JP2007211619A - Fuel-cut control device of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent engine stall from occurring due to friction of the engine or variation of friction materials of a lock-up clutch at the time of sudden stop during slip control of the lock-up clutch, while lowering a fuel-cut reset rotating speed as much as possible so as to prevent fuel consumption from being worsened. <P>SOLUTION: It is judged whether the engine stall has occurred or will occur at the time of sudden stop during the slip control of the lock-up clutch (S5). When it is judged that the engine stall has occurred or will occur, learning correction is performed to increase the fuel-cut reset rotating speed nefckyuteisi (S6). Thus, irrespective of the friction of the engine or the individual difference such as the variation of the friction materials of the lock-up clutch, the fuel-cut reset rotating speed nefckyuteisi is set within a range where the engine stall does not occur and at a value as low as possible, thereby preventing the fuel consumption from being worsened. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an engine fuel cut control device, and more particularly to a fuel cut that performs fuel cut to as low a rotation as possible while preventing engine stall when a sudden braking is applied during slip control of a lockup clutch. The present invention relates to a control device.

(a) For an engine to which an automatic transmission is connected via a fluid transmission device having a lock-up clutch, (b) on the condition that the engine is decelerated and the engine rotational speed is equal to or higher than the fuel cut return rotational speed. 2. Description of the Related Art There is known a fuel cut control device for an engine that performs fuel cut for stopping the fuel supply and restarts the fuel supply of the engine when the engine rotational speed is lower than the fuel cut return rotational speed. The device described in Patent Document 1 is an example, and by controlling slip-up of the lock-up clutch at the time of deceleration, a reduction in engine rotation speed is suppressed and a fuel cut region (vehicle speed range) is expanded, thereby improving fuel efficiency. It is like that. Also, if the engine speed falls below the fuel cut return speed, the engine stall is prevented by restarting the fuel supply to the engine, but the fuel cut return speed depends on the vehicle condition such as the load condition of the auxiliary equipment. This makes it possible to improve both fuel efficiency and prevent engine stall.
JP-A-2005-98522

  By the way, if sudden braking is performed during slip control of the conventional lock-up clutch, engine stall is likely to occur. For this reason, in that case, it is conceivable to increase the fuel-cut return rotational speed so that engine stall does not occur. However, if the fuel cut return rotational speed is increased, fuel consumption is deteriorated. Therefore, it is desirable to set the fuel cut return rotational speed as low as possible without causing engine stall. However, if the fuel cut return rotational speed is set as low as possible to improve fuel efficiency, there is a problem that engine stall occurs due to variations in engine friction and friction material of the lockup clutch.

  The present invention has been made against the background of the above circumstances. The purpose of the present invention is to make a sudden stop during slip control of the lockup clutch while suppressing deterioration of fuel consumption by setting the fuel cut return rotational speed as low as possible. It is to prevent the engine stall from occurring due to the friction of the engine and the friction material of the lock-up clutch.

  In order to achieve the above object, the first invention relates to (a) an engine to which an automatic transmission is connected via a fluid transmission device having a lock-up clutch, and (b) at the time of deceleration and the engine rotational speed is a fuel. The fuel of the engine that performs fuel cut to stop the fuel supply of the engine on the condition that it is equal to or higher than the cut return rotational speed, and resumes the fuel supply of the engine when the engine rotational speed falls below the fuel cut return rotational speed In the cut control device, (c) sudden stop determination means for determining whether or not the vehicle is suddenly stopped during slip control of the lockup clutch, and (d) the sudden stop determination. When the engine determines that the lockup is on, the engine stalls. Or engine stall determining means for determining whether or not there is a risk of occurrence, and (e) when it is determined by the engine stall determining means that the engine is stalled or is likely to occur, Learning means for performing learning correction so as to increase the fuel cut return rotational speed.

  The second aspect of the present invention is the engine fuel cut control device according to the first aspect of the present invention, wherein (a) the fuel cut return rotational speed is set for each oil temperature region of the fluid transmission device, and (b) the learning means is The fuel cut return rotational speed is learned and corrected for each oil temperature region.

  According to a third aspect of the present invention, in the engine fuel cut control device according to the first or second aspect of the invention, the sudden stop determination means has at least a reduction rate of the input shaft rotational speed of the automatic transmission equal to or greater than a predetermined value, or the engine rotation speed. It is characterized in that it is determined that the lock-up ON is suddenly stopped on condition that the rate of decrease in speed is a predetermined value or more.

  In such a fuel cut control device for an engine, if it is determined that an engine stall may or may occur during a sudden stop during slip control of the lockup clutch, the fuel cut return rotational speed is increased. Therefore, the fuel cut return rotation speed is set as low as possible within the range where engine stall does not occur, regardless of individual differences such as engine friction and variations in friction material of the lock-up clutch. Thus, deterioration of fuel consumption is suppressed.

  On the other hand, the ease of occurrence of engine stall differs depending on the oil temperature of the fluid transmission. When the oil temperature is low, the viscosity of the fluid increases and the engine rotation speed is difficult to increase, so engine stall is likely to occur. . In this case, if the fuel cut return rotation speed is learned and corrected regardless of the oil temperature, the fuel cut return rotation speed at high oil temperature, which is low in viscosity and difficult to cause engine stall, also increases. Fuel supply will be resumed and fuel economy will deteriorate. In contrast, in the second aspect of the invention, the fuel cut return rotational speed is learned and corrected for each oil temperature region. Therefore, the fuel cut return rotational speed is increased only in the low oil temperature region where engine stall is likely to occur. Both prevention of occurrence and suppression of deterioration of fuel consumption can be achieved.

  In the third aspect of the invention, it is determined whether or not the lockup is suddenly stopped in consideration of the input shaft rotational speed or the decrease rate of the engine rotational speed, which is closely related to the occurrence of engine stall. When the engine stall occurs or is likely to occur, the fuel cut return rotational speed can be appropriately learned and corrected.

  The present invention includes at least an engine that generates power by combustion of fuel as a driving power source for traveling. However, the present invention can also be applied to a hybrid vehicle including another power source such as an electric motor in addition to the engine. .

  The engine includes a fuel injection device that can automatically stop the fuel supply by the fuel cut means. As the throttle valve for adjusting the amount of intake air, an electronic throttle valve that can be electrically opened and closed is preferably used, but it has a throttle valve that is mechanically opened and closed according to the driver's accelerator operation (output request). Things can be used.

  The fuel cut is performed on condition that the engine speed is equal to or higher than a predetermined value. The predetermined value is, for example, the fuel cut return rotational speed, and the fuel cut is stopped when the fuel cut return rotational speed is lower than the predetermined value. However, as a fuel cut start condition, a rotational speed different from the fuel cut return rotational speed may be determined. The fuel cut return rotational speed is a rotational speed at which the engine can be immediately started (self-rotating) when the fuel supply is resumed. For example, as in the second invention, the oil temperature region of the fluid transmission device is determined as a parameter. It is desirable to increase the return rotation speed as the engine speed is lower, but various modes are possible, such as setting the engine load in consideration of changes in engine load accompanying the operation of auxiliary equipment such as air conditioners. is there.

  As an automatic transmission, for example, a stepless automatic transmission such as a planetary gear type or a parallel shaft type or a continuously variable transmission such as a belt type can be adopted, but the reverse input from the drive wheel side is locked. It is transmitted to the engine side via the up clutch, and is configured to rotationally drive the engine. Various modes are possible, such as an automatic transmission for forward / reverse switching that switches between forward and reverse.

  The automatic transmission is configured such that, for example, a plurality of forward shift speeds are automatically switched using parameters such as the vehicle speed and the throttle valve opening as parameters, but the downshift during coast deceleration with the throttle valve fully closed is performed. For example, the coast down vehicle speed is set for each forward gear so that the fuel cut is continued. Specifically, the fuel cut return rotational speed and each forward gear are set such that a downshift is performed before the engine rotational speed reaches the fuel cut return rotational speed and the engine rotational speed is increased with the downshift. What is necessary is just to set according to the gear ratio of a stage.

  As the fluid transmission device, a torque converter having a torque amplifying function is preferably used, but other fluid transmission devices such as a fluid coupling can also be adopted. The lock-up clutch directly connects the input side and the output side of the fluid transmission device, and a hydraulic friction engagement device that is frictionally engaged by the differential pressure of the fluid is preferably used. Various modes are possible, such as an engagement device arranged in parallel with a fluid transmission device.

  The lock-up clutch is slip-controlled during coast deceleration with the throttle valve fully closed in order to suppress a decrease in engine rotation speed and expand a fuel cut region (vehicle speed range). In the slip control, for example, an engagement torque, for example, a hydraulic pressure difference between the engagement side and the release side is feedback-controlled so that a target slip amount is obtained.

  The sudden stop determination means is configured to determine whether or not the lock-up is suddenly stopped in consideration of the reduction rate of the input shaft rotational speed and the engine rotational speed, for example, as in the third aspect of the invention. Various modes are possible, such as whether the hydraulic pressure is higher than a predetermined value, whether the rate of increase in brake hydraulic pressure is higher than a predetermined value, or whether the rate of decrease in vehicle speed is higher than a predetermined value. is there.

  The fuel cut control device according to the present invention is, for example, a fuel for a sudden stop at a higher rotation speed than that at the time of normal deceleration when the sudden stop determination means determines that the lock-up ON is suddenly stopped. It has fuel cut return rotation speed setting means for switching to the cut return rotation speed. In this case, the learning means is configured to learn and correct the fuel cut return rotational speed for the sudden stop. For example, a plurality of maps are used for switching the fuel cut return rotational speed, but a single basic map may be used to correct as necessary. Regardless of whether or not the vehicle is suddenly stopped, the same fuel cut return rotational speed determined by using the common fuel cut return rotational speed map or the like as a parameter such as the oil temperature is set. Also good.

  The engine stall judging means detects, for example, the minimum value of the engine speed at the time of a sudden stop, and whether or not the engine stall has occurred or is likely to occur depending on whether the minimum value is a predetermined value or less. Judgment can be made.

  The learning means performs learning correction so as to increase the fuel cut return rotational speed under a certain condition. As an initial value of the fuel cut return rotational speed, for example, considering the individual difference (variation) of the engine, Although it is desirable to improve the fuel efficiency by setting an engine where engine stall is unlikely to occur, it may be set based on an average engine. In addition, for example, when the state where the engine stall does not occur even when the lockup ON suddenly stops continues for a predetermined number of times, it is possible to perform learning correction so as to gradually decrease the fuel cut return rotation speed. In that case, a relatively high rotational speed can be set as an initial value.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a skeleton diagram of a horizontally-mounted vehicle drive device such as an FF (front engine / front drive) vehicle. An output of an engine 10 constituted by an internal combustion engine such as a gasoline engine includes a torque converter 12, The power is transmitted to drive wheels (front wheels) (not shown) through a power transmission device such as the automatic transmission 14 and the differential gear device 16. The torque converter 12 includes a pump impeller 20 connected to the crankshaft 18 of the engine 10, a turbine impeller 24 connected to the input shaft 22 of the automatic transmission 14, and a non-rotating member via a one-way clutch 26. And a stator 30 fixed to the housing 28, which transmits power between the pump impeller 20 and the turbine impeller 24 via a fluid, and between the pump impeller 20 and the turbine impeller 24. Is provided with a lock-up clutch 32 for direct connection. The lock-up clutch 32 is a hydraulic friction clutch that is frictionally engaged by a differential pressure ΔP between the hydraulic pressure in the engagement side oil chamber 32a and the hydraulic pressure in the release side oil chamber 32b. The impeller 20 and the turbine impeller 24 are rotated together. Further, the differential pressure ΔP, that is, the engagement torque is feedback-controlled so as to be engaged in a predetermined slip state, so that the turbine impeller 24 is driven to the pump impeller 20 with a predetermined slip amount of, for example, about 50 rpm during driving. On the other hand, at the time of reverse input (driven), the pump impeller 20 can be rotated following the turbine impeller 24 with a predetermined slip amount of about −50 rpm, for example. A mechanical oil pump 21 such as a gear pump is connected to the pump impeller 20 and is driven to rotate together with the pump impeller 20 by the engine 10 so as to generate hydraulic pressure for shifting or lubricating. The engine 10 is a driving force source for traveling the vehicle, and the torque converter 12 is a fluid transmission device.

  The automatic transmission 14 is coaxially disposed on the input shaft 22 and a carrier and a ring gear are connected to each other to thereby form a so-called CR-CR coupled planetary gear mechanism. A first planetary gear unit 40 and a second planetary gear unit 42; a set of third planetary gear units 46 arranged coaxially on a counter shaft 44 parallel to the input shaft 22; and a shaft end of the counter shaft 44 An output gear 48 that is fixed and meshes with the differential gear device 16 is provided. The components of the planetary gear units 40, 42, 46, that is, the sun gear, the ring gear, and the carrier that rotatably supports the planet gears meshing with them are selectively connected to each other by four clutches C0, C1, C2, and C3. Alternatively, the three brakes B1, B2, and B3 are selectively connected to the housing 28 that is a non-rotating member. The two one-way clutches F1 and F2 are engaged with each other or with the housing 28 depending on the rotation direction. Since the differential gear device 16 is configured symmetrically with respect to the axis (axle), the lower side is not shown.

  The first planetary gear unit 40, the second planetary gear unit 42, the clutches C0, C1, C2, the brakes B1, B2, and the one-way clutch F1 arranged coaxially with the input shaft 22 are moved forward and reverse by four stages. A one-stage main transmission unit MG is configured, and a set of planetary gear unit 46, clutch C3, brake B3, and one-way clutch F2 arranged on the counter shaft 44 constitute a sub-transmission unit, that is, an underdrive unit U / D. It is configured. In the main transmission unit MG, the input shaft 22 is connected to the carrier K2 of the second planetary gear device 42, the sun gear S1 of the first planetary gear device 40, and the sun gear S2 of the second planetary gear device 42 via the clutches C0, C1, and C2. Each is connected. The ring gear R1 of the first planetary gear unit 40 and the carrier K2 of the second planetary gear unit 42 are connected, and the ring gear R2 of the second planetary gear unit 42 and the carrier K1 of the first planetary gear unit 40 are connected to each other. The sun gear S2 of the second planetary gear unit 42 is connected to the housing 28 that is a non-rotating member via a brake B1, and the ring gear R1 of the first planetary gear unit 40 is a housing 28 that is a non-rotating member via a brake B2. It is connected to. A one-way clutch F1 is provided between the carrier K2 of the second planetary gear unit 42 and the housing 28 which is a non-rotating member. The first counter gear G1 fixed to the carrier K1 of the first planetary gear device 40 and the second counter gear G2 fixed to the ring gear R3 of the third planetary gear device 46 are meshed with each other. In the underdrive unit U / D, the carrier K3 and the sun gear S3 of the third planetary gear unit 46 are connected to each other via the clutch C3, and between the sun gear S3 and the housing 28 that is a non-rotating member, A brake B3 and a one-way clutch F2 are provided in parallel.

  The clutches C0, C1, C2, and C3 and the brakes B1, B2, and B3 (hereinafter simply referred to as the clutch C and the brake B unless otherwise distinguished) are controlled by a hydraulic actuator such as a multi-plate clutch or a band brake. This is a hydraulic friction engagement device, and is hydraulically driven by excitation, de-energization, or a manual valve (not shown) of solenoid valves S4, SR and linear solenoid valves SL1, SL2, SL3, SLT, SLU, etc. of a hydraulic control circuit 98 (see FIG. 3). When the circuit is switched, for example, as shown in FIG. 2, the engaged and released states are switched, and the forward gear, the reverse gear, and the neutral gear according to the operation position (position) of the shift lever 72 (see FIG. 3). Each gear stage is established. “1st” to “5th” in FIG. 2 mean the first to fifth forward gears, “◯” means engagement, “×” means release, and “△” means only during driving. Means engagement.

  The shift lever 72 is, for example, in accordance with the shift pattern shown in FIG. 4, a parking position “P”, a reverse travel position “R”, a neutral position “N”, a forward travel position “D”, “4”, “3”, “2”. In the “P” and “N” positions, a neutral gear stage is established as a non-drive gear stage that cuts off power transmission, but in the “P” position, a mechanical gear (not shown) is established. The parking mechanism mechanically prevents the drive wheels from rotating. Further, each of the five forward gears and one reverse gear established at the forward travel position such as “D” or the “R” position corresponds to a drive gear stage.

FIG. 3 is a block diagram for explaining a control system provided in the vehicle for controlling the engine 10 and the automatic transmission 14 of FIG. 1, and the operation amount (accelerator opening) Acc of the accelerator pedal 50 is an accelerator operation. It is detected by the quantity sensor 51. The accelerator pedal 50 is largely depressed according to the driver's required output amount, and corresponds to an accelerator operation member, and the accelerator pedal operation amount Acc corresponds to an output request amount. In addition, an electronic throttle valve 56 whose opening degree θ _TH is changed by a throttle actuator 54 is provided in the intake pipe of the engine 10. In addition, an intake air amount sensor 60 for detecting an intake air quantity Q of the engine rotational speed sensor 58, the engine 10 for detecting the rotational speed NE of the engine 10, the intake for detecting the temperature T _A of intake air An air temperature sensor 62, a throttle sensor 64 with an idle switch for detecting the fully closed state (idle state) of the electronic throttle valve 56 and its opening θ _TH, and the rotational speed (output shaft) of the counter shaft 44 corresponding to the vehicle speed V a vehicle speed sensor 66 for detecting the corresponding) N _OUT of the rotational speed, the cooling water temperature sensor 68 for detecting the cooling water temperature T _W of the engine 10, a brake switch 70 for detecting the presence or absence of foot brake operation, the shift lever 72 lever position sensor 74 for detecting a lever position (operating position) P _SH of the turbine rotational speed NT (= input Turbine rotational speed sensor 76 for detecting force shaft rotational speed N _IN ), AT oil temperature sensor 78 for detecting AT oil temperature T _OIL which is the temperature of hydraulic oil in torque converter 12 and hydraulic control circuit 98, A counter rotational speed sensor 80 for detecting the rotational speed NC of the first counter gear G1, an ignition switch 82, and the like are provided. From these sensors, the engine rotational speed NE, the intake air amount Q, and the intake air temperature T _{A are provided.} , Throttle valve opening θ _TH , vehicle speed V (output shaft rotation speed N _OUT ), engine cooling water temperature T _W , presence / absence of brake operation, lever position P _SH of shift lever 72, turbine rotation speed NT, AT oil temperature T _OIL , Signals representing the counter rotation speed NC, the operation position of the ignition switch 82, and the like are supplied to the electronic control unit 90. Also, the brake hydraulic pressure sensor 84 for detecting the brake hydraulic pressure P _BK of the brake master cylinder pressure or the like, together with a signal representing the brake pressure P _BK is supplied, whether or operating state of the working from auxiliaries 86 such as an air conditioner ( A signal representing the load) is supplied.

  The electronic control unit 90 includes a so-called microcomputer having a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU uses a temporary storage function of the RAM, and signals according to a program stored in the ROM in advance. By performing processing, output control of the engine 10, shift control of the automatic transmission 14, slip control of the lockup clutch 32, and the like are executed, and for engine control and shift control as necessary. Separately configured. FIG. 5 is a block diagram illustrating functions executed by signal processing of the electronic control unit 90, and functionally includes an engine control unit 120, a shift control unit 122, and a lockup clutch control unit 124.

The engine control means 120 basically controls the output of the engine 10, controls the opening and closing of the electronic throttle valve 56 by the throttle actuator 54, controls the fuel injection device 92 for controlling the fuel injection amount, and sets the ignition timing. For the control, an ignition device 94 such as an igniter is controlled. The electronic throttle valve 56 is controlled by, for example, driving the throttle actuator 54 based on the actual accelerator pedal operation amount Acc from the relationship shown in FIG. 6, and increasing the throttle valve opening θ _TH as the accelerator pedal operation amount Acc increases. . When the engine 10 is started, the crankshaft 18 of the engine 10 is cranked by a starter (electric motor) 96.

The engine control means 120 includes a fuel cut means 130, and performs fuel cut control to stop fuel supply to the engine 10 during coast deceleration of forward travel where the throttle valve opening θ _TH is substantially 0 and coasting. , To improve fuel economy. This fuel cut control is performed on condition that the engine speed NE is equal to or higher than a predetermined fuel cut return rotational speed NEFC. When the engine speed is lower than the fuel cut return rotational speed NEFC, the fuel supply to the engine 10 is resumed and the engine is restarted. 10 is activated.

Shift control means 122 performs transmission control in accordance with the lever position P _SH of the shift lever 72, for example, "D" position, performs a shift control using all the forward gear position "1st" to "5th" D Establish the range. In the D range, for example, a gear stage to be shifted in the automatic transmission 14 is determined based on the actual throttle valve opening θ _TH and the vehicle speed V from a pre-stored shift diagram (shift map) shown in FIG. The hydraulic control circuit executes a shift output for starting the shift operation to the determined gear stage, and prevents a shift shock such as a change in driving force from occurring or impairing the durability of the friction material. The 98 solenoid valves S4 and SR are switched ON (excitation) and OFF (de-excitation), and the energization amounts of the linear solenoid valves SL1 to SL3 and SLU are continuously changed. The solid line in FIG. 7 is an upshift line, and the broken line is a downshift line. As the vehicle speed V decreases or the throttle valve opening _θTH increases, the gear ratio (= input shaft rotational speed N _IN / output shaft). rotational speed N _OUT) being adapted to be switched to a large low-speed side gear stage, the "1" to "5" first gear "1st" to the fifth speed gear stage "5th" in FIG. I mean.

  Further, when the shift lever 72 is operated to the lever positions “4”, “3”, “2”, and “L”, the maximum speed stage, that is, the shift range in which the shift range on the high speed side with a small gear ratio is different. “4”, “3”, “2”, and “L” are established. In the 4th range, the shift control is performed from the first speed gear stage “1st” to the fourth speed gear stage “4th”, and in the third range, the speed change is performed from the first speed gear stage “1st” to the third speed gear stage “3rd”. In the second range, the shift control is performed at the first speed gear stage “1st” and the second speed gear stage “2nd”, and in the L range, the first speed gear stage “1st” is fixed.

The lock-up clutch control means 124 basically engages the lock-up clutch 32 according to a lock-up diagram set in advance with the throttle valve opening θ _TH and the vehicle speed V as parameters as in the above-described shift diagram (completely). Engagement), release, and slip engagement in a certain region. Further, a deceleration slip control means 126 is provided, and the lockup clutch 32 has a predetermined target slip amount SLP (for example, about −50 rpm) during coasting deceleration in forward traveling where the throttle valve opening θ _TH is substantially zero and coasting. The duty ratio D _SLU of the exciting current of the linear solenoid valve SLU involved in the differential pressure ΔP is feedback-controlled so that it can be engaged with the differential pressure ΔP. When the lock-up clutch 32 is slip-engaged in this way, the reverse input from the drive wheel side is transmitted to the engine 10 side, and the engine rotation speed NE is raised to the vicinity of the turbine rotation speed NT. The fuel cut region (vehicle speed range) due to the fuel consumption is expanded and fuel efficiency is further improved. This deceleration slip control is canceled to avoid engine stall when the engine speed NE reaches around the fuel cut return speed NEFC, or when a sudden stop of the vehicle is determined. The clutch 32 is released.

  Here, if sudden braking is performed during slip control of the lockup clutch 32, the engine speed NE decreases as the vehicle speed V decreases, and therefore engine stall is likely to occur. For this reason, in this embodiment, the fuel cut return rotation speed setting means 132 and the sudden stop determination means 134 are provided, and when the sudden stop determination means 134 determines that the stop is sudden, the fuel cut return is performed. As the rotational speed NEFC, a fuel cut return rotational speed nefcuiteisi for a sudden stop at a higher speed than that during normal deceleration is set. Although it varies depending on the operating characteristics of the engine 10, the fuel cut return rotation speed during normal deceleration is, for example, about 850 rpm, and the fuel cut return rotation speed nefckuteisi for sudden stop is, for example, about 900 rpm.

FIG. 9 is an example of a set value (data map) of the fuel cut return rotational speed nefckuteisi for sudden stop, and the AT oil temperature T _OIL is determined as a parameter. This occurs ease of engine stall, depend AT oil temperature T _OIL of the torque converter 12, the engine rotational speed NE is higher the viscosity of the fluid when AT oil temperature T _OIL is lower hardly rises Therefore, engine stall is likely to occur. For this reason, the fuel cut return rotational speed nefckuteisi is set to a relatively high rotation in the region where the AT oil temperature T _OIL is low, and the fuel cut return rotational speed nefckuteisi is set to a relatively low rotation in the region where the AT oil temperature T _OIL is high. It is. The fuel cut return rotational speed during normal deceleration is also set with the AT oil temperature T _OIL as a parameter. In addition, since the engine load changes depending on the operating state of the auxiliary equipment 86 such as an air conditioner, and the ease of occurrence of the engine stall changes, it is desirable to set the operating state of the auxiliary equipment 86 in consideration. .

  On the other hand, when setting the fuel cut return rotational speed nefkyuteisi at the time of the sudden stop, if this is increased, fuel consumption is deteriorated. Therefore, it is desirable to set the value as low as possible without causing engine stall. However, if the fuel cut return rotational speed nefckuteisi is set as low as possible to improve fuel efficiency, engine stall may occur due to friction of the engine 10 or variations in the friction material of the lockup clutch 32. For this reason, in this embodiment, the engine stall determining unit 136 and the learning unit 138 are provided. When the engine stall determining unit 136 determines that the engine stall has occurred or is likely to occur, the learning unit A learning correction is performed to increase the fuel cut return rotational speed nefkyuteisi by 138 so that engine stall is less likely to occur. As a result, regardless of individual differences such as friction of the engine 10 and variations in the friction material of the lockup clutch 32, the fuel cut return rotational speed nefckuteisi as low as possible is set within a range where engine stall does not occur. Deterioration of fuel consumption is suppressed.

  The initial value of the fuel cut return rotational speed nefckuteisisi is set to the lowest speed, taking into account individual differences (variations) of the engine 10, the lockup clutch 32, etc., for example, with reference to the case where engine stall is least likely to occur. Although it is desirable in terms of fuel consumption, an initial value may be set based on an average case, and when engine stall occurs, learning correction may be performed toward the high rotation side. The data of the fuel cut return rotational speed nefkyuteisi is stored in a storage device such as an EEPROM that can be rewritten and can retain the stored contents even when the power is turned off.

  FIG. 8 is a flowchart for specifically explaining the processing contents of the fuel cut return rotation speed setting means 132, the sudden stop determination means 134, the engine stall determination means 136, and the learning means 138. Step S2 is the sudden stop determination means 134. Steps S3 and S4 correspond to the fuel cut return rotational speed setting means 132, Step S5 corresponds to the engine stall determination means 136, and Step S6 corresponds to the learning means 138.

In step S1 of FIG. 8, it is determined whether or not the control precondition I is satisfied. The control precondition I is satisfied when the following (1) and (2) are both YES (positive). The determination of whether or not (1) and (2) are normal can be performed using, for example, a fail-safe flag indicating a failure, a failure flag, a diagnosis, or the like.
(1) Automatic transmission 14 is normal
(2) EFI (Electronically Controlled Fuel Injection) system is normal

If the control precondition I is satisfied and the determination in step S1 is YES, step S2 is executed to determine whether or not the control precondition II is satisfied. The control precondition II is satisfied when the following (1) to (4) are all YES. (1), the lever position P _SH detected by a lever position sensor 74 can be determined by whether or not the "D" position. (2) the engine coolant temperature T _W detected by the coolant temperature sensor 68 can be determined by whether or not a predetermined value T _W ^* above, the predetermined value T _W ^* is not normally necessary warm-up operation of the engine control It is possible temperature. These conditions (1) and (2) correspond to the execution conditions of the slip control during deceleration of the lock-up clutch 32. In (3), the deceleration slip control means 126 determines whether or not the deceleration slip control of the lockup clutch 32 is actually being executed. Whether or not (4) is a sudden stop is determined by whether or not the decrease rate ΔNT of the turbine rotational speed NT is equal to or greater than a predetermined value ΔNT ^* . The predetermined value ΔNT ^* is set based on whether or not it is necessary to switch the fuel cut return rotational speed NEFC from the one during normal deceleration to the fuel cut return rotational speed nefkuteisisi during a sudden stop in order to avoid engine stall. Is done. If (3) and (4) are satisfied, it means that the lockup clutch 32 is in a sudden stop when the lockup clutch 32 is in the slip control and the control precondition II is satisfied. Lock-up is on and sudden stop. The deceleration slip control means 126 stops the slip control of the lockup clutch 32 and releases the lockup clutch 32 according to the same determination as the vehicle sudden stop determination of (4). Therefore, when step S3 and subsequent steps in FIG. 8 are executed, the lockup clutch 32 is released.
(1) D range
(2) T _W ≥ Predetermined value T _W ^*
(3) During slip control during deceleration
(4) Vehicle sudden stop judgment

If the control precondition II is satisfied and the determination in step S2 is YES, step S3 is executed to determine whether or not a return rotation speed change condition is satisfied. The return rotational speed changing condition is satisfied if at least one of the following (1) and (2) is YES (affirmed). (1) can be determined by calculating an increase rate ΔP _BK of the brake hydraulic pressure P _BK detected by the brake hydraulic pressure sensor 84 and determining whether the increase rate ΔP _BK is equal to or greater than a predetermined value ΔP _BK ^* . (2) can be determined based on whether or not the brake hydraulic pressure P _BK detected by the brake hydraulic pressure sensor 84 is equal to or greater than a predetermined value P _BK ^* . Whether the predetermined values ΔP _BK ^* and P _BK ^* need to switch the fuel cut return rotational speed NEFC from that during normal deceleration to the fuel cut return rotational speed nefcuteeisi at the time of sudden stop, for example, in order to avoid engine stall It is set based on whether or not. Note that since the sudden stop determination is performed in step S2, step S3 is not necessarily required and may be omitted. Also, it is possible to set relatively small values as the predetermined values ΔP _BK ^* and P _BK ^{* so} as to determine whether or not a sudden stop has occurred due to actual braking operation.
(1) ΔP _BK ≧ predetermined value ΔP _BK ^*
(2) P _BK ≧ predetermined value P _BK ^*

  If the return rotational speed change condition is satisfied and the determination in step S3 is YES, step S4 is executed, and the fuel cut return rotational speed nefquiteisis at the time of sudden stop is set as the fuel cut return rotational speed NEFC. The fuel cut means 130 performs a return control from the fuel cut based on the new fuel cut return rotational speed nefckuteisi, that is, determines whether to stop the fuel cut and restart the fuel supply.

  In the next step S5, it is determined whether or not an engine stall has occurred or is likely to occur during a sudden stop. This determination can be made, for example, by determining a minimum value NEmin of the engine speed NE during a sudden stop and determining whether the minimum value NEmin is equal to or less than a predetermined value (for example, about 300 rpm). If it is determined that the engine stall has occurred or has not occurred (NO in step S5), the current fuel cut return rotational speed nefkyuteisi is maintained, but the engine stall occurs or occurs. If it is determined that there is a fear (YES in step S5), step S6 is executed. In step S6, the fact that an engine stall has occurred at the time of a sudden stop is set as a history, and the value of the corresponding temperature region of the fuel cut return rotational speed nefckuteisi in FIG. 9 is rewritten to “current value + predetermined value α”, and the subsequent sudden At the time of stoppage, the return control from the fuel cut is performed using the new fuel cut return rotational speed nefkueisei. The predetermined value α may be a constant value, for example, about 50 rpm. However, when the value is low based on the minimum value NEmin, or when an engine stall actually occurs and NEmin ≈0, As a relatively large value, it is possible to prevent the engine stall by increasing the fuel-cut return rotational speed nefkyuteisi at a stretch.

  Note that the learning means 138 of the present embodiment only performs learning correction so as to increase the fuel cut return rotational speed nefkyuteisi when an engine stall occurs or is likely to occur. When the state where the engine stall does not occur continues for a predetermined number of times or more, it is possible to perform the learning correction so as to gradually decrease the fuel cut return rotational speed nefckuteisi.

  As described above, in this embodiment, at the time of a sudden stop during the slip control of the lockup clutch 32, it is determined whether or not there is an engine stall in step S5, and the engine stall occurs or occurs. If it is determined that there is a fear, learning correction is performed in step S6 so as to increase the fuel cut return rotational speed nefckuteisi. For this reason, regardless of individual differences such as the friction of the engine 10 and the friction material of the lock-up clutch 32, the fuel cut return rotational speed nefckuteisi that is as low as possible is set within a range where engine stall does not occur. Deterioration of fuel consumption is suppressed.

On the other hand, the ease of occurrence of engine stall differs depending on the hydraulic oil temperature of the torque converter 12, that is, the AT oil temperature T _OIL , and when the AT oil temperature T _OIL is low, the viscosity of the fluid becomes high and the engine speed NE becomes low. Since it is difficult to rise, engine stall is likely to occur. In this case, if the fuel cut return rotational speed nefckuteisi is learned and corrected regardless of the AT oil temperature T _OIL , the fuel cut return rotational speed nefckuteisi at a high oil temperature at which the viscosity is low and engine stall is unlikely to occur is also high. As described above, the fuel supply is resumed from the high speed, and the fuel consumption is deteriorated. On the other hand, in this embodiment, the fuel cut return rotational speed nefkyuteisi is set with the oil temperature region of the AT oil temperature T _OIL as a parameter, and learning correction is performed for each oil temperature region. The fuel cut return rotational speed nefkyuteisi is increased only in the low oil temperature region that is likely to be generated, and it is possible to more appropriately achieve the prevention of engine stall and the suppression of deterioration of fuel consumption.

Further, in this embodiment, when it is determined in step S2 (4) whether or not there is a sudden stop, is the decrease rate ΔNT of the turbine rotation speed NT closely related to the occurrence of the engine stall larger than a predetermined value ΔNT ^* ? In order to determine whether or not the engine stall has occurred or is likely to occur due to a sudden stop, it is possible to appropriately learn and correct the fuel cut return rotational speed nefkyuteisi.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention is implemented in the aspect which added various change and improvement based on the knowledge of those skilled in the art. Can do.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a skeleton diagram illustrating an example of a laterally mounted vehicle drive device to which the present invention is preferably applied. FIG. 2 is a diagram illustrating engagement and disengagement states of clutches and brakes for establishing each gear stage of the automatic transmission of FIG. 1. It is a figure explaining the input-output signal of the electronic control apparatus provided in the vehicle of the Example of FIG. It is a figure which shows an example of the shift pattern of the shift lever of FIG. It is a functional block diagram explaining the principal part of the control function of the electronic control apparatus of FIG. It is a diagram showing an example of a relationship between the accelerator pedal operation amount Acc and the throttle valve opening theta _TH used in the throttle control performed by the engine control unit of FIG. It is a figure which shows an example of the shift map (map) used by the shift control of the automatic transmission performed by the shift control means of FIG. 6 is a flowchart for specifically explaining an operation when learning correction of the fuel cut return rotational speed nefckuteisi is performed by the engine stall determining unit, the learning unit, or the like of FIG. 5. It is a figure which shows an example of the map of the fuel cut reset rotational speed nefckuteisi corrected by learning according to the flowchart of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10: Engine 12: Torque converter (fluid transmission device) 14: Automatic transmission 22: Input shaft 32: Lock-up clutch 90: Electronic control device 130: Fuel cut means 134: Sudden stop determination means 136: Engine stall determination means 138: Learning means NE: Engine rotation speed NT: Turbine rotation speed (input shaft rotation speed) T _OIL : AT oil temperature (oil temperature of fluid transmission device) nefkuteisisi: Fuel cut return rotation speed

Claims (3)

For an engine to which an automatic transmission is connected via a fluid transmission device with a lock-up clutch,
When the engine is decelerated and the engine speed is equal to or higher than the fuel cut return rotational speed, fuel cut is performed to stop the fuel supply of the engine, and when the engine rotational speed falls below the fuel cut return rotational speed, the engine In the fuel cut control device of the engine that resumes the fuel supply of
A sudden stop determination means for determining whether or not the vehicle is suddenly stopped during the lock-up clutch slip control;
An engine stall determining means for determining whether or not an engine stall has occurred or is likely to occur in the engine when it is determined by the sudden stop determining means that the lock-up is suddenly stopped;
Learning means for correcting the learning so as to increase the fuel cut return rotational speed when the engine stall determination means determines that the engine stall or may occur in the engine;
A fuel cut control device for an engine characterized by comprising: The fuel cut return rotational speed is set for each oil temperature region of the fluid transmission device,
The engine fuel cut control device according to claim 1, wherein the learning means learns and corrects the fuel cut return rotation speed for each oil temperature region. The sudden stop determination means is configured to stop the lockup ON suddenly on condition that at least the rate of decrease of the input shaft rotation speed of the automatic transmission is equal to or greater than a predetermined value or the rate of decrease of the engine speed is equal to or greater than a predetermined value The engine fuel cut control device according to claim 1, wherein it is determined that it is time.

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