JP2018132018A - Exhaust emission control device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an engine capable of appropriately suppressing an emission amount of hydrocarbon, in a structure including an HC adsorption catalyst and an exhaust emission control catalyst provided on a downstream side thereof.SOLUTION: An exhaust emission control device of an engine includes a cooler 60 configured to cool an HC adsorption catalyst, and a cooling control unit 71 configured to operate the cooler at predetermined operation rate depending on a start state of the engine. The cooling control unit 71 comprises: a start state determination unit 72 configured to determine whether start of the engine originates from start in restoration of idling stop; and an operation rate adjustment unit 73 configured to, when the start state determination unit determines that start the engine originates from the start in restoration of idling stop, make an operation rate lower compared to a case where it is determined that the start of the engine does not originate from the start in restoration of idling stop.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an exhaust purification device for an engine (internal combustion engine) including an HC adsorption catalyst having a function of adsorbing hydrocarbons in exhaust.

  In exhaust gas discharged from an engine mounted on a vehicle such as an automobile, exhaust components such as carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) are included. For this reason, an exhaust purification catalyst such as a three-way catalyst or an oxidation catalyst for decomposing (oxidizing / reducing) the substance is provided in the exhaust passage of the engine.

  These exhaust purification catalysts, for example, have a high purification efficiency for hydrocarbons (HC). However, when the noble metal constituting the catalyst is below its oxidation activation temperature, it is difficult to exhibit catalytic performance. Therefore, when the catalyst is at the oxidation activation temperature or lower, such as when the engine is cold-started, there is a possibility that the amount of hydrocarbon emissions may temporarily increase.

  In view of this, some HC adsorption catalysts are further provided on the downstream side of these exhaust purification catalysts so as to suppress the amount of hydrocarbon emissions in a state below the oxidation activation temperature. The HC adsorption catalyst is composed of an adsorption layer that functions to adsorb and desorb hydrocarbons (HC), and a catalyst layer (three-way catalyst or oxidation catalyst) that oxidizes and removes hydrocarbons desorbed from the adsorption layer. The That is, in the HC adsorption catalyst, hydrocarbons are adsorbed by the adsorption layer in a state where the catalyst layer has not reached the oxidation activation temperature, and when the catalyst layer reaches the oxidation activation temperature, in the exhaust gas containing hydrocarbons desorbed from the adsorption layer. The harmful substances are purified by the catalyst layer.

  However, the desorption temperature at which hydrocarbons desorb from the adsorption layer is lower than the oxidation activation temperature. For this reason, even when an HC adsorption catalyst is provided, there is a possibility that the amount of discharged hydrocarbons may temporarily increase when the adsorption layer reaches the desorption temperature and the catalyst layer does not reach the oxidation activation temperature. .

  Therefore, there is one in which the HC adsorption catalyst is cooled by a cooling means (cooling device) until the warming-up of the engine is finished, thereby suppressing hydrocarbon emissions (for example, Patent Document 1).

  In the invention described in Patent Document 1, for example, while the engine has not been warmed up and the temperature of the HC adsorption catalyst has risen to near the HC desorption temperature, the engine is stopped by so-called idle stop. In addition, by cooling the HC adsorption catalyst by the cooling means, the amount of hydrocarbons discharged during restart is suppressed.

JP 2004-285933 A

  By the way, there is also an apparatus that further includes an exhaust purification catalyst for purifying hydrocarbons discharged from the HC adsorption catalyst on the downstream side of the HC adsorption catalyst. In this configuration, if the exhaust purification catalyst reaches the oxidation activation temperature, hydrocarbons flowing out from the HC adsorption catalyst can be purified by the exhaust purification catalyst. Therefore, it is less necessary to cool the HC adsorption catalyst while the engine is stopped due to idle stop.

  However, even if the exhaust purification catalyst has reached the oxidation activation temperature, at the time of start of idling stop return, for example, when the required output greatly increases, the exhaust gas is discharged from the HC adsorption catalyst as the temperature of the HC adsorption catalyst rises. The amount of hydrocarbons may increase. For example, hydrocarbons contained in exhaust gas discharged from the engine together with adsorbed hydrocarbons may flow out without being adsorbed by the HC adsorption catalyst. In this case, there is a possibility that the amount of hydrocarbons flowing into the exhaust purification catalyst will increase suddenly and the amount of unburned hydrocarbons discharged from the exhaust purification catalyst will increase. Such a problem is particularly likely to occur when a large amount of hydrocarbons are adsorbed on the HC adsorption catalyst by cooling the HC adsorption catalyst, for example.

  The present invention has been made in view of such circumstances, and in a configuration including an HC adsorption catalyst and an exhaust purification catalyst provided on the downstream side thereof, the amount of hydrocarbons discharged outside the vehicle can be appropriately suppressed. An object of the present invention is to provide an engine exhaust gas purification device.

  One aspect of the present invention that solves the above problems is an HC adsorption catalyst that is provided in an exhaust passage of an engine and has a function of adsorbing hydrocarbons in the exhaust, and an HC adsorption catalyst that is provided on the downstream side of the HC adsorption catalyst. An exhaust purification device for an engine having an exhaust purification catalyst for purifying a substance containing hydrocarbons, the cooling device for cooling the HC adsorption catalyst, and the cooling at a predetermined operating rate according to the engine start state A cooling control unit that operates the apparatus, and the cooling control unit determines whether or not the engine is started at the time of return from idle stop. If it is determined that the start of the engine is the start at the time of return from the idle stop, the operation is performed compared to the case where it is determined that the start of the engine is not the start at the time of return from the idle stop. Certain that the exhaust gas purification apparatus for an engine, characterized in comprising, a utilization rate adjustment unit for a low value.

  Here, it is preferable that the operating rate adjusting unit keeps the operating rate at a maximum value when the starting state determining unit determines that the engine is not started at the time of return from idle stop.

  In addition, when the start state determination unit determines that the start of the engine is the start at the time of idling stop return, the start of the engine is not based on a normal start based on a start operation by the driver and a start operation by the driver It is determined whether the engine is forcibly started, and when the start state determining unit determines that the start of the engine is the normal start, the operation rate adjusting unit outputs a request output when starting the engine. It is preferable to make the said operation rate small, so that it is small.

  In this case, when the start state determination unit determines that the engine start is the forced start, the operation rate adjustment unit maintains the operation rate at the minimum value until the accelerator pedal is depressed by the driver. It is preferable to do.

  Furthermore, it is preferable that the operating rate adjustment unit sets the minimum value of the operating rate to a higher value as the engine stop time by the idle stop control is longer.

  In the present invention, since the operating rate of the cooling device is appropriately adjusted depending on whether the engine start (restart) is the start at the time of return from idle stop, an appropriate amount of HC adsorption catalyst is used. Hydrocarbons can be adsorbed. Specifically, when the engine is started at the time of idle stop return (at the time of warm start), the operating rate of the cooling device is lower than when it is not started at the time of idle stop return (at the time of cold start). As a result, excessive adsorption of hydrocarbons to the HC adsorption catalyst is suppressed.

  Therefore, it is possible to suppress the amount of hydrocarbons discharged from the HC adsorption catalyst when starting at the time of idling stop return. Accordingly, the amount of hydrocarbons discharged from the exhaust purification catalyst provided downstream of the HC adsorption catalyst can also be suppressed.

1 is a diagram showing a schematic configuration of an engine including an exhaust purification device according to an embodiment of the present invention. It is a figure which shows the circulation flow path member of the cooling device which concerns on this invention, and is AA 'sectional drawing of FIG. 1 is a block diagram showing a schematic configuration of an exhaust emission control device according to the present invention. It is a figure which shows an example of the relationship between the request output with respect to an engine, and the operation rate of a cooling device. It is a figure which shows an example of the change of the operating rate of a cooling device. It is a flowchart which shows an example of the operation rate adjustment control by the exhaust gas purification apparatus which concerns on this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, the overall configuration of the engine including the exhaust emission control device according to the present invention will be briefly described. An engine 10 shown in FIG. 1 is an in-cylinder injection type gasoline engine, and includes a cylinder head 12 and a cylinder block 13. A plurality of cylinders 14 are formed in the cylinder block 13, and a piston 15 is accommodated in each cylinder 14 so as to be reciprocally movable. A combustion chamber 16 is formed by the piston 15, the cylinder 14, and the cylinder head 12. The piston 15 is connected to the crankshaft 18 via a connecting rod 17. The reciprocating motion of the piston 15 is transmitted to the crankshaft 18 via the connecting rod 17.

  An intake port 19 is formed in the cylinder head 12. An intake manifold 20 is connected to the intake port 19, and an intake pipe 21 is connected to the intake manifold 20. An intake valve 22 is provided in the intake port 19, and the intake port 19 is opened and closed by the intake valve 22. Further, an exhaust port 23 is formed in the cylinder head 12. One end of an exhaust manifold 24 is connected to the exhaust port 23, and an exhaust pipe 25 is connected to the other end of the exhaust manifold 24. The exhaust port 23 is provided with an exhaust valve 26, and the exhaust port 23 is opened and closed by the exhaust valve 26 in the same manner as the intake valve 22 in the intake port 19.

  A spark plug 27 is attached to the cylinder head 12 for each cylinder. Each spark plug 27 is connected to an ignition coil 28 that outputs a high voltage. Further, the cylinder head 12 is provided with an electromagnetic fuel injection valve 29 together with a spark plug 27. Each fuel injection valve 29 is connected to a fuel supply device (not shown) having a fuel tank via a fuel valve. In each combustion chamber 16, the fuel in the fuel tank is directly injected from each fuel injection valve 29.

  The intake pipe 21 on the upstream side of the intake manifold 20 is provided with a throttle valve 31 that adjusts the amount of intake air, and a throttle position sensor 32 that detects the valve opening of the throttle valve 31. Further, an air flow sensor 33 for measuring the intake air amount is interposed upstream of the throttle valve 31.

  On the upstream side of an exhaust pipe (exhaust passage) 25 connected to the exhaust manifold 24, a first three-way catalyst (upstream catalyst) 51 constituting the exhaust purification device 50 is provided close to the cylinder block 13 and the like. . Further, on the downstream side of the exhaust pipe 25, an HC adsorption catalyst 52 and a second three-way catalyst 53 constituting the exhaust purification device 50 are provided, for example, in a lower part of the floor of the vehicle. In this embodiment, the HC adsorption catalyst 52 and the second three-way catalyst 53 are accommodated in a single casing 54 made of metal. The HC adsorption catalyst 52 and the second three-way catalyst 53 may be accommodated in separate casings.

  Here, the first three-way catalyst 51 and the second three-way catalyst 53 that are exhaust purification catalysts have platinum (Pt), rhodium (Rh), or palladium (Pd) as an active noble metal on the carrier. ing. The active noble metal has an oxygen adsorption function (oxygen storage function) not only when it contains an oxygen storage material composed of cerium (Ce), zirconia (Zr), etc., but also when such an oxygen storage material is not included. doing.

  For this reason, when the first three-way catalyst 51 and the second three-way catalyst 53 adsorb oxygen in an oxidizing atmosphere in which the exhaust air-fuel ratio (exhaust A / F) is lean, the exhaust A / F becomes rich and a reducing atmosphere. The oxygen is retained as storage oxygen until By releasing (supplying) this storage oxygen when the reducing atmosphere is reached, harmful substances such as hydrocarbons (HC) and carbon monoxide (CO) are removed by oxidation even in the reducing atmosphere state. ing. The exhaust purification catalyst only needs to be able to purify harmful substances including hydrocarbons, and may be, for example, an oxidation catalyst.

  The HC adsorption catalyst 52 is made of, for example, platinum (Pt), for example, on a carrier made of a metal material, an adsorption layer (not shown) made of zeolite or the like that adsorbs HC, and the first three-way catalyst 51 etc. And a three-way catalyst layer (not shown) made of palladium (Pd), rhodium (Rh), or the like.

  The HC adsorption catalyst 52 efficiently adsorbs HC contained in the exhaust gas by the adsorption layer when the temperature is lower than the predetermined temperature, and the HC adsorbed by the adsorption layer when the temperature is raised by the exhaust gas heat and exceeds the predetermined temperature. Is removed and oxidized (purified) by the three-way catalyst layer. Either the adsorption layer or the three-way catalyst layer may be the upper layer.

  The HC adsorption catalyst 52 is provided with a cooling device 60 for cooling the HC adsorption catalyst 52. In this embodiment, the cooling device 60 includes a cooling pump (water pump) 61 for supplying cooling water, and a circulation channel member 62 that forms a circulation channel through which the cooling water supplied by the cooling pump 61 circulates. And. A part of the circulation flow path member 62 is provided so as to surround a portion of the casing 54 in which the HC adsorption catalyst 52 is accommodated, as shown in the sectional view of FIG.

  Then, the HC adsorption catalyst 52 in the casing 54 is cooled by driving the cooling pump 61 and circulating the cooling water in the circulation flow path member 62. In this embodiment, since the carrier of the HC adsorption catalyst 52 is formed of a metal material together with the casing 54, the HC adsorption catalyst 52 can be effectively cooled by the cooling water.

  The configuration of the cooling device 60 is not particularly limited as long as the HC adsorption catalyst 52 can be cooled. For example, the cooling device 60 may be configured to cool the HC adsorption catalyst 52 by a Peltier element or the like.

  The engine 10 includes a control device 70 that is an electronic control unit (ECU). The control device 70 includes an input / output device, a storage device (ROM, RAM, etc.), a central processing unit (CPU), a timer counter, and the like. The control device 70 performs overall control of the engine 10 based on information from various sensors (not shown) in addition to the throttle position sensor 32 and the airflow sensor 33 described above, for example.

  The control device 70 also functions as the exhaust gas purification device 50 according to the present invention, and appropriately controls the operating rate of the cooling device 60 described above based on the starting state of the engine 10. As shown in FIG. 3, the control device 70 includes a cooling control unit 71 that controls the operating state of the cooling device 60 for cooling the HC adsorption catalyst 52. The cooling control unit 71 includes a start state determination unit 72 and an operation rate adjustment unit 73, and operates the cooling device 60 (cooling pump 61) at a predetermined operation rate according to the start state of the engine 10.

  The start state determination unit 72 determines whether or not the start of the engine 10 is a start at the time of return to idle stop based on information from various sensors provided in the engine 10. Specifically, the start state determination unit 72 determines whether the engine 10 is started from a so-called ready-on state when the engine 10 is started from a stopped state or is restarted when the engine is stopped by so-called idle stop control. It is determined whether it is a start (start at idle stop return). That is, the start state determination unit 72 determines whether the engine 10 is started in a cold start in which the engine 10 is below a predetermined temperature or whether the engine 10 is in a warm start higher than the predetermined temperature. .

  The operating rate adjusting unit 73 appropriately adjusts the operating rate of the cooling device 60 (cooling pump 61) based on the determination result of the starting state determining unit 72. Specifically, when the start state determination unit 72 determines that the start of the engine 10 is not the start at the time of return to idle stop, the operation rate adjustment unit 73 holds the operation rate of the cooling device 60 as the maximum value. For example, the operating rate adjustment unit 73 appropriately adjusts the operating rate of the cooling device 60 based on a map that defines the relationship between the required output and the operating rate as illustrated in FIG. 4.

  When the start state determination unit 72 determines that the start of the engine 10 is a start from a so-called ready-on state (cold start), as shown by a dotted line in FIG. Regardless, the operating rate of the cooling device 60 is maintained as the maximum value Wa. The cooling control unit 71 operates the cooling device 60 at the operating rate (maximum value Wa) adjusted by the operating rate adjusting unit 73.

  When the engine 10 is started from the ready-on state, the temperature of the engine 10 and each catalyst is relatively low, and it is estimated that the first three-way catalyst 51 and the second three-way catalyst 53 have not reached the oxidation activation temperature. Is done. In this state, the amount of unburned hydrocarbons flowing into the HC adsorption catalyst 52 becomes relatively large, and unburned hydrocarbons discharged from the HC adsorption catalyst 52 are sufficiently purified by the second three-way catalyst 53. It is not (oxidized), and the amount of hydrocarbons discharged outside the vehicle tends to increase.

  However, in this embodiment, since the operating rate is set to the maximum value Wa and the cooling device 60 is operated, the temperature rise of the HC adsorption catalyst 52 is suppressed, and the amount of adsorption of hydrocarbons by the HC adsorption catalyst 52 is increased. Further, it is possible to effectively suppress the amount of hydrocarbons discharged outside the vehicle.

  However, regardless of the starting state of the engine 10, if the hydrocarbon adsorption amount of the HC adsorption catalyst 52 is increased, the hydrocarbons discharged from the HC adsorption catalyst 52 when the temperature of the HC adsorption catalyst 52 rises. The amount (peak value) of the catalyst increases greatly, and there is a possibility that the second three-way catalyst 53 may not be able to purify the hydrocarbons temporarily.

  For this reason, as described above, the operation rate adjustment unit 73 maintains the operation rate of the cooling device 60 as the maximum value Wa when the engine 10 is started from the ready-on state (cold start). When the engine 10 is started at the time of idling stop return (temperature start), the operating rate of the cooling device 60 is limited so that an appropriate amount of hydrocarbon is adsorbed by the HC adsorption catalyst 52. Yes.

  Specifically, when the start state determination unit 72 determines that the start of the engine 10 is a start at the time of return to idle stop, the operation rate adjustment unit 73 is compared to a case where it is determined that the start is not at the time of return to idle stop. The operating rate of the cooling device 60 is adjusted (limited) to a low value.

  Further, in the present embodiment, when the start of the engine 10 is a normal start based on a start operation (starting intention) by the driver, the operation rate adjusting unit 73 decreases the required output to the engine 10 (for example, depressing the accelerator pedal). The smaller the amount), the lower the operating rate of the cooling device 60 is adjusted. In other words, the operation rate of the cooling device 60 is adjusted to increase as the required output for the engine 10 increases.

  Specifically, when the start state determination unit 72 determines that the start of the engine 10 is a start at the time of return to idle stop, whether the start of the engine 10 is a normal start based on a start operation by the driver or a start by the driver It is determined whether the forced start is not based on the operation.

  Here, the normal start refers to a start of the engine 10 accompanied by a start operation (starting intention) by the driver such as a brake release operation or depression of an accelerator pedal, for example. On the other hand, the forced start is a start of the engine 10 that is forcibly performed regardless of whether or not the driver performs a starting operation, for example, when an electric load required from the vehicle becomes a predetermined value or more. Since the technology itself for starting or forcibly starting the engine at the time of idling stop is already existing, detailed description thereof will be omitted.

  When the start state determination unit 72 determines that the start of the engine 10 is a normal start, the operation rate adjusting unit 73 adjusts the operation rate of the cooling device 60 to be lower as the required output to the engine 10 is smaller. . For example, as indicated by a solid line in FIG. 4, the operating rate of the cooling device 60 at the normal start is limited to a value lower than the maximum value Wa, and from the minimum value Wb according to an increase in the required output to the engine 10. Increase at a substantially constant gain (rate of change). That is, the operating rate of the cooling device 60 is lowered as the required output to the engine 10 is smaller.

  On the other hand, when the start state determination unit 72 determines that the start of the engine 10 is a forced start, the operation rate adjustment unit 73 holds the operation rate of the cooling device 60 at the minimum value Wb (for example, Wb = 0). To do. After the engine 10 is started (forced start), the operating rate of the cooling device 60 is set to the minimum value Wb (for example, Wb = 0) until the accelerator pedal is depressed by the driver, that is, while the idling state is continued. ) To keep the cooling device 60 stopped. Thereafter, when the accelerator pedal is depressed by the driver, the operating rate of the cooling device 60 is adjusted according to the required output to the engine 10 as in the case of the normal start described above. For example, the operating rate of the cooling device 60 is increased according to an increase in the amount of depression of the accelerator pedal.

  As described above, the amount of hydrocarbons discharged outside the vehicle (the amount of hydrocarbons contained in the exhaust discharged outside the vehicle) is adjusted by appropriately adjusting the operating rate of the cooling device 60 according to the starting state of the engine 10. It can be suppressed appropriately.

  When the engine 10 is started at the time of idle stop return, the temperature of the engine 10 and each catalyst is relatively high, and the first three-way catalyst 51 and the second three-way catalyst 53 are also temperatures close to the oxidation activation temperature. It is estimated to be. For this reason, most of the unburned hydrocarbons contained in the exhaust gas are purified (oxidized) by the first three-way catalyst 51 and the second three-way catalyst 53. Therefore, even if the operating rate of the cooling device 60 is limited to suppress the amount of hydrocarbon adsorbed on the HC adsorption catalyst 52, the amount of hydrocarbon discharged outside the vehicle can be appropriately suppressed.

  In particular, in the present embodiment, when the engine 10 is started normally, the operating rate of the cooling device 60 is lowered as the required output to the engine 10 is smaller (for example, the amount of depression of the accelerator pedal is smaller). Therefore, the adsorption amount of hydrocarbons to the HC adsorption catalyst 52 can be adjusted more appropriately. As a result, the amount of hydrocarbons discharged outside the vehicle can be appropriately suppressed.

  Further, for example, when the engine 10 is forcibly started, the engine 10 is idling and the amount of hydrocarbons contained in the exhaust gas is relatively small. For this reason, until the driver depresses the accelerator pedal, the operation rate of the cooling device 60 is kept at the minimum value Wb, whereby the hydrocarbon adsorption to the HC adsorption catalyst 52 can be more appropriately suppressed. As a result, the amount of hydrocarbons discharged outside the vehicle can be appropriately suppressed.

  Then, by appropriately restricting the adsorption of hydrocarbons to the HC adsorption catalyst 52 in this manner, when the temperature of the HC adsorption catalyst 52 rises after the engine 10 is started, the hydrocarbon is discharged from the HC adsorption catalyst 52 (first). Since the increase in hydrocarbons flowing into the second three-way catalyst 53 is suppressed, the second three-way catalyst 53 can appropriately purify (oxidize) the hydrocarbons contained in the exhaust gas. Therefore, regardless of the temperature of the HC adsorption catalyst 52, the amount of hydrocarbons discharged outside the vehicle can be more appropriately suppressed.

  In addition, by appropriately controlling the operating rate of the cooling device 60 according to the starting state of the engine 10 in this way, the carbonization can be performed without detecting the temperature of the first three-way catalyst 51 or the second three-way catalyst 53. The amount of hydrogen discharged outside the vehicle can be more appropriately suppressed.

  By the way, when adjusting the operating rate of the cooling device 60 according to the starting state of the engine 10 in this way, the operating rate adjusting unit 73 further operates the cooling device 60 as the stop time of the engine 10 by idle stop control is longer. It is preferable to adjust so that the minimum value of the operation rate at the time of making it become a high value.

  For example, as shown in FIG. 5, when the engine 10 is started at time t1 after the engine 10 is stopped at time t0, the operating rate of the cooling device 60 is increased from the minimum value Wb1 to the required output for the engine 10. In response, the gain is increased with a substantially constant gain. Further, for example, when the engine 10 is started at time t2 later than the time t1, the operating rate of the cooling device 60 is set at a substantially constant gain according to an increase in required output for the engine 10 from the minimum value Wb2 (> Wb1). Raise. Further, for example, when the engine 10 is started at a time t3 later than the time t2, the operating rate is increased from the lowest value Wb3 (> Wb2) with a substantially constant gain according to an increase in the required output to the engine 10.

  Thus, by appropriately changing the minimum value of the operating rate of the cooling device 60 according to the stop period of the engine 10, it is possible to more appropriately suppress the amount of hydrocarbons discharged outside the vehicle.

  The longer the stop time of the engine 10 by idle stop control, the easier the temperatures of the first three-way catalyst 51 and the second three-way catalyst 53 fall. That is, the longer the stop time of the engine 10 by the idle stop control, the lower the temperature of the first three-way catalyst 51 and the second three-way catalyst 53 is lower than the oxidation activation temperature when the engine 10 is started. easy. For this reason, the longer the stop time of the engine 10, the higher the minimum value of the operating rate of the cooling device 60, so that hydrocarbons are appropriately adsorbed by the HC adsorption catalyst 52 and the hydrocarbons are discharged outside the vehicle. The amount can be further appropriately suppressed. The method for measuring the stop time of the engine 10 by idle stop control is not particularly limited, and may be measured by, for example, a counter timer provided in the control device 70.

  Thus, by appropriately adjusting the operating rate of the cooling device 60, even when the engine 10 is forcibly started, the amount of hydrocarbons discharged outside the vehicle can be appropriately suppressed.

  Next, an example of the operation rate adjustment control for adjusting the operation rate of the cooling device in the exhaust emission control device according to the present invention will be described with reference to the flowchart of FIG.

  As shown in FIG. 6, when the engine 10 is started, first, in step S1, it is determined whether or not the engine 10 is started at the time of idling stop return. Here, when it is determined that the engine 10 is started at the time of return from idle stop (step S1: Yes), the process proceeds to step S2, and the stop time of the engine 10 by idle stop control is acquired. Next, in step S3, the minimum value of the operation rate when the cooling device 60 is operated is adjusted according to the stop time of the engine 10. That is, the minimum value of the operating rate of the cooling device 60 is adjusted as the stop time of the engine 10 is longer (see FIG. 5).

  Next, it is determined whether or not the engine 10 is normally started (step S4). If it is determined that the start of the engine 10 is a normal start (step S4: Yes), the operating rate is adjusted according to the magnitude of the required output for the engine 10 to operate the cooling device 60 (step). S5). That is, the cooling device 60 is operated at a higher operation rate as the required output to the engine 10 is larger. Then, when a predetermined time elapses after the engine 10 is started (step S6: Yes), the operation of the cooling device 60 (cooling pump 61) is stopped in step S7, and a series of operation rate adjustment control ends.

  On the other hand, when it is determined in step S4 that the start of the engine 10 is a forced start (step S4: No), the operating rate is adjusted to the lowest value and the cooling device 60 (cooling pump 61) is operated ( Step S8). As described above, it is assumed that the minimum value of the operation rate includes zero. That is, the process of step S6 includes maintaining the cooling device 60 in a stopped state.

  Thereafter, if the accelerator pedal is not depressed by the driver (step S9: Yes), the process proceeds to step S10, and after a predetermined time has elapsed after the engine 10 is started (step S10: Yes), similarly to step S6, step S7 is performed. Then, the operation of the cooling device 60 (cooling pump 61) is stopped, and the series of operation rate adjustment control ends.

  If the driver depresses the accelerator pedal (step S9: No) until the predetermined time has elapsed (step S10: No), the process proceeds to step S5, and the engine 10 is turned on in the same manner as during normal start. The operating rate is adjusted according to the magnitude of the required output, and the cooling device 60 is operated.

  If it is determined in step S1 that the engine 10 is started from a so-called ready-on state and is not started at the time of idling stop return (step S1: No), the process proceeds to step S11, and the engine 10 is started. Regardless of the required output, the operating rate is adjusted to the maximum value, and the cooling device 60 (cooling pump 61) is operated. Thereafter, the process proceeds to step S6, and when a predetermined time has elapsed from the start of the engine 10 (step S6: Yes), the operation of the cooling device 60 (cooling pump 61) is stopped (step S7), and a series of operation rate adjustment control is completed. To do.

  As described above, according to the present invention, the operating rate of the cooling device 60 is appropriately adjusted in accordance with the starting state of the engine 10, so that the amount of hydrocarbons discharged outside the vehicle can be appropriately suppressed.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.

  For example, in the above-described embodiment, when the engine is started at the time of idling stop return and is a normal start, the operating rate of the cooling device is changed according to the required output to the engine. The operating rate may be substantially constant. If the operating rate of the cooling device is limited at least when the engine is not started at the time of idling stop return, the amount of hydrocarbons discharged outside the vehicle can be suppressed.

  Further, in the above-described embodiment, the in-cylinder injection type engine has been exemplified, but the present invention can be applied to other types of engines such as an intake pipe injection type engine.

DESCRIPTION OF SYMBOLS 10 Engine 12 Cylinder head 13 Cylinder block 14 Cylinder 15 Piston 16 Combustion chamber 17 Connecting rod 18 Crankshaft 19 Intake port 20 Intake manifold 21 Intake pipe 22 Intake valve 23 Exhaust port 24 Exhaust manifold 25 Exhaust pipe 26 Exhaust valve 27 Spark plug 28 Ignition coil DESCRIPTION OF SYMBOLS 29 Fuel injection valve 31 Throttle valve 32 Throttle position sensor 33 Air flow sensor 50 Exhaust purification device 51 1st three way catalyst 52 HC adsorption catalyst 53 2nd three way catalyst 54 Casing 60 Cooling device 61 Cooling pump 62 Circulation flow path member 70 Control device 71 Cooling control unit 72 Start state determination unit 73 Operation rate adjustment unit

Claims (5)

An HC adsorption catalyst that is provided in the exhaust passage of the engine and has a function of adsorbing hydrocarbons in the exhaust; and an exhaust purification catalyst that is provided downstream of the HC adsorption catalyst and purifies substances containing hydrocarbons in the exhaust. An exhaust purification device for an engine having
A cooling device for cooling the HC adsorption catalyst;
A cooling control unit that operates the cooling device at a predetermined operation rate according to a start state of the engine,
The cooling control unit
A starting state determination unit that determines whether or not the start of the engine is a start at the time of return from idle stop;
When the start state determination unit determines that the engine start is the start at the time of return from the idle stop, the operating rate is set as compared to the case where it is determined that the start of the engine is not the start at the time of return from the idle stop. An exhaust emission control device for an engine, comprising: an operating rate adjustment unit configured to have a low value. The exhaust emission control device for an engine according to claim 1,
The operating rate adjusting unit maintains the operating rate at a maximum value when the starting state determining unit determines that the engine is not started at the time of return from idle stop. apparatus. The engine exhaust gas purification apparatus according to claim 1 or 2,
When the start state determination unit determines that the start of the engine is the start at the time of idling stop return, the start of the engine is further compulsory not based on a normal start based on a start operation by the driver and a start operation by the driver. Determine whether it is a start,
The operating rate adjusting unit reduces the operating rate as the required output at the time of starting the engine is smaller when the starting state determining unit determines that the starting of the engine is the normal starting. Exhaust gas purification device for the engine. The engine exhaust gas purification apparatus according to claim 3,
The operating rate adjusting unit holds the operating rate at a minimum value until an accelerator pedal is depressed by a driver when the start state determining unit determines that the engine is started forcibly. Exhaust gas purification device for the engine. The engine exhaust gas purification apparatus according to claim 3 or 4,
The engine exhaust purification device according to claim 1, wherein the operating rate adjusting unit sets the minimum value of the operating rate to a higher value as the engine stop time by the idle stop control is longer.

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