JP4012291B2 - Exhaust gas purification device for turbocharged engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification device for a turbocharged engine, and more particularly to an exhaust gas purification device provided with a bypass exhaust passage so as to bypass the turbocharger with respect to a main exhaust passage.
[0002]
[Prior art]
BACKGROUND ART An exhaust gas purification device for an engine mounted on a vehicle or the like is generally equipped with a catalyst for purifying exhaust gas discharged from the engine. As the catalyst, a three-way catalyst using three kinds of catalyst materials of platinum, rhodium and palladium is often used. As a structure, there are a pellet type in which these three kinds of catalyst materials are attached to alumina having a diameter of 2 to 4 mm, and a monolith type in which these three catalyst materials are attached to alumina formed in a lattice shape. By letting it pass, the concentration of CO, HC and NOx in the exhaust gas is reduced.
[0003]
Such a catalyst exhibits its intended function only after reaching a predetermined temperature due to the nature of the catalyst material. For this reason, at the time of cold start, that is, when the engine is cold, the function is deteriorated, and there is a possibility that exhaust gas cannot be sufficiently purified.
[0004]
Therefore, a technique for providing a pre-catalyst upstream of the main catalyst in addition to the main catalyst in order to accelerate the temperature rise of the catalyst is disclosed in, for example, Japanese Patent Laid-Open No. 5-321463.
[0005]
In the technology disclosed herein, a bypass exhaust passage is provided in a main exhaust passage where a turbine of a turbocharger in an engine exhaust system is disposed so as to bypass the turbine. That is, a bypass exhaust passage having a branch point and a junction is provided on the upstream side and the downstream side of the turbine, respectively, and a pre-catalyst is provided in the bypass exhaust passage.
[0006]
The flow of the exhaust gas is adjusted by appropriately opening and closing the first valve provided on the main exhaust passage side and the second valve provided on the bypass exhaust passage side. For example, when starting the engine, the main exhaust passage valve on the turbo side is closed, the bypass exhaust passage valve on the pre-catalyst side is opened to increase the temperature of the pre-catalyst, and the downstream side of the junction When the temperature of the main catalyst arranged at is sufficiently activated by raising the temperature, the turbo side valve is opened and the pre-catalyst side valve is closed. By doing so, the catalyst function and the turbo function (supercharging function and supercharging response) are made compatible.
[0007]
[Problems to be solved by the invention]
However, in the above-described conventional technique, when the turbocharger is switched from the non-operating state to the operating state, that is, when the exhaust gas is suddenly supplied when the turbine is stopped, the drivability deteriorates. There is a risk of adverse effects on the turbocharger body.
[0008]
Further, since the valve on the main exhaust passage side is arranged downstream of the turbocharger and upstream of the junction, this valve is closed and the pre-catalyst side valve is opened to increase the temperature of the pre-catalyst. When the acceleration is promoted, a part of the exhaust gas is supplied to the turbocharger and heat is taken away by the turbocharger, so that the temperature rise of the pre-catalyst is delayed by that amount.
[0009]
Further, the opening / closing valve of the bypass exhaust passage provided with the pre-catalyst is disposed upstream of the pre-catalyst, and the heat absorption from the exhaust gas by the valve is also performed, and the space for installing the valve is the engine. There was a situation that the pre-catalyst was far from the main body.
[0010]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust gas purifying device for a turbocharged engine that sufficiently secures the function of the turbocharger and accelerates the temperature rise of the pre-catalyst. It is to provide.
[0011]
[Means for Solving the Problems]
An exhaust gas purification device for an engine with a turbocharger according to claim 1 comprises:
A bypass exhaust passage having a branch point on the upstream side of the turbine of the turbocharger and having a junction on the downstream side is provided with respect to the main exhaust passage, and a pre-catalyst is disposed in the bypass exhaust passage.
Further, on the downstream side of the branch point of the main exhaust passage and the upstream side of the turbine, a first opening / closing means constituted by a first valve whose opening degree can be adjusted includes the pre-opening of the bypass exhaust passage. On the downstream side of the catalyst and on the upstream side of the confluence, second opening / closing means constituted by a second valve whose opening degree can be adjusted is arranged, and further, the opening degree of the first and second valves. And a control unit for controlling the opening / closing timing. Then, after the engine is started, the control unit closes the first valve when the engine water temperature does not reach the first set temperature, opens the second valve, and sets the initial valve control state. Thereafter, when the water temperature of the engine is equal to or higher than the second set temperature set to be equal to or lower than the first set temperature, the opening operation of the first valve is started. The second valve closing operation is started, and the second valve closing operation is controlled to end after the first valve opening operation is completed over a predetermined time.
[0012]
As a result, the pre-catalyst is installed without a valve on the upstream side, and the main exhaust passage is shielded on the upstream side of the turbocharger by the first opening / closing means, so that heat is absorbed by other members. You will receive no exhaust gas. As a result, the temperature is raised by the hotter exhaust gas, and rapid activation is achieved.
[0013]
Further, for example, when the first opening / closing means is closed and the second opening / closing means is opened, the exhaust gas from the engine body is not supplied to the turbine side but is supplied only to the pre-catalyst side. . Therefore, the temperature rise of the pre-catalyst is accelerated. Conversely, when the first opening / closing means is opened and the second opening / closing means is closed, the exhaust gas from the engine body is not supplied to the pre-catalyst side but is supplied only to the turbine side. Therefore, the supercharging pressure and supercharging response of the turbocharger are improved.
[0015]
In addition, since the control unit can individually set the opening degree and the opening / closing timing of the first and second valves individually, the opening degree and timing are suitably different from the simple on / off control of the valve. It becomes possible to set. For example, it is possible to perform control such as gradually opening one valve while closing the other valve in parallel with this, and appropriately performing pre-rotation of the turbocharger. Is also possible. Therefore, adverse effects due to sudden turbocharger operation can be avoided.
[0016]
An exhaust gas purifying device for a turbocharged engine according to claim 3 is:
After the engine is started, the control unit closes the first valve when the engine water temperature has not reached the first set temperature, opens the second valve, sets the valve control initial state, and then When the water temperature of the engine is equal to or higher than a second set temperature set to a temperature lower than the first set temperature, an opening operation of the first valve is started, and the second valve is started after the start of the operation. The closing operation of the second valve is started, and the closing operation of the second valve is controlled to end after the opening operation of the first valve performed over a predetermined time.
[0017]
Furthermore, according to the first aspect of the present invention , the valve can be opened and closed smoothly according to the water temperature of the engine. That is, switching between opening and closing of the first valve and the second valve is not performed at the same time, but is performed over a predetermined time, and a time zone in which both are in an open state (not a fully closed state) is created. . Therefore, it is possible to prevent a large amount of exhaust gas from being suddenly supplied to the turbine of the turbocharger that is stopped. In the present invention, the reason why the water temperature of the engine is to be detected is that it can be detected relatively easily, and it can be estimated from this temperature whether or not the temperature of the main catalyst has increased.
[0018]
An exhaust gas purification apparatus for a turbocharged engine according to claim 2 is provided.
When the engine water temperature after starting the engine has not reached the first set temperature, the control unit closes the first valve, opens the second valve, and sets the initial valve control state. Thereafter, after a predetermined time elapses, the first valve is started to open, and after the start of the operation, the second valve is closed to start the first valve. Control is performed so that the closing operation of the second valve is finished after the opening operation of the valve is finished.
[0019]
In the present invention, the opening and closing operations of the first and second valves in the initial state are operated based on time conditions rather than engine water temperature. The time condition is set with a time during which the temperature of the main catalyst is likely to be increased based on normal engine operating conditions. This facilitates valve opening / closing control.
[0020]
Exhaust gas purification device according to claim 3 turbocharged engine, the arrangement of the second closing means are performed at a downstream side of the and the branch point upstream of the pre-catalyst of the bypass exhaust passage. Thus, even if the installation position of the second opening / closing means is on the upstream side of the pre-catalyst, the sudden exhaust gas supply to the turbine of the same turbocharger is avoided by performing the valve control according to claim 1 or 2. And adverse effects on engine operation can be prevented.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram of an exhaust gas purifying device for a turbocharged engine according to the present invention.
[0022]
The illustrated exhaust gas purification device for a turbocharged engine (hereinafter simply referred to as “exhaust gas purification device”) has exhaust pipes 9 extending from the exhaust ports of the two cylinder groups of the engine body 10. A main exhaust passage 12 passing through the exhaust pipe 9 and the turbine 14a of the turbocharger 14 and a bypass exhaust passage 15 provided with a pre-catalyst 16 on the way extend. That is, the bypass exhaust passage 15 is communicatively coupled between the branch point P1 and the junction point P2.
[0023]
A first valve (first opening / closing means) 13 that opens and closes the main exhaust passage 12 is installed upstream of the turbine 14 a in the main exhaust passage 12, while a second valve (second second) that opens and closes the bypass exhaust passage 15. Open / close means) 17 is provided downstream of the pre-catalyst 16 in the bypass exhaust passage 15. A main catalyst 26 is installed on the downstream side of the junction P2 in the exhaust system.
[0024]
Here, the first valve 13 and the second valve 17 are valves whose opening degree and opening / closing timing can be controlled, respectively, and are controlled by an ECU (Engine Control Unit) 27.
[0025]
The pre-catalyst 16 is generally a three-way catalyst using three kinds of catalyst substances, that is, platinum, rhodium, and palladium. The basic structure of the main catalyst 26 is substantially the same as that of the pre-catalyst 16, and a larger catalyst than the pre-catalyst 16 is used. In order to fully exhibit the functions of these catalysts, it is necessary to raise the temperature of the pre-catalyst 16 to a predetermined temperature.
[0026]
An intake manifold 21 is connected to the intake side of the engine body 10, an intercooler 23 is installed upstream of the intake manifold 21, and an intake passage 22 is connected further upstream. A compressor 14 b of the turbocharger 14 is installed further upstream in the intake passage 22.
[0027]
According to the above configuration, the pre-catalyst 16 can be installed at a position closer to the engine without a valve on the upstream side, and the main exhaust passage 12 is located upstream of the turbocharger 14 by the first opening / closing means. Can be closed. Therefore, the pre-catalyst 16 is supplied with high-temperature exhaust gas that is not thermally absorbed by other members. Thereby, rapid activation by the exhaust gas of the pre-catalyst is achieved.
[0028]
Next, the operation of the exhaust gas purification apparatus having the above-described configuration will be described based on the flowchart of FIG. 2 and the valve operation graph of FIG. In the following description, “first valve 13” in FIG. 1 is referred to as “valve V1”, and “second valve 17” is referred to as “valve V2”.
[0029]
First, in step (hereinafter simply referred to as “S”) 101, the ignition (IG) is turned on and the engine is started. Next, in S102, it is determined whether or not the engine water temperature Tw is equal to or higher than T1 (for example, 50 ° C.). If it is higher (YES), the valve V1 is opened and the valve V2 is closed in S103. State. This state is a state in which the water temperature is relatively high, that is, a state in which not much time has passed yet after traveling, and the temperature of the main catalyst 26 is also moderately high and activated.
[0030]
Therefore, it is not necessary to particularly raise the temperature of the pre-catalyst 16 using the bypass exhaust passage 15, and all the exhaust gas from the engine body 11 is supplied to the turbocharger 14 side of the main exhaust passage 12 to function the turbocharger 14. (Supercharging function and supercharging response) are prioritized.
[0031]
On the other hand, when it is determined in S102 that the water temperature Tw is less than T1 (in the case of NO), the valve control operation by the ECU 27 is performed in S104 with the valve V1 closed and the valve V2 open. The initial state of Then, after the ignition is turned on in S105, it is determined whether or not the time t1 (for example, 120 seconds) has been exceeded, and when the time is exceeded (YES), the opening / closing control of the valves V1 and V2 is started.
[0032]
In S106, valve opening / closing control is performed by the operation as shown in FIG. The horizontal axis in FIG. 3 indicates the elapsed time t based on the ignition ON being 0 seconds, and the vertical axis indicates the opening degree of the valves V1 and V2. In the figure, the vertical axis “open” indicates that the valve is fully open, and “closed” indicates that the valve is fully closed.
[0033]
After the ignition is turned on, until time t1, as shown in S104, the valve V1 is closed and the valve V2 is kept open. Then, the opening operation of the valve V1 is started when the reference time t1 has elapsed. Then, the opening is gradually increased. On the other hand, the valve V2 maintains the fully open state until t2 elapses, starts the closing operation from t2, and gradually decreases the opening degree. Then, the opening operation of the valve V1 is terminated at t3. At this time, the valve V2 is not completely closed yet, and thereafter the closing operation is terminated at t4. After the control shown in FIG. 3 is completed, the open state of the valve V1 and the closed state of the valve V2 are continued as in S103 until the ignition is turned off in S107.
[0034]
As described above, the valves V1 and V2 are not simply turned ON / OFF (fully opened / closed), but the opening thereof is duty-controlled, and the valve V2 closing operation start (t2) and the closing operation end ( By delaying the respective timings of t4) after the respective timings of the opening operation start (t1) and the opening operation end (t3) of the valve 1, rapid supply of exhaust gas to the turbocharger 14 is avoided. Thereby, the drivability at the time of valve switching improves. Here, the term “after each timing” includes the case of simultaneous timing. That is, the initial action can be achieved by setting the closing operation start (t2) and the closing operation end (t4) of the valve V2 almost simultaneously with the opening operation start (t1) and the opening operation end (t3) of the valve 1, respectively. Play.
[0035]
According to the above control, as can be understood from FIG. 3, the opening operation of the valve V1 for opening the main exhaust passage 12 connected to the turbine 14a starts when the valve V2 of the bypass exhaust passage 15 is fully opened. Therefore, the exhaust gas is not suddenly supplied to the turbine 14a. During the period from t1 to t4, a state is created in which both valves are somewhat open.
[0036]
Further, according to the exhaust gas purification device 10 described above, by controlling the opening and closing of the valves V1 and V2, the exhaust gas supply destination can be switched between the turbocharger 14 and the pre-catalyst 16, and if necessary, It is possible to select whether to give priority to the function of the turbocharger 14 or to give priority to the function of the pre-catalyst 16, and the ratio can be adjusted.
[0037]
FIG. 4 shows another control example of the valve V1 and the valve V2. 4 is different from the operation of FIG. 2 in that S205 is performed instead of S105. That is, in FIG. 2, duty control of the valve V1 and the valve V2 is started after the time t1, but in the operation of FIG. 4, when the engine water temperature becomes T2 (for example, 30 ° C.) or more, the duty is controlled. Control is started. That is, a reference temperature equal to or lower than the temperature of T1 is set, and when T2 is reached, the operation of S206 similar to S106 is gradually performed. Also by this operation, the same effect as the above-described embodiment can be obtained. The relationship between the temperatures T1 and T2 is T1 ≧ T2, and the same temperature is also included.
[0038]
In the above-described embodiment, the second valve 17 (V2) disposed in the bypass exhaust passage 15 is disposed downstream of the pre-catalyst 16 and upstream of the junction P2. Instead of this, it may be arranged downstream of the branch point P1 and upstream of the pre-catalyst 16. Even in this case, the same operation and effect can be obtained by the valve opening and closing operation according to the above embodiment.
[0039]
In addition, this invention is not limited to the structure of said each embodiment, A various deformation | transformation is possible within the range of the summary of invention. For example, various valve opening / closing speeds can be set as long as the valve V2 can be controlled to open at the start and end of the opening operation of the valve V1.
[0040]
【The invention's effect】
As described above, according to the exhaust gas purification apparatus for an engine with a turbocharger according to the present invention, early activation of the pre-catalyst in the bypass exhaust passage and ensuring a good turbocharging function and supercharging response of the turbocharger. This makes it possible to improve the utilization of the pre-catalyst in a turbocharged engine.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an exhaust gas purifying device for a turbocharged engine according to an embodiment.
FIG. 2 is a flowchart showing valve opening / closing control in the embodiment;
FIG. 3 is a valve operation explanatory diagram showing the relationship between time and valve opening in the embodiment.
FIG. 4 is a flowchart showing another valve opening / closing control in the embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Engine main body 12 Main exhaust passage 13, V1 1st valve 14 Turbocharger 14a Turbine 14b Compressor 15 Detour exhaust passage P1 Branch point P2 Junction point 16 Pre-catalyst 17, V2 2nd valve 26 Main catalyst 27 ECU

Claims (3)

In an exhaust gas purifying apparatus for a turbocharged engine having a main exhaust passage that is opened to the outside air from the exhaust port of the engine via the turbine of the turbocharger and further through the main catalyst,
Has a branching point upstream of the turbine is provided for the main exhaust passage, a bypass exhaust passage having a meeting point on the downstream side,
A pre-catalyst disposed in the bypass exhaust passage;
A first opening / closing means constituted by a first valve having an adjustable opening disposed on the downstream side of the branch point of the main exhaust passage and on the upstream side of the turbine;
A second opening / closing means configured by a second valve having an adjustable opening degree disposed downstream of the pre-catalyst in the bypass exhaust passage and upstream of the junction;
A control unit for controlling the opening degree and opening / closing timing of the first and second valves;
With
When the engine water temperature has not reached the first set temperature after the engine is started, the control unit closes the first valve, opens the second valve, and sets an initial valve control state. When the water temperature of the engine is equal to or higher than the second set temperature set to a temperature equal to or lower than the first set temperature, the opening operation of the first valve is started, and the second operation is started after the start of the operation. With a turbocharger , wherein a valve closing operation is started, and the closing operation of the second valve is controlled after the opening operation of the first valve is completed over a predetermined time . Engine exhaust gas purification device. When the water temperature of the engine after starting the engine has not reached the first set temperature, the control unit closes the first valve, opens the second valve, and sets a valve control initial state. Thereafter, after a predetermined time elapses, the first valve is started to open, and after the start of the operation, the second valve is closed to start the first valve. exhaust gas purifying device for turbocharged engine according to claim 1, closing of the second valve opening operation completion subsequent valve and controls to end. The second opening / closing means is disposed not downstream of the pre-catalyst in the bypass exhaust passage and upstream of the junction, but upstream of the pre-catalyst in the bypass exhaust passage and downstream of the branch point. 3. The exhaust gas purifying device for a turbocharged engine according to claim 1 , wherein the exhaust gas purifying device is a turbocharger engine.

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