JPH0445657B2 - - 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 equipped with an exhaust gas recirculation device, and particularly relates to a fuel injection device that injects fuel into a diesel engine equipped with an exhaust gas recirculation device. The present invention relates to a measure for correcting the fuel injection characteristics of the fuel injection nozzle according to the exhaust gas recirculation rate in a device equipped with a pintle-type fuel injection nozzle in which the opening area of the fuel injection hole is changed according to the lift amount. In the present invention, the term "pintle type fuel injection nozzle" is used to include a throttle type in which the throttle range in which the needle valve throttles the fuel injection hole is relatively wide 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 Japanese Patent Application Laid-Open No. 57-151058, etc., there is a A slidable plunger member is provided on the plunger member, 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 touches the fuel injection hole. A so-called central plunger type is known that allows atomization of injected fuel, change of fuel injection rate, etc. by maintaining a throttle range in a constricted state for a certain period of time.

(Problem to be Solved by the Invention) However, when this conventional pintle-type fuel injection nozzle is applied to a diesel engine equipped with an exhaust gas recirculation device, the pressure applied to the plunger member of the fuel injection nozzle is usually constant. When the needle valve is lifted within the throttle range of its lift range, the lift is uniformly suppressed, so when the engine air-fuel ratio decreases due to an increase in the exhaust recirculation rate by the exhaust recirculation device, the There was a problem in that fuel properties were deteriorated due to insufficient atomization of the fuel, and as a result, the generation of smoke (black smoke) was promoted.

The present invention has been made in view of the above, and its purpose is to reduce the pressure applied to the plunger member for suppressing the lift of the needle valve described above, that is, the needle valve determined by the pressure applied to the plunger member. By linearly (proportionally) correcting and controlling the lift suppression start position according to the exhaust recirculation rate, when the exhaust recirculation rate increases, the fuel injection characteristics of the fuel injection nozzle to the engine are changed and fuel atomization is performed. The object of the present invention is to accelerate the combustibility and thereby reduce the deterioration of smoke caused by an increase in the exhaust gas recirculation rate of a diesel engine.

(Means for Solving the Problem) In order to achieve the above object, the solving means of the present invention changes the opening area of the fuel nozzle hole according to the lift amount as described above, and provides the fuel nozzle hole in the lift range. A needle valve is provided with a throttle range to be throttled, and a plunger member that is aligned with the axis of the needle valve and whose one end faces the needle valve and is slidable in the axial direction thereof, and the other end face of the plunger member is provided with pressure. In the fuel injection device for a diesel engine, the fuel injection device has a pintle-type fuel injection nozzle configured to apply a predetermined pressure from a source to suppress the lift amount of the needle valve at a predetermined pressure, and is equipped with an exhaust gas recirculation device. A pressure control valve for controlling the pressure is provided in a pressure passage that applies pressure to the other end surface of the plunger member of the fuel injection nozzle.

Further, a control device controls the operation of the pressure control valve so that the pressure acting on the other end surface of the plunger member increases in proportion to the increase in the exhaust gas recirculation rate by the exhaust gas recirculation device, thereby lengthening the throttle range of the needle valve. will be established.

(Function) With this configuration, the present invention makes good use of the lift characteristics of the needle valve in the pintle-type fuel injection nozzle, and when the exhaust gas recirculation rate by the exhaust gas recirculation device increases, the pressure control valve is operated in proportion to the increase in the exhaust gas recirculation rate. The pressure applied to the other end of the plunger member is maintained at a high level by control, and the lift is suppressed for a long time in the throttle range of the needle valve, so that regardless of changes in the exhaust recirculation rate, fuel particles are reduced in this throttle range. It is possible to maintain good combustibility by promoting oxidation.

(Effects of the Invention) Therefore, according to the present invention, in a pintle-type fuel injection nozzle used in a diesel engine equipped with an exhaust gas recirculation device, the application of voltage to the plunger member for suppressing the lift of the needle valve is Since the pressure is variably controlled so that it increases in proportion to the increase in the engine exhaust recirculation rate, when the exhaust recirculation rate increases, the throttle range of the needle valve is lengthened to promote fuel atomization. It is possible to improve combustibility and thus effectively reduce the deterioration of smoke caused by an increase in the exhaust gas recirculation rate of a diesel engine.

(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 into the cylinder 2 so as to be able to reciprocate, and a cavity 4a for forming a combustion chamber 5 is recessed in the top surface of the piston 4.

On the other hand, although not shown in the drawings, the cylinder head 3 includes an intake port as a downstream end portion of an intake passage that supplies intake air to the combustion chamber 5;
An exhaust port is formed as the upstream end portion of the exhaust passage for discharging the exhaust gas in the combustion chamber. 5 to generate a swirl (eddy current).

Also, although not shown, the intake passage and the exhaust passage are connected via an exhaust recirculation passage having an exhaust recirculation control valve, and as shown in FIG. The exhaust gas recirculation rate (EGR rate) is increased as the engine load decreases.
An exhaust gas recirculation device (EGR device) is configured in which the exhaust gas is recirculated to the intake passage while controlling the flow rate using an exhaust gas recirculation control valve so that the amount of exhaust gas increases.

The cylinder head 3 includes a glow plug 6 that heats the inside of the combustion chamber 5 when starting the engine, etc.
A pintle-type fuel injection nozzle 7 for injecting and supplying fuel into the combustion chamber 5 is installed, and 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 on the tip side (lower side in the figure), and a fuel injection hole 8 on the rear side (upper side in the figure). a nozzle body 10 in which each fuel inlet port 9 connected to a fuel injection pump (not shown) opens;
In the nozzle body 10, a spring chamber 12, a needle valve support hole 13, and a fuel pressure chamber 14 are formed in order from the rear end side to the front end side, and these cavities are coaxial with the fuel injection hole 8. are provided above and in communication with each other. Further, the fuel inlet 9 and the fuel pressure chamber 14 (fuel injection hole 8) are communicated through a fuel passage 15 formed in the nozzle body 10. Furthermore, the spring chamber 12
There is a needle valve 1 in the cavity from the fuel injection hole 8 to the fuel nozzle hole 8.
6 is fluid-tightly supported and slidably fitted in the needle valve support hole 13.
6a, a pressure receiving part 16b that receives the fuel pressure in the fuel pressure chamber 14, a valve part 16c that opens and closes the fuel injection hole 8, and a throttle part 16d arranged in the fuel injection hole 8, The throttle section 16
A certain distance is formed between d and the wall surface of the fuel nozzle hole 8. Further, a nozzle spring 17 for biasing the needle valve 16 in the closing direction is compressed in the spring chamber 12, and high-pressure fuel from the fuel injection pump is supplied from the fuel inlet 9 to the fuel passage 15.
When the fuel is introduced into the pressure chamber 14 through the fuel pressure, the needle valve 16 is opened against the urging force of the nozzle spring 17 due to the action of the fuel pressure on the pressure receiving part 16b of the needle valve 16, and the fuel is injected. The fuel is injected into the combustion chamber 5 of the engine through the hole 8, and at that time, the distance between the throttle portion 16d and the wall surface of the fuel injection hole 8 changes depending on the lift amount of the needle valve 16. 16 and the opening area of the fuel injection hole 8 are configured to change. That is, after the needle valve 16 is opened,
First, the throttle portion 16d is located within the fuel nozzle hole 8, and enters the throttle range where the opening area of the fuel nozzle hole 8 is kept approximately constant by the throttle of the fuel nozzle hole 8 of the throttle portion 16d. When the throttle part 16d escapes from the position, the opening area of the fuel injection hole 8 increases in proportion to the lift amount of the needle valve 16, and then the throttle part 16d shifts to a proportional change range, and then is lifted to the frill lift position. Reference numeral 19 denotes an exhaust gas recirculation passage, through which leaked fuel leaked from the fuel pressure chamber 14 into the spring chamber 12 through the small gap between the needle valve 16 and the needle valve support hole 13 is transferred to the fuel tank outside the nozzle (Fig. (not shown).

Furthermore, a cylinder 11 that communicates with the spring chamber 12 is formed coaxially with the needle valve 16 in the nozzle body 10 on the rear side of the spring chamber 12, and the cylinder 11 is connected to the outside of the nozzle body 10 through a pressure passage 20. , and a pressure source (not shown) using fuel as a pressure medium. Furthermore, a plunger member 18 that coincides with the axis of the needle valve 16 is slidably fitted in the cavity extending from the cylinder 11 to the spring chamber 12. The plunger member 18 includes a rod portion 18a disposed within the spring chamber 12, a plunger portion 18b fitted within the cylinder 11, and a rod portion 18a disposed within the spring chamber 12.
8a and a flange portion 18c located between the plunger portion 18b, and the stroke until the flange portion 18c abuts against the rear end wall of the spring chamber 12 and a stopper portion 27 disposed at an intermediate portion of the spring chamber 12. The tip of the rod portion 18a is movable within a range, and when the movement of the plunger member 18 toward the needle valve 16 side is restricted by the contact of the collar portion 18c with the stopper member 27, the tip of the rod portion 18a,
That is, the tip of the plunger member 18 is positioned so as to face the spring receiving portion 16a, which is the rear end of the needle valve 16, with a predetermined distance d therebetween. Thus, when the needle valve 16 is lifted and its spring receiving portion 16a is in contact with the tip of the rod portion 18a of the plunger member 18, a predetermined pressure from the pressure source is applied to the rear end surface of the plunger portion 18b of the plunger member 18. The lift amount of the needle valve 16 is suppressed by this.

Further, in a pressure passage 20 communicating with the rear end surface of the plunger portion 18b of the plunger member 18, the fuel discharge passage 19 is connected to the outer side of the nozzle body 10 via a communication passage 28. A pressure control valve 21, which is a duty valve, is arranged in the pressure passage 20 at the connection portion with the plunger member 18 to reduce the fuel pressure acting on the rear end surface of the plunger portion 18b of the plunger member 18. The control system for controlling the operation of the pressure control valve 21 is as follows: 22 is a rotation speed sensor for detecting the engine rotation speed, 23 is a load sensor for detecting the engine load state, and 24 is an exhaust gas recirculation system. an exhaust gas recirculation rate sensor for detecting the exhaust gas recirculation rate by the device;
25 is a control circuit that receives the outputs of the sensors 22, 23, and 24 and controls the operation of a solenoid drive circuit 26 for driving the duty solenoid of the pressure control valve 21; The drive circuit 26 constitutes a control device 29 . The control device 29 controls the pressure control valve 21 according to the operating state of the engine.
As shown in FIG. 4, when the engine is in a low load and low rotation state, the duty ratio sent to the pressure control valve 21 is lowered to increase the pressure applied to the plunger member 18, and the engine In order to correct the basic control, the duty ratio to the pressure control valve 21 is increased and the pressure applied to the plunger member 18 is lowered when the pressure control valve 21 is in a high-load, high-speed region. As shown in the figure, as the exhaust gas recirculation rate by the exhaust gas recirculation device increases, the duty ratio to the pressure control valve 21 is corrected to be lower in proportion to the increase, and the fuel pressure acting on the rear end surface of the plunger member 18 is increased. Correction control is performed so that the throttle range of the valve 16 becomes longer.

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 16b of the needle valve 16, causing the needle valve 16 to be connected to the nozzle spring 17.
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. Then, when the lift amount of the needle valve 16 increases due to an increase in the fuel pressure introduced into the fuel pressure chamber 14 and the spring receiving part 16a comes into contact with the plunger member 18, from then on, the needle valve 16 moves to the plunger member 18. It becomes one with the lift.

Further, the fuel pressure introduced from the pressure source into the cylinder 11 of the fuel injection nozzle 7 through the pressure passage 20 acts on the rear end surface of the plunger member 18 in the cylinder 11 to press the plunger member 18 toward the needle valve 16 side. By applying pressure to the plunger member 18, the lift operation of the needle valve 16 after the spring receiving portion 16a contacts the plunger member 18 is controlled. The control of the needle valve 16 will be explained according to the control _flowchart shown in FIG _. The load signals from S3 are respectively input to the control device 29, and then step _S3
Based on the rotational speed signal and load signal, the basic duty ratio corresponding to the operating state of the engine is read from a previously stored duty ratio map as shown in FIG. Next, in step _S4 , the exhaust gas recirculation rate sensor 24 to the control device 29
The exhaust gas recirculation rate (EGR rate) is determined by the signal input to the
is read, at step _S5 , a correction coefficient is read that lowers the duty ratio signal to the pressure control valve 21 as the exhaust gas recirculation rate increases, as shown in FIG. In _{step S6} , the basic duty ratio is corrected by the correction coefficient, and finally, in step _S7 , the duty solenoid of the pressure control valve 21 is driven in accordance with the corrected duty ratio.
1 controls the fuel pressure applied to the plunger member 18, and then returns to step _S1 and repeats steps _S2 to _S7 .

In this case, when the engine is in the exhaust recirculation region (low-medium load rotation region) as shown in Fig. 5, when the exhaust recirculation rate is low, that is, when the engine is in the low-medium load low rotation region, By sending a high duty ratio signal as a corrected duty ratio signal obtained by correcting the basic duty ratio signal from the device 29 to the pressure control valve 21, the fuel pressure applied to the plunger member 18 is lowered, and the fuel pressure applied to the plunger member 18 is lowered. Needle valve 16
Due to the reduction in the lift resistance force, the needle valve 16 is lifted smoothly without being subjected to lift suppression until the throttle portion 16d reaches a lift position within the proportional change range on the way out of the fuel injection hole 8. As a result, the amount of fuel injected into the engine (fuel injection rate) is ensured at an appropriate amount, and the output of the engine can be improved.

On the other hand, when the exhaust gas recirculation rate is high, that is, when the engine is in a low load and low rotation region, the control device 2
9 as a corrected duty ratio signal is sent to the pressure control valve 21, the fuel pressure applied to the plunger member 18 increases, and the lifting resistance force of the needle valve 16 by the plunger member 18 increases. However, due to the increase in the lift resistance force of the plunger member 18, the needle valve 16 is in the throttle range where the throttle part 16d throttles the fuel nozzle hole 8 after the spring receiving part 16d contacts the plunger member 18. 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 is improved, and therefore it is possible to reduce the deterioration of smoke when the exhaust gas recirculation rate increases.

Note that when the engine is in an operating range (high load range or high rotation range) in which exhaust gas recirculation is not performed, the correction coefficient for correcting the basic duty ratio signal becomes zero, and the basic duty ratio signal is sent as is to the pressure control valve 21. As a result, emission performance and output can be improved depending on the operating state of the engine.

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 engine operating status and the duty ratio signal output to the pressure control valve. Figure 5 is an explanatory diagram showing the relationship between the engine operating status and the exhaust gas recirculation rate. Figure 6 is an explanatory diagram showing the relationship between the engine operating status and the exhaust gas recirculation rate. FIG. 3 is an explanatory diagram showing the relationship between a duty ratio signal and a duty ratio signal. 5... Combustion chamber, 7... Fuel injection nozzle, 8... Fuel injection hole, 9... Fuel inlet, 11... Cylinder, 14... Fuel pressure chamber, 16... Needle valve, 16c... Valve part, 1
6d...Throttle part, 18...Plunger member, 1
8a...Rod part, 18b...Plunger member, 20
...Pressure passage, 21...Pressure control valve, 22...Rotation speed sensor, 23...Load sensor, 24...Exhaust gas recirculation rate sensor, 29...Control device.

Claims (1)

[Scope of Claims] 1. A needle valve that is provided with a throttle range that changes the opening area of the fuel nozzle hole according to the lift amount and throttles the fuel nozzle hole within the lift range; A plunger member whose one end faces the needle valve and is slidable in its axial direction is provided, and a predetermined pressure is applied from a pressure source to the other end surface of the plunger member to suppress the lift amount of the needle valve at a predetermined pressure. In a diesel engine fuel injection device having a pintle-type fuel injection nozzle and equipped with an exhaust gas recirculation device, the pressure is controlled in a pressure passage that applies pressure to the other end surface of a plunger member of the fuel injection nozzle. A pressure control valve is provided, and the pressure control valve is configured such that the pressure acting on the other end surface of the plunger member increases in proportion to the increase in the exhaust gas recirculation rate by the exhaust gas recirculation device, and the throttle range of the needle valve increases. A fuel injection device for a diesel engine, characterized in that it is provided with a control device for controlling operation.