JPS634070B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a proportional control valve in which the starting current of a solenoid does not change depending on the type of gas. Commercially available fuel gas can be roughly divided into liquefied petroleum gas, natural gas, and manufactured gas (city gas).
It is well known that these have different supply pressures. Even if gases are supplied at the same pressure to appliances that use these gases, the characteristics such as calorific value differ depending on the gas type, so the secondary pressure of the gas cover installed in the appliance must be adjusted for each gas type. The current situation is that Therefore, in a gas proportional control valve that attempts to control the gas flow rate by controlling the gap between the valve and the valve seat, the valve body must be adjusted in the entire range from gas flow rate = 0 (fully closed state) to maximum gas flow rate (fully open state). It can be considered that the pressure loss caused around the gas varies depending on the gas type. On the other hand, the relationship between the inner diameter of the valve seat, the gas flow rate, and the pressure loss of the proportional control valve is expressed by the following equation when the flow rate coefficient is 1. However, D: Valve seat inner diameter Q _nax : Gas flow rate (maximum) γ: Specific weight of gas g: Acceleration of gravity △P _Vnio : Maximum gas flow rate Allowable pressure loss of the proportional control valve when flowing Equation (1) ), no matter what the type of valve and valve seat, the minimum diameter of the valve seat inner diameter D is determined by the allowable proportional control when the calorific value, specific weight, and maximum gas flow rate of the gas are flowed. determined by the pressure loss of the valve. Therefore, the outer diameter of the valve body is set to be slightly larger than the inner diameter D of the valve seat. Furthermore, when a solenoid is used as an actuator for operating a valve body, it is desirable that the relationship between the displacement of the valve body and the excitation current has small hysteresis as a characteristic of the solenoid. There have also been proposals in which the relationship between the excitation current and the displacement of the valve body is linearly proportional, but in either case there is a lot of magnetic flux leakage, so the force of the solenoid is small compared to its size. In this way, the outer diameter of the valve body varies depending on the type of gas, and since the pressure difference that occurs before and after the valve body (pressure loss around the valve body) also differs depending on the type of gas, this pressure difference acts on the valve body. Since the force cannot be ignored compared to a solenoid, the pressure loss around the valve body that acts on the valve body changes when the type of gas changes, and this is thought to affect the control current of the solenoid. The present invention provides a proportional control valve in which the outer diameter of the valve body is determined so that the control current of the solenoid does not change depending on the type of gas. That is, as a configuration of the invention, a gas throttle valve uses a solenoid as an actuator for operating a valve body of a gas proportional control valve, and controls the fluid flow rate by controlling the gap between the valve body and the valve seat with the excitation current of the solenoid. a valve seat having a valve seat inner diameter determined for each type of gas used depending on the gas supply pressure that changes depending on the gas type or the secondary pressure of the gas governor that differs depending on the gas type; and a valve body having an outer diameter determined by the inner diameter of the valve seat, and furthermore, for each type of gas used, the pressure loss generated around the valve body is equal to the maximum value of the force acting on the valve body. The above-mentioned problem was solved by modifying the outer diameter of the valve body and the inner diameter of the valve seat so that the starting current of the solenoid was constant regardless of the gas type. . By having the above-mentioned structure, the present invention has the advantage that even when commercially available fuel gases have different characteristics such as calorific value due to differences in gas type, supply pressure, etc., the gas supply pressure that changes depending on the gas type, Alternatively, by determining the valve seat and valve body according to the secondary pressure of the gas governor, which varies depending on the gas type, the solenoid starting current can be made constant regardless of the gas type, and the gas flow rate can be changed from the minimum flow rate to the maximum flow rate. It is possible to exhibit effects that can be precisely controlled up to a point. Hereinafter, a description will be given using a gas appliance (gas combustor) as an example. FIG. 1 is a block diagram when combustion gas is supplied to a gas appliance 2 via a governor 1. In a conventional gas appliance, the balance of the head pressure of gas between the outlet of the governor 1 and the nozzle outlet of the gas appliance 2 is given by the following equation. P ₂ + γ / 2gW ² _Gnax = △P _nax + γ / 2gW ² _Nnax …(2) However, P ₂ … Secondary pressure of governor γ … Specific weight of gas g … Acceleration of gravity W _Gnax … Maximum of gas at governor outlet Flow velocity W _Nanx ...Maximum flow velocity of gas at the nozzle outlet △P _nax ...Pressure loss from the governor outlet to the nozzle outlet of the gas appliance when the gas flows at the maximum flow rate. When the proportional control valve 3 is installed as shown in Fig. 2, P ₂ +△P _Vnio +γ/2gW ² _Gnax =△P _nax +γ/2gW ² _Nnax +△P _Vnio …(3) However, △P _Vnio …Pressure loss of the throttle valve when gas flows at maximum flow rate Also, when any gas flow rate is flowing, P ₂ +△P _Vnio +γ/2gW ² _G =△P+γ/2gW ² _N +△P _V … (4) In equation (4), △P _Vnio in the second term on the left side does not equal △P _V when the gas flows at its maximum flow rate due to the provision of a proportional control valve in the system through which the gas passes. Since the system pressure loss increases by the pressure loss of the throttle valve (△P _Vnio ), this means that the governor's secondary pressure (P ₂ ) is increased by △P _Vnio . There may be some method for reducing the pressure loss in the system from the governor outlet to the nozzle outlet by ΔP _Vnio without increasing the secondary pressure of the governor, for example, by increasing the thickness of the piping system. Furthermore, P ₂ +△P _Vnio = P _2S・Q/Q _nax = ε(Q
is the gas flow rate), W _G = W _Gnax ε・W _N =
W _Nnax ε・△P=△P _nax ε ² and substituting equation (2) into equation (4), △P _V −△P _Vnio ／P _2S −△P _Vnio =1−ε ² …(5) obtain. Equation (5) is the fluid supply pressure (the governor's secondary pressure
P _2S ) is an equation showing the throttle characteristic of the throttle valve 3 in a certain gas appliance. However, in general, the relationship between the governor's secondary pressure P ₂ and the gas flow rate Q (hereinafter referred to as P ₂ ~Q characteristic) is
As shown in Figures a and b. Therefore, in practical terms, it is preferable to express the throttling characteristics as a variable in the secondary pressure of the governor as the gas flow rate changes. The formula showing the P ₂ ~Q characteristics of the governor is P' _2S = _G (Q) = _G (ε)...(6) However, P' _2S ...Governor secondary pressure _G when an arbitrary gas flow rate Q flows... If we substitute equation (6) in place of P _2S in equation (5) as a function of gas flow rate Q, that is, a function of ε, we get (7)
Get the formula. △P _V = (1 - ε ² ) {(ε) - △P _Vnio } + △P _Vnio ...(7) Equation (7) is used when the secondary pressure of the governor changes with changes in the gas flow rate. This is a general formula showing the throttle characteristics of a proportional control valve. Next, let's consider a case where the same gas appliance (gas combustion appliance) is compatible with three types of gas. To simplify the explanation, it is assumed that the gases have the same properties except for the difference in calorific value per unit volume. Three types of gases are G1, G2, and G3, and the calorific value H per unit volume of these gases is H ₁
＞H ₂ ＞H ₃ , the maximum gas flow rate of each gas is Q _nax1 ＜Q _nax2 ＜Q _nax3 , and if the throttling characteristics given by formula (7) are also the same, then from formula (1) The inner diameter of the valve seat is D ₁ <D ₂ <D ₃ . The force acting on the valve body is given by the product of the area of the valve body and the pressure loss that occurs around the valve body, so if that force is F, then
The general formula is F=△P _V・π/4D ² =π/4D ² [(1−ε ² ){
(ε)△P _Vnio }+△P _Vnio ]...(8) However, in this case, the outer diameter of the valve body and the inner diameter of the valve seat were made equal. This F
is defined as buoyancy. FIG. 5 shows a proportional control valve using a solenoid 9 as an actuator. In the figure, 10 is a yoke, 11
12 is a coil, 12 is a plunger, 13 is a spring, and 14 is a valve shaft formed at the lower end of the plunger. The plunger 12, which is slidably provided at the center of the coil 11, is absorbed into the coil bobbin by energizing the coil, but its displacement is caused by the strength of the spring 13 installed in the direction of repelling the action of the plunger. The displacement of the plunger 12, that is, the displacement of the valve body 4, is determined by the magnitude of the excitation current. Generally, there is no linear proportional relationship between the displacement of the plunger 12 and the excitation current of the solenoid coil. In order to have a linear proportional relationship, the leakage of magnetic flux must be increased. That is, if the attraction force is the same, a linear proportional solenoid has a larger coil and consumes more power than a general solenoid. According to the present invention, when a solenoid is used as an actuator, a linear proportional relationship between the excitation current and the stroke of the valve body (plunger) is not desirable, but only the hysteresis is reduced. Just do it. In FIG. 5, when the valve body 4 and the valve seat 6 are in contact with each other, that is, when the valve is fully closed and the gas flow rate is "0", ε in equation (7) becomes 0, and ( ε)
A pressure P _i shown in FIGS. 3a and 3b acts on the valve body 4. In order to maintain the fully closed state of the valve, the mounting load F _B of the solenoid spring 13 must satisfy F _B ≧π/4D ² P _i . However, as explained earlier, the inner diameter of the valve body D ₁ <
Since there is a relationship of D ₂ <D ₃ , the value F _B (buoyancy) of π/4 D ² P _i differs depending on the gas type. In order to cope with the different buoyancy forces for each type of gas, it is easy to think of changing or adjusting the mounting load of the solenoid spring for each type of gas.
The purpose is to make the outer diameter d of the valve body large in order to keep F _B constant at the maximum value F _B0 and to match the buoyancy of other gas types to the same buoyancy of the gas type that produces the largest buoyancy.
In other words, if the buoyancy force in G ₃ gas is the largest among the three types, and that buoyancy force is F ₃ , then

The outer diameter of the valve body is corrected to d so that the following condition is satisfied. That is, d is determined by F _B0 =π/4 d ² P _i . This has the following advantages: (1) The mounting load of the solenoid spring can be fixed at F _B0 , so there is no need for adjustment, and (2) the starting current does not change depending on the gas type. If the direction of gas flow is opposite to that in Figure 5,
The force acting on the valve body is F=F _B +π/4D ² P _i (9), and the buoyancy varies depending on the outer diameter of the valve body. FIG. 4 illustrates the relationship between the displacement of the plunger 12 (displacement of the valve body 4) and the exciting current.
Since the displacement S of the plunger is determined by the balance between the load of the coil spring 13 and the excitation current, it can be read as the attraction force of the solenoid. Therefore, the valve cannot begin to open unless an excitation current exceeding the point at which the attraction force of the solenoid balances the force acting on the valve body (F _B +π/4D ² P _i ) is applied. The current at the beginning of opening of this valve changes depending on the buoyancy force, as shown in equation (9), and the countermeasure for this is, as before, by increasing the buoyancy force of the largest gas type and the buoyancy force of other gas types. The valve diameter is increased to match. In addition, in the above explanation, we talked about the case where the valve body is in contact with the valve seat (fully closed state), but the valve does not have a fully closing function and there is a slight gap between the valve and the valve seat. Even if a bypass is provided in addition to the main valve so that gas flows from the bypass even when the main valve is closed, the pressure difference that occurs before and after the valve depending on the gas flow rate can be expressed by equation (7). Since the conditions are satisfied, it can be said that the present invention is put into practice. As described above, the present invention is designed to equalize the force acting on the valve body from the pressure loss that occurs around the valve body depending on the gas supply pressure or the secondary pressure of the gas governor, which varies depending on the type of gas. Since the diameter of the valve body is determined, the starting current of the solenoid can be made constant regardless of the gas type, and the gas flow rate can be accurately controlled from the minimum to the maximum.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a combustion device consisting of a governor and gas appliances, Figure 2 is a block diagram of a case where a proportional control valve is interposed between the governor and gas appliances,
Figures 3a and b are diagrams showing the relationship between governor secondary pressure and gas flow rate, Figure 4 is a diagram showing the relationship between solenoid excitation current and plunger (valve body) displacement, and Figure 5 is a diagram showing the relationship between the governor's secondary pressure and gas flow rate. It is a sectional view showing one example of a control valve. DESCRIPTION OF SYMBOLS 1... Governor, 2... Gas appliance, 3... Proportional control valve, 4... Valve body, 6... Valve seat, 9... Actuator (solenoid), 11... Coil, 12... Plunger,
13...Spring.

Claims (1)

[Claims] 1. In a gas throttle valve that uses a solenoid as an actuator to operate the valve body and controls the fluid flow rate by controlling the gap between the valve body and the valve seat with the excitation current of the solenoid, the gas that changes depending on the gas type is used. A valve seat having an inner diameter determined for each type of gas used according to the supply pressure of the gas governor or the secondary pressure of the gas governor which varies depending on the type of gas, and an outer diameter determined from the inner diameter of the valve seat. Furthermore, for each type of gas used, the diameter of the valve body is modified so that the pressure loss occurring around the valve body is equal to the maximum value of the force acting on the valve body. A gas proportional control valve characterized in that the starting current of the solenoid is constant regardless of the type of gas.