JPH11159422A - Fuel injection valve for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly detect the lift of the needle of a fuel injection valve for an internal combustion engine. SOLUTION: In this fuel injection valve formed in a manner that the force of a spring 10 is transmitted to a nozzle needle 8 through a pressure pin 9, a hollow bottomed cylindrical part 9c formed of a magnetic material is formed at the end part of either the pressure pin 9 or the nozzle needle 8, and also the other end part is loosely inserted in the bottomed cylindrical part 9c and a induction coil 21 is fixed on the circumferential of the bottomed cylindrical part 9c, thereby a magnetic circuit is formed by these bottomed cylindrical part 9c and induction coil 21. A permanent magnet 22 may be arranged in the magnetic circuit. When receiving a valve opening command, first, the nozzle needle 8 is lifted after compressive strain applied to the pressure pin 9 and the nozzle needle 8 is removed however, if these members to which compressive strain is applied are included in the magnetic circuit, a signal which is almost indistinguishable from lift is produced by a magnetostrictive phenomenon when compressive strain is removed, therefore the bottomed cylindrical part 9c to which compressive strain may not be applied is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve for an internal combustion engine capable of detecting a fuel injection timing by detecting a movement of a nozzle needle.

[0002]

2. Description of the Related Art In a pressure-accumulation type fuel injection valve, in order to detect fuel injection or a lift state of a nozzle needle, it is close to an upper end of a long push rod continuously provided so as to engage above the nozzle needle. A magnetic core consisting of a portion and a downwardly projecting portion of a push piece integrated so as to grip the upper end of the push rod is provided inside the induction coil fixedly supported in the nozzle holder. There is known a lift sensor which is configured to be able to move up and down together with a valve opening operation, and to take out an electric signal indicating a lift of a nozzle needle from the induction coil thereof to the outside (Japanese Unexamined Patent Publication No. Hei. 196161).

When such a lift sensor is applied to an electronic control type common rail fuel injection valve, or when other types of fuel injection valves are used in a full lift state, the fuel pressure is applied to a long push rod. When actuated, not only is compression distortion (elastic distortion) generated on the thin and long nozzle needle and push rod, but also the magnetic core itself that constitutes the lift sensor is subjected to compression distortion. As a result, the signal detected from the induction coil is affected by the compression distortion, and the lift signal detected by the lift sensor may not necessarily indicate the lift of the nozzle needle. Hereinafter, this problem will be described in more detail.

FIG. 2 illustrates a conventionally known electronically controlled common rail fuel injection valve. In this fuel injection valve, when the solenoid 16 is not energized, the valve 11 is closed, so that the pressure of the high-pressure fuel supplied from the high-pressure fuel passage 13 acts on the control chamber 12. As a result, the command piston 14 receives a downward force in FIG. 2 and pushes down the pressure pin 9 and the nozzle needle 8, so that the injection port 6 closes and no fuel is injected. In this state, that is, when the solenoid 16 is not energized, the command piston 14, the pressure pin 9, and the nozzle needle 8 receive a force due to the high pressure of the control chamber 12, so that a vertical compressive strain is generated.

Next, when the solenoid 16 is energized, the valve 11 is opened, and the high pressure in the control chamber 12 is released to the low-pressure fuel passage 15.
The pressure in the control chamber 12 having the pressure drop decreases, and the pressure is higher than the combined force of the force for pushing down the command piston 14 downward in FIG. 2 and the urging force of the spring 10 in the oil reservoir 5 formed in the nozzle body 1. When the fuel for pushing up the shoulder 8a and the like of the nozzle needle 8 upward becomes larger, the command piston 14, the pressure pin 9 and the nozzle needle 8, which have been reduced due to the compressive strain, start to expand and extend to some extent. Only afterwards do they move upward together, whereby the injection port 6 opens and the high-pressure fuel in the oil sump 5 is injected into the combustion chamber of the internal combustion engine. As described above, when the pressure in the control chamber 12 is reduced, there is a stage where the compression distortion of the command piston 14, the pressure pin 9, and the nozzle needle 8 is reduced before the injection port 6 is opened.

Accordingly, the compression distortion of the command piston 14, the pressure pin 9 and the nozzle needle 8 does not occur at the moment when fuel is injected, but occurs before that, so that the fuel injection timing and the compression distortion decrease. Not in time. Further, in order to detect the lift amount of the nozzle needle 8, for example, a part of the pressure pin 9 shown in FIG.
In the case where a lift sensor is formed by attaching an induction coil to the periphery, not only the state of magnetization changes due to the magnetostriction phenomenon as described above, but also the pressure pin 9 and the command piston 14 other than the magnetic core. Since the magnetic material that moves integrally with the nozzle needle 8 is near the induction coil, the amount of compressive distortion of the nozzle needle 8 and the pressure pin 9 can be reduced even if the lift amount of the nozzle needle 8 does not change. Since the intensity of the magnetization of the magnetic material changes when changing as described above, a signal confusing with the lift of the nozzle needle 8 is generated in the induction coil.

[0007]

Therefore, in the lift sensor provided in the conventional fuel injection valve, the fuel injection timing of the fuel injection valve is caused by the compression distortion of the nozzle needle and the members related thereto and the magnetic distortion accompanying the distortion. Cannot be detected accurately. The present invention addresses the above-described problems in the prior art and provides an improved lift sensor that can accurately detect the lift state of the nozzle needle of the fuel injection valve or the fuel injection timing by simple means. It is an object of the present invention to provide a fuel injection valve for an internal combustion engine provided.

[0008]

According to the present invention, there is provided a fuel injection valve for an internal combustion engine as described in the claims as means for solving the above-mentioned problems.

According to the first aspect of the present invention, a change in the relative position between the induction coil forming the magnetic circuit and the portion where no mechanical distortion occurs due to the lift of the nozzle needle is determined. It is detected by the electromotive force of the induction coil. The part that does not cause mechanical distortion is made of a magnetic material, which forms a part of the magnetic circuit, so that magnetic flux passes through the inside, but the force for activating the nozzle needle is thereby No mechanical distortion occurs because it is not transmitted, so even if the mechanical distortion is eliminated in the nozzle needle itself or a member interlocked with the nozzle needle prior to the lift of the nozzle needle, mechanical distortion occurs. The non-existing portion does not cause a change in the magnetic flux number of the magnetic circuit due to the magnetostriction phenomenon. Therefore, the induction coil can accurately detect substantially only the lift of the nozzle needle.

According to a second aspect of the present invention, there is provided an induction coil forming a magnetic circuit in association with the lift of the nozzle needle, a pressure pin and a hollow bottomed cylindrical portion formed at one end of the nozzle needle. Is detected by the electromotive force of the induction coil. The hollow bottomed cylindrical part is made of a magnetic material, and because it forms a part of a magnetic circuit, magnetic flux passes through the inside, but the force for operating the nozzle needle has a hollow bottomed part. Since it is not transmitted by the cylindrical portion and does not cause mechanical distortion, even when mechanical distortion is eliminated in the nozzle needle itself or a member interlocked with the nozzle needle prior to the lift of the nozzle needle, The hollow bottomed cylindrical portion does not cause a change in the magnetic flux number of the magnetic circuit due to the magnetostriction phenomenon. Therefore, the induction coil can accurately detect only the lift of the nozzle needle.

In this case, as a part of the magnetic circuit, at least a part of the hollow bottomed cylindrical portion is magnetized to be a permanent magnet, or a permanent magnet fixed near the induction coil is separately provided. it can. Further, between the hollow bottomed cylindrical portion and the portion inserted so that a gap remains around it, a positioning means for holding the gap is provided to positively hold the gap, Since it is possible to prevent mechanical distortion from occurring in the hollow bottomed cylindrical portion, it is possible to reliably prevent noise from entering the detection of the lift of the nozzle needle.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a partial longitudinal sectional view showing a characteristic portion of a fuel injection valve as a first embodiment of the present invention in an enlarged manner. Portions other than the characteristic portions have the same configuration as the conventional common rail fuel injection valve shown in FIG. As shown in FIGS. 1 and 2, the nozzle body 1 is integrally connected to a holder body 3 via a distance piece 4 by a retaining nut 2. Reference numeral 5 denotes an oil reservoir formed in the nozzle body 1 and supplied with high-pressure fuel from a common rail (not shown) together with the control chamber 12. Reference numeral 6 denotes an injection port opened at the tip of the nozzle body 1. A nozzle needle 8 movably supported in the vertical direction in the nozzle body 1 is connected to a spring 10 via a pressure pin 9.
In FIG. 1, a downward force for closing the valve is received.

The feature of the first embodiment resides in a portion of the lift sensor formed at the joint between the nozzle needle 8 and the pressure pin 9 as shown in FIG. More specifically, the small diameter portion 8a at the upper end of the nozzle needle 8 is loosely fitted into the bottomed hole 9a formed at the lower end of the pressure pin 9. That is, a gap is provided in the radial direction between the hole 9a of the pressure pin 9 and the small-diameter portion 8a of the nozzle needle 8, so that strong fitting contact is prevented.

By providing the bottomed hole 9a at the lower end of the pressure pin 9, the lower end of the pressure pin 9 forms a hollow cylindrical portion 9c. In the distance piece 4, an annular permanent magnet 22 is attached so as to surround the lower end surface 9b of the pressure pin 9, and is wound in a cylindrical shape so as to surround the hollow cylindrical portion 9c of the pressure pin 9 thereon. The mounted induction coil 21 is attached.

The position of the lower end face 9b of the pressure pin 9 in the up-down direction (moving direction) is such that the lower end face 9b of the lower end face 9b Is set to be within the vertical width (thickness). The electromotive force (signal) of the induction coil 21 is taken out to the outside by the lead wire 23 and processed.

When the lift sensor of the first embodiment having the essential configuration shown in FIG. 1 is applied to an electronically controlled common rail type fuel injection valve similar to the conventional example shown in FIG. 2, the following is obtained. Operate. As described above, when the solenoid 16 is not energized, the high pressure of the supplied fuel acts on the control chamber 12 through the throttle 7, and the command piston 14, the pressure pin 9, and the nozzle needle 8 are compressed by the force. Distortion has occurred. However, the pressure pin 9 as an overlapping portion with the nozzle needle 8
Of the hollow cylindrical portion 9c is loosely fitted to the small diameter portion 8a of the nozzle needle 8, and the lower end surface 9 of the hollow cylindrical portion 9c
Since no force acts on b, no compressive strain is generated in the hollow cylindrical portion 9c.

When the solenoid 16 is energized in this state, the valve 11 rises and opens, the pressure in the control chamber 12 decreases, and first, the command piston 14 and the pressure pin 9
In addition, the compression distortion of the nozzle needle 8 is reduced. Even if the magnitude of the amount of compressive strain changes in this way, the pressure pin 9 covering the small diameter portion 8a at the upper end of the nozzle needle 8
The change in the amount of compressive strain of the hollow cylindrical portion 9c is zero. When the pressure in the control chamber 12 further decreases to the valve opening pressure,
The nozzle needle 8 rises (lifts) together with the command piston 14 and the pressure pin 9, and fuel is injected from the injection port 6.

Since the lower end surface 9b of the pressure pin 9 moves within the vertical width of the permanent magnet 22 with the rise of the nozzle needle 8, the overlap width t between the permanent magnet 22 and the hollow cylindrical portion 9c of the pressure pin 9 is large. Changes. As a result, the number of magnetic fluxes coming out of the permanent magnet 22 and sequentially passing through the hollow cylindrical portion 9c and the induction coil 21 arranged on the outer periphery thereof changes, so that the induction coil 21 has a value corresponding to the change in the number of magnetic fluxes. Electric power is generated. This electromotive force is
If the nozzle needle 8 is taken out and monitored through the outside, the lift of the nozzle needle 8 can be detected. In the lift sensor according to the first embodiment, the members constituting the magnetic circuit are configured not to receive any compressive strain. Therefore, the lift sensor is not affected by the magnetic strain caused by the compressive strain as in the related art, and is more accurate. Thus, the lift state of the nozzle needle 8 can be detected.

FIG. 6 is a timing chart showing the results of a comparative experiment conducted by applying a conventional lift sensor and a lift sensor of the present invention (FIG. 1) to an electronically controlled common rail fuel injection valve (FIG. 2). It is shown as. In this case, a conventional power generation type lift sensor having a configuration as shown in FIG. 7 was used. In the conventional method shown in FIG. 7, the small diameter portion 8a 'which is a part of the nozzle needle 8 and passes through the inside of the induction coil 21 is magnetized into a permanent magnet. As a result, the number of magnetic fluxes acting on the induction coil 21 changes to generate an electromotive force.

When a fuel injection command is sent to these fuel injection valves by a drive pulse generated by an electronic control unit (not shown), the pressure in the control chamber 12 decreases as described above. At this time, the small diameter portions 8a and 8
Since the force acting on a ′ is reduced and the amount of compressive strain at that portion is reduced, the small diameter portion 8a ′ where the amount of compressive strain changes
In the conventional lift sensor shown in FIG. 7 which is itself magnetized, at the same time as the pressure in the control chamber 12 decreases,
Since the induction coil 21 generates an electromotive force signal corresponding to the change in the amount of compressive strain due to the magnetostriction phenomenon, the signal is erroneously recognized as indicating the lift state of the nozzle needle 8.

On the other hand, in the case of the present invention, no compression distortion occurs in the hollow cylindrical portion 9c of the pressure pin 9 in the magnetic circuit, so that no signal is generated due to the magnetostriction phenomenon.
A remarkable electromotive force is generated in the induction coil 21 only when the nozzle needle 8 is actually lifted and the injection port 6 is opened, and the injection rate rises. If the electromotive force is recognized as a signal indicating the lift, the influence of the compression distortion is reduced. The lift state of the nozzle needle 8 can be accurately detected without being substantially received. Further, it is not necessary to explain that the end of the lift, the timing of the start of the valve closing, and the like can be accurately detected for the same reason.

In the first embodiment as well, when the fuel injection is stopped, the command piston 14, the pressure pin 9, and the nozzle needle 8, including the small diameter portion 8a of the nozzle needle 8, undergo compression strain. However, the distance that the lower end surface 9b of the pressure pin 9 moves when the compression distortion is eliminated prior to the lift of the nozzle needle 8 should be ignored compared to the lift amount of the nozzle needle 8 when the injection port 6 opens. Therefore, the signal voltage generated in the induction coil 21 in response to the movement cannot be a value that can be mistaken for the lift state of the nozzle needle 8.

Since the lift sensor in the fuel injection valve of the present invention is of a power generation type using the induction coil 21, its output voltage is proportional to the speed of change in the number of magnetic fluxes passing through the induction coil 21. Therefore, by setting the shape and position of the hollow cylindrical portion 9c including the lower end surface 9b of the permanent magnet 22 and the pressure pin 9 and the induction coil 21 so that the moving speed of the nozzle needle 8 is proportional to the change speed of the magnetic flux number. The lift amount of the nozzle needle 8 can be detected from the integrated value of the output voltage of the induction coil 21 of the present invention shown in FIG. In this manner, in the fuel injection valve of the present invention, it becomes possible to detect the start and end times of the injection, the lift amount, and the like with high accuracy.

FIG. 3 shows a second embodiment of the present invention. In this example, as described in the first embodiment, the lower end portion of the pressure pin 9 which is not affected by the compressive strain is magnetized to the hollow cylindrical portion 9c which is the overlapping portion with the nozzle needle 8, and the hollow cylindrical portion is formed. The portion 9c is a permanent magnet. Also,
The induction coil 21 is arranged in the dish-shaped distance piece 4 so as to surround the lower end surface 9 b of the pressure pin 9. The lower end surface 9b of the pressure pin 9 is disposed so as to be located within the vertical width of the induction coil 21 in the entire movement range of the pressure pin 9.

In the second embodiment, when the pressure pin 9 moves vertically in conjunction with the nozzle needle 8, the pressure pin 9 protrudes into the induction coil 21 in the hollow cylindrical portion 9c of the magnetized pressure pin 9. Since the length of the portion changes, an electromotive force is generated in the induction coil 21, and the signal is extracted to the outside by the lead wire 23.
As in the case of the first embodiment, the movement of the nozzle needle 8 can be accurately detected.

FIG. 4 shows a third embodiment of the present invention. In this example, a small projection 8b projecting upward from the nozzle needle 8 at the contact portion between the hollow cylindrical portion 9c at the lower end of the pressure pin 9 and the small diameter portion 8a at the upper end of the nozzle needle 8 is connected to the pressure pin 9 Is characterized in that it is fitted into a concave portion 9d formed on the bottom surface of the hole of the hollow cylindrical portion 9c to form a relative positioning mechanism in the radial direction. In this case, the nozzle needle 8 and the pressure pin 9
Is preferably slidable in the direction of rotation about the projection 8b and the recess 9d.

In the third embodiment, a small gap is reliably maintained between the small diameter portion 8a of the nozzle needle 8 and the hollow cylindrical portion 9c of the pressure pin 9 by the engagement between the recess 9d and the projection 8b. Therefore, no compressive strain can be generated in the hollow cylindrical portion 9c. Therefore, generation of a signal due to the magnetostriction phenomenon can be prevented. In addition, it is possible to prevent noise or wear as a tapping sound from being generated even by a small amount due to contact between the two members in the gap.

The fourth embodiment shown in FIG. 5 is a modification of the third embodiment shown in FIG. 4. In this case, a projection 9e is formed on the bottom surface of the hollow cylindrical portion 9c at the lower end of the pressure pin 9, and The small diameter portion 8 of the nozzle needle 8
A concave portion 8c is formed on the upper end surface of a. The operation and effect of the fourth embodiment are the same as those of the third embodiment.

In the illustrated embodiment, a portion (hollow cylindrical portion 9c) that does not generate compressive strain is formed on the pressure pin 9 side, and a portion (small diameter portion 8) inserted therein is formed.
Although a) is formed on the nozzle needle 8 side, the same operation and effect can be obtained by forming a portion where no compression distortion occurs on the nozzle needle 8 or a portion which moves in conjunction with the nozzle needle 8. .

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing a main part of a first embodiment of the present invention.

FIG. 2 is a vertical sectional front view showing the structure of an electronically controlled common rail fuel injection valve.

FIG. 3 is a longitudinal sectional front view showing a main part of a second embodiment.

FIG. 4 is a longitudinal sectional front view showing a main part of a third embodiment.

FIG. 5 is a longitudinal sectional front view showing a main part of a fourth embodiment.

FIG. 6 is a timing chart showing the results of a comparison experiment between the fuel injector of the present invention and a conventional fuel injector in order to explain the effect of the present invention.

FIG. 7 is a longitudinal sectional front view showing a main part of a conventional fuel injection valve used for a comparative experiment.

[Explanation of symbols]

 Reference Signs List 5 oil reservoir 8 nozzle needle 8a small diameter portion 8b projection 8c recess 9 pressure pin 9a bottomed hole 9b bottom end surface 9c hollow cylindrical portion 9d recess 9e projection 10 spring 11 valve 12 ... control room 13 ... high-pressure fuel passage 14 ... command piston 16 ... solenoid 21 ... induction coil 22 ... permanent magnet 23 ... lead wire

Claims (5)

[Claims] 1. A fuel injection valve for an internal combustion engine that injects fuel by opening an injection port by lift of a nozzle needle, wherein the nozzle needle itself made of a magnetic material or a member that moves in a lift direction in conjunction with the nozzle needle. A part that does not generate mechanical distortion is formed, and the part that does not generate mechanical distortion and the fixed induction coil form one part.
By configuring two magnetic circuits and detecting the electromotive force of the induction coil corresponding to a change in the relative position between the induction coil and the portion where the mechanical distortion does not occur due to the lift of the nozzle needle A fuel injection valve, wherein the lift of the nozzle needle is detected. 2. A fuel injection valve for an internal combustion engine configured to transmit a force of a spring to a nozzle needle via a pressure pin, wherein one of the pressure pin and the nozzle needle at a contact portion between the pressure pin and the nozzle needle. A hollow bottomed cylindrical portion made of a magnetic material is formed at one end of the hollow bottomed cylindrical portion, and the other end is inserted into the hollow bottomed cylindrical portion with a gap left therearound. An induction coil fixed so as to surround the periphery of the portion, a magnetic circuit is constituted by at least a part of the hollow bottomed cylindrical portion and the induction coil, and the induction accompanying the lift of the nozzle needle is formed. By detecting the electromotive force of the induction coil corresponding to a change in the relative position between the coil and the hollow bottomed cylindrical portion, the lift of the nozzle needle is reduced. A fuel injection valve characterized by detecting. 3. The fuel injection valve according to claim 2, wherein at least a part of the hollow bottomed cylindrical portion is magnetized to form a permanent magnet. 4. The fuel injection valve according to claim 2, wherein a permanent magnet fixed near the induction coil forms a part of the magnetic circuit. 5. A hollow bottomed cylindrical portion formed at one end of the pressure pin and the nozzle needle, and the other inserted into the hollow bottomed cylindrical portion such that a gap remains around the hollow bottomed cylindrical portion. 5. A positioning means for holding the gap is provided between the end portion of the first member and the second member.
A fuel injection valve according to any one of the above.