JP6817926B2 - engine - Google Patents

Description

The present invention relates to an engine, and more particularly to an engine capable of increasing the EGR rate and suppressing thermal deterioration of the EGR valve device.

Conventionally, there is an engine provided with a main water channel for cooling an engine body, an EGR cooler, and an EGR valve device (see, for example, Patent Document 1).

JP-A-2010-185340 (see FIGS. 1, 4, and 6)

<< Problem >> The EGR rate becomes low.
In Patent Document 1, an EGR cooler and an exhaust gas recirculation device are connected in series to a single bypass channel, the channel resistance of the bypass channel is large, the amount of cooling water supplied to the EGR cooler is small, and the temperature of the EGR gas is reduced. Increases, the density of EGR gas decreases, and the EGR rate decreases.
<< Problem >> The EGR valve device is prone to thermal deterioration.
In Patent Document 1, the EGR valve device is cooled by air cooling having low cooling efficiency, the temperature of the EG device does not easily drop, and the EGR valve device tends to be thermally deteriorated.

An object of the present invention is to provide an engine capable of increasing the EGR rate and suppressing thermal deterioration of the EGR valve device.

The matters specifying the invention of the present invention are as follows.
As illustrated in FIG. 2, in an engine provided with a main water channel (21) for water-cooling the engine body (20), an EGR cooler (23), and an EGR valve device (27).
The EGR cooler (23) and the EGR valve device (27) are provided with a pair of bypass channels (22) (24) individually branched from the main channel (21), and the pair of bypass channels (22) (24). Connected to each individually ,
An engine characterized in that an exhaust gas recirculation device (8) and an EGR valve device (27) are connected in series to a bypass water channel (22) to which an EGR valve device (27) is connected.

The present invention has the following effects.
<< Effect >> The EGR rate increases.
The resistance of each of the pair of bypass channels (22) and (24) to which the EGR cooler (23) and the EGR valve device (27) are individually connected is small, and the bypass cooling water (24a) to the EGR cooler (23) The supply amount of the EGR gas (23a) is increased, the temperature of the EGR gas (23a) is lowered, the density of the EGR gas (23a) is increased, and the EGR rate is increased.
<< Effect >> Thermal deterioration of the EGR valve device is suppressed.
The EGR valve device (27) is cooled by water cooling having high cooling efficiency, the temperature of the EGR valve device (27) is lowered, and the thermal deterioration of the EGR valve device (27) is suppressed.
<< Effect >> The thermal deterioration suppressing function of the EGR valve device is enhanced.
The resistance of each of the pair of bypass channels (22) and (24) is small, the amount of cooling water supplied to the EGR valve device (27) increases, the temperature of the EGR valve device (27) decreases, and the EGR valve device (10) )'S thermal deterioration suppression function is enhanced.
<< Effect >> The number of bypass canals is reduced.
By sharing the bypass passage (22), the number of bypass passages will be reduced.
<< Effect >> The EGR rate does not decrease.
There is no risk that the supply amount of the bypass cooling water (24a) to the EGR cooler (23) will decrease due to the water channel resistance of the exhaust gas recirculation device (8) and the EGR valve device (27), and the cooling efficiency of the EGR cooler (23) is high. It is maintained and the EGR rate does not decrease.

FIG. 1 (A) is a basic example, FIG. 1 (B) is a modified example in which the mounting structure of the catalyst case is different, and FIG. 1 (C) is an exhaust gas in a schematic diagram illustrating an engine exhaust device according to an embodiment of the present invention. A modified example in which the arrangement of the temperature sensors is different is shown. It is a schematic diagram explaining the water cooling system of the engine of FIG. It is a flowchart explaining the control of the clogging elimination mode of the engine of FIG. It is a flowchart explaining the control of the DPF regeneration mode of the engine of FIG.

1 to 4 are views for explaining an engine according to an embodiment of the invention.
In the embodiment, a vertical water-cooled in-line multi-cylinder diesel engine is used.

The engine according to the embodiment of the present invention will be described.
As shown in FIG. 1 (A), this engine includes a cylinder block (20a) and a cylinder head (20b) attached to the top of the cylinder block (20a). A cooling water pump (25) and a pacing transmission case (15) are assembled to the front part of the cylinder block (20a) with the erection direction of the crankshaft (14) in the front-rear direction, one in front and the other in rear. There is. An engine cooling fan (16) is attached to the pump input shaft of the cooling water pump (25), and the cooling water pump (25) and the engine cooling fan (16) are connected to the crankshaft (14) via a fan belt (17). Driven by. A radiator (26) is arranged in front of the engine cooling fan (16). A flywheel (14a) attached to the rear end of the crankshaft (14) is arranged at the rear of the cylinder block (20a).

As shown in FIG. 1 (A), the exhaust manifold (1) is assembled on one lateral side of the cylinder head (20b) with the width direction of the engine as the lateral direction, and the exhaust manifold (1) is connected from the manifold outlet (1a). The exhaust derivation path (2) is derived. The exhaust lead-out path (2) includes a supercharger (6), a catalyst case (3), an exhaust throttle device (8), and an exhaust purification case (18) arranged in order from the exhaust upstream side, and exhausts. The exhaust gas (5) flowing out from the manifold outlet (1a) of the manifold (1) passes through the turbocharger (6) turbine, catalyst case (3), exhaust throttle device (8), and exhaust purification case (18) in this order. Is released.

As shown in FIG. 1 (A), the intake manifold (30) is assembled on the lateral other side of the cylinder head (20b), and the intake manifold (30) is connected to the manifold inlet (30a) via the supercharging pipe (31). The compressor outlet (6b) of the supercharger (6) is connected, the air cleaner (33) is connected to the compressor inlet (6c) via the airflow sensor case (32), and the air (34) is the air cleaner (33). ), The compressor of the supercharger (6), the supercharging pipe (31), and the manifold inlet (30a) are supercharged to the intake manifold (30) in this order.

As shown in FIG. 1 (A), the EGR gas derivation path (19) is derived from the exhaust manifold (1), and the EGR gas derivation path (19) is the EGR cooler (23) and the EGR in order from the derivation upstream side. A valve device (27) is provided, and the outlet end of the EGR gas outlet path (19) is connected to the manifold inlet (30a) of the intake manifold (30), and the exhaust gas diverged from the exhaust (5) of the exhaust manifold (1). A part of the EGR gas (23a) is supplied to the intake manifold (30) via the EGR cooler (23) and the EGR valve device (27) in this order.

This engine includes a fuel injection valve (35) of a common rail type combustion injection device and a control device (10) for controlling the opening of the fuel injection valve (35), and the control device (10) is a predetermined sensor. The fuel injection timing and injection amount from the fuel injection valve (35) are set based on the detected engine target rotation speed, engine actual rotation speed, engine load, intake amount, and intake temperature.
An engine ECU is used in the control device (10). ECU is an abbreviation for electronic control unit and is a microcomputer.

As shown in FIGS. 1A and 1B, this engine has an exhaust manifold (1), an exhaust lead-out path (2) derived from the manifold outlet (1a) of the exhaust manifold (1), and an exhaust lead-out path. It includes a catalyst case (3) provided in (2) and a catalyst (4) housed in the catalyst case (3).
The exhaust manifold (1) and the catalyst case (3) are both erected in the front-rear direction with the erection direction of the crankshaft (14) as the front-rear direction, and are arranged side by side in the direction orthogonal to the front-rear direction.

This engine has the following advantages:
The catalyst case (3) is arranged near the manifold outlet (1a) of the exhaust manifold (1), and the temperature of the exhaust (5) flowing out from the manifold outlet (1a) drops by the time it reaches the catalyst (4). It is difficult and the activation of the catalyst (4) is promoted.
The heat radiation from the catalyst case (3) is suppressed by the radiant heat from the wall (1b) of the exhaust manifold (1), the temperature of the catalyst (4) is unlikely to decrease, and the activation temperature of the catalyst (4) is easily maintained.
The exhaust manifold (1) and the catalyst case (3) are arranged one above the other, with the catalyst case (3) at the top and the exhaust manifold (1) at the bottom.
The catalyst case (3) is made of metal and is arranged above the upper wall (1b) of the exhaust manifold (1) and along the wall (1b).
The exhaust manifold (1) and the catalyst case (3) may have the catalyst case (3) at the bottom and the exhaust manifold (1) at the top.
The exhaust manifold (1) and the catalyst case (3) may be arranged side by side at the same height, or may be arranged side by side at different heights.

The catalyst (4) on the upstream side of the exhaust of the exhaust throttle device (8) is a catalyst for purifying the exhaust gas and raising the temperature of the exhaust gas by purifying the harmful components in the exhaust gas (5) and catalytically burning the unburned fuel.
DOC is used for the catalyst (4). DOC is an abbreviation for diesel oxidation catalyst. The DOC is a flow-through honeycomb type in which a large number of cells along the axial length direction are arranged side by side in a penetrating manner. An oxidation catalyst component is supported in the cell of the DOC. In DOC, HC (hydrocarbon) and CO (carbon monoxide) in the exhaust gas (5) are oxidized to H ₂ O (water) and CO ₂ . Further, in the DOC, the unburned fuel supplied into the exhaust gas (5) is catalytically burned, the temperature of the exhaust gas (5) rises, and the DPF (12) arranged downstream is regenerated. When the catalyst downstream side catalyst (13) is used instead of the DPF (12), its temperature rises and activation is achieved.

DPF is an abbreviation for diesel particulate filter, which captures PM contained in the exhaust gas (5). PM is an abbreviation for particulate matter.
The DPF (12) is a wall-flow honeycomb type in which a large number of cells along the axial length direction are arranged side by side, and the exhaust inlets (12a) and exhaust outlets (12b) of adjacent cells are alternately sealed. is there.

The catalyst (4) of the exhaust upstream side of the exhaust aperture device (8), can be used SCR catalyst and, NO _X occluding and reducing catalyst.
As the catalyst (4), an SCR catalyst or a NO _X storage reduction catalyst can be used.
The SCR catalyst is an abbreviation for Selective Catalytic Reduction type catalyst, and a flow-through honeycomb type catalyst in which a large number of cells along the axial length direction are arranged side by side in a penetrating manner is used, and the exhaust upstream thereof. A urea water injector is arranged on the side, and ammonia gas is obtained at high temperature by injecting urea water into the exhaust gas, and NOx (nitrogen oxide) is reduced by this ammonia to N ₂ (nitrogen gas) and H ₂ Obtain O (water vapor).
The NO _X storage reduction catalyst is a catalyst that temporarily stores NO _X in the exhaust gas and then reduces (converts to N ₂ ) NO _X.

As shown in FIG. 1 (A), the supercharger (6) is provided at the manifold outlet (1a) of the exhaust manifold (1), and the catalyst case (3) is the turbine outlet of the supercharger (6). It is attached to (6a).
This engine has the following advantages:
The catalyst case (3) is arranged at a position close to the manifold outlet (1a) of the exhaust manifold (1), and the activation of the catalyst (4) is easily promoted.

As shown in FIG. 1 (B), the attachment of the catalyst case (3) may be modified as follows.
That is, the exhaust relay pipe (7) attached to the manifold outlet (1a) of the exhaust manifold (1) is provided, and the catalyst case (3) is attached to the relay pipe outlet (7a) of the exhaust relay pipe (7). It may be a thing.
In this case as well, the engine has the following advantages similar to those described above.
That is, the catalyst case (3) is arranged at a position close to the manifold outlet (1a) of the exhaust manifold (1), and the activation of the catalyst (4) is promoted.
An elbow pipe is used for the exhaust relay pipe (7).

As shown in FIG. 1 (A), an exhaust throttle device (8) provided downstream of the exhaust of the catalyst (4) is provided.
This engine has the following advantages:
Due to the increase in back pressure due to the throttle of the exhaust throttle device (8), the temperature of the exhaust (5) rises, the temperature of the catalyst (4) rises, and the unburned material adhering to the exhaust inlet (4a) of the catalyst (4) Incineration of deposits and activation of catalyst (4) are promoted.

The unburned deposit adhering to the exhaust inlet (4a) of the catalyst (4) is a mixture of unburned fuel and PM of the main injection fuel, and when the engine load is small and the exhaust temperature is low, the catalyst (4) It easily accumulates in the exhaust port (4a) of the catalyst (4) and clogs it.

As shown in FIG. 1 (C), the exhaust temperature sensor (9) arranged at the position closest to the exhaust downstream side of the exhaust throttle device (8) is linked with the exhaust temperature sensor (9) and the exhaust throttle device (8). The control device (10) is provided, and the control device (10) is configured to adjust the opening degree of the exhaust throttle device (8) based on the temperature of the exhaust (5) detected by the exhaust temperature sensor (9). It may have been.
In this case, the engine has the following advantages:
The exhaust temperature sensor (9) that detects the temperature of the exhaust (5) at the position closest to the exhaust downstream side of the exhaust throttle device (8) quickly raises the temperature of the exhaust (5) on the upstream side of the exhaust throttle device (8). The control delay of the opening degree of the exhaust throttle device (8) is unlikely to occur, the temperature of the exhaust (5) does not rise too much, and the thermal deterioration of the exhaust throttle device (8) is suppressed.
The separation distance from the exhaust throttle device (8) to the exhaust temperature sensor (9) is sufficiently shorter than the separation distance from the exhaust throttle device (8) to the catalyst (11) on the downstream side of the throttle, and the former is half of the latter. It is preferably less than one, and more preferably less than one-third of the latter.

As shown in FIG. 1 (A), a catalyst (11) on the downstream side of the throttle is provided downstream of the exhaust throttle device (8), and the control device (10) is detected by the exhaust temperature sensor (9). Based on the temperature of the exhaust (5), the temperature of the exhaust (5) on the exhaust inlet (11a) side of the catalyst (11) on the downstream side of the throttle of the exhaust throttle device (8) is estimated, and the temperature of the exhaust (5) Based on the estimation, it is configured to control the exhaust gas treatment using the catalyst (11) on the downstream side of the throttle.
This engine has the following advantages:
The exhaust temperature sensor (9) used for controlling the exhaust throttle device (8) is also used for controlling the exhaust treatment using the throttle downstream side catalyst (11), and the number of exhaust temperature sensors is reduced.

The same catalyst as the catalyst (4) on the upstream side of the drawing can be used for the catalyst (11) on the downstream side of the drawing. The same DOC as that of the catalyst (4) on the upstream side of the drawing is used for the catalyst (11) on the downstream side of the drawing.

As shown in FIG. 1 (A), in the exhaust treatment using the throttle downstream side catalyst (11), the exhaust gas temperature rise in which the unburned fuel supplied into the exhaust (5) is catalytically burned by the throttle downstream side catalyst (11). With processing.
This engine has the following advantages:
When the DPF (12) is arranged on the downstream side of the throttle downstream side catalyst (11), the DPF (12) can be regenerated by the exhaust temperature raising process.
When the catalyst downstream side catalyst (13) is arranged on the downstream side of the throttle downstream side catalyst (11) instead of the DPF (12), the catalyst downstream side catalyst (13) can be activated by the exhaust gas temperature raising treatment. It becomes.

The throttle downstream side catalyst (11) and DPF (12) are housed in the exhaust purification case (18), the throttle downstream side catalyst (11) is arranged on the exhaust upstream side, and the DPF (12) is arranged on the exhaust downstream side. ing.
When the catalyst downstream side catalyst (13) is used instead of the DPF (12), the catalyst downstream side catalyst (13) is arranged on the exhaust downstream side of the throttle downstream side catalyst (11).
A catalyst similar to that of the catalyst (4) on the upstream side of the drawing can be used for the catalyst (11) on the downstream side of the drawing. It is desirable to use the same DOC as the catalyst (4) on the upstream side of the drawing for the catalyst (11) on the downstream side of the drawing.
The catalyst downstream catalyst (13), can be used SCR catalyst and _the NO _X storage and reduction catalyst or the like in place of DOC.
When an SCR catalyst is used as the throttle downstream side catalyst (11), it is desirable to use DOC as the catalyst downstream side catalyst (13) to purify the ammonia that has passed through the SCR catalyst.

The configuration of the water cooling device is as follows.
As shown in FIG. 2, a main water channel (21) for cooling the engine body (20) and a bypass water channel (22) branched from the main water channel (21) are provided, and an exhaust throttle device (8) is provided in the bypass water channel (22). ) Is connected.
This engine has the following advantages:
The exhaust throttle device (8) heated by the exhaust (5) is water-cooled, the temperature of the exhaust throttle device (8) is lowered, and the thermal deterioration of the exhaust throttle device (8) is suppressed.

The exhaust throttle device (8) includes an exhaust throttle valve (8a), a valve case (8b), a water jacket (8c) along the valve case (8b), and a valve drive actuator (8d) penetrating the water jacket (8c). The bypass cooling water (22a) to the exhaust throttle device (8) passes through the water jacket (8c) and water-cools the valve case (8b) and the valve drive actuator (8d).

As shown in FIG. 2, this engine includes a main water channel (21) for water-cooling the engine body (20), an EGR cooler (23), and an EGR valve device (27).
The EGR cooler (23) and the EGR valve device (27) are provided with a pair of bypass channels (22) and (24) individually branched from the main channel (21), and the pair of bypass channels (22) (24). Are individually connected to each other.
This engine has the following advantages:
The resistance of each of the pair of bypass channels (22) and (24) to which the EGR cooler (23) and the EGR valve device (27) are individually connected is small, and the bypass cooling water (24a) to the EGR cooler (23) The supply amount of the EGR gas (23a) is increased, the temperature of the EGR gas (23a) is lowered, the density of the EGR gas (23a) is increased, and the EGR rate is increased.
The EGR valve device (27) is cooled by water cooling having high cooling efficiency, the temperature of the EGR valve device (27) is lowered, and the thermal deterioration of the EGR valve device (27) is suppressed.
The resistance of each of the pair of bypass channels (22) and (24) is small, the amount of cooling water supplied to the EGR valve device (27) increases, the temperature of the EGR valve device (27) decreases, and the EGR valve device (10) )'S thermal deterioration suppression function is enhanced.

The EGR cooler (23) includes a plurality of heat radiating pipes (23b) through which the EGR gas (23a) passes, and a water jacket (23c) surrounding the radiating pipes (23b) arranged side by side, and the water jacket (23c) is provided. The EGR gas (23a) is water-cooled by the bypass cooling water (22a) passing through.

As shown in FIG. 2, the main water channel (21) is driven by the cooling water pump (25), and the main cooling water (21a) is the water jacket (20d) of the cylinder block (20a) and the cylinder head (20b). The water jacket (20e) and the radiator (26) are configured to circulate in this order.
The bypass channel (24) to which the EGR cooler (23) is connected is branched from the water jacket (20d) of the cylinder block (20a).
This engine has the following advantages:
The bypass cooling water (24a) separated from the relatively low temperature main cooling water (21a) before the temperature of the cylinder head (20b) becomes high is supplied to the EGR cooler (23), and the cooling performance of the EGR cooler (23) is improved. ..

As shown in FIG. 2, the water jacket (20e) of the cylinder head (20b) is attached to the radiator (26) with the erection direction of the crankshaft (14) in the front-rear direction, any one of them on the front side, and the other on the rear side. A main cooling water outlet (20c) for sending out the main cooling water (21a) is provided on the front side.

As shown in FIG. 2, the exhaust gas recirculation device (8) and the EGR valve device (27) are connected in series to the bypass water channel (22) to which the EGR valve device (27) is connected.

This engine has the following advantages:
By sharing the bypass passage (22), the number of bypass passages will be reduced.
Further, since the EGR cooler (23) is not connected to the bypass water channel (22) to which the exhaust gas recirculation device (8) and the EGR valve device (27) are connected, the exhaust gas recirculation device (8) and the EGR valve device (27) are not connected. ), There is no possibility that the supply amount of the bypass cooling water (24a) to the EGR cooler (23) will be reduced, the cooling efficiency of the EGR cooler (23) will be maintained high, and the EGR rate will not decrease.

The EGR valve device (27) includes an EGR valve (27a), a valve case (27b), a water jacket (27c) along the valve case (27b), and a valve drive actuator (27d) penetrating the water jacket (27c). The bypass cooling water (28a) to the EGR valve device (27) passes through the water jacket (27c) and water-cools the valve case (27b) and the valve drive actuator (27d).

As shown in FIG. 2, the EGR valve device (27) is connected to the upstream side of the bypass channel (22) to which the EGR valve device (27) and the exhaust throttle device (8) are connected, and the exhaust throttle device (27) is connected to the downstream side. (8) is connected.
The bypass cooling water (28a) having an appropriate temperature that has absorbed the heat of the EGR valve device (27) is supplied to the high-temperature exhaust throttle device (8), and malfunction due to overcooling of the exhaust throttle device (8) is suppressed.

As shown in FIG. 1 (A), the EGR valve device (27) is arranged on the downstream side of the flow path of the EGR gas (23a) with respect to the EGR cooler (23).
This engine has the following advantages:
Since the relatively low temperature EGR gas (23a) cooled by the EGR cooler (23) is supplied to the EGR valve device (27), the heat load of the EGR valve device (27) is small, as shown in FIG. Even if the supply amount of the bypass cooling water (22a) is reduced due to the water channel resistance of the exhaust gas recirculation device (8), there is no problem in cooling the EGR valve device (27), and the heat of the EGR valve device (27) is not hindered. Deterioration is suppressed.

As shown in FIG. 2, the main water channel (21) is driven by the cooling water pump (25), and the main cooling water (21a) is the water jacket (20d) of the cylinder block (20a) and the cylinder head (20b). The water jacket (20e) and the radiator (26) are configured to circulate in this order.
The bypass passage (22) to which the EGR valve device (27) and the exhaust throttle device (8) are connected is derived from the water jacket (20d) of the cylinder block (20a).
This engine has the following advantages:
The bypass cooling water (22a) separated from the relatively low temperature main cooling water (21a) before the temperature of the cylinder head (20b) becomes high is supplied to the EGR valve device (27) and the exhaust gas recirculation device (8), and the EGR valve. The cooling performance of the device (27) and the exhaust gas recirculation device (8) is improved.

As shown in FIG. 2, as described above, the bypass passage (22) to which the exhaust throttle device (8) is connected is derived from the water jacket (20d) of the cylinder block (20a).
This engine has the following advantages:
The bypass cooling water (22a) separated from the relatively low temperature main cooling water (21a) before the temperature of the cylinder head (20b) becomes high is supplied to the exhaust throttle device (8), and the cooling performance of the exhaust throttle device (8). Will increase.

As shown in FIG. 2, as described above, the bypass passage (22) to which the EGR valve device (27) is connected is derived from the water jacket (20d) of the cylinder block (20a).
This engine has the following advantages:
The bypass cooling water (22a) separated from the relatively low temperature main cooling water (21a) before the temperature of the cylinder head (20b) becomes high is supplied to the EGR valve device (27), and the cooling performance of the EGR valve device (27). Will increase.

The flow of engine control is as follows.
In this engine, the following control is performed by the control device (10).
The clogging clearing mode shown in FIG. 3 is performed when it is determined that the exhaust inlet (4a) of the catalyst (4) is clogged with unburned deposits.
The DPF regeneration mode shown in FIG. 4 is carried out when PM is deposited on the DPF (12) and a DPF regeneration request is made.
If a DPF regeneration request is made during the execution of the clogging clearing mode, the DPF regeneration mode is carried out after the clogging of the exhaust inlet (4a) of the catalyst (4) is cleared in the clogging clearing mode. ..
If the clogging determination of the catalyst (4) is affirmed during the execution of the DPF regeneration mode, the DPF regeneration is performed after the clogging of the exhaust inlet (4a) of the catalyst (4) is cleared in the clogging clearing mode. The mode is resumed.

As shown in FIG. 3, in step (S1), it is determined whether or not the exhaust inlet (4a) of the catalyst (4) is clogged with unburned deposits. If the determination of clogging in step (S1) is denied, step (S1) is repeated until the determination is affirmed.
When the cumulative temperature of the exhaust (5) detected by the exhaust temperature sensor (9) at the exhaust outlet (4b) of the catalyst (4) has not reached the predetermined time. Is presumed not to be clogged, the determination in step (S1) is denied, and when the accumulation of the above times reaches a predetermined time, it is presumed to be clogged and in step (S1). Judgment is affirmed. The differential pressure between the exhaust inlet (4a) and the exhaust outlet (4b) of the catalyst (4) is detected, and if the differential pressure is greater than or equal to the predetermined pressure, the determination of clogging is affirmed and the differential pressure is less than the predetermined pressure. In some cases, the determination of clogging may be denied.
If the determination in step (S1) is affirmed, the process proceeds to step (S2-1).

In step (S2-1), it is determined whether or not the temperature of the exhaust (5) detected by the exhaust temperature sensor (9) is in the incineration temperature region of the unburned deposit adhering to the exhaust inlet (4a). If the determination is affirmed, the process proceeds to step (S3). If the determination in step (S2-1) is denied, the opening degree of the exhaust throttle device (8) is adjusted in step (S2-2). The incineration temperature range is set to, for example, 400 ° C to 450 ° C, and when the detection temperature of the exhaust (5) is less than this range, the opening degree of the exhaust throttle device (8) is adjusted to be small. When the temperature of the exhaust (5) exceeds this range, the opening degree of the exhaust throttle device (8) is adjusted to be large.

In step (S3), it is determined whether or not the clogging of the catalyst (4) has been cleared. If the determination in step (S3) is affirmed, the process proceeds to step (S4). If the determination in step (S3) is denied, the process returns to step (S2-1).
In step (S3), when the cumulative time during which the temperature of the exhaust gas (5) detected by the exhaust gas temperature sensor (9) is maintained at the incineration temperature of the unburned deposit reaches a predetermined time, clogging occurs. Is presumed to have been resolved, the judgment in step (S3) is affirmed, and if the accumulation of the above times has not reached the predetermined time, it is presumed that the clogging has not been resolved and the step (S3). ) Is denied. The differential pressure between the exhaust inlet (4a) and the exhaust outlet (4b) of the catalyst (4) is detected, and if the differential pressure is less than the predetermined pressure, the determination in step (S3) is affirmed and the differential pressure is predetermined. If the pressure is greater than or equal to the pressure, the determination in step (S3) may be denied.
In step (S4), the opening degree of the exhaust throttle device (8) is fully opened, and the process returns to step (S1).

As shown in FIG. 4, in step (S5), it is determined whether or not there is a DPF regeneration request, and if the regeneration request determination is affirmed, the process proceeds to step (S6-1) and the DPF regeneration mode is set.
The DPF regeneration request is made by the control device (10) when the estimated deposition value of PM deposited on the DPF (12) reaches a predetermined value.
The PM deposition estimate detects the differential pressure between the exhaust inlet (12a) and the exhaust outlet (12b) of the DPF (12), and if the differential pressure is equal to or higher than the predetermined pressure, DPF regeneration is required and the differential pressure is generated. If is less than a predetermined pressure, DPF regeneration is not required.

In the DPF regeneration mode shown in FIG. 4, the target exhaust temperature of the exhaust (5) detected by the exhaust temperature sensor (9) matches the activation of the catalyst (4) and the downstream side catalyst (11). Set in the temperature range.
In step (S6-1) shown in FIG. 4, it is determined whether or not the temperature of the exhaust (5) detected by the exhaust sensor (9) is in the catalyst activation temperature region, and the determination in step (S6-1) is made. If affirmed, the process proceeds to step (S7). If the determination in step (S6-1) is denied, the opening degree of the exhaust throttle device (8) is adjusted in step (S6-2), and the process returns to step (S6-1).

The catalyst activation temperature range is set to, for example, 250 ° C to 300 ° C, and when the temperature of the exhaust (5) detected by the exhaust temperature sensor (9) is lower than this range, the exhaust throttle device The opening degree of (8) is adjusted to be small, and when the temperature of the exhaust (5) exceeds this range, the opening degree of the exhaust throttle device (8) is adjusted to be large, and the exhaust (5) The temperature is within the catalyst activation temperature range, which is the target exhaust temperature.
After the temperature of the exhaust (5) reaches the catalyst activation temperature region which is the target exhaust temperature, the target exhaust temperature of the exhaust (5) detected by the exhaust sensor (9) by the control means (10) is the DPF. It is set in the DPF regeneration temperature range that matches the regeneration temperature of (12). The DPF regeneration temperature region is higher than the catalyst activation temperature region, and is set to, for example, 500 ° C to 550 ° C.
As a result, the temperature of the exhaust inlet (12a) of the DPF (12) is adjusted to 600 ° C to 650 ° C suitable for regeneration of the DPF (12).

In step (S7), post-injection is performed, and the process proceeds to step (S8-1).
The post-injection is a fuel injection performed in the combustion chamber (36) in the expansion stroke or the exhaust stroke after the main injection from the fuel injection valve (35) during the combustion cycle.
The unburned fuel supplied into the exhaust gas (5) by the post injection was catalytically burned by the catalyst (4) and the throttle downstream side catalyst (11), the temperature of the exhaust gas (5) rose, and the fuel was deposited on the DPF (12). The PM is incinerated and removed, and the DPF (12) is regenerated.
The injection timing and injection amount of the post injection injected from the fuel injection valve (35) are the intake amount detected by the airflow sensor case (32) and the back pressure between the catalyst (4) and the exhaust throttle device (8). The back pressure and the temperature of the exhaust (5) detected by the sensor (40) and the exhaust temperature sensor (9), and the exhaust (5) detected by the exhaust temperature sensor (38) of the exhaust inlet (12a) of the DPF (12). ) Is set and controlled by the control device (10) based on the temperature and the like.
In addition to post-injection, the supply of unburned fuel to the exhaust (5) can also be performed by exhaust pipe injection in which fuel is injected by a fuel injection nozzle into the exhaust lead-out path (2).

In step (S8-1), it is determined whether or not the temperature of the exhaust (5) detected by the exhaust temperature sensor (9) is in the catalyst combustion temperature range, and the determination in step (S8-1) is affirmed. Then, the process proceeds to step (S9), and when the determination in step (S8-1) is denied, the opening degree of the exhaust throttle device (8) is adjusted in step (S8-2), and the step (S7) is performed. Return. When the temperature of the exhaust (5) detected by the exhaust temperature sensor (9) is less than the catalyst combustion temperature range, the opening of the exhaust throttle device (8) is adjusted to be small, and the exhaust (5) is adjusted. When the temperature exceeds this region, the opening degree of the exhaust throttle device (8) is adjusted to be large, and the detected temperature of the exhaust (5) is contained in the catalyst combustion temperature region which is the target exhaust temperature.
In step (S9), it is determined whether or not the temperature of the exhaust (5) detected by the exhaust temperature sensor (38) at the exhaust inlet (12a) of the DPF (12) is in the DPF regeneration temperature range, and in step (S9). If the determination is denied, the process proceeds to step (S10), and if the determination in step (S9) is affirmed, the process returns to step (S7).

In step (S10), it is determined whether or not the DPF regeneration is completed, and if the determination is affirmed, the opening degree of the exhaust throttle device (8) is fully opened in step (S11), and the process returns to step (S5). .. If the determination in step (S10) is denied, the process returns to step (S7).
When the cumulative time during which the temperature of the exhaust (5) detected by the exhaust temperature sensor (38) at the exhaust inlet (12a) of the DPF (12) is maintained in the DPF regeneration temperature region reaches a predetermined time, step (S10) If the determination in step (S10) is affirmed and has not been reached, the determination in step (S10) is denied. This DPF regeneration temperature region is set to, for example, 600 ° C to 650 ° C. The differential pressure sensor (37) detects the differential pressure between the exhaust inlet (12a) and the exhaust outlet (12b) of the DPF (12), and if the differential pressure is less than the predetermined pressure, the determination in step (S10) is made. If it is affirmed and the differential pressure is equal to or higher than the predetermined pressure, the determination in step (S10) may be denied. When the temperature of the exhaust (5) detected by the exhaust temperature sensor (39) on the exhaust outlet (12b) side of the DPF (12) reaches an abnormal temperature exceeding a predetermined upper limit temperature, the DPF regeneration is urgently stopped. The upper limit temperature is set to, for example, 700 ° C.

The main configurations and advantages of DPF regeneration are as follows.
As shown in FIGS. 1A to 1C, the catalyst (4), the exhaust temperature sensor (9), the exhaust throttle device (8), and the exhaust temperature sensor (8) arranged on the exhaust upstream side of the DPF (12) It is provided with a control device (10) in which the 9) and the exhaust throttle device (8) are linked.
As shown in FIGS. 1 (A) to 1 (C) and FIG. 4, the catalyst activation treatment and the subsequent DPF regeneration treatment are performed under the control of the control device (10), and in the catalyst activation treatment, the catalyst (4) The target temperature of the exhaust (5) at the exhaust outlet (4b) of the above is set to the first temperature region (E1), the opening degree of the exhaust throttle device (8) is controlled, and in the DPF regeneration process, the target temperature is described. Is set in the second temperature region (E2), and the target temperature of the exhaust (5) of the exhaust inlet (12a) of the DPF (12) is set in the third temperature region (E3). The opening degree of (8) is controlled, and unburned fuel is supplied to the exhaust gas (5).
As shown in FIG. 4, the second temperature region (E2) is higher than the first temperature region (E1), and the third temperature region (E3) is higher than the second temperature region (E2). The temperature difference (T12) between the first temperature region (E1) and the second temperature region (E2) becomes larger than the temperature difference (T23) between the second temperature region (E2) and the third temperature region (E3). Is set to.

This engine has the following advantages:
Even if the exhaust (5) rises due to the catalytic combustion of unburned fuel during the transition from the catalyst activation treatment to the DPF regeneration treatment, the exhaust throttle device is used in the DPF regeneration treatment in which the high second temperature region (E2) is the target temperature. The opening of (8) becomes gentle, and the temperature of the exhaust (5) drops sharply due to an unforeseen situation associated with the sudden opening of the exhaust throttle device (8), that is, a sudden drop in back pressure, resulting in post-injection or the like. The supply of unburned fuel is stopped, the unforeseen situation that the DPF regeneration is stagnant is unlikely to occur, and the DPF regeneration is promoted.

As shown in FIG. 4, the temperature difference (T12) between the first temperature region (E1) for catalyst activation and the second temperature region (E2) for catalyst combustion is in the range of a minimum of 200 ° C to a maximum of 300 ° C. Therefore, the temperature difference (T23) between the temperature region (E2) of the catalyst combustion and the third temperature region (T3) of the DPF regeneration is in the range of a minimum of 50 ° C to a maximum of 150 ° C.
As shown in FIG. 4, the ratio of the temperature difference (T12) (T23) is a maximum of 300:50 and a minimum of 200:150, that is, a maximum of 6: 1 and a minimum of 1.3: 1.
When the ratio of the temperature difference (T12) (T23) exceeds 6: 1 and the temperature difference (T12) becomes large, the second temperature region (E2) of the catalytic combustion becomes too high, and the exhaust particulate filter (8) becomes hot. It is easily deteriorated, and when the temperature difference (T12) becomes smaller than less than 1.3: 1, the second temperature region (E2) of catalytic combustion becomes too low, and the exhaust throttle device (8) in the DPF regeneration process The opening becomes abrupt, and an unexpected situation due to the abrupt opening of the exhaust throttle device (8), that is, the sudden drop in back pressure causes the temperature of the exhaust (5) to drop sharply, and the unburned fuel due to post injection or the like Unexpected situations such as supply suspension and stagnant DPF regeneration are likely to occur, and DPF regeneration stagnates.
The post injection is stopped when the temperature of the exhaust gas (5) falls below the catalyst activation temperature range.

(8) ... Exhaust gas recirculation device, (20) ... Engine body, (20a) ... Cylinder block, (20b) ... Cylinder head, (21) ... Main water channel, (21a) ... Main cooling water, (22) ... Bypass water channel , (23) ... EGR cooler, (24) ... Bypass channel, (25) ... Cooling water pump, (26) ... Radiator, (27) ... EGR valve device.

Claims (5)

In an engine provided with a main water channel (21) for water-cooling the engine body (20), an EGR cooler (23), and an EGR valve device (27).
The EGR cooler (23) and the EGR valve device (27) are provided with a pair of bypass channels (22) and (24) individually branched from the main channel (21), and the pair of bypass channels (22) (24). Connected to each individually ,
An engine characterized in that an exhaust gas recirculation device (8) and an EGR valve device (27) are connected in series to a bypass water channel (22) to which an EGR valve device (27) is connected. In the engine according to claim 1,
The main water channel (21) is driven by a cooling water pump (25), and the main cooling water (21a) includes a water jacket (20d) of the cylinder block (20a) and a water jacket (20e) of the cylinder head (20b). , The radiator (26) is configured to circulate in that order,
An engine characterized in that the bypass channel (24) to which the EGR cooler (23) is connected is branched from the water jacket (20d) of the cylinder block (20a). In the engine according to claim 1 or 2 .
The EGR valve device (27) is connected to the upstream side of the bypass water channel (22) to which the EGR valve device (27) and the exhaust throttle device (8) are connected, and the exhaust throttle device (8) is connected to the downstream side. An engine characterized by being. In the engine according to any one of claims 1 to 3 .
The engine characterized in that the EGR valve device (27) is arranged on the downstream side of the flow path of the EGR gas (23a) with respect to the EGR cooler (23). In the engine according to any one of claims 1 to 4 .
The main water channel (21) is driven by a cooling water pump (25), and the main cooling water (21a) includes a water jacket (20d) of the cylinder block (20a) and a water jacket (20e) of the cylinder head (20b). , The radiator (26) is configured to circulate in that order,
The engine is characterized in that the pipe pass passage (22) to which the EGR valve device (27) and the exhaust throttle device (8) are connected is derived from the water jacket (20d) of the cylinder block (20a).

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