JP5787090B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that purifies nitrogen oxides contained in exhaust gas on the catalyst by adding a liquid reducing agent from the upstream side of the catalyst provided in the exhaust passage of the internal combustion engine through an addition mechanism. About.

  Conventionally, in order to purify nitrogen oxides (hereinafter referred to as NOx) contained in the exhaust gas of an internal combustion engine, a selective reduction catalyst (hereinafter referred to as catalyst 104) is provided in the exhaust passage 102 of the internal combustion engine as shown in FIG. An exhaust emission control device in which an addition valve 144 for adding urea water as a reducing agent from the upstream side of the catalyst 104 is provided is well known (see, for example, Patent Document 1). The urea water is stored in a dedicated tank 110 mounted on the vehicle, and the urea water in the tank 110 is added by the pump 142 provided in the middle of the supply pipe 130 connecting the tank 110 and the addition valve 144. 144 to be pumped. According to such an exhaust purification device, urea water is decomposed into ammonia by adding urea water to the exhaust under high temperature by the addition valve 144, and NOx contained in the exhaust is reduced and purified on the catalyst 104 by ammonia. Is done.

  By the way, urea water starts to freeze when it becomes -7 ° C. or lower. Therefore, an electric heater 120 for heating urea water in the tank 110 is provided, and the urea water is defrosted by energizing the electric heater 120 when the urea water is frozen. (For example, refer to Patent Document 2). Incidentally, the electric heater 120 is provided in the tank 110 in the vicinity of a portion to which the supply pipe 130 is connected.

JP 2010-71270 A JP 2008-115784 A

  By the way, when the internal combustion engine is started from the state in which the urea water in the tank 110 is completely frozen, and the heating by the electric heater 120 is performed along with this, the urea water in the tank 110 is sequentially supplied from the periphery of the electric heater 120. It will be thawed. Here, when the operation continuation time of the internal combustion engine is short, that is, when the heating time by the electric heater 120 is short, only the urea water around the electric heater 120 is thawed. Therefore, when all the thawed urea water is added through the addition valve 144 and there is no liquid urea water that can be added, as shown by a one-dot chain line in FIG. A cavity is created in the vicinity. In such a situation, the driving of the addition mechanism such as the pump 142 and the addition valve 144 is continued, that is, if the idle driving is performed, the urea water cannot be added and wear of the drive part of the addition mechanism occurs. The problem that it becomes easy arises.

  For such a problem, it is conceivable to prohibit the addition mechanism from being driven until the urea water in the tank is completely thawed. That is, the time required for the urea water to be completely thawed (hereinafter referred to as required time) is set in advance, and the drive of the addition mechanism is prohibited until the required time elapses. However, in this case, another problem arises that the addition of the reducing agent cannot be started at an early stage.

Such a problem is not limited to the exhaust gas purification apparatus using urea water, but similarly occurs in an exhaust gas purification apparatus using a liquid reducing agent that freezes at a low temperature.
The present invention has been made in view of such circumstances, and its purpose is to accurately suppress deterioration of the addition mechanism while starting the addition of the reducing agent early when the reducing agent in the tank is frozen. An object of the present invention is to provide an exhaust gas purification device for an internal combustion engine that can be used.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
The invention described in 請 Motomeko 1 purifies nitrogen oxides contained in exhaust the addition of the liquid reducing agent through an addition mechanism from the upstream side of the catalyst provided in an exhaust passage of the internal combustion engine on the catalyst In the exhaust gas purification apparatus for an internal combustion engine, the exhaust gas purification apparatus comprising a heating device provided in a tank for storing the reducing agent and heating the reducing agent, when the reducing agent in the tank is frozen, The heating device is used for heating and the addition of the reducing agent by the addition mechanism is restricted, and the addition of the reducing agent is limited according to the total thawing amount of the reducing agent after the heating is started. The total amount of reducing agent added since the start of heating is defined as the total amount of reducing agent added, and when the total thawing amount of the reducing agent is less than the total amount of reducing agent added, the reducing agent is reduced. Additive It has as its subject matter that is prohibited.

  According to this configuration, when the reducing agent in the tank is frozen, the reducing agent is thawed by heating with the heating device. In addition, the thawed urea water is added from the upstream side of the catalyst through the addition mechanism. At this time, according to the above configuration, the restriction mode of addition of the reducing agent is changed according to the total thawing amount, which is the total amount of the reducing agent thawed after the start of the heating. That is, when the total thawing amount is large and the amount of liquid reducing agent that can be added is large, the restriction on the addition of the reducing agent is relaxed. On the other hand, when the total amount of thawing of the reducing agent is small and the amount of liquid reducing agent that can be added is small, the restriction on the addition of the reducing agent is strengthened. Therefore, according to the present invention, it is possible to accurately suppress deterioration of the addition mechanism while starting the addition of the reducing agent at an early stage when the reducing agent in the tank is frozen.

  Further, according to the same configuration, when the total thawing amount of the reducing agent is less than the total addition amount that is the total amount of the reducing agent added since the start of the heating, the addition of the reducing agent is prohibited. Become. For this reason, for example, during the previous engine operation, only the reducing agent around the heating device in the tank has been thawed, and all the thawed reducing agent has been added and consumed, so that the liquid reducing agent that can be added In a situation where no is present, the driving of the addition mechanism, so-called idling is not performed. Therefore, deterioration of the addition mechanism can be suppressed more accurately.
  The total amount of the reducing agent added can be estimated based on the travel distance of the vehicle after the operation of the internal combustion engine is started, as in the second aspect of the invention.

  Incidentally, it is desirable to estimate the total thawing amount of the reducing agent based on the heating history of the heating device. For example, when the amount of heat input from the heating device to the reducing agent per unit time is constant, the total amount of the thawed reducing agent increases as the heating time by the heating device increases. If other conditions are constant, the total amount of the thawed reducing agent increases as the amount of heat input from the heating device to the reducing agent per unit time increases. Therefore, if the total thawing amount of the reducing agent is estimated based on the heating history of the heating device, the total thawing amount can be estimated with high accuracy.

  It is desirable to estimate the total amount of the reducing agent based on at least one of the operation history of the internal combustion engine and the travel history of the vehicle. For example, the total amount of the reducing agent added increases as the operation duration time of the internal combustion engine increases. Moreover, the total amount of the reducing agent added increases as the travel distance of the vehicle increases. For these reasons, if the total addition amount of the reducing agent is estimated based on at least one of the operation history of the internal combustion engine and the travel history of the vehicle, the total addition amount can be estimated with high accuracy. .

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the whole structure about the exhaust gas purification apparatus of the internal combustion engine which concerns on 1st Embodiment of this invention. The flowchart which shows the execution procedure of the addition restriction routine of urea water in the same embodiment. The flowchart which shows the execution procedure of the freezing flag setting routine in the embodiment. A map that defines the relationship between the volume of urea water and the freezing time for each temperature of urea water. The map which prescribed | regulated the relationship between the driving | operation continuation time of an internal combustion engine, and the total defrosting amount estimated value of urea water. The map which prescribed | regulated the relationship between the travel distance of a vehicle, and the total addition amount estimated value of urea water. The flowchart which shows the execution procedure of the urea water addition restriction | limiting routine in 3rd Embodiment. A map that defines the relationship between the estimated amount of total thawing amount of urea water and the delay time. Sectional drawing which shows the cross-section of a tank when only the urea water around an electric heater is thawed | decompressed about the conventional exhaust gas purification apparatus of an internal combustion engine.

<First Embodiment>
Hereinafter, an embodiment embodying an exhaust emission control device for an internal combustion engine according to the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the exhaust purification apparatus according to this embodiment includes a selective reduction catalyst (hereinafter referred to as catalyst 4) provided in an exhaust passage 2 of an in-vehicle internal combustion engine, and liquid urea water from the upstream side of the catalyst 4. And an addition valve 44 for adding. The drive control of the addition valve 44 is executed by the electronic control unit 50. Nitrogen oxide (hereinafter referred to as NOx) contained in the exhaust gas is purified on the catalyst 4 by adding urea water from the addition valve 44.

  Further, the exhaust purification device includes a tank 10 in which urea water is stored. A concave portion 14 a is formed on the bottom surface 14 (surface on the lower side in the vertical direction) of the tank 10, and a supply pipe 30 for supplying urea water to the addition valve 44 is connected to the concave portion 14 a. A pump 42 for pumping urea water is provided in the supply pipe 30. The drive control of the pump 42 is executed by the electronic control unit 50.

  A heating device 20 for heating urea water is provided in the recess 14a. The heating device 20 includes an electric heating coil 22 that generates heat when energized, and a metal piece 24 that extends from both ends of the electric heating coil 22 and extends along the bottom surface 14 of the tank 10. The energization control to the electrothermal coil 22, that is, the heating control by the heating device 20, is executed by the electronic control device 50.

  In addition to a temperature sensor 51 that detects the temperature of urea water and a liquid level sensor 52 that detects the liquid level of urea water, various sensors that detect the operating state of the internal combustion engine and the running state of the vehicle are connected to the electronic control unit 50. Has been.

  In the present embodiment, it is determined whether or not the urea water in the tank 10 is completely frozen through the electronic control unit 50, and when it is determined that the urea water is completely frozen, the heating device is used. The urea water is defrosted by energizing 20. Here, energization control to the electric heating coil 22 is performed so that the amount of heat input per unit time to the urea water by the heating device 20 becomes constant.

  By the way, as described above, when the internal combustion engine is started from a state in which the urea water in the tank 10 is completely frozen, and the heating device 20 is heated along with this, the urea water in the tank 10 is heated. The decompression starts from the periphery of the apparatus 20. Here, when the operation duration time of the internal combustion engine, that is, the heating time by the heating device 20 is short, only the urea water around the heating device 20 is thawed. Therefore, when all the thawed urea water is added through the addition valve 44 and there is no liquid urea water that can be added, a cavity is formed in the tank 10 near the connection portion of the supply pipe 30. In such a situation, if the pump 42 and the addition valve 44 continue to be driven, that is, if idle driving is performed, urea water cannot be added, and wear of the drive parts of the pump 42 and the addition valve 44 occurs. The problem that it becomes easy arises.

  Therefore, in this embodiment, when the urea water in the tank 10 is frozen in order to eliminate such inconvenience, the heating device 20 performs heating to thaw the urea water, and the heating is started. When the total thawing amount estimated value VA of the urea water exceeds the total addition amount estimated value VB of the urea water, the pump 42 and the addition valve 44 are allowed to be driven. Further, when the estimated total thawing amount value VA of the urea water is less than the estimated total addition amount value VB of the urea water, the pump 42 and the addition valve 44 are prohibited from being added and the addition of the reducing agent is prohibited.

Next, with reference to FIG. 2, the execution procedure of the routine for restricting the addition of urea water will be described. This routine is repeatedly executed at predetermined intervals during the operation of the internal combustion engine.
As shown in FIG. 2, in this series of processing, it is first determined whether or not the freezing flag F1 is “ON” (step S1). The freezing flag F1 is a flag that is set to “ON” when it is determined that the urea water in the tank 10 is completely frozen.

  Here, with reference to FIG. 3, the execution procedure of the routine for setting the freezing flag F1 will be described. The routine is repeatedly executed every predetermined period while the engine is stopped. The freezing flag F1 is initially set to “OFF”.

  As shown in FIG. 3, in this series of processing, first, the volume Vurea of urea water immediately after the engine is stopped is read (step S11). The volume Vurea of the urea water is calculated in a known manner based on the detection result of the liquid level sensor 52 in a state where the urea water in the tank 10 is completely thawed. Next, the temperature of the urea water at that time is read (step S12).

  When the urea water temperature Turea is thus read, it is next determined whether or not the urea water temperature Turea is equal to or lower than the freezing point temperature Tfrz (step S13). Here, when the temperature Turea of the urea water is not below the freezing point (step S13: “NO”), it is determined that the urea water is not frozen, and this series of processing is performed with the freezing flag F1 kept “OFF”. Exit once.

  On the other hand, if the temperature Turea of the urea water is equal to or lower than the freezing point temperature Tfrz (step S13: “YES”), then referring to the map (MAP1) shown in FIG. 4, the volume Vurea of the urea water and the urea water The freezing time β is derived based on the temperature Turea (step S14). The freezing time β is the time required until the urea water is completely frozen. As shown in FIG. 4, if the volume Vurea of the urea water is constant (for example, V1), the lower the temperature of the urea water ( T1 <T2 <T3), which is set to a small value (β1 <β2 <β3). The relationship between the urea water volume Vurea, the urea water temperature Turea, and the freezing time β is set in advance through experiments and the like.

  If the freezing time β is derived in this way, it is next determined whether or not the post-stop elapsed time Δtstp, which is the elapsed time since the engine operation was stopped, is equal to or greater than the freezing time β (step S15). As a result, when the post-stop elapsed time Δtstp is not equal to or longer than the freezing time β (step S15: “NO”), the urea water is not completely frozen and the freezing flag F1 is kept “OFF”. This series of processes is temporarily terminated.

  On the other hand, when the post-stop elapsed time Δtstp is equal to or longer than the freezing time β (step S15: “YES”), it is assumed that the urea water is completely frozen, and then the freezing flag F1 is set to “ON” ( Step S16), this series of processes is temporarily terminated.

  As shown in FIG. 2, when the freezing flag F1 is not “ON” (step S1: “NO”), it is assumed that urea water can be added. Next, urea water is added. Is permitted (step S6), and this series of processing is terminated.

On the other hand, when the freezing flag F1 is “ON” (step S1: “YES”), energization to the electric heating coil 22 is started (step S2).
Then, referring to a map (MAP2) shown in FIG. 5, a total thawing amount estimated value VA that is the total amount of urea water thawed after the start of heating is calculated based on the operation duration time ΔtA of the internal combustion engine. (Step S3).

  Since the amount of heat input per unit time from the heating device 20 to the urea water is constant, the total amount of thawed urea water increases as the heating time by the heating device 20 increases. The heating time by the heating device 20 is substantially the same as the operation duration time ΔtA of the internal combustion engine. Therefore, the total defrosting amount estimated value VA can be accurately calculated based on the operation duration time ΔtA. The relationship shown in FIG. 5 between the operation continuation time ΔtA and the total thawing amount estimation value VA is set in advance through experiments or the like.

  Then, referring to the map (MAP3) shown in FIG. 6, the total amount of urea water added since the start of the heating based on the travel distance D of the vehicle since the operation of the internal combustion engine was started. A total addition amount estimated value VB is calculated (step S4).

  The total amount of urea water added increases as the travel distance D of the vehicle increases. Therefore, the total addition amount estimated value VB can be accurately calculated based on the travel distance D of the vehicle. The relationship shown in FIG. 6 between the vehicle travel distance D and the total addition amount estimated value VB is set in advance through experiments or the like.

  When the total thawing amount estimation value VA and the total addition amount estimation value VB are thus calculated, it is next determined whether or not the total thawing amount estimation value VA is less than the total addition amount estimation value VB (step S5). As a result, when the total thawing amount estimation value VA is not less than the total addition amount estimation value VB, that is, when the total thawing amount estimation value VA is equal to or greater than the total addition amount estimation value VB (step S5: “NO”), the tank 10 Assuming that there is a liquid urea solution that can be added, the addition of the urea solution is permitted (step S7), and this series of processing is terminated.

  On the other hand, when the total thawing amount estimated value VA is less than the total addition amount estimated value VB (step S5: “YES”), it is assumed that there is no liquid urea water that can be added in the tank 10, and In addition, the addition of urea water is prohibited, and this series of processing ends.

Hereinafter, the operation of the present embodiment will be described.
When the urea water in the tank 10 is frozen, the urea water is defrosted by heating by the heating device 20. Further, the thawed urea water is added from the upstream side of the catalyst 4 through the addition valve 44.

  Here, when the total thawing amount estimated value VA of urea water is less than the total addition amount estimated value VB, the driving of the pump 42 and the addition valve 44 is prohibited. For this reason, for example, only the urea water around the heating device 20 in the tank 10 was thawed at the time of the previous engine operation, and all the thawed urea water was added and consumed. Under the situation where urea water does not exist, the pump 42 and the addition valve 44 are not driven, so-called idle driving.

  Further, when the total thawing amount estimation value VA is equal to or greater than the total addition amount estimation value VB, the pump 42 and the addition valve 44 are allowed to be driven. For this reason, even if the urea water in the tank 10 is not completely thawed, the urea water is added when there is a liquid urea water that can be added.

According to the exhaust gas purification apparatus for an internal combustion engine according to the present embodiment described above, the following effects (1) to (3) can be obtained.
(1) When the urea water in the tank 10 is frozen through the electronic control device 50, the heating device 20 performs heating to thaw the urea water. In addition, when the estimated total thawing amount VA of urea water after the start of heating is equal to or greater than the total estimated amount VB of urea water, the pump 42 and the addition valve 44 are allowed to be driven, while the estimated total thawing amount is estimated. When the VA is less than the total addition amount estimated value VB, the driving of the pump 42 and the addition valve 44 is prohibited. Therefore, when the urea water in the tank 10 is frozen, the deterioration of the pump 42 and the addition valve 44 can be accurately suppressed while starting the addition of the urea water at an early stage.

  (2) The estimated total thawing amount VA is calculated based on the operation continuation time ΔtA. That is, the total thawing amount estimated value VA is calculated based on the heating history by the heating device 20. Therefore, the total defrosting amount estimated value VA can be calculated easily and accurately.

  (3) The total addition amount estimated value VB is calculated based on the travel distance D of the vehicle after the operation of the internal combustion engine is started. Therefore, the total addition amount estimated value VB can be calculated easily and accurately.

Second Embodiment
Hereinafter, a second embodiment of the present invention will be described.
In the first embodiment, the pump 42 and the addition valve 44 are allowed to be driven when the total thawing amount estimation value VA exceeds the total addition amount estimation value VB.

  However, if the pump 42 and the addition valve 44 are actuated immediately after a slight amount of liquid urea water that can be added is generated, there is no liquid urea water that can be added immediately thereafter, and urea water is added. , You will not be able to continue for a certain period of time.

  Therefore, in the present embodiment, when the driving of the pump 42 and the addition valve 44 is prohibited because the total thawing amount estimated value VA is less than the total addition amount estimated value VB, the predetermined time τ from the prohibited timing. Until the time elapses, the drive inhibition of the pump 42 and the addition valve 44 is continued, and the drive of the pump 42 and the addition valve 44 is allowed after the lapse of the predetermined time τ.

  Here, when the addition of the urea water is resumed while allowing the pump 42 and the addition valve 44 to be driven, the required manner of adding the urea water varies depending on the operation state of the internal combustion engine and the running state of the vehicle at that time.

  Therefore, in the present embodiment, the predetermined time τ is variably set based on the operating state of the internal combustion engine. Specifically, the flow rate of NOx is grasped from the amount of intake air detected by the air flow meter and the concentration of NOx detected by the NOx sensor, and the amount of urea water added to purify the NOx (hereinafter referred to as “NOx”). , Required addition amount). The longer the required addition amount, the longer the predetermined time τ is set.

  According to the exhaust gas purification apparatus for an internal combustion engine according to the present embodiment described above, the following effects (4) and (5) are newly added to the effects (1) to (3) of the first embodiment. It will be obtained.

  (4) The pump 42 and the addition valve 44 are driven after a predetermined time τ has elapsed since the drive of the pump 42 and the addition valve 44 is prohibited by the total thawing amount estimation value VA being less than the total addition amount estimation value VB. Was allowed. Thereby, when the drive of the pump 42 and the addition valve 44 is restarted, the addition of urea water can be suitably continued for a certain period of time.

  (5) The predetermined time τ is variably set based on the operating state of the internal combustion engine, specifically, the required addition amount of urea water. Thereby, the addition of urea water can be continued accurately.

<Third Embodiment>
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS.
In the first and second embodiments, the total thawing amount estimation value VA and the total addition amount estimation value VB are compared, and when the total thawing amount estimation value VA is less than the total addition amount estimation value VB, The addition was prohibited.

On the other hand, in the present embodiment, the urea water addition start timing is delayed as compared to when the urea water total thawing amount estimation value VA is small compared to when it is large.
Hereinafter, the difference from the first and second embodiments will be mainly described.

Next, with reference to FIG. 7, the routine execution procedure for limiting the addition of urea water will be described. This routine is repeatedly executed at predetermined intervals during the operation of the internal combustion engine.
As shown in FIG. 7, in this series of processing, it is first determined whether or not the delay time Δtdly is set (step S21). The delay time Δtdly is set in the subsequent step S26. Therefore, in the first control cycle, an affirmative determination is made in step S21, and then it is determined whether or not the freezing flag F1 is “ON” (step S22).

Here, when the freezing flag F1 is not “ON” (step S22: “NO”), the addition of urea water is then permitted (step S29), and this series of processing ends.
On the other hand, when the freezing flag F1 is “ON” (step S22: “YES”), next, energization to the electric heating coil 22 is started (step S23). Next, it is determined whether or not a urea water addition request has been issued (step S24). Here, when the urea water addition request is not issued (step S24: “NO”), it is not necessary to add the urea water in the first place, and this series of processes is temporarily performed, assuming that the situation is not limited. finish.

  On the other hand, if the urea water addition request has been issued (step S24: “YES”), then referring to the map (MAP2) shown in FIG. 5, urea is determined based on the operation duration time ΔtA of the internal combustion engine. A water total thawing amount estimation value VA is calculated (step S25).

  Next, with reference to the map (MAP4) shown in FIG. 8, the delay time Δtdly is set based on the total thawing amount estimated value VA of the urea water (step S26). The delay time Δtdly is a time from when the urea water addition request is issued until the urea water addition actually starts, that is, a time for delaying the urea water addition start timing. Here, as shown in FIG. 8, the delay time Δtdly is set to a larger value as the total defrosting amount estimated value VA is smaller. That is, when the urea water addition request is issued, when the total thawing amount estimated value VA of the urea water is large, it is determined that the amount of liquid urea water that can be added is large, and the urea water addition start timing is advanced. On the other hand, when the estimated total thawing amount VA of the urea water is small, the amount of liquid urea water that can be added is small, and it is necessary to start adding urea after waiting for a lot of urea water to be thawed. The addition start time is delayed. The relationship shown in FIG. 8 between the total defrosting amount estimated value VA and the delay time Δtdly is set in advance through experiments or the like.

  If the delay time Δtdly is thus set, it is next determined whether or not the delay time Δtdly has elapsed since the timing when the urea water addition request was issued (step S27). As a result, when the delay time Δtdly has not elapsed (step S27: “YES”), the addition of urea water is then prohibited (step S28), and this series of processes is temporarily terminated.

  On the other hand, if a negative determination is made in step S21 in the subsequent control cycle, the process proceeds to step S27, and it is determined again whether or not the delay time Δtdly has elapsed. If the delay time Δtdly has elapsed (step S27: “NO”), the addition of urea water is then permitted (step S29), and this series of processes is temporarily terminated.

According to the exhaust gas purification apparatus for an internal combustion engine according to the present embodiment described above, the following effect (6) can be obtained.
(6) The urea water addition start timing is delayed when the total thawing amount estimated value VA of the urea water is small compared to when it is large. According to such a configuration, deterioration of the pump 42 and the addition valve 44 can be accurately suppressed while starting the addition of the urea water at an early stage when the urea water in the tank 10 is frozen.

  The exhaust gas purification apparatus for an internal combustion engine according to the present invention is not limited to the configuration exemplified in the above embodiment, and can be implemented as, for example, the following form appropriately modified.

  In the second embodiment, the NOx flow rate is grasped based on the engine operating state. Instead, the NOx flow rate is indirectly grasped from the traveling state of the vehicle such as the vehicle speed. Also good.

  In the second embodiment, the predetermined time τ is variably set based on the required addition amount of urea water. Alternatively, the predetermined time can be a fixed value. In this case, an increase in calculation load in the electronic control device 50 can be suitably suppressed.

  In the above-described embodiment, the total addition amount estimated value VB of urea water is calculated based on the travel distance D of the vehicle after the operation of the internal combustion engine is started, but instead of this, from a car navigation system or the like You may make it calculate the total addition amount estimated value of urea water based on the other parameter regarding the driving | running | working log | history of vehicles, such as the positional information on the vehicle which can be grasped | ascertained. In addition to the traveling history of the vehicle, it is also possible to calculate the estimated total addition amount of urea water based on the operating history such as the engine speed of the internal combustion engine and the engine load.

  In each of the above embodiments, the energization control of the electric heating coil 22 is performed so that the amount of heat input to the urea water per unit time by the heating device 20 is constant. Further, the total thawing amount estimated value VA of urea water is calculated based on the operation duration time ΔtA of the internal combustion engine. However, the present invention is not limited to such an embodiment. In addition, for example, it is possible to change the amount of heat input per unit time with respect to the urea water by the heating device. In this case, the total amount of heat input to the urea water by the heating device is calculated by integrating the amount of heat input to the urea water by the heating device per unit time, and the urea water is calculated based on the total heat amount. What is necessary is just to calculate the total defrosting amount estimated value.

  In each of the above embodiments and modifications thereof, the estimated total defrosting amount of urea water is calculated from the total amount of heat input to the urea water by the heating device. In addition to this, if the total defrost amount estimated value is calculated based on the outside air temperature detected by the outside air temperature sensor, the total defrost amount estimated value can be calculated with higher accuracy.

  The reducing agent according to the present invention is not limited to urea water, and can be replaced with reducing agents of other components as long as nitrogen oxides contained in exhaust gas are purified on the catalyst.

  DESCRIPTION OF SYMBOLS 2,102 ... Exhaust passage, 4,104 ... Catalyst, 10,110 ... Tank, 14 ... Bottom surface, 14a ... Recess, 20 ... Heating device, 22 ... Electric heating coil, 24 ... Metal piece, 30, 130 ... Supply pipe, 42 , 142 ... pump, 44, 144 ... addition valve, 50 ... electronic control device, 51 ... temperature sensor, 52 ... liquid level sensor, 120 ... electric heater.

Claims (2)

An exhaust purification device for purifying nitrogen oxides contained in exhaust gas on the catalyst by adding a liquid reducing agent from an upstream side of a catalyst provided in an exhaust passage of an internal combustion engine through an addition mechanism, the reducing agent In an exhaust gas purification apparatus for an internal combustion engine comprising a heating device provided in a tank for storing the reducing agent,
When the reducing agent in the tank is frozen, heating by the heating device is restricted and addition of the reducing agent by the addition mechanism is restricted, and the total amount of the reducing agent after the heating is started. The mode of limiting the addition of the reducing agent is changed according to the amount of thawing ,
The total amount of reducing agent added since the start of heating is defined as the total amount of reducing agent added,
An exhaust gas purification apparatus for an internal combustion engine, wherein addition of a reducing agent is prohibited when the total thawing amount of the reducing agent is less than the total adding amount of the reducing agent . The exhaust gas purification apparatus for an internal combustion engine according to claim 1,
An exhaust emission control device for an internal combustion engine , wherein the total addition amount of the reducing agent is estimated based on a travel distance of the vehicle after the operation of the internal combustion engine is started .