JP2008286153A - Vehicle control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the possibility of causing such trouble that a sensor with a heater is cracked by condensed water in exhaust gas. <P>SOLUTION: This vehicle control device comprises the air-fuel ratio sensor 22 with the heater provided in an exhaust pipe 24, and an exhaust pipe heater 25 provided on the exhaust pipe 24 and located on the upstream side beyond the air-fuel ratio sensor 22. When the temperature of the exhaust pipe 24 is a predetermined reference value or lower before starting an engine 10, the exhaust pipe heater 25 is energized before the air-fuel ratio sensor heater 32 is energized. A control unit 11 determines a timing for energizing the air-fuel ratio sensor heater 32 depending on the temperature of the exhaust pipe after energizing the heater 25. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle control device in which a gas sensor with a heater is provided in an exhaust pipe of an engine.

  For example, a technique is known in which an air-fuel ratio sensor for detecting an oxygen concentration in exhaust gas is provided in an exhaust pipe of an engine (see, for example, Patent Document 1). The air-fuel ratio sensor has a built-in heater for heating the sensor to the activation temperature. The air-fuel ratio sensor has a characteristic of outputting a signal corresponding to the oxygen concentration when heated to the activation temperature.

JP 2000-249679 A

  For example, in winter when the outside air temperature is low, the temperature of the exhaust pipe of the engine is low. When the engine is started in such a case, the exhaust gas discharged from the engine is cooled when passing through the exhaust pipe. Then, water vapor in the exhaust gas is condensed and moisture is generated.

  When moisture in the exhaust gas comes into contact with the heated air-fuel ratio sensor, the sensor is cooled and a large temperature difference is generated in the sensor. As a result, there is a risk that the sensor may malfunction, for example, a large thermal stress is generated in the sensor and the sensor breaks.

  The present invention includes a sensor element for detecting a gas concentration in exhaust gas discharged from an engine, and a first heater for heating the sensor element, and a gas sensor provided in an exhaust pipe of the engine, And control means for determining the energization timing of the first heater according to the temperature of the exhaust pipe. According to this configuration, it is possible to reduce the occurrence of problems such as cracks in the gas sensor.

  In the vehicle control device of the present invention, it is preferable to include a second heater provided in the exhaust pipe and positioned on the upstream side of the gas sensor. According to this configuration, the exhaust pipe can be sufficiently warmed by the second heater, and the occurrence of problems such as cracks in the sensor can be reduced.

  In the vehicle control apparatus of the present invention, the control means applies the power to the second heater before energizing the first heater when the temperature of the exhaust pipe before starting the engine is not more than a predetermined reference value. It is preferable to energize. According to this configuration, the exhaust pipe can be warmed before the first heater is energized, and the occurrence of defects such as cracks in the sensor can be reduced.

  In the vehicle control apparatus according to the present invention, it is preferable that the control means determines the energization timing of the first heater in accordance with the exhaust pipe temperature after the second heater is energized. According to this configuration, it is possible to advance the energization timing of the first heater while reducing the occurrence of problems in the gas sensor.

  In the vehicle control apparatus according to the present invention, the control means is configured such that when the exhaust pipe temperature at the time of starting the engine is equal to or lower than a predetermined reference value, the first heater is compared to when the exhaust pipe temperature is higher than the predetermined reference value. It is preferable to delay the energization timing. According to such a configuration, the first heater can be energized at an appropriate time according to the exhaust pipe temperature.

  The vehicle control device according to the present invention is an electric vehicle including a battery that can be charged by being supplied with electric power from an external power source, and the battery is supplied with electric power from an external power source. Charge detecting means for detecting that the battery is being charged is further provided, and the control means detects that the battery is being charged by the charge detecting means and the temperature of the exhaust pipe before starting the engine is below a predetermined reference value. It is preferable to energize the second heater before energizing the first heater. According to such a configuration, the second heater can be energized using the power of the external power source. Thereby, it can suppress that the capacity | capacitance of a battery reduces.

  The present invention includes a sensor element for detecting a gas concentration in exhaust gas discharged from an engine, and a first heater for heating the sensor element, and a gas sensor provided in an exhaust pipe of the engine, And a second heater that is provided in the exhaust pipe and is located upstream of the gas sensor. According to this configuration, the exhaust pipe can be sufficiently warmed by the second heater. Thereby, it is possible to reduce the occurrence of defects such as cracks in the sensor.

  ADVANTAGE OF THE INVENTION According to this invention, it can reduce that a malfunction generate | occur | produces in the gas sensor with a heater.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[Constitution]
FIG. 1 is a cross-sectional view showing a schematic configuration of a vehicle engine according to the present embodiment. The engine 10 is controlled by the control unit 11. A piston 13 is provided inside the cylinder 12 of the engine 10 so as to be able to reciprocate up and down. The space above the piston 13 inside the cylinder 12 is a combustion chamber 14. An intake passage 15 and an exhaust passage 16 communicate with the combustion chamber 14. An intake valve 17 and an exhaust valve 18 for opening and closing are provided at communication portions between the intake passage 15 and the exhaust passage 16 and the combustion chamber 14, respectively.

  In the intake passage 15, a throttle valve 19, a surge tank 20, and a fuel injection valve 21 are provided. The throttle valve 19 is opened and closed in conjunction with the accelerator operation. A throttle position sensor (not shown) is provided on the valve body of the throttle valve 19, and the throttle position sensor is connected to the control unit 11. The surge tank 20 smoothes air pulsation. The fuel injection valve 21 is connected to the control unit 11 and injects fuel into the intake passage 15 in accordance with a control signal from the control unit 11.

  The exhaust passage 16 is provided with an air-fuel ratio sensor 22 for detecting the oxygen concentration in the exhaust gas and a catalyst 23 for reducing harmful components (CO, HC, NOx, etc.) in the exhaust gas. The air-fuel ratio sensor 22 is connected to the control unit 11. On the upstream side of the air-fuel ratio sensor 22, an exhaust pipe heater 25 for warming the exhaust pipe 24 and a temperature sensor 26 for detecting the temperature of the exhaust pipe 24 are provided. The exhaust pipe heater 25 is connected to the control unit 11 via an energization circuit 27. The energization circuit receives a control signal from the control unit 11 and energizes the exhaust pipe heater 25 with a current using the in-vehicle battery 28 as a power source. The temperature sensor 26 is connected to the control unit 11.

  The exhaust pipe heater 25 may be a sheet heater in which a heating resistance wire is provided in the seat, provided in the exhaust pipe 24, or a cord heater in which the heating resistance wire is covered with a resin material is provided in the exhaust pipe. 24 may be wound. The exhaust pipe heater 25 is preferably capable of warming the entire exhaust pipe upstream of the air-fuel ratio sensor 22. For example, a cord heater may be wound around the entire exhaust pipe 24 upstream of the air-fuel ratio sensor 22, or a cord heater may be wound around a part of the exhaust pipe 24. The temperature sensor 26 may be any sensor as long as it can detect the temperature of the exhaust pipe 24 upstream of the air-fuel ratio sensor 22. A plurality of temperature sensors 26 are provided in the exhaust pipe 24, and an average value of the temperatures detected by them. May be detected as the temperature of the exhaust pipe 24. Alternatively, only one temperature sensor 26 may be provided at a suitable position of the exhaust pipe 24 and the temperature detected thereby may be detected as the temperature of the exhaust pipe 24. Further, when the exhaust pipe 24 has a curved portion (elbow), it is preferable to provide a heater 25 at the curved portion. This is because moisture easily collects in the curved portion of the exhaust pipe 24.

  In the present embodiment, the temperature sensor 26 is directly provided in the exhaust pipe 24. However, the temperature of the exhaust pipe 24 may be calculated and detected without providing the sensor 26. For example, the temperature of the exhaust pipe 24 can be estimated based on the attachment position of the heater 25 to the exhaust pipe 24, the energization amount to the heater 25, the outside air temperature, the elapsed time after the engine is stopped, and the like. If the elapsed time after the engine is stopped is long, the exhaust pipe temperature may be regarded as the same as the engine coolant temperature. According to such an aspect, the temperature sensor 26 is not necessary, so that the part cost can be reduced and it is not necessary to secure the sensor mounting position in the exhaust pipe 24.

  Further, an ignition sensor 29, a seat sensor 30, and a door lock sensor 31 are further connected to the control unit 11. The control unit 11 detects the ignition switch position based on the output signal from the ignition sensor 29. The control unit 11 detects the driver's seating on the seat based on the output signal from the seat sensor 30. Further, the control unit 11 detects the door lock state based on the output signal from the door lock sensor 31. Note that these sensors 29 to 31 may be provided as necessary.

  FIG. 2 is a diagram showing a schematic configuration of the air-fuel ratio sensor 22. The air-fuel ratio sensor 22 has the same configuration as that of a conventionally known air-fuel ratio sensor. The air-fuel ratio sensor 22 includes a sensor element 33 inside the case 32 and an air-fuel ratio sensor heater 34 for heating the sensor element 33. The case 32 is provided with a plurality of through holes, and the exhaust gas flows into the case 32 through the through holes. The sensor element 33 is made of, for example, a zirconia material and is connected to the control unit 11. When the sensor element 33 is heated by the heater 34 and reaches the activation temperature, the sensor element 33 outputs a signal corresponding to the oxygen concentration. The control unit 11 detects the air / fuel ratio based on the output signal from the sensor element 33.

  The heater 34 is made of, for example, a nickel-chromium resistance heating wire, and is connected to the control unit 11 via an energization circuit 35. The energization circuit 35 receives a control signal from the control unit 11 and energizes the heater 34 with a current using the in-vehicle battery 28 as a power source. After the temperature of the sensor element 33 reaches the activation temperature, the control unit 11 controls energization to the heater 34 so as to maintain the temperature.

[Exhaust pipe preheat control]
Next, exhaust pipe preheat control executed by the control unit 11 will be described. FIG. 3 is a flowchart showing an example of the exhaust pipe preheat control executed by the control unit 11.

  In step 101, it is determined whether or not the engine 10 is before starting. When it is determined that the engine 10 is not started, the routine proceeds to step 102. Whether or not the engine has been started may be determined, for example, by detecting that the ignition position is the off position based on an output signal from the ignition sensor 29.

  In step 102, it is determined whether or not the exhaust pipe temperature is equal to or lower than a predetermined reference value. When it is determined that the exhaust pipe temperature is equal to or lower than the predetermined reference value, the process proceeds to the next step 103. In step 103, the exhaust pipe heater 25 is energized for a predetermined period. When the predetermined period elapses, the process returns to step 101 again. Thereafter, the above control is repeatedly performed until the engine 10 is started or the exhaust pipe temperature exceeds a predetermined reference value.

  According to the configuration of the present embodiment, the exhaust pipe 24 can be warmed before starting the engine. If it does so, the exhaust gas which passes the exhaust pipe 24 after engine startup will be cooled, and it can suppress that the water vapor | steam in exhaust gas condenses and a water | moisture content generate | occur | produces. As a result, it is possible to reduce the possibility of problems such as cracks occurring in the air-fuel ratio sensor 22.

  In step 101 according to the present embodiment, when it is detected that the engine is not started, the process proceeds to the next step 102. For example, the timing at which the engine 10 is started soon, that is, immediately before the engine is started. When it is determined that, it is possible to proceed to the next step 102. For example, when the door lock is released by the driver's key operation, the engine 10 is likely to be started after a while. Therefore, when it is determined that the door lock is released based on the output signal from the door lock sensor 31, the process may proceed to the next step 102. Further, when it is determined that the driver is seated on the seat based on the output signal from the seat sensor 30, the process may proceed to the next step 102. According to this aspect, since exhaust pipe preheating for a long time before the engine is started can be prevented, the remaining capacity of the in-vehicle battery can be sufficiently secured.

[Air heater control for air-fuel ratio sensor]
Next, air-fuel ratio sensor heater energization control executed by the control unit 11 will be described. FIG. 4 is a flowchart showing an example of air-fuel ratio sensor heater energization control executed by the control unit 11.

  In step 201, it is determined whether it is time to start the engine 10 or not. When it is determined that it is time to start the engine 10, the process proceeds to the next step 202. Here, whether or not it is the timing at which the engine 10 is started may be determined by detecting that the ignition position is the ON position based on an output signal from the ignition sensor 29.

  In step 202, the energization timing to the air-fuel ratio sensor heater 34 is determined. In the present embodiment, the control unit 11 determines the energization timing to the air-fuel ratio sensor heater 34 according to the temperature of the exhaust pipe 24 at the time of engine start.

  Here, the straight line A shown by the solid line in FIG. 5 represents the exhaust pipe temperature at the time of starting the engine and the time until the water vapor in the exhaust gas is condensed in the exhaust pipe 24 after the engine is started and no moisture is generated. It is a graph which shows the relationship. Further, a straight line B shown by a dotted line in FIG. 5 indicates the exhaust pipe temperature at the time of engine start and until the air-fuel ratio sensor 22 reaches the activation temperature when energization to the air-fuel ratio sensor heater 34 is started at the time of engine start. It is a graph which shows the relationship with time. The graph of FIG. 5 is obtained in advance by experiments or the like, and the data may be stored in the control unit 11 or may be stored in another device.

  In the present embodiment, the control unit 11 starts energization of the air-fuel ratio sensor heater 34 simultaneously with the engine start when the exhaust pipe temperature at the time of engine start is greater than a predetermined reference value. When the exhaust pipe temperature at the time of starting the engine is larger than a predetermined reference value, as shown in FIG. 5, the time from the start of the engine until the water vapor in the exhaust gas is condensed and no moisture is generated is empty at the time of starting the engine. It is shorter than the time until the air-fuel ratio sensor 22 reaches the activation temperature when energization of the heater 34 for the fuel ratio sensor is started. That is, when the air-fuel ratio sensor 22 that has started energizing the heater 34 at the same time as the engine start reaches the activation temperature, the exhaust pipe 24 is heated to a temperature at which water vapor in the exhaust gas has already condensed and no moisture is generated. ing. In this case, there is little possibility that the heated air-fuel ratio sensor 22 is cooled and a defect such as a crack occurs in the sensor 22, and the heater 34 can be energized simultaneously with the engine start.

  On the other hand, when the exhaust pipe temperature at the time of engine start is equal to or lower than a predetermined reference value, as shown in FIG. 5, the time from the start of the engine until the water vapor in the exhaust gas is condensed and no moisture is generated is Sometimes it takes longer than the time until the air-fuel ratio sensor 22 reaches the activation temperature when energization of the air-fuel ratio sensor heater 34 is started.

  In the present embodiment, the control unit 11 energizes the air-fuel ratio sensor heater 34 when the exhaust pipe temperature at the time of starting the engine is equal to or lower than a predetermined reference value compared to when the exhaust pipe temperature is higher than the predetermined reference value. The time is delayed. According to such a configuration, the air-fuel ratio sensor heater 34 can be energized at an appropriate time according to the exhaust pipe temperature, and the occurrence of problems such as cracks in the sensor 22 can be reduced.

  When the exhaust pipe temperature at engine start is t1 shown in FIG. 5, the control unit 11 delays the energization timing of the air-fuel ratio sensor heater 34 by at least Δt shown in FIG. 5 from the engine start. As shown in FIG. 5, Δt is a time t3 from when the engine is started to when water vapor in the exhaust gas is condensed and no moisture is generated when the exhaust pipe temperature at the time of engine start is t1, This represents the difference between the time t2 until the air-fuel ratio sensor 22 reaches the activation temperature when the energization of the air-fuel ratio sensor heater 34 is started at the time of engine startup when the exhaust pipe temperature at the time of engine startup is t1.

  The hatched area in FIG. 5 indicates the above-described Δt area. As shown in FIG. 5, the Δt increases as the exhaust pipe temperature at the time of starting the engine decreases. In the present embodiment, when the exhaust pipe temperature at the time of starting the engine is equal to or lower than a predetermined reference value, the control unit 11 sets the energization timing to the air-fuel ratio sensor heater 34 as the exhaust pipe temperature at the time of starting the engine is lower. It is greatly delayed from the start.

  As described above, the control unit 11 according to the present embodiment preheats the exhaust pipe 24 when the exhaust pipe temperature is equal to or lower than a predetermined reference value before starting the engine. In the present embodiment, the timing of energization of the air-fuel ratio sensor heater 32 can be determined according to the exhaust pipe temperature after exhaust pipe preheating. The exhaust pipe preheat can increase the exhaust pipe temperature at the start of the engine, so that Δt can be reduced. As a result, it is possible to shorten the energization timing of the heater 34 compared to the case where there is no exhaust pipe preheating, while reducing the occurrence of problems in the air-fuel ratio sensor 22. In the present embodiment, the exhaust pipe preheating is performed before the engine is started. However, the exhaust pipe preheating may be performed after the engine is started, or the preheat is started before the engine is started. An aspect in which preheating is continuously performed afterward may also be used. The control unit 11 may be configured to determine the energization timing to the air-fuel ratio sensor heater 34 in accordance with the exhaust pipe temperature at the time of starting the engine without preheating the exhaust pipe 24.

  Returning to FIG. 4, the description will be continued. When the energization timing for the air-fuel ratio sensor heater 34 is determined in step 202, the routine proceeds to step 203. In step 203, the heater 34 is energized at the energization time determined in step 202.

[Another embodiment]
As mentioned above, although the form for implementing this invention was demonstrated, this invention detects the battery which can be charged, for example by receiving the electric power supply from an external power supply, and the battery is charging. The present invention can also be applied to an electric vehicle including a charge detection unit. The charge detection unit may detect that the battery is being charged, for example, by detecting that a charging plug is connected to the battery. FIG. 6 is a flowchart showing an example of the exhaust pipe preheat control executed by the control unit 11 according to another embodiment.

  In step 301 of FIG. 6, it is determined whether or not the battery is being charged with power supplied from an external power source. If it is detected from the detection signal from the charge detection means that the charging plug is connected to the battery, and it is determined that the battery is being charged by receiving power from the external power supply, the process proceeds to step S302. The flow after step 302 is the same as the flow after step 101 in FIG.

  According to such a configuration, the exhaust pipe heater 34 can be energized using the power from the external power source. Thereby, it can suppress that the capacity | capacitance of a battery reduces. In such an electric vehicle, the control unit 11 can also perform the heater energization control for the air-fuel ratio sensor. The present invention is not limited to an air-fuel ratio sensor, and can be applied to various gas sensors with a heater provided in an exhaust pipe of an engine.

It is a schematic block diagram of the engine of the vehicle which concerns on this embodiment. It is a schematic block diagram of the air fuel ratio sensor which concerns on this embodiment. It is a flowchart explaining the exhaust pipe preheat control performed by the control unit which concerns on this embodiment. It is a flowchart explaining the air-fuel ratio sensor electricity supply control performed by the control unit which concerns on this embodiment. The relationship between the exhaust pipe temperature at the time of engine start and the time from when the engine starts until the water vapor in the exhaust gas condenses in the exhaust pipe and no moisture is generated, the exhaust pipe temperature at the time of engine start, and at the time of engine start It is a graph which shows the relationship with the time until an air fuel ratio sensor reaches activation temperature when energization to the heater for air fuel ratio sensors is started. It is a flowchart explaining the exhaust pipe preheat control performed by the control unit which concerns on another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine, 11 Control unit, 12 Cylinder, 13 Piston, 14 Combustion chamber, 15 Intake passage, 16 Exhaust passage, 17 Intake valve, 18 Exhaust valve, 19 Throttle valve, 20 Surge tank, 22 Fuel injection valve, 22 Air-fuel ratio sensor , 23 Catalyst, 24 Exhaust pipe, 25 Exhaust pipe heater, 26 Temperature sensor, 27 Energizing circuit, 2
8 Onboard battery, 29 Ignition sensor, 30 Seat sensor, 31 Door lock sensor, 32 Case, 33 Sensor element, 34 Air-fuel ratio sensor heater, 35
Energizing circuit.

Claims (7)

A sensor element for detecting a gas concentration in exhaust gas discharged from the engine; and a first heater for heating the sensor element; and a gas sensor provided in an exhaust pipe of the engine;
And a control means for determining a timing of energizing the first heater according to the temperature of the exhaust pipe. The vehicle control device according to claim 1,
A vehicle control device comprising a second heater provided in the exhaust pipe and located upstream of the gas sensor. The vehicle control device according to claim 2,
The control means energizes the second heater before energizing the first heater when the temperature of the exhaust pipe before starting the engine is equal to or lower than a predetermined reference value. A vehicle control device. The vehicle control device according to claim 3,
The vehicle control apparatus according to claim 1, wherein the control means determines the energization timing to the first heater in accordance with the exhaust pipe temperature after the second heater is energized. The vehicle control device according to claim 4,
The control means delays the energization timing of the first heater when the exhaust pipe temperature at the time of starting the engine is equal to or lower than a predetermined reference value compared to when the exhaust pipe temperature is higher than the predetermined reference value. A control apparatus for a vehicle. The vehicle control device according to any one of claims 2 to 5,
The vehicle is an electric vehicle including a battery that can be charged by receiving power from an external power source,
Further comprising charge detection means for detecting that the battery is being charged with power supplied from an external power source;
The control means energizes the first heater when the charge detection means detects that the battery is being charged and the temperature of the exhaust pipe before starting the engine is below a predetermined reference value. A control apparatus for a vehicle, wherein power is supplied to the second heater before performing the operation. A sensor element for detecting a gas concentration in exhaust gas discharged from the engine; and a first heater for heating the sensor element; and a gas sensor provided in an exhaust pipe of the engine;
A vehicle control device comprising: a second heater provided in the exhaust pipe and positioned upstream of the gas sensor.

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