JPS58210357A - Fuel injection device - Google Patents

Abstract

PURPOSE:To obtain a small-sized fuel injection device with an expanded control range of its injection amount by providing several fuel injection pumps to give phase differences to reciprocations of plungers for increasing the amount of fuel injection. CONSTITUTION:When a voltage is added, a piezo-stack 8 of a fuel injection pump 3 is extended to move a plunger 9 to the right against a coned disc spring 10. The fuel in a pump chamber 14 pushes a piston 26 away to be introduced from a discharge port 15 into a piston hole 22, and supplied to a fuel injection valve 2 via a discharge passage 27. Meanwhile, when the voltage of the piezo- stack 8 is removed and a voltage is added to a piezo-stack 30 of a fuel injection pump 4, the piston 26 is moved to the left, and a similar fuel supply process with the piezo-stack 8 is carried on. In this construction, piezo-stacks 8 and 30 are alternately operated, and high-pressure fuel is continuously supplied to the fuel injection valve 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device that is mounted on a vehicle or the like and includes an electrically operated fuel injection pump.

Conventionally, this type of fuel injection device drives a plunger by applying a force that is electrically generated by energizing a solenoid, an electrostrictive element, etc., or by applying a magnetic force to a magnetostrictive element. A fuel injection pump is known that includes a fuel injection pump that performs a pumping action by reciprocating the plunger, and a fuel injection valve that injects fuel supplied from the fuel injection pump into the engine.

A fuel injection device having a configuration in which the plunger is electrically driven in this way has the advantage of being able to perform control with high precision and having a large degree of freedom in control, but on the other hand, it is , it is generally difficult to obtain a large stroke of the plunger. In other words, conventional fuel injection devices cannot increase the amount of fuel injected;
Another problem is that the control range of the injection amount is small.

In view of the above points, the present invention has been made with the object of obtaining a fuel injection device that can increase the fuel injection amount, expand the control range of the fuel injection amount, and has a small external size. The present invention is characterized in that a plurality of fuel injection pumps are provided, and the reciprocating motion of the plunger of at least one of these pumps is configured to have a phase difference with respect to the plunger of the other pumps.

The present invention will be explained below with reference to the illustrated embodiments. In FIG. 1, a unit injector 1 is composed of a fuel injection valve 2 and two piezo injection pumps 3 and 4 arranged on both sides of the injection valve 2, and is located inside the combustion chamber of a diesel engine. Used as a device to inject and supply fuel. The piezo injection pumps 3.4 each have exactly the same construction.

It is screwed onto both sides of the body 5 of the unit injector 1 at right angles to its central axis.

A casing 6 of the piezo injection pump 3 located on the left side of the figure has a substantially cylindrical shape, and a cylindrical piezo stack 8 is housed in an internal hole 7 of the casing 6 . A bottomed cylindrical plunger 9 is fitted into the end surface of the piezo stack 8 on the side of the body 5, and a disc spring 10 is elastically mounted between the front end surface of the plunger 9 and the wall surface of the internal hole 7. The disc spring 10 always urges the plunger 9 to the left in the figure, and the more the plunger 9 is displaced to the right, the greater the urging force becomes. The plunger 9 is slidable in the internal hole 7, and when the piezo stack 8 extends, it moves to the right against the elastic force of the disc spring 10, and when the piezo stack 8 contracts, it moves to the left together with it. .

On the other hand, a holder 11 is attached to the rear end of the piezo stack 8 . The tip of this holder 11 protrudes outward from the casing 6 from an opening s12 having a slightly smaller diameter than the internal hole 7, and is always attached to the end wall surface of the internal hole 7 due to the elastic force of the holder shoulder 12fi and disc spring 10. come into contact with bullets.

The piezo stack 8 is a sintered body (ceramics) formed by stacking piezoelectric elements called PZT in the axial direction. A platinum electrode is baked on the bonding surface of the piezoelectric element, and this platinum electrode is A! In the state.

The structure is such that the potential is positive, negative, positive, and negative in the axial direction. A lead wire 13 for energizing the piezoelectric element passes through the holder 11 and is blown out of the casing 6. Thus, when the piezo stack 8 is energized once, it expands and causes the plunger 9 to move to the right against the disc spring 10. As a result, the fuel in the pump chamber 14 formed between the front end surface of the plunger 9 and the wall surface of the internal hole 7 is compressed, and is discharged from the discharge hole 15 and fed to the injection valve 2 under pressure. On the other hand, when the power supply to the piezo stack 8 is cut off, the plunger 9 is activated by the elastic force of the disc spring 10 and the supply port 1 which will be described later.
6, moves to the left under the pressure of the fuel supplied, and opens the intake port 1.
Fuel is drawn into the pump chamber 14 through the pump 7.

Note that the outer end surface of the piezo-type injection pump 3.4 in which the discharge hole and suction port are formed is formed into a flat shape, and these pumps 31 and 4 have this outer end surface tightly attached to the body 5. be installed.

In the supply port 16 formed in the upper part of the body 5.

Fuel is supplied to an accumulator (not shown) at a pressure of about 100 #/-. A supply passage 18 is bored below the supply port 16 . The supply passage 18 extends downward along the axis of the body 5, branches to both sides, and connects the pump 3.
It communicates with the intake port 17 and 19 of No. 4. Pole-shaped check valves 20 and 21 are housed in the branched portions of the supply passage 18, respectively.

Fuel in the pump chamber 14 is prevented from flowing into the supply passage 18.

Below the branch of the supply passage 18 in the body 5, there is a
A piston hole 22 extending in the radial direction of the body 5 and having an inner diameter of about 4 mm is bored. Both ends of the piston hole 22 are formed to have a larger diameter in a stepped manner by approximately 1 mm than the central portion, and the chain hole 22 is connected to the discharge port 1 of the pump through its large diameter portions 23 and 24.
It communicates with 5.25. A cylindrical piston 26 that is approximately 100 μm shorter than the axial length of the chain hole 22 is slidably supported in the center of the piston hole 22 . The piston 26 has both end surfaces formed into a flat shape, and has a discharge port 15.25.
It can move to either the left or right depending on the fuel pressure discharged from the outlet, and can come into close contact with one of these discharge ports 15, 25 to close it.

A discharge passage 27 extending in the axial direction of the body 5 is formed below the piston hole 22 . The main force of the discharge passage 27 is 1
It branches and communicates with the large diameter portions 23 and 24 of the piston hole 22, respectively, and the lower portion communicates with the fuel injection valve 2. The fuel injection valve 2 is a diesel engine injection valve having a known structure.

When the fuel pressure rises above the set value μ, the needle 28 rises against the spring 29, opening the valve.

The embodiment device having the above configuration operates in a first-order manner to perform fuel injection.

When a voltage is applied to the piezo stack 8, the piezo stack 8 expands, causing the plunger 9 to move to the right against the disc spring 10. As a result, the fuel in the pump chamber 14 is compressed and pressurized, pushes the piston 26 away from the discharge port 15, flows into the piston hole 22, is supplied to the fuel injection valve 2 via the discharge passage 27, and is injected to the outside. be done. Next, when the voltage of the piezo stack 8 is released and a voltage is applied to the piezo stack 30 of the injection pump 4, the piezo stack 8
contracts, the piezo stack 30 expands, and as a result, the fuel pressure on the discharge port 25 side increases and the piston 2
6 moves to the left, the outlet 15 is closed, and the outlet 25 is opened. Thus, the piezo stack 30 performs the same fuel supply process as the piezo stack 8 described above, but during this time, the plunger 9 of the piezo stack 8
The pump moves to the left under the pressure of the fuel supplied through the suction port 17 and the repulsive force of the pump, and new fuel is sucked into the pump chamber 14 via the check valve 20.

In this way, the piezo stack 8.30 operates in an alternating manner,
As a result, high-pressure fuel is continuously supplied to the injection valve 2.

The state of fuel supply by this piezo stack 8.30 is explained in detail in Figure 2. Figure 2 (,) shows the injection valve 2.
When the amount of fuel injected from is small.

Figure 2 (b) shows that when this amount of fuel is large, Figure 2 (C)
indicates a case where the injection rate per hour is high, that is, a case where the fuel pressure is high.

In FIG. 2(a), curve A shows the voltage of the piezo stack 8, and this voltage increases linearly from time Tt to time T2, that is, for about 400 μsec.
At time T2, ■1=approximately 500V is reached, and this t' is maintained until time T3. on the other hand.

As shown in curve B, a voltage is applied to the piezo stack 30 at one time T8, and this voltage increases at the same rate of increase as the increase rate of the voltage of the piezo stack 8 from time T1 to time T2. It is canceled at T3. Moreover, at this time T, the voltage of the piezo stack 8 is also released at the same time.

Since the voltage increase rates of the piezo stacks 8.30 are equal, the pressure of the fuel supplied to the injection valve 2 from time T1 to time T3 is substantially constant, Pl, as shown by curve 1. becomes. Further, at time T3, the voltages of both piezo stacks 8.30 are released simultaneously, so that the piezo injection pump 3.4 performs the suction process at the same time, and the piston 26 connects the two outlet ports 15.25. open at the same time. Therefore, the discharge passage 2
The fuel in the fuel injector 7 is sucked back into the pump chamber 14, etc., causing a sudden pressure drop, and fuel injection from the fuel injection valve 2 is smoothly stopped. That is, time T3 is the time when all the required amount of fuel is injected from the injection valve 2. Note that 1 time T, and T3
The interval is shorter than the interval between times T1 and T, and therefore the maximum voltage Vs of the piezo stack 30 is smaller than the maximum voltage 1 of the piezo stack 8.

In the example shown in Fig. 2(b), unlike the case in Fig. 2(-), power is supplied to the piezo stack 8.30 twice, and the time required to maintain the fuel pressure P1 is , is much longer than the case in Figure 2 (,). That is, one curve, as shown by E.

The voltage of the piezo stack 8 is from time TI to time T.

The voltage increases linearly until it reaches 1 at time T2, and is released, and at the same time, the voltage across the piezo stack 3° increases. This voltage reaches 1 at time T4 and is released, and at the same time the voltage is applied to the piezo stack 8 again. The voltage of the piezo stack 8 increases linearly until time 5 Ts.

From time TI to time T-, it is held at Vl and released at time T6. On the other hand, at 1 time Ts, the voltage of the piezo stack 3o increases again, and this voltage is also released after reaching 3 at time T6. In this example, the voltage increase rates of the piezo stacks 8.30 are all equal and T2-Tl=T4-Tx=TH-T4 and T6-Tll<T2-Tl.

Therefore, the voltage Vl is smaller than Vl.

Therefore, as shown by curve 1 F, the pressure of the fuel supplied to the injection valve 2 is as follows from time TI to time T6.
The constant value Pi is maintained for a longer period of time than in the example shown in FIG.

Now, in the above two examples, the fuel pressure P1 in the discharge passage 27 is equal to each other, and therefore the fuel injection rate per hour is also equal to each other. In order to increase the injection rate per hour, it is necessary to increase the fuel pressure in the discharge passage 27, but this can be done by increasing the rate of increase per hour of the voltage applied to the piezo stack 8.30. .

FIG. 2(c) shows this, and the voltage of the piezo stack 8 is at one time T as shown by one curve G.

to time T7, it increases linearly at a higher rate of increase than the rate of increase in the examples shown in FIGS. 2(a) and 2(b) above.

It reaches Vl at time T7 and is released immediately thereafter. That is, the time from time T1 to time T1 is shorter than the time from time T1 to time T2. On the other hand, as shown by a curve H, the voltage of the piezo stack 3o increases at a high rate of increase from time 1 to time T8, like the voltage of the piezo stack 8, and at time Tl, the voltage increases at a high rate.
After reaching Vl, Vl is held until one time Ts, and then released. Moreover, from time 1 Ts to time T11, the voltage of the piezo stack 8 increases linearly again, and
It will be canceled in . As a result, the moving speed of the plunger becomes larger than the example shown in FIG.
, is higher than the fuel pressure P1 in the example of (b).

The process explained above is one fuel injection.

In the case of a four-stroke diesel engine, this fuel injection is repeated every near top dead center in each compression stroke, that is, every two revolutions of the engine.

As described above, the device of this embodiment has a structure in which fuel is alternately supplied to the common injection valve 2 from a plurality of electric injection pumps 3.4, so that the disadvantage of the electric injection pump that the plunger 90 stroke is small can be overcome. Can be removed. In particular, since the plunger 9 can be stroked several times for one injection, the total injection amount can be increased, and the excellent effect that the pump itself can be made small can be obtained. Furthermore, the device of this embodiment has a fuel injection pump 3.
．． 4 through a common control valve, and the piston 26 of this control valve is structured to close the discharge port of the pump with lower discharge pressure, so the stroke of the piston 26 can be made smaller. Therefore, it is possible to reduce the fuel trap volume, improve fuel feeding efficiency, and increase responsiveness. Moreover, since the injection pump 3.4 simultaneously performs the suction stroke at the end of fuel injection from the fuel injection valve 2, the fuel pressure in the discharge passage 27 quickly decreases.

Fuel injection stops smoothly.

In addition, fuel ambiguity and fuel pressure are controlled by applying and releasing voltage from a controller (not shown) to the piezo stack 8.30 according to the opening degree of the accelerator lever and the engine speed. Various control methods are possible, not limited to the examples shown in FIGS. Further, in the above embodiment, the voltage application to the piezo stacks 8.30 is completely alternated, but it is of course possible to energize both piezo stacks 8.30 somewhat overlappingly.

This allows for smoother fuel injection.

Furthermore, 1. In normal operation, fuel injection occurs continuously, but once on either side of the piezo stack 8.
Apply pulse voltage.

It is also possible to perform pilot fuel injection, which is a small amount of fuel injection performed prior to main injection.

Further, in the above embodiment, the supply port 16 is common, but it may be configured to be separated and supply different types of fuel to each, and a renoid or magnetostrictive element may be used as the source of the force acting on the plunger. may also be used.

Furthermore, the present invention can be applied to intake pipe injection in gasoline engines, continuous combustion engines such as gas turbines, or external combustion engines.

As described above, according to the present invention, it is possible to obtain a small fuel injection device that can increase the fuel injection rate by 1 t even though the stroke of the injection pump is small, and can expand the control range of the injection amount. be effective.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing an embodiment of the present invention, Figure 2 (,)
, (b) and (c) show the operating states of the embodiment apparatus. 2. Fuel injection valve. 3.4. Fuel injection pump. 9... Plunger, 26... Piston. Patent Applicant Co., Ltd. Japan Auto Parts Research Institute Patent Attorney Akira Aoki Patent Attorney Kazuyuki Nishidate Patent Attorney Kyo Nakayama Patent Attorney Akira Yamaguchiffi 8 TI 73 τ1T3 TI T2 T4 T6T+
T6■1T7
T8 T9 TI T9

Claims (1)

[Scope of Claims] 1. A fuel injection device comprising a fuel injection valve and a fuel injection pump that electrically drives a pusher to reciprocate and supplies fuel to the fuel injection valve, wherein the fuel injection pump A fuel injection device characterized in that a plurality of pumps are provided, and the reciprocating motion of the plunger of at least one of these pumps is configured to have a phase difference with respect to the motion of the plungers of the other pumps. 2. The fuel injection device according to claim 1, wherein the fuel injection valve is a single fuel injection valve. 3. Claim 1, characterized in that a valve mechanism is provided which operates based on the differential pressure between the discharge pressures of the plurality of fuel injection pumps and closes the discharge port of the fuel injection pump having the lower discharge pressure. Or the fuel injection device according to item 2. 4. Claims 1 to 3, characterized in that the plurality of fuel injection pumps perform the compression stroke with a mutually reduced phase difference, and simultaneously perform the suction stroke. The fuel injection device according to any one of the items.