JPH11153068A - Pressure accumulation type fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten an injection time by increasing a flow rate of injecting fuel without increasing a demand pressure reducing amount of the pump chamber of a pressure accumulation type fuel injection valve for an internal combustion engine and increasing size. SOLUTION: A diameter of a push rod 1 is set to a value lower than that of the guide part 26 of a nozzle needle 9 or the sectional area of the push rod 1 is reduced to a value lower than that of the guide part 26, and set to a value higher than a difference between the sectional area of the guide part 26 and that of a sheet part 32. Since this constitution reduces a stroke volume of the push rod 1, a demand pressure reduction amount of a pump chamber 5 to hold the nozzle needle 9 in an opening state is decreased and the load of an actuator 4 is decreased. When the output of the actuator 4 is the same, a lift amount higher than that of the nozzle needle 9 is obtained and a sheet diameter is expanded, whereby an injection period is shortened through the increase of a flow rate of fuel. The nozzle needle 9 may be formed integrally with the push rod 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve which can be used in an internal combustion engine, and more particularly, to a fuel injection valve having a pressure accumulator, in which fuel pumped by an intermittent pressure pump is once accumulated in a pressure accumulator and then injected. The present invention relates to a so-called accumulator type fuel injection valve.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 4-67026 discloses a conventional example of an accumulator type fuel injection valve. In fuel injection valves used for internal combustion engines as well as pressure-accumulation type fuel injection valves, it is an issue to shorten the injection period as much as possible,
As a general method for that, increasing the fuel pressure is considered, but if the pressure of the fuel supplied to the fuel injection valve is increased, the penetrating force of the injected fuel spray increases, so that the cylinder bore and the piston It is inevitable that fuel adheres to the walls and causes problems.

Therefore, as another method, it is conceivable to shorten the injection period by enlarging the flow path of the injected fuel by enlarging the flow path in the fuel injection valve. , Or the amount of lift needs to be increased. However, if the seat diameter or the lift amount is set to be large, the stroke volume in the operation of the nozzle needle becomes large. Therefore, in the case of the pressure accumulating type fuel injection valve, the pressure reduction amount of the pump chamber for holding the nozzle needle in the open state is increased. As a result, there arises a problem that the physical size of the actuator of the fuel injection valve increases and the load on the drive circuit increases.

[0004]

SUMMARY OF THE INVENTION The present invention addresses the above-mentioned problems in the prior art by increasing the seat diameter of the nozzle needle or increasing the lift amount in a pressure accumulating type fuel injection valve. Even when the flow rate of the fuel to be increased is increased, it is not necessary to increase the pressure reduction amount of the pump chamber, and therefore, there is no problem that the actuator becomes large or the load on the drive circuit increases, and the fuel injection does not occur. It is an object of the present invention to provide an improved accumulator type fuel injection valve capable of sufficiently shortening the period.

[0005]

According to the present invention, there is provided a pressure-accumulation type fuel injection valve as a means for solving the above-mentioned problems.

[0006] In the pressure accumulating fuel injection valve according to the first aspect, the diameter of the push rod is set smaller than the diameter of the guide portion of the nozzle needle, and in the second aspect, the cross-sectional area of the push rod is set. Is set to be smaller than the cross-sectional area of the guide portion of the nozzle needle and larger than the difference between the cross-sectional area of the guide portion of the nozzle needle and the cross-sectional area of the seat portion. Since the area of the end face of the push rod receiving the fuel pressure in the chamber becomes smaller and the stroke volume of the push rod for the same lift amount also becomes smaller, the pressure in the pump chamber required for the pump piston to drive the push rod and the nozzle needle is reduced. The value of the quantity decreases. Therefore, even if the flow rate of the injected fuel is increased by enlarging the seat diameter of the nozzle needle or increasing the lift amount, it is not necessary to increase the decompression amount of the pump chamber. The fuel injection period of the accumulator type fuel injection valve can be shortened without the problem that the load on the circuit increases.

In the case where the nozzle needle and the push rod are separated from each other and any one of them has at least one contact engagement portion, the nozzle needle and the push rod are sealed around the nozzle needle and the push rod. Means are provided to prevent the fuel from entering the contact engagement portion, and in the invention according to claim 4, the fuel entering the contact engagement portion is discharged to the outside by a discharge means such as a drain port. In either case, fuel is prevented from entering the nozzle needle and the push rod contact engagement portion and the interval is prevented from expanding, and the integrity of the two is maintained, so that high responsiveness to control can be maintained. Become. Of course, claim 5
Such a problem does not occur if the nozzle needle and the push rod are integrated as in the method described in (1).

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a split type accumulator type fuel injection valve according to the present invention. This fuel injection valve is used for injecting fuel into the combustion chamber of a direct injection diesel engine, and one fuel injection valve is provided for each cylinder, for example, four in the case of four cylinders. Fuel pumped from a known intermittent pumping pump (not shown) flows from the fuel inlet 19 into the split accumulator type fuel injection valve as described later, and is filled with the fuel. It is injected from the injection hole 20. The timing of pumping the fuel to the fuel injection valve by the fuel injection pump is not the side with the compression top dead center of each cylinder as in the case of the normal fuel injection valve, but is much earlier than, for example, 180 before the compression top dead center. ° (crank angle) is already over. The amount of oil supplied by the fuel injection pump at one time is adjusted by the lever opening of the injection pump as is conventionally known.

In FIG. 1, reference numeral 1 denotes a push rod (for convenience of manufacture, an upper and lower part is illustrated), the lower end surface of which is in contact with the upper end surface of the nozzle needle 9. The end face faces the control chamber 13, which is urged downward by the set spring 28 and communicates with the pump chamber 5, which is increased and reduced in pressure by the electrostrictive actuator 4, through the fuel passage 12. Reference numeral 2 denotes a holder, above which a fuel inlet port 19 for leading pressurized fuel from an intermittent pressure feed pump (fuel injection pump) (not shown) and a fuel passage 23 thereof, and a fuel for holding the fuel in the pump chamber 5. A check valve sub-assembly 15, which incorporates a first check valve 6 and a second check valve 7 for holding fuel in a pressure accumulating chamber 8, which will be described later, a pump piston 16, and a cylinder 18 for receiving the same in a vertically slidable manner. The piezo holder 14 is fastened to the head by screws.

The piezo holder 14 has a bottomed cylindrical shape, in which the electrostrictive actuator 4, the head of the pump piston 16, and the disc spring 17 are housed. The upper end of the electrostrictive actuator 4 is fixed to the bottom (upper inner surface) of the piezo holder 14, and the lower end is in contact with the upper surface of the pump piston 16. Lower end face of pump piston 16, cylinder 1
8 and the upper end surface of the check valve sub-assembly 15 form the aforementioned pump chamber 5. The pump piston 16 is slidable up and down following the expansion and contraction of the electrostrictive actuator 4. Further, the disc spring 17 urges the pump piston 16 upward and makes the pump piston 16 abut on the electrostrictive actuator 4. As a result, a preset load of about 50 kgf acts on the electrostrictive actuator 4. The pump chamber 5 contracts and increases when the electrostrictive actuator 4 expands and pushes down the pump piston 16 against the disc spring 17, and expands when the electrostrictive actuator 4 contracts. The pressure is reduced.

The electrostrictive actuator 4 is formed by alternately stacking a large number of disk-shaped PZT elements having a diameter of 20 mm and a thickness of 0.5 mm and SUS plates having a diameter of 15 mm and a thickness of 0.02 mm into a columnar shape. The lead wire 22 and the SUS plate are connected so that a voltage can be applied by connecting each PZT element in parallel. The lead wire 22 extends outside the piezo holder 14 and is electrically connected to a drive circuit (not shown) controlled by an electronic control device. The PZT element is typically made of a ferroelectric ceramic obtained by sintering a material mainly containing lead zirconate titanate, and has a strong piezo effect. For example, when a voltage of 500 V is applied in the thickness direction, the thickness increases by 0.5 μm, and conversely, when the battery is discharged from a state where a voltage of 500 V is applied, the thickness decreases by 0.5 μm. Specifically, since the electrostrictive actuator 4 of the present embodiment mechanically couples 200 PZT elements in series and electrically in parallel, a voltage of 500 V is applied or discharged. Thereby, expansion and contraction of 100 μm can be obtained.

The check valves 6 and 7 are provided in parallel fuel passages 24 and 25 penetrating the check valve assembly 15 in the vertical direction, and are formed by a cone or a steel ball and a spring which are pointed toward the upstream side. As long as the fuel from the pump is not pumped, the spring force urges the cone or the steel ball toward the upstream side, and seals with the seat surface to block the flow of fuel.

Reference numeral 3 denotes a hollow accumulator. The push rod 1 penetrates a central vertical hole 29 so as to be slidable in the vertical direction, and an annular accumulator 8 is formed around the accumulator. Second check valve 7 and nozzle body 1
Each oil reservoir 30 communicates with the oil sump 30 formed in the inner space. The accumulator 3 and the nozzle body 10 are positioned by the knock pin 21 and fastened to the holder 2 by the retainer 11. The capacity of the accumulator 8 is set in the range of 3 to 15 ml according to the required injection amount and the injection mode.

A nozzle needle 9 is provided in a nozzle body 10.
Are slidably accommodated in a vertical direction by a large diameter portion 26 serving as a guide portion. The upper end surface of the nose needle 9 is in contact with the lower end surface of the push rod 1 and is thereby urged downward. Oil tightness is maintained by a sheet portion 32 including a conical sheet surface that is pointed downward at the lower end of the nozzle needle 9 and a sheet surface formed on the inner surface of the nozzle 20 of the nozzle body 10. Then, when the two seat surfaces are separated from each other, the fuel in the oil sump 30 is injected from the injection port 20.

The nozzle needle 9 has a stepped shape composed of a large diameter portion 26 and a small diameter portion 27 and a shoulder 39 between them, and the clearance between the nozzle needle 9 and the stepped space in the nozzle body 10 is: Although it is several μm in the large diameter portion 26,
The small-diameter portion 27 is as large as several hundreds to several thousands μm, in which the above-described oil reservoir 30 communicating with the pressure accumulating chamber 8 and the fuel hole 31 is formed.

In the embodiment, the diameter φDp of the push rod 1 is smaller than the diameter (guide diameter) φDg of the guide portion of the needle 9, that is, the large diameter portion 26, and therefore, the sectional area (π / 4) φDp of the push rod 1. ^2, a large cross-sectional area of diameter 26 (π / 4) φDg less than ^2, and (π / 4) (φ
Dg ² −φDs ² ). Where φ
Ds is the sheet diameter, that is, the diameter of the annular sheet portion 32 where the sheet surface at the tip of the needle 9 and the sheet surface of the nozzle 20 are in contact.

The large diameter portion 26 of the needle and the push rod 1 are provided with sealing means such as O-rings 33 and 35 and backup rings 34 and 36 so that fuel can flow between the push rod 1 and the needle 9. Intrusion is prevented, and both members can move up and down as a unit.

[0018] Since accumulator fuel injection valve of the embodiment shown in FIG. 1 has as described above arrangement, in the time chart of the control shown in FIG. 2, the fuel from the intermittent pressure pump at time t ₁ is the injection valve When the pressure is sent to the inlet port 19, the first check valve 6 and the second check valve 7 open when the force generated by the fuel pressure on the upstream side becomes larger than the biasing force of each spring, and the fuel is checked by each check. Flows downstream through the valve. First check valve 6
Is filled in the pump chamber 5, the fuel passage 28 to the upper end face of the push rod 1, and the control chamber 13.
The fuel that has passed through the second check valve 7 is charged into the accumulator 8 and the oil sump 30. When the pressures in the accumulator chamber 8 and the oil sump 30 reach the set pressure, that is, at time t ₂ , the check valves 6 and 7 are closed by the fuel pressure and the spring force, and the fuel passages 24 and 25 are shut off.
By accumulating high-pressure fuel in the pressure accumulating chamber 8 and the oil reservoir 30, preparation for fuel injection is completed.

Next, at time t ₃ , when an electronic control device (not shown) applies a valve opening signal to the drive circuit (the injection signal is turned on), the drive circuit is charged and extended in advance. Since the placed electrostrictive actuator 4 is short-circuited, the electrostrictive actuator 4 is discharged and contracted, whereby the pump chamber 5 is expanded and reduced in pressure, and the pressure in the control chamber 13 is also reduced through the fuel passage 12. Therefore, the acting force acting on the upper end surface of the push rod 1 in the valve closing direction is reduced, and the acting force is the acting force of the fuel pressure of the oil reservoir 30 that pushes up the needle 9, that is, the large diameter of the needle 9. The pressure acting on the area corresponding to the difference between the portion 26 and the seat portion 32 is smaller than the force acting in the valve opening direction caused by the pressure of the pressure accumulating chamber 8 (and the oil sump 30). The needle 9 is raised, the fuel injection valve is opened, and the pressurized fuel in the oil sump 30 is injected from the injection port 20.

Next, at time t ₄ , when the control device applies a valve closing signal (the injection signal is turned off), the electrostrictive actuator 4 is charged and extended by the drive circuit, and the pump chamber 5 is closed. Since the pressure is reduced, the fuel pressure in the control chamber 13 is increased through the fuel passage 12. Thereby, the acting force in the valve closing direction acting on the upper end face of the push rod 1 increases again, and becomes larger than the acting force in the valve opening direction acting on the needle 9 in the oil reservoir 30 upward. Then, the needle 9 is lowered, and the seat portion 32 is closed to be in the valve closed state, so that the injection is stopped. And at a time point t _5, the fuel is pumped from the intermittent pressure pump again. Because it thereafter is the repetition of the same cycle, is one cycle from time t ₁ to time t _5.

Next, the effect of the fuel injection valve of this embodiment will be described. The present invention relates to a conventional injection valve (Japanese Patent Publication 4-6).
Unlike the one described in Japanese Patent No. 7026), by using the push rod 1 smaller than the diameter of the guide portion (large diameter portion 26) of the needle 9, the stroke volume (push) of the push rod 1 (and the needle 9) is increased. It is the value of the cross-sectional area of the rod times the lift amount, and this volume must be absorbed by the pump chamber 5).
Is reduced, the load on the electrostrictive actuator 4 is reduced, and the physique is reduced in size.

For this purpose, in this embodiment, as described above, the cross-sectional area of the push rod 1 is defined as (π / 4) φDg ² > push rod cross-sectional area,> (π /
4) It is set in the range of (φDg ² −φDs ² ). The reason for setting the lower limit to the cross-sectional area of the push rod 1 is that when the cross-sectional area (π / 4) Dp ² of the push rod 1 is equal to (π / 4) (φDg ² −φDs ² ), the intermittent pressure feed is performed. When the fuel is filled in the pressure accumulating chamber 8, the oil sump 30, etc., the fuel acts on the needle 9 upward in the valve opening direction due to the fuel pressure of the oil sump 30, and acts on the upper end surface of the push rod 1 downward. This is because the action force in the valve closing direction due to the fuel pressure in the control chamber 13 is balanced, and it cannot be guaranteed that the fuel injection valve will close reliably.

Incidentally, the spring 28 urged in the valve closing direction at the upper end face of the push rod 1 causes the in-cylinder pressure to be applied to the seat portion 32 of the needle 9 (the area is (π / 4) φDs ² ) during operation of the engine. It has a role of preventing the valve from opening when actuated, and is set so as to balance when the in-cylinder pressure becomes maximum (near top dead center). Accordingly, when the diameter of the push rod 1 is made smaller than this, the biasing force of the spring 28 must be increased to compensate.
The effect of the present invention will be offset.

The upper limit of the cross-sectional area (and diameter) of the push rod 1 is when the push rod diameter φDp and the guide diameter φDg of the needle 9 match. If the push rod diameter is further increased, the stroke volume of the push rod 1 increases, and the amount of pressure reduction in the pump chamber 5 must be increased.

The sealing means including the O-rings 33 and 35 and the backup rings 34 and 36 is provided on the guide portions of the push rod 1 and the nozzle needle 9 because the lower end face of the push rod 1 and the nozzle needle When the push rod 1 and the push rod 1 are formed of a plurality of parts, this is to prevent fuel from penetrating into the contact parts between the push rod 1 and the push rod 1. Since the nozzle needle 9 can move up and down integrally, the needle 9 can be operated while maintaining high responsiveness to control. The sealing means can be modified such as providing only the O-rings 33 and 35 or using other sealing means. The push rod 1 is also divided into two parts in the illustrated example. It is also possible to change to one rod or to divide it into three or more rods. Further, in the illustrated embodiment, the push rod 1 is formed of two parts separate from the nozzle needle 9, but the push rod 1 and the nozzle needle 9 may be integrated in some cases.

FIG. 3 shows another embodiment of the present invention. FIG.
The difference from the embodiment shown in FIG. 13 is that the large diameter portion 26 (guide portion) of the push rod 1 and the nozzle needle 9 is not provided with a sealing means such as an O-ring, but is instead connected to a low pressure side such as a fuel tank. A port 37 is provided in the holder 2, and the port 37 communicates with the vertical hole 29 into which the push rod 1 is inserted by a drain passage 38.

By providing the drain port 37 and the drain passage 38, the pressure near the contact portion between the push rod 1 in the vertical hole 29 and the upper end of the nozzle needle 9 becomes low, and the vertical hole 29
Since the fuel leaked into the inside is discharged to the outside from the drain port 37 and does not remain in the abutting portion, the push rod 1
The nozzle needle 9 is not separated from the nozzle needle 9 and operates integrally, so that the responsiveness of the fuel injection valve to the control can be kept high, and the number of parts is reduced because the sealing means is not required. can do.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an accumulator type fuel injection valve of the present invention.

FIG. 2 is a time chart for explaining the operation of the pressure accumulating fuel injection valve.

FIG. 3 is a longitudinal sectional view showing another embodiment of the accumulator type fuel injection valve of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Push rod 4 ... Electrostrictive actuator 5 ... Pump chamber 8 ... Accumulation chamber 9 ... Nozzle needle 13 ... Control room 16 ... Pump piston 17 ... Disc spring 19 ... Fuel inlet port 20 ... Injector 26 ... Large diameter part (guide part) ) 30 ... oil pool 32 ... seat part 33, 35 ... O-ring 34, 36 ... backup ring 37 ... drain port

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 61/16 F02M 61/16 K (72) Inventor Takehiko Kato 14 Iwatani, Shimowasumicho, Nishio-shi, Aichi Japan Automotive Parts Co., Ltd. Inside the laboratory (72) Inventor Yasuo Sato 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (5)

[Claims] A pressure accumulating chamber for temporarily holding the fuel pumped by an intermittent pressure feed pump in a state of accumulating and communicating with the nozzle, a nozzle needle for opening and closing the nozzle, and an extension for opening and closing the nozzle needle. A push rod provided as a part, a pump piston for controlling fuel pressure of a pump chamber acting on one end surface of the push rod for controlling operation of the nozzle needle, and an actuator for driving the pump piston. A pressure accumulating fuel injection valve, wherein the diameter of the push rod is set smaller than the diameter of a guide portion of the nozzle needle. 2. When the diameter of the push rod is φDp, the diameter of the guide portion of the nozzle needle is φDg, and the diameter of the sheet portion between the nozzle and the nozzle needle is φDs, the cross-sectional area (π / 4) φDp ²
2. The pressure accumulating fuel injection valve according to claim 1, wherein the following conditions are satisfied. (Π / 4) φDg ² > (π / 4) φDp ² > (π / 4) (φ
Dg ² -φDs ² ) 3. A seal means is provided around the nozzle needle and the push rod when the nozzle needle and the push rod are separate bodies and one of them has at least one contact engagement portion. The pressure accumulating fuel injection valve according to claim 1, wherein fuel is prevented from entering the contact engagement portion. 4. When the nozzle needle and the push rod are separate bodies and one of them has at least one contact engagement portion, the fuel that enters the contact engagement portion is discharged to the outside. 4. An accumulator-type fuel injection valve according to claim 1, further comprising means for reducing the pressure. 5. The accumulator type fuel injection valve according to claim 1, wherein the nozzle needle and the push rod are integrated.