JPH0437269B2 - - 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 fuel injection 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 use functions that aim to atomize the fuel or change the fuel injection rate depending on the various operating conditions of the engine, and it is difficult to promote engine combustion.
It was difficult to perform switching control such as improving output.

(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, the combustion promotion, output improvement, etc. of the diesel engine can be switched and controlled in accordance with the operating state of the diesel engine.

(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 apart from each other in the direction (direction), and a switching valve is provided to selectively switch each of the fuel discharge passages, and the switching valve is operated according to operating conditions such as engine speed and load. A control device is provided to control the system.

As a result, the switching valves are used to switch the opening and closing of each fuel discharge passage according to the operating state of the engine, thereby changing the position at which lift suppression of the needle valve by the plunger member starts.

(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, it is possible to atomize the fuel and change the fuel injection rate depending on the operating state of the engine. It is useful because it can be used to control switching to promote engine combustion, improve output, etc.

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

FIG. 1 shows a combustion 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 the 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 injection 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 enters a throttle range in which it is kept approximately constant by the throttle of the fuel nozzle hole 8 e, and then becomes proportional to the lift amount of the needle valve 16 as the throttle portion 16e escapes from the fuel nozzle hole 8. 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 projection 11a formed on the side wall of the cylinder 11 and an engagement groove 18a recessed on the outer circumferential surface of the plunger member 18.
It is engaged with and slidably inserted by a predetermined stroke. That is, the plunger member 18
is disposed on the rear end side of the needle valve 16 so as to be slidable coaxially with 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 when the needle valve 16 is in the throttle range of its lift range (when the fuel injection hole 8 is throttled by the throttle portion 16e of the needle valve 16). The opening area of the second fuel discharge passage 20 is set to a position where it is closed by the piston portion 16a of the needle valve 16 when the opening area is kept small (in a range where the opening area is kept small). The needle valve 16 is set at a position beyond the maximum lift range of the valve 16, that is, a position where the needle valve 16 is not blocked by the piston portion 16a even when the needle valve 16 is lifted to 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 fuel pressure acting on the rear end surface of the plunger member 18 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 extending outside the nozzle body 10. ing. The control system for controlling the operation of this electromagnetic on-off valve 21 is as follows: 22 is a rotational speed sensor for detecting the rotational speed of the engine; 23 is a load sensor for detecting the load state of the engine;
4 is a valve drive circuit 25 for receiving the outputs of both the sensors 22 and 23 and driving the electromagnetic on-off valve 21;
The control circuit 24 and the valve drive circuit 25 described above control the operation of the electromagnetic on-off valve 21 (switching valve) according to the operating state of the engine, and when the engine is in a low-medium load state and When the rotation is in the medium rotation state, the electromagnetic on-off valve 21 is closed and leaked fuel is discharged through the first fuel discharge passage 19.
When the engine is under high load and high speed, the electromagnetic on-off valve 21 is opened to discharge leaked fuel through the first and second fuel discharge passages 1.
Control device 2 for controlling both 9 and 20
6 are configured.

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 of the needle valve 16 will be explained according to the control _flowchart shown in FIG _. The load signals from the engine are input to the control device 26, and then, in step _S3 , it is determined whether or not the engine is in the high load, high rotation region based on the rotation speed signal and the load signal. is NO, that is, when the engine is in the low-medium load low-medium rotation region as shown in zone A in FIG _.
Steps S ₂ and S ₃ are repeated. 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 in the piston part 16 through the first fuel discharge passage 19, the piston part 16 is freely lifted using the biasing force of the nozzle spring 17 as a resistance force.
a closes the first fuel discharge passage 19, fuel is sealed in the cylinder 11 between the piston portion 19 and the plunger member 18, and the plunger member 18
The fuel pressure acting on the rear end surface is transmitted to the needle valve 16 via the sealed leak fuel, and the opening pressure of the needle valve 16 increases, thereby controlling the lift to be suppressed. The opening of the first fuel discharge passage 19 to the cylinder 11 is opened when the needle valve 16 is in the throttle range in which the fuel injection hole 8 is throttled by the throttle portion 16e within its lift range. Since the needle valve 16 is arranged so as to be closed by the piston portion 16a of the needle valve 16, the lift of the needle valve 16 is suppressed 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 and the emission performance is improved.

On the other hand, when the determination in step _S3 is YES, that is, when the engine is in the high load rotation region as shown in zone B in _FIG . The electromagnetic on-off valve 21 is opened by the output, and then the process returns to the first step _S1 and the subsequent steps _S2 ,
S ₃ ,... are repeated. As a result, the needle valve 16 of the fuel injection nozzle 7 directs the leaked fuel in the cylinder 11 to the first and second fuel discharge passages 19 and 20 until the piston portion 16a closes the first fuel discharge passage 19. After the piston portion 16a closes the first fuel discharge passage 19, the piston portion 16a is controlled to lift while discharging the leaked fuel only from the second fuel discharge passage 20. The cylinder 11 of the second fuel discharge passage 20
Since the opening of the needle valve 16 is set at a position beyond the full lift range of the needle valve 16, as shown by the upper broken line in FIG. As a result, the engine output can be improved by ensuring the amount of fuel injected into the engine.

Note that the present invention is not limited to the above-mentioned embodiment, and includes various modifications. For example, in the above-mentioned embodiment, when the engine is in a low-medium load low-medium rotation region, the fuel injection nozzle The lift of the needle valve 16 of 7 is suppressed within its throttle range,
When the engine is in a high-load, high-speed region, the lifting of the needle valve 16 is released from being suppressed. The lift of the needle valve may be suppressed within the throttle range when the engine is in the low-medium load area, and the lift of the needle valve may be suppressed within the proportional change range when the engine is in the high-load area. It is possible to improve emission performance in a load region and to improve output performance in a high load region.

In addition, the throttle part of the needle valve is formed into a two-stage structure of a large diameter part and a small diameter part, and the throttle range of the needle valve lift range is divided into two stages: minimum and normal. When using a fuel injection nozzle and the engine is operating in a white smoke generation region, for example when the engine is cold or when the engine is operating at low atmospheric pressure, the needle valve should be The lift may be suppressed in the minimum throttle range, and when the engine is in an operating range other than the white smoke generation range, the lift of the needle valve may be suppressed in the normal throttle range. transformation,
It can promote combustibility and reduce white smoke (HC).

Furthermore, in the configuration of the above embodiment, a rotary valve is added that switches the cylinder 11 of the fuel injection nozzle 7 into communication with the fuel inlet 9 or the second fuel discharge passage 20 downstream of the electromagnetic on-off valve 21,
By controlling the rotary valve and the electromagnetic on-off valve 21, for example, when the engine is in a low-load, low-speed range, the lift of the needle valve is set to the throttle range, and when the engine is in a medium-load, medium-speed range, the lift of the needle valve is set to that proportion. The needle valve lift may be suppressed in each range of change, and the suppression of the needle valve lift may be released when the engine is in a high load and high rotation range, and when the engine is in a low load and low rotation range.
It is possible to reduce HC, improve output torque in the low speed range, and improve output in the high speed range. That is, the present invention provides a plurality of fuel discharge passages separated by a predetermined distance in the cylinder axis direction on the cylinder side wall between the needle valve and the plunger member of a pintle-type fuel injection nozzle, and selectively operates each of the fuel discharge passages. The present invention is characterized in that it is provided with a switching valve that switches to the switching valve, and a control device that controls the operation of the switching valve according to the operating state of the engine.

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 vertical cross-sectional view of the main parts of a diesel engine, FIG. 2 is an overall configuration diagram of a fuel injection device, FIG. 3 is a flowchart of a control system, and FIG. The figure is an explanatory diagram showing the relationship between the injection hole area and the needle valve opening pressure with respect to the lift amount of the needle valve of the fuel injection nozzle. Figure 5 shows the relationship between the engine operating state and the lift suppression area of the needle valve of the fuel injection nozzle. FIG. 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...Rotation speed sensor, 23...Load sensor, 24...Control circuit, 2
6...control device.

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. It is characterized by providing a plurality of fuel discharge passages separated by a distance, a switching valve that selectively switches each of the fuel discharge passages, and a control device that controls the operation of the switching valve according to the operating state of the engine. Fuel injection system for diesel engines.