JPS5914690B2 - fuel supply control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply control device that attempts to keep the temperature rise almost constant by controlling the amount of burner combustion according to the flow rate of the fluid to be heated, and in particular, the present invention relates to a fuel supply control device that attempts to keep the temperature rise almost constant by controlling the amount of burner combustion depending on the flow rate of the fluid to be heated. This relates to an instantaneous gas water heater that allows you to obtain hot water.It improves control performance by absorbing the difference between the pressure level on the water supply side and the pressure level on the fuel side and comparing the two river forces, and also increases the control performance depending on the amount of combustion. Taking into account the change in thermal efficiency, the proportional relationship between the flow rate of the fluid to be heated and the amount of fuel supplied is changed depending on the amount of fuel supplied, thereby improving the performance of keeping the temperature rise constant.

Supplying the amount of gas in proportion to the amount of water supplied in an instantaneous gas water heater is disclosed in Utility Model Publication No. 49-38623 and Utility Model Publication No. 53-1.
As already known in No. 4989, when the amount of combustion is proportional to the amount of water supplied, the heat exchange efficiency changes depending on the amount of combustion, so the output heat amount is not proportional to the amount of water supplied (as a result, the amount of water The disadvantage is that the heating temperature rise is not constant.

The present invention eliminates these conventional drawbacks, and embodiments thereof will be described below with reference to the drawings.

In one embodiment of the present invention, a case will be described in particular of an instantaneous gas water heater in which the object to be heated is water and the fuel is gas, but the present invention is not particularly limited to this.

In FIG. 1, water enters from a water pipe 1, passes through a pressure difference generator 4 having a constriction part 2 and an enlarged part 3 connected thereto, is heated by a heat exchanger 7, and is discharged from a faucet 8.

The water pressure just before the throttle part 2 of the pressure difference generator 4 is detected from the high pressure tap 5, and the water pressure at the throttle part 2 is detected from the low pressure tap 6, and the pressure is guided to the force generator 13 and the on-off valve drive part 29, which will be described later. It will be destroyed.

Next, the gas enters from the gas pipe 9, passes through the on-off valve 10, is controlled by the fuel pressure controller 11 to a supply gas pressure that has a certain relationship with the amount of water, and then reaches the burner 12 where it is combusted.

Reference numeral 13 denotes a force generator, in which a main diaphragm 14 and two balance diaphragms 16 and 15 having a slightly smaller diameter and arranged concentrically are fixed together by a shaft 19.

One chamber narrowed by the three diaphragms becomes a high pressure chamber 17 and is connected to the high pressure tap 5, and the other chamber becomes a low pressure chamber 18 and is connected to the low pressure tap 6.

The outsides of the balance diaphragms 15 and 16 are both open to atmospheric pressure.

At the upper end 19a of the shaft 19, a water control spring 20 acts in the direction from the low pressure chamber 18 to the high pressure chamber 17.

Further, the shaft 19 is engaged with the lever 21 near the upper end 19a, and the displacement of the shaft 19 is magnified at the lever free end side due to the positional relationship with the lever fulcrum 22.

Next, the fuel pressure controller 11 has an actuator 23 that adjusts the opening degree of a control hole 24 in the gas passage, and this actuator 23 is fixed to a fuel diaphragm 25.

A fuel control spring 26 is always acting on the fuel diaphragm 25 in a direction to open the actuator 23, and the other end of the fuel control spring 26 is fitted into an internal thread of a slide body 28 that is slidable in the opening/closing direction of the actuator 23. Support screw 27
is supported by

Since the effective pressure receiving area of the fuel diaphragm 25 is designed to be approximately equal to the area of the control hole 24, the gas supply source pressure acts on the fuel diaphragm 25 to cause a force in the direction of closing the actuator 23 and a force acting on the actuator 23. This generates a force in the direction of opening the actuator 23, but since the two forces are equal and opposite in direction, as a result no force is generated to move the actuator 23.

On the other hand, the pressure supplied to the burner that has passed through the control hole 24 is acting on the actuator 23, and the position of the actuator 23 is determined by the balance point between this force and the force of the control spring 26.

If the slide body 28 does not move, the force of the fuel control spring 26 will not change, so even if the gas supply source pressure changes, the gas pressure supplied to the burner 12 will remain almost constant, just like a normal gas pressure regulator. It has the function of keeping the

Since the slide body 28 is supported by the free end of the aforementioned lever 21 in the present invention, the displacement of the lever 21 results in a change in the load on the fuel control spring 26, which in turn causes a change in gas pressure.

Reference numeral 29 is a drive unit to which the high pressure tap 5 and low pressure tap 6 of the pressure difference generator 4 are connected, and the pressure difference generates force to open and close the on-off valve 10 of the gas circuit.

This part may have the same mechanism as a normal instantaneous water heater, so a detailed explanation will be omitted.

Conventional instantaneous gas water heaters have a diaphragm that receives a pressure difference depending on the amount of water, and uses this force to open the valve in the gas circuit, but this is a safety device that prevents combustion in the event of a water outage. As shown in FIG. 2, when the water amount slightly exceeds the set value, the gas valve opens and the gas flow rate reaches the saturation value.

Therefore, a change in the amount of water directly corresponds to a change in the hot water temperature.

Also, it was necessary to set the amount of water at which the gas valve was opened to be relatively large so that a fire would not start if the amount of water was less than the boiling amount that could be calculated from the amount of water burned.

The present invention aims to make the amount of water and the amount of heat absorbed by the water proportional.

In the pressure difference generator 4 of FIG. 1, the relationship between the change ΔPw in the pressure difference between the high pressure tap 5 and the low pressure tap 60 due to the water amount change ΔΩ9 is as follows.

ΔPw−kwΔQw” (1) Here, “pregnancy” is a constant determined by the shape and dimensions of the pressure difference generating body 4 such as the constriction portion.

This water pressure is guided to the high pressure chamber 17 and low pressure chamber 18 of the force generating body 13, so if the effective area of the main diaphragm 14 is S, and the effective area of the balance diaphragms 15 and 16 is S, then the water pressure in the force generating body 13 is The change in force is as follows.

(S-s)32w ・・・・・・・・・・・・ (→
Here, if S-s is expressed as ΔS, a force change of ΔSΔ~ will occur.

This force change causes the lever 21 to change its position.

In FIG. 1, let X be the distance from the position where the shaft 19 abuts the lever to the lever fulcrum 22, and let Y be the distance from the lever fulcrum 22 to the position where the free end abuts the slide body 28.

The amount of lever movement due to the water amount change ΔQW is assumed to be Δy at the free end and ΔX at the shaft 19.

Furthermore, when the spring constant of the water control spring 20 is expressed as K and the spring constant of the fuel control spring 26 is expressed as k, the balance condition of the rotational moment acting on the lever 21 is determined as follows: ΔSΔPwX=ΔxKX+Δy ky −−−−−・
(3) Here, since the lever 21 is a rigid body, α is called the lever ratio.

Then, the third equation is ΔSΔPw=ΔxK+αΔyk, and further obtained.

Now, the movement of the free end of the lever Δy results in a change in the force of the fuel control spring 26, which in turn results in a change in the gas supply pressure to the burner 12, ΔPq.

The relationship is as follows ΔP(lA=Δyk...
(6) However, A is the effective area of the fuel diaphragm 25, which is approximately equal to the area of the control hole 240 as described above.

becomes.

It is generally known that gas pressure and gas amount have the following relationship, where Kq is a constant between them.

However, the change in gas amount is expressed as ΔQq. In this equation (8), (
Substituting equations 1) and ('i), therefore, when Qw=00, Q/(1=0), and the water amount change ΔQw and the gas amount change ΔQq become proportional.

The right side of FIG. 3 shows equation (1), and the left side shows equation (2).

Further, the right side of FIG. 4 shows the moving amounts ΔX and Δy of the lever 21 caused by the force change (S-s)32w shown in equation (2).

The left side shows the change in ΔPq due to Δy.

If the amount of gas is supplied proportionally to the amount of water supplied and the heat exchange efficiency is constant, the amount of heat absorbed by water is proportional to the amount of water supplied, and the rise in heating temperature of water is constant.

However, it is well known that heat exchange efficiency varies depending on the gas-air mixture ratio (air-fuel ratio) and the amount of combustion.

Figure 5 is a graph showing the heat exchange efficiency depending on the amount of combustion, where a is the relationship for a normal atmospheric-pressure Bunsen burner without air-fuel ratio control, and b is the relationship when the air-fuel ratio is controlled to be constant. It is.

Even if fuel is supplied proportionally to the amount of water, in a combustor with the thermal efficiency characteristics shown in Figure 5a, heat is supplied to the water at a rate greater than the rate of increase in the amount of water; Heat is supplied.

For this reason, the amount of heat absorbed by the water is no longer proportional to the increase or decrease in the amount of water, making it impossible to keep the hot water supply temperature constant.

In order to keep the temperature rise constant regardless of the amount of water supplied, this can be achieved by correcting the amount of fuel supplied relative to the amount of water supplied from a proportional relationship, taking into account heat exchange efficiency.

In other words, with the heat exchange efficiency characteristic shown in Figure 5a, when the water supply amount is small as shown in Figure 6a, it is sufficient to supply a slightly larger amount of gas than the proportional relationship to compensate for the decrease in heat exchange efficiency. If the heat exchange efficiency characteristic shown in FIG. 6 is used, it is sufficient to correct the increase in heat exchange efficiency by supplying a gas amount slightly smaller than the proportional relationship when the water supply amount is small as shown in FIG. 6.

A specific means to obtain the characteristics shown in FIG. 6a is to shorten the water control spring 20 so that the displacement of the force generator 13 is adjusted to a length X as shown in FIG. 7 even when the amount of water supplied is zero.

Keep it. Displacement X of force generator 13 when water supply amount is 0
.

is enlarged by the lever and becomes y at the free end of the lever.

Therefore, the gas supply pressure becomes P qo .

Of course, at this time, the on-off valve 10 is not open, so the gas will not burn out silently.

The amount of gas relative to the amount of water supplied is determined by equation (10). When the amount of water supplied is small, the gas amount is supplied in a proportional relationship, and when the amount of water supplied is large, the relationship is close to proportionality. Therefore, the difference in hot water temperature due to heat exchange efficiency is Corrected.

In the case of the heat exchange efficiency characteristics shown in FIG. 5, if the water control spring 20 is set long, the opposite effect to that described above will be obtained, and the characteristics shown in FIG. 6 will be obtained.

In other embodiments, the objectives of the invention may be achieved by pre-adjusting the fuel spring 26.

In other words, if the fuel spring 26 is set strongly in advance, the control pressure Pq□ will be reduced when the displacement is 0 according to the displacement-control pressure characteristics shown in Fig. 7.
can be obtained.

In yet another embodiment, as shown in FIG. 8, the object of the present invention can be achieved by changing the contact position between the shaft 19 and the lever 21 depending on the displacement of the shaft 19, that is, the change in the amount of water supplied.

That is, when the amount of water supplied is small, the shaft 19 is located downward and comes into contact with the lever 21 as shown by the solid line, and the distance from the lever fulcrum 22 is Xl. When the amount of water supplied increases, the shaft 19 moves upward and the lever 21 is moved as shown by the imaginary line. 21, and the distance is X2, and since Xl<X2, α in equation 4) with respect to the displacement of the shaft 19 of the force generator 13 gradually decreases as shown in FIG. 10. The change in Δy is as shown in (), and the control pressure is higher than the proportional relationship at low water volumes, and approaches the proportional relationship as the water volume increases (.

Another embodiment utilizes the fact that the effective pressure receiving area of the main diaphragm 14 changes depending on the diaphragm position.

As shown in FIG. 11, the effective pressure-receiving area of the diaphragm varies depending on its position, and in the case of the shape shown in FIG. 11, the effective pressure-receiving area changes as shown in FIG. 12.

Therefore, the equation (10) becomes: The proportional relationship between the amount of water supply and the amount of gas can be adjusted, and changes in thermal efficiency can be corrected.

As described above, according to the present invention, the amount of fuel is controlled almost proportionally to the amount of water supplied, and by correcting the heat exchange efficiency accompanying changes in the amount of combustion, the outlet hot water temperature can be adjusted accurately in response to changes in the amount of water supplied. Can be controlled well and consistently.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the overall configuration of an instantaneous gas water heater according to an embodiment of the present invention, Fig. 2 is a graph showing the relationship between water supply amount and gas amount of a conventional instantaneous gas water heater, and Fig. 3 is a graph showing the relationship between the water supply amount and gas amount of a conventional instantaneous gas water heater. FIG. 4 is a graph showing the relationship between the water supply amount and the differential pressure of the pressure difference generating body and the relationship between the differential pressure of the pressure difference generating body and the force of the force generating body in the embodiment of the present invention. A graph showing the relationship between the force of the force generator and the displacement of the lever, and a relationship between the displacement of the lever and the fuel control pressure. Figure 5 is a graph showing the relationship between combustion amount and heat exchange efficiency. Figure 6 is a graph showing the relationship between the combustion amount and heat exchange efficiency. FIG. 7 is a graph showing the relationship between the amount of water supply and the amount of gas in the embodiment of the invention, and FIG. Graph showing the relationship, FIG. 8 is a diagram showing the lever of the embodiment of the present invention, FIG. 9 is a graph showing the relationship between the displacement of the force generator and the lever ratio in the embodiment of FIG. are graphs showing the relationship between the force of the force generator and the displacement of the lever and the relationship between the lever displacement and the fuel control pressure in the embodiment of FIG. 8; FIG. 11 is a graph showing the change in the shape of the diaphragm; The figure is a graph showing changes in the effective pressure receiving area of the diaphragm in FIG. 11. 1... Water piping, 4... Pressure difference generator,
7... Heat exchanger, 8... Faucet, 9...
...Gas piping, 11...Fuel pressure controller, 1
3...force generator, 14...main diaphragm, 15,16°°°...balance diaphragm,
19... shaft, 20... water control spring, 21... lever, 22... lever fulcrum, 23... actuator, 25 ...Fuel diaphragm, 26...Fuel control spring,
28...Sliding body.

Claims (1)

[Claims] 1. A heat exchanger through which a fluid to be heated passes, a burner that heats the heat exchanger, a fuel pressure controller provided in a fuel supply path to the burner to control the combustion amount of the burner, and a A flow rate detector that emits a signal according to the flow rate of the heating fluid, and a control unit that controls the fuel pressure controller in response to the signal from the flow rate detector,
The system from the flow rate detector to the fuel pressure controller is configured to maintain a nearly proportional relationship between the flow rate of the flow rate to be heated and the amount of fuel supplied, and to correct the proportional relationship according to the flow rate of the fluid to be heated. A fuel supply control device characterized by: 2. The flow rate detector is mainly composed of a pressure difference generator that detects a pressure difference depending on the flow rate of the fluid to be heated, and a force generator that generates a force corresponding to this pressure difference. The fuel supply control device described in . 3. The fuel supply control device according to claim 1 or 2, wherein the proportional relationship is corrected by the flow rate by setting the fuel control spring of the fuel pressure controller. 4. The fuel supply control device according to claim 2, wherein the proportional relationship is corrected by the flow rate by setting the water control spring of the force generator. 5. A patent claim in which a force generator and a fuel pressure controller are connected via a lever mechanism, and the lever ratio of the lever mechanism is changed depending on the displacement of the force generator, so that the proportional relationship is corrected by the flow rate. 2. The fuel supply control device according to item 2. 6. The fuel supply control device according to claim 2, wherein the force generating body is mainly composed of a diaphragm, and the effective pressure receiving area is changed by the displacement of the diaphragm, so that the proportional relationship is corrected according to the flow rate.