JPS591964B2 - Area flow metering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for metering and controlling fluid flow.

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, the one shown in FIG. 1 is an example of an air flow metering device with a feedback control mechanism, which is used in a fuel supply device for an internal combustion engine. In the same figure,
1 is an air intake pipe of the engine, and 2 is a feedback control mechanism, which has 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 this upstream valve 5 is P1, and the air pressure in the intermediate chamber 8 partitioned into the upstream valve 5 and downstream valve 6 is P2, then
By keeping the pressure difference (P1-P2) constant, the air flow rate is proportional to the opening area of the upstream valve 5, making it possible to measure the flow rate from the opening area of the valve. This is the so-called area type flow meter system, and the pressure difference (P1-P2) is controlled to be constant by the following feedback control mechanism 2. That is, when the pressure difference (P1-P2) slightly deviates from a certain constant value, the servo mechanism 4 detects and amplifies the deviation.
Valve opening is when the output from the servo mechanism 4 directly controls the opening and closing of the upstream valve 5 in response to the difference in pressure before and after the upstream valve 5, correcting the pressure difference (P1-P2) to a constant value. This is mechanism 3. This valve opening mechanism 3 has a diaphragm 9 disposed 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 an A chamber and a B chamber separated by an internal differential pressure setting diaphragm 11, and a valve 12 that is linked to the diaphragm 11.
It has a C chamber and a D chamber separated by a variable orifice 13 whose opening area changes depending on the displacement of the chamber. 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. Furthermore, the A chamber and the D chamber communicate with the upstream side of the upstream valve 5, and the air pressure is P.
1, and that of chamber B becomes P2, and the pressure difference (P
1-P2) is due to the diaphragm 1 that separates chambers A and B.
It is detected as a displacement of 1. In addition, the above pressure difference (P7-P
2) is set by differential pressure setting springs 17 and 18. That is, the spring pressure of the springs 17 and 18 is equal to the air pressure P1 and P2 acting on both sides of the diaphragm 11.
It is set to balance the force caused by the pressure difference between 19
is an adjustment screw for finely adjusting the spring pressure. 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. This is to correct the magnitude of (P, -P2), and it is sealed with a gas that has the same temperature and pressure as the atmosphere in the standard state, and one end of it is in contact with the valve 12 side without leaving it, and the other end is of the main body. Fixed to a fixed part.

The bellows 16 is not required when the opening area of the upstream valve 5 is made proportional to the air flow rate at atmospheric pressure and 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) before and after the upstream valve 5 slightly deviates from a certain predetermined value, the diaphragm 11 is displaced and the valve 12 moves, and the opening area of the variable orifice 13 between the CD chambers changes. The pressure PO in chamber C changes between P and P2. As mentioned above, when the pressure difference (P1-P2) shifts and the pressure PO in chamber C 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 amount of shift. Operate. 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
1-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. As mentioned above, the device shown in Fig. 1 is used to maintain a constant ratio of air and fuel, but the pressure difference (P
1-P2), the negative pressure source P that drives the valve opening mechanism 3 is insufficient, making it difficult to obtain normal operation of the flow rate detection valve 5.

The present invention provides this type of metering device equipped with a differential pressure generating valve 20 that acts to compensate for the pressure to reliably operate the valve opening mechanism 3 even when the pressure difference (P1-P2) as described above is not sufficient. It provides:

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described below with reference to embodiments shown in the drawings. In FIG. 2, the differential pressure generating valve 20 is provided in the intermediate chamber 8 between the flow rate detection valve 5 and the flow rate adjustment valve 6, and its shaft 21
is located offset from the center of the valve 20.

If the pressures before and after this differential pressure generating valve 20 are respectively P2 and P4, then the pressure difference (P2-P4) causes the differential pressure generating valve 20 to
0, a rotational moment M is generated. This rotational moment M is set so that the force of the spring 22 and the moment generated by the arm 23 are balanced, and by adjusting the spring constant and preload force of the spring 22, the differential pressure before and after the differential pressure generating valve 20 can be adjusted appropriately. It is possible to select a value. Incidentally, the C chamber of the servo mechanism 4 communicates between the differential pressure generating valve 20 and the flow rate regulating valve 6 via an orifice 15, which is different from the conventional servo mechanism 4 shown in FIG. . By configuring the device of the present invention as described above, the pressure PO in the C chamber acting on the valve opening mechanism 3 is displaced in terms of the pressure difference (P, -P, etc.) to control the flow rate detection valve 5. become. That is, the pressure acting on the diaphragm 11 of the servo mechanism 4 is
Since the chamber is at the pressure P on the upstream side of the flow rate detection valve 5, and the pressure in chamber B is at the pressure P2 on the downstream side of the flow rate detection valve 5, the diaphragm 1
1 is displaced due to the pressure change between P and P2, and the valve 12
Determine the opening area of the variable orifice 13 between the CD chambers. Therefore, the pressure PO in chamber C is the pressure P1 in chamber D.
and P4, which communicates through the orifice 15. Here, to explain the pressure relationship inside the air suction pipe 1, it is P1>P2>P>P3, and the operating pressure PO of the conventional valve opening mechanism 3 shown in FIG. 1, that is, (P, -P2) In the case of the present invention, (P1-P6) and (P2-P
4) becomes larger. Therefore, even if the pressure difference (P, -P2) across the flow rate detection valve 5 is small, the valve opening mechanism 3 can sufficiently operate, and the flow rate detection valve 5 can operate normally. By the way, although the above description has been made of the case where the pressure difference (P2-P6) generated before and after the differential pressure generating valve 20 is set by the spring 22, this is not limited to a simple thing like the spring 22. , it is also possible to apply other means.

For example, the fixed end of the spring 22 can be connected to a controller to change the pressure difference of the differential pressure generating valve 20 depending on the surrounding conditions, or the pressure difference before and after the differential pressure generating valve 20 can be changed. It may be controlled to a predetermined value by a valve opening device equipped with a servo mechanism. FIG. 3 shows a second embodiment of the present invention, in which a differential pressure generating valve 20 is provided upstream of the flow rate detection valve 5, and a bypass circuit connects the upstream side of the differential pressure generating valve 20 and the intermediate chamber 8. 24, and a bench lily 25 is installed in the middle of this bypass circuit 24 to connect the servo mechanism 4.
The orifice 15 that communicates with the C chamber is connected to the bench lily 12.
It is connected to the narrowest part 26 of No. 5.

The A-D chambers of the servo mechanism 4 are communicated between the differential pressure generation valve 20 and the flow rate detection valve 5, and the pressure thereof is equal to the pressure P1 on the most upstream side.
PS is lower than . On the other hand, the B chamber communicates with the intermediate chamber 8 and becomes P2, and the diaphragm 11 has a pressure difference (P{-P2
) to determine the opening area of the orifice 13. By the way, the air flow rate is high in the narrowest part 26 of the bench lily 25, and the pressure detected at the orifice 15 is a negative pressure greater than P2, that is, a so-called low pressure P6. Therefore, the pressure Pn in chamber C of the servo mechanism 4 is the pressure Pn between the differential pressure generating valve 20 and the flow rate detection valve 5 (and the pressure Pn between the orifice 15
changes between the pressure P6 and the pressure difference (P{-P6),
Controls the flow rate detection valve 5. The pressure difference (P{-P6), which is the operating pressure of the valve opening mechanism 3, is only the pressure drop (P2-P≦) compared to the pressure difference (P{-P2) before and after the flow rate detection valve 5 of the conventional device. becomes large, and the pressure difference (P{
Even when -P2) is small, it is possible to maintain the valve opening mechanism 3 in a good operating condition. In FIG. 3, the amount of air flowing through the bypass circuit 24 is determined by the cross-sectional area of the narrowest part 26 of the bench lily 25 and the pressure difference (P-P).
(P-P) is small (for example, 300m71LAq), and the cross-sectional area of the narrowest part 26 of the bench lily 25 can also be designed to be sufficiently small (for example, 1.5φ1L7!L)
Therefore, this air flow rate can be smaller than the air flow rate when the engine is idling.

Also, the pressure difference (P-P) is constant, so
Since the flow rate flowing through the bypass circuit 24 is also constant,
By measuring this flow rate in advance, the measured value of the air flow rate by the flow rate detection valve 5 can be corrected.

FIG. 4 shows a third embodiment.

In this embodiment, a differential pressure generating valve 20 is provided upstream of the flow rate detection valve 5, and the communication hole 14 (see FIG. 1) of the valve 12 of the servo mechanism 4 is closed to make the A chamber and the D chamber independent. The pressure P{ on the upstream side of the flow rate detection valve 5 acts on the A chamber, and the pressure P1 on the upstream side of the differential pressure generation valve 20 acts on the D chamber. Others are the same as before. The servo mechanism 4 detects the pressure difference (
P{-P2) is detected and the opening area of the variable orifice 13 is changed, and the pressure in the C chamber changes between the pressure difference (P1-Pi) between the pressure P1 in the D chamber and the pressure P2 in the intermediate chamber 3. In this case, the pressure difference increases by (P, -P(j) compared to the conventional pressure difference. Therefore, the same effect as in each of the above embodiments is achieved. As explained above, this invention An upstream valve and a downstream valve are arranged in the passage, 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 flow rate is determined from the opening area of the upstream valve. In addition to the upstream and downstream valves, a differential pressure generating valve is installed in an area type flowmeter that measures The feedback control mechanism uses the pressure difference to control the opening of the upstream valve and corrects the pressure difference before and after the upstream valve, so if the pressure difference before and after the flow rate detection valve is not sufficient. It is possible to ensure the operating pressure of the valve opening mechanism even when the valve opening mechanism is in use, and it is possible to provide this type of device with stable operation.

[Brief explanation of drawings]

Figure 1 is a vertical sectional view of a conventional device of this type, and Figures 2 to 4 are
The figure is a longitudinal sectional view showing each embodiment of the area type flow metering device of the present invention. 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... Differential pressure generation valve.

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 an area type flow metering device that measures the flow rate of An area type flow metering device characterized in that a feedback control mechanism performs a control operation on the opening degree of an upstream valve using the pressure difference between the pressure and the pressure, thereby correcting the pressure difference before and after the upstream valve.