JP3503784B2 - Accumulation type fuel injection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention accumulates high pressure fuel in a pressure accumulating pipe (hereinafter referred to as common rail) which is a kind of surge tank, and injects the accumulated high pressure fuel into a diesel engine by an electrically controlled injector. The present invention relates to a pressure accumulating fuel injection device.

[0002]

2. Description of the Related Art Conventionally, high-pressure fuel is pressurized and pressure-fed to a common rail by a high-pressure supply pump to accumulate pressure, and
A pressure-accumulation fuel injection device is known in which high-pressure fuel of this common rail is injected into a diesel engine by an electrically controlled injector. In this configuration, it is necessary to provide a safety device that stops the fuel supply to the injector when an abnormality occurs in the injector.

Further, since the pressure of the high-pressure fuel accumulated in the common rail is extremely high, for example, 150 MPa,
The reflected wave generated from the injector of one cylinder is propagated to the other cylinders via the common rail, affecting the opening / closing timing of the injectors of the other cylinders, and the injection amount and the injection timing vary, so It has already been proposed by the present applicant to provide a check valve for restricting the pressure propagation of fuel from the injector to the common rail by allowing only the fuel supply from the common rail to the injector (Japanese Patent Laid-Open No. 3-124957, Japanese Patent Laid-Open No. Hei 4
-287866).

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The pressure-accumulation fuel injection device disclosed in Japanese Patent No. 957 has a mechanism for interrupting the flow of fuel from the injection valve to the common rail by a ball valve and a compression coil spring.
The pressure-accumulation fuel injection device disclosed in Japanese Patent Laid-Open No. 4-287866 allows only the fuel flow from the common rail to the injector, and interrupts the fuel flow from the injector to the common rail with a plunger valve and a compression coil spring. It has a mechanism.

In any of these prior arts, a valve opening / closing mechanism using a check valve is provided, and a movable portion that is movable according to a vertical pressure difference between the valve inlet side and the valve outlet side is provided. The structure is complicated because a large number of parts are included in the mechanism that allows only the flow of fuel from the common rail to the injector and prevents the reverse flow of fuel from the injector to the common rail side, and the movable part is provided. There is a problem that the injection timing and the fuel injection amount become non-uniform because the reflected wave generated by opening and closing the injector of one cylinder affects the injector opening and closing timing and injection pressure of the own cylinder or another cylinder.

The object of the present invention is to allow only the fuel flow from the common rail to the injector with a simple structure, and to limit the maximum flow rate of the fuel from the common rail to the injector so as to prevent the reverse flow of the fuel from the injector to the common rail side. An object of the present invention is to provide a pressure-accumulation fuel injection device that cuts off the flow.

Another object of the present invention is to reduce the influence of the pressure pulsation generated on the injector side with the opening / closing of the injector on the next injection to the cylinder corresponding to the injector, and to open / close the injection valve. An object of the present invention is to provide a pressure-accumulation fuel injection device in which a reflected wave generated due to the above-mentioned influence on injection in other cylinders is small.

[0008]

According to the pressure-accumulation type fuel injection device of the first aspect of the present invention, the large diameter hole, the conical hole, and the orifice hole of the fluid diode are continuously formed from the pressure accumulation container side toward the injector side. Since it is formed, it allows the high-pressure fuel to be supplied from the pressure accumulator container side to the injector side, and restricts the flow of fuel from the injector side to the pressure accumulator container side. Therefore, the pressure pulsation generated on the inlet side of the injector is limited by the fluid diode. Therefore, it is possible to reduce the influence of the pressure pulsation generated by the opening and closing of the injector on the next injection into the own cylinder, and reduce the influence of the reflected wave generated by the opening and closing of the injector on the injection of other cylinders. it can.

[0009] According to an accumulator fuel injection device according to claim 1, since the conical hole is the passage area in only one direction of the injector-side pressure from the pressure accumulating container side of the fluid diode is gradually reduced, with a simple structure, the injector It is possible to reduce the influence of the pressure pulsation generated by opening and closing on the next injection of the own cylinder, and the water hammer wave is reduced, so that the influence on the injection of other cylinders can be reduced.

[0010] According to an accumulator fuel injection system according to claim 1, conically bevelled seat surface of the fluid diode conical seat surface formed on the pressure accumulating container to abut, is sealed liquid-tightly. According to the pressure-accumulation fuel injection device of the second aspect, the sheet surface of the fluid diode comes into liquid-tight contact with the sheet surface of the pressure accumulator by screwing the screw member on the female screw portion of the accumulator. Thus, the fluid diode
Only processing the Bode I of, since it is possible to secure a fluid flow in one direction, it restricts the fluid flow in the reverse direction,
The pressure pulsation reducing means has an effect that it has a desired fuel supply function and a pressure pulsation reducing function which are both effective and have an extremely simple shape.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 2 shows the entire structure of a fuel injection device for a diesel engine according to one embodiment of the present invention, and FIG. 3 shows injectors provided for each combustion chamber of each cylinder of the engine. First, the configuration of the injector 36 provided for each cylinder of the engine will be described.

In FIG. 3, the lower casing member 1 is composed of a body lower 2, a connecting portion 3 and a nozzle body 4, and the members 2, 3 and 4 are integrated by a retaining nut 5. A valve body sliding hole 6 and a fuel storage chamber 7 are formed in the nozzle body 4, and the fuel storage chamber 7 is formed at the tip.
Is formed with a nozzle hole 8 communicating with. A large diameter portion 10 of a nozzle needle 9 is slidably fitted in the valve body sliding hole 6. A connecting portion 11 is formed on the large diameter portion 10 of the nozzle needle 9, and a small diameter portion 12 and a valve body portion 13 are integrally formed on the lower tip end portion. Then, the valve portion 13 opens and closes the seat portion X to turn on and off the injection from the nozzle hole 8.

A flange 14, a piston pin 15 and a piston 16 are integrally connected to the tip of the connecting portion 11 of the nozzle needle 9. Further, the nozzle needle 9 is biased in the closing direction by the spring 17. The piston 16 is slidably fitted in a cylinder 18 formed in the body lower 2, and a pressure control chamber 19 that faces the end of the front piston 16 is formed in the cylinder 18. A plate valve 20 having an orifice is provided above the pressure control chamber 19 and the plate valve 2
A spring 21 for pressing 0 is provided.

A three-way control valve 22 is provided on the body lower 2.
An upper casing member 23 having (a solenoid valve) is closely connected. That is, the cylindrical body upper 24
Is screwed onto the body lower 2, and the three-way valve body 25 is arranged in the inner hole of the body upper 24.
6 is screwed into the inner hole of the body upper 24. An outer valve 27 is slidably fitted in the three-way valve body 25, and an inner valve 28 is provided in an inner hole of the outer valve 27. When the coil 29 is demagnetized, the outer valve 27 is at the lower position by the force of the spring 30, and the high pressure side passage 31 and the pressure control chamber 19 are located.
And are communicated with each other via the oil passage 32. Also, the coil 29
Is excited, the outer valve 27 moves upward,
The pressure control chamber 19 and the drain passage (low-pressure side passage) 33 communicate with each other through the oil passage 32.

A fuel supply passage 34 is formed in the lower casing member 1, one end of which is exposed at the surface of the casing member (body lower 2) 1 and the other end communicates with the fuel reservoir chamber 7 and the upper portion. Is communicated with the high pressure side passage 31 of the casing member 23. Further, an inlet 35 is screwed into the surface portion of the casing member (body lower 2) 1 at the lower portion thereof and communicates with the fuel supply passage 34.

The high-pressure fuel in the common rail 38, which will be described later, is supplied to the fuel reservoir chamber 7 via the inlet 35 and the fuel supply passage 34, and is also supplied to the three-way control valve 22. The fuel in the drain passage 33 can be drained to the drain tank. Therefore, when high-pressure fuel is supplied to the pressure control chamber 19, the force in the valve closing direction applied from the piston 16 to the nozzle needle 9 under this pressure is applied in the valve opening direction by the pressure in the fuel reservoir chamber 7. Above the nozzle needle 9
Closes the nozzle hole 8. From this state, the three-way control valve 2
2 is controlled so that the pressure control chamber 19 has a drain passage 3 on the low pressure side.
When the fuel in the pressure control chamber 19 flows out to the low pressure side in communication with the nozzle 3, the nozzle needle 9 moves in the valve opening direction and the fuel is injected. At this time, the hydraulic pressure slowly drops due to the action of the orifice of the plate valve 20.

As shown in FIG. 2, the injector 36 provided for each cylinder is connected to a high pressure accumulating pipe common to all cylinders, a so-called common rail 38, via an injection pipe 37. The common rail 38 has a supply pipe 39,
A high pressure supply pump 41 is connected via a check valve 40. The high pressure supply pump 41 is a fuel tank 42.
The fuel sucked through the low pressure supply pump 43 from the above is boosted to a predetermined high pressure and controlled to a predetermined high pressure. That is, the cam 45 rotates in synchronization with the rotation of the engine 44, the piston 47 in the cylinder 46 moves forward to pressurize the fuel from the low pressure supply pump 43, and the high pressure supply pump 41.
In order to constantly control the common rail pressure to a predetermined pressure, that is, to control the amount of fuel to be pressure-fed to the common rail 38, a discharge amount control solenoid valve 48 that closes at a predetermined timing during the pressure-feeding stroke of the piston 47 is provided. .

Electronic control unit (hereinafter referred to as ECU)
Reference numeral 49 is input with information on the number of revolutions and the load from the cylinder discrimination sensor 50, the crank angle sensor 51 and the load sensor 52,
The ECU 49 outputs a control signal to the three-way control valve 22 so that the optimum injection timing and injection amount (injection timing) are determined according to the engine state determined from these signals.

Further, a pressure sensor 53 for detecting the common rail pressure is arranged on the common rail 38, and the ECU 49 controls the discharge amount so that the signal of the pressure sensor 53 becomes an optimum value set in advance in accordance with the load and the rotation speed. . That is,
By performing negative feedback control of pressure, more precise pressure setting is performed. As shown in FIG. 1, the safety device 54 is provided between the common rail 38 and the injection pipe 37. In the safety device 54, as shown in FIG. 1, the screw portion 60 of the housing 55 is a female screw portion 87 of the common rail 38.
It is screwed to. A through hole 57 extending in the axial direction is formed inside the housing 55, a recess 56 is formed at one end of the through hole 57, and a fluid diode 61 is fitted into the recess 56. A tapered surface 58 is formed on the other end of the housing 55, and the injection pipe 37 is formed on the tapered surface 58.
The seat surface 37a of the above is liquid-tightly seated, and the screw member 59 is screwed to the housing 55 from the outside.

The fluid diode 61 has a structure shown in FIGS. 4 and 5. An orifice 66, a conical hole 67, and a large-diameter hole 68 are continuously formed inside the body 62. A convex portion 64 that fits into the concave portion 56 of the housing 55 shown in FIG. 1 is formed on the outside of the body 62, and a conical inclined surface contacting a seat surface 69 formed on the common rail 38 is formed at the other end. A seat surface 63 is formed. The inner diameter of the orifice hole 66 is d, the conical hole 6
The divergence angle of 7 is 2θ, and the inner diameter of the large diameter hole 68 is D. For example, it is desirable that d: 0.5 to 1.0 with respect to D: 4 mm. The spread angle 2θ is, for example, 40 to 120 degrees or more.
This is because the conical hole 67 has a divergence angle 2θ of less than 40 degrees.
Manufacturing process becomes difficult and the strength decreases, and divergence angle 2
This is because if θ is too large, the throttling effect of the fuel becomes great and the flow rate securing is excessively restricted.

Next, FIG. 6 shows the relationship between the spread angle 2θ of the fluid diode 61 and the injection amount. As shown in FIG.
The maximum injection amount is secured when the divergence angle 2θ is, for example, about 20 degrees. It can be seen that the injection amount gradually decreases as the divergence angle 2θ increases. next,
FIG. 7 shows pressure change characteristics on the inlet side of the fluid diode when this fluid diode is provided.

As shown in FIG. 7, in the non-injection region,
A small pressure fluctuation is seen under the influence of the pressure wave of the previous one's own cylinder injection or the injection of another cylinder. Immediately before the injection, the pressure fluctuation is ΔP. Next, when the injection starts, the pressure drops, and the pressure continues to drop until the injection ends. Then, after the injection is completed, the pressure rises, the degree of rise is large, and the maximum pressure value is recorded.

In the conventional non-return member using a ball valve, a plunger valve, etc., the pressure fluctuation before the injection was large and the variation among the cylinders was large. It is presumed that this is because the pressure fluctuation is large because a movable member such as a compression coil spring is used. In addition, there was a large variation in the pressure decay characteristics after injection between cylinders. On the other hand, in this embodiment, since the fluid diode does not use the movable member, the pressure fluctuations before and after the injection become uniform. That is, there is a characteristic that the influence of the pressure reflection wave by the previous self-injection and the other-cylinder injection becomes substantially uniform among the cylinders. Such a pressure fluctuation characteristic is an effect that cannot be obtained by a conventional ball valve or plunger valve having a movable member.

Next, the maximum value of the injection pressure pulsation at the fluid diode inlet side is measured when the inner diameter D of the large diameter hole 68 in the fluid diode 61 shown in FIG. 4 is fixed and the inner diameter d of the orifice hole 66 is changed. did. The result is shown in FIG. It can be seen that the smaller the inner diameter d of the orifice hole 66, the smaller the maximum value of the injection pressure pulsation, and the larger the inner diameter d of the orifice hole 66, the larger the maximum value of the injection pressure pulsation.

Next, the operation of the fuel injection system will be described. With the operation of the injector 36, fuel corresponding to the valve opening timing and time is supplied from the common rail 38 to the injector 36 via the large diameter hole 68, the conical hole 67, the orifice hole 66 of the fluid diode 61 and the injection pipe 37.
Is injected into the combustion chamber of the engine. After the injection is completed, the orifice hole 66 of the fluid diode 61 is introduced from the injection pipe 37 side.
A water hammer wave propagates from the conical hole 67 side. Since this water hammer wave is restricted by the orifice 66, this conical hole 6
7. The pressure fluctuation applied to the pressure accumulating chamber inside the common rail 38 through the large diameter hole 68 is reduced. That is, the pressure change in the common rail 38 is reduced. This allows
Since the pressure propagation to the other cylinders is limited, the non-uniformity of the injection timing and the injection amount to the other cylinders is reduced and also the non-uniformity of the injection timing and the injection amount to the next injection of the own cylinder is reduced. .

As described above, according to the fuel injection device of the present invention, the common rail 38 to the fluid diode 61 are connected.
Through the injection pipe 37, fuel is supplied to the injector 36 in an amount corresponding to the opening period of the injection valve. After the injection is completed, the injector 36 and the common rail 38
Since the amplitude of the pressure wave propagating to the side is regulated by the orifice hole 66 of the fluid diode 61 before reaching the pressure accumulating chamber,
The attenuation of the reflected wave becomes reliable, and the influence on the injection from that cylinder to another cylinder is reduced.

According to this embodiment, the fluid diode 61
Since the fluid flow rate in one direction can be secured and the fluid flow rate in the opposite direction can be limited only by processing the body 62 of No. 1, it is possible to obtain the desired desired pressure pulsation reducing means with an extremely simple shape. This has the effect of having both the fuel supply function and the pressure pulsation reducing function. Further, in the embodiment shown in FIG. 1, the seal is ensured by bringing the seat surface 63 of the fluid diode 61 into contact with the seat surface 69 of the common rail 38. In the structure shown in FIG. 1, the fluid diode 61 is inserted into the seat surface 69 of the common rail 38 during assembly,
From the upper side of the fluid diode 61, the housing 55 of the safety device 54 is screwed and fixed by screwing, and the convex portion 64 and the concave portion 56 are fitted and clamped and fixed.

(Second Embodiment) A second embodiment of the present invention is shown in FIG.
Shown in. The second embodiment shown in FIG. 9 is a fluid diode 61.
This is an example in which the assembling property of is improved. In this example, the safety device 5
The body 6 of the fluid diode 61 by the caulking portion 71 of 4
Crimp 2 in the direction of the arrow. After crimping, fluid diode 6
1 and the housing 55 are integrally inserted into the screw portion of the common rail 38, screwed, the seat surface 63 is brought into contact with the seat surface 69 of the common rail 38, and the screw portion 60 is tightened. Secure a seal with.

According to this second embodiment, the fluid diode 61 is previously caulked to the housing 55 when assembled.
Since they are temporarily fixed and tightened by 1, and they are integrally screwed and fixed to the common rail 38, there is an effect that the positioning of the fluid diode 61 is facilitated and the assembling work can be facilitated. (Third Embodiment) A third embodiment of the present invention is shown in FIG.

The third embodiment shown in FIG. 10 is an example in which a second fluid diode 73 is further attached to the housing 55 on the injector side of the first fluid diode 61. The second fluid diode 73 includes a second orifice 74 and a second
The body 76 has a conical hole 75. The body 76 is press-fitted and fixed in the stepped recess 77 of the housing 55. In addition, the first diode 61 is similar to the above-described embodiment in that the caulking portion 7
It is fixed to the housing 55 by crimping.

According to the third embodiment, since the first orifice hole 66 and the second orifice hole 74 are provided, there is a synergistic effect of reducing the pressure of the fuel propagating from the injector 36 after injection to the common rail 38 side. It becomes big. Further, it does not limit the supply of fuel from the common rail 38 to the injector 36. (Fourth Embodiment) A fourth embodiment of the present invention will be described with reference to FIGS.
2 shows.

The fourth embodiment shown in FIGS. 11 and 12 is
A small-diameter hole 82 and a large-diameter hole 83 are continuously provided in a body 84 of the fluid diode 81, and a conical plate 85 is provided at a stepped portion at the boundary thereof.
This is an example in which is fixed by welding. The conical plate 85 has a narrowed hole 86 formed in the center thereof in the thickness direction. Conical plate 8
A throttle hole 86 is provided at the center of 5. According to the fourth embodiment, the body 84 can be machined relatively simply by forming the small diameter hole 82 and the large diameter hole 83 in the body 84. The throttling pressure pulsation reducing mechanism can be easily configured only by taking the step of inserting the conical plate 85 from the large diameter hole 83 of the body 84 and fixing it by welding. Conical plate 8
5 can be formed by pressing.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing a pressure pulsation reducing means according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a pressure-accumulation fuel supply system of the present invention.

FIG. 3 is a cross-sectional view of an injector used in the present invention.

FIG. 4 is a cross-sectional view of a fluid diode.

FIG. 5 is a perspective view of a fluid diode.

FIG. 6 is a divergence angle 2 of the conical hole of the fluid diode of the present invention.
It is a data figure which shows the relationship of (theta) and injection quantity.

FIG. 7 is a characteristic diagram showing inlet side pressure characteristics of the fluid diode according to the first embodiment of the present invention.

8 is a data diagram showing the maximum value of injection pressure pulsation when the diameter of the large diameter hole of the fluid diode shown in FIG. 1 is fixed and the diameter of the orifice hole is changed.

FIG. 9 is a sectional view showing a fluid diode according to a second embodiment of the present invention.

FIG. 10 is a sectional view of a fluid diode according to a third embodiment of the present invention.

FIG. 11 is a sectional view of a fluid diode according to a fourth embodiment of the present invention.

FIG. 12 is a perspective view showing a conical plate according to a fourth embodiment of the present invention.

[Explanation of symbols]

36 injectors 37 injection pipe 38 Common rail (accumulation container) 39 supply pipe 41 High-pressure supply pump 42 Fuel tank 43 Low pressure supply pump 44 engine 54 Safety device 61 Fluid diode 62 body 63 seat surface 64 convex 66 Orifice hole 67 Conical hole 68 Large hole 69 seat surface

Continuation of the front page (56) Reference JP-A-3-124957 (JP, A) JP-A-4-241767 (JP, A) Actually open 59-168572 (JP, U) Actually open 59-148468 (JP , U) Actual exploitation 51-147820 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02M 55/02 310 F02M 55/02 330 F02M 55/02 350 F02M 47/00 F16L 41/08

Claims (2)

(57) [Claims] 1. A pressure accumulator for storing high-pressure fuel and an intermittent operation type.
Fluid diode in the fuel line connecting with the injector of
Equipped with, the fluid diode, the accumulator volume in the interior of the body
Large diameter hole from the device side toward the injector side, a conical hole,
Orifice holes are formed continuously, and the conical holes are
The passage area is next only in one direction from the container side to the injector side.
It is smaller to the said body has have a contact with conical bevelled seat surface conical seat surface formed in the pressure accumulator, before
The fuel pipe is fixed to the accumulator vessel so that the body
The seat surface of the container is liquid-tightly fixed to the seat surface of the accumulator.
蓄 pressure fuel injection system you characterized in that it is. 2. A pressure accumulating chamber, a conical seat surface communicating with the accumulator, comprising a pressure accumulator and a female screw portion provided in an outer wall near the communicating with the seat surface, fittable to the female screw portion the orifice connects an external thread portion and the through hole and the threaded member having, as well as one end of the hole, with a fluid diode having a seat surface that contacts the seat surface of the pressure accumulator to the fuel pipe The pressure-accumulation fuel injection device according to claim 1 .