FR2861424A1 - IC engine exhaust gas purification system for vehicle with hybrid drive uses electric motor to supply power while catalyzer temperature is boosted - Google Patents

Abstract

The exhaust gas purification system consists of a catalyzer (4) in the exhaust circuit (2) from an IC engine (1) in a vehicle with a hybrid IC engine/electric motor power unit. The efficiency of the catalyzer is restored by means of a temperature booster (5) which is operated when the IC engine is cut out and the vehicle drive power is supplied by the electric motor (32). The electric motor is normally used when the vehicle power requirement is low, but when the catalyzer temperature needs boosting the electric drive is extended towards a higher power requirement until the necessary catalyzer temperature is reached, IC when its accumulated NOx has been reduced or particulates trapped in a filter have been oxidized.

Description

T 1 2861424

  DEVICE FOR PURIFYING THE EXHAUST GAS OF AN ENGINE

INTERNAL COMBUSTION

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for purifying the exhaust gas of an internal combustion engine.

  2. Description of the Related Art

  It has been proposed a technology to have a NO storage reduction catalyst (which will then simply be called a NO catalyst) in an exhaust pipe of an internal combustion engine, and to store the NO contained in the exhaust gas in the NO catalyst.

  In this connection, the NO catalyst stores the sulfur oxide (SON) generated by burning a sulfur compound contained in the fuel according to the same mechanism by which NO is stored. SO, which has been stored, is more difficult to release than NO and is accumulated in the NO catalyst.

  This is called sulfur poisoning (SOUND poisoning). Sulfur poisoning causes a decrease in the NO purification rate, and it is therefore required that a recovery process against poisoning to recover from sulfur poisoning be performed. at a suitable time. This process of recovery against poisoning is carried out in such a way that the exhaust gas, whose oxygen concentration is decreased, passes through the NO catalyst while carrying the NO catalyst at a temperature of 50.degree. high (e.g., approximately 600 ° C. to 650 ° C.) (see, for example, patent document 1).

  In addition, a known technology for a hybrid vehicle is such that, when the catalyst temperature is in an inactive state, the electric motor is prevented from being activated, and the internal combustion engine is set to an idle state ( see for example the patent document 2).

  [Patent Document 1] Japanese Patent Application Laid-open Publication No. 7-217474-22861424 [Patent Document 2] Japanese Patent Application Laid-open Publication No. 10-288,063 [ Patent Document 3] Japanese Patent Application Laid-open Publication No. 2001-241341 [Patent Document 4] Japanese Patent Application Laid-open Publication No. 2000-186 536.

  In this regard, when the internal combustion engine is operated with a low power, a low temperature exhaust gas is exhausted from the internal combustion engine. Therefore, the sulfur poisoning recovery process is performed, and, if the internal combustion engine is operated with the low power when the catalyst temperature is increased, the exhaust gas At low temperature enters the catalyst, which results in the catalyst temperature decreasing. With this decrease, the temperature of the catalyst must be increased again, which takes a considerable amount of time until recovery from sulfur poisoning is complete in some cases.

Claims (6)

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention, which is designed to avoid the problems described above, to provide a technology to prevent the temperature of a catalyst from being lowered by the fact that an internal combustion engine is operated in a low power state in an exhaust gas purification device of the internal combustion engine in a hybrid vehicle. To achieve the above purpose, the exhaust gas purifying device of the internal combustion engine according to the present invention adopts the following means. Namely, in an exhaust gas purification device of an internal combustion engine of a hybrid vehicle capable of moving using an electric motor as a power source while stopping an internal combustion engine, the exhaust gas purification device comprising a catalyst disposed in an exhaust gas duct of the internal combustion engine, an improvement is characterized in that it further comprises a catalyst temperature increase means for to increase the temperature of the catalyst, and is characterized in that, if an operating state of the internal combustion engine goes to a state of decrease of the catalyst temperature when it is required to increase the temperature of the catalyst, the operation of the internal combustion engine is stopped, and when moving the vehicle, the electric motor is used as a source of power. this. The most remarkable feature of the present invention is that, if there is a possibility that the catalyst temperature can be lowered due to a low temperature of the exhaust gas, the decrease of the catalyst temperature is prevented by stopping the entry of the low temperature exhaust gas into the catalyst while stopping the internal combustion engine. Namely, in the case where both the increase of the temperature of the catalyst and the maintenance of the temperature thereafter are required, if the catalyst receives the incoming flow of the exhaust gas at low temperature at the time of the weak power, it follows that the temperature of the catalyst decreases. In this respect, the hybrid vehicle can be propelled by the electric motor even when stopping the internal combustion engine. In such a case, if there is the possibility that the low temperature exhaust gas can enter the catalyst, the internal combustion engine is stopped, and the vehicle is propelled by the electric motor, whereby the decrease of the temperature of the catalyst can be limited. According to the present invention, the hybrid vehicle is propelled by the electric motor at least in a low power area of the vehicle, and when the temperature of the catalyst is increased by the means of increasing the temperature of the catalyst, the zone intended to propel the vehicle through the electric motor can be extended to a higher power side than when the temperature is not increased. The hybrid vehicle moves in such a way that it switches between the electric motor and the internal combustion engine according to the power state of the vehicle. For example, if the power of the internal combustion engine becomes less than or equal to s kW, the internal combustion engine is stopped, and the power source is switched to the electric motor. A vehicle power condition for tipping is determined based on fuel consumption, handling, etc. Then, in accordance with the present invention, when the catalyst temperature is increased, the power condition of the vehicle for tilting between the internal combustion engine and the electric motor is set on the side of a much higher power. With this invention, it follows that the internal combustion engine is stopped in a state where the temperature of the exhaust gas becomes much higher, and the temperature of the catalyst can be prevented from decreasing. It should be noted that the power condition of the vehicle controlling the tilting between the internal combustion engine and the electric motor may also be a vehicle power condition for stopping the internal combustion engine. In addition, the power of the vehicle may be a required power of the vehicle. In accordance with the present invention, the catalyst may be a NOM storage reduction catalyst, and the time of the catalyst temperature increase may correspond to the time of recovery of the NOX storage reduction catalyst from screw of sulfur poisoning. In addition, the catalyst is a catalyst carried by a particulate filter or a catalyst disposed further upstream than the particulate filter, and the time of increase at the temperature of the catalyst may correspond to the moment of oxidation of the particulate matter. collected by the particulate filter. When the NOX storage reduction catalyst recovers from sulfur poisoning and upon oxidation and thus removal of particulate matter collected by the particulate filter, the temperature of the catalyst is increased. . At this time, if the catalyst temperature decreases, the catalyst temperature must be increased again, and this takes a considerable amount of time until the recovery from sulfur poisoning and removal of particulate matter is complete. In addition, additional energy to increase the temperature of the catalyst is required, and degraded fuel consumption could be induced. From this point of view, in accordance with the present invention, it is possible to prevent the decrease of the catalyst temperature during the recovery process from poisoning and during the oxidation of particulate matter and to terminate quickly recover from sulfur poisoning or complete the removal of particulate matter. In the exhaust gas purification apparatus of the internal combustion engine according to the present invention, when the need to increase the temperature of the catalyst occurs, the decrease of the catalyst temperature can be prevented. The foregoing and other objects, features and advantages of the present invention and others will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments of the present invention taken in conjunction with attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing a hybrid system and an exhaust system design of an internal combustion engine of an example, Fig. 2 is a graph showing the relationship between the number of turns and the generated torque (load) of the internal combustion engine and a stopping zone of the internal combustion engine in the case where the recovery control vis-à-vis a sulfur poisoning is not achieved FIG. 3 is a graph showing the relation between the number of revolutions and the generated torque (load) of the internal combustion engine and the stopping area of the internal combustion engine in the case where the recovery control with respect to Fig. 4 is a flow chart showing the flow of a stop condition change control of the internal combustion engine of the example. 6 2861424   DESCRIPTION OF THE PREFERRED EMBODIMENT   The specific embodiment of an exhaust gas purification device of an internal combustion engine according to the invention will be described hereinafter with reference to the drawings. [Example 1]   FIG. 1 is a simplified view showing a hybrid system and a design of an exhaust system of the internal combustion engine according to example 1.   A hybrid car according to the present embodiment consists of an internal combustion engine 1, a power distribution mechanism 31, an electric motor 32, a generator 33, a battery 34, a converter 35, an axle 36, a speed reducer (reduction gear) 37 and wheels 38.   The power distribution mechanism 31 divides and distributes power supplied from the internal combustion engine 1 to the generator 33 and to the axle 36. This power distribution mechanism 31 also has the function of transferring power from the engine electrical motor 32 to the axle 36. The electric motor 32 is rotated through the speed reducer 37 with a number of revolutions proportional to that of the axle 36. The electric motor 32 is also capable of contributing to the power of the internal combustion engine 1 when the need arises during normal operation. In addition, the battery 34 is connected via the converter 35 to the electric motor 32 and to the generator 33. Then, the generator 33 generates the electricity by obtaining power from the internal combustion engine 1 and charges the battery 34 with electricity.   In the hybrid system thus designed, during a normal displacement, the axle 36 is rotated by the power of the internal combustion engine 1 or the electric motor 32, thus driving the wheels 38. In addition, the axle 36 can also be rotated by synthesizing the power of the internal combustion engine 1 and the power of the electric motor 32, whereby the drive wheels 38 can be driven. While, furthermore, during a deceleration, the electric motor 32 is operated as a generator 28 by a rotating force of the wheels 38, whereby the electric energy, into which the kinetic energy is converted, can also be converted. to be collected (accumulated) in the battery 34. Thus, the kinetic energy is converted into electrical energy when the vehicle decelerates, and thus the deceleration of the vehicle can be assisted.   Then, the internal combustion engine is classified as a gasoline engine with a direct injection system in which the fuel is injected directly into the cylinders. This internal combustion engine 1 is an engine capable of operating with poor combustion.   The internal combustion engine 1 is provided with fuel injection valves 5 for injecting the fuel into the cylinders. In addition, an exhaust gas duct 5 communicating with a combustion chamber is connected to the internal combustion engine 1. The exhaust gas duct 2 communicates with the atmospheric air on the downstream side.   An NO storage reduction catalyst (which will simply be hereinafter referred to as NOX 4 catalyst) is located midway in the exhaust gas conduit 2.   The function of the NO 4 catalyst is to store NO in the exhaust gas when the oxygen concentration of the exhaust gas is high and to reduce the NOX stored when the oxygen concentration of the exhaust gas is high. input exhaust decreases and when a reducing agent exists.   The NO4 catalyst 4 also stores the sulfur compound contained in the fuel. This is called sulfur poisoning (SO poisoning). Sulfur poisoning causes a decrease in the amount of NO, which can be occluded, resulting in a lower NO purification rate. It is therefore necessary to perform a recovery process against poisoning for the NOX 4 catalyst to recover from sulfur poisoning. This process of recovery from poisoning is carried out in a manner which brings the NO 4 catalyst to a high temperature state (eg, approximately 600 ° C to 650 ° C) and which causes the gas to pass. exhaust with its reduced oxygen concentration, by the NOX 4 catalyst.   For example, the temperature of the exhaust gas is increased by delaying the moment when the fuel is injected from the fuel injection valve 5, thus allowing the catalyst temperature of NO. 4 increases. In addition, the internal combustion engine 1 is operated at a rich air-fuel ratio, whereby the exhaust gas whose oxygen concentration is reduced can pass through the NO 4 catalyst.   In addition, a method of increasing the NO 4 catalyst temperature or decreasing the oxygen concentration of the exhaust gas is exemplified by methods such as performing low temperature combustion. wherein an amount of exhaust gas recirculation gas (EGR) of the gas to be recirculated is increased relative to a maximum amount of soot produced, changing the injection timing of the fuel in the cylinder and the number of injections of fuel, the addition of fuel in the exhaust gas, supply to the catalyst of NO, 4 of secondary air while using the internal combustion engine with a rich air-fuel ratio, etc. These methods can also be executed. That is, in Example 1, these methods can be used as a catalyst temperature increase means in accordance with the present invention.   The ECU 6 defined as an electronic control unit for controlling the internal combustion engine 1 is provided in the internal combustion engine 1 designed as described above. This ECU unit 6 is a unit for controlling the operating state of the internal combustion engine 1 according to an operating condition of the internal combustion engine 1 and in response to a request from the driver.   An accelerator pedal divergence sensor 7 capable of outputting an electrical signal corresponding to a pedal depressing amount in which a driver depresses an accelerator pedal and detecting a state of charge on the pedal. vehicle, a crank position sensor 8 for detecting the number of revolutions of the internal combustion engine 1 and further, various sensors are also connected via electrical wiring to the ECU 9 2861424 unit. output signals from the various sensors described above are inputted to the ECU 6.   Furthermore, the fuel injection valve 5, etc., is connected via the electrical wiring to the ECU 6 and can thus be controlled by the ECU 6.   In addition, the ECU 6 has in memory various categories of application programs and control maps.   Here, as explained above, when the NOX 4 catalyst recovers from sulfur poisoning, it is required that the temperature of the NO 4 catalyst be kept high. When the power of the internal combustion engine 1 is reduced due to a decrease in the required power of the vehicle when recovering from sulfur poisoning, the exhaust gas temperature of the engine internal combustion 1 is decreased. In addition, when this exhaust gas passes through the NO 4 catalyst, it follows that the temperature of the NOX 4 catalyst decreases. From this point of view, when the internal combustion engine 1 is stopped and the vehicle moves thanks to the electric motor 32, the exhaust gas does not pass through the exhaust pipe 2, and consequently the fact that the catalyst temperature of NO 4 is decreased by the exhaust gas does not occur.   In such a case, in Example 1, during the recovery against sulfur poisoning, the internal combustion engine 1 is stopped in a state where the power of the internal combustion engine is maintained much higher so that the temperature decrease of the NO44 catalyst, which is necessary for recovery from sulfur poisoning, can be limited, and the vehicle is propelled by the electric motor 32 while the internal combustion engine 1 is stopped.   FIG. 2 is a graph showing the relationship between the number of revolutions and the generated torque (load) of the internal combustion engine and a stopping zone of the internal combustion engine in the case where the recovery control is opposite Sulfur poisoning is not performed. The charge of the internal combustion engine decreases when the torque generated by the internal combustion engine 1 is smaller. In addition, the required power of the vehicle becomes smaller when the number of revolutions of the load of the internal combustion engine decreases, that is, when the abscissa or ordinate axis approaches the lower left corner of the vehicle. whereas, moreover, the required power of the vehicle becomes greater when the number of revolutions or the load of the internal combustion engine becomes greater, that is to say when the x-axis and the y-axis come closer to the upper right corner of Figure 2.   Here, if the number of revolutions or the load of the internal combustion engine 1 is shifted below the line indicated by "ENGINE OFF" from one side with high revolutions / high load, that is ie, shifts to a side where the number of revolutions or the load decreases, the internal combustion engine 1 is stopped. Note that the internal combustion engine 1 remains stopped on the side below the line indicated by "MOTOR OFF", and therefore the number of revolutions and the generated torque (load) becomes really zero. Even when the operating state of the internal combustion engine 1 shifts below the line indicated by "ENGINE OFF", however, FIG. 2 shows the torque generated by the number of revolutions assuming that the internal combustion engine 1 must remain in the unstopped state. In addition, the generated torque of the internal combustion engine 1 may be interchangeable with the vehicle load.   On the contrary, the internal combustion engine 1 is not started, even when the required power of the vehicle goes from the high rev / high load side from the low / low load side under the line indicated by " ENGINE OFF, but it is started when the number of revolutions or the load increases to a line indicated by "ENGINE ON". So, we get from a request in terms of maneuverability, etc. that the internal combustion engine 1 is started and stopped in different operating states.   In addition, in an area on the side of the number of higher revolutions or the higher load with respect to a recovery limit line for sulfur poisoning, the temperature of the exhaust gas flowing through the NO catalyst, 4 is high. This zone is an operating zone (hereinafter referred to as the sulfur poisoning recovery zone) in which the temperature of the NOX 4 catalyst can be raised to a necessary temperature. for recovery against sulfur poisoning. Here, the recovery limit line vis-à-vis sulfur poisoning involves a similar power line or an exhaust gas temperature distribution.   Then, in FIG. 2, the line indicated by "STOP MOTOR" is positioned closer to the low / low load number side than the recovery limit line to poisoning by the sulfur. In this type of positioning, when the sulfur poisoning recovery command is executed, if the operating state of the internal combustion engine 1 is shifted closer to the low number of turns side / low load of the recovery zone from sulfur poisoning, it follows that the temperature of the NOX 4 catalyst decreases when the low temperature gas passes through the NO catalyst for a period of time. until the internal combustion engine 1 is stopped, i.e. in the operating zone between the recovery limit line for sulfur poisoning and the line indicated by "STOP MOTOR".   From this point of view, according to Example 1, during the recovery vis-à-vis a poisoning by sulfur, a stopping state (the line indicated by "ENGINE OFF") of the engine 1 is established so that the line indicated by "STOP MOTOR" exists within the recovery zone with respect to sulfur poisoning, that is to say that the line indicated by "STOP MOTOR" is closer to the high rev high load side (the high power side) than the recovery limit line to poisoning by the sulfur.   Here, FIG. 3 is a graph showing the relationship between the number of revolutions and the generated torque (load) of the internal combustion engine and the stopping zone of the internal combustion engine in the case where the recovery control -vis of poisoning by sulfur is carried out. Therefore, when performing the recovery command against sulfur poisoning, the operating state of the internal combustion engine 1 goes to the low / low load number side (the side of low power) and the result is that the internal combustion engine 1 can be stopped before the low temperature exhaust gas passes through the NO 4 catalyst.   An explanation of the control of the change of an operating condition in order to stop the internal combustion engine 1 during recovery against sulfur poisoning according to Example 1, is then given.   Fig. 4 is a flow chart showing the progress of the stop condition change control of the internal combustion engine of Example 1.   In step S101, it is evaluated whether or not a recovery condition for sulfur poisoning of the NO 4 catalyst is established.   This condition can be illustrated as indicating whether a quantity of SON stored in the NO 4 catalyst exceeds a specified amount, etc. The amount of SON storage can be obtained here from the fuel consumption, an output signal from a NO sensor, a vehicle mileage, etc. That is, the NO 4 catalyst suffers from poisoning by the sulfur compound contained in the fuel. As a result, the fuel consumption is integrated and stored in the ECU unit 6, and the amount of SON storage can also be obtained from this fuel consumption. In addition, if the sulfur poisoning of the NO catalyst progresses, the NO occluding capacity of the NO 4 catalyst decreases, and hence the proportion of NO passing through the NO 4 catalyst towards the downstream side without being stored. in the NO 4 catalyst is increased. Therefore, the NO sensor may be disposed downstream of the NO 4 catalyst, and the amount of SON storage can also be obtained based on an output signal of this NO sensor. In addition, assuming that the amount of SOUND stored increases according to the mileage of the vehicle, the amount of SOx storage can also be obtained based on the mileage of the vehicle fuel.   If an affirmative evaluation is obtained at step 5101, processing proceeds to step S102. Whereas if a negative assessment is obtained, the process of recovering from sulfur poisoning is not performed, and therefore the program is terminated.   In step S102, the stopping condition of the internal combustion engine 1, ie a tilting condition for propelling the vehicle by the electric motor 32, passes to the high load side or the number of high revolutions, that is, a high power side.   The tipping condition suggested here involves the line indicated by "ENGINE OFF". However, the line indicated by "ENGINE ON" can also be shifted to the high power side.   Thus, it is possible to prevent the temperature of the NO 4 catalyst from decreasing when the internal combustion engine 1 is started in the low power state. In addition, when the internal combustion engine 1 is started the next time, the catalyst temperature of NO4 4 can be increased rapidly to the temperature necessary for the recovery process vis-à-vis sulfur poisoning. . As a result, the period until recovery from sulfur poisoning is complete can be reduced, and fuel consumption can be improved.   It will be appreciated that other catalysts having an oxidation function such as an oxidation catalyst and a three-way catalyst may also be available as the NO 4 catalyst. [Example 2]   Example 1 described how to limit the decrease in NOX 4 catalyst temperature in the recovery process from sulfur poisoning of this NOX 4 catalyst. Example 2 will show how a case in which a particulate filter is provided midway in the exhaust gas duct 2, and the temperature of this particulate filter is increased so as to carry out an oxidation removal of the particulate matter collected by this filtered. Other configurations are identical to those of Example 1, and therefore their explanations are omitted. Here, it is assumed that the NOX 4 catalyst is supported by the particulate filter 40.   The particulate filter 40 (which will then simply be called filter 40) is disposed in the exhaust duct of the internal combustion engine 1, whereby the particulate materials (which will be referred to hereinafter as abbreviation "PM materials") existing in the exhaust gas can be collected by the filter 40. Then, a known technology is such that the temperature of the filter 40 is increased by providing the filter 40 with fuel, thus achieving the elimination by oxidation of the PM material collected by the filter 40. The removal of the PM material thus collected by the filter is called regeneration of the filter 40.   Here, similarly to the recovery from sulfur poisoning explained in Example 1, the temperature of the filter 40 can be increased by adding fuel to the exhaust gas, and so on. On this occasion, when the state of operation of the internal combustion engine 1 passes to the operating zone at low revolutions / low load (low power), the low temperature exhaust gas enters the filter 40, decreasing thus the temperature of the filter 40.   Then, according to example 2, the internal combustion engine 1 is stopped before the temperature of the filter 40 decreases, and the vehicle is moved in such a way that it switches the power source from the vehicle to the engine electric 32.   In this case, the possible regeneration zone of the filter is established in replacement of the regeneration zone with respect to sulfur poisoning explained in example 1. The possible regeneration zone of the filter suggested here represents a operating zone in which the exhaust gas entering the filter 40 has a high temperature, and the temperature of the filter 40 can be set to a temperature at which regeneration of the filter can be obtained. Then, the line indicated by "MOTOR OFF" is positioned inside this possible regeneration zone of the filter.   Therefore, even when the operating state of the internal combustion engine 1 passes into the zone of low revolutions / low load (low power) in the middle of the regeneration of the filter 40, it is possible to prevent the temperature of the filter 40 from decreasing. by stopping the internal combustion engine 1. This allows a reduction in the time required for the regeneration of the filter 40, whereby the fuel consumption 40 can be prevented from degrading.   It should be noted that the NOX 4 catalyst is carried by the filter 40, however, in place of this design, the NO4 4 catalyst may be disposed further upstream than the filter 40. In addition, other catalysts comprising the Oxidation function such as the oxidation catalyst and the three-way catalyst, may be available as a NO44 catalyst.   Although the invention has been described in terms of preferred embodiments, it will be appreciated by those skilled in the art that the invention may be practiced with modifications within the spirit and scope of the appended claims. . 16 2861424 CLAIMS   A device for purifying the exhaust gas of an internal combustion engine in a hybrid vehicle for traveling using an electric motor (32) as a power source while stopping an internal combustion engine (1) , said exhaust gas purification device comprising a catalyst (4, 40) disposed in an exhaust gas duct (2) of said internal combustion engine (1), an improvement being characterized in that it comprises in addition to a temperature increase means (5) for increasing the temperature of said catalyst (4, 40), and characterized in that, if an operating state of said internal combustion engine (1) becomes a state of decrease of the temperature of said catalyst (4, 40) when an increase of the temperature of said catalyst (4, 40) is required, the operation of said internal combustion engine (1) is stopped, and during the displacement of said vehicle, said word Electric power (32) is used as a power source.   An exhaust gas purifying device of an internal combustion engine according to claim 1, wherein said hybrid vehicle is propelled by said electric motor (32) at least in a low power area of said vehicle, and, when a temperature of said catalyst (4, 40) is increased by said catalyst temperature increasing means (5), the propulsion zone of said vehicle by said electric motor (32) is extended to a higher power side than when the temperature is not increased.   An exhaust gas purification device of an internal combustion engine according to claim 1 or 2, wherein said catalyst (4, 40) is a NO storage reduction catalyst, and the time of increase. the temperature of said catalyst (4, 40) corresponds to the time of recovery of said NOx storage reduction catalyst with respect to sulfur poisoning.   An exhaust gas purification device of an internal combustion engine according to claim 1 or 2, wherein said catalyst (4, 40) is a catalyst carried by a particulate filter or a catalyst is arranged further upstream than said particulate filter, and the time of increase of the temperature pressure of said catalyst (4, 40) corresponds to the moment of oxidation of the particulate matter collected by said particulate filter.