JPH03225064A - Variable static flow type fuel injection device - Google Patents

Abstract

PURPOSE:To enlarge practical injectable flow from the minimum flow to the maximum flow with a leap by increasing/decreasing the passage sectional area of a fuel measuring part on the basis of the position switching of a stopper so as to obtain both small and large flow characteristics with one fuel injection device. CONSTITUTION:When a movable stopper 58 is in a first position to give a small flow stroke to a valve member 22, a valve side measuring part 44 corresponds to a body side first measuring part 54 in the movement of the valve member 22 in the opening direction so as to form a fuel measuring part of small passage sectional area by both parts. A small flow characteristic sufficiently low in the lowest practical value of injection flow can be thereby obtained. When the movable stopper 58 is moved from the first position to a second position by a stopper moving means 62, the valve side measuring part 44 is placed in the state of corresponding to a body side second measuring part 56 in the movement of the valve member 22 in the opening direction so as to form a fuel measuring part of larger passage sectional area, thus obtaining a large flow characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a fuel injection device that is installed in a fuel supply system of an engine and injects fuel, and particularly relates to an improvement in the structure for setting the amount of fuel injection per injection. .

<Prior art> A type of well-known fuel injection device (so-called injector) has a body, a fuel passage passing through the body, an injection port formed at the tip of the fuel passage, and an injection port that opens and closes. There is a known type of valve that includes a ring-shaped valve member and a valve drive means that opens and closes the valve member in the axial direction. For example, Japanese Utility Model Application Publication No. 58-132162 discloses this type of injector.

In such an injector, it is necessary to set the amount of fuel injected 91 per injection as accurately as possible, and for this purpose, a fuel metering section, which is a type of throttle, is installed in the fuel passage, close to the upstream side of the injection port. is provided. This gives a passage cross-sectional area corresponding to the difference between the cross-sectional area of the fuel passage and the cross-sectional area of the valve member, and the injection amount per injection is determined based on the product of this passage cross-sectional area and the injection time (inter-valve time). is defined.

Then, the valve member opens for a certain period of time in response to the intake stroke of the engine to perform injection, and the injection time is generally duty-controlled using a pulse signal. Here, when the engine output is low, the intake air amount is small, so the injection time (pulse width) per injection is short, and when the engine output is high, the intake air amount is large, so the pulse width is long.

<Problems to be Solved by the Invention> Conventionally, the passage cross-sectional area of the fuel metering section in such an injector is uniquely determined at the design and manufacturing stage, and the flow rate of the injector is determined by the fixed passage cross-sectional area. Characteristics are also uniquely determined.

FIG. 5 shows the characteristic (2) of a small flow rate injector in which the passage cross-sectional area of the fuel metering section is set small, and the characteristic (2) of a large flow rate injector in which the passage cross-sectional area of the fuel metering section is set large. In both characteristics, as the pulse width (injection time) increases, the injection flow rate increases from zero to Ql and Q2 at full opening, respectively, but in reality, it is difficult to determine the usable range of this pulse width for practical use. The range is limited to the range W in which the pulse width and the injection flow rate have a linear relationship due to the problem of flow rate variations. Therefore, in practice, the minimum flow rate q for the small flow rate characteristic ■
The flow capacity is determined by the area IQs from 1 min to the maximum flow rate qllaX, and in the area Q[ from the minimum flow rate q2sin to the maximum flow rate q2iax for large flow characteristics ■, but each has its advantages and disadvantages. .

In other words, with the small flow rate characteristic ■, fuel consumption can be kept low in the engine's lowest output state (such as when the vehicle engine is idling), but when high output is required (such as when the vehicle is accelerating), the injection flow rate is The disadvantage is that the output has reached a plateau and the output limit is low. On the other hand, with the large flow rate characteristic (3), a sufficient high output can be obtained, but it is difficult to suppress the injection flow rate to the necessary minimum in the lowest output state, resulting in more fuel being consumed than necessary.

An object of the present invention is to provide a single injector (fuel injection device) with both small flow characteristics and large flow characteristics, and to enjoy the advantages of each.

Means for Solving the Problems> A fuel injection 9A device according to the present invention has a body as described above,
It is assumed that it includes a fuel passage, an injection port, a valve member, a valve driving means, and a fuel metering section, and is configured with the following requirements.

That is, there is a first passage disconnection between (1) a valve-side metering section formed on the valve member to constitute the fuel metering section, and (2) the valve-side metering section formed on the inner circumferential surface of the fuel passage. a body-side first measuring section that provides an area; a body-side second measuring section that provides a larger second passage cross-sectional area;
Valve stroke switching means for switching the movement stroke of the valve member in the opening direction between a small flow rate stroke in which the valve side metering section corresponds to the body side first meter chain section and a large flow rate stroke that reaches the body side second metering section; , and the valve stroke switching means includes (a) a movable stopper that is movable along the axial direction of the valve member and defines a moving end of the valve member in the opening direction; and (b) a movable stopper that is movable along the axial direction of the valve member. A stopper moving device is provided for moving the stopper between a first position that provides the small flow stroke to the valve member and a second position that provides the large flow stroke.

In the fuel injection device 9A according to the present invention, when the movable stopper is in the first position and applies a small flow rate stroke to the valve member, the valve pointer moves toward the body when the valve member moves in the opening direction. Corresponding to the side first metering section, both constitute a fuel metering section with a small passage cross-sectional area, and therefore a small flow rate characteristic with a sufficiently low practical minimum value of the injection flow is obtained.

On the other hand, when the movable stopper is moved from the first position to the second position by the stopper moving means, a large flow stroke is given to the valve member, and when the valve member moves in the opening direction, the valve side metering part is moved toward the body side. In a state corresponding to the second metering section, a fuel metering section with a larger passage cross-sectional area is constructed, and in this state, a large flow rate characteristic with a sufficiently high practical maximum value of the jet rA flow suspension is obtained.

<Example> Hereinafter, one embodiment of the present invention will be described based on the drawings.

The fuel injection device (injector) 2 shown in FIG. 1 includes a body 10 in which body components 3, 4, 6 and 8 are assembled in a liquid-tight manner. Inside the body 10, a fuel supply port 12 at the base end passes through a filter 14 and an injection port 16 at the tip end.
A fuel passage 18 is formed that leads to. The injection nozzle 16 is a tapered hole-shaped portion with an inner diameter increasing toward the tip, and an elongated ring-shaped valve member 2 is provided at the tip with a valve head 20 that opens and closes the nozzle 16.
2 is provided so as to be movable in the axial direction within the body 10. The valve head 20 is a truncated cone-shaped portion that roughly corresponds to the injection port 16, but its outer circumferential surface has a slightly gentler taper angle than the inner circumferential surface of the injection port 16, and the injection port 20 is injected from the outside to the inside of the body 10. In a state where the valve head 20 is seated in the mouth 16, the peripheral edge of the distal end of the valve head 20 comes into close contact with the peripheral edge of the opening of the injection port 16, thereby forming a seal portion.

The valve member 22 is biased by the main spring 24 in the direction of closing the injection port 16 (rightward in FIG. 1), while receiving a spring force in the opposite direction (lFi1 direction) by the weaker cushion spring 26. but,
As a result, the spring is always biased in the opening direction due to the difference in spring force of 1A. The cushion spring 26 serves to soften the impact when the valve head 20 is seated on the injection port 16.

A first solenoid 28 for driving a valve that pushes the valve member 22 in the opening direction against the main spring 24 is provided in the body 10 .

A core 30 of the first solenoid 28 is fixed to the body 10, and a coil 34 is wound around the core 0 via a bobbin 32, and an excitation current is supplied to the coil 34 through terminals 36 and 38.

The valve member 22 passes through the aperture 30 and has an armature 40 fixed to its end. Within the air gap between the armature 40 and the core 30, the valve member 22
The travel stroke of is determined. Note that the fuel passage 18 passes through the armature 40 and connects the core 30 and the valve member 22.
It extends between.

A fuel metering section 42 is provided in the front fuel passage 18 in close proximity to the upstream side of the injection port 16 . The fuel metering portion 42 is a constricted portion that provides an annular passage cross-sectional area corresponding to the difference in cross-sectional area between the fuel passage 18 and the valve member 22 over a predetermined short length in the flow direction. It is configured to straddle the side and the body 10 side.

As shown in an enlarged view in FIG. 3(a), the valve member 22 is provided with a valve side metering portion 44 immediately before the valve head 20, and further provided with a small diameter portion 46 adjacent to the upstream side. . In other words, the valve side metering section 44 is located between the small diameter section 46 and the valve head 20, and the valve member 22 is located between the small diameter section 46 and the valve head 20.
It is formed with a cylindrical outer peripheral surface that is concentric with the center line of and larger than the small diameter portion 46.

As shown in FIG. 1, the valve member 22 is fitted into a guide hole 48 formed in the body component 8 so as to be movable in the axial direction. The guide portions 50 and 5 are provided with two guide portions 50 and 52 that are spaced apart and have a larger diameter than other portions.
2, the valve member 22 is guided within the body guide hole 48. The aforementioned fuel passage 18 passes between the valve member 22 and the body guide hole 48, and the outer circumferential surface of the guide portions 50 and 52 of the valve member 22 is centered around the cylindrical outer circumferential surface as shown in FIG. It has a cross-sectional shape cut off at four planes A1 to A4 along the direction, and the above-mentioned fuel passage 18 is secured by four gaps associated therewith.

Returning to FIG. 3(a), the fuel passage 1 in the body 10
8, a body-side first metering section (hereinafter also simply referred to as the first metering section) 54, which is made up of a cylindrical inner peripheral surface, is located, and further on the injection port 16 side, a first metering section 54 is located on the injection port 16 side. A body side second measuring part (hereinafter also referred to as a second measuring part on a skewer) 5 having a diameter larger than that of the part 54 and consisting of a concentric cylindrical inner circumferential surface.
6 is formed. The inner diameter of the second measuring portion 54 is equal to the inner diameter of the body guide hole 48, and is constituted by an extension thereof.

The valve stroke of the valve member 22 can be switched between two stages by a plate-shaped movable stopper (hereinafter simply referred to as a stopper) 58 shown in FIG.

This stopper 58 is provided at right angles to the valve member 22,
The valve member 22 loosely passes through the center of the stopper 58, but a large diameter portion 5 for abutting the stopper is provided at a portion of the valve member 22 on the opposite side of the injection 016 with respect to the stopper 58.
9 is formed, and when this large diameter portion 59 hits the stopper 58, the movement limit (stroke in the opening direction) of the valve member 22 is determined. The stopper 58 is connected to the body component 6
is supported movably in the axial direction of the valve member 22 by the inner circumferential surface of the injection port 16.
It is urged toward the side and is always maintained at a position where it is in contact with a stopper facing surface 57 constituted by the inner end surface of the body component 8.

A second solenoid 62 is built into the body 10 as a means for moving the stopper 58.

The arrow 4 of the second solenoid 62 has a cylindrical shape with flanges and is fixed in the body 10, and the coil 68 wound around the coil 68 via the bobbin 66 has two terminals 70 (
(only one is shown in the figure) supplies the excitation current. The valve member 22 loosely passes through the core 64, with the fuel passage 18 passing between the two, and the large diameter portion 59 enters into the core 64 in the valve closed state.

Further outside the coil 68, an annular member 74 (constituting a part of these bodies 10) is provided, and the body constituent member 6
is fixed to the inner circumferential surface of the The end surface of this annular member 74 on the stopper 58 side constitutes a stopper facing surface 76 that is perpendicular to the valve portion 51122.

When the second solenoid 62 is energized, the stopper 58 is maintained at a position where it contacts the stopper facing surface 76 against the biasing force of the spring 60. This position is the first position of the stopper 58, and the second solenoid 62
is demagnetized and the stopper 58 is pressed against the stopper facing surface 57 by the spring 60.
This is the second position of 8.

Next, the operation will be explained.

As shown in FIG. 2(a), when the second solenoid 62 is energized and the stopper 58 is in the first position in contact with the stopper facing surface 76, the first solenoid 28 of FIG.
is excited for a time corresponding to the pulse width based on duty control, the valve member 22 is moved in the opening direction,
During that stroke, the large diameter portion 59 moves to the stopper 58 in FIG. 2(a).
It hits and prevents further movement. When this stroke is viewed from the side of the fuel metering section 42, the valve member 22 moves from the valve closed position shown in FIG. 3(a) to the limit of movement in the opening direction shown in FIG. 3(b). With this valve stroke,
The valve-side metering section 44 of the valve member 22 constitutes a small-flow fuel metering section 42 with the body-side first metering section 54, and the annular passage cross-sectional area at this time is Sl. Assume that the static flow rate characteristic corresponds to characteristic 1 in FIG.

In this state, as shown in FIG. 2(b), when the second solenoid 62 is demagnetized and the stopper 58 is moved to the second position on the stopper facing surface 57 side by the spring 60, the valve member 22 is The movement stroke in the opening direction becomes longer by the distance that the stopper 58 has moved. and,
When the large part 59 of the valve member 22 moves until it comes into contact with the stopper 58 in the second position, the valve side measuring part 44 moves to the second body side measuring part 5, as shown in FIG. 3(C).
6 constitutes a large-flow fuel metering section 42, and the annular passage cross-sectional area at this time becomes S2, which is larger than the previous 81.

Now, if the static flow rate characteristic in this state corresponds to the characteristic (2) in FIG. By switching to the second position that gives , the flow rate characteristic changes from characteristic 1 to characteristic (2). If the stopper position is switched (movement) at point b of characteristic 1 and the injection time is adjusted at the same time, the flow rate characteristic will shift from point b of characteristic ■ to point 0 of characteristic ■ at that point, and from then on, Follow its characteristics ■. Therefore, before and after switching the stopper position, the overall flow rate characteristic changes from a → b of characteristic ■ to characteristic ■
c-+d, and the practical injectable flow rate range is expanded from qlmin to q2max. Therefore, when supplying fuel to the engine of a vehicle, the amount of injection during idling can be kept to the minimum necessary, and the number of injection ports can be set to a sufficiently large amount when accelerating.

Although one embodiment of the present invention has been described above, this is literally an illustration, and it goes without saying that the present invention can be implemented in various modifications based on the knowledge of the person concerned.

<Effects of the Invention> According to the present invention, by increasing/decreasing the passage cross-sectional area of the fuel metering section based on switching of the stopper position, it is possible to achieve both small flow characteristics and large flow characteristics even though it is a single fuel injection device. Composite characteristics that combine the characteristics of Can be set. Therefore, in the case of a vehicle engine, a small flow rate characteristic is selected in the idle state to minimize fuel consumption during the idle state, and the acceleration I
), etc., the large flow rate characteristic can be selected to ensure a sufficient amount of wA injection and obtain higher il force.

Although one embodiment of the present invention has been described above, this is literally an illustration, and it goes without saying that the present invention can be implemented in various modifications based on the knowledge of the person concerned.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a fuel injection device that is an embodiment of the present invention, and FIG. (b) shows the first position of the stopper, and (b) shows the second position. FIG. 3 is a cross-sectional view of the fuel metering section, with (a) showing the valve in the closed state and (b) showing the valve in the closed state.
(C) shows a small flow stroke of the valve member, and (C) shows a large flow stroke. Figure 4 shows ■rV in Figure 3(a).
The IFi plane view in FIG. 5 is a graph used to explain the prior art and the operation of the present invention. 2...Fuel injection device 10...Body 16...Injection port 18...Fuel passage 20...Valve head 22...Valve member 28...First solenoid 42...Fuel metering section 44...Valve side measuring part 54...Body side first measuring part 56...Body side second metering part 57.76...Stopper facing surface 59...Large diameter part 62...No. Two solenoids (valve driving means) (stopper moving means)

Claims (1)

[Scope of Claims] A body, a fuel passage passing through the body, an injection port formed at the tip of the fuel passage, a shaft-shaped valve member that opens and closes the injection port, and a valve member that opens and closes in the axial direction. a valve driving means, which is provided in the fuel passage close to the upstream side of the injection port, and provides a constant passage cross-sectional area corresponding to the difference between the cross-sectional area of the fuel passage and the cross-sectional area of the valve member, and A fuel injection device including: a fuel metering section that defines an injection amount; a valve-side metering section formed on the valve member to constitute the fuel metering section; a body-side first measuring section that provides a first passage cross-sectional area with the valve-side measuring section; a body-side second measuring section that provides a larger second passage cross-sectional area; and movement of the valve member in the opening direction. a valve stroke switching means for switching the stroke between a small flow rate stroke in which the valve side metering section corresponds to the body side first metering section and a large flow rate stroke that reaches the body side second metering section; The stroke switching means includes: a movable stopper movable along the axial direction of the valve member that defines a moving end of the valve member in the opening direction; and a first movable stopper that provides the small flow rate stroke to the valve member. a stopper moving means for moving the stopper between the two positions and a second position that provides the large flow rate stroke.