JPH0336423A - Overheat prevention system of combustion device - Google Patents

Abstract

PURPOSE:To make it possible to use equal microcomputers for all kinds of combustion devices having different overheat judgement levels by providing the arrangement such that temperature levels to judge abnormal overheat states can be optionally set using values of overheat judgement level set resistor provided outside a microcomputer. CONSTITUTION:Voltages which are determined by resistors 9, 10 are inputted into an analogue input terminal 11 so as to be taken into a microcomputer 1 as overheat judgement levels. And temperatures of heat exchangers of a hot-air heater are detected by a temperature sensor 4, which temperatures are taken into an analogue input terminal 8 of the microcomputer 1 through detected temperature signal input resistors 5, 6 as detected temperature signals. In the microcomputer 1, when the detected temperatures exceed overheat judgement levels, it is judged that an abnormal overheat state has occurred and combustion suspension command is outputted to a burner 2 to cut off fuel, while, in a normal state, revolution number control commands to control a convection blower 3 to revolution corresponding to the detected temperatures are outputted from the microcomputers 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an overheat prevention device for a combustion device such as a hot air heater.

[Prior Art] Fig. 2 is a schematic configuration diagram showing a conventional overheating prevention device for a hot air heater. In the figure, (1) is a microcomputer for controlling the hot air heater, (2) is a burner (3). is a convection blower, (4) is a temperature sensor attached to the heat exchanger part of burner (2), (5) and (6) are resistors for inputting the detected temperature signal, (7) is a DC power supply, (8) ) is an analog input terminal.

Next, its operation will be explained. The temperature of the heat exchanger of the warm air heater is detected by the temperature sensor (4), and the detected temperature signal is input to the resistors (5) and (6).
) from the analog input terminal (8) of the microcomputer (1). The relationship between the temperature of the heat exchanger and the voltage at the analog input terminal (8) is as shown in FIG. Normally, this heat exchanger temperature input is used to control the rotational speed of the convection blower (3) so that the heat exchanger does not become overheated. In other words, if the heat exchanger temperature is 60℃, the rotation speed of the convection blower is 2000rp+i
, 2500 rpm at 80℃, 3000 rpm at 100℃
A rotation speed control command, such as rpm, for controlling the rotation speed to a rotation speed corresponding to the temperature detected by the temperature sensor (4) is output from the microcomputer (1) to the convection blower (3). In this way, when the heat exchanger temperature rises, the rotational speed of the convection blower (3) increases, the convection speed of heated hot air increases, and a sudden rise in the heat exchanger temperature is prevented. Incidentally, the temperature input to this heat exchanger is also used as a temperature signal for preventing abnormal overheating of the hot air heater. In other words, when the temperature of the heat exchanger reaches a predetermined temperature level programmed in the ROM of the microcomputer (1), for example, 150°C or higher, it is determined that an abnormal overheating condition has occurred, and the microcomputer (1>) switches the burner (2>). In response, a combustion stop command is output and combustion is stopped.

[Problems to be Solved by the Invention] Conventional overheating prevention devices for combustion equipment are configured as one or more, and the temperature level for determining the overheating state is set as a fixed value in the microcomputer (1). .

By the way, warm air heaters are manufactured and sold in several types, mainly with different heating capacities, in response to user needs, but most of the control specifications, that is, the microcomputer (1) programs, can be shared. It is something.

However, the temperature level for determining the overheating state mentioned above is
Since the heating capacity and shape of hot air heaters vary, the fixed temperature level set in the microcomputer (1) is often optimal for one model but cannot be used for another model. . This problem can be solved by changing the values of the detection temperature signal input resistors (5) and (6) and adjusting the relationship between the temperature of the temperature sensor (4) and the voltage to the analog input terminal (8). Even if an attempt is made to do so, this temperature signal is also used to control the rotation speed of the convection blower (3), and this would affect that control, so it cannot be implemented.

In other words, although most control specifications can be shared, the temperature level for determining overheating is different, so a dedicated microcomputer must be created for each hot air heater model. This invention was made in order to solve the above-mentioned conventional problems, and it is possible to use the same microcomputer for all types of warm air heaters, that is, for various overheating judgment levels. The object of the present invention is to provide an overheat prevention device for a combustion device.

[Means for Solving the Problems] The overheating prevention device for a combustion device according to the present invention is a superheating prevention device in which a voltage for setting a temperature level for overheating state determination is inputted to the outside of the microcomputer in the above-mentioned overheating prevention device. A resistor for setting the judgment level is provided.

[Function] In the overheating prevention device for a combustion device of the present invention, a temperature level arbitrarily set by a resistor for setting an overheating judgment level is input to a microcomputer, and only the overheating judgment level is compared with other detected temperatures and convective temperatures. It is set independently, leaving the relationship with the blower rotation speed unchanged. Therefore, it is possible to use the same microcomputer for various types of combustors having different overheat determination levels.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a schematic configuration diagram showing an embodiment of the present invention. In the figure, (1) is a microcomputer, (2) is a burner, (3) is a convection blower, and (4) is a heat exchanger for burner (2). Temperature sensor attached to the organ (5),
(6) is a resistor for inputting a detected temperature signal, (7) is a DC power supply, and (8) is an analog input terminal, which are the same as in the conventional example. (9) and (10) are overheat judgment level setting resistors that set the overheat judgment level.
), (10) is input to the analog input terminal (11) and taken into the microcomputer (1) as an overheating determination level. In addition, the temperature of the heat exchanger of the hot air heater is detected by a temperature sensor (4), and a detected temperature signal input resistor (5) is used as a detected temperature signal.
), (6) from the analog input terminal (8) of the microcomputer (1). In the microcomputer (1), when the detected temperature exceeds the overheating determination level, it is determined that there is an abnormal overheating state, and the burner (2) is
), a combustion stop command is output to stop combustion.

on the other hand.

During normal operation, as described above, the microcomputer (1) outputs a rotation speed control command to control the convection blower (3) to a rotation speed corresponding to the detected temperature.

In one or more of the embodiments, a hot air heater is used as the combustion device, but it goes without saying that the present invention can be applied to other combustion devices.

[Effects of the Invention] As described above, according to the present invention, the temperature level at which an abnormal overheating state is determined can be arbitrarily set by the value of the overheating determination level setting resistor outside the microcomputer. The same microcomputer can be used for all types of combustion devices with different overheat determination levels. In other words, it eliminates the waste of manufacturing multiple types of microcomputers that differ only in the overheating judgment level for each combustion equipment model, and is completely common in all other respects, and has the effect of providing a standardized and low-cost overheating prevention device for combustion equipment. .

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, and FIG. 2 is a schematic diagram showing an overheating prevention device for a conventional warm air heater.
FIG. 3 is a temperature-voltage characteristic diagram of the heat exchanger temperature sensor. In the figure, (1) is a microcomputer, (2) is a burner, (3) is a convection blower, and (4) is a burner (
2) Temperature sensor (5) attached to the heat exchanger section
, (6) is the detected temperature fi-j) input resistor 1. (
9) and (10) are resistors for setting the overheating determination level. The same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] A temperature sensor that detects the temperature of the burner heat exchanger, a convection blower that circulates heated hot air, and a rotation speed control that inputs the temperature signal detected by the temperature sensor and controls the rotation speed to correspond to the detected temperature. In an overheating prevention device for a combustion device, the overheat prevention device is provided with a microcomputer that outputs a command to the convection blower, and determines an overheating state when the temperature detected by the temperature sensor exceeds a predetermined temperature level, and outputs a combustion stop command to the burner. An overheat prevention device for a combustion device, characterized in that the microcomputer is provided with an overheat determination level setting resistor for inputting a voltage for setting the predetermined temperature level for overheat determination.