Pre-mixing device

Abstract

The present invention provides a premixing device with a simple structure and low cost. The downstream end of the gas supply path is connected to a gas suction part provided on the air intake path connected to the burner, and includes an air impedance switching mechanism capable of switching the magnitude of the ventilation impedance of a specified part through which air in the air intake path flows. The air impedance switching mechanism is composed of a plate-like member that can rotate freely between a small impedance position where the ventilation impedance of the specified part of the air intake path is reduced and a large impedance position where the ventilation impedance is increased. When the plate-like member is in the large impedance position, a part of the plate-like member is opposed to a part of the gas suction part in a close proximity, increasing the gas suction impedance from the gas suction part. An electromagnet capable of attracting or repelling a magnetic body mounted on the plate-like member is provided outside the specified part of the air intake path where the plate-like member is provided. By energizing and exciting the electromagnet, the plate-like member is rotated to the small impedance position, and when the electromagnet is energized and excited in the reverse direction, the plate-like member is rotated to the large impedance position.

Description

Technical Field

[0001] The present invention relates to a premixing device that mixes fuel gas and air and supplies the mixture to a burner. Background Art

[0002] In the past, it has been well known that, according to Patent Document 1, as such a premixing device, there are provided: an intake passage provided with a blower connected to a burner, and a fuel gas supply passage provided with a flow control valve for supplying fuel gas. A fuel gas suction portion provided in the intake passage is connected to the downstream end of the fuel gas supply passage, so that air flowing in the intake passage is mixed with fuel gas sucked from the fuel gas suction portion. Further, in a predetermined portion where air flows in the intake passage, there is provided an air impedance switching mechanism capable of switching the magnitude of the ventilation impedance of the predetermined portion. Also, a fuel gas impedance switching mechanism is provided to switch the magnitude of the ventilation impedance of a portion of the fuel gas supply passage on the downstream side of the flow control valve.

[0003] However, in the case where a proportional valve is used as the flow control valve, the proportional valve is controlled to supply an amount of fuel gas corresponding to the required combustion amount, and the rotational speed of the blower is controlled according to the required combustion amount so that the air-fuel ratio of the mixture supplied to the burner is constant. However, when the required combustion amount is lower than a specified value, the rotational speed of the blower is lower than the lower limit rotational speed that can maintain the proportional characteristics of the air supply amount, or the proportional valve current (the current supplied to the proportional valve) is lower than the lower limit current that can maintain the proportional characteristics of the fuel gas supply amount, it is impossible to supply an amount of air and fuel gas corresponding to the required combustion amount.

[0004] In addition, sometimes a zero-pressure valve that maintains the secondary fuel gas pressure at atmospheric pressure is used as the flow control valve. In this case, the supply amount of fuel gas varies according to the pressure difference between the secondary fuel gas pressure (i.e., atmospheric pressure) and the negative pressure in the intake passage. Moreover, since the negative pressure in the intake passage varies with the rotational speed of the blower, the supply amount of fuel gas also varies with the rotational speed of the blower, that is, the supply amount of air. Therefore, the rotational speed of the blower is controlled according to the required combustion amount, thereby supplying to the burner: an amount of air and fuel gas corresponding to the required combustion amount.

[0005] Even so, once the rotational speed of the blower is lower than the lower limit rotational speed that can maintain the proportional characteristics of the air supply amount, it is impossible to supply the burner with an amount of air and fuel gas corresponding to the required combustion amount. Therefore, when the required combustion amount is lower than the specified value, it is necessary to use the air impedance switching mechanism to increase the ventilation impedance of the intake passage so that the rotational speed of the blower is not lower than the above-mentioned lower limit rotational speed, thereby enabling the supply of an amount of air corresponding to the required combustion amount below the specified value. And, merely increasing the ventilation impedance of the intake passage, since the negative pressure in the intake passage increases, the supply amount of fuel gas will exceed the amount corresponding to the required combustion amount. Therefore, in coordination with increasing the ventilation impedance of the intake passage, it is necessary to increase the ventilation impedance of the fuel gas supply passage.

[0006] Therefore, in the above prior examples, when the required combustion amount is lower than the specified value, the air flow resistance switching mechanism is used to increase the air flow resistance of the intake passage, and at the same time, the gas flow resistance switching mechanism is used to increase the air flow resistance of the gas supply passage, thereby serving as a low-capacity state, and it is possible to supply an amount of air and gas corresponding to the required combustion amount below the specified value. When the combustion amount is higher than the specified value, the air flow resistance switching mechanism is used to reduce the air flow resistance of the intake passage, and at the same time, the gas flow resistance switching mechanism is used to reduce the air flow resistance of the gas supply passage, thereby restoring to the high-capacity state.

[0007] Here, in the premixing device described in Patent Document 1, the air flow resistance switching mechanism is constituted by the following butterfly valve, that is, the butterfly valve can rotate between an open position parallel to the length direction of the above-mentioned specified portion in the intake passage and a closed position orthogonal to the length direction. The gas flow resistance switching mechanism is constituted by a switching valve provided to be capable of opening and closing freely in the gas supply passage. And, in the description of Patent Document 1, in addition to the butterfly valve, it is also necessary to provide: a motor for driving the butterfly valve to rotate, a switching valve, and a linkage mechanism that is linked to the rotation of the butterfly valve between the open position and the closed position and causes the switching valve to perform opening and closing operations. As a result, the structure becomes complex and the cost becomes high.

[0008] Patent Document

[0009] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2015 - 230113 Summary of the Invention

[0010] The present invention has been completed in view of the above problems, and its object is to provide a premixing device with a simple structure and low cost.

[0011] In order to solve the above problems, a premixing device of the present invention is used to mix fuel gas and air and supply the mixture gas to a burner. The premixing device includes: an air inlet passage provided with a blower connected to the burner, and a fuel gas supply passage provided with a flow regulating valve for supplying fuel gas. A fuel gas suction part provided on the air inlet passage is connected to the downstream end of the fuel gas supply passage to mix the air flowing in the air inlet passage with the fuel gas sucked from the fuel gas suction part. Moreover, at a specified part where the air flows in the air inlet passage, there is provided: an air impedance switching mechanism capable of switching the magnitude of the ventilation impedance of the specified part. The air impedance switching mechanism is composed of a plate-shaped member, and the plate-shaped member can rotate freely between a small impedance position where the ventilation impedance of the specified part of the air inlet passage is reduced and a large impedance position where the ventilation impedance is increased. When the plate-shaped member is in the large impedance position, a part of the plate-shaped member is opposed to a part of the fuel gas suction part in a close proximity manner, so that the fuel gas suction impedance from the fuel gas suction part becomes larger. And, a magnetic body is installed on the plate-shaped member, and at the same time, an electromagnet is provided outside the specified part of the air inlet passage where the plate-shaped member is provided. The installation position of the magnetic body on the plate-shaped member is set such that when the plate-shaped member is in the large impedance position state and the electromagnet is energized and magnetized, the magnetic body is attracted or repelled by the electromagnet, causing the plate-shaped member to rotate towards the small impedance position. When the plate-shaped member is in the small impedance position state and the electromagnet is energized in the opposite direction to the above-mentioned energization and magnetization, the magnetic body is repelled or attracted by the electromagnet, causing the plate-shaped member to rotate towards the large impedance position.

[0012] According to the present invention, when the plate-shaped member is in the large impedance position, since the fuel gas suction impedance from the fuel gas suction part can be increased by the plate-shaped member itself, there is no longer a need for the switching valve and the linkage mechanism of the fuel gas impedance switching mechanism in the prior art example. Therefore, the structure becomes simple. In addition, a magnetic body and an electromagnet, which are cheaper than a motor, are used as the rotation driving source of the plate-shaped member. Compared with the premixing device in the prior art example, a significant reduction in cost can be achieved. Description of the Drawings

[0013] Figure 1 It is a sectional side view of the premixing device according to the embodiment of the present invention.

[0014] Figure 2 It is a perspective view of the premixing device according to the embodiment.

[0015] Figure 3 It is a perspective view of the plate-shaped member in the premixing device according to the embodiment.

[0016] Description of the Reference Numerals

[0017] A... Premixing device, 1... Burner, 2... Blower, 3... Intake passage, 3a... Specified portion of the intake passage, 31... Gas suction portion, 4... Gas supply passage, 6... Flow regulating valve, 8... Plate-like member, 85... Magnetic body, 9... Electromagnet. Detailed implementation

[0018] Refer to Figure 1 , 1 is a burner composed of a full-premix combustion burner or the like, and the full-premix combustion burner has a combustion surface 1a for ejecting and burning the mixed gas. And, according to the premixing device A of the embodiment of the present invention, gas and air are mixed, and the mixed gas is supplied to the burner 1.

[0019] The premixing device A has: an intake passage 3 provided with a blower 2 connected to the burner 1, and a gas supply passage 4 for supplying gas. Upstream of the gas supply passage 4, a primary valve 5 and a flow regulating valve 6 composed of a proportional valve or a zero-pressure valve are provided. In addition, the gas suction portion 31 provided on the intake passage 3 is connected to the downstream end of the gas supply passage 4. And, the air flowing in the intake passage 3 is mixed with the gas sucked from the gas suction portion 31 to generate a mixed gas, and this mixed gas is supplied to the burner 1 via the intake passage 3. Moreover, an air impedance switching mechanism capable of switching the magnitude of the ventilation impedance of the specified portion 3a is provided in the specified portion 3a where the air flows in the intake passage 3. In addition, in the embodiment of the present invention, although the specified portion 3a of the intake passage 3 is located upstream of the blower 2, the specified portion 3a may also be located downstream of the blower 2.

[0020] If described more specifically, two-layer cylinders 7in and 7out formed of a non-magnetic body such as synthetic resin are provided, and the internal space of the inner cylinder 7in is used as the specified portion 3a of the intake passage 3. A gas inlet 41 connected to the gas supply passage 4 is provided by opening on the circumferential wall of the outer cylinder 7out. In addition, a gas chamber 42 connected to the gas inlet 41 is formed between the inner circumferential surface of the outer cylinder 7out and the outer circumferential surface of the inner cylinder 7in. And, on the circumferential wall of the inner cylinder 7in, a gas suction portion 31 that connects the intake passage 3 inside the inner cylinder 7in and the gas chamber 42 is provided. The gas suction portion 31 is composed of a pair of first suction holes 31a and second suction holes 31b, and the gas from the gas supply passage 4 is sucked into the intake passage 3 via the suction holes 31a and 31b. In addition, in the present embodiment, although the cylinders 7in and 7out are arranged in an upright posture, they may also be arranged in a horizontal posture.

[0021] A plate-like member 8 constituting an air impedance mechanism is also provided inside the inner cylinder 7in. As Figure 3As shown, the plate-like member 8 includes: a semi-circular impedance plate portion 81 at one end, a balance weight portion 82 at the other end, an elongated connecting rod portion 83 connecting the impedance plate portion 81 and the balance weight portion 82, and a shaft portion 84 orthogonal to the connecting rod 83 and axially supported by being inserted through the circumferential wall of the inner cylinder 7in. And the plate-like member 8 can rotate freely between the following two positions with the shaft portion 84 as the center, that is: a small impedance position where the impedance plate portion 81 can reduce the ventilation impedance of the specified portion 3a along the length direction of the intake passage 3 of the inner cylinder 7in ( Figure 1 the position shown by the solid line), and a large impedance position where the impedance plate portion 81 is orthogonal to the length direction of the specified portion 3a of the intake passage 3 of the inner cylinder 7in and can increase the ventilation impedance of the specified portion 3a ( Figure 1 the position shown by the imaginary line).

[0022] Refer to Figure 2 , a wall thickness portion 71 extending from the middle portion in the vertical direction of the air flow direction to the lower side is provided at a circumferential position on the inner peripheral surface of the inner cylinder 7in. And when the plate-like member 8 rotates to the large impedance position, the step 71a at the upper end of the wall thickness portion 71 abuts against the edge of the impedance plate portion 81. Moreover, a small protrusion 72 protruding radially inward is provided at the lower part of the wall thickness portion 71, and when the plate-like member 8 rotates to the small impedance position, the small protrusion 72 abuts against the balance weight portion 82.

[0023] The above-mentioned second suction hole 31b is formed in a portion adjacent to the step 71a. Therefore, when the plate-like member 8 is in the large impedance position, the edge of the impedance plate portion 81 abutting against the step 71a will be opposed to a part of the gas suction portion 31, that is, the second suction hole 31b, in close proximity, and the second suction hole 31b is actually blocked, and the gas suction impedance from the gas suction portion 31 will become larger. Therefore, without providing the above-mentioned conventional gas impedance mechanism, that is, the switching valve, the increase in the negative pressure in the intake passage 3 caused by the rotation of the plate-like member 8 to the large impedance position can prevent the increase in the gas supply amount.

[0024] In addition, a magnetic body 85 made of a permanent magnet or the like is installed on the plate-like member 8. In addition, an electromagnet 9 is installed on the outer surface of the outer cylinder 7out, which is the outside of the specified portion 3a of the intake passage where the plate-like member 8 is provided. In addition, the electromagnet 9 is composed of a coil 92 wound around a bobbin 91 and a fixed iron core 93 inserted into the inner circumference of the bobbin 91.

[0025] The installation position of the magnetic body 85 on the plate-like member 8 is set such that when the plate-like member 8 is in the high-impedance position state and the electromagnet 9 is energized and excited, the magnetic body 85 is attracted by the electromagnet 9 and causes the plate-like member 8 to rotate towards the low-impedance position. When the plate-like member 8 is in the low-impedance position state and the electromagnet 9 is energized and excited in the opposite direction to the above-mentioned energization and excitation, the magnetic body 85 is repelled by the electromagnet 9 and causes the plate-like member 8 to rotate towards the high-impedance position. Specifically, the magnetic body 85 is installed at a portion of the impedance plate portion 81 that faces the installation portion of the electromagnet 9 in the low-impedance position.

[0026] According to the above structure, when the plate-like member 8 is in the high-impedance position, the gas suction impedance from the gas suction portion 31 can be increased by the plate-like member 8 itself. Therefore, neither the switching valve nor the linkage mechanism of the gas impedance switching mechanism of the above-mentioned conventional example is required, and the structure becomes simple. In addition, a magnetic body 85 and an electromagnet 9, which are cheaper than a motor, are used to rotate the plate-like member 8 between the low-impedance position and the high-impedance position. Coupled with the simple structure, the cost can be significantly reduced compared to the conventional pre-mixing device.

[0027] In addition, when the plate-like member 8 is in the high-impedance position state, the Figure 1 counterclockwise rotational torque acting on the plate-like member 8 due to the weights of the impedance plate portion 81 and the magnetic body 85 is greater than the Figure 1 clockwise rotational torque acting on the plate-like member 8 due to the weight of the balance weight portion 82. Therefore, after the plate-like member 8 is switched to the high-impedance position, even if the power supply to the electromagnet 9 is stopped, in the region where the rotational speed of the blower 2 is low, the plate-like member 8 is held in the high-impedance position. However, once the rotational speed of the blower 2 exceeds the specified rotational speed, due to the influence of the wind pressure acting on the impedance plate portion 81, the impedance plate portion 81 will float up from the step 71a, and the posture of the plate-like member 8 will become unstable. Therefore, when the rotational speed of the blower 2 exceeds the specified rotational speed when the plate-like member 8 is in the high-impedance position state, the plate-like member 8 can be switched to the low-impedance position by energizing and exciting the electromagnet 9.

[0028] As described above, the embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited thereto. For example, the installation position of the electromagnet 9 can also be offset to be more Figure 1At a position lower than that, a magnetic body is installed on the balance weight portion 82. In this case, when the plate-like member 8 is in the high impedance position state and the electromagnet 9 is energized and excited, the magnetic body will be repelled by the electromagnet 9 and cause the plate-like member 8 to rotate to the low impedance position. When the plate-like member 8 is in the low impedance position state and the electromagnet 9 is energized and excited in the opposite direction to the above-mentioned energization and excitation, the magnetic body will be attracted by the electromagnet 9 and cause the plate-like member 8 to rotate to the high impedance position. In addition, when magnetic bodies are installed on both the impedance plate portion 81 and the balance weight portion 82, when the plate-like member 8 is in the high impedance position state and the electromagnet 9 is energized and excited, the attractive force of the electromagnet 9 will act on the magnetic body on the impedance plate portion 81, and at the same time, the repulsive force from the electromagnet 9 will also act on the magnetic body on the balance weight portion 82, so that the plate-like member 8 rotates to the low impedance position; when the plate-like member 8 is in the low impedance position state and the electromagnet 9 is energized and excited in the opposite direction to the above-mentioned energization and excitation, the repulsive force from the electromagnet 9 will act on the magnetic body on the impedance plate portion 81, and at the same time, the attractive force from the electromagnet 9 will also act on the magnetic body on the balance weight portion 82, so that the plate-like member 8 rotates to the high impedance position.

[0029] In addition, in the above-described embodiment, although the balance weight portion 82 is provided at the end portion on the opposite side of the impedance plate portion 81 of the plate-like member 8, an impedance plate portion may be provided at the end portion on the opposite side. Once the plate-like member 8 temporarily rotates to the high impedance position, as long as the electromagnet 9 is not energized and excited, due to the influence of the wind pressure acting on the impedance plate portion, regardless of the rotational speed of the blower, the plate-like member 8 is held at the high impedance position.

Claims

1. A premixing device for mixing fuel gas and air and supplying the mixture gas to a burner. The premixing device includes: an air inlet passage provided with a blower connected to the burner, and a fuel gas supply passage provided with a flow regulating valve for supplying fuel gas. A fuel gas suction part provided on the air inlet passage is connected to the downstream end of the fuel gas supply passage, so that the air flowing in the air inlet passage is mixed with the fuel gas sucked from the fuel gas suction part. In addition, an air impedance switching mechanism capable of switching the magnitude of the ventilation impedance of a specified part is provided at a specified part where the air flows in the air inlet passage. It is characterized in that There is a two-layer cylinder body composed of an inner cylinder body and an outer cylinder body provided on the intake passage, and the inner space of the inner cylinder body is used as the specified part of the intake passage. A gas inlet connected to the gas supply passage is provided on the circumferential wall of the outer cylinder body. A gas chamber connected to the gas inlet is formed between the inner circumferential surface of the outer cylinder body and the outer circumferential surface of the inner cylinder body. First suction ports and second suction ports serving as gas suction parts for communicating the intake passage in the inner cylinder body and the gas chamber are provided on the circumferential wall of the inner cylinder body. The air impedance switching mechanism is composed of a plate-like member that can rotate freely between a small impedance position where the ventilation impedance of the specified part of the intake passage is reduced and a large impedance position where the ventilation impedance is increased. When the plate-like member is in the large impedance position, a part of the plate-like member is opposed to the first suction port in proximity, increasing the gas suction impedance from the gas suction part. Moreover, a magnetic body is installed on the plate-like member, and an electromagnet is provided outside the specified part of the intake passage where the plate-like member is provided. The installation position of the magnetic body on the plate-like member is set such that when the electromagnet is energized and excited in the state where the plate-like member is in the large impedance position, the magnetic body is attracted or repelled by the electromagnet, causing the plate-like member to rotate towards the small impedance position; when the electromagnet is energized and excited in the opposite direction to the above-mentioned energization and excitation in the state where the plate-like member is in the small impedance position, the magnetic body is repelled or attracted by the electromagnet, causing the plate-like member to rotate towards the large impedance position.

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