Exhaust control device for internal combustion engine

Abstract

To provide an exhaust control device for an internal combustion engine capable of lowering pressure in an exhaust pipe with a GPF by a simple configuration.SOLUTION: An exhaust control device is for an internal combustion engine 1 having a GPF 5 provided in the middle of an exhaust pipe 3 for discharging combustion exhaust gas. A first exhaust pipeline 6 communicated with the atmosphere and a second exhaust pipeline 7 opened / closed by an on-off valve 8 and communicated with the atmosphere are connected to a downstream side of the GPF 5. The exhaust control device includes: a sensor 10 for detecting pressure on an upstream side of the GPF 5; and a controller 9 for performing control to open the on-off valve 8 when the pressure detected by the sensor 10 reaches predetermined reference pressure or greater.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a device for controlling exhaust gas from an internal combustion engine such as a gasoline engine. [Background technology]

[0002] Since PM (particulate matter) and the like are generated when an internal combustion engine is operated, a filter is provided in the exhaust system to capture PM. One example is described in Patent Document 1, and the invention described in Patent Document 1 is an exhaust purification system in which an exhaust purification catalyst and a filter for capturing PM and the like are arranged in order from the upstream side of the exhaust system, and in order to reduce pressure loss due to the filter, a catalytic metal or a composite oxide is supported on the filter to give the filter a catalytic function. Patent Document 2 also describes an exhaust gas purification device in which an exhaust throttle valve is provided downstream of a particulate collection filter (DPF) communicating with an exhaust port of a diesel engine, and the device is configured to compare the maximum pressure at which the exhaust valve does not open during the exhaust stroke with the back pressure of the exhaust valve, and close the exhaust throttle valve when the back pressure is low. Furthermore, Patent Document 3 also describes a device in which a spare filter is arranged in parallel with a DPF main body, and a pressure valve is provided to selectively introduce exhaust gas into the spare filter, and the device is configured to flow exhaust gas to the spare filter side when the pressure in the DPF device increases. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-194478 A [Patent Document 2] JP 2010-156296 A [Patent Document 3] JP 2005-240652 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a filter for capturing PM or the like is provided on the exhaust side of an internal combustion engine, the filter becomes an exhaust resistance, so in order to avoid a decrease in the output or operating efficiency of the internal combustion engine, it is desirable to eliminate or reduce as much as possible the causes of pressure loss, such as clogging in the filter. Therefore, in the invention described in Patent Document 1, a catalyst function is imparted to the filter. However, in such a configuration, even if it is possible to suppress or delay the increase in pressure loss by suppressing the adhesion or deposition of PM or the like, it is not possible to completely avoid the adhesion or deposition of PM or the like, so that the pressure loss will eventually increase due to clogging or the like. In other words, in the invention described in Patent Document 1, it is difficult to eliminate or correct the increase in pressure loss due to clogging or the like and the associated decrease in output or operating efficiency of the internal combustion engine.

[0005] In addition, the invention described in Patent Document 2 is configured to open and close an exhaust throttle valve provided downstream of the DPF, but in the invention described in Patent Document 2, the back pressure of the exhaust valve when the exhaust throttle valve is closed is compared with the maximum pressure at which the exhaust valve does not open during the intake stroke, and the opening and closing of the exhaust throttle valve is controlled based on the result of the comparison. This is to promote the combustion of PM by introducing high-temperature and high-pressure exhaust gas into the DPF, and therefore, if the back pressure of the exhaust valve when the exhaust throttle valve is closed is lower than the above-mentioned maximum pressure, the exhaust throttle valve is closed to increase the back pressure. This is similar to a state in which the DPF is clogged due to adhesion or deposition of PM, etc. In other words, the invention described in Patent Document 2 creates a state similar to a state in which pressure loss is increased due to clogging of the DPF, etc., and there is a possibility that problems such as a decrease in output due to an increase in back pressure and exhaust gas leakage may occur.

[0006] Furthermore, the invention described in Patent Document 3 is configured to reduce the amount of exhaust gas flowing through a filter that has increased pressure loss due to clogging, etc., and purify the reduced amount of exhaust gas with a spare filter. However, the invention described in Patent Document 3 is not configured to reduce the pressure in the exhaust pipe by utilizing a filter that has increased pressure loss, but rather is configured to additionally provide a spare filter, which may result in an increased device size and cost.

[0007] This invention has been made with attention to the above technical problems, and aims to provide an exhaust control device for an internal combustion engine that can reduce the pressure inside an exhaust pipe equipped with a gasoline particulate filter (GPF) with a simple configuration. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention provides an exhaust control device for an internal combustion engine in which a gasoline particulate filter is provided in an exhaust pipe that discharges combustion exhaust gas, and which is connected to a first exhaust pipe line downstream of the gasoline particulate filter that is connected to the atmosphere, and a second exhaust pipe line that is opened and closed by an on-off valve and is connected to the atmosphere, and which further comprises a sensor that detects the pressure upstream of the gasoline particulate filter, and a controller that controls the on-off valve to open when the pressure detected by the sensor becomes equal to or higher than a predetermined reference pressure. Effect of the Invention

[0009] The gasoline particulate filter (GPF) installed in the exhaust pipe itself generates pressure loss due to flow resistance. Therefore, a pressure difference occurs between the pressure on the upstream side of the GPF, which is the pressure inside the exhaust pipe, and the pressure on the downstream side, which is the pressure on the upstream side, of the GPF, depending on the pressure loss in the GPF. When PM and other substances adhere and accumulate on the GPF and the pressure loss increases, the internal pressure of the exhaust pipe, which is the pressure on the upstream side, increases accordingly. On the other hand, the first exhaust pipe line and the second exhaust pipe line connected to the downstream side of the GPF generate pressure loss depending on their length and inner diameter, and when the opening and closing valve is closed, the total cross-sectional area of ​​the pipe line from the GPF to the atmosphere is the cross-sectional area of ​​the first exhaust pipe line, so the pressure loss is large and the pressure on the downstream side of the GPF is high by that amount. In other words, the pressure inside the exhaust pipe is maintained at a specified pressure, and the combustion of PM is promoted. On the other hand, when the internal pressure of the exhaust pipe detected by the sensor becomes high, the on-off valve opens, and the total cross-sectional area of ​​the pipe that connects the GPF to the atmosphere increases accordingly, causing the pressure downstream of the GPF to decrease. Therefore, even if the pressure loss due to the GPF increases, the pressure upstream decreases in response to the decrease in the downstream pressure. In other words, the increase in the exhaust pressure of the internal combustion engine or the back pressure of the exhaust valve is prevented or suppressed, so that the inevitable decrease in the output of the internal combustion engine can be prevented or suppressed, and exhaust gas leakage and damage to the exhaust pipe can be avoided or suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram for explaining a configuration of an embodiment of the present invention. [Diagram 2] 4 is a flowchart illustrating an example of a control executed in the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Next, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely one example of the case where the present invention is implemented, and is not intended to limit the present invention.

[0012] FIG. 1 is a schematic diagram for explaining an embodiment of the present invention. An internal combustion engine (hereinafter, referred to as engine) 1 is, as an example, a gasoline engine, which burns a mixture of gasoline and air to output power. The engine is configured to exhaust exhaust gas generated by the combustion of the mixture into the atmosphere through an exhaust pipe 3 connected via an exhaust manifold 2. The exhaust pipe 3 is provided with an exhaust purification catalyst 4 and a GPF 5 in this order from the upstream side. The exhaust purification catalyst 4 is an exhaust purification catalyst that has been conventionally used in vehicles, such as an oxidation catalyst that oxidizes environmental pollutants such as hydrocarbons and carbon monoxide, and an occlusion reduction type catalyst that captures nitrogen oxides as nitrate nitrogen and then reduces them to make them harmless. The GPF 5 is a filter that captures PM generated by burning gasoline and burns it as necessary, and is a known filter that is mainly used in direct injection gasoline engines that directly inject gasoline into the intake port or into the cylinder.

[0013] A first exhaust pipe 6 and a second exhaust pipe 7 are connected to the downstream side (discharge side) of the GPF 5. These exhaust pipes 6, 7 are pipes for discharging the exhaust gas discharged from the GPF 5 to the atmosphere, and are connected to the atmosphere. The first exhaust pipe 6 is for constantly flowing the exhaust gas, whereas the second exhaust pipe 7 is for flowing the exhaust gas as needed, and is provided with an on-off valve 8 for selectively allowing the exhaust gas to flow into the second exhaust pipe 7 or preventing the flow of the exhaust gas. Although FIG. 1 shows a configuration including two first exhaust pipes 6 and one second exhaust pipe 7, the number of these exhaust pipes 6, 7 may be any number as needed.

[0014] The on-off valve 8 is a valve whose opening can be electrically controlled, and can be switched between two states, "fully open" and "fully closed," or can be set to an appropriate opening. A controller 9 is provided to control the opening of this on-off valve 8. The controller 9 is a computing device mainly composed of a microcomputer, and is configured to perform calculations according to a predetermined program using input data and pre-stored data, and to output the results of the calculations as a control command signal.

[0015] A pressure sensor 10 is provided to detect the internal pressure of the exhaust pipe 3 on the upstream side of the GPF 5. The pressure sensor 10 is connected to the controller 9 and configured to detect the internal pressure of the exhaust pipe 3 on the upstream side of the GPF 5 and input the detection signal (data) to the controller 9.

[0016] Increasing the output of the engine 1 also increases the amount of exhaust gas, causing an increase in the pressure inside the exhaust pipe 3. The internal pressure of the exhaust pipe 3 is limited in terms of strength, etc., and therefore, if the internal pressure of the exhaust pipe 3 increases, the increase in the output of the engine 1 is limited. Also, if pressure loss in the GPF 5 increases, the internal pressure of the exhaust pipe 3 increases, which may limit the output of the engine 1. In order to eliminate or alleviate the limitation on the output of the engine 1 caused by such an increase in the internal pressure of the exhaust pipe 3, the control device in the above-mentioned embodiment of the present invention is configured to execute the control described below.

[0017] FIG. 2 is a flowchart for explaining an example of the control, which is executed by the controller 9 described above. The control shown in the flowchart in FIG. 2 is repeatedly executed by the controller 9 described above while the engine 1 is operating. When the engine 1 is operating, combustion exhaust gas is discharged according to its output, and the inside of the exhaust pipe 3 is at a predetermined pressure. The pressure is detected by the pressure sensor 10 described above. When the internal pressure of the exhaust pipe 3 (the pressure upstream of the GPF 5) increases due to an increase in the output of the engine 1 or an increase in pressure loss in the GPF 5, the detection value by the pressure sensor 10 increases. In the control example shown in FIG. 2, it is determined in step S1 whether such an increase in pressure has occurred. For example, it is determined whether the internal pressure of the exhaust pipe 3 has become equal to or higher than a predetermined reference pressure P.

[0018] The second exhaust pipe 7 and the on-off valve 8 are provided in preparation for the case where the internal pressure of the exhaust pipe 3 rises, and therefore the on-off valve 8 is closed in a normal state in which the output of the engine 1 is not particularly large after starting. Therefore, if the result of the determination in step S1 is negative, the routine shown in FIG. 2 is temporarily terminated without performing any particular control.

[0019] In this case, the on-off valve 8 is maintained in a "closed state," and the exhaust gas discharged from the GPF 5 is discharged into the atmosphere through the first exhaust pipe 6. Therefore, the pressure on the discharge side of the GPF 5 is determined by the pressure loss between the discharge port of the GPF 5 and the open end of the first exhaust pipe 6. Also, the pressure on the upstream side of the GPF 5 (the internal pressure of the exhaust pipe 3) is a pressure according to the pressure loss in the GPF 5 and the pressure on the discharge side. The GPF 5, the exhaust pipe 3, the first exhaust pipe 6, etc. are configured so that the internal pressure of the exhaust pipe 3 determined in this way is a pressure that does not interfere with the operation of the engine 1 and does not interfere with the collection and combustion of PM and the like in the GPF 5. In other words, the internal pressure of the exhaust pipe 3 does not rise excessively, and the output of the engine 1 is not restricted as a result, and the engine 1 can be operated according to demand.

[0020] On the other hand, when the internal pressure of the exhaust pipe 3 rises due to an increase in the output demand or the like and the result of the affirmative determination in step S1 is the control for opening the on-off valve 8 to the "open state" (step S2). When the on-off valve 8 is opened, the exhaust gas discharged from the GPF 5 is discharged into the atmosphere through not only the first exhaust pipe 6 but also the second exhaust pipe 7. That is, the resistance (pressure loss) on the downstream side (discharge side) of the GPF 5 is reduced by increasing the cross-sectional area of ​​the pipe from the GPF 5 to the atmosphere by the amount of the second exhaust pipe 7. The pressure on the upstream side (inlet side) of the GPF 5, i.e., the internal pressure of the exhaust pipe 3, is determined by the pressure loss due to the GPF 5 and the pressure on its downstream side (discharge side). Therefore, when the pressure on the downstream side of the GPF 5 is reduced by opening the on-off valve 8 to reduce the pressure loss, the internal pressure of the exhaust pipe 3, which is the pressure on the upstream side of the GPF 5, is reduced. As a result, the factors limiting the engine output are eliminated, and the output of the engine 1 can be increased according to the drive demand.

[0021] In the end, in the embodiment of the present invention, a second exhaust pipe 7 is provided downstream of the GPF 5 in addition to the above-mentioned first exhaust pipe 6, and the on-off valve 8 is opened to exhaust from the second exhaust pipe 7 when the internal pressure of the exhaust pipe 3 rises, so that it is possible to prevent or suppress an increase in the internal pressure of the exhaust pipe 3 and avoid limiting the output of the engine 1. Also, since there is no need to additionally provide a separate exhaust system having a filter or the like, the overall configuration can be simplified.

[0022] In the above-described embodiment, the on-off valve 8 is fully opened when the internal pressure of the exhaust pipe 3 becomes equal to or higher than a predetermined reference pressure P. However, the present invention is not limited to this configuration. If the internal pressure of the exhaust pipe 3 is equal to or higher than a predetermined reference pressure, the opening of the on-off valve may be increased in accordance with the pressure. [Explanation of symbols]

[0023] 1 Engine 2 Exhaust manifold 3. Exhaust pipe 4. Exhaust purification catalyst 5 Gasoline Particulate Filter (GPF) 6. First exhaust pipe 7 Second exhaust pipe 8. On-off valve 9. Controller 10 Pressure Sensor

Claims

[Claim 1] An exhaust control device for an internal combustion engine, comprising: a gasoline particulate filter provided in an exhaust pipe for discharging combustion exhaust gas; a first exhaust pipe line connected to the atmosphere downstream of the gasoline particulate filter, and a second exhaust pipe line opened and closed by an on-off valve and connected to the atmosphere; a sensor for detecting a pressure upstream of the gasoline particulate filter; a controller that controls the on-off valve so as to open when the pressure detected by the sensor becomes equal to or higher than a predetermined reference pressure; An exhaust control device for an internal combustion engine, further comprising:

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