JP2013113204A - Exhaust emission control system for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control system in which the problem such as deterioration of fuel consumption or oil dilution can be avoided, the risk of making combustion of an engine instable is also eliminated and temperature elevation of a post-processor on early stage can be attained.SOLUTION: An exhaust emission control system includes: an engine (10); an intake gas passage (12) in which an intake gas to be supplied to the engine passes; an exhaust gas passage (14) in which exhaust gas discharged from the engine passes; post-processors (22, 24, 34, 36) provided to the exhaust gas passage for cleaning exhaust gas to pass; and a cooling water passage (50) in which cooling water for cooling the engine passes. In the exhaust emission control system, temperature elevation means (17, 21, 23, 26, 52, 54, 60) are provided which elevate the temperature of exhaust gas flowing into the post-processors by controlling a passage of at least any one fluid among the intake gas, exhaust gas and cooling water.

Description

  The present invention relates to an engine, an intake passage through which intake gas supplied to the engine passes, an exhaust passage through which exhaust gas discharged from the engine passes, and a post-treatment that is provided in the exhaust passage and purifies exhaust gas that passes through the exhaust passage The present invention relates to an exhaust purification system including an apparatus and a cooling water passage through which cooling water for cooling an engine passes.

2. Description of the Related Art Post-treatment devices such as DPF devices and SCR systems are known as exhaust gas purification devices for diesel engines.
FIG. 9 is a diagram showing an overall configuration of a conventional diesel engine system including a post-processing device such as a DPF device or an SCR system.

  As shown in FIG. 9, a conventional diesel engine system 100 includes an engine 110, an intake passage 112 that supplies intake gas (air) to the engine 110, and an exhaust passage through which exhaust gas discharged from the engine 110 passes. 114, an intercooler 116 that cools intake gas passing through the intake passage 112, an intake throttle 118 that controls the flow rate of the intake gas flowing through the intake passage, and the intake passage 112 and the exhaust passage 114. The supercharger 120 that compresses the intake gas, various post-treatment devices that are provided in the exhaust passage 114 to purify the exhaust gas that passes through, and the high pressure that recirculates the exhaust gas exhausted from the engine 110 to the intake passage 112 An EGR passage 140 is provided. Further, although not shown, a cooling water passage through which cooling water for cooling the engine passes is provided.

  As the aftertreatment device described above, the diesel engine system 100 includes a pre-stage oxidation catalyst 122 and a DPF device 124. Further, an SCR system 138 including a urea water injection device 132, an SCR catalyst 134, and a post-stage oxidation catalyst 136 is provided.

The pre-stage oxidation catalyst 122 oxidizes and removes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas, and oxidizes nitrogen monoxide (NO) in the exhaust gas to generate nitrogen dioxide (NO ₂ ). It has the function to do. The DPF device 124 is a device that collects particulate matter (PM) such as soot contained in the exhaust gas with a filter and removes it from the exhaust gas.

The SCR system 138 is a system in which ammonia (NH ₃ ) is reacted with NO _X in the exhaust gas under the catalytic action of the SCR catalyst 134 to reduce NO _X to nitrogen and water, thereby detoxifying. NH ₃ supplied to the SCR catalyst 134 is generated by injecting urea water into the exhaust passage 114 by the urea water injection device 132 and decomposing the injected urea water at the exhaust temperature of the exhaust gas. The injected urea water is stored in the urea water tank 132a. Further, a downstream oxidation catalyst 136 is disposed on the downstream side of the SCR catalyst 134, and NH ₃ slipped from the SCR catalyst 134 is oxidized and rendered harmless.

JP 2010-151058 A

  The above-described pre-oxidation catalyst 122 and SCR catalyst 134 do not fully exhibit their exhaust purification function unless the supported catalyst is heated to a predetermined temperature or higher. Therefore, when the engine is started or under cold conditions, the exhaust gas temperature is low, and therefore, there is a problem that the exhaust purification function is not sufficiently exhibited in the pre-stage oxidation catalyst 122 and the SCR catalyst 134.

  Further, the DPF device 124 needs to periodically execute a treatment for regenerating the filter by forcibly burning the accumulated PM (DPF forced regeneration operation). During the DPF forced regeneration operation, the DPF device 124 is set to a predetermined value. It is necessary to heat above the temperature. As a means for heating the DPF device 124, fuel is injected into the combustion chamber immediately before the exhaust stroke, the unburned fuel is discharged into the exhaust passage 114, and the unburned fuel is burned by the pre-oxidation catalyst 122 so that the high temperature exhaust gas is discharged. Conventionally, gas is generated and the DPF device 124 is heated (late post injection).

  However, the above-described late post-injection injects fuel for purposes other than the combustion purpose of the engine, resulting in deterioration of fuel consumption. Further, there is a problem (oil dilution) that unburned fuel injected into the combustion chamber adheres to the cylinder liner and mixes with the lubricating oil, leading to early deterioration of the lubricating oil.

  Patent Document 1 discloses a technique for reducing the opening of a throttle valve as means for increasing the temperature of exhaust gas at an early stage by the present applicant. However, since the combustion of the engine may become unstable if the throttle valve opening is reduced, the development of further means is desired as a means for quickly raising the temperature of the exhaust gas.

  The present invention is an invention made in view of such problems of the prior art, and can avoid problems such as deterioration of fuel consumption and oil dilution, and there is no fear that engine combustion becomes unstable. It aims at providing the exhaust gas purification system which can aim at an early temperature rise.

The present invention has been invented in order to achieve the problems and objects in the prior art as described above,
The exhaust purification system of the present invention comprises:
An engine, an intake passage through which intake gas supplied to the engine passes, an exhaust passage through which exhaust gas discharged from the engine passes, and a post-processing device that is provided in the exhaust passage and purifies exhaust gas that passes through the exhaust passage And an exhaust purification system comprising a cooling water passage through which cooling water for cooling the engine passes,
A temperature raising means for raising the temperature of the exhaust gas flowing into the aftertreatment device by controlling a flow path of at least one of the intake gas, the exhaust gas, and the cooling water; Features.

  The exhaust purification system of the present invention controls the temperature of the exhaust gas flowing into the aftertreatment device by controlling the flow path of at least one of the intake gas, the exhaust gas, and the cooling water. Means. In this way, the exhaust gas temperature is raised not by controlling the fuel injection timing but by controlling the flow path of the fluid, so that problems such as fuel consumption deterioration and oil dilution occur as in the case of late post injection. Will not occur. Further, since the flow rate of the intake gas (air) supplied to the engine is not restricted, there is no possibility that engine combustion becomes unstable.

  In the present invention, “controlling the flow path” means not only to selectively switch the flow path of the fluid but also to which flow path when there are two or more flow paths through which the fluid can flow. This also includes controlling whether to flow only the flow rate (flow rate control).

In the above invention,
The temperature raising means passes through a supercharger bypass passage formed so as to bypass an exhaust turbine of a supercharger provided upstream of the aftertreatment device of the exhaust passage, and the supercharger bypass passage. A first bypass valve for controlling a flow rate of the exhaust gas and a flow rate of the exhaust gas passing through the exhaust turbine; and the first bypass so that a temperature of the exhaust gas flowing into the aftertreatment device becomes a predetermined set temperature. And a control device for controlling the valve.

  When the exhaust gas passes through the exhaust turbine of the supercharger, the exhaust gas expands and the temperature decreases. Therefore, the control device controls the first bypass valve, increases the flow rate of exhaust gas passing through the turbocharger bypass passage (bypassing the exhaust turbine), and reducing the flow rate of exhaust gas passing through the exhaust turbine. The exhaust gas flowing into the processing apparatus can be heated to a predetermined set temperature.

At this time, in the above invention,
An intercooler bypass passage formed so that the temperature raising means bypasses an intercooler provided in the intake passage, a flow rate of the intake gas passing through the intercooler bypass passage, and an intake gas passing through the intercooler And a control device for controlling the second bypass valve so that the temperature of the exhaust gas flowing into the aftertreatment device becomes a predetermined set temperature. You can also.

  When the intake gas passes through the intercooler, it is cooled and the temperature decreases. For this reason, the control device controls the second bypass valve, increases the flow rate of the intake gas passing through the intercooler bypass passage (bypassing the intercooler), and reducing the flow rate of the intake gas passing through the intercooler. The temperature of the supplied intake gas rises. Thereby, the temperature of the exhaust gas discharged from the engine also rises, and the exhaust gas flowing into the aftertreatment device can be raised to a predetermined set temperature.

At this time, in the above invention,
In the case of a high load operation in which the engine is in a load state greater than or equal to a predetermined load, the flow rate of the intake gas passing through the intercooler bypass passage by the second bypass valve and the flow rate of the intake gas passing through the intercooler are By controlling, the temperature of the exhaust gas flowing into the aftertreatment device is controlled to be a predetermined set temperature,
In the case of low load operation in which the engine is under a predetermined load state, in addition to the temperature increase control by the second bypass valve, the exhaust gas passing through the supercharger bypass passage by the first bypass valve is added. By controlling the flow rate and the flow rate of the exhaust gas passing through the exhaust turbine, the temperature of the exhaust gas flowing into the aftertreatment device can be controlled to be a predetermined set temperature.

  According to the present invention, in the case of high load operation, in order to prioritize the driving of the supercharger, only the temperature increase control by the second bypass valve is performed without performing the temperature increase control by the first bypass valve. To increase the temperature of the exhaust gas flowing into the aftertreatment device. On the other hand, in the case of low load operation, the exhaust gas temperature is given priority over the driving of the supercharger, and in addition to the exhaust gas temperature increase control by the second bypass valve, the exhaust gas is also controlled by the first bypass valve. Temperature control is performed. That is, according to the present invention, it is possible to perform appropriate temperature increase control according to the load state of the engine.

In the above invention,
The cooling water passage includes a radiator for cooling the cooling water passing therethrough, and an annular passage formed so that the cooling water circulates between the radiator and the engine,
The temperature raising means controls a radiator bypass passage that branches from the annular passage so as to bypass the radiator, a cooling flow that controls a flow rate of cooling water that passes through the radiator bypass passage, and a flow rate of cooling water that bypasses the radiator A water bypass valve, and a control device that controls the cooling water bypass valve so that the temperature of the cooling water passing through the engine and / or the temperature of the exhaust gas flowing into the aftertreatment device becomes a predetermined set temperature. It can also be configured to include.

  When the cooling water passes through the radiator, it is cooled and the temperature decreases. Since the temperature of the exhaust gas discharged from the engine affects the temperature of the cooling water that cools the engine, the temperature of the exhaust gas discharged from the engine is increased by increasing the temperature of the cooling water that passes through the engine. be able to. Therefore, by controlling the cooling water bypass valve, increasing the flow rate of the cooling water passing through the radiator bypass passage (bypassing the radiator), and reducing the flow rate of the cooling water passing through the radiator, It is possible to raise the temperature of the exhaust gas flowing into the aftertreatment device by raising the temperature to the set temperature. At this time, the temperature of the exhaust gas flowing into the aftertreatment device can be controlled to be a predetermined set temperature.

  In general, the cooling water that has passed through the engine is controlled by a thermostat so as to have a predetermined set temperature (for example, 80 ° C.) during normal operation. The temperature control by the thermostat is controlled by automatically opening and closing the valve inside the thermostat in accordance with the temperature of the cooling water, etc., so the set temperature of the cooling water described above cannot be easily changed. . In contrast, in the present invention, since the cooling water bypass valve can be controlled by the control device, the set temperature of the cooling water itself can be easily changed by the control device. Therefore, when it is desired to raise the exhaust gas temperature quickly during the DPF forced regeneration operation, the set temperature of the cooling water is changed to be higher than that during the normal operation (for example, 85 ° C.), and the setting after the change is made. By controlling the flow path of the cooling water according to the temperature, it is possible to increase the temperature of the exhaust gas flowing into the DPF device during the DPF forced regeneration operation.

  According to the present invention, the temperature of the exhaust gas is raised not by controlling the fuel injection timing but by controlling the fluid flow path, so that problems such as deterioration in fuel consumption and oil dilution can be avoided, and It is possible to provide an exhaust purification system capable of achieving an early temperature increase of the aftertreatment device without fear of unstable combustion of the engine.

1 is an overall configuration diagram of a diesel engine system including an exhaust purification system of a first embodiment. It is the flowchart which showed the control flow of the exhaust gas purification system of 1st Embodiment. It is the flowchart which showed the control flow in the case of performing feedback control. It is a whole block diagram of the diesel engine system provided with the exhaust gas purification system of 2nd Embodiment. It is a whole block diagram of the diesel engine system provided with the exhaust gas purification system concerning the modification of 2nd Embodiment. It is the flowchart which showed the control flow of the exhaust gas purification system of 2nd Embodiment. It is the block diagram which showed the whole structure of the cooling water channel | path of 3rd Embodiment. It is the flowchart which showed the control flow of the exhaust gas purification system of 3rd Embodiment. It is the figure which showed the whole structure of the conventional diesel engine system provided with the aftertreatment apparatus.

Hereinafter, embodiments of the present invention will be described in more detail based on the drawings.
However, the scope of the present invention is not limited to the following embodiments. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the following embodiments are merely illustrative examples and are not intended to limit the scope of the present invention only unless otherwise specified.

<First Embodiment>
FIG. 1 is an overall configuration diagram of a diesel engine system including an exhaust purification system according to a first embodiment of the present invention. First, with reference to FIG. 1, the whole structure of the diesel engine system provided with the exhaust gas purification system of this invention is demonstrated.

  As shown in FIG. 1, the diesel engine system 1 of the present invention includes an engine 10, an intake passage 12 that supplies intake gas (air) to the engine 10, and exhaust gas through which exhaust gas discharged from the engine 10 passes. The exhaust passage 14 is provided with various post-treatment devices for purifying exhaust gas passing therethrough.

  In the engine 10, the high-pressure fuel accumulated in the common rail 10 a is controlled in injection timing and injection amount by a common rail control device (not shown), and from the fuel injection valve 11 provided for each cylinder to the combustion chamber in each cylinder. It is injected towards. The injected high-pressure fuel is combusted by mixing with the intake gas (air) supplied from the intake passage 12. Further, the engine 10 is provided with a rotation speed detector 13, and the engine rotation speed detected by the detector 13 is input to a control device 60 described later. The engine 10 is cooled by cooling water flowing through a cooling water passage (not shown in FIG. 1) described later.

  The control device 60 is composed of a microcomputer including a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), an I / O interface, and the like. Signals related to data measured by the above-described rotation speed detector 13 and other sensors are input to the CPU via the I / O interface. The CPU is configured to execute various controls in accordance with a control program stored in the ROM and an input signal.

  A supercharger 20 is provided between the intake passage 12 and the exhaust passage 14. The supercharger 20 includes an exhaust turbine 20b disposed in the exhaust passage 14 and a compressor 20a disposed in the intake passage 12, and the compressor 20a is coaxially driven by the exhaust turbine 20b. Further, an intercooler 16 and a throttle valve 18 are provided in the intake passage 12, and after the compressed air discharged from the compressor 20a is cooled by the intercooler 16, the flow rate is controlled by the throttle valve 18, and the engine 10 It flows into the combustion chamber in each cylinder.

  In addition, a downstream oxidation catalyst 22 and a DPF device 24 are disposed downstream of the exhaust turbine 20b in the exhaust passage 14 as the above-described post-processing devices. Further, an SCR system 138 including a urea water injection device 32, an SCR catalyst 34, and a post-stage oxidation catalyst 36 is disposed on the downstream side of the DPF device 24.

The pre-stage oxidation catalyst 122 oxidizes and removes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas, and oxidizes nitrogen monoxide (NO) in the exhaust gas to generate nitrogen dioxide (NO ₂ ). It has the function to do. The DPF device 24 is a device that collects particulate matter (PM) such as soot contained in the exhaust gas with a filter and removes it from the exhaust gas. Further, for the DPF device 24, a treatment (forced regeneration operation) for forcibly burning the PM deposited on the filter to regenerate the filter is periodically executed.

The SCR system 38 is a system that detoxifies NO _X into nitrogen dioxide and water by reacting ammonia (NH ₃ ) with NO _X in the exhaust gas under the catalytic action of the SCR catalyst 34. . Ammonia (NH ₃ ) supplied to the SCR catalyst 34 is generated by injecting urea water into the exhaust passage 14 by the urea water injection device 32 and decomposing the injected urea water at the exhaust temperature of the exhaust gas. The urea water to be injected is stored in the urea water tank 32a. Further, a downstream oxidation catalyst 36 is disposed on the downstream side of the SCR catalyst 34, and the NH ₃ slipped from the SCR catalyst 34 is oxidized and rendered harmless.

  The exhaust passage 14 is formed with a high-pressure EGR passage 40 that branches from the upstream side of the exhaust turbine 20 b and is connected to the downstream side of the intake throttle 18 of the intake passage 12. Part of the gas is returned to the intake passage 12. The high-pressure EGR passage 40 is provided with an EGR cooler 42 that cools the exhaust gas that passes therethrough and an EGR valve 44 that controls the flow rate of the exhaust gas that recirculates. In the exhaust purification system of the present invention, the high-pressure EGR passage 40, the EGR cooler 42, and the EGR valve 44 are not necessarily installed.

  Further, in the present embodiment, as shown in FIG. 1, the exhaust passage 14 branches from the upstream side of the exhaust turbine 20 b, bypasses the exhaust turbine 20 b, and the exhaust passage 14 upstream of the upstream oxidation catalyst 22. A supercharger bypass passage 21 that merges with the turbocharger is formed. Further, an exhaust temperature sensor 25 is disposed between the junction point of the exhaust passage 14 and the supercharger bypass passage 21 and the pre-stage oxidation catalyst 22, and measures the temperature of the exhaust gas flowing into the aftertreatment device. ing. The temperature of the exhaust gas measured by the exhaust temperature sensor 25 is input to the control device 60 described above.

A first bypass valve 23 is disposed at a branch point of the supercharger bypass passage 21. Then, by adjusting the valve opening degree of the first bypass valve 23, the flow rate of the exhaust gas passing through the supercharger bypass passage 21 and the flow rate passing through the exhaust turbine 20b through the exhaust passage 14 are controlled. Further, the opening degree of the first bypass valve 23 is controlled by a control signal transmitted from the control device 60.

  When the exhaust gas passes through the exhaust turbine 20b of the supercharger 20, the exhaust gas expands and the temperature decreases. For this reason, the opening degree of the first bypass valve 23 is controlled by the control device 60, the flow rate of the exhaust gas passing through the supercharger bypass passage 21 (bypassing the exhaust turbine) is increased, and the exhaust gas passing through the exhaust turbine 20b. By reducing the flow rate of the exhaust gas, the temperature of the exhaust gas flowing into the aftertreatment device can be raised. That is, the above-described supercharger bypass passage 21, the first bypass valve 23, and the control device 60 that controls the first bypass valve 23 constitute the temperature raising means of the present embodiment.

Next, the control flow of the exhaust purification system of the present invention will be described with reference to FIG.
After the start (S10), first, the engine operating state is acquired (S11). The engine operating state is grasped based on the engine speed and the fuel injection amount. Next, the temperature T1 of the exhaust gas flowing into the aftertreatment device is acquired (S12). The temperature T1 of the exhaust gas is grasped as the temperature of the exhaust gas measured by the exhaust temperature sensor 25 described above.

  Next, the target temperature T2 is acquired. The target temperature T2 is calculated by a target temperature map using the engine speed and the fuel injection amount as input data. At this time, it is determined whether or not the DPF device 24 is in the forced regeneration operation (S13). When the DPF device 24 is in the forced regeneration operation, the target temperature T2 is calculated from the target temperature map for forced regeneration operation (S14b). Otherwise, the target temperature T2 is calculated from the target temperature map for normal operation (S14a). The target temperature maps for forced regeneration operation and normal operation are stored in advance in the ROM of the control device 60.

  Next, the target temperature T2 is compared with the temperature T1 of the exhaust gas flowing into the aftertreatment device (S15). When T2> T1 (Yes in S15), the valve opening degree of the first bypass valve 23 described above is controlled, and at least a part of the exhaust gas bypasses the exhaust turbine 20b and passes through the supercharger bypass passage 21. Such control (supercharger bypass control) is executed (S17). If T1> T2 (No in S15), the supercharger bypass control is not executed (S16) and the process is terminated (S18).

  Further, when the supercharger bypass control described above is executed (S17), the feedback control as shown in FIG. 3 is performed to control the valve opening degree of the first bypass valve 23, thereby flowing into the aftertreatment device. The temperature T1 of the exhaust gas can be accurately matched with the target temperature T2.

  As described above, the exhaust purification system of the present invention includes the temperature raising means including the supercharger bypass passage 21, the first bypass valve 23, and the control device 60, and the control device 60 opens the first bypass valve 23. The exhaust gas flowing into the aftertreatment device is controlled by increasing the flow rate of exhaust gas passing through the supercharger bypass passage 21 (bypassing the exhaust turbine 20b) and decreasing the flow rate of exhaust gas passing through the exhaust turbine. The temperature can be increased. In such an exhaust purification system of the present invention, problems such as deterioration of fuel consumption and oil dilution do not occur unlike the late post injection. Further, since the flow rate of the intake gas supplied to the engine is not restricted, there is no possibility that the combustion of the engine becomes unstable.

<Second Embodiment>
FIG. 4 is an overall configuration diagram of a diesel engine system including an exhaust purification system according to a second embodiment of the present invention. The overall configuration of the diesel engine system 1 of the present embodiment is basically the same as that of the above-described embodiment, and the same reference numerals are given to the same configurations, and detailed descriptions thereof are omitted.

  In the present embodiment, unlike the above-described embodiment, as shown in FIG. 4, the air flows from the intake passage 12, bypasses the intercooler 16, and merges with the intake passage 12 on the upstream side of the throttle valve 18. An intercooler bypass passage 17 is formed. A second bypass valve 26 is disposed at the branch point of the intercooler bypass passage 17, and the flow rate of the exhaust gas passing through the intercooler bypass passage 17 by adjusting the valve opening degree of the second bypass valve 26. And the flow rate passing through the intercooler 16 through the intake passage 12 is controlled. The valve opening degree of the second bypass valve 26 is controlled by a control signal transmitted from the control device 60.

  When the intake gas passes through the intercooler 16, it is cooled and the temperature is lowered. For this reason, the control device 60 controls the second bypass valve 26 to increase the flow rate of the intake gas passing through the intercooler bypass passage 17 (bypassing the intercooler 16) and to decrease the flow rate of the intake gas passing through the intercooler 16. As a result, the temperature of the intake gas supplied to the engine 10 rises. Thereby, the temperature of the exhaust gas discharged from the engine 10 also increases, and the temperature of the exhaust gas flowing into the aftertreatment device can be raised. That is, the above-described intercooler bypass passage 17, the second bypass valve 26, and the control device 60 that controls the second bypass valve 26 constitute the temperature raising means of the present embodiment.

  Further, in addition to or instead of the intercooler bypass passage 17 and the second bypass valve 26 described above, as shown in FIG. 5, a branch is made from the intake passage 12 on the upstream side of the compressor 20 a, and the compressor 20 a and the intercooler are branched. 16, an intercooler bypass passage 17 ′ that merges with the intake passage 12 is formed on the upstream side of the throttle valve 18, and a second bypass valve 26 ′ is disposed at a branch point of the intercooler bypass passage 17 ′. May be. When the intake gas is compressed (supercharged) by the compressor 20a, the heat capacity of the intake gas supplied to the engine 10 increases, so that the temperature of the exhaust gas discharged from the engine 10 is higher than that when the intake gas is not supercharged. Lower. Therefore, the control device 60 adjusts the valve opening degree of the second bypass valve 26 ′, increases the flow rate of the exhaust gas passing through the intercooler bypass passage 17 ′, and passes through the compressor 20 a and the intercooler 16 through the intake passage 12. By reducing the flow rate of the exhaust gas, the temperature of the exhaust gas flowing into the aftertreatment device can be increased.

Next, the control flow of the exhaust purification system of this embodiment will be described with reference to FIG.
Note that the control flow of this embodiment is basically the same control flow as that of the above-described embodiment, and the same steps are denoted by the same reference numerals and detailed description thereof is omitted.

  In the present embodiment, when the engine 10 is operating at a high load, the second bypass valve 26 controls the flow rate of the intake gas passing through the intercooler bypass passage 17 and the flow rate of the intake gas passing through the intercooler 16. By doing so, the temperature of the exhaust gas flowing into the aftertreatment device is controlled to be a predetermined set temperature (intercooler bypass control), and when the engine 10 is not in a high load operation (in a low load operation) In addition to the above-described intercooler bypass control, the first bypass valve 23 controls the flow rate of the exhaust gas passing through the supercharger bypass passage 21 and the flow rate of the exhaust gas passing through the exhaust turbine 20b. The point which performs control (supercharger bypass control) so that the temperature of the exhaust gas flowing into the processing apparatus becomes a predetermined set temperature is the above-described embodiment. It is different.

  Specifically, as shown in FIG. 6, after comparing the target temperature T2 with the temperature T1 of the exhaust gas flowing into the aftertreatment device in S15, the engine in T2> T1 (Yes in S15). It is determined whether or not the vehicle is in a high load operation in which 10 is in a load state greater than or equal to a predetermined value (S19). The determination as to whether or not it is a high load operation is made based on the engine operation state determination map stored in advance in the ROM of the control device 60 based on the engine operation state acquired in S11.

  When the high load operation is being performed (Yes in S19), the control device 60 adjusts the valve opening degree of the second bypass valve 26 and executes only the intercooler bypass control (S19b). On the other hand, when the engine 10 is in a low load operation in a load state less than a predetermined value (No in S19), in addition to the intercooler bypass control, the valve opening of the first bypass valve 23 is adjusted by the control device 60. Then, supercharger bypass control is executed (S19a).

  In such an exhaust purification system of the present embodiment, in the case of high load operation, in order to give priority to the drive of the supercharger 20, the temperature increase control (supercharger bypass control) by the first bypass valve 23 is performed. Instead, only the temperature increase control (intercooler bypass control) by the second bypass valve 26 is performed to increase the temperature of the exhaust gas flowing into the aftertreatment device. On the other hand, in the case of low load operation, priority is given to the temperature rise of the exhaust gas over the driving of the supercharger 20, and in addition to the temperature rise control (intercooler bypass control) of the exhaust gas by the second bypass valve 26, The exhaust gas temperature raising control (supercharger bypass control) is also performed by the 1 bypass valve 23. That is, according to the control flow of the present embodiment, it is possible to perform appropriate temperature increase control according to the engine load state.

<Third Embodiment>
Next, a third embodiment of the present invention will be described with reference to FIG.
Note that the overall configuration of the diesel engine system 1 of the present embodiment is basically the same as that of the above-described embodiment.

In the present embodiment, the cooling water passage through which the cooling water for cooling the engine 10 passes is configured as shown in FIG.
That is, the cooling water passage 50 of this embodiment includes a radiator 56 that cools the cooling water that passes therethrough, and an annular passage 51 is formed between the radiator 56 and the engine 10. The annular passage 51 is provided with a cooling water pump 58 that discharges the cooling water in one direction. The cooling water pump 58 circulates the cooling water through the annular passage 51.

  A radiator bypass passage 52 is formed on the upstream side of the radiator 56 in the annular passage 51. The radiator bypass passage 52 branches from the annular passage 51, bypasses the radiator 56, and merges with the annular passage 51 on the downstream side of the cooling water pump 58. ing. Further, a cooling water bypass valve 54 is disposed at a branch point between the annular passage 51 and the radiator bypass passage 52, and cooling that passes through the radiator bypass passage 52 (bypasses the radiator 56) by adjusting the valve opening degree. The flow rate of water and the flow rate of cooling water passing through the radiator 56 are controlled. Further, the opening degree of the coolant bypass valve 54 is controlled by a control signal transmitted from the control device 60.

  The cooling water passage 50 is formed with an EGR cooler passage 53 for cooling the EGR cooler 42. The EGR cooler passage 53 branches from the downstream side of the cooling water pump 58, bypasses the engine 10, and merges with the annular passage 51 on the downstream side of the engine 10. Further, a cooling water temperature sensor 55 is disposed on the downstream side of the engine 10 and measures the temperature of the cooling water passing therethrough. The temperature of the cooling water measured by the cooling water temperature sensor 55 is input to the control device 60.

  When the cooling water passes through the radiator 56, the cooling water is cooled and the temperature is lowered. Since the temperature of the exhaust gas discharged from the engine 10 is proportional to the temperature of the cooling water that cools the engine 10, the exhaust gas discharged from the engine 10 is increased by increasing the temperature of the cooling water that passes through the engine 10. The temperature can be raised. Therefore, the control device 60 controls the cooling water bypass valve 54, increases the flow rate of the cooling water passing through the radiator bypass passage 52 (bypassing the radiator 56), and reducing the flow rate of the cooling water passing through the radiator 56. It is possible to raise the temperature of the cooling water passing through 10 to a predetermined set temperature, thereby raising the temperature of the exhaust gas flowing into the aftertreatment device. That is, the above-described radiator bypass passage 52, the cooling water bypass valve 54, and the control device 60 that controls the cooling water bypass valve 54 constitute the temperature raising means of the present embodiment.

  Generally, the cooling water that has passed through the engine 10 is controlled by a thermostat so as to have a predetermined set temperature (for example, 80 ° C.). Temperature control by the thermostat is controlled by automatically opening and closing a valve inside the thermostat in accordance with the temperature of the cooling water or the like. For this reason, the set temperature of the cooling water described above cannot be easily changed. In contrast, in the present invention, the cooling water bypass valve 54 can be controlled by the control device 60, so that the set temperature of the cooling water itself can be easily changed by the control device 60. Therefore, when it is desired to raise the exhaust gas temperature quickly during the DPF forced regeneration operation, the set temperature of the cooling water is set higher than that during the normal operation (for example, 85 ° C.), and the cooling water is set according to the set temperature. By controlling the flow path, the temperature of the exhaust gas flowing into the DPF device 24 can be increased.

Next, the control flow of the exhaust purification system of this embodiment will be described with reference to FIG.
In the following control flow, description will be made assuming that the above-described temperature rise control by the cooling water bypass valve 54 is executed during the DPF forced regeneration operation.

  After the start (S20), first, the engine operating state is acquired (S21). The engine operating state is grasped based on the engine speed and the fuel injection amount. Next, the temperature Tw1 of the cooling water at the outlet of the engine 10 is acquired (S22). The cooling water temperature Tw1 is grasped as the cooling water temperature measured by the cooling water temperature sensor 55 described above. Note that the cooling water temperature Tw1 is preferably measured near the engine 10 in order to accurately grasp the temperature of the cooling water passing through the engine 10. For example, the cooling water temperature at the inlet of the engine 10 or the cooling water around the engine 10 is measured. It can also be measured in the passage 50 (water jacket).

  Next, the target temperature Tw2 for the cooling water is acquired (S23). The target temperature Tw2 is calculated by a cooling water target temperature map using the engine speed and the fuel injection amount as input data. The cooling water target temperature map is stored in advance in the ROM of the control device 60.

  Next, the target temperature Tw2 is compared with the cooling water temperature Tw1 at the outlet of the engine 10 (S24). When Tw2> Tw1 (Yes in S24), the valve opening degree of the cooling water bypass valve 54 described above is controlled so that at least a part of the cooling water bypasses the radiator 56 and passes through the radiator bypass passage 52. Radiator bypass control to be controlled is executed (S26). If Tw1> Tw2 (No in S24), the radiator bypass control is not executed (S25), and the process ends (S27).

  At this time, the temperature Tw1 of the cooling water passing through the engine 10 is accurately matched with the target temperature Tw2 by controlling the valve opening degree of the cooling water bypass valve 54 by the feedback control as shown in FIG. 3 described above. be able to. Also in the present embodiment, similarly to the above-described embodiment, the temperature of the exhaust gas flowing into the post-processing device can be controlled to be a predetermined set temperature.

  As mentioned above, although the preferable form of this invention was demonstrated, this invention is not limited to said form, A various change in the range which does not deviate from the objective of this invention is possible.

  According to the present invention, the engine, the intake passage through which the intake gas supplied to the engine passes, the exhaust passage through which the exhaust gas discharged from the engine passes, and the exhaust gas that is provided in the exhaust passage and passes therethrough are purified. As an exhaust purification system including an aftertreatment device and a cooling water passage through which cooling water for cooling the engine passes, the exhaust purification system can be suitably used for a diesel engine or the like.

1 diesel engine system,
10 Engine 10a Common rail 11 Fuel injection valve 12 Intake passage 13 Revolution detector 14 Exhaust passage 16 Intercooler 17 Intercooler bypass passage (temperature raising means)
18 Throttle valve 20 Supercharger 20a Compressor 20b Exhaust turbine 21 Supercharger bypass passage (temperature raising means)
22 Pre-stage oxidation catalyst (post-treatment equipment)
23 First bypass valve (temperature raising means)
24 DPF device (post-processing device)
25 Exhaust temperature sensor 26 Second bypass valve (temperature raising means)
32 Urea water injection device 34 SCR catalyst (post-processing device)
36 Post-stage oxidation catalyst (post-treatment equipment)
38 SCR system 40 High pressure EGR passage 42 EGR cooler 44 EGR valve 50 Cooling water passage 51 Annular passage 52 Radiator bypass passage (temperature raising means)
53 EGR cooler passage 54 Cooling water bypass valve (temperature raising means)
55 Cooling water temperature sensor 56 Radiator 58 Cooling water pump 60 Control device (temperature raising means)

Claims (6)

An engine, an intake passage through which intake gas supplied to the engine passes, an exhaust passage through which exhaust gas discharged from the engine passes, and a post-processing device that is provided in the exhaust passage and purifies exhaust gas that passes through the exhaust passage And an exhaust purification system comprising a cooling water passage through which cooling water for cooling the engine passes,
A temperature raising means for raising the temperature of the exhaust gas flowing into the aftertreatment device by controlling a flow path of at least one of the intake gas, the exhaust gas, and the cooling water; A featured exhaust purification system.   The temperature raising means passes through a supercharger bypass passage formed so as to bypass an exhaust turbine of a supercharger provided upstream of the aftertreatment device of the exhaust passage, and the supercharger bypass passage. A first bypass valve for controlling a flow rate of the exhaust gas and a flow rate of the exhaust gas passing through the exhaust turbine; and the first bypass so that a temperature of the exhaust gas flowing into the aftertreatment device becomes a predetermined set temperature. The exhaust purification system according to claim 1, further comprising a control device that controls the valve.   An intercooler bypass passage formed so that the temperature raising means bypasses an intercooler provided in the intake passage, a flow rate of the intake gas passing through the intercooler bypass passage, and an intake gas passing through the intercooler A second bypass valve that controls the flow rate of the exhaust gas, and a control device that controls the second bypass valve so that the temperature of the exhaust gas flowing into the aftertreatment device becomes a predetermined set temperature. The exhaust gas purification system according to claim 2. In the case of a high load operation in which the engine is in a load state greater than or equal to a predetermined load, the flow rate of the intake gas passing through the intercooler bypass passage by the second bypass valve and the flow rate of the intake gas passing through the intercooler are By controlling, the temperature of the exhaust gas flowing into the aftertreatment device is controlled to be a predetermined set temperature,
In the case of low load operation in which the engine is under a predetermined load state, in addition to the temperature increase control by the second bypass valve, the exhaust gas passing through the supercharger bypass passage by the first bypass valve is added. The control of controlling the flow rate and the flow rate of exhaust gas passing through the exhaust turbine so that the temperature of the exhaust gas flowing into the aftertreatment device becomes a predetermined set temperature. The exhaust gas purification system described in 1. The cooling water passage includes a radiator for cooling the cooling water passing therethrough, and an annular passage formed so that the cooling water circulates between the radiator and the engine,
The temperature raising means controls a radiator bypass passage that branches from the annular passage so as to bypass the radiator, a cooling flow that controls a flow rate of cooling water that passes through the radiator bypass passage, and a flow rate of cooling water that bypasses the radiator A water bypass valve, and a control device that controls the cooling water bypass valve so that the temperature of the cooling water passing through the engine and / or the temperature of the exhaust gas flowing into the aftertreatment device becomes a predetermined set temperature. The exhaust gas purification system according to any one of claims 1 to 4, further comprising: The post-processing device includes at least a DPF device;
The exhaust gas purification system according to claim 5, wherein the temperature rise control by the cooling water bypass valve is executed during a DPF forced regeneration operation in which PM accumulated in the DPF device is forcibly burned.

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