JPH0471008A - Flow rate adjustor and its using method - Google Patents

Abstract

PURPOSE:To obtain an flow rate adjustor preventing the generation of hunching, overshooting, or the like due to the difference of fluid pressure and having the highest control speed by controlling a flow rate by a control variable almost like an exponential function. CONSTITUTION:In the case of changing a detected flow rate Qs up to Qg, the controlled variable DELTAtheta of a control variable theta is found out by using the flow rate ratio, and the control variable theta is changed from the state of the flow rate Qs by the DELTAtheta, all fluid pressure values p1 to p3 reach the same flow rate. In the case of increasing the flow rate Q to twice, threefold or the like, the controlled variable DELTAtheta of the control variable theta is the same independently of the initial flow rate and the flow rate adjustor can easily be controlled. Thereby, the controlled variable DELTAtheta of the control variable theta is not changed in accordance with the difference of the fluid pressure (p), arrival at an objective flow rate can quickly be obtained without generating hunching and the stable flow rate adjustor having a high control speed can be obtained.

Description

[Detailed description of the invention] [Industrial application field] TECHNICAL FIELD This invention relates to a flow regulator and method of using the same.

[Background Art] The relationship between a control variable θ, such as a valve rotation angle, and a flow rate Q in a flow rate regulator such as a flow rate regulating valve has been linear as shown in FIG. That is, the conventional flow rate regulator was designed so that the flow rate Q or the linear function of the control variable θ was Q=H, (θ+β,) . . .■. Here, H2 and β are variables that depend on the fluid pressure p. FIG. 8 is a diagram showing the relationship between the flow rate Q and the control variable θ in a conventional fluid regulator.
It shows the relationship in cases 1) and 3). Therefore, when such a flow regulator is used, when the control variable is rotated by Δθ, the flow rate Q is changed by an amount ΔQ=HpXΔθ . . . ■ proportional to the variable Δθ of the control variable.

However, in such a flow rate regulator, the coefficient Hp in equation (2) changes depending on the fluid pressure p, so even if the control variable θ such as the valve rotation angle is changed by the same amount, the flow rate Q changes depending on the fluid pressure p. are different.

When using such a flow rate regulator, it is usually not equipped with a means to detect the fluid pressure p, and the relationship between the flow rate Q and the control variable θ for a typical water pressure (for example, the fluid pressure p2 in FIG. The flow rate is adjusted using the straight line of Therefore, the current flow rate detected by the flow rate detector is Q
When the target flow rate is Q2 at 1, the variable Δθ of the control variable θ is determined according to the straight line of the fluid pressure p2 in FIG.

However, in reality, the water pressure is lower than p2, and pl(<p
2), as shown in Figure 8, even if the control variable θ is rotated by Δθ, the flow rate remains Q3 (Ql<03<
02). Therefore, the control variable θ is changed again to obtain the target flow rate Q2 by detecting the flow rate, and if the target flow rate is still not reached, the control variable must be changed again, and the target flow rate is asymptotically approached. Therefore, there was a problem in that it took time to reach the target flow rate and the control speed became slow.

In addition, when the water pressure is higher than p2 and p3 (>p2), if the control variable is changed by 80, the flow rate becomes Q4 (>02) as shown in Figure 8, and the flow rate becomes Since the target flow rate Q2 becomes too large, it is necessary to measure the flow rate again and return the control variable to the opposite side to obtain the target flow rate. There was a problem that a stable flow rate could not be obtained.

[Problems to be Solved by the Invention] The present invention has been made in view of the drawbacks of the conventional examples described above, and its purpose is to prevent hunting, overshoot, etc. caused by differences in fluid pressure, To provide a flow regulator having the highest control speed without reducing the control speed or causing hunting or the like.

[Means for Solving the Problems] The flow regulator of the present invention is characterized in that the flow rate is controlled almost exponentially by the control variable in the flow regulator that controls the flow rate by a control variable. .

More specifically, the flow rate regulator of the present invention is configured such that the flow rate Q is controlled by the control variable θ approximately according to the relationship Q=Kp×Cθ including a coefficient Kp that depends on the fluid pressure p. There is.

In addition, the method of using the above-mentioned flow rate regulator is to find the amount of change in the control variable from the ratio of the flow rate detected by the flow rate detector and the target flow rate, and to change the control variable by the amount of change in the control variable that has been found. It is a feature.

[Operation] In the present invention, since the flow rate Q is controlled approximately exponentially by the control variable θ, it is approximately expressed as Q-Keaθ. Here, the coefficient is a variable that depends on the fluid pressure p, so if we write K and set e'=c (a is a constant), the above equation is expressed as Q= and Cθ.

In such a flow rate regulator, if the flow rates when the control variables θ and θ + Δθ are Ql and Q2, respectively, then when the control variable is increased by a unit amount, the flow rate Q becomes independent of the fluid pressure p. It becomes 0 times. Further, the control variable θ can be arbitrarily selected, and for example, the rotation angle of the valve body, the rotation angle of the motor, the sliding distance of the valve body, etc. can be selected.

In the past, instead of handling the difference between the flow rate detected by a flow rate detector and the target flow rate as in the past, the ratio between the detected flow rate and the target flow rate was calculated, and the control variable was calculated based on how many times the flow rate should be increased. By determining the control amount Δθ of θ, it is possible to determine the control amount Δθ of the control variable θ that is unrelated to the value of the fluid pressure p. If the control variable θ is changed by the control amount Δθ obtained in this way to reach the target flow rate, the flow rate will become unstable due to hunting or the like, or the control speed will decrease and the target flow rate will not reach the target flow rate. This can prevent it from taking a long time to reach the destination.

Also, the amount of change in the control variable obtained in this way is
Since it is determined only by the flow rate ratio and does not depend on the flow rate detected by the flow rate detector, -layer flow rate adjustment becomes easy.

[Example] The flow regulator of the present invention is designed so that the relationship between the flow rate Q and the control variable θ is determined according to the following equation. Here, K9 is a coefficient that changes depending on the fluid pressure p, and as the fluid pressure p increases,
becomes larger.

Therefore, in a flow regulator designed in this way, when the control variable is increased by a unit amount from 00, the flow rate becomes (θ.+1) Q=, C=CC1o...■. That is, each time the control variable θ increases by a unit amount, the fluid pressure p and the flow rate Q increase. Regardless of this, the flow rate Q is multiplied by a constant (0 times).

An example of how to use this flow rate regulator will be explained.

FIG. 2 shows a bypass mixing type water heater, in which a bypass waterway 3 is provided in a main channel 6 having a heat exchanger 7 so as to bypass the heat exchanger 7, and a flow rate servo valve is installed in the bypass waterway 3. A flow rate regulator 1 and a flow rate detector 2 are provided to determine the temperature T of the inflow water. temperature sensor 8 for detecting the water temperature T II on the side of the heat exchanger 6 mouth, temperature sensor 9 for detecting the pressure of the hot water temperature T II, and the mixing temperature T of the mixture of hot water and water.
A temperature sensor 10 for detecting M is provided. By adjusting the amount of water Qs to be mixed using the flow rate regulator 1, hot water T8 at a set temperature is dispensed.

Further, the control unit 4 controls the set temperature T8 and the water temperature T input from the hot water temperature setting device 5. , hot water temperature T, , mixing temperature TM and flow rate Qs are read, and the flow rate regulator 1 is controlled to dispense hot water at a set temperature T8.

That is, the control unit 4 determines the current hot water distribution ratio between the heat exchanger 7 side and the bypass waterway S side (Ql (where Ql is a constant flow rate passing through the heat exchanger), and the current hot water distribution ratio between the heat exchanger 7 side and the bypass waterway S side, The hot water distribution ratio can be found. ■From the relationship of the formula, the flow rate ratio Q, /Q.

The relationship between Δθ and the control amount Δθ of the control variable θ is expressed as follows.

The control unit 4 calculates the value of the control amount Δθ according to equation 0, controls the control variable θ (for example, valve rotation angle) of the flow rate regulator l based on this value, and adjusts the flow rate flowing through the bypass waterway 3 or Q,
Adjust the temperature so that it becomes hot water at the set temperature T3.

In addition, as the value of C above, as an experimental value, C=1.0
Good results were obtained using a value of 135.

The operation when controlling the flow rate as described above will be explained with reference to the drawings. FIG. 1 shows the relationship between the flow rate Q and the control variable θ in a flow regulator according to an embodiment of the present invention.
I)2. T) This is shown for Fl. For the detected flow rate Q, the flow rate is Q.

Let's change it to . Then, if the control variable Δθ of the control variable θ is determined using the flow rate ratio Q, /Q, and the control variable θ is changed by Δθ from the state of the flow rate Q, as shown in FIG. Since there is a relationship between the pressure p++, the control amount Δθ reaches the same flow rate Q for 1)2.1)3.

Also, if you want to double or triple the flow rate Q, the control amount Δθ of the control variable will be
are the same, making it easier to control the flow rate regulator 1.

Therefore, when such a flow regulator is used, the control amount Δθ of the control variable θ does not differ due to differences in fluid pressure p, and the target flow rate can be quickly reached without hunting, resulting in stable control. A flow regulator with high speed can be manufactured. However, when the valve of the flow regulator is opened, the fluid pressure decreases, so the flow rate tends to decrease slightly from the target flow rate, and when the valve is closed, the fluid pressure increases, so the flow rate tends to decrease slightly from the target flow rate. Since the flow rate also tends to become slightly larger, the control of the flow rate may become somewhat gentler. Therefore, the flow rate regulator of the present invention provides a control method that is less likely to cause hunting or the like. Therefore, if the target flow rate has not been reached, the control variable Δθ of the control variable θ can be found and the flow regulator can be controlled again to reach the target flow rate. Since the fluctuation in is small, convergence to the target flow rate is faster than in the conventional example, and a large control speed can be obtained.

As a result, it can be said that the flow rate regulator of the present invention can realize the maximum control repeat without causing hunting or the like.

Various configurations are possible as a specific configuration of the flow rate regulator as described above.

For example, what is shown in FIG. 3 is an example of a flow rate regulator 11 that includes a flow rate sensor 12 and a flow rate adjustment section 13. The flow rate adjustment section 13 converts the rotation of a motor 14 into linear motion by a converter 15. The converter 15 slides the valve body 16 to adjust the degree of opening between the valve body 16 and the valve seat 17. Here, the motor 14 is a DC motor or a pulse step motor, and rotates by an angle proportional to the current supply time or the number of pulses, and the converter 15 slides the valve body 16 by a linear distance proportional to the rotation angle of the motor 14.

The valve body 16 has an axially symmetrical shape around the axis 18,
The shape of the outer peripheral surface is determined as follows. As shown in FIG. 4, if the distance from the axis 18 of the valve body 1G to the inner circumferential surface of the valve seat 17 is R1 and the radius of the valve body 16 at the distance X from the rear end of the valve body 16 is r, then As shown in the figure, valve seat 1
The opening area S between the valve body 16 and the valve seat 17 in a state where the rear end of the valve body 16 is protruded by X from 7 is S−π
It becomes R2-πr2. Considering that the flow rate Q flowing through the flow rate regulator 11 is proportional to this opening area S, it can be expressed as Q=yrG (R2-r''), where G is the proportional coefficient.This flow rate Q is an exponential function with respect to the control variable. For example, if the amount of sliding of the valve body 18 is selected as the control variable, the amount of sliding of the valve body 16 will change depending on the valve seat 1 of the valve body 16.
Since it can be expressed by the length
B is a constant). That is, the radius r of the valve body 16 is a function of the distance X from the rear end. As the control variable θ, if it is a quantity that has a linear relationship with the moving distance X of the valve body IG, then B・
-B('''e+b)-B...(B.)0=A-Cθ, and since an exponential relationship can be maintained between Q and θ, such a variable can be used as a control variable.

Therefore, as a control variable, in addition to the linear movement distance of the valve body 16, the rotation angle of the motor, the ON time of the DC motor, the number of pulses of the pulse step motor, etc. can also be used as the control variable θ.

What is shown in FIG. 5 is a sectional view showing a part of the other side of the flow rate regulator 21 of the present invention, in which a fixed sliding contact plate 24 having openings 22 and 23 and a rotating sliding contact plate 25 are slid together. The degree of opening between the fixed sliding contact plate 24 and the rotating sliding contact plate 25 can be changed by freely press-contacting them and rotating the rotating sliding contact plate 25 with a motor (not shown). . The fixed sliding contact plate 24 and the rotating sliding contact plate 25 are each provided with openings 22 and 23 shaped as shown in FIG. 6. FIG. 7 shows how to determine the shape of this opening, and the fixed sliding contact plate 24 has an opening in the shape of a fan, for example, with a central angle n. On the other hand, the area of the opening of the rotating sliding contact plate is divided into units of angle, and the opening area of each part is calculated as ΔS1. ΔS2. ..., it is decided that ΔS,=SoC' (So=ΔS,). Therefore, ΔS, ~ΔSj+
If the opening area when n-1 overlaps with the opening of the fixed sliding contact plate 24 is S, and the opening area when the rotary sliding contact plate is rotated by 1 degree from this state is S, +1, then S 4= S o(C'+ C"'+ -ten C"'-'
) S 4-+= S o (C"'+ C"'-
'+ - ten C'''')=CS.

Therefore, the aperture ratio and flow rate follow an exponential function using the rotation angle of the rotary sliding contact plate, etc. as control variables (see equation 0). In addition,
In FIG. 7, the outer edge radius of the aperture is set to a constant value R1, and the inner edge radius r1 is expressed as a function of the angle φ, rl−(R1” So
Cφ)... is determined to be.

Although not shown, the rotating sliding contact plate 25 and the fixed sliding contact plate 2
A plurality of openings 22 and 23 may be provided. Also, 2
The portion G is not opened and is an inclined surface.

[Effects of the Invention] According to the present invention, the flow can be adjusted without using fluid pressure. Therefore, the flow rate can be adjusted at the fastest control speed without causing hunting or the like in the flow rate. Moreover, the amount of change in the control variable is
Since it is determined only by the flow rate ratio and does not depend on the flow rate detected by the flow rate detector, the flow rate adjustment becomes easy.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the usage and operation of the flow regulator of the present invention, Fig. 2 is a schematic diagram showing a flow rate regulation mechanism using the flow regulator of the present invention, and Fig. 3 is an embodiment of the present invention. FIG. 4 is an enlarged side view showing the same valve body as above; FIG. 5 is a partial sectional view showing a valve body according to another embodiment of the present invention; FIG. FIG. 7 is a front view of the rotating sliding contact plate and the fixed sliding contact plate, FIG. 7 is an explanatory diagram showing a method of determining the openings as described above, and FIG. 8 is a diagram explaining the operation of the conventional example. 1.11...Flow rate regulator 2...Flow rate detector 4...Control unit Patent applicant Noritz Co., Ltd. Agent Patent attorney Masafusa Nakano

Claims (3)

[Claims] (1) A flow rate regulator that controls the flow rate using a control variable, characterized in that the flow rate is controlled approximately exponentially by the control variable. (2) The flow rate Q is controlled by the control variable θ substantially in accordance with the relationship Q=K_p×C^θ including a coefficient K_p dependent on the fluid pressure p. Flow regulator. (3) A method for using the flow rate regulator according to claim 1 or 2, comprising: determining the amount of change in the control variable from the ratio of the flow rate detected by the flow rate detector to the target flow rate; A method of using a flow rate regulator characterized by changing a control variable by the amount of change.