JPH0854933A - Liquid level controller - Google Patents

Abstract

PURPOSE:To provide a liquid level controller which can be suitably applied also to the oil level control of a flier by combining a controller with a weight sensor which detects the apparent weight of a weight that receives the liquid buoyancy and adding an empty weight correction circuit to the controller. CONSTITUTION:A weight sensor LC consisting of a load cell, for example, is placed above a universal joint W1, measures the apparent weight w of the weight w which receives the buoyancy by the oil A, and outputs a detection signal S1. When the lever L of the oil A is low and the oil A does not reach the lower end of the weight w, the sensor LC detects the empty weight wo of the weight w as w=wo. When the level L rises and the weight w sinks in the oil A by depth Lf, the weight w receives the buoyancy wf and w=wo-wf is satisfied. The empty weight correction circuit of a controller 10 calculates the difference wo-(wo-wf)=wf between the weight w and the weight wo. In this instance, the buoyancy wf is proportional to the depth Lf of the weight w measured in the oil A and shows the level Lf of the oil A set on the basis of the lower end of the weight w.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level control device which can be incorporated in, for example, a kitchen fryer and can be suitably used to maintain the level of cooking oil at a predetermined set level.

[0002]

2. Description of the Related Art Level control systems for detecting the level of liquid and maintaining it at a predetermined set level are widely used in all industrial fields.

Such a system generally comprises a sensor for detecting the level of a liquid and a control device which operates based on a detection signal from the sensor. Here, there are a great number of types of level detection sensors known depending on the type of target liquid, the operating atmosphere, etc., and can be roughly classified into mechanical type and electric type. As the former, the weight type such as machine, load cell only, float type such as arm float, displacer, pressure type such as differential pressure type pressure gauge, load cell type pressure gauge, and weight type are known. , The latter belong to electrostatic type, electromagnetic type such as conductivity type, reflection type such as ultrasonic type, microwave type, and vibrating piece type using a tuning fork or a cantilever vibrating piece. There is. These sensors are
Many have been developed and developed for incorporation into large scale process control systems.

[0004]

According to the prior art, when the level detecting sensor is incorporated in a kitchen flyer, both have advantages and disadvantages, and it is difficult to find the optimum one. It was Since conventional sensors are mainly developed for large-scale process control, they are large and complicated and expensive, and mechanical sensors have a difficulty in operation reliability and electrical sensors. This is because it is often difficult to apply high temperature cooking oil as a detection target.

Therefore, in view of the above problems of the prior art, an object of the present invention is to combine a weight sensor for detecting the apparent weight of a weight receiving a buoyancy force by a liquid with a control device so that the oil level of the flyer is increased. Another object of the present invention is to provide a liquid level control device that can be suitably applied to control.

[0006]

A structure of the present invention for achieving the above object is to input a weight sensor for detecting an apparent weight of a weight receiving buoyancy by a liquid and a detection signal from the weight sensor, A control device that outputs a control signal for liquid replenishment in comparison with the setting signal, and the control device includes a self-weight correction circuit that corrects a correction signal corresponding to the self-weight of the weight with respect to the detection signal. The summary will be given.

The control device can be provided with a safety circuit which permits the output of the control signal on condition that the detection signal is within a predetermined level range.

Further, the control device can include a setting switching circuit for selecting a setting signal by an external signal.

[0009]

According to the structure of the present invention, since the weight is buoyant by the liquid, the weight sensor can detect the level of the liquid by detecting the apparent weight of the weight. This is because when the liquid level changes, the buoyancy received by the weight changes, and the apparent weight of the weight changes. On the other hand, the control device can directly read the liquid level by including the self-weight correction circuit. This is because the self-weight correction circuit can correct the correction signal corresponding to the self-weight of the weight with respect to the detection signal from the weight sensor, and calculate the buoyancy proportional to the liquid level. Since the correction signal at this time is a constant value corresponding to the weight of the weight to be used, it may be manually set.

When the control device is provided with a safety circuit, the safety circuit is provided, for example, when a detection signal deviates from a predetermined level range due to a failure of a weight sensor, a drop of a weight, or the like.
The output of the control signal can be blocked, and the entire operation can be made safer.

When the control device has a setting switching circuit,
The control device can control the level of the liquid so as to be the optimum level suitable for the operating condition by selecting the setting signal via the setting switching circuit.

[0012]

Embodiments Embodiments will be described below with reference to the drawings.

The liquid level control device includes a weight sensor LC.
And the control device 10 are combined (FIG. 1). However, here, a case where the level L of the cooking oil A is controlled in the kitchen flyer will be exemplified.

The flyer has an oil tank F heated by a burner B. The oil tank F is connected to an oil supply tank (not shown) via the control valve V, and by opening the control valve V, the oil A can be supplied to the oil tank F. A measuring cylinder F1 is attached to the oil tank F, and the measuring cylinder F1 communicates with the oil tank F via a communication pipe F2. That is, the measuring cylinder F1 is filled with the oil A so as to be at the same level as the oil tank F.

A bar-shaped weight W is suspended from the measuring cylinder F1 via a universal joint W1. A weight sensor LC composed of, for example, a load cell is disposed above the universal joint W1. The weight sensor LC measures the apparent weight w of the weight W that receives the buoyancy force by the oil A and outputs a detection signal S1. can do.

The detection signal S1 from the weight sensor LC is input to the control device 10. In addition, the oil tank F has oil A
A temperature sensor TC for measuring the temperature T of
The detection signal St from the temperature sensor TC is also input to the control device 10. A manual control switch SW is attached to the control device 10, and the control signal S2 from the control device 10 is guided to the control valve V.

The detection signal S1 from the weight sensor LC is input to the control device 10 (FIG. 2), and is also input to the level control circuit 12 via the combining point 11a of the self weight correction circuit 11. However, the detection signal S1 is input to the subtraction terminal of the addition point 11a, and the correction signal S11 from the setter 11b is input to the addition terminal of the addition point 11a. In addition, the weight wo of the weight W is set in the setter 11b. Further, the level control circuit 12 is additionally provided with a setter 12a for setting the control level width ΔL.

The detection signal St from the temperature detector TC is input to the switch element 13c of the setting switching circuit 13. The setting switching circuit 13 includes setting devices 13a and 13b, and outputs of the setting devices 13a and 13b are connected to the level control circuit 12 via a switch element 13c.

The output of the level control circuit 12 is connected to a relay R1 via an AND gate 12b, and a control switch SW is also connected to the AND gate 12b.

The control circuit 10 includes a safety circuit 14, and the output of the self-weight correction circuit 11 and the output of the setting switching circuit 13 are branched and connected to the safety control circuit 14a of the safety circuit 14, respectively. The output of the self-weight correction circuit 11 is also branched and connected to the level check circuit 14b of the safety circuit 14, and the output of the level check circuit 14b is also connected to the safety control circuit 14a. The output of the safety control circuit 14a is connected to the relay R2 via the AND gate 14c, and the output of the power supply establishment detection circuit 14d is branched and connected to the AND gates 14c and 12b. Also,
The normally-open contacts R1a and R2a of the relays R1 and R2 are connected in series and are drawn out as a control signal S2.

The output of the self-weight correction circuit 11 is the summing point 15
Is also led to the subtraction terminal of No. 1, and the addition terminal of the addition point 15 is connected to the setter 15a for setting the alarm level La. The output of the summing point 15 is taken out as an alarm signal Sa via the waveform shaping circuit 15b,
It is led to an alarm display device (not shown).

When the level L of the oil A in the oil tank F is small and the oil A does not reach the lower end of the weight W, the weight sensor LC detects w = wo as the apparent weight w of the weight W. To do. However, wo is the dead weight of the weight W. on the other hand,
When the level L becomes higher and the weight W sinks in the oil A by the depth Lf, the weight W receives the buoyancy wf proportional to the depth Lf by the oil A, so the apparent weight w is w = w.
o −wf.

On the other hand, the self-weight correction circuit 11 of the controller 10
Sets the self weight wo of the weight W in the setter 11b so that the difference wo − between the apparent weight w of the weight W indicated by the detection signal S1 from the weight sensor LC and the self weight wo −
(Wo-wf) = wf can be calculated. That is, the self-weight correction circuit 11 receives the weight W with respect to the detection signal S1.
By correcting the correction signal S11 corresponding to the own weight wo of
The buoyancy force wf received by the weight W can be calculated and output. The buoyancy force wf at this time is the depth L of the weight W sinking in the oil A.
The level L of oil A relative to the lower end of the weight W in proportion to f
shows f.

Next, the setter 13 of the setting switching circuit 13
a and 13b are set level L for oil A, respectively.
s1 and Ls2 (where Ls1 ≠ Ls2) are set,
The set levels Ls1 and Ls2 are input to the switch element 13c as set signals Ss1 and Ss2. The switch element 13c receives the detection signal St from the temperature sensor TC, selects one of the setting signals Ss1 and Ss2 depending on the temperature T of the oil A indicated by the detection signal St, and sets the setting level Lsi (i
= 1, 2) can be output to the level control circuit 12. Therefore, the level control circuit 12 compares the level Lf from the self-weight correction circuit 11 with the set level Lsi from the setting switching circuit 13, and when Lf≤Lsi, outputs the output signal S12.
Can be output (time t ≦ to in FIG. 3, below,
Simply write as (t≤to)).

Output signal S12 from the level control circuit 12
Activates relay R1 via AND gate 12b. Therefore, the relay R1 can generate the control signal S2 on condition that the relay R2 is operating. Further, since the control signal S2 is guided to the control valve V, the control valve V can replenish the oil tank F with the oil A from the oil replenishment tank (not shown).

When the level Lf of the oil A becomes Lf = Lsi (t = to), the level control circuit 12 erases the output signal S12 and restores the relay R1.
Disappears, and the control valve V stops the supply of the oil A. Therefore, after that, the oil A is consumed and the level Lf decreases, but the level control circuit 12 at this time refers to the control level width ΔL set in the setter 12a to obtain Lf.
While .gtoreq.Lsi-.DELTA.L, the output signal S12 is not output (to <t.ltoreq.t1), and when Lf = Lsi-.DELTA.L, the output signal S12 is output (t = t1) and Lf = Lsi
The output signal S12 is continuously output until (t1≤t≤
t2). Further, the level control circuit 12 can operate similarly thereafter (t> t2). That is, the level control circuit 12 sets the level Lf of the oil A to Lsi−ΔL ≦ Lf ≦.
It can be controlled in the range of Lsi.

The AND gate 12b does not open unless the control switch SW is turned on. That is,
The control switch SW is manually operated by the level control circuit 12
The level control operation of the oil A by means of can be arbitrarily started and stopped. Further, since the output of the power supply establishment detection circuit 14d is also connected to the AND gate 12b, the control signal S2 is supplied with the power of the control circuit 10,
No output is made unless the establishment is checked via the power supply establishment detection circuit 14d.

Level check circuit 14b of the safety circuit 14
Indicates that the level Lf from the self-weight correction circuit 11 does not deviate from a predetermined level range, that is, the weight sensor LC.
It is checked that the detection signal S1 from the above is within a predetermined level range, and the fact is output to the safety control circuit 14a.
Therefore, the safety control circuit 14a includes the level check circuit 1
AND gate 14c only when there is an output from 4b
Relay R2 can be activated via. That is, the safety circuit 14 uses the detection signal S from the weight sensor LC.
The output of the control signal S2 can be permitted provided that 1 is within a predetermined level range. The level check circuit 14b controls the oil A by the level control circuit 12.
3 is controlled as shown in FIG. 3, when the level Lf is between a predetermined lower limit value smaller than Lsi-ΔL and a predetermined upper limit value larger than Lsi, the detection signal S1 is at a predetermined level. Judge that it is within the range.

However, the safety control circuit 14a, if Lf ≤ Lsi immediately after the power is turned on, the level check circuit 1
Regardless of the output of 4b, the relay R2 is forcibly operated via the AND gate 14c. When there is no oil A in the oil tank F, even if the detection signal S1 is not within the predetermined level range, the control signal S2 is output and the oil A is supplied to the oil tank F to set the level Lf to the set level Lsi. This is because it must be reached (time t≤to in FIG. 3).
). That is, the safety control circuit 14a connects the output of the level check circuit 14b to the AND gate 14c after the power is turned on and the first Lf = Lsi is achieved, and shifts the level check circuit 14b to the steady monitoring state. I shall.

The summing point 15 is the level Lf and the setter 1
The alarm level La set to 5a is compared, and Lf <La
, The alarm signal S is sent via the waveform shaping circuit 15b.
can generate a. However, the alarm level La
Is set to an appropriate value, for example, La <Lsi-ΔL. Further, the alarm signal Sa can activate an alarm display device (not shown) to display a malfunction of the weight sensor LC and the control device 10.

In the above description, the detection signal St from the temperature sensor TC is input to the switch element 13c of the setting switching circuit 13 because the temperature L of the oil A in the oil tank A changes the level Lf of the oil A. This is because by switching to one of the set levels Ls1 and Ls2, a better operating condition as a flyer can be obtained. Therefore, for the oil tank F, the oil A
When a device that may change the level Lf of the device, such as an oil circulation pump for oil purification, is attached, the switch element 13c indicates the operating state of these devices instead of the detection signal St. The set levels Ls1 and Ls2 may be selected by an external signal.

Further, the level check circuit 14b of the safety circuit 14 sets a predetermined level range of the level Lf to Lsi-ΔL.
It may be set to −δ2 <Lf <Lsi + δ1 (where δ1 and δ2 are predetermined small margin values). However, the level switching circuit 14b at this time includes the setting switching circuit 13
It is also necessary to input the setting level Lsi from the.
However, it is not always necessary to set the predetermined level range of the level Lf to such a narrow range in order to check the fall of the weight sensor LC, etc., and as described above, regardless of the set level Lsi. , Even if the upper limit value and the lower limit value of the level Lf are set to constant fixed values, they can be sufficiently used.

The present invention is not limited to the level control of the oil A in the oil tank F in the fryer, but can be applied as it is to the level control of any liquid in any other application.

[0034]

As described above, according to the present invention, the weight sensor which detects the apparent weight of the weight receiving the buoyancy of the liquid is combined with the control device, and the self-weight correction circuit is provided in the control device. This allows the weight to be immersed in high-temperature oil without any problems, and the level detection sensor including the weight sensor has a simple structure and high operation reliability, and self-weight correction. Since the circuit can calculate the liquid level from the apparent weight of the weight and can simplify the configuration of other control devices, it is suitable for controlling the oil level of the fryer as a whole. It has an excellent effect that it can be applied.

[Brief description of drawings]

1 is an explanatory diagram of the overall configuration

[Fig. 2] Block diagram of main parts

[Fig. 3] Operation explanatory diagram

[Explanation of symbols]

 W ... Weight w ... Apparent weight wo ... Own weight LC ... Weight sensor S1 ... Detection signal S11 ... Correction signal S2 ... Control signal Ss1, Ss2 ... Setting signal 10 ... Controller 11 ... Own weight correction circuit 13 ... Setting switching circuit 14 ... Safety circuit

Claims (3)

[Claims] 1. A weight sensor for detecting an apparent weight of a weight receiving a buoyancy force by a liquid, and a control for inputting a detection signal from the weight sensor and comparing the setting signal with a control signal for supplying liquid. A liquid level control device, comprising: a device, wherein the control device includes a self-weight correction circuit that corrects a correction signal corresponding to the self-weight of the weight with respect to the detection signal. 2. The liquid according to claim 1, wherein the control device includes a safety circuit that permits the output of the control signal on condition that the detection signal is within a predetermined level range. Level control device. 3. The liquid level control device according to claim 1, wherein the control device includes a setting switching circuit that selects the setting signal by an external signal.