JP2886766B2 - Oxygen sensor drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for starting a limiting current type oxygen sensor using a solid electrolyte, and more particularly, to checking whether or not the oxygen sensor has become stable and checking whether the oxygen measurement device is normal. The present invention relates to a driving device for an oxygen sensor capable of indicating whether or not the driving is performed.

[0002]

2. Description of the Related Art Conventionally, a limiting current type oxygen sensor (hereinafter referred to as an oxygen sensor) using a solid electrolyte has been mainly used for an oxygen deficiency alarm, an industrial oxygen meter, and the like. ing. Although this oxygen sensor is used after being heated, the solid electrolyte is susceptible to thermal shock, and the temperature is generally increased stepwise. Therefore, it takes about 10 minutes for the oxygen sensor to reach a stable equilibrium state.

Conventionally, the start time is described in a specification or the like, so that the user is entrusted with a measure for the start time. Further, in a device having a numerical display function, 0.0% is displayed immediately after startup, the display changes with time, and the true oxygen concentration of the test gas is displayed after 3 to 7 minutes. However, if the device is reset once due to a momentary power failure and the user does not notice that the device has been reset, the user may think that the device is out of order or may cause an accident.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a drive device capable of measuring whether or not an oxygen sensor is stable and notifying a user of a usable state of an oxygen concentration measuring device. It is.

[0005]

As a result of intensive studies in view of the above object, the present inventor has found that the end of the start-up process can be determined from a change in the output current of the oxygen sensor during start-up, and completed the present invention. I let it.

That is, a driving device for starting a limiting current type oxygen sensor comprising an oxygen ion conductive solid electrolyte according to the present invention comprises: (a) means for detecting an output value of the oxygen sensor at predetermined intervals; b) means for calculating the absolute value of the difference between the output value of the oxygen sensor and the output value before a predetermined time; (c) means for comparing the absolute value of the difference with a predetermined value; and (d) the difference. (E) means for terminating the activation process when the count value reaches a target value.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A driving device for a limiting current type oxygen sensor according to an embodiment of the present invention will be described with reference to the block diagram of FIG. The driving device according to the present embodiment includes a voltage application device 10, a sensor 1, a current detection device 2, an A / D
The converter 3, the CPU 4, the output port 5, the lamp drive circuit 6, and the lamp 7, the program storage device 8 and the data storage device 9 connected to the CPU 4, and the heater control device 11 connected to the sensor 1 Become.

The voltage applied to the sensor 1 is output by a voltage application device 10. The current flowing to the heater on the sensor 1 is controlled by the heater control device 11. The output current of the sensor 1 is detected by the current detection device 2 and is taken into the CPU 4 via the A / D converter 3. Although the CPU 4 takes in the output of the oxygen sensor in the form of a voltage value via the A / D converter 3, it is of course possible to convert this voltage value into a current value flowing through the sensor 1 or an oxygen concentration. Hereinafter, the description will be made in a manner that the CPU 4 takes in the output value or the current value of the sensor 1 from the A / D converter 3. In accordance with the program written in the program storage device 8, the CPU 4 writes the fetched data in the data storage device 9 and performs calculations, comparisons, and the like.

The CPU 4 determines a stable state of the output of the oxygen sensor based on the calculation result of the CPU 4, and outputs a signal to the output port 5. This signal is input to the lamp driving circuit 6 through the output port 5, and the lamp driving circuit 6
Is turned on or off to indicate whether or not the oxygen sensor is in a usable state.

The CPU 4 operates in accordance with a control program written in the program storage device 8. The main operation of the program is described below. First, it is displayed that the activation process of the oxygen sensor is being performed. Next, the output value of the oxygen sensor 1 is input at regular time intervals and stored in the data storage device 9. This fixed time interval (detection time interval) is set to 0.1 to 10 seconds, preferably 0.5 to 5 seconds.

When the number of stored output values reaches a required number, for example, 2 to 20, preferably 4 to 10, the stability of the sensor output is determined. For example, when output values are input every second, the time required to store all the required number of output values is 2 to 20 seconds, and preferably 4 to 10 seconds. Compare the two output values that were separated by this time,
The stable state of the oxygen sensor 1 is determined. Therefore, this time interval is hereinafter referred to as a determination time interval.

Subsequently, after the detection time interval has elapsed, the output value I (0) of the oxygen sensor 1 is input and compared with the output value I (n) before the determination time interval. This predetermined value is converted to an oxygen concentration of 0.01% to 0.2% O ₂ . If the absolute value | I (n) -I (0) | of this difference is less than a predetermined value, this is counted as one time. On the other hand, if the absolute value | I (n) -I (0) | of the difference between this output value and the output value before the determination time interval is equal to or larger than a predetermined value, the count is not performed, and after the detection time interval elapses. , The output value I (0) of the oxygen sensor 1 is input, and the above comparison is repeated.

When the count value reaches the target value, it is determined that the output of the oxygen sensor 1 has been stabilized. Then, the end of the activation process of the oxygen sensor is displayed. The target value which is the upper limit of the count value is 2 to 10.

In the method of displaying the start-up process, the lamp is turned on at the start of the start-up process and turned off at the end of the process. However, the reverse is of course also possible.

According to the present invention, the oxygen sensor is started by the above-described device. The following configuration can be added to the above-described device.

When comparing the output value I (0) of the oxygen sensor 1 with the output value I (n) before the predetermined judgment time interval, the absolute value | I (n) -I (0) of the difference between the two. When | becomes equal to or greater than a predetermined value, the count is initialized. This initialization refers to setting the count value to the target value, which is the upper limit, when performing the subtraction counting, and setting the count value to zero when performing the addition counting. By this means, the absolute value | I (n) of the difference is continuously obtained by the number of times of the target value.
If −I (0) | is less than the predetermined value, it is determined that the oxygen sensor is stable, and erroneous diagnosis can be prevented.

The operation of the control program will be described with reference to FIGS. When the device is started, the CPU 4 first turns on a lamp to indicate that the CPU 4 is in the process of starting (step 1). Then, 5 is substituted for the variable n representing the number of stored output values, and the target value Cr is substituted for the variable C representing the count (step 2).

Next, it is determined whether or not one second as a detection time interval has elapsed (step 3). After the detection time interval has elapsed, the output value of the oxygen sensor is input and the variable I
(0) (step 4). And I (0) is I
Substitute (n) (step 5), subtract 1 from n (step 6), and compare whether n has become zero (step 7). If n is not zero, return to step 3. In this way, by repeating steps 3 to 7, when n becomes zero, the variables I (1) to I (5)
Stores the oxygen sensor output value at each detection time interval.

If n becomes zero, it is determined whether or not one second, which is the detection time interval, has elapsed (step 8).
When the detection time interval has elapsed, the output value of the oxygen sensor is input and substituted into the variable I (0) (step 9). Then, the absolute value of the difference between the current value I (0) and the current value I (5) before the judgment time interval is calculated, and the result is | I (5) −I (0). Is compared with a predetermined value Ir (step 10). If the value of | I (5) -I (0) | is greater than or equal to Ir, the target value Cr is substituted for the count C (step 16), and the process proceeds to step 13. if,
If the value of | I (5) -I (0) | is less than Ir, 1 is subtracted from the value of count C (step 11), and it is determined whether the value of count C has become zero (step 12). ). If the value of the count C becomes zero, the start-up process ends, and the process of detecting the oxygen concentration and issuing a warning is started. By means of this part, continuously Cr times, | I
(5) When the value of -I (0) | is less than Ir, it is determined that the output of the oxygen sensor has become stable, the startup process is terminated, and the original function is entered.

If the value of the count C is not zero,
First, 5 is substituted for a variable n (step 13), and then I
I (n-1) is substituted for (n) (step 14), and n-
Determine whether 1 has become zero (step 1
5). If n-1 is not zero, n-1 is substituted for the variable n (step 17), and steps 14 and 15 are repeated.
By this means, the value of I (4) becomes I (5) and I (5)
The value of (3) becomes I (4), the value of I (2) becomes I (3),
The value of I (1) enters I (2) and the value of I (0) enters I (1). At the next judgment, the current value before the judgment time interval becomes I (2).
(5). If n-1 becomes zero, the process returns to step 8 to perform the next determination.

In step 2, 5 is substituted for a variable n representing the number of stored output values. However, in the present invention, the number of stored output values can be set to 2 to 20. Further, the upper limit value of the count C, Cr, can be 2 to 10.

In the above-mentioned diagnosis routine, input means for each predetermined value can be further provided by a known method. Further, a known means for displaying the measurement result with time, printing, and the like can be provided.

According to the above configuration, the sensor driving device according to the present invention performs the start-up process for determining the stability of the output value of the oxygen sensor 1, notifies the user that the start-up process is being performed, and eliminates erroneous diagnosis. An oxygen measurement can be performed.

Example 1 The limiting current type oxygen sensor was driven using the apparatus shown in FIGS. The detection time interval was 1 second, and the judgment time interval was 5 seconds. The predetermined value Ir is 0.1% in terms of oxygen concentration.
O ₂ , and the target value Cr was 5.

FIG. 4 shows the variation of the output current of the oxygen sensor 1 and the end point of the start-up processing determined by the present apparatus. FIG.
As can be seen, the drive device according to the present invention was able to determine the correct output balance of the oxygen sensor 1.

Although the present invention has been described with reference to the embodiment, the present invention is not limited to this embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in this embodiment, the output value of the oxygen sensor is treated as a current value. However, the output value may be converted into a voltage value or an oxygen concentration. Further, the counting is performed by a subtraction method, but may be performed by an addition method.

[0027]

As described above, by using the oxygen sensor driving device of the present invention, it is possible to inform the user that the oxygen sensor is in the process of being started, and to operate the sensor even after a power failure. The user can be notified of the restart, and an accurate and safe device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a driving device of an oxygen sensor according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a process flow of the oxygen sensor driving device according to one embodiment of the present invention.

FIG. 3 is a flowchart illustrating a process flow of the oxygen sensor driving device according to the embodiment of the present invention.

FIG. 4 is a graph showing a change in output current at the time of starting a sensor according to an embodiment of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 27/41

Claims (3)

(57) [Claims] 1. A driving device for starting a limiting current type oxygen sensor comprising an oxygen ion conductive solid electrolyte, comprising: (a) means for detecting an output value of the oxygen sensor at predetermined intervals; (C) means for calculating the absolute value of the difference between the output value of the oxygen sensor and the output value before a predetermined time; (c) means for comparing the absolute value of the difference with a predetermined value; A limiting current type oxygen sensor comprising: means for counting when the absolute value is smaller than the predetermined value; and (e) means for terminating the start-up process when the value of the count reaches a target value. Drive. 2. The driving device for a limiting current type oxygen sensor according to claim 1, further comprising means for displaying that the starting process is being performed. 3. The driving device according to claim 1, wherein the predetermined value is 0.01% to 0.1% in terms of oxygen concentration.
2% O ₂ , wherein the target value is 2 to 10;