FR2808049A1 - EXHAUST GAS CLEANER FOR INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

An exhaust gas purifier for an internal combustion engine according to the invention comprises a particle filter (60) placed in an engine exhaust system, a supply means (61) for supplying nitrogen dioxide to the particle filter (60), and a flow means (62) for causing the flow of particles trapped by the particle filter (60) mainly in the particle filter (60). It is possible to burn the particles well using the nitrogen dioxide supplied to the particle filter (60) and prevent clogging of the particle filter (60).

Description

EXHAUST GAS CLEANER FOR A COMBUSTION ENGINE

INTERNAL

PRIOR ART

1. Field of the invention

  The present invention relates to an exhaust gas purifier for an internal combustion engine.

  2. Description of the related technique

  The exhaust gas from an internal combustion engine and, in particular, from a diesel engine, contains particles mainly composed of soot. Since the particles are harmful substances, it has been proposed that a filter serving to trap the particles before they are emitted into the atmosphere is placed in an engine exhaust system. Such a particulate filter is required to burn the trapped particles in order to prevent the resistance to exhaust gases from increasing due to clogging. In this regeneration of the filter, the particles ignite and burn as soon as they reach the temperature of about 600 degrees C. However, the gas temperature

  exhaust in a diesel engine is normally much less than 600 degrees C. It is generally necessary to provide some means for heating the filter itself.

  According to the content of the Japanese publication Japanese Patent Application Laid Open n 1-318715, if the nitrogen monoxide NO contained in an exhaust gas is converted into nitrogen dioxide NO2 using an oxidation catalyst , NO2 dioxide can burn particles on a filter

  at normal exhaust gas temperature even in the absence of heating means.

  However, the NO2 dioxide produced in the conversion by the oxidation catalyst does not necessarily come into contact with all of the particles trapped on the filter. Naturally, particles that do not come into contact

  with NO2 dioxide remain on the filter without being burnt.

  More particles from the exhaust gas are stacked on the particles that remain on the filter. These remaining particles covered with the stacked particles do not come into contact with the NO2 dioxide and certainly remain where they are. If a number of the stacked particles remain on the filter without coming into contact with the NO2 dioxide,

  more particles will be stacked on them and a similar phenomenon will occur. The particles that remain on the filter gradually become tumid and clog the filter.

SUMMARY OF THE INVENTION

  An object of the invention is to provide an exhaust gas purifier for an internal combustion engine capable of

  burn the particles well using the nitrogen dioxide15 supplied to a filter and prevent clogging of the particle filter.

  An exhaust gas purifier for an internal combustion engine according to a first aspect of the invention comprises a particulate filter placed in an engine exhaust system, a supply means for supplying nitrogen dioxide to the filter of particles, and a flow means for causing the circulation of the particles trapped by the particle filter mainly in the particle filter. According to the exhaust gas purifier of the invention, the particles circulating in the particle filter enter more

  frequently in contact with nitrogen dioxide and are well burned. Thus, there is no possibility that a large amount of particles will accumulate on the particle filter. Therefore, it is possible to prevent clogging of the particle filter.

  The flow means can be designed to reverse the upstream and downstream sides of the particulate filter.

  The feed means can be a catalyst

  oxidation placed in the engine exhaust system.

  The aspect of the invention is not limited to the exhaust gas purifier for the internal combustion engine as mentioned above. For example, another aspect of

  the invention relates to a vehicle equipped with an exhaust gas purifier for an internal combustion engine and to a technique for purifying the exhaust gas in an internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

  Figure 1 is a schematic longitudinal sectional view of a four-stroke diesel engine equipped with an exhaust gas purifier according to the present invention; Figure 2 is a plan view of a region near a switching part and a particle filter in

  an engine exhaust system. Figure 3 is a side view of Figure 2.

  Figure 4 shows a blocking position of a valve body in the switching part other than the position of

  blockage illustrated in Figure 2. Figure 5 shows an intermediate position of the valve body in the switching part.

  Figure 6 shows the structure of a particle filter.

  Figure 7 is an enlarged view of a partition wall of a particle filter Figure 8 is a first flowchart to prevent a large amount of particles from piling up on a filter

particles.

  Figure 9 is a second flow chart to prevent a large amount of particles from piling up on a particle film. Figure 10 is a third flowchart for emoecker

  that a large amount of particles is stacked on a particle filter.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS

  Figure 1 is a schematic sectional view of a four-stroke diesel engine equipped with an exhaust gas scrubber according to the present invention. As shown in Figure 1, the diesel engine comprises an engine body 1, a cylinder block 2, a cylinder head 3, a piston 4, a combustion chamber 5 formed on the upper face of the piston 4, an injection valve of electrically controlled fuel 6, a pair of intake valves 7, an intake port 8.5, a pair of exhaust valves 9 and an exhaust port 10. The intake port 8 is coupled to a expansion tank 12 via a corresponding connection tube 11 and the expansion tank 12 is coupled to an air filter 14 via an inlet pipe 13. A throttle valve 16 driven by an electric motor 15 is placed in the intake pipe 13. On the other hand, the exhaust orifice 10 is connected to a pipe

  exhaust 17. As shown in Figure 1, an air-

  fuel 21 is placed in the exhaust manifold 17. The exhaust manifold 17 and the expansion tank 12 are coupled to each other via an EGR passage 22. A valve for regulating RGE electrically controlled 23 is placed in the RGE passage 22. A cooling unit 24 is placed around the RGE passage 22 in order to cool the RGE gases circulating in the RGE passage 22. In the diesel engine illustrated in FIG. 1, the liquid of engine cooling is introduced into the cooling unit 24 in order to cool the RGE gas. 25 Each fuel injection valve 6 is coupled to a fuel tank, i.e., a common groove 26, via a fuel supply tube 25. The fuel is delivered to the common groove 26 by an electrically controlled fuel pump 27 whose quantity of discharge is variable. The fuel supplied in the common groove 26 is conveyed to the fuel injector 6 via the fuel supply tube 25. A fuel pressure sensor 28 serving to detect a fuel pressure in the common groove 26 is installed in the common groove 26. Based on the output signal from the fuel pressure sensor 28, the quantity supplied by the fuel pump 27 is controlled so that the fuel pressure in the common groove 26 becomes equal at a target fuel pressure. The output signals delivered by the air-fuel ratio sensor 21 and by the fuel pressure sensor 28 are injected at the input of an electronic control unit 30. A load sensor 41 which generates a proportional output voltage to the amount of vacuum .. L of an accelerator pedal 40 is connected to the accelerator pedal 40. The output signal delivered by the load sensor 41 is also injected at the input of the control unit electronics 30. In addition, the output signal from a crankshaft angle sensor 42, which generates an output pulse every time the crankshaft rotates, for example, 30 degrees AC, is also injected at the input of the electronic control unit 30. Thus, on the basis of the various signals, the electronic control unit 30 controls the fuel injection valve 6, the electronic engine 15, the EGR regulating valve 23, and the pump at fuel 27. Figure 2 is a plan view of an exhaust gas purifier according to an embodiment of the invention. Figure 3 is a side view of the exhaust gas scrubber. This exhaust gas purifier comprises a catalytic converter 61 which is connected to the downstream side of the exhaust pipe 17 of the diesel engine and which contains a noble metal such as platinum Pt as an oxidation catalyst, part of switching 62 located downstream of the catalytic converter 61, a particle filter 60, and an exhaust passage 64 downstream of the switching part 62. The particle filter has first30 and second faces 60a, 60b. The exhaust gas enters the particle filter through the first face 60a or through the second face 60b, and the exhaust gas exits the particle filter through the second face 60b or through the first face 60a. The first face 60a of the particle filter 60 and the switching part 62 are connected by a first connection part 63a while the second face 60b of the particle filter 60 and the switching part 62 are connected by a second connection part 63b . The switching part 62 includes a valve body 62a capable of blocking the flow of exhaust gas in the switching part 62. The valve body 62a is controlled by a negative pressure actuator, a stepping motor or the like. . When the valve body 62a takes a first blocking position, the upstream side of the switching part 62 communicates with the first connection part 63a while the downstream side of the switching part 62 communicates with the second connection part 63b. Thus, as shown by the arrows in FIG. 2, the exhaust gas circulates through the catalytic converter 61 and then in the direction going from the first face 60a to the second face 60b of the particle filter 60.15 FIG. 4 illustrates a second blocking position of the valve body 62a. When the valve body 62a takes the second blocking position, the upstream side of the switching part 62 communicates with the second connection part 63b while the downstream side of the switching part 62 communicates with the first connection part 63a. Thus, as shown by the arrows in FIG. 4, the exhaust gas circulates through the catalytic converter 61 and then in the direction going from the second face 60b to the first face 60a of the particle filter 60. Thus permuting the valve body 62a, it becomes possible to reverse the direction of the exhaust gas entering the particulate filter 60, that is to say, reverse the upstream and downstream sides of the particulate filter 60. Thus, the exhaust gas purifier of the invention allows to reverse the upstream and downstream sides of the particulate filter 60 using a very simple structure. A particulate filter requires a large opening area so that exhaust gas can easily enter and exit the particulate filter. As shown in Figures 2, 3.35 the exhaust gas purifier of the invention allows the use of a particulate filter 60 having a large opening area without adversely affecting its ability to be mounted to the vehicle. On the other hand, in the exhaust gas purifier of the invention, when the valve body 62a is rotated from the first blocking position to the second blocking position or from the second blocking position to the first blocking position, the exhaust gas is emitted into the atmosphere without passing through the particle filter 60 as shown in Figure 5. In the exhaust gas purifier of the invention, a throttle valve exhaust 65, the opening of which can be controlled by a stepping motor or similar device is placed downstream of the exhaust passage 64. FIGS. 6A, 6B illustrate the structure of the particle thread 60. FIG. 6A is a front view of the particle filter 60 while FIG. 6B is a side sectional view of the particle filter 60. As shown in FIGS. 6A, 6B, the particle filter 60 has an ellipsoidal front shape, is designed as being dimpled partition type20 having a honeycomb structure formed of a porous material such as cordierite, and has several axial spaces defined by several partition walls 54 yes extend in the axial direction. One of the two axial spaces is closed on the downstream side by a cork stopper 53 while the other space is closed on the upstream side by a stopper 52. Thus, one of the two adjacent axial spaces serves as a passage for entry 50 of the exhaust gas while the

  serves as an outlet passage 51 for the exhaust gas. As indicated by the arrows in FIG. 6B, the exhaust gas 30 inevitably flows through the partition walls 54.

  The particles contained in the exhaust gas are much smaller than the pores of the partition walls 54 and collide with the surfaces on the upstream side of the partition walls 54 and with the surfaces of the pores in the partition walls 54 and are trapped. Thus, each of the partition walls 54 acts as a trapping partition serving to trap the particles. In the present: embodiment, the exhaust gas containing particles circulates through the catalytic converter 61 before entering the particle filter 60. As is the case with the particle filter 60, the catalytic converter5 61 has a multitude of partition walls which extend in the axial direction, each containing a catalyst. However, unlike the particle filter 60, the axial spaces of the catalytic converter 61 are not closed on the downstream side by cork stoppers, and the exhaust gas does not circulate through the partition walls. Consequently, the particles are not trapped by the partition walls. In a diesel engine, combustion normally takes place with an excess amount of oxygen. So the gas

  exhaust includes a large amount of oxygen O2 and nitrogen monoxide NO generated in a combustion chamber.

  In the exhaust gas purifier of the invention, 02 and NO circulate through the catalytic converter 61 before entering the particulate filter 60, and are converted into nitrogen dioxide NO2 by an oxidation catalyst as indicated below

NO + M 02 NO2

  As indicated below, NO2 reacts well with particles mainly composed of carbon C at a temperature

relatively low.

  2N02 + 2C N2 + 2C02 or NO2 + C NO + CO Thus, if all the particles trapped on a particle filter come into contact with NO2, there will be no particles remaining on the particle filter. However, particles which have struck the upstream side surfaces of the particle filter partition walls and the pore surfaces in the partition walls facing the exhaust gas flow and which have been trapped do not necessarily enter contact with NO2. That is, it is all

  quite likely that a number of trapped particles will remain on the partition walls.

  More particles from the exhaust gas are stacked on the particles remaining on the filter and can come into contact with NO2. However, the remaining particles covered with the stacked particles will remain without coming into contact with NO2. If a number of the stacked particles remain on the filter without coming into contact with the NO2 dioxide, more particles will be stacked on them and a similar phenomenon will occur. Thus, as shown in FIG. 7A, the particles "Pa" which have been trapped pile up on the filter, even if it is in stages, on the surfaces on the upstream side of the partition walls 54 of the particle filter and on the pore surfaces in the partition walls 54 facing the flow of exhaust gas. The exhaust gas mainly strikes the surfaces on the upstream side of the partition walls 54. When the particles as shown in Figure 7A stack up, the exhaust gas resistance of the particle filter does not adversely affect the performance driving. However, if more particles pile up, there is a problem such as a substantial decrease in engine efficiency. In the present embodiment, the electronic control unit 30 performs the switching control of the valve body 62a according to a first flowchart illustrated in Figure 8 so as to prevent a large amount of particles from stacking on the particle filter. This flow chart is repeated at intervals of a predetermined time. First of all, in step 101, the cumulative value A of the operating distance of the vehicle is calculated. Then, in step 102, it is checked whether or not the cumulative value A of the operating distance is greater than or equal to a defined operating distance As. If the result of this check is negative, the operation is immediately ended. routine. On the other hand, if the result of the verification is positive, the operation continues in step 103. In step 103, the cumulative value A of the operating distance is reset to 0. In step 104 , for example, the valve body 62a is switched from the first blocking position to the second blocking position. That is, the upstream and downstream sides of the particle filter are reversed. While the vehicle is covering the defined operating distance As, the particles as shown in Fig. 7A can remain on the surfaces of the upstream side of the partition walls 54 of the particle filter and on the surfaces of the pores in the partition walls 54 facing the flow of exhaust gas, as described above. In this flowchart, the upstream and downstream sides of the particle filter are at this stage reversed. Thus, as shown in Figure 7B, the

  remaining particles are easily destroyed and broken down by the flowing exhaust gas generally flowing downward in the pores, and widely dispersing in the pores of the partition walls.

  The particles, which have therefore been broken and which circulate in the partitions, come more frequently into contact with the NO2 produced in the conversion by the catalytic oxidation converter 61. These particles are much more likely to burn than the

  remaining particles which remain covered with the stacked particles. Thus, it becomes possible to reliably burn the remaining particles through NO2 by ensuring that the particles remaining on the particle filter circulate in the partition walls.

  In the first flowchart, the valve body is switched each time the vehicle travels the predetermined operating distance. However, the valve body 35 can be switched at fixed time intervals. In fact, the valve body can be switched irregularly. If the particles remaining on the particle filter are left as they are for a long time, they may turn into carbonaceous material which is not likely to oxidize. Therefore, it is preferable that the valve body be switched so as to cause the flow of the remaining particles at least once during a period from starting the engine to stopping the engine. If the particles are burned before a large amount is stacked, problems are prevented. For example, the particle filter 10 is prevented from being damaged by dissolution caused by a large amount of combustion heat resulting from the sudden ignition of a large amount of stacked particles. Even if a large amount of particles have been stacked on the particle filter partition walls for some reason during switching of the valve body, the driving performance of the vehicle is not adversely affected. If the valve body has been switched, the stacked particles are destroyed and broken relatively easily by the reverse flow of the exhaust gas. Therefore, a number of the broken particles which have not been burnt by NO2 in the pores of the partition walls are removed from the particle filter. However, since the exhaust gas resistance of the particulate filter is further enhanced, the performance of

  driving is not adversely affected.

  Figure 9 illustrates a second flowchart for switching control of the valve body 62a. This flowchart is also repeated at intervals of a predetermined time. First of all, in step 201, the pressure of the exhaust gas P1 on a given side of the particulate filter 60, i.e., the pressure of the exhaust gas in the first connection part 63a (see Figure 2) is detected using a pressure sensor placed in the first connection portion 63a. Then in step 35 202, the pressure of the exhaust gas P2 on the other side of the particle filter 60, i.e., the pressure of the exhaust gas in the second connection part 63b (refer to FIG. 2 ) is detected using a pressure sensor placed in the second connection part 63a. In step 203, it is checked whether or not the absolute value of the difference in the exhaust gas pressures S detected in steps 201 and 202 is greater than or equal to a defined differential pressure Ps. The absolute value of the differential pressure is used herein to capture an increase in differential pressure regardless of whether the first connection portion 63a or the second connection portion 63b is located on the upstream side. If the result of the verification in step 203 is negative, the routine is immediately terminated. If the result of the check in step 203 is positive, a certain amount of particles remains on the particle filter. Thus, in step 204, the valve body 62a is switched so that the upstream and downstream sides

  of the particle filter are reversed. Therefore, as described above, the remaining particles burn and disappear from the particle filter.

  Thus, it is possible to indirectly detect, on the basis of the differential pressure between the opposite sides of the particle filter, that a certain amount of particles remains on the particle filter and to reliably prevent a substantial decrease in engine efficiency. having its origin in the stacking of more particles. In fact, it is also possible to use parameters other than differential pressure. For example, it is possible to monitor the changes in electrical resistance on a determined partition of the particle filter30 and to estimate, if the electrical resistance becomes less than or equal to a predefined value due to the stacking of particles, that 'a certain amount of particles remains on the particle filter. In addition, it is also possible to estimate, if the transmission factor or the reflection factor of light has decreased on a determined partition of the particle filter due to the stacking of the particles, that a certain amount of particles remains on the particle filter. By switching

  thus the valve body on the basis of the direct judgment relating to the remaining particles, it becomes possible to more reliably prevent a substantial decrease5 in the engine efficiency.

  Thus, inverting the upstream and downstream sides of the particle filter is highly effective in allowing the remaining particles to be burnt using NO2. Even if the valve body is sometimes switched regardless of timing, it is possible to sufficiently prevent a substantial decrease in engine efficiency resulting from the stacking of a large amount of particles. As previously described, the switching part 62 of this embodiment is constructed so that part of the exhaust gas bypasses the particle filter while the valve body 62a is moving from a blocked position given to the other blocking position. Thus, if the exhaust gas includes particles at this stage, the particles are emitted into the atmosphere. In order to prevent this phenomenon, the switching command of the valve body 62a is carried out according to a third flowchart illustrated in FIG. 10. As shown in the third flowchart, it is judged in step 301 whether or not a cutoff control fuel to stop the fuel supply to the internal combustion engine is running. If the result of this judgment in

  step 301 is negative, the routine ends immediately. On the other hand, if the result of the judgment in step 301 is positive, the operation continues in step 302 where the valve body 62a is switched from a given blocking position to the other blocking position. .

  Since combustion does not take place in the cylinders during the fuel cut-off command, no particles are included in the exhaust gas. Thus, if the valve body 62a is switched during the fuel cutoff control, no particles are emitted into the atmosphere while the valve body 62a is being switched. If a power failure command is not in progress, the switching of the valve body 62a is prevented so as to prevent the emission of particles into the atmosphere. In order to judge the need for the execution of a fuel cut command, it is possible to use a fuel cut signal transmitted to the fuel injection valve, or to detect the depression of the fuel pedal. brake when the vehicle is in

  movement, or to detect the release of the accelerator pedal10 when the vehicle is in motion.

  If the particle filter is at an extremely low temperature, it is unlikely that NO2 will react with the particles. Thus, as described above, it is effective in eliminating the drop in temperature of the particle filter15 that part of the exhaust gas bypasses the particle filter during the fuel cut-off control, while the exhaust gas is at a extremely low temperature. In the present embodiment, the upstream and downstream sides of the valve body 62a are reversed by switching the valve body 62a, and the result is that the particles remaining on the particle filter circulate in the partition walls. This is not intended to limit the invention. For example, during the switching period of the valve body 62a, the opening of the exhaust throttle valve 65 can be reduced once from its fully open state instead of switching the valve body 62a. As a result, the pressure on the upstream side of the particulate filter 60 increases once. If the exhaust throttle valve 65 is then returned to its fully open state, the exhaust gas enters the particulate filter at a high speed. Thus, even if the direction of flow of the exhaust gas is not reversed, the high speed exhaust gas easily destroys and breaks up the remaining particles. Since the broken particles circulate in the partition walls of the particle filter, they come into contact with NO2 more frequently and are well burned. In addition, in the case where the exhaust gas butterfly valve is placed upstream of the particle filter, the exhaust gas butterfly valve 65 is opened and closed in the same way. Therefore, the high speed exhaust gas flows through the particle filter when the exhaust gas valve 65 is in its fully open state. It is thus possible to cause the flow of the remaining particles. If the exhaust gas valve 65 is used to cause the flow of the remaining particles, it is not necessary to provide a special structure to invert the upstream and downstream sides of the particle filter. Reducing the opening of the exhaust throttle valve 65, which is used to cause the flow of particles, temporarily increases the pressure on the upstream side of the particle filter and increases the flow of exhaust gas through the filter of particles. Instead of reducing the opening of the exhaust throttle valve, a high pressure exhaust gas such as air can be supplied

  at high pressure on the upstream side of the particle filter.

  When a partition wall of the particulate filter traps particles, its upstream surface and the surfaces of the pores facing the flow of exhaust gas serve as the collection surface (a given collection surface). The exhaust gas mainly strikes the surface on the upstream side of the partition. If the upstream and downstream sides of the particle filter are reversed as in this embodiment, a collection surface located on the opposite side of the collection surface is used. In other words, after the inversion, the surface on the upstream side and the surfaces of the pores facing the flow of the exhaust gas serve as a collection surface (the other collection surface). is then triggered. 35 Thus, when the upstream and downstream sides of the particle filter are reversed, there is no possibility that more particles will be stacked on the particles remaining on a given collection surface. Thus, even if a certain number of particles remain on a given collection surface without circulating after reversing the direction of flow of the exhaust gas, these remaining particles5 can be gradually burned and eliminated from this surface by NO2. They can be completely burnt before the direction of flow of the exhaust gas is reversed again. Consequently, the inversion of the upstream and downstream sides of the particle filter means that the two collection surfaces of the partition wall of the particle filter are alternately used for the purpose of collecting

  particles. Therefore, reversing the upstream and downstream sides of the particle filter is highly beneficial not only for causing the flow of the remaining particles but also for burning them.

  In the present embodiment, the oxidation catalytic converter 61 is separated from the particle filter by a space. However, this does not limit the invention. Namely, the catalytic oxidation converter 61 can be placed so as to be adjacent to the particle filter. In the case of such an adjacent configuration, when the upstream and downstream sides of the particle filter are reversed with the intention of causing the flow of particles, it is preferable to place the catalytic oxidation converters upstream and downstream of the particle filter in an adjacent manner. However, after the remaining particles are gone and dispersed in the partition walls due to the inversion, the upstream and downstream sides of the particle filter are inverted again to burn the remaining particles with NO2. In this case, it is possible to place a catalytic oxidation converter only upstream of the particle filter. In the present embodiment, immediately after the NO2 used to burn the particles has been produced by conversion by the oxidation catalyst from the NO contained in the exhaust gas, the NO2 is fed to the particle filter. However, this does not limit the invention. For example, it is also possible to produce NO2 using another technique and feed it to the particle filter. The NO2 which has been produced by conversion from the NO contained in the exhaust gas can be temporarily stored in a container such as a tank and be fed to the particle filter by regulating the quantity as a function of the quantity of particles. created, which

  changes each time the engine operating state changes. The invention is also applicable to a gasoline engine which emits particles.

Claims (9)

  1. An exhaust gas purifier of an internal combustion engine comprising: a particle filter (60) placed in an engine exhaust system and on which the exhaust gas flows; supply means (61) for supplying nitrogen dioxide to the particle filter (60); and flow means (62) for agitating the particles trapped by the particle filter (60) mainly in the particle filter (60) 2. The exhaust gas purifier according to claim 1, wherein: the flow means (62, S104, S204, S302) reverses the   upstream and downstream sides of the particle filter.   The exhaust gas scrubber according to claim 2, further comprising: calculating means (S201, S202, S203) for calculating the absolute value of the difference between an upstream exhaust gas pressure of the particle filter (60) and an exhaust gas pressure downstream of the particle filter (60), wherein the flow means (S204) reverses the upstream and downstream sides of the particle filter if the absolute value of the differential pressure has become greater than or equal to a predetermined value.   4. The exhaust gas purifier according to claim 1, in which the particle filter (60) has a first face (60a) and a second face (60b) into which the exhaust gas penetrates or from which the gas exhaust comes out; and the flow means (S204) switches the direction of flow of the exhaust gas between a first direction in which the exhaust gas enters the particle filter (60) through the first face (60a) and then leaves the particle filter (60) through the second face (60b) and a second direction in which the exhaust gas enters the particle filter (60) through the second face (60b) and then leaves the particle filter (60) by the first face (60a).   I0 5. The exhaust gas purifier according to claim 4, further comprising: fuel cut-off control means (6, S301) for stopping the supply of fuel to the internal combustion engine (1) in which: the flow means (62, S302) switches the direction of flow of the exhaust gas between the first and second directions when the fuel cut control means (6) executes a fuel cut command. The exhaust gas purifier according to claim 1, further comprising: judging means (S102, S203, S301) for judging whether or not the amount of particles remaining on the particle filter (60) is greater than or equal to a predetermined amount, in which: the flow means (62) agitates the particles trapped by the particle filter (60) mainly in the particle filter (60) if the judgment means (S102, S203, S301 ) judges that the quantity of particles remaining   is greater than or equal to a predetermined amount.   The exhaust gas purifier according to claim 1, further comprising: calculating means (S101) for calculating an operating distance of the vehicle, wherein: the flow means (S104) agitates the particles trapped by the particle filter (60) mainly in the particle filter (60) if the operating distance   is greater than or equal to a predetermined distance.   8. The exhaust gas purifier according to claim 1, wherein: the flow means (62) increases the flow rate of the exhaust gas flowing through the particulate filter (60).   9. The exhaust gas purifier according to any one of claims   1 to 8, in which: The supply means (61) is a catalyst   oxidation placed in the engine exhaust system.