JPS6121321B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device that automatically controls the ratio of fuel and air supplied to a combustion chamber such as a furnace to a predetermined value. Conventional air-fuel ratio control devices of this type include the following, for example. That is, an air differential pressure corresponding to the flow rate of air supplied to the combustion chamber is generated by the air differential pressure generating section, and this air differential pressure is converted into force by the air differential pressure/force converting section. On the other hand, a fuel pressure difference corresponding to the fuel flow rate supplied to the combustion chamber is generated in the fuel pressure difference generating section, and a force is generated in response to this fuel pressure difference.
The force due to the fuel differential pressure and the force due to the air differential pressure are applied to the differential pressure response section, and as a result, the lever of the differential pressure response section is displaced, and the opening degree of the valve consisting of the nozzle facing this lever is controlled. . Due to this change in the opening degree of the valve, the fuel differential pressure changes, and the force resulting from this is negatively fed back to the differential pressure response section, so that the entire valve operates so as to be in force balance. As a result, in an equilibrium state, the air flow rate and the fuel flow rate are maintained at a constant ratio. Next, this type of air-fuel ratio control device will be explained with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a cross section of this type of air-fuel ratio control device, and the explanation will be made using this. Air supplied to a combustion chamber (not shown) passes through an air passage 1 , for example, from the right side to the left side in FIG. 1, as indicated by an arrow 2. air passage 1
A recess 1a is formed at the bottom to determine the air flow characteristics. An air pressure difference corresponding to the flow rate of air flowing through the air passage 1 is generated by the air pressure difference generation section 3 . The air differential pressure generating section 3 includes, for example, a vane 3b whose one end 3a is rotatably attached to the air passage 1 , and a recess 1a of the air passage 1 . The difference between the air pressure on the upstream side and the air pressure on the downstream side of the vane 3b changes depending on the air flow rate. The air differential pressure generated by the air differential pressure generator 3 is converted into force by the air differential pressure/force converter 4 . The air differential pressure/force converter 4 is composed of, for example, a pressure receiving plate 4a disposed in a hole 1b provided in the upper part of the air passage 1 . The pressure receiving plate 4a is inserted through the hole 1c provided in the air passage 1 on the downstream side of the air differential pressure generating section 3.
The air pressure difference generated on both sides is converted into force by the pressure receiving plate 4a. On the other hand, a fuel flow rate setting chamber 5 is provided on both sides of the air differential pressure generating section 3 provided on the side surface of the air passage 1 , that is, on the upstream side and the downstream side. The fuel flow rate setting chamber 5 and the air passage 1 communicate with each other through holes 1b and 1c formed in intermediate walls 6 and 7 thereof. The fuel differential pressure receiving part 8 is provided on the downstream side of the air flow in the fuel flow rate setting chamber 5, that is, on the hole 1c side, and includes a bellows 9 and a bellows 10, each of which has one end fixed.
, a first lever 11 disposed at the other end of these bellows at right angles to the intermediate walls 6 and 7 and rotatably fixed at both ends;
It consists of a lever 11 and a nozzle 12 fixed opposite to it. The differential pressure responsive part 13 includes a second lever 14 which is parallel to the intermediate walls 6 and 7 and rotatably fixed to the first lever 11, and a second lever 14 which is rotatably fixed to the fixed wall at one end and a second lever 14 which is parallel to the intermediate walls 6 and 7 and rotatably fixed to the first lever 11. A third lever 1 is rotatably fixed to the lever and is arranged diagonally at an angle θ with respect to the intermediate wall.
5, and the second lever 14 has a pressure receiving plate 4.
The structure is such that a force is applied from a. The fuel 16 supplied to the combustion chamber is branched into pipes 17a and 17b within the fuel flow rate setting chamber 5, and the pressure of the fuel is transferred to the bellows 9 through the pipe 17a.
A variable fuel orifice 19 is used as the fuel differential pressure generating section 18 , and the fuel flow is applied to the bellows 10 through the variable fuel orifice 19 and passes through the nozzle from the opposing portion between the first lever 11 and the nozzle 12. The fuel is then supplied to the combustion chamber. The variable fuel orifice 19 is composed of an orifice 19a and a leaf spring 19b provided so that the opening area of the orifice can be varied. This variable fuel orifice 19 has a differential pressure-flow characteristic that increases the differential pressure change in response to a change in fuel flow rate when the fuel flow rate is small, thereby reducing the error in the fuel flow rate in response to the differential pressure detection error at low flow rates. This is not necessarily a variable orifice, but may be a fixed orifice. In the above configuration, when the air flow rate flowing through the air passage 1 increases, the pressure P ₁ on the upstream side of the air differential pressure generating section 3 becomes larger than the pressure P ₂ on the downstream side, and the pressure receiving plate 4a moves toward the fuel flow rate setting chamber 5 side. Displaced to. As a result, the first lever 11 is slightly rotated clockwise in the figure, and the second lever 14 is also displaced slightly away from the intermediate wall 7 of the air passage 1 .
Displaced to the downstream side of 1 . Therefore, the first lever 11 is rotated clockwise about the fulcrum 11a in the figure by the second lever 14, that is, rotated in a direction away from the nozzle 12, and the fuel flow rate increases. That is, when the air flow rate increases, the fuel flow rate increases accordingly. When the fuel flow rate increases, the variable fuel orifice 19
The difference in fuel flow pressure generated at the bellows 9, 1
The pressure difference between the fuels in the nozzle 1 increases, and the pressure difference acts to rotate the first lever 11 toward the nozzle 12. Therefore, the force due to the differential pressure of the fuel flow rate and the force corresponding to the differential pressure of the air flow rate converted by the pressure receiving plate 4a come to be balanced. In this way, the fuel flow rate corresponding to the air flow rate is discharged. The pressure difference P ₁ - P ₂ between the upstream side and the downstream side of the air pressure generating part 3 of the air flow rate is △Pa, the area of the pressure receiving plate 4a is A ₁ , and the fuel pressure P ₃ in the bellows 9 and the pressure in the bellows 10 are The differential pressure (P ₃ − P ₄ ) with the fuel pressure P ₄ is △P
The effective area of the bellows 9, 10 is _A2 , and the angle between the third lever 15 and the extension direction of the second lever 14 is θ, as shown in FIG.
The distance between the connection point of the lever 14 and the first lever 11 and the pressure receiving plate 4a is l ₁ , the length of the second lever 14 is l ₂ ,
Assuming that the distance from the fulcrum 11a of the first lever 11 to the center point of the part where the differential pressure of the fuel flow acts on the first lever 11 is l ₃ and the length of the first lever 11 is l ₄ , the differential pressure of the fuel flow is received from the pressure receiving plate 4a. The second lever 14 is displaced as shown by the dotted line by the force A ₁ ·ΔPa, and the first lever 11 is further displaced away from the nozzle 12 . The force that the first lever 11 tends to separate from the nozzle 12 due to the force received by the second lever 14 from the pressure receiving plate 4a and the differential pressure between the fuel flow rates cause the first lever 11 to move away from the nozzle 12.
In a state where the force pushing the lever toward the nozzle 12 is balanced, the displacement of each lever 11, 14, 15 is small, and the following equation holds true. This equation indicates a condition in which the vector sum of the force due to the air differential pressure and the force due to the fuel differential pressure is in the direction of the third lever 15. Equation (1) can be simplified and expressed as the following equation, where D is a constant determined by the area of the pressure receiving plate, the effective area of the bellows, and the dimensions of the lever system. tanθ=D・4Pa/4P (2) As described above, the air flow rate differential pressure ΔPa is proportional to the fuel flow rate differential pressure ΔP. In other words, since the differential pressure and the flow rate have a one-to-one correspondence, the fuel flow rate is discharged in correspondence with the air flow rate. In an air-fuel ratio control device that operates with such a conventional configuration, when the air pressure and temperature change, the specific weight of the air changes, and the weight ratio of fuel and air supplied to the combustion chamber changes to meet the true requirements. The disadvantage is that the air-fuel ratio cannot be obtained. In the present invention, a correction means is provided at one end of the lever, which is a part of the element of the differential pressure responsive part, to be displaced in accordance with at least one of the temperature and pressure of the air supplied to the combustion chamber, and the air is supplied to the combustion chamber. This is an air-fuel ratio control device configured so that the air-fuel ratio expressed in weight flow rate ratio does not change even if the temperature or pressure of air changes. Next, the present invention will be explained in detail with reference to the drawings, and parts having the same functions as those of the conventional air-fuel ratio control device will be designated by the same reference numerals, and the explanation will be omitted if necessary. FIG. 3 is a longitudinal sectional view showing one embodiment of the present invention. A bellows 20 is provided at a position corresponding to the fulcrum 15a in the conventional example of the third lever 15 constituting the differential pressure responsive section 13 . One end of the bellows 20 is fixed to the inner wall of the fuel flow rate setting chamber 5, and the other end is rotatably fixed to the third lever 15. Gas is sealed inside the bellows 20. The enclosed gas need not be limited to air, and other gases such as nitrogen may be included. It is desirable that the bellows 20 be placed at a position where the pressure and temperature are close to the pressure and temperature of the air in the air passage 1 .
1 of the coupling structure between the bellows 20 and the third lever 15
A more concrete example is shown in FIG. Third lever 15
and the second lever 14 are movably coupled by a leaf spring 21, and the other end of the third lever 15 is movably fixed to the central portion 23a of the fourth lever 23 by a leaf spring 22, and at the same time, to one end of the bellows 20. Fixed. The fourth lever is formed in a U-shape, and its both ends 23b and 23c are movably fixed to the inner wall of the fuel flow rate setting chamber 5 via leaf springs 24 and 25, respectively. Next, the operation of the present invention in the above configuration will be explained. Fuel weight flow rate is W, air weight flow rate is
Wa, Ca are the flow coefficients at the air differential pressure generating part, C
is the flow coefficient at the fuel variable orifice, Aa
is the opening area of the vane in the air differential pressure generating part, A
is the opening area in the fuel variable orifice, γa
and γ are the specific weights of air and fuel, respectively,
When g is the acceleration of gravity and the air differential pressure ΔPa is small, the following equation generally holds. Wa=Ca・Aa√2・△……(3) W=C・A√2・△……(4) For simplicity, assume that each opening area changes in proportion to each differential pressure. Then, Aa∞ΔPa ………(5) A∞ΔP ………(6) Substituting equations (5) and ( ^{6) into equations (3) and (4) and rearranging them, Wa=Ka・γa 0.5 ・△Pa 1.5 …… (} 7) W=K・γ ⁰ . ⁵・△P ¹ . ⁵
......(8) becomes. Here, Ka and K are constants. Therefore, the air-fuel ratio R expressed as the weight flow rate ratio is
From formulas (7) and (8), R=Wa/W=Ka/K(γa/γ ^{) 0.5 ・}(
△Pa/ ^{△P) 1.5 ...} (9) Since the fuel differential pressure in the fuel differential pressure receiving section 8 is simultaneously equal to the fuel differential pressure on both sides of the variable fuel orifice, in equation (9), θ is small in equation (2).
Substituting tanθ≒θ, R=Ka/K(・γa/γ ^{) 0.5 ・}(θ ^/ D) ^1.5
...(10) becomes. If the specific weight γ of the fuel changes little due to pressure or temperature, the air-fuel ratio R expressed as a weight flow rate ratio becomes a function of θ and γa. Here, since we have ignored the change in γ, if we replace γ=γa, it can be expressed as a function symbol as shown in the following equation. R = (θ・γ) ......(11) Therefore, if θ and γ slightly change from the reference states θ ₀ and γ ₀ by △θ and △γ, respectively, then △R=(∂/ ∂θ) ₀ Δθ+(∂/∂γ) ₀ △
γ……(12) becomes. However, (∂/∂θ) ₀ , (∂/∂θ)
γ) ₀ indicates the differential value at θ ₀ and γ ₀ , respectively.
Here, in order to set △R=0, from equation (12), It is sufficient if the relationship is satisfied. On the other hand, the air flowing through the air passage 1 is
The fuel flows into the fuel flow rate setting chamber 5 through the gap between the air passage 1 and the hole 1b, and flows from the hole 1c to the downstream side of the vane 3b.
The pressure and temperature of the air inside are equal to each other. Therefore, the specific weight of the air in the bellows 20 is equal to the specific weight γa of the air in the air passage, and changes in these specific weights change similarly. The amount of elongation Δx of the bellows 20 when the specific weight of the air within the bellows 20 changes by Δγ is calculated using the operation explanatory diagram of FIG. If the internal volume of the bellows is V, the weight of the enclosed air is G, and the specific weight is γ, which is equal to the specific weight in the air passage, then γV=G (14) The slight change from the reference state V ₀ , γ ₀ △V, △
If γ, then γ ₀・ΔV+V ₀・△γ=0 ∴△V=−V ₀ /γ ₀・△γ……(15) If the effective area of the bellows is S, then △V=S・△ x......(16) Therefore, by substituting equation (15) into equation (16), it becomes △x=-V ₀ /Sγ ₀・△γ...(17). Here, since the amount of extension △x of the bellows and the amount of change △θ in θ are proportional, △θ=K ₁ · △x (K ₁ is a constant) ...(18) If we set Equation (17) and (18) ) formula, △θ=-K ₁ V ₀ /Sγ ₀・△γ……(19
) becomes. Therefore, from equations (13) and (19),
Even if the specific weight γ of air changes, the conditions for the change ΔR in the air-fuel ratio expressed by the weight flow rate ratio to become zero are as follows. As described above, in the configuration of the present invention, K ₁ ,
If V ₀ and S satisfy equation (20), the air-fuel ratio R can be kept constant even if the air pressure and temperature change. In the above embodiments, an example was described in which a bellows was used as a correction means for the pressure and temperature of the air-fuel ratio R, but the correction means is not limited to this and may be realized by a capsule, for example. Also, since pressure changes in air are generally smaller than temperature changes, if you want to compensate for only temperature changes at low cost, you can achieve the same purpose by using bimetals, etc., without using expensive compensation means such as bellows or capsules. can be reached. FIG. 6 shows an embodiment in which bimetal is used for correction. Bellows 20 in Figure 3
Instead, one end of the bimetal 26 is fixed to the fuel flow rate setting chamber 5, and the other end is fixed to the third lever 15 via a wire 27. A perspective view of the bimetal fixing structure in this case is shown in FIG. In this case, since the air-fuel ratio R in equation (11) is considered to be a function only of θ and the air temperature T, the following equation is obtained. R = (θ, T) ...... (21) If θ, T are changed by △θ, △T from the reference state θ ₀ , T ₀ , then △R = (∂/∂θ ₀ )・△ θ+(∂/∂T ₀
)・△T To make △R=0, becomes. The rotation angle △θ of the third lever due to the temperature change △T and the deflection of the bimetal is proportional in the range where the amount of change is small, so it can be expressed as △θ=K ₂ · △T (K ₂ is a constant) ...(23) Ru. Therefore, from equations (22) and (23), If the constant K ₂ is set so that the air-fuel ratio expressed as a weight flow rate ratio will not change even if the temperature changes. The above description is about an embodiment in which a vane is used as the air differential pressure generating section and a pressure receiving plate is used as the air differential pressure/force converting section, but the present invention is not limited to this. Figure 8 shows the air differential pressure generating section.
3. Use a full plate as air differential pressure/force converter.
An embodiment is shown in which a spring is used as 4 and a bellows is used as temperature and pressure correction means. The inside of the air passage 1 is formed into a tapered tube 28, and at the position of the tapered tube 28, a baffle plate 29 is disposed downstream of the air flow 2 at right angles to the air flow. Hole 30 in part of air passage 1
A rotating rod 31, which passes through this hole and has one end fixed to the baffle plate 29, is provided so as to be rotatable about a fulcrum 32. The rotating rod 31 is rotated by the buff-full plate 29 being displaced downstream of the air flow in accordance with the air flow rate.
This rotation is transmitted to the spring 33 connecting the other end of the rotation rod 31 and the second lever 14 as a displacement corresponding to the air flow rate. This displacement is converted into force by the spring 33 and transmitted to the second lever 14. The subsequent operation is the same as the embodiment shown in FIG.
A similar effect can be obtained by using a capsule or a bimetal instead of the bellows 20 in the embodiment of FIG. Various embodiments have been described above, but in the present invention, the air-fuel ratio expressed in weight flow rate ratio can be obtained with a simple configuration, so an air-fuel ratio control device that is not affected by ambient temperature and pressure is realized. The industrial benefits are great.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a conventional air-fuel ratio control device, FIG. 2 is an explanatory diagram of the operation of the conventional device, FIG. 3 is a longitudinal sectional view showing the air-fuel ratio control device of the present invention, and FIG. 4 is a longitudinal sectional view showing the present invention. A perspective view showing the correction means in the invention, FIG. 5 is an explanatory diagram of the operation of the invention, FIG. 6 is a vertical sectional view showing another embodiment of the invention, and FIG. 7 is a correction in another embodiment of the invention. FIG. 8 is a perspective view showing the means, and a longitudinal sectional view showing a third embodiment of the present invention. 3 : Air differential pressure generator, 4 : Air differential pressure/force converter, 8 : Fuel differential pressure receiver, 11: First lever, 1
2: Nozzle, 13 : Differential pressure responsive section, 14: Second lever, 15: Third lever, 18: Fuel differential pressure generating section,
20: Bellows, 26: Leaf spring.

Claims (1)

[Claims] 1. An air differential pressure generation section that generates an air differential pressure corresponding to the air flow rate supplied to the combustion chamber, an air differential pressure/force conversion section that converts the air differential pressure into force, and an air differential pressure/force conversion section that generates an air differential pressure corresponding to the air flow rate supplied to the combustion chamber. A fuel differential pressure generating section that generates a corresponding fuel differential pressure, a fuel differential pressure receiving section that converts the fuel differential pressure into force, and forces corresponding to the fuel differential pressure and the air differential pressure, respectively, are applied. The air flow rate and fuel are supplied to the combustion chamber by changing the fuel flow rate by the displacement of the differential pressure response part in a state where the displacing differential pressure response part and the forces corresponding to the fuel differential pressure and the air differential pressure are respectively balanced. In an air-fuel ratio control device that controls the ratio between the weight flow rate and the weight flow rate, a correction means is provided at one end of the differential pressure responsive part to change the ratio according to at least one of the temperature and pressure of the air supplied to the combustion chamber. An air-fuel ratio control device configured so that the air-fuel ratio, expressed as , does not change.