JP2010053807A - Reducing agent supply control device and exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reducing agent supply control device and an exhaust emission control device of an internal combustion engine capable of efficiently mixing and dispersing a reducing agent into exhaust gas and efficiently reducing NO<SB>X</SB>. <P>SOLUTION: The reducing agent supply control device supplies a reducing agent on an upstream side of NO<SB>X</SB>catalysts arranged in an exhaust passage of the internal combustion engine. Supply of the reducing agent is delayed from an exhaust timing, according to delay time which is a difference between the exhaust timing at which the exhaust gas is emitted from the internal combustion engine, and time at which a peak of a pressure wave generated by exhaust gas emission reaches a position of the reducing agent supply. This allows the reducing agent to be supplied in accordance with the peak of a pressure wave. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a reducing agent supply control device and an exhaust purification device for an internal combustion engine. In particular, by supplying a reducing agent into the exhaust gas, the exhaust gas of the internal combustion engine provided with an exhaust purification device provided the reducing agent supply control device and such a reducing agent supply control apparatus for purifying NO _X contained in the exhaust gas The present invention relates to a purification device.

In order to purify NO _{x in} exhaust gas discharged from an internal combustion engine such as a diesel engine, a catalyst is disposed in the exhaust passage, and by supplying a reducing agent into the exhaust gas upstream of the catalyst, Exhaust gas purification devices that reduce NO _x are used.

Conventionally, in such an exhaust purification device, unburned fuel or aqueous urea solution is used as a reducing agent. When unburned fuel is used as the reducing agent, NO _x is occluded while the unburned fuel in the exhaust gas is lean, while NO _x is released when the unburned fuel in the exhaust gas is rich and unburned. A NO _x storage catalyst that reduces the fuel and NO _x is used. When a urea aqueous solution is used as the reducing agent, a selective reduction catalyst that adsorbs ammonia generated from the urea aqueous solution and selectively performs a reduction reaction with NO _x in the flowing exhaust gas is used.

In such an exhaust purification device using a reducing agent, in order to achieve an efficient NO _x reduction reaction with the catalyst, the reducing agent can be uniformly dispersed and introduced into the entire front surface of the catalyst. Needed. Therefore, it has been studied to efficiently atomize the supplied reducing agent to improve the mixing property with exhaust gas.

  For example, the supply timing of the reducing agent from the reducing agent supply means is adjusted to the timing until the exhaust gas discharged in the exhaust process of each cylinder of the internal combustion engine reaches the supply position of the reducing agent, and the supply amount of the reducing agent An exhaust purification system for an internal combustion engine has been proposed in which the gas is changed in accordance with the state of exhaust gas reaching each reductant supply position from each cylinder. More specifically, with regard to the supply timing of the reducing agent, paying attention to the density of the exhaust gas flowing through the exhaust passage, the reducing agent is supplied at the timing when the reducing agent is exposed to the highest exhaust gas density. Is disclosed (see Patent Document 1).

JP 2007-71142 A (paragraphs [0028] to [0036])

  By the way, in the exhaust gas purification system of the internal combustion engine described in Patent Document 1, the timing at which the exhaust gas discharged from the internal combustion engine reaches the reducing agent supply position, that is, the exhaust gas density is the highest, and as many reducing agents as possible. The timing at which can be supplied is determined as the supply timing of the reducing agent. Further, in the exhaust gas purification system for an internal combustion engine described in Patent Document 1, the state of combustion exhaust in which the efficiency of atomization (vaporization or atomization) of the supplied reducing agent reaches the reducing agent supply position, that is, Estimated from the viewpoint of the temperature of the exhaust gas, the supply amount of the reducing agent is also determined.

  However, considering the atomization efficiency of the supplied reducing agent, it is desirable to supply the reducing agent at a timing at which the flow rate of the exhaust gas at the reducing agent supply position is relatively fast. That is, when the reducing agent is supplied to the flow of the exhaust gas having a high flow velocity and a large kinetic energy, the collision energy between the reducing agent and the exhaust gas is increased, and the atomization of the reducing agent is easily promoted. In the exhaust gas purification system for an internal combustion engine of Patent Document 1, this point is not taken into consideration.

Accordingly, the inventors of the present invention have made diligent efforts to reduce the exhaust gas flow rate at the reducing agent supply position, that is, at the timing when the peak of the exhaust gas pressure wave reaches the reducing agent supply position. It has been found that such a problem can be solved by supplying an agent, and the present invention has been completed. That is, an object of the present invention is to provide a reducing agent supply control device and an exhaust gas purification device for an internal combustion engine that can efficiently reduce and reduce NO _x by efficiently mixing and dispersing the reducing agent in the exhaust gas. To do.

According to a reducing agent supply control apparatus of the present invention, there is provided a reducing agent supply controller for supplying the reducing agent to the upstream side of the NO _X catalyst arranged in an exhaust passage of an internal combustion engine, an exhaust gas from an internal combustion engine By supplying the reducing agent with a delay from the exhaust timing according to the delay time until the peak of the pressure wave caused by the exhaust gas discharge reaches the reducing agent supply position from the exhaust timing at which the exhaust gas is discharged, the pressure wave A reducing agent supply control device characterized by supplying a reducing agent corresponding to the peak of the above can be provided, and the above-described problems can be solved.

  Further, in configuring the reducing agent supply control device of the present invention, an exhaust timing detection unit for detecting the exhaust timing and a delay time until the peak of the pressure wave reaches the reducing agent supply position are estimated from the exhaust timing. It is preferable to include a pressure wave delay time calculation unit and a reducing agent supply instruction unit that supplies the reducing agent in correspondence with the peak of the pressure wave reaching the supply position.

  In configuring the reducing agent supply control device of the present invention, it is preferable to estimate the delay time based on at least the rotational speed of the internal combustion engine and the torque or exhaust flow rate of the internal combustion engine.

  Further, in configuring the reducing agent supply control device of the present invention, it is preferable to supply the reducing agent at a supply frequency set corresponding to the frequency of the pressure wave obtained at least based on the rotational speed of the internal combustion engine.

  Further, in configuring the reducing agent supply control device of the present invention, it is preferable to set the supply frequency corresponding to the frequency of the pressure wave so that the supply cycle of the reducing agent is a predetermined value or less.

Another aspect of the present invention comprises any one of the reducing agent supply control device described above, is disposed in an exhaust passage of an internal combustion engine, NO _X for the selective reduction of NO _X contained in the exhaust gas An exhaust emission control device for an internal combustion engine comprising a catalyst and a reducing agent supply means capable of supplying a reducing agent into the exhaust passage on the upstream side of the NO _x catalyst.

According to the reducing agent supply control device and the exhaust gas purification device for an internal combustion engine of the present invention, the reducing agent is supplied in correspondence with the peak of the pressure wave of the exhaust gas at the reducing agent supply position. A reducing agent is supplied to a portion where the kinetic energy of the exhaust gas is highest. Therefore, the reducing agent supplied using the kinetic energy of the exhaust gas is efficiently atomized. Therefore, the reducing agent is uniformly mixed and dispersed in the exhaust gas, and NO _x is efficiently reduced in the catalyst.

  In addition, the reducing agent supply control device of the present invention includes a predetermined exhaust timing detection unit, a pressure wave delay time calculation unit, and a reducing agent supply instruction unit, so that the peak of the pressure wave generated in the exhaust passage due to exhaust gas discharge. The reducing agent is easily supplied at a supply frequency corresponding to.

  In addition, the reducing agent supply control device of the present invention estimates the delay time based on at least the rotational speed of the internal combustion engine and the torque or exhaust flow rate of the internal combustion engine, thereby causing a pressure wave due to exhaust gas exhaust from the internal combustion engine. The timing at which the peak reaches the reducing agent supply position is accurately estimated.

  Further, the reducing agent supply control device of the present invention supplies the reducing agent at a supply frequency set corresponding to the rotational speed of the internal combustion engine, that is, the frequency of the pressure wave, so that regardless of the exhaust gas discharge frequency. The reducing agent is supplied at an appropriate frequency according to the injection capability of the reducing agent supply means such as the reducing agent injection valve and the processing capability of the reducing agent supply control device.

  Further, the reducing agent supply control device of the present invention sets the supply frequency so that the reducing agent supply cycle is a predetermined value or less, thereby reducing the reducing agent supply means such as the reducing agent injection valve and the reducing agent supply control device. The load is reduced. Moreover, if it is avoided that the supply frequency of the reducing agent is excessively high, overheating of the equipment constituting the reducing agent supply means is prevented, the reducing agent is stably supplied, and variation in the supply amount is prevented. The

  Hereinafter, embodiments of the reducing agent supply control device and the exhaust gas purification device for an internal combustion engine according to the present invention will be described. However, this embodiment shows one aspect of the present invention, does not limit the present invention, and can be arbitrarily changed within the scope of the present invention. In addition, in each figure, what has attached | subjected the same code | symbol has shown the same member, and description is abbreviate | omitted suitably.

1. FIG. 1 shows a configuration example of an exhaust purification device 20 of the present embodiment. The exhaust gas purifying device 20 is provided in the exhaust passage 11 of the internal combustion engine 10 such as a diesel engine, the NO _X catalyst 21 for selectively reducing the NO _X contained in the exhaust gas, NO _X catalyst 21 And a reducing agent supply means 25 capable of supplying a reducing agent at the upstream side. Upstream and downstream of the NO _X catalyst 21, etc. respectively upstream oxidation catalyst 23a and the downstream oxidation catalyst 23b may be provided as appropriate.

Examples of the liquid reducing agent used in the exhaust purification device 20 include an aqueous urea solution and unburned fuel. Among these, the urea aqueous solution is supplied into the exhaust gas, so that it is decomposed by the heat of the exhaust gas to generate ammonia, and this ammonia is used for the NO _x reduction reaction. The unburned fuel is used for the reduction reaction of contained hydrocarbons (HC) of NO _x .

The NO _X catalyst 21 can selectively reduce NO _X contained in exhaust gas using a reducing agent such as an aqueous urea solution supplied from the reducing agent supply means 25 and decompose it into nitrogen, water, carbon dioxide, or the like. If it is, it will not be restrict | limited in particular. Usable NO _x catalysts include, for example, strontium or barium as an active ingredient on a porous carrier, alkaline earth metals such as magnesium, rare earth metals such as cerium and lanthanum, noble metals such as platinum and rhodium, etc. The thing containing is mentioned.

Reducing agent supply means 25, a reducing agent injection valve 27 mounted to face the injection port between the upstream side oxidation catalyst 23a and the NO _X catalyst 21, a storage tank (not shown.) Of a reducing agent A reducing agent supply unit 29 that supplies the reducing agent injection valve 27 and a reducing agent supply control unit (DCU) 31 that controls the reducing agent injection valve 27 and the reducing agent supply unit 29 are provided.

  Although the detailed illustration of the reducing agent supply unit 29 is omitted, for example, the reducing agent in the tank is configured to be pumped by a pump or the like and supplied to the reducing agent injection valve 27 via the supply path 29a. The reducing agent injection valve 27 is composed of, for example, an electromagnetic control valve or the like, and is configured to be able to supply the reducing agent intermittently. Each device such as the pump and the reducing agent injection valve 27 is driven based on a signal from the DCU 31.

Such a reducing agent supply means 25 can supply the exhaust gas flowing in the reducing agent supply position 25a at the time of supply so that the reducing agent can be mixed while being dispersed as much as possible. It is desirable. If the dispersion state of the reducing agent is insufficient, the ratio of the reducing agent to the exhaust gas tends to be locally excessive or insufficient, and the use efficiency of the reducing agent and the NO _x purification efficiency may be reduced. is there. In particular, when the reducing agent remains in a liquid state without being dispersed and vaporized after the supply, it adheres to the inner wall surface of the exhaust passage 11 near the reducing agent supply position 25a in the form of droplets or the like. Crystallization may occur, and the reducing agent cannot reach the NO _x catalyst 21, which may reduce the utilization efficiency of the reducing agent.

Therefore, the DCU 31 of the exhaust purification device 20 is supplied with an appropriate amount of reducing agent intermittently more easily distributed in the exhaust gas than the exhaust gas flowing in the reducing agent supply position 25a. In addition, the reducing agent supply means 25 and the reducing agent supply unit 29 are configured to be controllable.
Specifically, the DCU 31 can be controlled to supply the reducing agent from the reducing agent injection valve 27 in correspondence with the peak of the pressure wave of the exhaust gas in the exhaust passage 11.

2. Reducing agent supply control unit (DCU)
FIG. 2 is a diagram for explaining an example of the configuration of the DCU 31 provided in the exhaust gas purification apparatus of the present embodiment, and shows a configuration example represented by functional blocks regarding a portion related to the reducing agent supply control. Has been.
The DCU 31 is configured around a microcomputer having a known configuration, and an exhaust timing detection unit (in FIG. 2, “exhaust timing detection” detects exhaust timing at which exhaust gas is discharged from the internal combustion engine toward the exhaust passage. ), A delay time calculation unit (indicated as “delay time calculation” in FIG. 2) for calculating the time until the pressure wave peak reaches the reducing agent supply position, and a reducing agent injection valve. A supply frequency determination unit (denoted as “supply frequency determination” in FIG. 2) that determines the supply frequency of the reducing agent, and a supply timing determination unit (“supply” in FIG. 2) that determines the supply timing of the reducing agent by the reducing agent injection valve. "Determined timing"), a reducing agent supply amount calculation unit (indicated as "supply amount calculation" in FIG. 2) for calculating the reducing agent supply amount, and a reducing agent supply instruction to the reducing agent injection valve The Cormorant reducing agent supply instructing section (in FIG. 2 "supply instruction" denoted.) Are provided as main elements and the like. Each of these units is specifically realized by executing a program by a microcomputer (not shown).

  Among these, the exhaust timing detection unit detects the exhaust timing Tg at which exhaust gas is discharged from the internal combustion engine based on information such as the rotational speed Ne of the internal combustion engine and the fuel injection timing Qt in the internal combustion engine, and the supply timing A signal of the exhaust timing Tg is sent to the determination unit. Further, in the delay time determination unit, the peak of the pressure wave caused by exhaust gas discharge is at the reducing agent supply position based on at least the information on the rotational speed Ne of the internal combustion engine and the torque Tr of the internal combustion engine or the exhaust flow rate Fg. The time Tdelay until reaching is calculated, and a signal of the delay time Tdelay is sent to the supply timing determination unit. The supply frequency determination unit determines the supply frequency Ndos of the reducing agent by the reducing agent injection valve based on at least the rotational speed Ne of the internal combustion engine, and sends a signal of the supply frequency Ndos to the supply timing determination unit.

Further, the supply timing determining unit determines the reducing agent supply timing Tdos by the reducing agent injection valve based on the received exhaust timing Tg, delay time Tdelay, and supply frequency Ndos. A signal of supply timing Tdos is sent.
Further, the reducing agent supply amount calculation unit determines the amount of reducing agent supplied to the exhaust passage based on information such as the amount of ammonia adsorbed on the NO _x catalyst, the NO _x flow rate in the exhaust gas, and the exhaust gas temperature. A signal of the reducing agent supply amount Qdos is sent to the reducing agent supply instruction unit.

  Then, the reducing agent supply instruction unit outputs a supply instruction signal to the drive portion of the reducing agent injection valve based on the received supply timing Tdos and the reducing agent supply amount Qdos.

In the exhaust emission control device 20 of the present embodiment, the reducing agent supply control is performed as follows by the DCU 31 configured as described above.
First, in the exhaust passage, the exhaust gas flows in an extruding flow, and at the supply position of the reducing agent in the exhaust passage, the pressure fluctuation according to the exhaust gas discharge from the internal combustion engine is a pressure as shown in FIG. It is transmitted as a wave. This pressure fluctuation pattern matches the fluctuation pattern of the exhaust gas flow velocity at the reducing agent supply position. The period of the pressure wave of the exhaust gas varies depending on the number of cylinders, the number of revolutions, etc. of the internal combustion engine.

  Therefore, in this DCU 31, control is performed in which the reducing agent is intermittently supplied from the reducing agent injection valve every period ta corresponding to the peak of the pressure wave. Thereby, the reducing agent is supplied to the portion where the kinetic energy of the exhaust gas pulsating in the exhaust passage is the highest, and the supplied reducing agent is atomized using the kinetic energy of the exhaust gas. This is, for example, a state in which a high Weber number indicating the ratio between the inertial force acting on the boundary surface of the droplet and the surface tension is realized, and a state in which surface breakage of the liquid is further promoted is easily achieved. Therefore, the reducing agent is efficiently dispersed and easily mixed in the exhaust gas.

  The DCU 31 also receives a signal from a control unit (ECU: Electronic Control Unit) 33 for controlling the operation of the internal combustion engine in order to supply the reducing agent intermittently for each period ta corresponding to the peak of the pressure wave. Based on this, the reducing agent injection valve can be controlled. In general, in the ECU 33, various state values such as the rotational speed Ne, the torque Tr, and the exhaust flow rate Fg are always detected and inputted. For this reason, the supply timing Tdos is easily set in the DCU 31 by using the state value detected by the ECU 33.

  The peak of the pressure wave that reaches the reducing agent supply position in the exhaust passage is delayed with respect to the exhaust timing Tg of the internal combustion engine. As shown in FIG. 4, this delay has a correlation with the rotational speed Ne of the internal combustion engine and the torque Tr or the exhaust flow rate Fg of the internal combustion engine. Each curve A to C in FIG. 4 shows a change in the delay time Tdelay with respect to the rotational speed Ne of the internal combustion engine when the torque Tr or the exhaust flow rate Fg of the internal combustion engine is made constant. The torque Tr or the exhaust gas flow rate Fg of the internal combustion engine is A <B <C. That is, if the torque Tr or the exhaust flow rate Fg of the internal combustion engine is constant, the peak delay of the pressure wave with respect to the exhaust timing Tg decreases as the rotational speed Ne of the internal combustion engine increases. If the rotation speed of the internal combustion engine is the same, the longer the torque Tr of the internal combustion engine or the greater the exhaust flow rate Fg, the smaller the delay time of the peak of the pressure wave with respect to the exhaust timing Tg.

  Therefore, in the delay time calculation unit of the DCU 31 of the present embodiment, when the supply of the reducing agent is controlled, the rotational speed Ne and at least one of the torque Tr or the exhaust flow rate Fg are acquired from the ECU 33, and based on these values. Thus, the delay time Tdelay is obtained with reference to a map stored in advance as shown in FIG. Therefore, it is possible to control the supply of the reducing agent at an appropriate timing in correspondence with the exhaust timing Tg detected by the exhaust timing detection unit.

  Further, the pressure wave peak interval (cycle) becomes shorter as the rotational speed of the internal combustion engine is higher. Therefore, the supply timing Tdos for supplying the reducing agent from the reducing agent injection valve becomes shorter as the rotational speed of the internal combustion engine is higher. In this case, in addition to opening and closing of the reducing agent injection valve in a shorter time, the flow state of the reducing agent in the supply path of the reducing agent supply unit also pulsates violently. If the pulsation of the reducing agent becomes excessively strong in the reducing agent supply section, the amount of reducing agent supplied during each supply from the reducing agent injection valve tends to become unstable, and depending on the injection capacity of the reducing agent injection valve, the reducing agent This makes it difficult to adjust the supply timing to the peak of the pressure wave. Further, the reducing agent injection valve and the reducing agent supply unit are easily overheated by repeatedly operating the reducing agent injection valve and the reducing agent supply unit in a shorter time. In addition, as the supply cycle from the reducing agent injection valve becomes shorter, the performance of the reducing agent injection valve and the processing capacity of the DCU cannot catch up, and the injection control may become difficult.

  Therefore, as shown in FIG. 5, the supply frequency determination unit of the DCU 31 of the present embodiment sets a threshold f1 in the supply cycle of the reducing agent, and the reducing agent supply frequency Ndos with respect to the rotational speed of the internal combustion engine decreases. It is configured as follows. Here, when the threshold f1 or more is reached, control for setting the supply frequency Ndos with respect to the frequency of the pressure wave is possible so that the supply cycle of the reducing agent is not more than a predetermined value. Thereby, injection of the reducing agent is performed at an appropriate frequency according to the performance of the DCU 31 and the reducing agent injection valve, and overheating of the equipment constituting the reducing agent supply means is prevented, and in the reducing agent supply path. The pulsation cycle of the reducing agent is prevented from becoming excessively short, the reducing agent is easily supplied stably, and variations in the amount of reducing agent supplied are prevented.

3. Flow of Reducing Agent Supply Control Method The flow of control by the DCU of the exhaust purification apparatus as described above will be described with reference to FIG.

First, it is determined whether to supply a reducing agent (S101). This determination is made based on, for example, the elapsed time from the previous supply, the NO _x emission amount from the internal combustion engine, the ammonia adsorption amount on the NO _x catalyst, and the like. In addition, this step can be omitted when the reducing agent is always supplied.

  When it is determined that the reducing agent is to be supplied, the ECU 33 obtains the rotational speed Ne of the internal combustion engine, the rotational torque Tr or the exhaust flow rate Fg, and the fuel injection timing Qt of the internal combustion engine (S102). In this embodiment, the rotational speed Ne, the rotational torque Tr, and the fuel injection timing Qt are acquired. The rotational speed Ne is a value detected from the output shaft or the like of the internal combustion engine, the rotational torque Tr is calculated from the rotational speed Ne and the fuel injection amount Q of the internal combustion engine, and the fuel injection timing Qt is an injection instruction signal of the ECU 33. Detected from.

  Next, the exhaust timing Tg of the internal combustion engine is detected based on the acquired rotational speed Ne and fuel injection timing Qt (S103). Further, based on the acquired rotational speed Ne and rotational torque Tr, a delay time Tdelay until the peak of the pressure wave caused by exhaust gas discharge reaches the reducing agent supply position is calculated from the exhaust timing Tg of the internal combustion engine. (S104). This delay time Tdelay can be calculated using a preset map as shown in FIG. For example, the delay time Tdelay is set to be shorter as the rotational speed Ne is higher and as the rotational torque Tr is larger.

  Further, the supply frequency Ndos for the frequency of the pressure wave is set based on the acquired rotation speed Ne (S105). This supply frequency Ndos is set by using a map showing correlation as shown in FIG. Here, the supply frequency Ndos is set so that the supply cycle of the reducing agent is equal to or less than the threshold value f1. For example, if the rotational speed Ne of the internal combustion engine is equal to or less than r1, the reducing agent is supplied once every rotation cycle of the internal combustion engine. If the rotational speed of the internal combustion engine is equal to or greater than r1 and equal to or less than r2, two rotations of the internal combustion engine are performed. If the reducing agent is supplied once every cycle and the rotational speed of the internal combustion engine is equal to or greater than r2, the reducing agent is set to be supplied once every four rotation cycles of the internal combustion engine.

  The setting of the supply frequency Ndos (S105) and the setting of the delay time Tdelay (S104) may be reversed.

  Next, the reducing agent supply timing Tdos is determined based on the exhaust timing Tg, the supply frequency Ndos, and the delay time Tdelay (S106). The supply timing Tdos set in this way is the timing at which the peak of the pressure wave of the exhaust gas reaches the reducing agent supply position in the exhaust passage.

  Thereafter, it is determined whether or not the determined supply timing Tdos is different from the previous reducing agent supply timing Tdos ′ (S107). If the determined supply timing Tdos is different, the supply timing Tdos is changed to a new supply timing Tdos (S108). Then, intermittent supply of the reducing agent is executed (S109), and the supply of the reducing agent is completed.

According to the exhaust purification apparatus of the present embodiment as described above, since the reducing agent is intermittently supplied from the reducing agent supply means in correspondence with the peak of the pressure wave of the exhaust gas, the shape and distance of the exhaust passage, etc. Regardless of this, the reducing agent is stably supplied at an optimal timing. Furthermore, since the reducing agent is supplied to the portion where the kinetic energy of the exhaust gas pulsating in the exhaust passage is the highest, the supplied reducing agent is efficiently atomized using the kinetic energy. This is, for example, a state in which a high Weber number indicating the ratio between the inertial force acting on the boundary surface of the droplet and the surface tension is realized, and a state in which surface breakage of the liquid is further promoted is easily achieved. Therefore, the reducing agent is uniformly dispersed in the exhaust gas, and NO _x is efficiently reduced.
Moreover, the reducing agent for being atomized are dispersed in the exhaust gas, the supplied reducing agent such as adhering to the inner wall surface of the exhaust passage in the vicinity supply position remains the reducing agent in liquid form is reduced, NO _X The reduction efficiency of can be easily improved.

  Further, in this exhaust purification device, since the reducing agent is supplied corresponding to the delay of the peak of the pressure wave with respect to the exhaust timing, which is obtained based on the rotational speed of the internal combustion engine and the torque or exhaust flow rate of the internal combustion engine, An appropriate supply timing of the reducing agent is easily set.

  Furthermore, since the reducing agent is supplied in correspondence with the supply frequency with respect to the frequency of the pressure wave, which is obtained based on the rotation speed of the internal combustion engine, the supply frequency is avoided from becoming excessively high, and the supply of the reducing agent supply means is performed. It is possible to supply the reducing agent at an appropriate supply timing according to the capacity. Moreover, if the supply frequency of the reducing agent is prevented from becoming excessively high, failure due to overheating of the equipment constituting the reducing agent supply means can be prevented, the reducing agent can be supplied stably, and the supply amount can vary. Is prevented.

It is a figure showing an example of composition of an exhaust-air-purification device concerning an embodiment of the invention. It is a block diagram which shows the structural example of the reducing agent supply control apparatus concerning embodiment of this invention. It is a graph which shows the pressure fluctuation of the exhaust gas in the supply position of a reducing agent. It is a graph which shows the correlation with the rotation speed of the internal combustion engine set beforehand and the delay time of the peak of a pressure wave, using the torque of an internal combustion engine or an exhaust flow as a parameter. It is a graph which shows the correlation with the rotation speed of a preset internal combustion engine, and the supply frequency of a reducing agent. It is a flowchart for demonstrating the reducing agent supply control method concerning embodiment of this invention.

Explanation of symbols

10: an internal combustion engine, 11: exhaust passage 20: exhaust gas purification apparatus, 21: NO _X catalyst 25: reducing agent supply means, 25a: supply position, 27: reducing agent injection valve, 29: reducing agent supply portion, 31: DCU, 33: ECU

Claims (6)

In the reducing agent supply control device for supplying the reducing agent to the upstream side of the NO _x catalyst disposed in the exhaust passage of the internal combustion engine,
The reducing agent is discharged to the exhaust timing according to a delay time from the exhaust timing at which the exhaust gas is discharged from the internal combustion engine until the peak of the pressure wave generated by the exhaust gas discharge reaches the supply position of the reducing agent. The reducing agent supply control device is characterized in that the reducing agent is supplied in correspondence with a peak of the pressure wave by supplying it after a delay. An exhaust timing detector for detecting the exhaust timing;
A pressure wave delay time calculating unit that estimates a delay time from the exhaust timing until the peak of the pressure wave reaches the supply position of the reducing agent;
A reducing agent supply instructing unit for supplying the reducing agent in correspondence with the peak of the pressure wave reaching the supply position;
The reducing agent supply control device according to claim 1, comprising:   3. The reducing agent supply control device according to claim 1, wherein the delay time is estimated based on at least a rotation speed of the internal combustion engine and a torque or an exhaust flow rate of the internal combustion engine.   The said reducing agent is supplied with the supply frequency set corresponding to the frequency of the said pressure wave calculated | required based on the rotation speed of the said internal combustion engine at least. Reducing agent supply control device.   5. The reducing agent supply control device according to claim 4, wherein a supply frequency is set corresponding to a frequency of the pressure wave so that a supply cycle of the reducing agent is equal to or less than a predetermined value. A reducing agent supply control device according to any one of claims 1 to 5, a NO _x catalyst arranged in an exhaust passage of an internal combustion engine, for selectively reducing NO _x contained in exhaust gas, An exhaust gas purification apparatus for an internal combustion engine, comprising: a reducing agent supply means capable of supplying a reducing agent into the exhaust passage upstream of the NO _x catalyst.

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