CONTROLAPPARATUS AND METHOD FOR VEHICLE

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a control apparatus and a control method for a vehicle, and particularly to a control apparatus and a control method for a vehicle in which an exhaust filter is provided in an exhaust passage of an engine.

2. Description of the Related Art

[0002] Japanese Patent Publication No. 2003-222041 (JP-A-2003-222041) describes an exhaust purification device for an engine in which a filter is provided in the exhaust passage to trap particulates discharged from the engine. This exhaust purification device sets the fuel injection amount so as to provide additional engine torque to compensate for a decrease in the engine torque that is caused by an increase in the exhaust pressure resulting from accumulation of particulates at the filter.

[0003] According to this exhaust purification device, the engine torque characteristic obtained when a large amount of particulates are accumulated in the filter is made equal to the engine torque characteristic obtained when almost no particulates are accumulated in the filter. Thus, regardless of whether particulates are accumulated in the filter, desired engine torque can be obtained under the full load condition (See JP-A-2003-222041).

[0004] For appropriate shifting of an automatic transmission coupled with the output shaft of the engine, the engine and the automatic transmission need to cooperate with each other in various ways. In the case where the shift control of the automatic transmission is performed based on the target engine torque that is used in the control of the output torque of the engine, if there is a deviation between the target engine torque and the actual engine torque, the automatic transmission may fail to shift at an

appropriate timing, and therefore large shift shocks may be caused.

[0005] As described above, when particulates are accumulated in the filter provided in the exhaust passage of the engine, the actual engine torque becomes smaller than the target engine torque, creating a deviation between the target engine torque and the actual engine torque. Such a deviation between the target engine torque and the actual engine toque may cause large shift shocks as mentioned above.

[0006] According to the technology described in JP-A-2003-222041, the engine torque is corrected by producing additional engine toque in accordance with the accumulation state of particulates. However, such engine torque correction can not prevent a deviation between the target engine torque and the actual engine torque.

SUMMARY OF THE INVENTION

[0007] The invention provides a control apparatus and a control method for a vehicle, by which the vehicle can be appropriately controlled even when the amount of particulates accumulated in a filter provided in the exhaust passage of the engine has increased.

[0008] A first aspect of the invention relates to a control apparatus for a vehicle, including: torque calculating means for calculating a target engine torque that is used to control an output torque of an engine; controlling means for controlling a controlled component other than the engine based on the target engine torque; estimating means for estimating an accumulation state of particulates trapped by an exhaust filter that is provided in an exhaust passage of the engine; and correcting means for correcting the target engine torque used by the controlling means based on the accumulation state of particulates which has been estimated by the estimating means. [0009] According to the control apparatus described above, the target engine torque used by the controlling means is corrected so as to approach the actual engine torque that has decreased according to the accumulation state of particulates in the exhaust filter.

[0010] Therefore, a deviation between the target engine torque and the actual engine torque is reduced. As a result, the controllability of the controlled component in a state

where the amount of particulates accumulated in the exhaust filter has increased improves.

[0011] The correcting means may correct the target engine torque such that the target engine torque decreases as a state amount indicating the accumulation state of particulates increases.

[0012] Also, the correcting means may correct the target engine torque when a state amount indicating the accumulation state of particulates is equal to or larger than a reference amount.

[0013] According to these structures, the calculation for correcting the target engine torque is not performed when the amount of accumulated particulates is small. Therefore, the calculation load for the correction of the target engine torque can be reduced.

[0014] Further, the controlled component may include an automatic transmission. In this case, when a state amount indicating the accumulation state of particulates is equal to or larger than a reference amount, the controlling means may control the automatic transmission such that a shift characteristic of the automatic transmission becomes a high torque shift characteristic, as compared to when the state amount is smaller than the reference amount.

[0015] According to this structure, a decrease in the output torque of the engine resulting from an increase in the amount of accumulated particulates is compensated for by the high torque shift characteristic. Thus, it is possible to provide the acceleration feeling required by the driver even when the output torque of the engine has decreased due to an increase in the amount of accumulated particulates.

[0016] Further, the controlled component may include an automatic transmission that is coupled with an output shaft of the engine. This automatic transmission may include a constant-mesh shift mechanism and a clutch that is provided between the output shaft of the engine and the shift mechanism and is operable to allow and interrupt transmission of torque from the engine to the shift mechanism. In this case, the controlling means may control the clutch to allow or interrupt the torque transmission from the engine, based on

the target engine torque that has been corrected by the correcting means.

[0017] Further, the control apparatus may include pressure detecting means for detecting an exhaust gas pressure of the engine. In this case, the estimating means estimates the accumulation state of particulates based on the exhaust gas pressure detected by the pressure detecting means.

[0018] Further, the control apparatus may include pressure detecting means for detecting an amount of pressure loss caused by the exhaust filter. In this case, the estimating means estimates the accumulation state of particulates based on the pressure loss amount detected by the pressure detecting means. [0019] Another aspect of the invention relates to a method for controlling a vehicle, which includes: calculating a target engine torque that is used to control an output torque of an engine; estimating an accumulation state of particulates trapped by an exhaust filter that is provided in an exhaust passage of the engine; correcting the target engine torque based on the estimated accumulation state of particulates; and controlling a controlled component other than the engine based on the corrected target engine torque.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The foregoing and further objects, features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:

FIG 1 is a functional block diagram showing the main components of a vehicle incorporating a control apparatus according to an exemplary embodiment of the invention; FIG 2 is a chart illustrating how the engine torque and the engagement state of the clutch change in time;

FIG 3 is a chart illustrating the relation between the drive power and the vehicle speed;

FIG 4 is a chart indicating exemplary shift curves defining shift timings; and

FIG 5 is a flowchart showing a control routine that is executed by the powertrain manager shown in FIG 1.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS [0021] Hereinafter, an exemplary embodiment of the invention will be described with reference to the accompanying drawings. Note that like components and elements are denoted by link reference numerals in the drawings and their descriptions are not repeated.

[0022] FIG 1 is a functional block diagram showing the main components of a vehicle incorporating a control apparatus according to an exemplary embodiment of the invention. Referring to FIG 1, a vehicle 10 includes an engine 100, a fuel injection system 110, an exhaust pipe 120, a DPF (Diesel Particulate Filter) 130, a pressure sensor 140, and an ENG-ECU (Electronic Control Unit) 150. The vehicle 10 further includes an automatic transmission 200, a shift-select actuator 210, a clutch actuator 220, an MMT-ECU (Multi-mode Manual Transmission ECU) 230, and a powertrain manager 300.

[0023] The engine 100 is a compression-ignition type internal combustion engine, such as a diesel engine. The fuel injection system 110 includes fuel injection valves provided in the upper portions of the respective engine cylinders and a fuel pump that pumps fuel up from the fuel tank and supplies the fuel to the fuel injection valves. Note that the fuel injection valves and the fuel pump are not shown in the drawings. Then, the fuel injection system 110 injects the fuel into the respective engine cylinders at specific timings based on the fuel injection commands output from the ENG-ECU 150.

[0024] The DPF 130 is arranged in the exhaust pipe 120 and traps particulates discharged from the engine 100. The DPF 130 is a resistance against the flow of the exhaust gas that is discharged from the engine 100 to the outside of the vehicle through the exhaust pipe 120. Thus, as the amount of particulates accumulated in the DPF 130 increases, the exhaust gas pressure of the engine 100 increases. Such an increase in the exhaust gas pressure causes the amount of intake air supplied to the engine 100 to

decrease, which causes a decrease in the output toque of the engine 100. That is, even if the operation conditions of the engine 100 are unchanged, the output torque of the engine 100 decreases as the amount of particulates accumulated in the DPF 130 increases.

[0025] The pressure sensor 140 detects the exhaust gas pressure of the engine 100 and outputs signals P corresponding to the detected exhaust gas pressures to the

ENG-ECU 150. The pressure sensor 140 is used for estimation of the accumulation amount of particulates trapped by the DPF 130. The pressure sensor 140 may be adapted to detect the difference between the exhaust pressure at the inlet side of the DPF

130 and the exhaust pressure at the outlet side of the DPF 130, that is, the amount of pressure loss at the DPF 130.

[0026] The ENG-ECU 150 receives signals NE indicating the speed of the engine 100 and output from an engine speed sensor (not shown in the drawings), signals THR indicating the opening degree of the throttle valve and output from a throttle sensor (not shown in the drawings), and signals P output from the pressure sensor 140. The ENG-ECU 150 is connected to the powertrain manager 300 via a CAN (Controller Area Network) communication and sends the signals NE, THR, and P to the powertrain manager 300.

[0027] The ENG-ECU 150 obtains, from the powertrain manager 300, the target engine torque of the engine 100 that is calculated by the powertrain manager 300, and generates fuel injection commands in accordance with the obtained target engine torque and output them to the fuel injection system 110.

[0028] The automatic transmission 200 includes a constant-mesh geartrain and a clutch, which are not shown in the drawings. The input shaft of the clutch is coupled with the crankshaft of the engine 100 and the output shaft of the clutch is coupled with the input shaft of the geartrain.

[0029] The shift-select actuator 210 actuates the shift operation and the select operation of the automatic transmission 200 in accordance with the commands output from the MMT-ECU 230. The clutch actuator 220 engages and releases the clutch of the automatic transmission 200 in accordance with the commands output from the

MMT-ECU 230. Note that the shift-select actuator 210 and the clutch actuator 220 may be either electric actuators using a motor or hydraulic actuators.

[0030] The MMT-ECU 230 receives signals GP indicating the gear position from a gear position sensor (not shown in the drawings) and signals NI indicating the rotation speed of the input shaft of the automatic transmission 200 from an input shaft rotation speed sensor (not shown in the drawings). Also, the MMT-ECU 230 receives, from a brake lamp switch (not shown in the drawings), signals BP indicating the brake pedal being stepped down, and receives signals SP indicating the position of the shift lever from a shift lever position sensor (not shown in the drawings). [0031] The MMT-ECU 230 is connected to the powertrain manager 300 via the CAN communication and obtains, from the powertrain manager 300, a corrected engine torque that is set by correcting the target engine torque in accordance with the signals from the pressure sensor 140. Then, the MMT-ECU 230 controls the shifting of the automatic transmission 200 based on the received signals and the corrected engine torque obtained from the powertrain manager 300.

[0032] The powertrain manager 300 receives signals ACC indicating the operation amount of the accelerator pedal from an accelerator pedal position sensor (not shown in the drawings) and signals SPD indicating the vehicle speed from a vehicle speed sensor

(not shown in the drawings). Also, the powertrain manager 300 receives, via the CAN communication, the signals NE, THR from the ENG-ECU 150.

[0033] Then, using these signals, the powertrain manager 300 calculates a target engine torque of the engine 100 and transmits the calculated engine torque to the ENG-ECU 150 and to the MMT-ECU 230 via the CAN communication.

[0034] The powertrain manager 300 receives the signals P, which are detected by the pressure sensor 140, from the ENG-ECU 150 via the CAN communication and estimates the accumulation state of particulates in the DPF 130 based on the exhaust gas pressure of the engine 100 that is indicated by the signals P. More specifically, for example, the powertrain manager 300 has a map identifying a reference exhaust gas pressure that corresponds to the operation state of the engine 100 where the exhaust gas pressure is not

increased by the DPF 130, and the powertrain manager 300 estimates the amount of particulates accumulated in the DPF 130 to be larger as the increase rate (or increase amount) of the exhaust pressure indicated by the signals P from the pressure sensor 140 with respect to the reference exhaust gas pressure is greater. Alternatively, in the case where the signals P from the pressure sensor 140 are signals indicating the pressure loss at the DPF 130, the powertrain manager 300 may estimate the amount of accumulated particulates to be larger as the pressure loss is larger.

[0035] When the exhaust gas pressure of the engine 100 is equal to or higher than the reference exhaust gas pressure, the powertrain manager 300 corrects the target engine torque to be transmitted to the MMT-ECU 230 based on the accumulation state of particulates which has been estimated as descried above. At this time, more specifically, the power train manager 300 corrects the target engine torque such that the target engine torque decreases as the estimated amount of accumulated particulates is larger. Then, the powertrain manager 300 transmits the corrected target engine torque to the MMT-ECU 230 via the CAN communication.

[0036] Meanwhile, because the output torque of the engine 100 decreases as the amount of particulates accumulated in the DPF 130 increases as described above, in order to compensate for the decrease in the engine torque, the target engine torque to be transmitted to the ENG-ECU 150 may be increased as the amount of accumulated particulates increases. In this case, the powertrain manager 300 corrects the target engine torque to be transmitted to the MMT-ECU 230 based on the accumulation state of particulates and using the target engine torque to be transmitted to the ENG-ECU 150 as the basis of the correction.

[0037] FIG. 2 is a chart illustrating how the engine torque and the engagement state of the clutch change in time. In FIG. 2, the dotted line Ll represents the change in the target engine torque during a control that does not perform the correction of the target engine torque based on the accumulation state of particulates (i.e., a conventional control) and the solid line L2 represents the change in the actual engine torque.

[0038] Referring to FIG 2, when a shift operation of the automatic transmission 200

starts at time tθ, the target engine torque is reduced so that the engine torque decreases. Then, in response to the target engine torque becoming smaller than a threshold Tth at time t2, the clutch, which has been engaged so far, is then released. The threshold Tth is set so as to enable smooth shift operation. If the timing for releasing the clutch is too early, the engine races. On the other hand, if the timing is too late, an engine brake force is generated and a large shift shock therefore occurs.

[0039] Then, in response to the shift of the automatic transmission 200 being completed, the target engine torque is then controlled so as to restart the engine torque output. Then, in response to the target engine toque exceeding the threshold Tth at time t3, the clutch is engaged.

[0040] Meanwhile, because the engine torque decreases as particulates accumulate in the DPF 130 as mentioned above, the actual engine torque indicated by the line L2 is smaller than the target engine torque indicated by the line Ll. Therefore, if the clutch is released at time t2 based on the target engine torque indicated by the line Ll, an engine brake force is generated and a large shift shock therefore occurs.

[0041] In view of this, in this exemplary embodiment, the target engine torque that is used by the MMT-ECU 230 that performs the shifting control is corrected based on the accumulation state of particulates such that the target engine torque approaches the actual engine torque. According to this exemplary embodiment, specifically, the clutch is released at a time point close to time tl at which the actual engine torque becomes smaller than the threshold Tth, and the clutch is engaged at a time point close to time t4 at which the actual engine torque exceeds the threshold Tth, whereby the automatic transmission 200 can shift smoothly.

[0042] Note that, because the time needed for the shifting of the automatic transmission 200 is always the same regardless of whether the target engine torque is corrected, the clutch may be engaged at a time point earlier than time t4 so that the time period during which the engine torque is reduced matches that indicated by the line Ll.

[0043] Next, the concept of the shift timings in this exemplary embodiment will be described. FIG 3 is a chart illustrating the relation between the drive power provided to

the vehicle 10 and the speed of the vehicle 10. In FIG 3, the ordinate represents the drive power and the abscissa represents the vehicle speed. The curves kl to k3 represent the drive power characteristics at the first gear, the second gear, and the third gear, respectively, with the accelerator operation amount being maximum (100%). Note that the vehicle 10 also has gears higher than the third gear, although FIG. 3 only shows the drive power characteristics of the first gear to the third gear.

[0044] The shift timing of the automatic transmission 200 is determined based on these drive power characteristics. At the first gear, the vehicle 10 is accelerated as indicated by the curve kl and the automatic transmission 200, in response to the vehicle speed reaching the shift point Pl, shifts from the first gear to the second gear, whereby the drive power characteristic shifts from the point Pl to the point P21. At the second gear, the vehicle 10 is accelerated as indicated by the curve k2, and the automatic transmission 200, in response to the vehicle speed reaching the shift point P22, shifts from the second gear to the third gear, whereby the drive power characteristic shifts from the point P22 to the point P3.

[0045] The shift points Pl, P22 are set to appropriate points based on the drive power characteristic at each speed such that the vehicle 10 can be smoothly and sufficiently accelerated. Note that such shift points are appropriately set based on the drive power characteristic at each speed of the automatic transmission 200 with each level of the accelerator operation amount, not only with the maximum operation amount described above.

[0046] FIG 4 is a chart indicating shift curves each defining the shift timing. Note that FIG 4 only shows the shift curve for an upshift from the first gear to the second gear and the shift curve for an upshift from the second gear to the third gear as examples, not showing the shift curves for upshifts to the gears higher than the third gear and the shift curves for downshifts.

[0047] In FIG 4, the ordinates represents the accelerator operation amount (%) and the abscissa represents the vehicle speed. The curve kl2 is the shift curve defining the timing of an upshift from the first gear to the second gear and the curve k23 is the shift

curve defining the timing of an upshift from the second gear to the third gear. For example, when the accelerator operation amount is A(%), the automatic transmission 200 shifts from the first gear to the second gear in response to the vehicle speed reaching Sl.

[0048] These shift curves are determined based on the drive power characteristics shown in FIG 3. That is, appropriate shift points for each level of the accelerator operation amount is determined based on the drive power characteristics of each speed of the automatic transmission 200, and the determined shift points are plotted and the plotted shift points are then connected to generate a shift curve as those indicated in FIG 4. [0049] As described above, as particulates accumulate in the DPF 130, the output torque of the engine 100 decreases, and the acceleration power of the vehicle decreases accordingly, which causes a deviation between the actual acceleration of the vehicle and the acceleration feeling required by the driver. In this exemplary embodiment, therefore such a decrease in the engine torque that is caused by the accumulation of particulates is compensated for by shifting the shift characteristic of the automatic transmission 200 to a high torque shift characteristic based on the particulate accumulation state that has been estimated in accordance with the exhaust gas pressure of the engine 100.

[0050] At this time, more specifically, the MMT-ECU 230 shifts the shift curves kl2, k23 to the shift curves kl2A, k23A on the high speed side, so that these shift points are shifted to the high speed side. As a result, the automatic transmission 200 remains at a low gear until the vehicle speed reaches a certain high speed range, thus providing the acceleration feeling required by the driver.

[0051] Such shifting of the shift characteristic of the automatic transmission 200 to a high torque shift characteristic may be performed by presetting the shift curves kl2A, k23A and switching the shift curves kl2, k23 to the shift curves kl2A, k23A, respectively, in response to the estimated amount of accumulated particulates reaching a reference amount or by gradually shifting the shift curves to the high speed side in accordance with the estimated amount of accumulated particulates.

[0052] FIG 5 is a flowchart showing a control routine that is executed by the

powertrain manager 300 shown in FIG 1. This control routine is repeatedly executed at a constant time interval or is executed every time a specific condition comes into effect, as a routine called from the main control routine.

[0053] Referring to FIG 5, the powertrain manager 300 calculates the target engine torque based on the signals ACC indicating the accelerator operation amount, the signals SPD indicating the vehicle speed, and other various signals transmitted from the ENG-ECU 150 via the CAN communication (Step 10). Then, the powertrain manager 300 transmits the calculated target engine torque to the ENG-ECU 150 via the CAN communication (Step 20). Then, the ENG-ECU 150 controls the engine 100 in accordance with the target engine torque obtained from the powertrain manager 300.

[0054] Next, the powertrain manager 300 receives the signals P from the pressure sensor 140 via the CAN communication and thus obtains the exhaust gas pressure of the engine 100 (Step 30). Then, the powertrain manager 300 determines whether the obtained exhaust gas pressure is equal to or higher than a predetermined reference pressure (Step 40). If the powertrain manager 300 determines that the obtained exhaust gas pressure is lower than the reference pressure (Step 40: NO), the powertrain manager 300 then proceeds to Step 70 described below.

[0055] On the other hand, if the powertrain manager 300 determines that the obtained exhaust gas pressure is equal to or higher than the reference pressure (Step 40: YES), the powertrain manager 300 then estimates the particulate accumulation state in the DPF 130 based on the exhaust gas pressure (Step S50). Then, the powertrain manager 300 corrects the target engine torque based on the estimated particulate accumulation state (Step S60). More specifically, the powertrain manager 300 corrects the target engine torque such that the target engine torque decreases as the estimated amount of accumulated particulates is larger.

[0056] Then, the powertrain manager 300 transmits the target engine torque to the MMT-ECU 230 via the CAN communication (Step 70). That is, if it is determined in Step 40 that the exhaust gas pressure is equal to or higher than the reference pressure, the powertrain manager 300 transmits the target engine torque corrected in Step S60 to the

MMT-ECU 230, and if it is determined in Step 40 that the exhaust gas pressure is lower than the reference pressure, the powertrain manager 300 transmits the target engine torque calculated in Step 10 to the MMT-ECU 230.

[0057] Meanwhile, when the exhaust gas pressure is low, it indicates that the amount of accumulated particulates is small. In such a case, therefore, the need for correcting the target engine torque is considered to be small. So, by correcting the target engine torque used by the MMT-ECU 230 only when the exhaust gas pressure of the engine 100 is equal to or higher than the reference pressure as described above, it is possible to prevent a significant increase in the calculation load, which may otherwise be caused if the calculation for correcting target engine torque is always performed.

[0058] As described above, in this exemplary embodiment, the powertrain manager 300 estimates the state of accumulated particulates, which may cause a decrease in the output torque of the engine 100, based on the exhaust gas pressure of the engine 100. Also, the powertrain manager 300 corrects the target engine torque to be used by the MMT-ECU 230 such that the target engine torque decreases as the estimated amount of accumulated particulates is larger. As such, the target engine torque is corrected so as to approach the actual engine torque that has decreased according to the amount of accumulated particulates.

[0059] In this way, in this exemplary embodiment, the deviation between the target engine torque and the actual engine torque is reduced. As a result, the shift control is appropriately performed even when the amount of particulates accumulated in the DPF 130 increases.

[0060] Also, because the target engine torque is corrected only when the exhaust gas pressure of the engine 100 is equal to or higher than the reference pressure, when the amount of accumulated particulates is small, the calculation for correcting the target engine torque is not performed. Thus, the calculation load for the correction of the target engine torque is reduced.

[0061] Also, because the shift characteristic of the automatic transmission 200 is shifted to the high torque shift characteristic when the amount of accumulated

particulates is large, a decrease in the output torque of the engine 100 resulting from an increase in the amount of accumulated particulates is compensated for by the high torque shift characteristic. Thus, it is possible to provide the acceleration feeling required by the driver even when the output torque of the engine 100 has decreased due to an increase in the amount of accumulated particulates.

[0062] While the ENG-ECU 150 receives the signals P from the pressure sensor 140 and the powertrain manager 300 receives the signals P from the ENG-ECU 150 via the CAN communication and corrects the target engine torque as needed in the exemplary embodiment described above, the MMT-ECU 230 may alternatively perform the calculation for correcting the target engine torque after receiving the signals P from the pressure sensor 140.

[0063] Also, while the automatic transmission 200 has been described as an MMT constituted by a constant-mesh geartrain and a clutch in the exemplary embodiment described above, the automatic transmission 200 may alternatively be an AT (Automatic Transmission) constituted by a torque converter and planetary gearsets or a belt-drive type CVT (Continuously Variable Transmission). However, note that the invention can be especially effectively applied to MMTs that usually require a relatively high accuracy in controlling the timings for engaging and releasing the clutch.

[0064] The process in Step 10 that is executed by the powertrain manager 300 can be regarded as one example of a process executed by "torque calculating means" and the automatic transmission 200 can be regarded as one example of "controlled component". Also, the MMT-ECU 230 can be regarded as one example of "controlling means" and the DPF 130 can be regarded as one example of "exhaust filter". Also, the process in Step 50 that is executed by the powertrain manager 300 can be regarded as one example of a process executed by "estimating means" and the process in Step 60 that is executed by the powertrain manager 300 can be regarded as one example of a process executed by "correcting means". Further, the pressure sensor 140 can be regarded as one example of "pressure detecting means".

[0065] While some embodiments of the invention have been illustrated above, it is to

be understood that the invention is not limited to details of the illustrated embodiments, but may be embodied with various changes, modifications or improvements, which may occur to those skilled in the art, without departing from the spirit and scope of the invention.