JPH08296520A - Accumulator fuel injection device - Google Patents

Abstract

PURPOSE: To provide an accumulator fuel injection device in which high pressure of injection pressure and the reduction of leak fuel amount are compatible. CONSTITUTION: In an accumulator fuel injection device in which fuel stored in an accumulator chamber is led into an injection chamber 19 at a tip of a needle valve and a control chamber 22 at the root of the needle valve and fuel in the control chamber 22 is escaped into a recovery system 24 to lift the needle valve and jet fuel in the injection chamber 19, the accumulator chamber is divided into a high pressure chamber 3 and a low pressure chamber 4, and an injection passage 17 which connects the high pressure chamber 3 to the injection chamber 19 is provided. Furthermore, a control passage 21 which connects the low pressure chamber 4 to the control chamber 22 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-accumulation type fuel injection device for injecting high-pressure fuel stored in a pressure accumulation chamber to a diesel engine or the like.

[0002]

2. Description of the Related Art FIG. 7 shows the entire system of a pressure accumulating fuel injection device. As shown in the figure, the fuel in the fuel tank a is
It is pumped up by the high-pressure pump b, is pressure-fed to a pressure accumulating chamber c called a common rail, and is stored in a high-pressure state. The pressure in the accumulator c is fed back by the pressure sensor d, and is kept constant by controlling the amount of oil fed by the high-pressure pump b.

The high-pressure fuel in the accumulator c is guided to an injector g through a supply system f, and an electromagnetic valve (a three-way valve q described later) provided inside the injector g is opened and closed to inject an injection port at the tip of the nozzle. It is injected from h into the combustion chamber of a diesel engine or the like. A recovery system i for returning excess fuel to the fuel tank a is connected to the injector g. Further, the high pressure pump b, the pressure accumulating chamber c, and the injector g are appropriately controlled by the control unit j.

An outline of the injector g is shown in FIG. As shown in the figure, the high-pressure fuel stored in the pressure accumulating chamber c is guided to the injection chamber m on the tip end side of the needle valve 1 through the injection passage k branched from the supply system f, and also through the control passage n. It is guided to the control chamber o on the base side of the needle valve 1 via the. The fuel in the control chamber o is returned to the recovery system i via the leak passage p. A three-way valve q (solenoid valve) is provided at the junction of the leak passage p, the control passage n, and the control chamber o. The three-way valve q switches between a feed state in which the control passage n communicates with the control chamber o and a leak state in which the control chamber o communicates with the leak passage p.

According to the above construction, the fuel pressure in the injection chamber m acts on the cone portion r of the needle valve l to raise (open) it, and the fuel pressure in the control chamber o causes the needle valve l to rise. Down (valve closed)
Work to let. Therefore, if the three-way valve q is made to leak from the state where these fuel pressures are balanced, the pressure balance is broken and the needle valve 1 rises, and the fuel in the injection chamber m is injected from the injection port h at the tip of the nozzle. It After that, when the three-way valve q is switched to the feed state, the upper and lower pressures are balanced again, the needle valve 1 descends to close the injection port h, and the injection ends.

[0006]

In the system described above, the injection chamber m for accumulating substantially injected fuel and the needle valve 1 are provided.
Is connected to a control chamber o for controlling the raising and lowering (opening and closing) of the same from one pressure accumulating chamber c via a supply system f and passages k and n. Therefore, if the pressure of the pressure accumulating chamber c is increased to increase the injection pressure, not only the pressure of the injection chamber m but also the control chamber o
It will also increase the pressure.

As a result, the amount of leak fuel escaped from the control chamber o to the leak passage p (recovery system i) by the three-way valve q increases, and the wasteful work of the high-pressure pump b increases correspondingly, which deteriorates the fuel efficiency of the vehicle. To do.

Further, since the side pressure is generated in the three-way valve q due to its structure when the pressure becomes higher, the operating force must be increased when the pressure becomes higher, and the three-way valve q
The current consumption of the (solenoid valve) also increases.

Further, if the pressure in the control chamber o is increased in this way, the inside of the three-way valve q may be twisted or deformed, so that its durability and reliability are deteriorated. In addition, since the operation of the three-way valve q becomes slow due to kinking etc., the three-way valve q
Operation response is deteriorated.

Further, the pressure in the injection chamber m fluctuates according to the opening / closing of the needle valve 1, but the influence of the fluctuation is transmitted to the three-way valve q via the passages k and n, and the three-way valve q is damaged. It is also possible.

An object of the present invention, which was devised in view of the above circumstances, is to provide a pressure accumulating fuel injection device capable of both increasing the injection pressure and reducing the amount of leaked fuel.

As a related technique, Japanese Patent Laid-Open No. 6-108948
Publications and the like are known.

[0013]

In order to achieve the above object, the present invention guides fuel stored in a pressure accumulating chamber to an injection chamber on the needle valve tip side and a control chamber on the needle valve base side, and the control chamber In the pressure-accumulation fuel injection device that lifts the needle valve by letting the fuel in the recovery system escape and injects the fuel in the injection chamber,
The pressure accumulating chamber is divided into a high pressure chamber and a low pressure chamber, an injection passage connecting the high pressure chamber and the injection chamber is provided, and a control passage connecting the low pressure chamber and the control chamber is provided. .....

A bypass passage for connecting the injection passage and the control passage is provided, and a first opening / closing valve is provided in the injection passage upstream of the connection portion of the bypass passage to leak the fuel in the control chamber to the recovery system. A second on-off valve may be provided in.

A throttle portion may be provided in the injection passage downstream of the first opening / closing valve and upstream of the connection portion of the bypass passage.

[0016]

According to the constitution of the function, the high pressure fuel in the high pressure chamber is
It is introduced into the injection chamber on the needle valve tip side through the injection passage, and is injected in a high pressure state when the needle valve is lifted. On the other hand, the low-pressure fuel in the low-pressure chamber is introduced into the control chamber on the base side of the needle valve through the control passage, used as the working fluid for the needle valve, and then released to the recovery system in a low pressure state. As described above, since the high-pressure fuel in the high-pressure chamber is used as the injection fuel and the low-pressure fuel in the low-pressure chamber is used as the working fluid for the needle valve, the fuel injection pressure is increased and the leaked fuel amount is reduced at the same time.

According to the construction of (1), the first of the injection passages is first provided.
Both the on-off valve and the second on-off valve in the leak passage are closed, and then only the second on-off valve is opened. Then, the fuel in the control chamber is released to the recovery system through the leak passage, the needle valve is lifted, and the fuel in the injection chamber is injected. At this time, since the low-pressure fuel in the low-pressure chamber is supplied to the injection chamber through the bypass passage, low-pressure fuel injection is performed. afterwards,
When the first on-off valve is opened, high-pressure fuel in the high-pressure chamber is supplied to the injection chamber through the injection passage, so high-pressure fuel injection is performed.
This suppresses premixed combustion in the early stages of combustion,
A rapid increase in combustion temperature is suppressed, and NOx is reduced.

According to the above construction, since the fuel flowing through the injection passage is throttled by the throttle portion during the high-pressure fuel injection, the injection rising characteristic at the time of high-pressure fuel injection becomes gentle. As a result, a rapid increase in combustion temperature during premixed combustion is suppressed, and NOx is further reduced.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing the entire system of a pressure accumulation type fuel injection device according to this embodiment. As shown in the figure, this pressure-accumulation fuel injection device includes a high-pressure pump 2 that pressurizes and pumps the fuel in a fuel tank 1, and a high-pressure chamber 3 that is connected to the high-pressure pump 2 and stores the fuel at high pressure (about 1200 bar). A low pressure chamber 4 which is connected to the high pressure chamber 3 and stores the fuel at a low pressure (about 600 bar), and an injector which uses the fuel in the high pressure chamber 3 as an injection fuel and uses the fuel in the low pressure chamber 4 as a working fluid for the needle valve 5. It is mainly composed of 6 and 6.

The high pressure pump 2 reciprocates the plunger 8 against the spring 9 by rotating the cam shaft 7 which is interlocked with the crank shaft of the engine, and is sucked up from the fuel tank 1 by the suction pump 10. Cylinder fuel
It is pressurized in 1 and sent to the high-pressure chamber 3 by pressure. The inflow passage 12 and the discharge passage 13 of the high-pressure pump 2 are the return passage 1
Bypassed by 4. An opening / closing valve 15 is provided in the return passage 14. In addition, in the discharge passage 13,
A check valve 16 is provided.

The high pressure chamber 3 has a discharge passage 13 of the high pressure pump 2.
The fuel sent from the company is stored under high pressure (about 1200 bar). Further, an injection passage 17 of the injector 6 and a connection passage 18 to the low pressure chamber 4 are connected to the high pressure chamber 3. Therefore, a part of the fuel in the high pressure chamber 3 is guided to the low pressure chamber 4 through the connection passage 18, and the rest is guided to the injection chamber 19 on the tip side of the needle valve 5 of the injector 6 through the injection passage 17. . The fuel introduced into the injection chamber 19 is
It is used as substantially injected fuel and is injected from the injection port 20 by the lift of the needle valve 5. Also, in the high pressure chamber 3,
A pressure sensor 21a is provided.

The low-pressure chamber 4 stores the fuel introduced from the high-pressure chamber 3 via the connecting passage 18 in a low-pressure state (about 600 bar). The control passage 21 of the injector 6 is connected to the low pressure chamber 4. The fuel flowing out of the low pressure chamber 4 through the control passage 21 is guided to the control chamber 22 on the base side of the needle valve 5 of the injector 6 and used as a working fluid of the needle valve 5 and finally through the leak passage 23. Collection system 24
Be escaped to. A pressure sensor 25 is provided in the low pressure chamber 4, and an opening / closing valve 26 (electromagnetic valve) is provided in the connection passage 18.

The injector 6 uses the high-pressure fuel in the high-pressure chamber 3 as an injection fuel and the low-pressure fuel in the low-pressure chamber 4 as a working fluid for the needle valve 5. Inside the injector 6, a needle valve 5 that is movable in the axial direction is housed, an injection chamber 19 is formed at the tip end side of the needle valve 5, and a control chamber 22 is formed at the root side. Specifically, the injection chamber 19 is formed so as to surround the cone portion 27 of the needle valve 5, and the control chamber 22 is formed in a cylinder 29 that guides the piston portion 28 of the needle valve 5. Also, the needle valve 5
Is biased in the valve closing (down) direction by the coil spring 30.

A forked passage 31 is connected to the control chamber 22, and an orifice 32 is provided in one of the passages 31a,
The check valve 33 is provided on the other side 31b. The bifurcated passages 31a and 31b are reassembled, and the assembly passage 34 is connected to the leak passage 23 and the control passage 21 via the three-way valve 35 (electromagnetic valve). The three-way valve 35 is connected to the control passage 2
1 is switched between a feed state that communicates the collecting passage 34 (control chamber 22) and a leak state that communicates the leak passage 23 and the collecting passage 34 (control chamber 22). Leak passage 23
Is a passage for allowing the fuel in the control chamber 22 to escape to the recovery system 24.

Needle valve 5 of injector 6 having such a configuration
Is urged in the rising (valve opening) direction by the fuel pressure in the injection chamber 19, and the fuel pressure in the control chamber 22 and the coil spring 2
It is urged in the descending (valve closing) direction by 0. Therefore, if the three-way valve 35 is brought into a leak state from the state where the fuel pressures in the upper and lower chambers 19, 22 are balanced, the pressure balance is broken and the needle valve 5 rises, so that the fuel in the injection chamber 19 is injected at the nozzle tip portion. Ejected from the mouth 20. After that, when the three-way valve 35 is switched to the feed state, the upper and lower pressures are balanced again, the needle valve 5 descends to close the injection port 20, and the injection ends.

The pressure sensor 21a for the high pressure chamber 3, the pressure sensor 25 for the low pressure chamber 4, the engine speed and cam angle sensor 36, the cylinder selection sensor 37, the engine load sensor 38, and various other engines. A sensor that detects the operating information (such as the intake air amount) is connected to the control unit 39 (ECU). The control unit 39 appropriately controls the three-way valve 35 of the injector 6, the opening / closing valve 26 of the connecting passage 18, and the opening / closing valve 15 of the high-pressure pump 2 based on these pieces of information.

Specifically, the control unit 39
Controls the on-off valve 15 of the high-pressure pump 2 based on the detection value of the pressure sensor 21a of the high-pressure chamber 3 so that a part of the fuel pressurized by the plunger 8 is introduced into the inflow passage 12 via the return passage 14.
By returning to the side, the inside of the high-pressure chamber 3 is controlled to have a substantially constant fuel pressure (about 1200 bar). Further, the control unit 39 controls the inside of the low pressure chamber 4 to a substantially constant fuel pressure (about 600 bar) as follows.

As shown in FIG. 2, first, the pressure P in the high pressure chamber 3 is set.
₁ and the pressure P ₂ of the low pressure chamber 4 are respectively detected by the pressure sensor 21.
It is detected by a and 25. Then, (P ₁ / n)> P ₁ is determined. Here, n is a pressure ratio between the high pressure chamber 3 and the low pressure chamber 4, and is usually set to about 2 to 4. If the determination is yes, the open / close valve 26 of the connecting passage 18 is opened, and if the determination is no, the open / close valve 26 of the connecting passage 18 is closed. By such control, the pressure ratio between the high pressure chamber 3 and the low pressure chamber 4 can be maintained at n.

Therefore, according to this flow, if the fuel pressure in the high pressure chamber 3 is kept constant (for example, about 1200 bar) by the opening / closing control of the opening / closing valve 15 of the high pressure pump 2, the fuel pressure in the low pressure chamber 4 becomes 1 / n thereof. Can be kept at In this embodiment, since n = 2, the fuel pressure in the low pressure chamber 4 is maintained at about 600 bar.

Further, the control unit 39 appropriately switches the three-way valve 35 of the injector 6 between the feed state and the leak state based on the information obtained from the engine speed and the cam angle sensor 36 and the like. In the leak state, the needle valve 5 rises and the fuel in the injection chamber 19 is injected from the injection port 20 at the tip of the nozzle as described above, and in the feed state, the needle valve 5 descends to close the injection port 20.

The operation of this embodiment having the above configuration will be described.

The high-pressure (about 1200 bar) fuel in the high-pressure chamber 3 is introduced into the injection chamber 19 on the tip side of the needle valve 5 through the injection passage 17, and is injected in a high pressure state when the needle valve 5 is lifted.
On the other hand, the low-pressure (about 600 bar) fuel in the low-pressure chamber 4 passes through the control passage 21 and the needle valve 5 when the three-way valve 35 is in the feed state.
After being introduced into the control chamber 22 on the root side and used as a working fluid for the needle valve 5, the three-way valve 35 is released to the leak passage 23 in a low pressure state when the valve is in a leak state.

As described above, since the high pressure fuel in the high pressure chamber 3 is used as the injection fuel and the low pressure fuel in the low pressure chamber 4 is used as the working fluid of the needle valve 5, the fuel injection pressure increases,
At the same time, the amount of leaked fuel is reduced. That is, it is possible to achieve both high injection pressure and low leak fuel amount. In this way, the amount of leaked fuel is reduced even if the injection pressure is increased, so that wasteful work of the high-pressure pump 2 is reduced and fuel consumption is improved.
At the same time, the current consumption of the three-way valve 35 (solenoid valve) is also reduced.

Further, since the low-pressure fuel is supplied to the three-way valve 35 as a working fluid, there is no possibility that the inside of the three-way valve 35 will be twisted or deformed, and its durability and reliability will be improved. Further, the operation of the three-way valve 35 does not become uncomfortable due to bending and the operation response of the three-way valve 35 can be favorably maintained even if the injection pressure is increased.

Further, the pressure in the injection chamber 19 fluctuates according to the opening and closing of the needle valve 5. The fluctuation is buffered by the high pressure chamber 3 and the low pressure chamber 4 via the injection passage 17, and then the control passage 21 is closed. Is transmitted to the three-way valve 35 via the three-way valve 3
There is no damage to 5. Further, since the pressure in the control passage 21 can be kept constant regardless of whether the needle valve 5 is opened or closed in this way, the three-way valve 35 can be accurately controlled in the feed state and the leak state.

[Modified Embodiment 1] FIG. 5 shows an embodiment according to claim 2 of the present invention.

As shown in the figure, this embodiment has the same basic structure as the previous embodiment, and therefore the same members are designated by the same reference numerals and their description is omitted, and only the differences will be described below. .

First, the injection passage 17 and the control passage 21 of the injector 6 are the bypass passage 4 having the one-way valve 40.
Connected by 1. Then, the first passage is provided in the injection passage 17a upstream of the connecting portion 42 of the bypass passage 41.
An on-off valve 43 is provided. The three-way valve 35 in the previous embodiment corresponds to the second opening / closing valve in claim 2. The three-way valve 35, when leaking, controls the control chamber 22.
This is because the function of letting the fuel inside escape to the recovery system 24 via the leak passage 23 is exhibited.

The operation of this embodiment having the above configuration will be described.

In FIG. 5, first, the first opening / closing valve 43 of the injection passage 17a is closed, and the three-way valve of the injector is in the feed state. Then, the three-way valve 35 is switched to the leak state. Then, the fuel in the control chamber 22 leaks into the leak passage 2
3 is discharged to the recovery system 24, the needle valve 5 is lifted, and the fuel in the injection chamber 19 is injected. At this time, the injection chamber 1
Since the low-pressure fuel in the low-pressure chamber 4 is supplied into the chamber 9 through the control passage 21 → the bypass passage 41 → the injection passage 17, low-pressure fuel injection is performed.

After that, when the first on-off valve 43 is opened, the high-pressure fuel in the high-pressure chamber 3 is supplied to the injection chamber 19 through the injection passages 17a, 17, so that high-pressure fuel injection is performed. Such changes in the injection pressure are shown in FIG. As shown in the figure, at T ₁ , the three-way valve 35 is switched to the leak state to perform low pressure injection (P _L ), and at T ₂ , the first opening / closing valve 43 is opened to perform high pressure injection (P _H ), The first opening / closing valve 43 at the time of T ₃
Is closed, the three-way valve 35 is switched to the feed state, and the injection is ended.

The two-stage injection suppresses premixed combustion at the initial stage of combustion, suppresses a rapid rise in combustion temperature, and reduces NOx.

[Modified Embodiment 2] FIG. 6 shows an embodiment according to claim 3 of the present invention.

As shown in the figure, this embodiment has the same basic construction as the previous embodiment, and restricts the injection passage 17b downstream of the first opening / closing valve 43 and upstream of the connecting portion 42 of the bypass passage 41. The only difference is that the portion 44 is provided.

According to this structure, at the time of high-pressure fuel injection for opening the first on-off valve 43, the fuel flowing through the injection passage 17b is throttled by the throttle portion 44, so that the injection rising characteristic at the time of high-pressure fuel injection becomes gentle. . This is shown in FIG.
As shown in the figure, at t ₁ , the three-way valve 35 is switched to the leak state to perform low-pressure injection ( _pl ), and at t ₂ , the first on-off valve 43 is opened to smoothly perform high-pressure injection ( _ph ). Then, at t ₃ , the first on-off valve 43 is closed, the three-way valve 35 is switched to the feed state, and the injection is finished.

As described above, when the injection rising characteristic at the time of high-pressure fuel injection becomes gentle, the rapid increase of the combustion temperature at the time of premixed combustion is suppressed, and NOx is further reduced.

[0048]

As described above, according to the pressure-accumulation type fuel injection device of the present invention, the following excellent effects can be exhibited.

(1) According to the first aspect of the invention, the high pressure fuel in the high pressure chamber is used as the injection fuel, and the low pressure fuel in the low pressure chamber is used as the working fluid for the needle valve. And reduction of the amount of leaked fuel can be achieved at the same time.

(2) According to the second aspect of the present invention, by controlling the opening and closing of the first opening / closing valve and the second opening / closing valve continuously, it is possible to perform high pressure injection linked to low pressure injection. Therefore, the premixed combustion in the early stage of combustion can be suppressed, and the rapid increase in the combustion temperature can be suppressed, so that NOx can be reduced.

(3) According to the third aspect of the invention, since the throttle portion throttles the fuel flowing through the injection passage at the time of high-pressure fuel injection, the injection rising characteristic at the time of high-pressure fuel injection can be made gentle. Therefore, a rapid increase in combustion temperature during premixed combustion can be suppressed, and NOx can be further reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view of a pressure-accumulation type fuel injection device showing an embodiment of the present invention (claim 1).

FIG. 2 is a diagram showing a control flow of an opening / closing valve provided between a high pressure chamber and a low pressure chamber.

FIG. 3 is a diagram showing injection characteristics of the pressure accumulation type fuel injection device shown in FIG.

FIG. 4 is a diagram showing injection characteristics of the pressure accumulation type fuel injection device shown in FIG. 6.

FIG. 5 is an explanatory view of a pressure accumulation type fuel injection device showing a modified embodiment (claim 2).

FIG. 6 is an explanatory view of a pressure-accumulation type fuel injection device showing another modified embodiment (claim 3).

FIG. 7 is an explanatory view of a pressure accumulation type fuel injection device showing a conventional example.

FIG. 8 is a diagram showing an outline of an injector of a conventional pressure accumulation type fuel injection device.

[Explanation of symbols]

 3 High-pressure chamber 4 Low-pressure chamber 5 Needle valve 17 Injection passageway 19 Injection chamber 21 Control passageway 22 Control chamber 23 Leakage passageway 24 Recovery system 35 Three-way valve as second opening / closing valve 41 Bypass passageway 42 Connection portion 43 First opening / closing valve 44 Throttling portion

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[Procedure amendment]

[Submission date] February 23, 1996

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

Claims (3)

[Claims] 1. A needle valve is lifted by guiding fuel stored in a pressure accumulating chamber to an injection chamber on the needle valve tip side and a control chamber on the needle valve base side, and letting the fuel in the control chamber escape to a recovery system,
In a pressure accumulation type fuel injection device for injecting fuel in an injection chamber, the pressure accumulation chamber is divided into a high pressure chamber and a low pressure chamber, and an injection passage connecting the high pressure chamber and the injection chamber is provided,
A pressure-accumulation fuel injection device comprising a control passage that connects the low-pressure chamber and the control chamber. 2. A bypass passage that connects the injection passage and the control passage is provided, and a first opening / closing valve is provided in the injection passage upstream of the connection portion of the bypass passage to allow the fuel in the control chamber to escape to the recovery system. The pressure-accumulation fuel injection device according to claim 1, wherein a second opening / closing valve is provided in the leak passage. 3. The pressure-accumulation fuel injection device according to claim 2, wherein a throttle portion is provided in an injection passage downstream of the first opening / closing valve and upstream of a connection portion of the bypass passage.