JPS59203864A - Fuel injection device for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve the combustion noise, the NOx concentration in exhaust gas, the fuel consumption or the like of small sized high speed diesel engine or the like by a method wherein a two-way valve device, communicating a pressure chamber with low pressure side sooner or later than the opening of a needle valve and interrupting the communication after a predetermined time has elapsed, is provided to control easily and highly accurately a pilot injection effected prior to the main injection. CONSTITUTION:When a coil 42 is conducted, an armature 39 is attracted to a core 43 against a leaf spring 40, therefore, the valve 32 is closed. According to this operation, the pressures of the pressure chamber 24 and the pressure chamber 27 are increased to lift the needle valve 29 and fuel injection is initiated. Simultaneously, or sooner or later than the injection, a check valve 44a is opened, therefore, the pressure of fuel is dropped and an injection amount is reduced or the injection is stopped immediately after the initiation of injection. When the small diametral end of the valve 44a is seated onto a downstream side seat part 45b, however, the releasing operation of the fuel is stopped, therefore, the pressure is increased again after a minute time has elapsed and the injection is reopened.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Scope The present invention relates to a fuel injection device equipped with a pylond injection mechanism used in an internal combustion engine.

(Prior art) As a conventional fuel injection device for an internal combustion engine, for example, Japanese Patent Application Laid-open No. S4-5, 5ov26t ÷ Publication (U.S. Pat. No. 5'I No. 4.1)
There is a unit injector as shown in US Pat. No. 29,253 (Po). This is constructed as shown in Fig. 1, and a plunger 3 is slidably inserted into the 7-herel 2 of the injector 1 via a cam or a rocking body (not shown) in synchronization with the rotation of the engine. When the pressure moves downward, the fuel pressure in the pressure chamber 4 and the discharge passage 5, which are formed facing the lower end of the plunger 3, decreases by -1,A or +
1'f! Due to the relief action of the nitric orifice 6, the pressure -L does not rise above a predetermined value.

The λ1 quantity orifice 6 communicates the pressure chamber 4 with the low pressure side via a fuel passage 7 and a solenoid valve 8. When a current is applied to the coil 9, the coil 9 is excited and the spring 14 is activated. In response, the solenoid valve 8 moves downward in FIG. 1 and seats on the valve seat 10, so that the outflow of fuel from the metering orifice 6 is blocked. Then, the pressure of the fuel increases by L, and the needle valve 12 floats from the valve seat against the seat spring 11, and the nozzle hole 1
Fuel is injected from 3.

``When the upstream application ends, the coil 9 is demagnetized, so the solenoid valve 8 floats from the valve seat 10 by the tension of the spring 14, and the fuel flows out from the metering orifice 6 again, ending the injection. The operating mode of the solenoid valve 8 is said to allow the injection pressure to be controlled arbitrarily using the characteristics of the electronic drive circuit, making it possible to perform both pilot injection and main injection.

However, in such a conventional fuel injection device, if the injection pressure is 1000 atm and the seat diameter between the solenoid valve and the valve seat is 211 IIn, it is difficult to inject the solenoid valve with a force of at least 30 kg or more. In order to control the injection pressure with an electronic drive circuit, it is necessary to use a powerful solenoid valve.In addition, in order to control the injection pressure with an electronic drive circuit, it is necessary to use a powerful solenoid valve. It is necessary to perform accurate control with extremely high precision, and in particular, if this is to be applied to small, high-speed internal combustion engines, solenoids and
There is a problem in that the injector becomes larger and the fuel injection device becomes more expensive, and at the same time, pilot injection varies from cycle to cycle due to the influence of parts precision and control precision. Incidentally, such a problem also occurs in a distribution type injection device and a row type injection device having a similar injection amount control mechanism.

<Object of the Invention> The present invention has been made to solve the above-mentioned conventional problems, and it is possible to easily and precisely control the Byron i injection that is executed prior to the main injection. The purpose is to improve combustion noise, NOx concentration in exhaust gas, fuel efficiency, etc. of small high-speed diesel engines.

<Summary of the Invention> In order to achieve the object as described in L, the present invention provides a needle 1< in addition to the lubricant, which is provided to control the fuel injection amount.
By providing a two-way valve device that connects the pre-shisha chamber to the low-pressure side before and after the valve opens, and shuts off the communication after a predetermined period of time, the relief action of this two-way valve device will eliminate the problem.・This allows for easy and highly accurate control of jet injection.

<Embodiment> FIG. 2 shows a first embodiment of the present invention, in which a /< barrel 22 is mounted on the main body 21 of the unit injector 20, and a plunger 23 is slidably mounted on this barrel 22. By fitting, the lower surface of the plunger 23 and the 7-herel 2
2 to form a pressure channel/~24). In addition, the plunger 23 is urged to move in one direction (1 in the figure) by a spring 25, and the upper surface of the plunger '-23- (i) is brought into contact with the circumferential surface (cam surface) of the cam (not shown), so that the cam is When the plunger 23 descends against the spring 25 in synchronization with the rotation (rotation of the engine), the fuel in the pressure chamber 24 is pressurized.

The pressure chamber 24 is connected to a pressure chamber 27 at the tip of the unit injector via a fuel passage 26, and a normally closed needle/< By installing the valve 29, when the pressure in the pressure chamber 27 becomes higher than a predetermined value, the two-relevant valve 28 is lifted against the tension of the needle spring 30, and fuel flows from the nozzle hole 28 into a combustion chamber (not shown). It is designed to be sprayed.

On the other hand, the fuel passage 26 is connected to a return passage 35 via a valve 32 of a solenoid valve 31, an oil guide passage 33, and a pressure regulator 34, and when the valve 32 of the solenoid valve 31 is open, The fuel in the pressure chamber 24 is returned to the oil guide path 33 so that the pressure in the pressure chamber 27 hardly increases. A fuel pump 36 pumps and supplies fuel in the fuel tank 37 to the oil guide path 33 via a foot tube 38.

Here, the /help 32 of the solenoid valve 31 is fixed to the armature 39, and the armature 39 is pushed and biased to the right in 1 Δ by a plate spring 40 in the direction in which the valve 32 is always open. Karako・r
When a current is applied to the leaf spring 42, the armature 3θ
0 and moves to the left side in the figure, and moves the valve 32 in the same direction to close the valve 32.

The two-way valve device 44 that connects the fuel passage 26 and the return tube 35 is a two-way check valve 44a of different diameters, with a larger diameter on the upstream side (fuel passage side) and a smaller diameter on the downstream side (return tube side). and an upstream seat portion 45a and a downstream seat portion 45b formed on the upstream and downstream sides of the check valve 44a, respectively, and a spring that urges the check valve 44a to sit on the 1-1 downstream seat portion 45a. 44b. By setting the opening pressure of the check valve 44a to be approximately equal to the opening valve F pressure of the needle valve 29, the check valve 44a is opened at the same time as the needle valve 28 is opened, or before or after the opening of the needle valve 28. The valve 44a opens to allow some of the fuel to escape into the passage 26.
When the valve is opened and pressure is applied to its entire cross section, the spring 4
4b, the valve 44a moves to the right in the figure, and its right end ff1 (small diameter section g) is seated to stop the pJ fuel release action. In addition, the fuel valve opening pressure,
Escape ¥ and period are pa r mouth y)'! +? period of radiation,
Although it may affect the acid, the opening f' JE is the strength of the spring 44b that urges the check valve 44a to slide to the left in the figure, the check, and the area of the L flow side seat portion 45a located on the left side of the valve. The relief j- and period can be set arbitrarily by adjusting the movement 44 of the check valve 44a, the cross-sectional area, and the size of the orifice or slit 46.

In the fuel injection device configured as shown in L, when the engine is operated, the fuel in the fuel tank 37 is transferred to the fuel pump 36.
is pressurized by the foot tube 38 to the oil guide path 33
supplied to Note that the pressure in the oil guide path 33 is kept constant by the pressure regulating action of the pressure regulator 34, and excess fuel is returned to the fuel tank 37 through the return tube 35. Further, since the valve 32 of the solenoid valve 31 is always open, the fuel supplied to the oil guide path 33 is supplied to the pressure chamber 24.

When the plunger 23 is raised by rotation of a cam (not shown), the fuel in the pressure chamber 24 is compressed and returns to the oil guide path 33 via the valve 32.

Next, when the control circuit 41 energizes the coil 42 at a time and period depending on the engine speed, accelerator opening, ice temperature, etc., the armature 39 absorbs water into the core 43 against the plate/henne 40. Therefore, the noherb 32 is closed. Then, the 1f1 force in the pressure chamber 24 and the pressure chamber 27 increases, the needle valve 29 is lifted, and fuel injection is started.

Nu, 1. When the injection is started S as described above, the check valve 44a opens at the same time or before or after this, so the pressure of the fuel decreases and the injection amount decreases or stops immediately after the start of the injection. However, when the small diameter end of the valve 44a is seated on the downstream seat portion 45b on the right side in the figure, the fuel release action is stopped.
．． After a short time of 7 m5ec has passed, the pressure rises again and the injection is opened by Ilr.

When the coil 42 is de-energized, the valve 32 opens due to the tension of the leaf spring 40.
The fuel flows out into the oil guide path 33 through the fuel, and the injection ends.

In the above embodiments, injection rate control or pilot injection is always performed, but engine specifications or.

Depending on the operating conditions, there may be times when it is desired to stop pilot injection. In such a case, a solenoid valve may be provided in series with the check valve to control the injection rate, as in the second embodiment shown in FIG.

That is, in the fJS2 embodiment shown in FIG. 3, a solenoid valve 47 for controlling the injection rate is provided downstream of the check valve 44a.
is provided, and while the coil 48 of the valve 47 is energized, the armature 50 is attracted to the core 51 against the leaf spring 49, and the valve 52 identified by the armature 50 is opened to open the check valve 44a. The downstream side of the fuel injection valve 47 is connected to the return tube 35, so that when the injection valve 47 is energized, injection rate control such as pilot injection can be performed as in the first embodiment.

On the other hand, when the coil 48 of the NRENOIT *47 is not energized, the valve 52 is closed by the leaf spring 49, so even if the check valve 44a is opened, fuel oil does not flow out into the return tube 35. , pilot injection is not performed.

FIG. 4 shows a third embodiment of the present invention, in which the configuration of the second embodiment is simplified and at the same time the valve opening pressure of the check/help 44a can be variably controlled. be.

That is, when the coil 48 is not energized, the valve 52
Since the valve is held closed by the leaf spring 49, fuel does not escape even if the change valve 44a opens, and byronto injection is not performed.

On the other hand, when the coil 48 is passed, the valve 52 is opened against the plate spring 48. For this purpose, the fuel passage 26
Check that the pressure of the spring 44a is 1-stream side sea i 81145 The sum of the force applied to a and the tension of the leaf spring 48 is the tension of the spring 44b and the armature 50.
When the force becomes stronger than the sum of the suction force of the core 51 acting on the fuel, the check valve 44a opens to let the fuel escape, and then, when the check/help 44a moves to the right and the valve 52 closes, the fuel flows out or stops.

Further, when the current supplied to the coil 48 is changed, the attraction force to the armature 50 due to the electromagnetic force generated in the core 51 is changed, so that the opening force of the check valve 44a is changed. Thereby, the timing and timing of pilot injection can be changed depending on the engine rotational speed, etc., and matching can be achieved under each condition. Therefore, as shown in the embodiment shown in FIG. 1, as the rotational speed of the engine increases, the descending speed of the plunger 23 increases, resulting in a higher oil delivery rate, which causes the check valve 44a to move faster. Therefore, it is possible to avoid shortening the fuel 4 release period (pylon i/injection period).

In all of the embodiments described in L, the solenoid valve 47 is used to control the injection rate, so there is an inconvenience that the unit injector becomes somewhat larger.
By using a hydraulic valve instead of a solenoid valve, the unit injector can be made smaller.

That is, in the fourth embodiment shown in FIG. 5, the valve 54 of the hydraulic valve 53 disposed in the check valve current is fixed to the hydraulic piston 55, and the help 54 is held closed by the spring 56. There is. and.

By connecting the foot tube 38 and a control chamber 57 formed facing the hydraulic piston 55 via a three-way switching valve 58, when foot pressure is introduced into the control chamber in response to a command from the control circuit, the hydraulic piston 54 is spring 5
6 to the left in the figure to open the valve 54.
Pilot injection is performed.

Also, the three-way switching valve 58 is switched to the control chamber 57#! by a command from the control circuit 41. When connected to the 1-ring tube 35, the tension of the ring 56 causes the hydraulic piston 55 to move as shown in the figure.
- Since the valve 54 is held closed, pylon I injection is not performed. Although the three-way switching valve 58 may be provided for each injector, it is clear that the configuration can be simplified by simultaneously controlling the pilot injections of all unit injectors with one three-way switching valve 58 as shown in the embodiment. Needless to say.

In all of the above embodiments, the present invention is applied to a unit injector, or the present invention can also be applied to a distribution type injection pump as in the fifth embodiment shown in FIGS. 6 and 7.

In this fifth embodiment, the plunger 23 and the barrel 22
A return tube 35 is connected to the pressure chamber 24 formed by the above through a valve case 58.

Inside the valve case 59, a valve 44a having the same shape as that shown in the 7fJl embodiment is housed so as to be freely movable. Then, the valve 44a is moved toward the pressure channel/toward 24 side by a spring 44b to be seated and held on the first flow side seat portion 45a formed inside the valve case 59, and is connected to the tip of the return tube 35. A downstream seat portion 45b is formed on the seat 61 which is sandwiched and fixed between the connector 6o and the valve case 587, so that the valve 44a behaves and performs pilot injection in the same manner as in the first embodiment. There is.

In the distribution type injection pump shown in FIG. 6, when the eccentric disk 62 rotates in synchronization with the rotation of the engine, the plunger 23 rotates and reciprocates within the barrel 22, sucking, compressing and distributing the fuel. The fuel compressed in the pressure chamber 24 is sent to the injection valve (not shown) via the delivery hull pro 3, and the injection foot of the fuel is transferred to the plunger 2.
Control sleeve 6 is slidably inserted into and held in 3.
The position of 4 is controlled by the Kapana mechanism.

Further, although not shown, the present invention can also be applied to a rectangular injection pump.

<Effects of the Invention> As explained above, according to the present invention, in addition to the valve that releases high-pressure fuel and controls the injection end, there is a valve that opens before and after the opening of the needle valve and after a predetermined period of time has elapsed. By providing a two-way valve device that returns to closed state, the fuel pressure immediately after the start of injection is lowered by opening the two-way valve device, so it can be easily and easily applied to small high-speed engines. Pilot injection can be performed with high precision, improving combustion noise, NOx, fuel efficiency, etc. of diesel engines]
,can.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of the main part of the conventional example, FIG. 2 is a sectional view of the first embodiment of the present invention, FIG. 3 is a sectional view of the main part of the second embodiment of the invention, and FIG. The figure is a sectional view of the main part of the third embodiment of the invention, FIG. 5 is a sectional view of the fourth embodiment of the invention, FIG. 6 is a sectional view of the fifth embodiment of the invention, and FIG. FIG. 7 is an enlarged cross-sectional view of a part of FIG. 6; 20... Unit injector 22... Barrel 23... Plunger 24... To Brennyachan 7 26... Fuel passage 28... Nozzle hole 29.
...Needle valve 30...Needle spring
31...Solenoid(・Bu"32...Valve 33...
・Oil guide path 34...Pressure regulator 3
5...Return tube 36...Fuel pump
37... Fuel tank 38... Foot tube 44... Bidirectional valve device 44a... Check valve 44b... Spring 45a...
"-Stream side seat part 45b...Downstream seat part 46
...Slit 47...Solenoid valve 52...
Valve 58... Valve case patent applicant Nissan Motor Co., Ltd. agent Patent attorney Fujio Sasashima Figure 1 Figure 2 44 Figure 4

Claims (1)

[Claims] a plunger that reciprocates within a barrel by a predetermined amount in synchronization with the rotation of the engine; a pressure chamber formed facing one end of the plunger; a nozzle hole communicating with the pressure chamber via a fuel passage; A normally closed needle valve that opens the nozzle hole when the pressure of the fuel sent out from the pressure chamber is equal to or higher than a predetermined value, and a valve that connects and shuts off the pressure chamber to the low pressure side at a timing depending on the operating state of the engine. In an internal combustion engine equipped with a fuel injection device comprising: a flow-side seat portion and a downstream-side seat portion interposed to face the fuel passage extending from the pressure chamber to the low pressure side; and both of these seat portions. a bidirectional check valve that selectively closes the needle valve, and a spring that urges the check valve to seat on the side seat portion at an opening pressure substantially equal to the opening pressure of the needle valve;
1. A fuel injection device for an internal combustion engine, characterized in that a bidirectional valve device is provided.