JPH0437271B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection device that injects 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, with the above-mentioned conventional systems, it is not possible to use functions for the purpose of atomizing the fuel or changing the fuel injection rate depending on the operating state of the engine.
It is not possible to control engine combustion acceleration, etc., and in particular,
When the engine is in an operating state where white smoke is likely to be generated, i.e. when the engine is not yet warmed up and the coolant temperature is low, such as when the engine is started,
When the intake air compression temperature is low, such as when the outside air temperature is low or the atmospheric pressure is low, the ignitability of the fuel becomes poor, the amount of unnatural gas (HC) generated increases, and the unmixed gas and water vapor become mixed. There is a problem in that white smoke is produced in the exhaust gas.

(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 adjust the intake air compression temperature of the engine. By using the plurality of fuel discharge passages accordingly and changing the lift suppression start position of the needle valve, when the engine is still in a cold state such as when starting the engine,
In engine operating conditions where white smoke is likely to occur, such as when the outside temperature or atmospheric pressure is low, the injected fuel is atomized to promote its combustion, reduce the amount of gas in advance, and prevent the generation of white smoke. It's about trying.

(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 having a pindle-type fuel injection nozzle configured to suppress the lift, the throttle portion at the tip of the needle valve of the fuel injection nozzle has a two-stage structure of a small diameter throttle portion and a large diameter throttle portion, Further, a plurality of fuel discharge passages are provided on the cylinder side wall between the needle valve and the plunger member at predetermined intervals in the cylinder axial direction, and among the fuel discharge passages, a first
The fuel discharge passage is located at a lift position within the first stage throttle range due to the large diameter throttle portion of the needle valve, and the second fuel discharge passage is located at a lift position within the second stage throttle range due to the small diameter throttle portion of the needle valve. switching valves arranged to correspond to each other and selectively switching the fuel discharge passage;
When the intake air compression temperature in the engine is low, the lift of the needle valve is suppressed by blocking the first fuel discharge passage of the needle valve, and when the intake air compression temperature in the engine is high, the switching valve is set to and a control device that performs switching control so that the lift of the needle valve is suppressed due to the closure of the second fuel discharge passage.

With this, the two-stage structure of the large diameter throttle part and the small diameter throttle part of the needle valve throttle part changes the nozzle hole area in the nozzle throttle range in stages according to the lift amount of the needle valve. If the operating condition of the engine is such that white smoke is likely to occur, i.e. when the engine cooling water temperature is, for example, below 60°C, the outside temperature is, for example, below 15°C, or the atmospheric pressure is, for example, below 0.9 atmospheres, By controlling the switching operation of the switching valve under the control of the control device, the position at which lift suppression of the needle valve by the plunger member starts is set within the first stage throttle range where the nozzle hole area is small.

(Effects of the Invention) Therefore, according to the diesel engine fuel injection device of the present invention, the fuel is sealed between the needle valve and the plunger member in accordance with the lift position of the needle valve of the pintle type fuel injection nozzle. A plurality of fuel discharge passages are provided so as to form a fuel discharge passage, and by switching the switching valve, the plurality of fuel discharge passages are switched and the lift suppression start position of the needle valve is arbitrarily adjusted. In operating conditions where white smoke is particularly likely to occur, the nozzle nozzle hole area can be narrowed by setting the lift suppression start position of the needle valve within the first stage throttle range where the nozzle hole area is small due to the large diameter throttle part. By increasing the fuel injection speed, promoting atomization, and improving combustibility, unforeseen gas and HC
can be reduced and the generation of white smoke can be prevented.

(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 the shape, 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 desired 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 has a nozzle body 10 in which a fuel inlet 9 connected to a fuel injection pump (not shown) opens, and a cylinder 11 and a spring chamber 12 are arranged in this order from the rear end side to the front end side. ,
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 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 is equipped with a valve part 16d that opens and closes, and a two-stage throttle part consisting of a large-diameter throttle part 16e disposed in the fuel nozzle hole 8 and a small-diameter throttle part 16f on the tip side thereof, and the throttle part 16e, 16f
A certain gap is formed between the fuel nozzle hole 8 and the wall surface of the fuel injection hole 8, respectively. In addition, the spring chamber 1
A nozzle spring 17 that biases the needle valve 16 in the closing direction is compressed in the inside of the valve 2, 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. When it is done,
The action of the fuel pressure on the pressure receiving part 16c of the needle valve 16 causes the needle valve 16 to close to the nozzle spring 1.
The valve is opened against the biasing force of 7, and the fuel flows into the fuel nozzle hole 8.
The needle valve 16
The lift amount and the opening area of the fuel nozzle hole 8 are configured to change as shown in the lower part of FIG. 3. That is, after the needle valve 16 is opened, the large diameter and small diameter throttle portions 16e and 16f are first located within the fuel nozzle hole 8, and the fuel nozzle hole 8 is throttled by the throttle of the fuel nozzle hole 8 of the large diameter throttle portion 16e. It enters the first stage throttle range where the opening area is extremely small and is kept approximately constant, and then the fuel injection hole 8 of the large diameter throttle portion 16e.
The opening area of the fuel injection hole 8 becomes slightly larger than the opening area in the first stage throttle range due to the narrowing of the fuel injection hole 8 of the small-diameter throttle portion 16f as the throttle exits from the second stage, but remains approximately constant. After entering the throttle range, the small-diameter throttle portion 16f escapes from the fuel nozzle hole 8, shifting to a proportional change range where the opening area of the fuel nozzle hole 8 increases in proportion to the lift amount of the needle valve 16, and then lifts to the full lift position. be done.

Furthermore, a plunger member 18 is slidably inserted into the cylinder 11 by a predetermined stroke by engaging an engagement groove 18a formed in the outer circumferential surface of the plunger member with a protrusion 11a formed on the side wall of the cylinder 11. That is, the plunger member 18 is slidably disposed coaxially with the needle valve 16 on the rear end side of the needle valve 16, and the tip of the plunger member 18 is opposed to the piston portion 16a, which is the rear end of the needle valve 16. , so that fuel pressure from the fuel inlet 9 acts on the rear end surface.

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 into the cylinder 11 is in the throttle range where the fuel injection hole 8 is throttled by the large-diameter throttle portion 16e of the needle valve 16 and its opening area is kept small. The opening position of the second fuel discharge passage 20 to the cylinder 11 is set to a position where it is closed by the piston part 16a of the needle valve 16, and the opening position of the second fuel discharge passage 20 to the cylinder 11 is set to a position where it is closed by the small diameter throttle part 16f of the needle valve 16. is closed by the piston portion 16a of the needle valve 16 when the opening area is kept slightly larger than the opening area of the first throttle range. is set to . Therefore, as the needle valve 16 lifts, its piston portion 16a closes the first fuel discharge passage 19, and the piston portion 16a and the plunger member 1
8, the fuel pressure acting on the rear end surface of the plunger member 18 suppresses the lift amount of the needle valve 16 via the sealed leak fuel. has been done.

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. To explain the control system that controls the operation of this electromagnetic on-off valve 21, 22 is a water temperature switch that detects the engine cooling water temperature and opens and closes when the water temperature is, for example, 60°C or less, and 23 is a water temperature switch that controls the outside temperature. 24 is an outside temperature switch that detects atmospheric pressure and opens and closes when the outside temperature is, for example, 15 degrees Celsius or less, and an atmospheric pressure switch that detects atmospheric pressure and opens and closes when the atmospheric pressure is, for example, 0.9 atm or less. The switches 22, 23, and 24 are respectively connected in parallel to the electromagnetic on-off valve 21. and,
If any of the following conditions apply: the water temperature drops to 60 degrees Celsius or less, the outside temperature drops to 15 degrees Celsius or less, or the atmospheric pressure falls to 0.9 atmospheres or less, that is, if the intake air compression temperature in the engine is low, Solenoid on-off valve 2
1 is closed so that the leaked fuel is discharged only through the first fuel discharge passage 19, and the lift of the needle valve 16 is suppressed by the blockage of the large 1 fuel discharge passage 19 by the needle valve 16. In other words, when the intake air compression temperature in the engine is high, the electromagnetic on-off valve 21 is opened to discharge the leaked fuel through both the first and second fuel discharge passages 19 and 20, and the second A control device 25 is configured to control the fuel discharge passage 20 so that the lift of the needle valve 16 is suppressed when the needle valve 16 closes. Note that 26 is a power source.

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.
If any of the following conditions apply: the engine cooling water temperature drops to 60 degrees Celsius or less, the outside temperature drops to 15 degrees Celsius or less, or the atmospheric pressure drops to 0.9 atmospheres or less, the engine tends to produce white smoke. If the temperature is within the range, either the water temperature switch 22, the outside temperature switch 23, or the atmospheric pressure switch 24 is closed, and the electromagnetic on-off valve 21 is energized and closed. When this electromagnetic on-off valve 21 is closed, the needle valve 1
6 is the piston portion 16a within the lift range.
Until the leak fuel in the cylinder 11 that has flowed in from the spring chamber 12 is discharged through the first fuel discharge passage 19, the nozzle spring 17 is freely lifted using the biasing force of the nozzle spring 17 as a resistance force until it closes the first fuel discharge passage 19. However, when the piston part 16a closes the first fuel discharge passage 1, fuel is sealed in the cylinder 11 between the piston part 19 and the plunger member 18, and the fuel pressure acting on the rear end surface of the plunger member 18 is applied to the seal. The lift is controlled by being transmitted to the needle valve 16 via the leaked fuel and the opening pressure of the needle valve 16 increases, so that the lift of the needle valve 16 is suppressed as shown in FIG. As shown by the upper solid line, this is performed when the large diameter throttle portion 16e of the needle valve 16 does not escape from the fuel injection hole 8 and the needle valve 16 is within the first stage throttle range. By suppressing the lift of the needle valve 16 inside the fuel injection hole 8, the state in which fuel is injected at high speed from the fuel nozzle hole 8 is maintained for a long time, promoting atomization of the injected fuel, increasing the combustibility of the fuel, and reducing the amount of gas. In other words, white smoke caused by HC is suppressed.

On the other hand, if none of the above conditions apply, as shown in the lower part of FIG. The nozzle spring 17 at once until the second fuel discharge passage 20 is closed.
When the piston part 16a closes the second fuel discharge passage 20 by using the biasing force as a resistance force, the piston part 16a closes the second fuel discharge passage 20, and a leakage fuel sealing state is formed between the needle valve 16 and the plunger member 18. suppressed. Therefore, as shown in the upper broken line in FIG.
Only f is located in the fuel injection hole 8 and the needle valve 16
is in the second stage throttle range, the lift of the needle valve 16 is suppressed, and normal white smoke is prevented.

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 It is an explanatory view showing the relationship between nozzle hole area and needle valve opening pressure. 7... Pintle type fuel injection nozzle, 11... Cylinder, 16... Needle valve, 16e... Large diameter throttle part, 16f... Small diameter throttle part, 18
... Plunger member, 19, 20 ... 1st, 2nd
Fuel discharge passage, 21... switching valve, 25... control device.

Claims (1)

[Claims] 1. A plunger member is provided on the rear end side of the needle valve and is slidable coaxially with the needle valve, one end of the plunger member faces the needle valve, and the other end face is configured to apply fuel pressure, and A fuel discharge passage is formed in the 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 causes the needle to be discharged. In a diesel engine fuel injection device equipped with a pintle-type fuel injection nozzle configured to suppress valve lift, the throttle portion at the tip of the needle valve of the pintle-type fuel injection nozzle is used as a first-stage fuel injection hole with a small opening area. a large-diameter throttle portion for forming a throttle range; and a large-diameter throttle portion located on the tip side of the large-diameter throttle portion
It has a two-stage structure with a small diameter throttle part for forming a second stage throttle range with a large opening area of the nozzle hole, and a predetermined interval is provided in the cylinder axial direction on the cylinder side wall between the needle valve and the plunger member. A plurality of separated fuel discharge passages are provided, and among the fuel discharge passages, a first fuel discharge passage is provided with a plurality of separated fuel discharge passages.
At a lift position within the stage throttle range, a second fuel discharge passage is formed by the small diameter throttle portion.
A switching valve is arranged to correspond to each lift position within the stage throttle range and selectively switches the fuel discharge passage, and the switching valve is connected to the needle when the intake air compression temperature in the engine is low. The lift of the needle valve is suppressed by blocking the first fuel discharge passage of the valve, and when the intake air compression temperature in the engine is high, the lift of the needle valve is suppressed by blocking the second fuel discharge passage of the needle valve. 1. A fuel injection device for a diesel engine, comprising: a control device for controlling switching so that the fuel injection device performs switching control.