Vehicle control apparatus and method

A vehicle control apparatus includes a controller. When predetermined conditions are satisfied, the controller executes a neutral control that forcibly places an automatic transmission in a substantially neutral state, the predetermined conditions including the shift position of the automatic transmission being in the drive position. When it is determined that the amount of exhaust matter accumulated in a catalyst provided in an exhaust system of a vehicle has exceeded a first reference value, the controller executes a catalyst heating control that increases the temperature of the catalyst so as to remove the exhaust matter accumulated in the catalyst. When it is determined during the catalyst heating control that the amount of the exhaust matter accumulated in the catalyst has exceeded a second reference value that is larger than the first reference value, the controller prohibits the execution of the neutral control.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2006-352581 filed on Dec. 27, 2006 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a vehicle control apparatus and method that executes a neutral control that forcibly places an automatic transmission of a vehicle in a substantially neutral state when the shift position of the automatic transmission is in the drive position and a catalyst heating control that increases the temperature of a catalyst provided in the exhaust system.

2. Description of the Related Art

An exhaust gas purification device for internal combustion engines, such as vehicle diesel engines, reduces the particulate matter (PM: Particulate Matter) discharged outside of the internal combustion engine by trapping the particulate matter contained in the exhaust gas discharged from the internal combustion engine using an exhaust gas purification catalyst provided in an exhaust passage. Normally, the function of such an exhaust gas purification catalyst deteriorates as the amount of the particulate matter accumulated in the exhaust gas purification catalyst increases. Therefore, in response to the amount of the accumulated particulate matter exceeding a reference amount, a catalyst heating control is executed to increase the temperature of the exhaust gas purification catalyst so that the accumulated particulate matter is combusted and thus removed.

Meanwhile, in vehicles having an automatic transmission, even when the shift position of the automatic transmission is in the drive position, a so-called neutral control, which is a control for forcibly placing the automatic transmission in a substantially neutral state, is executed in order to improve the fuel economy if predetermined conditions, such as the accelerator operation amount being equal to or smaller than a predetermined amount, are satisfied. However, because the load of the internal combustion engine decreases during the neutral control, if the duration of the neutral control is excessively long, it leads to a decrease in the exhaust gas temperature. As such, in vehicles in which the neutral control and the aforementioned catalyst heating control are both executed, if the neutral control is executed during the catalyst heating control, it may cause a decrease in the exhaust gas temperature and thus may make it difficult for the accumulated particulate matter to be combusted and thus removed, resulting in a delay in recovering the function of the exhaust gas purification catalyst.

In view of this, in the vehicle recited in Japanese Patent Application Publication No. JP-2004-44722 (JP-A-2004-44722), the execution of the neutral control is restricted during the catalyst heating control. As such, the foregoing decrease in the exhaust gas temperature is suppressed, whereby the temperature of the exhaust purification catalyst is reliably increased. Therefore, the accumulated particulate matter is efficiently combusted and thus removed, so that the function of the exhaust gas purification catalyst is recovered reliably.

However, in the vehicle recited in Japanese Patent Application Publication No. JP-2004-44722, the reduction of the fuel economy resulting from the restriction on the neutral control is not ignorable although it is true that such restriction on the neutral control helps recover the function of the exhaust gas purification catalyst reliably as mentioned above. Further, executing the neutral control unavoidably causes a delay in recovering the function of the exhaust gas purification catalyst although contributing to improving the fuel economy.

Such problems occur not only to vehicle control apparatuses adapted to execute a control for increasing the temperature of a catalyst to combust and thus remove particulate matter in the catalyst, but also to vehicle control apparatuses that execute a catalyst heating control for various other purposes, such as those adapted to execute a control for increasing the temperature of a catalyst to remove sulfur in the catalyst.

SUMMARY OF THE INVENTION

The invention provides a vehicle control apparatus and a vehicle control method that achieve both the improvement of the fuel economy and the recovery of the catalyst function effectively.

Aspects of the invention relates to a vehicle control apparatus and a vehicle control method including a controller, wherein: when predetermined conditions are satisfied, the controller executes a neutral control that forcibly places an automatic transmission in a substantially neutral state, the predetermined conditions including a shift position of the automatic transmission being in a drive position; and when it is determined that the amount of exhaust matter accumulated in a catalyst provided in an exhaust system of a vehicle has exceeded a first reference value, the controller executes a catalyst heating control that increases the temperature of the catalyst so as to remove the exhaust matter accumulated in the catalyst. According to the vehicle control apparatus and a vehicle control method described above, when it is determined during the catalyst heating control that the amount of the exhaust matter accumulated in the catalyst has exceeded a second reference value that is larger than the first reference value, the controller prohibits the execution of the neutral control.

According to the vehicle control apparatus and a vehicle control method described above, when the amount of exhaust matter accumulated in the catalyst has exceeded the second reference value, that is when the function of the catalyst has largely deteriorated and the necessity of executing the catalyst heating control is high, the execution of the neutral control is prohibited. This feature helps recover the function of the catalyst although the fuel economy improving effect by the neutral control lessens. On the other hand, when the amount of exhaust matter accumulated in the catalyst is equal to or smaller than the second reference value, that is when the necessity of executing the catalyst heating control is low, the neutral control is executed and therefore the fuel economy improves accordingly. According to the vehicle control apparatus and a vehicle control method descried above, as such the execution of the neutral control is prohibited in accordance with the degree of deterioration of the function of the catalyst during the catalyst heating control, so that the improvement of the fuel economy and the recovery of the catalyst function are both achieved effectively.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a vehicle control apparatus according to an example embodiment of the invention will be described with reference toFIG. 1andFIG. 2.

First, the overall configuration of the vehicle control apparatus of this example embodiment will be described with reference toFIG. 1. Referring toFIG. 1, in an engine10of the vehicle, air-fuel mixtures formed of the fuel injected from fuel injection valves12and the intake air supplied from an intake passage13are combusted in combustion chambers11, and the exhaust gas produced from the combustion is discharged to an exhaust passage14. The engine10has a crankshaft15that is the output shaft of the engine10. The crankshaft15is rotated by the energy produced from the combustion in each combustion chamber11. The engine10is connected to an automatic transmission20via the crankshaft15. The automatic transmission20changes the output torque of the engine10. More specifically, the automatic transmission20changes the torque transmitted from the crankshaft15to the output shaft of the automatic transmission20by applying and releasing various gears and clutches incorporated in the automatic transmission20.

A catalyst unit30is provided in the exhaust passage14. The catalyst unit30is constituted of a PM filter31that traps particulate matter (PM) in the exhaust gas flowing in the exhaust passage14and an oxygen catalyst32that is provided upstream of the PM filter31and removes hydrocarbon (HC) and carbon monoxide (CO), which are unburned components in the exhaust gas, by oxidizing them. The catalyst unit30reduces the amount of particulate matter discharged outside from the exhaust passage14by trapping the particulate matter using the PM filter31. In this catalyst unit30, the temperature of the exhaust gas is increased by the heat generated through the above-described oxidization at the oxygen catalyst32, whereby the particulate matter trapped in the PM filter31is combusted and thus removed using the heat generated.

In the vehicle, various sensors for detecting the state of the vehicle are provided. For example, an exhaust gas temperature sensor40that detects an upstream side exhaust gas temperature TOB representing the temperature of exhaust gas upstream of the PM filter31and an exhaust gas temperature sensor41that detects a downstream side exhaust gas temperature TOA representing the temperature of the exhaust gas downstream of the PM filter31are provided in the exhaust passage14of the engine10. Further, a coolant temperature sensor42that detects a coolant temperature THW representing the temperature of the coolant circulated in the engine10and a rotation speed sensor43that detects an engine speed NE representing the rotation speed of the crankshaft15are provided in the engine10. Further, in the vehicle in which the engine10is mounted, a vehicle speed sensor44that detects a vehicle speed SPD and a shift position sensor45that detects the position of the shift lever of the automatic transmission20and outputs a shift position signal SHIFT indicating the detected position of the shift lever are provided. The shift position of the shift lever is selected by the driver from among, basically, “P (Parking range)”, “N (Neutral range)”, “D (Drive range)”, and “R (Reverse range)”.

The signals output from these sensors40to45, etc. are input to an electronic control unit50. The electronic control unit50is a component that is provided with a processing unit, memories, etc. and governs the control of the engine10, the automatic transmission20, and other components and devices. The electronic control unit50determines various conditions related to the operation of the vehicle mainly based on the outputs of the foregoing sensors40to45and executes various controls for the vehicle based on the determined vehicle operation conditions. Note that the electronic control unit50may be regarded as one example of “controller” of the invention.

For example, the electronic control unit50sets a fuel injection amount Q based on the detected vehicle operation conditions and executes a fuel injection control in which the fuel injection pattern of each fuel injection valve12is changed based on the fuel injection amount Q. Further, the electronic control unit50executes a catalyst heating control when it is determined that the amount of the particulate matter accumulated in the catalyst unit30(i.e., the PM filter31) has exceeded a reference value PMt1that is a threshold for determining the degree of deterioration of the function of the catalyst unit30. In the catalyst heating control, the injection pattern of each fuel injection valve12is changed so as to increase the temperature of the catalyst unit30so that the accumulated particulate matter is combusted and thus removed. Further, when given conditions are satisfied while the shift position of the automatic transmission20is in the “D” position (i.e., the drive position), the electronic control unit50executes a neutral control in which some of the clutches in the automatic transmission20are released to forcibly place the automatic transmission20in a substantially neutral state. This neutral control is executed in order to suppress the waste of the output of the engine10at the automatic transmission20(in particular at the torque converter of the automatic transmission20).

With regard to the catalyst heating control and the neutral control described above, the vehicle control apparatus of the invention is adapted to prohibit the execution of the neutral control in accordance with the degree of deterioration of the function of the catalyst unit30during the catalyst heating control, so that the improvement of the fuel economy and the recovery of the catalyst function for trapping particulate matter are both achieved effectively.

FIG. 2illustrates the procedure of the neutral control of this example embodiment. Hereinafter, this procedure will be described in detail with reference toFIG. 2. Referring toFIG. 2, in the neutral control, it is first determined whether a neutral control execution flag is presently “ON” (step100). The neutral control execution flag is set to “ON” when, for example, the following AND conditions are all satisfied: (A1) the shift position of the automatic transmission20is in the drive position; (A2) the engine10has already been warmed up; (A3) the engine speed NE is stable; and (A4) the vehicle is at a standstill.

Whether these conditions (A1) to (A4) are satisfied is determined as follows. The condition (A1) is satisfied if the shift position signal SHIFT is indicating that the shift position of the automatic transmission20is in the “D” position. The condition (A2) is satisfied if the coolant temperature THW is higher than a reference value. The condition (A3) is satisfied if the deviation between the maximum value and the minimum value of the engine speed NE in a given time period is equal to or smaller than a reference value for determining fluctuation of the engine speed NE. The condition (A4) is satisfied if the vehicle speed SPD is zero.

If all of these conditions (A1) to (A4) are satisfied, the neutral control execution flag is set to “ON”. Note that other condition or conditions may be added to the conditions (A1) to (A4) or one or more of the conditions (A1) to (A4) may be omitted as needed.

When it is determined, in the manner described above, that the neutral control execution flag is presently “ON” (step100: YES), an accumulated particulate matter amount PMA representing the amount of the particulate matter accumulated in the catalyst unit30(that is, in the PM filter31) is calculated (step101). More specifically, the accumulated particulate matter amount PMA is calculated based on the engine speed NE, the fuel injection amount Q, and so on. The relation among the engine speed NE, the fuel injection amount Q, and the accumulated particulate matter amount PMA is stored in the memory of the electronic control unit50in the form of a function map, and the electronic control unit50calculates the accumulated particulate matter amount PMA by referring to this function map.

After the accumulated particulate matter amount PMA has been calculated in the manner described above, it is then determined whether a catalyst heating control execution flag is presently “ON” (step102). The catalyst heating control execution flag is set to “ON” if the accumulated particulate matter amount PMA calculated as described above is larger than a reference value PMt1. If the catalyst heating control execution flag is presently “ON”, the catalyst heating control is being executed.

Thus, when it is determined, in the manner described above, that the catalyst heating control execution flag is “ON” (step102: YES), that is when it is determined that the catalyst heating control is being executed, it is then determined whether the amount of particulate matter accumulated in the catalyst unit30has exceeded a reference value PMt2that is larger than the reference value PMt1. That is, at this time, it is determined whether the accumulated particulate matter amount PMA calculated as described above is larger than the reference value PMt2. Note that the reference value PMt2is a threshold for determining whether the function of the catalyst unit30has largely deteriorated and the necessity of executing the catalyst heating control is presently high.

If it is determined, in the manner described above, that the amount of particulate matter accumulated in the catalyst unit30has exceeded the reference value PMt2(step103: YES), that is if it is determined that the necessity of executing the catalyst heating control is high, the execution of the neutral control is then prohibited (step104). This prohibition of the neutral control helps recover the function of the catalyst unit30although the fuel economy improving effect by the neutral control lessens.

On the other hand, if it is determined in step103that the amount of particulate matter accumulated in the catalyst unit30is equal to or smaller than the reference value PMt2(step103: NO), that is if the necessity of executing the catalyst heating control is low, it is then determined whether the temperature of the catalyst unit30is equal to or higher than an activation temperature TC of the catalyst unit30(step105). More specifically, an estimated catalyst temperature TPC is calculated from the upstream side exhaust gas temperature TOB detected by the exhaust gas temperature sensor40and the downstream side exhaust gas temperature TOA detected by the exhaust gas temperature sensor41. Then, if the estimated catalyst temperature TPC is equal to or higher than the activation temperature TC of the catalyst unit30, it is determined that the temperature of the catalyst unit30is equal to or higher than the activation temperature TC.

The execution of the neutral control is prohibited (step104) also when it is determined that the temperature of the catalyst unit30is equal to or higher than the activation temperature TC (step105: YES). As such, even in the case where the accumulated particulate matter amount PMA is relatively small, that is the amount of the particulate matter accumulated in the catalyst unit30is relatively small and therefore the necessity of executing the catalyst heating control is low, if the temperature of the catalyst unit30is high, the execution of the neutral control is prohibited. This improves the efficiency of the catalyst heating control and thus helps recover the function of the catalyst unit30promptly. Further, because the activation temperature TC of the catalyst unit30is used as the reference value for the temperature of the catalyst unit30, the function of the catalyst unit30can be reliably recovered by executing the catalyst heating control.

On the other hand, if it is determined that the catalyst heating control execution flag is presently “OFF” (step102: NO), or if it is determined that the temperature of the catalyst unit30is lower than the activation temperature TC (step105: NO), the neutral control is executed (step106). More specifically, when the catalyst heating control is not being performed (step102: NO), the neutral control is executed to improve the fuel economy (step106). Further, when the necessity of executing the catalyst heating control is low while the catalyst heating control is being executed (step103: NO) and it is considered that it would take long time to heat the catalyst unit30up to the activation temperature TC through the catalyst heating control (step105: NO), the neutral control is executed to improve the fuel economy (step106).

Accordingly, the vehicle control apparatus of this example embodiment provides the following effects.

(Effect 1) The execution of the neutral control is prohibited when the amount of particulate matter accumulated in the catalyst unit30(that is, in the PM filter31) is larger than the reference value PMt2, that is when the function of the catalyst unit30has deteriorated significantly and thus the necessity of executing the catalyst heating control is high. This feature helps recover the function of the catalyst unit30although the fuel economy improving effect by the neutral control lessens. On the other hand, when the amount of particulate matter accumulated in the catalyst unit30is equal to or smaller than the reference value PMt2, that is when the necessity of executing the catalyst heating control is low, the neutral control is executed on the condition that the temperature of the catalyst unit30is not equal to or higher than the activation temperature30. This feature helps improve the fuel economy. In this way, by prohibiting the execution of the neutral control in accordance with the degree of deterioration of the function of the catalyst unit30during the catalyst heating control, the improvement of the fuel economy and the recovery of the function of the catalyst unit30can be both achieved effectively.

(Effect 2) Because the catalyst heating control is executed on the condition that the accumulated particulate matter amount PMA has exceeded the reference value PMt1, the execution of the catalyst heating control reduces the negative pressure of the exhaust gas in the exhaust passage14, which improves the fuel economy as well as recovering the function of the catalyst.

(Effect 3) Even in the case where it is determined that the accumulated particulate matter amount PMA, that is the amount of particulate matter accumulated in the catalyst unit30is equal to or smaller than the reference value PMt2, the execution of the neutral control is prohibited if the temperature of the catalyst unit30is equal to or higher than its activation temperature TC. Therefore, even in the case where the accumulated particulate matter amount PMA is relatively small, if the temperature of the catalyst unit30is high, the execution of the neutral control is prohibited and this improves the efficiency of the catalyst heating control and thus helps recover the function of the40promptly.

(Effect 4) Because the reference value for the temperature of the catalyst unit30is set substantially equal to the activation temperature TC of the catalyst unit30, the function of the catalyst unit30can be reliably recovered through the catalyst heating control.

The vehicle control apparatus of the foregoing example embodiment may be modified in various forms such as those described below.

(a) While the vehicle control apparatus of the foregoing example embodiment is adapted to execute the catalyst heating control for the purpose of combusting and thus removing the particulate matter accumulated in the catalyst unit30, it may alternatively be adapted to execute the catalyst heating control for the purpose of combusting and thus removing sulfur in the catalyst unit30(that is, the oxygen catalyst32), or for other similar purposes. In this case, for example, in order to recover the function of the catalyst unit30that has deteriorated due to sulfur poisoning, the vehicle control apparatus executes the catalyst heating control when it is determined that the amount of sulfur accumulated in the catalyst unit30has exceeded a reference value.

(b) While the vehicle control apparatus of the foregoing example embodiment is adapted to use the activation temperature TC of the catalyst unit30, which is a fixed value, as the reference value for the temperature of the catalyst unit30in step105, the reference value for the temperature of the catalyst unit30may alternatively be a value that changes in accordance with, for example, the accumulated particulate matter amount PMA calculated in step101.

In this case, for example, the reference value may be set using a function map, or the like, which is formulated such that the reference value decreases as the accumulated particulate matter amount PMA increases. Setting the reference value in this manner provides the following advantages. That is, when the amount of particulate matter accumulated in the catalyst unit30is large, the neutral control is more likely to be prohibited, and therefore the particulate matter accumulated in the catalyst unit30can be combusted and removed more efficiently. On the other hand, when the amount of particulate matter accumulated in the catalyst unit30is small, the neutral control is more likely to be executed, and therefore the fuel economy can be further improved.

(c) As described above, the vehicle control apparatus of the foregoing example embodiment is adapted to determine whether the temperature of the catalyst unit30is equal to or higher than the predetermined temperature after determining that the amount of particulate matter accumulated in the catalyst unit30is equal to or smaller than the reference value PMt2. Alternatively, the vehicle control apparatus may be adapted to execute the neutral control only on the condition that the amount of particulate matter accumulated in the catalyst unit30is equal to or smaller than the reference value PMt2.

(d) As described above, the vehicle control apparatus of the foregoing example embodiment is adapted to use, as the temperature of the catalyst unit30, the catalyst temperature TPC estimated from the upstream side exhaust gas temperature TOB and the downstream side exhaust gas temperature TOA. Alternatively, the vehicle control apparatus may be adapted to use, as the temperature of the catalyst unit30, a temperature directly detected from the catalyst unit30or a temperature estimated from the engine speed NE, the intake air amount in the intake passage13, the fuel injection amount Q, etc.

(e) As described above, the vehicle control apparatus of the foregoing example embodiment is adapted to calculate the accumulated particulate matter amount PMA based on the engine speed NE, the fuel injection Q, etc. Alternatively, the vehicle control apparatus may be adapted to calculate the accumulated particulate matter amount PMA based on the differential pressure between the exhaust gas on the upstream side of the catalyst unit30and the exhaust gas on the downstream side of the catalyst unit30.