JP5819765B2 - Gas sensor temperature estimation system and gas sensor temperature control system - Google Patents

Description

  The present invention relates to a temperature estimation system for a gas sensor using model data considering thermal radiation, and a temperature control system for a gas sensor using the temperature estimation system.

A gas sensor such as an oxygen sensor is used to detect the concentration of a measurement target gas (oxygen or the like) in a gas to be measured such as exhaust gas. In using such a gas sensor, for example, when using a sensor element made of a zirconia solid electrolyte, the temperature needs to be several hundred degrees or more. For this purpose, there is known a gas sensor in which the sensor element has a bottomed cylindrical shape, and a heater is inserted into the sensor element to heat the sensor element.
And in patent document 1, based on the element temperature model predetermined to express the temperature change of the element part accompanying the heat transfer between the element part (sensor element) and the exhaust gas contacting the element part, Disclosed is a temperature control device or the like having temperature estimation means for sequentially estimating the temperature of the element portion and heater control means for controlling the heater so that the temperature of the element portion becomes a predetermined target value using the estimated value. ing.

JP 2003-315305 A

However, in the technique of Patent Document 1, heat transfer between the element portion (the gas contact portion of the sensor element) and the exhaust gas is considered, but for example, the gas contact portion of the cylindrical sensor element from the heating portion of the heater. The influence of the heat radiation between each member such as the heat radiation toward the head is not considered. For this reason, in the technique of Patent Document 1, when the temperature of the element part (the gas contact part of the sensor element) is relatively stable (for example, in the range of 700 ± 50 ° C.), the element part It is considered that the temperature can be estimated appropriately.
By the way, in a gas sensor, the temperature of an element part (gas contact part of a sensor element) may change a lot. For example, immediately after the start of driving of the internal combustion engine and the gas sensor, the temperature of the gas contact portion of the sensor element rises rapidly. Further, at the time of so-called fuel cut in which the engine brake is applied by releasing the accelerator, the contact portion of the sensor element is cooled because the outside air flows in the exhaust pipe instead of the combustion gas. Therefore, the temperature of the gas contact portion of the sensor element is rapidly decreased during the fuel cut, and the temperature is increased after the fuel cut.
However, when such a transient temperature change occurs in the gas contact portion of the sensor element, the technique of Patent Document 1 cannot appropriately estimate the temperature of the gas contact portion of the sensor element.

  The present invention has been made in view of such a problem, and includes a temperature estimation system and a site that can appropriately estimate the site temperature of a temperature estimation site in a gas sensor, including a case where a transient temperature change occurs. An object of the present invention is to provide a temperature control system of a gas sensor that controls energization to a heater using temperature.

One aspect of the present invention for solving the above problems is a bottomed cylindrical shape with a closed tip side, a cylindrical sensor element that includes a gas contact portion in contact with a gas to be measured on its tip side, and a rod-shaped tip. The portion has a heat generating portion that generates heat when energized, is inserted loosely into the cylindrical sensor element, and at least a part of the heat generating portion is in contact with the inner wall surface of the gas contact portion of the cylindrical sensor element. A temperature estimation system for estimating a part temperature that is a temperature of a temperature estimation part in the gas sensor, wherein the heat generating part of the heater and the cylindrical sensor element are Among the gas contact parts, the heat conduction between the heat generating part of the heater and the contact part with which the heat generating part contacts, and from the heat generating part of the heater to the gas sensor part of the cylindrical sensor element other than the contact part. Heat release toward non-contact parts It has a site-temperature estimation means for estimating the site temperature using model data in consideration of the thermal conduction between the contact portion of the gas-contact portion of the tubular sensor element and the heating portion of the heater A second thermal circuit describing heat radiation from the heat generating portion of the heater toward a non-contact portion other than the contact portion of the gas contact portion of the cylindrical sensor element, Thermal circuit data storage means for storing thermal network data of a thermal network modeled on the gas sensor including the gas sensor, wherein the part temperature estimation means uses the thermal network data as the model data, The temperature of the part is estimated by a network method, and the gas sensor surrounds a base end side gas contact part on the base end side of the gas contact part of the cylindrical sensor element while being spaced apart from the gas contact part. On the base end side The holding element that indirectly holds the sensor element and has a coupling part that couples itself to an external member, and is disposed on the distal end side of the holding metal part so as to be separated from the gas contact part of the cylindrical sensor element And a protector that covers the gas contact part so as to allow the gas to be measured to flow between the holding metal fitting and the gas contact part, and the thermal circuit network that models the gas sensor, A third thermal circuit that describes heat radiation from the gas contact portion of the cylindrical sensor element toward the holding bracket; and heat radiation from the gas contact portion of the cylindrical sensor element toward the protector. Is a temperature estimation system for a gas sensor that also includes a fourth thermal circuit .

  In this gas sensor temperature estimation system, a cylindrical sensor element, a rod-like heater inserted into the cylindrical sensor element in a loose-fitting manner, and arranged in contact with the inner wall surface of the gas contact portion of the cylindrical sensor element; With respect to the gas sensor provided with, the part temperature which is the temperature of the temperature estimation part in the gas sensor is estimated.

Usually, in this gas sensor, the temperature of the heat generating part of the heater is the highest. Then, the heat generated in the heat generating portion of the heater is first transmitted in the form of heat conduction to the contact portion of the cylindrical sensor element that is in contact with the heat generating portion. In addition, the heat is transmitted to the non-contact portion of the cylindrical sensor element that is not in contact with the heat generating portion in the form of heat radiation. By considering this thermal radiation, transient thermal analysis (temperature estimation) can be performed more appropriately. Thus, it is possible to appropriately estimate the part temperature of the predetermined temperature estimation part of the gas sensor including the cylindrical sensor element and the heater, including the case of a transient response.

The temperature estimation part may be any part of the gas sensor. For example, the gas contact part of the cylindrical sensor element, the part where the heat generating part of the heater is in contact with the inner wall surface of the gas contact part, or adjacent thereto Examples include a part, a heating part of a heater, and a metal fitting holding a cylindrical sensor. In particular, the temperature of the gas contact portion, and further, the temperature of the portion of the gas contact portion where the heater heat generating portion is in contact with the inner wall surface greatly affects the sensor sensitivity and sensor resistance value of the gas sensor. Therefore, obtaining these pieces of information is useful for gas sensor control, gas sensor state detection, sensor output correction, and the like.
Examples of the gas sensor include an oxygen sensor that detects the oxygen concentration of the gas to be measured using a cylindrical sensor element made of a zirconia solid electrolyte.

In addition, as the temperature estimation system, a temperature estimation system that estimates the temperature of a specific temperature estimation part (for example, “a part of the gas contact part where the heat generating part of the heater is in contact with the inner wall surface)” of the gas sensor; can do. In addition, the temperature of a plurality of specific temperature estimation parts (for example, "the part where the heat generating part of the heater is in contact with the inner wall surface of the gas contact part" and "the metal fitting holding the cylindrical sensor") A temperature estimation system for estimation may be used. Or it is good also as a temperature estimation system which selects the appropriate position of a gas sensor at any time, and estimates the temperature about the selected said part.
This temperature estimation system can be realized by installing a thermal analysis program and data in a personal computer separately from an actual gas sensor or the like for behavioral analysis (temperature estimation) of the temperature of each part of the gas sensor. .
Or it has an energization control device which controls energization of a gas sensor (cylindrical sensor element and heater), and controls the gas sensor with this energization control device in accordance with an instruction from another control device (electronic control unit: ECU) The thermal analysis program for estimating the temperature and the model data of the gas sensor or the like can be stored in a microcomputer including a microprocessor, ROM, RAM, etc. that constitutes the energization control device, and this can be realized as a temperature estimation system. Alternatively, a thermal analysis program and model data such as a gas sensor are stored in a microcomputer including a microprocessor, ROM, RAM, and the like that constitute another control device (for example, ECU) described above, and this is realized as a temperature estimation system. You can also.
In the case of the latter two, when driving the gas sensor (cylindrical sensor element, heater), for example, a specific part such as “a part of the gas contact part where the heat generating part of the heater is in contact with the inner wall surface” is selected. The temperature of the temperature estimation part can be estimated in real time. Furthermore, using this estimated temperature (without performing feedback control using a temperature sensor or the like), the heater is energized (by controlling the energization of the heater to the energization control device), thereby providing a temperature control system for the gas sensor. You can also.

In addition, in this temperature estimation system for the gas sensor, the temperature of the part is estimated by the thermal network method using the thermal network data of the thermal network that models the gas sensor.
By using the thermal network method, the temperature of the gas sensor, for example, the temperature of the gas contact part of the cylindrical sensor element is estimated not only when it is relatively stable but also when it changes transiently. The site temperature of the site can be appropriately estimated.

In addition, the heat circuit data includes the first heat circuit describing the heat conduction between the heat generating portion of the heater and the contact portion with which the heat generating portion is in contact with the gas sensor portion of the cylindrical sensor element. The data of the thermal circuit network including the 2nd thermal circuit which describes the thermal radiation toward the non-contact part among the gas contact parts of the cylindrical sensor element from the part is also included.
When estimating the part temperature of a predetermined temperature estimation part, such as a gas contact part of a cylindrical sensor element, using a thermal circuit method, first, as a thermal circuit network, heat between members and the like in each part Establish a thermal network that takes transmission into consideration.
As described above, the gas sensor described above has a heater in addition to the cylindrical sensor element. Moreover, normally, in this gas sensor, the temperature of the heat generating portion of the heater is the highest. Then, the heat generated in the heat generating portion of the heater is first transmitted in the form of heat conduction to the contact portion of the cylindrical sensor element that is in contact with the heat generating portion. In addition, the heat is transmitted to the non-contact portion of the cylindrical sensor element that is not in contact with the heat generating portion in the form of heat radiation. By considering this thermal radiation, transient thermal analysis (temperature estimation) can be performed more appropriately.
Therefore, in this system, as described above, in addition to the first thermal circuit showing the heat conduction between the heat generating portion of the heater and the contact portion of the cylindrical sensor element, heat radiation from the heat generating portion toward the non-contact portion is performed. The thermal network method is applied using the data of the thermal network including the second thermal circuit to be described.
As a result, the thermal circuit network becomes closer to reality, and it is possible to appropriately estimate the temperature of the part including the case of a transient response for the predetermined temperature estimation part of the gas sensor including the cylindrical sensor element and the heater. Become.

  As the second thermal circuit, in addition to the one that describes heat radiation from the heat generating part of the heater toward the non-contact part of the gas contact part of the cylindrical sensor element (thermal circuit element), the cylindrical sensor from the heat generating part of the heater It can also include one (thermal circuit element) that describes heat transfer through the gas in the cylindrical sensor element towards the non-contact portion of the element.

This temperature estimation system can be realized by installing a thermal analysis program and data in a personal computer separately from an actual gas sensor or the like for behavioral analysis (temperature estimation) of the temperature of each part of the gas sensor. .
Or it has an energization control device which controls energization of a gas sensor (cylindrical sensor element and heater), and controls the gas sensor with this energization control device in accordance with an instruction from another control device (electronic control unit: ECU) , A thermal analysis program for temperature estimation using a thermal network method and thermal circuit data such as a gas sensor are stored in a microcomputer including a microprocessor, a ROM, a RAM, etc. that constitute an energization control device, and this is estimated. It can also be realized as a system. Alternatively, a thermal analysis program for temperature estimation using a thermal network method and thermal circuit data such as a gas sensor are stored in a microcomputer including a microprocessor, a ROM, a RAM, etc. that constitute another control device (for example, ECU) described above. This can be realized as a temperature estimation system.

By the way, the heat transmitted from the heating part of the heater to the gas contact part of the cylindrical sensor element is transmitted to the above-described holding metal fitting and protector by heat radiation.
As described above, since transient thermal analysis (temperature estimation) can be performed more appropriately by considering thermal radiation, this system holds from the gas contact part of the cylindrical sensor element as described above. Using the data of the thermal circuit network including the third thermal circuit describing the thermal radiation toward the metal fitting and the fourth thermal circuit describing the thermal radiation toward the protector from the gas contact part of the cylindrical sensor element, Apply the thermal network method.
Thereby, about the predetermined | prescribed temperature estimation site | part of a gas sensor provided with the above-mentioned cylindrical sensor element and a heater, including the case of a transient response, it becomes possible to estimate site | part temperature more appropriately.

In addition, as a connecting method of the holding metal fitting and the protector, in addition to fixing by welding or the like, the engagement of the convex part provided on the holding metal fitting and the concave part provided on the protector, or conversely, the concave part provided on the holding metal fitting and the protector Connection by engagement with the provided convex part is included.
Further, examples of the external member to which the holding metal fitting is coupled include an exhaust pipe of an internal combustion engine, an intake pipe, a sensor attachment member for attaching a gas sensor (holding metal fitting) thereto, an attachment member for attaching a gas sensor to the gas chamber, and the like. It is done.

  Further, in the temperature estimation system for a gas sensor described above, the external member is a metal vent pipe through which the gas to be measured flows, and has a coupled portion formed around a through-hole penetrating itself. The gas sensor is configured such that the gas contact portion of the cylindrical sensor element is disposed in the vent pipe through the through hole, and the coupling portion of the holding fitting of the gas sensor is the coupled portion of the vent pipe. The thermal circuit network that is coupled to the gas sensor and models the gas sensor includes a fifth thermal circuit that describes heat conduction between the coupling portion of the holding fitting and the coupled portion of the vent pipe. The temperature estimation system is good.

The gas sensor may be connected to a vent pipe through which the gas to be measured flows. For example, a gas sensor may be connected to an exhaust pipe of an internal combustion engine (the gas to be measured is exhaust gas) or an intake pipe of the internal combustion engine (the gas to be measured is outside air or a mixture of outside air and exhaust gas).
In this case, a part of the heat transferred from the gas contact portion of the cylindrical sensor element to the holding metal is transferred from the connecting portion to the exhaust pipe through the connected portion of the vent pipe. Note that when the exhaust pipe is an exhaust pipe and the exhaust pipe becomes hot due to high-temperature exhaust gas, contrary to the above, the holding metal is heated from the joined part of the vent pipe through the joint of the holding metal. May be reported.
Therefore, in this system, as described above, using the data of the thermal circuit network including the fifth thermal circuit describing the heat conduction between the coupling portion of the holding metal fitting and the coupled portion of the vent pipe, the thermal circuit is used. Apply the net method. Thereby, about the predetermined temperature estimation part of the gas sensor provided with the above-mentioned cylindrical sensor element and heater, it is possible to analyze the thermal behavior including the influence of heat radiation to the vent pipe (or the inflow of heat from the vent pipe), Furthermore, it is possible to estimate the part temperature appropriately.

  Furthermore, in the temperature estimation system for a gas sensor according to the above item 2, the gas sensor is tubular, is located outside the external member, and is located on the base end side with respect to the coupling portion of the holding metal. The thermal circuit network having an outer cylinder connected to the base end and extending to the base end side, the gas sensor being modeled, is a sixth thermal circuit describing heat conduction between the holding metal fitting and the outer cylinder, and A temperature estimation system for a gas sensor including a seventh heat circuit describing heat transfer between the outer cylinder and the outside air surrounding the outer cylinder may be used.

When the gas sensor has the above-described outer cylinder, a part of the heat transmitted from the holding metal fitting to the outer cylinder is dissipated through the outside air surrounding the outer cylinder.
Therefore, in this system, as described above, the sixth heat circuit describing the heat conduction between the holding metal fitting and the outer cylinder, and the second heat circuit describing the heat conduction between the outer cylinder and the outside air surrounding the outer cylinder. The thermal network method is applied using the data of the thermal network including 7 thermal circuits.
As a result, it is possible to analyze the thermal behavior of the predetermined temperature estimation part of the gas sensor including the cylindrical sensor element and the heater, including the influence of heat dissipation to the outside air through the outer cylinder, and more appropriately Estimation is possible.

  Furthermore, in the temperature estimation system for a gas sensor described above, the gas sensor is mounted on a vehicle, and the seventh thermal circuit includes an outer cylinder and an outer air surrounding the outer cylinder according to the vehicle speed of the vehicle. A temperature estimation system for a gas sensor, which is a variable seventh thermal circuit that also describes changes in heat transfer, may be used.

When the gas sensor is mounted on the vehicle, heat transfer between the outer cylinder and the outside air surrounding the outer cylinder is relatively low when the vehicle speed is low (when the vehicle is low). On the other hand, heat transfer is relatively high when the vehicle speed is high (in the case of high speed). That is, it changes according to the vehicle speed.
Therefore, in this system, as described above, regarding the seventh thermal circuit describing the heat conduction between the outer cylinder and the outside air, the heat of the outer cylinder and the outside air surrounding the outer cylinder according to the vehicle speed of the vehicle. A variable seventh thermal circuit that also describes the change in transmission is used, and the thermal network method is applied using data of the thermal network including the seventh thermal circuit.
As a result, it is possible to analyze the thermal behavior of the predetermined temperature estimation part of the gas sensor including the cylindrical sensor element and the heater described above, including the influence of the heat dissipation to the outside air through the outer cylinder, including the change in the influence due to the vehicle speed. In addition, it is possible to estimate the part temperature more appropriately.

The temperature estimation system for a gas sensor according to any one of the preceding claims, wherein the temperature estimation part is in contact with the heat generating part of the heater on the inner wall surface of the gas contact part of the cylindrical sensor element. The contact portion temperature is the contact portion temperature in the contact portion, and the portion temperature estimation means is a temperature estimation system of a gas sensor which is a contact portion temperature estimation means for estimating the contact portion temperature. good.
In particular, it has a bottomed cylindrical shape with the tip side closed, a cylindrical sensor element that includes a gas contact part that contacts the gas to be measured on its tip side, and a rod-like heating part that generates heat when energized at the tip part, A gas sensor comprising: a heater that is loosely inserted into the cylindrical sensor element, and at least a part of the heat generating part is disposed in contact with an inner wall surface of the gas contact part of the cylindrical sensor element. A temperature estimation system for estimating a part temperature which is a temperature of a temperature estimation part in the gas sensor, wherein the heat generating part of the heater out of the heat generating part of the heater and the gas contact part of the cylindrical sensor element is provided. Model data in consideration of heat conduction with the contacting part and heat radiation from the heat generating part of the heater toward a non-contact part other than the contact part in the gas contact part of the cylindrical sensor element Using the above part A first thermal circuit that describes heat conduction between the heat generating part of the heater and the contact part of the gas contact part of the cylindrical sensor element; A thermal circuit that models the gas sensor, including a second thermal circuit that describes heat radiation from the heat generating portion of the heater toward a non-contact portion other than the contact portion of the gas contact portion of the cylindrical sensor element. Thermal network data storage means for storing thermal network data of the network is included, and the part temperature estimation means estimates the part temperature by the thermal circuit method using the thermal network data as the model data. The temperature estimation part is the contact part that is in contact with the heat generating part of the heater on the inner wall surface of the gas contact part of the cylindrical sensor element, and the part temperature is at the contact part. Contact part temperature, before Site temperature estimating means, may the temperature estimation system of the gas sensor is a contact portion temperature estimation means for estimating the contact portion temperature.

Among the gas contact parts of the cylindrical sensor element, the contact part that is in contact with the heat generating part of the heater on the inner wall surface is the part where the temperature is highest among the gas contact parts, and the temperature of this contact part is the temperature of the gas sensor. It greatly affects sensor sensitivity and sensor resistance.
Therefore, detecting the temperature of the contact portion is important for control of the gas sensor and sensor output processing.
In this system, since the contact part temperature is estimated by the contact part temperature estimation means, it is possible to easily obtain information important for the control of the gas sensor and the processing of the sensor output including the case where the contact part temperature is changing. .
Further, the gas sensor surrounds the base contact gas portion on the base end side of the gas contact portion of the cylindrical sensor element while being spaced apart, and is located on the base end side of the gas contact portion. In addition to holding the element indirectly, it is provided with a holding metal fitting having a coupling portion that couples itself to an external member, and the external member is a metal vent pipe through which the gas to be measured flows, and penetrates through the self. The gas sensor is configured such that the gas contact portion of the cylindrical sensor element is disposed in the vent pipe through the through hole. The thermal circuit network in which the coupling portion of the metal fitting is coupled to the coupled portion of the vent pipe, and the gas sensor is modeled, includes the coupling portion of the holding metal fitting and the coupled portion of the vent pipe. 5th heat describing heat conduction between May the temperature estimation system of the gas sensor including road.
In addition, the gas sensor surrounds a base end side gas contact portion on the base end side of the gas contact portion of the cylindrical sensor element while being spaced apart, and the cylindrical sensor element is positioned on the base end side with respect to the gas contact portion. A holding fitting having a coupling part for coupling itself to an external member, and in a cylindrical shape, located outside the external member and closer to the proximal side than the coupling part of the holding fitting The thermal circuit network having an outer cylinder connected to the holding metal fitting and extending to the proximal end side, and modeling the gas sensor, is a sixth thermal circuit describing heat conduction between the holding metal fitting and the outer cylinder, And the temperature estimation system of the gas sensor also including the 7th thermal circuit describing the heat transfer of the said outer cylinder and the external air which surrounds this outer cylinder. And good.
In addition, the gas sensor is an in-vehicle gas sensor mounted on a vehicle, and the seventh thermal circuit changes a heat transfer between the outer cylinder and outside air surrounding the outer cylinder according to a vehicle speed of the vehicle. It is preferable to use a temperature estimation system for a gas sensor, which is a variable seventh thermal circuit.

  In another aspect, based on the temperature estimation system for the gas sensor according to any one of the above-described items and the part temperature estimated by the part temperature estimation unit, the heater temperature is adjusted so that the part temperature becomes a target temperature. It is a temperature control system of a gas sensor having a heater control means for controlling energization.

  In this temperature control system of a gas sensor, when performing heater control to control the temperature of the temperature estimation portion of the gas sensor to a target temperature, the temperature of the temperature estimation portion in the gas sensor is determined using a thermal circuit network that models the gas sensor. Therefore, it is not necessary to actually measure the temperature of the estimated temperature using a temperature sensor or the like. For this reason, the structure of a temperature control system can be simplified.

  Furthermore, it has a bottomed cylindrical shape with the tip side closed, and has a cylindrical sensor element that includes a gas contact part that contacts the gas to be measured on its tip side, and a bar-like heating part that generates heat when energized at the tip part, A gas sensor comprising: a heater that is loosely inserted into the cylindrical sensor element, and at least a part of the heat generating part is disposed in contact with an inner wall surface of the gas contact part of the cylindrical sensor element. Thermal network data of a thermal network modeled so as to be analyzable using a thermal network method, wherein the heat generation of the heater out of the heat generation portion of the heater and the gas contact portion of the cylindrical sensor element Data of the first thermal circuit describing heat conduction with the contact part with which the part contacts, and non-contact other than the contact part of the gas contact part of the cylindrical sensor element from the heat generating part of the heater Of the second thermal circuit describing the heat radiation towards the part Preferably over data, and thermal network data of the thermal network that models the gas sensor including.

In this thermal circuit data, in addition to the first thermal circuit indicating the heat conduction between the heater heat generating portion and the contact portion of the cylindrical sensor element, the heat radiation from the heat generating portion toward the non-contact portion is described. Includes thermal network data including two thermal circuits.
For this reason, by performing thermal analysis (temperature estimation) using the thermal network method using this thermal network data, the thermal network becomes closer to reality, and the above-described cylindrical sensor element, heater, As for a predetermined temperature estimation part of the gas sensor including the part temperature including the transient response, the part temperature can be appropriately estimated.

  Furthermore, it is thermal circuit network data of a thermal circuit network that models the gas sensor described above, and the gas sensor is spaced apart from a proximal end gas contact portion on the proximal end side of the gas contact portion of the cylindrical sensor element. However, it surrounds and holds the cylindrical sensor element indirectly on the base end side with respect to the gas contact part, and has a holding fitting having a coupling part for coupling itself to an external member, and the tip on the distal end side of the holding fitting. A protector that is disposed apart from the gas contact portion of the cylindrical sensor element, is connected to the holding metal fitting, and covers the gas contact portion so that the gas to be measured can flow between the gas contact portion and The thermal circuit network data includes data of a third thermal circuit describing heat radiation from the gas contact portion of the cylindrical sensor element toward the holding metal, and the cylindrical sensor element. From the gas contact part of the Preferably a gas sensor including a data of the fourth heat circuit describing the thermal radiation and the modeled thermal circuitry thermal network data for the connector.

In this thermal network data, the third heat circuit describing the heat radiation from the gas contact part of the cylindrical sensor element toward the holding bracket, and the heat radiation from the gas contact part of the cylindrical sensor element toward the protector The data of the thermal network including the fourth thermal circuit to be described is included.
For this reason, using this thermal network data, by performing thermal analysis (temperature estimation) using the thermal network method, for a predetermined temperature estimation part of the gas sensor comprising the above-described cylindrical sensor element and heater, It is possible to estimate the part temperature more appropriately including the case of the transient response.

FIG. 3 is an explanatory diagram illustrating a configuration of a personal computer according to the first embodiment and forming a temperature estimation system for an oxygen sensor. It is a longitudinal cross-sectional view which shows the structure of the oxygen sensor of the state attached to the exhaust pipe. It is explanatory drawing which shows the flow of the heat | fever in the oxygen sensor attached to the exhaust pipe. It is the schematic of the thermal circuit network which simulated the oxygen sensor attached to the exhaust pipe. It is explanatory drawing which shows the legend of the symbol used for the thermal circuit network. FIG. 5 is a detailed view of a thermal circuit network simulating an oxygen sensor attached to an exhaust pipe shown in FIG. 4 according to the first embodiment. FIG. 4 is a schematic diagram of a thermal circuit network according to Embodiments 2 and 3 and Comparative Examples 1 and 2, simulating an oxygen sensor attached to an exhaust pipe. Shows the measurement results and estimation results using the thermal network method for the temperature change of the contact part that contacts the heater heating part among the gas contact parts of the sensor element that occurs when the oxygen sensor is heated from room temperature It is a graph. (A) shows an actual measurement result. (B) relates to the first embodiment, and shows an estimation result in the case where all of the thermal radiation elements (R1, R2, R3) are considered (existing). (C) relates to the comparative example 1, and does not consider only the heat radiating element (R1) from the heater heat generating part to the non-contact part of the gas contact part of the sensor element among the heat radiating elements (R1, R2, R3). The result is shown. It is explanatory drawing explaining the oxygen sensor with the electricity supply control apparatus concerning the modification which implement | achieved the electricity supply control apparatus which drives an oxygen sensor as a temperature estimation system of this oxygen sensor, and was mounted in the vehicle. It is explanatory drawing which shows the relationship with the structure of an electricity supply control apparatus, an oxygen sensor, etc. in connection with a deformation | transformation form.

(Embodiment 1)
An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory diagram illustrating a configuration of a personal computer PC that forms a temperature estimation system 100 of the oxygen sensor 1 according to the first embodiment. The system 100 includes a microprocessor 102, a ROM 103, a RAM 104, an external storage device 105, a monitor 106, and a printer 107, which can communicate with each other via a bus 101. The external storage device 105 of the personal computer PC stores a thermal analysis program PG1 by a thermal network method and thermal circuit data ND described later. In this personal computer PC, the thermal analysis program PG1 and thermal network data ND are read from the external storage device 105 into the RAM 104, processed by the microprocessor 102, and the analysis (temperature estimation) result is displayed on the monitor 106. If necessary, it is stored in the external storage device 105 and printed using the printer 107. Thereby, in this system 100 and PC, estimation of the temperature of each site | part of the oxygen sensor 1 using the thermal network method is possible.

  Next, the oxygen sensor 1 and the exhaust pipe EP, which are targets for thermal analysis, will be described. FIG. 2 is a longitudinal sectional view of the oxygen sensor 1 according to the first embodiment, with the oxygen sensor 1 attached to the exhaust pipe EP, and shows the internal structure of the oxygen sensor 1. The oxygen sensor 1 includes a hollow shaft-shaped oxygen sensor element 2 having a closed tip, and a heater 15 inserted into the bottomed hole 2 a of the oxygen sensor element 2. The oxygen sensor element 2 is formed in a hollow shaft shape from a solid electrolyte having oxygen ion conductivity.

  On the inner surface of the bottomed hole 2a of the oxygen sensor element 2, a sensor internal electrode layer 2c made of, for example, Pt or a Pt alloy is formed so as to cover almost the entire surface. On the other hand, a similar porous sensor external electrode layer 2 b is provided at the tip of the outer surface of the oxygen sensor element 2. Further, an engagement flange portion 2s protruding outward in the radial direction is provided at an axial intermediate portion of the oxygen sensor element 2. When the engagement flange portion 2s is engaged and held by the ceramic holders 5 and 7 made of insulating ceramic and the ceramic powder 6 made of talc, the oxygen sensor element 2 is inserted through the oxygen sensor element 2 at the center. It is airtightly held by a cylindrical metal shell 3 having a hole. The tip of the oxygen sensor element 2 than the engagement flange portion 2S constitutes a gas contact portion 2d in contact with the exhaust gas. In the present specification, of the directions along the axis of the oxygen sensor element 2 (vertical direction in FIG. 2), the side toward the distal end (closed side, lower in FIG. 2) is referred to as “front end side” PD. The side toward the opposite direction (upward in FIG. 2) is referred to as a “base end side” BD.

  The metal shell 3 has a screw portion 3b and a hexagonal portion 3c for attaching the oxygen sensor 1 to an attachment portion such as an exhaust pipe, and the protector 4 is connected to the protector connection portion 3a by laser welding. The protector 4 is attached so as to cover the distal end portion of the oxygen sensor element 2 protruding from the distal end side opening of the metal shell 3. The oxygen sensor 1 is used by disposing the distal end side PD in the exhaust pipe EP from the threaded portion 3b of the metal shell 3, and disposing the proximal end side BD in the outside atmosphere. The protector 4 is formed with a plurality of gas permeation holes 4a through which the exhaust gas permeates.

  On the other hand, the base end portion 3 e of the metal shell 3 is crimped between the ceramic holder 7 via the ring packing 9 and is kept airtight. The distal end portion 22a of the first outer cylinder portion 22 of the cylindrical outer cylinder 21 is fixed to the connecting portion 3d on the base end side BD of the hexagonal portion 3c by laser welding from the outside. On the other hand, the base end side opening 21a of the outer cylinder 21 is hermetically sealed by fitting and closing a grommet 51 made of rubber or the like and caulking from the outer periphery. At the center of the grommet 51, a filter member 52 that introduces air into the outer cylinder 21 and prevents moisture from entering is disposed. A separator 31 made of an insulating alumina ceramic is provided on the front end side PD of the grommet 51. The sensor output lead wires 13 and 14 and the heater lead wires 18 and 19 extend through the separator 31 and the grommet 51 (see FIG. 2).

The separator 31 has a proximal end side portion 32, a distal end side portion 33, and a flange portion 34 having a larger diameter than these. Within the separator 31, the lead wires 13 and 14 and the first and second sensor terminal fittings 11 and 12 connected to them, the proximal end BD portion, the lead wires 18 and 19, and the heater terminal fitting 16 connected thereto. , 17 are held in the separator 31 while being insulated from each other.
The heater 15 is positioned in the axial direction (vertical direction in the drawing) of the heater 15 with respect to the separator 31 by the base end surface 15d of the heater 15 contacting the heater contact surface 31e of the separator 31.

  As will be described below, the heater 15 is inserted into the oxygen sensor 2 so that the heat generating portion 15a is eccentric (inclined) with respect to the axis of the bottomed hole 2a of the oxygen sensor element 2. As a result, the heat generating portion 15 a comes into contact with a part of the inner peripheral surface of the bottomed hole 2 a of the oxygen sensor element 2. That is, since heat energy can be concentrated and transmitted from the heat generating part 15a to a small volume part (contact part 2e) in the element 2, it is effective in shortening the activation time of the oxygen sensor 1. .

  The heater 15 is a rod-shaped ceramic heater, and a tip portion thereof is a heat generating portion 15a in which a resistance heat generating element (not shown) is formed around a core material mainly composed of alumina. In addition, electrode pads 15e and 15f are provided at the base end portion, and are connected to the heater terminal fittings 16 and 17 by brazing. When the heater 15 is energized from the heater drive power source S1 through the heater terminal fittings 16 and 17 and the heater lead wires 18 and 19, the heat generating portion 15a generates heat and the tip of the oxygen sensor element 2 is heated. The heater terminal fitting 17 has a connector portion (not shown) that holds the core wire of the heater lead wire 18 and electrically connects the heater terminal fitting 17 and the heater lead wire 18. Similarly, the heater terminal fitting 16 has a connector portion for holding the core wire of the heater lead wire 19. The heater 15 is held by the holding insertion portion 11a of the first sensor terminal fitting 11 at a position closer to the base end than the center.

The outer cylinder 21 is made of metal and has a substantially cylindrical shape. The outer cylinder 21 is positioned at the distal end PD (lower side in the figure), and the first end 22a of the distal end PD is joined to the metal shell 3 as described above. It has the outer cylinder part 22 and the 2nd outer cylinder part 23 which is located in proximal end BD rather than this and is smaller diameter than a 1st outer cylinder part. In the intermediate portion in the axial direction of the second outer cylinder portion 23, there are formed four inner convex portions 24 that protrude radially inwardly at four locations in the circumferential direction. The inner convex portion 24 is in contact with the flange portion 34 of the separator 31 obliquely.
Further, an urging metal fitting 41 is mounted around the front end side portion 33 of the separator 31. The urging metal fitting 41 has a base end portion 41a bent inward in a J shape and is in contact with the flange portion 34 of the separator 31. Then, as will be described later, as the deformed portion 23b is formed in the second outer cylinder portion 23 of the metal outer cylinder 21, the base end portion 41a of the urging metal fitting 41 moves the flange portion 34 of the separator 31 accordingly. The separator 31 is biased toward the base end side BD (upward in the figure).

  The oxygen sensor 1 is manufactured as follows. In advance, sensor output leads 13 and 14 are connected to the connector portions of the first and second sensor terminal fittings 11 and 12, respectively. In addition, heater lead wires 18 and 19 are connected to connector portions (not shown) of the heater terminal fittings 16 and 17. Then, with the heater 15 held by the first sensor terminal fitting 11, the lead wires 13, 14, 18, 19 are inserted into the separator 31, and the first and second sensor terminal fittings 11 are inserted into the separator 31d. , 12, the entire heater terminal fittings 16, 17, and the rear end portion 15 c of the heater 15 are kept insulated from each other.

Further, the urging metal fitting 41 is mounted on the outer periphery of the distal end side portion 33 of the separator 31 so that the J-shaped base end portion 41 a of the urging metal fitting 41 abuts on the flange portion 34 of the separator 31.
Next, the lead wire 13 or the like is inserted inside, the separator 31 holding the first sensor terminal fitting 11 or the like is loosely inserted into the metal outer cylinder 21, and each lead wire 13 or the like is inserted into the grommet 51.

Separately, using ceramic holders 5 and 7 and ceramic powder 6, the base end portion 3 e of the metal shell 3 is crimped, the oxygen sensor element 2 is assembled to the metal shell 3, and the protector connection portion 3 a of the metal shell 3 is attached. The protector 4 is welded.
Both positions are adjusted so that the axis of the oxygen sensor element 2 and the axis of the metal outer cylinder 21 coincide with each other, the outer cylinder 21 is moved to the distal side PD (downward in the figure), and the flange portion 34 of the separator 31 is moved. And the inner convex portion 24 of the outer cylinder 21 are in contact with each other obliquely, and the separator 31 is loosely inserted into the outer cylinder 21, and the grommet 51 is fitted into the proximal end side opening 21 a of the outer cylinder 21. Further, the outer cylinder 21 is moved to the front end side PD (downward in the figure). Then, the heater 15 is inserted into the bottomed hole 2 a of the oxygen sensor element 2, and the outer cylinder 21 is moved to the distal end side PD until the distal end portion 22 a of the outer cylinder 21 contacts the hexagonal portion 3 c of the metal shell 3.

  Thereby, together with the heater 15, the holding insertion portion 11 a of the first sensor terminal fitting 11 holding the heater 15 is also inserted into the bottomed hole 2 a of the oxygen sensor element 2 and is electrically connected to the sensor inner electrode layer 2 c. Further, by inserting the holding insertion portion 11 a into the bottomed hole 2 a of the oxygen sensor element 2, the axis of the heater 15 is inclined and eccentric with respect to the axis of the oxygen sensor element 2, so that the heat generating portion 15 a of the heater 15 is It adjusts so that a part (this site | part shall be contact part 2e) is contact | connected among the inner walls of the bottomed hole 2a. Accordingly, heat is transmitted to the contact portion 2e of the oxygen sensor element 2 from the heat generating portion 15a of the heater 15 by heat conduction due to contact.

  In the first embodiment, since the heater 15 is inserted into the bottomed hole 2a of the oxygen sensor element 2 with the base end surface 15d of the heater 15 in contact with the heater contact surface 31e of the separator 31, The insertion depth of the heater 15 into the bottomed hole 2 a of the oxygen sensor element 2 is uniquely determined by the dimensions of the metal outer cylinder 21, the separator 31, and the heater 15.

Thereafter, the connecting portion 3d of the metal shell 3 and the distal end portion 22a of the outer cylinder 21 positioned on the outer peripheral side are caulked in a radial direction while pressing the outer cylinder 21 against the distal end side PD (downward in the drawing). Connecting.
Further, in the second outer cylinder portion 23 of the outer cylinder 21, a part of the portion located on the outer periphery of the urging metal fitting 41 is annularly pressed and deformed into a concave shape (reduced diameter). It is formed in a ring shape. Along with this, the deformed portion 23 b of the outer cylinder 21 comes into close contact with the urging metal fitting 41, and the urging metal fitting 41 is held and fixed to the outer cylinder 21. Further, by pressing the urging metal fitting 41 in the radial direction in this way, the J-shaped base end portion 41a of the urging metal fitting 41 is slightly moved to the base end side BD (upward in the drawing). For this reason, the flange part 34 of the separator 31 is urged | biased by the base end part 41a to base end side BD (upward in the figure). Thus, the flange portion 34 of the separator 31 is sandwiched between the inner convex portion 24 of the outer cylinder 21 and the proximal end portion 41 a of the biasing fitting 41, and the separator 31 is fixed to the outer cylinder 21.

  Next, of the second outer cylinder portion 23 of the outer cylinder 21, a portion (base end side opening 21 a) located around the grommet 51 is crimped, and the outer cylinder 21, each lead wire 13, and the like are hermetically sealed. . Further, the connecting portion 3d of the metal shell 3 that has been temporarily connected and the tip portion 22a of the outer cylinder 21 are hermetically connected by laser welding to complete the oxygen sensor 1.

  The oxygen sensor 1 is used by being connected to an exhaust pipe EP of an internal combustion engine. Specifically, it is fastened using the mounting hole EPH provided in the exhaust pipe EP and the threaded portion 3 b of the metal shell 3. A gasket 8 is interposed between the exhaust pipe EP and the hexagonal portion 3c.

  Next, in order to perform thermal analysis (temperature estimation) using a thermal circuit method to be described later on the thermal behavior of the oxygen sensor 1 attached to the exhaust pipe EP, in addition to the oxygen sensor 1, the oxygen sensor 1, the exhaust pipe EP, The heat transfer between the exhaust gas EG flowing inside the exhaust pipe EP and the outside air OG outside the exhaust pipe EP will be considered with reference to FIG. 3 in addition to FIG. FIG. 3 is an explanatory diagram showing an outline of the heat flow in the oxygen sensor 1, the exhaust pipe EP, the exhaust gas EG, and the outside air OG. In FIG. 3, black arrows indicate heat paths that are transmitted mainly by heat conduction. The white arrow indicates the path of heat transmitted mainly by thermal radiation.

  In the oxygen sensor 1, as described above, when the heater 15 is energized and electric energy is injected, the heat generating portion 15a at the tip of the heater 15 mainly generates heat and becomes high temperature. Then, the heat generated in the heat generating portion 15a is transmitted to the non-heat generating portion 15b on the base end side BD in the heater 15 by heat conduction. Of the gas contact part 2d of the oxygen sensor element 2, it is also transmitted by heat conduction to the contact part 2e with which the heat generating part 15a is in contact. In addition, heat is transmitted to the non-contact portion 2f of the oxygen sensor element 2 where the heat generating portion 15a is not in contact by the heat radiation from the heat generating portion 15a.

  Of these, the heat transmitted to the non-heat generating portion 15b of the heater 15 is conducted by heat conduction to the separator 31 through the base end face 15d of the heater 15, or through the electrode pads 15e and 15f of the heater 15 and the heater terminal fittings 16 and 17. Reportedly. Further, it is transmitted from the separator 31 to the outer cylinder 21 (of which the second outer cylinder portion 23 on the base end side BD) and radiated to the outside air OG.

  Further, the heat transferred from the contact portion 2e or the heat generating portion 15a to the non-contact portion 2f of the gas contact portion 2d of the oxygen sensor element 2 is transferred to the proximal end BD of the oxygen sensor element 2, and the ceramic holders 5, 7 And, it is transmitted to the metal shell 3 through the ceramic powder 6. In parallel with this, the non-contact portion 2f of the gas contact portion 2d of the oxygen sensor element 2 is not contacted to the tip portion (for example, the protector connection portion 3a) of the metal shell 3 that is in close proximity thereto. Heat is transferred by thermal radiation from 2f. The heat transmitted to the metal shell 3 is radiated to the outside air OG through the outer cylinder 21 (first outer cylinder portion 22).

  Further, the metal shell 3 is also moved by heat conduction between the metal shell 3 and the protector attached to the front end side PD. In addition, heat is transmitted to the metal shell 3 with the exhaust pipe EP through the screw portion 3b. In addition, between the metal shell 3 and the protector 4, and between the metal shell 3 and the exhaust pipe EP, heat is transferred between them due to a mutual temperature difference.

Heat is directly transmitted to the protector 4 by heat radiation from the contact portion 2e of the oxygen sensor element 2 which is particularly likely to reach a high temperature. The protector 4 also receives heat from the exhaust gas EG flowing in the exhaust pipe EP. The gas contact part 2d of the oxygen sensor element 2 also receives heat from the exhaust gas EG.
Further, the exhaust pipe EP receives heat from the exhaust gas EG and contacts the outside air OG to radiate heat.

  The oxygen sensor 1 attached to the exhaust pipe EP is generally considered to have the heat path as described above. Therefore, the thermal network HC1 in FIG. 4 shows this path as a thermal network. A legend of the symbols is shown in FIG. In this thermal circuit network HC1, the oxygen sensor 1 and the exhaust pipe EP are divided into 10 thermal conduction elements E1 to E10, and mutual thermal conduction is considered through thermal circuits C2, C4 to C7, C9, and C11 to C14. In addition, heat transfer with the exhaust gases F1 to F3 through the heat circuits C16 to C20, heat transfer with the outside air F4 and F5 through the heat circuits C21 to C24, and further through the heat circuits C3, C8, and C10. Thermal radiation by the thermal radiation elements R1 to R3 was assumed.

Specifically, in the thermal circuit network HC1, the heater energy that flows from the power source S1 through the thermal circuit C1 becomes heat in the element E1 that is the heater heating portion. Further, the element E1 is transmitted to the heat conducting elements E2, E3, E4 (heater non-heat generating portion 15b, heater base end face 15d and separator 31, outer cylinder 21) through the thermal circuits C4, C5, C6.
Further, heat is transmitted from the element E1 which is the heater heat generating portion to the element E5 which is the contact portion 2e of the gas sensor element 2 through the thermal circuit C2, and further, through the thermal circuits C7, C9 and C11, the heat conducting elements E6 and E6. Heat is transmitted to E7, E8 (non-contact part 2b of oxygen sensor element 2, ceramic holders 5, 7 and ceramic powder 6, metal shell 3). The element E8 that is the metal shell 3 is also connected to the element E4 (outer cylinder 21), the element E9 (protector 4), and the element E10 (exhaust pipe EP) by thermal circuits C12, C13, and C14.

  In addition, heat is directly transmitted from the element E1 which is the heat generating part 15a to the element E6 (non-contact part 2f) also by the thermal circuit C3 via the heat radiation element R1. In addition, heat is directly transmitted from the element E5, which is the contact portion 2e, to the element E9 (protector 4) also by the thermal circuit C8 through the heat radiation element R2. Furthermore, heat is directly transmitted from the element E6, which is the non-contact portion 2f, to the element E8 (the metal shell 3) also by the thermal circuit C10 through the heat radiating element R3.

In order to describe heat transfer between the element V1 indicating the exhaust gas EG and the gas contact part (element E6), the protector 4 (element E9), and the exhaust pipe EP (element E10) of the oxygen sensor element 2, In between, the elements F1-F3 which show exhaust gas EG are interposed, and these are connected by thermal circuit C15-C20.
Further, in order to describe heat transfer between the element V2 indicating the outside air OG and the outer cylinder 21 (element E4) and the exhaust pipe EP (element E10), elements F1 to F3 indicating the outside air OG are interposed between them. They are interposed, and these are connected by thermal circuits C21 to C24.

When this thermal circuit network HC1 is described as a more detailed thermal circuit network that approximates an electric circuit network, it is expressed as shown in FIG. Here, as shown in the legend of FIG. 5, the heat conduction element (for example, the element E <b> 1) shown in a rectangular box shape in FIG. 4 is a heat resistance element (electric resistance element) when transferring heat to another heat conduction element. Equivalent) and an element (for example, E11, E12, E13) indicating a heat capacity element (corresponding to a grounded capacitor) that stores heat is represented by a T-type circuit. In addition, in the heat transfer elements (elements F1 to F5) indicated by parallelogram boxes in FIG. 4, the state of heat transfer varies depending on, for example, the flow rate and gas temperature of the exhaust gas EG and the temperature and flow rate (vehicle speed) of the outside air OG. Therefore, it is indicated by a variable resistance. Further, the heat radiating element (for example, element R1) is shown as a variable current source whose value changes with temperature.
In addition, since the heater driving power source can change the heater energy injected into the heater 15, it is shown as a variable current source (element S1). Further, the exhaust gas EG and the outside air OC are shown as variable voltage sources (elements V1 and V2) because their temperatures themselves change.
Then, the thermal circuit network HC1 is converted into thermal network data (model data) ND expressed so as to be analyzed (temperature estimation) in the thermal analysis program PG1 of the thermal network method.

  In addition, the thermal circuit C2 between the element E1 which is a heater heat generating part and the element E5 which is the contact part 2e of the gas sensor element 2 corresponds to a first thermal circuit. Further, the thermal circuit C3 through the heat radiation element R1 from the element E1 which is the heat generating part 15a to the element E6 (non-contact part 2f) corresponds to the second thermal circuit. Further, the thermal circuit C10 through the heat radiation element R3 from the element E6 to the element E8 (the metal shell 3) which is the non-contact portion 2f corresponds to the third thermal circuit. Furthermore, the thermal circuit C8 through the thermal radiation element R2 from the element E5 which is the contact portion 2e to the element E9 (protector 4) corresponds to a fourth thermal circuit. Furthermore, with the element E8 which is the metal shell 3, the thermal circuit C13 connecting the element E9 (the protector 4) corresponds to a fifth thermal circuit. Further, the thermal circuit C12 connecting the element E8 (the metal shell 3) and the element E4 (the outer cylinder 21) corresponds to a sixth thermal circuit. In addition, the thermal circuit C21 connecting the element E4 (outer cylinder 21) and the element F4 (outside air OG) corresponds to a seventh thermal circuit and a variable seventh thermal circuit.

The thermal circuit network data ND is stored in the external storage device 105 of the personal computer PC, and the microprocessor 102 is caused to execute the thermal analysis program PG1 by the thermal network method to analyze the thermal circuit network HC1. Thereby, the temperature (partial temperature) in each of the elements E1 to E10 is changed by changing the initial state, the energization (heater energy) pattern from the heater drive power supply S1, the vehicle speed, the temperature / flow velocity of the exhaust gas EG, and the temperature of the outside air OG. ) And temperature change can be analyzed and acquired by a thermal network method.
In the first embodiment, the external storage device 105 of the personal computer PC corresponds to thermal circuit data storage means. Further, the microprocessor 102 executing the thermal analysis program PG1 corresponds to the part temperature estimation means. Further, the personal computer PC corresponds to the temperature estimation system 100.

For example, an example of an analysis result of the temperature Ts (t) of the contact part 2e of the gas contact part 2d of the oxygen sensor element 2 indicated by the element E5 is shown by a solid line graph (b) in FIG. In addition, an actual measurement result of the temperature Ts (t) of the contact portion 2e is shown by a dashed-dotted line graph (a). In this example, the contact part 2e of the gas contact part 2d of the oxygen sensor element 2 corresponds to the temperature estimation part X, and the contact part temperature Ts of the contact part 2e obtained by analysis and obtained as a graph (a) Ts (t) corresponds to the site temperatures Tx and Tx (t) of the temperature estimation site X.
In this analysis, the initial state is normal temperature (25 ° C.), the outside air OG temperature is 25 ° C., the vehicle speed (outside air flow rate) is 50 km / h, the exhaust gas EG temperature is 500 ° C., and the exhaust gas flow rate is 30 m / s. Changed. Further, a DC voltage of 8V was continuously applied to the heater 15 from the heater driving power source S1 including the battery BT.

  As a result, in the actually measured oxygen sensor 1, the temperature Ts (t) of the contact portion 2e rises for about 200 seconds as shown by the dashed-dotted line graph (a) in FIG. As a result, the value approached (in this example, Ts (800) = 660 ° C. at 800 seconds from the start of energization).

  In contrast, the estimation result of the temperature Ts (t) of the contact portion 2e obtained by thermal analysis of the above-described thermal circuit network HC1 (thermal network data ND) is as shown by a solid line (b) in FIG. , Changes in almost the same way as the actual measurement (dotted line graph (a)), and finally the temperature (estimated temperature) Ts (800) at the time of 800 seconds from the start of energization is Ts (800) = 670 ° C. became. That is, the difference from the actually measured value was 10 deg. From this result, the thermal analysis (temperature estimation) by the thermal circuit method of the oxygen sensor 1 and the exhaust pipe EP using the thermal circuit network HC1 (thermal circuit data ND) of the first embodiment is effective. I understand. Further, it can be seen that an appropriate temperature can be estimated over the entire period (0 to 800 seconds in FIG. 8) including the period in which the temperature Ts changes transiently.

  Next, Embodiments 2 and 3 and Comparative Embodiments 1 and 2 will be described using thermal networks HC2, HC3, HR1, and HR2 shown in FIG. Among them, the thermal circuit network HR2 of the second embodiment is substantially the same as the thermal circuit network HC1 according to the first embodiment shown in FIG. 4, but as shown by a broken line in FIG. 7, the thermal radiation element R2 (thermal circuit C8). ) Is different only in that it is excluded. The thermal circuit network HC3 of the third embodiment is substantially the same as the thermal circuit network HC1 of the first embodiment, but differs only in that the thermal radiation element R3 (thermal circuit C10) is excluded. Similarly, the thermal circuit network HR1 of the comparative form 1 is different from the thermal circuit network HC1 only in that the thermal radiation element R1 (thermal circuit C3) is excluded. Furthermore, the thermal circuit network HR2 of the comparative form 2 is different from the thermal circuit network HC1 in that all three of the heat radiation elements R1, R2, and R3 (thermal circuits C3, C8, and C10) are excluded.

The thermal analysis (temperature estimation) was similarly performed for the thermal networks HC2, HC3, HR1, and HR2 of Embodiments 2 and 3 and Comparative Examples 1 and 2. The results are shown in Table 1 together with the first embodiment. Further, the temperature Ts (t) of the contact portion 2e obtained in the comparative form 1 is shown as a broken line graph (c) in FIG.
First, the comparative form 1 is examined. The estimation result (FIG. 8 (c)) of the temperature Ts (t) of the contact portion 2e obtained by analyzing the thermal circuit network HR1 of the comparative form 1 is as rapid as the actual measurement (dotted line graph (a)). The temperature increased, and then gradually approached a certain value. However, the temperature (estimated temperature) Ts (800) at the time point of 800 seconds from the start of energization is Ts (800) = 727 ° C. (actual value + 67 deg), and the graph (c) is also the actual graph (a) and the embodiment. Compared to the graph (b) in FIG.
From this result, it is necessary to consider at least the thermal radiation element R1 in the thermal circuit network HC1 in the first embodiment, and plays a large role in thermal analysis (temperature estimation) of the oxygen sensor 1 by the thermal network method. I understand that.

Next, Embodiment 2 will be examined. From the estimation result (see Table 1) of the temperature change of the contact portion 2e obtained by thermal analysis (temperature estimation) of the thermal circuit network HC2 of Embodiment 2, the temperature (699 ° C.) after 800 seconds from the energization and the actual measurement value Although the difference from (660 ° C.) is 39 deg., Which is a better result than that of the comparative example 1, it can be seen that it is biased toward the high temperature side as compared with the actual measurement and the first embodiment.
Also from this result, it is understood that it is important to consider the thermal radiation element R1. In addition, from the results of the second embodiment, it can be seen that consideration of the heat radiating element R2 in the thermal circuit network is also a major factor in the thermal analysis of the oxygen sensor 1 by the thermal circuit method.

Next, Embodiment 3 will be discussed. From the estimation result (see Table 1) of the temperature change of the contact portion 2e obtained by thermal analysis of the thermal circuit network HC3 of Embodiment 3, the temperature (704 ° C.) after 800 seconds from the energization and the actual measurement value (660 ° C.) The difference is 44 deg., Which is better than that of the first comparative example, but is found to be biased toward the high temperature side compared to the actual measurement and the first embodiment.
Also from this result, it is understood that it is important to consider the thermal radiation element R1. Also, from the results of the third embodiment, it can be seen that considering the heat radiating element R3 in the thermal circuit network is also a major factor in the thermal analysis of the oxygen sensor 1 by the thermal circuit method.

Further, Comparative Mode 2 will be examined. The estimation result (see Table 1) of the temperature change of the contact portion 2e obtained by thermal analysis of the thermal circuit network HR2 of the comparative form 2 is also not shown in the drawing, but is initially rapid as in the actual measurement (dotted line graph (a)). As a result, the temperature gradually increased and then gradually approached a certain value. However, compared with the actual measurement and the first embodiment, the temperature is greatly biased toward the high temperature side, the temperature 800 seconds after energization (803 ° C.) becomes a very high value, and the difference from the actual measurement value (660 ° C.) is also 143 deg. It was a very large value.
From this result, in the thermal circuit network HC1 in the first embodiment, the three of the heat radiating elements R1, R2, and R3 (thermal circuits C3, C8, and C10) are extremely different in the thermal analysis by the thermal circuit method of the oxygen sensor 1. It turns out that it plays a big role.
On the contrary, the thermal circuit network HR2 of the comparative form 2 that does not consider all of the thermal radiation elements R1, R2, R3 (thermal circuits C3, C8, C10) does not consider thermal radiation at each part of the oxygen sensor 1 at all. In this respect, it approximates the conventional thermal analysis. The result of Comparative Example 2 shows that even if the thermal analysis is performed on the oxygen sensor 1 and the exhaust pipe EP without considering the heat radiation in this way, the thermal analysis with a transient temperature change has an appropriate temperature. It is difficult to estimate.
For example, the constants of the elements (E11, E12,..., See FIG. 6) of each part of the thermal network HR2 are set so that the estimated temperature (803 ° C.) at the time of 800 seconds becomes the actual measurement value (660 ° C.). Suppose that the estimated temperature at this time is adjusted to be lowered by about 140 deg. Thus, for example, for a temperature in a stable state after 300 seconds from the start of energization, an estimated temperature close to actual measurement is obtained. However, at the beginning of energization, conversely, the estimated temperature is calculated to be significantly lower than the actually measured value, and it can be assumed that the temperature cannot be estimated properly over the entire period.

(Deformation)
Next, modified embodiments of the first, second, and third embodiments will be described with reference to FIGS. 9 and 10. In the first embodiment described above (see FIG. 1), the temperature estimation system 100 of the oxygen sensor 1 using the thermal circuit networks HC1 to HC3 (thermal circuit network data ND) is realized by the personal computer PC.
On the other hand, in this modification, in the microcomputer 70 built in the energization control device 61 that controls energization of the oxygen sensor 1 mounted on the vehicle, the thermal circuit network HC1 and the like (thermal circuit data ND) are heated according to the thermal circuit method. Analysis is performed to estimate a part temperature Tx (t) (contact part temperature (Ts (t))) of a predetermined part (for example, the contact part 2e). Further, a temperature control system 210 that controls the temperature of the heater 15 using the estimated part temperature Tx (t) is also configured.

The temperature estimation system 200 and the temperature control system 210 of the oxygen sensor 1 in this modification will be described (see FIG. 9). The vehicle AM is equipped with an engine ENG. The engine ENG is controlled by the electronic control unit ECU. Further, the electronic control unit ECU detects the vehicle speed of the vehicle AM, the temperature of the outside air OG, the temperature of the exhaust gas EG, and the like by a speedometer, a tachometer, an accelerator opening sensor, an outside air temperature sensor, an exhaust air temperature sensor, etc. (not shown). If necessary, these pieces of information are transmitted to the energization control device 61 described below.
The above-described oxygen sensor 1 is attached to the exhaust pipe EP of the engine ENG. The oxygen sensor 1 is connected to the energization control device 61 via the sensor output lead wires 13 and 14 and the heater lead wires 18 and 19, and both are combined to form an oxygen sensor 60 with a control circuit.

  The energization control device 61 is connected to the electronic control device ECU via the serial bus BS, and can communicate data with each other. As shown in FIG. 10, the energization control device 61 includes a microcomputer 70, a sensor output detection circuit 62, and a heater drive circuit 63. Among these, the microcomputer 70 includes an EPROM 74 as an auxiliary storage device in addition to the CPU 71, ROM 72, RAM 73, and interface circuits 75, 76, 77. In this EPROM, the thermal network HC1 (thermal network data ND) is solved by the thermal network method, and the part temperature Tx or Tx (t) of the predetermined temperature estimation part X (for example, the contact part temperature Ts of the contact part 2e). , Ts (t)), a thermal analysis program PG2 by a thermal network method, and thermal network data ND are stored.

  On the other hand, the sensor output detection circuit 62 is connected to the oxygen sensor element 2 of the oxygen sensor 10 via the sensor output lead wires 13 and 14, detects the output of the oxygen sensor element 2, and passes through the interface circuit 75 to Input to the computer 70. The heater drive circuit 63 is connected to the heater 15 via the heater lead wires 18 and 19 of the oxygen sensor 1 and is connected to the battery BT. The output voltage of the battery BT is turned on / off according to instructions from the microcomputer 70. Then, the duty ratio of the energization power to the heater 15 is controlled.

In the oxygen sensor 60 with a control circuit, the microcomputer 70 is activated by the activation of the vehicle AM (key switch ON), the heater driving circuit 63 is driven, and the electric power from the battery BT is supplied to the heater 15 of the oxygen sensor 1. Energized.
In parallel with this, the microcomputer 70 (CPU 71) executes the thermal analysis program PG2 stored in the EPROM 74 by the thermal circuit method, and the thermal circuit such as the thermal circuit network HC1 stored in the EPROM 74. The network data ND (see FIGS. 4 and 6) is solved, and the part temperature Tx or Tx (t) (specifically, the contact part temperatures Ts and Ts (t) of the contact part 2e) of the temperature estimation part X are sequentially determined. presume. Thereby, in this oxygen sensor 60 with a control circuit, the temperature of the contact portion 2e of the oxygen sensor element 2 can be accurately estimated without using any temperature sensor or the like.

  When the oxygen sensor element 2 (gas contact portion 2d) is sufficiently heated and activated, the output of the oxygen sensor 1 (element 2) is detected by the sensor output detection circuit 62, and the exhaust gas EG is detected by the microcomputer 70 (CPU 71). Is converted to the oxygen concentration of the gas and transmitted to the electronic control unit ECU.

It should be noted that the heater 15 of the oxygen sensor 1 does not require heating of the element 2 because the exhaust gas EG has reached a high temperature, while the engine ENG is being driven, the temperature of the gas contact part 2d of the oxygen sensor element 2 ( In particular, it is preferable to control energization of the heater 15 through the heater drive circuit 63 so that the temperature Ts of the contact portion 2e is constant (target temperature To: for example, To = 660).
In this energization control, in this modification, the thermal circuit data ND is solved to estimate the contact part temperatures Ts and Ts (t) of the contact part 2e, and the estimated contact part temperature Ts becomes the target temperature To. As described above, the driving of the heater 15 in the heater driving circuit 63 is controlled by the microcomputer 70 (CPU 71). Specifically, the duty ratio of the electric power supplied to the heater 15 is controlled. Note that the outside air temperature OG related to the element V2, the vehicle speed, the temperature of the exhaust gas EG related to the element V1, the flow velocity, and the like are reflected in the thermal circuit data ND based on information obtained from the electronic control unit ECU. . The magnitude of energy supplied from the heater drive power source S1 (battery BT and heater drive circuit 63) to the heater 15 is reflected based on the voltage of the battery BT, the duty ratio controlled by the heater drive circuit 63, and the like.

  As described in the embodiment, also in this modification, in order to solve the above-described thermal circuit HC1 by the thermal circuit method, the oxygen sensor 1 and the exhaust pipe EP are rapidly heated by the heater 15 and rapidly cooled by the exhaust gas EG (fuel). Even if the introduction of outside air at the time of cutting), rapid heating (high load, high rotation operation), etc. occurs, the transitional change in the contact portion temperature Ts of the contact portion 2e is also appropriately estimated in accordance with the reality. be able to.

  In this modification, the microcomputer 70 (CPU 71) of the energization control device 61 corresponds to the part temperature estimation means and the contact part temperature estimation means. Further, the EPROM 74 corresponds to a thermal network data storage means. The microcomputer 70 (CPU 71) and the heater control circuit 63 correspond to heater control means.

In the above, the present invention has been described according to the first to third embodiments and modified embodiments. However, the present invention is not limited to the above-described embodiments and the like, and can be appropriately modified and applied without departing from the gist thereof. Needless to say, it can be done.
For example, in the modified embodiment, an example is shown in which the thermal analysis by the thermal network method is performed by the microcomputer 70 (CPU 71) in the oxygen sensor 60 with a control circuit, and the contact portion temperature Ts is estimated. On the other hand, the electronic control unit ECU, specifically, a built-in microcomputer (not shown) can perform thermal analysis by a thermal network method to estimate the contact temperature Ts and the like. In this case, the heater 15 is controlled by the microcomputer 70 (CPU 71) and the heater control circuit 63 in accordance with information (contact portion temperature Ts and the like) obtained from the electronic control unit ECU. In this example, the electronic control unit ECU corresponds to the part temperature estimating means and the contact part temperature estimating means.

PC Personal computer (computer)
100, 200 Temperature estimation system 102 Microprocessor (part temperature estimation means, contact temperature estimation means)
105 External storage device (thermal network data storage means)
PG1, PG2 Thermal analysis program by thermal network method ND Thermal network data (model data)
210 Temperature Control System 60 Oxygen Sensor 61 with Control Circuit (Oxygen Sensor) Energization Control Device 63 Heater Drive Circuit (Heater Control Unit)
70 microcomputer (part temperature estimation means, contact temperature estimation means, heater control means)
71 CPU (part temperature estimation means, contact temperature estimation means, heater control means)
74 EPROM (thermal network data storage means)
AM vehicle ENG engine ECU electronic control unit EP exhaust pipe (external member)
EPH mounting hole EPS Sensor mounting part (bonded part)
EG Exhaust gas (measured gas)
OG Outside air BD Base end PD Front end X Temperature estimation part Tx, Tx (t) Part temperature Ts, Ts (t) (Temperature estimation part) Contact part temperature To Target temperature HC1 to HC3, HR1, HR2 Thermal network S1 Variable current source (heater drive power supply)
E1-E10 Thermal conduction elements F1-F5 Heat transfer elements R1-R3 Thermal radiation elements V1, V2 Variable voltage sources C1-C24 Thermal circuit C2 First thermal circuit C3 Second thermal circuit C10 Third thermal circuit C8 Fourth thermal circuit C13 Fifth thermal circuit C12 Sixth thermal circuit C21 Seventh thermal circuit, variable seventh thermal circuit 1 Oxygen sensor (gas sensor, vehicle-mounted gas sensor)
2 Oxygen sensor element (tubular sensor element)
2d Gas contact portion 2di Inner wall surface 2e (of the gas contact portion) Contact portion 2f (of the gas contact portion) Non-contact portion 2g (of the gas contact portion) Base end gas contact portion 3 Main metal fitting (holding metal fitting)
3b Screw part (joint part)
4 Protector 5, 7 Ceramic holder 6 Ceramic powder 15 Heater 15a Heating part 15b Non-heating part 21 Outer cylinder 31 Separator

Claims (10)

A cylindrical sensor element having a closed bottomed cylindrical shape, including a gas contact portion in contact with a gas to be measured on its distal end side,
It has a rod-like shape and has a heat generating portion that generates heat when energized at its tip, and is inserted into the cylindrical sensor element in a loose fit, and at least a part of the heat generating portion is connected to the gas contacting portion of the cylindrical sensor element. A gas sensor including a heater arranged in contact with an inner wall surface,
A temperature estimation system for estimating a part temperature which is a temperature of a temperature estimation part in the gas sensor,
Heat conduction between the heat generating portion of the heater and a contact portion with which the heat generating portion of the heater contacts among the gas contact portions of the cylindrical sensor element; and
Part temperature estimation means for estimating the part temperature using model data in consideration of heat radiation from the heat generating part of the heater toward the non-contact part other than the contact part in the gas contact part of the cylindrical sensor element Have
A first thermal circuit describing heat conduction between the heat generating part of the heater and the contact part of the gas contact part of the cylindrical sensor element; and
A second thermal circuit that describes heat radiation from the heat generating portion of the heater toward a non-contact portion other than the contact portion of the gas contact portion of the cylindrical sensor element; a thermal circuit that models the gas sensor A thermal network data storage means for storing thermal network data of the network;
The part temperature estimating means includes
Using the thermal network data that is the model data, the temperature of the part is estimated by a thermal network method,
The gas sensor
Out of the gas contact portion of the cylindrical sensor element, the base end side gas contact portion on the base end side is surrounded while being spaced apart, and the cylindrical sensor element is indirectly held on the base end side with respect to the gas contact portion. And a holding bracket having a coupling portion for coupling itself to an external member;
It is arranged at the front end side of the holding fitting and spaced from the gas contact portion of the cylindrical sensor element, and is connected to the holding fitting so that the gas to be measured can flow between the gas contact portion, A protector for covering the gas contact part,
The thermal network that models the gas sensor is:
A third thermal circuit describing heat radiation from the gas contact portion of the cylindrical sensor element toward the holding metal fitting, and
A temperature estimation system for a gas sensor, which also includes a fourth thermal circuit that describes thermal radiation from the gas contact part of the cylindrical sensor element toward the protector. The temperature estimation system for a gas sensor according to claim 1,
The external member is
A metal vent pipe through which the gas to be measured flows,
Having a coupled portion formed around a through-hole penetrating itself;
The gas sensor
In the form in which the gas contact part of the cylindrical sensor element is disposed in the vent pipe through the through hole, the coupling part of the holding fitting of the gas sensor is coupled to the coupled part of the vent pipe,
The thermal network that models the gas sensor is:
A temperature estimation system for a gas sensor including a fifth thermal circuit describing heat conduction between the coupling portion of the holding metal fitting and the coupled portion of the vent pipe. A temperature estimation system for a gas sensor according to claim 1 or 2,
The gas sensor
A cylindrical shape, located outside the external member, and connected to the holding fitting on the base end side with respect to the coupling portion of the holding fitting and having an outer cylinder extending to the base end side;
The thermal network that models the gas sensor is:
A sixth thermal circuit describing heat conduction between the holding metal fitting and the outer cylinder; and
A temperature estimation system for a gas sensor, which also includes a seventh thermal circuit describing heat transfer between the outer cylinder and the outside air surrounding the outer cylinder. The temperature estimation system for a gas sensor according to claim 3,
The gas sensor is an in-vehicle gas sensor mounted on a vehicle,
The seventh thermal circuit is
A temperature estimation system for a gas sensor which is a variable seventh heat circuit that also describes a change in heat transfer between the outer cylinder and the outside air surrounding the outer cylinder according to the vehicle speed of the vehicle. A temperature estimation system for a gas sensor according to any one of claims 1 to 4,
The temperature estimation part is the contact part in contact with the heat generating part of the heater on the inner wall surface of the gas contact part of the cylindrical sensor element,
The part temperature is a contact part temperature in the contact part,
The temperature estimation system for a gas sensor, wherein the part temperature estimation means is contact part temperature estimation means for estimating the contact part temperature. A cylindrical sensor element having a closed bottomed cylindrical shape, including a gas contact portion in contact with a gas to be measured on its distal end side,
It has a rod-like shape and has a heat generating portion that generates heat when energized at its tip, and is inserted into the cylindrical sensor element in a loose fit, and at least a part of the heat generating portion is connected to the gas contacting portion of the cylindrical sensor element. A gas sensor including a heater arranged in contact with an inner wall surface,
A temperature estimation system for estimating a part temperature which is a temperature of a temperature estimation part in the gas sensor,
Heat conduction between the heat generating portion of the heater and a contact portion with which the heat generating portion of the heater contacts among the gas contact portions of the cylindrical sensor element; and
Part temperature estimation means for estimating the part temperature using model data in consideration of heat radiation from the heat generating part of the heater toward the non-contact part other than the contact part in the gas contact part of the cylindrical sensor element Have
A first thermal circuit describing heat conduction between the heat generating part of the heater and the contact part of the gas contact part of the cylindrical sensor element; and
A second thermal circuit that describes heat radiation from the heat generating portion of the heater toward a non-contact portion other than the contact portion of the gas contact portion of the cylindrical sensor element; a thermal circuit that models the gas sensor A thermal network data storage means for storing thermal network data of the network;
The part temperature estimating means includes
Using the thermal network data that is the model data, the temperature of the part is estimated by a thermal network method,
The temperature estimation part is the contact part in contact with the heat generating part of the heater on the inner wall surface of the gas contact part of the cylindrical sensor element,
The part temperature is a contact part temperature in the contact part,
The temperature estimation system for a gas sensor, wherein the part temperature estimation means is contact part temperature estimation means for estimating the contact part temperature. The temperature estimation system for a gas sensor according to claim 6,
The gas sensor
Out of the gas contact parts of the cylindrical sensor element, the base sensor side gas part of the base end side is surrounded and spaced apart, and the cylindrical sensor element is indirectly held at the base end side of the gas contact part. And a holding bracket having a coupling portion for coupling itself to an external member,
The external member is
A metal vent pipe through which the gas to be measured flows,
Having a coupled portion formed around a through-hole penetrating itself;
The gas sensor
In the form in which the gas contact part of the cylindrical sensor element is disposed in the vent pipe through the through hole, the coupling part of the holding fitting of the gas sensor is coupled to the coupled part of the vent pipe,
The thermal network that models the gas sensor is:
A temperature estimation system for a gas sensor including a fifth thermal circuit describing heat conduction between the coupling portion of the holding metal fitting and the coupled portion of the vent pipe. A temperature estimation system for a gas sensor according to claim 6 or 7,
The gas sensor
Out of the gas contact portion of the cylindrical sensor element, the base end side gas contact portion on the base end side is surrounded while being spaced apart, and the cylindrical sensor element is indirectly held on the base end side with respect to the gas contact portion. And a holding bracket having a coupling portion for coupling itself to an external member, and
A cylindrical shape, located outside the external member, and connected to the holding fitting on the base end side with respect to the coupling portion of the holding fitting and having an outer cylinder extending to the base end side;
The thermal network that models the gas sensor is:
A sixth thermal circuit describing heat conduction between the holding metal fitting and the outer cylinder; and
A temperature estimation system for a gas sensor, which also includes a seventh thermal circuit describing heat transfer between the outer cylinder and the outside air surrounding the outer cylinder. The temperature estimation system for a gas sensor according to claim 8,
The gas sensor is an in-vehicle gas sensor mounted on a vehicle,
The seventh thermal circuit is
A temperature estimation system for a gas sensor which is a variable seventh heat circuit that also describes a change in heat transfer between the outer cylinder and the outside air surrounding the outer cylinder according to the vehicle speed of the vehicle. A temperature estimation system for a gas sensor according to any one of claims 1 to 9,
A gas sensor temperature control system comprising heater control means for controlling energization of the heater based on the part temperature estimated by the part temperature estimation means so that the part temperature becomes a target temperature.

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