JP5030927B2 - Condensed water detection device, condensed water detection method, and exhaust purification device - Google Patents

Description

  The present invention relates to a condensed water detection device, a condensed water detection method, and an exhaust purification device that detect the presence or absence of condensed water in exhaust gas. In particular, a condensed water detection device and a condensed water detection method for detecting the presence or absence of condensed water in exhaust gas flowing through an exhaust passage provided with a specific gas concentration sensor equipped with a heater, and such a condensed water detection device are provided. The present invention relates to an exhaust purification device.

In an exhaust passage connected to an internal combustion engine such as a diesel engine, a NO _x sensor for detecting the concentration of nitrogen oxides (hereinafter referred to as “NO _x ”), an oxygen concentration or an air-fuel ratio is detected. A specific gas concentration sensor such as an oxygen sensor is provided. Among these, the NO _X sensor is used, for example, for controlling the amount of reducing agent supplied in an exhaust purification device that reduces and purifies NO _X. The oxygen sensor is used, for example, for controlling operating conditions of the internal combustion engine.

  These specific gas concentration sensors are provided with sensor elements for detecting specific gas components. Since the sensor element has a property of being activated when the activation temperature is reached, the sensor element is heated to the activation temperature in order to enable detection of the specific gas concentration by the specific gas concentration sensor. It is necessary to keep it active. Therefore, a specific gas concentration sensor is known in which a heater is provided inside and the sensor element is heated using the heater.

  By the way, the exhaust gas discharged from the internal combustion engine contains water vapor, and when the temperature in the exhaust passage is low, such as immediately after the start of the internal combustion engine, the water vapor may be cooled and condensed. As described above, when the temperature in the exhaust passage is low, the sensor element of the specific gas concentration sensor is often not activated, and the sensor element is often heated by the heater. When the condensed water adheres to the sensor element when the sensor element is heated in this way, the heat of the surface of the sensor element is taken away by latent heat when the condensed water is heated and vaporized. As a result, a local distortion occurs in the sensor element and the sensor element is cracked, so-called element cracking occurs, and there is a possibility that measurement of the specific gas concentration may become impossible.

  Here, while the condensed water is present in the exhaust gas, the energization to the heater provided in the specific gas concentration sensor is made to stand by, while the control to start energizing the heater after it is estimated that the condensed water has disappeared. For this purpose, an exhaust gas detection device has been proposed in which condensed water present in the exhaust passage can be detected with high accuracy. Specifically, as shown in FIG. 9, a specific gas concentration sensor 302 is provided that includes a sensor element and a heater that heats the sensor element, and is provided in an exhaust passage through which exhaust gas discharged from the internal combustion engine flows. The exhaust gas detection device 310 is disposed on the downstream side of the specific gas concentration sensor 302 in the exhaust passage and retains moisture in the exhaust passage, and moisture staying in the moisture retention portion 303 An exhaust gas detection device 310 that includes a moisture detection means 320 that detects water is disclosed (see Patent Document 1).

JP 2004-360563 A (the whole sentence, all figures)

  However, since the exhaust gas detection device 310 described in Patent Document 1 detects the presence or absence of moisture in the exhaust passage based on the presence or absence of moisture that remains in the moisture retention portion 303 that easily retains moisture. If moisture does not stay in the staying part 303, the moisture is not detected by the moisture detecting means 320. For this reason, the condensed gas exists in the exhaust gas, and the condensed gas may adhere to the surface of the specific gas concentration sensor 302. Energization of the heater at 302 is started, and there is a risk of element cracking.

  Further, the exhaust gas detection device 310 described in Patent Document 1 has a moisture retention part 303 even when condensed water does not already exist in the exhaust gas and the condensed water adhering to the specific gas concentration sensor 302 disappears. As long as moisture remains in the water, the water detection means 320 detects the water. For this reason, energization to the heater in the specific gas concentration sensor 302 is delayed without being started, and activation of the sensor element is delayed. As a result, there is a possibility that the standby time until the start of control of the exhaust gas purification apparatus using the specific gas concentration sensor 302 or the internal combustion engine becomes long.

  Therefore, the inventors of the present invention have made diligent efforts and detected by the first temperature sensor that is provided in the exhaust pipe and is easily attached with condensed water, and the second temperature sensor that is not attached with condensed water. The inventors have found that such a problem can be solved by comparing the temperature and detecting the presence or absence of condensed water in the exhaust gas, and have completed the present invention. That is, an object of the present invention is to provide a condensed water detection device and a condensed water detection method that can accurately detect the disappearance timing of condensed water in exhaust gas, and an exhaust purification device including the condensed water detection device. And

  According to the present invention, in exhaust gas flowing through an exhaust passage connected to an internal combustion engine and provided with a specific gas concentration sensor having a sensor element for detecting a specific component in exhaust gas and a heater for heating the sensor element. In the condensed water detection device for detecting the presence or absence of condensed water in the first, the first temperature detected by the first temperature sensor that is easily attached to the condensed water provided in the exhaust pipe forming the exhaust passage is detected. A first temperature detection unit, a second temperature detection unit for detecting a second temperature detected by a second temperature sensor to which condensed water provided in the exhaust pipe does not adhere, a first temperature and a second temperature A condensed water detection device comprising: a condensed water presence / absence determining unit that determines whether condensed water exists in exhaust gas by comparing temperatures is provided, and solves the above-described problem Can do.

  In configuring the condensed water detection device of the present invention, the condensed water detection device includes a start detection unit that detects the start of the internal combustion engine, and the condensed water presence / absence determination unit is detected after a predetermined period of time has elapsed since the start of the internal combustion engine. The determination is preferably performed using the first temperature and the second temperature.

  Further, in configuring the condensed water detection device of the present invention, the condensed water presence / absence determining unit calculates the temperature difference between the detected first temperature and the second temperature, and the temperature difference is less than a predetermined value. It is preferable to determine that condensed water is not present in the exhaust passage.

  Further, in configuring the condensed water detection device of the present invention, the condensed water presence / absence determining unit calculates the temperature difference between the detected first temperature and the second temperature, and the temperature difference continues for a predetermined period. It is preferable to determine that there is no condensed water in the exhaust passage when it is less than the value.

  In configuring the condensed water detection device of the present invention, the detected first temperature and second temperature, and the exhaust pipe from the position where the first temperature sensor is disposed to the position where the second temperature sensor is disposed. Based on the length, the length of the circumference of the exhaust pipe, the heat transfer coefficient of the exhaust pipe, and the outside air temperature, the exhaust gas moves from the arrangement position of the first temperature sensor to the arrangement position of the second temperature sensor. Based on the heat radiation amount, the heat radiation amount calculation unit that calculates the heat radiation amount from the exhaust gas during the flow or between the second temperature sensor placement position and the first temperature sensor placement position, It is preferable to include a temperature correction unit that corrects at least one of the temperature and the second temperature.

  Further, when configuring the condensed water detection device of the present invention, the apparatus may include a heater drive control unit that permits energization of the heater when the condensed water presence / absence determining unit determines that no condensed water exists in the exhaust gas. preferable.

  Further, in configuring the condensed water detection device of the present invention, a third temperature sensor that is different from the first temperature sensor and the second temperature sensor and that is detected by a third temperature sensor that easily or does not adhere to condensed water. It is preferable that a third temperature detection unit for detecting the temperature is provided, and the condensed water presence / absence detection unit performs the determination in consideration of the third temperature.

  Another aspect of the present invention provides an exhaust passage provided with a specific gas concentration sensor connected to an internal combustion engine and having a sensor element for detecting a specific component in the exhaust gas and a heater for heating the sensor element. In a condensed water detection method for detecting the presence or absence of condensed water in flowing exhaust gas, a first temperature sensor provided in an exhaust pipe that forms an exhaust passage after the internal combustion engine is started is attached to the first temperature sensor. By detecting the first temperature detected and the second temperature detected by the second temperature sensor to which the condensed water does not adhere, and comparing the first temperature and the second temperature in the exhaust gas It is a condensed water detection method characterized by detecting the presence or absence of condensed water.

  According to still another aspect of the present invention, a specific gas concentration is provided in an exhaust passage of an internal combustion engine and includes a sensor element for detecting a specific component in the exhaust gas and a heater for heating the sensor element in the exhaust passage. In the exhaust gas purification apparatus provided with the sensor, the first temperature sensor provided in the exhaust pipe that forms the exhaust passage is easily attached with the condensed water in the exhaust gas, and the first temperature sensor provided in the exhaust pipe is not attached with the condensed water. The first temperature detected by the first temperature sensor and the second temperature detected by the second temperature sensor after the start of the internal combustion engine and the second temperature detected by the second temperature sensor are detected. And a condensed water detector that detects the presence or absence of condensed water in the exhaust gas by comparing the temperatures of the two.

  In configuring the exhaust emission control device of the present invention, it is preferable to provide a waterproof structure for preventing the condensed water from adhering to the second temperature sensor.

According to the condensed water detection device of the present invention, the first temperature detected by the first temperature sensor to which the condensed water is likely to adhere and the second temperature detected by the second temperature sensor to which the condensed water is difficult to adhere. And a first and second temperature detection unit for detecting the presence of the condensed water, and a condensed water presence / absence determination unit for comparing the detected first and second temperatures to determine the presence / absence of condensed water in the exhaust gas. Therefore, based on the temperature difference between the first temperature and the second temperature, the presence or absence of latent heat at the first temperature sensor to which condensed water is likely to adhere is estimated, and the presence or absence of condensed water in the exhaust gas is accurately determined. It is well detected. Therefore, the disappearance time of the condensed water in the exhaust gas can be determined with high accuracy, the element cracking due to the energization of the heater can be prevented, and the control using the specific gas concentration sensor can be started quickly.
Further, since the condensed water detection device of the present invention performs detection using a temperature sensor, it detects the presence or absence of condensed water using an existing temperature sensor provided in the exhaust pipe, and suppresses an increase in cost. Is also possible.

  In addition, the condensed water detection device of the present invention includes a start detection unit for the internal combustion engine, and the condensed water presence / absence determination unit uses the first and second temperatures detected after a predetermined period has elapsed since the start of the internal combustion engine. By determining whether or not there is, the determination is executed during a period in which the operating state of the internal combustion engine is unstable immediately after the start of the internal combustion engine, avoiding erroneous determination, and improving the accuracy of the determination result.

  Further, in the condensed water detection device of the present invention, the condensed water presence / absence determining unit determines that condensed water does not exist in the exhaust gas when the temperature difference between the first and second temperatures is less than a predetermined value. The presence of condensed water in the exhaust gas can be detected based on the fact that the latent heat accompanying the evaporation of the condensed water at the first temperature sensor where the condensed water is likely to adhere is less than a predetermined amount.

  In the condensed water detection device of the present invention, the condensed water presence / absence determining unit has no condensed water in the exhaust gas when the temperature difference between the first and second temperatures is less than a predetermined value continuously for a predetermined period. By determining that the condensed water is temporarily lost and then re-condensed in a short time, it is avoided that the condensed water is not present in the exhaust gas, and the accuracy of the determination result is reduced. Enhanced.

  In addition, the condensed water detection device of the present invention includes the predetermined heat radiation amount calculation unit and the temperature correction unit, so that the exhaust gas is between the position where the first temperature sensor is disposed and the position where the second temperature sensor is disposed. Or the first and second based on the presence or absence of latent heat in the first temperature sensor in consideration of the amount of heat of the exhaust gas radiated between the position of the first temperature sensor and the position of the second temperature sensor. The temperature difference of the second temperature sensor can be calculated with high accuracy. Therefore, even when the arrangement positions of the first and second temperature sensors are different, the presence / absence of condensed water in the exhaust gas is accurately determined based on the presence / absence of heat of evaporation at the first temperature sensor. Can do.

  In addition, since the condensed water detection device of the present invention includes a predetermined heater drive control unit, energization to the heater is started when it is determined that no condensed water is present in the exhaust gas, and the sensor element is cracked. The sensor element is quickly activated while preventing.

  Moreover, the condensed water detection apparatus of this invention is provided with the 3rd temperature detection part which detects the temperature detected by the 3rd temperature sensor provided in the position different from a 1st and 2nd temperature sensor. Therefore, the presence or absence of latent heat in the first temperature sensor can be grasped more accurately, and the presence or absence of condensed water in the exhaust gas can be determined with higher accuracy.

In addition, according to the condensed water detection method of the present invention, the first temperature detected by the first temperature sensor to which the condensed water is likely to adhere and the second temperature sensor to be detected by the second temperature sensor to which the condensed water is unlikely to adhere. In order to detect the presence or absence of condensed water in the exhaust gas by comparing the temperatures of the first and second temperatures, the first temperature sensor to which condensed water is likely to adhere is based on the temperature difference between the first temperature and the second temperature. The presence or absence of latent heat is estimated, and the presence or absence of condensed water in the exhaust gas is detected with high accuracy. Therefore, the disappearance time of the condensed water in the exhaust gas can be determined with high accuracy, the element cracking due to the energization of the heater can be prevented, and the control using the specific gas concentration sensor can be started quickly.
Moreover, since the condensed water detection method of this invention is a detection method using a temperature sensor, the presence or absence of condensed water can be detected using the existing temperature sensor provided in an exhaust pipe, and the increase in cost is suppressed.

Moreover, according to the exhaust gas purification apparatus of the present invention, the first temperature sensor that is easy to adhere condensed water and the second temperature sensor that is difficult to adhere condensed water are provided, and the first and second temperature sensors respectively. Based on the temperature difference between the first temperature and the second temperature in order to provide a condensed water detector that compares the detected first and second temperatures and detects the presence or absence of condensed water in the exhaust gas. The presence or absence of latent heat at the first temperature sensor where condensed water is likely to adhere is estimated, and the presence or absence of condensed water in the exhaust gas is detected with high accuracy. Therefore, after the condensed water in the exhaust gas disappears, the control of the exhaust gas purification apparatus using the specific gas concentration sensor is started immediately, and deterioration of the exhaust emission over a long time is prevented.
In addition, since the exhaust gas purification apparatus of the present invention performs detection using a temperature sensor, the presence or absence of condensed water can be detected using an existing temperature sensor provided in the exhaust pipe, and an increase in cost can be suppressed.

  Moreover, in the exhaust emission control device of the present invention, a waterproof structure for preventing the condensed water from adhering to the second temperature sensor is provided, so that the second temperature sensor to which the condensed water does not adhere is easily configured. Therefore, the exhaust gas based on the temperature of each of the first temperature sensor to which the condensed water easily adheres and the second temperature sensor to which the condensed water does not adhere is added using the existing temperature sensor without newly adding a temperature sensor. The presence or absence of condensed water in the inside can be detected.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments relating to a condensed water detection device, a condensed water detection method, and an exhaust gas purification device including the condensed water detection device according to the present invention will be specifically described below with reference to the drawings as appropriate. However, the following embodiment shows one aspect of the present invention and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention.
In addition, in each figure, what has attached | subjected the same code | symbol has shown the same member, and description is abbreviate | omitted suitably.

1. Exhaust Purification Device (1) Basic Configuration FIG. 1 shows a basic configuration of an exhaust purification device 10 for an internal combustion engine according to the present embodiment.
This exhaust purification device 10 is provided in an exhaust pipe 11 connected to the internal combustion engine 5, a reduction catalyst 13 provided in an exhaust passage for purifying NO _{x in} exhaust gas using a reducing agent, and a reduction catalyst 13. A reducing agent supply device 40 for supplying the reducing agent into the exhaust passage on the upstream side, and a control device 60 for controlling the operation of the reducing agent supply device 40 are provided. In the exhaust pipe 11, the exhaust pipe 11 upstream of the reduction catalyst 13 includes a first temperature sensor 16 and a second temperature sensor 17, and a specific gas concentration sensor that detects the NO _x concentration in the exhaust gas. NO _x sensor 20 is provided. A third temperature sensor 18 is provided in the exhaust pipe 11 downstream of the reduction catalyst 13.

Reduction catalyst 13 is a catalyst used for purifying NO _X in the exhaust gas, for example, by using a reducing agent such as supplied aqueous urea solution or unburned fuel in the upstream side of the reduction catalyst 13 NO _X A selective reduction catalyst that selectively reduces and purifies is used.

  The control device 60 can read not only information on the operating state of the internal combustion engine 5 including the fuel injection amount, fuel injection timing, rotation speed, etc. of the internal combustion engine 5, but also the specific gas concentration sensor 18 and the Sensor values of the first temperature sensor 16, the second temperature sensor 17, the third temperature sensor 18, and the like can be read. The control device 60 also has a function as a condensed water detection device that detects the presence or absence of condensed water in the exhaust gas.

(2) NO _X Sensor In the exhaust purification device 10 of the present embodiment, the NO _X sensor 20 provided on the upstream side of the reduction catalyst 13 is used to calculate the flow rate of NO _X flowing into the reduction catalyst 13. However, the NO _X sensor is provided on the downstream side of the reduction catalyst 13 and may be used to calculate the flow rate of NO _X that has passed through the reduction catalyst 13.

FIG. 2 is a cross-sectional view schematically showing an example of the configuration of the NO _x sensor 20 as the specific gas concentration sensor provided in the exhaust purification device 10 of the present embodiment. The NO _X sensor 20 includes a protective cover 37 provided with a plurality of gas passage holes 33, a sensor element 29 disposed in the protective cover 37, and a heater 24 for heating the sensor element 29. The exhaust gas is configured to be able to flow inside and outside the protective cover 37 through the gas passage hole 33.

The sensor element 29 includes two solid electrolyte bodies 19, 21 and an exhaust gas passage 22 formed by the solid electrolyte bodies 19, 21, and the first space 25 a is disposed in the middle of the exhaust gas passage 22. And the 2nd space 25b is provided. The first element 26a is provided facing the first space 25a of the exhaust gas flow path 22, and the second element 26b is provided facing the second space 25b.
The first element 26a is configured by arranging the first inner electrode 27a and the first outer electrode 28a on both surfaces of the solid electrolyte body 21, and the first inner electrode 27a faces the first space 25a. The first outer electrode 28 a faces the reference gas space 30. The second element 26b is configured by arranging the second inner electrode 27b and the second outer electrode 28b on both surfaces of the solid electrolyte body 21, and the second inner electrode 27b is formed in the second space 25b. The second outer electrode 28 b faces the reference gas space 30.

The fixed electrolyte body 21 constituting the first element 26a and the second element 26b is typically a ceramic body containing, for example, ZrO ₂ , but may be a conventionally known solid electrolyte body constituting an oxygen pump element. It can be used suitably.
Further, the first and second inner electrodes 27a, 27b and the first and second outer electrodes 28a, 28b arranged on both surfaces of the solid electrolyte body 21 are respectively porous electrodes capable of dissociating oxygen molecules. Similar to the solid electrolyte body, any conventionally known porous electrode can be suitably used.

  Both the first element 26a and the second element 26b are used as oxygen pump elements, and the first inner electrode 27a and the first outer electrode 28a constituting the first element 26a and the second element 26b. The second inner electrode 27b and the second outer electrode 28b are connected to the external connection circuit 32, respectively, and a voltage is applied between the pair of electrodes.

Since the sensor element 29 configured as described above has a property of being activated when the temperature is equal to or higher than the activation temperature, the NO _X sensor 20 is provided with a heater 24 adjacent to the sensor element 29. The heater 24 is configured by embedding a heating wire 24a whose energization is controlled by the control device 60 in the substrate layer 24b, and the temperature in the exhaust pipe 11 is low when the internal combustion engine 5 is started. Energization is performed in a situation where the element 29 is lower than the activation temperature, the sensor element 29 is heated to the activation temperature or higher, and the temperature of the sensor element 29 is maintained to the activation temperature or higher. The sensor element 29 is heated to, for example, 700 ° C. or higher by the heater 24.

(3) Temperature sensor In the exhaust purification apparatus 10 of this embodiment, the 1st temperature sensor 16, the 2nd temperature sensor 17, and the 3rd temperature sensor 18 are used in order to detect the exhaust temperature in each arrangement position. It is done. For example, these temperature sensors include a thermistor element as a temperature-sensitive element inside a metal tube, and are attached to an exhaust pipe. Then, the thermistor element is disposed in the exhaust pipe through which the exhaust gas flows, and is used for temperature detection of the exhaust gas. The thermistor element is composed of a temperature-sensitive part (thermistor sintered body) whose electric resistance value changes with temperature and a pair of electrode wires for taking out the change in electric resistance value of the temperature-sensitive part. Unlike the specific gas concentration sensor, the temperature sensor is a sensor that can measure regardless of the ambient temperature and has no risk of element cracking.

Among these temperature sensors, the sensor value of the first temperature sensor 16 is used for control of the internal combustion engine 5 and the like, and the sensor values of the second temperature sensor 17 and the third temperature sensor 18 are the values of the reduction catalyst 13. Used for temperature estimation.
Further, in the exhaust purification apparatus 10 of the present embodiment, the sensor values of the first temperature sensor 16 and the second temperature sensor 17 are also used for detecting the presence or absence of condensed water in the exhaust gas. That is, the exhaust gas purification apparatus 10 is configured to detect the presence or absence of condensed water in the exhaust gas using an existing temperature sensor without adding a new temperature sensor.

Here, of the first temperature sensor 16 and the second temperature sensor 17 used for detecting the presence or absence of condensed water in the exhaust gas, the first temperature sensor 16 is a sensor to which condensed water in the exhaust gas is likely to adhere. On the other hand, the second temperature sensor 17 is configured as a sensor to which condensed water in the exhaust gas does not adhere. In this embodiment, by providing a difference in whether or not the condensed water adheres between the two temperature sensors, the generation of latent heat in the first temperature sensor 16 where the condensed water is likely to adhere is estimated, and depending on the presence or absence of the latent heat, It is configured to detect the presence or absence of condensed water in the exhaust gas.
The configuration of the first temperature sensor 16 to which the condensed water easily adheres and the second temperature sensor 17 to which the condensed water does not adhere may be realized at an arrangement position of each temperature sensor, or may be provided in the second temperature sensor 17. It may be realized by applying a waterproof structure. In the example of the exhaust gas purification apparatus 10 shown in FIG. 1, whether or not the condensed water can be attached is realized depending on the arrangement position of each temperature sensor.

Specifically, the exhaust gas G discharged from the internal combustion engine 5 contains water vapor generated by the combustion reaction of fuel and air. However, when the internal combustion engine 5 is started, the exhaust gas G When the temperature is low, water vapor in the exhaust gas may be cooled and condensed.
The condensed water generated in the exhaust gas is affected by, for example, the mass of the condensed water itself, the inertial force of the exhaust gas, the shape of the exhaust pipe 11, etc., and the sensor facing the inside of the exhaust pipe 11 and the exhaust pipe 11. However, in the exhaust pipe 11, depending on the shape of the exhaust pipe 11, as shown in FIG. 3, there are positions where the condensed water is likely to adhere and positions where the condensed water does not adhere. Mainly, since the exhaust gas G easily hits the outer peripheral surface of the bent exhaust pipe 11, the condensed water tends to adhere to the inner peripheral surface of the bent exhaust pipe 11, while the exhaust gas G hardly hits the inner peripheral surface of the bent exhaust pipe 11. Hard to adhere. In the exhaust purification apparatus 10 of the present embodiment, in consideration of such an entity, the first temperature sensor 16 is provided at a position where the condensed water easily adheres, and the second temperature sensor 17 is located at a position where the condensed water does not adhere. Is provided, and whether or not the condensed water adheres to each temperature sensor is realized.

On the other hand, when it is desired to completely prevent the condensed water from adhering to the second temperature sensor 17, it is preferable that the second temperature sensor 17 includes a waterproof structure 12 as shown in FIG. If such a waterproof structure 12 is provided, a state in which condensed water does not adhere is easily formed regardless of the arrangement position of the second temperature sensor 17.
In the waterproof structure 12 shown in FIG. 4, the second temperature sensor 17 is disposed in a box-shaped cover 12A, the cover 12A is fixed to the outer peripheral surface of the exhaust pipe 11, and outside air and exhaust gas are contained in the cover 12A. It is the waterproof structure 12 comprised so that it might not penetrate | invade. The cover 12A is made of the same stainless steel as the exhaust pipe 11 and efficiently receives heat from the exhaust pipe 11, while the second temperature sensor 17 is not directly in contact with outside air. The temperature inside is accurately detected by the second temperature sensor 17. In addition, since the cover 12A is attached to the outer peripheral surface side of the exhaust pipe 11, it is not affected by latent heat due to condensed water adhering to the cover 12A itself surrounding the second temperature sensor 17.

In addition, in the exhaust purification apparatus 10 of this embodiment, although the 2nd temperature sensor 17 to which condensed water does not adhere rather than the 1st temperature sensor 16 to which condensed water adheres is provided in the exhaust gas downstream, conversely The first temperature sensor 16 to which the condensed water is more likely to adhere than the second temperature sensor 17 to which the condensed water does not adhere may be provided on the exhaust downstream side. Furthermore, the first temperature sensor 16 and the second temperature sensor 17 may be provided at the same position.
Further, the exhaust purification device 10 of the present embodiment shown in FIG. 1 uses a temperature sensor used for control of the first internal combustion engine 5 and control of the exhaust purification device 10 for detecting the presence or absence of condensed water. A new temperature sensor can also be added.

(4) Reductant supply device The reductant supply device 40 is a device for supplying the reductant to the reduction catalyst 13, and includes a reductant supply valve 44 fixed to the exhaust pipe 11 upstream of the reduction catalyst 13. The main components are a storage tank 41 in which the reducing agent is stored, and a pump 42 that pumps the reducing agent in the storage tank 41 to the reducing agent supply valve 44. A first supply path 58 is connected between the storage tank 41 and the pump 42, and a second supply path 59 is connected between the pump 42 and the reducing agent injection valve 44. The reducing agent supply device 40 supplies the exhaust pipe 11 with an amount of reducing agent calculated based on the operating state of the internal combustion engine 5, the NO _X concentration detected by the NO _X sensor 18, the temperature of the reduction catalyst 13, and the like. As described above, supply control is performed by the control device 60.

In the reducing agent supply device 40, during operation of the internal combustion engine 5, the reducing agent in the storage tank 41 is pumped up by the pump 42 and is pumped toward the reducing agent injection valve 44. The control device 60 determines the amount of reducing agent to be supplied based on information such as the operating state of the internal combustion engine 5 and the NO _x concentration measured by the NO _x sensor 18, and sends a control signal corresponding thereto to the reducing agent injection valve. 44 for output. In the reducing agent injection valve 44, duty control is performed based on this control signal, and an appropriate amount of reducing agent is supplied into the exhaust pipe 11.

2. Control device (Condensate detection device)
(1) Basic Configuration In the control device 60 provided in the exhaust emission control device 10 shown in FIG. 1, basically, the pump 42 and the reducing agent are supplied so that an appropriate amount of the reducing agent is supplied into the exhaust pipe 11. Operation control of the injection valve 44 is performed. Further, the control device 60 provided in the exhaust purification device 10 of the present embodiment has a function as a condensed water detection device for detecting the presence or absence of condensed water in the exhaust gas.

In the control device 60 of FIG. 1, each function of the control device 60 is represented by a block. The control device 60 calculates a reducing agent injection valve while calculating a reducing agent amount to be supplied into the exhaust pipe 11, a pump driving control unit (indicated as “pump driving control” in FIG. 1) that controls the driving of the pump 42. The reducing agent injection valve drive control unit (indicated as “Udv drive control” in FIG. 1) that performs the drive control of 44 and the condensed water detection unit (in FIG. 1, “condensation”) detects the presence or absence of condensed water in the exhaust pipe 11. The main elements include a heater control unit (indicated as “heater control” in FIG. 1) and the like that perform energization control on the heater provided in the NO _X sensor 18. Specifically, each of these units is realized by executing a program by a microcomputer (not shown).

The pump drive control unit is based on the sensor value Sp of the pressure sensor 43 indicating the pressure of the reducing agent in the second supply path 59 so that the pressure in the second supply path 59 is maintained at a predetermined pressure. The feedback control of the pump 42 is performed. Further, the reducing agent injection valve drive control unit reduces NO _X in the exhaust gas based on the information regarding the operating state of the internal combustion engine 5 and the sensor value Sn of the NO _X sensor 18 provided in the exhaust purification device 10. Therefore, the supply amount of the reducing agent necessary for the calculation is calculated, and a drive signal is output to the reducing agent injection valve 44.
The heater control unit controls on / off of energization to the heater 24 provided in the NO _X sensor 18.

Among heater control unit, the condensed water detector to be described later, while the condensed water is determined to be present in the exhaust gas is shut off power supply to the heater 24 provided in the NO _X sensor 18. On the other hand, when it is determined that condensed water does not exist in the exhaust gas, the heater control unit starts energizing the heater 24. Further, the reducing agent injection valve drive control unit controls the driving of the reducing agent injection valve 44 after energization of the heater 24 provided in the NO _X sensor 18 is started and the sensor element 29 of the NO _X sensor 18 is activated. To start.

(2) Condensed water detection part FIG. 5: shows the block diagram which shows the part concerning a condensed water detection part further in detail among the structures of the control apparatus 60. As shown in FIG. The condensate detection unit detects the start of the internal combustion engine 5 (referred to as “start detection” in FIG. 5), and the first temperature based on the sensor value St1 of the first temperature sensor 16. A first temperature detection unit for detecting T1 (indicated as “T1 detection” in FIG. 5) and a second temperature for detecting the second temperature T2 based on the sensor value St2 of the second temperature sensor 17 And at least one of a first temperature T1 and a second temperature T2 detected by the detection unit ("T2 detection" in FIG. 5) and the first temperature detection unit and the second temperature detection unit. Based on the temperature correction unit (indicated as “temperature correction” in FIG. 5) and the detected or corrected first temperature T1 and second temperature T2, the exhaust pipe 11 is condensed. Condensed water presence / absence determination unit (denoted as “condensed water presence / absence determination” in FIG. 5) for determining whether or not water is present. ing. Each of these units is also realized by executing a program by a microcomputer (not shown).

  The start detection unit detects the start of the internal combustion engine 5 based on the rotational speed Ne of the internal combustion engine 5 or the like. When the start of the internal combustion engine 5 is detected, the start detection unit outputs a signal indicating that the start of the internal combustion engine 5 has started to the condensed water presence / absence determination unit.

  The first and second temperature detection units continuously read the sensor value St1 of the first temperature sensor 16 or the sensor value St2 of the second temperature sensor 17, respectively, and the first temperature T1 or the second temperature T2 Is calculated. In the control device 60 of the present embodiment, the first and second temperature detectors detect changes in the resistance values in the first temperature sensor 16 and the second temperature sensor 17, and the first temperature T1 is determined from the resistance values. Alternatively, the second temperature T2 is calculated. When the temperature sensor itself is a sensor having a function of calculating the temperature, the function of calculating the temperature based on the sensor value of the temperature sensor is omitted from the first and second temperature detection units.

The temperature correction unit corrects at least one value of the first temperature T1 and the second temperature T2 detected by the first and second temperature detection units.
In the exhaust gas purification apparatus 10 of the present embodiment shown in FIG. 1, the first temperature sensor 16 and the second temperature sensor 17 are provided at different positions in the exhaust gas flow direction. The temperature in the exhaust pipe 11 differs between the position where the second temperature sensor 17 is provided and the position where the second temperature sensor 17 is provided. Therefore, the comparison between the first temperature T1 and the second temperature T2 is performed under the assumption that the first temperature sensor 16 and the second temperature sensor 17 are arranged under the same temperature condition. To do. The temperature correction unit of the control device 60 takes into consideration the amount of heat released from the exhaust pipe 11 from the arrangement position of the upstream first temperature sensor 16 to the arrangement position of the downstream second temperature sensor 17. The value of either one of the first temperature T1 and the second temperature T2 is corrected.

For example, the temperature correction unit of the control device 60 includes the length of the exhaust pipe 11 from the arrangement position of the first temperature sensor 16 to the arrangement position of the second temperature sensor 17, the circumferential length of the exhaust pipe 11, and the exhaust gas. Based on the heat transfer coefficient of the tube 11, the exhaust temperature, the outside air temperature, etc., it is discharged from the surface of the exhaust tube 11 between the position where the first temperature sensor 16 is disposed and the position where the second temperature sensor 17 is disposed. After calculating the amount of heat to be corrected, correction is performed by adding the temperature corresponding to the calculated heat release amount to the second temperature T2, and the corrected second temperature T2 ′ is calculated.
However, the temperature correction method may be correction by subtracting the temperature corresponding to the calculated heat radiation amount from the first temperature T1, or subtracting a predetermined temperature from the first temperature T1. On the other hand, the correction may be performed by adding a predetermined temperature to the second temperature T2. In any case, it is only necessary to perform correction so that the temperature difference due to the difference between the arrangement position of the first temperature sensor 16 and the arrangement position of the second temperature sensor 17 is absorbed.

  By performing such temperature correction by the temperature correction unit, even if the arrangement position of the first temperature sensor 16 and the arrangement position of the second temperature sensor 17 are different, the condensed water tends to adhere. The temperature difference between the first temperature T1 and the second temperature T2 caused by the latent heat due to the evaporation of the condensed water in the first temperature sensor 16 is detected with high accuracy.

  The condensed water presence / absence determining unit reads the detected or corrected first temperature T1 and second temperature T2, and compares the two temperatures to determine whether condensed water exists in the exhaust pipe 11. Determine whether. In the temperature determination unit of the control device 60 of the present embodiment, the first temperature T1 is compared with the corrected second temperature T2 ′, and the first temperature T1 and the corrected second temperature T2 ′ are compared. The temperature difference ΔT is calculated, and it is determined whether or not the temperature difference ΔT is continuously less than the predetermined threshold value ΔT0 during the predetermined determination period tm2. This determination period tm2 is set by experimentally determining a period during which it can be reliably determined that condensed water is no longer generated in the exhaust gas. This determination period tm2 is measured by a timer counter.

  Further, the condensed water presence / absence determining unit of the control device 60 of the present embodiment is configured to detect the first temperature T1 and the second temperature detected after the predetermined waiting period tm1 measured by the timer counter after the internal combustion engine 5 is started. The above determination is performed using T2. Specifically, after the internal combustion engine 5 is started, the first and second temperature detection units continuously read the sensor value St1 of the first temperature sensor 16 and the sensor value St2 of the second temperature sensor 17. The temperature correction unit corrects the value of one of the first temperature T1 and the second temperature T2, but the condensed water presence / absence determination unit reads the temperature read after the preset waiting period tm1 has elapsed. Based on the above, the above determination is performed, and the determination result is output to the heater control unit and the reducing agent injection valve drive control unit.

3. Condensed water detection method Next, a condensed water detection method performed by the control device 60 of the present embodiment will be described with reference to timing charts shown in FIGS. 6 and 7 and a flowchart shown in FIG.

(1) Timing Chart FIGS. 6 and 7 are timing charts for explaining the condensed water detection method performed by the control device 60. The timing charts are obtained with the passage of time after the start of the internal combustion engine 5 (t0). 1 shows the temporal change of the temperature T1, the corrected second temperature T2 ′, the temperature difference ΔT between the first temperature T1 and the second temperature T2 ′, the amount of condensed water in the exhaust gas, and the timer value. Yes.
6 shows an example in which the condensed water in the exhaust gas continuously decreases and disappears, and FIG. 7 shows the case where the operating state of the internal combustion engine is unstable and the exhaust gas An example is shown in which condensed water in the inside decreases and disappears once, then condensed water appears again, and then disappears again. That is, FIG. 7 shows an example in which the disappearance and generation of condensed water are repeated in a short time.
6 and 7, the first temperature T1 obtained based on the sensor value St1 of the first temperature sensor 16 is a solid line, and after correction obtained based on the sensor value St2 of the second temperature sensor 17 The second temperature T2 ′ is represented by a dotted line.

  First, in FIGS. 6 and 7, the control device 60 starts a timer count when it detects the start of the internal combustion engine 5 (t0). After the internal combustion engine 5 is started, calculation of the first temperature T1, the corrected second temperature T2 ′, and the temperature difference ΔT between the first temperature T1 and the corrected second temperature T2 ′ is started. The However, since the operating state of the internal combustion engine 5 is unstable immediately after the start of the internal combustion engine 5, the condensed water in the exhaust gas is kept until the timer value has passed the predetermined standby time tm1 (t1, t11). The presence / absence determination is not performed.

If the condensed water is present in the exhaust gas after the start of the internal combustion engine 5, the first temperature sensor 16, to which the condensed water is likely to adhere, has the surface of the first temperature sensor 16 due to latent heat when the condensed water that has adhered evaporates. Since the temperature is deprived, the temperature difference ΔT between the first temperature T1 and the corrected second temperature T2 increases. Thereafter, the presence or absence of condensed water in the exhaust gas based on the difference ΔT between the first temperature T1 and the corrected second temperature T2 ′ from the time point t1, t11 when the timer value has passed the predetermined waiting time tm1 The determination is started.
Then, as the condensed water in the exhaust gas decreases, the temperature difference ΔT also starts to decrease, and the control device 60 starts timer counting at time t2 when the temperature difference ΔT becomes less than the predetermined threshold value ΔT0.

  Thereafter, in the example of FIG. 6, the condensed water in the exhaust gas disappears at the time t3, the temperature difference ΔT between the first temperature T1 and the corrected second temperature T2 ′ becomes zero, and t4 At that time, the temperature difference ΔT remains less than the threshold value ΔT0, the timer value has passed the determination period Tm2, and the control device 60 determines that the condensed water in the exhaust pipe 11 has disappeared.

  On the other hand, in the example of FIG. 7 in which the operating state of the internal combustion engine 5 is unstable, the condensed water in the exhaust gas once disappears at the time t13 after the timer count is started, but thereafter, the condensed water is condensed again in the exhaust gas. In the first temperature sensor 16 where the water is generated and the condensed water is likely to adhere, the surface temperature is deprived by the latent heat due to the evaporation of the attached condensed water, and the first temperature T1 and the corrected second temperature T2 ′ are obtained. The temperature difference ΔT starts to open again. Therefore, when the temperature difference ΔT reaches the threshold value ΔT0 at time t14, the control device 60 resets the timer value.

  Thereafter, the condensed water in the exhaust gas begins to decrease again, and the temperature difference ΔT also starts to decrease, and the control device 60 starts timer counting at time t15 when the temperature difference ΔT becomes less than the predetermined threshold value ΔT0. Then, the condensed water in the exhaust gas disappears at the time t16, the temperature difference ΔT between the first temperature T1 and the corrected second temperature T2 ′ becomes 0, and the temperature at the time t16. While the difference ΔT remains less than the threshold ΔT0, the timer value has passed the determination period Tm2, and the control device 60 determines that the condensed water in the exhaust pipe 11 has disappeared.

  In the condensed water detection method of the present embodiment, the control device 60 sets the predetermined determination period tm2 while the temperature difference ΔT is less than the threshold value ΔT0, not at the times t2, t12, and t15 when the temperature difference ΔT is less than the threshold value ΔT0. It is determined that the condensed water in the exhaust gas has disappeared at the time points t4 and t17. Therefore, even when the generation and disappearance of condensed water in the exhaust gas are repeated in a relatively short period, it is determined that the condensed water has disappeared when the condensed water in the exhaust gas is no longer present. The

(2) Control Flow The condensate detection method of this embodiment executed by the exhaust purification apparatus 10 of this embodiment shown in FIG. 1 will be described based on the control flow of FIG. The detection unit reads the rotational speed Ne of the internal combustion engine 5, and then in step S12, the start detection unit determines whether the internal combustion engine 5 has started based on the rotational speed Ne of the internal combustion engine 5. Steps S11 and S12 are repeated until the internal combustion engine 5 is started. When it is determined that the internal combustion engine 5 has been started, the process proceeds to step S13.

  In step S13, the timer TM1 is activated. Next, in step S14, the first and second temperature detection units obtain the sensor value St1 of the first temperature sensor 16 to which the condensed water easily adheres and the sensor value St2 of the second temperature sensor 17 to which the condensed water does not adhere. After reading, in step S15, the first and second temperature detectors calculate the first temperature T1 and the second temperature T2 based on the sensor values St1 and St2.

Next, in step S16, it is determined whether or not the value of the timer TM1 has passed the waiting period tm1, and if the value of the timer TM1 has not passed the waiting period tm1, the process returns to step S14, while the value of the timer TM1 When the waiting period tm1 has elapsed, the process proceeds to step S17.
In step S17, the comparison between the first temperature T1 and the second temperature T2 is performed under the assumption that the first temperature sensor 16 and the second temperature sensor 17 are arranged under the same temperature condition. In order to achieve this, the temperature correction unit corrects at least one of the first temperature T1 and the second temperature T2. In the present embodiment, the temperature correction unit corrects the second temperature T2.

  Next, in step S18, the condensed water presence / absence determining unit compares the first temperature T1 and the corrected second temperature T2 ′ to calculate the temperature difference ΔT, and in step S19, the condensed water presence / absence determining unit. Determines whether the calculated temperature difference ΔT is less than a threshold value ΔT0. When the temperature difference ΔT is greater than or equal to the threshold value ΔT0, the process proceeds to step S24, and it is determined whether or not the timer TM2 is operating. If the timer TM2 is stopped, the process returns to step S14 as it is. If the timer TM2 is in operation, the timer TM2 is reset in step S25, and the process returns to step S14.

  On the other hand, if it is determined in step S19 that the temperature difference ΔT is greater than or equal to the threshold value ΔT0, the process proceeds to step S20, and it is determined whether the timer TM2 is operating. If the timer TM2 is stopped, the timer TM2 is activated in step S26, and then the process returns to step S14. On the other hand, if the timer TM2 is operating, it is determined in step S21 whether or not the value of the timer TM2 has passed the determination period tm2. If the value of the timer TM2 has not passed the determination period tm2, the process returns to step S14, whereas if the value of the timer TM2 has passed the determination period tm2, the process proceeds to step S22.

  In step S22 in which the determination period tm2 has elapsed with the temperature difference ΔT between the first temperature T1 and the corrected second temperature T2 ′ being less than the threshold value ΔT0, the condensed water presence / absence determination unit In step S23, the heater control unit starts energizing the heater 24 and ends this routine.

  As described above, the method for detecting condensed water in the exhaust gas according to the present embodiment determines whether condensed water exists in the exhaust gas depending on the presence or absence of latent heat in the first temperature sensor 16 where the condensed water tends to adhere. Can be accurately determined. Then, since it is determined that the condensed water has disappeared from the exhaust gas, the energization of the heater is started, so that element cracking of the sensor element due to local distortion of the sensor element due to latent heat is reliably prevented. .

4). Application Example One embodiment of the present invention has been described so far, but the present invention is not limited to the above embodiment and can be implemented in various forms.
For example, in addition to the first temperature sensor to which condensed water easily adheres and the second temperature sensor to which condensed water does not adhere, a third temperature sensor to which condensed gas of exhaust gas tends to adhere or does not adhere is provided, and the exhaust gas is exhausted. A purification device may be configured.

  For example, the first temperature sensor and the third temperature sensor to which the condensed water is likely to adhere are arranged with the positions shifted upstream and downstream of the exhaust passage, and the heat in the exhaust passage is radiated from the exhaust pipe surface. The second in which condensed water does not adhere to a position where the temperature is an intermediate temperature between the first temperature at the position where the first temperature sensor is disposed and the third temperature at the position where the third temperature sensor is disposed. The exhaust gas purification apparatus can be configured by arranging the temperature sensor. In the case of the exhaust gas purification apparatus configured as described above, the first temperature at the position where the first temperature sensor where the latent heat is generated and the third temperature where the third temperature sensor where the latent heat is also generated are the same. Can be used as the sensor value of a virtual temperature sensor to which condensed water provided at the arrangement position of the second temperature sensor is likely to adhere. Therefore, by comparing the average value and the second temperature at the position where the second temperature sensor to which the condensed water does not adhere is determined to determine whether the temperature difference is less than a predetermined threshold value, The presence or absence of condensed water in the exhaust gas can be detected more accurately.

  Alternatively, the second in which condensed water does not adhere to a position that is an intermediate temperature between the first temperature at the arrangement position of the first temperature sensor and the third temperature at the arrangement position of the third temperature sensor. Even if the temperature sensor is not arranged, if the amount of heat released from the exhaust pipe surface is taken into consideration, the condensed water provided at the arrangement position of the second temperature sensor is based on the first temperature and the third temperature. A sensor value of a virtual temperature sensor that easily adheres can be obtained. Therefore, when a plurality of existing temperature sensors are provided in the exhaust system of the internal combustion engine, if any one of the temperature sensors is configured as a temperature sensor to which condensed water does not adhere, without significantly increasing the cost, The condensed water detection method of the present invention becomes feasible.

The specific gas concentration sensor is not limited to the NO _x sensor, but may be other air-fuel ratio sensors or the like.

It is a figure which shows the whole structure of the exhaust gas purification apparatus of this embodiment. It is sectional drawing which shows the structural example of a specific gas concentration sensor. It is a figure for demonstrating the area | region where condensed water tends to adhere. It is a figure which shows an example of the waterproof structure for comprising the temperature sensor to which condensed water does not adhere. It is a block diagram which shows the structural example of the condensed water detection apparatus concerning this embodiment. It is a timing chart for demonstrating the condensed water detection method concerning this embodiment. It is a timing chart for demonstrating the condensed water detection method concerning this embodiment. It is a control flow for demonstrating the condensed water detection method concerning this embodiment. It is a figure which shows the structure of the conventional exhaust gas detection apparatus.

Explanation of symbols

5: internal combustion engine, 10: exhaust purification device, 11: exhaust passage, 12: waterproof structure, 13: reduction catalyst, 16: first temperature sensor, 17: second temperature sensor, 18: third temperature sensor, 19.21: solid electrolyte body, 20: specific gas concentration sensor (NO _X sensor), 22: exhaust gas flow path, 24: heater, 24a: heating wire, 24b: substrate layer, 25a: first space, 25b: first 2 spaces, 26a: first element, 26b: second element, 27a: first inner electrode, 27b: second inner electrode, 28a: first outer electrode, 28b: second outer electrode, 29: sensor Element: 30: Reference gas space, 32: External connection circuit, 33: Gas passage hole, 37: Protective cover, 40: Reducing agent supply device, 41: Storage tank, 42: Pump, 43: Pressure sensor, 44: Reducing agent Injection valve, 58: first supply passage, 5 : Second supply passage, 60: control device (condensed water detector)

Claims (10)

Condensed water in the exhaust gas flowing through an exhaust passage provided with a specific gas concentration sensor connected to an internal combustion engine and having a sensor element for detecting a specific component in the exhaust gas and a heater for heating the sensor element In the condensed water detector for detecting the presence or absence,
A first temperature detection unit that detects a first temperature detected by a first temperature sensor that is easily attached to the condensed water provided in an exhaust pipe that forms the exhaust passage;
A second temperature detection unit that detects a second temperature detected by a second temperature sensor that is not attached to the condensed water provided in the exhaust pipe;
A condensed water presence / absence determining unit that determines whether the condensed water exists in the exhaust gas by comparing the first temperature and the second temperature;
A condensed water detection device comprising:   The condensed water detection device includes a start detection unit that detects start of the internal combustion engine, and the condensed water presence / absence determination unit is configured to detect the first temperature and the second temperature detected after a predetermined period has elapsed since the start of the internal combustion engine. The condensate detection device according to claim 1, wherein the determination is performed using a temperature.   The condensed water presence / absence determining unit calculates a temperature difference between the detected first temperature and the second temperature, and the condensed water is contained in the exhaust passage when the temperature difference is less than a predetermined value. It determines with not existing, The condensed water detection apparatus of Claim 1 or 2 characterized by the above-mentioned.   The condensed water presence / absence determining unit calculates a temperature difference between the detected first temperature and the second temperature, and when the temperature difference is continuously less than a predetermined value for a predetermined period, It determines with the said condensed water not existing in the condensed water detection apparatus as described in any one of Claims 1-3 characterized by the above-mentioned. The detected first temperature and the second temperature, the length of the exhaust pipe from the arrangement position of the first temperature sensor to the arrangement position of the second temperature sensor, and the circumference of the exhaust pipe The exhaust gas flows from the arrangement position of the first temperature sensor to the arrangement position of the second temperature sensor based on the length of the gas, the heat transfer coefficient of the exhaust pipe, and the outside air temperature, or A heat dissipation amount calculation unit that calculates a heat dissipation amount from the exhaust gas during the flow from the position where the second temperature sensor is disposed to the position where the first temperature sensor is disposed;
A temperature correction unit that corrects at least one of the first temperature and the second temperature based on the heat dissipation amount; and
The condensed water detection apparatus according to any one of claims 1 to 4, further comprising:   6. The heater drive control unit that permits energization of the heater when the condensed water presence / absence determining unit determines that the condensed water is not present in the exhaust gas. The condensed water detection apparatus according to claim 1. A third temperature detection unit that detects a third temperature that is different from the first temperature sensor and the second temperature sensor and that is detected by a third temperature sensor to which the condensed water tends to adhere or does not adhere. Prepared,
The condensed water detection apparatus according to claim 1, wherein the condensed water presence / absence detecting unit performs the determination in consideration of the third temperature. Condensed water in the exhaust gas flowing through an exhaust passage provided with a specific gas concentration sensor connected to an internal combustion engine and having a sensor element for detecting a specific component in the exhaust gas and a heater for heating the sensor element In the condensed water detection method for detecting the presence or absence,
After the start of the internal combustion engine, a first temperature detected by a first temperature sensor provided in an exhaust pipe forming the exhaust passage to which the condensed water is likely to adhere, and a second temperature in which the condensed water does not adhere. And detecting the presence or absence of the condensed water in the exhaust gas by detecting the second temperature detected by the temperature sensor and comparing the first temperature and the second temperature. Condensate detection method. In an exhaust gas purification apparatus provided with a specific gas concentration sensor interposed in an exhaust passage of an internal combustion engine and having a sensor element for detecting a specific component in exhaust gas and a heater for heating the sensor element in the exhaust passage. ,
A first temperature sensor that is easily attached to the condensed water in the exhaust gas provided in an exhaust pipe that forms the exhaust passage;
A second temperature sensor provided in the exhaust pipe to which the condensed water does not adhere;
After the internal combustion engine is started, a first temperature detected by the first temperature sensor and a second temperature detected by the second temperature sensor are detected, and the first temperature and the second temperature are detected. A condensed water detector for detecting the presence or absence of the condensed water in the exhaust gas by comparing the temperature of
An exhaust emission control device comprising:   The exhaust emission control device according to claim 9, further comprising a waterproof structure for preventing the condensed water from adhering to the second temperature sensor.

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