JP2013130073A - Exhaust emission control device and method of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device and method of an internal combustion engine, capable of effectively generating a gaseous reducing agent by properly using a solid reducing agent and liquid reducing agent according to a temperature of exhaust gas, and capable of reducing consumption of fuel.SOLUTION: An exhaust emission control device 3 has a liquid reducing agent supplying means 12 for feeding urea water to an exhaust gas passage 2 and a reducing agent heating supplying means 13 for heating a solid reducing agent 38, generating ammonium, and supplying the ammonium to the exhaust gas passage 2 in the upstream side more than a SCR catalyst 10. The ammonium is generated by heating the solid reducing agent 38 and is supplied into the exhaust gas immediately upstream of the SCR catalyst 10 when a temperature of the exhaust gas is increased to about 200°C or higher. The heating of the solid reducing agent 38 is stopped, the ammonium is generated by supplying the urea water into the exhaust gas in the case the temperature of the exhaust gas becomes not lower than 200°C.

Description

  The present invention relates to an exhaust gas purification apparatus and a purification method for an internal combustion engine that purify NOx (nitrogen oxide) contained in exhaust gas discharged from the internal combustion engine with a reduction catalyst.

As an exhaust gas purification device that reduces NOx discharged from an internal combustion engine, particularly a diesel engine, for example, Patent Document 1 discloses a reduction catalyst provided in an exhaust gas passage of a diesel engine, and a diesel engine and a reduction catalyst. In addition, an exhaust gas purification apparatus including a bypass channel that bypasses the exhaust gas channel and a solid reducing agent provided in the bypass channel is disclosed. Part of the exhaust gas discharged from the diesel engine flows into the bypass flow path, sublimates the solid reducing agent provided in the bypass flow path to generate ammonia, and then flows into the reduction catalyst containing the ammonia To do. Thereafter, NOx contained in the exhaust gas is reduced by ammonia in the reduction catalyst, and purified as nitrogen and water.
Since this exhaust gas purifying apparatus does not include a solid reducing agent heating means such as a heater for heating and sublimating the solid reducing agent, the exhaust gas temperature is used to sublimate the solid reducing agent. Therefore, when the temperature of the exhaust gas at the time of starting or the like is low, the NOx may not be reduced because the solid reducing agent does not sublime even if the exhaust gas is allowed to pass through.

  Therefore, in Patent Document 2, a reduction catalyst provided in an exhaust gas passage of a diesel engine, a bypass channel provided between the diesel engine and the reduction catalyst, bypassing the exhaust gas channel, and a bypass channel are provided. An exhaust gas purifying apparatus comprising a solid reducing agent and a solid reducing agent heating means for heating and sublimating the solid reducing agent is disclosed. In this exhaust gas purifying apparatus, a solid reducing agent is constantly heated by a solid reducing agent heating means to be sublimated to generate ammonia. That is, ammonia can always be generated regardless of the temperature of the exhaust gas. The exhaust gas that has passed through the bypass flow path contains ammonia and flows into the reduction catalyst. Thereafter, NOx contained in the exhaust gas is reduced by ammonia in the reduction catalyst, and purified as nitrogen and water.

  Patent Document 3 discloses a reduction catalyst provided in an exhaust gas passage of a diesel engine, a solid or liquid reducing agent disposed adjacent to an exhaust gas passage downstream of the reduction catalyst, and a downstream of the reduction catalyst. A heating unit for heating the solid or liquid reducing agent using the heat of the exhaust gas, and a supply means for supplying ammonia generated by heating of the heating unit to the upstream side of the reduction catalyst. An exhaust gas purification device is disclosed. This exhaust gas purification device generates ammonia by transmitting heat of exhaust gas to a solid or liquid reducing agent via a heating unit. Ammonia is supplied into the exhaust gas by the supply means and flows into the reduction catalyst. Thereafter, NOx contained in the exhaust gas is reduced by ammonia in the reduction catalyst, and purified as nitrogen and water.

JP 2010-65648 A JP 2001-159308 A JP 2010-138883 A

However, in the exhaust gas purifying apparatus described in Patent Document 2, since the solid reducing agent is constantly heated by the solid reducing agent heating means, the amount of fuel consumed for operating the solid reducing agent heating means increases. In general, the fuel for operating the solid reductant heating means is also used as the fuel supplied to the internal combustion engine. Therefore, if the fuel is consumed by the solid reductant heating means, the fuel consumption is reduced. There was a problem. Furthermore, when the internal combustion engine is under a high load, the amount of exhaust gas increases, so that the amount of reducing agent required also increases. Therefore, it is necessary to sublimate a large amount of reducing agent by increasing the heating temperature of the solid reducing agent. Therefore, when the heating output of the solid reducing agent heating means is increased, the amount of fuel consumed is also increased, so that there is a problem that the fuel consumption is greatly reduced.
Moreover, in the exhaust gas purification apparatus described in Patent Document 3, the solid or liquid reducing agent is provided downstream of the reduction catalyst, and the temperature of the exhaust gas is low, so that the generation efficiency of the gaseous reducing agent is low. there were.

  Therefore, the present invention solves such a problem, it is possible to generate a gaseous reducing agent efficiently by properly using a solid reducing agent and a liquid reducing agent according to the temperature of exhaust gas, and An object of the present invention is to provide an exhaust gas purification device and a purification method for an internal combustion engine that reduce fuel consumption.

An exhaust gas purification apparatus for an internal combustion engine according to the present invention that solves the above-mentioned problems is provided in an exhaust gas passage connected to the internal combustion engine, and a reduction catalyst that reduces NOx contained in the exhaust gas,
Reducing agent heating and supplying means for heating the solid reducing agent and supplying the fluid reducing agent released by heating the solid reducing agent to the exhaust gas passage upstream of the reduction catalyst;
Liquid reducing agent supply means for supplying the liquid reducing agent to the exhaust gas passage upstream of the reduction catalyst;
A temperature sensor for measuring the temperature of the exhaust gas passing through the exhaust gas passage;
Control means for controlling the supply of the reducing agent from at least one of the reducing agent heating supply means and the liquid reducing agent supply means in accordance with the measurement result of the temperature sensor.

According to the exhaust gas purification apparatus for an internal combustion engine, since the reducing agent heating and supplying means is provided, the fluid reducing agent released by heating the solid reducing agent is always supplied into the exhaust gas regardless of the temperature of the exhaust gas. Can do. Therefore, the fluid reducing agent can be supplied into the exhaust gas even in a low temperature range where the temperature of the exhaust gas is low. As a result, NOx in the low temperature exhaust gas can be reduced and purified, and deposits in the exhaust gas passage can be suppressed. In addition, since it is not necessary to quickly raise the temperature, such as post injection, which has been conventionally performed, fuel efficiency is improved.
Further, since the liquid reducing agent supply means capable of supplying the liquid reducing agent is provided, in a high temperature region where the temperature of the exhaust gas is high, the liquid reducing agent is hydrolyzed by supplying the liquid reducing agent into the exhaust gas. It becomes a gaseous reducing agent. Thereby, a gaseous reducing agent can be supplied in high temperature exhaust gas.
And when using a liquid reducing agent supply means, the consumption of the fuel for driving a reducing agent heating supply means can be reduced by stopping a reducing agent heating supply means. In particular, when the fuel for heating the reducing agent heating and supplying means is also used as the fuel supplied to the internal combustion engine, the fuel consumption of the reducing agent heating and supplying means is reduced, thereby reducing the fuel consumption. The influence can be reduced.

The control means includes
When the measurement result by the temperature sensor is lower than the hydrolysis temperature at which the liquid reducing agent is hydrolyzed, the reducing agent heating and supplying means is controlled to heat the solid reducing agent to release the fluid reducing agent. ,
When the measurement result by the temperature sensor is equal to or higher than the hydrolysis temperature, the liquid reducing agent supply means may be controlled to supply the liquid reducing agent into the exhaust gas.

  In this way, when the liquid reducing agent is at or above the hydrolysis temperature at which it is hydrolyzed, the liquid reducing agent is supplied into the exhaust gas, so that the temperature of the exhaust gas can be used to make the liquid reducing agent a gaseous reducing agent . As a result, it is possible to prevent the liquid reducing agent from flowing into the reduction catalyst as a liquid without being vaporized and being discharged into the atmosphere as a liquid without serving as a reducing agent.

  Further, the fluid reducing agent released by heating the solid reducing agent may be supplied to the exhaust gas passage between the position where the liquid reducing agent is supplied and the reduction catalyst.

  In this way, in order to supply the fluid reducing agent released by heating the solid reducing agent downstream from the position where the liquid reducing agent is supplied, the fluid reducing agent and the liquid reducing agent are simultaneously supplied into the exhaust gas passage. However, the fluid reducing agent is not cooled.

And regenerative power supply means for regenerating brake energy during deceleration of the vehicle traveling by the driving force of the internal combustion engine to generate electric power and supplying the electric power to the reducing agent heating supply means,
The reducing agent heating and supplying means may heat the solid reducing agent with electric power supplied by the regenerative power supplying means.

  Thus, since the regenerative electric power supply means is provided, electric power can be supplied to the reducing agent heating supply means without consuming fuel. Thereby, the consumption of fuel can be reduced. Therefore, the influence on fuel consumption can be reduced.

Further, the regenerative power supply means includes a regenerative generator that generates regenerative power from the brake energy, and a regenerative power battery that stores regenerative power generated by the regenerative generator,
Electric power may be supplied from the regenerative power battery to the reducing agent heating and supplying means.

  Thus, since the regenerative power supply means includes the regenerative generator and the regenerative power battery, the regenerative power can be stored. Thereby, regenerative power can be used effectively. Specifically, electric power can be supplied when the solid reducing agent is heated by the reducing agent heating supply means.

The purification method of the present invention is provided in an exhaust gas passage connected to an internal combustion engine, and heats the reduction catalyst for reducing NOx contained in the exhaust gas and the solid reducing agent, and is released by heating the solid reducing agent. A reducing agent heating / supplying means for supplying the fluid reducing agent to the exhaust gas passage upstream of the reduction catalyst; and a liquid reducing agent supply means for supplying the liquid reducing agent to the exhaust gas passage upstream of the reduction catalyst; A temperature sensor for measuring the temperature of the exhaust gas passing through the exhaust gas passage, and reduction from at least one of the reducing agent heating supply means and the liquid reducing agent supply means according to a measurement result by the temperature sensor. A purification method using an exhaust gas purification device of an internal combustion engine comprising a control means for controlling supply of the agent,
A reducing agent is supplied from at least one of the reducing agent heating supply unit and the liquid reducing agent supply unit in accordance with a measurement result by the temperature sensor.

According to the purification method, the fluid reducing agent released by heating the solid reducing agent can be always supplied into the exhaust gas regardless of the temperature of the exhaust gas. Therefore, the fluid reducing agent can be supplied into the exhaust gas even in a low temperature range where the temperature of the exhaust gas is low. As a result, NOx in the low temperature exhaust gas can be reduced and purified, and deposits in the exhaust gas passage can be suppressed. In addition, since it is not necessary to quickly raise the temperature, such as post injection, which has been conventionally performed, fuel efficiency is improved.
In a high temperature range where the temperature of the exhaust gas is high, the liquid reducing agent is hydrolyzed to become a gaseous reducing agent by supplying the liquid reducing agent into the exhaust gas. Thereby, a gaseous reducing agent can be supplied in high temperature exhaust gas.
And when using a liquid reducing agent supply means, the consumption of the fuel for driving a reducing agent heating supply means can be reduced by stopping a reducing agent heating supply means. In particular, when the fuel for heating the reducing agent heating and supplying means is also used as the fuel supplied to the internal combustion engine, the fuel consumption of the reducing agent heating and supplying means is reduced, thereby reducing the fuel consumption. The influence can be reduced.

  According to the present invention, an exhaust gas purifying apparatus for an internal combustion engine that can generate a gaseous reducing agent efficiently by selectively using a solid reducing agent and a liquid reducing agent according to the temperature of the exhaust gas, and reduces fuel consumption. And a purification method can be provided.

It is the schematic which shows the structure of the exhaust gas purification apparatus which concerns on 1st embodiment of this invention. It is the schematic which shows the apparatus connected to the exhaust gas path which concerns on this embodiment. It is the schematic which shows the relationship between the ammonia supply control part which concerns on this embodiment, and its peripheral device. It is a figure which shows the exhaust gas purification flow of an exhaust gas purification apparatus. It is a figure which shows the detailed flow which heats a solid reducing agent. It is a figure which shows the detailed flow which injects urine water supply. It is the schematic which shows the structure of the exhaust gas purification apparatus which concerns on 2nd embodiment of this invention. It is the schematic which shows the relationship between the reducing agent control means which concerns on this embodiment, and its peripheral device. It is a figure which extracts and shows a part of regenerative electric power supply means and the traveling system of a vehicle. It is a figure explaining the heating mechanism for heating a coil heater. It is a figure which shows the detailed flow which heats a reducing agent with an exhaust gas purification apparatus.

  Hereinafter, an exhaust gas purification apparatus for an internal combustion engine and a purification method using the exhaust gas purification apparatus according to the present invention will be described in detail with reference to the drawings. It should be noted that the dimensions, materials, shapes, relative arrangements, and the like of the components described in the following examples are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative. It is just an example. Further, the case where a diesel engine is used as the internal combustion engine will be described, but the present invention is not limited to this, and the present invention can also be applied to an in-cylinder direct injection type lean burn gasoline engine or the like.

FIG. 1 is a schematic diagram showing a configuration of an exhaust gas purification apparatus according to the first embodiment of the present invention. Further, FIG. 2 is a schematic view showing a device connected to the exhaust gas passage according to the present embodiment. FIG. 3 is a schematic diagram showing the relationship between the ammonia supply control unit and its peripheral devices according to this embodiment.
As shown in FIGS. 1 to 3, an exhaust gas purification device 3 of a diesel engine (hereinafter referred to as “engine 1”) includes a DOC (Diesel Oxidation Catalyst) 6 and a DPF (Diesel Particulate Filter) 8. And an SCR (Selective Catalyst Reduction) catalyst 10, which are disposed in the exhaust gas passage 2.

  In the engine 1, the fuel injection timing and the injection amount are electronically controlled by an ECU (Electronic Control Unit, not shown), and the combustion chamber 7 is connected to the fuel injection valve 5 provided for each cylinder at the injection timing and the injection amount. Fuel is injected into the inside. The ECU includes a microcomputer including a CPU, a ROM, and a RAM (not shown). The ECU also controls the operating state of the engine 1 according to the operating conditions of the engine 1 and the driver's request.

The exhaust gas purification device 3 is provided between an ammonia supply control unit 18 that controls supply of ammonia, which will be described later, a first temperature sensor 20 that measures the temperature of exhaust gas flowing into the DOC 6, and the DOC 6 and the DPF 8. A second temperature sensor 22 that measures the temperature of the exhaust gas flowing into the exhaust gas, and a third temperature sensor 24 that is provided immediately downstream of the DPF 8 and measures the temperature of the exhaust gas.
Each temperature sensor 20, 22, 24 outputs the measurement result as an electrical signal to the ammonia supply controller 18.

Further, the exhaust gas passage 2 is provided on the downstream side of the DPF 8 and is provided on the downstream side of the first NOx concentration sensor 28 for measuring the concentration of NOx contained in the exhaust gas. An oxygen concentration sensor 26 that measures the oxygen concentration and a second NOx concentration sensor 30 that is provided downstream of the SCR catalyst 10 and measures the concentration of NOx contained in the exhaust gas are disposed.
The first NOx concentration sensor 28, the second NOx concentration sensor 30, and the oxygen concentration sensor 26 each output a measurement result as an electric signal to the ammonia supply control unit 18. The ammonia supply control unit 18 estimates the amount of ammonia contained in the exhaust gas based on the measurement result by the oxygen concentration sensor 26.

In Doc6, NO contained in the exhaust gas is oxidized NO ₂ is generated. The exhaust gas containing NO ₂ after passing through the DOC 6 subsequently flows into the DPF 8. The DPF 8 captures PM (Particulate Matter) contained in the exhaust gas. The DOC 6 and the DPF 8 are accommodated in one case 9. When the amount of PM trapped in the DPF 8 exceeds a predetermined amount, the exhaust gas temperature is raised and PM is burned. The temperature of the exhaust gas entering the DPF 8 is measured by the second temperature sensor 22.

  Further, in the exhaust gas passage 2, the liquid reducing agent supply means 12 for supplying urea water to the exhaust gas passage 2 and the solid reducing agent 38 are heated, and the gaseous reducing agent released by the heating is supplied from the SCR catalyst 10. A reducing agent heating and supplying means 13 for supplying the exhaust gas passage 2 on the upstream side is disposed.

  The liquid reducing agent supply means 12 is provided in the exhaust gas passage 2 between the DPF 8 and the SCR catalyst 10, and supplies the urea water to the injection nozzle 46, the urea water to the injection nozzle 46, and the supply amount of the urea water. And a urea water supply pump 47 having a variable mechanism capable of adjusting the temperature and a urea water tank 48 for storing urea water.

The operation and stop of the urea water supply pump 47 are controlled by the ammonia supply controller 18. The ammonia supply control unit 18 stops the urea water supply pump 47 when the temperature of the exhaust gas measured by the third temperature sensor 24 is less than about 200 ° C., and urea water when the temperature of the exhaust gas is about 200 ° C. or more. The supply pump 47 is operated.
In general, when the temperature of the exhaust gas is less than about 200 ° C., the decomposition reaction of urea water injected into the exhaust gas hardly proceeds, and ammonia slip may occur. Therefore, when the temperature of the exhaust gas measured by the third temperature sensor 24 is about 200 ° C. or higher, the ammonia supply control unit 18 operates the urea water supply pump 47 to inject urea water.

  The urea water supplied from the urea water supply pump 47 is injected into the exhaust gas from the injection nozzle 46. The urea water sprayed into the exhaust gas is hydrolyzed to produce ammonia. The exhaust gas containing ammonia flows into the SCR catalyst 10. In the SCR catalyst 10, NOx contained in the exhaust gas is reduced by ammonia. The exhaust gas that does not contain NOx is discharged into the atmosphere through the exhaust gas passage 2.

By the way, when ammonia is supplied in excess of the amount of ammonia necessary for reducing NOx, ammonia that has not been used for NOx reduction causes ammonia slip, and the SCR catalyst 10 is not used for NOx reduction reaction. It may pass through and be discharged to the atmosphere. Therefore, the ammonia supply control unit 18 calculates the amount of ammonia necessary for reducing NOx contained in the exhaust gas based on the measurement result by the first NOx concentration sensor 28, and generates the ammonia amount. Calculate the necessary supply amount of urea water.
The adjustment of the urea water supply amount is performed by the ammonia supply control unit 18 controlling the variable mechanism of the urea water supply pump 47. The urea water injected into the exhaust gas passage 2 is hydrolyzed to become ammonia.

  Further, the ammonia supply control unit 18 estimates the ammonia amount contained in the exhaust gas based on the measurement result by the oxygen concentration sensor 26, and confirms whether or not the ammonia amount is included in a predetermined range set in advance. To do. That is, it is confirmed whether or not ammonia generated by the urea water injection is included in a predetermined range. If the estimated ammonia amount is not included in the predetermined range, the ammonia supply control unit 18 calculates the urea water supply amount again.

  Further, the ammonia supply control unit 18 calculates the NOx purification rate based on the measurement results by the first NOx concentration sensor 28 and the second NOx concentration sensor 30, and whether or not the NOx purification rate is equal to or higher than a preset target purification rate. Confirm. If the NOx purification rate is less than the target purification rate, the ammonia supply control unit 18 calculates the urea water supply amount again.

  When the temperature of the exhaust gas is about 200 ° C. or higher, the ammonia supply control unit 18 operates the urea water supply pump 47 to supply urea water into the exhaust gas as described above. On the other hand, when the temperature of the exhaust gas is less than about 200 ° C., the urea water supply pump 47 is stopped to stop the injection of urine water supply, and ammonia is generated from the reducing agent heating supply means 13.

  The reducing agent heating and supplying means 13 includes a storage container 34 for storing the solid reducing agent 38, a coil heater 36 for heating the solid reducing agent 38, one end connected to the storage container 34, and the other end to the exhaust gas passage 2. A connected reducing agent feed pipe 37 and a check valve 42 provided in the reducing agent feed pipe 37 are provided.

A solid reducing agent 38 is stored in the storage container 34. A coil heater 36 is provided so as to surround the outer periphery of the storage container 34. By heating the solid reducing agent 38 with the coil heater 36, ammonia can be generated.
Operation and stop of the coil heater 36 are controlled by the ammonia supply controller 18. The ammonia supply controller 18 operates the coil heater 36 simultaneously with the operation of the engine 1, and stops the coil heater 36 when the temperature of the exhaust gas measured by the third temperature sensor 24 is about 200 ° C. or higher.

  The amount of ammonia released by heating the solid reducing agent 38 varies depending on the heating temperature. Specifically, the amount of ammonia increases as the heating temperature increases. The heating output of the coil heater 36 is controlled by the ammonia supply controller 18. Based on the NOx concentration in the exhaust gas measured by the first NOx concentration sensor 28, the ammonia supply control unit 18 calculates the heating output of the coil heater 36 so that an amount of ammonia necessary for the reduction of the NOx is generated. At the same time, the coil heater 36 is adjusted to achieve the heating output.

  As the solid reducing agent 38, an adsorbent that adsorbs ammonia or a complex that chemically contains ammonia can be used. For example, when ammonia is adsorbed on the adsorbent, the ammonia is desorbed from the adsorbent by the heat of the exhaust gas. In the case of a complex containing ammonia, ammonia is generated by the decomposition of the complex or sublimation from the complex by the heat of the exhaust gas.

  The check valve 42 is provided at the end of the reducing agent supply pipe 37 on the exhaust gas passage side. The check valve 42 has a function of supplying the generated ammonia to the exhaust gas passage 2 and preventing the exhaust gas from flowing into the reducing agent supply pipe 37 from the exhaust gas passage 2.

Ammonia released by heating the solid reducing agent 38 passes through the check valve 42 and is supplied to the exhaust gas passage 2. Since the other end of the reducing agent supply pipe 37 is connected to the exhaust gas passage 2 between the urea water injection nozzle 46 and the SCR catalyst 10, ammonia is supplied downstream from the injection nozzle 46.
The amount of ammonia contained in the exhaust gas flowing in the exhaust gas passage 2 is estimated by the oxygen concentration measured by the oxygen concentration sensor 26 disposed between the other end of the reducing agent supply pipe 37 and the SCR catalyst 10. The

  Ammonia supplied into the exhaust gas passage 2 flows into the SCR catalyst 10 together with the exhaust gas. In the SCR catalyst 10, NOx contained in the exhaust gas is reduced by ammonia. The exhaust gas that does not contain NOx is discharged into the atmosphere through the exhaust gas passage 2.

When the temperature of the exhaust gas immediately downstream of the DPF 8 is less than about 200 ° C., the exhaust gas purification apparatus 3 having the above-described configuration generates ammonia by heating the solid reducing agent 38 with the coil heater 36, and the ammonia is generated by the SCR catalyst 10. Supplied into the exhaust gas immediately upstream. In such a case, urea water is not injected.
On the other hand, when the temperature of the exhaust gas immediately downstream of the DPF 8 becomes about 200 ° C. or more, the coil heater 36 is stopped and the urea water supply pump 47 is operated to supply urea water into the exhaust gas. And the ammonia is supplied into the exhaust gas immediately upstream of the SCR catalyst 10. That is, when the temperature of the exhaust gas immediately downstream of the DPF 8 becomes about 200 ° C. or higher, only the liquid reducing agent supply means 12 is operated and the coil heater 36 is stopped. Thereby, the fuel for heating the coil heater 36 is not consumed. Since the fuel for heating the coil heater 36 is also used as the fuel supplied to the engine 1, the fuel consumption can be greatly reduced by reducing the fuel consumption. When the amount of NOx contained in the exhaust gas is larger than the maximum ammonia amount that can be generated by injecting urea water when the engine 1 is under a high load, etc., solid reduction is performed by using the coil heater 36 together. The agent 38 is heated to generate ammonia.

Next, an exhaust gas purification flow of the exhaust gas purification apparatus 3 having the above-described configuration will be described with reference to FIG.
As shown in FIG. 4, first, the ignition switch is turned on to start the engine 1 (step S1).

Next, to measure the temperature _{T 3} of the exhaust gas immediately below DPF8 by the third temperature sensor 24 (step S2). Subsequently, the ammonia supply control unit 18 determines the temperature T ₃ of the exhaust gas of the urea water hydrolysable temperature, whether for example 200 ° C. or higher (step S4).
Ammonia supply control unit 18, in step S4, when the temperature _{T 3} of the exhaust gas is below 200 ° C., by heating the solid reductant 38 (step S6), and to generate ammonia.
On the other hand, in step S4, the temperature _{T 3} of the exhaust gas is not less than 200 ° C., the ammonia supply control unit 18 injects urea water into the exhaust gas passage 2 (step S8). The urea water injected into the exhaust gas is hydrolyzed to generate ammonia. The generated ammonia flows into the SCR catalyst 10 together with the exhaust gas.
Incidentally, by operating continuously engine 1, if the temperature T ₃ of the exhaust gas is equal to or higher than 200 ° C. from the state of less than 200 ° C., stop the coil heater 36 which was running, injects urea water To do.

Next, the ammonia supply control unit 18 determines whether or not the amount of NOx contained in the exhaust gas is larger than the maximum amount of ammonia that can be generated by injecting urea water (step S10). The amount of NOx contained in the exhaust gas is calculated based on the NOx concentration measured by the first NOx concentration sensor 28. The maximum ammonia amount is the ammonia amount supplied into the exhaust gas when the supply amount of the urea water supply pump 47 is maximized, and is a value determined in advance by design or the like.
In step S10, when the amount of NOx contained in the exhaust gas is larger than the maximum ammonia amount, the reducing agent heating and supplying means 13 is also used. That is, the solid reducing agent 38 is heated by the coil heater 36 (step S6) to generate ammonia.
On the other hand, in step S10, when the amount of NOx contained in the exhaust gas is equal to or less than the maximum ammonia amount, only the liquid reducing agent supply means 12, that is, only the injection of urea water is performed to generate ammonia.

Next, the detailed flow which heats the solid reducing agent 38 is demonstrated using FIG.
As shown in FIG. 5, the ammonia supply control unit 18 first operates the coil heater 36 (step S20).

Next, the NOx concentration D1 contained in the exhaust gas is measured by the _first NOx concentration sensor 28 (step S22). The ammonia supply control unit 18 based on the NOx concentration D _1, to calculate the amount of ammonia required for reducing NOx contained in the exhaust gas, the solid reducing agent required to generate the ammonia amount A heating temperature of 38 is calculated. Subsequently, the heating output of the coil heater 36 is adjusted so that the coil heater 36 reaches the heating temperature (step S24).

Next, the oxygen concentration contained in the exhaust gas is measured by the oxygen concentration sensor 26 (step S26). Then, the ammonia supply control unit 18 estimates the amount of ammonia contained in the exhaust gas based on the measurement result by the oxygen concentration sensor 26.
Further, the NOx concentration D2 contained in the exhaust gas is measured by the _second NOx concentration sensor 30. Then, based on the NOx concentration _{D 1} measured by the NOx concentration _{D 2} and step S22, the ammonia supply control unit 18 calculates the NOx purification ratio.

Next, the ammonia supply control unit 18 determines whether or not the amount of ammonia contained in the exhaust gas is included in a predetermined range set in advance and the NOx purification rate is equal to or higher than a preset target purification rate ( Step S28).
If the amount of ammonia contained in the exhaust gas is not within the predetermined range or if the NOx purification rate is less than the target purification rate, the heating output of the coil heater 36 is adjusted again in step S24.
On the other hand, the amount of ammonia contained in the exhaust gas within a predetermined range, and the NOx purification rate is not less than the target purification rate, again, to measure the exhaust gas temperature T ₃ at Step 2.

Next, a detailed flow for injecting urea water will be described with reference to FIG.
As shown in FIG. 6, for measuring the NOx concentration _{D 1} contained in the exhaust gas at a first 1NOx concentration sensor 28 (step S30). The ammonia supply control unit 18 based on the NOx concentration D _1, determines the supply amount of the urea water required for reducing the NOx contained in the exhaust gas (step S32).

  Next, the ammonia supply control unit 18 operates the urea water supply pump 47 to inject urea water into the exhaust gas passage 2 (step S34). The adjustment of the urea water supply amount is performed by controlling the variable mechanism of the urea water supply pump 47. The urea water injected into the exhaust gas passage 2 is hydrolyzed to become ammonia.

Next, to measure the oxygen concentration in the oxygen concentration sensor 26 and the 2NOx concentration sensor 30 contained in the exhaust gas and the NOx concentration _{D 2,} respectively (step S36). The ammonia supply control unit 18 estimates the amount of ammonia contained in the exhaust gas based on the NOx concentration D _2. Further, the ammonia supply control unit 18 based on the NOx concentration _{D 1} and the NOx concentration _{D 2,} and calculates the NOx purification ratio.

Next, the ammonia supply control unit 18 determines whether or not the amount of ammonia contained in the exhaust gas is included in a predetermined range set in advance and the NOx purification rate is equal to or higher than a preset target purification rate ( Step S38).
When the ammonia amount contained in the exhaust gas is not within the predetermined range or when the NOx purification rate is less than the target purification rate, the supply amount of urea water is calculated and determined in step S32.
On the other hand, when the amount of ammonia contained in the exhaust gas is within the predetermined range and the NOx purification rate is equal to or higher than the target purification rate, the NOx amount and the maximum ammonia amount are compared in step S10.

  While the engine 1 is in operation, the above-described steps S2 to S38 are repeated to continue supplying ammonia into the exhaust gas.

As described above, according to the exhaust gas purifying apparatus 3 according to the present embodiment, since the reducing agent heating supply means 13 and the liquid reducing agent supply means 12 are provided, ammonia is always contained in the exhaust gas regardless of the temperature of the exhaust gas. Can be supplied to. Specifically, since the reducing agent heating and supplying means 13 is provided, ammonia can be supplied into the exhaust gas even in a low temperature region where the temperature of the exhaust gas is low, for example, below about 200 ° C. where urea water cannot be hydrolyzed. Thus, NOx in the low temperature exhaust gas can be reduced and purified, and deposits in the exhaust gas passage 2 can be suppressed. Therefore, the NOx purification efficiency by the SCR catalyst 10 can be improved. In addition, since it is not necessary to quickly raise the temperature, such as post injection, which has been conventionally performed, fuel efficiency is improved.
Further, since the liquid reducing agent supply means 12 is provided, ammonia is generated by supplying urea water into the exhaust gas in a high temperature region where the temperature of the exhaust gas is high, for example, about 200 ° C. or higher where urea water can be hydrolyzed. Can be made. When the liquid reducing agent supply unit 12 is used, the consumption of fuel for driving the reducing agent heating supply unit 13 can be reduced by stopping the reducing agent heating supply unit 13. In particular, when the fuel for heating the coil heater 36 is also used as the fuel supplied to the engine 1, the fuel consumption of the reducing agent heating and supplying means 13 is reduced, thereby affecting the fuel efficiency. Can be reduced.

  Next, a second embodiment of the present invention will be described. In the following description, portions corresponding to the above-described embodiment are denoted by the same reference numerals, description thereof is omitted, and differences are mainly described. The exhaust gas purification apparatus of the second embodiment has a function of heating the coil heater 36 using regenerative power.

FIG. 7 is a schematic diagram showing the configuration of the exhaust gas purifying apparatus according to the second embodiment of the present invention. FIG. 8 is a schematic view showing the relationship between the reducing agent control means according to the present embodiment and its peripheral devices.
As shown in FIGS. 7 and 8, the exhaust gas purifying apparatus 23 according to the present embodiment stores an alternator 4 in which rotation of the crankshaft of the engine 1 is transmitted via a belt, and stores electric power generated by the alternator 4. A first battery 43 for measuring, a first voltmeter 44 for measuring the voltage of the first battery 43, and a reducing agent control means 16 to be described later. The first battery 43 is charged by the power generation of the alternator 4. The voltage of the first battery 43 measured by the first voltmeter 44 is output to the reducing agent control means 16.
The reducing agent control means 16 includes an ammonia supply control unit 18 and a heating device power control unit 45. The heating device power control unit 45 controls the regenerative power supply means 14 described later.

FIG. 9 is a diagram showing a part of the regenerative power supply means 14 and a part of the vehicle traveling system.
As shown in FIG. 9, the exhaust gas purifying device 23 regenerates brake energy at the time of deceleration of the vehicle traveling by the driving force of the engine 1 to generate electric power and supplies the electric power to the coil heater 36. 14 is provided.
The regenerative power supply means 14 includes a retarder 32 that generates regenerative power from brake energy, a second battery 40 that stores regenerative power generated by the retarder 32, and a second voltmeter that measures the voltage of the second battery 40. 41.
The retarder 32 includes a rotor (not shown) that rotates integrally with the propeller shaft 11 and an electromagnet (not shown) fixed to the transmission 15, and can generate electric power by the rotation of the propeller shaft 11. . When detecting the depression of the brake pedal, the heating device power control unit 45 regenerates brake energy when the vehicle is decelerated and causes the retarder 32 to generate electric power. The generated regenerative power is stored in the second battery 40. Further, the voltage of the second battery 40 measured by the second voltmeter 41 is output to the reducing agent control means 16.

FIG. 10 is a diagram illustrating a heating mechanism that heats the coil heater 36.
As shown in FIG. 10, when the voltage of the second battery 40 measured by the second voltmeter 41 is larger than a predetermined voltage (normal time), the battery changeover switch 50 is connected to the second battery 40 side. The electric power from the second battery 40 is supplied to the coil heater 36.
On the other hand, when the voltage of the second battery 40 measured by the second voltmeter 41 is lower than the predetermined voltage and the coil heater 36 cannot be heated, the battery changeover switch 50 is connected to the first battery 43 side. Then, electric power is supplied from the first battery 43 to the coil heater 36. Switching of the battery selector switch 50 is controlled by the heating device power control unit 45.

  When power is supplied from the first battery 43, the heating device power control unit 45 periodically measures the voltage of the second battery 40, and the regenerative power obtained when the second battery 40 is decelerated. When the voltage of the second battery 40 becomes larger than the predetermined voltage, the battery changeover switch 50 is operated to supply the electric power from the second battery 40 to the coil heater 36.

Next, the detailed flow which heats the solid reducing agent 38 with the exhaust gas purification apparatus 23 which consists of the structure mentioned above is demonstrated using FIG.
As shown in FIG. 11, first, similarly to the first embodiment, steps S20 to S28 are performed.
Next, to measure the voltage _{V 2} of the second battery 40 at a second voltmeter 41 (step S42).
Subsequently, a heating device for a power control unit 45 determines the voltage V ₂ of the second battery 40 whether greater than the predetermined voltage (step S44).
Then, when the voltage _{V 2} of the second battery 40 is greater than a predetermined voltage, it is connected to the second battery 40 side by operating the battery switching switch 50 (step S46). And the electric power from the 2nd battery 40 is supplied to the coil heater 36 (step S48).
On the other hand, the voltage _{V 2} of the second battery 40 may less than the predetermined voltage, is connected to the first battery 43 side by operating the battery switching switch 50 (step S50). And the electric power from the 1st battery 43 is supplied to the coil heater 36 (step S52).

As described above, according to the exhaust gas purifying apparatus 23 according to the present embodiment, since the regenerative power supply means 14 is provided, it is possible to supply power to the coil heater 36 without consuming fuel. Thereby, the consumption of fuel can be reduced. Therefore, the influence on fuel consumption can be reduced.
Further, the regenerative power supply means 14 includes the retarder 32 and the second battery 40, and can store regenerative power. Thereby, regenerative power can be used effectively. Furthermore, according to the exhaust gas purification apparatus 23, the effect demonstrated by 1st embodiment can also be acquired.

1 Engine 2 Exhaust gas passage 3 Exhaust gas purification device 4 Alternator 5 Fuel injection valve 6 DOC
7 Combustion chamber 8 DPF
9 Case 10 SCR catalyst 11 Propeller shaft 12 Liquid reducing agent supply means 13 Reducing agent heating supply means 14 Regenerative power supply means 15 Transmission 16 Reducing agent control means 18 Ammonia supply control unit 20 First temperature sensor 22 Second temperature sensor 23 Exhaust gas Purifying device 24 Third temperature sensor 26 Oxygen concentration sensor 28 First NOx concentration sensor 30 Second NOx concentration sensor 32 Retarder 34 Storage container 36 Coil heater 37 Reductant feed pipe 38 Solid reductant 40 Second battery 41 Second voltmeter 42 Reverse Stop valve 43 First battery 44 First voltmeter 45 Electric power control unit 46 for heating device Injection nozzle 47 Pump for urea water supply 48 Urea water tank 50 Battery switch

Claims (6)

A reduction catalyst provided in an exhaust gas passage connected to the internal combustion engine for reducing NOx contained in the exhaust gas;
Reducing agent heating and supplying means for heating the solid reducing agent and supplying the fluid reducing agent released by heating the solid reducing agent to the exhaust gas passage upstream of the reduction catalyst;
Liquid reducing agent supply means for supplying the liquid reducing agent to the exhaust gas passage upstream of the reduction catalyst;
A temperature sensor for measuring the temperature of the exhaust gas passing through the exhaust gas passage;
An internal combustion engine comprising: control means for controlling supply of the reducing agent from at least one of the reducing agent heating supply means and the liquid reducing agent supply means in accordance with a measurement result of the temperature sensor. Exhaust gas purification equipment. The control means includes
When the measurement result by the temperature sensor is lower than the hydrolysis temperature at which the liquid reducing agent is hydrolyzed, the reducing agent heating and supplying means is controlled to heat the solid reducing agent to release the fluid reducing agent. ,
2. The internal combustion engine according to claim 1, wherein when the measurement result by the temperature sensor is equal to or higher than the hydrolysis temperature, the liquid reducing agent supply means is controlled to supply the liquid reducing agent into the exhaust gas. Exhaust gas purification equipment.   The fluid reducing agent released by heating the solid reducing agent is supplied to the exhaust gas passage between the position where the liquid reducing agent is supplied and the reduction catalyst. An exhaust gas purification device for an internal combustion engine. Regenerative power supply means for regenerating brake energy at the time of deceleration of the vehicle traveling by the driving force of the internal combustion engine to generate electric power, and supplying the electric power to the reducing agent heating supply means,
The exhaust gas of the internal combustion engine according to any one of claims 1 to 3, wherein the reducing agent heating and supplying means heats the solid reducing agent with electric power supplied from the regenerative power supplying means. Purification equipment. The regenerative power supply means includes a regenerative generator that generates regenerative power from the brake energy, and a regenerative power battery that stores regenerative power generated by the regenerative generator,
The exhaust gas purifying apparatus for an internal combustion engine according to claim 4, wherein power is supplied from the regenerative power battery to the reducing agent heating and supplying means. A reduction catalyst that is provided in an exhaust gas passage connected to the internal combustion engine and that reduces NOx contained in the exhaust gas, heats the solid reducing agent, and releases the fluid reducing agent released by heating the solid reducing agent from the reduction catalyst. A reductant heating supply means for supplying the exhaust gas passage on the upstream side, a liquid reductant supply means for supplying the liquid reductant to the exhaust gas passage on the upstream side of the reduction catalyst, and the gas passing through the exhaust gas passage. A temperature sensor that measures the temperature of the exhaust gas; and a control unit that controls supply of the reducing agent from at least one of the reducing agent heating supply unit and the liquid reducing agent supply unit according to a measurement result of the temperature sensor. A purification method using an exhaust gas purification apparatus for an internal combustion engine comprising:
A purification method, wherein a reducing agent is supplied from at least one of the reducing agent heating supply means and the liquid reducing agent supply means in accordance with a measurement result by the temperature sensor.

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