JPH0486410A - Air/fuel ratio controller - Google Patents

Abstract

PURPOSE:To easily control an air/fuel ratio without labor in manufacture by outputting a dynamic brake signal to a dynamically braking circuit from a central controller when the rotating speed of a DC motor is fallen to reduce an air amount in a combustion chamber, and dynamically braking the motor by the braking circuit. CONSTITUTION:When present rotating speed of a DC motor 10 is reduced to a target speed to reduce an air flow rate, a central controller 16 inputs the present speed of the motor 10, and outputs an air flow rate regulation signal to a DC motor drive power source 22 corresponding to a difference between the target speed and the present speed. Simultaneously, a dynamic brake signal of a high level is output to the base of a transistor 28 of a dynamically braking circuit 24. Thus, the source 22 applies a DC voltage corresponding thereto to the motor 10 to reduce the speed of the motor 10 toward the target speed. On the other the opening of a gas flow control valve 6 is immediately controlled by the controller 16 to reduce gas amount, and an air/fuel ratio in a combustion chamber 4 is greatly controlled constantly at an excellent timing.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an air-fuel ratio control device.

(Prior art and its problems) For example, as an air-fuel ratio control device in the combustion chamber of a bathtub, gas II adjustment, which is a fuel adjustment means, is used according to the load applied to the combustion chamber, that is, the amount of hot water, the temperature of hot water, etc. Some systems control valves to increase or decrease the amount of fuel supplied, and also drive a blower fan, which is an air amount adjustment means, to increase or decrease the amount of air blown, thereby keeping the air-fuel ratio constant.

FIG. 2 is a schematic block diagram of a conventional example of such an air-fuel ratio control device. This air-fuel ratio control device 2 controls the combustion chamber 4 at a constant air-fuel ratio.
The amount of gas 8, which is a fuel, is increased or decreased from a gas amount adjustment valve 6, which is a gas amount adjustment means, and the amount of air 14 blown is controlled by a blower fan 12, which is an air amount adjustment means, driven by a DC motor 10. It is an attempt to increase or decrease.

The above air-fuel ratio control device 2 includes a central control circuit 16 consisting of a microcomputer, an air amount control circuit 18,
This includes a gas amount control circuit 20. The central control circuit 16 detects and inputs the oxygen concentration from an oxygen sensor (not shown) provided in the combustion chamber 4, and also controls the DC motor lO.
The current rotational speed is detected and inputted from the rotational speed detection means (not shown), and the amount of air blown to maintain a constant air-fuel ratio, that is, the target rotational speed, is set based on the gas amount and oxygen concentration, and the set target rotational speed is set. The current rotation speed is compared with the current rotation speed, and the rotation of the DC motor 10 is controlled according to the comparison,
For this purpose, an air amount adjustment signal corresponding to the comparison is output to the air amount control circuit 18, and the gas amount control circuit 20 is used to control the amount of gas in the combustion chamber 4 according to the air-fuel ratio. A corresponding gas amount adjustment signal is output for each.

The air amount control circuit 18 is connected to the DC motor drive power source 2.
2 and the DC motor 10. The DC motor drive power supply 22 applies a DC voltage to the DC motor 10 in response to the input of the air amount adjustment signal from the central control circuit 16, thereby rotating the DC motor IO.

The gas amount control circuit 20 is configured to adjust the opening degree of the gas amount adjustment valve 6 in response to the input of the gas amount adjustment signal.

Of the gas amount and air amount that determine the air-fuel ratio, the control operation of the air-fuel ratio using the air amount will be described with reference to FIG. In Fig. 3, time is plotted on the horizontal axis, and (a) in the figure shows the waveform of the drive signal for the waste amount adjustment valve 6, (b) shows the waveform of the DC motor power supply, and (C) shows the waveform of the DC motor power supply. The number of revolutions is shown respectively.

If you want to reduce the gas amount in the combustion chamber 4 by reducing the opening degree of the gas amount adjustment valve 6 from HO to Hl (<HQ) to lower the bath water temperature, etc., the air-fuel ratio must be kept constant. It is necessary to reduce the amount of gas while maintaining the amount of gas. Therefore,
The amount of air in the combustion chamber 4 must also be reduced in proportion to the reduction in the amount of gas.

Therefore, the current rotational speed of the DC motor 10 at time to is rO, and the rotational speed (target rotational speed) rl (<ro
), the central control circuit 16 inputs the current rotation speed ro of the DC motor 10, and also controls the DC motor according to the difference between the target rotation speed rl and the current rotation speed rO. An air amount adjustment signal is output to the drive power source 22.

As a result, the DC motor drive power supply 22 correspondingly applies a DC voltage that has decreased from 0 to Vl (<VO) to the DC motor lO, thereby reducing the rotation speed of the DC motor 10 to the target rotation speed r1. let

In this way, the rotational speed of the DC motor IO reaches the target rotational speed r1, the amount of air blown is adjusted, and the air-fuel ratio in the combustion chamber 4 is controlled to be constant.

However, according to the well-known operating characteristics of the DC motor lO, unlike when the rotational speed increases, when the rotational speed decreases, the rotational speed rises to the rotational speed rl immediately from the time to, which is the timing for applying the DC voltage. Instead of decreasing, the rotational speed decreases to rl at time t2, which is much later than that.

In this way, while it takes time for the rotation speed of the DC motor 10 to fall to the target rotation speed, the gas amount adjustment valve 6
The response speed for reducing the gas amount by adjusting the opening is good.
During the transition period between time 10 and t2, the amount of gas in the combustion chamber 4 decreases, but the amount of air remains at its original state, so during that transition period, the ratio of the amount of air to the amount of gas decreases. increases, and as a result, the air-fuel ratio collapses.

In extreme cases, such a collapse of the air-fuel ratio may cause problems such as the gas flame being blown away by air and extinguished.

In order to eliminate such a problem, conventionally, the timing of changing the opening degree of the gas amount regulating valve 6 from HO to Hl is delayed by Δ to time t1, and the opening degree of the gas tH regulating valve 6 is adjusted. The timing of reducing the amount of gas and the timing of reducing the amount of air were made to match as much as possible, but this timing was set by repeating experimental work and also by controlling the combustion control sequence in the central control circuit 16. It is necessary to incorporate it into the software. Repetition of such experimental work and incorporation into software has the drawback of requiring more time and effort in the manufacturing process, resulting in increased costs.

Therefore, the present invention does not require the above-mentioned experimental work or incorporation of software, and in other words, it does not require much effort in manufacturing.It also makes it possible to reduce costs while controlling the air-fuel ratio at a constant level. The purpose of this invention is to reduce the amount of air flowing into the combustion chamber by responsively decreasing the rotational speed of the DC motor in accordance with the decrease in the amount of gas.

(Means for Solving the Problems) In order to achieve such an object, in the air-fuel ratio control device of the present invention, the air is blown into the combustion chamber together with the fuel by an air amount adjusting means driven by a DC motor. It has a central control circuit and an air amount control circuit, and the central control circuit outputs an air ffi adjustment signal to the air amount control circuit in accordance with a predetermined air-fuel ratio, and also outputs an air ffi adjustment signal to the DC motor. It outputs a dynamic braking signal when reducing the amount of air in the combustion chamber by adjusting the applied voltage and lowering its rotation speed. It has a dynamic braking circuit, and the DC motor drive power supply applies voltage to the DC motor in response to the input of the air volume adjustment signal to rotate the DC motor. It drives the adjustment means, and the dynamic braking circuit is characterized in that it dynamically brakes the DC motor in response to input of a dynamic braking signal.

(Function) According to the above configuration, when the number of rotations of the DC motor is decreased to reduce the amount of air in the combustion chamber, a dynamic braking signal is output from the central control circuit to the dynamic braking circuit, and the dynamic braking circuit operates the DC motor. Since dynamic braking is used, when reducing the amount of gas in response to the load in the combustion chamber, the rotational speed of the DC motor is increased in accordance with the decrease in the amount of gas and while controlling the air-fuel ratio in the combustion chamber to a constant level. The amount of air blowing can be reduced by standing down.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an air-fuel ratio control device according to an embodiment of the present invention, and parts corresponding to those in FIG. 2 are given the same reference numerals. In FIG. 1, a detailed explanation of parts having the same reference numerals as in FIG. 2 according to the conventional example will be omitted.

This embodiment is characterized in that a dynamic braking circuit 24 is provided in the DC motor 10. The dynamic braking circuit 24 is constructed by inserting and connecting a resistor 26 and the collector/emitter of a transistor 28 in series in parallel with the DC motor 10 . The transistor 28 is configured to receive a dynamic braking signal from the central control circuit 16.

The operation will be explained with reference to FIG. 3. At time t.

From the current rotation speed rO of the DC motor 10 to the target rotation speed rl
When reducing the air blow rate, the central control circuit 16
inputs the current rotation speed rO of the DC motor 10, outputs an air il adjustment signal to the DC motor drive power source 22 in accordance with the difference between the target rotation speed r+ and the current rotation speed rO, and at the same time outputs an air il adjustment signal to the DC motor drive power source 22. A high-level dynamic braking signal is output to the base of the transistor 28.

Accordingly, the DC motor drive power supply 22 changes the DC voltage from 0 to Vl and applies it to the DC motor 10, thereby decreasing the rotational speed of the DC motor 10 toward the target rotational speed r1.

In this case, since the transistor 28 of the dynamic braking circuit 24 is turned on by the input of the dynamic braking signal, the rotational energy of the DC motor 10 is consumed by the resistor 26, so the rotational speed of the DC motor 10 increases at time t2'. The rotational speed is braked to the target rotational speed r1 and rapidly decreases.

On the other hand, the opening degree of the gas amount regulating valve 6 is immediately controlled by the central control circuit 16 at time to, and the gas amount changes from HO to Hl, and the gas amount decreases, but at time t, the gas amount decreases.
Although there is a time difference between O and the time t2' when the air amount decreases, the time difference is small, so the air-fuel ratio in the combustion chamber 4 is controlled to be constant with much better timing than in the conventional example. The state will be as follows.

(Effects of the Invention) As is clear from the above explanation, according to the present invention,
When adjusting the amount of gas in a decreasing direction in response to combustion, there is no need to delay the timing of the reduction in gas amount, so there is the need for experimental work to set the timing of the reduction, or to incorporate software related to the timing of the reduction into the central control circuit. This eliminates the need for manufacturing, and as a result, it is possible to reduce manufacturing costs. Also,
When reducing the amount of gas, the rotational speed of the DC motor can be decreased with good responsiveness in accordance with the reduction in the amount of gas, so the air-fuel ratio in the combustion chamber can be easily controlled.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram of an air-fuel ratio control device according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional air-fuel ratio control device, and FIG. 3 is a block diagram of an air-fuel ratio control device according to an embodiment of the present invention and a conventional example. Examples are provided to explain the operation of each example. (a) is a waveform diagram regarding the opening degree of the gas amount adjustment valve, (b) is a waveform diagram of the voltage applied to the DC motor, and (C) is a change in the rotation speed of the DC motor. FIG. 4...Combustion chamber, 6...Gas amount adjustment valve, lO/DC motor, 12...Blower fan (air amount adjustment means), 16.Central control circuit, 18...Air amount control circuit, 20.Cass Quantity control circuit, 22. DC motor drive power supply, 24. Dynamic braking circuit.

Claims (1)

[Claims] (1) Direct current motor (10
), the air-fuel ratio control device blows the air with an air amount adjusting means (12) driven by a central control circuit (16) and an air amount control circuit (18).
The central control circuit (16) outputs an air amount adjustment signal to the air amount control circuit (18) in accordance with a predetermined air-fuel ratio, and adjusts the voltage applied to the DC motor (10). The air amount control circuit (18) outputs a dynamic braking signal when decreasing the rotation speed of the combustion chamber (4) to reduce the amount of air in the combustion chamber (4).
), DC motor (10), and dynamic braking circuit (24)
The DC motor drive power source (22) applies a voltage to the DC motor (10) in response to the input of the air amount adjustment signal to rotationally drive the DC motor (10), and The DC motor (10) drives the air amount adjusting means (12), and the dynamic braking circuit (24) dynamically brakes the DC motor (10) in response to input of a dynamic braking signal. An air-fuel ratio control device characterized by: