JPS61123759A - Variable opening pressure/variable needle lift type fuel injection valve - Google Patents

Abstract

PURPOSE:To drop the injection rate forcefully upon droppage of valve-open pressure by limiting the lift of nozzle needle through utilization of tubular cam mechanism for varying the setting load of spring which will energize the nozzle needle in valve-close direction. CONSTITUTION:Under normal operation, the lever 78 is rotated through lever operating mechanism (not shown) untill the fixed cam 38 and the movable cam 40 are most separated. Under this condition, the spring 42 is compressed with strongest setting load thus to set the opening pressure of injection valve 10 at high level. Under low speed low load operation, the lever 78 is rotated reversely to bring the closest positional relation between said cams 38, 40 thus to reduce the setting load of spring 42. Second movable cam 62 is rotated together with said cam 40 to be separated from second fixed cam 56 thus to bring the stopper rod 76 near to the pressure pin 44 and to limit the lift of nozzle needle 24.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection valve for a diesel engine, in particular a swirl chamber diesel engine. More specifically, the present invention relates to a fuel injection valve that can simultaneously change the valve opening pressure and injection rate of the injection valve depending on engine operating conditions.

[Conventional technology]

So-called differential pressure type fuel injection valves are well known, and in this type of injection valve, the nozzle needle is elastically biased toward a closed position by a preflexure spring. The force due to the fuel pressure in the pressure chamber and the force due to the spring pressure of the pressure spring act on the nozzle needle in opposition to each other, and when the former force overcomes the latter force, the nozzle needle lifts and the fuel is released. is injected. Generally, a set load is applied to the pressure spring, and the opening pressure of the injection valve can be adjusted each time this preset load is applied by an adjustment screw.

It is known that engine noise (commonly referred to as idle knock) during the explosion stroke can be reduced by lowering the valve opening pressure when a diesel engine is running at low speed and under low load. In addition, lowering the valve opening pressure at low speeds and low loads reduces the initial injection rate during the injection cycle, which reduces fuel adhesion to the walls and reduces HC emissions.
The maximum combustion temperature decreases and NOx in exhaust gas decreases.

Therefore, in the prior art, it has been proposed to provide a cam mechanism that changes the set load of the pressure spring in a differential pressure type fuel injection valve, thereby changing the valve opening pressure (Japanese Patent Application Laid-Open No. 173557/1982). .

[Problem that the invention seeks to solve]

The present invention further improves the variable valve opening pressure type fuel injection valve of the type described above, and aims to provide a fuel injection valve that can further effectively reduce noise, HC, and NOx emissions at low speeds and low loads. It is a purposeful thing.

[Means and actions for solving problems] For this reason,
The present invention is a variable valve opening pressure type fuel injection valve characterized by providing means for regulating the lift amount of the nozzle needle.

This lift amount regulating means includes a stopper rod which is operatively connected to the cam mechanism and abuts against the nozzle needle, and limits the lift I of the nozzle needle to reduce the injection rate in response to a decrease in valve opening pressure.

[Example] Next, the present invention will be described in detail with reference to the accompanying drawings. In different drawings illustrating different embodiments, common components are designated by the same or similar reference numerals and redundant description will be omitted.

1 to 3 represent a fuel injection valve according to a first embodiment of the present invention. This injection valve 10 has a nozzle holder 12, and a nozzle retainer 14 is screwed into the nozzle holder 12. The retainer 14 is attached as usual (, nozzle body 1
6 and distance piece 1 day. The retainer 14 is provided with a threaded portion 20 for attaching the injection valve 10 to a mounting hole of a cylinder head (not shown), and
It is equipped with a hexagonal head 22 for wrench action.

Nozzle body 16 is of conventional type and has an axial bore 26 into which a nozzle needle 24 is slidably fitted. A pressure chamber 28 is formed in the nozzle body 16 adjacent to the shaft hole 26, and this pressure chamber 28 communicates with the outside through a nozzle hole 30.

A shaft hole 32 is formed in the nozzle holder 12. This shaft hole 32 constitutes a spring chamber 34 and accommodates various constituent members to be described later. That is, the fixed cam 3 is attached to the bottom of the shaft hole 32 via a shim 36 for adjusting the thickness.
8 is fixed.

Further, a movable cam 40 is mounted in the shaft hole 32 so as to be rotatable and movable in the axial direction. A pressure spring 42 is inserted into the spring chamber 34 in a compressed state, one end of which is supported by a pressure pin 44, and the other end of which is a spring receiver that is slidably installed in the shaft hole 32 and sealed with an O-ring. It is supported by 46. Pressure pin 44
acts as a spring holder for the pressure spring 42, and at the same time transfers the spring force of the spring 42 to the nozzle needle 2.
4. In order to prevent smooth rotation of the movable cam 40 from being disturbed by the thrust load caused by the pressure spring 42, a plurality of steel balls 48 and a perforated disc-shaped race 5 are provided between the movable cam 40 and the spring receiver 46.
A thrust bearing consisting of 0 is arranged. As will be apparent to those skilled in the art, the steel balls 48 can also be housed in a cage (not shown) and equally circumferentially spaced from one another.

As shown in FIGS. 1 and 2(a), the fixed cam 38
and movable cam 40 have complementary cam surfaces 52 that cooperate with each other.
, 54, and when the movable cam 40 is rotated relative to the fixed cam 38, the movable cam 40 is displaced in the axial direction, displacing the spring receiver 46 and changing the set load of the pressure spring 42. It has become. A second fixed cam 56 is further integrally molded in the center of the fixed cam 38 and has a cam surface 58 . On the other hand, the movable cam 40 is provided with a square-shaped through hole 60, and a second movable cam 62 having a square cross section is housed in the through hole 60 so as to be movable in the axial direction but not rotatable. Second movable cam 6
2 is a cam surface 6 complementary to the cam surface 58 of the second fixed cam 56;
4, and when the second movable cam 62 is rotated relative to the second fixed cam 56, the second movable cam 62 is displaced in the axial direction. As shown in Figure 2 fbl and (C1,
Fixed cam 38, movable cam 40, second fixed cam 56, second
The cam surface of the movable cam 62 is connected to the fixed cam 38 and the movable cam 40.
The second fixed cam 56 and the second movable cam 62 are closest to each other when they are at the farthest angular position (at this time, the set load of the pressure spring 42 is maximum), as shown in FIG. 2(b).
), and when the fixed cam 38 and the movable cam 40 are at the angular position where they are closest to each other (at this time, the set load of the spring 42 is the minimum), the second fixed cam 56 and the second movable cam 62 are farthest apart ( They are arranged in the relationship shown in FIG. 2(C)). That is, the movable cam 40 can be displaced by a distance d, and the second movable cam 62 can be displaced by a distance d in the direction opposite to the displacement of the movable cam 40 (see FIGS.
)reference).

The movable cam 40 is provided with an integral or separate radial projection 66 which projects slightly radially outwardly through an axial slot 6B formed through the wall of the nozzle holder 12.

A rotating sleeve 70 is rotatably fitted around the outer periphery of the nozzle holder 12, and this sleeve 70 abuts against a flange 72 of the nozzle holder 12 (1). sleeve 70
An axial groove 74 is formed in the inner surface of the holder, and the protrusion 66 is engaged in the groove 74 so as to be able to move in the axial direction but not to rotate relative to the other. Therefore, when the sleeve 70 is rotated in either direction, the movable cam 40 is rotated via the protrusion 66, and the movable cam 40 approaches or moves away from the fixed cam 38. At the same time, the second movable cam 62 moves to the second fixed cam 56.
move away from or approach. A stopper rod 76 is integrally connected to the second movable cam 62 so that it can move integrally with the second movable cam 62. Strike
The collar rod 76 passes through the race 50 and the spring receiver 46 and extends toward the pressure bin 44. The clearance between the stopper rod 76 and the pressure bin 44 determines the amount of lift of the nozzle needle 24, and its maximum value can be approximately one fin, for example. Figure 2 (C
The second movable cam 62 is adjusted so that when the second movable cam 62 rotates to the position >, the clearance becomes a value within the range of 0.3 to 0.90.
The cam surfaces of the cams 56 and 62 can be set.

Sleeve 70 is rotated by lever 78.

The lever 78 can also be fixed directly to the sleeve 70. However, when the injection valve 10 is mounted on the cylinder head, it is desirable to arrange the levers 78 of the injection valves of all cylinders in a desired direction and parallel to each other. For this purpose, as shown in FIG. 3, a rotating ring 80 spline-fitted to the outer periphery of the sleeve 70 is provided, and one end of the lever 78 is fixed to this ring 80 by, for example, spot welding.

A lock nut 82 is attached to the right end of the nozzle holder 12 in FIG.
The cap 84 is fastened. The cap 84 constitutes a part of the fuel return passage and also serves to prevent the rotating sleeve 70 and the rotating ring 80 from being removed. An annular groove 86 is formed in the shoulder of the nozzle holder 12 and communicates with the spring chamber 34 via a fuel return passage (not shown) provided within the nozzle holder. On the other hand, the cap 84 is also provided with an annular groove 88 opposite to the groove 86, and these grooves 86 and 88 cooperate to form a part of the return passage. Groove 88 communicates with an outlet fitting 90 attached to camp 84. A fuel return hose leading to the fuel tank can be connected to the metal fitting 90. A fuel supply pipe 92 from the injection pump is connected to the nozzle holder 12 by a cap nut 94 screwed onto the nozzle holder 12. The pressurized fuel is supplied to the pressure chamber 28 through the fuel inlet 96 of the nozzle holder 12, the fuel passage 98, the passage 100 of the distance piece 18, and the passage 102 of the nozzle body 16.

FIG. 4 schematically shows an example of an operating mechanism for the lever 78 of the injection valve 10, and shows an example of application to any type of four-cylinder diesel engine. Each injection valve 10 is mounted on a cylinder head (not shown) facing a combustion chamber or a swirl chamber. As mentioned above, by spline fitting the rotary ring 80 into the nozzle holder 12 with appropriate orientation, the levers 78 of each injection valve are arranged parallel to each other. Each lever 78 is connected to a tie rod 104. Tie rod 104 is pulled in one direction by tension reinforcement 106 and in the opposite direction by Bowden cable 108. cable 10
The other end of 8 is connected to a rotating lever 112 driven by a motor of an actuator 110. The actuator 110 is controlled by the control circuit 11B based on the load signal from the accelerator switch 114 constituting the load sensor, the vehicle speed signal from the vehicle speed sensor 116 provided on the output shaft of the transmission, and other signals (for example, engine rotational speed signal). controlled.

Under normal operating conditions (here, the case where both the load and the number of revolutions are above the set value), each lever 78 is rotated to the left in FIG. 4 by the tension spring 106 of the lever operating mechanism, and the fixed cam 38 and the movable cam 40 are in the relative positions shown in the second example). For this reason, pressure spring 4
2 is compressed with a strong set load, and the opening pressure of the injection valve is high (for example, it can be set to about 150 kt/-).

Also, since the convex surface 64 of the second movable cam 62 is fitted into the concave surface of the second fixed cam 56, the second movable cam 62 has moved to the right by the amount shown in FIG. The gap between the stopper rod 76 and the stopper rod 76 is maximum (for example, 1 fl). Therefore, the lift amount of the nozzle needle 24 is not restricted.

Next, when the engine load becomes less than the set value and the rotational speed becomes less than the set value (for example, about 11000 rpm), the control circuit 118 detects this and moves the lever 112 of the actuator 110 as shown in FIG. , and pull the cable 108. Therefore, the lever 78 of the injection valve rotates clockwise in FIG. 4, rotating the movable cam 40 via the protrusion 66 as shown in FIG. 2(C). As a result, the movable cam 40 itself moves to the right in the figure, and accordingly the spring receiver 46 also moves to the right, so the set load of the pressure spring 42 decreases, and therefore the biasing force of the spring 42 becomes weaker. Therefore, the nozzle needle 24 opens at a smaller opening pressure, for example, about 80 kg/ad. At the same time, the second movable cam 62 is rotated together with the movable cam 40, so the second movable cam 62 is separated from the second fixed cam 56 by the cam action, and the Stosobalon door 6 approaches the pressure bin 44, and the space between the two moves. Reduce gaps.

As a result, the pressure bin 44 hits the stopper rod 7G when the nozzle needle 24 is lifted, and the lift amount of the nozzle needle is limited.

Figure 5 shows the injection rate curves of the injector of the present invention for three engine conditions. Curve A corresponds to high speed and high load conditions, curve B corresponds to medium speed and medium load conditions, and curve C corresponds to low speed and low load conditions. do. The vertical axis represents the injection flow rate, and the horizontal axis represents time. As can be seen from curve 8, at high speed and high load, the injection rate curve rises rapidly, the injection rate is high, and the injection time is short. At medium speed and medium load, the rise is gradual as shown by curve B. At low speed and low load, the injection rate is kept low and the injection time is extended (curve C). This softens the explosion pulse and lengthens the combustion period, resulting in less engine noise and more complete combustion of the fuel.

FIG. 6 shows an injection valve 200 according to a second embodiment of the present invention. The difference from the first embodiment is that a screw mechanism is used instead of the cam mechanism consisting of the second movable cam and the second fixed cam, and the other configurations are basically the same as the first embodiment. be. In this embodiment, the stosova loft 76 is integrally connected to a screw member 202 having a square cross-section base 204 and a threaded head 206. The base portion 204 is fitted into the square hole 60 of the movable cam 40 so as to be relatively movable in the axial direction and non-rotatably. The threaded head 206 is attached to the fixed cam 3
It is screwed into the screw hole number 8. Therefore, when the sleeve 70 rotates in response to the rotation of the lever 7 and the movable cam 40 rotates, the screw member 202 also rotates and the threaded head 20 rotates.
6 is removed from the fixed cam 3 by screw action or introduced into the fixed cam 38. This allows Stosova Loft 7
6 is displaced in the axial direction, the lift amount of the nozzle needle increases or decreases. 7 and 8 show an injection valve 300 and a portion thereof according to a third embodiment of the present invention. This embodiment differs from the first embodiment in the configuration of both the cam mechanism for adjusting the valve opening pressure and the needle lift regulating means.

In this embodiment, the cam mechanism consists of a rotating cam 302 rotated by a rotating sleeve 70 and a sliding cam 306 prevented from rotating by a pin 304. The rotating cam 302 and the sliding cam 306 are also cylindrical cams that cooperate with each other in this embodiment. The thrust bearing is provided behind the rotating cam 302, and the rotating cam 302 cannot be moved in the axial direction. The stopper rod 76 is integrally joined to this rotating cam 302. In this embodiment, the sliding cam 306 is integrally formed with the spring receiver and supports one end of the pressure spring 44.

The detent pin 304 engages an axial slot in a sliding cam 306, so that the sliding cam 306 is axially displaceable but not rotatable. The pressure bin 44 is similarly prevented from rotating appropriately. As shown in FIGS. 7 and 8, the opposing ends of the pressure bin 44 and the strike collar rod 76 are stepped into a semi-cylindrical shape.

As shown in FIG. 8 (al), during normal operation, these stepped portions are in positions complementary to each other and the stroke, or lift amount, of the nozzle needle is dl. Lever 78
When the sliding cam 306 moves to the right in the figure due to the rotation of , and the valve opening pressure decreases, the stopper rod 76 moves as shown in FIG.
Since the nozzle needle rotates as shown in 1, the stroke or lift amount of the nozzle needle is shortened to d2.

〔Effect of the invention〕

As described above, the present invention forcibly reduces the injection rate at the same time as the valve opening pressure by regulating the lift amount of the nozzle needle using a cylindrical cam mechanism.

Therefore, it is possible to reduce engine noise at low speeds and low loads, and to reduce exhaust emissions of HC and NOx, without impairing engine performance under normal loads.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the first embodiment of the present invention, a part of which is shown exploded, and FIG. 2 (al is an exploded perspective view of the cam mechanism, FIG. A cross-sectional view of the cam mechanism.
Each figure shows the relationship between the components before and after the rotation of the lever. Figure 3 is an exploded perspective view of the rotating sleeve and rotating ring, Figure 4 is a schematic diagram of the lever operation mechanism, and Figure 5 shows the injection rate under different operating conditions. 6 is a sectional view of the second embodiment, FIG. 7 is a sectional view of the third embodiment, and FIGS. 8(a) and (
bl indicates the positional relationship between the opposing ends of the pressure pin and the stopper rod under different operating conditions. 10.200.300... Fuel injection valve, 12... Nozzle holder, 14... Retainer, 16... Nozzle body, 24... Nozzle needle, 28... Pressure chamber, 34... Spring Chamber, 38... Fixed cam, 40... Movable cam, 42... Pressure spring, 44... Pressure pin, 46... Spring receiver 52
, 54 , 58 , 64 ... cam surface, 56 ... second
Fixed cam, 60... Through hole (square hole), 62... Second movable cam, 66... Protrusion, 70... Rotating sleeve, 76... Stopper rod, 78... Lever.

Claims (1)

[Claims] 1. A differential pressure fuel injection valve equipped with a pressure spring that biases a nozzle needle in the valve closing direction, which injects fuel by changing the set load of the pressure spring according to engine operating conditions. The pressure spring set load changing means includes a pair of coaxially arranged relatively rotatable cylindrical cams that cooperate with each other and have cam surfaces that engage with each other. ,
A variable valve opening pressure fuel injection valve comprising: operating means for relatively rotating the pair of cams; 1. A fuel injection valve, characterized in that the injection rate is reduced in response to a reduction in valve opening pressure. 2. The pressure spring is supported by a pressure pin so that the pressure of the pressure spring is transmitted to the nozzle needle via the pressure pin, and the lift amount regulating means is a stopper rod that can abut against the pressure pin. 2. The fuel injection valve according to claim 1, wherein the nozzle needle, pressure pin, stopper rod, and cylindrical cam are coaxial with the axis of the injection valve. 3. One of the pair of cylindrical cams is a fixed cam, and the other is a movable cam that is rotatable and movable in the axial direction;
The movable cam has a through hole that is coaxial with the injection valve axis, and the lift amount regulating means has a second fixed cam provided at the center of the fixed cam and an axially relative portion in the through hole of the movable cam. a second movable cam fitted movably but not relatively rotatable; the second fixed cam and the second movable cam have cam surfaces that engage with each other; and the stopper rod is fitted to the second movable cam. The fuel injection valve according to claim 2, wherein the fuel injection valve is integrally connected to the second movable cam so as to be able to move in the axial direction together with the second movable cam. 4. One of the pair of cylindrical cams is a fixed cam, and the other is a movable cam that is rotatable and movable in the axial direction,
The movable cam has a through hole coaxial with the injection valve axis, the movable cam has a screw hole aligned with the through hole, and the lift amount regulating means is arranged in the through hole of the movable cam in an axial direction. The screw member includes a screw member having a base portion fitted so as to be relatively movable but not relatively rotatable, and a threaded head screwed into the screw hole of the fixed cam, and the base portion of the screw member is integrally connected to the stopper rod. 3. The fuel injection valve according to claim 2, wherein the fuel injection valve is configured to be able to move in the axial direction together with the threaded member. 5. One of the pair of cylindrical cams is a rotating cam that can rotate but cannot move in the axial direction, and the other is a sliding cam that can move in the axial direction but cannot rotate, and the sliding cam is aligned with the axis of the injection valve. The stopper rod has a through hole coaxial with the through hole, and the stopper rod extends through the through hole so as to be relatively rotatable and relatively movable in the axial direction. 2. The device according to claim 2, wherein the lift amount regulating means includes stepped portions formed at opposing ends of the pressure pin and the stopper rod and cooperating with each other. fuel injection valve.