JPH03225063A - Variable static flow type fuel injection device - Google Patents

Abstract

PURPOSE:To enlarge injectable flow by providing a fuel pressure switching solenoid valve, positioned on the upstream side of a fuel measuring part in the fuel flowing direction, for repeating the switching of a fuel passage on the basis of high frequency duty control so as to generate plural mutually different kinds of fuel pressure alternatively on its downstream side. CONSTITUTION:A fuel pressure switching solenoid valve 64 switches fuel pressure on its downstream side into plural set values P1, P2 to generate plural flow characteristics. That is, when high frequency duty control is performed to the valve body 40 of this solenoid valve 64, the inner fuel pressure of an injector body 2 is kept to the low fuel pressure P1, and in this state, when a valve member 22 is operated to open by a first solenoid 28, the fuel quantity injected from a nozzle 16 becomes relatively small, thus obtaining the small flow characteristic. On the other hand, the large flow characteristic is obtained by performing fuel injection under such a state that a duty ratio in the driving of the valve body 40 is made large to maintain the internal fuel pressure to the high fuel pressure P2.

Description

[Detailed Description of the Invention] <Industrial Application Field> 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. Regarding.

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

In such injectors, it is necessary to set the amount of fuel injected per injection as accurately as possible.
For this purpose, a fuel metering section is provided as a throttle section in the fuel flow direction. This fuel metering section may also serve as the injection port, or may be provided separately from the injection port. In any case, if the fuel pressure (fuel pressure) is constant, the amount of injection per injection is determined based on the product of the passage cross-sectional area of the fuel metering section and the injection time (valve opening time).

Then, in response to the intake stroke of the engine, the valve member is opened for a certain period of time to perform injection, and the injection period 'f is generally duty-controlled by a pulse signal. Here, when the engine output is low, the amount of intake air is small, so
The injection time (pulse width) per injection is short, and when the engine output is high, the amount of intake air is large, so the pulse width becomes 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 as a result, the flow rate characteristics of the injector are also uniquely determined. It is decided.

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, for small flow characteristic machining, the minimum flow rate q
Area MQS from 1n+in to maximum flow rate q 1 max
In addition, in the case of the large flow rate characteristic (2), the flow capacity is determined by the region Q [from the minimum flow rate ff11m1n to the maximum flow rate q2iax, but each has its advantages and disadvantages.

In other words, with a small flow rate characteristic, it is possible to keep fuel consumption low at the lowest engine output state (such as when the vehicle engine is idling), but when high output is required (such as when the vehicle is accelerating), the fuel consumption 1 can be kept low. 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 ■, high output can be obtained sufficiently, but
In the lowest output state, it is difficult to suppress the injection flow ω to the necessary minimum, resulting in consumption of more fuel than necessary.

This is generally expressed as the dynamic range Rd (Rd - QllaX /
This is due to the fact that qlin ) is small, but modern vehicle engines are required to have both low fuel consumption and high output at the same time, and the air area required for engine operation has become extremely wide. Therefore, injectors are also required to have a wide measurement range.

An object of the present invention is to provide one injector with a plurality of flow characteristics to obtain a larger dynamic range.

<Means for solving the problem> First, the principle of solving this problem will be explained. In general, the injection gAim is determined by the product of the passage cross-sectional area of the fuel metering section and the injection time, and the characteristics of the injector are also uniquely determined by the passage cross-sectional area. If the fuel pressure changes, the injection flow rate also changes. Therefore, if the fuel pressure in the injector can be switched to two levels, high and low, for example, the characteristics of a small flow rate in a low fuel pressure state will be
Furthermore, in a high fuel pressure state, a large flow rate of fuel pressure can be obtained.

That is, the fuel injection device (injector) according to the present invention
is assumed to include the body, fuel passage, injection port, valve member, valve driving means, and fuel metering section as described above, and the following fuel switching solenoid valve, that is, from the fuel metering section in the direction of fuel flow. Located at the upstream side,
It includes a fuel pressure switching electromagnetic valve that repeatedly opens and closes the fuel passage based on high frequency duty control so as to selectively generate a plurality of mutually different fuel pressures downstream from that position.

<Function> In the fuel injection device according to the present invention, the fuel pressure on the downstream side (fuel metering section side) is switched to a plurality of set values by the fuel pressure switching electromagnetic valve, and a plurality of flow characteristics are correspondingly changed. occurs. For example, if a first fuel pressure value and a higher second fuel pressure value are set, a small flow rate characteristic occurs at the first fuel pressure value, and a large flow rate characteristic occurs at the second combustion pressure value.

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

The fuel injection device (injector) 1 shown in FIG. The fuel pressure setting section 4 is responsible for setting (switching) the fuel pressure. The injector main body 2 is a body component member 6a
, 6b, 6C, and 6d, and the fuel pressure setting section 4 includes a body 8 consisting of body component members 8a and 8b, and both bodies 6.8 are integrated into one device as a whole. It makes up 10 small days. A fuel passage 18 is formed in the device body 10 from a fuel port 12 at the base end to an injection port 16 at the tip via a filter 14. The injection port 16 is a small hole tapered toward the tip, and in this embodiment, the injection port 16 also functions as a constriction portion and the fuel gauge 11 that regulates the injection flow rate.

Inside the injector body 2, this injection port 16 is
? A hollow shaft-shaped valve member 22 having a spherical valve head 20 is provided so as to be movable in the axial direction. The valve member 22 is biased in the opening direction (to the left in FIG. 1) by a spring 24, and the fuel passage 18 extends through the interior of the valve member 22 to the injection port 16.

An armature 26 is fixed to the rear end of the valve member 22, and a first solenoid 28 functioning as a valve driving means is provided opposite to the armature 26.

A coil 34 is wound around the core 30 of the first solenoid 28 via a bobbin 32, and an excitation voltage is applied to this coil 34 through two terminals 36 (only one is shown in the figure). The armature 26 and the core 30 have a hollow structure, and the hollow portion serves as the fuel passage 18.
Further, the movement stroke of the valve member 22 is defined by the air gap between the armature 26 and the core 30.

On the other hand, in the fuel pressure setting section 4, a valve body (armature) 40 made of a magnetic material is provided in the middle of the fuel passage 18 so as to be movable in the fuel flow direction. The valve body 40 has a short shaft-shaped guide part 42 and a flange-shaped plate part 44 formed at one end thereof, and is movable in the axial direction into the fuel passage 18 of the body component 8a at the guide part 42. It is fitted. As shown in FIG. 2, the fitting portion has a circular cross section, but the outer peripheral surface of the valve body guide portion 42 is cut on four sides to form the fuel passage 18.
Spaces are ensured.

FIG. 4 is an enlarged view of the fuel pressure setting section 4, and the body component 8a has a valve seat (hereinafter simply referred to as the seat surface) 46 parallel to the plate section 44 of the valve body 40.
A plurality of communication holes 48 are formed in the plate portion 44 at a portion thereof facing the sheet surface 46, penetrating the plate portion 44 in the thickness direction. The valve body 40 is biased by a spring 50 to a closed position where the plate portion 44 is in close contact with the seat surface 46;
0 and is pulled away from the sheet surface 46.

The second solenoid 52 includes a flanged cylindrical core 54 and an I coil 5 wound around the core via a bobbin 56.
8, a case 60 that covers the coil 58 from the outside, and a 2@ terminal 62 (only one is shown in the figure), and an excitation voltage is applied through these terminals 62. In this embodiment, the above-mentioned valve body 40. spring 50
and the second solenoid 52 etc. as a whole constitute one solenoid valve 6
4.

The center hole 66 of the core 54 becomes a part of the fuel passage 18, and the downstream opening end surface of the core 54 serves as a stopper surface 68. (open position). Stopper surface 68
Four communication grooves 70 (see FIG. 3) are formed in the radial direction, which allows fuel to flow downstream from the core center hole 66 even when the valve body 40 is in close contact with the stopper surface 68. be done.

In addition to the electromagnetic valve 64, the fuel pressure setting section 4 includes a fuel pressure sensor 7.
2 is provided so that fuel pressure in a portion of the fuel passage 18 adjacent to the downstream side of the valve body 40 is detected. This sensor 72 is fitted into the body component 8a in a state where it is liquid-tightly sealed by an O-ring 74, and its tip is exposed in the fuel passage 18 immediately downstream of the valve body 42.

Next, the operation will be explained.

As shown in FIG. 4(a), when no voltage is applied to the second solenoid 52, the valve body 40 is kept in the closed position pressed against the seams 1 to 46 by the spring 50. In this state, the fuel passage 18 is closed by the plate portion 44 of the valve body, and the flow of fuel toward the injection port 16 is blocked.

On the other hand, when voltage is applied to the second solenoid 52, the fourth
As shown in Figure (b), the valve body 40 is drawn toward the core 54 and held in the open position in close contact with the stopper surface 68. In this state, the fuel passage 18 is opened, so that fuel can flow downstream through the center hole 66 of the core 54, the communication 'f470, and the communication hole 48 of the valve plate portion 44.

Here, the valve body 40 is in the closed position in FIG. 4(a) and in the same figure (
b) The opening and closing operations are repeated in a short period of time between the open position and the open position. This opening/closing operation is duty-controlled using high-frequency pulse waves, and the duty ratio (opening time/one period) is set so that the fuel pressure downstream of the valve body 40 becomes a predetermined fuel pressure. As this fuel pressure, for example, a relatively low first fuel pressure P1 and a higher second fuel pressure P2 are determined in advance.

That is, by shortening the open time of the valve body 40 (reducing the duty ratio), a low fuel pressure is generated, and by increasing the open time of the valve body 40 (increasing the duty ratio), a high fuel pressure is generated. The actual fuel pressure is detected by the fuel pressure sensor 72 and immediately fed back to the duty ratio, thereby maintaining the low fuel pressure P1 or the high fuel pressure P2. Valve body 4
The frequency of the pulse wave that drives the injector body 2 is
The fuel pressure setting accuracy is better if the pulse frequency is sufficiently higher than the pulse frequency that drives the valve member 22. In addition, the maximum value of fuel pressure is
For example, it is determined by the pressure of fuel supplied from a delivery vibe (not shown). Furthermore, if the valve body 40 is kept closed, the lowest value of the fuel pressure can be determined by the injector body 2.
The internal fuel pressure immediately becomes equal to the external pressure outside the injection port 16 when fuel is injected from the injection port 16, so it is said to be the same pressure as the external pressure.

Now, the internal fuel pressure of the injector body 2 is maintained at a low fuel pressure P1 by the high frequency duty control of the hull 1 body 40, and when the valve member 22 is opened by the first solenoid 28 in this state, fuel is injected from the injection port 16. The amount of fuel used is relatively small, and, for example, the small flow rate characteristic I shown in FIG. 5 can be obtained. On the other hand, the duty in driving the valve body 40 is
If the fuel injection ratio is increased and fuel injection is performed with the internal fuel pressure maintained at the high fuel pressure P2, then, for example, the characteristic (1) of the flow rate for one person shown in FIG. 5 is obtained.

That is, by switching the fuel pressure from Pl to P2, the flow rate characteristic changes from I to ■. If the switching is performed at point b of characteristic [ and the injection time is adjusted at the same time, the flow rate characteristic will shift from point b of characteristic (2) to point 0 of characteristic (2) at that point, and thereafter will follow that characteristic (2). In this case, the overall flow rate characteristics are a-+b of characteristic ■ before and after the fuel pressure switching.
The injectable flow rate range of Practical-F is expanded from qlmin to q2max. Therefore, when supplying fuel to the engine of a vehicle, the injection amount during idling can be kept to the necessary minimum, and the injection amount during acceleration can be made sufficiently large.

Note that the set fuel pressure can be selected from two types, Pi and P2, for example, P
If there are three types i, P2, and P3, (Pl P2 <
P3), a plurality of flow characteristics corresponding to the number are obtained. Figure 6 shows an example of this, and the overall characteristic is 1.
．． I [, DI can be obtained. For example, if the fuel is changed stepwise from P1 → P2 → P3, the characteristic will be a−+b−+c−+d−+e−+f, which is a very large dynamic characteristic. Range (Rd = qla
x/amin) is obtained.

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

<Effects of the Invention> According to the present invention, based on switching the fuel pressure upstream of the injection port into multiple stages, although it is a single fuel injection 9A device,
Composite characteristics with multiple characteristics can be obtained, and the practically injectable flow ω from the minimum flow rate to the maximum flow rate is faster than before.
The minimum flow rate can be set smaller and the maximum flow rate larger. Therefore, in the case of a vehicle engine, a small flow characteristic is selected in the idling state to minimize fuel consumption during idling, and a large flow characteristic is selected in conditions that require high output such as during acceleration to ensure sufficient fuel consumption. It is possible to secure the injection flow rate, obtain higher output, and meet the two demands of low fuel consumption and high output at the same time.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a fuel injection device that is an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along I-II in Fig. 1, Fig. 3 is a cross-sectional view taken along the same line <m-m, and Fig. 4 is a fuel pressure FIG. 3 is a cross-sectional view of the setting section, with (a) showing the valve in a closed state and (b) showing the valve in an open state. FIG. 5 is a graph used to explain the prior art and the operation of the present invention (two-stage fuel pressure switching), and FIG. 6 is a graph used to explain the operation of three-stage fuel pressure switching. 2... Injector body 4... Fuel pressure setting section 16... Injection port 18... Fuel passage 20... Valve head 28... First solenoid 40... Valve body 42... Guide section 44...Plate portion 46...Valve seat surface 48...Communication hole 50...Spring 52...Second solenoid 64...Solenoid valve 68...Stopper surface 70...Communication groove 72 ...Fuel pressure sensor 2nd figure ) April 3, 1990 1, Indication of the incident 1990 Special I: + Application No. 022583 2, Name of the invention Static flow rate variable fuel control! 8 device 4, Address: 460 Sakae, Naka-ku, Nagoya 2T110 No. 19 Nagoya Chamber of Commerce and Industry Building Telephone 052 (221>-6141 6434 Patent Attorney Oka 1) Hidehiko, ---15, Subject of amendment (1) Meiji H1, page 8, line 11 ~ The statement in the 13th line, ``This is the fuel passage I8, and the movement stroke is defined.'' is corrected as follows. This is a fuel passage 18. Further, the movement stroke of the valve member 22 is the same as that of the body component 6b. It is defined by a gap between a stopper 6e fixed between 6O and a stopper opposing portion 22a formed on the valve member 22. (2) "Second solenoid 50" on page 9, line 13 of the specification
．． The description has been corrected to "second solenoid 52." (3) 1 valve body 42 on page 10, lines 19 to 20 of the specification. The description has been corrected to read "valve body 40." (4) Figure 1 in the drawings shall be corrected as shown in the attached corrected drawing Figure 1.

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 valve member that opens and closes the injection port, and a valve driving means that opens and closes the valve member. A fuel injection device including a fuel metering section that serves as a throttle section in the fuel flow direction to regulate the injection flow rate per injection, the fuel injection device being provided at a position upstream of the fuel metering section in the fuel flow direction; A variable static flow rate characterized by including a fuel pressure switching electromagnetic valve that repeatedly opens and closes a fuel passage based on high frequency duty control so as to selectively generate a plurality of different fuel pressures downstream from the position. fuel injection device.