JP5387553B2 - Vehicle control device - Google Patents

Description

  The present invention relates to a vehicle control device mounted on a vehicle having an idling stop function.

In a vehicle having an internal combustion engine, an exhaust gas purification catalyst is provided in an exhaust pipe of the internal combustion engine, and the exhaust gas is purified by reacting harmful substances in the exhaust gas and making them harmless.
In this case, the catalyst temperature is maintained at the activation temperature (for example, about 300 ° C. or higher), and the fuel injection amount in the internal combustion engine is controlled based on the air-fuel ratio detected by the air-fuel ratio sensor provided in the exhaust pipe. .
Further, a heater for heating the air-fuel ratio sensor to about 300 ° C. or more is provided so that the air-fuel ratio sensor can be activated immediately after the engine is started.
By the way, in recent years, in order to improve fuel consumption and reduce emissions, vehicles having an idling stop function for automatically stopping and restarting an internal combustion engine in accordance with driving conditions have been provided.
In such a vehicle, when the internal combustion engine is automatically stopped, the catalyst temperature gradually decreases. Therefore, if the stop period is long, the catalyst temperature may be lower than the activation temperature at the time of restart. If the catalyst temperature falls below the activation temperature, there is a concern that the exhaust gas is not sufficiently purified by the catalyst and is discharged into the atmosphere at the time of restart.
Therefore, when the internal combustion engine is automatically stopped, the internal combustion engine is automatically restarted when the catalyst temperature is equal to or lower than a predetermined restart determination temperature, so that the catalyst temperature does not fall below the activation temperature. Has been proposed (see Patent Document 1).

JP 2010-19178 A

By the way, when the temperature of the exhaust pipe decreases after the internal combustion engine is automatically stopped, the water vapor of the exhaust gas is condensed on the inner wall of the exhaust pipe, and water droplets adhere.
Since the air-fuel ratio sensor is heated to about 300 ° C. or more by a heater or exhaust gas, if water droplets adhering to the inner wall of the exhaust pipe adhere to the air-fuel ratio sensor, the air-fuel ratio sensor may be deteriorated or broken down due to heat shock. is there.
However, the above-described prior art is limited to suppressing a decrease in the catalyst temperature, and does not take into account avoiding deterioration or failure of the air-fuel ratio sensor.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a vehicle control device capable of improving the durability of an air-fuel ratio sensor without impairing the idling stop function.

  In order to achieve the above object, a vehicle control apparatus according to the present invention comprises an idling stop control means for automatically stopping the internal combustion engine when an automatic stop condition is satisfied during operation of the internal combustion engine of the vehicle, and an exhaust system of the internal combustion engine. The exhaust pipe wall temperature detecting means for detecting the exhaust pipe wall temperature of the inner wall of the exhaust pipe upstream from the location where the air-fuel ratio sensor is provided, and the internal combustion engine being automatically stopped by the idling stop control means Forcibly restarting means for forcibly restarting the engine when a condition that the exhaust pipe wall temperature detected by the exhaust pipe temperature detecting means falls below a predetermined threshold temperature is satisfied. It is characterized by.

  According to the present invention, when the exhaust pipe wall temperature falls below the threshold temperature, the exhaust pipe wall temperature is raised by forcibly restarting the internal combustion engine, thereby suppressing the attachment of water droplets to the exhaust pipe inner wall. can do. Therefore, it is possible to avoid deterioration or failure of the air-fuel ratio sensor due to being flooded, and it is possible to ensure a stop period of the internal combustion engine within a range in which adhesion of water droplets to the inner wall of the exhaust pipe can be suppressed. Therefore, it is possible to ensure the stop period of the internal combustion engine when idling is stopped while improving the durability of the air-fuel ratio sensor.

It is a block diagram which shows the structure of the vehicle control apparatus in this Embodiment. It is a flowchart which shows operation | movement of a vehicle control apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a vehicle on which a vehicle control device 10 of the present embodiment is mounted.
In the present embodiment, the vehicle includes an engine 12 as an internal combustion engine that is a driving source for traveling, an intake pipe 14, an exhaust pipe 16, a catalyst 18, an air flow sensor 20, an air-fuel ratio sensor 22, an accelerator. A sensor 24, a brake sensor 26, a vehicle speed sensor 28, an outside air temperature sensor 30, and an ECU 32 are included.
Moreover, the vehicle control apparatus 10 is comprised including ECU32.

  The engine 12 is started and stopped by the ECU 32, and the fuel injection timing and the injection amount are controlled. The engine 12 may be a diesel engine or a gasoline engine.

The intake pipe 14 introduces air into the engine 12.
The exhaust pipe 16 guides exhaust generated by the combustion of fuel in the engine 12 to the outside of the vehicle and discharges it.

  The air flow sensor 20 is provided in the intake pipe 14 and detects the intake flow rate Gin of the engine 12 and supplies the detection signal to the ECU 32.

The catalyst 18 is provided in the exhaust pipe 16 and purifies exhaust exhausted from the engine 12.
As the catalyst 18, various conventionally known catalysts 18 such as a three-way catalyst, an oxidation catalyst, and a NOx storage catalyst can be used, and any combination of two or more catalysts 18 is optional.
The catalyst 18 is heated above the activation temperature by the ECU 32 controlling the fuel injection amount in the engine 12 based on the air-fuel ratio detected by the air-fuel ratio sensor 22 and controlling the exhaust temperature of the exhaust gas flowing through the catalyst 18. The exhaust gas is purified by reacting harmful substances in the exhaust gas and making them harmless.

The air-fuel ratio sensor 22 is provided at the location of the exhaust pipe 16 upstream of the location where the catalyst 18 is provided, in other words, at the location of the exhaust pipe 16 between the engine 12 and the catalyst 18. The air-fuel ratio is detected, and the detection result is supplied to the ECU 32.
More specifically, the air-fuel ratio sensor 22 includes a sensor element configured using a ceramic material and a heater that heats the sensor element.
A plurality of air-fuel ratio sensors 22 may be provided, and the air-fuel ratio sensor 22 may be attached at any arbitrary position such as upstream or downstream of the catalyst 18 or between the catalysts.
The heater is connected to a heater control circuit 34 that controls energization of the heater.
The heater control circuit 34 controls energization of the heater so as to activate the sensor element at an early stage by heating the sensor element to about 300 ° C. or more immediately after the engine 12 is started based on the control of the ECU 32.
Since the sensor element is configured using a ceramic material, there is a risk of damage or failure due to heat shock if water droplets adhere to the sensor element while being heated to a high temperature of about 300 ° C. or higher.

The accelerator sensor 24 detects whether the accelerator pedal has been operated (depressed) or has been canceled (depressed), and supplies a detection signal to the ECU 32.
The brake sensor 26 detects whether the brake pedal has been operated (depressed) or has been released (depressed), and supplies the detection signal to the ECU 32.
The vehicle speed sensor 28 constitutes vehicle speed detection means, detects the vehicle speed V, and supplies the detection signal to the ECU 32.
The outside air temperature sensor 30 constitutes outside air temperature detection means, detects an outside air temperature To outside the vehicle, and supplies a detection signal to the ECU 32.

The ECU 32 includes a CPU, a ROM that stores and stores a control program, a RAM as an operation area of the control program, an interface unit that interfaces with peripheral circuits and the like.
The ECU 32 functions as an idling stop control means 36, an exhaust pipe wall temperature detection means 38, and a forced restart means 40 when the CPU executes the control program.

The idling stop control means 36 automatically stops and restarts the engine 12 according to the driving situation of the vehicle.
Specifically, the engine 12 is automatically stopped when the automatic stop condition is satisfied, and the engine 12 is restarted when the restart condition is satisfied.
The automatic stop condition is, for example, that the vehicle speed V detected by the vehicle speed sensor 28 is zero, and that the brake sensor 26 detects that the brake pedal is being operated.
The restart condition is, for example, that the brake sensor 26 detects that the brake pedal operation has been released, or the accelerator sensor 24 detects that the accelerator pedal operation is being performed.

The exhaust pipe wall temperature detection means 38 detects the exhaust pipe wall temperature Te on the inner wall of the exhaust pipe 16 upstream from the location where the air-fuel ratio sensor 22 is provided.
In the present embodiment, the exhaust pipe wall temperature detecting means 38 includes a stop timer 38A and an estimated map 38B.
The stop timer 38A detects a stop period Δts during which the engine 12 is stopped when the engine 12 is automatically stopped by the idling stop control means 36.
The estimated map 38B shows the exhaust pipe wall temperature Te (init) when the automatic stop condition of the engine 12 is satisfied, the engine stop period Δts, the outside air temperature To, and the current exhaust pipe wall temperature Te (real). It represents a relationship. In this embodiment, the exhaust pipe wall temperature Te is calculated by making various corrections based on the exhaust flow rate Gout. However, the exhaust flow rate Gout is assumed to be equal to the intake flow rate Gin detected by the air flow sensor 20, and therefore The intake flow rate Gin is treated as the exhaust flow rate Gout.
The estimated map 38B includes, for example, the exhaust pipe wall temperature Te (init) when the automatic stop condition of the engine 12 is satisfied, the engine 12 stop period Δts, the outside air temperature To, and the exhaust pipe wall temperature Te (real). It is comprised based on the actual measurement value.
The exhaust pipe wall temperature detecting means 38 is detected by the exhaust pipe wall temperature Te (init) when the automatic stop condition of the engine 12 is established, the stop period Δts detected by the stop timer 38A, and the outside air temperature sensor 30. The exhaust pipe wall temperature Te (real) is detected by estimating the exhaust pipe wall temperature Te (real) from the estimation map 38B based on the outside air temperature To.
In other words, the exhaust pipe wall temperature detecting means 38 uses the value of the exhaust pipe wall temperature Te (init) of the engine 12 when the automatic stop condition is satisfied as a reference value, and according to the stop period Δts of the engine 12 from this reference value. The exhaust pipe wall temperature Te (real) is detected by subtracting the obtained value.
A technique for estimating the exhaust pipe wall temperature Te based on the exhaust flow rate Gout is disclosed in Japanese Patent No. 4464613, and the exhaust pipe wall temperature detecting means 38 can be realized by using such a technique. .
The exhaust pipe wall temperature detecting means 38 only needs to be able to detect the exhaust pipe wall temperature Te. A temperature sensor is provided in the exhaust pipe 16 as the exhaust pipe wall temperature detecting means 38, and the ECU 32 detects a detection signal from the temperature sensor. Thus, the exhaust pipe wall temperature Te may be obtained.

In the forced restart means 40, the exhaust pipe wall temperature Te detected by the exhaust pipe wall temperature detection means 38 is lower than a predetermined threshold temperature TX in a state where the engine 12 is automatically stopped by the idling stop control means 36. When the above condition is satisfied, the engine 12 is forcibly restarted.
In the present embodiment, threshold temperature TX is set to a lower limit temperature at which moisture contained in the exhaust of engine 12 is condensed on the inner wall of exhaust pipe 16 and does not adhere as water droplets.
Here, the lower limit temperature is, for example, a temperature range of 20 ° C to 80 ° C.
Further, the threshold temperature TX is set in correlation with each condition exemplified below, which is a condition for generating water droplets in the exhaust pipe 16.
1) Dimensions of the exhaust pipe 16 from the engine 12 to the catalyst 18 2) Thickness of the exhaust pipe 16 3) Presence / absence of a supercharger provided in the exhaust pipe 16

Next, the operation of the vehicle control device 10 will be described.
FIG. 2 is a flowchart showing an operation in the case where the engine 12 of the traveling vehicle is automatically stopped by the idling stop function.
The idling stop control means 36 determines whether or not an automatic stop condition is satisfied (step S10). The idling stop control means 36 repeats step S10 if the determination result is negative, and automatically stops the engine 12 if the determination result is affirmative (step S12).
The idling stop control means 36 determines whether or not an automatic stop condition is satisfied (step S10). The idling stop control means 36 repeats step S10 if the determination result is negative, and automatically stops the engine 12 if the determination result is affirmative (step S12).
Simultaneously with the automatic stop of the engine 12, the exhaust pipe wall temperature detecting means 38 starts the stop timer 38A and measures the stop period Δts of the engine 12 (step S14).
The idling stop control means 36 determines whether or not a restart condition is satisfied (step S16). If this determination result is affirmative, the idling stop control means 36 restarts the engine 12 (step S26) and returns to step S10.
If this determination result is negative, the exhaust pipe wall temperature detecting means 38 detects the exhaust pipe wall temperature Te (init) when the automatic stop condition of the engine 12 is established, the engine 12 stop period Δts, and the outside air temperature sensor 30. The exhaust pipe wall temperature Te (real) is detected based on the outside air temperature To (step S18).
The exhaust pipe wall temperature detecting means 38 determines whether or not the detected exhaust pipe wall temperature Te is lower than the threshold temperature TX (step S20).
If this determination result is negative, the process returns to step S16, and if the determination result is affirmative, the forced restart means 40 forcibly restarts the engine 12 (step S22).
Therefore, when the exhaust pipe wall temperature Te falls below the threshold temperature TX, exhaust gas is discharged to the exhaust pipe 16 by forcibly restarting the engine 12, thereby increasing the exhaust pipe wall temperature Te. Exceeds the threshold temperature TX. In other words, it is possible to suppress the exhaust pipe wall temperature Te from decreasing to a temperature at which water droplets adhere.
Next, the exhaust pipe wall temperature detecting means 38 clears the stop timer 38A (step S24) and returns to step S10.

As described above, according to the present embodiment, when the exhaust pipe wall temperature Te falls below the threshold temperature TX, the exhaust pipe wall temperature Te is raised by forcibly restarting the engine 12. The water droplets can be prevented from adhering to the inner wall of the exhaust pipe 16. Therefore, it is possible to avoid deterioration or failure of the air-fuel ratio sensor 22 due to water. Further, the stop period of the engine 12 can be ensured within a range in which the adhesion of water droplets to the inner wall of the exhaust pipe 16 can be suppressed.
Therefore, it is possible to ensure the stop period of the engine 12 at the time of idling stop while improving the durability of the air-fuel ratio sensor 22, in other words, to improve the durability of the air-fuel ratio sensor without impairing the idling stop function. be able to.

  Further, in the present embodiment, the threshold temperature TX is set to the lower limit temperature at which the moisture contained in the exhaust of the engine 12 is condensed on the inner wall and does not adhere as water droplets, so that the water droplets adhere to the inner wall of the exhaust pipe 16. It is possible to ensure a long stoppage period of the engine 12 while avoiding it with certainty.

Further, in the present embodiment, the exhaust pipe wall temperature detecting means 38 uses the value of the exhaust pipe wall temperature Te when the automatic stop condition of the engine 12 is satisfied as a reference value, and the stop period Δts of the engine 12 from this reference value. The exhaust pipe wall temperature Te is detected by subtracting a value corresponding to the above.
Therefore, as compared with the case where the exhaust pipe wall temperature detecting means 38 is provided with a temperature sensor for detecting the exhaust pipe wall temperature Te in the exhaust pipe 16, the cost of components can be reduced.

Further, in the present embodiment, the exhaust pipe wall temperature detection means 38 estimates the exhaust pipe wall temperature Te based on the outside air temperature Tout in addition to the stop period Δts of the engine 12.
That is, the exhaust pipe wall temperature detecting means 38 uses the value of the exhaust pipe wall temperature Te (init) of the engine 12 when the automatic stop condition is satisfied as a reference value, and according to the stop period Δts of the engine 12 from this reference value. The exhaust pipe wall temperature Te (real) is detected by subtracting the value, and the degree of subtraction is increased as the outside air temperature Tout is lower.
Therefore, the exhaust pipe wall temperature Te can be accurately estimated in consideration of the influence of the outside air temperature, and adhesion of water droplets to the inner wall of the exhaust pipe 16 can be avoided more reliably.

In the present embodiment, the case where the vehicle uses the engine 12 as a driving power source has been described. However, the present invention can also be applied to a hybrid vehicle that uses both the engine 12 and a motor as a driving power source. It is.
In the case of a hybrid vehicle, for example, when the engine 12 that has been operating is automatically stopped during traveling by a motor, the traveling wind strikes the exhaust pipe 16, so the exhaust pipe wall temperature Te is affected by the traveling wind. Will fall sooner.
In this case, the exhaust pipe wall temperature detecting means 38 performs the estimation operation of the exhaust pipe wall temperature Te as in 1) and 2) below.
1) The exhaust pipe wall temperature detecting means 38 estimates the exhaust pipe wall temperature Te based on the vehicle speed V in addition to the stop period Δts of the engine 12. That is, the exhaust pipe wall temperature detecting means 38 detects the exhaust pipe wall temperature Te (real) by subtracting a value corresponding to the stop period Δts from the exhaust pipe wall temperature Te (init) serving as a reference value, and the vehicle speed V is large. As the degree of subtraction increases.
2) The exhaust pipe wall temperature Te is estimated based on both the outside air temperature Tout and the vehicle speed V in addition to the stop period Δts of the engine 12. That is, the exhaust pipe wall temperature detecting means 38 detects the exhaust pipe wall temperature Te (real) by subtracting a value corresponding to the stop period Δts from the exhaust pipe wall temperature Te (init) serving as a reference value, and the outside air temperature Tout is The degree of subtraction is increased as the vehicle speed V decreases and the vehicle speed V increases.
In this way, the exhaust pipe wall temperature Te can be accurately estimated in consideration of the influence of the traveling wind on the exhaust pipe wall temperature Te, and adhesion of water droplets to the inner wall of the exhaust pipe 16 can be avoided more reliably.
In the case of 1), the estimated map 38B represents the relationship among the stop period Δts of the engine 12, the vehicle speed V, and the exhaust pipe wall temperature Te. And the estimation map 38B is comprised based on the measured value of the stop period (DELTA) ts of the engine 12, the vehicle speed V, and the exhaust pipe wall temperature Te, for example.
In the case of 2), the estimated map 38B represents the relationship among the stop period Δts of the engine 12, the outside air temperature Tout, the vehicle speed V, and the exhaust pipe wall temperature Te. And the estimation map 38B is comprised based on the measured value of the stop period (DELTA) ts of the engine 12, the external temperature To, the vehicle speed V, and the exhaust pipe wall temperature Te, for example.

  DESCRIPTION OF SYMBOLS 10 ... Control apparatus for vehicles, 12 ... Engine, 14 ... Intake pipe, 16 ... Exhaust pipe, 18 ... Catalyst, 20 ... Air flow sensor, 22 ... Air-fuel ratio sensor, 24 ... Accelerator sensor, 26 …… Brake sensor, 28 …… Vehicle speed sensor, 30 …… Outside air temperature sensor, 32 …… ECU, 34 …… Heater control circuit, 36 …… Idling stop control means, 38 …… Exhaust pipe wall temperature detection means, 38A ... ... stop timer, 38B ... estimation map, 40 ... forced restart means.

Claims (5)

An idling stop control means for automatically stopping the internal combustion engine when an automatic stop condition is satisfied during operation of the internal combustion engine of the vehicle;
Exhaust pipe wall temperature detecting means for detecting the exhaust pipe wall temperature of the inner wall of the exhaust pipe upstream of the location where the air-fuel ratio sensor is provided in the exhaust system of the internal combustion engine;
When the condition that the exhaust pipe wall temperature detected by the exhaust pipe temperature detecting means falls below a predetermined threshold temperature while the internal combustion engine is automatically stopped by the idling stop control means is satisfied. A forced restart means for forcibly restarting the engine;
A vehicle control device comprising: The threshold temperature is a lower limit temperature at which moisture contained in the exhaust gas of the internal combustion engine is condensed on the inner wall and does not adhere as water droplets.
The vehicle control device according to claim 1. The exhaust pipe wall temperature detecting means uses a value of the exhaust pipe wall temperature of the internal combustion engine when the automatic stop condition is satisfied as a reference value, and according to a stop period in which the internal combustion engine is stopped from the reference value. Subtract the value to detect the exhaust pipe wall temperature,
The vehicle control device according to claim 1, wherein the control device is a vehicle control device. Vehicle speed detecting means for detecting the vehicle speed of the vehicle,
The exhaust pipe wall temperature detection means increases the degree of subtraction as the vehicle speed detected by the vehicle speed detection means increases.
The vehicle control device according to claim 3. An outside temperature detecting means for detecting outside temperature is provided,
The exhaust pipe wall temperature detecting means increases the degree of subtraction as the outside air temperature detected by the outside air temperature detecting means is lower.
5. The vehicle control device according to claim 3 or 4,

Images