JPS591965B2 - Area flow metering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a device for metering and controlling the flow rate of fluid.

In general, there are various types of devices for measuring and controlling the flow rate of this type of fluid, and they are widely used.

For example, what is shown in FIG. 1 is an example of an air flow metering device with feedback control, which is used in a fuel supply device for an internal combustion engine. In the same figure, 1
2 is a feedback control mechanism, which includes a valve opening mechanism 3 and a servo mechanism 4 for differential pressure control.

Two upstream valves 5 and downstream valves 6 as air throttle valves are provided in the air suction pipe 1. For example, one upstream valve 5 is connected to the valve opening mechanism 3 as a flow rate detection valve, and the other downstream valve 6 is connected to the valve opening mechanism 3 as a flow rate detection valve. is connected to the accelerator pedal T as a flow control valve. If the air pressure on the upstream side of the upstream valve 5 is P1, and the air pressure in the intermediate chamber 8 partitioned between the upstream valve 5 and the downstream valve 6 is P2, then the pressure difference (P1-P2) should always be constant. As a result, the air flow rate is proportional to the opening area of the upstream valve 5, and the flow rate can be measured from the opening area of the upstream valve 5. This is the so-called area type flow meter system, and the pressure difference (P, -Po) is controlled to be constant by the following feedback control mechanism 2. That is, when the pressure difference (P, -P2) slightly deviates from a certain constant value, the servo mechanism 4 detects and amplifies the deviation.
The valve opening mechanism directly controls the opening and closing of the upstream valve 5 according to the difference in pressure before and after the upstream valve using the output from the servo mechanism 4 to correct the pressure difference (P1-P2) to a constant value. 3
It is. This valve opening mechanism 3 has a diaphragm 9 installed inside the main body via a spring 10, and an upstream valve 5 connected to a movable portion of the diaphragm 9. Next, the servo mechanism 4 has chambers A and B separated by an internal differential pressure setting diaphragm 11, and chamber C separated by a variable orifice 13 whose opening area changes depending on the displacement of a valve 12 that is linked to the diaphragm 11. and room D. The A chamber and the D chamber communicate with each other at the same pressure through the communication hole 14, the B chamber communicates with the intermediate chamber 8 downstream of the upstream valve 5, and the C chamber communicates with three valve opening mechanisms and a throttle valve. It communicates with the intermediate chamber 8 via 15. Further, the A chamber and the D chamber communicate with the upstream side of the upstream valve 5, and the air pressure is P1.
Then, that of chamber B becomes P2, and the pressure difference (P1
-P2) is the diaphragm 11 that separates chamber A and chamber B.
is detected as the displacement of In addition, the above pressure difference (P1-P2
) is set by the differential pressure setting spring IT, 18. That is, the spring pressures of the springs 17 and 18 are set to be balanced with the air pressure P acting on both sides of the diaphragm 11, and the force generated by the pressure difference between P2, and 19 is an adjustment for finely adjusting the spring pressure. It is a screw. The bellows 16 provided in parallel with the springs 17 and 18 is designed to make the opening area of the upstream valve (flow rate detection valve) 5 proportional to the weight flow rate. How big is the difference (P1-P2)? It is used for correction, and is sealed with a gas having the same temperature and pressure as the standard atmosphere, and one end of the valve 12 is kept in contact with the valve 12, and the other end is fixed to a fixed part of the main body. The bellows 16 is not required when the opening area of the upstream valve 5 is made proportional to the volumetric flow rate at atmospheric pressure and atmospheric temperature during operation. Next, the operating principle of the conventional air weight measuring device for an internal combustion engine having the above configuration will be explained.

When the pressure difference (P1-P2) across the upstream valve 5 slightly deviates from a certain predetermined value, the diaphragm 11 is displaced, the valve 12 is moved, and the opening area of the variable orifice 13 between the CD chambers is displaced. The pressure Pn in chamber C changes between P1 and P2. As mentioned above, when the pressure difference (P, -P2) shifts and the pressure Pn in the C chamber changes, the diaphragm 9 of the valve opening mechanism 3 that communicates with it is displaced, and the upstream valve 5 eventually moves in the direction of correcting the shift amount. is activated. In this case, if there is a change in the temperature or pressure of the incoming air, the volume of the gas sealed in the bellows 16 changes, and the force acting on the diaphragm 11 from the bellows 16 via the valve 12 changes. This change is caused by the pressure difference (P
, -P2) decreases, and as a result, the opening area of the upstream valve 5 becomes proportional to the weight flow rate. If a fuel control mechanism is connected so that the fuel flow rate is proportional to this opening area, the weight ratio of intake air to fuel can be kept constant regardless of changes in atmospheric pressure and temperature.
In this way, the device shown in Figure 1 is used to maintain a constant ratio of air and fuel, but if the pressure difference before and after the flow rate detection valve 5 cannot be made sufficiently large, it is necessary to open the valve. The negative pressure source P2 that drives the mechanism 3 is insufficient, making it difficult to obtain reliable operation of the flow rate detection valve 5.

In view of the above points, the present invention provides a conduit that bypasses the flow rate detection valve 5 and allows the pressure generated in the pressure difference multiplier mechanism to act on the valve opening mechanism 3 and the C chamber in the conduit. Even when the pressure difference before and after the flow rate detection valve 5 cannot be made sufficiently large, pressure is obtained so that the valve opening mechanism 3 can operate reliably.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described below with reference to embodiments shown in the drawings. FIG. 2 shows a first embodiment of the present invention. In the figure, 20 is a pressure difference multiplier mechanism located in the middle of a bypass pipe 21 connecting the upstream side of the flow rate detection valve 5 and the intermediate chamber 8. A bench lily tube 22 is provided, and an orifice 23 is provided at the narrowest part 22a.
It is constructed by providing the following.

The orifice 23 communicates with chamber C of the valve opening mechanism 4 via a conduit 24. In addition, the narrowest part 22a of the bench lily tube 22
The pressure detected at is P6, which is lower than the pressure P2 in the intermediate chamber 8, as shown in FIG. In such a configuration, the pressure detected by the diaphragm 11 of the servo mechanism 4 is the pressure difference (P, -P2) before and after the flow rate detection valve 5, and is variable according to the pressure difference (P, -P2). The opening area of the orifice 13 changes. However, the C chamber communicates with the pressure P on the upstream side of the flow rate detection valve 5 and the pressure P6 at the narrowest part 22a of the bench lily pipe 22 via the D chamber, and the variable orifice 1
The pressure Pn of chamber C is (P1-P≦) according to the frontage area of 3.
Varies between. As a result, compared to the pressure between (P, -P±), which is the pressure in chamber C in the conventional case, the pressure difference increases by (P2-P6), and the pressure difference between before and after the flow rate detection valve 5 increases. Even if the pressure difference (P, -P2) is relatively small, the valve opening mechanism 3 can operate reliably. In the embodiment, the downstream side of the bypass pipe 21 is communicated with the intermediate chamber 8, but it may also be communicated with the downstream side of the flow control valve 6. In this case, the pressure in the C chamber is equal to the pressure P on the most upstream side. , and the pressure P, which is lower than the pressure P3 at the most downstream side, increases by (P6-P6) compared to when it communicates with the intermediate chamber 8. By the way, in FIG. 2, the amount of air flowing through the bypass pipe 21 is determined by the cross-sectional area of the narrowest part 22a of the bench lily 22 and the pressure difference (P-P), but (P-P) is small (
For example, 300 mmAq), and since the cross-sectional area of the narrowest part 22a of the bench lily 22 can be designed to be sufficiently small (for example, 1.5φ7ftm), this air flow rate should be smaller than the air flow rate when the engine is idling. I can do it.

Further, the pressure difference (P-P) is constant, and therefore the flow rate flowing through the bypass pipe 21 is also constant, so this flow rate is measured in advance and the measured value of the air flow rate by the flow rate detection valve 5 is corrected. be able to. 4 and 5 show a pressure difference multiplier mechanism 20 according to a second embodiment of the present invention.

In this case, the pressure difference multiplier mechanism 20 includes a tube 25 that has an outer diameter smaller than the inner diameter of the tube 24 passing through the tube 24 forming a part of the bypass conduit 21 so that their respective center lines intersect at right angles. An orifice 26 is provided on the downstream side of the cylindrical surface of the tube 25 exposed in the conduit 24. When fluid flows through tube 24, tube 2
The pressure distribution around 5 is as shown in FIG. 6, and the pressure P6 on the downstream side where the orifice 26 is located is lower than P2.
According to experiments, (P1-P6) is about 1.
It was 5 times hotter. Therefore, by communicating the pipe 25 with the valve opening mechanism 3 and the C chamber of the servo mechanism 4, the same effect as in the first embodiment shown in FIG. 2 can be obtained. FIGS. 7 and 8 show one type of bench lily tube for pressure difference multiplication, in which a notch 27 is bored in the narrowest part 22a of the bench lily tube 22 shown in FIG.

The notch 27 is open to the downstream side of the bench lily tube 22, and the orifice 23 is provided within this notch 27. This not only ensures reliable operation of the valve opening mechanism 3, but also reduces flow resistance when fluid flows from the pipe line 24 to the narrowest part 22a, improving the responsiveness of the servo mechanism 4. . Figures 9 and 10 show a method for inexpensively manufacturing a mechanism that has the same function as the bench lily pipe 22. A part of the pipe 28 is flattened as shown in Figure 10, and an orifice is installed in this part. 23 is provided.

11 and 12 show still another embodiment of the pressure difference multiplication mechanism 20. FIG.

The embodiment shown in FIG. 11 combines the principle of the bench lily tube 22 shown in FIGS. 2, 7, and 8 with the principle of the mechanism shown in FIGS. 4 and 5. On the other hand, FIG. 12 shows a combination of 222 bench lilies and the mechanisms shown in FIGS. 4 and 5. Both are aimed at increasing the multiplication factor of the pressure difference. In summary, the present invention arranges an upstream valve and a downstream valve in a fluid flow path, and maintains the pressure difference before and after the upstream valve (flow rate detection valve) at a constant value by a feedback control mechanism using fluid. In area type flow metering devices that measure the flow rate of fluid from the opening area of the valve, a conduit is provided that bypasses the upstream valve, and a mechanism is provided that uses the fluid flow to multiply the pressure difference. Since the valve opening mechanism is driven using the pressure of performance is improved.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view showing a conventional device, Fig. 2 is a longitudinal cross-sectional view showing a first embodiment of the present invention, Fig. 3 is a view showing the pressure inside the bench lily, and Fig. 4 is a longitudinal cross-sectional view showing a conventional device. is a vertical sectional view of the pressure difference multiplier mechanism showing the second embodiment, and FIG.
A line sectional view, FIG. 6 is a pressure distribution diagram showing the principle of the same embodiment,
FIG. 7 is a vertical sectional view of the same mechanism showing the third embodiment, and
The figure is a sectional view taken along the Y-Y line, FIG. 9 is a longitudinal sectional view of the same mechanism showing the fourth embodiment, and FIG. 10 is a sectional view taken along the Z-Z line.
FIG. 11 is a longitudinal cross-sectional view of the same mechanism showing the fifth embodiment;
FIG. 2 is a longitudinal sectional view of the same mechanism showing a sixth embodiment. DESCRIPTION OF SYMBOLS 1... Air suction pipe, 2... Feedback control mechanism, 3... Valve opening mechanism, 4...
...Servo mechanism for differential pressure control, 5...
...Upstream valve (flow rate detection valve), 6...Downstream valve (flow rate adjustment valve), 20...Pressure difference multiplication mechanism, 21.
... Bypass pipe, 22 ... Bench lily pipe, 22a ... Narrowest part, 23, 26 ...
... Orifice, 27 ... Cutting part.

Claims (1)

[Claims] 1. An upstream valve and a downstream valve are arranged in the fluid flow path, and the pressure difference before and after the upstream valve (flow rate detection valve) is kept at a constant value by a feedback control mechanism using fluid, and the fluid is determined from the opening area of the upstream valve. In the area type flow metering device for measuring the flow rate of , a pipe line is provided that bypasses the upstream valve, and a mechanism is provided in the pipe line that uses the flow of fluid to multiply the pressure difference,
An area type flow metering device characterized in that the pressure generated within this mechanism is used to drive a valve opening mechanism.