JP2010216427A - Fuel cut control device - Google Patents

Abstract

A fuel cut control device capable of suppressing the occurrence of engine stall due to a decrease in engine speed due to an increase in a load of an internal combustion engine during a downshift while improving fuel efficiency by fuel cut control. I will provide a.
An electronic control device detects an undershoot amount of an engine speed Ne generated at each of a plurality of shift stages during downshift execution during fuel cut, and the detected undershoot amount is determined in advance. When the fuel cut return rotational speed Nef in the next downshift of the same gear stage is equal to or greater than the threshold value, the fuel cut when the above-described undershoot has not occurred or the undershoot amount is less than the above-described threshold th A fuel cut return rotation speed changing process is executed to set the fuel cut return rotation speed Nef ₂ lower than the return rotation speed Nef ₁ .
[Selection] Figure 8

Description

  The present invention relates to a fuel cut control device, and in particular, it is possible to improve fuel consumption by fuel cut while suppressing the occurrence of engine stall due to a decrease in engine speed of an internal combustion engine during downshifting of a shift stage. The present invention relates to a possible fuel cut control device.

  Conventionally, in vehicles equipped with automatic transmissions, so-called fuel cut control that stops the fuel supply to the engine has been executed during deceleration of the vehicle that does not require engine output, thereby improving fuel efficiency by reducing fuel consumption. The ones that are aimed at are known. In a vehicle that performs this type of fuel cut control, if the fuel cut return condition is satisfied, for example, when the engine speed is lower than a predetermined fuel cut return speed during deceleration, fuel is used to prevent engine stall. Is resumed from the fuel cut state.

  In a vehicle equipped with a fuel cut control device that executes this type of fuel cut control, when the gear of the automatic transmission is temporarily in a neutral state during downshift, There is a case where an undershoot of the so-called engine speed occurs, in which the actual engine speed decreases with respect to the target engine speed corresponding to. At this time, if the above-described undershoot amount is large, the engine rotational speed becomes equal to or lower than the fuel cut return rotational speed, so that the fuel cut state may be recovered during the downshift, and fuel supply to the engine may be resumed.

  In the fuel cut control as described above, the longer the stop period of fuel supply to the engine, the better the fuel consumption can be improved. Therefore, it is desirable to set the fuel cut return rotational speed as low as possible.

  Therefore, in recent years, fuel supply to the engine is stopped when the engine speed is equal to or higher than a predetermined fuel cut speed while the vehicle is decelerating, and the engine is stopped when the engine speed is equal to or lower than the predetermined fuel cut return speed. A fuel cut control device having a fuel supply control means for restarting the supply of fuel to the vehicle, and when a downshift of the transmission is detected during decelerating traveling, the fuel cut return rotational speed is determined until the end of the shift operation. What is made to reduce from the normal fuel cut return rotation speed is known (for example, refer patent document 1).

  In the conventional fuel cut control device described in Patent Document 1, the fuel supply to the engine is stopped by preventing return from the fuel cut state due to an undershoot of the engine speed during the downshift. The period can be lengthened.

JP-A-3-182658

  However, in the conventional fuel cut control device as described above, when a downshift is detected during deceleration traveling, the fuel cut return rotational speed is always reduced. Therefore, during the downshift, the fuel cut return is always performed. The engine speed is approaching the start limit engine speed limit that will cause engine stall.

  In such a state, in addition to the undershoot amount of the engine speed due to the neutral state during the downshift, a change occurs in the operating state of the auxiliary machine, for example, the power generation amount of the alternator increases, and accordingly, the engine load increases. When the engine speed increases and the engine speed further decreases, the engine speed becomes equal to or lower than the fuel cut return speed. In addition, as a change of an auxiliary machine operating state, generation | occurrence | production of the electrical load increase by headlight ON etc. is assumed, for example.

  At this time, during the downshift, the fuel cut return rotation speed is always close to the start limit rotation speed, so even if the fuel supply to the engine is restarted, the start limit rotation speed is increased before the engine rotation speed increases. The following was likely to lead to an engine stall.

  For this reason, in the conventional fuel cut control device as described above, although the fuel supply control to the engine by the fuel cut control can be prolonged to improve the fuel consumption, for example, during the downshift There has been a problem that the possibility of an engine stall increases due to a decrease in the engine speed due to a change in the machine operating state.

  The present invention has been made to solve the above-described conventional problems, and is due to a decrease in engine speed due to an increase in the load of the internal combustion engine during a downshift while improving fuel efficiency by fuel cut control. It is an object of the present invention to provide a fuel cut control device that can suppress the occurrence of engine stall.

  In order to achieve the above object, the fuel cut control device according to the present invention (1) stops the fuel supply to the internal combustion engine when the vehicle is traveling at a reduced speed and a predetermined condition is satisfied, and the engine rotation of the internal combustion engine When the number is equal to or less than a predetermined first fuel cut return rotational speed, the fuel cut control means for executing fuel cut control for restarting fuel supply to the internal combustion engine, and a plurality of friction engagement elements, An automatic transmission that establishes a plurality of shift speeds by switching engagement and disengagement of the plurality of friction engagement elements and outputs the power of the internal combustion engine to an output shaft at a gear ratio according to the shift speeds. A fuel cut control device, wherein when the fuel cut control means stops the fuel supply to the internal combustion engine, the gear shift downshift Downshift determining means for determining whether or not is executed, and when the downshift determining means determines that the downshift has been executed, the downshift is executed for each of the plurality of shift stages during the downshift. Undershoot amount detecting means for detecting the undershoot amount of the engine speed, and when the undershoot amount detected by the undershoot amount detecting means is equal to or greater than a predetermined threshold, And a fuel cut return rotation speed setting means for setting the fuel cut return rotation speed to a second fuel cut return rotation speed lower than the first fuel cut return rotation speed.

  With this configuration, when the fuel cut return rotation speed setting means detects that the undershoot amount detected by the undershoot amount detecting means during execution of the downshift of the shift stage is equal to or greater than a predetermined threshold, the next downshift of the same shift stage is performed. Since the fuel cut return rotational speed in the shift is set to the second fuel cut return rotational speed that is lower than the first fuel cut return rotational speed, the engine speed is returned to the first fuel cut return during downshift execution. Even when the rotational speed is equal to or lower than the rotation speed, the fuel cut state can be continued, and fuel consumption can be improved.

  In addition, the fuel cut return rotational speed is set to the second fuel cut return rotational speed that is lower than the first fuel cut return rotational speed only during downshift execution in which the undershoot amount of the engine speed is equal to or less than a predetermined threshold. Since it is set, the period during which the internal combustion engine is close to the start limit rotational speed at which the internal combustion engine reaches the engine stall can be minimized by reducing the fuel cut return rotational speed. For this reason, it is possible to suppress the occurrence of an engine stall of the internal combustion engine due to a decrease in the engine speed due to an increase in the load of the internal combustion engine during the downshift.

  According to the present invention, a fuel that can suppress the occurrence of an engine stall due to a decrease in engine speed due to an increase in the load of the internal combustion engine during a downshift while improving fuel efficiency by fuel cut control. A cut control device can be provided.

It is a figure which shows the outline of a structure of the drive device for vehicles to which the fuel cut control apparatus which concerns on embodiment of this invention is applied. It is a figure which shows the relationship between the combination of the action | operation of the some hydraulic friction engagement apparatus in the automatic transmission which concerns on embodiment of this invention, and the gear stage established by it. It is a figure which shows the outline of a structure of the control system of the vehicle to which the fuel cut control apparatus which concerns on embodiment of this invention is applied. It is a figure explaining the operation position of the shift lever of FIG. It is a figure which shows an example of the shift map used for the shift control performed in the electronic controller of the fuel cut control apparatus which concerns on embodiment of this invention. It is a figure which shows the relationship between the engine speed during downshift execution, and fuel cut return rotation speed. It is a figure which shows the fuel cut return rotational speed setting map used for the fuel cut return rotational speed change process performed in the fuel cut control apparatus which concerns on embodiment of this invention. It is a flowchart explaining the fuel cut return rotation speed change process performed in the fuel cut control apparatus which concerns on embodiment of this invention. Fuel cut return rotation by deceleration used when setting the fuel cut return rotation speed set by the fuel cut return rotation speed change process executed in the fuel cut control device according to the embodiment of the present invention for each deceleration. It is a figure which shows a number setting map.

Embodiments of the present invention will be described below with reference to the drawings.
First, the configuration of a vehicle drive device to which a fuel cut control device according to an embodiment of the present invention is applied will be described with reference to FIG.

  As shown in FIG. 1, the vehicle drive device includes an engine 11 that is mounted on a vehicle such as an automobile and is configured by an internal combustion engine as a drive source for travel, and an automatic transmission 20. In this vehicle drive device, the output of the engine 11 is input to the automatic transmission 20 via the torque converter 12 and transmitted to the drive wheels via a differential gear device and an axle (not shown).

  The torque converter 12 is provided on a power transmission path between the engine 11 and the automatic transmission 20, and is connected to a pump impeller 12 p connected to the output shaft 14 of the engine 11 and an input shaft 21 of the automatic transmission 20. The turbine runner 12t and the stator 12s whose rotation in one direction is restricted by the one-way clutch 15 are provided. Such a torque converter 12 is configured to transmit power through a fluid between the pump impeller 12p and the turbine runner 12t.

  Further, the torque converter 12 includes a lockup clutch 16, and this lockup clutch 16 is directly connected between the pump impeller 12 p and the turbine runner 12 t and is transmitted from the output shaft 14 of the engine 11. Is directly transmitted to the input shaft 21 of the automatic transmission 20. Further, the lockup clutch 16 is subjected to lockup slip control in order to expand the fuel cut region by suppressing a decrease in the engine speed, for example, when the throttle valve is in a fully closed coast deceleration.

  The automatic transmission 20 includes a double pinion type first planetary gear unit 22, a Ravigneaux type second planetary gear unit 23, a clutch C1 to a clutch C4 as a plurality of friction engagement elements, a brake B1, and a brake B2. It has.

  The first planetary gear device 22 includes a first sun gear S1, a first ring gear R1, a plurality of inner pinion gears P1a, a plurality of outer pinion gears P1b, and a first carrier CA1.

  The first sun gear S1 is fixed to the case 20a of the automatic transmission 20 so as not to rotate. The first ring gear R1 is selectively connected to the first intermediate drum D1 via the clutch C3 and is selectively connected to the second intermediate drum D2 via the clutch C1.

  The plurality of inner pinion gears P1a and the plurality of outer pinion gears P1b are interposed in an annular space formed between the first sun gear S1 and the first ring gear R1, and support shaft portions of the first carrier CA1. It is supported to be able to rotate and revolve. Thus, each inner pinion gear P1a and each outer pinion gear P1b can rotate about the support shaft of the first carrier CA1 as a rotation axis, and can revolve around the input shaft 21 as a rotation axis.

Each inner pinion gear P1a meshes with the first sun gear S1 and each outer pinion gear P1b, and each outer pinion gear P1b meshes with the first ring gear R1 and each inner pinion gear P1a.
The first carrier CA1 has a central shaft portion integrally connected to the input shaft 21 and a support shaft portion selectively connected to the first intermediate drum D1 via the clutch C4.

The first intermediate drum D1 is rotatably disposed on the outer diameter side of the first ring gear R1, and is selectively connected to the case 20a via the brake B1. The first intermediate drum D1 selectively connects the first ring gear R1 via the clutch C3, and selectively connects the first carrier CA1 via the clutch C4.
The second intermediate drum D2 is disposed on the inner peripheral side of the first intermediate drum D1, and selectively connects the first ring gear R1 via the clutch C1.

  The second planetary gear unit 23 includes a second sun gear S2, a third sun gear S3 having a smaller diameter than the second sun gear S2, a second ring gear R2, a plurality of long pinion gears P2, and a plurality of short pinion gears P3. It has a second carrier CA2 and a one-way clutch F1.

The second sun gear S2 is connected to the first intermediate drum D1, is selectively connected to the first ring gear R1 via the clutch C3, and is selectively connected to the first carrier CA1 via the clutch C4. It has become.
The third sun gear S3 is connected to the second intermediate drum D2, and is selectively connected to the first ring gear R1 via the clutch C1.

  The second ring gear R2 is connected to the output shaft 25 of the automatic transmission 20, and a plurality of long pinion gears P2 are formed in an annular space formed between the second ring gear R2, the second sun gear S2, and the third sun gear S3. In addition, a plurality of short pinion gears P3 are interposed.

  Each long pinion gear P2 and each short pinion gear P3 are supported by the second carrier CA2 so as to be capable of rotating and revolving, and can rotate with the support shaft portion of the second carrier CA2 as a rotation shaft, and the input shaft 21 is a rotation shaft. It is possible to revolve as.

  Each long pinion gear P2 meshes with the second sun gear S2, each short pinion gear P3, and the second ring gear R2, and each short pinion gear P3 meshes with the third sun gear S3 and the long pinion gear P2.

  The second carrier CA2 has a central shaft portion selectively connected to the input shaft 21 via the clutch C2, and a support shaft portion selectively connected to the case 20a via the brake B2 and the one-way clutch F1. It is like that. The second carrier CA2 is allowed to rotate only in one direction by the one-way clutch F1.

The clutches C1 to C4 and the brakes B1 and B2 are hydraulic friction engagement devices that are controlled to be engaged by a hydraulic actuator such as a multi-plate clutch or brake.
In addition, the clutch C1 to the clutch C4 and the brake B1 and the brake B2 are switched by the hydraulic circuit being switched by excitation, de-excitation, a manual valve (not shown) of various solenoid valves of a hydraulic control circuit 80 (see FIG. 3) described later, For example, as shown in FIG. 2, the engaged and disengaged states are switched to establish eight forward shift stages (1st to 8th) and one reverse shift stage (Rev) according to the operation position of a shift lever described later. It is like that. That is, the automatic transmission 20 establishes a plurality of shift stages “1st” to “8th” by switching engagement and disengagement of the above-described clutch C1 to clutch C4 and brake B1 and brake B2. .

  Next, the relationship between the combination of the operations of the plurality of hydraulic friction engagement devices in the automatic transmission 20 according to the embodiment of the present invention and the shift speed established thereby will be described with reference to FIG.

“1st” to “8th” shown in FIG. 2 indicate the first to eighth forward speeds, and the gear ratio (the rotational speed Nin of the input shaft 21 increases from the first speed “1st” to the eighth speed “8th”. / The rotational speed Nout of the output shaft 25 is set to be small. In FIG. 2, “◯” represents the engaged state, “×” represents the released state, “* 1” represents the engaged state during engine braking, and “* 2” represents the engaged state during driving. Represents.
That is, the automatic transmission 20 outputs the power of the engine 11 (see FIG. 1) to the output shaft 25 (see FIG. 1) at a gear ratio corresponding to each of the above-mentioned first to eighth forward speeds. It is like that.

Next, the configuration of a vehicle control system to which the fuel cut control device according to the embodiment of the present invention is applied will be described with reference to FIG.
As shown in FIG. 3, the fuel cut control device 1 includes an automatic transmission 20 and an electronic control device 100 having various functions.

  The electronic control device 100 is configured to include a microcomputer including, for example, a CPU, RAM, ROM, input / output interface, and the like. The CPU uses a temporary storage function of the RAM and signals according to a program stored in advance in the ROM. Processing is to be performed. As a result, the electronic control unit 100 performs output control of the engine 11, shift control of the automatic transmission 20, lockup slip control, and the like, and is used for engine control and shift control as necessary. Separately configured. The ROM previously stores a shift map, a fuel cut return rotation speed setting map, and the like, which will be described later.

  The electronic control unit 100 includes an accelerator operation amount sensor 51, a throttle actuator 52, an engine speed sensor 54, an intake air amount sensor 56, an intake air temperature sensor 57, an idle switch throttle sensor 59, a vehicle speed sensor 60, a brake switch. 62, a shift position sensor 64, a turbine speed sensor 66, an acceleration sensor 68, a fuel injection device 71, an ignition device 73, and the like are connected.

  The accelerator operation amount sensor 51 detects an operation amount (accelerator opening) Acc of the accelerator pedal 74 and outputs an accelerator opening signal corresponding to the accelerator opening Acc to the electronic control unit 100.

  The slot actuator 52 changes an opening degree (hereinafter referred to as a throttle valve opening degree) θth of an electronic throttle valve 76 provided in the intake pipe 75 of the engine 11 in accordance with an operation amount of the accelerator pedal 74.

The engine rotation speed sensor 54 detects the rotation speed Ne of the engine 11 and outputs a signal corresponding to the rotation speed Ne to the electronic control device 100.
The intake air amount sensor 56 detects the intake air amount Q of the engine 11 and outputs a signal corresponding to the intake air amount Q to the electronic control unit 100.

Intake air temperature sensor 57 detects a temperature T _A of intake air, and outputs to the electronic control unit 100 a signal corresponding to the temperature T _A of intake air.
The throttle sensor 59 with an idle switch detects the fully closed state (idle state) of the electronic throttle valve 76 and the throttle valve opening θth, and outputs a signal corresponding to the fully closed state and the throttle valve opening θth to the electronic control unit 100. It is supposed to be.

The vehicle speed sensor 60 detects the rotation speed Nout of the output shaft 25 corresponding to the vehicle speed V, and outputs a signal corresponding to the rotation speed Nout, that is, the vehicle speed V, to the electronic control device 100.
The brake switch 62 detects the presence / absence of an operation of a foot brake, which is a service brake, and outputs a signal corresponding to the presence / absence of a brake operation to the electronic control unit 100.

The shift position sensor 64 detects a shift position (operation position) Psh of the shift lever 77 and outputs a signal corresponding to the operation position Psh to the electronic control device 100.
The turbine speed sensor 66 detects a turbine speed Nt corresponding to the speed Nin of the input shaft 21 and outputs a signal corresponding to the turbine speed Nt to the electronic control unit 100.

  The acceleration sensor 68 is disposed, for example, at a substantially center of gravity position of the vehicle, and detects acceleration acting in the front-rear direction of the vehicle, that is, deceleration G (negative acceleration) acting in the front-rear direction of the vehicle. A corresponding signal is output to the electronic control unit 100.

The fuel injection device 71 controls the amount of fuel injected in accordance with the injection signal output from the electronic control device 100, and in the fuel cut control described later, a stop command signal Sfc output from the electronic control device 100. Accordingly, the fuel supply to the engine 11 is stopped.
The ignition device 73 is configured to control the ignition timing of the engine 11 in accordance with the ignition timing signal output from the electronic control device 100.

The aforementioned shift lever 77 is disposed, for example, in the vicinity of the driver's seat, and is manually moved to five lever positions “P”, “R”, “N”, “D” or “S” as shown in FIG. It is designed to be operated. Here, the “P” position is a parking position for blocking the power transmission path in the automatic transmission 20 and mechanically locking the rotation of the output shaft 25 by a mechanical parking lock mechanism (not shown). The position is a reverse travel position for reversing the rotation direction of the output shaft 25 of the automatic transmission 20, and the “N” position is for a neutral state that blocks the power transmission path in the automatic transmission 20. The “D” position is a shift range (D) that allows a shift from the first speed “1st” to the eighth speed “8th” established by a plurality of friction engagement elements in the automatic transmission 20. Range) is a forward travel position where automatic shift control is executed, and the “S” position is a forward travel position where manual shift is possible by switching the shift range.
In the aforementioned “S” position, the shift range or gear position is shifted to the down side every time the shift lever 77 is operated, the “+” position for shifting the shift range or gear position to the up side, and the shift lever 77 being operated. A “−” position is provided for shifting.

In addition, a hydraulic control circuit 80 is connected to the electronic control unit 100, and for example, excitation and de-excitation of the linear solenoids SL1 to SL6 in the hydraulic control circuit 80 are controlled in order to switch the gear position of the automatic transmission 20, for example. For example, a valve command signal for controlling the pressure, a drive signal to the linear solenoid SLT for controlling the line pressure PL, and the like are output.
The linear solenoids SL <b> 1 to SL <b> 6 are configured in substantially the same manner, and are excited and de-energized independently by the electronic control device 100. In this way, the linear solenoids SL1 to SL6 are independently controlled to regulate the hydraulic pressures of the hydraulic actuators provided corresponding to the clutches C1 to C4 and the brakes B1 and B2, respectively, and the clutches C1 to C4 and the brakes are controlled. The engagement pressures of B1 and brake B2 are controlled.

Next, each function of the electronic control device 100 will be described below.
Further, the electronic control unit 100 determines whether or not to shift the automatic transmission 20 based on a shift map stored in advance with the vehicle speed V and the accelerator operation amount Acc as parameters, for example, as shown in FIG. The automatic transmission control of the automatic transmission 20 is executed so that the determined gear position is established. In this shift map, for example, as the vehicle speed V decreases or the accelerator operation amount Acc increases, a low speed shift stage with a large gear ratio is established. In the automatic shift control, for example, so-called clutch-to-clutch shift control is performed in which release and engagement of the clutch C and brake B relating to shift are controlled simultaneously. Note that the solid line in the shift map in FIG. 5 is the upshift shift line, and the broken line is the downshift shift line. Further, in the shift map of FIG. 5, a shift from the first speed “1st” to the sixth speed “6th” among the first speed “1st” to the eighth speed “8th”, which is a shift stage established by the automatic transmission 20. A line is shown as an example.

  For example, when the electronic control unit 100 determines that the actual vehicle speed V has exceeded the downshift line for 5th speed → 4th speed, that is, when downshifting from 5th speed to 4th speed is performed based on the shift map. When the determination is made, as shown in the operation table of FIG. 2, the excitation / non-excitation of the linear solenoid valve SL2 and the linear solenoid valve SL4 is controlled so that the clutch C2 is released and the clutch C4 is engaged. It has become.

  Here, in the clutch-to-clutch shift control described above while the vehicle is decelerating, the clutch C2 is disengaged at the time of downshift from the fifth speed (shift stage before the shift) to the fourth speed (shift stage after the shift). If the timing is too early, the duration of the neutral state becomes longer, and so-called undershoot occurs in which the engine speed Ne decreases.

  As shown in FIG. 6, the above-described undershoot of the engine speed Ne is a phenomenon in which the actual engine speed Ne decreases with respect to the target engine speed Ne corresponding to the gear position before the shift. The amount of decrease (drop amount) is the amount of undershoot. Note that the target engine speed Ner corresponding to the speed stage before the shift described above is obtained by multiplying the speed Nout of the output shaft 25 of the automatic transmission 20 detected by the vehicle speed sensor 60 by the speed ratio γ of the speed stage before the speed change. It is obtained by subtracting the lockup slip rotational speed described later from the above.

  Further, the electronic control unit 100 is configured to perform learning control and correct the engagement or disengagement timing of the clutch or brake so as to be the optimum timing in order to suppress the occurrence of the above-described undershoot. For example, when the above-described undershoot at the engine speed Ne occurs in the downshift from the fifth speed to the fourth speed, the learning control sequentially corrects the release timing of the clutch C2. Specifically, the electronic control unit 100 corrects the valve command signal output to the linear solenoid SL2 corresponding to the clutch C2 of the hydraulic control circuit 80 by learning control, thereby setting the release timing of the clutch C2 at the next shift. It can be delayed. Thereby, generation | occurrence | production of the above-mentioned undershoot can be suppressed now. In the present embodiment, the downshift from the fifth speed to the fourth speed has been described, but the same learning control is also performed in the downshift of other shift stages that perform clutch-to-clutch shift. ing.

  Further, the electronic control unit 100 performs feedback control of the hydraulic pressure supplied to the lockup clutch 16 based on the lockup slip rotation speed difference of the lockup clutch 16 during execution of fuel cut while the vehicle is decelerating. Slip control is executed. As a result, a decrease in the engine speed Ne can be suppressed and the fuel cut region can be expanded. The above-described lockup slip rotational speed is calculated by subtracting the engine rotational speed Ne from the turbine rotational speed Nt.

  In addition, when the vehicle enters a predetermined driving state and the fuel cut condition is satisfied, the electronic control unit 100 executes a fuel cut that stops the fuel supply to the engine 11, while the predetermined fuel cut return condition If the condition is satisfied, fuel cut control for returning from the fuel cut state is executed. For example, the electronic control unit 100 is a vehicle in which the throttle is turned off such that the throttle valve opening θth obtained from the throttle sensor 59 with an idle switch is substantially fully closed or is slightly opened at about 2-3% or less. When the vehicle travels at a reduced speed, the engine speed Ne obtained from the engine speed sensor 54 is equal to or lower than a predetermined fuel cut start speed Nek (for example, about 1400 rpm), and the engine speed Ne decreases. When a predetermined fuel cut condition such as a predetermined delay time Tfc has passed, a stop command signal Sfc for stopping fuel supply to the engine 11 is sent to the fuel injection device 71 so as to start fuel cut. It is designed to output. The fuel cut conditions described above are merely examples and are not limited thereto.

  On the other hand, when the engine speed Ne reaches a predetermined fuel cut return speed Nef by decelerating traveling of the vehicle and satisfies the fuel cut return condition, the electronic control unit 100 turns off the fuel cut to the engine 11. The output of the fuel supply stop command signal Sfc is stopped. As a result, when the fuel cut is turned off, the engine 11 restarts the fuel supply and starts up quickly.

  The above-described fuel cut return rotational speed Nef is appropriately changed by a fuel cut return rotational speed changing process described later. Further, in the present embodiment, the electronic control device 100 that performs the above-described fuel cut control constitutes a fuel cut control means.

  Further, the electronic control unit 100 determines whether or not a downshift has been executed based on a signal corresponding to the operation position Psh of the shift lever 77 input from the shift position sensor 64. In the present embodiment, electronic control device 100 that performs the above-described determination constitutes a downshift determination means.

  In addition, when it is determined that the above-described downshift has been performed in a state where the fuel cut is being performed (hereinafter referred to as “fuel cut being performed”), the electronic control apparatus 100 The undershoot amount of the engine speed Ne with respect to the target engine speed Ner corresponding to the gear position is detected.

Specifically, the electronic control unit 100 corresponds to the fifth speed, which is the gear position before the shift, when it is determined that the downshift from the fifth speed to the fourth speed is performed, for example, during the fuel cut. By comparing the target engine speed Ner ₅ with the actual engine speed Ne ₅ , it is determined whether or not an undershoot has occurred in the engine speed Ne. If the electronic control unit 100 determines that an undershoot has occurred in the engine speed Ne, the target engine speed Ner ₅ corresponding to the fifth speed, which is the gear position before the shift, and the actual engine speed are determined. according to the difference between the number Ne ₅ and detects (calculates) an undershoot amount of the engine speed Ne. In other words, the electronic control unit 100 compares the target engine speed Ner corresponding to the speed stage before the shift and the actual engine speed Ne in the downshift of each speed stage, so that the engine speed is changed for each speed stage. It is determined whether or not Ne undershoot has occurred, and if it is determined that undershoot has occurred, it is determined for each gear position according to the difference between the target engine speed Ner and the actual engine speed Ne. The undershoot amount is detected (calculated).
In the present embodiment, the electronic control device 100 described above constitutes an undershoot amount detecting means.

In addition, when the undershoot amount of the engine speed Ne described above is equal to or greater than the threshold th that has been experimentally obtained and stored in advance, the electronic control unit 100 performs the fuel cut return speed Nef in the next downshift of the same gear stage. Is set to the fuel cut return rotational speed Nef ₂ lower than the fuel cut return rotational speed Nef ₁ when the above-described undershoot does not occur or the undershoot amount is less than the above-described threshold th. The change process is executed. It should be noted that the above-described threshold th is a value that can be determined in advance when it is determined that the engine speed Ne may be equal to or lower than the fuel cut return speed Nef during downshift when the undershoot amount is equal to or greater than this value. Is set to seek. Further, the fuel cut return rotational speed Nef ₁ described above is a rotational speed (for example, 800 rpm) that is about the rotational speed that is generally employed in the past, and does not cause engine stall and maintains stable rotation of the engine 11. The speed is set.

Specifically, as shown in FIG. 6, when an undershoot occurs in, for example, a downshift from the fifth speed to the fourth speed during fuel cut, the electronic control device 100 determines the amount of undershoot at the engine speed Ne. When the threshold value th is equal to or greater than the threshold th that is experimentally obtained and stored in advance, a difference value Δ between the lowest engine speed Ne _min and the fuel cut return speed Nef ₁ when an undershoot occurs is calculated. The electronic control unit 100 then sets the fuel cut return rotational speed Nef in the next downshift from the fifth speed to the fourth speed to a fuel cut lower than the fuel cut return rotational speed Nef ₁ according to the calculated difference value Δ. The return rotational speed Nef ₂ is set. That is, the electronic control unit 100 sets the fuel cut return rotation speed Nef ₂ corresponding to the above-described difference value Δ by referring to a fuel cut return rotation speed setting map as shown in FIG. 7 stored in the ROM, for example. It is supposed to be. For example, when the difference value Δ is 50 (rpm), the electronic control unit 100 sets the fuel cut return rotational speed Nef in the next downshift of the same gear as the fuel cut return rotational speed Nef _1. The fuel cut return rotational speed Nef ₂ lower than 800 (rpm) is set to 550 (rpm). On the other hand, for example, when the above-described difference value Δ is 300 (rpm) or 500 (rpm), the electronic control unit 100 increases the engine load due to a change in the operation state of the auxiliary machine during the occurrence of undershoot and the like. the engine speed Ne is less likely to be fuel cut rotation speed Nef ₁ below, without changing the fuel cut rotation speed Nef at downshift next identical shift speed sets the fuel cut rotation speed Nef ₁ It is also possible to maintain 800 (rpm) as the fuel cut return rotational speed Nef. Here, as the change in the operation state of the auxiliary machine described above, for example, an increase in the amount of power generated by the alternator due to an increase in the electric load due to the headlight ON or the like or an increase in the electric load due to the air conditioner ON is assumed.
In the present embodiment, the case where an undershoot occurs in the downshift from the fifth speed to the fourth speed is illustrated, but the same applies to the downshifts in other shift stages.

In addition, when undershoot occurs during downshifting during vehicle deceleration while the fuel cut is being executed, the electronic control unit 100 causes the engine speed Ne to be equal to or less than the fuel cut return speed Nef ₁ because the undershoot amount is large. When returning from the cut state, the engine speed at which the fuel cut is restored at the next downshift of the same gear position is obtained by subtracting a fixed value that is experimentally obtained and stored in advance from the minimum engine speed Ne _{min at} this time. Nef ₂ is set. As the above-mentioned fixed value, it is possible to suppress the possibility that the engine load increases due to a change in the operating state of the auxiliary machine during the occurrence of undershoot and the engine speed Ne becomes the fuel cut return speed Nef ₁ or less, and fuel cut rotation speed Nef ₂ is a limitation of the starting limit speed Ne _s leading to engine stall (e.g., 300Rpm～400rpm about) values such that more speed is set by experimentally determined in advance.

Here, the above-described fuel cut rotation speed Nef ₁ and fuel cut rotation speed Nef ₂ or speed set as the starting limit speed Ne _s (rpm) are illustrative, specifications such as an engine, a downshift It is arbitrarily set according to the shift stage at the time, the deceleration of the vehicle, and the like.

In the present embodiment, the electronic control device 100 that executes the above-described fuel cut return rotational speed changing process constitutes the fuel cut return rotational speed setting means. In the present embodiment, the above-described fuel cut return rotational speed Nef ₁ and fuel cut return rotational speed Nef ₂ constitute the first fuel cut return rotational speed and the second fuel cut return rotational speed, respectively. .

Further, the electronic control unit 100, when the fuel cut rotation speed Nef ₂ described above was performed downshift at the same speed stage next and subsequent in a state of being set, during the downshift, undershoot is not generated, Alternatively, when the undershoot amount is less than the above threshold value th, the engine load increases due to a change in the auxiliary machine operating state or the like during the occurrence of undershoot, and the engine speed Ne becomes the fuel cut return speed Nef ₁ or less. Since the possibility is low, the fuel cut return rotational speed Nef set to the fuel cut return rotational speed Nef ₂ is returned to the fuel cut return rotational speed Nef ₁ .

Next, the operation of the fuel cut control device according to the embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 8, the electronic control unit 100 determines whether or not a fuel cut that stops the supply of fuel to the engine 11 is being executed (step S101). If it is determined that the fuel cut is not being executed, the electronic control unit 100 ends this process.

  On the other hand, when it is determined that the fuel cut is being performed, the electronic control unit 100 determines whether or not the downshift is being performed based on the signal input from the shift position sensor 64 (step S102). . If it is determined that the downshift is not being performed, the electronic control device 100 ends the process.

On the other hand, if it is determined that the downshift is being performed, the electronic control unit 100 determines whether the engine speed Ne has become equal to or lower than the fuel cut return speed Nef during the downshift, and the fuel cut state has been restored. Is determined (step S103). If the electronic control unit 100 determines that a return from the fuel cut state has been made during downshift execution, the electronic control unit 100 subtracts a fixed value that has been experimentally obtained and stored in advance from the minimum engine speed Ne _{min at} this time. the rotational speed and ends the process by setting the fuel cut rotation speed Nef ₂ in downshift next identical shift speed (step S104).

In step S103, if the electronic control unit 100 determines that the fuel cut state has not been returned during the downshift execution, the gear stage before the shift during the downshift execution, for example, the gear stage is the fifth speed. actual detection undershoot amount of the engine speed Ne ₅ with respect to the target engine speed Ner ₅ corresponding to the fifth speed as long as (calculated) (step S105).

Specifically, the electronic control unit 100 detects (calculates) an undershoot amount of the engine speed Ne according to the difference between the target engine speed Ner ₅ and the actual engine speed Ne ₅ . At this time, if the above-described undershoot amount is not detected, that is, if no undershoot has occurred, the electronic control unit 100 sets 800 (rpm), which is set as the fuel cut return rotation speed Nef ₁ , to the fuel. This is maintained as the cut return rotational speed Nef.

Next, the electronic control unit 100 determines whether or not the fuel cut return rotational speed Nef has already been changed before the downshift from the fifth speed to the fourth speed during the downshift from the fifth speed to the fourth speed, for example. Is determined (step S106). That is, the electronic control unit 100 determines whether or not the fuel cut return rotational speed Nef has already been set from the fuel cut return rotational speed Nef ₁ to the fuel cut return rotational speed Nef ₂ .

If the electronic control unit 100 determines that the fuel-cut return rotational speed Nef has not yet been changed, is the undershoot amount detected in step S105 equal to or greater than the threshold th that has been experimentally determined and stored in advance? It is determined whether or not (step S107). Here, if the electronic control unit 100 determines that the detected undershoot amount is not equal to or greater than the threshold th that has been experimentally obtained and stored in advance, that is, less than the threshold th, the auxiliary control unit during the occurrence of the undershoot since the engine rotational speed Ne the engine load is increased due to changes in the operating conditions is less likely to be fuel cut rotation speed Nef ₁ below, maintains the 800 (rpm) is set as the fuel cut rotation speed Nef ₁ Then, this process ends.

On the other hand, when it is determined that the detected undershoot amount is equal to or greater than the above-described threshold th, the electronic control unit 100 executes a fuel cut return rotation speed changing process (step S108). Specifically, the electronic control unit 100 calculates a difference value Δ between the lowest engine speed Ne _min when the undershoot occurs and the fuel cut return speed Nef ₁ . Then, the electronic control unit 100 sets the fuel cut return rotational speed Nef ₂ corresponding to the above-described difference value Δ by referring to the fuel cut return rotational speed setting map (see FIG. 7). For example, when the difference value Δ is 50 (rpm), the electronic control unit 100 sets the fuel cut return rotational speed Nef at the next downshift from the fifth speed to the fourth speed as the fuel cut return rotational speed. The fuel cut return rotational speed Nef ₂ lower than 800 (rpm) set as Nef ₁ is set to 550 (rpm), and this process is terminated.

At this time, for example, when the difference value Δ is 300 (rpm) or 500 (rpm), the electronic control unit 100 increases the engine load due to a change in the operating state of the auxiliary machine during the undershoot. Therefore, it is unlikely that the engine speed Ne will be equal to or lower than the fuel cut return speed Nef _1. Therefore, without changing the fuel cut return speed Nef at the next downshift from the fifth speed to the fourth speed, the fuel cut It is also possible to end this process while maintaining 800 (rpm) set as the return rotational speed Nef ₁ .

On the other hand, if it is determined in step S106 that the fuel cut return rotational speed Nef has already been changed, the electronic control unit 100 determines whether the undershoot amount detected in step S105 is less than the threshold th. Determination is made (step S109). When the electronic control unit 100 determines that the undershoot amount is less than the threshold th, the fuel cut return rotational speed Nef set to the fuel cut return rotational speed Nef ₂ is returned to the fuel cut return rotational speed Nef ₁ . To complete the process.

On the other hand, when it is determined that the undershoot amount is less than the threshold th, that is, the undershoot amount is equal to or greater than the threshold th, the electronic control unit 100 executes the fuel cut return rotation speed changing process again in step S108. Then, the fuel cut return rotational speed Nef ₂ corresponding to the difference value Δ is set.

As described above, in the fuel cut control device 1 according to the present embodiment, the electronic control device 100 experimentally obtains the undershoot amount of the engine speed Ne calculated during the downshift of the gear stage in advance. When it is equal to or greater than the stored threshold th, the fuel cut return rotational speed Nef in the next downshift of the same gear is set to the fuel cut return rotational speed Nef ₂ lower than the fuel cut return rotational speed Nef ₁ . Even when the engine speed Ne becomes equal to or lower than the fuel cut return speed Nef ₁ during downshifting, the fuel cut state can be continued and fuel consumption can be improved.

Further, the fuel cut return rotational speed Nef is lower than the fuel cut return rotational speed Nef ₁ only while the downshift is executed when the undershoot amount of the engine rotational speed Ne is experimentally determined and stored in advance. since so as to set the restoration speed Nef _2, it can be minimized to a period in which a state of approaching the starting limit speed Ne _s of the engine 11 by lowering the fuel cut rotation speed Nef. For this reason, it is possible to prevent the engine 11 from stalling due to a decrease in the engine speed Ne due to an increase in the load of the engine 11 during the downshift.

  In the present embodiment, the electronic control unit 100 sets the fuel cut return rotation speed Nef regardless of the deceleration G of the vehicle. For example, as shown in FIG. The fuel cut return rotational speed Nef set in the return rotational speed change process is set in the fuel cut return rotational speed map for each deceleration G for each deceleration G according to the deceleration G detected by the acceleration sensor 68. It may be. In this case, a deceleration-by-deceleration fuel cut return rotational speed map is stored in advance in the ROM of the electronic control unit 100.

Further, the fuel cut return rotation speed for each deceleration G shown in the deceleration-specific fuel cut return rotation speed map of FIG. 9 is an example, and for example, during downshift execution from 6th speed to 5th speed, When the deceleration G of the vehicle is 0.03 and the difference value Δ between the minimum engine speed Ne _min and the fuel cut return speed Nef ₁ when an undershoot occurs is 150 (see FIG. 7), In the next downshift from the sixth speed to the fifth speed, 700 (rpm) is set as the fuel cut return rotational speed Nef ₂ when the deceleration G of the vehicle is 0.03. In addition, in the fuel cut return rotation speed map for each deceleration shown in FIG. 9, the downshift of each gear stage from the 8th speed to the 3rd speed is described as an example, but the downshift of other gear stages is also described. It is the same.

  As a result, the fuel cut return rotational speed Nef can be set in accordance with the deceleration G of the vehicle, so that the vehicle deceleration G is low, for example, the possibility of undershooting at the engine rotational speed Ne is low. It is possible to prevent the fuel cut return rotational speed Nef from being set low until such time. Accordingly, it is possible to set the optimum fuel cut return rotational speed Nef corresponding to the possibility of occurrence of the undershoot described above.

Further, in the present embodiment, when the undershoot amount of the engine speed Ne is equal to or more than the threshold th that is experimentally obtained and stored in advance, the fuel cut return speed Nef in the next downshift of the same gear is set. The fuel cut return rotational speed Nef ₂ is set lower than the fuel cut return rotational speed Nef ₁ when no undershoot occurs or the undershoot amount is less than the above-mentioned threshold value th. When the possibility of engine stall is relatively high, such as during braking, and when determining other low-μ roads, when the snow mode is on, or when the ABS is operating, regardless of the amount of undershoot described above, Without changing the fuel cut return speed Nef in downshift, the fuel cut return speed You may make it maintain 800 (rpm) set as rotation number Nef ₁ as fuel cut return rotation speed Nef.

  In addition, the embodiment disclosed this time is illustrative in all respects and is not limited to this embodiment. The scope of the present invention is shown not by the above description of the embodiments but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  As described above, the fuel cut control device according to the present invention improves the fuel consumption by the fuel cut control, and causes the engine stall due to the decrease in the engine speed due to the increase in the load of the internal combustion engine during the downshift. This has the effect of suppressing the occurrence and is useful for all fuel cut control devices.

1 Fuel Cut Control Device 11 Engine (Internal Combustion Engine)
20 automatic transmission 25 output shaft 100 electronic control device (fuel cut control means, downshift determination means, undershoot amount detection means, fuel cut return rotational speed setting means)
C1-C4 clutch (friction engagement element)
B1, B2 Brake (Friction engagement element)

Claims (1)

When the vehicle is traveling at a reduced speed and a predetermined condition is satisfied, the fuel supply to the internal combustion engine is stopped, and when the engine speed of the internal combustion engine is equal to or lower than a predetermined first fuel cut return rotational speed, Fuel cut control means for executing fuel cut control for restarting fuel supply to the internal combustion engine;
A plurality of friction engagement elements are provided, and a plurality of shift speeds are established by switching engagement and release of the plurality of friction engagement elements, and power of the internal combustion engine is output at a gear ratio corresponding to the shift speeds. A fuel cut control device comprising an automatic transmission for output to a shaft,
Downshift determining means for determining whether or not the shift stage has been downshifted in a state where fuel supply to the internal combustion engine is stopped by the fuel cut control means;
When the downshift determining unit determines that the downshift has been executed, an undershoot amount detecting unit that detects an undershoot amount of the engine speed that occurs at each of the plurality of shift speeds during execution of the downshift. When,
When the undershoot amount detected by the undershoot amount detection means is equal to or greater than a predetermined threshold, the fuel cut return rotational speed at the next downshift of the same gear stage is determined from the first fuel cut return rotational speed. A fuel cut control device, comprising: a fuel cut return rotation speed setting means for setting a lower second fuel cut return rotation speed.

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