JPH0437270B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a fuel injection device that injects and supplies fuel to a diesel engine, and in particular, injects fuel according to the lift amount of a needle valve that lifts in response to fuel pressure. This invention relates to an improvement in a pintle-type fuel injection nozzle in which the opening area of the nozzle hole is changed. In the present invention, the term pintle-type fuel injection nozzle is used to include a throttle-type nozzle having a comparatively wide throttle range in which the needle valve throttles the fuel injection hole within the lift range of the needle valve.

(Prior Art) Conventionally, as an example of this type of pintle-type fuel injection nozzle, as disclosed in, for example, Japanese Unexamined Patent Publication No. 57-151058, a needle valve is provided on the rear end side of the needle valve coaxially with the needle valve. A slidable plunger member is provided, and by applying a predetermined pressure to the plunger member, lift of the needle valve above a predetermined lift amount is suppressed, and within the lift range of the needle valve, the needle valve throttles the combustion nozzle hole. There is a so-called central plunger type, which allows the injected fuel to be atomized and the fuel injection rate to be changed by maintaining the throttle range in the closed state for a certain period of time.

In such a central plunger type fuel injection nozzle, as a structure for suppressing the lift of the needle valve, conventionally, a structure is installed at a predetermined part of the cylinder side wall between the needle valve and the plunger member from the gap around the needle valve. A fuel discharge passage (leak passage) is formed to discharge leaked fuel out of the nozzle, and the pressure acting on the plunger member is used as fuel pressure, and the needle valve closes the fuel discharge passage as it lifts. When the fuel is sealed in the cylinder between the needle valve and the plunger member, the pressing force from the plunger member is transmitted to the needle valve via the sealed fuel, and the lift of the needle valve is suppressed. What has been done is known.

However, in this conventional structure, there is usually only one fuel discharge passage opening in the cylinder side wall, and when the needle valve is lifted within the throttle range of its lift range, the lift is uniformly suppressed. It is not possible to change the fuel injection characteristics according to engine load fluctuations, and it is possible to improve the emission performance by atomizing the fuel in the low engine load range and improve the output by securing the fuel injection amount in the high load range. It was difficult to control.

(Object of the Invention) The present invention has been made in view of the above points, and its object is to provide a plurality of fuel discharge passages that determine the above-mentioned lift suppression start position of the needle valve, and to By selectively using the plurality of fuel discharge passages and changing the lift suppression start position of the needle valve, it is possible to switch control to improve the emission performance in the low load range and the output increase in the high load range of the diesel engine. It's about doing.

(Structure of the Invention) In order to achieve the above object, the solution means of the present invention is such that the plunger member presses the needle valve from the time when the needle valve closes the fuel discharge passage opening in the cylinder side wall. In a fuel injection device for a diesel engine equipped with a pintle-type fuel injection nozzle designed to suppress the lift, the cylinder side wall between the needle valve of the fuel injection nozzle and the plunger member is attached in the cylinder axial direction (the lift of the needle valve). A plurality of fuel discharge passages are provided at a predetermined distance in a direction (direction), and among the plurality of fuel discharge passages, a first fuel discharge passage is located at a lift position within the throttle range of the needle valve, and a second fuel discharge passage is provided at a lift position within the throttle range of the needle valve. is arranged to correspond to the lift position between the throttle range of the needle valve and the full lift position, and is provided with a switching valve that selectively switches each of the fuel discharge passages, and the switching valve is connected to the low load of the engine. A control device that controls the operation so that the lift of the needle valve is sometimes suppressed by blocking the first fuel discharge passage of the needle valve, and the lift of the needle valve is suppressed by blocking the second fuel discharge passage of the needle valve when the load is high. It has been established.

As a result, the opening and closing of each fuel exhaust passage is switched by the switching valve according to the engine load condition, and the lift suppression start position of the needle valve by the plunger member is changed, and when the engine is in a low load range, the needle valve is The valve lift is suppressed in the throttle range to promote fuel atomization, while the needle valve lift is suppressed at a lift position between the throttle range and the full lift position when the engine is in a high load range. This is to ensure the amount of injection.

(Effects of the Invention) Therefore, according to the diesel engine fuel injection device of the present invention, a plurality of fuel discharge passages are provided for determining the lift suppression start position of the needle valve in the pintle type fuel injection nozzle, and the engine operation is controlled. Since the lift suppression start position of the needle valve is changed by switching the opening and closing of the plurality of fuel passages depending on the state, the fuel injection characteristics can be changed depending on the engine load state, and the engine This is useful because it can perform switching control to reduce unburned gas (HC) by promoting atomization of fuel in the low load range and to improve output by ensuring the amount of fuel injection in the high load range.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows a fuel chamber portion of a direct injection diesel engine according to an embodiment of the present invention, in which 1 is a cylinder block having a cylinder 2, 3 is a cylinder head joined to the upper surface of cylinder block 1, and 4 is a cylinder block having a cylinder 2;
A piston is fitted in the cylinder 2 so as to be reciprocally movable, and a cavity 4a for forming a combustion chamber 5 is recessed in the top surface of the piston 4.

On the other hand, the cylinder head 3 is formed with an intake port that supplies intake air to the combustion chamber 5 and an exhaust port that discharges exhaust gas from the combustion chamber 5, although not shown. Due to its shape, the intake air drawn into the combustion chamber 5 during the intake stroke of the engine generates a swirl within the combustion chamber 5.

Further, the cylinder head 3 is equipped with a glow plug 6 that heats the inside of the combustion chamber 5 when starting the engine, etc., and a pintle-type fuel injection nozzle 7 that injects fuel into the combustion chamber 5. The fuel injection direction of the fuel injection nozzle 7 is set along the intake swirl.

As shown in enlarged detail in FIG. 2, the pintle-type fuel injection nozzle 7 has a fuel injection hole 8 facing the combustion chamber 5 at the tip side (lower side in the figure), and a fuel injection hole 8 facing the combustion chamber 5 at the rear end side (upper side in the figure). The nozzle body 10 includes a nozzle body 10 in which a fuel inlet 9 connected to an injection pump (not shown) opens, and a cylinder 11, a spring chamber 12, a spring chamber 12,
A needle valve support hole 13 and a fuel pressure chamber 14 are formed, and these cavities are provided coaxially with the fuel inlet 9 and fuel injection hole 8 and in communication with each other. Further, the fuel inlet port 9 and the fuel pressure chamber 14 (fuel nozzle hole 8) are connected to the nozzle body 10.
The fuel passages 15 are connected to each other by a fuel passage 15 formed in the fuel passages 15 and 15 . Furthermore, a needle valve 16 is fluid-tightly supported and slidably fitted in the cavity from the cylinder 11 to the fuel injection hole 8. A piston portion 16a that is fitted into the front side portion, a spring receiving portion 16b that is placed within the spring chamber 12, a pressure receiving portion 16c that receives fuel pressure within the fuel pressure chamber 14, and the fuel injection hole 8. It comprises a valve part 16d that opens and closes, and a throttle part 16e disposed within the fuel injection hole 8, and a certain gap is formed between the throttle part 16e and the wall surface of the fuel injection hole 8. . In addition, the spring chamber 12
A nozzle spring 17 that biases the needle valve 16 in the closing direction is compressed inside, and high-pressure fuel from the fuel injection pump is introduced into the fuel pressure chamber 14 from the fuel inlet 9 through the fuel passage 15. Then, the needle valve 16 is moved to the nozzle spring 17 due to the action of the fuel pressure on the pressure receiving part 16c of the needle valve 16.
The valve is opened against the urging force of the needle valve 16, and fuel is injected into the combustion chamber 5 of the engine through the fuel nozzle hole 8. By changing the gap between the hole 8 and the wall surface, the lift amount of the needle valve 16 and the opening area of the fuel injection hole 8 are changed as shown in the lower part of FIG. 4. That is, after the needle valve 16 is opened, the throttle portion 16 is first opened.
e is located within the fuel nozzle hole 8 and the throttle portion 16
The opening area of the fuel nozzle hole 8 is kept approximately constant by the throttle of the fuel nozzle hole 8 at e, and the opening area of the fuel nozzle hole 8 enters the throttle range where it is kept approximately constant, and the throttle portion 16e escapes from the fuel nozzle hole 8 in proportion to the lift amount of the needle valve 16. After shifting to a proportional change range in which the opening area of the fuel injection hole 8 increases, it is lifted to the full lift position.

Further, within the rear side of the cylinder 11, a plunger member 18 is provided with a protrusion 11a formed on the side wall of the cylinder 11 with an engagement groove 18a recessed in its outer peripheral surface.
It is engaged with and slidably inserted by a predetermined stroke. That is, the plunger member 18
is disposed coaxially and slidably on the rear end side of the needle valve 16, and the plunger member 18
The tip of the needle valve 16 faces the piston portion 16a, which is the rear end of the needle valve 16, and the fuel inlet 9 is provided on the rear end surface.
The structure is such that the fuel pressure from the

Also, the piston portion 16a of the needle valve 16
(rear end of needle valve 16) and plunger member 18
The side wall of the cylinder 11 (nozzle body 10) between the nozzle and the nozzle is used to collect leaked fuel that has leaked from the fuel pressure chamber 14 into the spring chamber 12 and the cylinder 11 through the minute gap between the needle valve 16 and the needle valve support hole 13. Two fuel discharge passages 1, a first and a second, for discharging to an external fuel tank (not shown)
9 and 20 are provided, and the two fuel discharge passages 1
9 and 20 open into the cylinder 11 at positions separated by a predetermined distance in the axial direction of the cylinder 11 (the lift direction of the needle valve 16). The opening position of the first fuel discharge passage 19 to the cylinder 11 is determined within the throttle range of the lift range of the needle valve 16 (throttle section 1 of the needle valve 16).
6e, the piston portion 16a of the needle valve 16 corresponds to the lift position in the range where the fuel injection hole 8 is throttled and its opening area is kept small, that is, when the needle valve 16 is in the throttle range.
It is set to be blocked by On the other hand, the opening position of the second fuel discharge passage 20 to the cylinder 11 is set so as to correspond to the lift position in the proportional change range between the throttle range and the full lift position in the lift range of the needle valve. The valve 16 is configured to be closed by its piston portion 16a when the valve 16 is lifted to a lift position between the throttle range and the full lift position. Therefore, when the needle valve 16 is lifted, its piston portion 16a closes the first fuel discharge passage 19, and leaked fuel is sealed in the cylinder 11 between the piston portion 16a and the plunger member 18. , the plunger member 1
The fuel pressure acting on the rear end surface of the needle valve 8 is configured to suppress the lift amount of the needle valve 16 via the sealed leak fuel.

Furthermore, a normally closed electromagnetic on-off valve 21 serving as a switching valve for selectively switching between the fuel exhaust passages 19 and 20 is disposed in a portion of the second fuel exhaust passage 20 that extends outside the nozzle body 10. ing. This electromagnetic on-off valve 21 is connected to a battery 23 via a load switch 22, and the load switch 22 is turned OFF when the engine is in a low load range as shown in zone A in FIG. Turns on when the load is high (for example, 75% or more of the maximum load) as shown in zone B in the diagram.
It works. Therefore, the load switch 22
By controlling the operation of the electromagnetic on-off valve 21 (switching valve) according to the engine load condition, and closing the electromagnetic on-off valve 21 when the engine is in a low load condition, leak fuel is discharged from the first fuel discharge passage 19. When the first fuel discharge passage 19 of the needle valve 16 is closed, the lift of the needle valve 16 is suppressed, and when the engine is in a high load state, the electromagnetic on-off valve 21 is opened to prevent leakage fuel from being discharged. first and second fuel discharge passages 19,
A control device 26 is configured to control both of the fuel discharge passages 20 so that the lift of the needle valve 16 is suppressed by closing the second fuel discharge passage 20 of the needle valve 16.

Next, to explain the operation of the above embodiment,
Basically, when high-pressure fuel is pumped from the fuel injection pump to the fuel injection nozzle 7, the high-pressure fuel is transferred from the fuel inlet 9 of the fuel injection nozzle 7 to the fuel passage 15.
The fuel is introduced into the pressure chamber 14 through the fuel pressure chamber 14, where it presses the pressure receiving part 16c of the needle valve 16, and the nozzle spring 17 of the needle valve 16 is introduced into the fuel pressure chamber 14.
When the needle valve 16 is opened, the fuel in the fuel pressure chamber 14 is injected into the combustion chamber 5 of the engine through the fuel injection hole 8.

Further, the pressure of the high-pressure fuel introduced into the fuel inlet 9 of the fuel injection nozzle 7 also acts on the rear end surface of the plunger member 18 in the cylinder 11, pressing the plunger member 18 toward the needle valve 16 side, and this plunger member The lift operation of the needle valve 16 is controlled by applying fuel pressure to the needle valve 18 . The control for this needle valve 16 will be explained as follows.
When the engine is in a low load region as shown in zone A in FIG. 4, the load switch 22 is not turned on and the electromagnetic on-off valve 21 is kept closed.
As a result, the needle valve 16 of the fuel injection nozzle 7 is operated until the piston portion 16a closes the first fuel discharge passage 19 within its lift range.
While discharging the leaked fuel inside through the first fuel discharge passage 19, the piston part 16a is freely lifted using the biasing force of the nozzle spring 17 as a resistance force.
When the first fuel discharge passage 19 is closed, the fuel is sealed in the cylinder 11 between the piston portion 19 and the plunger member 18, and the fuel pressure acting on the rear end surface of the plunger member 18 drains the sealed leaked fuel. The pressure is transmitted to the needle valve 16 via the valve and the opening pressure of the needle valve 16 increases, thereby controlling the lift to be suppressed. And the above first
The opening of the fuel discharge passage 19 to the cylinder 11 is located at the piston portion 16a of the needle valve 16 when the needle valve 16 is in the throttle range in which the fuel injection hole 8 is throttled at the throttle portion 16e within its lift range. Since the lift of the needle valve 16 is suppressed by closing the needle valve 16 as shown by the solid line in the upper part of FIG.
is in the throttle range, and by suppressing the lift of the needle valve 16 in this throttle range, the state in which fuel is injected from the fuel injection hole 8 at high speed is maintained for a long time, and the atomization of the injected fuel is promoted. ,
The combustibility of the fuel is increased, the amount of unburned gas is reduced, and the emission performance at low loads is thus improved.

On the other hand, when the engine is in a high load region as shown in zone B in FIG.
is turned on and the electromagnetic on-off valve 21 is opened. As a result, the needle valve 16 of the fuel injection nozzle 7
, the piston portion 16a is connected to the first fuel discharge passage 1
Until the piston part 16a closes the leak fuel in the cylinder 11 from both the first and second fuel discharge passages 19 and 20, the piston part 16a
9 is closed, the leak fuel is controlled to be lifted while being discharged only from the second fuel discharge passage 20. The opening of the second fuel discharge passage 20 to the cylinder 11 is connected to the needle valve 1.
6 is set to be closed by the piston portion 16a of the needle valve when it is lifted to a lift position between the throttle range and the full lift position within its lift range.
Lift control 6 is performed when the needle valve 16 is between its throttle range and the full lift position as shown by the broken line at the top of Figure 3, ensuring the amount of fuel injected into the engine and increasing the injection rate. Therefore, it is possible to improve the engine output under high load.

In the above embodiment, the load switch 22 is used as a control device for controlling the operation of the electromagnetic on-off valve 21 (switching valve), but a microcomputer may also be used, and highly accurate control can be performed. .

Furthermore, it goes without saying that the present invention can be applied not only to the direct injection type diesel engine as in the above embodiment, but also to other types of diesel engines such as the swirl chamber type diesel engine.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal cross-sectional view of the main parts of a diesel engine, FIG. 2 is an overall configuration diagram of a fuel injection device, and FIG. 3 is a diagram showing the relationship between the needle valve lift amount of the fuel injection nozzle FIG. 4 is an explanatory diagram showing the relationship between the nozzle hole area and the needle valve opening pressure, and FIG. 4 is an explanatory diagram showing the relationship between the operating state of the engine and the lift suppression area of the needle valve of the fuel injection nozzle. 5... Combustion chamber, 7... Fuel injection nozzle, 8...
Fuel injection hole, 9...Fuel introduction port, 11...Cylinder, 14...Fuel pressure chamber, 16...Needle valve,
16a...Piston part, 16d...Valve part, 16e
... Throttle part, 18 ... Plunger member, 1
9...First fuel discharge passage, 20...Second fuel discharge passage, 21...Solenoid on-off valve, 22...Load switch.

Claims (1)

[Claims] 1. A sliding plunger member is provided on the rear end side of the needle valve coaxially with the needle valve, one end of the plunger member is opposed to the rear end of the needle valve, and fuel pressure is applied to the other end surface, A fuel discharge passage is formed in a cylinder side wall between the needle valve and the plunger member, and when the fuel discharge passage is closed due to lift of the needle valve, the fuel pressure acting on the other end surface of the plunger member is used to discharge the needle valve. In a fuel injection device for a diesel engine equipped with a pintle-type fuel injection nozzle configured to suppress lift of the pintle-type fuel injection nozzle, a predetermined portion is provided on the cylinder side wall in the axial direction of the cylinder between the needle valve of the pintle-type fuel injection nozzle and the plunger member. A plurality of fuel discharge passages separated by a distance are provided, and among the plurality of fuel discharge passages, the first fuel discharge passage is located at a lift position within the throttle range of the needle valve, and the second fuel discharge passage is located at a lift position within the throttle range of the needle valve. A switching valve is arranged to correspond to the lift position between the throttle range and the full lift position, and selectively switches each of the fuel discharge passages, and the switching valve is connected to the needle valve when the engine is under low load. A control device is provided for controlling the operation so that the lift of the needle valve is suppressed by blocking the first fuel discharge passage, and the lift of the needle valve is suppressed by blocking the second fuel discharge passage of the needle valve when the load is high. A diesel engine fuel injection device featuring: