JPS6125924A - Fuel injection device in internal-combustion engine - Google Patents

Abstract

PURPOSE:To obtain an optimum injection rate in accordance with the operating condition of an engine, by disposing a one-way valve, an accumulating device and a variable orifice device, in the mentioned order from the upstream side, in fuel pressure-feed passage between the fuel injection part of a fuel injection device and an injection nozzle. CONSTITUTION:When high pressure fuel fed from a distributing type fuel injection pump 5 through a fuel pressure-feed passage 6 increases its pressure above a pressure P1 corresponding to a set load of a spring 2 in an injection nozzle 1, a needle valve 4 is lifted to allow fuel to be injected from a jet port 3. Further, a variable orifice device 9 which is disposed in a fuel nozzle body 1a, is controlled by a control device 8 to restrict the passage area of a fuel pressure-feed passsage section 6c to a small degree in a high load operating range, but to a large degree in a low speed operating range. Further, the fuel pressure-feed passage 6 is disposed therein with a delivery valve 15, an accumulating device 16 and a one-way valve 17 in the mentioned order from the downsteam side. With this arrangement, the amount of fuel injection may be appropriately changed in accordance with the operating condition of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fuel injection device for an internal combustion engine, and more particularly to a fuel injection rate (fuel injection amount versus time) control device for a fuel injection device.

<Prior art> In fuel injection systems for internal combustion engines such as diesel engines, the ignition delay of the injected fuel is affected by the swirl strength in the combustion chamber, the atomization properties of the injected fuel, the combustion chamber temperature, etc. in the low engine speed and low load region. As a result, a noise called so-called diesel noise is generated and the amount of NOx emissions tends to increase. Therefore, in this operating range, it is desirable to lower the fuel injection rate to cause slow combustion. On the other hand, in a high load region, the combustion chamber becomes hot and combustion is good, so it is desirable to have a high injection rate in order to improve engine output and fuel efficiency.

In order to obtain such a required fuel injection rate, conventional methods (J, August 1, 1980, published by Nissan Motor Co., Ltd., technical manual "Diesel Engine J No. 115," A throttle-type injection nozzle that injects fuel through a ring-shaped gap between the needle valve and the throttle part formed at the tip is adopted, and the nozzle area is small in the low lift region of the needle valve. The shape of the throttle portion is set so as to narrow the gap so that it becomes larger.

<Problems to be Solved by the Invention> According to the above four conventional throttle type injection nozzles, the lift amount of the needle valve varies somewhat depending on the engine operating state, so a mechanism for variable control of the ring-shaped gap is not required. Although it can be said that the injection rate is slightly controlled depending on the operating condition, basically the oil delivery rate of the injection pump is fixed, so the injection rate is low at low speed and under low load, and the injection rate is controlled slightly depending on the operating condition. However, it was not possible to satisfy the two demands of high injection rate at the same time.

In view of the above-mentioned disadvantages of the conventional device, the present invention variably controls the injection rate between low speed rotation, low load, and high load, and the injection rate variable control that increases the required injection amount does not have the adverse effect of causing excess or deficiency. The aim is to prevent this from occurring.

Means for Solving the Problems> To this end, the present invention provides a fuel injection device for an internal combustion engine that includes an injection pump section that sucks in and pumps fuel, and a fuel pressure pump that pumps the fuel pumped from the injection pump section. an injection nozzle that opens at a predetermined value or more to supply injection to the internal combustion engine; a fuel pressure passage that communicates the injection pump section and the injection nozzle; a variable throttle device that controls the passage area of the fuel pressure passage; a pressure accumulator that controls the volume of a fuel pressure passage upstream of the throttle device to be increased or decreased in response to passage pressure equal to or higher than a second predetermined value higher than the first predetermined value; a one-way valve that allows fuel flow in the forward direction.

As a result, for example, in a low engine speed rotation and low load region, the variable throttle device greatly throttles the fuel pressure passage to lower the injection pressure, reduces the valve lift of the injection nozzle to lower the injection rate, and reduces the throttle effect described above. Taking advantage of the fact that the pressure in the fuel pressure passage upstream increases due to this, the pressure accumulator is activated to raise the pressure in the fuel pressure passage to a second level higher than the injection nozzle valve opening pressure (first predetermined value). The injection period is increased by increasing the fuel volume between the one-way valve and the injection nozzle while maintaining the pressure above a predetermined value, and by holding the injection nozzle in an open state until the increased volume of high-pressure fuel is injected. Increase the length to obtain the required injection amount.

In addition, in the engine high load region, by loosening or opening the throttle of the variable throttle device to minimize the fuel pressure loss, the injection pressure is increased and a high injection rate is obtained. By suppressing the increase in fuel pressure and reducing the effect of the pressure accumulator, or by making it inactive, the fluctuations in the pump oil supply pressure and the pressure fluctuations in the fuel pressure passage are shortened and the injection period is shortened. Avoid injecting too much fuel.

<Example> Embodiments of the present invention will be described below based on the drawings.

In the figure, the injection nozzle 1 is connected to the injection port 3 by the spring 2.
The needle valve 4 is elastically biased in the valve closing direction, and the high-pressure fuel guided from the injection pump 5 through the fuel pressure passage 6 is applied at a pressure corresponding to the set load of the spring 2 (first predetermined pressure). When the value P1) is exceeded, the needle valve 4 receives the fuel pressure and lifts against the set load, opens the valve, and fuel is injected and supplied from the injection port 3.

A variable throttle device 9 is attached to the main body 1a of the injection nozzle 1, and variably controls the passage area of the fuel pressure passage portion 6c in the injection nozzle 1 to adjust the flow rate of fuel flowing therethrough. Specifically, this variable throttle device 9 is controlled by a control device 8 which receives an engine operating state signal from a microcomputer or the like via an actuator 7 such as a step motor.
The passageway area is controlled to advance and retreat with respect to the fuel pressure J path portion 6c, and in the engine high load region, the passage area is narrowed or fully opened, and in the engine low load region, it is increased.

On the other hand, the injection pump 5 basically employs a so-called Bosch type distribution fuel injection pump in this embodiment, and has a plunger 11 that rotates and reciprocates around its own shaft in synchronization with engine rotation. A section 5A is configured. When the plunger 11 moves to the left in the figure, the fuel in the low-pressure pump chamber 12 is sucked into the high-pressure chamber 14 via the suction boat 13, and when the plunger 11 moves to the right in the figure, the fuel in the high-pressure chamber 14 is sucked into the high-pressure chamber 14 through the discharge port 14.
It is pumped to a.

The discharge bow) 14a of the pump part and the spout 3 of the jet nozzle 1
In addition to the variable throttle device 9, the fuel pressure feeding passage 6 communicating with the variable throttle device 9 includes delivery valves 15.
A pressure accumulator 16 and a one-way valve 17 are interposed.

Of these, the delivery valve 15 has a known configuration, and opens and closes the fuel pressure passage 6 based on the differential pressure across it, but even after closing the fuel pressure passage 6, the delivery valve 15 has a predetermined stroke (
The suction back stroke) is configured to be able to move toward the pump section, and this movement greatly reduces the pressure in the fuel pressure feeding passage 6 downstream of the delivery valve 15, thereby preventing fuel from swinging back when the injection nozzle 1 is closed. do.

The pressure accumulator 16 has a spring 19 interposed in a spring chamber 18 that communicates with the low pressure pump chamber 12.
A pressure accumulation valve 20 elastically biased by the spring 19
passes through the piston guide 21 and faces the pressure accumulation chamber 22. The pressure accumulating chamber 22 is connected to the fuel pressure feeding passage 6 in the pump body 5B.
a, and the fuel pressure in the pressure accumulator 22 is higher than the valve opening pressure (first predetermined value) P of the injection nozzle part.
When the pressure reaches a predetermined value of 22 or more, the pressure accumulation valve 20 that receives this pressure retreats into the spring chamber 18 against the elastic force of the spring 19, and the volume in the pressure accumulation chamber 22, that is, the volume in the fuel pumping passage 6, is accumulated. It increases in accordance with the backward stroke of the valve 20.

The one-way valve 17 is configured to close the fuel pressure passage 6a between the discharge boat 14a and the pressure accumulation chamber 22 from the downstream side by the elastic force of a spring 25, and is freely reciprocated by a valve guide 26. Supported.

And an arm 17a extending from a part of the one-way valve 17
and the arm 20a protruding from the pressure accumulation valve 20 are in contact with each other, and when the pressure accumulation valve 20 is most protruded into the pressure accumulation chamber 22, the force of the spring 19 (greater than the elastic force of the spring 25) is applied to the elastic force of the spring 25. The configuration is such that the one-way valve 17 is opened by lowering it as shown in the figure.

The fuel pressure feeding passage 6a having the pressure accumulation chamber 22 and the fuel pressure feeding passage 6b having the delivery valve 15 are both open to the inner surface of the plunger barrel 27, and are inserted into a predetermined position of the plunger 11 through a groove 28 provided in a corresponding portion of the plunger 11. communicate with each other in angular phase.

A cut-off boat 29 that communicates with the high-pressure chamber 14 opens toward the inside of the pump chamber 12 on the outer circumference of the plunger 11, and a control sleeve 30 that opens and closes the cut-off boat 29 can freely slide in the axial direction around the outer circumference of the plunger 11. They are mated. The axial position of the control sleeve 30 is controlled by a mechanical governor mechanism or an electronically controlled governor mechanism in accordance with the engine operating state, but this is well known and will not be explained here. The same applies to the timer mechanism that controls the angular phase of the reciprocating motion of the plunger 11 to advance or retreat the fuel injection timing.

On Naoki Naoki's side, there is one suction boat13. Although one fuel pressure passage 6 (6a, 6b, 6c and groove 28) is shown, it goes without saying that these are provided for each cylinder.

Therefore, according to the above configuration, the high pressure fuel in the high pressure chamber 14 is discharged from the discharge boat 14a by the pumping movement of the plunger 11, pushes open the one-way valve 17, enters the pressure accumulation chamber 22, and enters the fuel pressure passage portion 5a, the groove 28. The delivery valve 15 is pushed open via the fuel pressure passage section 6b, and the fuel passes through the variable throttle device 9 at the injection nozzle 1 and reaches the oil reservoir 1b in the nozzle section while the flow rate is controlled. When the pressure of the pumped fuel rises above the valve opening pressure (first predetermined value p), the knee fuel valve 4 is lifted against the spring 2, the injection port 3 is opened, and fuel is injected and supplied to the engine.

Here, if the engine is operated at low speed and low load, the control device 8 inputting this operating state operates the variable throttle device 9 via the actuator 7 to reduce the passage area of the fuel pressure passage 6a. do.

For this reason, the flow resistance of the fuel increases, and the fuel pressure (injection pressure) downstream of the throttle portion decreases, resulting in an injection characteristic with a low injection rate.

On the other hand, on the upstream side of the variable throttle device 9, the fuel pressure increases significantly due to the increase in passage resistance, and reaches the second predetermined value 22 or more. The operating pressure of the spring 19 in the pressure accumulator 16 is set to such an extent that it does not operate under normal conditions, but when the fuel pressure increases in this way, the pressure accumulator valve 2o that receives this pressure resists the set load of the spring 19. and rise in the figure,
The volume inside the pressure accumulation chamber 22 is increased. This prevents damage to the fuel injection system such as piping breakage and fuel leakage due to an abnormal increase in the pressure within the fuel pressure passage 6.

Here, when the plunger 11 moves to the right by a predetermined pressure stroke in the figure, the cant-off port 29 comes off from the right end surface of the control sleeve 30 and is opened to the pump chamber 12, releasing the high pressure fuel in the high pressure chamber 14 to the pump chamber 12. do. In the conventional distribution type fuel injection pump of this type (Bososhquib), the fuel pressure in the high pressure chamber 14 decreases at this point and fuel injection ends, but in the present invention, the fuel pressure in the high pressure chamber 14 decreases as described above. When the pressure decreases, the one-way valve 7 is closed due to the pressure difference, and the fuel pressure upstream of the one-way valve 17 is maintained at a high pressure to keep the nozzle 3 open and the fuel pressure passage 6 In balance with the internal pressure, the elastic force of the spring 19 pushes the pressure accumulation valve 2° into the pressure accumulation chamber 22 to continue fuel injection. This fuel injection state continues until the arm 20a of the pressure accumulation valve 2o comes into contact with the arm 17a of the one-way valve 17 and the one-way valve 17 is forcibly opened by the elastic force of the spring 19 against the elastic force of the spring 25'. continue. If the one-way valve 17 opens, the fuel pressure in the fuel pressure passage 6 is relieved to the low pressure side via the cant-off boat 29 and instantly drops below the opening pressure of the injection nozzle 1. 1 is closed and fuel injection ends. When the fuel pressure in the pressure accumulation chamber 22 decreases in this way, the delivery valve 15 performs the above-mentioned suction action due to the pressure difference, lowers the fuel pressure in the fuel pressure passage 6 upstream from this, and improves injection cut-off. This prevents dripping and secondary injection from the injection nozzle 1.

In this way, the throttle action of the variable throttle device 9 injects and supplies fuel at a low injection rate, and the control sleeve 30
Since the injection ends due to the action of the one-way valve 17 and the pressure accumulator 16 after the fuel pressure control in the high pressure chamber 14 based on The injection amount is ensured.

When the load on the engine increases, the throttle device 8 opens the variable throttle device 9 via the actuator 7 in accordance with the load. For this reason, for example, when the engine is under high load, the throttle of the variable throttle device 9 is fully opened or opened to a small degree to eliminate or reduce the throttle loss and to increase the downstream fuel pressure, which causes the needle valve 4 that receives this pressure to also be lifted significantly. The fuel is injected and supplied from the injection port 3 at a high injection rate. On the other hand, the variable aperture device 9
Since there is no throttling loss or it is small on the upstream side of the pressure, the pressure inside the pressure accumulating chamber 22 rises to the second predetermined value P2.
Therefore, normal fuel injection is performed without the pressure accumulator 16 operating. In other words, when the control sleeve 30 relieves the high pressure in the high pressure chamber 14, the pressure in the pressure accumulator 22 decreases and fuel injection is terminated. There is no increase in the injection period and the injection amount is not increased too much.

It is unnecessary to explain that in the partial load region of the engine, the injection rate and injection period, that is, the injection amount can be variably controlled by the action of the one-way valve 17 corresponding to the throttling effect of the variable throttling device 9 and the pressure accumulator 16. . The throttling effect by the variable throttling device 9 may be applied only in the low engine speed rotation and low load region.

Furthermore, the pump section 5A that sucks in and pumps fuel is not limited to the above-mentioned type of distribution injection pump. The injection nozzle is not limited to a hole type, a throttle type, or the like. Variable diaphragm device9. Pressure accumulator 16. The location of the one-way valve 17 is also the same as in the embodiment of the injection nozzle body]a
Alternatively, it goes without saying that it is not necessary to provide it only in one or the other of the pump main bodies 5B, and that it may be provided independently from these parts.

<Effects of the Invention> As described above, according to the present invention, a one-way valve, a pressure accumulator, and a variable throttle device are installed in the fuel pressure passage between the pump section and the injection nozzle in order from upstream. can be changed according to engine operating conditions, and this does not adversely affect the injection amount.

[Brief explanation of the drawing]

The figure is a schematic configuration diagram showing one embodiment of the present invention.

Claims (1)

[Claims] An injection pump section that sucks in and pressure-feeds fuel;
an injection nozzle that opens at a predetermined value or more to supply injection to the internal combustion engine; a fuel pressure passage that communicates the fuel injection pump section and the injection nozzle; a variable throttle device that controls a passage area of the fuel pressure passage; a pressure accumulator that controls the volume of the fuel pressure passage upstream of the variable throttle device to be increased or decreased in response to passage pressure equal to or higher than a second predetermined value that is higher than the first predetermined value; and a pressure accumulator disposed on the upstream side of the pressure accumulator. 1. A fuel injection device for an internal combustion engine, comprising: a one-way valve that allows forward fuel flow;