WO2017013989A1

WO2017013989A1 - Exhaust gas purifier

Info

Publication number: WO2017013989A1
Application number: PCT/JP2016/068633
Authority: WO
Inventors: 浩康河内; 野口　幸宏; 康佐竹; 松栄上田; 進長野; 直樹馬場; 明志知
Original assignee: 株式会社豊田自動織機
Priority date: 2015-07-17
Filing date: 2016-06-23
Publication date: 2017-01-26
Also published as: JP2017025729A

Abstract

In the present invention, exhaust gas heating by a heating device is preferentially selected when activation of a catalytic device is necessary. When the heating device has sufficient capability to heat exhaust gas, the heating device is used to heat the exhaust gas. When the capability of the heating device to heat the exhaust gas is insufficient, combustion timing control for an internal combustion engine is employed to heat the exhaust gas. This reduces unnecessary power consumption, and improves purification efficiency of the catalytic device.

Description

Exhaust purification device

The present invention relates to an exhaust gas purification device that activates a catalyst device attached to an exhaust system of an internal combustion engine to purify exhaust gas.

In a catalyst device attached to an exhaust system of an internal combustion engine, it is preferable to raise the temperature of the catalyst to a temperature at which exhaust purification performance is sufficiently exhibited. The technique disclosed in Patent Document 1 relates to control for warming a catalyst using an electric heater before starting an engine internal combustion engine which is an 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 the temperature of the catalyst is equal to or higher than the predetermined value, the electric heater is not energized.

The technique disclosed in Patent Document 1 is suitable for control for raising the temperature of the catalyst in a low temperature state before starting the engine. However, during engine operation, depending on the temperature measurement location of the catalyst, the electric heater may continue to be energized even though the catalyst is already activated. In such a case, power is wasted. For example, if the purification rate at the catalyst inlet and outlet is already sufficient, but the temperature at the center of the catalyst is still low, controlling the energization of the electric heater using the temperature at the center of the catalyst will waste current. Will continue. In addition, since the heat source is only the electric heater, it is necessary to constantly monitor the state of the in-vehicle battery that is the power source of the electric heater.

JP-A-10-169433

An object of the present invention is to obtain an exhaust emission control device in which energy consumption, including power consumption and fuel consumption for increasing the temperature to promote the activity of a catalyst device attached to an exhaust system of an internal combustion engine, is reduced, and catalyst activity is improved at an early stage. There is.

In order to solve the above problems, according to the first aspect of the present invention, an exhaust gas purification device that purifies exhaust gas by activating the catalytic device by raising the temperature of the catalytic device attached to the exhaust system of the internal combustion engine. Is provided. The exhaust purification device is attached to the upstream side of the catalyst device in the exhaust system, stores heat by the desorption reaction of the fluid medium, and dissipates heat by the adsorption reaction with the fluid medium. Adsorption of a fluid medium that circulates through the chemical heat storage unit, comprising a storage unit that can circulate the medium and that stores the fluid medium, and a flow rate control unit that controls opening and closing of the circulation path between the chemical heat storage unit and the storage unit. A heating device that heats the exhaust gas discharged from the internal combustion engine using heat, an adjustment means that can adjust the temperature of the exhaust gas discharged from the internal combustion engine by controlling the combustion timing of the internal combustion engine, and a purification rate of the catalyst device When the purification rate of the purification device and the purification rate of the catalyst device acquired from the purification rate acquisition unit is lower than a predetermined value, the exhaust flowing upstream from the catalyst device is heated by driving the heating device or adjusting the adjustment unit. You It has a heating control means.

According to the present invention, the heating device includes a chemical heat storage unit and a storage unit. As the fluid medium circulates between the chemical heat storage section and the storage section, the chemical heat storage section is chemically stored. 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 heating device or adjusts the combustion timing by the adjustment unit to adjust the upstream side of the catalyst device. Heat the flowing exhaust. For example, the flow control unit of the heating device is controlled to open the circulation path between the chemical heat storage unit and the storage unit. Thereby, a fluid medium circulates between a chemical heat storage part and a storage part, and exhaust gas is heated by heat exchange being performed between exhaust gas in a chemical heat storage part. As a result, the temperature of the catalyst device is increased and activated, and the exhaust gas purification rate is improved. When the adjusting means is applied, the exhaust gas flowing in the exhaust system is heated by a heat source different from the heating device. This also activates the catalyst device and improves the exhaust gas purification rate. Thus, the heating function using the heating device and the adjusting means is provided as means for heating the exhaust gas of the internal combustion engine. Thereby, even if any of a heating apparatus and an adjustment means becomes unnecessary, activation of a catalyst apparatus can be maintained. In this case, the heating device and the adjusting means can be used in combination, or can be used alternately, or one can function as a spare for the other.

In the above exhaust purification apparatus, it has a state detection means for detecting a state including at least one of the temperature or the pressure of the fluid medium in the chemical heat storage section and the storage section, and the heating control means uses the detection result of the state detection means. Based on the calculation of the amount of the fluid medium held in either the chemical heat storage unit or the storage unit, and when the amount of the fluid medium stored in the storage unit is greater than or equal to a predetermined amount, the drive of the heating device is controlled and the catalyst device It is also preferable to heat the exhaust gas flowing upstream.

The state detection means detects at least one of temperature and pressure of the fluid medium in the chemical heat storage section and the storage section of the heating device. 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 detection accuracy is higher when the contact pressure is directly detected using a pressure sensor. Therefore, in consideration of price and accuracy, either the temperature sensor or the pressure sensor may be selected or used in combination.

The heating control means calculates the amount of the fluid medium held in either the chemical heat storage section or the storage section based on the detection result of the state detection means. In addition, since the total amount of the fluid medium basically does not change, it is only necessary to calculate the possessed amount of one of the chemical heat storage unit and the storage unit. Here, when the holding amount of the fluid medium in the storage unit is greater than or equal to a predetermined amount, the fluid medium can be normally circulated. Therefore, the driving of the heating device is controlled to heat the exhaust gas flowing upstream from the catalyst device. .

In the above exhaust purification apparatus, the combustion timing control of the adjusting means is after-injection or retarded-angle injection of the internal combustion engine selected according to the load state of the internal combustion engine, and the heating control means cannot use the adjusting means and the heating device In this case, it is preferable to use for exhaust heating.

The adjusting means can adjust the temperature of the exhaust gas discharged from the internal combustion engine by after-combustion or retarded combustion of the internal combustion engine selected according to the load state of the internal combustion engine. Therefore, the combustion timing control of the internal combustion engine is used for heating the exhaust when the heating device cannot be used. In this case, for example, by controlling the flow rate control unit of the heating device to close the circulation path between the chemical heat storage unit and the storage unit, the exhaust gas can be heated and then efficiently moved to the catalyst device.

In the above exhaust purification apparatus, the purification rate acquisition means is provided on the upstream side and the downstream side of the catalyst device, respectively, and one or more purification rate determination sensors of a CO sensor, a THC sensor, and a NO _x sensor, and a catalyst It is preferable to include a calculation unit that calculates the ratio of the downstream purification rate discrimination sensor to the detection value of the upstream purification rate discrimination sensor as the purification rate of the apparatus.

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, _by calculating any of the CO sensor, THC sensor, and NO _x sensor on the upstream side and downstream side of the catalyst device, the purification rate is calculated based on the ratio of the amount of the detected component contained in the exhaust gas. Can do.

It is preferable that the exhaust gas purification apparatus includes a bed temperature detection sensor for detecting the bed temperature of the catalyst device, and the purification rate acquisition unit 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.
The exhaust purification apparatus preferably includes a bed temperature detection sensor for detecting the bed temperature of the catalyst device, and the bed temperature by the bed temperature detection sensor is used for determining whether or not the heating control of the exhaust by the heating control means is necessary.

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 the above exhaust purification apparatus, the heating control means does not need to heat the exhaust gas passing through the catalyst device and the pressure of the chemical heat storage section is stored when the amount of the fluid medium in the storage section is equal to or less than a predetermined value. With the condition that the pressure is lower than the pressure in the section, the flow control section is controlled to close the circulation path between the chemical heat storage section and the storage section, and the adjustment means is desorbed from the fluid medium in the chemical heat storage section. Used for heating for reaction, when the pressure of the chemical heat storage unit becomes higher than the pressure of the storage unit by a predetermined level or more, the flow rate control unit is controlled to open the circulation path between the chemical heat storage unit and the storage unit It is preferable.

The amount of fluid medium held in the storage part of the heating device may be below 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 heating device is controlled so that the circulation path between the chemical heat storage unit and the storage unit is closed. In the state where the circulation path is closed, the fluid medium in the chemical heat storage unit is heated and pressurized by heating the exhaust gas by the adjusting means. Moreover, in a heating control means, an adjustment means is used for the heating for the pressurization of the fluid medium in a chemical heat storage part. At this time, 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 heating of the exhaust by the adjusting unit is finished, and the flow rate control unit of the heating device is controlled to control the chemical heat storage unit and the storage unit Open the circuit between them. 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. Therefore, the heating device is regenerated and can be used for heating the next exhaust.

In the present invention, energy consumption including power consumption and fuel consumption for increasing the temperature of the catalyst device attached to the exhaust system of the internal combustion engine is promoted, and the catalyst activity is improved early.

1 is a schematic view of an exhaust system of an internal combustion engine to which an exhaust emission control device according to an embodiment of the present invention is attached. (A) is a temperature-pressure characteristic diagram of the fluid medium applied to the heating device, and (B) is a pressure-residual property diagram of the fluid medium applied to the heating device. 7 is a flowchart showing an exhaust heating control routine. (A) is a flowchart showing a combustion timing control routine, (B) is a flowchart showing a combustion timing OFF operation control routine. (A) is a graph showing the relationship between the crank angle and the injection amount in the after injection control, and (B) is a graph showing the relationship between the crank angle and the injection amount in the retard injection control. The characteristic view which shows the result of having compared this embodiment with two types of comparative examples about the relationship between the control form of a heating apparatus, and input energy. The flowchart which shows a heating apparatus reproduction | regeneration control routine. The flowchart which shows the heating apparatus forced regeneration control of step 226 of FIG. The schematic diagram of the exhaust system of the internal-combustion engine provided with the exhaust emission control device concerning a modification.

Hereinafter, an embodiment in which the exhaust emission control device of the present invention is attached to an exhaust system of an internal combustion engine will be described with reference to FIGS. An internal combustion engine is an engine mounted on a vehicle, and is a prime mover that burns fuel inside the engine and converts thermal energy of combustion gas into mechanical energy.

As shown in FIG. 1, an engine control unit 14 is connected to the internal combustion engine 12. When the internal combustion engine 12 is a diesel engine, heavy oil or light oil as fuel is injected into high-pressure and high-temperature air in the cylinder and burned. The engine control unit 14 controls the fuel injection amount, fuel injection timing, and the like. An exhaust pipe 16 for exhausting combustion gas (hereinafter referred to as “exhaust”) is attached to the internal combustion engine 12. The exhaust gas passes through the exhaust pipe 16 and is discharged out of the internal combustion engine 12.

A catalyst device 18 mainly constituting the exhaust purification device 10 is attached to the exhaust pipe 16. The catalytic device 18 reduces NO _x contained in the combustion gas and decomposes it into harmless N ₂ . The exhaust purification device 10 further includes a heating device 20 provided in the exhaust pipe 16 between the internal combustion engine 12 and the catalyst device 18 and for heating the exhaust. In addition to the function of heating the exhaust gas by the heating device 20, the exhaust gas purification device 10 also has a function as adjusting means for heating the exhaust gas by controlling the combustion timing of the internal combustion engine 12 by the engine control unit 14. The adjusting means mainly adjusts the temperature of the exhaust discharged to the exhaust pipe 16 under after-injection control or retarded-angle injection control as combustion timing control by the engine control unit 14.

The exhaust gas heating by the heating device 20 and the exhaust gas temperature adjustment by the adjusting means improve the catalytic activity by the catalyst device 18. The heating device 20 and the adjusting means constitute a part of the exhaust purification device 10 together with the catalyst device 18. The heating device 20 and the adjusting means are controlled by a heating control device 24 connected to the engine control unit 14.

As shown in FIG. 1, the heating device 20 is a chemical heat storage heater and is attached around the exhaust pipe 16. The heating device 20 includes a heat storage heater unit 26 as a chemical heat storage unit. The heat storage heater unit 26 has a ring-shaped housing structure. A chemical heat storage material is accommodated in the internal space of the heat storage heater section 26. In the present embodiment, ammonia (NH ₃₎ is used as the fluid medium.

Further, the lower end of the circulation pipe 28 is connected to the outer peripheral surface of the heat storage heater portion 26. The internal space of the heat storage heater portion 26 communicates with the internal space of the circulation pipe 28. The upper end of the circulation pipe 28 is connected to a box-shaped storage section 30 (hereinafter referred to as a heat storage storage 30) that stores a fluid medium. The internal space of the circulation pipe 28 is communicated with the internal space of the heat storage 30. For this reason, the heat storage heater unit 26 and the heat storage 30 are communicated with each other via the circulation pipe 28. The fluid medium can flow between the heat storage heater 26 and the heat storage 30 due to a pressure difference between the heat storage heater 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. By opening / closing the opening / closing valve 32, the flow of the fluid medium can be controlled. For example, as the simplest control mode, when the opening / closing valve 32 is opened, the fluid medium can flow between the heat storage heater unit 26 and the heat storage 30 and when the opening / closing valve 32 is closed, the heat storage heater unit 26 is opened. And the fluid storage medium between the heat storage 30 and the heat storage 30 are impossible.

The heat storage heater section 26 is filled with magnesium bromide (MgBr ₂ ) as a chemical heat storage material. MgBr ₂ generates heat due to a chemical reaction (adsorption reaction) with ammonia as a fluid medium. For this reason, when the fluid 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, the heat storage heater 26 heats the exhaust gas passing through the exhaust pipe 16. To do. When the exhaust gas heated by the heating device 20 reaches the catalyst device 18, the bed temperature of the catalyst device 18 is raised by the heat of the exhaust gas, and the catalyst function is activated. In particular, it is preferable to activate the catalyst function by raising the bed temperature of the catalyst device 18 in a transition period that is stable from the start of the internal combustion engine 12.

On the other hand, when the internal combustion engine 12 is sufficiently warmed up, the catalyst device 18 is sufficiently activated, and the amount of heat of the exhaust is sufficient, 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 of the exhaust. As a result, a desorption reaction in which the fluid medium is desorbed from the chemical heat storage material occurs, whereby the heat of the exhaust is stored. As a result, when the pressure of the heat storage heater unit 26 becomes higher than the pressure of the heat storage storage 30, the fluid medium flows from the heat storage heater unit 26 to the heat storage storage 30. As a result, the heat storage 30 stores a necessary and sufficient amount of fluid medium. That is, the heating device 20 can circulate and use the fluid medium for the heat treatment of the exhaust.

Next, exhaust temperature adjustment by combustion timing control will be described.
The adjustment control is control of the internal combustion engine 12 by the engine control unit 14. As the adjustment control, either after-injection control shown in FIG. 5A or retarded-angle injection control shown in FIG. 5B is selected and executed.

In the after injection control, combustion is continued by injecting fuel after the main injection with a smaller fuel injection amount than the main injection. As a result, the exhaust temperature when a valve (not shown) communicating with the exhaust pipe 16 is opened is higher than the exhaust temperature when there is no after injection. In the retarded angle injection control, the main injection itself at the calculated crank angle (steady injection angle) is delayed (retarded angle control) to burn the fuel. As a result, the exhaust temperature when the valve communicating with the exhaust pipe 16 is opened becomes higher than the exhaust temperature at the steady injection angle. In the case of retarded injection, it is preferable to increase the fuel injection amount in order to maintain the torque.

The heating control device 24 includes a valve control unit 34, an adjustment control instruction unit 36, and a main control unit 38. The valve control unit 34 controls the open / close valve 32 provided in the heating device 20. The adjustment control instruction unit 36 instructs the engine control unit 14 to adjust the exhaust temperature. The main control unit 38 comprehensively controls the valve control unit 34 and the adjustment control instruction unit 36 based on the purification rate of the catalyst device 18. A heat storage heater section temperature sensor 40 is attached to the heat storage heater section 26. The regenerative heater section temperature sensor 40 is connected to the main control section 38 via a detection signal line. A heat storage temperature sensor 42 is attached to the heat storage 30. The heat storage temperature sensor 42 is also connected to the main controller 38 via a detection signal line.

The main control unit 38 calculates the pressure based on the detected temperature. That is, as shown in FIG. 2A, the relationship between the temperature and pressure of the container containing ammonia is linearly approximated in the use region and is almost directly proportional. Therefore, the main control unit 38 recognizes 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 recognizes the pressure of the fluid medium stored in the heat storage 30 by detecting the temperature by the heat storage temperature sensor 42.

Further, 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 holding | maintenance amount of the fluid medium currently stored by the thermal storage 30, the temperature of the thermal storage 30 is detected by the thermal storage temperature sensor 42, pressure is converted from the detected temperature, Furthermore, conversion The remaining amount, which is the amount of the fluid medium, can be obtained from the applied pressure. In addition, although the heat storage heater part temperature sensor 40 and the heat storage storage temperature sensor 42 were used, instead of the inexpensive temperature sensor, pressure sensors may be attached to the heat storage heater part 26 and the heat storage storage 30 in order to place importance on accuracy. Good. 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 bed temperature detection sensor 44 is connected to the main control unit 38 via a detection signal line. Further, NO _x sensors 46 _in and 46 _out are attached to the upstream side (near the inlet) and the downstream side (near the outlet) of the catalyst device 18 in the exhaust pipe 16, respectively. The NO _x sensors 46 _in and 46 _out are connected to the purification rate calculation unit 48 via detection signal lines. The purification rate calculation unit 48 illustrated in FIG. 1 is separate from the heating control unit 24, but may be a part of the heating control unit 24.

The purification rate calculation unit 48 determines the amount of nitrogen oxides N _{in in the} exhaust gas entering the catalytic device 18 and the exhaust gas in the exhaust gas from the catalytic device based on the detection values input from the NO _x sensors 46 _in and 46 _out . A ratio (purification rate S) with the amount N _out of nitrogen oxide is calculated (S = N _in / N _out ). The purification rate calculation unit 48 is connected to the main control unit 38 and outputs 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 such as the start time, the transition period, and the steady operation timing based on the internal combustion engine control information input from the engine control unit 14. The heating control unit 24 executes exhaust heating control suitable for the state of the internal combustion engine 12. 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 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 is activated.

Exhaust heating control is executed while constantly monitoring the bed temperature and purification rate of the catalyst device 18. The heating control can be changed according to the state of the internal combustion engine 12 as the state transition of the internal combustion engine 12, that is, as the state transitions from the start time to the transition period and the steady operation timing. The heating control includes heating unnecessary.

In this embodiment, in addition to the heating device 20, the engine control unit 14 controls the combustion timing of the internal combustion engine 12. For this reason, the heating control device 24 maintains the activity of the catalyst device 18 by executing the control of the combustion timing of the internal combustion engine 12 instead of the heating by the heating device 20 when the heating device 20 cannot be used. Can do.

Hereinafter, the operation of the present embodiment will be described with reference to the flowcharts of FIGS. 3, 4 (A) and 4 (B). The order of signal detection and determination executed in each step of all flowcharts of this embodiment including FIG. 3, FIG. 4 (A), and FIG. 4 (B) may be appropriately changed.

In the exhaust heating control routine shown in FIG. 3, first, in step 100, it is determined whether or not the internal combustion engine 12 is in operation. The determination as to whether or not the vehicle is in operation is performed in order to determine whether or not fuel injection is being performed. “Not in operation” refers to an operation stop state in which combustion control is not performed. Apart from the operation suspension state, for example, the fuel cut control performed when the vehicle is going down a long hill may be “not in operation”.

When a negative determination is made in step 100 (N in step 100), it is not necessary to heat the exhaust because the internal combustion engine 12 is not in operation. Therefore, the control flow moves to step 102. When an affirmative determination is made in step 100 (Y in step 100), the internal combustion engine 12 is in operation and the catalyst device 18 needs to be activated. Therefore, the control flow proceeds to step 106, and it is determined whether or not the purification rate of the catalyst device 18 is equal to or higher than a reference value.

If an affirmative determination is made in step 106 (Y in step 106), that is, if it is determined that the purification rate is equal to or higher than the reference value, it is not necessary to heat the exhaust. Therefore, the control flow moves to step 102. If a negative determination is made in step 106 (N in step 106), the exhaust rate needs to be heated because the purification rate is less than the reference value. Therefore, the control flow proceeds to step 108 and it is determined whether or not the catalyst bed temperature is equal to or higher than the reference value.

When an affirmative determination is made in step 108 (Y in step 108), that is, since the bed temperature of the catalyst device 18 is stable, there is no need to heat the exhaust. Therefore, the control flow moves to step 102. Thus, when the control flow goes to Step 102 through Step 100, Step 106, and Step 108, the opening / closing valve 32 of the heating device 20 is closed, and this routine is finished. If a negative determination is made in step 108 (N in step 108), the control flow moves to step 110 because all the conditions that require exhaust heating are complete.

In step 110, the remaining amount of the fluid medium (NH ₃₎ of the heat storage storage 30 is detected. When it is determined that the remaining amount of the fluid medium (NH ₃ ) is less than the predetermined value, it is determined that the exhaust gas heating capability by the heating device 20 is inappropriate. Therefore, the control flow proceeds to step 128, and after the opening / closing valve 32 is closed, the process proceeds to step 130. In step 130, fuel injection timing control of the internal combustion engine 12 is executed based on an instruction from the adjustment control instruction unit 36 instead of the heating device 20. That is, the adjustment (mainly heating) of the exhaust temperature based on the catalyst bed temperature of the catalyst device 18 used in the internal combustion engine 12 is started, and this routine ends.

On the other hand, when it is determined that the remaining amount of the fluid medium (NH ₃ ) is equal to or greater than the predetermined value, it is determined that the exhaust heating function by the heating device 20 is appropriate. Therefore, the control flow moves to step 120. In step 120, after the temperature of the heat storage heater unit 26 and the temperature of the heat storage 30 are detected, the control flow proceeds to step 122. In step 122, based on the detected temperature, the equilibrium pressure Ph of the fluid medium (NH ₃ ) of the heat storage heater section 26 is calculated. Next, at step 124, the equilibrium pressure Ps of the fluid medium (NH ₃ ) of the heat storage 30 is calculated. Then, the control flow moves to step 126.

In step 126, the equilibrium pressure Ph of the fluid medium (NH ₃ ) of the heat storage heater section 26 is compared with the equilibrium pressure Ps of the fluid medium (NH ₃ ) of the heat storage 30 (Ph: Ps). When it is determined that Ph ≧ Ps, it is determined that the fluid medium (NH ₃ ) does not flow properly and the exhaust heating function is insufficient. Therefore, the control flow proceeds to step 128, and after the opening / closing valve 32 is closed, the process proceeds to step 130. In step 130, fuel injection timing control of the internal combustion engine 12 is executed based on an instruction from the adjustment control instruction unit 36 instead of the heating device 20. That is, the heating control based on the catalyst bed temperature of the catalyst device 18 used in the internal combustion engine 12 is started, 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. Therefore, the control flow moves to step 132, and the opening / closing valve 32 is opened. Therefore, the fluid medium (NH ₃ ) is supplied to the heat storage heater unit 26, the exhaust heating control by the heating device 20 is started, and this routine ends.

In the injection timing control routine of the internal combustion engine 12 shown in FIG. 4A, first, at step 150, it is determined whether or not the injection timing control is possible. If a negative determination is made in step 150 (N in step 150), this routine ends. If an affirmative determination is made in step 150 (Y in step 150), the control flow proceeds to step 151, and the load information of the internal combustion engine 12 is acquired. Subsequently, the control flow proceeds to step 152, and the load state of the internal combustion engine 12 is determined.

If it is determined in step 152 that the internal combustion engine 12 has a low load, the control flow proceeds to step 154, the after injection control shown in FIG. 5 (A) is started, and this routine ends. On the other hand, if it is determined in step 152 that the internal combustion engine 12 is at a medium load or a high load, the control flow proceeds to step 156 and the retarded injection control shown in FIG. finish. During the retarded angle injection control in step 156, the fuel injection amount is increased to maintain the torque.

In the injection timing control end operation control routine shown in FIG. 4B, first, in step 160, it is determined whether or not the injection timing control is being performed. If a negative determination is made in step 160 (N in step 160), this routine ends. On the other hand, if an affirmative determination is made in step 160 (Y in step 160), the control flow moves to step 162. In step 162, a signal is taken from the purification rate calculation unit 48. Next, the control flow proceeds to step 164, and it is determined whether the purification rate is equal to or higher than a reference value. If a negative determination is made in step 164 (N in step 164), it is determined that exhaust heating needs to be continued, and this routine ends. On the other hand, when an affirmative determination is made in step 164 (Y in step 164), the control flow proceeds to step 165, and it is determined 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 (N in step 165), it is determined that exhaust heating needs to be continued, and this routine ends. On the other hand, if an affirmative determination is made in step 165 (Y in step 165), the exhaust gas heating is unnecessary, and the control flow moves to step 166. And injection timing control is complete | finished and this routine is complete | finished.

According to the present embodiment, when the catalyst device 18 needs to be activated, the exhaust gas heating by the heating device 20 is preferentially selected. In addition, when the exhaust heating function of the heating device 20 is sufficient, exhaust heating using the heating device 20 is performed. On the other hand, when the exhaust heating function of the heating device 20 is insufficient, exhaust heating using fuel injection timing control by the internal combustion engine 12 is executed. By these, input energy is suppressed and the purification rate of the catalytic device 18 is effectively improved.

As shown in FIG. 6, compared to 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 this embodiment has an input energy of Less is enough.

Next, the regeneration control routine of the heating device 20 will be described.
In the regeneration control routine of the heating device 20 shown in FIG. 7, first, in step 200, it is determined whether or not the catalyst device 18 is already under temperature increase control. If an affirmative determination is made in step 200 (Y in step 200), this routine ends. On the other hand, if a negative determination is made in step 200 (N in step 200), the control flow proceeds to step 202, and after detecting the bed temperature (catalyst bed temperature) of the catalyst device 18, the process proceeds to step 204.

In step 204, it is determined whether the catalyst bed temperature is equal to or higher than a reference value. When a negative determination is made in step 204 (N in step 204), priority is given to using the heat of the exhaust gas obtained by the injection timing control of the internal combustion engine for the activation of the catalyst device 18. For this reason, this routine ends without performing the regeneration of the injection timing control of the internal combustion engine. On the other hand, when an affirmative determination is made in step 204 (Y in step 204), the heat of the exhaust gas obtained by the injection timing control of the internal combustion engine does not need to be used for the activation of the catalyst device 18 and is used for the regeneration of the heating device 20. Is available. Therefore, the control flow moves 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. Then, the control flow moves to step 208. In step 208, the equilibrium pressure Ph of the fluid medium (NH ₃ ) of the heat storage heater unit 26 is calculated based on the detected temperature. Next, the control flow proceeds to step 210, where the equilibrium pressure Ps of the fluid medium (NH ₃ ) of the heat storage 30 is calculated. Then, the control flow moves to step 212.

In step 212, the remaining amount of the fluid medium (NH ₃ ) 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 greater than or equal to a predetermined value, it is determined that regeneration control is not necessary, and the control flow proceeds to step 214. In step 214, it is determined whether or not the opening / closing valve 32 is open. If the determination in step 214 is affirmative, that is, if the opening / closing valve 32 is open (Y in step 214), the opening / closing valve 32 is closed in step 216. In addition, the fluid medium (NH ₃ ) is not supplied to the heat storage heater unit 26, and the control flow proceeds to step 218. On the other hand, if a negative determination is made in step 214 (N in step 214), the control flow proceeds to step 218.

In step 218, it is determined whether or not the injection timing of the internal combustion engine is being controlled. If an affirmative determination is made in step 218 (Y in step 218), the injection timing control of the internal combustion engine ends in step 220, and this routine ends. On the other hand, if a negative determination is made in step 218, that is, if the injection timing control of the internal combustion engine is not being executed (N in step 218), this routine ends.

In step 212, when it is determined that the remaining amount of the fluid medium (NH ₃ ) in the heat storage 30 is less than the predetermined value (N in step 212), it is determined that regeneration control is necessary, and the control flow proceeds to step 222. . In step 222, the equilibrium pressure Ph of the fluid medium (NH ₃ ) of the heat storage heater unit 26 calculated in step 208 and step 210 is compared with the equilibrium pressure Ps of the fluid medium (NH ₃ ) of the heat storage 30. (Ph: Ps). If it is determined that Ph ≧ Ps, the control flow proceeds to step 224, and the opening / closing valve 32 is opened. In addition, the fluid medium (NH ₃ ) is supplied to the heat storage 30 (hereinafter referred to as “normal regeneration”), and the control flow 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.

On the other hand, if it is determined in step 222 that Ph <Ps, normal playback is impossible, and the control flow proceeds to step 226. Then, forced regeneration control of the heating device 20 is executed, and this routine ends. The forced regeneration control in step 226 is control in which the exhaust device heated by the injection timing control of the internal combustion engine heats the heating device 20 to pressurize the heating device 20 so that Ph ≧ Ps.

In the forced regeneration control routine of the heating device 20 shown in FIG. 8, first, in step 250, the temperature of the heat storage heater section 26 is detected. Next, the control flow proceeds to step 252, and it is determined whether or not the temperature of the heat storage heater unit 26 is equal to or higher than a predetermined value. If an affirmative determination is made in step 252 (Y in step 252), that is, if the temperature of the heat storage heater unit 26 is determined to be equal to or higher than a predetermined value, the control flow proceeds to step 254, and the injection timing control of the internal combustion engine is possible. It is determined whether or not.

If a negative determination is made in step 254 (N in step 254), the routine ends. On the other hand, if an affirmative determination is made in step 254 (Y in step 254), the control flow proceeds to step 256, and load information of the internal combustion engine is acquired. Subsequently, the control flow proceeds to step 258, and the load state of the internal combustion engine 12 is determined.

When it is determined in step 258 that the internal combustion engine 12 has a low load, the control flow proceeds to step 260, and after the after injection control shown in FIG. 5A is started, the process proceeds to step 264. On the other hand, if it is determined in step 258 that the internal combustion engine 12 has a medium load or a high load, the control flow proceeds to step 262 and the injection control shown in FIG. Transition. During the retarded angle injection control in step 262, the fuel injection amount is increased to maintain the torque.

In step 264, the injection timing control of the internal combustion engine 12 is started for forced regeneration of the heating device 20. Then, the control flow moves to step 266. In step 266, a timer counter Ct, which will be described later, is reset (Ct ← 0), and this routine ends.

If a negative determination is made in step 252 (N in step 252), 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. Therefore, in order to wait for the regeneration control, the control flow shifts to step 268 and the timer counter Ct is incremented (Ct ← Ct + 1), and then shifts to step 270. The increment of the timer counter Ct in step 268 functions as a timer by accumulating the count value every time the routine of FIG. 8 is repeated.

In step 270, the count-up value Cs is read out. Next, at step 272, 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 step 272 (Ct> Cs), the control flow moves to step 270. On the other hand, if a negative determination is made in step 272, this routine ends.

(Modification)
In the present embodiment, the configuration specialized in raising the temperature of the exhaust gas as the exhaust gas purification device 10 has been described. Next, an exhaust purification device 50 including a selective reduction catalyst that purifies nitrogen oxides by supplying urea 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 gas temperature raising function according to the present embodiment, so that the 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 is provided with a selective reduction catalyst 54 that purifies nitrogen oxides (NO _x ) with urea supplied into the exhaust pipe 16. An oxidation catalyst 56 is provided between the internal combustion engine 12 and the selective reduction catalyst 54 in the exhaust pipe 16.

A device having a nitrogen oxide purification function supplies a diesel particulate filter (hereinafter referred to as DPF) 58 disposed downstream of the oxidation catalyst 56, a urea injection device 62 having a urea addition valve 60, and a urea injection device 62. And a urea tank 64 for storing the urea water. The urea addition valve 60 injects and adds urea water into the exhaust pipe 16 between the DPF 58 and the selective reduction catalyst 54.

An NO _x sensor 66 and a temperature sensor 70 are disposed in the exhaust pipe 16 upstream of the selective reduction catalyst 54. In addition, a NO _x sensor 68 may be disposed in the exhaust pipe 16 on the downstream side of the selective reduction catalyst 54.

The selective reduction catalyst 54 is a NO _x reduction catalyst. To the selective reduction catalyst 54, urea water supplied to the exhaust pipe 16 by the urea addition valve 60 is converted into ammonia gas, and flows into the selective reduction catalyst 54 together with the exhaust gas. In the selective reduction catalyst 54, the ammonia gas, NO _x in the exhaust gas is selectively reduced or decomposed. As a result, the NO _x 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 the urea water stored in the urea tank 64 through the suction pipe 72. The urea water sucked out by the urea pump through the suction pipe 72 is supplied to the exhaust pipe 16 through the supply pipe 74 and the urea addition valve 60. A filter (not shown) is provided at the end of the suction pipe 72 near the urea tank 64. The urea water stored in the urea tank 64 is supplied to the exhaust pipe 16 after foreign matters and the like are removed by a filter.

In the present embodiment and the modification, NH ₃ (ammonia) is used as the fluid medium, but CO ₂ (carbon dioxide), H ₂ O (water), or the like may be used. In addition, the chemical heat storage material of the heat storage heater unit 26 may be magnesium chloride (MgCl ₂ ) or calcium oxide (CaO) other than magnesium bromide (Mg). For example, when the chemical heat storage material is calcium oxide (CaO), H ₂ O (water) may be selected as the fluid medium.

In the present embodiment and the modification, the on-off valve 32 as the flow rate control unit may be either an electric valve or a pressure valve. Moreover, not only the on-off valve 32 but an electric, mechanical, or thermal displacement pump may be used. Furthermore, a plurality of circulation pipes may be arranged, and the opening / closing valve 32 or the pump and the check valve may be used in combination.

In the present embodiment, the heat storage heater unit 26 is attached around the exhaust pipe 16, but the heat storage heater unit 26 may be disposed inside the exhaust pipe 16. When the heat storage heater unit 26 is disposed inside the exhaust pipe 16, for example, a plurality of flat heater units and a plurality of corrugated fins (heat exchange units) are alternately stacked to form the heat storage heater unit 26. Also good.

Claims

An exhaust purification device that purifies exhaust by activating the catalyst device by raising the temperature of the catalyst device attached to the exhaust system of the internal combustion engine,
A chemical heat storage unit that is attached upstream of the catalyst device in the exhaust system and stores heat by a desorption reaction of the fluid medium and dissipates heat by an adsorption reaction with the fluid medium, and the flow between the chemical heat 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 is distributed through the chemical heat storage unit. A heating device for heating the exhaust gas discharged from the internal combustion engine using heat of adsorption of the fluid medium;
Adjusting means capable of adjusting the temperature of the exhaust gas discharged from the internal combustion engine by controlling the combustion timing of the internal combustion engine;
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 unit is lower than a predetermined value, the exhaust gas flowing upstream from the catalyst device is heated by driving the heating device or adjusting the adjustment unit. Heating control means;
Exhaust gas purification apparatus.
The exhaust emission control device according to claim 1, further comprising:
Having a state detecting means for detecting a state including at least one of temperature and pressure of the fluid medium in the chemical heat storage section and the storage section;
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,
An exhaust emission control device that heats exhaust gas flowing upstream from the catalyst device by controlling driving of the heating device when the amount of the fluid medium in the storage unit is greater than or equal to a predetermined amount.
The exhaust emission control device according to claim 1 or 2,
The combustion timing control of the adjusting means is after-injection or retarded-injection of the internal combustion engine selected according to the load state of the internal combustion engine;
The heating control means includes
An exhaust emission control device, wherein the adjusting means is used for exhaust gas heating when the heating device cannot be used.
The exhaust emission control device according to any one of claims 1 to 3,
The purification rate acquisition means includes
Provided 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 NO x sensor;
As the purification rate of the catalyst device, a calculation unit that calculates the ratio of the downstream purification rate discrimination sensor to the detection value of the upstream purification rate discrimination sensor;
An exhaust emission control device.
The exhaust emission control device according to any one of claims 1 to 4, further comprising:
Having a bed temperature detection sensor for detecting the bed temperature of the catalyst device;
The exhaust emission control device, wherein the purification rate acquisition means estimates a purification rate based on a bed temperature by the bed temperature detection sensor.
The exhaust emission control device according to any one of claims 1 to 4, further comprising:
Having a bed temperature detection sensor for detecting the bed temperature of the catalyst device;
An exhaust gas purification apparatus that uses the bed temperature by the bed temperature detection sensor to determine whether or not the heating control of the exhaust by the heating control means is necessary.
The exhaust emission control device according to any one of claims 1 to 6,
The heating control means includes
When the amount of the fluid medium in the storage unit 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 of controlling the flow rate control unit and closing the circulation path between the chemical heat storage unit and the storage unit,
The adjusting means is used for heating for the desorption reaction of the fluid medium in the chemical heat storage unit,
Exhaust gas purification that controls the flow rate control unit to open the circulation path between the chemical heat storage unit and the 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. apparatus.