JPH0475395B2 - - 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. The present invention relates to measures for optimizing the fuel injection characteristics of the fuel injection nozzle and the intake swirl of the engine in a device equipped with 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 Japanese Patent Application Laid-open 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, a lift of the needle valve exceeding a predetermined lift amount is suppressed, so that the needle valve throttles the fuel injection hole within the lift range of the needle valve. A so-called central plunger type is known, which allows atomization of fuel, change of fuel injection rate, etc. by maintaining the throttle range for a certain period of time.

(Problem to be Solved by the Invention) However, in this conventional device, the pressure of the fuel supplied from the fuel injection pump is directly applied to the plunger member, and the needle valve is used only when the needle valve is in the throttle position within its lift range. If the lift is within the range, the lift will be uniformly suppressed, so
It is not possible to actively use functions that aim to atomize the fuel or change the fuel injection rate depending on the various operating conditions of the engine.
It was difficult to perform switching control such as improving output.

Therefore, the pressure applied to the plunger member for suppressing the lift of the needle valve described above, that is, the lift suppression start position of the needle valve determined by the pressure applied to the plunger member, is linearly changed according to the operating state of the engine. By doing so, it is possible to change and control the characteristics of fuel injection into the engine by the fuel injection nozzle to characteristics intended to improve combustibility, improve engine output, etc., depending on the operating state of the diesel engine.

However, in reality, due to the influence of the intake swirl that occurs in the combustion chamber during the intake stroke, it is not possible to effectively achieve improvements in distribution performance, engine output, etc. even by controlling only the fuel injection characteristics as described above. The problem arises that it is not possible.

For example, when the engine load is low, even if the pressure applied to the plunger member is increased to atomize the injected fuel, if the swirl is too large, the ignited fuel may be blown out or the intake air may collide with the wall surface. The collision causes the fuel to cool down, resulting in poor ignitability of the fuel.
HC due to unburned gas is more likely to be generated. Furthermore, when the engine load is high and the engine speed is high, even if the pressure applied to the plunger member is lowered to ensure the fuel injection amount, if the swirl is large, the distribution of the injected fuel in the combustion chamber will be uneven. As a result, combustibility deteriorates, and ignitability deteriorates for the same reasons as mentioned above, making it impossible to effectively improve output. Furthermore, when the engine load is high and the rotation speed is low,
Even if the pressure applied to the plunger member is set to a medium level to ensure the fuel injection amount, if the swirl is small, it will not be possible to mix the air and fuel well, so the fuel will lack oxygen during the premix combustion stage. There is a problem that smoke occurs over time.

In view of the above points, the present invention has been made by further pushing the above idea, and it not only controls the fuel injection characteristics according to the operating condition of the diesel engine, that is, the engine speed and load, but also controls the intake air By simultaneously controlling the swirl strength of the The purpose is to enable optimal combustion to be performed depending on the operating conditions.

(Means for Solving the Problems) In order to achieve the above object, the solution means of the present invention is such that the rear end side of the needle valve has a shaft that coincides with the axis of the needle valve and has one end facing the needle valve. A diesel engine is provided with a pintle-type fuel injection nozzle configured to suppress the lift amount of the needle valve to a predetermined amount by applying a predetermined back pressure to the other end surface of a plunger member provided so as to be slidable in a direction. set to target. A swirl variable device that varies the intensity of the intake swirl generated in the combustion chamber of the engine; a pressure control valve that adjusts the back pressure acting on the other end surface of the plunger member of the fuel injection nozzle; controlling the strength of the intake swirl and the back pressure of the plunger member accordingly,
In the low engine load range, the strength of the intake swirl is reduced and the back pressure of the plunger member is set to high pressure. In the low speed and high load range, the strength of the intake swirl is increased and the back pressure of the plunger member is set to medium pressure, and in the high speed and high load range, the strength of the intake swirl is increased and the back pressure of the plunger member is set to medium pressure. In this case, a control device is provided for controlling the operation of the variable swirl device and the pressure control valve so as to reduce the strength of the intake swirl and lower the back pressure of the plunger member.

(Function) As a result, the fuel injection characteristics of the pintle-type fuel injection nozzle and the strength of the intake swirl can be simultaneously controlled according to various operating conditions of the diesel engine, and when the engine load is low, the swirl strength can be reduced. In addition, by increasing the back pressure of the plastic gear member, fuel atomization is promoted, and distribution of the injected fuel is improved due to low swirl.
Aim to reduce HC. In addition, when the engine load is high and the engine speed is low, by increasing the swirl strength and setting the back pressure of the plunger member to a medium pressure, the fuel injection amount can be secured at a medium level and the fuel amount can be reduced. Improves mixing with air to reduce smoke. On the other hand, when the engine load is high and the engine speed is high, by reducing the swirl strength and lowering the back pressure of the plunger member, a sufficient amount of fuel injection can be secured and its distribution can be improved. This is intended to improve output.

(Effects of the Invention) Therefore, according to the present invention, a control device that simultaneously controls the variable swirl device and the pressure control valve is provided, and the fuel injection characteristics and swirl intensity are simultaneously controlled according to the operating state of the diesel engine. This allows the diesel engine to perform good combustion according to its operating conditions, reducing HC at low loads, reducing smoke at low speeds and high loads, and improving output at high speeds and high loads. can be achieved all at once.

(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 the figure, 1 is a cylinder block having a cylinder 2;
3 is a cylinder head joined to the upper surface of the cylinder block 1; 4 is a piston fitted in the cylinder 2 so as to be able to reciprocate; the top surface of the piston 4 has a cylinder head for forming a combustion chamber 5; Cavity 4
A is recessed.

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 an intake swirl which will be described later.

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 is provided with a fuel inlet port 9 connected to an injection pump (not shown). A spring chamber 12, a needle valve support hole 13, and a fuel pressure chamber 14 are formed in the nozzle body 10 in this order from the rear end side to the front end side, and these cavities are coaxial with the fuel injection hole 8. and are provided so as to communicate 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 1
A needle valve 16 is fluid-tightly supported by a needle valve support hole 13 and is slidably fitted in the cavity between the fuel injection hole 2 and the fuel injection hole 8 . The needle valve 16 includes a spring receiving portion 16a disposed within the spring chamber 12, a pressure receiving portion 16b receiving fuel pressure within the fuel pressure chamber 14, and a fuel injection hole 8.
The fuel injection valve includes a valve portion 16c that opens and closes the fuel injection hole 8, and a throttle portion 16d disposed within the fuel injection hole 8. A certain distance is formed between the throttle portion 16d and the wall surface of the fuel injection hole 8. Further, a nozzle spring 17 is compressed within the spring chamber 12 and urges the needle valve 16 in the valve closing direction.
Then, high-pressure fuel from the fuel injection pump passes through the fuel passage 15 from the fuel inlet 9 to the fuel pressure chamber 14.
When the fuel pressure is applied to the pressure receiving part 16b of the needle valve 16, the needle valve 16 is opened against the urging force of the nozzle spring 17, and the fuel passes through the fuel nozzle hole 8 and enters the engine. The fuel is injected into the combustion chamber 5, and at that time, the distance between the throttle portion 16d and the wall surface of the fuel injection hole 8 changes according to the lift amount of the needle valve 16, thereby changing the lift amount of the needle valve 16 and the fuel injection. The opening area of the hole 8 is configured to change. That is, after opening the needle valve 16, first the throttle portion 16d
is located within the fuel nozzle hole 8 and the throttle portion 16d
The opening area of the fuel nozzle 8 enters a throttle range in which the opening area is kept approximately constant by the throttle of the fuel nozzle 8, and then, as the throttle portion 16d escapes from the fuel nozzle 8, the opening area increases in proportion to the lift amount of the needle valve 16. After the fuel injection hole 8 moves to a proportional change range in which the opening area increases, it is lifted to the full lift position. In addition, 19
is a fuel discharge passage, through which leaked fuel leaked from the fuel pressure chamber 14 into the spring chamber 12 through a small gap between the needle valve 16 and the needle valve support hole 13 is drained into a fuel tank (not shown) outside the nozzle. It is for discharging.

Furthermore, a cylinder 11 is formed coaxially with the needle valve 16 in the nozzle body 10 at the rear end of the spring chamber 12, and communicates with the spring chamber 12. The cylinder 11 is connected to the nozzle body 10 through a pressure passage 20. It is connected to an external 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 collar located between the rod portion 18a and the plunger portion 18b. The flange 18c is movable over a stroke range until the flange 18c comes into contact with the rear end wall of the spring chamber 12 and a stopper member 27 disposed at an intermediate portion of the spring chamber 12. In a state where the movement of the plunger member 18 toward the needle valve 16 is restricted by the contact of the plunger member 18c with the stopper member 27, the tip of the rod portion 18a, that is, the tip of the plunger member 18 is a spring serving as the rear end of the needle valve 16. It is positioned so as to face the receiving portion 16a with a predetermined distance d therebetween. As a result, the needle valve 16 is lifted and its spring receiving portion 16a is attached to the plunger member 1.
8, the needle valve 16 is opened by a predetermined pressure acting on the rear end surface of the plunger portion 18b of the plunger member 18.
The lift amount is suppressed to a predetermined amount.

Further, in the 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 outside portion of the nozzle body 10 of the pressure passage 20 via the communication passage 28. A pressure control valve 21 consisting of a duty valve for controlling the fuel pressure in the pressure passage 20 to decrease is disposed at a connection portion with the communication passage 28 .

Further, 29 is an intake passage for supplying intake air (air) to the combustion chamber 5 of the engine, and as shown in FIG. 3, the downstream end portion of the intake passage 29 is
It is composed of an intake port 30 formed into a cylinder head 3, and due to the arrangement shape of the intake port 30, the intake air taken into the combustion chamber 5 during the intake stroke is swirled around the shroud on the back side of the intake valve 31, and the intake air enters the combustion chamber. 5 is configured to flow in the form of a swirl. Further, in the middle of the intake port 30, a linear bypass passage is formed in the cylinder head 3 so that a part of the intake air in the intake port 30 does not swirl but goes straight and is sucked into the combustion chamber 5. The upstream end of 32 is opened, and the bypass passage 32
An opening/closing damper 33 for opening and closing the opening is provided at the upstream end opening. A pinion gear 34 is integrally attached to the support shaft 33a of the opening/closing damper 33, and a connecting rod 35 is attached to the pinion gear 34.
A rack 36 formed at one end is engaged, and the other end of the connecting rod 35 is drivingly connected to a swirl control actuator 36. The actuator 36 is compressed into a diaphragm 37 integrally attached to the connecting rod 35, a negative pressure chamber 38 defined by the diaphragm 37, and the opening/closing damper 33 is connected to the negative pressure chamber 38. The diaphragm device includes a spring 39 that urges the diaphragm 37 to open. The negative pressure chamber 38 is communicated with a vacuum pump 41 via a negative pressure introduction passage 40. Further, an electromagnetic three-way valve 42 is interposed in the middle of the negative pressure introduction passage 40 to normally open the negative pressure introduction passage 40 to the atmosphere. Then, by operating the three-way valve, negative pressure from the vacuum pump 41 is introduced into the negative pressure chamber 38 to bias the diaphragm 37 upward in the figure against the urging force of the spring 39, thereby closing the opening/closing damper 33. That's what I do. Therefore, this opening/closing damper 3
3 changes the strength of the intake swirl generated in the combustion chamber 5 of the engine, and when the opening/closing damper 33 is closed, the intake air flows into the combustion chamber 5 only through the intake port 30, increasing the strength of the intake swirl. When the damper 33 opens, a part of the intake air in the intake port 30 is diverted to the bypass passage 32 at its downstream end, and a straight flow of intake air flows through the bypass passage 32, thereby weakening the strength of the intake swirl. A variable device 43 is configured.

Then, the pressure control valve 21 and the three-way valve 42
To explain the control system that controls the operation, 22
23 is a load sensor for detecting the engine load condition; 24 is a duty solenoid for the pressure control valve 21 which receives the outputs of both sensors 22 and 23; and a control circuit that controls the operation of the solenoid drive circuit 25 for driving the swirl solenoids of the three-way valve 42, respectively. The above control circuit 24
The solenoid drive circuit 25 controls the operation of the pressure control valve 21 and the swirl variable device 43 according to the operating state of the engine, and when the engine is in a low load state, a low duty ratio signal is sent to the pressure control valve 21 to control the plunger member. increasing the fuel pressure applied to 18 and sending a low swirl intensity signal to the three-way valve 42 to suppress swirl;
Further, when the engine is under high load and high speed, a high duty ratio signal is sent to the pressure control valve 21 to lower the fuel pressure applied to the plunger member 18, and a low swirl intensity signal is sent to the three-way valve 42. Furthermore, when the engine is in a high load state and a low rotation state, a medium duty ratio signal is sent to the pressure control valve 21 to set the fuel pressure applied to the plunger member 18 to a medium level, and A controller 26 is configured to send a high swirl intensity signal to valve 42 to adjust it to promote swirl.

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 will lift as one. Further, the cylinder 11 of the fuel injection nozzle 7 is connected from the pressure source through the pressure passage 20.
The fuel pressure introduced into the cylinder 11 acts on the rear end surface of the plunger member 18, causing the plunger member 1
8 toward the needle valve 16, and by applying this pressure to the plunger member 18, the lift operation of the needle valve 16 after the spring receiving portion 16a abuts against the plunger member 18 is controlled.

On the other hand, by controlling the operation of the three-way valve 42 of the swirl variable device 43, the swirl control actuator 3
Introduction of negative pressure into the negative pressure chamber 38 of No. 6 and the negative pressure chamber 3
8 to the atmosphere is switched to control the operation of the actuator 36, and this actuator 36
As a result, the opening/closing damper 33 is opened and closed through the meshing movement of the rack 36 and the pinion gear 34, thereby controlling the swirl strength.

The control of the needle valve 16 and the three-way valve ₄₂ will be explained according to the control flowchart shown in FIG _. At step _S3 , the load signals from the load sensors 23 are input to the control device 26.
At step S4, the duty ratio corresponding to the operating state of the engine is read from a pre-stored duty ratio map based on the rotation speed signal and the load signal, and at step _S4 , the duty ratio corresponding to the engine operating state is read from the duty ratio map stored in advance. The stored swirl control values are read from the swirl control value map. Next, in step _S5 , the pressure control valve 2 is adjusted according to the duty ratio read above.
The duty solenoid No. 1 is driven and the fuel pressure applied to the plunger member 18 is controlled by the pressure control valve 21, and at the same time, in step _S6 , the swirl solenoid is driven according to the swirl control value read above. The swirl system generated in the combustion chamber 5 is controlled by the three-way valve 42.
Thereafter, the process returns to step _S1 and the subsequent steps _S2 to _S6 are repeated.

In this case, when the engine load is low, a low duty ratio signal and a low swirl intensity signal are sent from the control device 26 to the pressure control valve 21, respectively.
and the three-way valve 42, and the pressure control valve 21
When the throttle portion 16d of the needle valve 16 is in the throttle range where the fuel injection hole 8 is throttled, the needle valve 1
6 is suppressed, the state in which the fuel is injected at high speed is maintained for a long time, and the atomization of the fuel is promoted. At the same time, the opening/closing damper 33 is kept open by receiving the low swirl intensity signal from the three-way valve, and the intensity of the swirl in the combustion chamber 5 is weakened by the inflow of a portion of the intake air through the bypass passage 32. By promoting fuel atomization and reducing swirl strength, the injected fuel is dispersed well and its distribution is improved, which promotes combustibility and suppresses the generation of gas, thereby reducing HC. be able to.

Further, when the engine load is high and the engine speed is low, a medium duty ratio signal and a high swirl intensity signal are sent from the control device 26 to the pressure control valve 21 and the three-way valve 42, respectively. By receiving the duty ratio signal, the back pressure of the plunger member 18 is maintained at an intermediate pressure, thereby ensuring an appropriate amount of fuel injection. At the same time, three-way valve 4
Upon reception of the second high swirl intensity signal, the opening/closing damper 33 is closed and the swirl intensity increases.
By ensuring an appropriate amount of fuel injection and increasing the swirl strength, air and fuel are mixed well, so it is possible to suppress the occurrence of smoke.

Furthermore, when the load on the engine is high and its rotational speed is high, a high duty ratio signal and a low swirl intensity signal are sent from the control device 26 to the pressure control valve 21 and the three-way valve 42, respectively. By receiving the high duty ratio signal, the back pressure of the plunger member 18 becomes low and the fuel injection amount is ensured. At the same time, the three-way valve 42
Opening/closing damper 3 by receiving low swirl intensity signal
3 is kept open and the swirl strength is weakened. By ensuring the fuel injection amount and having a low swirl, the injected fuel is diffused well and the distribution property is improved, so that combustion can be promoted and the output of the engine can be improved.

It goes without saying that the present invention can be applied not only to the linear 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 the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a vertical sectional view of the main parts of a diesel engine, FIG. 2 is an overall configuration diagram of a fuel injection device, and FIG.
4 is a flowchart of the control system, and FIG. 5 is an explanatory diagram showing the relationship between the back pressure of the plunger member and the swirl strength with respect to the engine rotation speed and mean effective pressure (load). 7...Fuel injection nozzle, 16...Needle valve,
18... Plunger member, 20... Pressure passage, 2
1... Pressure control valve, 22... Rotation speed sensor, 23
... Load sensor, 26 ... Control device, 29 ... Intake passage, 43 ... Swirl variable device.

Claims (1)

[Scope of Claims] 1. A plunger member provided on the rear end side of the needle valve, aligned with the axis of the needle valve, and having one end facing the needle valve and slidable in the axial direction. In a diesel engine having a pintle-type fuel injection nozzle configured to suppress the lift amount of the needle valve to a predetermined amount by applying a back pressure of a swirl variable device; a pressure control valve that adjusts the back pressure acting on the other end surface of the plunger member of the fuel injection nozzle; and a pressure control valve that controls the intensity of the intake swirl and the back pressure of the plunger member according to the operating state of the engine; In the low engine load range, the strength of the intake swirl is reduced and the back pressure of the plunger member is set to high pressure. In the low speed and high load range, the strength of the intake swirl is increased and the back pressure of the plunger member is set to medium pressure, and in the high speed and high load range, the strength of the intake swirl is increased and the back pressure of the plunger member is set to medium pressure. A fuel injection device for a diesel engine, comprising: a control device that controls the operation of the variable swirl device and the pressure control valve so as to reduce the strength of the intake swirl and reduce the back pressure of the plunger member; .