JPS5968560A - Fuel injection nozzle - Google Patents

Abstract

PURPOSE:To contrive purification of exhaust gas and a reduction of a noise along with an improvement in fuel consumption efficiency, by controlling the maximum needle lift of a nozzle for changing fuel injection pressure arbitrarily according to a running condition of an internal combustion engine. CONSTITUTION:Guides 5 and 6 are fitted slidably over an external circumferential part 2c of a first control component 2 and two flat surface parts 2b for control of turning of a control rod 2 respectively. An external circumferential part 3b of a second control component 3 and an external circumferential part 3c of the second control component 3 are fitted slidably in the guide 5 and a cap 4 respectively. Force fit of a gear 24 over the second component 3 has been made and the bottom part of the second control component 3 and the top of the first component 2 are provided with a cam surfaces 3a and 2a of identical shape. The maximum lift of a needle 1 is controlled by adjusting a distance between surface 2a of the first control component 2 and the cam surface 3a of the second control component 3 by turning the first control component 2 and the second control component 3 relatively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection nozzle for an internal combustion engine, and more particularly to a fuel injection nozzle that variably controls the lift amount of a nozzle needle depending on the engine condition.

Hitherto, almost no method has been proposed for controlling injection pressure over a wide range according to the operating state of an internal combustion engine without significantly affecting the spray characteristics. Controlling the spray characteristics means indirectly controlling combustion, so there is a strong desire to control the spray characteristics, that is, the injection pressure, in diesel engines whose performance changes greatly depending on the spray conditions, especially direct injection diesel engines. was there.

An object of the present invention is to arbitrarily control the maximum needle reflux l-amount of a nozzle in accordance with the operating conditions of an internal combustion engine in order to change the fuel injection pressure.

The present invention will be explained below based on examples.

1 to 6 relate to the first embodiment of the present invention, and FIG. 1 is a longitudinal cross-sectional view of the first embodiment (B--B in FIG. 2).
Figure 2 is a cross-sectional view taken along the line A-A in Figure 1, Figures 3 and 4 are perspective views of the components, and Figures 5 and 6 are characteristic diagrams showing performance. There is.

The structure of the first embodiment will be explained with reference to FIGS. 1 to 4. In the nozzle body 8, the needle 1 is
is provided so that it can be reciprocated. A holder body 12 is screwed into the threaded portion of the retaining nut 11, and is tightened by sandwiching the nozzle body 8 therebetween. The needle biasing spring 1o is in contact with the first control member 2, and moves the top of the needle 1 via the connecting rod 9 in the valve closing direction (lower part of the figure) against the valve opening biasing force of the needle 1 due to fuel pressure. It functions to give an impetus to The holder body 12 is provided with a fuel hole 12a for supplying injected fuel and a leak hole 12b for allowing leakage fuel to pass through.

The guide 5 and the guide 6 are slidably fitted to the outer circumferential portion 2c of the first control member 2, and the guide 6 is fitted to the flat surface portion 2b for controlling rotation on two sides of the control rod 2, respectively. It is sandwiched between the cap 4 and the holder body 12, and is fixed by being tightened with a bolt 17.

The outer circumferential portion 3b of the second control member 3 and the guide 5 and the outer circumferential portion 3c of the second control member 3 and the cap 4 are respectively fitted to be rotatable, and in order to reduce rotational resistance, the second control member 3 A slight clearance is provided between the upper end of the cap 4 and the cap 4. A gear 24 is press-fitted into the second control member 3, and the lower end of the second control member 3 and the upper end of the first control member 2 have cam surfaces 3a and 2a of the same shape.

Further, a hydraulic piston 15 is slidably fitted into the cap 4 in an oil-tight manner, and the hydraulic piston 15 is fitted with a spring 1.
6 to the left in the figure. Further, the hydraulic piston 15 has a rack gear 15a, and when the hydraulic piston 15 moves left and right, the second control member 3 is rotated via the gear 24.

Reference numeral 18 denotes a hydraulic hole that allows passage of fluid at the control pressure P1 into the hydraulic chamber 14.

Before explaining the operation, the reason for controlling the lift amount of the nozzle needle 1 will be described. General throttle nozzles, bottle nozzles, etc. are needle riffs, as shown in Figure 7.
As tL increases, the flow rate coefficient μ and nozzle cross-sectional area F
The effective nozzle area μF, expressed as the product of , increases, and the upper limit is determined by the needle stopper position Lmax.

As is well known, when the pump rotates at a low speed, the oil delivery rate from the pump to the nozzle is low, so the pressure rise is suppressed and the injection pressure Po of the nozzle becomes low. When the nozzle injection pressure is low, the spray droplet size becomes large and the penetration force becomes weak, which has a negative effect on combustion.

Maximum value of nozzle needle lift amount L m at low speed rotation
By reducing ax, the maximum value μFmax of the effective nozzle area also becomes smaller, as shown in FIG.

Reducing μF is equivalent to narrowing the outlet.

If the pump rotation speed is constant, the pump oil delivery rate does not change. When the amount of fuel flowing into the pipe is constant, the pressure inside the pipe increases by squeezing the outlet, so the injection pressure
will rise.

When PO becomes large, due to the influence of the bulk modulus of oil in the pipe, etc.
A part of the amount of fuel flowing into the pipe is taken up by the expansion of the pipe and the increase in fuel density, so the fuel injection amount Q decreases somewhat, but the decreased amount of Q is replenished by the accelerator lever of the pump (not shown). By doing so, the injection period can be extended with the same injection amount.

Extending the injection period in the low speed range improves fuel efficiency and reduces noise.

Therefore, by controlling the nozzle needle lift amount, engine performance can be improved by improving combustion through the influence of spray particle size, penetration force, and injection period, as well as reducing noise.

Next, the operation will be explained with reference to FIGS. 1 to 6.

High-pressure fuel is pumped by a fuel injection pump (not shown).
After passing through an injection pump (not shown) and a fuel hole 12a, the nozzle needle 1 is urged upward in the figure, that is, in the valve opening direction.

When the fuel pressure PO reaches a cent pressure corresponding to the cent load of the spring 10 urging downward, the needle 1, the connecting rod 9, and the first control member 2 are lifted upward. Fuel is injected into the combustion chamber from a fuel injection hole 8a provided at the tip of the nozzle body 8.

・When the fuel pressure is not much larger than the valve opening pressure, the lift i of the nozzle 1 stops at a position where the upward biasing force due to the fuel pressure and the downward biasing force due to the spring IO are balanced, but when the fuel pressure further increases When the needle 1 is raised, the first control member 2 is further raised and the cam surface 2
a finally comes into contact with the cam surface 3a of the second control member 3.

The upward movement of the first control member 2 is restricted at the position in the central axis direction where the opposing cam surfaces 2a and 3a come into contact with each other, and the amount of lift of the needle 1 up to this point becomes the maximum amount of lift.

Next, when the fuel pressure po decreases and the upward biasing force of the needle 1 due to the fuel pressure decreases, the first control member 2 begins to descend together with the connecting rod 9 and the needle 1, and the fuel pressure po further decreases. Finally, the nozzle needle 1 descends to the lowest point and closes the fuel injection hole 8a at the tip of the nozzle body 8, thereby completing the injection.

While the above injection stroke is repeated, when the control oil pressure P1 of the fluid supplied to the left end of the cap 4 whose pressure is controlled by a pressure control device (not shown) is increased, the pressure chamber 14
The force applied to the hydraulic piston 15 in the right direction due to the fluid pressure P1 within the pressure chamber 14 increases, and the hydraulic piston 15 is biased in the right direction in the figure due to the fluid pressure in the pressure chamber 14 and to the left in the figure due to the spring 16. Slide to the right until the biasing force is balanced. At this time, the rack gear 15a rotates the second control member 3 via the gear 24 in the clockwise direction when viewed from above in FIG.

When the second control member 3 rotates, the cam surface 3a rotates, and the shortest distance that the needle 1 can move in the vertical direction between the cam surfaces 3a and 2a when it is at the lowest point position is It changes depending on the cam shape of the cam surface.

Note that this shortest distance corresponds to the needle maximum lift LmaX, and if the shortest distance at the lowest point of the needle 1 in the vertical direction between the cam surface 3a and the cam surface 2a becomes smaller, the tolerance of the first control member The amount of movement becomes smaller, and the needle I
The maximum lift iLmaX becomes smaller. The relationship between the rotation angle θ of the second control member 3 and the maximum lift amount Lmax of the needle is illustrated in FIG. 5.

As shown in FIG. 7, when Lmax becomes smaller, the maximum effective nozzle area μF max also becomes smaller, and due to the throttling effect, the fuel pressure po at the fuel inlet, that is, the fuel injection pressure increases. Conversely, when the control pressure P1 is decreased, Lmax increases,
Since μFmax also increases, the fuel injection pressure decreases.

This relationship is shown in Fig. 6 with respect to the change in fuel injection pressure over time, and it is often possible to change the fuel injection pressure by adjusting the rotation angle θ of the second control member 3. Garu.

Note that when the cam surfaces 2a and 3a of the first control member 2 and the second control member 3 come into contact, the rotational resistance of the second control member 3 becomes large, but the contact time is very short, and Since the operation is normally performed without contact, there is no problem.

A second embodiment of the invention is shown in FIG.

Focusing on the differences from the first embodiment, in the second embodiment, the receiving part of the connecting rod 9 of the first control member 2 of the first embodiment and the part having the cam surface 2a are divided, and the They are connected oil-tight using hydraulic pressure.

At the upper end of the connecting rod 9 is a piston 20 which is slidably fitted in an oil-tight manner to the spring chamber wall 12d of the holder body 12, and is biased downward by a needle biasing spring 1°. Further, the first control member 2 is a piston that is slidably fitted in a cylinder guide 6' in an oil-tight manner.

The guide 5' is slidably fitted into two opposing parallel planes $2b provided on a part of the first control member 2,
Rotation of the first control member 2 is restricted. Further, the spring chamber 21 is filled with fluid.

When the needle 1 rises, the piston 2
0 is pushed up and raised, and the first control member 2, which is oil-tightly connected by the fluid in the spring chamber 21, is raised by hydraulic pressure, and the first control is performed at the position where the cam surface 2a and the cam surface 3a contact. When the member 2 stops, the fluid in the spring chamber 2I can no longer move (and the piston 2o also stops because the inside of the spring chamber 21 is in a hydraulically locked state).

The advantages of this hydraulic coupling mechanism are explained below in 1) and 2).
This is the point.

1) Generally, the amount of needle lift is minute, and it is difficult to precisely control that minute amount, but by making the cross-sectional area of the first control member 2 smaller than the cross-sectional area of the piston 20, the first control can be performed. The amount of lift of the member 2 can be amplified. In other words, since the volume change due to the bulk elastic modulus of the fluid in the spring chamber 21 is minute, (the piston 2
0 cross-sectional area) x (amount of movement of the piston 20) - (cross-section a of the first control member 2) x (amount of movement of the first control member 2). Therefore, by amplifying the amount of movement of the piston 20 to the amount of movement of the first control member 2 and finely controlling the first control member 2, the piston 20 can be finely (accurately) controlled.

2) In the first embodiment, the cam surfaces 'la and 3a are subjected to an urging force equal to the upward urging force of 1 dollar 1) - the downward urging force of the 1 dollar urging spring 10), so that the cam surfaces 2a and 3a are If the pressure-receiving area is made small, the stress applied to the cam surface becomes extremely large, which tends to cause damage or wear to the cam surface. However, in the structure of the second embodiment, the load applied to the cam surface is divided by (the cross-sectional area of the first control member 2). (cross-sectional area of the piston 20), the force applied to the cam surface can be reduced.
It can protect the cam surface from damage and wear. In addition, the cam surface can be made smaller, and the structure around the camp 4 can also be made smaller, so there is an advantage that the weight can be reduced.

In addition, in the first and second embodiments, the cam surface 3a was controlled to rotate without rotating the cam surface 2a, but in FIG. A third embodiment of the present invention is shown in which the rotation of the surface 2a is controlled.

To explain the differences between the first and second embodiments, the first embodiment
The two planar parts 2b of the control member 2 are slidably fitted to the control member 30, and the first control member 2 can be rotationally controlled by rotating the control member 30. .

Further, the second control member 3 having a cam surface 3a on its end face is fixedly supported by the cap 4 by press fitting, welding, or the like.

Incidentally, the cam surface of the embodiments so far has been shown as a sine curve with respect to the circumferential direction as shown in FIG. 10 [a], but
The state of change in fuel injection pressure varies greatly depending on the nozzle shape, so the cam shape should be adjusted to suit each nozzle, such as a cam surface that changes linearly in the circumferential direction as shown in Figure 10 (bl), or a cam surface that changes linearly in the circumferential direction as shown in Figure 10 ( Various shapes can be selected, such as an axisymmetric shape as shown in C) or a bottle-shaped protrusion 3a' on either side as shown in FIG. 10 (c+).

If you want to increase the pressure-receiving area of the cam surface, it is desirable to use a cam shape like the one shown in Figure 10 (C1), which can lower the surface pressure of the cam surface and maintain pressure balance.

Moreover, FIG. 11 is a development view when the cam surface shown in FIG. 10 is developed in the circumferential direction.

The rotation control method uses a hydraulic control method using a rack gear, but the second control member 3 may also be rotated using a step motor, a DC motor, a linear solenoid, a rotary solenoid, or the like.

As described above in detail, the present invention includes a needle biasing spring 10 that biases the needle 1 in a direction in which the fuel injection hole 8a closes, and a first control member 2 that has a cam surface 2a on the end surface.
and a cam surface 3a opposite to the cam surface 2a of the first control member 2.
The first control member 2 and the second control member 3 are relatively rotated to control the cam surface 2a of the first control member 2 and the cam surface 3a of the second control member 3. Since the maximum lift amount of needle 1 is controlled by adjusting the distance between , has effects such as exhaust gas purification and noise reduction.

[Brief explanation of drawings]

1 to 6 relate to the first embodiment of the invention, and FIGS.
2 is a sectional view taken along the line A-A in FIG. 1, FIGS. 3 and 4 are perspective views of component parts, and FIGS. 5 and 6 are characteristic diagrams showing performance. FIG. 7 is a characteristic diagram of a general slot/nottle nozzle, bottle nozzle, etc. ta+ to tc) in FIGS. 8 and 9 relate to the second and third embodiments, and fa1 is a longitudinal cross-sectional view (
(B-B sectional view in (b)), fb1 is (A-A in Figure 81)
The cross-sectional view and Figure CC1 are perspective views of the constituent parts. Figures 10 and 11 are related to the shape of the cam surface, and Figure 10 (a+ or C)' is a front view, and Figure 11 is a front view.
The figure is a developed view when the cam surface is developed in the circumferential direction. ■... Needle, 2... First control member, 3... Second control member. Representative Patent Attorney Takashi Okabe Figure 1 Figure 2 Figure 6 (a) Figure 8 Figure 9 (21) Figure 9 (b) Figure 10 (a) (b) (C) (C
)′ Kagetsu diagram? a1 Indication of the case Patent Application No. 178082 filed in 19822 Name of the invention Fuel injection nozzle 3 Person making the amendment Relationship to the case Patent applicant Representative of Nippondenso Co., Ltd., 1-1 Showa-cho (426), Kariya City, Aichi Prefecture Person: Kengo Toda 4th, Masaru Address: 1-1-5 Showa-cho, Kariya-shi, Aichi Prefecture 448 Date of amendment order Date of dispatch: February 22, 1981 Column for detailed explanation of the invention in the specification to be amended, brief description of drawings Explanation column and drawings. 7 Contents of amendment (1) [Figure 10 (C1'
Correct J to "Figure 10 (d)". (2) In the third line of page 15 of the same book, ``Figure 10 fal or C)'' is a front view'' is replaced with ``Figure 10 (al, Figure 10 (
b), Figure 10 (cl) and Figure 10 (di are the respective front views for various cam surface shapes) are corrected. (3) Figure 10 of the drawing is corrected as shown in the attached sheet. (Correction of figure number) No. 10 [D (a) (b) (C”1 388-

Claims (1)

[Claims] In a fuel injection nozzle that injects fuel by opening and closing the fuel injection hole by reciprocating the needle in the direction of the central axis of a nozzle body having a fuel injection hole, the needle urges the needle in a direction in which the fuel injection hole closes. a biasing spring, a first control member having a cam surface on an end surface, and a second control member having a cam surface opposite to the cam surface of the first control member, the first control member and the second control member; A fuel injection system characterized in that the maximum lift amount of the needle is controlled by adjusting the distance between the cam surface of the first control member and the cam surface of the second control member by relatively rotating the cam surfaces of the first control member and the second control member. nozzle.