JPS60169908A - Device for discriminating cause of deviation - Google Patents

Abstract

PURPOSE:To attain precise discrimination by forming a differential value discriminating means for detecting the variation direction of a detected voltage and a temperature deviation discriminating means for comparing deviation values and discriminating the cause of the variation on the basis of the combination of both the discriminated results. CONSTITUTION:The deviation between temperature detecting voltage Va and reference voltage Vb is obtained from a temperature detecting bridge circuit S constituted of a thermistor RT to be a temperature detecting means, a variable resistor BR to be a temperature setting means, etc., and on the basis of the deviation, the opening of a proportional valve 2 is determined through a PID control circuit 1 provided with an integrator AI and a proportional valve driving circuit 3. In this case, an overshoot limiter 4 is formed as a deviation cause discriminating device. The limited 4 is constituted of a temperature deviation discriminating circuit 5 for detecting the generation of overshoot, a differential value discriminating circuit 6 for detecting the variation direction of a detecting voltage Vc and its variation speed and an AND circuit 7 obtaining the AND G of outputs E, F from both the circuits, and at the generation of overshoot, the operation of said control circuit 1 is temporally stopped.

Description

[Detailed description of the invention] This E! A is a deviation cause determination device, specifically, a temperature detection thermistor whose one end is connected to a power supply via a resistor is connected in series with a temperature setting variable resistor whose one end is grounded, and the power supply is connected to a predetermined ratio. Multiple resistors that divide the voltage and output the reference voltage? and a bridge circuit configured to output a voltage corresponding to a deviation between a set temperature and a detected temperature by a connection point between a resistor and a thermistor connected to the power supply and a connection point between the plurality of resistors. Is the voltage fluctuation of the detection voltage obtained from the connection point between the resistor and thermistor caused by a temperature change or by a change in set temperature? The present invention relates to a device for determining causes of deviation.

Conventionally, the bridge circuit described above has been employed as a water temperature detection means for proportionally controlling the amount of fuel supplied in gas water heaters, etc., as shown in FIG. 6, for example, but due to its configuration, Since the thermistor serving as the temperature detection means and the variable resistor serving as the temperature setting means are connected in series, fluctuations in the detected voltage obtained from the connection point between the resistor and thermistor are due to fluctuations in the detected temperature. mosquito,
It was not possible to determine whether this was due to a change in the set temperature.

The configuration of the conventional example shown in FIG. 6 above will be briefly described below.

In other words, in proportional control, overshoot of the water temperature is likely to occur during load fluctuations, especially when the flow rate decreases. An overshoot discrimination voltage (V
Overshoe (IJ) that detects the occurrence of overshoot, which is a load fluctuation, when the detected voltage (Va') is equal to or higher than the discrimination voltage (Vc') by comparing with C').
It is provided separately in M(4')', and is configured to temporarily stop the operation of the proportional control circuit (11) and reduce the fuel supply amount when the occurrence of overshoot is detected.

Therefore, in order to lower the set temperature, when the variable resistor (VR') as a temperature setting means is operated to decrease the resistance value, the input signal to the overshoot discrimination circuit (4), that is, the thermistor (RT) Detection voltage (Va
This causes the same change as when the water temperature rises, causing the four overshoot detection circuits to malfunction and reduce the amount of fuel supplied. There was a drawback that a chute was generated and the temperature of the hot water fluctuated greatly. In addition, (2') is a drive circuit controlled by the proportional control circuit (one output (V') (B) It is a proportional valve regulated.

The present invention has been made in view of the above circumstances, and its purpose is to reliably determine whether the cause of variation in the temperature deviation detection signal is due to a change in hot water temperature or a change in throwing temperature. An object of the present invention is to provide a device for determining the cause of deviation, which is equipped with means for determining the cause of deviation.

In order to achieve the above object, the deviation cause determination device according to the present invention provides differential value determination means for detecting the direction of variation in voltage obtained from the connection point of the resistor and the connection point of the thermistor and variable resistor. and a temperature deviation determining means for comparing the deviation amount r between the detected voltage and the reference voltage, krR, and determining the cause of variation in the detected voltage t'' based on the combination of the change detection results by the differential value determining means and the temperature deviation determining means. The feature is that it is structured to be different from FJ.

Below, the above #rLt! Based on the block diagram shown in Figure 1,
explain.

A resistor (R1), a thermistor (RT) as a temperature detection means, a bias correction resistor (R5), and a variable resistor CVR)' as a temperature setting means are connected in series between the power supply (Vcc) and the ground point. At the same time, the power supply (Vcc
) A resistor (
The temperature detection bridge circuit (S) constituted by R2) and (R8) is connected to the thermistor (RT), and the detection temperature (R The output (V) corresponding to the deviation (Δt) between the detected voltage (Va) corresponding to the reference voltage (vb)
) PID control circuit (
1), and a proportional valve drive circuit (3) that completely determines the opening degree of the proportional valve (2) that adjusts the fuel supply amount by the output (VJ) of the control circuit fl). Determine whether the cause of the change in (Va) is a change in the resistance of the thermistor (RT) due to temperature fluctuations, or a change in the resistance of the q resistor (VR) due to changes in the set temperature, and determine whether it is due to temperature fluctuations. In other words, if an overshoot occurs due to a change in flow rate, etc., the P
Supply fuel by temporarily stopping the operation of the ID control circuit +1+
In order to perform control to reduce the deviation to ', an overshoot limiter (4
) T-provision.

Said overshoot limiter (4)? To configure, the deviation (
Δt) t-check to detect overshoot occurrence, individual temperature difference, J separate circuit (5), IrI thermistor (R
The detection voltage (V) at the connection point (C) between T) and resistor (R5)
c) a differential value discrimination circuit (6) that detects the differential value (ΔG) of the voltage (VC) in order to detect the direction of variation and its rate of change; and the temperature deviation discrimination circuit (5) and the differential value discrimination circuit (w). ! An AND circuit (7) is provided to calculate the logical product of each output (E) and (F) of the rf61.

The temperature deviation determination circuit 1M+5) detects that the magnitude of the temperature change is greater than or equal to a predetermined value (αl), and
The differential value detection circuit (6) detects that the voltage change is an upward change and the rate of change (ΔG) is greater than or equal to a predetermined value (α2).
If detected, the output of gTI AND circuit (7) (
G), the integrator (A) of the PID control circuit (1)
I) Specified voltage at input? In addition, the operation sound is temporarily stopped and the fuel supply amount is controlled to be reduced. ◇Because of the above structure, the following excellent effects have been achieved.

That is, the overjudge rimming as the device for determining the cause of the deviation detects that when the magnitude of the deviation in the detected temperature is greater than or equal to a predetermined value,
Moreover, only when the direction of change is the direction in which the detected temperature increases and the rate of change is a predetermined value or more, that is, only when a transient response occurs in the detected temperature, is the fuel supply jt? Since it operates to decrease the fuel supply amount, even if you operate the variable resistor as a setting means to change the set temperature, the signal 9 that temporarily decreases the fuel supply amount will not be output by mistake, and it will not malfunction. It was.

Therefore, the operation of the combustion control device can be made extremely stable.

Hereinafter, specific embodiments of the present invention will be explained based on the specific examples.

As shown in Figure 2, the power supply (
A thermistor (RT) connected to Vc, a temperature setting variable resistor (VR) with one end grounded, and a t correction resistor (
The power supply (V
cc) l (divide the pressure to a predetermined ratio and connect each connection point (B),
(D)j A temperature detection bridge circuit (S) configured to output the D reference voltage (vb), (Vd), the reference voltage (vb), the resistor (R1), and thermistor (RT
) PID control circuit that calculates the output (V)' corresponding to the deviation (Δt) from the detected temperature ([) corresponding to the detected voltage (%'a) outputted from the connection point (A) with and a proportional valve drive circuit (3) that determines the opening degree of the proportional valve (2) that adjusts the amount of fuel supplied based on the output (V) of this control circuit (1). It consists of a combustion control device that controls the temperature in full proportion.

The PID control circuit +1)t- is configured by the detection voltage (Va) of the n bridge circuit (S), and the k receiver is a differentiator (AI
), a buffer 1 circuit (AO) that outputs to The output (V) is integrated so that the output (V) does not fall below the lower limit value (VL) by comparing it with the lower limit value (ML) corresponding to the minimum rotation of the proportional valve (2), that is, the minimum fuel supply amount. An operational amplifier (88) is provided as a saturation prevention means for regulating the active range of the amplifier (A2).

Furthermore, as described above, in order to prevent transient responses such as overshoot from occurring in the control response due to sudden changes in the amount of hot water dispensed, an overshoot limiter (4) as a deviation cause determination device configured as described later can be provided. be.

To configure the overshoot limiter (4), the detection voltage (Va) is compared with the voltage (Vd) for each overshoot layer output from the connection point CD between the resistors (R8) and (R4). The detected temperature (tO') is set a predetermined value higher than the set temperature (tO').
1), the IH# level output (E)
A4), the thermistor (RT) and variable resistor (VR)
Differential value (ΔG) of the deviation between the detected voltage (Vc) from the connection point (C) and the reference voltage (Vb) at the connection point (B)
A differentiator (8) as differential value determining means consisting of two operational amplifiers (A5) and (A6) that perform t-operation, and the output (ΔG) of the differentiator (8) and the power supply (Vcc)
Resistors (R5) and (R6) that output divided voltage at a constant ratio of tFr
Reference voltage (αg) from t - compared to detection voltage (Vc)
A comparator (A7) that generates an IHz level output (F) when the rate of change (ΔG) of , (F).

An AND circuit (7) composed of transistors (D2), transistors (Ql), (Qg), etc. is provided.

Then, an overshoot limiter (4
), due to flow rate changes etc., the thermistor (RT)
The output ( G) of the PID control circuit (1)
A2) is controlled to temporarily reduce the fuel supply amount to the lower limit value (ML) by adding a predetermined voltage corresponding to the resistor (R7).

Therefore, even if the variable resistor (VR) is operated to change the set temperature (to), the direction of the voltage fluctuation at the connection point (C) is opposite to the temperature fluctuation, so the overshoot limiter ( 4) does not operate, and there is no possibility that the control circuit (1) will malfunction.

Incidentally, FIG. 8 is a time chart showing the previous version of the combustion control device described above. The figure (b) shows the response of the hot water temperature when the amount of hot water changed.

Furthermore, the response indicated by the broken line in the figure shows the response when the deviation cause determination device according to the present invention is not provided, as in the conventional example.

Another embodiment will be described below with reference to the drawings.

As shown in FIG. 84, this embodiment is a combustion control device having basically the same configuration as the embodiment shown in FIG. 8, and the output (G) of the overshoot limiter (4)
Accordingly, a predetermined voltage is applied to the input of the differentiator (AI) to control the fuel supply amount to be reduced.

That is, since the polarities of the input signals of the differentiator (AI) and the integrator (A2) are reversed, the AND circuit (7)
In order to invert the output polarity of the transistor (Qg), the transistor (Qg) is omitted, and the polarity of the diode (D8) inserted between the output (G) and the differentiator (AI) is inverted.

In addition, as shown in FIG. 5, the resistor (RG) that determines the gain of the buffer 1 circuit (AO) is configured as a flow sensor whose resistance value changes in accordance with the flow rate, so that the flow rate t* The gain of the PID control circuit (1) may be automatically adjusted in response to the change in speed.

Also, it is possible to omit the differentiator (AI) from the FED control circuit (1) and configure it as an ordinary proportional control circuit. It may be configured by a computer, and various changes are possible.

[Brief explanation of drawings]

1Fg is a block diagram showing the configuration of the present invention, FIG. 2 is a circuit diagram of a combustion control device showing a specific configuration of the present invention, and 8th
FIGS. 4A and 5B are time charts showing the operation, FIGS. 4 and 5 are circuit diagrams showing another embodiment, and FIG. 6 is a block diagram showing the configuration of a conventional example. (R1), (Rg), (RB)...Resistor, (
vcc)...Power supply, CRT)...Thermistor, (VR)...Variable resistor, (Va)
...Detection voltage, (Wb), (Vc)
..."Reference voltage, (A), (B), (C)
-... Connection point, (5)... Temperature deviation determining means, (6)... Differential value determining means. Agent Patent Attorney Osamu Nanamura

Claims (1)

[Claims] A temperature detection thermistor (RT) whose one end is connected to a power supply (Vcc) via a resistor (R1) and a temperature setting variable resistor (VR) whose one end is grounded are connected in series. At the same time, the power supply (Vcc) is divided at a predetermined ratio to obtain a reference voltage (
Wb) t-output multiple resistors (Rjll), (
a connection point (A) between the resistor (R1) and the thermistor (RT) connected to the power supply (Vcc), and a connection point TB) between the plurality of resistors (R2) and (R8); Therefore, the bridge circuit (the resistor (R1
) and thermistor (RT) connection point (4), which determines whether the voltage fluctuation of the detected voltage (Vs+) is caused by a temperature change or a change in set temperature. The plurality of resistors (R
B), (R8) connection point (Bl and the thermistor (RT
) and the variable resistor (VR) connection,! (A differential value determining means (6) for detecting the direction of fluctuation of the voltage (Vc) obtained from the CJ, and the detection voltage (Va) and the reference voltage (Vb
) is provided, and the detection voltage (Va What is claimed is: 1. A deviation cause determining device, characterized in that the deviation cause determining device is configured to determine the cause of variation.