GB2152135A

GB2152135A - Control of fuel injector valve lift

Info

Publication number: GB2152135A
Application number: GB08429044A
Authority: GB
Inventors: Masatoshi Yamada; Akinori Saito; Kenji Imai; Kiyomi Kawamura; Masanobu Kimura
Original assignee: Toyota Central R&D Labs Inc
Current assignee: Toyota Central R&D Labs Inc
Priority date: 1983-11-16
Filing date: 1984-11-16
Publication date: 1985-07-31
Also published as: GB8429044D0; JPS60108560A; DE3442022A1; GB2152135B

Abstract

To vary the spray characteristics of a fuel injector a lift stop 22 is movable to increase the maximum lift of the valve 8 from S1 to S1+S2. The stop 22 can be moved by oil or fuel pressure applied to a piston thereon, an electromagnetic coil (31, Figs. 4, 5 and 7 or 77, Figs. 13 and 14) acting on the stop (32, 70) or against the bias of a spring (43, 57, Figs. 8, 11 and 12). The valve may be opened by an electromagnet (75, Figs. 13 and 14) rather than fuel pressure. The stop position is determined by engine speed and/or load. <IMAGE>

Description

SPECIFICATION Fuel injection control The present invention relates to fuel injection control for internal combustion engines.

A direct injection type internal combustion engine having a combustion chamber formed by a recess in the top of a piston has been extensively employed as a large engine because, when compared with an internal combustion engine having a swirl chamber or precombustion chamber, it requires no communication port between the chamber and the combustion chamber and provides a low compression ratio, and therefore it suffers less frictional loss and attains a lower fuel consumption. However, if a small engine is constructed as such a direct injection type engine, problems arise in the formation of mixture gas.

In a conventional direct injection type internal combustion engine, a fuel injection nozzle is arranged substantially at the center of a recess which is formed in the top of a piston, and a plurality of fuel sprays are jetted radially from a plurality of injection ports. The intake air swirls which are formed by the intake valve and the intake passage during the intake stroke linger even to the end of the compression stroke thereby causing the fuel sprays to flow in the recess in the direction of swirl during the formation of the mixture. The diameter of recess is 40% to 70% of the diameter of the piston or cylinder. Therefore, in a small engine having a piston having a diameter of less than 100 mm, the diameter of the recess is quite small. If it is required to increase the compression ratio, the diameter of the recess must be even smaller.Accordingly, the fuel sprays radially jetted from the injection ports of the fuel injection nozzle tend to strike the walls of the recess, resulting in films of fuel or relatively large fuel droplets being deposited on the walls of the recess.

Therefore, the fuel sprays are not effectively burned, and the amount of mixture gas used in combustion is decreased. As a result, the engine output is decreased, the fuel consumption is increased, and smoke is generated.

As is apparent from the above description, the performance of a direct injection type internal combustion engine depends greatly on the characteristics of the fuel injection system employed. Therefore, it is important to make the fuel injection system suitable for the engine. Especially in order to cause the fuel spray jetted into the cylinder by the fuel injection nozzle to form a most suitable mixture gas, the droplet diameter, the spray angle, and the force of penetration of the fuel spray should be made suitable for the intake air stream pattern in the cylinder. Furthermore, the injection timing and the injection period of the nozzle are also important factors to consider for heating efficiency and suppression of smoke.

As the engine speed increases, the intake air swirl and the squash stream become stronger and the optimum injection timing changes. Therefore, in order to obtain an optimum mixture gas at all time, it is desirable that the spray characteristics be varied according to the speed and load of the engine.

It has been known that, in a small direct injection type diesel engine using a swirl injection nozzle, the engine performance is improved if the spray angle is large and the force of penetration is small when the engine operates at low speeds and if the spray angle is small and the force of penetration large when the engine operates at high speeds.

Accordingly, it is desirable to develop an intermittent fuel injection control method in which the fuel spray characteristics can be varied according to the operating conditions of the engine, and also to develop a device for practicing the method.

In view of the foregoing, the inventors have performed several experiments and carried out analyses regarding the spray angle, force of penetration and atomization with the intent of determining spray characteristics which are optimum for the various operating conditions of the internal combustion engine.

Controlling a valve opening pressure to vary the spray characteristics is known in the art.

However, such is not adequate to obtain the optimum fuel spray characteristics according to the operating condition of the engine, and is not practical for ordinary use. That is, in order to optimize the characteristics of a fuel injection nozzle such as the fuel spray angle, penetration force, atomization, and flow coefficient in accordance with the operating condition of the internal combustion engine, the inventors have developed a method in which the maximum lift of the valve needle is controlled for effective utilization, and accomplished a fuel injection control method and device for an intermittent fuel injection nozzle which provides the desired advantages.

Provided according to one aspect of the invention is a fuel injection control method for an intermittent fuel injection nozzle in which, when a valve needle slidably fitted in a valve hole formed in a nozzle body is lifted from a valve seat in the valve hole by a valve needle operating device incorporated in the nozzle body to open the nozzle, fuel supplied through a fuel passage is jetted through an injection port, whereby, according to the invention, the maximum lift of the valve needle, which is obtained when the nozzle is opened, is regulated and/or changed by a valve needle lift control device according to the operating conditions of the engine to vary the fuel spray characteristics thereof.Provided according to a further aspect of the invention is a fuel injection control device for an intermittent fuel injection nozzle which comprises: a valve needle slidably fitted in a valve hole formed in a nozzle body, an injection port communicating with a valve seat in the valve hole against which the end of said valve needle is abutted, and a fuel passage communicating with the injection port; a valve needle operating device, incorporated in the nozzle body, to lift the valve needle from the valve seat in the valve hole to open the nozzle so that, when the valve needle is lifted to open the nozzle, fuel supplied through the fuel passage is jetted through the injection port; and a valve needle lift control device with which the maximum lift of the valve needle, which is obtained when the nozzle is opened, is regulated and/or changed by control means according to the operating conditions of the engine to vary the fuel spray characteristics thereof.

In a preferred fuel injection control device according to the invention, the control means comprises a stop for setting the lift of the valve needle, the position of the stop of the valve needle being varied according to the operating conditions of the engine. Further, in the preferred fuel injection control device according to the invention, the control means operates in response to an oil pressure which changes according to the operating conditions of the engine to vary the position of the stop which sets the lift of the valve needle, thereby to regulate and/or change the maximum lift of the valve needle.Still further, in one embodiment of the invention, the control means utilizes an electromagnetic force to vary the position of the stop which sets the lift of the valve needle according to the operating conditions of the engine, thereby to regulate and/or change the maximum lift of the valve needle. Yet further, in another embodiment of the invention, the control means utilizes the elastic force of a valve spring to vary the position of the stop which sets the lift of the valve needle according to the operating conditions of the engine, thereby to regulate and/or change the maximum lift of the valve needle.

In the above-described method and device, according to the invention, the maximum lift of the valve needle is regulated and/or changed according to the operating conditions of the engine, whereby desired fuel spray characteristics, such as spray angle, flow coefficient, travel distance and atomization, are obtained in accordance with the operating conditions of the engine.

Accordingly, with the use of the invention, fuel spray jetted by the intermittent fuel injection nozzle forms a satisfactory mixture gas with the aid of the intake air stream without striking the walls of the recess in the combustion chamber or adhering to the top of the piston. Therefore, the fuel spray is effectively burned. As a result, the engine output is increased, the fuel consumption is decreased, and the generation of smoke is eliminated. In addition, production of harmful components in the exhaust gas and generation of combustion noise are greatly decreased.

By way of example only, in the accompanying drawings: Figs. 1 and 2, and 3 are vertical sectional views and a diagram, respectively, showing a first embodiment of a fuel injection control device of the invention; Figs. 4 through 7 are diagrams showing a second embodiment of a fuel injection control device of the invention; Figs. 8 through 1 2 are diagrams illustrating a third embodiment of a fuel injection control device of the invention; and Figs. 1 3 and 1 4 are vertical sectional views showing a fourth embodiment of a fuel injection control device of the invention.

The invention will now be described with reference to examples of a method for controlling the lift of a valve needle in a fuel injection nozzle and a device for practicing the method.

First Embodiment In the first embodiment of the invention, a fuel injection nozzle A1 is a fuel-pressure operated automatic fuel injection nozzle in which, as shown in Fig. 1, the valve needle operating (opening and closing) device mazes the valve needle 8 in response to the fuel pressure or spring pressure to open and close the fuel passages and the injection port. The valve body of the fuel injection nozzle Al, namely, a nozzle body 1, has a nozzle member 4, at the end of which is formed the injection port 2, and a conical valve seat 3 which is provided inwardly of the port 2 and is communicated with the latter. A guide hole 5 and a valve hole 6 are formed in the nozzle body 1 and the nozzle member 4, extending along the central axes thereof.A push rod 7 and the valve needle 8 are slidably fitted in the holes 5 and 6, respectively, with close tolerances.

Inside the nozzle member 4, the conical end of the valve needle 8 can be pressed against the valve seat 3 to provide thereat a tight seal. The valve needle operating device operates so that the fuel pressure moves the valve needle 8 up and down, against the elastic force of a valve spring, into and out of engagement with the valve seat 3, whereby fuel is intermittently jetted through the injection port 2. In the nozzle member 4, a swirl chamber 11 having coaxial hollow spaces, each in the form of a frustum of circular cone and communicated with each other, is formed between the valve seat 3 communicated with the injection port 2 and a conical pressure receiving surface 10 provided on the side of the end of the valve needle 8 seated on the valve seat 3.

The swirl chamber 11 has tangential lines to the inside surface of the swirl chamber 11 from the outer wall of the nozzle member 4.

The direction of the axis of the opening of each tangential port 1 2 is the direction of a corresponding tangent line to the inside surface of the swirl chamber 11. Pressurized fuel supplied into the swirl chamber 11 is swirled around the central axis of the swirl chamber 11. Furthermore, the direction of the axis of the opening of each tangential port 1 2 is the same as the direction of swirl of the pressurized fluid. The tangential ports 1 2 are communicated with the swirl chamber. A plurality of fuel passages 1 5 and a plurality of fuel passages 1 6 are formed in the side walls 1 3 and 14 of the nozzle member 4 and the nozzle body 1, respectively, extending substantially parallel to the central axis of the swirl chamber 11.The fuel passages 1 5 are communicated with the fuel passages 1 6 through annular recesses 1 7 formed in the end faces of the nozzle member 4 and the nozzle body 1 which confront one another.

The fuel passages 1 5 are communicated through the tangential ports 1 2 and the swirl chamber 11 with the injection port 2. The fuel passages 1 6 are communicated with a fuel supply source including an external fuel pump (not shown). In the nozzle member 4, a closing member 1 8 is hermetically fitted in the opening of each tangential port 12, which closing member 1 8 is located outside a communicating part in the side wall of the nozzle member 4 where the tangential ports 1 2 meet the fuel passage 1 5 so that the tangential ports 1 2 penetrating through the side wall are closed outside the communicating part.The rear end of the valve needle 8 is in abutment with a push rod 1 9 which is coaxial with the valve needle 8 and which is slidably fitted in the guide hole 5. A spring seat 20 for the valve spring 8 which urges the valve needle 8 against the valve seat 3 is provided on the other end of the push rod 1 9.

In the fuel injection nozzle A1 of the first embodiment, the valve needle 8 is urged by the valve spring 9, which operates as the valve needle operating device, to close the injection port 2. When the pressure (injection pressure) of the fuel supplied under pressure from an injection pump becomes higher than the valve opening pressure determined by the initial compression of the valve spring 9, the valve needle 8 is lifted from the valve seat 3 of the valve hole 6 to open the latter so that the fuel is jetted through the injection port 2 communicated with the valve hole 6. As the fuel delivery pressure of the injection pump decreases, the injection pressure is decreased.

When the injection pressure becomes lower than the valve opening pressure, the valve needle 8 is seated on the valve seat 3 of the valve hole 6 to close the latter.

The fuel injection valve Al is designed so that the valve needle 8 is lifted until it abuts against a stop, and it cannot be lifted any further after it has been abutted against the -r z In the first example, the stop which determines the maximum lift of the valve needle 8 is driven by oil pressure so that the position of the stop is made variable to control the maximum iift of the valve needle. This will be described in more detail.

In Fig. 1, reference numeral 21 designates a retainer for the valve spring 9. A piston 22 serves as a stop for the rod 1 9 which abuts against the valve needle 8 through the push rod 7, forming a needle lift control device.

The piston 22 moves in the nozzle body in accordance with the magnitude of an oil pressure Pc When oil pressure is low, the piston 22 is forced into contact with the spring retainer 21 by a valve spring 23. The valve needle 8 has a maximum lift S, as indicated in Fig. 1. When the oil pressure becomes larger than the initial load of the valve spring 23, the piston 22 is moved against the elastic force of the valve spring, and therefore the lift of the valve needle 8 is increased by an amount determined by the movement of the piston.The amount of movement of the piston 22 is determined by the gap S2 between a stop 24 and a spring retainer 25 secured to the nozzle body 1. Accordingly, the maximum lift of the valve needle 8 can be changed from S, to S, + S2 by controlling the oil pressure Pc. If the value S, is set to zero, then the lift of the valve needle 8 can be changed from zero to S2.

In an injection system including an injection pump and a fuel injection nozzle, the pressure in the pump chamber of the injection pump can be employed instead of the oil pressure Pcs The pressure in the pump chamber increases substantially in proportion to the injection pump speed Nc, which is half of the engine speed, as shown in Fig. 2. In the fuel injection nozzle A, of the first example, the lift of the valve needle 8 reaches S, + S2 when the speed of the engine reaches 2Nc.

Since the maximum lift of the valve needle 8 can be controlled as described above, the spray characteristic of the intermittent fuel injection nozzle A, can be varied, and especially the spray angle can be made variable with the engine speed.

In the first embodiment described above, the maximum lift of the valve needle 8 is regulated and/or changed in accordance with the operating conditions of the engine, whereby desired fuel spraying characteristics, such as spray angle, flow coefficient, travel distance and atomization, are set in accordance with the operating conditions of the engine. Therefore, in the first embodiment, fuel spray jetted by the intermittent fuel injection nozzle Al is mixed with the intake air stream to form excellent mixture gas without fuel droplets striking the walls of the recess in the combustion chamber and without fuel sticking to the top of the piston. Also, the force of penetration of the fuel spray is maintained so that the fine fuel droplets move in the combustion chanmber until combustion ends. Thus, the fuel spray is effectively burned.As a result, the engine output is increased and the fuel consumption decreased. Furthermore, the generation of smoke can be eliminated. In addition, the production of hazardous components in the exhaust gas can be remarkably decreased and the combustion noise greatly reduced.

Not only on the swirl injection nozzle as in the above-described embodiment, but also in a throttle type injection nozzle or a pintle type injection nozzle, can the fuel passage area characteristic with respect to the lift of the valve needle be controlled in accordance with the operating conditions of the engine by controlling the lift of the valve needle. Therefore, in these injection nozzles as well, similarly to the case of the swirl injection nozzle, the spray characteristics can be selectively controlled. More specifically, the spray angle can be changed with the speed of the engine.

Thus, such nozzles can provide substantially the same effect as the swirl injection nozzle.

Fig. 3 illustrates a method and device in which a control device for controlling the maximum lift of a valve needle 28 in response to oil pressure is employed similarly to the first embodiment such that control is effected to increase the lift of the valve needle 28 and to decrease the lift of the valve needle 28 to S,.

As shown in Fig. 3, a circuit 26 for supplying oil pressure to a piston 22 adapted to control the lift of the valve needle 28 and an oil relief circuit 27 are selectively activated by an electromagnetic control valve 29. Therefore, controlling the piston 22 to increase the lift of the valve needle 28 or controlling the piston 22 to decrease the lift of the valve needle 28 can be selected by operating the electromagnetic control valve 29.

The intermittent fuel injection nozzle of the first embodiment described above is of the port type wherein tangential ports formed in the nozzle body 1 are used to swirl the fuel supplied to the injection port 2. On the other hand, the intermittent swirl injection nozzle A2 of Fig. 3 is of the screw type wherein tangential grooves 30 formed in the valve needle 28 are used to swirl the fuel supplied to the injection port 2. The nozzle A2 is substantially the same as the nozzle A, in other respects. Therefore, in Fig. 3, those components which have been previously described with reference to Fig. 1 are designated by the same reference numerals or characters and their detailed descriptions are omitted.

Second Embodiment A second embodiment of the invention is a method and device in which, instead of oil pressure as in the first embodiment described above, an electromagnetic force is used to control the lift of the valve needle. In the second embodiment. with reference to Fig. 4, the valve needle lift control device is an electromagnetic coil 31. When current is applied to the electromagnetic coil 31. the electromagnetic force acts on a movable core 32.

One end of the movable core 32 forms a part of the valve needle lift control device, serving as a stop for the rod 33 of the valve needle 38. By raising the movable core 32, the lift of the valve needle 38 is increased as much.

That is, the maximum lift of the valve needle 38 can be varied from S, to S, + S2. The value S, may be zero.

The fuel injection nozzle A3 of the second embodiment is an intermittent swirl injection nozzle in which. unlike the nozzle of the first embodiment, partition member 35 is provided between the inner wall 34 of the nozzle member 4 and the valve needle 38, tangential grooves 36 are formed in the outer wall of the partition member 35, and the partition member 35 has a valve hole 37 in which the valve needle 38 is slidably fitted. The outer components are substantially the same as those in first embodiment, and are designated by the same reference numerals or characters. The effects of the second embodiment are substantially the same as those of the first embodiment.

If, as shown in Fig. 5, a controller 39 is provided to control the current applied to the electromagnetic coil 31 by utilization of an engine speed detection signal VN, then the lift of the valve needle can be controlled according to the engine speed.

In another example, specifically, in the case of an electronic control fuel injection system as shown in Fig. 6, the controller 39 of the electromagnetic coil is adjusted using a pump speed sensor signal output VNP and a spill position sensor signal output V5 corresponding to the amount of injection of fuel, as shown in Fig. 7, so that the lift of the valve needle is controlled according to the speed and load of the engine because the pump speed corresponds to the engine speed and the amount of injection of fuel to the load of the engine.

Third Embodiment A third embodiment of the invention is a method and device for controlling the lift of the valve needle in a throttle type injection nozzle using an elastic force. As shown in Fig.

8, in the fuel injection nozzle A4, the rod 40 of the valve needle 48 is pushed upon by the elastic force of a first valve spring 41. A stop 42 for the first valve spring 41 is movable, but it is retained by the elastic force of a second valve spring 43. When lifted by S, against the elastic force of the first valve spring 41, the rod 40 of the valve needle 48 strikes the stop 42. When the force of lifting the valve needle 48 becomes larger than the initial set value of the elastic force of the second valve spring 43, the valve needle 48 is further lifted together with the stop 42 against the elastic force of the second valve spring 43.

If the spring constant k 1 of the first valve spring 41 is larger than that k2 of the second valve spring 43 (k, > k2), and the force F, which is provided when the first valve spring 41 initially set is compressed by S 1 is made equal to the initial set force of the second valve spring 43, then the relationship between the lift of the valve needle and the force is as indicated by the solid line in Fig. 9.

When the lift of the valve needle 48 is S, or more, the valve needle 48 can be readily lifted because the spring constant of the second valve spring 43 is smaller than that of the first valve spring 41. If the initial set value F2 of the valve spring 43 is made larger than the aforementioned force F1, then, as indicated by the solid line in Fig. 10, the lift of the valve needle 48 reaches S, and it is maintained unchanged until the valve needle lifting force reaches the initial set value F2 of the second valve spring 43. When the valve needle lifting force becomes larger than F2, th;, valve needle is further lifted.In the case of k, > k2, the relationships are as indicated by the single-dot chain ines in Figs. 9 and 1 0. As is apparent from the above description, the lift of the valve needle 48 can be controlled by suitably selecting the spring constants and the initial set values of the first and second valve springs 41 and 43.

An example of a device in which the control method of the invention is applied to a double-screw type swirl injection nozzle As whose spray characteristics are changed with the amount of lift is shown in Fig. 11. The injection nozzle A5 includes a nozzle holder 51 having double slits and springs in two stages.

That is, the injection nozzle A5 has a first slit 50 which has a relatively large inclination angle H, with respect to the central longitudinal axis of the valve needle 58 and a second slit 52 which has a relatively small inclination angle 02 with respect to the central axis of the valve needle and relatively large groove width.

The second slit 52 extends at a distance Y, from the entrance of the first slit 50 as shown in Fig. 11.

When fuel is supplied through a fuel passage 53, it reaches the end of the valve needle 58 through the first slit 50, thus lifting the valve needle 58 against the force of the first spring 54. The spring constant of the first spring 54 is so small that even when the engine speed (or the injection pump speed) is low with the result that the fuel supplying rate (per hour) is small and therefore the fuel pressure is not high enough the valve needle 58 can still be raised quickly. As the valve needle 58 is raised, a first pressure plate 55 is also raised, thus striking a second pressure plate 56 which forms a valve needle lift control device. The amount of lift of the valve needle 58 in this case is made smaller than y,. A second spring 57 is placed on the second pressure plate 56. The second spring 57 has a relatively large spring constant.

Therefore, in the case where the fuel pressure is low, when the first pressure plate strikes the second pressure plate 56, lifting of the valve needle 58 is stopped. In this operation, fuel flows through the first slit 50, thus becoming a swirl stream. Thus, the nozzle functions as a swirl injection nozzle.

When the engine speed (or the injection pump speed) is increased and the fuel supplying rate is increased, the pressure in the nozzle is increased. Therefore, the valve needle 58 is further raised against the elastic force of the second spring 57. As a result, the second slit 52 is opened and fuel flows through the second slit 52. The inclination angle 82 of the slit 52 is smaller and the groove width is larger. Therefore, the fuel is not swirled substantially; that is, it is jetted as in the case of a so-called hole nozzle rather than as in the case of a swirl injection nozzle.

When the engine speed (or the injection pumo speed) is low, the fuel injection nozzle A5 of the third embodiment operates like a swirl injection nozzle, that is, the force of penetration is small, and therefore, even if the speed of the air stream in the combustion chamber is low, the fuel spray is satisfactorily burned without sticking to the wall of the combustion chamber. When the engine speed is high, the force of penetration becomes substantially equal to that of a hole nozzle, and the speed of fuel spray becomes conformable to the speed of the air stream, and therefore overly broad scattering the fuel spray is prevented and the fuel spray is burned stably.

Fig. 1 2 shows a swirl injection nozzle A7 in which a valve spring 54 is arranged inside a valve spring 57. In Fig. 12, those components which have been previously described with reference to Fig. 11 are therefore designated by the same reference numerals or characters. The second valve spring 57 differs from that in Fig. 11 in that it suppresses the lifting of the valve needle 58. The other components are substantially the same in operation as those in Fig. 11.

Fourth Embodiment A swirl injection nozzle A5 of the fourth embodiment of the invention differs from the above-described fuel injection nozzles in that the nozzle A8 is an electromagnetic injection nozzle of a type in which, as shown in Fig.

13, a plunger is moved by a pulse voltage applied to an electromagnetic coil to move the valve needle thereby to open and close a pressurized fuel introducing passage so that the rate of injection of fuel is controlled by controlling the time of energization of the electromagnetic coil. This electromagnetic control type swirl injection nozzle or electronic fuel injector A8 has a nozzle member 64 formed as a pintle type nozzle (inclusive of a throttle type nozzle) at the end of a nozzle body 61. The nozzle member 64 has a fuel injection port 62, a hollow part communicated with the fuel injection port, and a conical valve seat 63 formed in the hollow part. A valve hole 66 for the valve needle 68 is formed in the nozzle member 64 extending along the central axis thereof. The valve needle and the plunger integral with the valve needle are slidably fitted in the hole with high accuracy.In the nozzle member 64, the conical end of the valve needle 68 can be tightly seated on the valve seat 63. In response to energization and deenergization of the electromagnetic coil by an electromagnetic control device, the valve needle 68 is moved up and down; that is, it is moved into and out of engagement with the valve seat 63 so that fuel is intermittently jetted from the nozzle.

In the nozzle, fuel passages 67 are communicated with a fuel supplying source T provided with an external fuel pump P. A first valve spring 69 is abutted against the other end of the plunger 65 so as to push the valve needle 68 against the valve seat 63. The other end of the first valve spring 69 is abutted against a first spring seat 70. Inside the inner wall of the nozzle body 61, the aforementioned valve needle electromagnetic control device 72, which is annular and is adapted to control the lift of valve needle, is provided around a fuel passage 71, hermetically and electrically insulated therefrom. The electromagnetic control device 72 has a stationary iron core which coaxially incorporates the member which forms the fuel passage 71, and a first electromagnetic coil 75 wound on the core a plurality of turns.A yoke is used to cover the first electromagnetic coil 75 and to fixedly secure the stationary iron core. The outer wall member of the nozzle body 61 covers the above-described stationary iron core, first electromagnetic coil 75, yoke and nozzle member 64, and forms a hermetically and electrically insulated unit therewith. The end portion of the plunger 65 is inserted into the iron core. Therefore, in the electromagnetic control device 72, an electromagnetic attraction force is produced when the pulse voltage is applied to the electromagnetic coil 75, thus attracting the plunger 65. As a result, the plunger 65 is lifted a distance S, and is stopped by the first spring seat 70 serving as a stop so that the valve needle 68 is disengaged from the valve seat 63 to allow the injection of fuel.When the application of the pulse voltage to the first electromagnetic coil 75 is interrupted, the electromagnetic attraction force is eliminated so that the plunger 65 is moved downwardly by the elastic force of the valve spring 69. As a result, the valve needle 68 is seated on the valve seat 63 so that the injection of fuel is stopped.

Connections to the first electromagnetic coil 75 are made through a connector 73. The connector 73 is electrically connected through conductors (not shown) to a computer (not shown). Therefore, the connector 73 can receive an injection electrical signal which is operated by the computer and amplified by a power amplifier (not shown).

In the fourth embodiment, a second valve spring 74 is abutted against the other end of the first spring seat 70, and the other end of the second valve spring 74 is abutted against a second spring seat 76. A second electromagnetic coil 77 is provided around the second spring seat 76. The electromagnetic force lifts the first spring seat 70 through a distance S2. The first spring seat is stopped when abutted against the second spring seat 76 serving a a stop, thereby to control the lift of the valve needle 68. Therefore, when a lift variable control current is applied to the second electromagnetic coil 77, the first spring seat 70 is lifted through the distance S2 against the elastic force of the second valve spring 74. At the same time, the end surface which has limited the movement of the plunger 65 of the valve needle 68 is also lifted.

Therefore, the valve needle 68 is lifted through a distance of S, + S2.

In addition to the above-described embodiment, an intermittent swirl injection nozzle A9 as shown in Fig.14 may be employed. In the nozzle, double slits 50 and 52 are formed in the valve needle 88 as was described above, and the plunger 85 of the valve needle 88 is in the form of a flat plate to improve the efficiency of the electromagnetic force.

The invention is not limited to the abovedescribed embodiments. In conformance to the operating condition of the internal combustion engine, the maximum lift of the valve needle is regulated, that is, the area of the gap in the fuel passage is geometrically changed, whereby the fuel spray characteristic can be varied over a wide range.

In the above-described method and device of the invention, the maximum lift of the valve needle is regulated and/or changed according to the operating conditions of the internal combustion engine, whereby the fuel spray characteristics such as spray angle, penetration force (travel distance), flow coefficient and atomization can be changed. Therefore, the method and device of the invention is suitable for the case where, when the speed of a direct fuel injection type internal combustion engine is low, the fuel spray angle should be large and the fuel spray penetration force should be small, and when the speed of the engine is high, the fuel spray angle should be small and the fuel spray penetration force should be large. Furthermore, the invention is applicable as well to the case where, when the speed of an internal combustion engine with an auxiliary chamber, air chamber or swirl chamber is low, the fuel spray angle should be relatively small and the penetration force should be large, and when the speed of the engine is high, the fuel spray angle should be large and the penetration force should be small. In addition, if the technical concepts of the above-described various embodiments of the invention are selectively combined, the lift of the valve needle can be controlled in conformance to the operating conditions of a variety of internal combustion engines.

Claims

1. A fuel injection control method for an intermittent fuel injection nozzle in wnich, when a valve needle slidably fitted in a valve hole formed in a nozzle body is lifted from a valve seat in said valve hole by a valve needle operating device disposed in the nozzle body to open the nozzle, fuel supplied through a fuel passage is jetted through an injection port, and wherein, with the nozzle installed on an internal combustion engine, the method further comprises: opening the nozzle with a needle valve lift control device and regulating a maximum lift of the needle according to at least one predetermined operating condition of the engine to vary the fuel spray characteristics.

2. A fuel injection control device for an intermittent fuel injection nozzle comprising: a valve needle slidably fitted in a valve hole formed in a nozzle body, an injection port communicating with a valve seat in the valve hole against which an end of the valve needle is abutted, and a fuel passage communicating with the injection port; and a valve needle operating device disposed in the nozzle body to lift the valve needle from the valve seat in the valve hole to open the nozzle, wherein when the valve needle is lifted to open the nozzle, fuel supplied through the fuel passage is jetted through the injection port: and wherein, with the device installed on an internal combustion engine, valve needle lift control means responsive to at least one predetermined operating condition of the engine establish a maximum lift of the needle to vary the fuel spray characteristics.

3. A device according to Claim 2, wherein the control means comprises a stop member for establishing the lift of the valve needle, the position of the stop being varied to establish the maximum lift of the needle valve according to the said operating condition of the engine.

4. A device according to Claim 3, wherein the said at least one operating condition is an oil pressure of the internal combustion engine, and wherein the control means comprises means for varying the position of the stop member.

5. A device according to Claim 3, wherein the control means comprises means for applying an electromagnetic force to vary the position of the stop member.

6. A device according to Claim 3, wherein the control means comprises means for applying the elastic force of a valve spring to vary the position of the stop member.

7. An internal combustion engine when fitted with a fuel injection control device according to any one of the Claims 2 to 6.

8. A fuel injection control device substantially as herein described with reference to Figs. 1 to 3 of the accompanying drawings.

9. A fuel injection control device substantially as herein described with reference to Figs. 4 to 7 of the accompanying drawinus.

1 0. A fuel injection control device substantially as herein described with reference to Figs. 8 to 1 2 of the accompanying drawings.

11. A fuel injection control device substantially as herein described with reference to Figs. 1 3 and 14 of the accompanying drawings.