JPS5823265A - Unit injector - Google Patents

Abstract

PURPOSE:To control injection timing of fuel and a quantity of injection fuel, by controlling feed and cut timing of fuel to a plunger chamber through a selector valve and regulating pressure of the fuel in the plunger chamber. CONSTITUTION:Fuel, fed out from a pressure control valve 15, is fed to a selector valve 19 through a pipe 18, and then supplied to an inlet 9 of a main unit 1. This selector valve 19 is driven by a digital pulse motor 20 relating to the operational state of an engine and movement of a plunger 6. In consequence, start and end timing of injection can be correctly and surely controlled in accordance with the operational state by very simple constitution.

Description

[Detailed Description of the Invention] This invention is designed so that the L re-plunger reciprocates with the rotation of a camshaft driven according to the engine rotational speed to suck in and pump fuel, and inject the fuel when pumping. , relates to improvements in unit injectors used in internal combustion engines, particularly diesel engines.

In a normal diesel engine fuel injection system, the fuel injection pump and injection valve are connected through a relatively long injection pipe.
Fuel is injected into the injection valve through an injection pipe that is force-fed by the plunger of the injection pump. Therefore, since the fuel pumped from the plunger is affected by the length and volume of the injection pipe, it is impossible to completely control the injection rate by the injection valve by the oil delivery rate of the plunger. Therefore, for example,
Even if the fuel delivery period by the plunger is the same depending on the cam angle,
Problems such as the actual injection period becoming longer with the rotational speed and difficulty in controlling the injection amount in a small injection amount region have occurred. In order to solve these problems, various unit injectors have been proposed in which an injection pump and an injection valve are integrated and the injection pipe is omitted.

However, in the unit injectors proposed so far, the injection start and end timings can be freely set according to the operating state of the engine.
There was no way to control it accurately.

The purpose of this invention is to provide a switching valve that is operated by an electric signal set according to the operating state of the engine, and to control the timing of supplying and shutting off fuel to the plunger chamber, thereby controlling the fuel pressure in the plunger chamber. It is an object of the present invention to provide a new unit injector that can be adjusted and made possible to control the injection timing and injection amount as described above.

Next, the present invention will be described with reference to illustrated embodiments.

It is located in the axial hole /a at the tip of the injector body l.

The nozzle spring l is housed in a shear spring chamber /l) that communicates with the axial hole la, and this spring chamber /l) is connected to the leak hole 4.
It communicates with the low pressure side through the axial hole 11 and the spring chamber/l.
) to allow leaked injected fuel to escape. −
There is a plunger spring in the axial hole lc at the base end of the blade body l! A plunger 6 receiving a spring force is inserted in an oil-tight and slidable manner.

Cam 7aK of camshaft 7 driven according to engine rotation speed
It is made to follow. Said plunger spring! is supported between a concave portion /d formed at the base end of the main body L and a flange portion 4a of the plunger B. Axial hole forming plunger chamber LC value Fuel inlet f, Gun 10
It communicates with the through hole /e, in which the delivery valve l/ is arranged. The through hole le communicates with the through hole If and the fuel reservoir 7g, and the fuel that is supplied from the inlet 2 into the plunger chamber r is fed to the plunger 6 under pressure through the delivery valve ii and into the through hole le.

The fuel is sent to the fuel reservoir /H via /f, and when its pressure overcomes the setting force of the nozzle spring, it depresses the needle valve 2 and is injected from the nozzle hole /11 at the tip of the main body.

The fuel in the fuel tank/2 is pumped up from the pipe/y by the independent magnetic pump/3, which is always in operation, and sent to the pressure control valve is', where it is pumped up by the electromagnetic pump 1.
The pulsation caused by 3 is removed and the pressure is constant V! - Pressure is regulated. Pressure control wandering valve I! The leakage fuel from the pipe/l,
17 and is returned to the fuel tank/, 2, but the pressure control valve l! The fuel that exits is supplied to the inlet rotor of the ridge main body l, which is fed to the switching valve/receiver via the pipe it. The switching valves are arranged perpendicularly to the pipe/Ir and alternately! PoO
It is a rotary type that performs a swinging motion to take the angular position of 5, and is driven by a digital noggles motor, 20K, in relation to the operating status of the five engines and the movement of the syringe. This digital nozzle motor is an electric motor that is set by a control unit (not shown) that inputs various factors related to the operating state of the engine (for example, engine rotation speed, camshaft rotation angle, load, cooling water temperature, etc.). It is designed to operate in response to a signal and drive the switching valve as described above. As shown in FIGS. 2, 3 and 7, the switching valve has a cylindrical body having one radial passage B, 21b and an axial passage wI-21c connecting these; 2/Main body-2/L fitted housing 2-
2, this housing has openings -2-2j and -2-2b to which the pipe it is connected and which communicates the pipe ttr with the radial passageway -2/ of the main body -21, and the pipe 17 is connected thereto. Opening 2-i which connects the tube 17 and the radial passage 21b! It is equipped with c. The position ■ in Fig. 2 indicates the position t that the switching valve l assumes when the plunger O rises, that is, during the fuel suction stroke of the plunger O. In this position, the radial direction M-2/a is supplied from the pressure control valve The pipe is' through which the fuel passes is communicated, and the fuel supplied in the pipe 1g is guided from the inlet to the plunger chamber r. At this time, the surplus fuel is transferred to the pipe it, the radial passage 21a, the axial passage -2/c,
#-Radial passage-21be 41 Te tube/7 [Feeded,
The fuel is returned to tank l-2, but an orifice 17a is provided in the pipe 17 to prevent a sudden pressure drop.
is being kept. The ■ position in FIG. 3 indicates 1k, which is the same as the 1st position IN, but the plunger t has completed the suction stroke and has begun to descend, performing a pressure stroke. Therefore, the volume of the plunger chamber gradually decreases, and the fuel in the plunger chamber pushes open the delivery valve 1/ against the spring lO, and accumulates in the fuel reservoir 1g.

Excess fuel is returned to fuel tank l-2 via switching valve l-2. In the position M in Figure 1, the switching valve l swings 20 degrees due to the action of the digital noggle motor O.

The tube that was communicating until then/7. /If is cut off. In this state, the plunger Aid pressure feeding stroke continues, so the fuel pressure in the fuel reservoir/g immediately rises, and when the set force of the nozzle spring also rises, injection is performed.

This fuel injection ends when the selector valve l swings back to O0 due to the operation of the digital knob ξ motor tacho θ and returns to the original 1 position in Fig. 2, and the fuel in the syringe chamber g is released to the low pressure side. do.

The operation of the unit injector constructed as described above will be explained with reference to FIG.

Initially, the switching valve is in position ■ in Fig. 2, and the plunger is 6 yen 1. It is assumed that the camshaft 70 is moved upward by the cam 7a due to the spring force of the plunger spring j, and is performing a suction stroke. Therefore, the fuel in the fuel tank 1-2 is sent to the electromagnetic pump 13 from the pipe 1 to the pressure control valve /J', and then guided to the switching valve 1 via the pipe /J'. It is supplied from the input rotor of the injector body to the plunger chamber r through the radial passage U/a of the body 21.

When the camshaft 7 further rotates, the plunger 6 moves as shown in FIG.
Plunger spring as shown in 11! It begins to descend against the pressure and begins to perform a pressure feeding stroke. The position of the switching valve 1 in this state is the position 3 in Figure 3, which is the same as the 1 position in Figure 2, and the plunger chamber is filled with the decrease in volume Vr of the plunger chamber t due to the lowering of the syringe. The fuel flows from the inlet to the passage of the pipe it% switching valve main body 21, 2/a.
,,2/c.

, 2/b, and is returned to the fuel tank l-2 through the construction passage 17. During this fuel pressure feeding process, W is sent from the control unit (not shown) to the Luz motor 20.
When a pulse as an injection timing signal is applied to the supply furnace as shown in Fig. J (2), the switching valve is immediately oscillated by θ0 due to the operation of the motor 20 as shown in Fig. V (Fig. V). ■Take a position. to this! Vv/ is shut off and the sylanger chamber is closed, so the fuel in the sylanger chamber r flows into the fuel reservoir /g through the push-open 5 hole /f of the delivery valve //f, as described above. The needle valve 3 is lifted against the nozzle spring λ in the process shown in Fig. 5 (4), and the injection hole /h
, C is injected. Thereafter, the control unit's command activates the elimator 20, and the switching valve returns to the 1 position shown in FIG. 2, and the pipe tr is connected to the plunger chamber. When it communicates with the pipe 17, the fuel pressure in the fuel reservoir/g that was acting on the needle valve 3 decreases, so the needle valve 3 is seated by the nozzle spring -0 centa, and injection ends.

Therefore, since injection is performed when the switching valve 1 closes the plunger chamber g, the injection start timing can be freely changed by changing the operating timing of the switching valve 1. In Fig. J, the broken line and the dashed-dotted line indicate the injection timing signal, the operation timing of the switching valve 1, and the needle valve lift when the injection start time is advanced or delayed, respectively.

The injection end timing can be arbitrarily set by changing the timing at which the switching valve 1 opens the syringe chamber 1 to the low pressure side as indicated by the two-dot chain line in FIG. Therefore, since the fuel injection amount can be determined from the start to the end of injection, that is, during the period when the plunger chamber is closed by the switching valve, it is possible to precisely and finely control the injection amount. can. For example, normally, if the injection start time is set earlier as shown by the broken line in Figure 5, the injection amount will also increase accordingly, but this can be reversed by making the injection end time earlier as shown by the two-dot chain line. With this, only the injection start timing can be made variable without changing the injection amount.

FIG. 6 shows another embodiment of the switching valve 1, in which an electromagnetic coil 23 receives the nozzle from the control unit described above, and a plunger 2 that reciprocates through the action of the thorn 21! have. The plunger 2 is inserted oil-tightly and slidably into the housing 16 through a radially penetrating passageway Zja, and the plunger 2 is inserted into the housing 16 in an oil-tight and slidable manner. is communicated with the plunger chamber r. When the electromagnetic coil 23 is excited, the plunger 2j is attracted and moves downward against the spring 2hi as shown.

It is designed to shut off the plunger chamber ff by shutting off the pipe 1. In this case, the return fuel pipe 17 is connected to the fuel supply pipe irK.

As described above, according to the present invention, in the unit injector, the fuel passage directly connected to the plunger chamber is provided with a switching valve that communicates with and shuts off this passage, and the switching valve is operated by an electric signal set according to the operating state of the engine. Crafted? fjl
Since the injection start and end times are controlled by J, the injection start and end times can be precisely controlled according to the operating conditions with a very simple configuration, and as a result, the injection amount can be controlled accurately and in a variety of ways. becomes. Therefore, it not only contributes to noise and exhaust gas purification measures, but also prevents car knock and engine crashing, improves fuel consumption rate, and contributes to improving engine performance. Also, regarding startability, an electromagnetic pump is used to supply fuel.

Since the engine uses a fuel supply system that is related to force (F), a predetermined injection pressure can be easily obtained and startability can be improved.Furthermore, since the switching valve is an on/off operating valve, the configuration is extremely simple. It is located perpendicular to the fuel supply passage.

Compared to the case where it is installed parallel to the fuel flow, it clearly does not receive direct fuel pressure and one operation is certain.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing one embodiment of a unit injector according to the present invention, and the second and third diagrams are 1. FIG. 5 is a longitudinal sectional view showing the operating position of the switching valve, FIG. 5 is a diagram explaining the operation of this embodiment, and FIG.
Schematic diagram ff1lJ shows another example of the switching valve. l...Injector body, 2...Plunger, 7.
...Camshaft, lr...Switching valve Fig. 5 Fig. 6

Claims (1)

[Claims] In a unit injector, a plunger reciprocates with the rotation of a camshaft driven according to the engine rotational speed to suck in and pump fuel, and inject the fuel during pumping. A unit injector, characterized in that a switching valve is provided to communicate and cut off the passage, and the switching valve is controlled by an electric signal set according to the operating state of the engine.