JPS6032971A - Fuel injector for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve the response and accuracy and to protect the engine by providing a check valve, normal-close solenoid valve, relief valve system and relief valve regulating system. CONSTITUTION:By the damping function of fuel existing between an armature 63 and sheet member and the resilient buffering function of the sheet member 67, the armature 63 is damped and contact against the core 65 to suppress bouncing of valve body 62 considerably thus to rise/fall the pressure of fuel in the needle chamber 42 quickly and to enable accurate control of injection timing and injection amount. In case of fault of solenoid valve 60, breakdown or runaway can be prevented reliably by means of a relief valve system 70 and a pressure regulator 76. electromagnetic actuator 80, etc. as the relief valve regulator.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an improvement of a fuel injection device using a solenoid valve in an internal combustion engine, and in particular to a unit that stabilizes the operation of the solenoid valve, reduces load, and provides safety in the event of an abnormality in the engine. Regarding injectors.

Background Art> Fuel injection devices for internal combustion engines, such as diesel engines, are generally required to be able to accurately and easily control the fuel injection amount and injection timing, and in line with this requirement, for example, S
As seen in AE Paper No. 750773, the so-called unit injector eliminates a long injection pipe and greatly reduces dead space by integrally configuring the injection pump and injection valve, thereby improving injection characteristics. is proposed.

However, in this case, the rotating position of the plunger is determined by the control position of the control rack, and the injection timing and injection amount are also uniquely determined, so the control of the injection timing and injection amount is not mutually independent. There was an inconvenience that it could not be done.

Therefore, in order to solve this problem, an attempt was made to electronically control the injection amount and injection timing independently and accurately using a solenoid valve.
It can be found in Publication No. 26.

As shown in FIG. 1, this device uses a plunger 1 that reciprocates in synchronization with engine rotation to forcefully feed fuel in a pump chamber 2 through an injection fuel passage 4 into a needle chamber 5. Fuel pressure acts on the needle valve 6,
By lifting the needle pulp 6 against the elastic force of the spring 70 acting in the valve closing direction and opening the nozzle 8,
The nozzles 8 and 9 are traps so as to inject and supply fuel into a combustion chamber (not shown).

A fuel supply passage 11 to which low-pressure fuel is sent by a feed pump from a fuel tank (not shown) is connected to the pump chamber 2, and the fuel supply passage 11 is opened and closed by a solenoid valve 12. That is, the solenoid 12a of the solenoid valve 12 is energized and excited in accordance with the engine operating state, thereby closing the valve body 13 against the elastic force of the spring 140 acting in the valve opening direction.

Therefore, even if there is a compression stroke (downward movement in the figure) of the plunger 1, if the solenoid valve 12 is open, the fuel in the pump chamber 2 will be relieved to the low pressure side through the fuel supply passage 11, so the needle chamber The fuel pressure in the fuel pump 5 does not rise, and therefore the needle valve 6 does not open, so fuel injection is not performed. On the other hand, when the solenoid valve 12 is closed, the fuel pressure in the needle chamber 5 rises rapidly from that point on, lifting the needle pulp 6 against the elastic force of the spring T, opening the nozzle 8, and injecting fuel. will be done.

In this way, by opening and closing the electromagnetic valve 12, the fuel injection timing and eventually the injection period can be freely controlled.

However, in the conventional unit injector described above, the solenoid valve 12 is of a so-called normally open type, in which the solenoid valve 12 is always kept open by the elastic force of the spring 140 when the solenoid is not energized. Therefore, during the fuel injection period, a large electromagnetic force must be applied to the valve body 13 by the solenoid 12a to maintain the valve closed state, resulting in the large size of the solenoid 12a. Furthermore, when the valve body 13 is seated on the valve seat during valve closing, the large fuel pressure in the pump chamber 2 and the valve opening force of the spring 14 act against the valve closing force.
A so-called bouncing phenomenon occurs, and for this reason, accurate control of the injection rate cannot be expected.

<Object of the Invention> The present invention is a unit injector using a solenoid valve, which uses a normally closed type solenoid valve to eliminate the drawbacks of the conventional device described above, and also reduces the load on the solenoid valve. The purpose is to improve responsiveness and accuracy.

In addition, in the present invention, the normally closed solenoid valve closes when there is a malfunction or failure of the solenoid valve, so at this time the maximum amount of fuel is injected from the unit injector, causing internal combustion. Since there is a risk that the engine will run out of control, in such a case, a so-called "fail" method is used to maintain the injection amount at a safe value by pumping an appropriate amount of fuel to the low pressure side even if the solenoid valve closes. The purpose is to protect the institution by attaching a safety mechanism.

<Structure of the Invention> In order to achieve the above object, the fuel system for an internal combustion engine according to the present invention has a fuel supply passage communicating with an injection fuel passage that guides injected fuel from a pump part to a nozzle part, in which only a flow is directed toward the pump part. A permissible check valve, a normally closed solenoid valve that receives the injected fuel passage internal pressure and the elastic force in a valve closing direction, and a normally closed relief valve device are interposed in parallel with each other, The present invention is characterized in that a relief valve adjustment device is provided that reduces the valve opening setting pressure of the IJ-F valve device to a predetermined value based on a signal from an engine abnormal state detection device.

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

Structure In one embodiment shown in FIG. 2, the plunger 22 of the unit injector 21 is pushed down by a cam mechanism 23 that rotates in synchronization with the crankshaft of a compression ignition internal combustion engine (not shown), such as a diesel engine, and is pushed down by a spring of a return spring 24. It moves upward in response to the force and slides back and forth within the cylinder 25.

The compression (downward) stroke of the plunger 22 forces the fuel in the pump chamber 26 facing the tip of the plunger 22 into the injection fuel passage 27, while the suction (upward) stroke forces the fuel into the fuel supply passage 28 in the pump chamber 26. A pump unit is configured to suck low-pressure fuel through the pump. Fuel supply passage 28, fuel tank 3
1 through a filter 32 to a feed pump 33
This is sucked in by the pump, and is force-fed at low pressure, maintained at a predetermined low pressure by the pressure regulating action of the pressure regulator 34, and guided into the pump chamber 26.

In the middle of the fuel supply passage 28, a check valve 50°, a solenoid valve 60, and a relief valve device 70, which will be described later, are arranged in parallel with each other.

On the other hand, the nozzle 41 is a high-pressure fuel that is pumped from the pump section.
In the nozzle section for injecting fuel into the combustion chamber of the engine, a needle chamber 42 is interposed in the injection fuel passage 27, and a needle pulp 43 whose pressure receiving surface faces the needle chamber 42 is interposed in the injection fuel passage 27.
On the other hand, the fuel pressure in the needle chamber 42 acts in the direction of opening the nozzle valve. A pulp gelling 44 that elastically biases the needle valve 43 in the valve closing direction is interposed and used as a part of the passage 46, and the surplus fuel passage 46 is supplied to the fuel outlet 31 via the return passage 41. Connected.

The needle pulp 43 opens the valve when the injected fuel pressure acting in the valve opening direction reaches a predetermined value or more against the unidirectional biasing force of the pulp spring 44 in the valve closing direction. Become. In the figure, 48 is a support for the needle pulp 43, and 49 is a holder that integrally connects the pump section and the injection valve section.

The fuel supply passage 28 is branched into three parallel passage parts 28a to 28c in the middle, and a check valve 50 installed in one of the passage parts 28a allows fuel to flow only in the direction of the pump chamber 26. do.

The solenoid valve 60 installed in the other passage section 28b is of a normally closed type, and the fuel pressure in the injection fuel passage 27 is controlled by the spring 61.
It has a valve body 62 that receives both zero elastic force in the valve closing direction, and an armature 63 connected to the valve body 62, and a solenoid 6.
A core 65, which is excited by 4, is opposed to each other through a gap 66.

When the armature 63 collides with the core 65 or the armature 63 at its maximum relative lift, it acts to buffer the collision force.

In addition, the relief valve device 7 interposed in the remaining passage portion 28c
θ is the valve body 71 that opens and closes the passage portion 28c and the piston T2.
Spring T3 biases the valve body 71 in the valve closing direction via
and has. A fuel tank 31 is connected to the spring chamber T4 in which the spring T3 is housed via a filter 32.
The fuel inside is pumped by a feed pump 75 and adjusted to a predetermined pressure by a pressure regulator 76 before being introduced, and the fuel pressure and the elastic force of the spring 610 close the valve body 71 via the piston 72.

Although the fuel pressure of the injection fuel passage 27 acts on the valve body T1 in the valve opening direction, one adjustment pressure of the pressure regulator 76 is set so that the force in the valve closing direction is sufficiently larger than this in normal conditions. .

The electromagnetic actuator 80, which functions as a relief valve adjustment device, is energized and energized when an abnormality occurs in the engine such as when the electromagnetic valve 60 breaks down.
The regulator pulp is shifted to lower the regulator discharge pressure to a predetermined value.

Therefore, the pressure inside the spring chamber 74 decreases and the valve body T
When the closing force of valve 1 weakens and the valve opening force due to the fuel pressure in the injection fuel passage 2T becomes stronger, the valve body T1 opens and relieves the fuel in the injection fuel passage 27 to the low pressure side through the passage part 28c. let

The electromagnetic valve 60 and the electromagnetic actuator 80 are controlled by a control device 90 such as a computer that also serves as an engine abnormal state detection device. That is, signals related to related factors such as 1 engine rotational speed 9 engine load and engine operating conditions such as engine cooling water temperature are input to the control device 90, and the fuel injection amount is predetermined here.

The injection timing is read out according to the engine operating state, and is output to the solenoid 64 of the electromagnetic valve 60 via the driver 91 to control the opening/closing timing of the valve body 62. Further, when an abnormality in the engine due to a failure of the electromagnetic valve 60 or the like is detected based on the engine operating state, an output signal is supplied to the electromagnetic actuator 80 via the driver 92 in order to reduce the discharge pressure of the pressure regulator 76.

action The operation of the above configuration will be explained.

Force feeding (pushing down) of plunger 22 by cam mechanism 23
Before starting the stroke, the solenoid 64 is energized and excited via the driver 91 by the output signal of the control device 90.
The valve body 62 is sucked downward as shown in the figure through the armature 63 to open the passage portion 28b.

Therefore, even if the plunger 22 is lowered by the cam mechanism 23 and enters the compression stroke, the fuel in the pump chamber 26 passes through the fuel supply passage 28 via the opened electromagnetic valve 60 and is relieved to the low-pressure fuel source. , fuel injection is not yet performed at this stage.

Then, at the start of fuel injection, the output signal from the control device 90 causes the solenoid 64 to be energized. As a result, the valve body 62 is moved upward by the elastic force of the spring 610.
The passage portion 28b is closed.

When the valve body 62 is closed and seated, if the clearance between the valve body 62 and its seat portion decreases, the pressure within the pump chamber 26 increases accordingly. This increased fuel pressure
2 in the valve closing direction (upward in the figure). Therefore, while the valve body 62 is closed by a large valve closing force that gradually increases, the pressure of the spring 61 on the storage chamber side decreases.

The valve is reliably closed and bouncing is minimized. Therefore, the fuel in the pump chamber 26 is efficiently compressed, and the pressure of the injected fuel in the needle valve 42 quickly rises to the point where the needle pulp 43 is blown.

The valve is opened with good response against the elastic biasing force of the lube spring 440, and injection is immediately made from the injection port 41. As is clear from this, the closing timing of the solenoid valve 60 determines the fuel injection start point.

Note that at this time, the reverse valve 50 is closed and the pump chamber 26 is closed.
There is no fuel relief from the inside to the low pressure side.

The end of fuel injection is determined by the control device 90, which applies current to the solenoid 64. Then, the solenoid 64 excites the core 65, attracts the armature 63, and lifts the valve body 62 downward in the figure.

By opening the solenoid valve 60 in this way, the fuel in the pump chamber 26 is relieved to the low-pressure fuel side via the fuel passage 28, and the fuel pressure in the needle chamber 42 decreases, causing the pulp spring 44 to The needle pulp 43 closes the nozzle 41 due to the elastic biasing force, and fuel injection ends.

From this, the injection timing is determined by the timing when the solenoid 64 is energized.

Moreover, once the solenoid valve 60 is opened, the injection fuel passage 27
Since the high-pressure fuel inside flows around to the low-pressure side of the valve body 62, the valve-opening force of the valve body 62 only needs to resist the elastic force of the spring 610, and the load on the solenoid valve 60 is not so large.

Furthermore, the armature 6 that houses the armature 63
Fuel in the fuel supply passage 28 downstream of the valve body 62 is introduced into the fuel passage 3 a through a passage 69 . Therefore, the solenoid valve 60
In the valve opening operation, the armature 63 and the sheet material 6T
The armature 63 comes into contact with the core 65 while being damped due to the damping effect of the fuel existing between the two and the elastic damping effect of the sheet material 67. For this reason, the valve body 6
2 bouncing can be suppressed to a very low level.

Therefore, the bouncing of the valve body 62 is reduced both when the electromagnetic valve 60 is closed and when it is opened, and the fuel pressure in the needle chamber 4 can quickly rise and fall, resulting in a large flow rate. The fuel injection timing and injection amount can be controlled accurately from low to low flow rates.

At the end of the pumping stroke of the plunger 22, the solenoid 64 is de-energized and the solenoid valve 60 is closed.

When the plunger 22 enters the suction stroke in which it moves upward in the figure, the check valve 50 opens and fuel is sucked into the pump chamber 26 through the passage 28a.

Therefore, in the suction stroke trap, it is not necessary to energize the solenoid 64, and the load on the solenoid valve 60 is reduced.

Immediately before the plunger 22 shifts to the pressure feeding stroke, the solenoid 64 is energized to open the solenoid valve 6o in preparation for the next injection control.

In addition, when the solenoid valve 600 is energized and excited, the armature 63 is =7.
It is better to set the voltage to 5 to lower the applied voltage after being attracted to 65. This can prevent the solenoid 640 from generating heat or speed up the response to the fall of the magnetic flux when the current is cut off.

The explanation of the operation so far shows a state in which the electromagnetic valve 60 and the like function normally, and the relief valve device 7o has not yet performed its opening function. Therefore, FIG. 3 (a diagram in which the P4 relief valve device 70 and the like are omitted) is shown to explain the occurrence of inconvenience due to a failure of the solenoid valve 60 and the like.

Generally, normally closed solenoid valves tend to remain closed when a failure or malfunction occurs.

That is, when the electric signal to the solenoid 64 is cut off, the valve is closed by the action of the spring 610.

Therefore, when the electromagnetic valve 6o is closed as shown in FIG. 3, the fuel in the pump chamber 26 is forced into the injection fuel passage 27 from the start to the end of the pumping stroke of the plunger 22 and is used for injection. The amount of fuel injected reaches its maximum, causing one engine to run out of control, and in the worst case, leading to engine damage.

When such a dangerous situation occurs, referring back to FIG. 2, in the present invention, the control device 90 is
learns that an abnormality has occurred in the engine, outputs this to the driver 92, activates the electromagnetic actuator 80,
Decrease the discharge pressure of pressure regulator T6. Therefore, the fuel pressure in the spring chamber 74 of the relief valve device TO (usually the discharge pressure of the pressure regulator 76 is sufficient to keep the relief valve device TO closed no matter how much the solvent pressure in the injection fuel passage 2T rises). .)
decreases.

On the other hand, since the electromagnetic valve 60 is closed and the check valve 50 is closed, the pressure in the injection fuel passage 27 rapidly increases due to the pressure feeding of the plunger 22.

Therefore, the pressure in the injection fuel passage 27 that acts on the valve body 71 in the valve opening direction and the pressure on the valve body T1 that acts on the piston 72
The balance between the elastic force of the spring 73 acting in the valve closing direction and the pressure inside the spring chamber T4 is lost, and the valve body T1
is lifted to the force balance position, and the passage portion 28c, which had been reliably closed until then, is opened to a predetermined passage area. If the fuel pressure P1 in the injection fuel passage 2T obtained by this is equal to or lower than the valve opening pressure Po of the needle pulp 43,
The needle pulp 43 does not lift, the nozzle 41 is closed, and no injection is performed. If Pl is larger than Po, the needle pulp 43 is lifted in accordance with the difference, and The amount of fuel is injected and supplied from the injection port 41.

Therefore, by appropriately selecting the set load of the spring 73 and the adjusted discharge pressure of the pressure regulator 76, it is possible to stop the target valve without injecting any fuel in the event of an abnormality, or to stop the target valve at the desired time. By obtaining a small amount of injection and preventing sudden deceleration while driving, it is possible to prevent an unexpected accident with a following vehicle, and in history, to make it possible to drive the vehicle to a nearby repair shop. It becomes possible to freely select and design. Of course, at this time, since the fuel pressure in the injection fuel passage 27 is maintained at Pl, it is possible to reliably prevent the destruction of the unit injector, the runaway of the nine engines, and the destruction of the first engine.

In addition, when the present invention is applied to a multi-cylinder engine, the pressure regulator 76 and the electromagnetic actuator 80 can be placed on either side of the cylinders, or they can be combined into one piece each.

In the above embodiment, the pressure regulator 76 and the electromagnetic actuator 80 as the IJ IJ valve adjustment device are not limited to this, and the pressure regulator 76f7) discharge pressure may be controlled by hydraulic or mechanical means, Other configurations of the relief valve device 70 may also be freely adopted.

<Effects of the Invention> As explained above, in the present invention, a normally closed electromagnetic valve that receives the pressure inside the injection fuel passage and the elastic biasing force in the valve closing direction is interposed in the fuel supply passage connected to the injection fuel passage. Therefore, since the fuel pressure can be used as a valve closing force, the load on the solenoid valve can be reduced, and the bouncing of the valve body can be reduced, thereby improving the responsiveness and accuracy of the solenoid valve and, by extension, the unit injector. In addition, since a check valve is installed in parallel with the electromagnetic valve, even if the electromagnetic valve is closed during the suction stroke of the pump part of the -1-knit injector, the fuel is supplied to the pump part through the check valve. This also reduces the load on the solenoid valve.Furthermore, a relief valve device is installed in parallel with these, and a relief valve adjustment device is installed to control the valve opening pressure of the relief valve device in the event of an engine abnormality. It is possible to prevent damage to the unit injector or engine runaway or damage when an engine abnormality occurs, such as when a solenoid valve malfunctions.Depending on the adjustment value of the valve opening pressure of the relief valve device, fuel You can choose to either reduce the injection amount to zero and keep the engine in the stopping direction, or inject a predetermined amount to obtain engine rotation that does not cause the engine to run out of control.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view showing an example of a conventional unit injector as a fuel injection device, Fig. 2 is a longitudinal cross-sectional view of a unit injector showing an embodiment of the present invention, and Fig. 3 is for explaining the operation of the same. FIG. 3 is an explanatory longitudinal cross-sectional view in which a relief valve device and the like are omitted. 21...Unit injector 22...Plunger 26...Bong chamber 2T...Injection fuel passage 28.
...Fuel supply passages 28a to 28c...Passage portion 41.
... Nozzle port 42 ... Needle chamber 43 ... Needle valve 50 ... Check valve 6o ... Solenoid valve 70 ...
・Relief valve device 76... Pressure regulator 80 River electromagnetic actuator 90... Control device patent applicant Fujio Sasashima, agent of Nissan Motor Co., Ltd., patent attorney

Claims (1)

[Claims] In a fuel injection device that integrally includes a pump part and a nozzle part, a check valve that allows flow only in the direction of the pump part is provided in a fuel supply passage communicating with an injection fuel passage that guides injected fuel from the pump part to the nozzle part. , a normally closed solenoid valve that receives the pressure in the injected fuel passage and the elastic biasing force in the valve closing direction, and a normally closed IJ valve device are interposed in parallel with each other, and the engine abnormality IJ- lowering the valve opening setting pressure of the relief valve device to a predetermined value based on the signal pressure of the state detection device.
A fuel injection device for an internal combustion engine, characterized in that it is provided with a valve adjustment device.