the plunger 14. In this case, there is a problem that a part of the flow path is closed at the moment when the plunger 14 collides with the stopper, thereby slightly affecting the flow rate characteristics. FIG. 22 and FIG.
FIG. 3 shows an embodiment for solving this problem.
In this example, a flow path is formed in a member 55 corresponding to the member 28 in FIG. 1 (which serves to guide the operation of the plunger 14 (has a function of preventing the eccentricity of the operation of the plunger 14)). In the example shown in FIG. 23, the fuel passage 54 is formed in the plunger 14 itself. That is, the ball valve 5
The flow path 54 is formed in the member 53 supporting the first member 1. Thus, the flow rate fluctuation when the plunger 14 collides with or approaches the member 55 can be suppressed. Also, it was found that by restricting the movement of the plunger 14 in the direction perpendicular to the axis by the member 55, the reproducibility of the injection characteristics can be improved and the frequency of breakage of the tip of the plunger 14 can be reduced.

Next, FIG. 24 is a view showing the operation of the injection system using the injector according to the embodiment of the present invention. FIG. 25 is a diagram illustrating the relationship between the premix ratio and the NOx emission amount according to the embodiment of the present invention.

FIG. 24 shows an embodiment relating to a fuel injection system using a piezoelectric injector according to the present invention. As shown in the right column of the figure, the cylinder 2 of the internal combustion engine (engine)
A piston 244 is provided in 43, and a piezoelectric injector 242 for supplying fuel in a direct injection manner into a combustion chamber formed by the spark plug 241 and the inner wall of the cylinder 243 and the piston 244 is provided above the piston 244. At present, purification of exhaust gas is strongly desired, and in particular, reduction of NOx is an important technically difficult task. As shown in the graph of the comparative example in the left column of FIG. 24, the general direct injection engine injected fuel once in the compression stroke (for example, 15 mcc). In this case, as shown in the upper right column of FIG. As described above, there is a problem that the fuel is concentrated, the combustion temperature is too high locally, and NOx is easily generated.

On the other hand, as shown in the graph of the multistage injection in the left column of FIG. 24, the fuel injection is divided into an intake stroke (for example, 12 mcc) and a compression stroke (for example, 3 mcc), and the fuel injection amount in the compression stroke is reduced. When the amount is reduced, the concentration of the fuel is prevented, and the local temperature rise can be reduced, so that the NOx can be reduced.

The ratio of the premixing in the intake stroke is set to 0.7 to
By setting the ratio to 0.9, the NOx emission can be reduced to about 1/2 as shown in FIG.

The features of the present invention will be exemplified below.

1. In an injector comprising a plunger for opening and closing the fuel passage, a solid piezoelectric element for driving the plunger, a spring for driving the plunger, a jig for fixing these, a housing (the outermost structural member of the injector), and the like, A structure (partition) is provided around the member supporting the element and the piezoelectric element to separate them from the fuel, and the fuel is passed between the housing and the partition, or a hole serving as a flow path is formed in a part of the housing. To supply the fuel to the injector tip, and to arrange the joint (fuel introduction part) between the fuel supply line and the injector behind (or behind) the piezoelectric element when viewed from the plunger.

2. The above 1. , A member having an electrode for mounting a lead wire of a piezoelectric element is provided, and a flow path through which fuel passes is provided at a position away from the electrode of the member.

3. Protection that protects the piezoelectric element against fuel in an injector composed of a plunger that opens and closes the fuel passage, a solid piezoelectric element that drives the plunger, a spring that drives the plunger, a jig that fixes these, and a housing. A film (overcoat) is applied to the piezoelectric element, fuel is supplied to the tip of the injector by passing between the piezoelectric element and the partition wall, and a joint (fuel introduction section) between the fuel supply line and the injector is moved from the plunger. To see, it is arranged behind the piezoelectric element.

4. Moving speed of a movable member that supports a piezoelectric element in an injector including a plunger that opens and closes a fuel passage, a solid piezoelectric element that drives the plunger, a spring that drives the plunger, a jig that fixes them, and a housing. Is 0.1 when the injector operates.
The range is from μm / s to 500 μm / s.

5. In an injector including a plunger that opens and closes a fuel passage, a solid piezoelectric element that drives the plunger, a spring that drives the plunger, a jig that fixes them, and a housing, the movable member that supports the piezoelectric element is at room temperature. When the stationary point at the time is set as the origin, it is possible to move at least from −150 μm to 40 μm.

6. The above 1. Or 3. , A piezoelectric element is supported by a movable member (for example, a damper) connected to a spring attached to a fixed member, a fluid is filled around the movable member, and a part of a partition (for example, a diaphragm or a bellows) is deformable. (Also referred to as bellows).

7. 6 above. In the above, a supporting member for the piezoelectric element is provided at the center of the deformable member, and the pressure receiving area of a surface of the supporting member perpendicular to the central axis in the longitudinal direction of the injector is reduced by the cross section of the region surrounded by the partition wall (the center of the injector). (Area perpendicular to the axis).

8. 6 above. In the, in the pressure received by the deformable member from the fuel, the axial force of the plunger,
This is to make the force smaller than the force of the spring attached to the movable member.

9. 6 above. , A deformable member (for example) is provided in the fluid on the side opposite to the piezoelectric element when viewed from a movable member (for example, a damper).

10. 6 above. In the above, two or more deformable members are provided on a partition provided around the movable member.

11. 6 above. Is to form a flow path through which fluid can pass inside the movable member.

12. The above 1. Or 3. In the above, the movable range of the movable member supporting the piezoelectric element is limited by a part of the partition wall or a member attached thereto.

13. The above 1. , 3. , 4. Or 5. In the above, an elastic member is provided inside a structure provided around the piezoelectric element and separating the fuel and the element.

14. The above 1. , 3. , 4. Or 5. , A ball joint is provided in a part of a member for mechanically connecting the piezoelectric element and the plunger.

15. The above 1. , 3. , 4. Or 5. In the above, the flow path cross-sectional area of the nozzle at the tip of the injector is made smaller than the flow path cross-sectional area between the plunger tip and the nozzle in the valve-open state.

16. The above 1. , 3. , 4. Or 5. In the above, a movable member of the plunger is limited and a structural member through which fuel can pass is provided.

17. The above 1. , 3. , 4. Or 5. Is to limit the movable range of the plunger and form a flow passage through which fuel passes inside the plunger.

18. The above 1. , 3. , 4. Or 5. In the above, there is provided a member for restricting the movement in the direction perpendicular to the axis of the plunger.

19. The above 1. , 3. , 4. Or 5. In the method, a member for restricting rotation of the piezoelectric element in the axial direction is joined to the piezoelectric element.

20. The above 1. , 3. , 4. Or 5. Is to inject fuel in both the intake stroke and the compression stroke by using the piezoelectric injector described in (1), and to make the injection amount in the compression stroke smaller than the injection amount in the intake stroke.

21. 20. In this case, the ratio of the injection amount in the intake stroke is set to 0.7 to 0.9.

As described above, it is possible to realize a high-speed response injector which has a space-saving structure, maintains soundness over a wide range of temperatures, and can exhibit stable characteristics. In addition, N in exhaust gas
A fuel injection system effective for reducing Ox can be constructed.

[0093]

According to the present invention, it is possible to provide a fuel supply injector suitable for an internal combustion engine. Further, according to the present invention, it is possible to provide a fuel injection system capable of reducing NOx in exhaust gas.

[Brief description of the drawings]

FIG. 1 is a diagram showing a sectional structure of a piezoelectric injector according to an embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional structure of a piezoelectric injector according to a comparative example of the present invention.

FIG. 3 is a view showing in detail an electrode take-out portion of the piezoelectric injector according to the embodiment of the present invention.

FIG. 4 is a diagram showing a cross-sectional structure of an electrode take-out portion of the piezoelectric injector according to the embodiment of the present invention.

FIG. 5 is a diagram showing a cross-sectional structure of an example of the present invention.

FIG. 6 is a diagram showing a cross-sectional structure of a piezoelectric injector according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a schematic configuration of a damper according to an embodiment of the present invention.

FIG. 8 is a diagram showing an allowable moving speed of the movable member according to the embodiment of the present invention.

FIG. 9 is a diagram showing a schematic configuration of an injector using a bellows according to an embodiment of the present invention.

FIG. 10 is a diagram showing a cross-sectional structure of an injector using an elastic member according to the embodiment of the present invention.

FIG. 11 is a diagram showing the relationship between the position of the diaphragm and the drag according to the embodiment of the present invention.

FIG. 12 is a diagram showing a cross-sectional structure of an injector having a bellows according to an embodiment of the present invention.

FIG. 13 is a diagram showing a cross-sectional structure of an injector having a flow path formed in a movable member according to the embodiment of the present invention.

FIG. 14 is a diagram showing a cross-sectional structure of an injector provided with a stopper according to the embodiment of the present invention.

FIG. 15 is a diagram showing a cross-sectional structure of an injector provided with a stopper according to the embodiment of the present invention.

FIG. 16 is a diagram showing a cross-sectional structure of an injector using an elastic member according to the embodiment of the present invention.

FIG. 17 is a diagram showing a cross-sectional structure of an injector using a ball joint according to an embodiment of the present invention.

FIG. 18 is a diagram showing a cross-sectional structure of an injector using a ball joint according to an embodiment of the present invention.

FIG. 19 is a diagram showing a cross-sectional structure of a nozzle portion of the injector according to the embodiment of the present invention.

FIG. 20 is a diagram showing the relationship between the stroke and the flow rate of the injector according to the embodiment of the present invention.

FIG. 21 is a diagram showing a cross-sectional structure of an injector using a fixing member according to an embodiment of the present invention.

FIG. 22 is a diagram showing a cross-sectional structure of an injector nozzle according to an embodiment of the present invention.

FIG. 23 is a diagram showing a cross-sectional structure of an injector nozzle according to an embodiment of the present invention.

FIG. 24 is a diagram showing the operation of the injection system using the injector according to the embodiment of the present invention.

FIG. 25 is a diagram illustrating a relationship between a premix ratio and a NOx emission amount according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Piezoelectric element, 12, 31 ... Inner tube, 13, 32 ... Outer tube, 14 ... Plunger, 15 ... Diaphragm, 16 ... Movable member, 17 ... Electrode, 18 ... Electric insulating part, 19 ... Fuel through hole, 20 ... Electrode take-out part, 21 ... welded part, 22 ... casing, 25, 26, 35 ... spring, 27 ... packing,
28, 53, 55 ... members, 29, 41, 43 ... bellows,
33: fuel introduction part, 34: movable member, 36: silicone oil, 42, 48 ... elastic member, 45, 54, 59 ... flow path, 46, 47 ... stopper, 50 ... ball joint,
51: ball valve, 52: injector nozzle, 56,
Reference numeral 60: housing, 57: support member, 58: fixing member.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Minoru Osuka 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Toshiharu Nogi 7-1 Omikacho, Hitachi City, Ibaraki Prefecture No. 1 Hitachi, Ltd., Hitachi Research Laboratory (72) Inventor Takuya Shiraishi 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Yoshio Okamoto Tsuchiura, Ibaraki Prefecture 502 Nachi-machi Machinery Research Laboratory Co., Ltd. (72) Inventor Yoshiyuki Tanabe 2520 Oji Takaba, Hitachinaka City, Ibaraki Prefecture Hitachi, Ltd.Automotive Equipment Division (72) Inventor Yasuhisa Hamada Takaba, Hitachinaka City, Ibaraki Prefecture 2477 F-term in Hitachi Car Engineering, Ltd. (reference) 3G066 AA02 AB02 AD12 BA19 BA25 BA 33 BA40 BA67 CC01 CC06T CC06U CC08U CC51 CC64U CC66 CD10 CD14 CD16 CD17 CD26 CD28 CD29 CD30 CE27 CE30 CE34

Claims (15)

[Claims] 1. An injector comprising: a plunger for opening and closing a fuel passage; a piezoelectric element having a solid structure for driving the plunger; a partition wall for separating the piezoelectric element from fuel; Is passed between the housing and the partition wall, or provided with a hole serving as a flow path in a part of the housing, and supplied to the tip of the injector,
Looking at the fuel introduction section to the injector from the plunger,
An injector, which is disposed behind a piezoelectric element. 2. The injector according to claim 1, further comprising a member having an electrode for mounting a lead wire of the piezoelectric element, and a flow path through which fuel passes at a position distant from the electrode. 3. An injector having a plunger for opening and closing a fuel passage, a piezoelectric element having a solid structure for driving the plunger via a solid or elastic body, and a housing for holding the same. And a piezoelectric element having a protective film for protecting the fuel from passing through the piezoelectric element and supplying the fuel to the tip of the injector, and having a fuel introduction portion for the injector on the rear side of the piezoelectric element when viewed from the plunger. And the injector. 4. A plunger for opening and closing a fuel passage, a solid piezoelectric element for driving the plunger, and a movable member for supporting the piezoelectric element, wherein the moving speed of the movable member is 0.1 μm / s when the injector operates. An injector characterized by being in the range of ５００500 μm / s. 5. A plunger for opening and closing a fuel passage, a solid piezoelectric element for driving the plunger, and a movable member for supporting the piezoelectric element, wherein the movable member for supporting the piezoelectric element sets a stationary point at room temperature. At least -150 μm from the origin
An injector capable of moving by 40 μm. 6. The piezoelectric element according to claim 1, wherein the piezoelectric element is supported by a movable member connected to a spring attached to the fixed member, a fluid is filled around the movable member, and a part of the partition can be deformed. An injector provided with a member. 7. The piezoelectric element according to claim 6, wherein a supporting member for the piezoelectric element is provided at a central portion of the deformable member, and a pressure receiving area of a surface of the supporting member perpendicular to a central axis in a longitudinal direction of the injector is surrounded by a partition wall. Characterized in that the area of the cross section (cross section perpendicular to the central axis of the injector) of the region is reduced to 1/3 or less. 8. The injector according to claim 6, wherein an axial component of the plunger of the pressure received by the deformable member from the fuel is smaller than a force of a spring attached to the movable member. 9. The injector according to claim 6, wherein a deformable member is provided in the fluid on a side opposite to the piezoelectric element as viewed from the movable member. 10. The injector according to claim 6, wherein a flow path through which a fluid can pass is formed inside the movable member. 11. The injector according to claim 1, wherein the movable range of the movable member supporting the piezoelectric element is limited by a part of the partition wall or a member attached thereto. 12. An injector according to claim 1, wherein an elastic member is provided inside a structure provided around the piezoelectric element and separating the fuel and the element. 13. A fuel injection system for an automobile,
A fuel injection system comprising the piezoelectric injector according to claim 1, claim 3, claim 4, or claim 5. 14. Injecting fuel in both an intake stroke and a compression stroke by using the piezoelectric injector according to claim 13.
A fuel injection system wherein the injection amount in the compression stroke is smaller than the injection amount in the intake stroke. 15. The method according to claim 13, wherein
A fuel injection system wherein the ratio of the injection amount in the intake stroke is set to 0.7 to 0.9.