JPS5884304A - Proportional controller - Google Patents

Abstract

PURPOSE:To eliminate the hysteresis and to increase the control accuracy, by compensating the current on the basis of the control characteristics obtained when the current increases and decreases with the current flow rate control characteristics of a proportional control valve. CONSTITUTION:A proportional controller S1 is provided with a storing part S3 which stores a relational equation of the current flow rate control characteristics of the hysteresis occuring within the controller S1 as well as an intermediate relational control characteristics of the hysteresis which is induced from the first mentioned relational equation, and a discriminating part S2 which discriminates the increase or decrease of the driving current, that is, which side the control is carried out centering on the hysteresis straight line. A hysteresis compensating arithmetic part S4 functions to compensate the hysteresis on the basis of the information signals given from the parts S3 and S2. A driving part S5 is driven by the part S4. Thus the electric signal is transmitted to a pressure type proportional control valve S6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control means for reducing the hysteresis of a proportional control valve used for controlling the output of combustion equipment.

Figure 1 is a schematic diagram of a pressure type proportional control valve.

The electromagnetic coil 2 is installed in the upper part of the pressure type proportional control valve train device.
,.

An electromagnetic plunger 4 supported by a leaf spring 3 is inserted into the center of the electromagnetic coil 2.

A diaphragm portion 6 and a valve body 6 are fixed to the lower part of the electromagnetic plunger 4. 7 is an electromagnetic plunger 4. A spring 5aVi is used to support the weight of the diaphragm 6 and the valve body 6, and 9a is a primary pressure chamber, 9b is a fuel inlet, 10iL is a secondary pressure chamber, and 10b is a fuel outlet.

In the above configuration, when a driving current i is applied to the electromagnetic coil 2, an attractive force acts on the electromagnetic plunger 4, and the valve body 6 is pushed down and stopped at a position balanced with the upward restoring force of the leaf spring 3. At this time, 1. Due to the large valve opening IJ~ formed by the valve body 6 and the valve seat 8, the pressure at the fuel inlet 9b/c is the primary production P1, and the pressure at the fuel outlet 10b, which is the pressure P2, is significant. controlled. In addition, in this type of pressure proportional control valve, the effective diameter of the diaphragm portion 6 that receives the secondary pressure P1 and the effective diameter of the upper surface of the valve body 6 that similarly receives the primary pressure P1 are the same, so that If the driving currents 3, -2-·i applied to the electromagnetic coil 2 are the same, even if the -order pressure P1 changes.

Secondary pressure P2 does not change. That is, secondary pressure P2
Is it a function of the driving current i applied to the electromagnetic coil 2 regardless of the change in the -order pressure? ), P2 = f(i). Therefore, in response to an increase or decrease in the drive current i, the secondary pressure P2
is controlled.

As a result of various experiments, more specifically, the secondary pressure P2 is P2 =
It can be expressed as k1i2...■ (where kl is a proportionality constant). Also, if the flow rate of fuel jetted into atmospheric pressure from a nozzle installed downstream of the pressure proportional control valve is expressed as Q, then if the cross-sectional area shape of the flow path is the same, then Q=
can be expressed as 2v/¥2...■ (where k2 is a proportionality constant). Therefore, from (1) and (2) above, it can be expressed as Q=kg, i...0 (where, 5 is a proportionality constant). That is, the current flow rate control characteristic diagram in FIG. 2 shows that the fuel flow rate Q is in direct proportion to the drive current i applied to the electromagnetic coil 2. The vertical axis represents the flow rate when the maximum flow rate is 100%, and the horizontal axis represents the drive current i.

As is clear from Figure 2, a certain dynamic current i
On the side where the drive current i increases from 0, the fuel flow rate q is expressed by a linear equation of the drive current 1, but hysteresis occurs when the drive current i increases and decreases. Therefore, when the drive current i is decreased, the fuel flow rate Q for the same drive current i when increased is Δ? with respect to the flow rate value 'i-u when the drive current i is increased? Only more value?
It becomes d. That is, the flow rates controlled for the same drive current i are g and u? There will be two copies of d.

Further, the point 4to indicates the maximum combustion flow rate determined by multiplying the minimum combustion flow rate by g-M, which is determined from the burner capacity.

Therefore, the control range of the fuel flow rate Q is a range from fl and o to fM.

When a pressure-type proportional control valve with the above-mentioned current flow control characteristics is applied to air-fuel ratio control of combustion equipment with the main purpose of increasing combustion efficiency, the relationship between the blower scenery and the drive current that controls the blower rotation speed will increase. whereas the hysteresis between them is negligible.

Hysteresis of the pressure-type proportional control valve that controls the measured fuel flow rate 5.7
- Because the lysis is large and the low flow rate control region is also large, if it works in the direction of increasing the combustion output, that is, if it works in the direction of increasing the drive current, it will lead to a state of excess air, or However, when the combustion output decreases, that is, when the drive current decreases, an air shortage occurs and highly accurate air-fuel ratio control cannot be achieved. In particular, in the area where hysteresis is large in the low combustion range, if an air shortage occurs, the carbon oxide concentration will suddenly increase, and there is a risk of the gas being extinguished, so the amount of air may be more than necessary. It is necessary to control the combustion efficiency as much as possible, and as a result, the combustion efficiency decreases, which becomes an impediment to air-fuel ratio control whose main purpose is to improve combustion efficiency.

The present invention eliminates the above-mentioned drawbacks of the conventional technology by correcting hysteresis in order to enable highly accurate air-fuel ratio control in which the magnitude of hysteresis cannot be ignored using an open-loop control method.

An embodiment of the present invention will be described below with reference to the illustrative drawings. Figure 3 is a schematic diagram showing the main block diagram of the proportional control device of the present invention and the electrical signal system to the pressure type proportional control valve, and sl indicates a part of the proportional control device. ,
This includes a determining section 82 that identifies an increase or decrease in the drive current i. There is a storage section S3 that stores the hysteresis straight line, a hysteresis correction calculation section s4 that operates in response to signals from the discrimination section S2 and the storage section s3, and is further controlled by a drive section S5 to send an electric signal to the pressure type proportional control valve S6. is transmitted. FIG. 4 is an explanatory diagram showing the hysteresis correction means in the current flow rate control characteristic diagram, and FIG. 6 is a current flow rate control characteristic diagram of the blower.

In FIG. 4, the flow rate control range is between the minimum combustion flow rate value to and the maximum combustion flow rate value fM determined from the combustion characteristics of the burner, and correspondingly, the current control range is between io and iM.

There is hysteresis in the current flow control characteristics, and its value is
It tends to increase as the flow rate becomes lower. In addition, when the load is changed in the current flow control characteristics of the proportional control valve alone, that is, when the load is increased,
It is controlled 71, 2 degrees according to the straight line (a), and conversely, when the load is decreased, it is controlled according to the straight line (b).

The straight line in (a) is 10 (i (iy (or to <
Q < g, M), Q=ai-4-b...
・・・・・・・・・・・・・・・・・・(b)(a,
b is a known constant) The straight line in (b) is Q=ci+d...
・・・・・・・・・・・・(b) (c and d are known constants) It is a straight line expressed as follows.

The already known relational expressions between the current and the flow rate of the pressure proportional control valve, that is, straight lines (a) and (b), are stored in advance in the storage section S3 shown in FIG. 3. Furthermore,
Let (c) be the straight line between the straight lines of (a) and (b) derived from the relational expressions of (a) and (b).

Q ='(''L+0)/2i+(b+(1)/2=e
i + f ・・・・・・・・・・・・・・・・・・
. . . (c) (a and f are known constants) The straight line (c) is similarly stored in the storage unit S3. Further, the straight line (C) is defined as the reference straight line for the current flow rate control characteristics.

With this definition, the flow when the drive current i is 8-2 What is the quantity value? is uniquely determined as .

In the above configuration, when the load fluctuates, highly accurate air-fuel ratio control is realized in which the drive currents of the proportional control valve and the blower are controlled in conjunction to change the fuel flow rate Q and air flow rate -Q. In order to do this, for the drive current i in FIG. 4, the fuel flow rate value t must be the air flow rate value in FIG. 6? It is necessary that there is always a one-to-one correspondence with .

In air flow rate control, the hysteresis is so small that it can be ignored, so in this case it is treated as having zero hysteresis.

That is, the single straight line (:=) shown in FIG. 6 indicates this.

Now, when the load increases, it is controlled by the straight line (A), but the control signal is first set in the discriminating section S2-, which first identifies 1, then turns on the hiss of S4, In the teresis correction calculation unit, the reference straight line (c) that has already been stored in the storage unit of S3 (memorized)
The reference control current facing the driving voltage i from the straight line (A) is the tree to be controlled as +Δ. Conversely, when the load decreases, the standard flow rate corresponding to the drive current i is drawn from the standard line (c) and the straight line (b) on the % (b) line. The corrected current value Δi・ is calculated so that the actual control current is i−
It is controlled as Δi'.

On the other hand, the air flow rate control is performed without hysteresis in response to load fluctuations along the line 2) in FIG. 6.

As is clear from the above description, the proportional control device of the present invention stores within the control device a relational expression of current flow rate control characteristics with hysteresis and an intermediate relational expression of hysteresis derived from this relational expression. The memory section to store and whether the drive current is increasing or decreasing, that is,
It operates to correct the hysteresis based on the information signal from the discrimination section for identifying which side of the hysteresis straight line the control is being carried out and from the discrimination section of the storage section 1. The configuration of the hysteresis correction calculation section provides the following effects. That is, 19... (1) In a control valve composed of an electromagnetic drive section, a diaphragm, a mechanical sliding section, etc., magnetic hysteresis and hysteresis caused by the diaphragm cannot be completely eliminated.

Because of these hysteresis, hysteresis also exists in the control characteristics, and when the control characteristics accompanied by hysteresis are expressed by a fixed relational expression, this hysteresis can be apparently eliminated.

(2) By eliminating hysteresis, it is possible to control air-fuel ratio control with high precision, especially in an open-loop system.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a conventional pressure type proportional control valve, Fig. 2 is a current flow control characteristic diagram of the same pressure type proportional control valve, and Fig. 3 is a main block diagram of a proportional control device in an embodiment of the present invention. FIG. 4 is a characteristic diagram showing the hysteresis correction means in the proportional control device, and FIG. 6 is a characteristic diagram of the current and air volume control of the blower. Sl...Proportional control device, 82...Discrimination unit, one aS1η,...Storage unit, 84...Hysteresis correction calculation unit, S6... ...proportional control valve. Figure 11 Figure 2 Q (%) Figure 3 Figure 4 1115 Figure O'

Claims (1)

[Claims] A proportional control valve that includes a valve body that can vary the cross-sectional area of the flow passage in a fluid flow passage, and controls an electromagnetic drive unit that operates in conjunction with the valve body to continuously vary the flow rate of the fluid, and the proportional control valve. A storage unit that stores both a control characteristic when the current increases and a control characteristic when the current decreases in the current flow control characteristics of the valve, and a discrimination unit that identifies whether the current is in an increasing direction or a decreasing direction. and a hysteresis correction calculating section that corrects the current so as to reduce the hysteresis of the current flow rate control characteristic.