JP2004011507A - Warming-up system for exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a warming-up system for an exhaust emission control device, which improves the warming-up performance at starting. <P>SOLUTION: The exhaust emission control device 4 for an exhaust pipe 3 of an engine 1 is connected at its upstream side to a negative pressure tank 52 via a pipe 50 having an on-off valve 51. At starting, an ECU 2 makes the on-off valve 51 temporarily open to introduce cold air from the exhaust pipe 3 to the negative pressure tank 52 via the pipe 50. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a warm-up system that promotes catalyst warm-up at the time of starting an exhaust purification device that purifies exhaust gas of an internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art As a device for purifying exhaust gas of an internal combustion engine, an exhaust gas purification device using a catalyst is widely used. Since such an exhaust gas purification device functions at or above a predetermined activation temperature, it is necessary to raise the temperature to or above the activation temperature immediately after startup to improve emission at startup.
[0003]
As a technique for improving the catalyst warm-up property, Japanese Patent Application Laid-Open No. 8-93466 discloses a technique for reducing the heat capacity of the exhaust passage on the upstream side of the catalyst to prevent the gas temperature from lowering. As a method of reducing the heat capacity, there are disclosed methods of reducing the heat dissipation area by reducing the tube diameter, and reducing the heat capacity taken by the tube by making the inner tube thinner as a double tube structure.
[0004]
[Problems to be solved by the invention]
However, at the time of starting, since cool air is present in the exhaust pipe, the heat energy of the exhaust is deprived by the cool air and the pipes, and the temperature of the exhaust gas reaching the catalyst is low because the temperature of the exhaust gas from the engine is low. It becomes low, and sufficient warm-up performance cannot be obtained.
[0005]
Therefore, an object of the present invention is to provide a warm-up system for an exhaust gas purification device that improves warm-up properties at the time of starting.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a warm-up system for an exhaust gas purifying apparatus according to the present invention is a warm-up system for promoting catalyst warm-up of an exhaust gas purifying apparatus that purifies exhaust gas of an internal combustion engine by a catalyst. It is provided with a suction device for sucking air in the pipe upstream of the catalyst.
[0007]
Prevents the introduction of low-temperature exhaust gas into the catalyst by sucking in the air in the exhaust pipe at the beginning of startup, that is, the cold air that was present in the exhaust pipe and engine before startup and the low-temperature exhaust gas at the beginning of startup. Then, the catalyst is warmed up by the high-temperature exhaust gas after the warm-up of the engine, whereby the warm-up property is improved.
[0008]
Preferably, the suction device includes a negative pressure tank and an on-off valve disposed between the negative pressure tank and the exhaust pipe. Alternatively, the suction device may include a passage connecting the exhaust pipe and the intake pipe, and an opening / closing valve for switching the opening / closing state of the passage.
[0009]
Since the cool air is guided to the negative pressure tank by the negative pressure or to the intake pipe, the cool air does not reach the catalyst, the suction can be reliably performed, and the device configuration can be simplified.
[0010]
Further, the warm-up system of the exhaust gas purifying apparatus according to the present invention may include a circulation passage that recirculates exhaust gas that has passed through the catalyst in the early stage of the start to the upstream side of the catalyst.
[0011]
In this case, by circulating the exhaust gas, the thermal energy of the exhaust gas is effectively transmitted to the catalyst, the temperature is promoted, and the warm-up property is improved.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components are denoted by the same reference numerals as much as possible in each drawing, and redundant description is omitted.
[0013]
FIG. 1 is a schematic diagram showing a first embodiment of a warm-up system for an exhaust gas purification apparatus according to the present invention, together with an internal combustion engine equipped with the same. An exhaust purification device 4 such as a three-way catalyst is connected to an exhaust pipe 3 of the engine 1. A negative pressure tank 52 is connected to the exhaust pipe 3 on the upstream side of the exhaust gas purification device 4 via an exhaust passage 50 having an on-off valve 51, and a negative pressure generation source 53 is connected to the negative pressure tank 52. . As the negative pressure source 53, for example, an electric pump, a mechanical pump mechanically driven by the engine 1, or the like can be used. Further, it may be constituted by a connecting flow path to an intake pipe and an opening / closing valve, not shown in the figure. The on-off valve 51 is connected to the ECU 2 that controls the engine 1. The exhaust passage 50, the on-off valve 51, the negative pressure tank 52, and the negative pressure source 53 constitute the warm-up system 5 according to the first embodiment.
[0014]
Immediately after the start of the engine 1, the ECU 2 opens the on-off valve 51. The ECU 2 drives the negative pressure source 53 with the on-off valve 51 closed before starting the engine 1, preferably during the previous operation of the engine 1, thereby discharging the air remaining in the negative pressure tank 52. Thus, the negative pressure tank 52 is maintained in a negative pressure state. When the on-off valve 51 is opened in this state, the cool air remaining in the exhaust pipe 3 and the low-temperature exhaust gas immediately after starting discharged from the engine 1 are guided to the negative pressure tank 52 through the exhaust passage 50, and the exhaust gas is purified. It does not reach the device 4. Therefore, the exhaust gas purifying device 4 is not cooled by the cool air remaining in the exhaust pipe 3 immediately after the start.
[0015]
After the complete explosion of the engine 1, the ECU 2 closes the on-off valve 51. Thus, the high-temperature exhaust gas discharged from the engine 1 is guided to the exhaust gas purification device 4, so that the temperature of the exhaust gas purification device 4 can be quickly and efficiently raised, that is, warmed up.
[0016]
FIG. 2 is a schematic diagram showing a second embodiment of a warm-up system for an exhaust gas purification apparatus according to the present invention, together with an internal combustion engine equipped with the same. In this embodiment, an exhaust passage 50a connecting the exhaust pipe 3 of the engine 1 (upstream of the exhaust gas purifying device 4) and the intake pipe 6 (downstream of the throttle 7) is provided. It has a valve 51a. The exhaust passage 50a and the on-off valve 51a constitute a warm-up system 5a according to the second embodiment.
[0017]
Immediately after the start of the engine 1, the ECU 2 opens the on-off valve 51a. When the engine 1 is started, the inside of the intake pipe 6 becomes a negative pressure state, and the pressure becomes lower than that of the exhaust pipe 3. For this reason, the cool air remaining in the exhaust pipe 3 and the low-temperature exhaust gas immediately after starting discharged from the engine 1 are guided to the intake pipe 6 through the exhaust passage 50a, and therefore do not reach the exhaust purification device 4. Therefore, the exhaust gas purifying device 4 is not cooled by the cool air remaining in the exhaust pipe 3 immediately after the start. In addition, by recirculating the exhaust gas to the engine 1, the temperature of the exhaust gas is quickly increased, and the warm-up of the engine is promoted.
[0018]
After the complete explosion of the engine 1, the ECU 2 closes the on-off valve 51a. Thus, the high-temperature exhaust gas discharged from the engine 1 is guided to the exhaust gas purification device 4, so that the temperature of the exhaust gas purification device 4 can be quickly and efficiently raised, that is, warmed up.
[0019]
FIG. 3 is a schematic diagram showing a third embodiment of a warm-up system for an exhaust emission control device according to the present invention, together with an internal combustion engine equipped with the same. As shown in FIG. 3A, a recirculation passage 54 that bypasses the exhaust gas purification device 4 is connected to the exhaust pipe 3 of the engine 1. A switching valve 55 is disposed at a connection portion between the recirculation passage 54 on the downstream side of the exhaust gas purification device 4 and the exhaust pipe 3. The recirculation passage 54 and the switching valve 55 constitute a warm-up system 5b according to the third embodiment.
[0020]
After the engine 1 is started, preferably after the complete explosion, the ECU 2 controls the switching valve 55 so that the switching valve 55 closes the atmosphere-side passage of the exhaust pipe 3 and exhaust pipe, as shown in FIG. 3 and the recirculation passage 54 are communicated with each other. Thereby, the exhaust gas discharged from the engine 1 that has passed through the exhaust gas purification device 4 is returned to the exhaust gas purification device 4 again by the recirculation passage 54. By circulating the exhaust gas in this manner, an increase in the amount of gas and a decrease in the exhaust gas temperature in the exhaust gas purification device 4 are suppressed, and the thermal energy of the exhaust gas is efficiently transferred to the exhaust gas purification device 4, thereby reducing the exhaust gas. Encourage temperature rise. Further, by circulating the exhaust gas, the emission is also improved.
[0021]
After the catalyst is warmed up, the ECU 2 controls the switching valve 55 to close the inlet of the recirculation passage 54 to the exhaust pipe 3 and shift to normal control, as shown in FIG.
[0022]
【The invention's effect】
As described above, according to the present invention, the warm-up of the exhaust gas purification device in the early stage of the start is promoted, so that the exhaust gas purification device is activated early and has an effect of improving the emission in the early stage of the start.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a first embodiment of a warm-up system for an exhaust gas purification apparatus according to the present invention, together with an internal combustion engine equipped with the same.
FIG. 2 is a schematic diagram showing a second embodiment of a warm-up system for an exhaust gas purification apparatus according to the present invention, together with an internal combustion engine equipped with the same.
FIG. 3 is a schematic diagram showing a third embodiment of a warm-up system for an exhaust purification device according to the present invention, together with an internal combustion engine equipped with the warm-up system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Internal-combustion engine (engine), 2 ... ECU, 3 ... Exhaust pipe, 4 ... Exhaust purification device (Three-way catalyst), 5 ... Warm-up system, 6 ... Intake pipe, 7 ... Throttle, 50 ... Exhaust passage, 51 ... Opening / closing valve, 52: negative pressure tank, 53: negative pressure generating source, 54: recirculation passage, 55: switching valve.

Claims (4)

In a warm-up system for promoting catalyst warm-up of an exhaust purification device that purifies exhaust gas of an internal combustion engine by a catalyst,
A warm-up system for an exhaust gas purification device that includes a suction device that suctions air in an exhaust pipe at the upstream of a catalyst at an early stage of startup. The warming-up system for an exhaust emission control device according to claim 1, wherein the suction device includes a negative pressure tank and an on-off valve disposed between the negative pressure tank and an exhaust pipe. The warming-up system for an exhaust emission control device according to claim 1, wherein the suction device includes a passage connecting the exhaust pipe and the intake pipe, and an opening / closing valve that switches an open / close state of the passage. In a warm-up system for promoting catalyst warm-up of an exhaust purification device that purifies exhaust gas of an internal combustion engine by a catalyst,
A warm-up system for an exhaust gas purification device including a circulation passage for circulating exhaust gas that has passed through a catalyst at an early stage of the start to an upstream side of the catalyst.

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