JP2003166416A - Internal combustion engine with turbocharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent any oil leakage from a center housing by maintaining the number of rotation of a turbocharger in a predetermined range when activating a catalyst by bypassing a turbine of a turbocharger. <P>SOLUTION: When the catalyst temperature Tcat is lower than the predetermined temperature T0, and the catalyst must be heated (S7), the exhaust emission is allowed to flow via a bypass passage to bypass the turbine of the turbocharger, and the exhaust emission of large calorie is fed to the catalyst. When the number of rotation Nt of the turbocharger is smaller than the predetermined lower limit number of rotation Nmin (S8), the bypassing is prohibited (S10), and the quantity of exhaust emission flowing into the turbine is increased to maintain the rotation of the turbocharger. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine with a supercharger, and more specifically, in an internal combustion engine having a turbocharger and an exhaust gas purification device downstream of the turbine, the exhaust gas bypasses the turbine. The present invention relates to an improvement in a technique for activating an exhaust gas purification catalyst provided in an exhaust gas purification device by causing it to flow.

[0002]

2. Description of the Related Art In recent years, in order to purify exhaust gas from a diesel engine, it has been possible to reduce HC (hydrocarbon), CO (carbon monoxide) and NOx (nitrogen oxide) in the exhaust gas by using a catalyst. Being put to practical use. Here, in a diesel engine, a turbocharger is generally provided to improve output, but since the exhaust temperature is essentially low, the operating conditions under which the catalyst reaches a temperature at which it becomes active are However, there is a problem that the exhaust gas purification effect by the catalyst is low.

To address this problem, a passage bypassing the turbine of the supercharger is provided, and when the catalyst is not activated, exhaust gas is flown through this passage to bypass the turbine and retain the amount of heat. It is known to supply the exhaust gas to the catalyst (see Japanese Patent Laid-Open No. 05-044448).

[0004]

However, if the exhaust gas is simply bypassed when the catalyst is inactive, the oil seal from the center housing of the turbocharger does not function sufficiently, and the lubricating oil is fed to the turbine side. May leak out. In other words, during the bypass, the power to rotate the turbine decreases and the turbocharger speed decreases, but if the catalyst is bypassed only when the catalyst is in a low temperature state, the speed is excessive. This is because the force of pressing the seal member of the turbine shaft against the center housing is weakened and the lubricating oil supplied to the bearing leaks to the turbine side. Such leakage of lubricating oil not only increases the amount of lubricating oil consumed, but also increases HC in exhaust gas, which adversely affects exhaust characteristics.

Therefore, the present invention aims to solve the conventional problem such as leakage of lubricating oil by maintaining the supercharger rotation speed within a predetermined range when activating the catalyst by bypassing the turbine. And

[0006]

Therefore, in the invention according to claim 1, an internal combustion engine with a supercharger, comprising a turbine of the supercharger in the exhaust passage and an exhaust gas purification device installed downstream of the turbine. In the engine, the upstream side of the turbine and the downstream side of the exhaust gas purification apparatus on the upstream side are connected by a bypass passage, and a bypass valve is installed in the bypass passage.
Then, a bypass valve control device that controls the bypass valve to control the bypass amount that is the flow rate of exhaust gas flowing through the bypass passage is provided. Increase the amount of catalyst to raise the temperature of the exhaust purification catalyst provided in the exhaust purification device, and reduce the bypass amount from that of the catalyst heating mode to keep the supercharger rotation speed above the specified rotation speed. A mode switching means for selectively switching between the rotation maintaining mode for raising and the rotation maintaining mode is provided. Further, the mode switching means selects the supercharging mode when the temperature of the exhaust purification catalyst is equal to or higher than the predetermined temperature, and when the temperature is lower than the predetermined temperature and the supercharger rotation speed is equal to or higher than the predetermined rotation speed. The catalyst temperature increasing mode is selected, and the rotation maintaining mode is selected when the temperature is lower than the predetermined temperature and the supercharger rotation speed is lower than the predetermined rotation speed.

According to such a structure, when the exhaust purification catalyst is at a high temperature, the supercharging mode minimizes the bypass amount to perform supercharging, but this is at a low temperature and requires compulsory heating. At times, the catalyst temperature raising mode or the rotation maintaining mode is selected. Here, the catalyst temperature increasing mode is selected when the heating is requested and when the supercharger rotation speed is high to some extent. The rotation speed as the threshold value is preferably set in relation to an oil seal provided on the turbine shaft, and more preferably increased or decreased according to the lubricating oil pressure as described later. In the catalyst temperature raising mode, the emphasis is placed on the temperature raising of the exhaust purification catalyst, but since the supercharger rotates at high speed, the oil seal can function properly.

On the other hand, the rotation maintaining mode is selected when the heating is requested, but the rotation speed of the supercharger is low (or the predetermined rotation range has never been reached since the engine was started). It's time. At this time, if the bypass amount is too large, the rotational speed of the supercharger may be insufficient and the oil seal may not function properly. Therefore, in the rotation maintaining mode, it is preferable to raise the temperature of the exhaust purification catalyst by bypass, but the rotation maintaining of the supercharger will also be considered. As a result, this temperature rise is performed to the extent that the oil seal can properly function, and oil leakage to the turbine side can be prevented and the exhaust purification catalyst can be activated early.

According to the second aspect of the present invention, in particular, in the bypass valve control device, (A) a supercharging mode in which supercharging is performed by minimizing the bypass amount, and an increase in the bypass amount to raise the exhaust purification catalyst. A mode switching means for selectively switching the catalyst temperature raising mode for performing the temperature and (B) a valve opening degree setting means for setting the opening degree of the bypass valve according to the selected mode are provided. Then, the mode switching means selects the supercharging mode when the temperature of the exhaust purification catalyst is equal to or higher than the predetermined temperature, and selects the catalyst temperature raising mode when the temperature is lower than the predetermined temperature. The opening degree setting means sets the opening degree of the bypass valve based on the supercharger rotation speed when in the catalyst temperature increasing mode, and when this rotation speed is lower than the predetermined rotation speed, it is By comparison, it was decided to reduce this opening.

In such a construction, unlike the one described in claim 1, the modes are roughly classified into a supercharging mode selected when there is no heating request and a catalyst heating mode selected when a heating request is made. Divided into However, in the catalyst temperature increasing mode, the opening degree of the bypass valve is set based on the supercharger rotation speed, and when the rotation speed is lower than the predetermined rotation speed, the bypass amount is reduced, so that the same as in claim 1. It is possible to obtain an effect.

According to the third aspect of the present invention, when the valve opening degree setting means sets the opening degree of the bypass valve in the catalyst temperature increasing mode, the opening degree is decreased as the supercharger rotation speed is lower. I did it. In the invention according to claim 4, when the valve opening degree setting means sets the opening degree of the bypass valve in the catalyst temperature increasing mode, if the supercharger rotation speed is lower than the predetermined rotation speed, this opening degree is set. Was decided to be the minimum.

According to the invention described in claim 5, immediately after the engine is started, the predetermined rotational speed is switched to the second value which is higher than the first value in the normal time. According to such a configuration, when the temperature of the exhaust purification catalyst is low at the time of engine startup, after the engine is started, the rotation maintaining mode (Claim 1) or the catalyst temperature increasing mode is first set according to the temperature of the exhaust purification catalyst and the supercharger speed. (Claim 2) is selected. Here, it is preferable that the bypass amount be minimized to achieve a rapid increase in rotation. After that, while the exhaust purification catalyst is not activated, the same mode continues to be selected until the supercharger rotation speed reaches the predetermined rotation speed. Here, immediately after the engine is started, the predetermined number of revolutions is set to a relatively high second value,
First, the supercharger rotation speed is forcibly increased to this second value. Therefore, even if the supercharger rotation speed is increased and the bypass amount is increased, the supercharger rotation speed does not immediately fall below the first value rotation speed. It can be continued.

In the invention according to claim 6, the predetermined rotational speed is set to a higher value as the lubricating oil pressure is higher. That is, even if the supercharger rotation speed is the same, if the lubricating oil pressure is high, the lubricating oil is more likely to leak to the turbine side. is there. Here, the predetermined speed may be either immediately after the engine is started (first value) or during normal time (second value), but both of them are set based on the lubricating oil pressure. It is suitable if it is.

In the invention according to claim 7, the bypass valve control device is provided with means for detecting the intake pressure downstream of the compressor of the supercharger, and the supercharger rotation speed is based on the intake pressure detected by this means. Was detected. According to the eighth aspect of the present invention, the bypass valve control device is provided with means for detecting the intake air amount, and the supercharger speed is detected based on the intake air amount detected by this means.

In the ninth aspect of the invention, the bypass valve control device is provided with means for estimating or detecting the temperature of the carrier of the exhaust purification catalyst.

[0016]

According to the invention of claim 1, when the temperature of the exhaust purification catalyst is raised by bypassing the turbine,
Since the rotational speed of the supercharger can be appropriately maintained, it is possible to secure the force with which the seal member of the turbine shaft is pressed against the center housing and prevent the discharge of HC due to oil leakage to the turbine side.

According to the invention of claim 2, it is possible to obtain the same effect as that of claim 1. According to the invention of claim 3, even when the supercharger rotation speed is low, the temperature of the exhaust purification catalyst can be raised to the extent that it can be maintained appropriately, so that the activation time of the catalyst is shortened. it can.

According to the fourth aspect of the present invention, when the supercharger rotation speed is lower than the predetermined rotation speed, the opening degree of the bypass valve is minimized to ensure an excessive decrease in the supercharger rotation speed. It can be prevented. According to the invention of claim 5, after the engine is started, the supercharger is first pulled up to a predetermined high rotation range, and thereafter, the state with a large bypass amount is continued for a long time,
The exhaust purification catalyst can be activated quickly.

According to the sixth aspect of the present invention, the higher the lubricating oil pressure, the higher the turbocharger rotational speed is maintained, so that oil leakage can be reliably prevented regardless of the operating state. According to the seventh and eighth aspects of the present invention, simple control is performed by detecting the supercharger rotation speed based on the intake pressure or the intake air amount (or both) downstream of the compressor of the supercharger. The above effect can be obtained only with logic and a relatively inexpensive sensor.

According to the invention of claim 9, the temperature of the exhaust gas purification catalyst can be accurately detected by the temperature of the carrier.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an internal combustion engine (hereinafter referred to as “engine”) 1 according to an embodiment of the present invention.
It is a block diagram of. An air filter (not shown) is attached to the introduction portion of the intake passage 3 connected to the engine body 2, where dust and the like floating in the intake air are removed. Then, a detection signal corresponding to the intake air amount is output from the air flow meter 31 installed immediately downstream of the air filter, and is input to an electronic control unit (hereinafter abbreviated as “ECU”) 41.

A compressor 4a of the turbocharger 4 is provided in the intake passage 3, and the intake air from the air flow meter 31 is compressed by the compressor section 4a and sent out. The intake air pressure-fed by the compressor unit 4a is distributed to each cylinder in the manifold unit. In the engine body 2, an electronically controlled fuel injection valve (hereinafter referred to as “injector”) 5 is installed so as to face the upper center of the combustion chamber of each cylinder. The fuel compressed to a predetermined pressure by the fuel pump is introduced into the common rail 6 through the fuel supply pipe and is supplied to each injector 5 from there. The injector 5 operates in response to a fuel injection control signal from the ECU 41, is driven to open at a predetermined fuel injection timing, and directly injects a predetermined amount of fuel into the cylinder.

A turbine 4b of the turbocharger 4 is installed in the exhaust passage 7. The turbine wheel of the turbine 4b and the compressor wheel of the compressor 4a are rigidly coupled to each other by a shaft.
Needless to say, the exhaust gas flowing into b rotates the turbine wheel, thereby rotating the compressor wheel and improving the charging efficiency.

In the exhaust passage 7, upstream of the turbine 4b of the turbocharger 4 is downstream of the confluence point of the manifold portion, and downstream of the turbine 4b is upstream of an exhaust purification device 8 described later. Are communicated by the bypass passage 9. A bypass valve (here, a butterfly valve) for adjusting the opening area is provided in the bypass passage 9.
10 are installed. An actuator 11 such as a stepping motor that controls the opening of the bypass valve 10 is connected to the bypass valve 10. Here, when the actuator 11 opens the bypass valve 10 in response to the bypass valve control signal from the ECU 41, the exhaust gas whose flow rate is controlled by the opening area at that time bypasses the turbine 4b and the turbine 4b is exhausted.
It joins the exhaust passage downstream of b. The exhaust gas passing through the turbine 4b and the exhaust gas bypassing the turbine 4b through the bypass passage 9 are both purified by the exhaust gas purification device 8 and then released into the atmosphere.

The exhaust purification device 8 carries an exhaust purification catalyst for purifying the exhaust of the diesel engine. As this catalyst, an oxidation catalyst or a NOx trap catalyst is suitable. Here, the oxidation catalyst means one having a function of oxidizing unburned fuel components such as CO and HC, and the NOx trap catalyst here means NOx in the exhaust gas when the air-fuel ratio is lean. While trapping
It has a function of releasing and reducing trapped NOx when the air-fuel ratio becomes rich.

Another example of the exhaust emission control device 8 is a device having a DPF (diesel particulate filter) built therein. Here, the DPF refers to a porous body made of ceramic or the like that is fine enough to filter and collect particulate matter discharged from a diesel engine. A catalyst layer containing an oxidation catalyst or the like as a catalyst component is formed on the DPF.

As a sensor provided in the engine 1, in addition to the air flow meter 31, the engine speed N
A crank angle sensor 32 that detects a unit crank angle or a reference crank angle used when calculating e, an accelerator sensor 33 that detects an accelerator opening Acc that corresponds to a driver's accelerator operation amount, a pressure of engine lubricating oil ( Hereinafter, referred to as "engine hydraulic pressure.") A hydraulic pressure sensor 34 for detecting Poil and a supercharging pressure sensor 35 for detecting the pressure in the collector 12 of the intake passage 3 as the supercharging pressure Pb are provided. Further, the exhaust gas purification device 8 is provided with a catalyst temperature sensor 36 for detecting the temperature (hereinafter referred to as “catalyst temperature”) Tcat of the carried exhaust gas purification catalyst. The catalyst temperature sensor 36 is configured to detect the temperature of the catalyst carrier. The detection signals of these sensors 31 to 36 are all input to the ECU 41.

Next, of the controls executed by the ECU 41, the opening degree control of the bypass valve 10 will be described with reference to the flowchart shown in FIG. Here, the ECU 4
For this control, 1 transmits a bypass valve control signal to the actuator 11 as described below. In step (hereinafter abbreviated as "S") 1, each sensor 31-.
Based on the input signal from 36, the engine speed Ne,
The accelerator opening Acc, the engine oil pressure Poil, the catalyst temperature Tcat, the supercharging pressure Pb, and the intake air amount Qa are read.

At S2, the intake air amount Qa and the boost pressure Pb
The supercharger rotation speed Nt of the supercharger 4 is detected based on
This detection is presumed by referring to a map simulating the operation characteristic diagram of the compressor 4a shown in FIG. Here, the supercharger rotation speed Nt is detected as a lower value as the intake air amount Qa is smaller and as the supercharging pressure Pb is lower. S
In 3, the supercharger lower limit rotation speed Nmin is set as shown in FIG. 4 based on the engine oil pressure Poil.

Here, the lower limit rotational speed Nmin is determined by the supercharger 4
Is set as a limit at which an appropriate oil seal function (generally, a piston ring is mounted on a turbine shaft as a seal member) can be obtained in the center housing. That is, if the supercharger rotation speed Nt is excessively reduced, the force with which the seal member is pressed against the center housing is weakened, and the oil seal function becomes insufficient, so the lower limit rotation speed Nmin is such that the pressing force of the seal member is obtained at a predetermined value. The minimum rotation speed within the range. However, even under the same supercharger speed Nt, comparing the case where the engine oil pressure Poil is high and the case where the engine oil pressure Poil is low, the former has a stronger force to push the lubricating oil to the outside. Easy to leak. Therefore, the lower limit rotation speed Nmi
It is preferable that n is appropriately changed according to the engine oil pressure Poil, and is set to a higher value as Poil is higher. Note that Nmin corresponds to the “first value” of the predetermined rotation speed related to the supercharger rotation speed.

In S4, it is determined whether or not the engine has just started. As this determination method, for example, an OFF signal of the start switch is input, the elapsed time from engine start is calculated, and if the elapsed time is within a predetermined time, it is determined that the engine has just been started. Alternatively, the period from the engine start to the time when the supercharger rotation speed Nt first exceeds an initial target rotation speed Ni described later may be set immediately after the engine start.

In the following, first, the flow of control limited to the time period immediately after the engine is started will be described. If it is determined that the engine has just started, the routine proceeds from S4 to S5, and the supercharger initial target rotation speed Ni is set as shown in FIG. 5 based on the engine oil pressure Poil.

Here, the initial target rotational speed Ni has a higher value as the engine oil pressure Poil is higher like the supercharger rotational speed Nt, and the lower limit rotational speed as a first value for a constant Poil. It is set to a value higher than Nmin. Note that Ni corresponds to the “second value” of the predetermined rotation speed related to the supercharger rotation speed. In S6, it is determined whether the supercharger rotation speed Nt is equal to or higher than the initial target rotation speed Ni. After the engine is started, while Nt is lower than Ni, the process proceeds to S10, and the bypass valve 10 is fully closed. This operation causes most of the exhaust gas to flow to the turbine 4a during this period. And
In this way, the state in which the bypass valve 10 is closed is continued from the engine start until the supercharger rotation speed Nt reaches the initial target rotation speed Ni (regardless of the catalyst temperature Tcat). It can be quickly raised to the high rotation range.

At S6, the supercharger 4 sets the initial target rotation speed N
If it is rotating at i or more, the processes of S7 and later described below are performed. Next, as a control after a predetermined time has elapsed from the engine start, the flow from S4 onward will be described. When it is determined in S4 that it is not immediately after the engine is started, the process proceeds to S7, and the catalyst temperature Tcat is equal to the predetermined temperature T.
It is determined whether it is lower than 0. Here, T0 is set to the activation lower limit temperature (for example, 200 ° C.) of the exhaust purification catalyst provided in the exhaust purification device 8. When it is determined that Tcat is lower than T0, the process proceeds to S8.

At S8, it is determined whether or not the supercharger rotation speed Nt is equal to or higher than the lower limit rotation speed Nmin. Here, only when it is determined that Nt is Nmin or more, the process proceeds to S9,
Bypass valve 10 is to be opened. On the other hand, Nt is Nm
When it is determined that the value is lower than in, S1 is set even when the exhaust purification catalyst is in the inactive state and needs to be heated.
0, and the bypass valve 10 is fully closed. According to this operation, the activation of the exhaust purification catalyst will be delayed a little. However, by prohibiting the bypass, the supercharger rotation speed Nt rises, the deterioration of the oil seal function is prevented, and the discharge of HC is prevented, so that the exhaust performance is improved overall.

On the other hand, when it is determined in S7 that the catalyst temperature Tcat is equal to or higher than the predetermined temperature T0, the exhaust gas purification catalyst has been activated, so the routine proceeds to S10, where the bypass valve 10 is fully closed to bypass. Stop. As described above, the supercharger rotation speed Nt is forcibly increased to the initial target rotation speed Ni immediately after the engine is started. According to this configuration, immediately after the engine is started, most of the exhaust gas is made to flow into the turbine 4b to increase the supercharger rotation speed Nt to a rotation speed higher than the lower limit rotation speed Nmin, and then the bypass amount is increased. I can go. Therefore, after the bypass amount is increased, the supercharger rotation speed Nt does not immediately fall below the lower limit rotation speed Nmin, so that the bypass can be continued for a long time and the activation of the exhaust purification catalyst can be accelerated. .

Next, another embodiment of the present invention will be described. In the first embodiment described above, when it is determined that the supercharger rotation speed Nt is lower than the lower limit rotation speed Nmin in the normal time when a predetermined time has elapsed from the engine start, the catalyst temperature Tc
The bypass valve 10 was uniformly closed regardless of at. The present embodiment is different in this respect, and only the difference will be described below.

FIG. 6 shows the bypass valve 10 according to this embodiment.
3 is a flow chart showing the flow of the opening degree control, in which the same steps as those in FIG. 2 according to the first embodiment are designated by the same reference numerals. After a lapse of a predetermined time from the engine start (the control immediately after the engine start is the same as that of the first embodiment), the catalyst temperature Tca in S7.
When it is determined that t is lower than the predetermined temperature T0 (for example, 200 ° C.), the process proceeds to S8.

In S8, it is determined whether or not the supercharger rotation speed Nt is equal to or higher than the lower limit rotation speed Nmin. Here, when it is determined that Nt is equal to or greater than Nmin, the process proceeds to S91, and the opening degree a of the bypass valve 10 is set to a predetermined opening degree α (for example, full opening degree). On the other hand, when it is determined that Nt is lower than Nmin, the process proceeds to S92. In S92, the bypass valve 10 is opened (in contrast to the case where the bypass valve 10 is fully closed in the first embodiment), but the opening degree a at this time is the predetermined opening degree α. Is a value that has been subjected to a predetermined reduction correction. And this reduction correction is
Difference Nmin between lower limit rotation speed Nmin and supercharger rotation speed Nt
-Nt, and the opening a is the predetermined opening α
Is set to a value obtained by subtracting the correction amount f (Nmin−Nt) according to the difference.

As a result, the bypass amount is increased as compared with the first embodiment in which the bypass valve 10 is fully closed, but the bypass amount at this time is adjusted in S91 in the present embodiment. Less than
According to the present embodiment, it is possible to raise the temperature of the exhaust purification catalyst within a range where the supercharger rotation speed Nt can be maintained, and it is possible to achieve both of these.

In the second embodiment, further,
When it is determined that the supercharger rotation speed Nt is lower than the initial target rotation speed Ni immediately after the engine is started (S6), the bypass valve 10 is not fully closed uniformly, but is set under a predetermined condition. It may be opened. That is,
In the above description, when it is determined in S6 that the supercharger rotation speed Nt is lower than the initial target rotation speed Ni, S10
Then, it was decided to fully close the bypass valve 10. As another example, when the process similarly proceeds to S10, a predetermined decrease correction is performed on a predetermined opening α (for example, a fully open opening) of the bypass valve 10 and only the corrected opening a is applied to the bypass valve 10.
To open.

As a result, even before the supercharger rotation speed Nt reaches the initial target rotation speed Ni, the temperature of the exhaust purification catalyst can be raised within a range in which Nt can be increased to Ni. . Here, this reduction correction is based on the above S92.
In the same manner as in, the difference is calculated based on the difference Ni−Nt between the initial target rotation speed Ni and the supercharger rotation speed Nt (a = α−g (N
i-Nt): g is a correction function. ).

[Brief description of drawings]

FIG. 1 is a configuration diagram of an internal combustion engine (diesel engine) with a supercharger according to an embodiment of the present invention.

FIG. 2 is a flowchart of a bypass valve opening control routine by the control device for an internal combustion engine of the same as above.

[Fig. 3] Turbocharger speed detection map

[Figure 4] Supercharger lower limit rotation speed setting map

[Figure 5] Supercharger initial target speed setting map

FIG. 6 is a flowchart of a bypass valve opening control routine by a control device for an internal combustion engine according to another embodiment of the present invention.

[Explanation of symbols]

1 ... Diesel engine 2 ... Engine body 3 ... Intake passage 4 ... Turbocharger 5 ... Injector 6 ... Common rail 7 ... Exhaust passage 8 ... Exhaust gas purification catalyst 9 ... Bypass passage 10 ... Bypass valve 11 ... Actuator 41 ... Electronic control unit

Continued front page    F-term (reference) 3G005 DA02 EA16 FA33 GB28 GB61                       GD11 JA16 JA24 JA29 JA39                       JA40 JA45 JB02                 3G091 AA10 AA18 AB02 BA02 BA04                       BA14 BA15 BA19 BA21 CA13                       DB10 EA01 EA05 EA06 EA07                       EA18 FA02 FB02 FB03 FC07                       FC08 HB03 HB06                 3G092 AA02 AA18 DB03 DC00 FA00                       FA15 GA01 GA04 GA05 HA01Z                       HA05Z HA06Z HA17X HA17Z                       HD02X HD02Z

Claims (9)

[Claims] 1. An internal combustion engine with a supercharger, comprising: a turbine of a supercharger in an exhaust passage; and an exhaust gas purification device installed downstream of the turbine, the upstream side of the turbine and the downstream side of the turbine. A bypass passage communicating with the upstream side of the exhaust purification device;
A bypass valve installed in the bypass passage; and a bypass valve control device that controls the bypass valve to control a bypass amount that is a flow rate of exhaust gas flowing through the bypass passage. A supercharging mode in which the amount is minimized to perform supercharging, a catalyst temperature raising mode in which the bypass amount is increased to raise the temperature of the exhaust purification catalyst provided in the exhaust purification device, and the bypass amount is increased in the catalyst It is configured to include a mode switching unit that selectively switches between a rotation maintaining mode in which the turbocharger rotational speed is made smaller than that in the mode to increase the supercharging engine rotational speed to a predetermined rotational speed or more, and the mode switching unit is the exhaust purification catalyst. The supercharging mode is selected when the temperature is equal to or higher than a predetermined temperature, and the catalyst is selected when the temperature is lower than the predetermined temperature and the supercharger speed is equal to or higher than the predetermined speed. Select temperature mode, an internal combustion engine with a supercharger, characterized in that and supercharger rotational speed lower than this temperature is the predetermined temperature is selected rotation maintaining mode when less than the predetermined rotational speed. 2. An internal combustion engine with a supercharger, comprising: a turbocharger turbine in an exhaust passage; and an exhaust gas purifying device installed downstream of the turbine, the upstream side of the turbine and the downstream side of the turbine. A bypass passage communicating with the upstream side of the exhaust purification device;
A bypass valve installed in the bypass passage; and a bypass valve control device that controls the bypass valve to control a bypass amount that is a flow rate of exhaust gas flowing through the bypass passage. Mode switching means for selectively switching between a supercharging mode in which the amount is minimized to perform supercharging, and a catalyst temperature raising mode in which the exhaust purification catalyst provided in the exhaust purification device is heated by increasing the bypass amount. And a valve opening degree setting means for setting the opening degree of the bypass valve according to the selected mode, wherein the mode switching means is operable when the temperature of the exhaust purification catalyst is equal to or higher than a predetermined temperature. While the supply mode is selected, when the temperature is lower than the predetermined temperature, the catalyst temperature increasing mode is selected, and the valve opening degree setting means determines when the catalyst temperature increasing mode is set.
It is characterized in that the opening of the bypass valve is set based on the rotation speed of the supercharger, and when the rotation speed is lower than a predetermined rotation speed, the opening degree is made smaller than when the rotation speed is higher than the predetermined speed. Internal combustion engine with supercharger. 3. The valve opening setting means, when the opening of the bypass valve is set in the catalyst temperature increasing mode, decreases the opening as the supercharger rotation speed is lower. Internal combustion engine with supercharger. 4. The valve opening setting means sets the opening of the bypass valve when the opening of the bypass valve is lower than the predetermined speed when setting the opening of the bypass valve in the catalyst temperature increasing mode. The internal combustion engine with a supercharger according to claim 2, which has a minimum size. 5. The internal combustion engine with a supercharger according to claim 1, wherein, immediately after the engine is started, the predetermined rotation speed is switched to a second value that is higher than the first value during normal times. organ. 6. The internal combustion engine with a supercharger according to claim 1, wherein the predetermined rotation speed is set to a higher value as the lubricating oil pressure is higher. 7. The bypass valve control device has means for detecting an intake pressure downstream of a compressor of the supercharger, and the supercharger speed is detected based on the intake pressure detected by the means. The internal combustion engine with a supercharger according to any one of claims 1 to 6. 8. The bypass valve control device has means for detecting an intake air amount, and the supercharger rotation speed is detected based on the intake air amount detected by this means.
An internal combustion engine with a supercharger according to any one of 1. 9. The internal combustion engine with a supercharger according to claim 1, wherein the bypass valve control device has means for estimating or detecting the temperature of the carrier of the exhaust purification catalyst.