JP2014238049A - Controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate, when a PM filter is installed in an exhaust passage, the amount of residing water or a dry condition downstream of the PM filter in the exhaust passage and to perform control accordingly.SOLUTION: The present invention is applied to an internal combustion engine where a PM filter for collecting fine particles in exhaust gas is installed in an exhaust passage and equipment is installed downstream of the PM filter. A controller of the internal combustion engine acquires a first correlation value to be an exhaust gas temperature on the upstream side of the PM filter or a value that correlates with the temperature, a second correlation value to be an exhaust gas temperature on the downstream side or a value that correlates with the temperature, and a third correlation value to be a temperature change of the PM filter or a value that correlates with the temperature change. In accordance with the acquired first to third correlation values, the amount of residing water in the exhaust passage downstream of the PM filter or the correlation value of the amount of residing water correlating with the amount of residing water is calculated. In accordance with the calculated correlation value of the amount of residing water, equipment downstream of the PM filter is controlled.

Description

  The present invention relates to a control device for an internal combustion engine. More specifically, the present invention relates to an internal combustion engine having a particulate collection filter in an exhaust passage of the internal combustion engine.

  Conventionally, various sensors for detecting exhaust characteristics are installed in an exhaust passage of an internal combustion engine. Some of these sensors are used in a state where the element portion is heated to a predetermined activation temperature by a built-in heater or the like. However, at the start of the internal combustion engine, if the element part is heated in a state where the accumulated water exists in the exhaust passage, the accumulated water may be scattered on the heated element part and the sensor may be damaged due to thermal shock. is there. For this reason, for example, control for avoiding damage to the sensor is performed such that heating of the element portion is started after the inside of the exhaust passage is in a dry state.

  Here, a method for estimating whether or not the inside of the exhaust passage at the start of the internal combustion engine is in a dry state is disclosed in Patent Document 1, for example. Specifically, in Patent Document 1, the amount of water remaining in the exhaust pipe at the start of the internal combustion engine and the amount of water that condenses and increases in the exhaust pipe after the start are estimated according to the outside air temperature, the cooling water temperature, and the like of the internal combustion engine. The The amount of staying water remaining in the exhaust passage is estimated from these amounts of water. In Patent Document 1, when the estimated water content is equal to or less than a predetermined value, it is determined to be in a dry state, and heating of the sensor is started.

Japanese Patent No. 4253511

  In the above-mentioned Patent Document 1, the relationship between the outside air temperature or water temperature and the amount of increase / decrease in accumulated water is stored in advance in the ECU, and the amount of accumulated water is calculated based on this relationship. However, the amount of accumulated water in the exhaust passage is easily influenced by the operating state of the internal combustion engine, and the estimation of the amount of retained water using the outside air temperature and the water temperature as in Patent Document 1 accurately determines the dry state in the exhaust passage. Is difficult.

  In addition, when a particulate collection filter (hereinafter also referred to as “PM filter”) for collecting particulates (hereinafter referred to as “PM”) is installed in the exhaust passage, a large amount of condensed water is generated from the PM filter during startup. To do. However, in Patent Document 1, no consideration is given to condensed water generated from a PM filter or the like upstream of the sensor. Therefore, in the estimation method of the amount of accumulated water as in Patent Document 1, it is difficult to correctly estimate the amount of accumulated water on the downstream side of the device when a device that generates a large amount of condensed water such as a PM filter is installed. It is difficult to estimate the dry state in the exhaust passage on the downstream side of the device.

  In addition to various sensors, various devices are installed downstream of the PM filter in the exhaust passage so that the amount of accumulated water in the exhaust passage affects its performance. In order to efficiently or effectively execute control of these various devices and various sensors under the situation where stagnant water is generated, it is desirable that the dry state of the exhaust passage at the installation position can be grasped with high accuracy.

  The present invention aims to solve the above problems, and when a PM filter is installed in the exhaust passage, the amount of accumulated water or the dry state downstream of the PM filter in the exhaust passage is estimated, and control according to this can be performed. An improved control device for an internal combustion engine is provided.

  The present invention is a control device for an internal combustion engine for achieving the above object, and a PM filter (a particulate collection filter) for collecting particulates in exhaust gas is installed in an exhaust passage of the internal combustion engine, A device is installed downstream of the PM filter. The control device includes first acquisition means for acquiring a first correlation value, second acquisition means for acquiring a second correlation value, and third acquisition means for acquiring a third correlation value. The first correlation value is an exhaust gas temperature upstream of the PM filter in the exhaust passage or a value correlated with the temperature. The second correlation value is an exhaust gas temperature downstream of the PM filter in the exhaust passage or a value correlated with the temperature. The third correlation value is a temperature change of the PM filter or a value correlated with the temperature change. Further, the control device is configured so that the amount of accumulated water in the exhaust passage downstream of the PM filter or the amount of accumulated water correlated with the amount of accumulated water is determined according to the acquired first correlation value, second correlation value, and third correlation value. Means for calculating the correlation value and control means for controlling the device in accordance with the calculated accumulated water amount correlation value are provided. In the present invention, “amount of staying water” means the amount of water present in a liquid state.

  In the present invention, when the above device is an exhaust gas sensor that emits an output corresponding to the concentration or amount of a specific component in the exhaust gas, the control means performs control to heat the exhaust gas sensor in accordance with the accumulated water amount correlation value. It is good also as what to do.

  In the present invention, when the above device is an EGR valve of an EGR device that recirculates a part of the exhaust gas as EGR gas to the intake passage of the internal combustion engine, the control means opens and closes the EGR valve according to the accumulated water amount correlation value. It is good also as what controls.

  In the present invention, when the above device is an SCR system for purifying exhaust gas, the control means may execute control for increasing the temperature of the catalyst of the SCR system in accordance with the accumulated water amount correlation value. .

  In the present invention, when the above device is an SCR system for purifying exhaust gas, the control means may control the exhaust gas flow rate flowing into the catalyst of the SCR system according to the water amount correlation value.

  According to the present invention, the temperature upstream and downstream of the PM filter and the temperature change of the PM filter are used in calculating the amount of accumulated water in the exhaust passage downstream of the PM filter or a value correlated therewith. Here, the PM filter is in contact with all the exhaust gas passing through, and exchanges heat energy with all the exhaust gas. Therefore, the amount of accumulated water in the exhaust passage downstream of the PM filter can be estimated with high accuracy based on the temperature of the exhaust gas and the temperature change of the PM filter. Therefore, according to the present invention, the amount of accumulated water or the dry state of the exhaust passage on the downstream side of the PM filter can be grasped more accurately, and the amount of accumulated water or Appropriate control according to the dry state can be executed.

It is a schematic diagram for demonstrating the whole structure of the system in embodiment of this invention. It is a figure for demonstrating transfer of the thermal energy at the time of PM filter passage in embodiment of this invention. It is a figure for demonstrating the change of the thermal energy which waste gas loses | emits when passing PM filter, and the change of the thermal energy which a PM filter obtains in embodiment of this invention. It is a flowchart for demonstrating the routine of control which a control apparatus performs in embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Embodiment.
[Entire configuration of system of this embodiment]
FIG. 1 is a schematic diagram for explaining an overall configuration of a system according to Embodiment 1 of the present invention. The system of FIG. 1 is used by being mounted on a vehicle or the like. The system of FIG. 1 includes an internal combustion engine 2. In the example of FIG. 1, the internal combustion engine 2 is a diesel engine. An oxidation catalyst 6 is installed in the exhaust passage 4, and a PM filter 8 (a particulate collection filter) is installed downstream of the oxidation catalyst 6. The PM filter 8 is a filter for collecting particulate matter (PM) contained in the exhaust gas.

  Various sensors are installed in the exhaust passage 4 of the internal combustion engine 2 in FIG. Specifically, an air-fuel ratio sensor 10 is installed upstream of the oxidation catalyst 6. The air-fuel ratio sensor 10 is an air-fuel ratio detection sensor that generates an output corresponding to the air-fuel ratio of exhaust gas. A temperature sensor 12 is installed in the exhaust passage 4 downstream of the oxidation catalyst 6, upstream of the PM filter 8 and in the vicinity of the inlet of the PM filter 8, and in the downstream of the PM filter 8 and in the vicinity of the outlet of the PM filter 8, the temperature of the PM sensor 14. A sensor 16 and a NOx sensor 18 are installed. The temperature sensors 12, 16 are sensors for temperature detection that emit an output corresponding to the temperature of exhaust gas (exhaust gas temperature). The PM sensor 14 is a fine particle detection sensor that generates an output corresponding to the amount of PM in the exhaust gas, and corresponds to the “exhaust gas sensor” of the present invention. The NOx sensor 18 is a sensor that emits an output corresponding to the amount of NOx in the exhaust gas, and this sensor also corresponds to the “exhaust gas sensor” of the present invention.

  This system includes a control device 20. In addition to the air-fuel ratio sensor 10, temperature sensors 12 and 16, PM sensor 14, NOx sensor 18, various sensors of the internal combustion engine 2 are connected to the input side of the control device 20. Various devices of the internal combustion engine 2 are connected to the output side of the control device 20. The control device 20 executes various programs related to the operation of the internal combustion engine 2 by executing predetermined programs based on input information from various sensors and operating various devices.

  Sensors such as the air-fuel ratio sensor 10, PM sensor 14, and NOx sensor 18 used in the above system have an element part formed in a ceramic part, and a heater is incorporated in the element part. These sensors are used in a state where the element portion is heated up to the activation temperature by the heater when each component is detected.

[Outline of control in this embodiment]
The control performed by the control device 20 in the present embodiment includes a dry determination for determining whether or not the exhaust passage 4 downstream of the PM filter 8 is in a dry state when the internal combustion engine 2 is started, and the dry determination result. Control for preventing element cracking of the corresponding PM sensor 14 and NOx sensor 18 is included.

(1) Drying determination FIG. 2 is a diagram for explaining the transfer of thermal energy when exhaust gas passes through the PM filter 8 in the system of the present embodiment. In FIG. 2, the exhaust gas temperature (hereinafter also referred to as “upstream exhaust gas temperature”) flowing into the PM filter 8 at time t is Tin (t) [° C.], the temperature of the PM filter 8 is Tm (t) [° C.], and the PM filter An example of thermal energy transfer is shown, where E [J] is the amount of heat released by 8 and Tout (t) [° C.] is the exhaust gas temperature discharged downstream of the PM filter 8 (hereinafter “downstream exhaust gas temperature”). Here, the flow rate of the exhaust gas is Ga [g / s], the specific heat of the exhaust gas is Cgas [J / gK], the specific heat of the PM filter 8 is [J / gK], and the weight of the PM filter 8 is W [g]. And

  As shown in FIG. 2, when exhaust gas passes through the PM filter 8, almost all of the exhaust gas contacts the surface of the PM filter 8. Therefore, it is considered that all exhaust gas exchanges heat energy with the PM filter 8 when passing through the PM filter 8. Therefore, the amount of change in the heat energy of the exhaust gas before and after passing through the PM filter 8 is the amount of heat energy given to and received from the PM filter 8 and the heat energy due to condensation (ie, liquefaction) or evaporation of moisture in the exhaust gas. This corresponds to the sum of the amount and the amount of heat energy radiated from the PM filter 8.

Here, the thermal energy that the exhaust gas passing through the PM filter 8 loses during the time Δt is expressed by the following equation (1) according to the upstream exhaust gas temperature Tin (t), the downstream exhaust gas temperature Tout (t), and the gas flow rate Ga. Is calculated by
Heat energy lost by exhaust gas = {Tin (t) -Tout (t)} · Ga · Cgas · Δt (1)

The thermal energy obtained by the PM filter 8 during the time Δt is calculated by the following equation (2) according to the temperature change (Tm (t + Δt) −Tm (t)) during Δt of the PM filter 8.
Thermal energy obtained by the PM filter 8 = {Tm (t + Δt) −Tm (t)} C · W (2)

Moreover, the thermal energy by drying or condensation is calculated by the following equation (3).
Thermal energy from drying or condensation = Q (VL) (3)
In the formula (3), L is a liquefaction amount [g] due to condensation, and V is an evaporation amount [g]. Q is the heat of evaporation, and its value is 2266 [J / gK] here. If the thermal energy calculated by Equation (3) is a negative value, condensed water is generated, and if the thermal energy is positive, the accumulated water is in a evaporated state.

From the above (1) to (3), the energy [{Tin (t) −Tout (t)} · Ga · Cgas · Δt] that the exhaust gas loses can be calculated by the following equation (4).
{Tin (t) -Tout (t)} · Ga · Cgas · Δt = {Tm (t + Δt) −Tm (t)} C · W + Q (VL) + E (4)

By the way, depending on whether the value of the thermal energy Q (VL) due to evaporation or liquefaction is positive or negative in the above formula (4), the accumulated water is currently evaporating or condensed water is being generated. I understand. Therefore, in the present embodiment, the above formula (4) is modified, and the condensed water generation coefficient ΔQ is calculated by the following formula (5) as a value correlated with the thermal energy Q (VL).
ΔQ = K1 {Tin (t) -Tout (t)} · Ga · Δt-K2 {Tm (t + Δt) −Tm (t)} − K3 · E (5)
Here, K1, K2, and K3 are predetermined constants.

  FIG. 3 is a diagram for explaining the change in thermal energy lost by the exhaust gas when passing through the PM filter 8 and the change in thermal energy obtained by the PM filter 8 in the present embodiment, and calculation of the condensed water generation coefficient ΔQ. It is a figure showing the change of the value of the 1st term and a 2nd term in a formula (5). FIG. 3 shows measurement data as an example. In FIG. 3, line a1 and line a2 represent the value of the first term and the reciprocal of the value of the second term when both sides of Equation (5) are divided by Δt, respectively.

  Assuming that the amount of time change of the heat dissipation amount in the equation (5) is negligible, the difference between the line a1 and the line a2 in FIG. 3 indicates whether condensed water is generated or evaporated, When a1 is smaller than the line a2, condensed water is generated, and when the line a2 is smaller than the line a1, the staying water is evaporated. Of the difference area, the shaded portion b1 corresponds to the amount of condensed water, and the shaded portion b2 corresponds to the amount of evaporated water. When the difference between the line a1 and the line a2 becomes zero, that is, when ΔQ becomes zero, condensation and evaporation are in an equilibrium state, and a dry state in which no accumulated water is present in the exhaust passage 4 is obtained. Can be judged.

  In order to avoid erroneous determination, in the present embodiment, it is determined that the condensed water generation coefficient ΔQ calculated by the equation (5) is in a dry state when the time during which the condensed water generation coefficient ΔQ is equal to or less than the reference value α continues for a certain time or longer. To do. Thus, the dry state can be determined only when the dry state is surely achieved. The reference value α is a value in the vicinity of zero, and is appropriately set in consideration of a margin for an error or the like and stored in the control device 20. The fixed time is appropriately set in consideration of determination accuracy, determination time, and the like.

  Note that the temperature Tm of the PM filter 8 has a correlation with the exhaust gas temperature Tout downstream of the PM filter 8. This correlation can be obtained in advance based on data such as experiments and simulations. In the present embodiment, the relationship between the temperature Tm and the downstream exhaust gas temperature Tout is set in advance based on this correlation, and is stored in the control device 20. In actual control, the temperature Tm of the PM filter 8 corresponding to the downstream exhaust gas temperature Tout is calculated according to this relationship.

  Further, immediately after the internal combustion engine 2 is started, generation of condensed water and evaporation on the downstream side of the PM filter 8 do not occur. That is, the condensed water generation coefficient ΔQ is zero. This is because condensed water is generated upstream of the PM filter 8, but the exhaust gas is in a dry state when it reaches the PM filter 8. Therefore, in order to avoid determining that the PM filter 8 is in a dry state by determining the period before the start of the generation of condensed water, after the start of the internal combustion engine 2, the drying determination is performed after the elapse of the reference time Tstart. Shall. The time until the start of the generation of condensed water in the PM filter 8 differs depending on the outside temperature and the stop time. The relationship between the time until the start of the condensed water generation and the outside temperature and the stop time is based on data from experiments and simulations. Based on. In the present embodiment, the relationship between the reference time Tstart, the outside air temperature, and the stop time is set in advance based on this relationship, and is stored in the control device 20. In actual control, the reference time Tstart corresponding to the outside air temperature and the stop time is set according to this relationship.

(2) Energization control of heater of exhaust gas sensor The control device 20 starts heating the PM sensor 14 and the NOx sensor 18 downstream of the PM filter 8 when it is recognized that the exhaust passage 4 is in a dry state. . That is, after the internal combustion engine 2 is started, the control device 20 stops energization of the heaters of the PM sensor 14 and the NOx sensor 18 until it is recognized in the dry determination that the dry state is detected. Prohibit heating with a heater. On the other hand, when the dry state is recognized as being dry, energization and control of the heaters of the PM sensor 14 and the NOx sensor 18 are started, and the element portions of the PM sensor 14 and the NOx sensor 18 are activated. Raise to temperature. As a result, when the internal combustion engine 2 is started, the sensor element is not cracked due to heating in the presence of stagnant water.

[Specific Control of this Embodiment]
FIG. 4 is a flowchart for illustrating a control routine executed by control device 20 in the embodiment of the present invention. The routine of FIG. 4 is a routine that is executed every time the internal combustion engine 2 is started. In the routine of FIG. 4, when the internal combustion engine 2 is started, first, in step S10, various data at the time of starting the internal combustion engine 2 are captured. The data acquired here is, for example, the outside air temperature when the internal combustion engine 2 is started, and the elapsed time from when the previous internal combustion engine 2 is stopped (that is, the latest).

  Next, a reference time Tstart is calculated in step S12. The reference time Tstart is a time serving as a reference for starting the drying determination, and is calculated according to the relationship stored in the control device 20 according to the outside air temperature and the stop time taken in step S10.

  Next, in step S14, it is determined whether or not the elapsed time T after the start has reached the reference time Tstart. If it is not recognized that the elapsed time T has reached the reference time Tstart, the determination in step S14 is repeated at regular intervals until the elapsed time T reaches the reference time Tstart.

  If it is determined in step S14 that the elapsed time T has reached the reference time Tstart, then, in step S16, various data is captured. Specifically, the upstream exhaust gas temperature Tin (t) is acquired according to the output of the temperature sensor 12 here. Further, the downstream exhaust gas temperature Tout (t) is acquired according to the output of the temperature sensor 16. Further, the intake air amount is acquired as the gas flow rate Ga according to the output of an air flow meter (not shown).

  Next, in step S18, the temperature Tm (t) of the PM filter 8 is calculated. The temperature Tm (t) of the PM filter 8 is calculated according to the relationship stored in advance in the control device 20 according to the downstream exhaust gas temperature Tout acquired in step S16.

  Next, in step S20, the condensed water generation coefficient ΔQ is calculated. Here, the above equation (5) is stored in the controller 20 in advance, and the condensed water generation coefficient ΔQ corresponding to the various data acquired in steps S16 and S18 is calculated according to this equation. In Equation (5), the temperature of the PM filter 8 calculated in step S18 is used as the temperature Tm (t + Δt) of the PM filter 8, and the previous step S18 is used as the temperature Tm (t). The previous temperature Tm (t−Δt) of the PM filter 8 calculated in (1) is used. Since Δt is a very short time, even if the data before Δt is used in this way, the difference that appears in the condensed water generation coefficient ΔQ is small, and the condensed water generation coefficient ΔQ can be calculated according to the current situation.

  Next, in step S22, it is determined whether or not the absolute value of the condensed water generation coefficient ΔQ is equal to or less than the reference value α. The reference value α is a determination reference value stored in the control device 20 in advance. If the establishment of | ΔQ | ≦ α is not recognized in step S22, the process returns to step S16. Until it is recognized in step S22 that | ΔQ | ≦ α is established, the arithmetic processing in steps S16 to S22 is repeated at regular time intervals Δt.

  On the other hand, if it is recognized that | ΔQ | ≦ α is established in step S22, then in step S24, 1 is added to the value of the counter count. The counter count is zero at the initial value immediately after the internal combustion engine 2 is started, and is a value for counting the number of times that | ΔQ | ≦ α is recognized. The counter count correlates with the time after the condensed water generation coefficient ΔQ becomes a value near zero. When the processes in steps S16 to S22 or steps S16 to S26 are repeated, these processes are repeated every certain time Δt, and the data acquisition in step S16 is executed every certain time Δt. Therefore, the elapsed time after the first establishment of | ΔQ | ≦ α is counter count × Δt.

  Next, in step S24, it is determined whether or not the counter count is larger than β. Further, here, the reference value β is a value for determining that a state in which | ΔQ | ≦ α is satisfied for a certain period of time, and is set to coincide with a value obtained by dividing the certain period by Δt. . Accordingly, by determining whether or not the counter count is greater than or equal to the reference value β, it is determined whether or not the elapsed time since the first establishment of | ΔQ | ≦ α has reached a certain time.

  If establishment of count ≧ β is not recognized in step S24, the process returns to step S16. Until the establishment of count ≧ β in step S24 is recognized, the processes in steps S16 to S24 are repeated every certain time Δt.

  On the other hand, if the establishment of count ≧ β is recognized in step S24, then heater control is started. Specifically, energization of the heaters of the PM sensor 14 and the NOx sensor 18 is started, and the element portions of the PM sensor 14 and the NOx sensor 18 are maintained within a predetermined activation temperature range by energization control of the heater. As a result, the PM amount can be detected by the PM sensor 14 and the NOx concentration can be detected by the NOx sensor. Thereafter, the current process is temporarily terminated.

  As described above, according to the present embodiment, it is possible to determine the presence or absence of stagnant water downstream of the PM filter 8 based on the change in the exhaust gas temperature and the temperature change in the PM filter 8. Therefore, the dry state downstream of the PM filter 8 can be detected more accurately, and heater control downstream of the PM filter 8 such as the PM sensor 14 and the NOx sensor 18 can be started early and at an appropriate timing. Thereby, compared with the conventional control, the exhaust gas sensor can be put into a usable state at a much earlier stage after the internal combustion engine 2 is started.

  In the present embodiment, by executing the process of step S16, the “first acquisition unit” and the “second acquisition unit” of the present invention are realized, and by executing the process of step S18, “ 3rd acquisition means "is implement | achieved. Further, the “calculating means” of the present invention is realized by executing the process of step S20, and the “control means” is realized by executing the processes of steps S22 to S28.

[Other examples of this embodiment]
In the present embodiment, the case where the heater control of the PM sensor 14 and the NOx sensor 18 is started when a dry state of the exhaust passage is recognized has been described. However, the present invention is not limited to this. In addition to the PM sensor 14 and the NOx sensor 18 other than the PM sensor 14 and the NOx sensor 18, this embodiment is similarly applied when other sensors that are preferably started to energize the heater in a dry state are installed. When it is confirmed that the heater is in a dry state, energization of the heater may be started.

  Moreover, in this Embodiment, after the dry state was recognized by dry determination, the case where energization control of a heater was started was demonstrated. However, the present invention is not limited to this. The present invention can be applied to a system having a configuration in which other internal combustion engine devices that are desirably used in a dry state or a state in which the amount of stagnant water is somewhat small are installed downstream of the PM filter 8.

  Specifically, for example, the present invention is a system having a configuration in which an EGR device that recirculates part of the exhaust gas to the intake passage is provided in addition to the configuration of FIG. 1 and an EGR cooler is installed downstream of the PM filter 8. It can be preferably applied. In this case, for example, the dry determination of the present embodiment is applied to the control of the EGR valve, and the control for opening the EGR valve when it is recognized that the condensed water generation coefficient ΔQ is equal to or less than the reference value α. I do. In this case, the reference value α that is a criterion for determination in the drying determination is not limited to the same value as when the drying determination is applied to the heater energization control of the sensor. What is necessary is just to set the specific value of the reference value (alpha) suitably according to the amount of staying water etc. which are accept | permitted in an EGR cooler.

  Further, for example, the purification performance of the SCR system decreases as the amount of water in the exhaust gas increases. Therefore, the present invention can be preferably applied to a system having a configuration in which an SCR system is installed on the downstream side of the PM filter 8 in addition to the configuration of FIG. In this case, when it is recognized that the condensed water generation coefficient ΔQ is equal to or less than the reference value α by the drying determination of the present embodiment, control for suppressing NOx emission is performed. Here again, the reference value α is appropriately set according to the allowable amount of staying water as long as the necessary purification performance is maintained in the SCR system. Alternatively, control for improving purification performance may be performed by changing the exhaust gas temperature and the gas flow rate to control the catalyst temperature instead of the control for suppressing NOx emission, and the stagnant water can be changed by changing the gas flow rate. It is also possible to perform control to make it easy to drain or dry.

  Further, the present invention is not limited to the case where whether or not to execute the above-described control for maintaining the purification performance of the SCR system is determined by comparing the condensed water generation coefficient ΔQ with the reference value α. For example, in order to maintain the purification performance of the SCR system when a value that correlates with the NOx purification capacity of the SCR system is first calculated in accordance with the condensed water generation coefficient ΔQ and this value falls below a predetermined threshold value. It is good also as what performs this control. The relationship between the condensed water generation coefficient ΔQ and the value correlated with the purification capacity can be obtained in advance based on data obtained through experiments, simulations, and the like. In specific control, this relationship may be stored in the control device 20, and a value correlated with the purification capacity may be calculated using this relationship.

  The dry determination according to the present embodiment can also be applied to other devices in which the amount of accumulated water in the exhaust passage 4 downstream of the PM filter 8 at the start of the internal combustion engine 2 affects the control. Specific examples of such devices include a urea addition valve, ASC, urea mixer, three-way catalyst, muffler, waste heat recovery device, and exhaust gas temperature sensor.

  Moreover, in this Embodiment, the case where the dry state in the exhaust passage 4 downstream of PM filter 8 was estimated was demonstrated. However, the present invention is not limited to this. The calculation of the condensed water generation coefficient ΔQ in the present embodiment can be similarly applied to a device in which almost all the exhaust gas is in contact with the device surface and transfers heat when passing through the device with the exhaust gas. it can. Examples of such equipment include a catalyst. Even when applied to a catalyst, the condensate generation coefficient ΔQ is calculated according to equation (5) according to the exhaust gas temperature upstream and downstream of the catalyst, and the temperature change of the catalyst, and the dryness determination is performed based on this. Just do it.

  Further, in the present embodiment, since the temperature Tm of the PM filter 8 has a correlation with the downstream exhaust gas temperature Tout, the case where the temperature Tm of the PM filter 8 is calculated based on the downstream exhaust gas temperature Tout has been described. However, the present invention is not limited to this. For example, since it is considered that the temperature of the PM filter 8 substantially matches the downstream exhaust gas temperature Tout, the acquired downstream exhaust gas temperature Tout may be used as it is as the temperature Tm of the PM filter 8. Alternatively, the temperature Tm of the PM filter 8 is not limited to that estimated from the downstream exhaust gas temperature Tout, but may be a value estimated from the temperature of other portions. Moreover, it is good also as a structure which installs the sensor for detecting temperature in PM filter 8, and detects the temperature of PM filter 8 directly.

  In the present embodiment, the temperature sensors 12 and 16 are installed upstream and downstream of the PM filter 8, respectively, and the upstream exhaust gas temperature Tin and the downstream exhaust gas temperature Tout are detected based on the outputs. However, the present invention is not limited to this, and the upstream and downstream exhaust gas temperatures Tin and Tout may be calculated based on temperature changes in other portions, for example.

  Further, in the present invention, instead of the temperatures Tin, Tout, Tm used in the present embodiment, temperature correlation values that correlate the upstream exhaust gas temperature, the downstream exhaust gas temperature, and the temperature of the PM filter 8 are calculated. May be used.

  In the present embodiment, it is determined whether or not the inside of the exhaust passage 4 downstream of the PM filter 8 is in a dry state based on whether or not the absolute value of the condensed water generation coefficient ΔQ is equal to or less than the reference value α. explained. However, the present invention is not limited to this. As described above, the condensed water generation coefficient ΔQ is a value having a correlation with the amount of accumulated water in the exhaust passage 4. Therefore, the amount of accumulated water in the exhaust passage 4 or a value correlated therewith can be calculated based on the condensed water generation coefficient ΔQ. The calculated amount of accumulated water or its correlation value can be used for control of various devices of the internal combustion engine 2 affected by the amount of accumulated water.

  In the above embodiment, when referring to the number of each element, quantity, quantity, range, etc., the reference is made unless otherwise specified or the number is clearly specified in principle. The invention is not limited to the numbers. Further, the structure and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

2 Internal combustion engine 4 Exhaust passage 6 Oxidation catalyst 8 PM filter 10 Air-fuel ratio sensor 12 Temperature sensor 14 PM sensor 16 Temperature sensor 18 NOx sensor 20 Control device

Claims (5)

A filter for collecting particulates that is installed in an exhaust passage of an internal combustion engine and collects particulates in exhaust gas;
Equipment installed downstream of the particulate collection filter in the exhaust passage;
A first acquisition means for acquiring an exhaust gas temperature upstream of the particulate collection filter or a value correlated with the temperature as a first correlation value;
A second acquisition means for acquiring an exhaust gas temperature downstream of the particulate collection filter or a value correlated with the temperature as a second correlation value;
Third acquisition means for acquiring, as a third correlation value, a temperature change of the particulate collection filter or a value correlated with the temperature change;
Based on the first correlation value, the second correlation value, and the third correlation value, the amount of accumulated water in the exhaust passage downstream of the filter for collecting particulates or a value correlated with the amount of accumulated water is retained. Means for calculating the water quantity correlation value;
Control means for controlling the device according to the accumulated water amount correlation value;
A control device for an internal combustion engine, comprising: The device is an exhaust gas sensor that emits output according to the concentration or amount of a specific component in exhaust gas,
2. The control device for an internal combustion engine according to claim 1, wherein the control unit executes control for heating the exhaust gas sensor in accordance with the correlation value of the accumulated water amount. The device is an EGR valve of an EGR device that recirculates a part of exhaust gas to the intake passage of the internal combustion engine as EGR gas,
The control device for an internal combustion engine according to claim 1 or 2, wherein the control means controls opening and closing of the EGR valve in accordance with the accumulated water amount correlation value. The device is an SCR system for purifying exhaust gas,
The control of the internal combustion engine according to any one of claims 1 to 3, wherein the control means executes control to increase a temperature of a catalyst of the SCR system according to the accumulated water amount correlation value. apparatus. The device is an SCR system for purifying exhaust gas,
The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the control means controls a flow rate of exhaust gas flowing into the catalyst of the SCR system in accordance with the accumulated water amount correlation value. .

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