Control device for engine

A control device for controlling an engine based on an operating state of a vehicle is provided. The control device includes a processor configured to execute a basic target torque determining module for determining a basic target torque based on an operating state of the vehicle, a torque reduction amount determining module for determining a torque reduction amount based on a part of the operating state of the vehicle, a final target torque determining module for determining a final target torque based on the basic target torque and the torque reduction amount, an engine controlling module for controlling the engine to output the final target torque, and a torque change smoothing module for smoothing a chronological change of the final target torque corresponding to the torque reduction amount at a smaller smoothing degree than that of the chronological change of the final target torque corresponding to the basic target torque.

BACKGROUND

The present invention relates to a control device for an engine, particularly to a control device which controls an engine based on an operating state of a vehicle.

Conventionally, devices for controlling, when a behavior of a vehicle becomes unstable due to slippage, etc., the behavior of the vehicle toward a safe direction (e.g., sideslip preventing device), are known. Specifically, devices for detecting a behavior, such as understeering or oversteering, in the vehicle when, for example, the vehicle corners, and applying a suitable deceleration to wheels so as to suppress the detected behavior, are known.

On the other hand, as opposed to such a control for improving safety under a traveling state where the vehicle behavior becomes unstable, vehicle operation control devices are known which control a load on front wheels (drive wheels) by adjusting a deceleration when the vehicle corners, so that a series of operations performed by a driver (braking, turning of steering, accelerating, and turning back the steering, etc.) in a normal traveling state of the vehicle becomes natural and stable. For example, JP2011-088576A discloses such a device.

Further, vehicle behavior control devices are known, which reduce a drive force of a vehicle according to a yaw rate related amount (e.g., yaw acceleration) corresponding to a steering operation by a driver, so as to promptly produce a deceleration in the vehicle when the driver starts the steering operation, and promptly apply a sufficient load on front wheels (drive wheels). For example, JP2014-166014A discloses such a device. According to such a vehicle behavior control device, by applying the load on the front wheels when the steering operation is started, a friction force between the front wheels and a road surface increases and a cornering force of the front wheels increases, and therefore, turning performance of the vehicle in a start of entering a curve improves, and responsiveness to a turning operation of the steering improves. Thus, a vehicle behavior intended by the driver is achieved.

Meanwhile, in a vehicle with an internal combustion engine, such as a gasoline engine or a diesel engine, a control device for controlling the engine determines a target torque based on an operating state of the vehicle (e.g., various operations of an accelerator pedal, a brake pedal, a steering, etc. performed by a driver, a traveling environment, such as a vehicle speed, an atmospheric temperature, an atmospheric pressure, a road gradient, a road surface μ, etc.), and controls the engine to output the target torque.

When the target torque is sharply changed, if the engine is controlled to reflect the change of the target torque as it is in an output torque, a sharp acceleration/deceleration is produced in the vehicle and a person on board may feel uncomfortable. Therefore, with the conventional control devices for engines, a chronological change of the target torque is smoothed to reduce the sharp acceleration/deceleration in the vehicle.

On the other hand, with the vehicle behavior control device described in JP2014-166014A, to accurately realize the vehicle behavior intended by the driver, the drive force of the vehicle needs to be reduced promptly in response to the steering operation. However, if the conventional control device for the engine smooths the chronological change of the target torque corresponding to this reduction request of the drive force, a response delay occurs in the drive force control of the vehicle in response to the steering operation by the driver. Therefore, a sufficient increase in the cornering force of the front wheels by the prompt application of the load on the front wheels cannot be achieved, and sufficient responsiveness to the turning operation of the steering cannot be secured. As a result, the vehicle behavior intended by the driver cannot accurately be achieved.

SUMMARY

The present invention is made in view of solving the issues of the conventional arts described above, and aims to provide a control device for an engine, which is capable of controlling the engine to accurately achieve a vehicle behavior intended by a driver while suppressing a sharp change of a target torque.

According to one aspect of the present invention, a control device for controlling an engine based on an operating state of a vehicle is provided. The control device includes a processor configured to execute a basic target torque determining module for determining a basic target torque based on an operating state of the vehicle including an operation of an accelerator pedal (first operating state), a torque reduction amount determining module for determining a torque reduction amount based on a part of the operating state of the vehicle, the part of the operating state excluding the operation of the accelerator pedal (second operating state), a final target torque determining module for determining a final target torque based on the basic target torque and the torque reduction amount, an engine controlling module for controlling the engine to output the final target torque, and a torque change smoothing module for smoothing a chronological change of the final target torque corresponding to the torque reduction amount at a smaller smoothing degree than a smoothing degree of the chronological change of the final target torque corresponding to the basic target torque.

With the above configuration, the torque change smoothing module smooths the chronological change of the final target torque corresponding to the torque reduction amount determined based on the second operating state of the vehicle at the smaller smoothing degree than the smoothing degree of the chronological change of the final target torque corresponding to the basic target torque determined based on the first operating state of the vehicle. Therefore, while a sharp change of the final target torque due to a sharp change of the first operating state is suppressed, the chronological change of the torque reduction amount determined based on the second operating state of the vehicle, without being smoothed excessively, can be reflected in the chronological change of the final target torque. Thus, the engine can be controlled to obtain the torque reduction amount with high responsiveness in the second operating state of the vehicle, a load can promptly be applied to front wheels of the vehicle, and a vehicle behavior intended by a driver can accurately be achieved.

The torque change smoothing module may not smooth the chronological change of the final target torque corresponding to the torque reduction amount.

With the above configuration, while the sharp change of the final target torque due to the sharp change of the first operating state of the vehicle is suppressed, the chronological change of the torque reduction amount determined based on the second operating state of the vehicle can be reflected in the chronological change of the final target torque as it is. Therefore, by controlling the engine to obtain the torque reduction amount with highest responsiveness to the second operating state of the vehicle, the vehicle behavior intended by the driver can accurately be achieved.

The torque reduction amount determining module may determine the torque reduction amount according to a steering operation of the vehicle.

With the above configuration, the chronological change of the torque reduction amount determined based on the steering operation, without being smoothed excessively, can be reflected in the chronological change of the final target torque. Therefore, by promptly applying a deceleration corresponding to the steering operation by the driver on the vehicle to add the load on the front wheels so as to promptly increase a cornering force, the responsiveness to the steering operation can be improved. Moreover, while the sharp change of the final target torque corresponding to the first operating state of the vehicle is suppressed, the engine can be controlled to accurately achieve the vehicle behavior intended by the driver.

The torque reduction amount determining module may determine the torque reduction amount to be increased while an increase rate thereof becomes lower, as a steering speed of the vehicle increases.

With the above configuration, once the steering operation of the vehicle is started and the steering speed of the vehicle starts to increase, the torque reduction amount can promptly be increased accordingly. Thus, the deceleration is promptly applied to the vehicle when the steering operation of the vehicle is started, and a sufficient load can promptly be applied to the front wheels which are drive wheels of the vehicle, which increases a friction force between the front wheels and a road surface and increases the cornering force of the front wheels. As a result, a turning performance of the vehicle in the start of entering a curve improves, and responsiveness to the turning operation of the steering improves while suppressing the sharp change of the final target torque corresponding to the first operating state of the vehicle.

The basic target torque determining module may determine a target acceleration of the vehicle based on the operating state of the vehicle including the operation of the accelerator pedal, and determine the basic target torque based on the target acceleration.

With the above configuration, the basic target torque is determined based on the target acceleration. Therefore, the engine can be controlled to accurately achieve acceleration intended by the driver while suppressing the sharp change of the final target torque corresponding to the first operating state of the vehicle.

The engine may be a diesel engine including a fuel injector for injecting fuel into a cylinder. The engine controlling module may control a fuel injection amount of the fuel injector so as to cause the diesel engine to output the final target torque.

With the above configuration, the fuel injection amount of the diesel engine is controlled according to the final target torque. Thus, the chronological change of the torque reduction amount determined based on the second operating state of the vehicle can accurately be achieved with high responsiveness, and the engine can be controlled to accurately achieve the vehicle behavior intended by the driver.

The engine may be a gasoline engine including an air amount controlling mechanism for controlling an amount of air introduced into a cylinder, and an ignitor for igniting mixture gas within the cylinder. The air amount controlling mechanism may be a throttle valve actuator or a variable valve mechanism. The engine controlling module may control at least one of the air amount by the air amount controlling mechanism and an ignition timing by the ignitor, so as to cause the gasoline engine to output the final target torque.

With the above configuration, the at least one of the air amount introduced into the cylinder of the gasoline engine and the ignition timing is changed according to the final target torque. Thus, the chronological change of the torque reduction amount determined based on the second operating state of the vehicle can accurately be achieved with high responsiveness, and the engine can be controlled to accurately achieve the vehicle behavior intended by the driver.

DETAILED DESCRIPTION OF EMBODIMENT

Hereinafter, a control device for an engine according to one embodiment of the present invention is described with reference to the appended drawings.

First, an engine system to which the control device for the engine according to this embodiment is applied is described with reference toFIG. 1which is a schematic configuration view of the engine system to which the control device for the engine according to this embodiment is applied.

As illustrated inFIG. 1, the engine system200mainly includes an engine E as a diesel engine, an intake system IN for supplying intake air to the engine E, a fuel supply system FS for supplying fuel to the engine E, an exhaust system EX for discharging exhaust gas of the engine E, sensors96to110for detecting various states regarding the engine system200, and a Power-train Control Module (PCM)60for controlling the engine system200.

The intake system IN includes an intake passage1through which the intake air passes. The intake passage1is provided with, from its upstream side in the following order, an air cleaner3for purifying air introduced externally, a compressor5aprovided to a turbocharger5and for compressing the intake air passing therethrough to increase an intake air pressure, an intake shutter valve7for adjusting a flow rate of the intake air passing therethrough, a water-cool-type intercooler8for cooling the intake air by using a coolant therein, and a surge tank12for temporarily storing the intake air to be supplied to the engine E.

Further in the intake system IN, an airflow sensor101for detecting an amount of the intake air and an intake air temperature sensor102for detecting an intake air temperature are provided to the intake passage1immediately downstream of the air cleaner3, a turbo-speed sensor103for detecting a rotational speed of the compressor5aof the turbocharger5(turbo-speed) is provided to the compressor5a, an intake shutter valve position sensor105for detecting an opening of the intake shutter valve7is provided to the intake shutter valve7, an intake air temperature sensor106for detecting an intake air temperature and an intake air pressure sensor107for detecting the intake air pressure are provided to the intake passage1immediately downstream of the intercooler8, and an intake manifold temperature sensor108is provided to the surge tank12. The various sensors101to103and105to108provided in the intake system IN output to the PCM60detection signals S101to S103and S105to S108corresponding to the detected parameters.

The engine E includes an intake valve15for introducing the intake air supplied from the intake passage1(specifically, intake manifold) into a combustion chamber17, a fuel injector20for injecting the fuel to the combustion chamber17, a piston23for reciprocating due to combustion of mixture gas within the combustion chamber17, a crankshaft25for rotating in conjunction with the reciprocation of the piston23, and an exhaust valve27for discharging, to an exhaust passage41, the exhaust gas produced by the combustion of the mixture gas within the combustion chamber17.

The fuel supply system FS includes a fuel tank30for storing the fuel and a fuel supply passage38for supplying the fuel from the fuel tank30to the fuel injector20. The fuel supply passage38is provided with, from its upstream side in the following order, a low-pressure fuel pump31, a high-pressure fuel pump33, and a common rail35.

The exhaust system EX includes the exhaust passage41through which the exhaust gas passes. The exhaust passage41is provided with, from its upstream side in the following order, a turbine5bprovided to the turbocharger5and for rotating with the exhaust gas passing therethrough and driving the compressor5aas described above with the rotation, a diesel oxidation catalyst (DOC)45and a diesel particulate filter (DPF)46that have a purifying function of the exhaust gas, and an exhaust shutter valve49for adjusting a flow rate of the exhaust gas passing therethrough. The DOC45is a catalyst for oxidizing hydrocarbons (HC), carbon monoxide (CO), etc. by using oxygen within the exhaust gas, to convert them into water and carbon dioxide. The DPF46traps particulate matter (PM) within the exhaust gas.

Further in the exhaust system EX, an exhaust gas pressure sensor109for detecting an exhaust gas pressure is provided to the exhaust passage41upstream of the turbine5bof the turbocharger5, and a linear O2sensor110for detecting an oxygen concentration is provided to the exhaust passage41immediately downstream of the DPF46. These sensors109and110provided in the exhaust system EX output to the PCM60detection signals S109and S110corresponding to the detected parameters.

Moreover in this embodiment, the turbocharger5has a compact structure so as to be able to efficiently perform the turbocharging even when rotating at a low speed (i.e., exhaust energy is low). Also, the turbocharger5is configured as a variable geometry turbocharger (VGT) provided with a plurality of movable flaps5cto surround an entire circumference of the turbine5b, and for varying with the flaps5ca channel cross-sectional area for the exhaust gas to flow to the turbine5b(nozzle cross-sectional area). For example, the flaps5care adjusted in magnitude of negative pressure to act on a diaphragm by an electromagnetic valve, and turned by an actuator. Further, a VGT opening sensor104for detecting an opening of each flap5c(corresponding to a flap opening, hereinafter, suitably referred to as “the VGT opening”) based on a position of the actuator is provided. The VGT opening sensor104outputs to the PCM60a detection signal S104corresponding to the detected VGT opening.

The engine system200of this embodiment further includes a high-pressure EGR device43and a low-pressure EGR device48. The high-pressure EGR device43has a high-pressure EGR passage43aconnecting the exhaust passage41upstream of the turbine5bof the turbocharger5and the intake passage1downstream of the compressor5aof the turbocharger5(specifically, downstream of the intercooler8), and a high-pressure EGR valve43bfor adjusting a flow rate of the exhaust gas passing through the high-pressure EGR passage43a. The low-pressure EGR device48has a low-pressure EGR passage48aconnecting the exhaust passage41downstream of the turbine5bof the turbocharger5(specifically, downstream of the DPF46and upstream of the exhaust shutter valve49) and the intake passage1upstream of the compressor5aof the turbocharger5, a low-pressure EGR cooler48bfor cooling the exhaust gas passing through the low-pressure EGR passage48a, a low-pressure EGR valve48cfor adjusting a flow rate of the exhaust gas passing through the low-pressure EGR passage48a, and a low-pressure EGR filter48d.

The exhaust gas amount recirculated to the intake system IN by the high-pressure EGR device43(hereinafter, referred to as “the high-pressure EGR gas amount”) is substantially determined based on the exhaust gas pressure at the upstream of the turbine5bof the turbocharger5, an intake air pressure produced based on the opening of the intake shutter valve7, and an opening of the high-pressure EGR valve43b. Further, the exhaust gas amount recirculated to the intake system IN by the low-pressure EGR device48(hereinafter, referred to as “the low-pressure EGR gas amount”) is substantially determined based on an intake air pressure at the upstream of the compressor5aof the turbocharger5, an exhaust gas pressure produced based on an opening of the exhaust shutter valve49, and an opening of the low-pressure EGR valve48c.

Next, an electric configuration of the control device for the engine according to this embodiment is described with reference toFIG. 2which is a block diagram illustrating this electric configuration of the control device for the engine. The control device includes several program modules, which are software stored in non-volatile memory or firmware.

The PCM60(the control device for the engine) of this embodiment outputs control signals S130to S133to control the turbocharger5, the fuel injector20, the high-pressure EGR device43, and the low-pressure EGR device48, based on detection signals S96to S100outputted by a steering angle sensor96for detecting a rotational angle of a steering wheel, an accelerator opening sensor97for detecting a position of an accelerator pedal (accelerator opening), a vehicle speed sensor98for detecting a vehicle speed, an outdoor air temperature sensor99for detecting an outdoor air temperature, and an atmospheric pressure sensor100for detecting an atmospheric pressure, respectively, in addition to the detection signals S101to S110from the various sensors101to110described above.

The PCM60includes a basic target torque determining module61for determining a basic target torque based on a first operating state of the vehicle including an operation of the accelerator pedal (hereinafter, simply referred to as “the first operating state of the vehicle”), a torque reduction amount determining module63for determining a torque reduction amount based on a second operating state of the vehicle excluding the operation of the accelerator pedal (hereinafter, simply referred to as “the second operating state of the vehicle”), a final target torque determining module65for determining a final target torque based on the basic target torque and the torque reduction amount, a torque change filter67(torque change smoothing module) for smoothing a chronological change of the final target torque, an engine controlling module69for controlling the engine E to output the final target torque, and a processor70for executing the various modules of the PCM60.

These various components of the PCM60are comprised of a computer including the processor70, various programs (including a base control program, such as an OS, and an application program which is activated on the OS and achieves a particular function) which are interpreted and executed on the processor70, and internal memories, such as a ROM and a RAM, for storing the programs and various data.

Next, processing performed by the control device for the engine is described with reference toFIGS. 3 to 5.

FIG. 3is a flowchart of engine control processing performed by the control device for the engine E.FIG. 4is a flowchart of torque reduction amount determination processing performed by the control device for the engine.FIG. 5is a map illustrating a relationship between a target applied deceleration and a steering speed determined by the control device for the engine.

The engine control processing ofFIG. 3is activated when an ignition switch of the vehicle is switched on and a power of the control device for the engine is turned on, and is repeatedly performed.

Once the engine control processing is started, as illustrated inFIG. 3, at S1, the PCM60acquires the operating state of the vehicle. Specifically, the PCM60acquires the detection signals S96to S110outputted by the various sensors96to110described above, etc., including the steering angle detected by the steering angle sensor96, the accelerator opening detected by the accelerator opening sensor97, the vehicle speed detected by the vehicle speed sensor98, and a gear position currently set in a transmission of the vehicle, as the operating state of the vehicle.

Next, at S2, the basic target torque determining module61of the PCM60sets a target acceleration based on the first operating state of the vehicle acquired at S1. Specifically, the basic target torque determining module61selects from acceleration characteristics maps defined for various vehicle speeds and gear positions (designed and stored beforehand in, for example, a memory), an acceleration characteristics map corresponding to the current vehicle speed and the current gear position, and determines the target acceleration corresponding to a current accelerator opening by referring to the selected acceleration characteristics map.

Next, at S3, the basic target torque determining module61determines a basic target torque of the engine E for achieving the target acceleration determined at S2. Here, the basic target torque determining module61determines the basic target torque based on the current vehicle speed, the current gear position, a road gradient, a road surface μ, etc., within a range of torque which the engine E is able to output.

Next, at S4, the torque change filter67smooths a chronological change of the basic target torque determined at S3. The method of the smoothing may specifically be any of various well-known methods (e.g., limiting a change ratio of the basic target torque to a threshold or below, calculating a variation average of the chronological change of the basic target torque, etc.).

Further, in parallel to the processes at S2to S4, at S5, the torque reduction amount determining module63performs the torque reduction amount determination processing for determining the torque reduction amount based on the second operating state of the vehicle. The torque reduction amount determination processing is described with reference toFIG. 4.

As illustrated inFIG. 4, once the torque reduction amount determination processing is started, at S21, the torque reduction amount determining module63determines whether an absolute value of the steering angle acquired at S1increases. If the absolute value of the steering angle increases as a result, the processing proceeds to S22where the torque reduction amount determining module63calculates the steering speed based on the steering angle acquired at S1.

Next, at S23, the torque reduction amount determining module63determines whether an absolute value of the steering speed reduces.

If the absolute value of the steering speed does not reduce, in other words, the absolute value of the steering speed neither reduces nor changes, the processing proceeds to S24where the torque reduction amount determining module63acquires a target applied deceleration based on the steering speed. The target applied deceleration is a deceleration to be applied to the vehicle in response to a steering operation in order to accurately achieve a behavior of the vehicle intended by a driver.

Specifically, the torque reduction amount determining module63acquires the target applied deceleration corresponding to the steering speed calculated at S22, based on a relationship between the target applied deceleration and the steering speed illustrated on the map ofFIG. 5.

InFIG. 5, the horizontal axis indicates the steering speed and the vertical axis indicates the target applied deceleration. As illustrated inFIG. 5, in a case where the steering speed is below a threshold Ts(e.g., 10 deg/s), the target applied deceleration corresponding thereto is zero (0). Specifically, if the steering speed is below the threshold Ts, the deceleration is not applied to the vehicle in response to the steering operation.

On the other hand, if the steering speed is the threshold Tsor above, the target applied deceleration corresponding thereto gradually approaches a given upper limit value Dmax(e.g., 1 m/s2) as the steering speed increases. Specifically, the target applied deceleration increases at an increase rate which becomes lower as the steering speed increases.

Next, at S25, the torque reduction amount determining module63determines an applied deceleration for the current processing (hereinafter, referred to as “the current applied deceleration”) within a range where an increase rate of the applied deceleration is a threshold Rmax (e.g., 0.5 m/s3) or below.

Specifically, the torque reduction amount determining module63, if the increase rate from the applied deceleration determined in previous processing (hereinafter, referred to as “the previous applied deceleration”) to the target applied deceleration determined at S24in the current processing (hereinafter, referred to as “the current target applied deceleration”) is Rmax or below, determines the current target applied deceleration to be the current applied deceleration.

On the other hand, if the change rate from the previous applied deceleration to the current target applied deceleration is higher than Rmax, the torque reduction amount determining module63determines a value obtained by increasing from the previous applied deceleration until the current processing at the increase rate Rmax, to be the current applied deceleration.

Further at S23, if the absolute value of the steering speed reduces, the processing proceeds to S26where the torque reduction amount determining module63determines the previous applied deceleration to be the current applied deceleration. Specifically, if the absolute value of the steering speed reduces, the applied deceleration when the steering speed is at its highest value (i.e., a highest value of the applied deceleration) is maintained.

Moreover at S21, if the absolute value of the steering angle does not increase (is fixed or reduces), the processing proceeds to S27where the torque reduction amount determining module63acquires an amount to reduce in the current processing, from the previous applied deceleration (deceleration decrease amount). This deceleration decrease amount is calculated based on a certain decrease rate (e.g., 0.3 m/s3) stored in, for example, a memory, beforehand. Alternatively, the deceleration decrease amount is calculated based on the first/second operating state of the vehicle acquired at S1and/or the decrease rate determined corresponding to the steering speed calculated at S22.

Then at S28, the torque reduction amount determining module63determines the current applied deceleration by subtracting from the previous applied deceleration, the deceleration decrease amount acquired at S27.

After S25, S26, or S28, at S29, the torque reduction amount determining module63determines the torque reduction amount based on the current applied deceleration determined at S25, S26, or S28. Specifically, the torque reduction amount determining module63determines the torque reduction amount required for achieving the current applied deceleration, based on the current vehicle speed, the current gear position, the current road gradient, etc. acquired at S1. After S29, the torque reduction amount determining module63terminates the torque reduction amount determination processing and returns to the main routine.

Returning toFIG. 3, after the processes at S2to S4and the torque reduction amount determination processing at S5, at S6, the final target torque determining module65determines the final target torque by subtracting from the basic target torque after smoothing at S4, the torque reduction amount determined in the torque reduction amount determination processing at S5.

Next, at S7, the engine controlling module69sets a required injection amount to be injected from the fuel injector20based on the final target torque determined at S6and an engine speed.

Next, at S8, the engine controlling module69sets an injection pattern of the fuel, a fuel pressure, a target oxygen concentration, a target intake air temperature, and an Exhaust Gas Recirculation (EGR) control mode (a mode in which at least one of the high-pressure and low-pressure EGR devices43and48is activated or a mode in which neither of the high-pressure and low-pressure EGR devices43and48is activated), based on the required injection amount set at S7, and the engine speed.

Next, at S9, the engine controlling module69sets state functions for achieving the target oxygen concentration and the target intake air temperature which are set at S8. For example, the state functions include the amount of exhaust gas to be recirculated to the intake system IN by the high-pressure EGR device43(high-pressure EGR gas amount), the amount of exhaust gas to be recirculated to the intake system IN by the low-pressure EGR device48(low-pressure EGR gas amount), and a turbocharging pressure produced by the turbocharger5.

Then at S10, the engine controlling module69controls various actuators for driving the respective components of the engine system200, based on the state functions set at S9. Here, the engine controlling module69performs the control by setting limit values and limit ranges corresponding to the state functions, and setting control amounts of the respective actuators so that the state functions follow the limitation based on the limit values and ranges.

After S10, the PCM60terminates the engine control processing.

Next, the operation of the control device for the engine according to this embodiment is described with reference toFIG. 6which shows diagrams illustrating chronological changes of parameters regarding the engine control performed by the control device for the engine in a case where the vehicle on which the control device for the engine is mounted turns.

Part (A) ofFIG. 6is a plan view schematically illustrating the vehicle turning rightward. As illustrated in Part (A) ofFIG. 6, the vehicle starts turning rightward from a position A, and continues to turn rightward at a fixed steering angle from a position B to a position C.

Part (B) ofFIG. 6is a chart illustrating a change of the steering angle of the vehicle turning rightward as illustrated in Part (A). In Part (B), a horizontal axis indicates time and a vertical axis indicates the steering angle.

As illustrated in Part (B) ofFIG. 6, the rightward steering operation is started at the position A, the rightward steering angle gradually increases as the steering is turned more, and the rightward steering angle reaches its largest angle at the position B. Then, the steering angle is fixed until reaching the position C (hold the steering).

Part (C) ofFIG. 6is a chart illustrating a change of the steering speed of the vehicle turning rightward as illustrated in Part (B). In Part (C), a horizontal axis indicates time and a vertical axis indicates the steering speed.

The steering speed of the vehicle is expressed by time derivative of the steering angle of the vehicle. Specifically, as illustrated in Part (C) ofFIG. 6, when the rightward steering operation is started at the position A, a rightward steering speed is produced and the steering speed is substantially fixed between the positions A and B. Then, the rightward steering speed decreases and, once the rightward steering angle reaches its largest angle at the position B, the steering speed becomes zero (0). Further, while the rightward steering angle is maintained from the position B to the position C, the steering speed remains zero.

Part (D) ofFIG. 6is a chart illustrating a change of the applied deceleration determined based on the steering speed illustrated in Part (C). In Part (D), a horizontal axis indicates time and a vertical axis indicates the applied deceleration. Further in Part (D), a solid line indicates a change of the applied deceleration determined in the torque reduction amount determination processing inFIG. 4, and a one-dotted chain line indicates a change of the target applied deceleration based on the steering speed. The target applied deceleration indicated by the one-dotted chain line, similarly to the change of the steering speed illustrated in Part (C) ofFIG. 6, starts increasing at the position A, is substantially fixed between the positions A and B, and then decreases until it becomes zero at the position B.

As is described with reference toFIG. 4, the torque reduction amount determining module63acquires the target applied deceleration based on the steering speed at S24if the absolute value of the steering speed does not reduce, in other words, the absolute value of the steering speed does not increase or change, as a result of S23. Next, at S25, the torque reduction amount determining module63determines the applied deceleration in each processing cycle within a range where the increase rate of the applied deceleration is the threshold Rmax or below.

Part (D) ofFIG. 6illustrates a case where the increase rate of the target applied deceleration which starts increasing at the position A, exceeds the threshold Rmax. In this case, the torque reduction amount determining module63increases the applied deceleration to achieve the increase rate=Rmax (i.e., the increase rate gentler than the target applied deceleration indicated by the one-dotted chain line). Further, when the target applied deceleration is substantially fixed between the positions A and B, the torque reduction amount determining module63determines that the applied deceleration=the target applied deceleration.

Moreover, as described above, if the absolute value of the steering speed reduces at S23ofFIG. 4, the torque reduction amount determining module63maintains the applied deceleration when the steering speed is at its highest value. In Part (D) ofFIG. 6, when the steering speed decreases toward the position B, the target applied deceleration indicated by the one-dotted chain line also decreases accordingly, whereas the applied deceleration indicated by the solid line is maintained at its highest value until reaching the position B.

Further as described above, if the absolute value of the steering angle is fixed or reduces at S21ofFIG. 4, the torque reduction amount determining module63acquires the deceleration decrease amount at S27and reduces the applied deceleration based on the deceleration decrease amount. In Part (D) ofFIG. 6, the torque reduction amount determining module63decreases the applied deceleration so that the decrease rate of the applied deceleration becomes gradually lower, in other words, an inclination of the solid line indicating the change of the applied deceleration gradually becomes gentler.

Part (E) ofFIG. 6is a chart illustrating a change of the torque reduction amount determined based on the applied deceleration illustrated in Part (D). In Part (E), a horizontal axis indicates time and a vertical axis indicates the torque reduction amount.

As described above, the torque reduction amount determining module63determines the torque reduction amount which is required for achieving the applied deceleration, based on the parameters, such as the current vehicle speed, the current gear position, and the current road gradient. Therefore, if these parameters are steady, the torque reduction amount is determined to change similarly to the change of the applied deceleration illustrated in Part (D) ofFIG. 6.

Part (F) ofFIG. 6is a chart illustrating a change of the basic target torque around a timing of smoothing by the torque change filter67. In Part (F), a horizontal axis indicates time and a vertical axis indicates torque. Further in Part (F), a dashed line indicates a basic target torque before the smoothing by the torque change filter67and a solid line indicates a basic target torque after the smoothing by the torque change filter67.

As indicated by the dashed line in Part (F), the basic target torque determined to achieve the target acceleration set based on the accelerator opening, the vehicle speed, the gear position, etc. may sharply vary due to various disturbances, noises, etc. By smoothing the basic target torque with the torque change filter67, the sharp variation indicated by the solid line of Part (F) is suppressed and a sharp acceleration of the vehicle is suppressed.

Part (G) ofFIG. 6is a chart illustrating a change of the final target torque determined based on the basic target torque and the torque reduction amount. In Part (G), a horizontal axis indicates time and a vertical axis indicates torque. Further in Part (G), a dashed line indicates the smoothed basic target torque illustrated in Part (F) and a solid line indicates the final target torque.

As is described with reference toFIG. 3, the final target torque determining module65determines the final target torque by subtracting the torque reduction amount determined in the torque reduction amount determination processing performed at S5, from the basic target torque after smoothing at S4. Between the basic target torque and the torque reduction amount used for determining the final target torque, the torque change filter67only smooths the basic target torque determined based on the first operating state of the vehicle. In other words, in the chronological change of the final target torque, the chronological change corresponding to the torque reduction amount determined based on the steering operation which is the second operating state is not smoothed by the torque change filter67. Therefore, as indicated by the solid line of Part (G) ofFIG. 6, the torque reduction amount is reflected in the final target torque as it is without being smoothed by the torque change filter67.

Part (H) ofFIG. 6is a chart illustrating a change of the fuel injection amount determined based on the final target torque. In Part (H) ofFIG. 6, a horizontal axis indicates time and a vertical axis indicates the required injection amount. Further in Part (H), a dashed line indicates a required injection amount corresponding to the smoothed basic target torque illustrated in Part (F) and a solid line indicates a required injection amount corresponding to the final target torque illustrated in Part (G).

In the example of Part (H) ofFIG. 6, the engine controlling module69controls, in the chronological change of the final target torque determined at S6, the chronological change corresponding to the torque reduction amount based on the fuel injection amount to be injected by the fuel injector20. Therefore, as indicated by the solid line of Part (H), the required injection amount changes similarly to the chronological change of the final target torque illustrated in Part (G).

Part (I) ofFIG. 6is a chart illustrating, in the vehicle steered as illustrated in Part (B), a change of a yaw rate (actual yaw rate) which occurs in the vehicle when the engine E is controlled to achieve the final target torque illustrated in Part (G), and a change of an actual yaw rate when the control corresponding to the torque reduction amount illustrated in Part (E) ofFIG. 6is not performed (i.e., the engine E is controlled to achieve the smoothed basic target torque indicated by the dashed line in Part (G) ofFIG. 6). In Part (I), a horizontal axis indicates time and a vertical axis indicates the yaw rate. Further in Part (I), a solid line indicates the change of the actual yaw rate when the engine E is controlled to achieve the final target torque and a dashed line indicates the change of the actual yaw rate when the control corresponding to the torque reduction amount is not performed.

When the rightward steering operation is started at the position A and the torque reduction amount is increased as illustrated in Part (E) ofFIG. 6as the rightward steering speed increases, a load on the front wheels (drive wheels) of the vehicle increases. As a result, a friction force between the front wheels and the road surface increases and a cornering force of the front wheels increases, and therefore, a turning performance of the vehicle improves. In other words, as illustrated in Part (I) ofFIG. 6, the yaw rate in a clockwise direction (CW) which occurs in the vehicle between the positions A and B becomes higher in the case where the engine E is controlled to achieve the final target torque reflecting the torque reduction amount (solid line) compared to the case where the control corresponding to the torque reduction amount is not performed (dashed line).

Further as illustrated in Parts (D) and (E) ofFIG. 6, when the steering speed toward the position B decreases, the target applied deceleration decreases, whereas the torque reduction amount is maintained at the highest value. Therefore, while the turning operation of the steering continues, the load on the front wheels is maintained and the turning performance of the vehicle is secured.

Moreover, if the absolute value of the steering angle is fixed between the positions B and C, since the torque reduction amount is smoothly reduced, the load on the front wheels is gradually reduced in response to the end of the turning operation of the steering and the cornering force of the front wheels is reduced, so as to resume an output torque of the engine E while stabilizing the vehicle body.

Next, a modification of this embodiment is described.

In the embodiment described above, the torque reduction amount determining module63acquires the target applied deceleration based on the steering speed and determines the torque reduction amount based on the target applied deceleration; however, the torque reduction amount may be determined based on the second operating state of the vehicle (the steering angle, the yaw rate, a slip rate, etc.).

For example, the torque reduction amount determining module63may calculate a target yaw acceleration to be produced in the vehicle based on a target yaw rate calculated based on the steering angle and the vehicle speed and a yaw rate inputted from a yaw rate sensor, and acquire the target applied deceleration based on the target yaw acceleration, so as to determine the torque reduction amount. Alternatively, a roll acceleration which occurs due to rolling of the vehicle may be detected by an acceleration sensor so as to determine the torque reduction amount based on the roll acceleration.

Further in the embodiment described above, in the chronological change of the final target torque, the chronological change corresponding to the torque reduction amount determined based on the steering operation is not smoothed by the torque change filter67; however, the chronological change corresponding to the torque reduction amount may be smoothed in a smoothing degree lower than that of the chronological change corresponding to the basic target torque.

Specifically, in the embodiment described above, at S4ofFIG. 3, the torque change filter67only smooths the chronological change of the basic target torque determined at S3; however, additionally, after the torque reduction amount is determined at S29in the torque reduction amount determination processing ofFIG. 4, the chronological change of the torque reduction amount is smoothed. Here, the smoothing degree of the torque reduction amount is reduced to be lower than that of the basic target torque. In other words, the smoothing degree of the chronological change of the final target torque corresponding to the torque reduction amount is reduced to be lower than that of the chronological change of the final target torque corresponding to the basic target torque.

Further in the embodiment described above, the engine system200to which the control device for the engine is applied includes the engine E as the diesel engine; however, the engine system200may include a gasoline engine having an air amount controlling mechanism for controlling an amount of air introduced into a cylinder and an ignitor for igniting mixture gas within the cylinder. In this case, the engine controlling module69controls the air amount introduced into the cylinder by the air amount controlling mechanism (e.g., a throttle valve actuator or a variable valve mechanism) and/or controls an ignition timing by the ignitor.

Next, effects of the control device for the engine according to the above-described embodiment and modification of the present invention are described.

First, the torque change filter67reduces the smoothing degree of the chronological change of the final target torque corresponding to the torque reduction amount determined based on the second operating state of the vehicle, to be lower than the smoothing degree of the chronological change of the final target torque corresponding to the basic target torque determined based on the first operating state of the vehicle. Therefore, while a sharp change of the final target torque due to a sharp change of the first operating state is suppressed, the chronological change of the torque reduction amount determined based on the second operating state of the vehicle, without being smoothed excessively, is reflected in the chronological change of the final target torque. Thus, the engine E is controlled to obtain the torque reduction amount with high responsiveness in the second operating state of the vehicle, the load is promptly applied to the front wheels, and the vehicle behavior intended by the driver is accurately achieved.

Especially since the torque change filter67does not smooth the chronological change of the torque reduction amount (i.e., the chronological change of the final target torque corresponding to the torque reduction amount is not smoothed), while the sharp change of the final target torque due to the sharp change of the first operating state of the vehicle is suppressed, the chronological change of the torque reduction amount determined based on the second operating state of the vehicle is reflected in the chronological change of the final target torque as it is. Therefore, by controlling the engine E to obtain the torque reduction amount with highest responsiveness to the second operating state of the vehicle, the vehicle behavior intended by the driver is accurately achieved.

Further, since the torque reduction amount determining module63determines the torque reduction amount according to the steering operation of the vehicle, the chronological change of the torque reduction amount determined based on the steering operation, without being smoothed excessively, is reflected in the chronological change of the final target torque. Therefore, by promptly applied the deceleration corresponding to the steering operation by the driver on the vehicle to add the load on the front wheels so as to promptly increase the cornering force, the responsiveness to the steering operation is improved. Moreover, while the sharp change of the final target torque corresponding to the first operating state of the vehicle is suppressed, the engine E is controlled to accurately achieve the vehicle behavior intended by the driver.

Especially the torque reduction amount determining module63determines the torque reduction amount to be increased as the steering speed of the vehicle increases while the increase rate of the torque reduction amount becomes lower. Therefore, once the steering operation of the vehicle is started and the steering speed of the vehicle starts to increase, the torque reduction amount is promptly increased. Thus, the deceleration is promptly applied to the vehicle when the steering operation of the vehicle is started, and a sufficient load is promptly applied to the front wheels which are the drive wheels, which increases the friction force between the front wheels and the road surface and increases the cornering force of the front wheels. As a result, the turning performance of the vehicle in the start of entering a curve improves, and the responsiveness to the turning operation of the steering improves while suppressing the sharp change of the final target torque corresponding to the first operating state of the vehicle.

Further the basic target torque determining module61determines the target acceleration of the vehicle based on the first operating state of the vehicle and determines the basic target torque based on the target acceleration. Therefore, the engine E is controlled to accurately achieve acceleration intended by the driver while suppressing the sharp change of the final target torque corresponding to the first operating state of the vehicle.

Further, the control device for the engine is the control device for the diesel engine including the fuel injector for injecting the fuel into the cylinder, and the engine controlling module69controls the fuel injection amount of the fuel injector20so as to cause the diesel engine to output the final target torque. Therefore, by changing the fuel injection amount, the chronological change of the torque reduction amount determined based on the second operating state of the vehicle is accurately achieved with high responsiveness, and the engine E is controlled to accurately achieve the vehicle behavior intended by the driver.

Further, the control device for the engine is the control device for the gasoline engine including the air amount controlling mechanism for controlling the air amount introduced into the cylinder and the ignitor for igniting the mixture gas within the cylinder. The engine controlling module69controls at least one of the air amount introduced into the cylinder by the air amount controlling mechanism and the ignition timing by the ignitor, so as to cause the gasoline engine to output the final target torque. Therefore, by changing the air amount introduced into the cylinder and/or the ignition timing, the chronological change of the torque reduction amount determined based on the second operating state of the vehicle is accurately achieved with high responsiveness, and the engine E is controlled to accurately achieve the vehicle behavior intended by the driver.

LIST OF REFERENCE CHARACTERS