JP2011179426A - Exhaust emission control system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve efficiency of heating in an exhaust emission control device using a heating device, concerning an exhaust emission control system of an internal combustion engine, the system including the heating device for heating the exhaust emission control device. <P>SOLUTION: The exhaust emission control system of the internal combustion engine includes: the exhaust emission control device which is installed on an exhaust system of the internal combustion engine; and the heating device which heats the exhaust emission control device. A gas amount passing through the exhaust emission control device during an operation of the heating device is designed to increase more than that during a non-operation. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine, and more particularly to an exhaust gas purification system provided with a mechanism for heating a catalyst.

  A technique is known in which an exhaust gas purification device including a catalyst is provided in an exhaust system of an internal combustion engine, and the exhaust gas purification device is heated by a heater (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 08-28252 Japanese Patent Application Laid-Open No. 07-102968 Japanese Patent Laid-Open No. 10-502149 Japanese Unexamined Patent Publication No. 07-250404 JP 2008-19780 A

  By the way, if the amount of gas passing through the exhaust purification device when the heater is operating is equivalent to that when the heater is not operating, the temperature of the exhaust purification device cannot be increased efficiently, leading to deterioration in exhaust emission and increase in heater consumption energy. There is a possibility of inviting.

  The present invention has been made in view of various circumstances as described above, and an object of the present invention is to provide an exhaust purification system for an internal combustion engine including a heating device for heating the exhaust purification device. The purpose is to increase the heating efficiency.

  In order to solve the above-described problems, the present invention provides an exhaust purification system for an internal combustion engine including an exhaust purification device provided in an exhaust system of the internal combustion engine and a heating device for heating the exhaust purification device. The amount of gas that passes through the exhaust purification device when the heating device is activated is made larger than the amount of gas that passes through the exhaust purification device during non-operation.

Specifically, the exhaust gas purification system for an internal combustion engine of the present invention includes:
An exhaust purification device including a catalyst disposed in an exhaust passage of the internal combustion engine and purifying exhaust;
A heating device for heating the exhaust purification device;
When the heating device is operated, a control means for performing an increase process for increasing the amount of gas passing through the exhaust purification device, compared to when the heating device is not operating under the same engine operating condition,
I was prepared to.

  According to this invention, when the heating device is not operating, the amount of heat transferred from the exhaust purification device to the gas can be reduced. As a result, the temperature reduction of the exhaust purification device can be suppressed. On the other hand, when the heating device is operated, the heat applied from the heating device to the exhaust purification device is diffused by the gas over a wide range of the exhaust purification device. As a result, the entire exhaust gas purification device can be heated uniformly, and the heating efficiency of the exhaust gas purification device can be increased.

Here, the increasing means may execute the above-described increasing process when the internal combustion engine is in the deceleration fuel cut state and the heating device is operating. When the internal combustion engine is in the deceleration fuel cut state, low-temperature air passes through the exhaust purification device. Therefore, when the heating device is not operated during the deceleration fuel cut of the internal combustion engine, it is preferable that the amount of gas passing through the exhaust purification device is reduced.

  On the other hand, when the heating device is operated during the deceleration fuel cut of the internal combustion engine, if the amount of gas passing through the exhaust purification device is reduced, a part of the exhaust purification device overheats or the entire exhaust purification device rises. There is a possibility that the time to warm up will become longer. In particular, a configuration in which the heating device heats a part of the exhaust purification device (for example, a portion on the upstream side in the gas flow direction), or a gas that flows into the exhaust purification device (hereinafter referred to as “inlet gas”). In the structure to heat, the above-mentioned problem becomes remarkable.

  On the other hand, when the internal combustion engine is in the deceleration fuel cut state and the heating device is operating, when the increase processing is executed, the heating device heats a part of the exhaust gas purification device or the heating device is turned on. Even in the configuration in which the gas is heated, the entire exhaust emission control device can be heated uniformly.

  In the present invention, as a method of increasing the amount of gas passing through the exhaust purification device, a method of increasing the opening of a throttle valve disposed in the intake passage of the internal combustion engine, an intake air from an exhaust passage downstream of the exhaust purification device, In a configuration including an EGR mechanism that guides part of the exhaust gas (EGR gas) to the passage, a method of increasing the recirculation amount of the EGR gas, or the like can be used.

  ADVANTAGE OF THE INVENTION According to this invention, in the exhaust gas purification system of the internal combustion engine provided with the heater which heats an exhaust gas purification apparatus, the heating efficiency of the exhaust gas purification apparatus by a heater can be improved.

1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. It is a figure which shows the structure of an electric power generation mechanism typically. It is a flowchart which shows the routine performed by ECU when an internal combustion engine is in a deceleration fuel cut state.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. The internal combustion engine 1 shown in FIG. 1 is a 4-stroke cycle spark ignition internal combustion engine (gasoline engine). The internal combustion engine 1 may be a compression ignition internal combustion engine (diesel engine).

  The internal combustion engine 1 includes a plurality of cylinders 2. However, in FIG. 1, only one cylinder among the plurality of cylinders 2 is shown. A piston 3 is slidably loaded in the cylinder 2 in the cylinder axial direction. The piston 3 is connected to the crankshaft 5 via a connecting rod 4.

The internal combustion engine 1 is provided with an intake port 6 and an exhaust port 7 that communicate with the cylinder 2. The opening end of the intake port 6 and the opening end of the exhaust port 7 are opened and closed by an intake valve 8 and an exhaust valve 9, respectively. The intake valve 8 and the exhaust valve 9 are driven to open and close by an intake cam 10 and an exhaust cam 11. Further, a fuel injection valve 12 that injects fuel into the intake port 6 and a spark plug 13 that generates a spark in the cylinder 2 are attached to the internal combustion engine 1.

  An intake passage 60 is connected to the intake port 6 described above. A throttle valve 14 is disposed in the intake passage 60. The fresh air (air) taken into the intake passage 60 is metered by the throttle valve 14 and then guided to the intake port 6. The fresh air guided to the intake port 6 flows into the cylinder together with the fuel injected from the fuel injection valve 12 when the intake valve 8 is opened. Fresh air (air) and fuel that have flowed into the cylinder 2 burn using the spark generated by the spark plug 13 as a spark.

  An exhaust passage 70 is connected to the exhaust port 7 described above. In the middle of the exhaust passage 70, an exhaust purification device 15 is disposed. The exhaust purification device 15 includes a catalyst having an oxidation function, and oxidizes or reduces harmful gas components in the exhaust. Gas (burned gas) burned in the cylinder 2 is discharged from the cylinder 2 to the exhaust port 7 when the exhaust valve 9 is opened. The burned gas discharged to the exhaust port 7 is guided to the exhaust purification device 15 by the exhaust passage 70, and after being purified by the exhaust purification device 15, is discharged into the atmosphere.

  A heating device 16 is disposed immediately upstream of the exhaust purification device 15. The heating device 16 is an electric heater that converts electric energy into heat energy, and heats the exhaust gas (incoming gas) flowing into the exhaust gas purification device 15. The heating device 16 operates, for example, when the temperature of the exhaust purification device 15 is lower than a temperature range in which the oxidation and reduction functions of the exhaust purification device 15 are activated, thereby increasing the early temperature rise and early activation of the exhaust purification device 15. Plan.

  Further, the internal combustion engine 1 is provided with a power generation mechanism 100. As shown in FIG. 2, the power generation mechanism 100 includes an alternator 101, a high voltage battery 102, a low voltage battery 103, a changeover switch 104, and a changeover switch 105.

  The alternator 101 is connected to the output shaft of the internal combustion engine 1 (or a member that rotates in conjunction with the output) via a pulley, a belt, or the like, and generates power that converts the kinetic energy (rotational energy) of the output shaft into electrical energy. Machine.

  Specifically, the alternator 101 includes a stator coil having a three-phase winding, a field coil wound around the rotor, a rectifier that rectifies an alternating current generated in the stator coil into a direct current, and a field current for the field coil. This is a three-phase AC generator including a regulator 101a that switches between energization (on) and non-energization (off) of (field current).

  The alternator 101 configured in this manner generates an induced current (three-phase alternating current) in the stator coil when a field current is applied to the field coil, and rectifies the generated three-phase alternating current into a direct current. Output.

  The output of the alternator 101 is input to the input terminal 104 a of the changeover switch 104. The change-over switch 104 is a circuit that includes one input terminal 104a and two output terminals 104b and 104c, and switches the connection destination of the input terminal 104a to one of the two output terminals 104b and 104c.

  One of the two output terminals 104 b and 104 c (hereinafter referred to as “first output terminal”) 104 b of the changeover switch 104 is connected to the high voltage battery 102. The other of the two output terminals 104 b and 104 c (hereinafter referred to as “second output terminal”) 104 c is connected to the low voltage battery 103.

The high voltage battery 102 is a battery capable of charging and discharging high voltage (for example, about 42 V) electricity, and is constituted by a lead storage battery, a nickel metal hydride battery, or a lithium ion battery. On the other hand, the low voltage battery 103 is a battery capable of charging and discharging electricity having a voltage (for example, about 14 V) lower than that of the high voltage battery 102, and is constituted by a lead storage battery, a nickel hydrogen battery, or a lithium ion battery.

  The changeover switch 105 includes two input terminals 105a and 105b and one output terminal 105c. One of the two input terminals 105 a and 105 b (hereinafter referred to as “first input terminal”) 105 a is connected to a power supply line that connects the changeover switch 104 and the high voltage battery 102. The other input terminal (hereinafter referred to as “second input terminal”) of the two input terminals 105 a and 105 b is connected to a power supply line that connects the changeover switch 104 and the low-voltage battery 103. Furthermore, the output terminal 105 c of the changeover switch 105 is connected to the heating device 16 described above.

  Hereinafter, the changeover switch 104 is referred to as a first changeover switch 104, and the changeover switch 105 is referred to as a second changeover switch 105.

  Returning to FIG. 1, the internal combustion engine 1 is provided with an ECU 17. The ECU 17 is an electronic control unit that includes a CPU, a ROM, a RAM, a backup RAM, and the like. The ECU 17 is supplied with output signals from various sensors such as a crank position sensor 18, an accelerator position sensor 19, and a temperature sensor 20.

  The crank position sensor 18 is a sensor that outputs an electrical signal correlated with the rotational position of the output shaft (crankshaft) of the internal combustion engine 1. The accelerator position sensor 19 is a sensor that outputs an electrical signal correlated with an operation amount (depression amount) of the accelerator pedal. The temperature sensor 20 is a sensor that outputs an electrical signal correlated with the temperature of the exhaust purification device 15 (catalyst bed temperature). The temperature sensor 20 may be a sensor that outputs an electrical signal correlated with the temperature of the exhaust gas flowing out from the exhaust purification device 15.

  The ECU 17 controls the various devices described above based on the output signals of the various sensors described above. For example, the ECU 17 changes the generated voltage of the alternator 101 by duty-controlling on / off of the regulator 101a. Specifically, when increasing the power generation voltage of the alternator 101, the ECU 17 determines the duty ratio so that the ON time of the regulator 101a is long (OFF time is short). On the other hand, when lowering the power generation voltage of the alternator 101, the ECU 17 determines the duty ratio so that the ON time of the regulator 101a is short (off time is long). Further, the ECU 17 senses the actual power generation voltage of the alternator 101, and also performs feedback control of the duty ratio according to the difference between the actual power generation voltage and the target power generation voltage.

  When charging the high-voltage battery 102, the ECU 17 controls the duty of the regulator 101a so that the power generation voltage of the alternator 101 matches the voltage (high voltage) suitable for charging the high-voltage battery 102, and the input terminal 104a. And the first output terminal 104b are controlled to control the first changeover switch 104.

  When charging the low-voltage battery 103, the ECU 17 controls the duty of the regulator 101a so that the power generation voltage of the alternator 101 matches the voltage (low voltage) suitable for charging the low-voltage battery 103, and the input terminal 104a. And the second output terminal 104c are controlled to control the first changeover switch 104.

When the traveling state of the vehicle is in a deceleration state, the rotor of the alternator 101 is rotated by the kinetic energy transmitted from the drive wheels to the internal combustion engine 1. At that time, alternator 1
If a field current is applied to 01, the kinetic energy of the driving wheel can be converted into electric energy (regenerative power generation).

  Therefore, the ECU 17 applies a field current to the alternator 101 when the internal combustion engine 1 is in the deceleration fuel cut state, and regenerative power generation control for charging the high voltage battery 102 or the low voltage battery 103 with the electric power regenerated by the alternator 101. To implement.

  Further, the ECU 17 operates the heating device 16 when the output signal value (catalyst bed temperature) of the temperature sensor 20 is lower than a desired temperature range. At that time, the catalyst bed temperature of the exhaust purification device 15 may be raised to a temperature range in which an oxidizing function such as hydrocarbon (HC) or carbon monoxide (CO) is activated (hereinafter referred to as “active temperature range”). For example, the ECU 17 supplies power from the low voltage battery 103 to the heating device 16. Specifically, the ECU 17 operates the heating device 16 by controlling the second changeover switch 105 so that the second input terminal 105b and the output terminal 105c of the second changeover switch 105 are connected.

  The HC oxidation function and CO oxidation function of the exhaust purification device 15 are activated in a low temperature range of approximately 200 ° C. or higher. Furthermore, when the internal combustion engine 1 is cold-started, it takes a relatively long time for the catalyst bed temperature to rise to the active temperature range. Therefore, when the exhaust purification device 15 is heated using the power of the high voltage battery 102, the power taken out from the battery (including the high voltage battery 102 and the low voltage battery 103) increases unnecessarily, or the exhaust purification device 15 The device 15 may overheat. On the other hand, when the exhaust gas purification device 15 is heated using the electric power of the low voltage battery 103, an unnecessary increase in the electric power taken out from the battery and overheating of the exhaust gas purification device 15 can be suppressed.

  When the alternator 101 is performing regenerative power generation at a high voltage, the heating device 16 may be operated using the high voltage power generated by the alternator 101. In that case, it is possible to quickly increase the catalyst bed temperature to the active temperature range while suppressing an unnecessary increase in electric power taken out from the battery.

  Next, the catalyst bed temperature of the exhaust purification device 15 is increased to a temperature range (hereinafter referred to as “SOF reaction temperature range”) where organic soluble components (SOF: Soluble Organic Fraction) attached or deposited on the exhaust purification device 15 are oxidized. When raising the temperature of the ECU 17, the ECU 17 supplies power from the high voltage battery 102 to the heating device 16. Specifically, the ECU 17 controls the second changeover switch 105 to operate the heating device 16 so that the first input terminal 105a and the output terminal 105c of the second changeover switch 105 are connected.

  The SOF accumulated in the exhaust purification device 15 is oxidized and removed in a high temperature range of about 400 ° C. or higher. Therefore, when the heating device 16 is operated using the power of the low voltage battery 103, it takes a long time for the catalyst bed temperature to rise to the SOF reaction temperature range, or the catalyst bed temperature rises to the SOF reaction temperature range. There is a possibility of not doing. In contrast, when the exhaust purification device 15 is heated using the power of the high voltage battery 102, the catalyst bed temperature can be quickly raised to the SOF reaction temperature range.

  When the alternator 101 is performing regenerative power generation at a high voltage, the SOF removal process is performed using the high-voltage power generated by the alternator 101 even if the conditions for executing the SOF removal process are not satisfied. You may be made to be. In that case, the amount of SOF adhering to or depositing on the exhaust purification device 15 can be constantly reduced. In addition, it is possible to omit a logic and a sensor for calculating the amount of SOF attached or deposited on the exhaust purification device 15.

  By the way, when the internal combustion engine 1 is in the deceleration fuel cut state, the exhaust purification device 15 is cooled by the low-temperature exhaust gas, so the catalyst bed temperature may be lower than the activation temperature range or the SOF reaction temperature range. On the other hand, conventionally, when the internal combustion engine 1 is in the deceleration fuel cut state, measures have been taken to reduce the amount of exhaust gas passing through the exhaust purification device 15 by reducing the opening of the throttle valve 14.

  However, as illustrated in the present embodiment, when the heating device 16 is provided separately from the exhaust purification device 15, in other words, the heating device 16 heats the exhaust gas (incoming gas) flowing into the exhaust purification device 15. In the case of being configured, when the exhaust amount is reduced during the operation of the heating device 16, a part of the exhaust purification device 15 (for example, a portion on the upstream side or a portion located in the center in the radial direction). It may be overheated or it may take time for the entire exhaust gas purification device 15 to reach a desired temperature range.

  Therefore, in this embodiment, the ECU 17 increases the exhaust amount when the heating device 16 is operated during the deceleration fuel cut as compared with the case where the heating device 16 is not operated. Specifically, the ECU 17 increases the opening of the throttle valve 14 when the heating device 16 is operated during the deceleration fuel cut as compared with the case where the heating device 16 is not operated.

  When the exhaust amount during the deceleration fuel cut is controlled in this way, the temperature reduction of the exhaust purification device 15 when the heating device 16 is not operating is suppressed, and the superheating efficiency when the heating device 16 is operating is improved. Is possible.

  Hereinafter, the procedure for adjusting the displacement when the internal combustion engine 1 is in the deceleration fuel cut state will be described with reference to FIG. FIG. 3 is a flowchart showing a routine executed by the ECU 17 when the internal combustion engine 1 is in the deceleration fuel cut state. This routine is a routine that is stored in advance in the ROM of the ECU 17 or the like, and is a routine that is periodically executed by the ECU 17.

  In the routine of FIG. 3, the ECU 17 first determines whether or not the internal combustion engine 1 is in a deceleration fuel cut state in S101. If a negative determination is made in S101, the ECU 17 ends the execution of this routine. On the other hand, if an affirmative determination is made in S101, the ECU 17 proceeds to S102.

  In S102, the ECU 17 determines whether or not the heating device 16 is in an operating state. In other words, it is determined whether or not the operating condition of the heating device 16 (for example, the output signal (catalyst bed temperature) of the temperature sensor 20 is lower than the activation temperature range or the SOF reaction temperature range) is established.

  If a negative determination is made in S102, the ECU 17 proceeds to S104 and controls the throttle valve 14 so that the opening of the throttle valve 14 matches the target opening at the time of deceleration fuel cut. On the other hand, if an affirmative determination is made in S102, the ECU 17 proceeds to S103 and controls the throttle valve 14 so that the opening of the throttle valve 14 is larger than the target opening at the time of deceleration fuel cut. The opening of the throttle valve 14 at that time is the opening at which the heating efficiency of the heating device 16 becomes the highest, in other words, the opening at which the entire exhaust purification device 15 reaches the target temperature the fastest. It is sought by conformity processing.

As described above, when the ECU 17 executes the routine of FIG. 3, the control means according to the present invention is realized. As a result, when the heating device 16 is not operating, the exhaust purification device 15
The amount of heat transferred from the exhaust to the exhaust can be reduced, and the heat generated by the heating device 16 can be diffused over a wide range of the exhaust purification device 15 when the heating device 16 is in operation. Therefore, it is possible to suppress the temperature of the exhaust purification device 15 when the heating device 16 is not operated, and it is possible to increase the heating efficiency of the exhaust purification device 15 when the heating device 16 is operated.

  In the present embodiment, the configuration including the high voltage battery 102 and the low voltage battery 103 is taken as an example. However, the present invention can be applied to a configuration having only one battery.

  Further, when the internal combustion engine 1 includes an EGR mechanism that guides part of the exhaust gas (EGR gas) from the exhaust passage 70 downstream of the exhaust purification device 15 to the intake passage 60, the exhaust gas purification is performed by increasing the EGR gas amount. The amount of gas passing through the device 15 may be increased.

  In that case, the increase in the gas passing through the exhaust purification device 15 mainly depends on the increase in the EGR gas. Therefore, the amount of gas passing through the exhaust purification device 15 can be increased while suppressing an increase in the amount of air passing through the exhaust purification device 15. Therefore, it is possible to reduce cooling loss due to low-temperature air. Furthermore, since the EGR gas is a high-temperature gas heated once by the heating device 16, the catalyst bed temperature of the exhaust gas purification device 15 rises in a shorter time. As a result, the heating efficiency of the exhaust purification device 15 by the heating device 16 can be further increased.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Piston 4 Connecting rod 5 Crankshaft 6 Intake port 7 Exhaust port 12 Fuel injection valve 13 Spark plug 14 Throttle valve 15 Exhaust purification device 16 Heating device 17 ECU
20 temperature sensor 60 intake passage 70 exhaust passage 100 power generation mechanism 101 alternator 101a regulator 102 high voltage battery 103 low voltage battery 104 first changeover switch 104a input terminal 104b first output terminal 104c second output terminal 105 second changeover switch 105a first Input terminal 105b Second input terminal 105c Output terminal

Claims (4)

An exhaust purification device including a catalyst disposed in an exhaust passage of the internal combustion engine and purifying exhaust;
A heating device for heating the exhaust purification device;
Control means for performing an increase process for increasing the amount of gas passing through the exhaust emission control device when the heating device is operating, compared to when the heating device is not operating under equivalent engine operating conditions;
An exhaust gas purification system for an internal combustion engine, comprising:   2. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the control means executes the increase processing when the internal combustion engine is in a deceleration fuel cut state and the heating device is operating.   3. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the heating device is disposed upstream of the exhaust gas purification device and heats a gas flowing into the exhaust gas purification device.   4. The exhaust gas purification of an internal combustion engine according to claim 1, wherein the control means performs an increase process by increasing an opening degree of a throttle valve disposed in an intake passage of the internal combustion engine. system.

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