JPH02267363A - Fuel injection valve - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection valve, and more particularly to a fuel injection valve that performs optimal fuel injection over a wide range of changes in engine speed and load.

[Prior art] When injecting fuel into a vehicle engine, it is effective to reduce the amount of injection at the initial stage of injection, or to perform pilot injection prior to main injection, especially when driving at low speeds, in terms of improving exhaust emissions and saving fuel consumption. It is.

Therefore, for example, in Japanese Patent Application Laid-open No. 120851/1985, a back pressure chamber is provided behind a needle valve that opens and closes a fuel injection hole, and the supply of pressurized fuel to the back pressure chamber is controlled so that it is operated by the fuel pressure. A fuel injection valve that realizes pilot injection by providing another needle valve has been proposed.

[Problems to be Solved by the Invention] However, the conventional fuel injection valve described above uses a mechanically operated needle valve to control the supply of pressurized fuel to the back pressure chamber, so it cannot be used over a wide range of engine speeds. The problem is that it is difficult to respond to changes in

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and it is an object of the present invention to provide a fuel injection valve that can always achieve an optimal fuel injection pattern over a wide range of changes in engine operating conditions.

[Means for Solving the Problems] The configuration of the present invention will be explained with reference to FIG. 1. The fuel injection valve includes a needle valve 2 that opens and closes a fuel injection hole 11 provided in a valve housing 1 with a tip valve portion 21, and a needle valve 2 that opens and closes a fuel injection hole 11 provided in a valve housing 1. Base end 2 of needle valve 2
A back pressure chamber 12 formed in the valve housing 1 in contact with two surfaces and urging the needle valve 2 in the closing direction;
A spring member 4 is provided inside to bias the needle valve 2 in the closing direction, and pressurized fuel supplied from the fuel injection pump is supplied to the pressure receiving surface 2a of the needle valve 2 to open the needle valve 2. a first supply passage 13 for operating the pressurized fuel to the back pressure chamber 12; and a second supply passage 14 for supplying the pressurized fuel to the back pressure chamber 12.
, a discharge passage 15 having a constriction part 151 in the middle and discharging the pressurized fuel from the back pressure chamber 12; and the second supply passage 14.
The electromagnetic on-off valve 3 opens and closes the electromagnetic on-off valve 3, and a driving means 5 that opens and closes the electromagnetic on-off valve 3 at a predetermined timing of the pressurized fuel supply cycle.

[Operation] The pressure of the pressurized fuel gradually increases from the beginning of the feeding cycle, and after reaching the maximum, gradually decreases. At the start of the feeding cycle, the electromagnetic on-off valve 3 is closed, and the back pressure chamber 1 is closed.
2, the pressurized fuel is discharged through the discharge passage 15 and has a low pressure.

In this state, when the pressure of the pressurized fuel increases, the needle valve 2, which receives the pressure on the pressure receiving surface 2a through the first supply channel 13, opens against the biasing force of the spring member 4, and the fuel is injected. When the electromagnetic on-off valve 3 is opened at an appropriate timing by the driving means 5, pressurized fuel is supplied to the back pressure chamber 12 via the second supply channel 14, and the fuel is supplied to the back pressure chamber 12 through the second supply channel 14.
Since the throttle part 151 is provided in the back pressure chamber 12
The internal pressure of increases. Due to this increase in internal pressure, the needle valve 2
is biased in the closing direction, and once it is completely closed or its opening degree is kept small, a predetermined amount of pilot injection or initial injection with a small injection rate is performed prior to the main injection.

When the electromagnetic on-off valve 3 is closed after a predetermined time,
The supply of pressurized fuel to the back pressure chamber 12 is stopped, the pressurized fuel in the back pressure chamber 12 is gradually discharged from the discharge passage 15 having the constriction part 151, and the internal pressure of the back pressure chamber 12 is gradually reduced. In this state, the pressure of the pressurized fuel further increases, so the needle valve 2 is opened again or its opening degree is increased, and main injection is performed.

If the electromagnetic on-off valve 3 is opened again when the pressure of the pressurized fuel approaches the maximum, the internal pressure in the back pressure chamber 12 increases again, but the pressure applied to the pressure receiving surface 2a of the needle valve 2 increases. Since the pressure of the pressurized fuel is high, the needle valve 2 does not close. When a predetermined amount of fuel is injected and the pressure gradually decreases to below a predetermined value in the final stroke of the injection, the needle is strongly urged in the closing direction by the spring force of the spring member 4 and the internal pressure of the back pressure chamber 12. Valve 2 closes rapidly, providing accurate fuel metering.

When the pressure of the pressurized fuel further decreases, the electromagnetic on-off valve 3 is closed, the pressurized fuel in the back pressure chamber 12 is gradually discharged from the discharge passage 15, and the internal pressure of the back pressure chamber 12 decreases. In this state, wait for the start of the next feeding cycle.

[First embodiment] In FIG. 1, the lower end of the cylindrical valve housing 1 includes:
A cylindrical nozzle body 16 with a fuel injection hole 11 at its tip
A needle valve 2 is disposed inside the nozzle body 16 so as to be slidable up and down, and the fuel injection hole 11 is opened and closed by the tip valve portion 21 of the needle valve 2 .

A back pressure chamber 12 is formed in the valve housing 1 facing the end surface of the pressing member 22 that is brought into contact with the proximal end of the needle valve 2. A coil spring 4 is provided in contact with the needle valve 2.
is biased downward in the closing direction.

A pressurized fuel supply boat 1 is provided on the side of the valve housing 1.
7 is formed protrudingly, to which pressurized fuel is fed from a flash-rated fuel injection pump. A first supply passage 13 is provided downward in the valve housing 1 from the supply port 17, and its tip reaches an annular groove around the pressure receiving surface 2a of the needle valve 2. A second supply channel 14 branches upward from the supply boat 17, bends downward midway, and opens into the back pressure chamber 12.

A stopper member 18 having an electromagnetic on-off valve 3 installed therein is fixed to the upper end of the valve housing 1. A valve 31 and an electromagnetic coil 32 that attracts the valve upward.
It is composed of

The base end of the auxiliary needle valve 31 is located in a low pressure chamber 19 communicating with the reservoir tank 6 outside the valve housing 1, and the auxiliary needle valve 31 is biased downward by a coil spring 33 provided in the low pressure chamber 19 to supply the above-mentioned gas. The flow path 14 is closed.

The electromagnetic coil 32 is connected to a drive circuit 5 outside the valve housing 1, and the drive circuit 5 operates at a predetermined timing in the pressurized fuel supply cycle from the fuel pump depending on the engine rotation speed and its load condition, as will be described later. The electromagnetic coil 32
energizes to open the auxiliary needle valve 31.

A discharge flow path 15 is provided passing through the valve housing 1 and the stopper member 18, and the flow path 15 communicates the back pressure chamber 12 and the low pressure chamber 19, and a throttle member 151 is disposed in the middle. be.

The operation of the fuel injection valve having the above structure is explained below with reference to FIG.
This will be explained below.

The pressure of the pressurized fuel gradually increases from the start of the feeding cycle, reaches a maximum, and then gradually decreases (FIG. 2 (1)).

Before the pressurized fuel supply cycle, the electromagnetic coil 32 is de-energized, and the auxiliary needle valve 31 is pushed down by the urging force of the coil spring 33 to close the second supply flow path 14. (Hereinafter, this state will be referred to as the solenoid valve closed).

In this state, the pressurized fuel is discharged from the back pressure chamber 12 through the discharge passage 15, and the pressure in the back pressure chamber 12 is low ((3) in FIG. 2).

When the fuel supply cycle is started and the pressure of the pressurized fuel increases, the pressure is applied to the pressure receiving surface 2a of the needle valve 2 through the first supply flow path 13, and the needle valve 2 It is opened against the urging force of , and fuel is injected (point A in FIG. 2 (1), (4) and (5) in the same figure). When the electromagnetic coil 32 is energized from the drive circuit 5 at an appropriate timing, the auxiliary needle valve 31 is attracted upward against the biasing force of the coil spring 33 (point B in FIG. 2, (2) in the same figure) and the supply flow path is drawn upward. 14 (hereinafter, this state will be referred to as the electromagnetic on-off valve open).

When the electromagnetic on-off valve 3 is opened, pressurized fuel is supplied to the back pressure chamber 12 via the supply channel 14. Since the exhaust flow path 15 is provided with the throttle member 151, the internal pressure of the back pressure chamber 12 increases with the inflow of pressurized fuel (Fig. 2 (3)).
. This increase in internal pressure urges the needle valve 2 in the closing direction, and it is then completely closed (point 0 in FIG. 2 (4)).

Thus, a predetermined amount of pilot injection is performed prior to the main injection.

After a predetermined time, the drive circuit closes the electromagnetic on-off valve 3 (point D in FIG. 2 (1), point D in the same figure (2)).

The supply of pressurized fuel to the back pressure chamber 12 is stopped, and the pressurized fuel in the back pressure chamber 12 is gradually discharged from the discharge passage 15 provided with the throttle member 151, and the internal pressure of the back pressure chamber 12 gradually decreases. (Figure 2 (3)) In this state, the fuel pressure increases further, so the needle valve 2 is opened again (Figure 2 (1) point E, Figure 2 (4), (5)), and the main injection will be held.

When the fuel pressure approaches the maximum, the electromagnetic on-off valve 3 is opened again. Point F in Figure 2 (1) and Point F in Figure 2 (2)
), the internal pressure of the back pressure chamber 12 increases again (Fig. 2 (3)
), the needle valve 2 does not close because the fuel pressure applied to the pressure receiving surface 2a of the needle valve 2 is large.

When a predetermined amount of fuel is injected and the pressure gradually decreases to below the predetermined value in the end stroke of injection (point G in Figure 2 (1))
The needle valve 2, which is strongly biased in the closing direction by the spring force of the spring member 4 and the internal pressure of the back pressure chamber 12, rapidly closes, and fuel injection is immediately stopped, allowing accurate fuel metering. .

When the pressure of the pressurized fuel further decreases, the electromagnetic on-off valve 3 is closed (point H in FIG. It is gradually discharged and the internal pressure of the back pressure chamber 12 decreases.In this state, the next feeding cycle is waited for.

As described above, according to the fuel injection valve having the above structure, the pilot injection and the main injection are performed at the optimum timing over a wide range according to changes in the operating condition of the vehicle engine by means of the electromagnetic on-off valve operated by the drive circuit. be able to.

In this embodiment, if the amount of current applied to the first electromagnetic coil 32 is adjusted to reduce the opening degree of the auxiliary needle valve 31,
The needle valve 21 is not completely closed, resulting in initial injection with a suppressed injection rate.

[Second Embodiment FIG. 3 shows another structure of the electromagnetic on-off valve 3. In this embodiment, the spring force of the coil spring 33 is reduced, and the electromagnetic coil 32 is provided below the base end of the auxiliary needle valve 31, so that the electromagnetic coil 33
Close and suction downward.

The operation in this case will be explained with reference to FIG. 2 above.

When the pressure of the pressurized fuel increases, the auxiliary needle valve 31 is pushed up and opened at point B in the figure. After the pilot injection is completed, when the electromagnetic coil 32 is energized, the auxiliary needle valve 31
is sucked downward and becomes closed (second target point).

Subsequently, when the power supply to the electromagnetic coil 32 is stopped at point F, the auxiliary needle valve 31 is opened again by the fuel pressure.

When the fuel pressure drops sufficiently near the end of the fuel supply cycle (point H in FIG. 2), the auxiliary needle valve 31 is closed by the coil spring 33.

In each of the above embodiments, a stopper member biased by a spring is provided so that the needle valve 2 is closed during pilot injection.
The injection amount is suppressed by the base end coming into contact with the stopper member and its rise is restricted, and during main injection when the fuel pressure increases, the needle valve 2 pushes up the stopper member and rises, resulting in a fully open injection. A configuration like this can also be adopted.

[Effects of the Invention] As described above, the fuel injection valve of the present invention is equipped with an electromagnetic on-off valve that controls the inflow of pressurized fuel into the back pressure chamber that urges the needle valve in the closing direction, so that it can be used in a wide range of engines. This makes it possible to achieve optimal fuel injection characteristics in the operating range.

[Brief explanation of drawings]

1 and 2 show a first embodiment of the present invention;
2 is a time chart showing its operation, and FIG. 3 is a longitudinal sectional view of the entire fuel injection valve showing a second embodiment of the present invention. 1... Valve housing 11... Fuel injection hole 12... Back pressure chamber 13... First supply channel 14... Second supply channel 15... Discharge channel 151... Throttle Member (throttle part) 19...Low pressure chamber 2...Needle valve 2a...Pressure receiving surface 21...Tip valve part 22...Press member (base end) 3...Solenoid shut-off valve 31...・Auxiliary needle valve 32...Electromagnetic coil 4...Coil spring (spring member) 5...Drive circuit (drive means) 6...Reservoir tank time

Claims (1)

[Claims] a needle valve that opens and closes a fuel injection hole provided in a valve housing with a tip valve portion; a back pressure chamber that is formed in the valve housing in contact with a proximal end surface of the needle valve and biases the needle valve in a closing direction; A spring member provided in a back pressure chamber biases the needle valve in the closing direction, and pressurized fuel supplied from a fuel injection pump is supplied to the pressure receiving surface of the needle valve to operate the needle valve in the opening direction. a first supply flow path that supplies the pressurized fuel to the back pressure chamber; a discharge flow path that has a constriction part in the middle and discharges the pressurized fuel from the pressure chamber; A fuel injection valve comprising: an electromagnetic on-off valve that opens and closes the second supply flow path; and a drive means that opens and closes the electromagnetic on-off valve at a predetermined timing of the pressurized fuel supply cycle.