JP2010150930A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine equipped with an LPL-EGR device (an LPL passage) and an air-fuel ratio sensor, hardly causing degrading, breaking, or the like of the air-fuel ratio sensor, and starting warm-up of the air-fuel ratio sensor more quickly. <P>SOLUTION: In the internal combustion engine, it is composed such that, at its starting, until a gas temperature before a turbocharger 16 starts to rise, an EGR valve and an exhaust throttle valve 17 are controlled such that EGR gas (exhaust gas) flows through the LPL passage 20, and then, the warm-up of the air-fuel ratio sensor 16 is started. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal combustion engine, and more particularly, to an internal combustion engine including an LPL passage (LPL-EGR device) and an air-fuel ratio sensor.

  Some internal combustion engines are provided with an air-fuel ratio sensor comprising a sensor element and a heater in the exhaust passage in order to enable feedback control based on the air-fuel ratio of the exhaust gas. The sensor element of the sensor is one that requires heating by a heater (one that does not function as a sensor unless the temperature becomes high).

  In addition, the sensor element of the air-fuel ratio sensor may be deteriorated or damaged when it is exposed to water during heating / after heating is completed. Then, condensed water may be accumulated in the internal combustion engine (such as in the exhaust passage) before starting. For this reason, in an internal combustion engine equipped with an air-fuel ratio sensor, after the engine is started, after a while (after waiting for a situation where the condensed water in the exhaust passage is estimated to evaporate), the air-fuel ratio sensor is heated. (For example, refer to Patent Document 1).

Also, the heating start timing of the air-fuel ratio sensor in the internal combustion engine equipped with an HPL (High Pressure Loop) -EGR (Exhaust Gas Recirculation) device is changed depending on whether or not the EGR control is performed (the EGR control is performed at the time of starting). In such a case, delaying the heating start timing of the air-fuel ratio sensor is also proposed (for example, see Patent Document 2).

Some internal combustion engines equipped with a turbocharger are equipped not with an HPL-EGR device (or with an HPL-EGR device) but with an LPL (Low Pressure Loop) -EGR device. However, such an internal combustion engine also basically starts heating the air-fuel ratio sensor after waiting for the condensed water in the exhaust passage to be estimated to have evaporated after the engine is started. It has become.

JP 2003-269231 A Japanese Patent Laid-Open No. 2003-232243 JP 2008-196439 A JP 2007-291973 A JP 2001-1953577 A Japanese Patent Application Laid-Open No. 11-93781 JP-A-10-141147 JP-A-5-256213

  Even in an internal combustion engine equipped with an LPL-EGR device and an air-fuel ratio sensor, if heating of the air-fuel ratio sensor is started after a certain amount of time has elapsed after starting, Deterioration and damage can be prevented. However, after the internal combustion engine is started, a considerable amount of time is required until the temperature of the EGR passage (hereinafter referred to as the LPL passage) of the LPL-EGR device reaches a temperature at which condensed water in the LPL passage can evaporate. Needed. This is because, even when the internal combustion engine is started, the exhaust gas whose temperature has been lowered by passing through a turbine or the like passes through the vicinity of the inlet of the LPL passage (connection portion with the exhaust passage).

  For this reason, in an existing internal combustion engine equipped with an LPL-EGR device and an air-fuel ratio sensor, heating (warming up) of the air-fuel ratio sensor is started after a considerable time has elapsed after starting. . If the heating of the air-fuel ratio sensor is not completed, the internal combustion engine cannot be operated with good fuel economy or the like (feedback control based on the air-fuel ratio cannot be started). Development of technology that can start earlier is desired.

  Accordingly, an object of the present invention is an internal combustion engine that is provided with an LPL-EGR device (LPL passage) and an air-fuel ratio sensor and that is unlikely to cause deterioration or damage of the air-fuel ratio sensor. Is to provide an internal combustion engine that is started earlier.

  In order to solve the above problems, an internal combustion engine of the present invention is a turbocharger having an internal combustion engine body, a turbine provided in an exhaust passage of the internal combustion engine body, and a compressor provided in an intake passage of the internal combustion engine body. An LPL passage for extracting exhaust gas from a portion of the exhaust passage downstream from the turbine and supplying the exhaust gas to a portion of the intake passage upstream of the compressor; and an EGR valve disposed in the middle of the LPL passage; An exhaust throttle valve disposed in a portion of the exhaust passage downstream of the portion to which the LPL passage is connected, and an air-fuel ratio having a heater disposed in a portion of the exhaust passage downstream of the turbine The EGR valve is controlled to be open and the exhaust throttle valve is closed only until a predetermined condition is satisfied after the sensor and the internal combustion engine main body are started. After controlling the state, and control means for starting the warm-up of the air-fuel ratio sensor by the heater.

  That is, when the internal combustion engine of the present invention is started, the EGR valve is controlled so that EGR gas (exhaust gas) flows through the LPL passage, and the pressure difference between the inlet portion and the outlet portion of the LPL passage is increased. The exhaust throttle valve is controlled. In the internal combustion engine of the present invention, when the predetermined condition is satisfied thereafter, the EGR valve and the exhaust throttle valve are returned to the normal state, and warming up of the air-fuel ratio sensor by the heater is started. It also has a configuration. If EGR gas flows in the LPL passage, the condensed water in the LPL passage, which may cause deterioration or breakage of the air-fuel ratio sensor, can flow to the intake passage side. Therefore, the internal combustion engine of the present invention is an internal combustion engine in which the air-fuel ratio sensor is unlikely to deteriorate or break, and is more air-fuel ratio than an existing internal combustion engine that does not actively scavenge the condensed water in the LPL passage. This is an internal combustion engine that starts warming up of the sensor very quickly.

  As the control means of the internal combustion engine of the present invention, for example, the EGR valve and the exhaust throttle valve are controlled to be in an open state and a closed state, respectively, only until a predetermined time has elapsed after the start of the internal combustion engine body. Thereafter, means for starting the warm-up of the air-fuel ratio sensor by the heater may be employed. However, if control means for determining that the predetermined condition is satisfied when the temperature of the gas (intake) supplied to the compressor rises is adopted, the warming of the air-fuel ratio sensor is completed when the replacement of the gas in the LPL passage is completed. The machine can be started. For this reason, when the internal combustion engine of the present invention is realized, when a temperature sensor for measuring the temperature of the gas supplied to the compressor is added and the measurement result of the temperature sensor rises as a control means. Further, it is desirable to adopt means for determining that the predetermined condition is satisfied.

  Further, the condensed water in the LPL passage hardly scatters to the upstream side of the exhaust passage. For this reason, by disposing the air-fuel ratio sensor in a portion of the exhaust passage upstream of the portion to which the LPL passage is connected, an internal combustion engine that is less prone to deterioration and damage of the air-fuel ratio sensor, An internal combustion engine in which heating of the air-fuel ratio sensor is started earlier can also be realized.

According to the present invention, an air-fuel ratio sensor is provided with an LPL-EGR device (LPL passage) and an air-fuel ratio sensor, and the air-fuel ratio sensor is less likely to be deteriorated or damaged. An internal combustion engine can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

<< First Embodiment >>
FIG. 1 shows the configuration of an internal combustion engine according to the first embodiment of the present invention.

  As illustrated, the internal combustion engine according to the first embodiment of the present invention includes an internal combustion engine body 10, an LPL passage 20, a control device 30, and the like.

  The internal combustion engine body 10 included in the internal combustion engine is a diesel engine having four cylinders. An intake passage 11 and an exhaust passage 12 are connected to the internal combustion engine body 10, and a compressor housing 13 a (component of the turbocharger 13) for compressing intake air is provided in the middle of the intake passage 11. Yes. A temperature sensor 14 for measuring the temperature of the intake air flowing into the compressor housing 13a is attached to the intake passage 11.

A turbine housing 13b (a component of the turbocharger 13) that is a drive source of the compressor housing 13a is provided on the upstream side of the exhaust passage 12 (side closer to the internal combustion engine body 10). A DPF (Diesel particulate filter) 15 for purifying exhaust gas is provided in a portion of the exhaust passage 12 downstream of the turbine housing 13b.

  An air-fuel ratio sensor 16 for measuring the air-fuel ratio is provided at a portion downstream of the DPF 15 in the exhaust passage 12. The air-fuel ratio sensor 16 is composed of a sensor element 16a for measuring the air-fuel ratio and a heater 16b for heating the sensor element 16a.

  An exhaust throttle valve 17 for adjusting the flow rate of the exhaust gas is provided in a portion of the exhaust passage 12 downstream of the air-fuel ratio sensor 16.

  The LPL passage 20 is a gas passage that communicates the portion of the exhaust passage 12 between the DPF 15 and the air-fuel ratio sensor 16 and the portion of the intake passage 11 upstream of the compressor housing 13a. An EGR cooler 21 for cooling the exhaust gas from the exhaust passage 12 is provided on the upstream side of the LPL passage 20. Further, an EGR valve 22 for adjusting the flow rate of the exhaust gas flowing through the LPL passage 20 (exhaust gas returning to the intake passage 11) is provided on the downstream side of the LPL passage 20.

  The control device 30 is provided in each part of the internal combustion engine according to the present embodiment (EGR valve 22, exhaust throttle valve 17, and internal combustion engine main body 10) according to the driver's request and the state of the internal combustion engine main body 10. An electronic control unit for a fuel injection valve, an intake / exhaust valve, and the like.

This control device 30 is a software improvement (reprogrammed) of an existing electronic control unit so as to start warming up of the air-fuel ratio sensor 16 at different timings / procedures. Therefore, only the warm-up procedure of the air-fuel ratio sensor 16 by the control device 30 will be described below, but the control device 30 (and the existing electronic control unit described above) Is completed (after the resistance value of the heater 16b reaches a predetermined value), various feedback controls based on the output of the air-fuel ratio sensor 16 are performed.

  When instructed to start the internal combustion engine (internal combustion engine body 10), the control device 30 starts a control process for operating the internal combustion engine body 10, and at the sensor warm-up start timing of the procedure shown in FIG. It is configured (programmed) as a unit that starts the adjustment process.

  That is, the control device 30 that has started the control process for operating the internal combustion engine main body 10 also starts this sensor warm-up start timing adjustment process, and first opens the EGR valve 22 and closes the exhaust throttle valve 17. (Step S101). More specifically, the control device 30 performs a process of controlling the EGR valve 22 to be in an open state and controlling the exhaust throttle valve 17 to be in a closed state in step S101.

  Next, the control device 30 measures the gas temperature before the turbocharger 13 (hereinafter referred to as a pre-T / C temperature) by the temperature sensor 14, and stores the measurement result as a reference temperature (step S102). Thereafter, the control device 30 starts a process of waiting (monitoring) that the pre-T / C temperature exceeds the reference temperature (loop process of steps S103 and S104).

  When it is detected that the measured value of the pre-T / C temperature exceeds the reference temperature (step S104; YES), the control device 30 closes the EGR valve 22 and opens the exhaust throttle valve 17 (step S105). ). That is, the control device 30 performs processing for returning the states of the EGR valve 22 and the exhaust throttle valve 17 to normal states.

  The control device 30 that has finished the process of step S105 performs a process of starting the warm-up of the air-fuel ratio sensor 16 (step S106). In addition, the process which the control apparatus 30 actually performs in this step S106 is a process which makes the drive circuit (not shown) for the heater 16b start the electric power supply to the heater 16b.

  And the control apparatus 30 which finished the process of step S106 complete | finishes this sensor warming-up start timing adjustment process.

  As is apparent from the above description, the internal combustion engine according to the first embodiment of the present invention controls the EGR valve 22 so that EGR gas (exhaust gas) flows through the LPL passage 20 at the time of start-up. The exhaust throttle valve 17 is controlled so that the pressure difference between the inlet portion and the outlet portion of the passage 20 is increased. Further, in the internal combustion engine according to the first embodiment, when the temperature before T / C rises thereafter, the state of the EGR valve 22 and the exhaust throttle valve 17 is returned to the normal state, and the air-fuel ratio sensor by the heater 16b. 16 (sensor element 16a) is also started to warm up.

  If the EGR gas flows in the LPL passage 20, the condensed water in the LPL passage 20 that may cause deterioration or breakage of the air-fuel ratio sensor 16 can flow to the intake passage 11 side. The internal combustion engine according to the embodiment is an internal combustion engine in which the air-fuel ratio sensor 16 is unlikely to deteriorate or break, and the air-fuel ratio sensor 16 starts warming up very quickly.

<< Second Embodiment >>
FIG. 3 shows the configuration of an internal combustion engine according to the second embodiment of the present invention.

  As apparent from a comparison between FIG. 3 and FIG. 1, the internal combustion engine according to the second embodiment of the present invention is the internal combustion engine according to the first embodiment only in the attachment position of the air-fuel ratio sensor 16 to the exhaust passage 12. It is different from the institution.

  Specifically, in the internal combustion engine according to the first embodiment, the air-fuel ratio sensor 16 is attached to a portion of the exhaust passage 12 downstream of the portion to which the LPL passage 20 is connected (see FIG. 1). However, in the internal combustion engine according to the present embodiment, the air-fuel ratio sensor 16 is attached to a portion of the exhaust passage 12 upstream of the portion where the LPL passage 20 is connected.

  Since the exhaust gas flows toward the downstream side of the exhaust passage 12, the condensed water in the LPL passage 20 hardly scatters to the upstream side of the exhaust passage 12. For this reason, the internal combustion engine according to the second embodiment is an internal combustion engine in which the air-fuel ratio sensor 16 is less likely to be deteriorated or damaged than the internal combustion engine according to the second embodiment.

<< Third Embodiment >>
FIG. 4 shows the configuration of an internal combustion engine according to the third embodiment of the present invention.

  As is clear from a comparison between FIG. 4 and FIG. 1, the internal combustion engine according to the third embodiment of the present invention is located at the most upstream portion of the LPL passage 20 with respect to the internal combustion engine according to the first embodiment. A shutoff valve 23 for turning on / off the flow of EGR gas in the LPL passage 20 is added, and an improvement / deformation is performed in which the control device 30 is changed to a control device 30 ′.

  The control device 30 ′ is an electronic control unit that, like the control device 30, performs control according to the driver's request and the state of the internal combustion engine body 10 for each part of the internal combustion engine according to the present embodiment.

  However, instead of the sensor warm-up start timing adjustment process (FIG. 2) described above, the control device 30 ′ “warms the air-fuel ratio sensor 16 when the predetermined time has elapsed after the start of the internal combustion engine body 10. It is a unit that is configured (programmed) to execute “processing for maintaining the shutoff valve 23 closed until it is necessary to start LPL-EGR (open the EGR valve 22)”. ing. The predetermined time is a time determined as a time when the condensed water in the exhaust passage 12 is expected to evaporate.

  In short, the internal combustion engine according to the present embodiment is in a state in which deterioration or breakage of the air-fuel ratio sensor 16 cannot occur even when condensed water is accumulated in the LPL passage 20 (a state where the shut-off valve 23 is closed). ), The warm-up of the air-fuel ratio sensor 16 is started. When the LPL-EGR is started, the condensed water in the LPL passage 20 flows to the intake passage 11 side, so that the air-fuel ratio sensor 16 is not deteriorated or damaged.

  Therefore, the internal combustion engine according to the third embodiment is also an internal combustion engine in which the air-fuel ratio sensor 16 is unlikely to deteriorate or break, and the air-fuel ratio sensor 16 starts warming up very quickly. It will be.

<Deformation>
The internal combustion engine according to each embodiment described above can be variously modified. For example, the condensed water existing on the upstream side of the LPL passage 20 moves downstream before the pre-T / C temperature rises. The condensed water existing downstream of the LPL passage 20 hardly enters the exhaust passage 12. For this reason, the control device 30 is transformed into a device that performs a sensor warm-up start timing adjustment process in which the processing after step S105 is started before the temperature before T / C rises (after a predetermined time after the start). I can leave.

Further, the configuration of the internal combustion engine according to the second embodiment is such that the condensed water in the LPL passage 20 is unlikely to scatter and come into contact with the air-fuel ratio sensor 16. Therefore, the control device 30 for the internal combustion engine according to the second embodiment is changed to “when the predetermined time has elapsed after the start of the internal combustion engine body 10, instead of the above-described sensor warm-up start timing adjustment process (FIG. 2). It can also be modified to perform a process for starting the warm-up of the air-fuel ratio sensor 16.

  In addition, it is natural that the internal combustion engine according to each embodiment may be modified to an internal combustion engine having a specific configuration different from that described above (for example, an internal combustion engine including an HPL-EGR device). is there.

1 is a configuration diagram of an internal combustion engine according to a first embodiment of the present invention. It is a flowchart of the sensor warming-up start timing adjustment process which the control apparatus with which the internal combustion engine which concerns on 1st Embodiment is provided performs at the time of starting of an internal combustion engine main body. It is a block diagram of the internal combustion engine which concerns on 2nd Embodiment of this invention. It is a block diagram of the internal combustion engine which concerns on 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine body 11 ... Intake passage 12 ... Exhaust passage 13 ... Turbocharger 13a ... Compressor housing 13b ... Turbine housing 14 ... Temperature sensor 15 ... DPF
16 ... Air-fuel ratio sensor 16a ... Sensor element 16b ... Heater 17 ... Exhaust throttle valve 20 ... LPL passage 21 ... EGR cooler 22 ... EGR valve 23 ... Shut-off valve 30 , 30 '... control device

Claims (3)

An internal combustion engine body;
A turbocharger having a turbine provided in an exhaust passage of the internal combustion engine body and a compressor provided in an intake passage of the internal combustion engine body;
An LPL passage for extracting exhaust gas from a portion of the exhaust passage downstream of the turbine and supplying it to a portion of the intake passage upstream of the compressor;
An EGR valve disposed in the middle of the LPL passage;
An exhaust throttle valve disposed in a portion of the exhaust passage downstream of the portion to which the LPL passage is connected;
An air-fuel ratio sensor having a heater disposed in a portion of the exhaust passage downstream of the turbine;
After the internal combustion engine body is started, the EGR valve is controlled to be in an open state and the exhaust throttle valve is controlled to be in a closed state only until a predetermined condition is satisfied, and then the air-fuel ratio sensor is warmed up by the heater. An internal combustion engine comprising: control means for starting the engine. A temperature sensor for measuring the temperature of the gas supplied to the compressor;
The control means is
2. The internal combustion engine according to claim 1, wherein when the measurement result of the temperature sensor rises, the internal combustion engine determines that the predetermined condition is satisfied. The air-fuel ratio sensor is
The internal combustion engine according to claim 1 or 2, wherein the internal combustion engine is disposed in a portion of the exhaust passage that is upstream of a portion to which the LPL passage is connected.

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