JP2007327454A - Exhaust system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for making both compatible in restraint of damage by flooding of an air-fuel ratio sensor and an early improvement in the purification ratio of exhaust emission, by raising the temperature of the air-fuel ratio sensor in the optimal timing in response to an attitude of a vehicle, when starting an internal combustion engine in a cold state. <P>SOLUTION: When starting the internal combustion engine in the cold state (S101 and S102), a forward inclination of the vehicle is detected (S103), and delay time Δt for starting heating of the air-fuel ratio sensor is derived in response to the detected forward inclination of the vehicle (S104). Starting of current-carrying to a heater of the air-fuel ratio sensor is delayed based on its delay time Δt (S105). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust system of an internal combustion engine, and more particularly to an exhaust system including an air-fuel ratio sensor that can acquire the air-fuel ratio of the exhaust of the internal combustion engine in a state where the temperature is raised by heating.

  Conventionally, in an internal combustion engine, an air-fuel ratio sensor (including an oxygen concentration sensor) is provided in an exhaust pipe and air-fuel ratio feedback control is performed by detecting the air-fuel ratio of exhaust gas. By this air-fuel ratio feedback control, the air-fuel ratio of the exhaust is optimized, and thereby the purification performance of the exhaust purification catalyst is properly maintained.

  In general, the sensor element provided in the air-fuel ratio sensor can measure the air-fuel ratio in a state of being heated to an activation temperature or higher. Accordingly, the air-fuel ratio sensor is often provided with a sensor heater for heating the sensor element.

  By the way, at the time of cold start of the internal combustion engine, the exhaust gas in the exhaust pipe is cooled after the previous engine stop, and the exhaust gas discharged from the engine after the start is cooled by touching the wall surface of the low temperature exhaust pipe. As a result, condensed water is generated, and this condensed water sometimes accumulates in the exhaust pipe. When the condensed water is applied to the air-fuel ratio sensor that has been heated to a high temperature, the air-fuel ratio sensor may be damaged due to thermal shock.

  To solve the above problem, the temperature of the exhaust pipe of the internal combustion engine is estimated from the amount of intake air to the internal combustion engine, and the estimated temperature of the exhaust pipe reaches a predetermined temperature at which no condensed water is generated. A technique for energizing a heater of an oxygen sensor with a heater has been proposed (see Patent Document 1).

However, in the above technique, depending on the attitude of the vehicle, it may be difficult to remove the condensed water that has already accumulated in the exhaust pipe at the time of starting, and the condensed water may not be completely removed by the time the temperature of the air-fuel ratio sensor rises. . As a result, the air-fuel ratio sensor may not be completely prevented from being damaged by water. On the other hand, when the vehicle is stopped in a posture in which the condensed water is difficult to accumulate, there is a possibility that the temperature rise of the air-fuel ratio sensor may be delayed although the condensed water does not accumulate in the exhaust pipe. As a result, there is a case where the improvement of the exhaust emission purification rate immediately after the start is hindered.
JP-A-8-15213 JP 2004-257261 A

  The present invention has been made in view of the above prior art, and its object is to raise the temperature of the air-fuel ratio sensor at an optimal timing according to the attitude of the vehicle at the time of cold start of the internal combustion engine, An object of the present invention is to provide a technique that achieves both suppression of damage to the air-fuel ratio sensor due to flooding and early improvement of the exhaust emission purification rate.

  The present invention for achieving the above object is characterized in that the timing at which the air-fuel ratio sensor is activated and the air-fuel ratio can be acquired is changed according to the forward lean angle of the vehicle.

More specifically, an exhaust line through which exhaust from the internal combustion engine passes,
An air-fuel ratio sensor disposed in the exhaust pipe and capable of acquiring the air-fuel ratio of the exhaust gas of the internal combustion engine in a state of being heated by heating;
Heating means for heating the air-fuel ratio sensor so that the air-fuel ratio can be acquired;
Inclination detecting means for detecting a forward inclination angle of a vehicle on which the internal combustion engine is mounted;
An exhaust system for an internal combustion engine comprising:
When the internal combustion engine is started, according to the forward lean angle of the vehicle detected by the inclination detection means, the time at which the air-fuel ratio sensor can acquire the air-fuel ratio by heating by the air-fuel ratio sensor heating means is changed. A temperature time changing means is further provided.

  Here, when the vehicle on which the internal combustion engine is mounted is tilted forward, it is difficult for water to escape from the exhaust port of the exhaust pipe to the outside of the vehicle. Therefore, when the vehicle is stopped with the vehicle leaning forward, there is a high possibility that condensed water is accumulated upstream of the air-fuel ratio sensor in the exhaust pipe at the next start. In addition, the greater the forward tilt angle of the vehicle, the more difficult it is for water to escape from the exhaust port of the exhaust pipe. Therefore, the time required for the temperature of the exhaust pipe to rise after the start and the condensed water is removed differs depending on the forward tilt angle when the vehicle is stopped.

  In view of this, in the present invention, there is provided an inclination detection means for detecting a forward inclination angle of a vehicle on which the internal combustion engine is mounted, and the front of the vehicle detected by the inclination detection means at the cold start of the internal combustion engine is provided. The timing at which the air-fuel ratio sensor can acquire the air-fuel ratio by the heating by the air-fuel ratio sensor heating means is changed according to the inclination angle.

  According to this, the air-fuel ratio sensor can be brought into a state in which the air-fuel ratio can be acquired at an optimal time according to the forward tilt angle of the vehicle. As a result, the temperature of the air-fuel ratio sensor rises too quickly with respect to the amount of condensed water, and the air-fuel ratio sensor is damaged by the water, or the temperature of the air-fuel ratio sensor is increased even though condensed water does not accumulate. However, it is possible to prevent the exhaust emission purification rate immediately after starting from being deteriorated unnecessarily. In the above, heating means heater heating by a heater, for example.

  Specifically, the temperature raising time changing means is such that the air-fuel ratio sensor acquires the air-fuel ratio by heating by the heating means when the forward lean angle of the vehicle detected by the inclination detecting means is equal to or greater than a predetermined angle. You may make it delay the time when it becomes possible.

  Here, the predetermined angle means that if the forward tilt angle of the vehicle is more than this, it is difficult for condensed water to escape from the exhaust pipe during stopping, and there is a high possibility that the condensed water has accumulated in the exhaust pipe during startup. This is a forward tilt angle that can be determined, and may be obtained experimentally in advance. In this case, when the forward leaning angle of the vehicle is equal to or greater than the predetermined angle, there is a high possibility that condensed water has accumulated in the exhaust pipe, so the time when the air-fuel ratio sensor can acquire the air-fuel ratio by heating is delayed. .

  Thus, when the air-fuel ratio sensor is heated when the internal combustion engine is started, only when there is a high risk that the air-fuel ratio sensor will receive condensed water, the time when the air-fuel ratio sensor can acquire the air-fuel ratio by heating is determined. Can be delayed. Although the air-fuel ratio sensor is less likely to get condensed water, it is possible to prevent the air-fuel ratio sensor from delaying the time when the air-fuel ratio sensor can acquire the air-fuel ratio, and to reduce the exhaust emission purification rate immediately after startup. Can be prevented.

  For example, when the predetermined angle is set to 0 degree, when the vehicle is parked in a backward tilted state, the time during which the air-fuel ratio sensor can acquire the air-fuel ratio is not delayed. The purification rate can be obtained.

In the present invention, the temperature raising time changing means is
The greater the forward lean angle of the vehicle detected by the inclination detection means, the later the time at which the air-fuel ratio sensor can acquire the air-fuel ratio by heating by the heating means may be delayed.

  Then, the higher the possibility that condensed water is accumulated in the exhaust pipe, or the more condensed water that is expected to be accumulated in the exhaust pipe, the slower the temperature rise of the air-fuel ratio sensor. be able to. Therefore, it is possible to more accurately balance the suppression of the damage due to the condensate of the air-fuel ratio sensor at the cold start and the suppression of the deterioration of the exhaust emission purification rate.

In the present invention, the temperature raising time changing means is
The timing when the air-fuel ratio sensor can acquire the air-fuel ratio may be delayed by delaying the heating start timing by the heating means.

  By doing so, there is no risk that the air-fuel ratio sensor will be damaged even if the air-fuel ratio sensor is exposed to condensate water when heating by the heating means is not started. Therefore, damage to the air-fuel ratio sensor can be suppressed more reliably.

In the present invention, the temperature raising time changing means is
The timing at which the air-fuel ratio sensor can acquire the air-fuel ratio may be delayed by reducing the temperature increase rate of the air-fuel ratio sensor by the heating means.

  Then, heating can be started without delaying the start of heating by the heating means, and the air-fuel ratio sensor can be gradually raised in temperature. Then, after the condensed water is actually removed and there is no danger of receiving the condensed water of the air-fuel ratio sensor, the air-fuel ratio sensor can be immediately brought into a state where the air-fuel ratio can be acquired. The exhaust gas purification rate can be improved more quickly.

  The exhaust pipe line may have an inclined part whose upstream side is inclined to the upper side of the vehicle from a predetermined portion of the exhaust pipe line, and the air-fuel ratio sensor may be provided in the inclined part.

  That is, by adopting a structure in which the upstream side of the exhaust pipe is inclined toward the upstream side of the vehicle, it is possible to make it difficult for condensed water to accumulate and to easily escape when the vehicle stops. Then, by providing the air-fuel ratio sensor at the inclined portion, it is possible to more reliably prevent the air-fuel ratio sensor from being damaged by water. Here, the predetermined location means a location on the downstream side of the air-fuel ratio sensor in the exhaust pipe.

Further, in the present invention, the exhaust pipe line has an inclined part whose upper side is inclined to the upper side of the vehicle from a predetermined portion of the exhaust pipe line, and the air-fuel ratio sensor is provided in the inclined part,
The temperature raising time changing means includes
When the forward inclination angle of the vehicle detected by the inclination detection means is greater than or equal to the inclination angle of the inclination portion, the timing at which the air-fuel ratio sensor can acquire the air-fuel ratio by heating by the heating means is delayed. May be.

  That is, when the vehicle stops in a state where the forward tilt angle of the vehicle is equal to or greater than the tilt angle of the tilt portion, the tilt portion is tilted forward from the horizontal. If it does so, compared with the case where the forward inclination angle of a vehicle is smaller than the inclination angle of the above-mentioned inclination part, the danger that condensed water will accumulate in an inclination part will become high. Therefore, in such a case, the time when the air-fuel ratio sensor can acquire the air-fuel ratio by heating by the heating means is delayed.

By doing so, even in a configuration having an inclined portion in the exhaust pipe, and when the risk of collecting condensed water is relatively high, the air-fuel ratio sensor delays the time when the air-fuel ratio can be acquired. It is possible to more reliably suppress damage due to the condensate of the fuel ratio sensor.

In the present invention, in the middle of the exhaust pipe, a flexible pipe formed of a flexible material and allowing the exhaust pipe to be bent is provided.
The air / fuel ratio sensor may be provided upstream of the flexible pipe in the exhaust pipe.

  That is, in a configuration in which a flexible pipe is provided in the middle of the exhaust pipe, condensed water tends to accumulate at the boundary between the exhaust pipe and the flexible pipe upstream or downstream of the flexible pipe or in the middle of the flexible pipe. I know it. Therefore, by placing the air-fuel ratio sensor on the upstream side of the flexible pipe, it is possible to more reliably suppress the condensate water from entering the air-fuel ratio sensor.

  The means for solving the above-described problems of the present invention can be used in combination as much as possible.

  In the present invention, when the internal combustion engine is cold-started, the air-fuel ratio sensor is heated at an optimal timing according to the attitude of the vehicle, so that the air-fuel ratio sensor is prevented from being damaged by water and the exhaust emission is purified. It is possible to achieve both an early improvement in rate.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  First, the configuration for suppressing water exposure to the air-fuel ratio sensor in this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 shows an internal combustion engine 1 and an exhaust system in the present embodiment. Four branch pipes of the exhaust manifold 2 are connected to four exhaust ports of the internal combustion engine 1 that is a four-cylinder internal combustion engine. In the exhaust system in this embodiment, in the exhaust manifold 2, two of the four branch pipes connected to the exhaust port are joined together, and the two branch pipes that have joined together are joined together. Alternatively, a long dual exhaust system in which exhaust gas is collected into one in the collecting portion 2a may be used.

  The exhaust manifold 2 is connected to the exhaust pipe 3. In the middle of the exhaust pipe 3, a flexible pipe 4 is provided for suppressing shaking and vibration of the internal combustion engine 1. Here, the upstream side of the flexible pipe 4 in the exhaust pipe 3 is an upstream exhaust pipe 3a, and the downstream side is a downstream exhaust pipe 3b. An exhaust purification catalyst 5 is provided in the downstream exhaust pipe 3b.

Here, the downstream exhaust pipe 3b is disposed substantially parallel to the floor surface of the vehicle, and is disposed so as to be substantially horizontal when the vehicle is in a horizontal state. The exhaust manifold 2 and the downstream exhaust pipe 3b are provided with an air-fuel ratio sensor 6 and a sub O ₂ sensor 7 for controlling the air-fuel ratio of the exhaust from the internal combustion engine 1 by feedback control. The air-fuel ratio sensor 6 and sub-O ₂ sensor 7 include an electric heater that raises the temperature of a sensor element (not shown) to an activation temperature and enables the air-fuel ratio sensor 6 and sub-O ₂ sensor 7 to detect the air-fuel ratio. 6a and 7a are provided. The sub O ₂ sensor 7 corresponds to an air-fuel ratio sensor in this embodiment. The electric heater 7a corresponds to a heating means in this embodiment.

In the present embodiment, a vehicle attitude sensor 10 is provided. A schematic configuration of the vehicle attitude sensor 10 is shown in FIG. The vehicle attitude sensor 10 includes a rotating body 10 that rotates constantly.
a is provided. Then, the tilt angle of the vehicle is measured with respect to two directions by the two sensor elements 10b and 10c by utilizing the property that the rotating body 10a always keeps the rotation axis in a constant direction with respect to the space unless an external force is applied. Make it possible. This vehicle attitude sensor 10 corresponds to an inclination detecting means in this embodiment.

The internal combustion engine 1 includes an electronic control unit (ECU: Electronic Control) for engine control.
Unit) 20 is attached. The ECU 20 includes a CPU, a ROM, a RAM, and the like that are connected to each other by a bidirectional bus. Various sensors including the vehicle attitude sensor 10, the air-fuel ratio sensor 6, and the sub O ₂ sensor 7 are connected via electric wiring. Connected.

  Also, the ECU 20 is connected to functional parts such as a fuel injection valve (not shown) in the internal combustion engine 1 through electric wiring, and the ECU 20 can control various functional parts using output signal values of various sensors as parameters. ing.

Incidentally, in the exhaust system 3, when the condensed water had accumulated on the upstream side of the sub-O ₂ sensor 7, the condensed water at the time and racing start of the internal combustion engine 1 according to the sub-O ₂ sensor 7, the sub-O ₂ sensor 7 could be damaged by temperature shock. On the other hand, there is a case in which the start of energization of the sub O ₂ sensor 7 to the electric heater 7a is delayed until the temperature of the exhaust pipe 3 rises and the condensed water is removed from the start of the cold start.

  Here, the amount of condensed water accumulated in the exhaust pipe 3 at the time of cold start is related to the forward tilt angle of the vehicle while the vehicle was stopped before starting. That is, for example, when the vehicle is parked in a backward leaning posture, the condensed water is likely to be discharged from the exhaust port of the exhaust pipe 3 to the outside of the vehicle. On the other hand, as shown in FIG. 3, when the vehicle is parked in a forward leaning position before starting, the condensed water tends to flow forward, so that a large amount of condensed water remains in the exhaust pipe 3. There is a high possibility of being.

In contrast to this tendency, in this embodiment, the delay time for delaying the start of heating of the sub O ₂ sensor 7 is changed depending on the forward tilt angle of the vehicle.

FIG. 4 shows a sub O ₂ sensor heating control routine in this embodiment. This routine is E
This program is stored in the ROM of the CU 20 and is executed by the ECU 20 every predetermined period while the vehicle is powered on.

  In S101 in this routine, it is determined whether or not the internal combustion engine 1 has been started. Specifically, the determination may be made by detecting a supply current to a starter motor or a spark plug (not shown). If it is determined in S101 that the internal combustion engine 1 has not been started, this routine is temporarily terminated. On the other hand, if it is determined that the internal combustion engine 1 has been started, the process proceeds to S102.

  In S102, it is determined whether the water temperature of the internal combustion engine 1 is equal to or lower than a predetermined value. Specifically, it is determined by inputting an output signal of a coolant temperature sensor (not shown) to the ECU 20. Here, if it is determined that the water temperature of the internal combustion engine 1 is higher than the predetermined value, it can be determined that the current start is not a cold start, and thus the present routine is terminated. On the other hand, when it is determined that the water temperature of the internal combustion engine 1 is equal to or lower than the predetermined value, the process proceeds to S103. Here, when the cooling water temperature of the internal combustion engine 1 is higher than the predetermined value, there is a possibility that the temperatures of the internal combustion engine 1 and the exhaust pipe 3 are already high, and condensed water is accumulated in the exhaust pipe 3. The cooling water temperature is considered to be extremely low, and may be obtained experimentally in advance.

  In S103, the forward lean angle of the vehicle is detected. Specifically, the output signal of the vehicle attitude sensor 10 is read into the ECU 20.

In S104, a delay time Δt for delaying the energization start time to the electric heater 7a for heating the sub O ₂ sensor 7 is derived. The delay time Δt is obtained by experimentally mapping the relationship between the inclination angle of the vehicle and the delay time Δt for suppressing the condensate water exposure of the sub O ₂ sensor 7. A delay time Δt corresponding to the detected forward tilt angle is read out.

  FIG. 5 shows the relationship between the forward tilt angle of the vehicle and the delay time Δt in this case. Here, when the forward tilt angle of the vehicle is equal to or greater than the condensed water generation angle θ1, the delay time Δt is set to be larger as the forward tilt angle increases. When the forward tilt angle of the vehicle is smaller than the condensed water generation angle θ1, the delay time Δt is set to zero.

  Here, the condensed water generation angle θ1 is a state in which condensed water can be accumulated in the exhaust pipe 3 when the forward tilt angle of the vehicle is greater than this, and the condensed water enters the exhaust pipe 3 as the forward tilt angle becomes larger than this angle. It is a forward tilt angle that makes it easy to accumulate, and may be obtained experimentally in advance. Although depending on the configuration of the vehicle, the condensed water generation angle θ1 may be set to 0 degrees, for example. When the process of S104 ends, the process proceeds to S105.

In S105, the electric heater 7a is energized based on the delay time Δt derived in S104, and the temperature rise control of the O ₂ sensor 7 is performed.

  As described above, in this embodiment, when the forward tilt angle of the vehicle is smaller than the condensed water generation angle θ1, the delay time Δt for energizing the electric heater 7a is set to zero. In addition, when the forward tilt angle is equal to or greater than the condensed water generation angle θ1, the delay time Δt is increased as the forward tilt angle of the vehicle is further increased.

By doing so, the delay time is set to zero in the forward tilt angle range where the condensed water does not accumulate in the exhaust pipe 3, so that the sub-O ₂ sensor 7 can be detected as early as possible. It is possible to improve the purification rate of exhaust emission immediately after starting.

Further, when the forward tilt angle of the vehicle is within an angle range in which condensed water can be collected in the exhaust pipe 3, the delay time Δt becomes longer as the forward tilt angle becomes larger. The delay time Δt can be set. As a result, it is possible to achieve both improvement in the purification rate of exhaust emission immediately after start-up and suppression of breakage of the sub O ₂ sensor 7 due to water. Here, the ECU 20 that executes the sub O ₂ sensor heating control routine corresponds to the temperature raising time changing means in the present embodiment.

  In the above embodiment, when the forward tilt angle of the vehicle is equal to or greater than the condensed water generation angle θ1, the delay time Δt is increased as the forward tilt angle increases. On the other hand, when the forward tilt angle of the vehicle is equal to or greater than the condensed water generation angle θ1, the delay time Δt may be set uniformly as shown in FIG. Then, by simpler control, when the forward tilt angle of the vehicle is an angle range in which condensed water does not collect, the delay time Δt is set to zero, and only in an angle range in which condensed water can be collected, the electric heater 7a is supplied to the electric heater 7a. A delay in starting energization can be executed.

Further, even when the vehicle is parked in a backward tilted state, if there is a possibility that condensed water is generated due to the structure of the vehicle, the condensed water generation angle is not θ1, but the angle θ2 on the rearward tilt side, For example, it may be −10 degrees. By doing so, it is possible to more reliably prevent the sub O ₂ sensor 7 from being damaged due to water. An example of the relationship between the forward tilt angle of the vehicle and the delay time Δt in this case is shown in FIG.

  In addition, even when the vehicle is parked in a backward tilted state, if there is a possibility that condensed water may be generated due to the structure of the vehicle, the forward tilt angle of the vehicle is smaller than the condensed water generation angle θ1. Alternatively, a slight delay time may be provided for energization of the electric heater 7a. An example of the relationship between the forward tilt angle of the vehicle and the delay time Δt in this case is shown in FIG.

In the above embodiments, the sub-O ₂ sub O ₂ sensor 7 by delaying the energization start timing for the electric heater 7a of the sensor 7 is capable of detecting the air-fuel ratio (element temperature of the sub-O ₂ sensor 7 is activated The timing at which the sub O ₂ sensor 7 can detect the air-fuel ratio by reducing the temperature gradient when heating the sub O ₂ sensor 7 (the element temperature of the sub O ₂ sensor 7) is delayed. May be delayed).

That is, as shown in FIG. 9, when the forward tilt angle of the vehicle is smaller than the condensed water generation angle θ1, the sub-O ₂ sensor 7 is heated to maximize the supply current to the electric heater 7a. ₂ The temperature gradient of the sensor 7 is the maximum. When the forward tilt angle of the vehicle is equal to or greater than θ1, the current value supplied to the electric heater 7a is decreased as the forward tilt angle becomes larger than that, and the temperature gradient of the sub O ₂ sensor 7 is gradually decreased. May be.

The control when the temperature gradient of the sub O ₂ sensor 7 is changed according to the forward tilt angle of the vehicle as shown in FIG. 9 will be further described. In this control, when the forward tilt angle of the vehicle is equal to or greater than the condensed water generation angle θ1, the temperature gradient of the sub O ₂ sensor 7 is reduced.
The temperature gradient of the sub O ₂ sensor 7 may be returned to the maximum when the cooling water temperature rises to a temperature at which condensed water is not generated. That way, when the risk of the water of condensation of the sub O ₂ sensor 7 is used up, the temperature of the sub-O ₂ sensor 7 is raised to a certain extent, then quickly sub O ₂ sensor 7 The air-fuel ratio can be detected (the element temperature of the sub O ₂ sensor 7 can be quickly raised to the activation temperature.) In the above, the condensed water generation angles θ1 and θ2 are set in this embodiment. In the example, it corresponds to a predetermined angle.

  Next, a second embodiment of the present invention will be described. In the present embodiment, the configuration and control of the exhaust system that more reliably suppress the generation of condensed water in the exhaust pipe will be described.

  FIG. 10 illustrates an internal combustion engine and an exhaust system in the present embodiment. The same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and description thereof is omitted. In addition, the display of ECU20 is abbreviate | omitted in FIG.

  In this embodiment, in addition to the exhaust purification catalyst 25, the exhaust pipe 13 is provided with a pre-catalyst 15 for the purpose of accelerating the temperature rise of the exhaust gas at the time of cold start or the like. The pre-catalyst 15 is provided so as not to protrude downward from the vehicle with respect to the exhaust pipe 13. A flexible pipe 14 is provided between the exhaust purification catalyst 25 and the front catalyst 15. The upstream exhaust pipe 13a is the exhaust pipe upstream of the pre-catalyst 15, the intermediate exhaust pipe 13b is the exhaust pipe between the pre-catalyst 15 and the flexible pipe 14, and the downstream exhaust pipe 13c is the downstream exhaust pipe of the flexible pipe 14. And

In the present embodiment, the exhaust pipe 13 is inclined at an inclination angle α on the upper side of the vehicle from the middle of the midstream exhaust pipe 13b. Then, the sub O ₂ sensor 17 and the electric heater 17a are disposed on the inclined portion.
Is provided. Here, the end of the inclined portion in the middle of the midstream exhaust pipe 13b corresponds to a predetermined location in the present embodiment. The inclined portion corresponds to the inclined portion in this embodiment.

According to this configuration, the sub O ₂ sensor 17 is provided in the middle-stream exhaust pipe 13b at a portion inclined to the upper side of the vehicle, so that condensed water is extremely difficult to collect on the upstream side of the sub O ₂ sensor 17. be able to. Thus, it is possible to suppress the water sub-O ₂ sensor 17 at the time of cold start.

Further, in the present embodiment, as described above, the pre-catalyst 15 is configured not to protrude below the vehicle with respect to the exhaust pipe 13, so that condensed water accumulates below the pre-catalyst 15. Can be suppressed. Further, in general, condensed water tends to accumulate in the middle of the flexible pipe 14 or in a joint portion between the flexible pipe 14 and the midstream exhaust pipe 13b or the downstream exhaust pipe 13c. In this embodiment, the sub O ₂ sensor 17 Is disposed on the upstream side of the flexible pipe 14, even if condensed water accumulates in the flexible pipe 14, it is possible to prevent the sub O ₂ sensor 17 from getting wet.

Next, the sub O ₂ sensor heating control routine in the present embodiment will be described. The difference between the sub O ₂ sensor heating control routine in the present embodiment and that described in Embodiment 1 is that the map from which the delay time Δt is read out in the processing of S104. In the first embodiment, the condensed water generation angle θ1 on the map is set to 0 degree, but in the present embodiment, the condensed water generation angle θ1 is set to α. In this way, heating of the sub O ₂ sensor 17 can be delayed when the inclined portion of the exhaust pipe 13 is tilted forward from the horizontal.

Therefore, the sub-O ₂ sensor 17 provided in the inclined portion, it is possible to delay the heating of sub-O ₂ sensor 17 only in a state where there is a risk of the water condensate at the time of cold start. As a result, when there is no possibility that the sub O ₂ sensor 17 is exposed to condensed water, the heating of the sub O ₂ sensor 17 is not delayed, and the purification rate of exhaust emission immediately after startup can be improved. it can.

1 is a diagram showing a schematic configuration of an internal combustion engine and an exhaust system according to Embodiment 1 of the present invention. It is a figure which shows schematic structure of the vehicle attitude | position sensor which concerns on the Example of this invention. It is a figure for demonstrating the forward leaning state of the vehicle which concerns on the Example of this invention. It is a flowchart showing a sub-O ₂ sensor heating control routine according to the first embodiment of the present invention. It is a graph showing the relationship between the delay time in the heating of the anteversion angle and the sub-O ₂ sensor for a vehicle according to a first embodiment of the present invention. It is a graph showing a second example of the relationship between the delay time in the heating of the anteversion angle and the sub-O ₂ sensor for a vehicle according to a first embodiment of the present invention. It is a graph showing a third example of the relationship between the delay time in the heating of the anteversion angle and the sub-O ₂ sensor for a vehicle according to a first embodiment of the present invention. It is a graph showing a fourth example of the relationship between the delay time in the heating of the anteversion angle and the sub-O ₂ sensor for a vehicle according to a first embodiment of the present invention. Is a graph showing the relationship between the temperature gradient (the current supplied to the heater) in the heating of the anteversion angle and the sub-O ₂ sensor for a vehicle according to a first embodiment of the present invention. It is a figure which shows schematic structure of the internal combustion engine and exhaust system which concern on Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Exhaust manifold 3, 13 ... Exhaust pipe 4, 14 ... Flexible pipe 5, 25 ... Exhaust gas purification device 6 ... Air-fuel ratio sensor 7, 17 ... Sub O ₂ sensor 10 ... vehicle attitude sensor 15 ... pre-catalyst 20 ... ECU

Claims (8)

An exhaust line through which the exhaust from the internal combustion engine passes;
An air-fuel ratio sensor disposed in the exhaust pipe and capable of acquiring the air-fuel ratio of the exhaust gas of the internal combustion engine in a state of being heated by heating;
Heating means for heating the air-fuel ratio sensor so that the air-fuel ratio can be acquired;
Inclination detecting means for detecting a forward inclination angle of a vehicle on which the internal combustion engine is mounted;
An exhaust system for an internal combustion engine comprising:
When the internal combustion engine is started, a temperature rise time change for changing the timing at which the air-fuel ratio sensor can acquire the air-fuel ratio by heating by the heating means, according to the forward lean angle of the vehicle detected by the inclination detecting means An exhaust system for an internal combustion engine, further comprising means. The temperature raising time changing means includes
The timing at which the air-fuel ratio sensor can acquire the air-fuel ratio is delayed by heating by the heating unit when the forward tilt angle of the vehicle detected by the tilt detection unit is greater than or equal to a predetermined angle. Item 6. An exhaust system for an internal combustion engine according to Item 1. The temperature raising time changing means includes
2. The timing at which the air-fuel ratio sensor can acquire the air-fuel ratio by heating by the heating unit is delayed as the forward tilt angle of the vehicle detected by the tilt detection unit increases. The internal combustion engine exhaust system. The temperature raising time changing means includes
The exhaust system for an internal combustion engine according to claim 2 or 3, wherein the timing at which the air-fuel ratio sensor can acquire the air-fuel ratio is delayed by delaying the heating start timing by the heating means. The temperature raising time changing means includes
4. The internal combustion engine according to claim 2, wherein a time at which the air-fuel ratio sensor can acquire the air-fuel ratio is delayed by decreasing a temperature rising rate of the air-fuel ratio sensor by the heating unit. Exhaust system.   6. The exhaust pipe according to claim 1, wherein the exhaust pipe has an inclined portion whose upstream side is inclined toward the vehicle upper side from a predetermined portion of the exhaust pipe, and the air-fuel ratio sensor is provided in the inclined portion. An exhaust system for an internal combustion engine according to any one of the above. The exhaust pipe has an inclined portion whose upstream side is inclined to the vehicle upper side from a predetermined portion of the exhaust pipe, and the air-fuel ratio sensor is provided in the inclined portion,
The temperature raising time changing means includes
When the forward inclination angle of the vehicle detected by the inclination detection means is equal to or greater than the inclination angle of the inclination portion, the time when the air-fuel ratio sensor can acquire the air-fuel ratio by heating by the heating means is delayed. The exhaust system for an internal combustion engine according to claim 1, wherein the exhaust system is an exhaust system. In the middle of the exhaust pipe, a flexible pipe that is formed of a flexible material and allows the exhaust pipe to bend,
The exhaust system for an internal combustion engine according to any one of claims 1 to 7, wherein the air-fuel ratio sensor is provided on the upstream side of the flexible pipe in the exhaust pipe.

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