JP2002155732A - Reducing agent feeder of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reducing agent feeder of internal combustion engine for feeding a prescribed quantity of a reducing agent immediately without delay in response to a command to feed the reducing agent. SOLUTION: The reducing agent feeder 16 is mounted in an exhaust pipe 10 of the internal combustion engine 1 for feeding a reducing agent to an NOx catalyst 9 to clean nitrogen oxides emitted from the internal combustion engine 1. The reducing agent feeder 16 comprises a main reducing agent storage tank 20 for storing the solid reducing agent, a reducing gas generating part 30 for gasifying the solid reducing agent stored in the main reducing agent storage tank 20, an auxiliary reducing agent storage tank 40 for temporality storing the reducing agent gasified by the reduced gas generating part 30, an ECU 15 for calculating the quantity of the reducing agent to be fed to the NOx catalyst 9 based on the operation condition of the main body of the engine, and a reducing agent applying valve 50 for applying the reducing agent stored in the auxiliary reducing agent storage tank 40 to the upstream side of the NOx catalyst 9 in the exhaust pipe 10 of the internal combustion engine 1 based on the quantity to be fed calculated by the ECU 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for supplying a reducing agent for an internal combustion engine, and more particularly to a reducing apparatus for supplying a reducing agent to a NOx catalyst for purifying nitrogen oxides (NOx) discharged from the internal combustion engine. The present invention relates to an agent supply device.

[0002]

2. Description of the Related Art As a reducing agent supply device which is provided in an exhaust system of an internal combustion engine and supplies a reducing agent to a NOx catalyst for purifying nitrogen oxides (hereinafter simply referred to as NOx) discharged from the internal combustion engine, for example, And a reducing agent supply device disclosed in JP-A-5-272331.

In the reducing agent supply apparatus disclosed in Japanese Patent Application Laid-Open No. 5-272331, urea CO (NH ₂ ) _2, which can reduce NOx at a high purification rate even at a low temperature, is employed as the reducing agent. It is supplied to the NOx catalyst to promote the purification of NOx contained in the exhaust gas.

More specifically, in response to a reducing agent supply command from an electronic control unit for engine control (hereinafter simply referred to as an ECU), solid urea stored in a storage tank is heated and gasified in a furnace tube. After that, the gasified urea is supplied to the upstream side of the NOx catalyst in the engine exhaust passage to promote the purification of NOx.

[0005] By the way, the solid reducing agent has a smaller volume than the gaseous reducing agent and the liquid reducing agent and is excellent in mountability on a vehicle, but cannot be supplied to the NOx catalyst because the particles are large as they are. Therefore, it is necessary to heat and gasify the solid reducing agent in the furnace tube as in the above-described reducing agent supply device, so that the NOx catalyst can be supplied to the NOx catalyst (transformation).

[0006]

However, in the conventional reducing agent supply device, after receiving the reducing agent supply instruction from the ECU, the reducing agent is gasified and supplied to the NOx catalyst, so that the reducing agent supply instruction is delayed. In some cases, a reducing agent was supplied.

In particular, a reducing agent containing solid urea as a main component not only takes a long time to gasify, but is also released to the atmosphere without reacting with NOx when supplied to a NOx catalyst at an appropriate timing. There is also a risk of emitting an unpleasant odor. Therefore, the development of a reducing agent supply device that can immediately respond to a reducing agent supply instruction is urgently required.

If the required supply amount of the reducing agent exceeds the amount of the reducing gas (reducing agent) generated in the furnace tube, the supply of the reducing gas cannot catch up with the required amount of the reducing agent. N
Could not supply Ox catalyst. Therefore, the purification rate of NOx in the NOx catalyst is greatly reduced, which may cause a reduction in exhaust emission.

Further, in the conventional reducing agent supply apparatus, the reducing gas generated in the furnace tube is directly supplied to the exhaust passage, so that the supply pressure of the reducing agent is not stable, and the appropriate amount of the reducing agent matches the required supply amount. Could not be supplied to the NOx catalyst.

It is therefore an object of the present invention to provide a reducing agent supply device for an internal combustion engine which can immediately supply a predetermined amount of reducing agent without delay in response to a reducing agent supply command.

[0011]

Means for Solving the Problems In order to solve the above technical problems, the present invention employs the following means. That is, a reducing agent supply device that is provided in an exhaust system of an internal combustion engine and supplies a reducing agent to a NOx catalyst that purifies nitrogen oxides discharged from the internal combustion engine. Agent storing means, reducing agent fluidizing means for fluidizing the solid reducing agent stored in the main reducing agent storing means so as to be supplied, and temporarily storing the reducing agent fluidized by the reducing agent fluidizing means. A reducing agent supply means for calculating a supply amount of the reducing agent to be supplied to the NOx catalyst based on an operating state of the engine body; and a reducing agent stored in the auxiliary reducing agent storing means. And a reducing agent adding means for adding the NOx catalyst upstream of the NOx catalyst in the exhaust system of the internal combustion engine based on the supply amount calculated by the reducing agent supply amount calculator.

According to the present invention employing such means, the reducing agent having fluidity which can be added by the reducing agent fluidizing means is prepared and stored in advance in the auxiliary reducing agent storage means. The reducing agent can be supplied immediately in response to the reducing agent supply instruction. Further, since the reducing gas is always stored in the auxiliary reducing agent storage tank 40, even when a large amount of the reducing agent is required, a stable supply of the reducing agent can be performed. The fluidization of the reducing agent is an action for facilitating the diffusion of the added reducing agent when the reducing agent is added by the reducing agent adding means. That is, in the present invention, fluidization generally refers to gasification, liquefaction, gelation, powdering, and other acts as fluidization.

The reducing agent fluidizing means desirably gasifies the solid reducing agent to give the reducing agent fluidity. That is, the solid reducing agent is gasified to improve the diffusion of the added reducing agent when added by the reducing agent adding means.

Further, the sub-reducing agent storage means includes a remaining amount calculating means for calculating a remaining amount of the reducing agent stored in the sub-reducing agent storing means, and the reducing agent fluidizing means comprises When the remaining amount calculated by the calculating means becomes less than a predetermined value, the solid reducing agent stored in the main reducing agent storing means is fluidized and supplied to the sub-reducing agent storing means. Is also good.

That is, according to this means, when the remaining amount of the reducing agent stored in the sub-reducing agent storage means becomes small, the solid reducing agent is newly fluidized and supplied to the sub-reducing agent storage means. I have. Therefore, the reducing agent can always be secured in the auxiliary reducing agent storage means without unnecessarily fluidizing the solid reducing agent. The volume of the solid reducing agent generally increases with gasification, liquefaction, and the like. Therefore, if the solid reducing agent is fluidized unnecessarily, it is necessary to increase the capacity of the storage means for the reducing agent in the device, which leads to an increase in the size of the device. Therefore, by fluidizing only the necessary amount as described above, the size of the apparatus can be minimized. Here, the predetermined value is a numerical value excluding zero, and is a value that can be arbitrarily set based on an empirical rule or the like.

The sub-reducing agent storage means includes a sub-reducing agent storage chamber for temporarily storing the fluidized reducing agent, a pressure detecting means for detecting a pressure in the sub-reducing agent storage chamber,
The remaining amount calculating means determines that the remaining amount of the reducing agent is large when the pressure detected by the pressure detecting means is high, and when the pressure detected by the pressure detecting means is low, It may be determined that the remaining amount is small. That is, the remaining amount of the reducing agent stored in the sub-reducing agent storage chamber is determined based on the pressure change in the sub-reducing agent storage chamber.

The sub-reducing agent storage means includes a sub-reducing agent storage chamber for temporarily storing the fluidized reducing agent, a pressure detecting means for detecting a pressure in the sub-reducing agent storage chamber,
Wherein the reducing agent addition means is provided in an exhaust system upstream of the NOx catalyst and adds a reducing agent stored in the sub-reducing agent storage chamber when the valve is opened to the upstream of the NOx catalyst; An addition valve control means for controlling the opening time of the reducing agent addition valve based on the pressure detected by the pressure detection means may be provided.

That is, in this means, the pressure in the secondary reducing agent storage chamber is detected by the pressure detecting means,
The supply pressure of the reducing agent acting on the reducing agent addition valve is grasped. Then, the supply amount of the reducing agent supplied from the reducing agent addition valve to the NOx catalyst is controlled so as to always reach the target value. Therefore, even if the pressure in the secondary reducing agent storage chamber fluctuates, the reducing agent that matches the required supply amount can be supplied to the NOx catalyst.

When the pressure in the secondary reducing agent storage chamber is high, the addition valve control means shortens the valve opening time of the reducing agent addition valve, and when the pressure in the secondary reducing agent storage is low,
The opening time of the reducing agent addition valve may be lengthened.

That is, when the pressure in the secondary reducing agent storage chamber is high, the valve opening time is shortened because the supply amount of the reducing agent per unit time increases, and conversely, when the pressure in the secondary reducing agent storage chamber is low, Since the supply amount of the reducing agent per unit time decreases, the valve opening time is lengthened, and the supply amount of the reducing agent added from the reducing agent addition valve is maintained at the target value.

In addition, the NOx catalyst is a selective reduction type NO that decomposes or reduces nitrogen oxides in the presence of a reducing agent.
x It is desirable to use a catalyst. Also, the solid reducing agent is
It is desirable to use a reducing agent that generates a reducing gas based on ammonia during gasification by the reducing agent fluidizing means.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings. The embodiment described below is an embodiment in which the reducing agent supply device of the present invention is applied to a vehicle diesel engine.

<Overview of Internal Combustion Engine> Before describing the reducing agent supply device of the present invention, a diesel engine equipped with the reducing agent supply device will be described with reference to FIG.

A diesel engine 1 (hereinafter simply referred to as an engine) includes a combustion chamber 2 including a piston 3, a cylinder 4, a cylinder head 5, and the like, and a fuel injection valve 6 for supplying engine fuel to the combustion chamber 2. And Further, an intake pipe 8 having an air flow meter 7 for measuring an air intake amount is connected to the combustion chamber 2. In the combustion chamber 2, air introduced through the intake pipe 8 and a fuel injection valve 6 are provided. And the engine fuel supplied by the engine is mixed to perform engine combustion by self-ignition.

On the other hand, the exhaust gas generated as a result of engine combustion in the combustion chamber 2 is connected to the combustion chamber 2 and is provided with an exhaust pipe having a selective reduction type NOx catalyst 9 and a muffler (not shown) in the middle of the path. It is exhausted to the atmosphere after 10. In the following description, the selective reduction type NOx catalyst may be simply referred to as a NOx catalyst.

Selective reduction type NOx provided in exhaust pipe 10
The catalyst 9 mainly includes nitrogen oxides (hereinafter simply referred to as N
Ox) is a catalyst that effectively purifies NOx, and is a catalyst that purifies NOx by reducing or decomposing it in the presence of a reducing agent.

The selective reduction type NOx catalyst 9 includes:
Examples thereof include a catalyst in which a transition metal such as Cu is supported on zeolite by ion exchange, a catalyst in which a noble metal is supported on zeolite or alumina, and a catalyst in which vanadium is supported on titanium.

On the upstream side of the NOx catalyst 9 in the exhaust pipe 10, a NOx sensor 11, an incoming gas pressure sensor 12,
An exhaust temperature sensor 13 and the like are provided.
On the downstream side, a reducing agent sensor 14 is provided. NO
The x sensor 11 is a sensor that measures the NOx concentration in the exhaust gas. The incoming gas pressure sensor 12 is a sensor that measures a pipe pressure (exhaust pressure) in the exhaust pipe 10. Further, the exhaust gas temperature sensor 13 is a sensor that measures the temperature of the exhaust gas flowing into the NOx catalyst 9. The reducing agent sensor 14 is a sensor that measures the concentration of the reducing agent in the exhaust gas. The various sensors are connected to input ports of an engine control electronic control unit 15 described later.

The engine 1 is controlled by an engine control electronic control unit 15 (hereinafter simply referred to as ECU 15) in accordance with the operating state. The ECU 15 includes a ROM (Read Only Memory), a RAM (Random Access Memory), a CPU (Central Processor Unit), an input port, an output port, an A / D converter, etc., which are interconnected by a bidirectional bus. For example, based on output signals from various sensors input to the input port and referring to various control maps developed on the ROM, for example, fuel injection control in the fuel injection valve 5 is performed. In the present invention,
The control of the reducing agent supply device 16 is also performed at the same time.

In the present invention, NOx in the exhaust gas discharged with the combustion of the engine of the engine 1 is converted into a NOx catalyst 9.
In order to purify the NOx catalyst 9, ammonia gas (NH3) ) Is provided. Hereinafter, the reducing agent addition device 16 which is the gist of the present invention will be described in detail with reference to FIG.

<Structure of Reducing Agent Supply Apparatus> First, the structure of the reducing agent supply apparatus 16 will be described. The reducing agent supply device 16 heats a main reducing agent storage tank 20 (main reducing agent storing means) for storing a solid reducing agent therein and a solid reducing agent stored in the main reducing agent storage tank 20. A reducing gas generating section 30 (reducing agent fluidizing means) for generating reducing gas, and a sub-reducing agent storage tank 40 (sub-reducing agent storing means) for temporarily storing the reducing gas generated by the reducing gas generating section 30. The reducing gas stored in the sub-reducing agent storage tank 40 is stored in the N
A reducing agent addition valve 50 (reducing agent adding means) for adding to the Ox catalyst 9.

The main reducing agent storage tank 20 has a tank body 21 for containing solid ammonium carbamate as a reducing agent therein, and a heat insulating member 22 provided so as to surround the tank body 21. , Is provided detachably with respect to a reducing gas generating unit 30 described later.

It should be noted that ammonium carbamate is a kind of reducing agent based on ammonia, and has the property of forming a solid at room temperature and gasifying at around 40 degrees Celsius.
Also, since it has a much stronger reducing action than conventional reducing agents such as hydrocarbons (HC) and carbon monoxide (CO), NOx can be purified with a high purification efficiency even at a relatively low temperature. It has such advantages.

The reason why the main reducing agent storage tank 20 is provided detachably with respect to the reducing gas generating section 30 is that when the ammonium carbamate stored inside is exhausted, a new product storing new ammonium carbamate is used. This is because it is possible to easily exchange the main reducing agent storage tank 20 with the empty main reducing agent storage tank after use. That is, the main reducing agent storage tank 20 is of a cartridge type.

The reducing gas generator 30 is connected to the main reducing agent storage tank 20 and has a heating chamber 31 for promoting gasification of the reducing agent stored in the main reducing agent storage tank 20. The heating chamber 31 surrounds the heating chamber 31. And an outer wall 32 provided. Also,
A space 33 is formed between the heating chamber 31 and the outer wall 32 and communicates with a water jacket (not shown) that serves as a circulation path for the engine cooling water. , The inside temperature of the heating chamber 31 rises.

Further, between the water jacket and the reducing gas generator 30 (space 33), the reducing gas generator 30 is provided.
An engine cooling water control valve 34 for regulating the flow of the engine cooling water to the engine is provided (see FIG. 1). The opening and closing operation of the engine cooling water control valve 34 is controlled by the ECU 15 so that the flow rate of the engine cooling water flowing into the heating chamber 31 is controlled so that the room temperature in the heating chamber 31 can be arbitrarily adjusted. ing.

Then, the engine cooling water control valve 34 is opened to guide the engine cooling water warmed by the engine combustion to the reducing gas generator 30 (space 33), and the room temperature in the heating chamber 31 rises. The ammonium carbamate in the main reducing agent storage tank 20 communicating with the heating chamber 31 is gasified for warming. In the following description, the gasified ammonium carbamate may be simply referred to as a reducing gas.

The sub-reducing agent storage tank 40 includes a tank body 41 for storing gaseous ammonium carbamate as a reducing agent, a heat insulating member 42 provided to surround the tank body 41, and a pressure inside the tank body 41. , And the tank main body 41 and the above-described reducing gas generating unit 30 are connected to each other through a connecting pipe 60. Therefore, the ammonium carbamate gasified in the reducing gas generator 30 is:
It flows into the auxiliary reducing agent storage tank 40 via the connecting pipe 60,
Once stored in the auxiliary reducing agent storage tank 40.

The reducing agent addition valve 50 is provided in the exhaust pipe 10 on the upstream side of the NOx catalyst 9 and receives a reducing agent supply command from the ECU 15 to convert the reducing gas stored in the auxiliary reducing agent storage tank 40 into NOx. The catalyst 9 is added to the exhaust pipe 10 on the upstream side.

The reducing agent addition valve 50 includes a nozzle portion 53 composed of a valve body 51 and a guide 52 for supporting the valve body 51, and a solenoid 54 for opening and closing the valve body 51 provided in the nozzle portion 53. The reducing gas connected to the connecting pipe 60 and stored in the auxiliary reducing agent storage tank 40 is supplied to the nozzle 53.
The reducing gas stored in the auxiliary reducing agent storage tank 40 flows down the introduction passage 55 and is guided to the nozzle portion 53. The reducing gas is added to the exhaust pipe 10 at an appropriate amount and at an appropriate timing by controlling the opening and closing of the valve element 51 by the solenoid 54.

A solenoid 5 for opening and closing the valve body 51
4 is controlled by the ECU 15 so that the valve element 51 is opened when the valve opening voltage is applied, and the reducing gas in the auxiliary reducing agent storage tank 40 is added to the exhaust pipe 10. In addition, the internal pressure of the auxiliary reducing agent storage tank 40 is always maintained higher than the exhaust pressure in the exhaust pipe 10,
When the reducing gas is added, the pressure difference is used to add the reducing gas. The pressure adjustment of the auxiliary reducing agent storage tank 40 will be described in detail in the following description of the reducing agent supply control.

<Control of Reducing Agent Supply Device> Hereinafter, the control of the reducing agent supply according to the above-described reducing agent supply device will be described. When the temperature of the engine cooling water reaches about 40 degrees Celsius with the start of operation of the engine 1 (start of engine combustion), the ECU 1
In 5, in order to gasify the reducing agent stored in the main reducing agent storage tank 20, first, the engine cooling water control valve 34 is opened and the engine cooling water is introduced into the reducing gas generation unit 30.

When the space temperature in the heating chamber 31 reaches about 40 degrees Celsius due to the engine cooling water, the ammonium carbamate in the main reducing agent storage tank 20 communicating with the reducing gas generator 30 is partially gasified. The secondary reducing agent is charged into the storage tank 40 via the connecting path 60.

At this time, the ECU 15 knows the amount of the reducing gas filled in the sub-reducing agent storage tank 40 based on the output value of the pressure sensor 43.
When the pressure in the auxiliary reducing agent storage tank 40 detected at 3 reaches a predetermined value, it is considered that the filling amount of the reducing gas has reached the specified amount, and the engine cooling water control valve 34 is closed, The gasification of ammonium carbamate is temporarily suspended.

Here, the predetermined value is a value obtained by various preliminary experiments, and includes, for example, the maximum allowable pressure of the auxiliary reducing agent storage tank 40, the average exhaust pressure in the exhaust pipe 10, and the amount of reducing gas per unit time. This value is arbitrarily set in consideration of the consumption amount and the like.

In the ECU 15, the pressure sensor 4
When the pressure of the sub-reducing agent storage tank 40 detected at 3 does not increase even after a predetermined time has elapsed, it is determined that the ammonium carbamate stored in the main reducing agent storage tank 20 has run out. A warning lamp 19 is lit on the indicator panel 18 to inform the driver of the fact.

Further, the ECU 15 controls the supply of the reducing agent to promote the purification of NOx, so that the engine load, the engine speed, the NOx concentration, the catalyst temperature, the charging pressure of the reducing gas,
The target supply amount of the reducing agent is calculated based on the above, and the control of the solenoid 54 in the reducing agent addition valve 50 is performed so that the reducing agent corresponding to the calculated target supply amount is added to the NOx catalyst 9 at an appropriate timing. Is going.

The control of the reducing agent addition valve 50 will be described in detail. The output signal from the air flow meter 7 and the output signal from the NOx sensor 11 are sent to the ECU 15 via the input port and the A / D converter as described above. Has been entered. Then, in the ECU 15, the air intake amount detected by the air flow meter 7 and the NO detected by the NOx sensor 11 are determined.
The amount of NOx discharged per unit time is calculated from the x concentration, and the target supply amount of the reducing agent corresponding to the calculated NOx discharge amount is set (reducing agent supply amount calculating means).

An output signal from the pressure sensor 43 provided in the sub-reducing agent storage tank 40 and an output signal from the incoming gas pressure sensor 12 provided in the exhaust pipe 10 are input to the ECU 15. The pressure sensor 43 outputs an output voltage proportional to the internal pressure of the auxiliary reducing agent storage tank 40, and the incoming gas pressure sensor 12 outputs an output voltage proportional to the exhaust pressure in the exhaust pipe 10. Then, the ECU 15 obtains a pressure difference between the pressure of the auxiliary reducing agent storage tank 40 and the pressure (discharge pressure) in the exhaust pipe 10 based on the output values from the pressure sensors 43 and 12. The supply pressure of the reducing gas to the exhaust pipe 10 is calculated.

The ECU 15 takes into consideration the calculated supply pressure of the reducing gas so that the supply amount of the reducing gas per unit time becomes equal to the target supply amount so that the duty of the valve body 51 of the reducing agent addition valve 50 is adjusted. The ratio is calculated, and duty ratio control of the reducing agent addition valve 50 is performed based on the calculated duty ratio (addition valve control means). Here, the duty ratio means the number of times the valve element 51 is opened and closed per unit time. Therefore, in the duty ratio control, as the number of times of opening and closing of the valve element 51 per unit time is increased, more reducing gas is supplied to the exhaust pipe 10.

That is, when the supply pressure of the reducing gas is high, the duty ratio is set small because the supply amount of the reducing gas per unit time is inevitably increased. Conversely, when the supply pressure of the reducing gas is low, the unit time is reduced. Since the supply amount of the reducing gas per hit decreases, the duty ratio is set large.

The ECU 15 has an exhaust temperature sensor 1
3 is input. Exhaust gas temperature sensor 1
3 outputs an output voltage proportional to the temperature of the exhaust gas;
It is used to determine the catalyst temperature of the Ox catalyst 9. And E
In the CU 15, when the catalyst temperature detected by the exhaust temperature sensor 13 reaches an activation temperature at which NOx can be purified, the reducing agent addition valve 5 corresponding to the calculated target supply amount is provided.
The duty control of 0 is performed, and the reducing gas is added to the NOx catalyst 9.

The ECU 15 includes a reducing agent sensor 14.
Output signal is input. And the ECU 15
In the case where a large amount of reductant is unintentionally supplied due to a failure of the reductant supply device 16 or the like, control is performed to sense the reductant by the reductant sensor 14 and immediately forcibly stop the supply of the reductant. Do.

On the other hand, the reducing gas stored in the auxiliary reducing agent storage tank 40 is consumed by the addition from the reducing agent addition valve 50, and the remaining amount thereof decreases with time. Therefore, the ECU 15 always grasps the remaining amount of the reducing gas in the sub-reducing agent storage tank 40 so as not to run out the reducing gas stored in the sub-reducing agent storage tank 40, and when the remaining amount decreases, Reducing gas replenishment control for replenishing the sub-reducing agent storage tank 40 with reducing gas is performed.

The remaining amount of the reducing gas is grasped by the ECU 15 by using the output signal of the pressure sensor 43 described above. That is, the auxiliary reducing agent storage tank 40
When the reducing gas in the tank is consumed, the secondary reducing agent storage tank 40
Internal pressure also decreases. Therefore, by monitoring the output value of the pressure sensor 43, the remaining amount in the auxiliary reducing agent storage tank 40 can be grasped (remaining amount detecting means).

In the ECU 15, the pressure sensor 43
In response to the fact that the pressure in the auxiliary reducing agent storage tank 40 (the charging pressure of the reducing gas) detected at
The engine cooling water control valve 34 is opened to heat the heating chamber 31 to newly gasify the ammonium carbamate stored in the main reducing agent storage tank 20. As a result, the newly gasified ammonium carbamate flows into the sub-reducing agent storage tank 40 and replenishes the sub-reducing agent storage tank 40 with the reducing gas.

Here, the predetermined value is a value that can be set arbitrarily, but it is preferable that the predetermined value is set to a value sufficiently larger than the exhaust pressure. That is, by increasing the filling pressure of the reducing gas, the diffusion of the reducing gas into the exhaust pipe 10 is improved, and the supply amount per unit time with respect to the change in the exhaust pressure is also stabilized.

When the internal pressure of the sub-reducing agent storage tank 40 exceeds a predetermined value, the engine cooling water control valve 34 is closed as described above to stop the gasification of ammonium carbamate. .

As described above, in the reducing agent supply device 16 of the present invention, the solid reducing agent is gasified and stored and prepared in the auxiliary reducing agent storage tank 40 in advance so that addition from the reducing agent addition valve 50 can be performed. In addition, it is possible to immediately respond to the reducing agent addition command from the ECU 15.

The above description is merely one embodiment of the present invention, and details can be arbitrarily changed. For example, when the ECU 15 calculates the NOx emission amount, the ECU 15 may prepare a NOx emission amount map and use the map to calculate the NOx emission amount.

The NOx emission map maps the relationship between these parameters and the NOx emission per unit time obtained by various preliminary experiments, using the engine load and the engine speed as parameters. Therefore, when the output signal of the accelerator opening sensor (not shown) and the output signal of the crank angle sensor are input to the ECU 15 and compared with the NOx emission map, the NOx emission per unit time can be calculated.

The accelerator opening sensor outputs an output voltage proportional to the accelerator opening to the ECU 15, and the output voltage is used for calculating the engine load. On the other hand, the crank angle sensor outputs an output pulse to the ECU 15 every time a crankshaft (not shown) of the engine 1 rotates by a certain angle,
The output pulse is used for calculating the engine speed.

In the above example, the reducing agent addition valve 50
Supply pressure of the reducing agent acting on the gas pressure sensor 12
And the output value of the pressure sensor 43, the pressure in the exhaust pipe 10 can be estimated from an exhaust pressure map created using the engine load and the engine speed as parameters. Therefore, the supply pressure of the reducing agent may be calculated based on the output value of the pressure sensor 43 and the exhaust pressure calculated on the exhaust pressure map.

In the above example, the output value of the incoming gas pressure sensor 12 and the output value of the pressure sensor 43 are taken into consideration, and
Although the duty ratio control in the reducing agent addition valve 50 is performed, if the storage pressure of the reducing gas in the auxiliary reducing agent storage tank 40 is sufficiently increased with respect to the pressure in the exhaust pipe 10, the unit pressure per unit time due to the influence of the exhaust pressure is reduced. Of the supply amount of the reducing agent can be relatively reduced. That is, if the storage pressure of the reducing gas in the sub-reducing agent storage tank 40 is set to be sufficiently large, the duty ratio control of the reducing agent addition valve 50 may be performed by considering only the pressure of the sub-reducing agent storage tank 40. Good.

In the above example, the gasified reducing agent is stored as it is in the auxiliary reducing agent storage tank 40, but the generated reducing agent is compressed and cooled to reduce the volume. It may be stored in the auxiliary reducing agent storage tank 40. That is, by compressing the reducing gas and storing it in the auxiliary reducing agent storage tank 40, the size of the apparatus can be further reduced. For example, in this case, a method of mechanically reducing the volume of the auxiliary reducing agent storage tank 40 to compress the reducing gas and providing cooling fins or the like around the reducing agent storage tank 40 to cool the reducing gas is used. Can be illustrated.

Further, an ammonia storage alloy is stored in the sub-reducing agent storage tank 40, and the reducing gas is stored in the ammonia storage alloy.
The reducing gas may be stored therein. In addition, since the ammonia storage alloy combines with the reducing gas and stores the reducing gas,
The reducing gas can be stored in the auxiliary reducing agent storage tank 40 at a higher density.

In the above example, the solid reducing agent is gasified and stored in the sub-reducing agent storage tank 40. However, the temperature of the reducing gas generating section 30 is reduced to such an extent that the reducing agent is liquefied. The solid reducing agent may be stored in the auxiliary reducing agent storage tank 40 in a liquefied state. That is, the form of the reducing agent stored in the sub-reducing agent storage tank 40 may be any form that can be added immediately by the reducing agent addition valve 50.

In the above example, ammonium carbamate is used as the solid reducing agent. However, other substances such as urea CO (NH ₂ ) ₂ may be used as the reducing agent. When a reducing agent that gasifies at a relatively high temperature, such as urea, is used, the reducing gas generator 30 may be configured with an electric heater or the like to gasify the reducing agent. Further, heating may be performed using heat of the engine lubricating oil.

Next, the operation and effect of the engine employing the reducing agent supply device having such a configuration will be described. As described above, the ECU 15 controls the duty ratio of the reducing agent addition valve 50 according to the NOx emission amount, and adds the reducing agent corresponding to the target supply amount to the NOx catalyst 9 at an appropriate timing. At this time, in the reducing agent supply device 16 of the present invention, solid ammonium carbamate is supplied to the reducing gas generating section 30.
Since it is heated and gasified in advance and stored and prepared in advance in the auxiliary reducing agent storage tank 40, it is possible to immediately respond to a reducing agent addition command. Further, since the reducing gas is always stored in the auxiliary reducing agent storage tank 40, even when a large amount of reducing agent is required, a stable supply of the reducing agent can be performed.

The duty ratio control in the reducing agent addition valve 50 is controlled in consideration of the reducing agent supply pressure. Moreover, since the gasified reducing agent is added after being temporarily stored in the auxiliary reducing agent storage tank 40, the supply pressure of the reducing gas to the reducing agent addition valve 50 is always stable. Therefore, the ECU 15 can easily control the duty ratio in the reducing agent addition valve 50, and can reliably supply the NOx catalyst 9 with the reducing agent corresponding to the target supply amount.

The remaining amount of the reducing gas is grasped by the ECU 15 by using the pressure change in the auxiliary reducing agent storage tank 40. Therefore, the ECU 15 can control the gasification of the solid reducing agent based on the remaining amount of the reducing gas, and does not unnecessarily gasify the reducing agent. Therefore, a stable supply of the reducing agent can be achieved without securing a large volume in the reducing agent supply device 16.

As described above, in the engine employing the reducing agent supply device 16 of the present invention, the reducing agent is supplied at an appropriate amount and at an appropriate timing, so that the NOx purification efficiency of the NOx catalyst 9 is dramatically improved. Can be enhanced. Further, since a stable addition of the reducing agent can be performed without securing a large volume in the reducing agent supply device 16, the device main body can be manufactured in a small size, and the mountability to the vehicle can be greatly improved.

In the engine 1 described above, a selective reduction type NOx catalyst is applied as a catalyst for purifying NOx. However, the reducing agent supply device 16 of the present invention is, of course, also useful for a storage reduction type NOx catalyst. It is. The storage reduction type NO
The x catalyst is a catalyst that stores NOx in an oxygen-excess atmosphere and releases and releases the stored NOx when the oxygen concentration decreases.

In the above-described embodiment, a diesel engine has been described as an example. However, the reducing agent supply device 16 of the present invention is applicable not only to a diesel engine but also to a lean burn gasoline engine capable of lean burn.
Extremely useful.

[0075]

As described above, according to the present invention, it is possible to provide a reducing agent supply apparatus for an internal combustion engine which can immediately supply a predetermined amount of reducing agent without delay in response to a reducing agent supply command.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a diesel engine employing a reducing agent supply device according to the present embodiment.

FIG. 2 is a schematic configuration diagram of a reducing agent supply device according to the present embodiment.

[Explanation of symbols]

Reference Signs List 1 diesel engine (engine) 2 combustion chamber 3 piston 4 cylinder 5 cylinder head 6 fuel injection valve 7 air flow meter 8 intake pipe 9 selective reduction type NOx catalyst (NOx catalyst) 10 exhaust pipe 11 NOx sensor 12 gas pressure sensor 13 exhaust gas temperature Sensor 14 Reducing agent sensor 15 Electronic control unit for engine control (EC
U) 16 reducing agent supply device 18 indicator panel 19 warning lamp 20 main reducing agent storage tank 21 tank body 22 heat insulating member 30 reducing gas generation unit 31 heating chamber 32 outer wall 33 space 34 engine cooling water control valve 40 auxiliary reducing agent storage tank 41 Tank body 42 Insulating member 43 Pressure sensor 50 Reducing agent addition valve 51 Valve body 52 Guide 53 Nozzle part 54 Solenoid 55 Introductory passage 60 Connecting pipe

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeki Omichi 14 Iwatani, Shimowakakucho, Nishio City, Aichi Prefecture Inside Japan Automotive Parts Research Institute (72) Inventor Naohisa Oyama 14 Iwatani, Shimowakakucho, Nishio City, Aichi Prefecture Stock Company F-term in the Japan Auto Parts Research Institute (reference) 3G091 AA18 AB04 BA01 BA14 CA17 DA08 DC05 EA00 EA01 EA03 EA05 EA07 EA16 EA18 EA32 EA33 GB05W GB09W GB09X GB10X GB17X HA36

Claims (8)

[Claims] A reducing agent supply device for supplying a reducing agent to a NOx catalyst provided in an exhaust system of an internal combustion engine for purifying nitrogen oxides discharged from the internal combustion engine, wherein the reducing agent supply device stores a solid reducing agent. Main reducing agent storage means, a reducing agent fluidizing means for fluidizing the solid reducing agent stored in the main reducing agent storing means so as to be supplied, and a reducing agent fluidized by the reducing agent fluidizing means. A reducing agent supply means for temporarily storing the reducing agent, a reducing agent supply amount calculating means for calculating a supply amount of the reducing agent to be supplied to the NOx catalyst based on an operation state of the engine body, and a reducing agent storage means for storing the reducing agent. Reducing agent adding means for adding a reducing agent upstream of the NOx catalyst in the exhaust system of the internal combustion engine based on the supply amount calculated by the reducing agent supply amount calculator. Supply device 2. The reducing agent supply device for an internal combustion engine according to claim 1, wherein said reducing agent fluidizing means gasifies said solid reducing agent to give said reducing agent fluidity. . 3. The sub-reducing agent storing means includes a remaining amount calculating means for calculating a remaining amount of the reducing agent stored in the sub-reducing agent storing means, and the reducing agent fluidizing means includes: When the remaining amount calculated by the calculating means is less than a predetermined value, the solid reducing agent stored in the main reducing agent storing means is fluidized and supplied to the sub-reducing agent storing means. The reducing agent supply device for an internal combustion engine according to claim 1 or 2, wherein 4. The sub-reducing agent storage means includes: a sub-reducing agent storage chamber for temporarily storing the fluidized reducing agent; and pressure detection means for detecting a pressure in the sub-reducing agent storage chamber. The remaining amount calculating unit determines that the remaining amount of the reducing agent is large when the pressure detected by the pressure detecting unit is high, and determines the remaining amount of the reducing agent when the pressure detected by the pressure detecting unit is low. The reducing agent supply device for an internal combustion engine according to claim 3, wherein it is determined that the amount is small. 5. The sub-reducing agent storage means includes: a sub-reducing agent storage chamber for temporarily storing the fluidized reducing agent; and pressure detection means for detecting a pressure in the sub-reducing agent storage chamber. The reducing agent adding means is provided in an exhaust system upstream of the NOx catalyst, and adds a reducing agent stored in the auxiliary reducing agent storage chamber to the upstream of the NOx catalyst when the valve is opened. Addition valve control means for controlling the opening time of the reducing agent addition valve based on the pressure detected by
The reducing agent supply device for an internal combustion engine according to any one of claims 1 to 4, comprising: 6. The addition valve control means, when the pressure in the secondary reducing agent storage chamber is high, shortens the valve opening time of the reducing agent addition valve, and when the pressure in the secondary reducing agent storage is low, The reducing agent supply device for an internal combustion engine according to claim 5, wherein a valve opening time of the reducing agent addition valve is lengthened. 7. The internal combustion engine according to claim 1, wherein said NOx catalyst is a selective reduction type NOx catalyst which decomposes or reduces nitrogen oxides in the presence of a reducing agent. Reducing agent supply device. 8. The method according to claim 1, wherein said solid reducing agent generates a reducing gas based on ammonia when gasified by said reducing agent fluidizing means. A reducing agent supply device for an internal combustion engine.