JP2001141685A - Method and apparatus for evaluating oxygen sensor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for evaluating oxygen sensor elements and an apparatus used in the method for evaluating oxygen sensor elements whereby a plurality of elements can be simultaneously evaluated, an amount used of a gas for evaluation can be saved, and many oxygen sensor elements can be correctly evaluated in a short time. SOLUTION: In the method and apparatus are set a base gas-feeding part 6, an air-fuel ratio adjustment gas-feeding part 7, an element characteristic- measuring part 3 where an evaluation gas composed of a base gas and an air-fuel adjustment gas and an element 1 are brought in contact with each other, an element-heating part 4 for holding the element 1 to a predetermined temperature, a gas-transferring pipe 8 for transferring the evaluation gas to the element characteristic-measuring part, an evaluation gas-preheating part 5 for heating the evaluation gas to be transferred to an element characteristic measurement chamber, and an element characteristic-evaluating means 2 for evaluating characteristics of the element by each signal outputted from the element 1 as a result of the contact with the evaluation gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for evaluating an oxygen sensor element and an apparatus for evaluating an oxygen sensor element used in the method.

[0002]

2. Description of the Related Art Conventionally, an evaluation method and an evaluation apparatus using an evaluation exhaust gas obtained by burning an evaluation gas are disclosed in Japanese Patent Application Laid-Open No. 63-2630.
No. 53248 and Japanese Patent Application Laid-Open No. 10-274635.

[0003]

However, these evaluation devices require a large amount of gas for evaluation,
There are problems such as the necessity of a large-sized combustion device, the inability to separately control the flow rate and the temperature of the exhaust gas for evaluation, and the difficulty of simultaneously measuring a plurality of elements.

[0004]

According to a first aspect of the present invention, there is provided a method for evaluating an oxygen sensor element, comprising contacting an unburned evaluation gas having a predetermined composition with a plurality of oxygen sensor elements arranged in an element characteristic measuring section. In this case, the characteristic of each oxygen sensor element is evaluated.

The "evaluation gas" is not particularly limited, but preferably comprises a base gas and an air-fuel ratio adjusting gas for changing the composition of the evaluation gas to rich or lean. In particular, it is preferable that the air-fuel ratio adjusting gas is a flammable gas. In this case, the base gas can be preliminarily adjusted to lean, and the air-fuel ratio adjusting gas can be richly adjusted by mixing with the base gas. it can. Also,
Usually, the evaluation gas can be a mixed gas containing nitrogen, hydrogen, carbon monoxide, carbon dioxide, and the like, in addition to combustible gases such as propane, propylene, and methane, and oxygen. Note that rich means a composition having a large amount of combustible components with respect to the stoichiometric air-fuel ratio, and lean means a composition having a small amount of combustible components with respect to the stoichiometric air-fuel ratio.

It is preferable that the gas for evaluation is maintained at 250 to 550 ° C. when it is transferred to the element characteristic measuring section as in the second invention. This temperature is 250-55
It is preferred to select the desired temperature between 0 ° C. In particular, the desired temperature near the oxygen sensor element is 400 ° C.
, The temperature of the evaluation gas is set to 390 to 410 ° C. (and further to 395 to 410 ° C.) immediately before being transferred to the element characteristic measuring section.
(405 ° C.) and maintained. Similarly, if the desired temperature is 450 ° C.,
It is preferable to keep the temperature at 0 ° C (further, 445 to 455 ° C). By accurately maintaining the temperature just before the evaluation gas is transferred to the element characteristic measuring section, the element characteristics can be measured with extremely high accuracy. Further, it is possible to maintain substantially equal temperature conditions for a plurality of elements arranged in the element characteristic measuring section.

Further, the composition of the evaluation gas is alternately switched between rich and lean and at regular intervals without feeding back a response signal from the element as in the third invention (hereinafter simply referred to as an open loop). Is preferred. In the case of the evaluation method in which the response signal of the element is fed back instead of this open loop, it is necessary to control the composition and the temperature of the evaluation gas by the response signal fed back from one element, and a plurality of times are required for one measurement Cannot be evaluated. On the other hand, in the open loop, the characteristics of a plurality of elements can be evaluated by one measurement, so that the efficiency is high and the consumption of the evaluation gas can be extremely reduced. In the evaluation method of the present invention, the signal width (voltage) of the signal output from the oxygen sensor element and the internal resistance of the oxygen sensor element can be simultaneously measured in addition to the response signal.

Further, as in the fourth invention, it is preferable that the response signal of each element is corrected based on the difference in time until the gas for evaluation reaches each element. In the measurement in the open loop, the time from the moment of switching to lean or rich to the time when the output voltage changes by a predetermined amount due to the change in the composition can be used as the response time. However, the arrival time of the evaluation gas differs depending on the distance from the outlet of the evaluation gas supply unit to each element (the catalyst layer of the element). Therefore, more accurate evaluation can be performed by performing the above-described correction.

The method of correcting the response signal is not particularly limited, but is calculated as a value from which the difference has been removed by element characteristic evaluation means to which data relating to the difference in the arrival time of the evaluation gas to each element has been input in advance. After that, it can be output to a display or the like for evaluation. Further, the response signal can be evaluated by using an actual measurement value including a difference in the arrival time of the evaluation gas to each element without correction, and by changing an evaluation reference to be evaluated depending on a mounting position of the sensor. That is, the evaluation criterion for evaluating the sensor attached to the position where the gas arrival time is long is set to be longer by the arrival time.

In the evaluation method of the present invention, any element can be used as long as it can burn the gas for evaluation by the catalytic action. For example, a reference gas self-generation type oxygen sensor element, a reference gas introduction type oxygen sensor element, a resistance semiconductor type oxygen sensor element, and the like. In addition, although the element is provided with a heater for heating the element integrally or separately, the heater may be evaluated or may be evaluated without operation.

According to a fifth aspect of the present invention, there is provided an oxygen sensor element evaluation apparatus, comprising: a base gas supply section, an air-fuel ratio adjustment gas supply section, a plurality of elements arranged therein, and element characteristic measurement in which the evaluation gas comes into contact with the element. Unit, an element heating unit, a gas transfer pipe, and an element characteristic evaluation unit.

The “base gas supply section” and the “air-fuel ratio adjustment gas supply section” adjust component gas storage sections constituting the base gas and the air-fuel ratio adjustment gas, respectively, and the flow rates at which these gases are delivered. And a flow rate adjusting means. The flow rate adjusting means may be capable of continuously changing the flow rate, or may be one capable of only stopping the flow or only performing the operation like an injector. The “element heating section” is provided so as to surround the “element characteristic measurement section”, and in addition to the temperature of the element, the temperature in the element characteristic measurement section is increased by feedback from a temperature sensor or the like disposed near each element. Temperature and the temperature of the evaluation gas in the element characteristic measuring section can be accurately maintained.

This device evaluation device is, as in the sixth invention,
Further, it is preferable to have an evaluation gas preheating unit for heating the evaluation gas transferred to the element characteristic measurement unit. The evaluation gas preheating section is located at a distance of 0 to 5 cm (preferably 0 to 3 cm, more preferably 0 to 1 cm) from the connection end of the gas transfer pipe with the element characteristic measurement section, and is located in the direction of the evaluation gas supply section. ~ 5m (more preferably 2-4m, even more preferably 2m
To 3 m).
The gas preheating section for evaluation can be formed by a pipe having a temperature control function and a tape heater wound around the outer peripheral surface of the gas transfer pipe. At least 15 to 30 cm (more preferably 15 to 50 cm, even more preferably 15 to 100 c) of the evaluation gas preheating section, in particular, the element characteristic evaluation section side.
The range of m) is preferably formed by a tape heater. The temperature of the evaluation gas transferred to the element characteristic measuring unit by the evaluation gas preheating unit can be easily and accurately controlled.

Further, as in the seventh invention, it is preferable that the exhaust pipe provided downstream of the element characteristic measuring section and the air-fuel ratio adjusting gas supply section are connected. That is, the air-fuel ratio adjusting gas can be directly exhausted without passing through the element characteristic measuring section. Accordingly, it is not necessary to change the flow rate of the air-fuel ratio adjusting gas sent from the air-fuel ratio adjusting gas supply unit by the flow rate adjusting means, and the flow direction is set to either the gas transfer pipe or the exhaust pipe while maintaining a constant flow rate. You only need to select the crab. Thereby, a particularly accurate evaluation gas composition can be maintained.

The device evaluation device of the present invention does not need to burn the gas for evaluation and does not require a gas combustion device or the like, so that it can be made extremely small and simple. In the device evaluation device of the present invention, 1 to 5 liters per minute (preferably 1 to 3 liters, more preferably 1 to 5 liters)
2 liters) of gas for evaluation is sufficient. Further, the transfer amount and transfer speed of the evaluation gas can be made desired by the flow control means of the base gas and the flow control means of the air-fuel ratio adjusting gas. The provision of the evaluation gas preheating unit in addition to these flow rate adjusting means makes it possible to separately and accurately control the flow rate and the temperature of the evaluation gas. Further, in addition to being able to separately control the flow rate and the temperature of the evaluation gas, a plurality of elements can be evaluated at once because the evaluation is performed in an open loop.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to FIGS. (1) Element Characteristic Evaluation Apparatus in which Air-Fuel Ratio Adjusting Gas is Not Directly Connected to Exhaust Pipe FIGS. 1 and 3 are explanatory views illustrating an oxygen sensor element evaluation apparatus of the present invention. Each of the component gases (propane, oxygen and nitrogen) constituting the base gas is stored in the component gas storage units 611 and 6.
12 and 613. The component gas flow rate adjusting means 621, 622 and 623 are provided in the component gas storage 61.
The amount of each component gas stored in 1, 612 and 613 is adjusted. The air-fuel ratio adjusting gas (hydrogen) is stored in the air-fuel ratio adjusting gas storage unit 71. The air-fuel ratio adjusting gas flow rate adjusting means 72 adjusts the delivery amount of the air-fuel ratio adjusting gas stored in the air-fuel ratio adjusting gas storage unit 71. The base gas is adjusted to a lean and constant composition, and the gas for evaluation is adjusted to rich or lean by adjusting the flow rate of the air-fuel ratio adjusting gas by the flow rate adjusting means 72.

The delivered base gas and air-fuel ratio adjusting gas are transferred to a gas transfer pipe 8 having a diameter of 3 to 10 cm and a length of 1.5 to 4.5 m to be used as an evaluation gas. On the outer peripheral surface of the gas transfer pipe 8, a 10
A tape heater 51 wound over about 20 cm, 1 to 5 m from the gas supply end of the tape heater to the gas supply side
And an evaluation gas preheating unit 5 including a pipe 52 having a temperature control function is provided, and the evaluation gas is heated while passing through the gas transfer pipe 8. 10 to 2 immediately before the element characteristic measurement section
A temperature sensor 53 composed of a thermocouple is provided at a portion of 0 cm, and the amount of heat generated by the tape heater 51 can be controlled by feedback. After that, the heated evaluation gas is transferred to the element characteristic measuring unit 3.

The element characteristic measuring section 3 is a tube having a diameter of 3 to 10 cm and a length of 10 to 30 m, and is provided with five element mounting holes so that the tip of the element 1 projects into the element characteristic measuring section. . Further, an element heating section 4 composed of a cartridge heater is provided so as to surround the element characteristic measuring section 3. Also, two temperature sensors 41 are provided for one element on the side of the element tip. This temperature sensor 4
Numeral 1 can control the amount of heat generated by the element heating unit 4 by feedback, and accurately adjust the temperature of the element tip to a predetermined temperature,
For example, it can be maintained at 400 ° C.

The evaluation gas transferred to the element characteristic measuring section 3 comes into contact with the element 1. Each element is provided with a lead wire to which a response signal is output, and the response signal is output to the element characteristic evaluation means 2 connected thereto. The element characteristic evaluation means 2 evaluates the characteristics of each element from these response signals according to a program input in advance, and outputs the result to a display (not shown). Note that this evaluation method can be suitably used when extracting and evaluating elements for each firing batch.

(2) Element Characteristic Evaluation Apparatus Where Air-Fuel Ratio Adjusting Gas is Directly Connected to Exhaust Pipe FIGS. 2 and 3 are explanatory views illustrating an oxygen sensor element evaluation apparatus of the present invention. The difference from (1) is that the air-fuel ratio adjusting gas does not pass through the
Can be discharged from Thereby, it is not necessary to adjust the flow rate by the flow rate adjusting means of the air-fuel ratio adjusting gas,
The gas for evaluation can be adjusted to rich or lean by changing the delivery direction with an injector while keeping the flow rate constant. Therefore, it is possible to change the air-fuel ratio of the gas for evaluation only to two kinds of compositions at regular intervals without changing the air-fuel ratio more continuously, so that the characteristics of the element can be evaluated with high accuracy.

[0021]

According to the first aspect of the present invention, a plurality of elements can be evaluated simultaneously, the amount of gas used for evaluation can be reduced, and a large number of oxygen sensor elements can be evaluated in a short time.
According to the second to fourth aspects of the present invention, a plurality of oxygen sensor elements can be evaluated more accurately. According to the fifth aspect of the present invention, a plurality of elements can be evaluated at the same time, a small amount of evaluation gas is used, and a small and simple oxygen sensor element evaluation apparatus can be obtained.
According to the sixth and seventh aspects of the present invention, an oxygen sensor element evaluation device capable of performing particularly accurate evaluation is obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing one example of an oxygen sensor element evaluation device of the present invention.

FIG. 2 is an explanatory view schematically showing another example of the oxygen sensor element evaluation device of the present invention.

FIG. 3 is an explanatory diagram schematically showing an enlarged view of the vicinity of an element characteristic measuring unit in FIGS. 1 and 2;

[Explanation of symbols]

A: oxygen sensor element evaluation device, 1: oxygen sensor element,
2; element characteristic evaluation means, 3; element characteristic measuring section, 4; element heating section, 5; evaluation gas preheating section, 51; tape heater,
52; pipes having a temperature control function, 41, 53; temperature sensors, 6; base gas supply units, 611, 612, 613; component gas storage units, 621, 622, 623;
7; air-fuel ratio adjusting gas supply unit, 71; air-fuel ratio adjusting gas storage unit, 72; flow rate adjusting means, 8; gas transfer pipe, 9; exhaust pipe.

Claims (7)

[Claims] An unburned evaluation gas having a predetermined composition is brought into contact with a plurality of oxygen sensor elements arranged in an element characteristic measuring section to evaluate the characteristics of each of the oxygen sensor elements. Characteristic evaluation method of oxygen sensor element. 2. The method for evaluating an oxygen sensor element according to claim 1, wherein the temperature of the evaluation gas transferred to the element characteristic measuring section is maintained at 250 to 550 ° C. 3. The method according to claim 1, wherein the composition of the evaluation gas is alternately switched between rich and lean and at regular intervals without feeding back a response signal from the oxygen sensor element due to the contact with the evaluation gas. 2. The method for evaluating an oxygen sensor element according to claim 1, wherein the characteristic of the oxygen sensor element is evaluated. 4. The method for evaluating an oxygen sensor element according to claim 1, wherein a response signal of each of the oxygen sensor elements is corrected based on a difference in time until the evaluation gas reaches each of the oxygen sensor elements. 5. A base gas supply unit for supplying a base gas constituting an evaluation gas, and an air / fuel ratio adjustment gas supply unit for supplying an air / fuel ratio adjustment gas which constitutes the evaluation gas and adjusts the composition thereof. A plurality of oxygen sensor elements are disposed therein, and an element characteristic measuring section in which the evaluation gas and the oxygen sensor element are in contact, one end of which is connected to the base gas supply section and the air-fuel ratio adjustment gas supply section, A gas transfer pipe having the other end connected to the element characteristic measuring section, an element heating section provided near the element characteristic measuring section, for holding the oxygen sensor element at a predetermined temperature, and contact with the evaluation gas. An element characteristic evaluation means for evaluating characteristics of the oxygen sensor element based on respective signals output from the oxygen sensor element. 6. An evaluation method for heating the evaluation gas to at least a part of the gas transfer pipe from a continuous portion to which the air-fuel ratio adjusting gas supply unit is connected to the element characteristic measuring unit. The oxygen sensor element evaluation device according to claim 5, further comprising a gas preheating unit. 7. An exhaust pipe for exhausting the evaluation gas is connected to a downstream side of the element characteristic measuring section, and the exhaust pipe is connected to the air-fuel ratio adjusting gas supply section. The oxygen sensor element evaluation device according to the above.