JPS63176920A - Exhaust device for combustion apparatus - Google Patents

Abstract

PURPOSE:To supply the stabilized amount of air and obtain the optimum air-fuel ratio, by controlling the driving current and the number of rotation of a fan motor automatically to keep the work done of the fan motor constant. CONSTITUTION:A current control circuit 8 compares a number-of-rotation control voltage 5, outputted from a micro-computer control circuit 9, with the output voltage of a current detecting circuit 7 and controls an electric power control circuit 4 so as to keep current, flowing through the current detecting circuit 7, constant. A micro-computer control circuit 9 reads information on the amount of combustion, operates the rotating number of an exhaust fan, which is determined by a formula related to a preset amount of combustion and the amount of supplied air, and controls the number-of-rotation control voltage 5 so that the number of rotation, read out of the output of the rotating number detecting device 2, becomes equal to the number of rotation operation by the circuit 9, whereby the fan motor 1 may be driven in constant rotation. The fan motor 1, driven by a constant rotation torque, achieves a constant work done and the exhaust fan is operated also by a constant work done, therefore, the stabilized amount of air may be supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an exhaust system for a combustion appliance that automatically controls the workload of an exhaust fan.

2. Description of the Related Art In general, combustion appliances that use gas, oil, or the like as fuel and have a relatively large amount of combustion do not rely on natural convection for exhaust, but are forced to exhaust using an exhaust fan. Among them, for those that vary the combustion amount, so-called air-fuel ratio control is performed, which controls the combustion amount and the amount of supplied air to an appropriate ratio. Speed control that automatically controlled by feedback of rotation speed was common.

Figure 3 is a configuration diagram of a conventional exhaust system for a combustion appliance using speed control, in which 1 is a fan motor for rotating the exhaust fan, 2
3 is a rotation speed detection device for detecting the rotation speed of the fan motor; 3 is a rotation speed detection device that compares the rotation speed control voltage with the output voltage of the rotation speed detection device and controls the power control circuit to keep the rotation speed of the fan motor constant. 4 is a power control circuit that is controlled by the output of the rotation speed control circuit and controls the power supplied to the fan motor.

5 is a rotation speed control voltage, which controls the rotation speed of the fan motor 1 and also controls the combustion amount, and adjusts the voltage distribution ratio so that the ratio between the fan motor rotation speed and the combustion amount is appropriate, and adjusts the air-fuel ratio. Take control. 6 indicates a power supply circuit.

Problems to be Solved by the Invention However, in the conventional configuration, since the rotation speed is controlled to be constant, the torque of the fan motor, which is the power source, fluctuates due to uncontrolled load fluctuations on the exhaust fan, and the work of the fan motor is affected. There was a problem in that the amount of air to be supplied fluctuated, and therefore the amount of work of the exhaust fan also fluctuated, making the amount of supplied air unstable.

Figure 4 shows the number of revolutions (N) on the vertical axis, which explains the operation of the exhaust fan.
), in which the horizontal axis represents the torque (T), 41 is the fan characteristic under normal load, and 42 and 43 are the fan characteristics under load fluctuation. In general, the amount of work of a rotating body is proportional to the product of torque and number of rotations, and the amount of work P is the number of rotations N,) Using the torque T1 coefficient Kp, P=Kp-T-N...・
It can be expressed as (1). 44 is the characteristic calculated based on the above-mentioned formula (1) and displayed when the amount of work is constant.
5 shows the control characteristics when the rotational speed is constant. Intersection P2 between characteristic 42 and characteristic 45 and intersection P3 between characteristic 43 and characteristic 45
Both deviate from characteristic 44, indicating that the amount of work fluctuates in response to load fluctuations.

Furthermore, since the ratio between the rotational speed of the fan motor 1 and the amount of combustion is fixed, there is a problem in that it is difficult to obtain the optimum air-fuel ratio over the entire variable range of the amount of combustion.

How does the present invention solve the above problems? Automatically controls the drive current and rotation speed of the unmotor to keep the amount of work constant.
It is an object of the present invention to provide an exhaust system for a combustion appliance that can supply a stable amount of air and obtain an optimum air-fuel ratio over the entire variable range of combustion amount.

Means for Solving the Problems In order to achieve the above object, an exhaust system for a combustion appliance according to the present invention includes a fan motor for rotating an exhaust fan, a current detection circuit for detecting a drive current of the fan motor, and a current detection circuit for detecting a drive current of the fan motor. a current control circuit that compares the output voltage of the current detection circuit with a rotation speed control voltage that determines the rotation speed of the fan motor, and controls a power control circuit to keep the drive current of the fan motor constant; A power control circuit that is controlled by the output of the current control circuit and controls power supplied to the fan motor, a rotation speed detection device that detects the rotation speed of the fan motor, and a rotation speed detection device that detects the rotation speed of the fan motor. It reads the output and the combustion amount information that controls the combustion amount, and controls and outputs the rotation speed control voltage so that the rotation speed of the exhaust fan determined by the preset relational expression between the combustion amount and the amount of supplied air is obtained. This configuration includes a microcomputer control circuit.

According to the above-described configuration, the fan motor is driven at a constant current and has a constant torque characteristic, and is also driven at a constant rotation and has a constant speed characteristic, so that the fan motor is operated at a constant workload and the exhaust fan is also driven at a constant speed. Constant work volume9, supplying a stable amount of air against load fluctuations. Furthermore, since the 7 ammonitor rotational speed is determined by arithmetic processing of the combustion amount information by the microcomputer control circuit, it is possible to easily realize the optimum air-fuel ratio over the entire variable range of the combustion amount.

Embodiment FIG. 1 is a block diagram showing an embodiment of the present invention. Components having the same functions as those in FIG. 3, which is a block diagram of a conventional exhaust system for a combustion appliance using speed control, are given the same reference numerals. , a detailed explanation will be omitted and the explanation will focus on the different parts. 7 is a current detection circuit, 8 is a current control circuit, and 9 is a microcomputer control circuit. The current control circuit 8 compares the rotation speed control voltage 5 output from the microcomputer control circuit 9 and the output voltage of the current detection circuit 7, and controls the power control circuit 4 to keep the current flowing through the current detection circuit 7 constant. Control as follows. The microcomputer control circuit 8 reads the combustion amount information, calculates the rotation speed of the exhaust fan determined from a preset relational expression between the combustion amount and the amount of supplied air, and the rotation speed read from the output of the rotation speed detection device 2 corresponds to the above calculation. The rotation speed control voltage 5 is controlled to be equal to the rotation speed, and the fan motor 1 is driven at a constant rotation speed.

Figure 5 is an example of a characteristic diagram showing the characteristics of a fan motor.The torque (T) on the horizontal axis is uniquely determined by the drive current (R) on the vertical axis, so if the fan motor 1 is driven at a constant current, it will drive at a constant torque. The fan motor 1 driven at constant rotation and constant torque has a constant work load as shown in equation (1) above,
The exhaust fan also operates at a constant work volume, so it supplies a stable amount of air.

Next, the operation of the microcomputer control circuit will be explained using the flowchart shown in FIG. The microcomputer control circuit is started repeatedly by a timer and constantly monitors the status of the equipment. When the start is applied, the combustion amount data that controls the combustion amount is read in step 21, and in step 22, the exhaust fan is selected to obtain the optimum air-fuel ratio from the preset relational expression between the combustion amount and the supply air amount. Determine the rotation speed Ng by calculation. In step 23, the rotation speed N of the calculation result is
The rotational speed control voltage Vc is calculated based on g and is output. In step 24, the actual rotation speed Nd of the fan motor 1 is read from the output of the rotation speed detection device 2, and in step 25, the deviation (Ns - Nd) between the Ns and Nd is calculated,
If the deviation is within the dead zone ΔNd, the process proceeds to step 26 and the rotational speed control voltage Vc is maintained. In step 25, the deviation (N
sNd) exceeds the dead band ΔNd, the process proceeds to step 27, corrects the rotation speed control voltage in proportion to the deviation, and repeats steps 23.24.25.27 i#,! The deviation is driven into the dead zone while checking the correction effect, and the speed is controlled so that Nd becomes equal to Ns.

Effects of the Invention As is clear from the above embodiments, the present invention drives the fan motor at a constant torque by automatically controlling the drive current of the fan motor, and the fan motor rotation speed is determined by the microcomputer control unit based on the combustion amount information. Since the configuration is such that the speed is controlled based on the calculated result, the fan motor is driven with a constant amount of work, and the exhaust fan is also operated with a constant amount of work, thereby supplying a stable amount of air against load fluctuations. In addition, if the relationship between the combustion amount and the air supply amount is set in detail, the fan motor rotation speed will accurately correspond to the combustion amount, making it easy to obtain the optimum air-fuel ratio over the entire combustion amount variable range. Accordingly, it is possible to realize an exhaust system for a combustion appliance that has the following effects.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a flowchart showing an example of a program of a microcomputer control circuit, Fig. 3 is a block diagram showing a conventional example, and Fig. 4 shows the operation of an exhaust fan. FIG. 5 is a characteristic diagram showing the characteristics of the fan motor. 1... Fan motor, 2... Rotation speed detection device, 3... Rotation speed control circuit, 4...
・Power control circuit, 7...Current detection circuit, 8...
...Current control circuit, 9...Microcomputer control circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 4 (bottom) Figure 5 (T)

Claims (1)

[Claims] Comparing a fan motor for rotating an exhaust fan, a current detection circuit that detects a drive current of the fan motor, and an output voltage of the current detection circuit and a rotation speed control voltage that determines the rotation speed of the fan motor, a current control circuit that controls the power control circuit to keep the drive current of the fan motor constant; a power control circuit that is controlled by the output of the current control circuit and controls the power supplied to the fan motor; A rotation speed detection device for detecting the rotation speed of the fan motor and combustion amount information for controlling the output of the rotation speed detection device and combustion amount are read, and a preset combustion amount and supply air amount are determined. An exhaust system for a combustion appliance that is equipped with a microcomputer control circuit that controls and outputs a rotation speed control voltage so that the rotation speed of an exhaust fan determined by a relational expression is obtained.