JP2017025728A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve catalyst activation in an early stage while reducing energy consumption including power consumption for temperature rise promoting activation of a catalyst device which is attached to an exhaust system of an internal combustion engine, and fuel consumption.SOLUTION: Exhaust heating by a first heating device 20 is preferentially selected when activation of a catalyst device 18 is required, exhaust heating is performed with the usage of the first heating device 20 when an exhaust heating function of the first heating device 20 is sufficient, and exhaust heating is performed with the usage of a second heating device 22 when the exhaust heating function of the first heating device 20 is insufficient. Accordingly, a purification ratio of the catalyst device 18 can be improved while suppressing unnecessary power consumption.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust emission control device for purifying exhaust gas by activating a catalyst device attached to an exhaust system of an internal combustion engine for purifying exhaust gas.

  The catalyst device attached to the exhaust system of the internal combustion engine is preferably heated to a temperature at which exhaust purification performance is sufficiently exhibited.

  Patent Document 1 discloses a technique related to control for warming a catalyst using an electric heater before starting an engine (internal combustion engine).

  In Patent Document 1, the energization time of the electric heater is determined from the temperature of the catalyst. That is, when the temperature of the catalyst is lower than a predetermined value, the electric heater is energized, and when it is higher than the predetermined value, the electric heater is not energized.

JP-A-10-169433

  However, Patent Document 1 is suitable for control for raising the temperature of the low-temperature state before starting the engine. However, when the engine is in operation, the activity of the catalyst is already obtained depending on the temperature measurement location of the catalyst. In some cases, energization may continue and wasteful power consumption may occur. For example, when energization of the electric heater is controlled using the temperature at the center of the catalyst, a sufficient purification rate is obtained at the inlet and outlet of the catalyst, but if the temperature at the center of the catalyst remains low, The energization of the heater is continued.

  Further, the heat source is only the electric heater, and it is necessary to constantly monitor the state of the electric power source of the electric heater (for example, in-vehicle battery in the case of a vehicle).

  In consideration of the above-mentioned fact, the present invention improves the catalyst activity at an early stage while reducing the power consumption for increasing the temperature to promote the activity of the catalyst device attached to the exhaust system of the internal combustion engine and the energy consumption including fuel consumption. An object of the present invention is to obtain an exhaust purification device capable of performing

  The present invention is an exhaust purification device that purifies exhaust by activating a catalyst device attached to an exhaust system of an internal combustion engine by raising the temperature, and is attached upstream of the catalyst device in the exhaust system and flows A fluid medium can be circulated between the chemical heat storage unit and the chemical heat storage unit that stores heat by performing a desorption reaction of the fluid medium and dissipates heat by an adsorption reaction of the fluid medium, and stores the fluid medium A storage unit, and a flow rate control unit that controls opening and closing of a circulation path between the chemical heat storage unit and the storage unit, and exhaust gas discharged from the internal combustion engine by heat of adsorption of a fluid medium flowing through the chemical heat storage unit A first heating device that heats and a second heating that is attached upstream of the catalyst device in the exhaust system and heats the exhaust discharged from the internal combustion engine using a heat source different from the first heating device. Device and said touch A purification rate acquisition means for acquiring the purification rate of the apparatus, and the first heating device or the second heating device when the purification rate of the catalyst device acquired from the purification rate acquisition means is lower than a predetermined value. And a heating control means for heating the exhaust gas upstream of the catalyst device.

  According to the present invention, the first heating device includes a chemical heat storage unit and a storage unit, and the chemical heat storage unit is chemically formed by circulating the fluid medium between the chemical heat storage unit and the storage unit. Heat is stored.

  In the heating control means, when the purification rate of the catalyst device acquired from the purification rate acquisition unit is lower than a predetermined value, the heating control unit controls the drive of the first heating device or the second heating device to upstream the catalyst device. Heat the side exhaust.

  For example, the flow control unit of the first heating device is controlled to open the circulation path between the chemical heat storage unit and the storage unit. As a result, the fluid medium circulates, and during the circulation, heat exchange is performed with the exhaust gas in the chemical heat storage unit, and the exhaust gas is heated.

  By heating the exhaust gas, the catalyst device is heated and activated, and the exhaust gas purification rate can be improved.

  When the second heating device is applied, the exhaust gas flowing in the exhaust system is heated by different heat sources. By heating the exhaust, the catalyst device is activated and the purification rate of the exhaust is improved.

  By providing a heating function using two different heat sources in the exhaust system of the internal combustion engine, the activation of the catalyst device can be maintained even if one of them becomes unnecessary. In this case, various application examples are conceivable, such as the combined use of the first heating device and the second heating device, alternate use, and one as the other preliminary function.

  In the present invention, the heating control unit further includes a state detection unit that detects a state including at least one of a temperature or a pressure of the fluid medium in the chemical heat storage unit and the storage unit of the first heating device. Is based on the detection result of the state detection means, calculates the amount of fluid medium retained in either the chemical heat storage unit or the storage unit, and the amount of fluid medium retained in the storage unit is greater than or equal to a predetermined amount In addition, the driving of the first heating device is controlled to heat the exhaust upstream of the catalyst device.

  The state detection means detects a state including at least one of the temperature or pressure of the fluid medium in the heater unit and the storage unit of the first heating device. For example, a temperature sensor and a pressure sensor are less expensive.

  For example, when a temperature sensor cheaper than the pressure sensor is provided, the pressure can be obtained by conversion. On the other hand, the accuracy is higher when the pressure is directly detected by the pressure sensor. Therefore, the selection may be made in consideration of the trade-off relationship between price and accuracy. Naturally, a temperature sensor and a pressure sensor may be used in combination.

  The heating control unit calculates the amount of the fluid medium held in either the chemical heat storage unit or the storage unit based on the detection result of the state detection unit. Since the total amount basically does not change, one of the possessed amounts may be calculated.

  Here, since the fluid medium can normally circulate when the holding amount of the fluid medium in the storage unit is greater than or equal to a predetermined amount, the drive of the first heating device is controlled to exhaust the exhaust upstream of the catalyst device. Heat.

  In the present invention, the second heating device is an electric heater using a heating element that generates heat when energized, and the heating control means is configured to exhaust the electric heater when the first heating device cannot be used. Applicable for heating.

  As the second heating device, an electric heater using a heating body that is heated by energization is used. The electric heater can be controlled to be heated relatively easily by energization or interruption.

  Therefore, the electric heater is used for heating the exhaust when the first heating device cannot be used. In this case, for example, by controlling the flow rate control unit of the first heating device to close the circulation path between the heater unit and the storage unit, the heated exhaust gas is efficiently moved to the catalyst device. be able to.

  In the present invention, the purification rate acquisition means includes, on the upstream side and the downstream side of the catalyst device, any one or more purification rate determination sensors of a CO sensor, a THC sensor, and a NOx sensor, and the catalyst device. And a calculation unit that calculates a ratio of the downstream purification rate determination sensor to the detection value of the upstream purification rate determination sensor.

  As for the purification rate, the transition state of the exhaust components between the upstream side and the downstream side of the catalyst device (the calculated value on the downstream side / upstream side) becomes the purification rate. Therefore, any one of the CO sensor, the THC sensor, and the NOx sensor can be arranged on the upstream side and the downstream side of the catalyst device, respectively, and the purification rate can be calculated based on the ratio of the amount of the detected component contained in the exhaust gas.

In the present invention, further comprising a bed temperature detection sensor for detecting the bed temperature of the catalyst device,
The purification rate acquisition means estimates the purification rate based on the bed temperature by the bed temperature detection sensor.

  The purification rate can be estimated from the bed temperature by the bed temperature detection sensor.

  In the present invention, a bed temperature detection sensor for detecting the bed temperature of the catalyst device is further provided, and the bed temperature by the bed temperature detection sensor is applied to the necessity determination of the exhaust heating control by the heating control means.

  By adding the detection value of the bed temperature of the catalyst device by the bed temperature detection sensor to the determination requirement for the necessity of heating the exhaust gas, it is possible to make a determination with higher accuracy.

  In this invention, the said 2nd heating apparatus is arrange | positioned upstream from the said 1st heating apparatus, The said heating control means is the said fluid medium of the said storage part of the said 1st heating apparatus. When the retained amount is less than or equal to a predetermined value, it is not necessary to heat the exhaust gas that passes through the catalyst device, and the first condition is that the pressure of the chemical heat storage unit is lower than the pressure of the storage unit. In the state which closed the circulation path between the said chemical heat storage part and the said storage part by controlling the said flow control part of the heating apparatus of this, the said 2nd heating apparatus is the said fluid medium in the said chemical heat storage part. When the pressure of the chemical heat storage unit is higher than the pressure of the storage unit by a predetermined level or more, the flow control unit of the first heating device is controlled to control the flow rate control unit. A circuit between the chemical heat storage unit and the storage unit is opened.

  There is a case where the amount of the fluid medium held in the storage unit of the first heating device is equal to or less than a predetermined value.

  In this case, the heating control means confirms that it is not necessary to heat the exhaust gas passing through the catalyst device. Moreover, in a heating control means, it confirms that the pressure of a chemical heat storage part is lower than the pressure of a storage part.

  Thereafter, the flow rate control unit of the first heating device is controlled to close the circulation path between the chemical heat storage unit and the storage unit.

  In a state where the circulation path is closed, the exhaust is heated by the second heating device. The fluid medium in the chemical heat storage section is heated and pressurized by the heat of the heated exhaust gas.

  Further, in the heating control means, when the second heating device is applied for heating for pressurization of the fluid medium in the chemical heat storage unit, the pressure of the chemical heat storage unit is set in the storage unit. When the pressure becomes higher than a predetermined pressure, the electric heater is turned off and the flow control unit of the first heating device is controlled to open the circulation path between the chemical heat storage unit and the storage unit. To do.

  Thereby, since the pressure of a chemical heat storage part is higher than the pressure of a storage part, a fluid medium can flow from a chemical heat storage part to a storage part, and can store a fluid medium in a storage part.

  For this reason, the first heating device is regenerated and can be applied as the heating of the next exhaust.

  As described above, according to the present invention, the catalyst activity can be improved early while reducing the power consumption and the energy consumption including fuel consumption for promoting the activity of the catalyst device attached to the exhaust system of the internal combustion engine. It has an excellent effect of being able to.

1 is a schematic view of an exhaust system of an internal combustion engine to which an exhaust purification device according to the present embodiment is attached. (A) Temperature-pressure characteristic diagram of a fluid medium applied to the first heating device according to the present embodiment, (B) is a fluid medium applied to the first heating device according to the present embodiment. FIG. 6 is a pressure-remaining characteristic diagram. It is a flowchart which shows the exhaust-gas heating control routine which concerns on this Embodiment. (A) is a flowchart which shows the applied voltage control routine to the heat generating body of the 2nd heating apparatus which concerns on this Embodiment, (B) is a flowchart which shows the OFF operation | movement control routine of a 2nd heating apparatus. It is a characteristic view which shows the relationship with the applied voltage with respect to the catalyst temperature at the time of the exhaust-gas heating control by the 2nd heating apparatus which concerns on this Embodiment. It is a characteristic figure which shows the relationship between the control form of a 1st heating apparatus, and input energy, and the result of having compared this Embodiment with two types of comparative examples. It is a flowchart which shows the 1st heating apparatus reproduction | regeneration control routine which concerns on this Embodiment. It is a flowchart which shows the detail of the 1st heating apparatus forced regeneration control of step 226 of FIG. It is the schematic of the exhaust system of the internal combustion engine provided with the exhaust emission control device which concerns on a modification.

  FIG. 1 shows an exhaust emission control device 10 according to the present embodiment.

  The internal combustion engine 12 is represented by an engine mounted on a vehicle, and is a prime mover in which fuel is burned inside the engine and heat energy of combustion gas is converted into mechanical energy.

  An engine control unit 14 is connected to the internal combustion engine 12. For example, when the internal combustion engine 12 is a diesel engine, heavy oil or light oil is injected as fuel into the air compressed in high pressure and high temperature in the cylinder and burned. The fuel injection timing is controlled.

  The internal combustion engine 12 is provided with an exhaust pipe 16 for discharging combustion gas (hereinafter referred to as “exhaust”) after the fuel is combusted inside.

  The exhaust gas passes through the exhaust pipe 16 and is discharged out of the internal combustion engine 12.

A catalyst device 18 constituting the main body of the exhaust gas purification apparatus of the present invention is attached to the exhaust pipe 16. The catalyst device 18 has a decomposing role in harmless N ₂ and reducing NOx contained in the combustion gas.

  Here, in the present embodiment, a first heating device 20 and a second heating device 22 for heating the exhaust gas are provided in the exhaust pipe 16 between the internal combustion engine 12 and the catalyst device 18.

  The first heating device 20 and the second heating device 22 have a role of improving the catalytic activity of the catalyst device 18 and constitute the other part of the exhaust gas purification device 10 together with the catalyst device 18.

  The first heating device 20 and the second heating device 22 are controlled by a heating control device 24 connected to the engine control unit 14.

(First heating device 20)
As shown in FIG. 1, the first heating device 20 is a chemical heat storage heater, and is attached around the exhaust pipe 16 as a chemical heat storage portion of a ring-shaped housing structure in which a chemical heat storage material is accommodated in an inner space. The heat storage heater section 26 is provided. In this embodiment, ammonia (NH 3) is applied as the fluid medium.

  Further, one end of the circulation pipe 28 is connected to a part of the outer periphery of the heat storage heater unit 26, and the inner space of the heat storage heater unit 26 and the inner space of the circulation pipe 28 are communicated with each other.

  The other end of the circulation pipe 28 is connected to a box-shaped storage 30 (hereinafter referred to as a heat storage 30) that stores the fluid medium, and the inner space of the circulation pipe 28 and the inner space of the heat storage 30 Is communicated.

  For this reason, the heat storage heater unit 26 and the heat storage 30 are communicated with each other through the circulation pipe 28, and the fluid medium can flow between each other due to a pressure difference. In other words, the fluid medium goes back and forth (circulates) between the heat storage heater unit 26 and the heat storage 30.

  An opening / closing valve 32 as a flow rate control unit is attached to an intermediate portion of the circulation pipe 28, and the flow of the fluid medium can be controlled by opening / closing the opening / closing valve 32. For example, the simplest control mode is opening / closing of the opening / closing valve 32. When the opening / closing valve 32 is opened, the flow of the fluid medium between the heat storage heater unit 26 and the heat storage storage 30 is possible, and when the opening / closing valve 32 is closed. The flow of the fluid medium between the heat storage heater unit 26 and the heat storage 30 becomes impossible.

  Here, the heat storage heater unit 26 is filled with magnesium bromide (MgBr2) as a chemical heat storage material, and generates heat by a chemical reaction (adsorption reaction) with ammonia as a fluid medium. For this reason, the flowable medium flows from the heat storage 30 to the heat storage heater 26 due to the pressure difference between the heat storage 30 and the heat storage heater 26, thereby heating the exhaust gas passing through the exhaust pipe 16 by the heat storage heater 26. be able to.

  When the exhaust gas heated by the first heating device 20 reaches the catalyst device 18, the catalyst device 18 (the bed temperature) is heated by the amount of heat of the exhaust gas, and the catalyst function can be activated. In particular, it is preferable to activate the catalyst function by raising the bed temperature of the catalyst device 18 in the transition period in which the internal combustion engine 12 is stable from the start.

  On the other hand, when the internal combustion engine 12 is sufficiently warmed up, the catalyst device 18 is sufficiently activated, and the exhaust has a sufficient amount of heat, it is not necessary to raise the bed temperature by the exhaust.

  At this time, the chemical heat storage material accommodated in the heat storage heater unit 26 is heated by the heat quantity of the exhaust, and heat can be stored by causing a desorption reaction in which the fluid medium is desorbed from the chemical heat storage material. As a result, when the pressure of the heat storage 30 becomes higher, the fluid medium flows from the heat storage heater unit 26 to the heat storage 30, and a necessary and sufficient amount of fluid medium can be stored in the heat storage 30. . That is, the first heating device 20 can be circulated for exhaust heat treatment.

(Second heating device 22)
As shown in FIG. 1, the second heating device 22 is an electric heater, which is attached around the exhaust pipe, and is an electric heater portion of a ring-shaped housing in which a heating element 22 </ b> A that converts current into heat is wired. 22B is provided. The electric heater portion 22B is preferably a member having high thermal conductivity.

  In the electric heater 22B, the heating element generates heat based on the applied voltage, and the exhaust passing through the exhaust pipe 16 is heated via a ring-shaped casing.

  In FIG. 1, the electric heater portion 22 </ b> B is provided around the exhaust pipe 16, but a heating element may be disposed inside the exhaust pipe 16.

(Heating control unit 24)
The heating control device 24 is applied to a valve control unit 34 that controls an on-off valve 32 provided in the first heating device 20 and an electric heater 22B (a heating element 22A) applied as the second heating device 22. A voltage control unit 36 that controls the voltage and a main control unit 38 that comprehensively controls the valve control unit 34 and the voltage control unit 36 based on the purification rate of the catalyst device 18 are provided.

  A heat storage heater section temperature sensor 40 is attached to the heat storage heater section 26 in the first heating device 20. A detection signal line of the heat storage heater temperature sensor 40 is connected to the main control unit 38.

  A heat storage storage temperature sensor 42 is attached to the heat storage 30 in the first heating device 20. A detection signal line of the heat storage temperature sensor 42 is connected to the main control unit 38.

  The main control unit 38 has a function of calculating a pressure based on the detected temperature. That is, as shown in FIG. 2A in which the relationship between temperature and pressure is linearly approximated in the use region, the relationship between temperature and pressure in a container containing ammonia is almost directly proportional.

  Therefore, the main control unit 38 can recognize the pressure of the fluid medium stored in the heat storage heater unit 26 by detecting the temperature by the heat storage heater unit temperature sensor 40. Further, the main control unit 38 can recognize the pressure of the fluid medium stored in the heat storage 30 by detecting the temperature by the heat storage temperature sensor 42.

  Here, as shown in FIG. 2B, the relationship between the pressure and the amount of the fluid medium also has a linear correlation. Note that the characteristic curve may differ depending on the temperature.

  For this reason, for example, when calculating | requiring the possession amount of the fluid medium currently stored by the thermal storage 30, the temperature of the thermal storage 30 is detected with the thermal storage temperature sensor 42, pressure is converted from the detected temperature, The retained amount (remaining amount) of the fluid medium can be obtained from the converted pressure.

  In the present embodiment, the heat storage heater section temperature sensor 40 and the heat storage storage temperature sensor 42 are applied. However, instead of the inexpensive temperature sensor, the heat storage heater section 26 and the heat storage storage 30 are respectively used in order to emphasize accuracy. A pressure sensor may be attached. Moreover, you may use a temperature sensor and a pressure sensor together.

  A bed temperature detection sensor 44 that detects the bed temperature of the catalyst device 18 is attached to the catalyst device 18. The detection signal line of the bed temperature detection sensor 44 is connected to the main control unit 38.

  Further, NOx sensors 46in and 46out are attached to the exhaust pipe 16 on the upstream side (near the inlet) and the downstream side (near the outlet) of the catalyst device 18, respectively.

  The detection signal lines of the NOx sensors 46in and 46out are connected to the purification rate calculation unit 48. In FIG. 1, the purification rate calculation unit 48 is configured separately from the heating control unit 24, but may be caused to function as a part of the heating control unit 24.

  In the purification rate calculation unit 48, the amount Nout of the exhausted nitrogen oxides coming out from the catalytic device relative to the amount Nin of the exhausted nitrogen oxides entering the catalytic device 18 based on the detection values received from the NOx sensors 46in, 46out, respectively. (Purification rate S) is calculated (S = Nin / Nout).

  The purification rate calculation unit 48 is connected to the main control unit 38 and sends the calculation result (purification rate S) to the main control unit 38.

  The heating control unit 24 analyzes the state of the internal combustion engine 12 (starting time, transient period, steady operation timing, etc.) based on the internal combustion engine control information received from the engine control unit 14 and detects the exhaust gas suitable for each state. Perform heating control.

  For example, when the internal combustion engine 12 is started, a desired catalytic activity may not be obtained because the purification rate of the catalyst device 18 is low and the bed temperature is low.

  Therefore, the heating control device 24 uses the first heating device 20 to heat the exhaust. By heating the exhaust, the bed temperature of the catalyst device 18 is raised, and the catalyst device 18 can be activated.

  This exhaust heating control is executed while constantly monitoring the bed temperature and the purification rate of the catalyst device 18, and as the state transition of the internal combustion engine 12, that is, the transition period and the steady operation timing, the heating is performed. By changing the control (including heating unnecessary), necessary and sufficient heating control according to the state of the internal combustion engine 12 becomes possible.

  In the present embodiment, in addition to the first heating device 20, a second heating device 22 is provided in the exhaust pipe 16. For this reason, in the heating control device 24, when the first heating device 20 cannot be used, the application voltage of the electric heater unit 22B, which is the second heating device 22, is controlled as a substitute for the first heating device 20, thereby The activity can be maintained.

  The operation of this embodiment will be described below with reference to the flowcharts of FIGS.

  In all the flowcharts of the present embodiment including FIG. 3 and FIG. 4, the order of signal detection and the order of determination performed in successive steps can be appropriately changed.

  FIG. 3 is a flowchart showing an exhaust heating control routine according to the present embodiment.

  In step 100, it is determined whether the internal combustion engine 12 is in operation. The determination as to whether or not the vehicle is in operation is to determine whether or not fuel injection is being performed, and refers to an operation stop state in which combustion control is not being performed. In addition, apart from the operation stop state, for example, the fuel cut control that is performed when the vehicle is going down a long downhill may be determined as “not in operation”.

  If a negative determination is made in step 100, the internal combustion engine 12 is not in operation and there is no need to heat the exhaust, so the routine proceeds to step 102.

  If an affirmative determination is made in step 100, the internal combustion engine 12 is in operation and the catalyst device 18 may need to be activated. Therefore, the routine proceeds to step 106, where the purification rate of the catalyst device 18 is greater than or equal to a reference value. It is determined whether or not.

  If the determination in step 106 is affirmative, that is, if the purification rate is determined to be equal to or higher than the reference value, the exhaust gas heating is not necessary, and the routine proceeds to step 102.

  If a negative determination is made in step 106, the purification rate is less than the reference value, and it may be necessary to heat the exhaust gas. Therefore, the routine proceeds to step 108, where it is determined whether the catalyst bed temperature is equal to or higher than the reference value. Is done.

  In this step 108, an affirmative determination is made, that is, the bed temperature of the catalyst device 18 is stable, and it is not necessary to heat the exhaust gas.

  On the other hand, if a negative determination is made in step 108, all the conditions that require exhaust heating are complete, so the routine proceeds to step 110.

  Here, in step 102 transferred from step 100, step 106, and step 108, the opening / closing valve 32 of the first heating device 20 is closed, and then the flow goes to step 104 to turn off the second heating device 22 (heat generation). The body 22A is de-energized), and this routine ends.

  On the other hand, in step 110, the remaining amount of the fluid medium (NH3) in the heat storage 30 is detected. If it is determined in step 110 that the remaining amount of the fluid medium (NH 3) is less than the predetermined value, it is determined that the exhaust heating capacity by the first heating device 20 is inappropriate, and the process proceeds to step 128 to open / close The valve 32 is closed and the routine proceeds to step 130.

  In step 130, the heating element 22 </ b> A of the electric heater unit 22 </ b> B is energized to activate the second heating device 22 instead of the first heating device 20. That is, the heating control based on the catalyst bed temperature of the catalyst device 18 is started by the second heating device 22, and this routine ends.

  If it is determined in step 110 that the remaining amount of the fluid medium (NH 3) is equal to or greater than the predetermined amount, it is determined that the exhaust heating function by the first heating device 20 is appropriate, and the process proceeds to step 120.

  In step 120, the temperature of the heat storage heater unit 26 and the temperature of the heat storage 30 are detected, and the process proceeds to step 122. In step 122, based on the detected temperature, the equilibrium pressure Ph of the fluid medium (NH3) of the heat storage heater section 26 is calculated, and then in step 124, the equilibrium pressure Ps of the fluid medium (NH3) of the heat storage 30 is calculated. Calculate and move to step 126.

  In step 126, the equilibrium pressure Ph of the fluid medium (NH3) in the heat storage heater section 26 is compared with the equilibrium pressure Ps of the fluid medium (NH3) in the heat storage 30 (Ph: Ps).

  If it is determined in this step 126 that Ph ≧ Ps, it is determined that the fluid medium (NH 3) does not flow properly and the exhaust heating function is insufficient, the process proceeds to step 128, and the open / close valve 32 is opened. The process closes and the process proceeds to step 130.

  In step 130, the heating element 22 </ b> A of the electric heater unit 22 </ b> B is energized to activate the second heating device 22 instead of the first heating device 20. That is, the heating control based on the catalyst bed temperature of the catalyst device 18 is started by the second heating device 22, and this routine ends.

  On the other hand, if it is determined in step 126 that Ph <Ps, it is determined that the fluid medium (NH 3) flows properly and the exhaust heating function is sufficient, the process proceeds to step 132, and the on-off valve 32 is opened. Then, the fluid medium (NH 3) is supplied to the heat storage heater unit 26, exhaust gas heating control by the first heating device 20 is started, and this routine ends.

  FIG. 4A is a flowchart illustrating a routine for controlling the voltage applied to the heating element 22 </ b> A of the second heating device 22.

  In step 150, the bed temperature Tc (catalyst bed temperature) of the catalyst device 18 is detected, and then the routine proceeds to step 152 where it is determined whether or not the detected catalyst bed temperature is equal to or higher than a predetermined temperature.

  If a negative determination is made in step 152, the process proceeds to step 154 to maximize the exhaust heating function, and the exhaust heating function when the second heating device 22 is on is switched to steady value control. That is, the voltage V applied to the heating element 22A is set to a constant value Vt (see range F in FIG. 5), and this routine is terminated.

  On the other hand, if the determination in step is affirmative, it is determined that the exhaust gas heating function can be improved without maximizing the exhaust heating function, and the step is changed to voltage adjustment control based on the catalyst bed temperature. The process proceeds to 156, the second heating device 22 is switched to control based on the catalyst bed temperature, and the process proceeds to step 158.

  In step 158, a heating function is set according to the detected catalyst temperature Tc. That is, the voltage V applied to the heating element 22A is obtained as a function of the catalyst temperature Tc (V = −a × Tc + b) (see range S in FIG. 5), and this routine ends. In addition, a is a proportionality constant (positive number).

  Next, FIG. 4 (B) is a flowchart showing a routine for controlling the operation (mainly off timing) of the second heating device 22.

  In step 160, it is determined whether or not the second heating device 22 is on. If a negative determination is made, this routine ends. If an affirmative determination is made in step 160, the process proceeds to step 162.

  In step 162, a signal is fetched from the purification rate calculation unit 48, and then the process proceeds to step 164 to determine whether or not the purification rate is equal to or higher than a reference value.

  If a negative determination is made in step 164, it is determined that exhaust heating needs to be continued, and this routine ends.

  If the determination in step 164 is affirmative, the process proceeds to step 165 to determine whether the bed temperature of the catalyst device is equal to or higher than a predetermined value.

  If a negative determination is made in step 165, it is determined that exhaust heating needs to be continued, and this routine ends.

  If the determination in step 165 is affirmative, exhaust heating is not necessary, so the routine proceeds to step 166, where the second heating unit 22 is turned off (the heating element 22A is de-energized), and this routine is terminated. To do.

  That is, the second heating device 22 performs on / off control in which switching is performed by selecting on in step 130 in FIG. 3 and off in step 166 in FIG. By controlling the voltage applied to the heating element 22A based on the floor temperature (see FIG. 5), appropriate exhaust heating control is realized.

  According to the present embodiment, when it is necessary to activate the catalyst device 18, the exhaust heating by the first heating device 20 is preferentially selected, and the exhaust heating function of the first heating device 20 is sufficient. Performs exhaust heating using the first heating device 20, and performs exhaust heating using the second heating device 22 when the exhaust heating function of the first heating device 20 is insufficient. Thus, it is possible to improve the purification rate of the catalyst device 18 while suppressing wasteful power consumption.

  FIG. 6 is a characteristic diagram for comparing the input energy in a plurality of types of control forms including the present embodiment.

  As shown in FIG. 6, compared with the control based on the catalyst bed temperature as a comparative example and the control based on the purification rate, the control based on the combined use of the catalyst bed temperature and the purification rate according to the present embodiment has an input energy of You can see that less is needed.

  FIG. 7 is a flowchart showing a regeneration control routine of the first heating device 20.

  In step 200, it is determined whether or not the temperature raising control of the catalyst device 18 is being performed. If the determination is affirmative, the routine ends.

  If a negative determination is made in step 200, the process proceeds to step 202 where the bed temperature (catalyst bed temperature) of the catalyst device 18 is detected, and the process proceeds to step 204.

  In step 204, it is determined whether or not the catalyst bed temperature is equal to or higher than a reference value. If the determination is negative, priority is given to the use of the heat quantity of the exhaust gas for the activation of the catalyst device 18, and therefore the second heating device. 20 is given up and the routine ends.

  If the determination in step 204 is affirmative, it is not necessary to use the heat quantity of the exhaust gas for the activation of the catalyst device 18 and can be used for the regeneration of the first heating device 20, and therefore the process proceeds to step 206.

  In step 206, the temperature of the heat storage heater unit 26 and the temperature of the heat storage 30 are detected, and the process proceeds to step 208.

  In step 208, based on the detected temperature, the equilibrium pressure Ph of the fluid medium (NH3) of the heat storage heater unit 26 is calculated, and then the process proceeds to step 210 to balance the fluid medium (NH3) of the heat storage 30. The pressure Ps is calculated, and the routine proceeds to step 212.

  In step 212, the remaining amount of the fluid medium (NH3) in the heat storage 30 is detected. If it is determined in step 212 that the remaining amount of the fluid medium (NH 3) in the heat storage 30 is equal to or greater than the predetermined value, it is determined that regeneration control is not necessary, and the process proceeds to step 214.

  In step 214, it is determined whether or not the open / close valve 32 is open. If it is open (affirmative determination), the open / close valve 32 is closed in step 216, and the fluid medium (NH3) to the heat storage heater unit 26 is determined. ) And the process proceeds to step 218. If the determination in step 214 is negative, the process proceeds to step 218.

  In step 218, it is determined whether or not the second heating device 22 is turned on (heating element 22A energization). If it is turned on (affirmative determination), the second heating device 22 is turned off in step 220 ( The heating element 22A is de-energized), and this routine ends. If a negative determination is made in step 218 (the second heating device 22 is turned off), this routine ends.

  On the other hand, if it is determined in step 212 that the remaining amount of the fluid medium (NH 3) in the heat storage 30 is less than the predetermined value, it is determined that regeneration control is necessary, and the process proceeds to step 222.

  In step 222, the equilibrium pressure Ph of the fluid medium (NH3) of the heat storage heater unit 26 calculated in steps 208 and 210 is compared with the equilibrium pressure Ps of the fluid medium (NH3) of the heat storage 30 (Ph: Ps).

  If it is determined in this step 222 that Ph ≧ Ps, the routine proceeds to step 224 where the on-off valve 32 is opened and the fluid medium (NH 3) is supplied to the heat storage 30 (hereinafter referred to as “normal regeneration”). ), The process proceeds to step 228. In step 228, a timer counter Ct used for forced regeneration control to be described later is reset (Ct ← 0), and this routine ends.

  If it is determined in step 222 that Ph <Ps, normal regeneration is impossible, and therefore, the process proceeds to step 226 to execute forced regeneration control of the first heating device 20, and this routine ends. To do. In the forced regeneration control in step 226, the heat amount of the second heating device 20 is pressurized by heating the first heating device 20 through exhaust, and Ph ≧ Ps.

  FIG. 8 is a flowchart showing details of the forced regeneration control routine of the first heating device 20 in Step 226 of FIG.

  In step 250, the temperature of the heat storage heater unit 26 is detected, and then the process proceeds to step 252 to determine whether or not the temperature of the heat storage heater unit 26 is equal to or higher than a predetermined value.

  If the determination in step 252 is affirmative, that is, if the temperature of the heat storage heater unit 26 is determined to be equal to or higher than the predetermined value, the process proceeds to step 254 and information on the battery for regeneration is read. For example, when the power source of the second heating device 22 is a battery mounted on a vehicle, information such as the voltage of the battery and the amount of stored electricity is read.

  In the next step 256, it is determined whether or not the battery for regeneration is applicable based on the information on the battery for regeneration acquired in step 254. If an affirmative determination is made in this step 256, the routine proceeds to step 258 where the second heating device 22 is turned on (energized to the heating element 22A, steady output in FIG. 5) for forced regeneration of the first heating device 20. The process proceeds to step 260.

  In step 260, a timer counter Ct, which will be described later, is reset (Ct ← 0), and this routine ends.

  If the determination in step 252 is negative, that is, if the temperature of the heat storage heater unit 26 is lower than a predetermined value, a considerable amount of heat is required for regeneration, and the process proceeds to step 262 to wait for regeneration control and the timer counter Ct Is incremented (Ct ← Ct + 1), and the process proceeds to Step 264. The increment of the timer counter Ct in step 262 accumulates the count value Ct every time the routine of FIG. 8 is repeatedly executed, and plays a role of a timer.

  In step 264, the count-up value Cs is read. Next, in step 266, it is determined whether or not the current count value Ct exceeds the count-up value Cs (Ct> Cs).

  If an affirmative determination is made in this step 266 (Ct> Cs), the process proceeds to step 268 to read out battery information for regeneration, and if it is determined in step 270 that a battery for regeneration is applicable (affirmative determination), step Then, the process proceeds to 272, the second heating device 22 is turned on (energization to the heating element 22A, the output is increased from the steady state in FIG. 5) for forced regeneration, and this routine ends.

(Modification)
In the present embodiment, the exhaust gas purification device 10 has been described with a configuration specialized for raising the temperature of the exhaust gas. However, the exhaust gas purification device including a selective reduction catalyst that purifies nitrogen oxides by supplying urea. 50 (see FIG. 9) will be described.

  As shown in FIG. 9, the exhaust system structure according to the modified example has a nitrogen oxide purification function in addition to the exhaust heating function according to the present embodiment, so that an exhaust purification device 50 is configured comprehensively. .

  The exhaust system structure according to the modification is intended for the internal combustion engine 12 of a diesel engine, as in the present embodiment.

  The exhaust gas purification apparatus 10 having the exhaust gas heating function described in the present embodiment is disposed on the exhaust pipe 16 on the downstream side of the internal combustion engine 12. The exhaust pipe 16 includes a selective reduction catalyst 54 that purifies nitrogen oxides (NOx) with urea supplied into the exhaust pipe 16, and an oxidation catalyst provided between the internal combustion engine 12 and the selective reduction catalyst 54. 56.

  The nitrogen oxide purifying function is performed by injecting urea water into a diesel particulate filter (hereinafter referred to as DPF) 58 disposed downstream of the oxidation catalyst 56 and the exhaust pipe 16 between the DPF 58 and the selective reduction catalyst 54. A urea injection device 62 having a urea addition valve 60 for addition, and a urea tank 64 for storing urea water supplied to the urea injection device 62 are provided.

  A NOx sensor 66 and a temperature sensor 70 are disposed in the exhaust pipe 16 upstream of the selective reduction catalyst 54, and a NOx sensor 68 is disposed in the exhaust pipe 16 downstream of the selective reduction catalyst 54. May be.

  The selective reduction catalyst 54 is a NOx reduction catalyst, and urea water supplied to the exhaust pipe 16 by the urea addition valve 60 is converted and flows into the selective reduction catalyst 54 together with the exhaust gas as ammonia gas. In the selective reduction catalyst 54, NOx in the exhaust gas is selectively reduced or decomposed by ammonia gas, whereby the NOx gas in the exhaust gas is purified and released into the atmosphere.

  The urea injection device 62 includes a urea pump (not shown) for sucking out urea water stored in the urea tank 64 through the suction pipe 72, and the urea pump is sucked out through the suction pipe 72 by the urea pump. Urea water is supplied to the exhaust pipe 16 via the supply pipe 74 and the urea addition valve 60. Note that a filter (not shown) is provided at the end of the suction pipe 72 on the urea tank 64 side, and foreign water is removed by the filter so that urea water is supplied to the exhaust pipe 16.

  In this embodiment (including modifications), NH3 (ammonia) is applied as the fluid medium, but other fluid media such as CO2 (carbon dioxide) and H2O (water) may be used. In addition, the chemical heat storage material of the heat storage heater unit 26 is not limited to magnesium bromide (MgBr2), and may be other chemical heat storage materials such as magnesium chloride (MgCl2) or calcium oxide (Ca0). For example, when the chemical heat storage material is calcium oxide (Ca0), H2O (water) may be selected as the fluid medium.

  In the present embodiment (including modifications), the opening / closing valve 32 is applied as the flow rate control unit. However, the opening / closing valve 32 may be either an electric valve or a pressure valve. Not limited to this, a pump (electric type, mechanical type, thermal displacement type, etc.) may be used. Further, a plurality of circulation pipes may be arranged so that the opening / closing valve 32 or the pump and the check valve are used in combination.

  Further, in this embodiment, the amount of heat is controlled by adjusting the voltage applied to the heating element 22A of the electric heater unit 22B applied as the second heating device 22 (see FIG. 5), but the applied voltage is constant, For example, the amount of heat may be controlled by duty control (pulse width control).

  In the present embodiment, the heat storage heater unit 26 is attached around the exhaust pipe 16. However, the present invention is not limited to this. For example, the heat storage heater unit 26 may be disposed inside the exhaust pipe 16. When the heat storage heater section 26 is disposed inside the exhaust pipe 16, for example, a plurality of flat heater sections and a plurality of corrugated fins (heat exchange sections) may be alternately stacked.

DESCRIPTION OF SYMBOLS 10 Exhaust gas purification device 12 Internal combustion engine 14 Engine control part 16 Exhaust pipe 18 Catalytic device 20 1st heating device 22 2nd heating device 24 Heating control device (heating control means)
26 Heat storage heater (chemical heat storage)
28 Circulating pipe 30 Thermal storage (reservoir)
32 Open / close valve (flow control unit)
22A Heating element 22B Electric heater unit 34 Valve control unit 36 Voltage control unit 38 Main control unit 40 Thermal storage heater unit temperature sensor (state detection means)
42 Thermal storage temperature sensor (state detection means)
44 bed temperature detection sensor 46in, 46out NOx sensor (purification rate acquisition means)
48 Purification rate calculator (Purification rate acquisition means)
50 Exhaust purification device 54 Selective reduction catalyst 56 Oxidation catalyst 58 Diesel particulate filter (DPF)
60 Urea addition valve 62 Urea injection device 64 Urea tank 66 NOx sensor 70 Temperature sensor 68 NOx sensor 72 Suction pipe 74 Supply pipe

Claims (7)

An exhaust purification device that purifies exhaust by activating a catalyst device attached to an exhaust system of an internal combustion engine by raising the temperature,
A chemical heat storage unit that is attached upstream of the catalyst device in the exhaust system, performs heat storage by performing a desorption reaction of the fluid medium, and dissipates heat by the adsorption reaction of the fluid medium, between the chemical heat storage unit A fluid medium can be circulated, and includes a storage unit that stores the fluid medium, and a flow rate control unit that controls opening and closing of a circulation path between the chemical heat storage unit and the storage unit, and distributes the chemical heat storage unit. A first heating device that heats the exhaust discharged from the internal combustion engine with the heat of adsorption of the fluid medium;
A second heating device that is attached upstream of the catalyst device in the exhaust system and that heats the exhaust gas discharged from the internal combustion engine using a heat source different from the first heating device;
A purification rate obtaining means for obtaining a purification rate of the catalyst device;
When the purification rate of the catalyst device acquired from the purification rate acquisition means is lower than a predetermined value, the drive of the first heating device or the second heating device is controlled and the upstream side of the catalyst device Heating control means for heating the exhaust of
Exhaust gas purification apparatus. A state detecting means for detecting a state including at least one of a temperature or a pressure of the fluid medium in the chemical heat storage section and the storage section of the first heating device;
The heating control means includes
Based on the detection result of the state detection means, calculate the amount of fluid medium held in either the chemical heat storage unit or the storage unit,
2. The exhaust emission control device according to claim 1, wherein when the amount of the fluid medium held in the storage unit is equal to or greater than a predetermined amount, the exhaust gas upstream of the catalyst device is heated by controlling driving of the first heating device. The second heating device is an electric heater using a heating element that generates heat when energized,
The heating control means includes
The exhaust gas purification device according to claim 1 or 2, wherein the electric heater is applied for exhaust gas heating when the first heating device cannot be used. The purification rate acquisition means
On the upstream side and the downstream side of the catalyst device, respectively, one or a plurality of purification rate determination sensors of a CO sensor, a THC sensor, and a NOx sensor,
A calculation unit that calculates the ratio of the downstream purification rate determination sensor to the detection value of the upstream purification rate determination sensor, the purification rate of the catalyst device;
An exhaust emission control device according to any one of claims 1 to 3, further comprising: A bed temperature detection sensor for detecting a bed temperature of the catalyst device;
The exhaust purification device according to any one of claims 1 to 4, wherein the purification rate acquisition means estimates a purification rate based on a bed temperature by the bed temperature detection sensor. A bed temperature detection sensor for detecting a bed temperature of the catalyst device;
The exhaust emission control device according to any one of claims 1 to 4, wherein the floor temperature detected by the floor temperature detection sensor is applied to determine whether or not exhaust heating control by the heating control means is necessary. The second heating device is disposed upstream of the first heating device;
The heating control means includes
When the amount of the fluid medium in the storage unit of the first heating device is a predetermined value or less,
On the condition that it is not necessary to heat the exhaust gas passing through the catalyst device, and that the pressure of the chemical heat storage unit is lower than the pressure of the storage unit,
In a state where the flow rate control unit of the first heating device is controlled to close the circulation path between the chemical heat storage unit and the storage unit,
Applying the second heating device for heating for the desorption reaction of the fluid medium in the chemical heat storage unit,
When the pressure of the chemical heat storage unit becomes higher than the pressure of the storage unit by a predetermined amount or more, the flow control unit of the first heating device is controlled to circulate between the chemical heat storage unit and the storage unit. The exhaust emission control device according to any one of claims 1 to 6, wherein the passage is opened.

Images