JPS61229930A - Distribution type fuel injection pump for internal-combustion engine - Google Patents

Abstract

PURPOSE:To lower injection rate in low load for reducing engine noise by holding the termination period of fuel injection constant for variably controlling the injection starting period and thereby injection amount. CONSTITUTION:In a distribution type fuel injection pump, an end of a plunger 22 is inserted into an insertion hole 21 to form a distribution groove 26 communicating along the center axis through a through hole 24 to a high pressure chamber 25. Also, two spill ports 28, 29 are provided which disconnectively communicate through the through hole 24 to the high pressure chamber 25 and a space 27 in a pump housing 51 of low pressure source. And into a plunger 22 is inserted a control sleeve 31 interlocked slidably with a governor device to control the fuel injection starting period and determine the injection termination period by a sleeve 33. Thus, the fuel injection rate in low load can be lowered to reduce noises.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improvement in a distribution type fuel injection pump for an internal combustion engine, and particularly to an improvement in fuel injection characteristics.

(Prior Art) As a distribution type fuel injection pump used in a small diesel engine, there is a conventional one as shown in FIG.

In the figure, a pump/distribution plunger 3 is slidably inserted into a plunger barrel 2 attached to a pump housing 1, and the plunger 3 is engaged with a cam disk 4 integrally formed at its base end. Coupling 5
The drive shaft 6 rotates around the axis via the drive shaft 6. The cam disk 4 has the same number of face cams 4a as the number of cylinders of the engine, and the arc-shaped cam surface of the face cams 4a is mounted on a roller (cam follower member) 8 disposed in a roller holder 7 by a plunger spring 9. It rotates while being pressed and reciprocates by a predetermined cam lift.

Therefore, the plunger 3 reciprocates while rotating.

When the plunger 3 is in the suction stroke moving to the left in the figure, the fuel filling the inner space of the pump housing 1 is transferred from the suction port 10 formed in the housing 1 and the plunger barrel 2 to the outer peripheral surface of the plunger 3. The liquid is sucked into the high pressure chamber 12 formed between the end surface of the plunger 3 and the insertion hole 2a of the plunger barrel 2 through the suction groove 11 formed by the plunger. Next, when the plunger 3 moves to the right in the drawing, the fuel in the high pressure chamber 12 is pressurized and communicates with the through hole 13 formed in the plunger 3, and then flows to the outer peripheral surface of the plunger. A discharge boat 15 opened from the distribution groove 14 to the inner peripheral surface of the insertion hole 2a and a discharge passage 16 formed in the housing 1. The fuel is injected into each cylinder from a fuel injection nozzle (not shown) via the delivery pulp 17. Here, the discharge boats 15 are formed in the circumferential direction at equal intervals equal to the number of cylinders, and oil is fed in a predetermined order as the plunger 3 reciprocates and rotates.

A control sleeve 18 is slidably inserted into the part of the plunger 3 that discharges to the outside of the insertion hole 2a, and a cut-off boat 19 that communicates with the through hole 13 and is opened on the outer peripheral surface of the plunger 3 is inserted into the control sleeve. 18, the fuel in the high pressure chamber 12 flows out from the cutoff port 19 into the low pressure space inside the housing 1, forming an injection path.

Therefore, the injection end timing, that is, the injection amount can be controlled by adjusting the position of the control sleeve 18, and the position of the control sleeve 18 is determined by a control lever 20 and a governor mechanism that are linked to an accelerator pedal (not shown) (for example, Sankai Co., Ltd. Do “Automotive Engineering Complete Book 5 Diesel Engine” No. 19 published in March 1982
(See pages 0 to 196) (Problems to be solved by the invention) As described above, in the conventional distribution type fuel injection pump,
The fuel injection amount is increased or decreased by controlling the injection end timing, and the injection start timing is always constant.

However, in this case, fuel injection is not performed from the start point of the plunger's discharge stroke, but the correction amount due to suction after the previous discharge stroke is fed, and injection begins only after the valve opening pressure is reached. Therefore, injection is performed at low load such as at idle when the stroke amount of the plunger changes with respect to the crank angle, that is, near the maximum value of the fuel injection rate per crank angle (2 to C in Figure 2). .

Because of this high fuel injection rate, explosive combustion occurs, causing engine noise, diesel knock, and
Emissions of carbon dioxide and NOx will also increase, and since injection is performed over a short period of time, there will be large variations in the amount of fuel supplied between cylinders, which will increase engine rotational fluctuations and increase vehicle body vibration, among other problems. was occurring.

The present invention has been made by focusing on these conventional problems, and provides a distributed fuel for internal combustion engines that solves the above problems by having a configuration that can reduce the fuel injection rate during low loads such as idling. The purpose is to provide injection pumps.

(Means for Solving the Problems) Therefore, the present invention provides two spill ports in the plunger that can freely communicate and cut off the high pressure chamber and the low pressure source, and in conjunction with a governor device, the one spill port Means for variably controlling fuel injection start timing by cutting off a port from a low pressure source in the middle of the plunger's discharge stroke, and means for variably controlling the fuel injection start timing by connecting the other spill port to a low pressure source near the end of the plunger's discharge stroke. The configuration includes means for terminating the process.

With such a configuration, during special low load such as idling, fuel injection can be performed at a portion near the end of the plunger's discharge stroke, that is, a portion where the amount of change in stroke of the plunger with respect to the crank angle is small. , the fuel injection rate decreases and the fuel injection period increases.

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

In FIG. 1 showing the first embodiment, a plunger 22 whose tip is inserted into a fitting hole 21 has several cylinder suction grooves 23 formed on the outer circumferential surface of the tip, and a center shaft portion. As in the conventional case, a distribution groove 26 is formed which communicates with the high pressure chamber 25 through the through hole 24, which is formed along the through hole 24. Two spill ports 28 and 29 are provided which can freely communicate with and block the space 27 within 51.

Then, the pin 3 is inserted into the plunger 22 so as to be able to slide freely.
The one spill port 28 is cut off from the space 27 in the middle of the discharge stroke of the plunger 22 by a control sleeve 31 that moves in the axial direction of the plunger 22 in conjunction with a governor device (not shown) via the control sleeve 31. .

That is, the control sleeve 31 determines when the spill port 28 is blocked from the space 27 and the fuel in the high pressure chamber 25 starts to be pumped out from the discharge port 32.
A means for variably controlling a fuel injection start timing slightly later than this is configured.

Further, the other spill port 29 communicates with the space 27 near the end of the discharge stroke of the plunger 22 by a sleeve 33 fitted into the plunger 22, so that the fuel in the high pressure chamber 25 flows out into the space 27. It is designed to end the injection.

The sleeve 33 has a protrusion 36 eccentrically provided at the end of a fuel injection timing adjustment bolt 35 screwed through the wall of the pump housing 51 engaged in a groove 34 formed on the outer peripheral wall of the sleeve 33. At the same time, the axial position of the plunger 22 is adjusted. Here, the adjustment bolt 35 is rotated around the axis by engaging a screwdriver or the like in a groove 37 formed on the outer end surface of the pump housing 51, and the protrusion 35 is rotated around the axis.
The axial position of the sleeve 33 is adjusted by adjusting the rotational position of the sleeve 33. After adjustment, the sleeve 33 is fastened and held to the pump housing 51 by a nut 38 screwed into the end of the port 35. 39 is an oil seal ring for preventing fuel leakage.

That is, the sleeve 33 and the fuel injection end timing adjustment bolt 35
This constitutes means for terminating fuel injection near the end of the plunger 22 discharge stroke.

Next, a series of operations of the distribution type fuel injection pump having such a configuration will be explained.

During the suction stroke, in which the plunger 22 moves to the left in the drawing, fuel is sucked into the high pressure chamber 25 from the suction groove 23, as in the conventional case.Next, the plunger 22 moves to the right in the drawing, moving to the discharge stroke. The fuel in the high pressure chamber 25 is pressurized, but since the spill port 28 is in communication with the space 27 at the beginning, the fuel in the high pressure chamber 25 is pressurized in the space 27.
7, the plunger 22 moves further to the right, the boat 28 is blocked by the inner peripheral wall of the control sleeve 31, and then discharge from the discharge boat 32 starts, and after a short delay, the opening pressure of the fuel injection valve (not shown) increases. Fuel injection starts after reaching .

Then, when the plunger 22 moves further to the right in the figure and the other spill port 29 comes off the sleeve 33 and communicates with the space 27, the fuel in the high pressure chamber 25 is transferred to the spill port 29.
The fuel flows out into the space 27 and becomes a discharge path, and fuel injection is also completed.

That is, in FIG. 2, A is the discharge end point, and the injection start point shifts to 1, C, and 2 depending on the injection amount. In other words,
The shielding point of the spill port 28 for starting fuel injection moves, for example, at the mouth point at idle, at point C at full load, and at point 2 at startup (maximum injection amount), and the injection amount changes accordingly. is Q
i, Qf, and Qs (are controlled to increase. Therefore, by setting the discharge end point as close to the end of the discharge stroke of the plunger 22 as possible, that is, near the top of the cam lift, the oil delivery rate can be adjusted to the same level as the conventional discharge start point. It is possible to significantly reduce the timing compared to constant control, and the fuel injection rate can be significantly reduced accordingly, reducing engine noise and suppressing the occurrence of diesel knock, and reducing HC and NOx. Emissions can also be reduced.

Furthermore, the fuel injection period increases in inverse proportion to the decrease in the injection rate, thereby reducing variations in the injection amount between cylinders, suppressing fluctuations in engine rotation, and suppressing vibrations of the vehicle body.

In this embodiment, the spill port 28 also communicates with the space 27 in the latter half of the suction stroke, and fuel is secondarily sucked from the spill port 28 as well. This does not pose any problem in terms of pump function, but the fuel pressure valve (see Figure 4) installed to cut off the fuel supply to the suction groove 23 in order to cut fuel during deceleration. The spill port 28 is formed to have a sufficiently small diameter so as not to impair the fuel cut function, so as to reduce the amount of secondary fuel intake as much as possible.

FIG. 3 shows a second embodiment, in which a circumferential groove 44 communicating with a high pressure chamber 43 is connected to a suction port 45 near the end of the discharge stroke of the plunger 41 via a suction groove 42 on the outer peripheral surface of the tip end of the plunger 41. It is placed at the position where polymerization occurs. In this case, the spill port 28 for ending fuel injection, the sleeve 33 for opening and closing it, the bolt 35 for adjusting the timing of ending fuel injection, etc. in the first embodiment are omitted.

To explain the operation of this device, the suction and discharge of fuel are performed in the same manner as in the first embodiment, but the discharge ends when the circumferential groove 44 overlaps with the suction port 45 inside the high pressure chamber 43. This is done by returning the fuel from the suction port 45 to the space 46 via the suction groove 428 and the circumferential groove 44. That is, the circumferential groove 44 functions as a spill port for terminating fuel injection, and the suction port 45 also serves as a means for terminating fuel injection near the end of the cylinder discharge stroke.

Compared to the first embodiment, this embodiment has the advantage that it is extremely simple in structure (almost the same as the conventional one) and that fuel injection control can be performed at extremely low cost.

(Effects of the Invention) As explained above, according to the present invention, the injection amount is controlled by keeping the injection end timing constant and controlling the injection start timing variably. The injection rate decreases as the load (lower injection amount) increases, thereby making it possible to significantly reduce engine noise at low loads, suppress the occurrence of diesel knock, and reduce HC and NOx.

Furthermore, by increasing the injection period, variations in fuel injection amount between cylinders are reduced, engine rotational fluctuations are also suppressed, and vehicle body vibration can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main parts of the first embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the crank angle, the oil feed rate, and the discharge stroke of the plunger, and FIG. 3 is the second embodiment of the present invention. FIG. 4 is a sectional view showing an example of a conventional general distribution type fuel injection pump. 21... Fitting hole 22.41... Plunger
25.43... Hyperbaric chamber 27.46... Space
28... Spill port 29... Spill port 31.
...Control sleeve 33...Sleeve 35
... Fuel injection end timing adjustment bolt 44 ... Circumferential groove Patent applicant Nissan Motor Co., Ltd. Representative Patent attorney Fujio Sasashima Figure 2 Figure 3

Claims (1)

[Claims] The proximal end engages with the cam and reciprocates in the axial direction, and the plunger, which rotates around the axis, injects fuel into the high pressure chamber formed between the plunger and the insertion hole into which the tip end is inserted. In a distribution type fuel injection pump for an internal combustion engine, which discharges fuel to an injection valve installed in the engine after suction, the plunger is provided with two spill ports that can freely communicate and cut off the high pressure chamber and the low pressure source, and a governor is provided. means for variably controlling the fuel injection start timing by interlocking with the device to cut off the one spill port from the low pressure source in the middle of the plunger's discharge stroke; 1. A distribution type fuel injection pump for an internal combustion engine, comprising means for terminating fuel injection by communicating with a source.