JP2005220889A - Supercharging system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supercharging system for an internal combustion engine capable of using an electric compressor in a wide range and suppressing the deterioration of exhaust emission. <P>SOLUTION: This supercharging system for the internal combustion engine comprises an intake tube 3 and an exhaust tube 3, and is applied to the engine 1 having an exhaust emission purification catalyst 4 installed in the exhaust tube 3. Also, the supercharging system comprises a turbo supercharger 5 having a compressor 5a and a turbine 5b and supercharging to the engine 1, an electric compressor 6 installed in the intake tube 2 on the upstream side of the compressor 5a of the turbo supercharger 5 and assisting supercharging, an air passage 10 connecting the intake tube 2 on the downstream side of the electric compressor 6 to the exhaust tube 3 on the upstream side of the exhaust emission purification catalyst 4, a flow regulating valve 11 installed in the air passage 10 and regulating the air amount flowing thereinto, and an air supply control means 15 controlling the flow regulating valve 11 so as to supply the air on the downstream side of the electric compressor 6 to the upstream side of the exhaust emission purification catalyst 4 according to the operating state of the electric compressor 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a supercharging system for an internal combustion engine.

As a supercharging system for an internal combustion engine, there is known a system in which an electric compressor is connected in series or in parallel with a turbocharger and supercharging assist is performed by the electric compressor (see, for example, Patent Document 1). In order to improve exhaust emission of an internal combustion engine, an exhaust purification catalyst is provided in the exhaust pipe, and secondary air is supplied upstream of the catalyst by an electric air pump (see, for example, Patent Document 2). In addition, Patent Document 3 and Patent Document 4 exist as prior art documents related to the present invention.
Special Table 2000-500544 JP-A-6-101460 JP 2001-214733 A JP-A-9-137740

  The supercharging assist by the electric compressor is not performed in the entire operation region of the internal combustion engine, but is performed in a limited operation region. For this reason, it is desirable to use the electric compressor for other purposes when supercharging assist is not performed in order to eliminate waste of the entire supercharging system. However, Patent Document 1 does not disclose using the electric compressor used for supercharging assist for other purposes. For this reason, for example, when the supercharging assist is not performed, the ability of the electric compressor cannot be utilized, and the electric compressor may not be used in a wide range.

  On the other hand, supplying secondary air to the catalyst provided in the exhaust passage in order to improve exhaust emission is not necessary in all operating regions as in the case of supercharging assist. For this reason, as described in Patent Document 2, providing a dedicated electric air pump for supplying secondary air may increase costs.

  Therefore, an object of the present invention is to provide a supercharging system for an internal combustion engine that can be used in an electric compressor in a wide range and can suppress deterioration of exhaust emission.

  A first supercharging system for an internal combustion engine according to the present invention is a supercharging system for an internal combustion engine that is applied to an internal combustion engine that includes an intake passage and an exhaust passage and is provided with an exhaust purification catalyst in the exhaust passage. A turbocharger that includes a compressor and a turbine and that supercharges the internal combustion engine; and an electric compressor that is provided in the intake passage upstream of the compressor of the turbocharger and assists the supercharging. An air passage connecting the intake passage downstream of the electric compressor and the exhaust passage upstream of the exhaust purification catalyst, and a flow rate adjusting valve provided in the air passage for adjusting the amount of air flowing into the air passage And an air supply for controlling the flow rate adjusting valve so as to supply air downstream of the electric compressor to the upstream of the exhaust purification catalyst according to an operating state of the electric compressor. To solve the above problems by comprising a control unit, a (claim 1).

  According to the present invention, the air compressed by the electric compressor can be supplied upstream of the exhaust purification catalyst to promote the oxidation of hydrocarbons (HC), carbon monoxide (CO), etc. in the exhaust gas. In addition, deterioration of exhaust emission can be suppressed. In addition, since the supply of air is performed by switching to the supercharging assist according to the operation state of the electric compressor, the electric compressor can be used in a wide range, and waste of the entire supercharging system can be saved.

  In the first supercharging system for an internal combustion engine of the present invention, a bypass passage that bypasses the electric compressor, a switching valve that is provided in the bypass passage and switches between inflow and prohibition of air into the bypass passage, the electric motor A throttle valve that is provided in the intake passage between the compressor and the compressor of the turbocharger and adjusts the amount of air flowing into the turbocharger, and the air supply control means includes: When supplying the air downstream of the electric compressor to the upstream of the exhaust purification catalyst, the switching valve may be controlled to be closed and the opening of the throttle valve may be controlled to be reduced (Claim 2). ). According to this aspect, when air is supplied to the upstream side of the exhaust purification catalyst, substantially all of the air in the intake passage is guided to the electric compressor and compressed. In addition, most of the air compressed by the electric compressor is guided upstream of the exhaust purification catalyst through the air passage. Therefore, the compressed air can be accurately supplied upstream of the exhaust purification catalyst.

  In the first supercharging system for an internal combustion engine of the present invention, the air supply control means includes a temperature of the exhaust purification catalyst that is equal to or higher than an activation start temperature, a rich exhaust air-fuel ratio, and the electric compressor. The flow rate adjusting valve may be controlled so that air downstream of the electric compressor is supplied upstream of the exhaust purification catalyst when there is no request for supercharging assistance. In this case, since air can be supplied to the upstream side of the exhaust purification catalyst at an appropriate time, the reliability of the supercharging system is improved.

  In the first supercharging system for an internal combustion engine according to the present invention, the air supply control means is configured to provide air downstream of the electric compressor when the pressure downstream of the electric compressor is higher than the pressure upstream of the exhaust purification catalyst. The flow rate adjustment valve may be controlled so as to be supplied upstream of the exhaust purification catalyst. By considering such conditions, it is possible to avoid exhaust gas from flowing backward into the air passage and flowing into the intake passage. In this case, the target pressure may be different between when the air downstream of the electric compressor is supplied upstream of the exhaust purification catalyst and when supercharging assist is performed (Claim 5). Further, the target pressure may be set so that the pressure downstream of the electric compressor is higher than the pressure upstream of the exhaust purification catalyst. By controlling in this way, the operation of the electric compressor becomes efficient and deterioration of fuel consumption can be suppressed.

  Further, in the first supercharging system for an internal combustion engine according to the present invention, the air supply control means has a rich exhaust air / fuel ratio if the temperature of the exhaust purification catalyst is equal to or higher than its activation start temperature immediately after completion of the supercharging assist. Even if this is not the case, the flow rate adjusting valve may be controlled so that the air downstream of the electric compressor is supplied upstream of the exhaust purification catalyst (claim 7). During the supercharging assist, the exhaust air-fuel ratio becomes rich and hydrocarbons (HC) and the like are likely to accumulate in the exhaust purification catalyst. Thus, if air is supplied to the upstream side of the exhaust purification catalyst immediately after the supercharging assist as in this aspect, hydrocarbons (HC) and the like accumulated during the supercharging assist can be oxidized.

  In the first supercharging system for an internal combustion engine according to the present invention, the air supply control means is a case where there is a request for assisting the supercharging by the electric compressor, and the air downstream of the electric compressor is supplied to the electric compressor. May be controlled so that air downstream of the electric compressor is supplied upstream of the exhaust purification catalyst (claim 8). According to this aspect, both the supercharging assist and the air supply to the exhaust purification catalyst can be performed at the same time, and the capacity of the electric compressor can be fully utilized. In this case, the air supply control means controls the opening of the flow rate adjusting valve so that the pressure downstream of the electric compressor does not become a predetermined value or less (Claim 9), and the supercharging assist and the air supply are controlled. Both may be appropriately balanced.

  A second supercharging system for an internal combustion engine according to the present invention includes an intake passage and an exhaust passage, and an internal combustion engine in which an NOx storage reduction catalyst is provided in the exhaust passage and an oxidation catalyst is provided downstream of the NOx catalyst. A supercharging system for an internal combustion engine to be applied, comprising a compressor and a turbine, and a turbocharger for supercharging the internal combustion engine, and an intake passage upstream of the compressor of the turbocharger An electric compressor provided to assist the supercharging, an air passage connecting the intake passage downstream of the electric compressor, the exhaust passage between the NOx catalyst and the oxidation catalyst, and the air passage. A flow rate adjusting valve for adjusting the amount of air flowing into the air passage, and when the NOx catalyst is in the sulfur poisoning regeneration period, the NOx catalyst is heated to a predetermined temperature or higher. Sulfur poisoning regeneration control means for controlling the internal combustion engine so that the exhaust air / fuel ratio becomes rich to perform sulfur poisoning regeneration of the NOx catalyst, and rich control of the exhaust air / fuel ratio by the sulfur poisoning regeneration control means Electric compressor control means for operating the electric compressor so as to synchronize, and air downstream of the electric compressor is supplied to the exhaust passage between the NOx catalyst and the oxidation catalyst according to the operating state of the electric compressor. Thus, the above-described problem is solved by providing an air supply control means for controlling the flow rate adjusting valve.

The sulfur poisoning regeneration of the NOx catalyst is performed by raising the temperature of the NOx catalyst and controlling the exhaust air / fuel ratio to be rich for a predetermined time, thereby decomposing the sulfate of the storage material of the NOx catalyst and releasing the sulfur component. It is intended to restore the performance of. However, in this sulfur poisoning regeneration, the sulfur component released from the NOx catalyst is changed to hydrogen sulfide (H ₂ S) due to the rich control of the air-fuel ratio, and there is a possibility that malodor and white smoke may be released to the atmosphere. is there. According to the present invention, the air downstream of the electric compressor is supplied to the exhaust passage between the NOx catalyst and the oxidation catalyst in synchronism with the rich control of the exhaust air / fuel ratio to make the exhaust air / fuel ratio downstream of the NOx catalyst lean. Therefore, H ₂ S generated by sulfur poisoning regeneration can be converted to SOx, and the emission of malodor and white smoke can be suppressed.

  In the second supercharging system for an internal combustion engine of the present invention, a bypass passage that bypasses the electric compressor, a switching valve that is provided in the bypass passage and switches between inflow and prohibition of air into the bypass passage, and the electric A throttle valve that is provided in the intake passage between the compressor and the compressor of the turbocharger and adjusts the amount of air flowing into the turbocharger, and the air supply control means includes: When the air downstream of the electric compressor is supplied to the exhaust passage between the NOx catalyst and the oxidation catalyst, the switching valve is controlled to be closed and the opening of the throttle valve is controlled to be reduced. (Claim 11). According to this aspect, when supplying the air downstream of the electric compressor to the exhaust passage between the NOx catalyst and the oxidation catalyst, substantially all the air in the intake passage is guided to the electric compressor and compressed. In addition, most of the air compressed by the electric compressor is led to the exhaust passage between the NOx catalyst and the oxidation catalyst via the air passage. Therefore, the compressed air can be accurately supplied to the exhaust passage between the NOx catalyst and the oxidation catalyst.

  In the second supercharging system for an internal combustion engine of the present invention, the electric compressor and the flow rate adjustment valve are controlled in anticipation of a delay in air supply from the electric compressor to the exhaust passage between the NOx catalyst and the oxidation catalyst. (Claim 12). In this case, the rich control and the air supply can be more accurately synchronized.

  In the second supercharging system for an internal combustion engine according to the present invention, air supply to the exhaust passage between the NOx catalyst and the oxidation catalyst has priority over the supercharging assist by the electric compressor. You may start (Claim 13). This is because suppression of deterioration of exhaust emission is more important than supercharging assistance. However, when the sulfur poisoning regeneration time comes during the supercharging assist by the electric compressor, the sulfur poisoning regeneration is not started until the assist is completed, and the assist is completed after the assist is completed. Sulfur poisoning regeneration may be started (claim 14). This is because the supercharging assist is completed in a relatively short time, and there is little inconvenience even if the sulfur poisoning regeneration is performed after the supercharging assist is completed.

  In the second supercharging system for an internal combustion engine of the present invention, the air supply control means has a request for assisting the supercharging by the electric compressor even during the sulfur poisoning regeneration, and performs the assist. When there is a surplus power, the flow control valve is controlled to supply the air downstream of the electric compressor to the upstream of the oxidation catalyst, and the throttle valve is controlled to be opened to perform the assist. (Claim 15). According to this aspect, the supercharging assist and the air supply to the exhaust passage between the NOx catalyst and the oxidation catalyst can be performed simultaneously, and the capacity of the electric compressor can be fully utilized.

  The third supercharging system for an internal combustion engine of the present invention is applied to an internal combustion engine that includes an intake passage and an exhaust passage and is provided with a filter that collects particulate matter in the exhaust gas in the exhaust passage. A turbocharging system for an internal combustion engine, comprising a compressor and a turbine, and a turbocharger that supercharges the internal combustion engine, provided in the intake passage upstream of the compressor of the turbocharger, An electric compressor that assists the supercharging, an air passage that connects the intake passage downstream of the electric compressor and the exhaust passage upstream of the filter, and air that is provided in the air passage and flows into the air passage A flow rate adjusting valve for adjusting the amount, and controlling the internal combustion engine to oxidize the particulate matter collected by the filter when it is time to regenerate the filter. A filter regeneration control means for regenerating the electric compressor, an electric compressor control means for operating the electric compressor when the temperature of the filter during the regeneration of the filter rises above a predetermined temperature, and an operating state of the electric compressor An air supply control means for controlling the flow rate adjustment valve so as to supply air downstream of the electric compressor to the upstream of the filter solves the above-mentioned problem (claim 16).

  When the particulate matter deposited on the filter exceeds a predetermined amount, filter regeneration control is performed to oxidize the particulate matter and restore the filter performance. However, since this filter regeneration control is to increase the temperature of the filter by controlling the temperature of the exhaust gas to a high temperature, the temperature may increase more than necessary. According to this invention, since the air downstream of the electric compressor can be supplied to the upstream of the filter during the filter regeneration control, an excessive temperature rise of the filter can be suppressed.

  In the third supercharging system for an internal combustion engine of the present invention, a bypass passage that bypasses the electric compressor, a switching valve that is provided in the bypass passage and switches between inflow and prohibition of air into the bypass passage, the electric motor A throttle valve that is provided in the intake passage between the compressor and the compressor of the turbocharger and adjusts the amount of air flowing into the turbocharger, and the air supply control means includes: When the air downstream of the electric compressor is supplied to the upstream of the filter, the switching valve may be controlled to be closed and the opening of the throttle valve may be controlled to be throttled (Claim 17). In this case, when air is supplied to the upstream side of the filter, substantially all the air in the intake passage is guided to the electric compressor and compressed. Moreover, much of the air compressed by the electric compressor is guided upstream of the filter through the air passage. Therefore, the compressed air can be accurately supplied upstream of the filter.

  Further, in the third supercharging system for an internal combustion engine of the present invention, the air supply to the upstream side of the filter may be started in preference to the supercharging assist by the electric compressor. This is because an excessive temperature rise of the filter leads to a failure of the filter. Therefore, when the filter regeneration start time comes during the supercharging assist by the electric compressor, the assist is interrupted, and the flow rate is set so that air downstream of the electric compressor is supplied upstream of the filter. It is preferable to control the regulating valve (claim 19).

  Further, in the third supercharging system for an internal combustion engine of the present invention, the air supply control means has a request for assisting the supercharging by the electric compressor even during regeneration of the filter, and the assist is provided. When there is remaining capacity to perform, the flow control valve is controlled to supply the air downstream of the electric compressor to the upstream of the filter, and the throttle valve is controlled to be opened to perform the assist. (Claim 20). According to this aspect, both the supercharging assist and the air supply to the upstream side of the filter can be performed simultaneously, and the capacity of the electric compressor can be fully utilized.

  As described above, according to the present invention, it is possible to provide a supercharging system for an internal combustion engine that can be used in an electric compressor in a wide range and can suppress deterioration of exhaust emission.

(First embodiment)
A supercharging system for an internal combustion engine according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the overall configuration of the present embodiment. This supercharging system is applied to a diesel engine 1 (hereinafter sometimes referred to as an engine) as an internal combustion engine. The engine 1 includes an intake pipe 2 as an intake passage and an exhaust pipe 3 as an exhaust passage. An exhaust purification catalyst 4 is provided in the exhaust pipe 3 in order to reduce exhaust emissions. As the exhaust purification catalyst 4, an oxidation catalyst for purifying hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas, an occlusion reduction type NOx catalyst for purifying nitrogen oxide (NOx) in the exhaust gas, or selection Various catalysts such as a reduced NOx catalyst can be used.

  The supercharging system includes a turbocharger 5 and an electric compressor 6. As is well known, the turbocharger 5 has a compressor 5a for compressing the sucked air and a turbine 5b for driving the compressor 5a. The compressor 5 a is provided in the intake pipe 2. Further, the turbine 5 b is provided in the exhaust pipe 3. The turbocharger 5 drives the compressor 5a by rotating the turbine 5b with the exhaust gas flowing through the exhaust pipe 3. Thereby, a desired supercharging pressure can be obtained.

  On the other hand, the electric compressor 6 is provided in the intake pipe 2 upstream of the turbocharger 5. The electric compressor 6 includes an electric motor 6a as a driving device. The electric motor 6a is connected to a power source (not shown). By driving the electric motor 6a, the electric compressor 6 operates and the air in the intake pipe 2 can be compressed.

  A desired supercharging pressure can be obtained by operating the turbocharger 5 and the electric compressor 6. Since the turbocharger 5 uses the energy of the exhaust gas as described above, a time lag occurs until a desired supercharging pressure is obtained (so-called turbo lag). This is particularly noticeable when rapid acceleration is required during low-speed traveling. Therefore, supercharging assistance is performed by the electric compressor 6 to compensate for the turbo lag and assist the turbocharger until a desired supercharging pressure is obtained.

  In the supercharging system, a bypass passage 7 that bypasses the electric compressor 6 is provided. In the middle of the bypass passage 7, a bypass valve 8 is provided as a switching valve for switching between inflow of air into the bypass passage 7 and prohibition thereof. The bypass valve 8 is basically closed when the electric compressor 6 is in operation, and the inflow of air into the bypass passage 7 is prohibited. Accordingly, substantially all the air upstream of the electric compressor 6 is guided to the electric compressor 3. On the other hand, when the electric compressor 6 is not in operation, the valve is basically opened and air is guided to the bypass passage 7. The bypass valve 8 may be linearly driven by a solenoid or the like, but only needs to be able to switch between opening and closing. For example, a shutter valve that is driven by a balance between the pressure downstream of the electric compressor 6 and the pressure of the inlet of the bypass passage 7 may be provided as the bypass valve 8. In this case, since the control of the bypass valve 8 becomes unnecessary, the structure can be simplified. A throttle valve 9 is provided in the intake pipe 2 on the downstream side of the bypass valve 8. The throttle valve 9 is linearly driven by a solenoid or the like from the fully closed state to the fully open state, and the flow rate of air guided to the engine 1 (or the compressor 5a) can be adjusted.

  The intake pipe 2 downstream of the electric compressor 6 and the exhaust pipe 3 upstream of the exhaust purification catalyst 4 are connected by an air passage 10. The air passage 10 is provided to guide the air compressed by the electric compressor 6 to the upstream side of the exhaust purification catalyst 4. A flow rate adjusting valve 11 is provided in the air passage 10. Like the throttle valve 9, the flow rate adjusting valve 11 is linearly driven from a fully closed state to a fully open state by a solenoid or the like, and can adjust the amount of air flowing into the air passage 10. The flow rate adjusting valve 11 is basically closed when air is not supplied upstream of the exhaust purification catalyst 4.

  An intercooler 12 is provided in the intake pipe 2 on the downstream side of the compressor 5a of the turbocharger 5 in order to cool the air compressed by the compressor 5a. Thereby, the supercharging efficiency can be increased. Further, for the same reason as described above, an intercooler 13 is provided in the intake pipe 2 between the electric compressor 6 and the compressor 5a of the turbocharger 5. By providing this intercooler 13, it is possible to further improve the supercharging efficiency, but it is not always necessary to provide it. In addition, an air cleaner 14 is provided in the intake pipe 2 upstream of the electric compressor 6 to remove foreign matter from the intake air.

  The electric motor 6a generates heat and is preferably cooled. In this case, it is difficult to cool by air cooling, and the operation time of the electric compressor 3 may be limited. Therefore, for example, a cooling system in which cooling water is circulated by a radiator (not shown) around the electric motor 6a may be employed. This radiator may also be used as the one used for the engine 1, but it is still more preferable that the cooling water for the engine 1 is prepared separately for the electric compressor 6 because the temperature is high. In this case, the temperature of the cooling water is preferably about 30 ° C. Furthermore, this radiator can be used for cooling the turbocharger 5. Such a configuration is very effective as a countermeasure against coking, which is a serious problem.

  With the above configuration, when supercharging assistance is performed by operating the electric compressor 6, the intake air that has passed through the air cleaner 14 is compressed by the electric compressor 6 and then guided to the compressor 5 a of the turbocharger 5. It is further compressed and guided to the engine 1 by a desired supercharging pressure. On the other hand, when air is supplied to the exhaust purification catalyst 4, in principle, the opening of the throttle valve 9 is reduced and the flow rate adjustment valve 11 is opened so that the air pressurized by the electric compressor 6 passes through the air passage 10 and is exhausted. It is supplied upstream of the purification catalyst 4. As a result, it is possible to prevent the air-fuel ratio of the exhaust gas led to the exhaust purification catalyst 4 from becoming too rich, so that oxidation of hydrocarbons (HC), carbon monoxide (CO), etc. in the exhaust gas is promoted. Deterioration of exhaust emission is suppressed.

  As shown in FIG. 1, the supercharging system of this embodiment is mainly controlled by an engine control unit (ECU) 15 that controls the fuel injection amount of the engine 1 and the like. ECU15 is comprised as a computer unit provided with peripheral devices, such as a microprocessor, ROM, and RAM. The ECU 15 controls the electric compressor 6, the bypass valve 8, the throttle valve 9, and the flow rate adjustment valve 11 based on input information from various sensors described later.

  As shown in FIG. 1, the supercharging system according to the present embodiment includes an accelerator opening sensor 20 that detects an accelerator opening and a change amount thereof, an engine speed sensor 21 that detects an engine speed, and an engine 1. A supercharging pressure sensor 22 for detecting the pressure (supercharging pressure) in the intake pipe 2, a turbo rotational speed sensor 23 for detecting the rotational speed of the turbocharger 5, and an inlet of the electric compressor 6. A pressure sensor 24 that is provided in the vicinity and detects the pressure of air sucked into the electric compressor 6, a pressure sensor 25 that detects the pressure of the intake pipe 2 downstream of the electric compressor 6, and a mass flow rate of air flowing into the intake pipe 2 The air flow meter 26 for detecting the exhaust gas, the temperature sensor 27 for detecting the catalyst bed temperature of the exhaust gas purification catalyst 4, the turbine 5 b of the turbocharger 5 and the exhaust gas purification catalyst A pressure sensor 28 for detecting the pressure of the exhaust gas upstream of the exhaust purification catalyst 4 and an A / F sensor 29 for detecting the exhaust air-fuel ratio are provided. ing. These various sensors are appropriately used according to the control modes described below. These various sensors may be sensors that detect the physical quantity itself that is a detection target, or may estimate the physical quantity.

  FIG. 2 is a flowchart showing an outline of a control routine of the supercharging system according to the present embodiment. This control routine is repeatedly executed at predetermined intervals according to a program stored in the ROM of the ECU 15 or the like. By causing the ECU 15 to execute this control routine, the ECU 15 functions as air supply control means.

  As shown in FIG. 2, the ECU 15 first determines in step S1 whether or not the electric compressor 6 is in an inactive (OFF) state. When an affirmative determination is made in step S1 that the electric compressor 6 is in an inoperative state, the ECU 15 advances the process to step S2. On the other hand, when a negative determination is made in step S1, the process proceeds to step S6. The processing after step S6 will be described later.

  In step S2, the ECU 15 determines whether or not a supercharging assist start condition is satisfied. The success or failure of the supercharging assist start condition is determined in consideration of the degree of acceleration request. For example, when the accelerator opening exceeds a predetermined threshold with reference to the output value of the accelerator opening sensor 20 (see FIG. 1), the supercharging assistance start condition may be affirmed. The success or failure of the operation start condition may be determined based on the required fuel injection amount estimated in consideration of the accelerator opening and the engine speed. The engine speed can be acquired with reference to the output value of the speed sensor 21 (see FIG. 1). In step S2, if the supercharging assist start condition is not satisfied, the ECU 15 advances the process to step S3, and whether or not a condition for supplying air to the exhaust purification catalyst 4 (air supply condition) is satisfied. Determine whether. On the other hand, when an affirmative determination is made in step S2, the process proceeds to step S11. The processing after step S11 will be described later.

  The determination process shown in step S3 is based on whether or not it is necessary to supply air to the exhaust purification catalyst 4. For example, it can be performed by executing the processing shown in FIG. 3 or FIG. As shown in FIG. 3, first, the ECU 15 obtains the value of the catalyst bed temperature of the exhaust purification catalyst 4 with reference to the output value of the temperature sensor 27 (see FIG. 1) in step S301. Next, in step S302, the exhaust air / fuel ratio is acquired with reference to the output value of the A / F sensor 29 (see FIG. 1). Subsequently, in step S303, the ECU 15 determines whether the catalyst bed temperature acquired in step S301 is equal to or higher than the catalyst activation start temperature. The catalyst activation start temperature is unique to the exhaust purification catalyst 4 and is a temperature at which the exhaust gas purification action starts to be exerted. If the catalyst activation start temperature is not equal to or higher than the catalyst activation start temperature in step S303, it is not effective to supply air to the exhaust purification catalyst 4, and thus the establishment of the air supply condition is denied (step S307).

  On the other hand, when the catalyst bed temperature is equal to or higher than the catalyst activation start temperature, the ECU 15 advances the processing to step S304, and determines whether or not it is immediately after supercharging assist. As is apparent from FIG. 2, in the present embodiment, when the supercharging assist start condition is satisfied, the supercharging assist is prioritized, and in principle, air is supplied to the exhaust purification catalyst 4 during the supercharging assist. Do not execute. However, during the supercharging assist, the exhaust air-fuel ratio becomes rich and hydrocarbons (HC) and the like are likely to accumulate in the exhaust purification catalyst 4. Therefore, in order to oxidize the hydrocarbon (HC) and the like accumulated during the supercharging assist, when it is determined immediately after the supercharging assist in step S304, step S305 is skipped, regardless of the exhaust air-fuel ratio. The establishment of the air supply condition is affirmed (step S306), and air is supplied upstream of the exhaust purification catalyst 4 (steps S4 and S5 in FIG. 2, details will be described later). On the other hand, if it is determined in step S304 that it is not immediately after the supercharging assist, the ECU 15 proceeds to step S305, and determines whether or not the exhaust air-fuel ratio acquired in step S302 is rich. When an affirmative determination is made in step S305 and the exhaust air-fuel ratio is rich, it is necessary to suppress the deterioration of exhaust emission, so that the establishment of the air supply condition is affirmed (step S306). On the other hand, when a negative determination is made in step S305, it is not necessary to supply air upstream of the exhaust purification catalyst 4, so the establishment of the air supply condition is denied.

  Instead of the air supply condition determination process described above, the determination process illustrated in FIG. 4 may be performed. This process determines the success or failure of the air supply condition in consideration of the pressure downstream of the electric compressor 6 and the pressure upstream of the exhaust purification catalyst 4. Note that the same steps as those shown in FIG. 3 are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 4, the ECU 15 refers to the output value of the pressure sensor 25 (see FIG. 1) and acquires the pressure downstream of the electric compressor 6 in step S308. In subsequent step S309, the pressure upstream of the exhaust purification catalyst 4 is acquired with reference to the output value of the pressure sensor 28 (see FIG. 1). In step S308 and step S309, each pressure is acquired by the pressure sensors 25 and 28. However, these pressures may be estimated or calculated from other physical quantities. For example, the downstream pressure of the electric compressor 6 can be obtained based on the rotation speed of the electric compressor 6 and the intake air amount. In this case, the rotation speed of the electric compressor 6 may be acquired from the electric motor 6a, and the intake air amount may be acquired from the air flow meter 26 (see FIG. 1). Further, the pressure upstream of the exhaust purification catalyst 4 can be obtained based on the rotational speed of the engine 1 and the intake air amount. In this case, the rotational speed of the engine 1 may be acquired from the rotational speed sensor 21 (see FIG. 1), and the intake air amount may be acquired from the air flow meter 26 as described above.

  In step S310, the ECU 15 determines whether the pressure downstream of the electric compressor 6 is higher than the pressure upstream of the exhaust purification catalyst 4. When it is affirmed in step S310 that the pressure downstream of the electric compressor 6 is higher than the pressure upstream of the exhaust purification catalyst 4, the establishment of the air supply condition is affirmed. On the other hand, when a negative determination is made in step S310, the establishment of the air supply condition is denied. In the process shown in FIG. 4, since the air supply condition is affirmed when the pressure downstream of the electric compressor 6 is higher than the pressure upstream of the exhaust purification catalyst 4 (step S306), the flow control valve 11 is turned on. When opened, the exhaust gas can be prevented from flowing back into the intake pipe 2.

  Returning to FIG. 2, the description of the control routine of the supercharging system will be continued. As shown in FIG. 2, when it is determined negative in step S3 that the air supply condition is not satisfied, the current routine is temporarily terminated. On the other hand, when an affirmative determination is made in step S3, the ECU 15 advances the process to step S4, applies a voltage to the electric motor 6a to operate the electric compressor 6, closes the bypass valve 8, and air to the bypass passage 7 Is prohibited (electric compressor operation control). In this case, the output of the electric compressor 6 is preferably feedback-controlled by setting a target pressure different from the target pressure when supercharging assist is performed. This is because the purpose of using the electric compressor 6 is different from the case of supercharging assist. For example, the output pressure may be controlled by monitoring the pressure upstream of the exhaust purification catalyst 4 and setting the target pressure so that the pressure downstream of the electric compressor 6 becomes higher than this pressure. By controlling in this way, the operation of the electric compressor 6 becomes efficient and deterioration of fuel consumption can be suppressed.

  In the subsequent step S5, the throttle valve 9 is throttled (throttle valve throttling control) and the flow rate adjusting valve 11 is controlled to open from the fully closed state (regulating valve opening control). The opening of the throttle valve 9 does not become the resistance of the engine 1 and is such that an appropriate amount of air is supplied upstream of the exhaust purification catalyst 4. As a result, the air downstream of the electric compressor 6 is supplied upstream of the exhaust purification catalyst 4, and the oxidation of hydrocarbons (HC), carbon monoxide (CO), etc. in the exhaust gas is promoted to suppress the deterioration of exhaust emission. be able to.

  Next, processing when a negative determination is made in step S1 will be described. When a negative determination is made in step S1, the electric compressor 6 is in an operating state, and therefore in step S6, the ECU 15 determines whether or not this operation is an operation by supercharging assistance (acceleration request). When a negative determination is made in step S6, the air supply to the exhaust purification catalyst 4 is being performed, so the ECU 15 advances the process to step S7, and the condition for stopping the air supply (air supply stop condition) ) Is determined. The air supply stop condition may be determined as appropriate so that air supply is unnecessary. For example, the establishment of the air supply stop condition can be affirmed on condition that the exhaust air-fuel ratio becomes lean. When a negative determination is made in step S7 and the air supply should not be stopped, the current routine is temporarily terminated and the air supply is continued upstream of the exhaust purification catalyst 4. On the other hand, when an affirmative determination is made in step S7, the ECU 15 advances the process to step S8, stops supplying electric power to the electric motor 6a, deactivates the electric compressor 6, opens the bypass valve 8, and bypasses. Control is performed so that air flows into the passage 7 (electric compressor non-operation control). When the electric compressor 6 is deactivated, the intake air can be guided to the bypass passage 7 by bypassing the electric compressor 6, so that the electric compressor 6 can be prevented from becoming an intake resistance.

  When an affirmative determination is made in step S6, it is understood that supercharging assist is being executed. Therefore, in the subsequent step S9, the ECU 15 determines whether or not the non-operation condition of the electric compressor 6 is satisfied, that is, whether or not the supercharging assist should be stopped. For example, a criterion for determining whether there is an excessive assist that causes the turbocharger 5 to over-rotate or that the electric compressor 6 may choke is set. The success or failure of the operating conditions is determined. In this case, from the viewpoint of preventing excessive rotation of the turbocharger 5, the number of revolutions of the turbocharger 5 is monitored by the turbo rotation number sensor 23 (see FIG. 1), and the turbocharger 5 is not activated by exceeding a predetermined threshold value. The establishment of the condition may be affirmed. Further, from the viewpoint of preventing choking of the electric compressor 6, the upstream and downstream pressures of the electric compressor 6 are acquired, and the non-operating condition is established when these pressure differences are below a predetermined threshold. You may affirm. These upstream and downstream pressures can be acquired by pressure sensors 24 and 25 (see FIG. 1), respectively.

  When the non-operation condition is established in step S9 and an affirmative determination is made, the ECU 15 stops supplying electric power to the electric motor 6a and deactivates the electric compressor 6 in the subsequent step S10, similarly to step S8 described above. In addition, the bypass valve 8 is opened and control is performed so that air flows into the bypass passage 7 (electric compressor non-operation control). On the other hand, when a negative determination is made in step S9, the current routine is temporarily terminated and the supercharging assist is continued.

  Next, the process when an affirmative determination is made in step S2 will be described. When an affirmative determination is made in step S2, supercharging assist is requested, so the ECU 15 advances the process to step S11, applies a voltage to the electric motor 6a to operate the electric compressor 6, and closes the bypass valve 8. Thus, the inflow of air into the bypass passage 7 is prohibited (electric compressor operation control). In this case, the output of the electric compressor 6 is controlled by storing a map in advance in the ROM of the ECU 15 with a target supercharging pressure based on the engine speed and the fuel injection amount, from the current engine speed and the fuel injection amount. What is necessary is just to specify the supercharging pressure used as a target and perform feedback control using this as the target pressure. The values of the engine speed and the supercharging pressure can be acquired by the speed sensor 21 and the pressure sensor 22 (see FIG. 1). The fuel injection amount can be estimated from the value of the accelerator opening sensor 20 (see FIG. 1) and the engine speed. Thereby, supercharging assistance is performed.

  Next, in step S <b> 12, the ECU 15 determines whether or not the electric compressor 6 has sufficient capacity to supply air upstream of the exhaust purification catalyst 4. In the present embodiment, even when the supercharging assist is being performed, if there is sufficient capacity to supply air to the electric compressor 6, the air is supplied upstream of the exhaust purification catalyst 4 as an exception. This determination can be made, for example, by monitoring the pressure upstream and downstream of the electric compressor 6 and determining whether or not the pressure difference is equal to or greater than a predetermined value. These pressures can be acquired by the pressure sensors 24 and 25 (see FIG. 1). The predetermined value may be determined as the lower limit value of the allowable range of the pressure difference that allows both the supercharging assist and the air supply to the exhaust purification catalyst 4 without choking by the electric compressor 6.

  In step S12, when an affirmative determination is made that the electric compressor has the remaining capacity, the ECU 15 advances the process to step S13 to determine whether or not the air supply condition is met. This air supply condition may be the same as step S3 (FIGS. 3 and 4) described above, or may be other conditions. On the other hand, when a negative determination is made in step S12 that there is no remaining power, the current routine is temporarily terminated and the supercharging assist is continued. If the establishment of the air supply condition is affirmed in step S13, the ECU 15 advances the process to step S14, controls the flow rate adjustment valve 11 to open from the fully closed state, and temporarily ends the current routine. In this case, the opening degree of the flow rate adjusting valve 11 is not fully opened in consideration of supercharging assist, and the opening degree control is performed so that the pressure downstream of the electric compressor 6 does not become a predetermined pressure or less. Is preferred. By controlling in this way, supercharging assistance and air supply to the exhaust purification catalyst can be performed in a well-balanced manner. On the other hand, if the establishment of the air supply condition is denied in step S13, it is not necessary to supply air to the exhaust purification catalyst 4, so the current routine is temporarily terminated and the supercharging assist is continued.

  As described above, according to the supercharging system according to the present embodiment, the air compressed by the electric compressor 6 is supplied to the upstream side of the exhaust purification catalyst 4, and hydrocarbons (HC) and carbon monoxide in the exhaust gas are supplied. Since oxidation of (CO) or the like can be promoted, deterioration of exhaust emission can be suppressed. In addition, the supply of air is performed by switching to the supercharging assist according to the operating state of the electric compressor 6, so that the electric compressor 6 can be used in a wide range.

(Second Embodiment)
Next, an internal combustion engine supercharging system according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a schematic diagram showing the overall configuration of the present embodiment. As shown in this figure, the main configuration of this embodiment is the same as that of the first embodiment shown in FIG. The difference in configuration from the first embodiment is that (1) an oxidation catalyst 16 is arranged as the exhaust purification catalyst 4 shown in FIG. 1, and the NOx storage reduction catalyst 17 (hereinafter referred to as the NOx catalyst 17) is disposed in the exhaust pipe 3 upstream thereof. , Referred to as NOx catalyst), (2) the point where the exhaust pipe 3 and the air passage 10 are connected between the NOx catalyst 17 and the oxidation catalyst 16, and (3) the catalyst bed temperature of the NOx catalyst 17. The temperature sensor 30 to detect is provided. Since the other configuration is the same as that of the first embodiment, the same reference numerals as those of the first embodiment are given, and redundant description is omitted.

As is well known, the oxidation catalyst 16 has a function of reducing exhaust emission by oxidizing and removing substances such as hydrocarbon (HC) and carbon monoxide (CO) in the exhaust gas. The form of the oxidation catalyst 16 is not particularly limited, but in this embodiment, a platinum-based oxidation catalyst is used. The NOx catalyst 17 absorbs nitrogen oxide (NOx) when the exhaust air-fuel ratio is lean, and releases the absorbed NOx and reduces it to nitrogen (N ₂ ) when the oxygen concentration of the exhaust gas decreases. It is a reduced catalyst. In general, when the operation of an internal combustion engine equipped with such a NOx catalyst is continued, sulfur compounds contained in the fuel become sulfur oxides (SOx) during the combustion process, and sulfate is formed on the NOx catalyst storage material. This causes a decrease in the performance of the NOx catalyst. Such a phenomenon is called sulfur poisoning. When this sulfur poisoning progresses, the NOx purification performance of the NOx catalyst deteriorates, and the exhaust emission deteriorates. For this reason, sulfur poisoning regeneration control for eliminating sulfur poisoning and restoring the performance of the NOx catalyst is performed.

In the sulfur poisoning regeneration control, the temperature of the NOx catalyst is raised, and the exhaust air-fuel ratio is controlled to be rich for a predetermined time, whereby the sulfate of the storage material of the NOx catalyst is decomposed to release the sulfur component. However, when this sulfur poisoning regeneration control is executed, the sulfur component released from the NOx catalyst is changed to hydrogen sulfide (H ₂ S) due to the rich control of the air-fuel ratio, and malodor and white smoke are released to the atmosphere. There is a risk. Therefore, in this embodiment, air downstream of the electric compressor 6 is supplied between the NOx catalyst 17 and the oxidation catalyst 16 in synchronization with the rich control of the exhaust air / fuel ratio, and the exhaust air / fuel ratio downstream of the NOx catalyst 17 is made lean. By converting to H ₂ S to SOx, the emission of malodor and white smoke is suppressed. Hereinafter, the control according to the present embodiment will be described in detail.

  FIG. 6 is a flowchart showing an outline of a control routine of sulfur poisoning regeneration control. Since the engine 1 according to this embodiment performs sulfur poisoning regeneration control, this control routine is repeatedly executed at predetermined intervals. This routine is performed by the ECU 15. When the ECU 15 executes this routine, the ECU 15 functions as sulfur poisoning regeneration control means. That is, as shown in FIG. 6, the ECU 15 first determines whether or not it is a sulfur poisoning regeneration time in step S21. The sulfur poisoning regeneration time can be specified by estimating the sulfur poisoning status of the NOx catalyst 17 from the operation time of the engine 1 or the integrated value of the fuel injection amount. If an affirmative determination is made in this step S21 that it is the sulfur poisoning regeneration time, the ECU 15 advances the process to step S22, and sets the regeneration execution flag F1. The regeneration execution flag F1 means an area allocated in advance in the RAM of the ECU 15, and the value of this area is set to 1. By referring to this regeneration execution flag F1, the ECU 15 can specify whether or not sulfur poisoning regeneration is being performed. In the following description, setting the value of the area previously allocated to the RAM to 1 in this way is referred to as setting a flag, and setting it to 0 is to clear the flag. On the other hand, when a negative determination is made in step S21, this routine is temporarily terminated because there is no need to perform sulfur poisoning regeneration.

  In continuing step S23, ECU15 determines whether the supercharging assistance by the electric compressor 6 is performing. In this embodiment, in principle, the start of air supply during sulfur poisoning regeneration is prioritized over the start of supercharging assist. However, when supercharging assist has already been started, the sulfur coverage is increased until the supercharging assist is completed. Control not to perform poison regeneration control and air supply. Accordingly, when it is determined affirmative in step S23 that supercharging assist is being performed, the current routine is temporarily terminated. On the other hand, if it is determined in step S23 that the supercharging assist is not being performed, the ECU 15 advances the process to step S24, and raises the catalyst bed temperature of the NOx catalyst 17 to a predetermined temperature or higher. The catalyst bed temperature is monitored with reference to the output value of the temperature sensor 30 (see FIG. 5) provided in the NOx catalyst 17. In order to raise the temperature of the NOx catalyst 17, the operating state of the engine 1 may be changed to raise the temperature of the exhaust gas. The predetermined temperature is set as a lower limit value of a temperature range suitable for decomposing the sulfate of the storage material of the NOx catalyst 17.

  In step S25, the ECU 15 sets the rich control flag F2 (F2 = 1). In the next step S26, the ECU 15 temporarily controls the exhaust air / fuel ratio to be rich (rich control). As will be described later, the rich control flag F2 is used to synchronize the rich control of the exhaust air-fuel ratio and the air supply. The rich control of the exhaust air / fuel ratio can be performed by retarding the fuel injection timing. One execution time of the rich control may be determined as appropriate, but is set to about 10 seconds in the present embodiment. When the rich control is completed, the ECU 15 clears the rich control flag F2 in the following step S27 (F2 = 0). In the subsequent step S28, the ECU 15 returns the operating state of the engine 1 to the normal control and pauses the rich control for a predetermined time. The predetermined time may be determined as appropriate, but is set to about 30 seconds in the present embodiment.

  Next, in step S29, the ECU 15 determines the end of the sulfur poisoning regeneration control. The end determination is made based on the fact that the number of executions of rich control reaches a predetermined number of times. When a negative determination is made in step S29, the ECU 15 returns the process to step S24, and repeatedly executes the processes from step S24 to step S28 until an affirmative determination is made in step S29. If an affirmative determination is made in step S29, the ECU 15 clears the regeneration execution flag F1 in the next step S30 (F1 = 0), and ends the current routine.

  Although the sulfur poisoning regeneration control according to the present embodiment is as described above, in the present embodiment, the rich control and the air supply are synchronized by executing the processing described below. 7 and 8 are flowcharts showing an outline of a control routine of the supercharging system according to the present embodiment. This control routine is repeatedly executed at predetermined intervals according to a program stored in the ROM of the ECU 15 or the like. When the ECU 15 executes this control routine, the ECU 15 functions as an electric compressor control unit and an air supply control unit.

  As shown in FIGS. 7 and 8, the ECU 15 first determines in step S31 whether or not the electric compressor 6 is in a non-operating (OFF) state. When an affirmative determination is made in step S31 that the electric compressor 6 is in an inoperative state, the ECU 15 advances the process to step S32 to determine whether or not the regeneration execution flag F1 is set. On the other hand, when a negative determination is made in step S31, the process proceeds to step S39. The processing after step S39 will be described later.

  When an affirmative determination is made in step S32, the ECU 15 advances the process to step S33, and determines whether or not the rich control flag F2 is set (F2 = 1). When the rich control flag F2 is not set in step S33, the ECU 15 returns the process to step S32. By executing Step S32 and Step S33, it is possible to specify the start point of the rich control. On the other hand, if a negative determination is made in step S32, the process proceeds to step S44. The processing after step S44 will be described later.

  When an affirmative determination is made in step S33, both the regeneration execution flag F1 and the rich control flag F2 are set. Therefore, the ECU 15 executes the processes shown in steps S34 to S38 below in order to supply the air downstream of the electric compressor 6 to the exhaust pipe 3 between the NOx catalyst 17 and the oxidation catalyst 16 in synchronization with the rich control. To do.

  First, in step S34, the ECU 15 performs electric compressor operation control. This is the same control as step S4 (FIG. 2) according to the first embodiment described above. That is, a voltage is applied to the electric motor 6a (see FIG. 1) to operate the electric compressor 6, and the bypass valve 8 (see FIG. 1) is closed to prohibit the inflow of air into the bypass passage 7. Next, the ECU 15 determines whether or not the supercharging assist start condition is satisfied in step S35. This determination process is provided for a process (steps S37 and S38) for simultaneously performing supercharging assist and air supply, which will be described later. When the supercharging assist start condition is denied in step S35 (NO), the ECU 15 advances the process to step S36, executes throttle valve throttle control and adjustment valve opening control, and temporarily terminates the current routine. . These controls are the same as the controls according to the first embodiment (step S5 in FIG. 2).

  On the other hand, when the establishment of the supercharging assist start condition is affirmed in step S35, the ECU 15 advances the processing to step S37, and determines whether or not the electric compressor 6 has the capacity to perform supercharging assist. This determination process may be performed based on the same criteria as in the first embodiment described above. That is, this determination can be made, for example, by monitoring the upstream and downstream pressures of the electric compressor 6 and determining whether the pressure difference is equal to or greater than a predetermined value. These pressures can be acquired by the pressure sensors 24 and 25 (see FIG. 1). Further, this predetermined value is the lower limit of the allowable range of the pressure difference at which the electric compressor 6 can perform both supercharging assist and air supply to the exhaust pipe 3 between the NOx catalyst 17 and the oxidation catalyst 16 without choking. It can be determined as a value. When an affirmative determination is made in step S37 that there is a surplus capacity, the ECU 15 advances the process to step S38, and executes adjustment valve opening control. In this case, control to throttle the throttle valve 9 (throttle valve throttling control) is not performed, and the control of the throttle valve 9 is a normal control. On the other hand, when a negative determination is made in step S37 that there is no remaining power, the ECU 15 advances the process to step S36, and executes the throttle valve throttle control and the adjustment valve opening control.

  By executing the above steps S34 to S38, the air downstream of the electric compressor 6 can be supplied to the exhaust pipe 3 between the NOx catalyst 17 and the oxidation catalyst 16 in synchronization with the rich control. However, in order to more accurately execute the synchronization between the rich control and the air supply, the electric compressor operation control is performed in anticipation of a delay in the air supply from the electric compressor 6 to the exhaust pipe 3 between the NOx catalyst 17 and the oxidation catalyst 16. It is desirable to perform the adjustment valve opening control. For example, the delay in the air supply is the time that the air reaches the exhaust pipe 3 from the start of the operation of the electric compressor 6 and the opening of the flow rate adjustment valve 11 and the time from the start of the rich control until the exhaust air-fuel ratio becomes rich. These times can be estimated by calculation or experimentally, and can be estimated from these differences. Then, in anticipation of the delay of the air supply, the start timing of the electric compressor operation control and the adjustment valve opening control is shifted and these controls are performed, so that the synchronization between the air supply and the rich control can be made more accurate. can do.

  Next, processing when a negative determination is made in step S31 will be described. If a negative determination is made in step 31, the ECU 15 executes the processes of steps S39 to S43. In principle, these processes correspond to Steps S6 to S10 (FIG. 2) according to the first embodiment, and redundant description is omitted. However, regarding the determination of the success or failure of the air supply stop condition in step S40, instead of or in addition to the determination criterion of step S7 (FIG. 2) according to the first embodiment, the execution time of air supply is after a predetermined time has elapsed. On the condition that there is, it may be affirmed that the air supply stop condition is satisfied. Thereby, excessive air supply can be suppressed. This predetermined time may be determined as a threshold of an execution time during which the air supply to the exhaust pipe 3 between the NOx catalyst 17 and the oxidation catalyst 16 becomes excessive.

  Next, processing when a negative determination is made in step S32 will be described. If a negative determination is made in step S32, since the sulfur poisoning regeneration control is not being executed, the ECU 15 advances the process to step S44 and determines whether or not the supercharging assist start condition is satisfied. Thereby, in this embodiment, the start of sulfur poisoning regeneration control has priority over the start of supercharging assist. When it is affirmed in step S44 that the supercharging assist condition is satisfied, the ECU 15 proceeds to step S45 to execute the electric compressor operation control. This is the same control as step S11 (FIG. 2) according to the first embodiment.

As described above, according to the supercharging system according to the second embodiment, the air downstream of the electric compressor 6 is supplied to the exhaust pipe 3 between the NOx catalyst 17 and the oxidation catalyst 16 in synchronization with the rich control of the exhaust air-fuel ratio. Since the exhaust air-fuel ratio downstream of the NOx catalyst 17 that is supplied can be made lean, H ₂ S generated by sulfur poisoning regeneration can be converted to SOx to suppress the emission of malodor and white smoke.

(Third embodiment)
Next, an internal combustion engine supercharging system according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a schematic diagram showing the overall configuration of the present embodiment. As shown in this figure, the main configuration of this embodiment is the same as that of the first embodiment shown in FIG. The difference from the first embodiment is that (1) an oxidation catalyst 16 is arranged as the exhaust purification catalyst 4 shown in FIG. 1, and particulate matter (patties) in the exhaust gas is placed in the exhaust pipe 3 upstream thereof. (2) The point where the connection part of the exhaust pipe 3 and the air passage 10 is arranged in the exhaust pipe 3 upstream of the filter 18, (3) The temperature of the filter 18 is detected. The temperature sensor 31 is provided. Since the other configuration is the same as that of the first embodiment, the same reference numerals as those of the first embodiment are given, and redundant description is omitted. Also, the same components as those in the second embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The filter 18 is mounted on the internal combustion engine in order to reduce particulate matter contained in the exhaust gas, and has a function of collecting particulate matter in the exhaust gas. The form of the filter 18 is not particularly limited. For example, the filter is a honeycomb-like filter in which a large number of cells are formed, and allows passage of exhaust gas as a material of partition walls that partition these cells. A material employing a material that prohibits the passage of the material can be used. Further, as the filter 18, a filter capable of collecting the particulate matter and NOx by adding a NOx adsorbent to the filter capable of collecting the particulate matter may be employed.

  In general, when the operation of an internal combustion engine equipped with such a filter is continued, the particulate matter collected by the filter gradually accumulates, eventually exceeding the collection capability and the function of the filter is lowered. For this reason, particulate regeneration deposited on the filter is oxidized by raising the temperature of the filter, and filter regeneration control is performed to restore the function of the filter. However, since this filter regeneration control is to increase the temperature of the filter by controlling the temperature of the exhaust gas to a high temperature, the temperature may increase more than necessary. Therefore, in this embodiment, in order to suppress an excessive temperature rise of the filter temperature, the air downstream of the electric compressor 6 is supplied to the upstream of the filter 18 during the regeneration of the filter, so that the excessive temperature rise of the filter 18 is increased. Suppressed. Hereinafter, the control according to the present embodiment will be described in detail.

  FIG. 10 is a flowchart showing an outline of a control routine for filter regeneration control. Since the engine 1 according to this embodiment performs filter regeneration control, this control routine is repeatedly executed at predetermined intervals. This routine is performed by the ECU 15. When the ECU 15 executes this routine, the ECU 15 functions as filter regeneration control means. That is, as shown in FIG. 10, first, the ECU 15 determines whether or not it is the filter regeneration time in step S51. For this determination, various known determination methods may be used. For example, the accumulation amount of the particulate matter is estimated from the integrated value of the fuel injection amount, and the determination is made based on whether or not the estimated accumulation amount has reached a predetermined level. If an affirmative determination is made in step S51 that it is the filter regeneration time, the ECU 15 advances the process to step S52. On the other hand, if it is determined in step S51 that the filter regeneration time is not reached, the current routine is temporarily terminated.

  In step S52, the ECU 15 sets a filter regeneration execution flag F3 (F3 = 1). By referring to the filter regeneration execution flag F3, the ECU 15 can specify whether or not the filter regeneration control is being performed. Next, in step S53, the ECU 15 changes the operating state of the engine 1 from the normal control state to increase the temperature of the exhaust gas. Various methods may be employed for raising the temperature of the exhaust gas. For example, the fuel injection amount is controlled so that fuel is injected (post injection) from an injector (not shown) at the end of the expansion stroke of the engine 1. Thereby, the temperature of exhaust gas rises and the filter 18 can be heated up. In continuing step S54, ECU15 determines whether the temperature of the filter 18 is more than predetermined temperature. The predetermined temperature in this case may be appropriately set as the lower limit value of the temperature range in which the particulate matter collected by the filter 18 can be oxidized. The temperature of the filter 18 can be acquired by referring to the output value of the temperature sensor 31 described above. Alternatively, the temperature may be estimated from a physical quantity that correlates with the temperature of the filter 18. If the filter 18 is above the predetermined temperature in step S54, the process proceeds to the next step S55. On the other hand, when the temperature is lower than the predetermined temperature, the process returns to step S53. Thereby, the temperature rise control of the exhaust gas is continued until the filter 18 reaches a predetermined temperature or higher.

  In step S55, the ECU 15 switches the control of the engine 1 to normal control. In subsequent step S56, the ECU determines completion of regeneration of the filter 18. This determination may be appropriately determined by managing the duration and number of times of the exhaust gas temperature raising control. If it is determined in step S56 that the regeneration of the filter 18 has not been completed, the process returns to step S53, and the processes from steps S53 to S55 are repeated until the regeneration of the filter 18 is completed. On the other hand, when it is determined affirmative in step S56 that the regeneration of the filter 18 has been completed, the ECU 15 advances the process to step S57, clears the regeneration execution flag F3 (F3 = 0), and ends the current routine.

  The filter regeneration control according to the present embodiment is as described above, but in the present embodiment, by performing the processing described below, air is supplied to the upstream side of the filter 18 during the filter regeneration control. 18 excessive temperature rise is prevented. 11 and 12 are flowcharts showing an outline of a control routine of the supercharging system according to this embodiment. This control routine is repeatedly executed at predetermined intervals according to a program stored in the ROM or the like of the ECU 15 as in the case of the first and second embodiments. When the ECU 15 executes this control routine, the ECU 15 functions as an air supply control unit and an electric compressor control unit.

  As shown in FIGS. 11 and 12, the ECU 15 first determines in step S61 whether or not the electric compressor 6 is in a non-operating (OFF) state. This process is the same process as step S1 according to the first embodiment described above. When an affirmative determination is made in step S61 that the engine is in an inoperative state, the ECU 15 advances the process to step S62. On the other hand, when a negative determination is made in step S61, the process proceeds to step S69. The processing after step S69 will be described later.

  In step S62, the ECU 15 determines whether or not the filter regeneration execution flag F3 is set (F3 = 1). If the determination in step S62 is affirmative, the filter regeneration control is being performed, and the process proceeds to the next step S63. On the other hand, if a negative determination is made in step S62, the process proceeds to step S76. The processing after step S76 will be described later.

  In step S63, the ECU 15 determines whether or not the filter 18 is at a predetermined temperature or higher. The predetermined temperature in this case means the upper limit value of the allowable range of the temperature of the filter 18 determined from the viewpoint of safety. For example, a value determined by adding a safety factor to the heat-resistant temperature of the filter 18 is set as the predetermined temperature. can do. If the temperature of the filter 18 is equal to or higher than the predetermined temperature in step S63, the ECU 15 executes the following steps S64 to S68 in order to suppress an excessive temperature rise of the filter 18. Since these processes (steps S64 to S68) correspond to steps S34 to S38 according to the above-described second embodiment, redundant descriptions are omitted.

  Next, processing when a negative determination is made in step S61 will be described. If a negative determination is made in step S61 that the electric compressor 6 is operating, the ECU 15 advances the process to step S69, and determines whether or not the operation of the electric compressor is due to supercharging assistance. If a negative determination is made in step 69, the ECU 15 advances the process to step S70, and determines whether or not an air supply stop condition is satisfied. This determination is performed in place of, or in addition to, the determination criterion in step S7 (FIG. 2) according to the first embodiment, that the temperature of the filter 18 is lower than a predetermined temperature (step S63), or the filter The establishment of the air supply stop condition may be affirmed when the regeneration execution flag F3 is cleared. When an affirmative determination is made in step S70 that the air supply stop condition is satisfied, electric compressor non-operation control is executed in the subsequent step S71. Since this control is the same as that in step S8 (FIG. 2) according to the first embodiment, the details are omitted. On the other hand, when a negative determination is made in step S <b> 70, the current routine is terminated and the air supply to the filter 18 is continued.

  If it is determined in step S69 that the operation of the electric compressor 6 is due to supercharging assistance, the ECU 15 advances the process to step S72, and the filter regeneration execution flag F3 is set (F3 = 1). It is determined whether or not. In this embodiment, in principle, the start of air supply at the time of filter regeneration is given priority over the start of supercharging assist, but the supercharging assist is interrupted particularly when the filter regeneration time comes after supercharging assist has started. Then, control is performed so that air is supplied during filter regeneration. Accordingly, when an affirmative determination is made in step S72, the ECU 15 advances the process to step S73 because the filter regeneration time has come after the supercharging assist has been started. On the other hand, when a negative determination is made in step S72, subsequent steps S74 and S75 are executed. Since these processes (step S74 and step S75) correspond to step S9 and step S10 (FIG. 2) according to the first embodiment described above, details are omitted.

  In step S73, the ECU 15 determines whether or not the filter 18 is at a predetermined temperature or higher. This step S73 is the same processing as step 63 above. When an affirmative determination is made in step S73 that the temperature is equal to or higher than the predetermined temperature, the ECU 15 advances the process to step S66, executes throttle valve throttle control and adjustment valve opening control, and interrupts the supercharging assist being executed. Then, air is supplied to the upstream side of the filter 18 and the current routine is temporarily terminated. On the other hand, when a negative determination is made in step S73, the processes in steps S74 and S75 are executed, and the current routine is temporarily ended.

  Next, processing when a negative determination is made in step S62 will be described. If a negative determination is made in step S62, the filter regeneration control is not in a situation to be started, so whether or not the supercharging assist start condition is met is determined (step S76), and the operation control of the electric compressor is performed according to the determination result. Execute (Step S77). Since these processes (step S76 and step S77) correspond to steps S44 and 45 (FIG. 8) according to the second embodiment described above, details thereof will be omitted. Thus, in this embodiment, in principle, the start of air supply during filter regeneration is prioritized over the start of supercharging assist.

  As described above, according to the supercharging system according to the third embodiment, the air downstream of the electric compressor 6 can be supplied to the upstream of the filter during the filter regeneration control. Can be suppressed.

  As mentioned above, although the supercharging system for internal combustion engines of this invention was demonstrated based on 1st-3rd embodiment, this invention is not limited to these. For example, in the first to third embodiments, the diesel engine 1 is used as an application target of the supercharging system of the present invention, but the type of the internal combustion engine is not limited. Therefore, the present invention may be applied to a spark ignition type gasoline engine or may be applied to other gasoline engines.

Schematic which shows the whole structure of 1st Embodiment which concerns on the supercharging system of this invention. The flowchart which showed the control routine of the supercharging system which concerns on 1st Embodiment. The flowchart which showed the determination routine of the air supply condition which concerns on 1st Embodiment. The flowchart which showed the other example of the routine shown in FIG. Schematic which shows the whole structure of 2nd Embodiment which concerns on the supercharging system of this invention. The flowchart which showed the control routine of the sulfur poisoning reproduction | regeneration control which concerns on 2nd Embodiment. The flowchart which showed the control routine of the supercharging system which concerns on 2nd Embodiment. 8 is a flowchart showing a control routine continued from FIG. Schematic which shows the whole structure of 3rd Embodiment which concerns on the supercharging system of this invention. The flowchart which showed the routine of the filter reproduction | regeneration process which concerns on 3rd Embodiment. The flowchart which showed the control routine of the supercharging system which concerns on 3rd Embodiment. 12 is a flowchart showing a control routine continued from FIG.

Explanation of symbols

1 Diesel engine (internal combustion engine)
2 Intake pipe (intake passage)
3 Exhaust pipe (exhaust passage)
4 Exhaust purification catalyst 5 Turbocharger 5a Compressor 5b Turbine 6 Electric compressor 7 Bypass passage 8 Bypass valve (switching valve)
9 throttle valve 10 air passage 11 flow rate adjusting valve 15 ECU (air supply control means, electric compressor control means)
16 Oxidation catalyst 17 NOx catalyst 18 Filter

Claims (20)

A supercharging system for an internal combustion engine that is applied to an internal combustion engine that includes an intake passage and an exhaust passage and is provided with an exhaust purification catalyst in the exhaust passage,
A turbocharger comprising a compressor and a turbine for supercharging the internal combustion engine; an electric compressor provided in the intake passage upstream of the compressor of the turbocharger and assisting the supercharging; An air passage that connects the intake passage downstream of the electric compressor and the exhaust passage upstream of the exhaust purification catalyst, a flow rate adjustment valve that is provided in the air passage and adjusts the amount of air flowing into the air passage; And air supply control means for controlling the flow rate adjusting valve so as to supply air downstream of the electric compressor to the upstream of the exhaust purification catalyst in accordance with the operating state of the electric compressor. Supercharging system for internal combustion engines. A bypass passage that bypasses the electric compressor, a switching valve that is provided in the bypass passage and switches between inflow and prohibition of air into the bypass passage, and between the electric compressor and the compressor of the turbocharger A throttle valve provided in the intake passage for adjusting the amount of air flowing into the turbocharger;
The air supply control means controls to close the switching valve and reduce the opening of the throttle valve when supplying air downstream of the electric compressor to the upstream of the exhaust purification catalyst. The supercharging system for an internal combustion engine according to claim 1.   When the temperature of the exhaust purification catalyst is equal to or higher than its activation start temperature, the exhaust air-fuel ratio is rich, and there is no request for assisting the supercharging by the electric compressor, the air supply control means The supercharging system for an internal combustion engine according to claim 1 or 2, wherein the flow rate adjusting valve is controlled so as to supply air downstream of the compressor to upstream of the exhaust purification catalyst.   The air supply control means is configured to supply the air downstream of the electric compressor to the upstream of the exhaust purification catalyst when the pressure downstream of the electric compressor is higher than the pressure upstream of the exhaust purification catalyst. The supercharging system for an internal combustion engine according to any one of claims 1 to 3, wherein the regulating valve is controlled.   5. The target pressure is different between when the air downstream of the electric compressor is supplied upstream of the exhaust purification catalyst and when supercharging assist is performed. 6. The supercharging system for internal combustion engines as described.   The supercharging system for an internal combustion engine according to claim 5, wherein a target pressure is set so that a pressure downstream of the electric compressor is higher than a pressure upstream of the exhaust purification catalyst.   If the temperature of the exhaust gas purification catalyst is equal to or higher than the activation start temperature immediately after the supercharging assist is finished, the air supply control means may remove the air downstream of the electric compressor even if the exhaust air-fuel ratio is not rich. The supercharging system for an internal combustion engine according to claim 3, wherein the flow rate adjustment valve is controlled so as to be supplied upstream of the exhaust purification catalyst.   The air supply control means is a case where there is a request for assisting the supercharging by the electric compressor, and the electric compressor has a surplus capacity for supplying air downstream of the electric compressor to the upstream of the exhaust purification catalyst. The supercharging system for an internal combustion engine according to claim 1 or 2, wherein the flow rate adjusting valve is controlled so that air downstream of the electric compressor is supplied upstream of the exhaust purification catalyst.   The supercharging system for an internal combustion engine according to claim 8, wherein the air supply control means controls the opening degree of the flow rate adjusting valve so that the pressure downstream of the electric compressor does not become a predetermined value or less. A supercharging system for an internal combustion engine that is applied to an internal combustion engine that includes an intake passage and an exhaust passage and has an NOx storage reduction catalyst in the exhaust passage and an oxidation catalyst downstream of the NOx catalyst,
A turbocharger comprising a compressor and a turbine for supercharging the internal combustion engine; an electric compressor provided in the intake passage upstream of the compressor of the turbocharger and assisting the supercharging; An air passage that connects the intake passage downstream of the electric compressor and the exhaust passage between the NOx catalyst and the oxidation catalyst, and a flow rate that is provided in the air passage and adjusts the amount of air flowing into the air passage. When the NOx catalyst is in the sulfur poisoning regeneration period and the NOx catalyst is heated to a predetermined temperature or higher, the internal combustion engine is controlled to be rich so that the exhaust air-fuel ratio becomes rich. Sulfur poisoning regeneration control means for performing poisoning regeneration;
Electric compressor control means for operating the electric compressor so as to synchronize with the rich control of the exhaust air-fuel ratio by the sulfur poisoning regeneration control means, and the air downstream of the electric compressor according to the operating state of the electric compressor, An air supply control means for controlling the flow rate adjusting valve so as to supply the exhaust passage between the NOx catalyst and the oxidation catalyst, and a supercharging system for an internal combustion engine. A bypass passage that bypasses the electric compressor, a switching valve that is provided in the bypass passage and switches between inflow and prohibition of air into the bypass passage, and between the electric compressor and the compressor of the turbocharger A throttle valve provided in the intake passage for adjusting the amount of air flowing into the turbocharger;
The air supply control means controls to close the switching valve when supplying air downstream of the electric compressor to the exhaust passage between the NOx catalyst and the oxidation catalyst, and controls the throttle valve The supercharging system for an internal combustion engine according to claim 10, wherein the opening degree is controlled to be reduced.   12. The electric compressor and the flow rate adjusting valve are controlled in consideration of a delay in air supply from the electric compressor to the exhaust passage between the NOx catalyst and the oxidation catalyst. Supercharging system for internal combustion engines.   12. The internal combustion engine according to claim 10, wherein the supply of air to the exhaust passage between the NOx catalyst and the oxidation catalyst starts in preference to the supercharging assist by the electric compressor. Supercharging system for engines.   The sulfur poisoning regeneration control means, when the sulfur poisoning regeneration time comes during the supercharging assist by the electric compressor, does not start the sulfur poisoning regeneration until the assist is completed, The supercharging system for an internal combustion engine according to claim 13, wherein the sulfur poisoning regeneration is started after the assist is completed.   The air supply control means, when there is a request for assisting the supercharging by the electric compressor even during the sulfur poisoning regeneration, and when there is remaining capacity to perform the assist, the air downstream of the electric compressor, The internal combustion engine engine according to claim 13, wherein the flow control valve is controlled so as to be supplied upstream of the oxidation catalyst, and the throttle valve is controlled to be opened so as to perform the assist. Supply system. A supercharging system for an internal combustion engine that is applied to an internal combustion engine that includes an intake passage and an exhaust passage and is provided with a filter that collects particulate matter in exhaust gas in the exhaust passage,
A turbocharger comprising a compressor and a turbine for supercharging the internal combustion engine; an electric compressor provided in the intake passage upstream of the compressor of the turbocharger and assisting the supercharging; An air passage connecting the intake passage downstream of the electric compressor and the exhaust passage upstream of the filter, a flow rate adjusting valve provided in the air passage for adjusting the amount of air flowing into the air passage; Filter regeneration control means for regenerating the filter by controlling the internal combustion engine so as to oxidize particulate matter collected by the filter when it is time to regenerate the filter; and An electric compressor control means for operating the electric compressor when the temperature rises above a predetermined temperature; and Internal combustion engine supercharging system characterized by comprising an air supply control means for controlling said flow control valve to supply the downstream of the air of the electric compressor upstream of said filter in accordance with the dynamic state, the. A bypass passage that bypasses the electric compressor, a switching valve that is provided in the bypass passage and switches between inflow and prohibition of air into the bypass passage, and between the electric compressor and the compressor of the turbocharger A throttle valve provided in the intake passage for adjusting the amount of air flowing into the turbocharger;
The air supply control means performs control so as to close the switching valve and throttle the opening of the throttle valve when supplying air downstream of the electric compressor to the upstream of the filter. The supercharging system for an internal combustion engine according to claim 16, wherein the supercharging system is an internal combustion engine.   18. The supercharging system for an internal combustion engine according to claim 16, wherein the air supply to the upstream side of the filter is started prior to the supercharging assist by the electric compressor.   The air supply control means interrupts the assist when the filter regeneration start time comes during the supercharging assist by the electric compressor, and supplies the air downstream of the electric compressor to the upstream of the filter. The supercharging system for an internal combustion engine according to claim 18, wherein the flow rate adjusting valve is controlled to do so. When there is a request for assisting the supercharging by the electric compressor even when the filter is being regenerated and there is a surplus capacity to perform the assist, the air supply control means converts the air downstream of the electric compressor into the air The supercharging system for an internal combustion engine according to claim 18, wherein the flow control valve is controlled to be supplied upstream of the filter, and the throttle valve is controlled to be opened so as to perform the assist. .

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