JPS6029690Y2 - Area flow metering device - Google Patents

Description

[Detailed description of the device] This device maintains the pressure difference before and after the variable area metering port through which fluid flows at a constant value, so that the opening area or degree of opening of the metering port is adjusted so that the fluid flows through the metering port. This invention relates to a constant pressure differential and variable area type flow metering device that is proportional to the flow rate of fluid.

This idea is based on the idea that the linear proportional relationship between the fluid flow rate and the opening area of the metering port in this type of flow metering device is affected by sudden changes in the course of the fluid or extreme changes in the cross-sectional area of the flow path, especially when the flow rate is large. In view of the fact that such linear proportionality or linearity may be adversely affected, the object of the present invention is to provide an area type flowmeter having a structure that can guarantee such linear proportionality or linearity.

Hereinafter, the invention will be described in detail with respect to the embodiments shown in the drawings.

Note that the following explanation takes as an example the case where the present invention is applied to a fuel metering device used in a fuel injection device for an internal combustion engine, but the present invention is not limited to this, and can be applied to a flow metering device of this type. Needless to say, it can be applied widely.

In FIG. 1, the fuel flow metering device consists of a metering section 10 and a constant differential pressure valve 30.

The measuring unit 10 includes a case 11 having a fuel inlet 12 and an outlet 13, a cylinder body or sleeve 14 slidably housed inside the case, and the sleeve 14 screwed into the case 11 via an indirect member 17. A compression spring 16 that presses against the adjustment screw 19, and another cylindrical body or plunger 20 that is fitted into the axial hole 15 of the sleeve 14 so as to be slidable in the axial direction.
and a control rod 24 for relating axial movement of the plunger to an air flow metering device (not shown).

The plunger 20 has a cylindrical shape and is provided with a slit or metering port 21 extending in the axial direction in the peripheral wall and one or more window holes 22, and the internal space serves as a fuel passage 23.

The indirect member 17 includes a window hole 18 through which fuel passes.

A large diameter portion 25 is formed at the end of the control rod 24, and this large diameter portion 25 fits into a recess 26 of the case 11.
The space defined by the shoulder of the large diameter portion 25 receives fuel and provides a buffering effect against sudden movement of the control rod 24 and undesirable vibrations.

The plunger 20 is energized by fuel pressure and the control rod 24
It abuts on the end surface of the large diameter portion 25 of.

The fuel from the pump 40 is maintained at a predetermined pressure by the pressure regulator 50 and fed to the fuel inlet 12 of the metering section 10, passes through the window hole 18 of the indirect member 17, and enters the fuel passage 23 inside the plunger 20 through the slit 21. The fuel flows through the window hole 22 of the plunger 20 and proceeds from the fuel outlet 13 of the case 11 to the constant differential pressure valve 30, which will be described later.

As can be seen from the figure, the opening area of the slit 21 changes depending on the axial position of the plunger 20.

The axial position of the plunger 20 is under the control of a control rod 24 that is axially displaced in response to the air flow rate in the intake pipe.

Therefore, the opening area of the slit 21 is linearly proportional to the displacement of the control rod 24 and therefore to the amount of intake air.

FIG. 2 is an enlarged view of the main parts of the metering section 10 according to the present invention. As shown in the figure, according to the present invention, fuel passes through the metering port or slit 21 and flows into the fuel passage 23 inside the plunger 20. The cross-sectional area of the fuel passage 23 is changed in the axial direction so that the cross-sectional area of the fuel passage 23 increases in the direction in which the opening area of the metering port 21 increases so that the fuel can flow smoothly.

As shown in the figure as an example, this is achieved by inserting a diagonally cut member, ie, a rectifier 27, into the hollow column of the plunger 20, which has a uniform axial cross section. However, it can also be realized by other methods, such as forming it integrally with the plunger 20.

When the flow straightener 27 is not provided, the fuel flows through the metering port 21 in a direction approximately perpendicular to the axis of the plunger 20, and furthermore, after passing the metering port 21, the flow rate decreases rapidly, and the flow direction changes from that of the plunger 20. The flow velocity increases again in the axial direction.

Such a change in flow velocity causes turbulence in the fuel flow, and this turbulence increases as the opening area of the metering port 21 increases, causing an adverse effect on the above-mentioned linearity.

According to the present invention, in the plunger 20, especially the metering port 21
Since there is no sudden change in the fuel path or sudden change in the cross-sectional area of the fuel path in the immediately following fuel passage 23, there is less change in the flow velocity of the fuel and less turbulence in the flow.

Linearity is improved, especially at high flow rates.

FIG. 3 shows the flow rate characteristics when the rectifying material 27 is provided (broken line A) and when it is not provided (broken line B).

As can be seen from the figure, when the flow straightener 27 is not provided, the deviation from the regression line is approximately -5% at the maximum flow rate, whereas by providing the flow straightener 27 according to the present invention, this deviation is approximately -5%.
It can be improved by up to 1.3%.

Returning to FIG. 1 again, the constant differential pressure valve 30 is not limited to the illustrated example, but can be of various types as long as it has the function of keeping the pressure difference before and after the slit or metering port 21 at a constant value. can.

The constant differential pressure valve 30 illustrated in the drawing includes a housing 31, a diaphragm 34 that partitions the inside of the housing into an upper chamber 32 and a lower chamber 33, and a variable orifice 35 whose opening area changes depending on the deflection of the diaphragm. .

The variable orifice 35 is connected to a conical or tapered valve seat 36 and a diaphragm 3 in a self-aligning state with respect to the valve seat.
4 and a valve ball 37 attached to the valve.

The pressure on the upstream side of the metering port 21, that is, the fuel supply pressure P1 maintained constant by the pressure regulator 50 acts on the lower chamber 33.

Fuel from the fuel outlet 13 of the metering section 10 described above is introduced into the upper chamber 32, and thus a fuel pressure P2 acts thereon.

Fuel passes from the upper chamber 32 through variable orifice 35 to a fuel injector (not shown), where diaphragm 3
4 pressure P1. Difference in P2 (Pl-P2)
deviates from the predetermined value defined by the spring 38, the diaphragm 34 is biased accordingly, and the variable orifice 3
The opening area of No. 5 is changed.

As a result, the fuel pressure P2 in the upper chamber 32 changes, and this change continues until the pressure difference (P□-P2) no longer deviates from the upper predetermined value.

In this way, the pressure difference (P□-
P2) is kept constant, ensuring a linear proportionality of the fuel flow rate to the opening area of the metering port 21 and thus also to the intake air amount.

In other words, the air-fuel ratio of the mixed gas supplied to the engine is maintained constant.

As explained above, this device is an area-type flow meter that maintains the pressure difference before and after the variable-area metering port through which fluid flows at a constant value, so that the opening area of the metering port is proportional to the fluid flow rate. In the apparatus, a first fluid passageway having a fluid passage therein;
The cylindrical body is provided with a metering port whose opening area can be changed in the axial direction by relative movement of a second cylindrical body fitted therewith with respect to the first cylindrical body, and a fluid passageway of the first cylindrical body is formed. Since the cross-sectional area of the metering port is increased in the direction in which the opening area of the metering port increases, it is possible to provide an area type flow metering device that can guarantee a linear proportional relationship between the fluid flow rate and the opening area of the metering port.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of an area-type flow metering device, Figure 2 is an enlarged view of the main part of the measuring section shown in Figure 1 according to the present invention, and Figure 3 shows the case with and without a rectifier. It is a graph which shows the flow rate characteristic of the area type flow meter device in . 10... Measuring part, 14... Second cylindrical body or sleeve, 20... First cylindrical body or plunger, 21... Measuring port, 23... Fluid passage, 27... Rectifying material.

Claims (1)

[Scope of utility model registration request] An area-type flow metering device that maintains the pressure difference before and after a variable-area metering port through which fluid flows at a constant value so that the opening area of the metering port is proportional to the fluid flow rate, which has a fluid passage inside. A measuring port whose opening area can be changed by relative movement of a second cylinder fitting thereto with respect to the first cylinder is formed in the first cylinder in the axial direction;
An area type flow rate metering device, characterized in that the cross-sectional area of the fluid passage of the cylindrical body is gradually increased in the direction in which the opening area of the metering port increases.