JP2010203318A - Drive force control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive force control device inhibiting an increase of harmful components of exhaust gas and avoiding engine torque from becoming excessively high when fuel is supplied to an engine. <P>SOLUTION: The drive force control device changes over and executes control for supplying fuel to a combustion chamber of the engine and control for reducing resistance by the engine by stopping the supply of fuel to the combustion chamber and increasing an intake air quantity to the combustion chamber. The device includes a demand determination means (step S3) determining whether a demand for the supply of fuel to the combustion chamber is raised when the resistance by the engine is reduced by stopping the supply of fuel to the combustion chamber and increasing the intake air quantity to the combustion chamber, and a recirculation means (step S4) recirculating part of exhaust gas discharged from the combustion chamber to the combustion chamber if fuel is supplied in the combustion chamber when the demand for the supply of fuel to the combustion chamber is raised by the demand determination means (step S3). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a driving force control device that performs control to stop the supply of fuel to an engine when a vehicle is in a coasting state.

  2. Description of the Related Art Conventionally, a technique for reducing fuel consumption by performing control to stop fuel supply to an engine when a vehicle is in a coast state is described, and an example thereof is described in Patent Document 1. . Patent Document 1 describes that when the vehicle is in a coast state, fuel cut control is executed and control is performed to increase the amount of air taken into the engine. At this time, in order to continue the fuel cut control, if the downshift is performed with the automatic transmission connected to the engine and the engine speed is increased, the engine braking force is strengthened and instantaneously decelerated. Gives discomfort. Therefore, it is described that the intake air amount is increased by opening the idle speed control valve to weaken the engine braking force. The control of the internal combustion engine mounted on the vehicle is also described in Patent Documents 2 to 4.

JP-A-7-229432 JP 2002-147217 A JP 2008-303743 A JP 2001-271673 A

  However, if the intake air amount is increased during the fuel cut in the engine as in the engine control device described in Patent Document 1, the intake air amount is reduced when fuel supply is subsequently started in the engine. In contrast, there is a shortage of fuel. As a result, harmful components contained in exhaust gas generated in the engine increase. On the other hand, if the fuel corresponding to the intake air amount is supplied, the engine torque may become excessive.

  The present invention has been made against the background of the above circumstances, and when the fuel supply is stopped by the engine and the intake air amount is increased, the engine starts supplying fuel to the exhaust gas. An object of the present invention is to provide a driving force control device capable of suppressing an increase in harmful components contained therein and avoiding an excessive increase in engine torque.

  In order to achieve the above object, the invention of claim 1 provides a control for supplying and burning fuel to a combustion chamber of an engine, stopping the supply of fuel to the combustion chamber, and reducing the amount of intake air in the combustion chamber. In a driving force control device that switches between increasing and decreasing control by the engine, the supply of fuel to the combustion chamber is stopped, and the intake air amount in the combustion chamber is increased to increase the intake air amount by the engine. A request determining means for determining whether or not a request for supplying fuel to the combustion chamber has occurred during control for reducing resistance, and a request for supplying fuel to the combustion chamber by the request determining means. A recirculation means for recirculating a part of the exhaust gas discharged from the combustion chamber when fuel is supplied in the combustion chamber to the combustion chamber; And it is characterized in that it comprises.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, a holding device is provided for holding exhaust gas supplied to the combustion chamber and exhausted from the combustion chamber, and held by the holding device. Pressure determining means for determining whether or not the pressure of the exhaust gas being set is less than a predetermined threshold, and the pressure of the exhaust gas held by the holding device is less than a predetermined threshold In this case, when the supply of fuel to the combustion chamber is stopped, an intake air amount control means that does not control to increase the intake air amount in the combustion chamber is provided.

  According to the first aspect of the present invention, the fuel is supplied to the engine when the supply of fuel is stopped by the engine and the control is performed to increase the intake air amount in the combustion chamber to reduce the resistance by the engine. When the request is generated, a part of the exhaust gas discharged from the combustion chamber is returned to the combustion chamber. Therefore, when exhaust gas (inert gas) is sucked into the combustion chamber, the combustion temperature of the fuel can be relatively lowered to suppress an increase in harmful components, while avoiding an increase in the ratio of fuel to the amount of air. It is possible to suppress the engine torque from becoming excessive.

  According to the second aspect of the invention, the same effect as that of the first aspect of the invention can be obtained, and the exhaust gas that is supplied to the combustion chamber and discharged from the combustion chamber is held by the holding device. If the pressure of the exhaust gas held by the holding device is less than a predetermined threshold value, then the fuel supply is stopped by the engine, and then the harmful component is started when the fuel supply is started. Cannot increase or suppress excessive torque. Therefore, when the fuel supply is stopped by the engine, control for increasing the intake air amount in the combustion chamber is not performed.

It is a flowchart which shows the example of control of the driving force control apparatus of this invention. It is a schematic diagram which shows the structure of the engine used as the object of the driving force control apparatus of this invention. It is a flowchart which shows the other example of control of the driving force control apparatus of this invention. 4 is a time chart corresponding to the control example of FIGS. 1 and 3 and showing a case of a stepped transmission. FIG. 4 is a time chart corresponding to the control example of FIGS. 1 and 3 and showing a case of a continuously variable transmission. FIG.

  Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 2, an engine 1 mounted on a vehicle is a power device that generates power by burning fuel in a combustion chamber 2, and the engine 1 includes an intake pipe 3 that communicates with the combustion chamber 2. The intake pipe 3 is provided with an electronic throttle valve 4 that electrically controls the amount of intake air into the combustion chamber 2. A piston 6 is disposed in the cylinder 5 of the engine 1 so as to be able to reciprocate, and the combustion chamber 2 is formed. An intake valve 7 for opening and closing an intake port formed between the combustion chamber 2 and the intake pipe 3 is provided. Further, a fuel injection valve 15 for injecting fuel to be supplied to the combustion chamber 2 is provided. Further, if the engine 1 is a gasoline engine, an ignition device (not shown) for igniting a mixed gas of combustion and air is provided. Further, an exhaust pipe 8 is provided through which exhaust gas generated by burning fuel in the combustion chamber 2 is discharged from the combustion chamber 2. The exhaust pipe 8 and the combustion chamber 2 are connected by an exhaust port, and an exhaust valve 9 for opening and closing the exhaust port is provided.

  Further, a pipe 10 is provided for returning a part of the exhaust gas discharged to the exhaust pipe 8 to the intake pipe 3. The end of the pipe 10 on the intake pipe 3 side is connected between the electronic throttle valve 4 and the intake port. A valve (EGR valve) 11 for connecting and blocking the pipe 10 and the intake pipe 3 is provided. The valve 11 is constituted by a solenoid valve capable of controlling the opening / closing timing and the opening degree. Moreover, the cooler 12 is provided in the pipe 10, and the exhaust gas which passes the pipe 10 is cooled. Further, a pressure accumulating device 13 is provided for temporarily holding the exhaust gas passing through the pipe 10 before returning it to the intake pipe 3. Further, another valve (not shown) is provided between the pressure accumulator 13 and the cooler 12, and the exhaust gas flowing into the pipe 10 from the exhaust pipe 8 is held in the pressure accumulator 13, and this valve When both of the valves 11 are closed, the exhaust gas held in the pressure accumulator 13 can be prevented from being sent to the exhaust pipe 8 or the intake pipe 3. Further, when the valve is closed and the valve 11 is opened, the exhaust gas held in the pressure accumulator 13 can be recirculated to the intake pipe 3 without returning to the exhaust pipe 8. That is, the exhaust gas recirculation device (EGR) is constituted by the pipe 10, the pressure accumulator 13, and the valve 11.

  Further, a transmission 14 is connected to the engine 1 so that power can be transmitted. The transmission 14 is configured to be able to change a gear ratio that is a ratio between the input rotation speed and the output rotation speed. As the transmission 14, either a stepped transmission that can change the gear ratio stepwise or a continuously variable transmission that can change the gear ratio steplessly may be used. Here, a case will be described in which the transmission 14 is a stepped transmission capable of selecting a first speed to a fifth speed. In the transmission 14, when the drive (D) position is selected, the first to fifth gears are selectively switched based on the vehicle speed and the accelerator opening. An electronic control device 17 for controlling the electronic throttle valve 4, the fuel injection valve 15, the ignition device, the valve 11 and the transmission 14 is provided. The electronic control device 17 includes the pressure inside the pressure accumulating device 13, the engine. Sensor and switch signals for detecting the rotational speed, the opening degree of the electronic throttle valve 4, the vehicle speed, the accelerator opening degree, the input rotational speed and the output rotational speed of the transmission 14, and the like are input.

  Next, the control of the vehicle shown in FIG. 2 will be described. When the accelerator pedal is depressed, air is sucked into the combustion chamber 2 through the intake pipe 3 and fuel is supplied to the combustion chamber 2. While being supplied, the mixed gas is ignited to burn the fuel, and the piston 6 reciprocates. The reciprocating motion of the piston 6 is changed to the rotational motion of the crankshaft, and the torque of the crankshaft is transmitted to the transmission 14. The torque output from the transmission 14 is transmitted to the drive wheels to generate driving force. In addition, when fuel burns in the combustion chamber 2, exhaust gas is generated, and the exhaust gas is discharged to the exhaust pipe 8 via the exhaust port. A part of the exhaust gas discharged to the exhaust pipe 8 is held by the pressure accumulator 13 via the pipe 10.

  On the other hand, in the electronic control unit 17, the transmission ratio of the transmission 14 is determined based on the vehicle speed and the accelerator opening, and the transmission ratio of the transmission 14 is controlled. On the other hand, when the drive position is selected and the vehicle is traveling, the fuel pedal is stopped (fuel cut control) when the accelerator pedal is returned and the vehicle is coasting (coast state). Can be done. When the condition for restarting the fuel supply is satisfied, the fuel supply to the combustion chamber 2 is restarted. Conditions for restarting the supply of fuel include that the accelerator pedal has been depressed, and that the engine speed has decreased to a predetermined speed (return speed). The predetermined rotational speed is a value corresponding to the lower limit of the rotational speed at which the engine 1 can autonomously rotate when ignition is performed by the ignition device. For this reason, during execution of fuel cut control, control for relatively increasing the gear ratio of the transmission 14 is performed for the purpose of continuing the fuel cut control.

  A control example of the engine 1 related to the fuel cut control will be described based on the flowchart of FIG. First, it is determined whether or not the fuel cut (F / C) control is being executed (step S1). If the determination in step S1 is affirmative, it is determined whether or not control for reducing the friction of the engine 1 is being executed (step S2). For the purpose of continuation of the fuel cut control, if control is performed to relatively increase the transmission ratio of the transmission 14, the engine braking force is excessively increased and the deceleration increases, and the driver may feel uncomfortable. There is. Therefore, it is possible to perform control to reduce the resistance accompanying the rotation of the engine 1 by relatively increasing the opening degree of the electronic throttle valve 4. Thus, during the execution of the fuel cut control, the control by which the resistance by the engine 1 is reduced by relatively increasing (opening) the opening of the electronic throttle valve 4 is the control for reducing the friction of the engine 1. is there.

  If the determination in step S2 is affirmative, it is determined whether or not a request for returning from fuel cut control to control for supplying fuel has occurred (step S3). For example, when the accelerator pedal is depressed, and the engine speed is reduced to the return speed, an affirmative determination is made in step S3, the fuel supply to the combustion chamber 2 and the ignition control are resumed, and the valve 11 is opened and control is performed to recirculate the exhaust gas to the intake pipe 3 (step S4), and the process returns. In this step S4, the exhaust gas recirculated to the intake pipe 3 may be either the exhaust gas held in the pressure accumulator 13 or the exhaust gas remaining in the exhaust pipe 8, and the exhaust pipe 3 and the pipe The exhaust gas in the pipe 10 is recirculated to the intake pipe 3 due to the pressure difference from the inside of the pipe 10.

  Thus, when supplying the fuel to the combustion chamber 2, if the exhaust gas is recirculated to the intake pipe 3, the inert gas ratio in the amount of intake air supplied to the combustion chamber 2 increases. Then, the combustion temperature of the fuel becomes relatively low, and an increase in the amount of harmful components (Nox (nitrogen oxide)) generated by the combustion of the fuel can be suppressed. Further, since the ratio of the fuel to the intake air amount becomes relatively small, it is possible to avoid an excessive increase in engine torque, and it is possible to avoid deterioration in drivability due to rapid acceleration. If a negative determination is made in step S1, a negative determination is made in step S2, or a negative determination is made in step S3, the process directly returns. Here, the correspondence between the functional means shown in FIG. 1 and the configuration of the present invention will be described. Step S3 corresponds to the request determining means of the present invention, and step S4 is the reflux means of the present invention. Equivalent to.

  Next, another control example of the present invention will be described with reference to FIG. 3, steps that perform the same processing as in FIG. 1 are given the same step numbers as in FIG. In FIG. 3, it is first determined whether or not the pressure inside the pressure accumulating device 13 is equal to or higher than a threshold value stored in advance in the electronic control device 17 (step S5). This threshold value is a value for determining whether or not the inert gas can be recirculated to the intake pipe 3 to the extent that the engine torque can be prevented from becoming excessive when the fuel supply is resumed. And if the pressure inside the pressure accumulator 13 is equal to or greater than the threshold value, it means that the engine torque can be prevented from becoming excessive when the fuel supply is resumed. Therefore, if a positive determination is made in step S5, the process proceeds to step S1. Further, the process proceeds from step S1 to step S2, and when an affirmative determination is made in step S2, control for relatively increasing the gear ratio of the transmission 14 is performed for the purpose of continuing fuel cut control (step S6). . Following step S6, the process proceeds to step S3 and step S4. Therefore, fuel cut control can be continued over a wider range, and fuel consumption can be improved.

  On the other hand, if the determination is negative in step S5, the inert gas cannot be supplied to such an extent that the engine torque can be prevented from becoming excessive. Therefore, the process returns via step S7. In step S7, the control for reducing the friction of the engine 1 is not performed when the fuel cut control is executed. Further, in step S7, "speed change control for relatively increasing the speed ratio of the transmission 14 for the purpose of continuing fuel cut control" is not performed, and the speed ratio is determined based on the vehicle speed and the accelerator opening. "Control" is executed. That is, when the vehicle travels by repulsion at a relatively low vehicle speed, a relatively low gear position (large gear ratio) is not selected. Therefore, there is no sense of incongruity that the engine braking force is excessively increased and the vehicle is decelerated too much. The correspondence between the functional means shown in FIG. 3 and the configuration of the present invention will be described. Step S5 corresponds to the pressure determination means of the present invention, and step S7 corresponds to the intake air amount control means of the present invention. It corresponds to. The correspondence relationship between the other functional means in FIG. 3 and the configuration of the present invention is the same as the correspondence relationship between the means shown in FIG. 1 and the configuration of the present invention.

  An example of a time chart corresponding to the control example of FIGS. 1 and 3 will be described with reference to FIG. FIG. 4 corresponds to the case where the transmission 14 is a stepped transmission. First, before time t1, the accelerator operation amount is zero, that is, the accelerator pedal is not depressed, and fuel cut control is executed. Prior to time t1, the vehicle speed gradually decreases as indicated by a solid line, and the engine speed also gradually decreases as indicated by a solid line. When the engine speed is reduced to the return speed, control (downshift) is performed to increase the transmission ratio of the transmission 14, and the engine speed is once increased. Thereafter, the engine speed is again increased due to the decrease in the vehicle speed. It is falling. In this embodiment, before the time t1, the transmission 14 is downshifted once. Further, the EGR rate before time t1 is 0%. The EGR rate is the ratio of the inert gas recirculated through the pipe 10 out of the amount of air supplied to the combustion chamber 2. When the accelerator operation amount increases at time t1 (accelerator pedal is depressed), fuel supply is started in the engine 1, the EGR rate increases, the vehicle speed increases, and the engine speed increases. It is rising.

  Next, a broken line in FIG. 4 shows a comparative example in which control is not performed to reduce engine friction while the vehicle is in a coast state and fuel cut control is being executed. In this comparative example, since control for reducing engine friction is not performed, the rate of decrease in engine speed in the comparative example is greater than the rate of decrease in engine speed in the example before time t1. For this reason, in the comparative example, the downshift is performed twice in the transmission before time t1. Furthermore, since the number of downshifts is one more in the comparative example than in the example, the vehicle speed reduction rate (deceleration) is greater in the comparative example than in the example.

  An example of a time chart corresponding to the control examples of FIGS. 1 and 3 will be described with reference to FIG. FIG. 5 corresponds to the case where the transmission 14 is a continuously variable transmission. In FIGS. 3 and 5, the time-dependent changes in the accelerator operation amount, the vehicle speed, the F / C state, and the EGR rate are the same. In FIG. 5, before the time t1, as the vehicle speed gradually decreases, the continuously variable transmission is downshifted so as to increase continuously, and the engine speed is controlled to be substantially constant. When the accelerator operation amount increases at time t1, the gear ratio of the continuously variable transmission increases stepwise, and the engine speed increases stepwise.

  Further, the correspondence relationship between the configuration shown in FIG. 1 and the configuration of the present invention will be described. The engine 1 corresponds to the engine of the present invention, the combustion chamber 2 corresponds to the combustion chamber of the present invention, and the accumulated pressure. The device 13 corresponds to the holding device of the present invention. In the example of FIG. 2, the opening degree of the electronic throttle valve 4 provided in the intake pipe 3 is controlled to reduce the friction of the engine 1, but the intake pipe 3 is reduced to reduce the friction of the engine 1. The intake air amount may be increased by increasing the opening of an idle speed control valve (ISC valve, not shown) of an auxiliary intake pipe (not shown) provided in parallel with the intake air pipe. When the engine 1 is a diesel engine, the ignition device is not provided, and the return rotational speed is a lower limit value of the rotational speed at which the engine 1 can autonomously rotate by self-ignition when fuel is supplied.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Combustion chamber, 13 ... Accumulator, 17 ... Electronic control unit.

Claims (2)

Control for supplying and burning fuel to the combustion chamber of the engine, and control for stopping the supply of fuel to the combustion chamber and decreasing the resistance by the engine by increasing the intake air amount in the combustion chamber. In the driving force control device that performs switching,
There is a demand for supplying fuel to the combustion chamber when control is performed to stop the supply of fuel to the combustion chamber and increase the amount of intake air in the combustion chamber to reduce the resistance of the engine. Request determination means for determining whether or not it occurred,
If the request determination means determines that a request to supply fuel to the combustion chamber has occurred, a part of the exhaust gas discharged from the combustion chamber when fuel is being supplied in the combustion chamber The driving force control apparatus is provided with a recirculation means for recirculating the fuel to the combustion chamber. A holding device for holding exhaust gas supplied to the combustion chamber and exhausted from the combustion chamber;
Pressure determining means for determining whether the pressure of the exhaust gas held by the holding device is less than a predetermined threshold;
Control that increases the amount of intake air in the combustion chamber when the supply of fuel to the combustion chamber is stopped when the pressure of the exhaust gas held by the holding device is less than a predetermined threshold value The drive force control device according to claim 1, further comprising: an intake air amount control unit that does not perform the operation.

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