JP6651363B2 - Control device for automatic transmission - Google Patents

Description

  The present invention relates to a control device for an automatic transmission, which is mounted on a vehicle and controls an automatic transmission having a lockable torque converter and an automatic transmission mechanism.

  In a stepped automatic transmission equipped with a vehicle and having a plurality of engagement elements, a technology has been developed for locking up a torque converter and setting the engine in a fuel cut state to improve fuel efficiency during coasting of the vehicle. . Since the vehicle speed gradually decreases during coasting, the vehicle speed crosses the shift line, and it is necessary to perform a downshift (coast downshift) by changing one of the engagement elements.

  Also, when the engine speed drops to the fuel recovery rotation speed during coast running in the fuel cut state, fuel recovery (FCR) is performed to terminate the fuel cut and restart fuel supply to the engine. That is, when the vehicle speed decreases during coasting, the engine rotation speed decreases to the fuel recovery rotation speed, and the fuel recovery is performed. For this reason, during coasting in the fuel-cut state, there may be a situation in which the fuel recovery is performed at the same time as the downshift is performed.

  In connection with this, Patent Document 1 discloses that when coast downshifting is performed during coasting in a fuel cut state, at the same time, fuel recovery is forcibly performed to increase the engine speed. A technique is disclosed in which the transmission input-side rotation speed is increased to reduce the possibility that the engine rotation speed drops to the lock-up release rotation speed, and that the fuel efficiency is improved by extending the lock-up time.

JP 2010-78124A

  By the way, although attention is not paid to Patent Document 1, during a coasting in a fuel-cut state, if the fuel is recovered at the same time as the downshift is performed, the fuel recovery is performed during the torque phase in the downshift (while the clutch is being changed). In some cases, the input torque suddenly changes and the vehicle behavior changes, giving the driver a sense of incongruity.

  The present invention has been made in view of such a problem, and when performing a downshift during coasting in a fuel cut state, it is possible to avoid a sudden change in input torque due to fuel recovery during a torque phase. It is an object of the present invention to provide a control device for an automatic transmission as described above.

(1) The control device for an automatic transmission according to the present invention performs a fuel cut for stopping a fuel supply to the engine while the torque converter is locked up during coasting with the engine in a no-load state, During the fuel cut, when the rotation speed of the engine decreases to the fuel recovery rotation speed, the vehicle is mounted on a vehicle that performs fuel recovery that terminates the fuel cut and restarts fuel supply to the engine. A stepped automatic transmission mechanism that receives rotation from the engine via a torque converter, the control device controlling an automatic transmission, wherein the turbine speed of the torque converter during the fuel cut. When the speed drops to the downshift speed, the downshift request is determined and the friction Comprising a shift control means for performing the down-shift control of the automatic transmission mechanism by the replacement of components, the shift control means, when estimated that overlap with the fuel recovery downshift, the fuel recovery to the downshift control Is given priority.
It is also preferable that the shift control means performs downshift control of the automatic transmission mechanism by changing a friction engagement element while the torque converter is in a slip lockup state.

  (2) The shift control means, upon determining the downshift request, estimating means for estimating whether or not the fuel recovery is started during the downshift when the downshift control is performed; and If it is estimated that the fuel recovery is performed during the downshift, it is preferable to have a downshift delay unit that delays the start of the downshift control until the fuel recovery is completed.

  (3) It is preferable that the estimating means estimates whether or not the fuel recovery is started before an inertia phase during the downshift is started.

  (4) The downshift delay means is configured to execute the downshift control after the completion of the fuel recovery and to set a state in which the turbine speed is expected not to exceed the engine speed even when the downshift is completed. It is preferable to delay the start of the downshift control until it is.

(5) It is preferable that the downshift delay unit delays the start of the downshift control until the engine rotation is stabilized after the completion of the fuel recovery.
Is preferred.

  (6) further comprising a lock-up control means for releasing the lock-up clutch of the torque converter when the engine speed falls below the lock-up release speed, wherein the lock-up release speed is a fuel recovery speed; It is preferably set to a higher value.

  (7) When the estimating means determines that the downshift is completed before the start of the fuel recovery, the lockup control means may temporarily reduce the lockup release rotation speed to the fuel recovery rotation speed. preferable.

  (8) The estimating means estimates whether or not the fuel recovery is started by determining whether or not the engine speed is lower than the lock-up release speed by the time the inertia phase during the downshift is started. It is also preferable to do so.

  According to the present invention, when a downshift is requested during coasting in the fuel cut state, the fuel and the fuel tank are overlapped with each other by performing the fuel recovery before the downshift is completed. If it is estimated that the fuel recovery will be completed, the start of the downshift control is delayed until the fuel recovery is completed, so that a sudden change in the input torque due to the fuel recovery can be prevented from occurring during the downshift, and the shift shock is reduced. be able to.

1 is an overall system configuration diagram showing a power train of a vehicle and a control system thereof according to an embodiment of the present invention. 1 is a skeleton diagram illustrating a configuration of an automatic transmission according to an embodiment of the present invention. 4 is a table illustrating a fastening operation of each friction engagement element for each gear position of the automatic transmission according to the embodiment of the present invention. FIG. 2 is a shift diagram of the automatic transmission according to the embodiment of the present invention. 4 is a term chart illustrating control by the control device for the automatic transmission according to one embodiment of the present invention, showing a case where the control is not performed. 5 is a term chart illustrating control by the control device for the automatic transmission according to one embodiment of the present invention, showing a case where the control is performed. 4 is a flowchart illustrating control by the control device for the automatic transmission according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are merely examples, and there is no intention to exclude various modifications and application of technology not explicitly described in the following embodiments. Each configuration of the following embodiments can be variously modified and implemented without departing from the spirit thereof, and can be selected or appropriately combined as needed.

[1. Overall system configuration]
As shown in FIG. 1, the power train of the vehicle according to the present embodiment includes an engine 1, an automatic transmission 4 including a torque converter 2 with a lock-up clutch and a stepped automatic transmission mechanism 3, and an automatic transmission 4. And a power transmission mechanism 5 provided between the output shaft and the drive wheel 6.

  The stepped automatic transmission mechanism 3 is connected to the engine 1 via a torque converter 2 having a lock-up clutch 20 and includes various friction engagement elements (clutches or brakes). Each gear is achieved by engaging or disengaging. The engagement or release of various friction engagement elements and the engagement state of the lock-up clutch of the torque converter 2 are performed by controlling a required solenoid valve provided in the hydraulic circuit unit 7 to switch the oil supply state.

  An automatic transmission controller (transmission control means) 10 is provided to control the hydraulic circuit unit 7, and an engine controller 100 is provided to control the engine 1. The automatic transmission controller 10 controls the hydraulic circuit unit 7 based on information from various sensors 11 to 15. The automatic transmission controller 10 and the engine controller 100 are connected so that information can be transmitted to each other, and can control the automatic transmission mechanism 3 and the engine 1 in cooperation with each other.

[2. Configuration of automatic transmission]
As shown in FIG. 2, the automatic transmission mechanism 3 includes a first planetary gear mechanism (PG1) 31, a second planetary gear mechanism (PG2) 32, a third planetary gear mechanism (PG3) 33, and a fourth planetary gear mechanism (PG4) 34. The two planetary gear mechanisms are coaxially arranged in series, and have nine forward speeds and nine reverse speeds of first to ninth speeds. Each of the planetary gear mechanisms 31 to 34 includes sun gears 31S to 34S, carriers 31C to 34C, and ring gears 31R to 34R.

  The automatic transmission mechanism 3 includes an input shaft 30 </ b> A to which rotation is input from the engine 1 via the torque converter 2, an output shaft 30 </ b> B for outputting rotation to driving wheels via the power transmission mechanism 5, and planetary gear mechanisms 31 to 34. Intermediate shafts 30C and 30D connecting specific elements are provided. By selectively combining required elements of each of the planetary gear mechanisms 31 to 34, a required power transmission path is formed and a corresponding shift speed is achieved.

  That is, the sun gear 31S of the first planetary gear mechanism 31 and the carrier 34C of the fourth planetary gear mechanism 34 are directly coupled to the input shaft 30A of the automatic transmission mechanism 3. Therefore, the sun gear 31S of the first planetary gear mechanism 31 and the carrier 34C of the fourth planetary gear mechanism 34 always rotate integrally with the input shaft 30A. The carrier 31C of the first planetary gear mechanism 31 is connected to the input shaft 30A of the automatic transmission mechanism 3 via the second clutch C2.

  The carrier 33C of the third planetary gear mechanism 33 is directly coupled to the output shaft 30B of the automatic transmission mechanism 3. Therefore, the carrier 33C of the third planetary gear mechanism 33 always rotates integrally with the output shaft 30B. Further, the ring gear 34R of the fourth planetary gear mechanism 34 is connected to the output shaft 30B of the automatic transmission mechanism 3 via the first clutch C1.

  The ring gear 31R of the first planetary gear mechanism 31 and the carrier 32C of the second planetary gear mechanism 32 are both directly connected to the intermediate shaft 30C. Therefore, the ring gear 31R of the first planetary gear mechanism 31 and the carrier 32C of the second planetary gear mechanism 32 always rotate integrally.

  The ring gear 32R of the second planetary gear mechanism 32, the sun gear 33S of the third planetary gear mechanism 33, and the sun gear 34S of the fourth planetary gear mechanism 34 are all directly connected to the intermediate shaft 30D. Therefore, the ring gear 32R of the first planetary gear mechanism 31, the sun gear 33S of the third planetary gear mechanism 33, and the sun gear 34S of the fourth planetary gear mechanism 34 always rotate integrally.

  The carrier 31C of the first planetary gear mechanism 31 is connected to the intermediate shaft 30D via the third clutch C3. Further, the carrier 31C of the first planetary gear mechanism 31 is connected to the transmission case 3A via the first brake B1. The sun gear 32S of the second planetary gear mechanism 32 is connected to the transmission case 3A via the third brake B3, and the ring gear 33R of the third planetary gear mechanism 33 is connected to the transmission case 3A via the second brake B2.

  In the automatic transmission mechanism 3 configured as described above, the engagement of each friction engagement element such as the first clutch C1, the second clutch C2, the third clutch C3, the first brake B1, the second brake B2, and the third brake B3. By the combination of any of the first to ninth speeds, any one of the nine forward speeds and the reverse speed is achieved.

  FIG. 3 is a fastening operation table showing a fastening state of each friction engagement element for each shift speed in the automatic transmission mechanism 3. In FIG. 3, the mark “○” indicates that the friction engagement element is in the engaged state, and the blank indicates that the friction engagement element is in the released state. The step numbers 1 to 9 indicate the first to ninth forward speeds, and the step number Rev indicates the reverse step.

  As shown in FIG. 3, to achieve the first speed, the second brake B2, the third brake B3, and the third clutch C3 are engaged, and the other friction engagement elements are released. To achieve the second speed, the second brake B2, the second clutch C2, and the third clutch C3 are engaged, and the other friction engagement elements are released. To achieve the third speed, the second brake B2, the third brake B3, and the second clutch C2 are engaged, and the other friction engagement elements are released.

  To achieve the fourth speed, the second brake B2, the third brake B3, and the first clutch C1 are engaged, and the other friction engagement elements are released. To achieve the fifth speed, the third brake B3, the first clutch C1, and the second clutch C2 are engaged, and the other friction engagement elements are released. To achieve the sixth speed, the first clutch C1, the second clutch C2, and the third clutch C3 are engaged, and the other friction engagement elements are released.

  To achieve the seventh speed, the third brake B3, the first clutch C1, and the third clutch C3 are engaged, and the other friction engagement elements are released. To achieve the eighth speed, the first brake B1, the first clutch C1, and the third clutch C3 are engaged, and the other friction engagement elements are released. To achieve the ninth speed, the first brake B1, the third brake B3, and the first clutch C1 are engaged, and the other friction engagement elements are released. To achieve the reverse gear, the first brake B1, the second brake B2, and the third brake B3 are engaged, and the other friction engagement elements are released.

[3. Shift control of automatic transmission]
Shift control by engagement and release of each friction engagement element of the automatic transmission mechanism 3 is performed by the automatic transmission controller 10. FIG. 4 is a shift diagram used for shift control when the D range is selected. In FIG. 4, a solid line indicates an upshift line, and a broken line indicates a downshift line. As shown in FIG. 1, the automatic transmission controller 10 includes an accelerator opening sensor 11, an engine speed sensor 12, an inhibitor switch 13, a turbine speed sensor 14, and an output shaft speed sensor (vehicle speed sensor) 15. Is input.

  The automatic transmission controller 10 includes a shift control unit (shift control unit) 10A and a lockup control unit (lockup control unit) 10B. The shift control unit 10A determines the selection of the D range from the range selection information of the inhibitor switch 13. When the D range is selected, the vehicle speed VSP obtained from the transmission output shaft speed No from the output shaft speed sensor 15 and the accelerator speed The position where the operating point determined based on the accelerator opening APO from the opening sensor 11 exists on the shift diagram is searched. Then, if the operating point does not move, or if the operating point remains within one shift speed range on the shift diagram in FIG. 4, the shift speed at that time is maintained as it is.

  On the other hand, when the operating point moves and crosses the upshift line on the shift diagram in FIG. 4, the gear position indicated by the region where the operating point before the crossing exists and the gear position indicated by the region where the operating point after the crossing exists Output upshift command to When the operating point moves and crosses the downshift line on the shift diagram in FIG. 4, the gear position indicated by the region where the operating point before crossing exists and the gear position indicated by the region where the operating point crosses exists Output a downshift command.

  For example, when the downshift command is output, if the shift stage in the region where the operating point before crossing the downshift line exists is the nth speed, the operating point after crossing the downshift line by the downshift operation is performed. Is switched to the (n-1) th speed in the area where. Further, when the upshift command is output, the shift speed switches from the (n-1) th speed to the nth speed. Here, n is a natural number from 9 to 2.

  During coast running, the accelerator opening APO is 0, and the operating point moves only in response to a change in vehicle speed. Since the vehicle speed is determined by the input speed of the automatic transmission mechanism 3 at that time (that is, the turbine speed Nt of the torque converter 2) and the shift speed, for example, when the operating point crosses the downshift line, the turbine speed Nt Is reduced until it crosses the downshift rotation speed corresponding to the downshift line.

[4. Control during coasting]
The engine controller 100 controls fuel injection and ignition of the engine 1 based on detection information from an accelerator opening sensor 11, an engine speed sensor 12, a crank angle sensor (not shown), and the like. In this vehicle, the fuel supply to the engine 1 is stopped on the condition that the accelerator opening is 0 (or less than a minute value) and the engine speed Ne is equal to or higher than the fuel recovery speed Nrec. Fuel cut is performed. In consideration of the prevention of control hunting, a fuel cut rotation speed Ncut larger than the fuel recovery rotation speed Nrec is set, and the engine rotation speed Ne must be equal to or higher than the fuel cut rotation speed Ncut. It is preferable that

  In other words, when the engine 1 is in a no-load state and the vehicle is coasting (coasting) without depressing the accelerator pedal, if the engine rotation speed Ne is equal to or higher than the fuel recovery rotation speed Nrec, the engine controller 100 performs the fuel cut. Do. At this time, in conjunction with the automatic transmission controller 10, the lockup control unit 10B controls the torque converter 2 to be in the lockup state.

  The torque converter 2 is brought into the lockup state by engaging a lockup clutch 20 interposed between the pump impeller side and the turbine runner side of the torque converter 2. In this case, the lock-up clutch 20 is engaged by a complete engagement (that is, a fastening) in which the pump impeller side and the turbine runner side are integrally rotated and a slippage between the pump impeller side and the turbine runner side while allowing the slippage. There is slip engagement to be combined.

  When the engine speed Ne falls below the lock-up release speed Noff, the lock-up clutch 20 is released and the lock-up of the torque converter 2 is released under the control of the automatic transmission controller 10.

  The fuel recovery rotation speed Nrec is set to a value lower than the lockup release rotation speed Noff. This is because when the fuel supply to the engine 1 is restarted by the fuel recovery, a sudden rise of the engine torque occurs, and if the torque converter 2 remains in the lock-up state, the suddenly increased engine torque becomes the lock-up state of the torque converter 2 or the like. This is to avoid a large shock which reaches the drive wheel 6 as it is and generates a large shock.

  If the torque converter 2 is locked up and fuel cut is performed during coasting, the vehicle speed naturally decreases, and the engine speed Ne and the turbine speed Nt of the torque converter 2 also decrease. Therefore, first, the engine speed Ne becomes lower than the lock-up release speed Noff, and the automatic transmission controller 10 releases the lock-up of the torque converter 2. Thereafter, when the engine rotation speed Ne becomes lower than the fuel recovery rotation speed Nrec, the engine controller 100 performs fuel recovery in which the fuel cut is terminated and fuel supply to the engine is restarted. As described above, when the fuel supply is restarted, the lock-up of the torque converter 2 is released, so that the engine 1 smoothly starts up with a complete explosion.

  When the vehicle is coasting while performing fuel cut, the operating point may move due to a decrease in vehicle speed, and may cross the downshift line on the shift diagram in FIG. At this time, downshifting (coast downshifting) is performed under the control of the automatic transmission controller 10, and during this downshifting, fuel recovery may be performed in parallel. In the case of the automatic transmission mechanism 3 of the present embodiment, as the downshift in which the fuel recovery is performed in parallel, for example, a downshift from the third speed to the second speed or a downshift from the fourth speed to the third speed. Can be assumed.

  In the coast downshift, after a shift start command, the frictional engagement element is replaced by releasing the disengagement side frictional engagement element and engaging the engagement side frictional engagement element. At this time, the engagement capacity of the release-side friction engagement element starts to decrease, and thereafter, the engagement-side friction engagement element starts to have the engagement capacity, and the engagement capacity increases. In the process of increasing the engagement capacity, the change of the actual gear ratio starts, and the actual gear ratio changes from the gear ratio of the shift stage before the shift to the gear ratio of the shift stage after the shift.

  From the time when the engagement side frictional engagement element starts to have the engagement capacity to the time when the actual gear ratio starts to change, a torque phase (TF) in which only the output shaft torque changes, and thereafter, the actual gear ratio is changed An inertia phase in which the transmission input rotation speed changes with a change in the inertia of the drive source system until the gear ratio of the shift stage changes to the gear ratio of the shift stage after the shift.

  FIG. 5 is a time chart illustrating a case where fuel recovery is performed during a coast downshift. In FIG. 5, (a) shows the change in the instruction gear stage Gp, (b) shows the change in the engine speed Ne and the turbine speed Nt together with the lockup release speed Noff and the fuel recovery speed Nrec, and (c) ) Indicates a change in the turbine torque Tt of the torque converter 2, and (d) indicates a change in the hydraulic pressure of the engagement-side friction engagement element.

  As shown in FIG. 5A, when a downshift is instructed at time t1, the hydraulic pressure of the disengagement-side frictional engagement element is instantaneously reduced (not shown), whereas the engagement-side frictional engagement is reduced. As shown by a chain line in FIG. 5D, the oil pressure of the element is initially increased in a step shape, then decreased, and then increased in a ramp shape. The initial increase in the step shape causes the engagement side frictional engagement element to be loosened.

  Immediately after the time point t1, the engagement-side friction engagement element starts to have the engagement capacity and enters the torque phase. During this torque phase, as shown in FIG. 5B, the engine speed Ne becomes the lock-up release speed Noff. If it drops to below, lockup is released. The engine 1 whose lockup is released and separated from the drive wheels 6 has the engine speed Ne reduced to the fuel recovery rotation speed Nrec, and the fuel recovery is performed.

  In this case, the magnitude (absolute value) of the turbine torque Tt (torque input to the automatic transmission mechanism 3) input to the turbine of the torque converter 2 sharply decreases (time t2), and the engagement-side friction engagement element May be excessively fastened, the vehicle may be rapidly engaged, the vehicle may be decelerated, and the driver may feel uncomfortable.

  In other words, during coast running, the engine 1 is being rotated by the rotational energy of the drive wheels 6 (kinetic energy due to the running of the vehicle). As shown in FIG. Tt is in a negative state. At time t2 in this state, when the fuel recovery is performed and the engine torque rises, the turbine torque Tt of the torque converter 2 changes in the positive direction, so that the magnitude (absolute value) of the turbine torque Tt rapidly decreases. .

  Therefore, the turbine torque Tt changes from a state larger than the engagement capacity of the engagement-side friction engagement element to a state smaller than the engagement capacity, and the turbine speed Nt sharply increases from the time point t3 as shown by a solid line in FIG. As can be seen from the figure, the engagement side frictional engagement element is suddenly engaged from time t3, and the actual gear ratio fluctuates rapidly. Therefore, the vehicle temporarily decelerates, and a shock (pulling shock) due to the deceleration occurs. In this case, the torque phase TP 'is from immediately after the time point t1 to the time point t3, and the inertia phase IP' is from the time point t3 to the time point t4.

  On the other hand, if the lockup is not released during the torque phase, the fuel recovery is not performed without decreasing the engine speed Ne to the fuel recovery speed Nrec. In this case, as shown by the broken line in FIG. 5C, the turbine torque Tt does not change, so that the engagement capacity of the engagement-side friction engagement element does not become excessive, and the turbine speed Nt is reduced by the broken line in FIG. From the time point t5 at which the gear ratio decreases, the actual gear ratio starts to change toward the gear ratio of the downshift destination shift speed, and the turbine speed Nt fluctuates upward. In this case, the engagement of the engagement-side frictional engagement element is performed gently, and no pulling shock is caused.

  As described above, if the fuel recovery is not performed before the start of the inertia phase even when the coast downshift is started, the inertia phase is completed without performing the fuel recovery during the coast downshift.

  Therefore, in the present control device, when it is determined that the downshift is to be performed based on the change in the operating point due to the decrease in the vehicle speed, when the downshift is performed, the fuel recovery is started before the downshift is completed. If it is estimated that the fuel recovery is started before the downshift is completed, that is, it is estimated that the downshift and the fuel recovery are performed in an overlapping manner, the shift control unit determines When it is estimated that the shift and the fuel recovery overlap, the fuel recovery is performed with priority over the downshift control, and the start of the downshift control is delayed until the fuel recovery is completed.

  When the turbine rotation speed Nt decreases to the downshift rotation speed, the shift control unit 10A of the automatic transmission controller 10 indicates at this time that the fuel recovery before the downshift is completed if the downshift control is performed is performed. Is started (that is, the downshift and the fuel recovery are performed in an overlapped manner), and an estimating unit (estimating unit) 10C and the estimating unit A determine whether the fuel shift is performed before the completion of the downshift. When it is estimated that the recovery will be performed, a downshift delay unit (downshift delay unit) 10D that performs the fuel recovery with priority over the downshift control and delays the start of the downshift control until the fuel recovery is completed is performed. Is provided.

  As described above, the estimation unit 10C estimates based on the idea that fuel recovery will not be performed during a coast downshift unless fuel recovery is performed before the start of the inertia phase. That is, the time from the start of the coast downshift to the start of the inertia phase is estimated, and it is estimated whether or not the fuel recovery is started at the start of the inertia phase.

  In the present embodiment, at the time when the inertia phase is started, first, it is determined whether or not lockup release, which is a prerequisite for fuel recovery, is started, that is, the engine speed Ne falls below the lockup release speed Noff. It is determined based on whether or not. That is, if it can be determined that the turbine speed Nt is equal to or higher than the lock-up release speed Noff at the time when the inertia phase is started, it can be determined that the fuel recovery will not be started at the time when the inertia phase is started.

  Here, as shown in FIG. 5 (b), the determination speed Njud relating to the engine speed Ne is used for this determination. At the time of downshift determination, the determination rotation speed Njud is set based on the current engine rotation speed Ne, the decreasing ramp state (deceleration) of the engine rotation speed Ne at that time, and the time until the start of the inertia phase. I do. That is, from the ramp-down state of the engine speed Ne at the time of the downshift determination and the time from the time of the downshift determination to the start of the inertia phase, it is possible to estimate the engine speed reduction amount ΔNt that decreases until the start of the inertia phase. The rotation speed obtained by adding the engine rotation speed reduction amount ΔNt to the lockup release rotation speed Noff is defined as the determination rotation speed Njud.

  If the engine speed Ne is equal to or greater than the determination speed Njud at the time of the downshift determination, the engine speed Ne is equal to or greater than the lockup release speed Noff at the start of the inertia phase, and the torque converter 2 is unlocked. It can be estimated that fuel recovery has not been started.

  The estimation of whether or not fuel recovery is started at the start of the inertia phase is based on the engine speed Ne at that time and the current engine speed Ne at the time of downshift determination without using the determination speed Njud. The engine speed Ne at the start of the inertia phase is estimated from the decreasing ramp state (deceleration) of the engine speed Ne and the time until the start of the inertia phase, and the estimated engine speed Ne and the lock-up release rotation are estimated. The comparison may be performed with the number Noff. In this case, if the estimated engine speed Ne is equal to or more than the lock-up release speed Noff, it can be estimated that fuel recovery has not been started at the start of the inertia phase.

  Since the time from the start of the coast downshift to the start of the inertia phase is determined by the state of the torque during the coasting (coast torque) and the schedule for incorporating the hydraulic pressure of the engagement side frictional engagement element, It can be estimated based on these. For example, the larger the coast torque (negative torque), the slower the increase in hydraulic pressure, the longer the time until the inertia phase starts, and the smaller the coast torque, and the steeper the increase in hydraulic pressure. The time until the inertia phase starts is shortened.

  In the downshift delay unit 10D, the start of the downshift control is delayed until the fuel recovery is completed. At this time, the conditions for starting the downshift control further include stabilizing the engine speed Ne after the fuel recovery, and In addition, two conditions are added that, even after the downshift control is performed and the downshift is completed, the turbine speed Nt is expected to be higher than the engine speed Nt.

  In other words, in the downshift delay unit 10D, even after the fuel recovery is completed (condition 1), the engine speed Ne is stabilized (condition 2), and the downshift control is performed and the downshift is completed, the turbine is not changed. The start of the downshift control is delayed until a state in which the rotation speed Nt does not exceed the engine rotation speed Nt can be expected (condition 3).

  FIG. 6 is a time chart for explaining delay control by the downshift delay unit 10D when it is estimated that the fuel recovery is performed during the coast downshift by the estimation unit 10C. FIG. 6 corresponds to FIG. 5, in which (a) shows a change in the commanded gear stage Gp, and (b) shows a change in the engine speed Ne and the turbine speed Nt based on the lock-up release speed Noff and the fuel. This is shown together with the recovery rotation speed Nrec, (c) shows a change in the turbine torque Tt of the torque converter 2, and (d) shows a change in the hydraulic pressure of the engagement-side friction engagement element.

  As shown in FIG. 6B, when the coast downshift is determined, if the engine speed Ne is less than the determination speed Njud, the estimating unit 10C starts fuel recovery at the start of the inertia phase. Therefore, the downshift delay unit 10D delays the start of the downshift control.

  If the start of the downshift control is delayed by giving priority to the fuel recovery, the engine rotation speed Ne becomes higher than the turbine rotation speed Nt due to the fuel recovery. Here, assuming that the downshift control is started on condition that the fuel recovery is completed, for example, when the downshift control is started at time t7 ', the turbine speed Nt is indicated by a chain line in FIG. 6B. And exceeds the engine speed Ne.

  In a situation where the engine speed Ne exceeds the turbine speed Nt, torque is transmitted from the engine 1 side (pump impeller side) to the automatic transmission mechanism 3 side (turbine runner side) in the torque converter 2, but the turbine speed Nt is reduced. In a situation where the engine speed is higher than the engine speed Ne, the torque is transmitted from the engine 1 to the automatic transmission mechanism 3 in the torque converter 2, and the torque transmission direction is reversed. As described above, when the torque transmission direction is reversed, a shock may be generated due to backlash of the power transmission gear interposed in the power transmission path, and the driver may feel uncomfortable.

  Therefore, when the downshift control is delayed, the start conditions of the downshift control include the completion of fuel recovery (condition 1), the stabilization of the engine speed Ne (condition 2), and the execution of the downshift control. In addition to the fact that even after the downshift is completed, the turbine rotation speed Nt can be expected to not exceed the engine rotation speed Nt (condition 3), the downshift delay unit 10D sets all the conditions 1 to 3 Is established, the start of the downshift control is permitted.

  Completion of the fuel recovery under the condition 1 can be determined from the fact that the engine speed Ne has reached the determination speed. Further, the stability of the engine speed Ne of the condition 2 may be determined from a change in the detected value of the engine speed Ne acquired periodically, and the elapsed time after the completion determination of the fuel recovery reaches a predetermined time. It may be determined from what has been done. Condition 3 is to determine the turbine speed Nt after the downshift at each shift timing from the decreasing ramp state (deceleration) of the turbine speed Nt and the increase amount of the turbine speed Nt due to the downshift, and the engine is stable. It can be determined by comparison with the rotation speed Ne.

  As shown by the solid line in FIG. 6B, when the downshift control is started at time t6 when all of the conditions 1 to 3 are satisfied, the turbine speed Nt is the highest after the downshift is completed. In this case, the engine speed Ne will not be exceeded. Therefore, the torque transmission direction does not reverse, and no shock is generated due to the play of the power transmission gear interposed in the power transmission path.

  On the other hand, if the estimating unit 10C performs the downshift without releasing the lock-up even if the engine speed Ne falls below the lock-up release speed Noff, the engine speed Ne will decrease without dropping below the fuel recovery speed Nrec. If the shift is completed and it is estimated that fuel recovery will not be performed during the coast downshift, the coast downshift is started immediately. At this time, the lock-up control unit 10B temporarily reduces the lock-up release rotation speed Noff to the fuel recovery rotation speed Nrec until the coast downshift ends.

  In the situation where the fuel recovery is not performed, even if the lock-up is not released, there is no influence of the sudden change of the input torque due to the fuel recovery, so that the fuel efficiency can be improved by continuing the fuel cut and the lock-up. When the downshift is completed, the speed ratio increases and the turbine speed Nt increases, so that a decrease in the engine speed is also prevented, and the possibility of engine stall is avoided.

[5. Action and effect]
Since the control device for the automatic transmission according to one embodiment of the present invention is configured as described above, during the coast running in the fuel cut state, for example, as shown in FIG. 7, the control of the automatic transmission is performed. Can be performed in cooperation with the engine control.

  As shown in FIG. 7, it is determined whether the vehicle is coasting (with fuel cut) (step S10). If the vehicle is coasting, it is determined whether a downshift is determined (step S20). ). If the vehicle is not coasting or if downshifting is not determined, the processing in this control cycle is terminated, and the processing is performed again from step S10 in the next control cycle.

  If the downshift is determined in step S20, the time until the start of the inertia phase (IP start time) assumed when the downshift is started at that time is estimated, and the engine speed Ne after the IP start time is locked up. It is determined whether the rotation speed is less than the release rotation speed (LU release rotation speed) Noff (step S30). This determination may be made using the above-mentioned determination rotational speed Njud.

If it is determined that the engine speed Ne after the IP start time is less than the lock-up release speed Noff, it is determined whether the engine speed Ne after the IP start time is less than the fuel recovery speed Nrec (step). S32). If it is determined that the engine rotation speed Ne after the IP start time is lower than the fuel recovery rotation speed Nrec, the downshift command is delayed (step S40), and the lockup is released (step S42, LU release).
Then, the fuel recovery is performed, and it is determined whether the rotation after the fuel recovery is stabilized (step S50). When the rotation is stabilized, if the downshift is performed at that time, the turbine speed Nt after the end of the downshift is determined. Is not higher than the engine speed Ne (step S60).

  While delaying the downshift command, steps S40, S50, and S60 are performed for each control cycle until a positive determination is made in steps S50 and S60. Then, when it is determined that the rotation after the fuel recovery is stabilized, and it is determined that the turbine speed Nt after the end of the downshift does not exceed the engine speed Ne, the downshift is performed according to the downshift command (step S90). .

On the other hand, if it is determined in step S30 that the engine speed Ne after the IP start time is equal to or greater than the lockup release rotation speed Noff, the downshift is immediately performed (step S90).
If it is determined in step S32 that the engine rotation speed Ne after the IP start time is equal to or higher than the fuel recovery rotation speed Nrec, the lock-up release rotation speed Noff is reduced to the fuel recovery rotation speed Nrec (a margin for the fuel recovery rotation speed Nrec). (Only) Temporarily lowers until the coast downshift ends (step S70). Then, the flag FR is set to 1 (step S80), and the downshift is immediately performed (step S90). The flag FR is set to 1 when the lockup release rotation speed Noff is temporarily reduced, and is set to 0 in other cases.

  When the downshift is performed, it is determined whether or not the downshift is completed (step S100). When the downshift is completed, it is determined whether or not the flag FR is 1 (step S110). Then, the lock-up release rotation speed Noff, which has been reduced, is increased to the fuel recovery rotation speed Nrec (by a margin with respect to the fuel recovery rotation speed Nrec) (step S120), and the flag FR is set to 0 (step S130).

  In this manner, if it is determined that the engine speed Ne after the IP start time is less than the lockup release speed Noff, the downshift command is delayed, so that the fuel recovery and the downshift (particularly, the torque phase) are performed. Are not executed at the same time, the input torque can be prevented from suddenly changing due to the fuel recovery during the torque phase, and the driver can be prevented from feeling uncomfortable.

  Further, if it is determined that the rotation after fuel recovery is stabilized, and it is determined that the turbine speed Nt after the end of the downshift does not exceed the engine speed Ne, the downshift is performed according to the downshift command. 2, the torque transmission direction does not reverse, and it is possible to prevent the occurrence of a shock due to the play of the power transmission gear interposed in the power transmission path due to the reverse rotation of the torque transmission direction, giving a sense of incongruity to the driver. Can not be.

  Also, when the engine rotation speed Ne after the IP start time is determined to be equal to or higher than the lock-up release rotation speed Noff and the downshift is performed immediately, the lock-up release rotation speed Noff is temporarily reduced. In addition, lockup release is prevented while avoiding the possibility of occurrence of engine stall, and lockup can be continued to improve fuel economy.

[6. Others]
As described above, the control device for the automatic transmission according to the embodiment of the present invention has been described. However, the present invention is not limited to the embodiment, and the gist of the present invention is that the downshift and the fuel recovery may overlap. If it is estimated, the fuel recovery is performed with a higher priority than the downshift control).
For example, in the above-described embodiment, a stepped automatic transmission mechanism having nine forward gears has been illustrated, but the number of gears of the stepped automatic transmission mechanism is not limited to this.

DESCRIPTION OF SYMBOLS 1 Engine 2 Torque converter 3 Automatic transmission mechanism 4 Automatic transmission 5 Power transmission mechanism 6 Drive wheel 7 Hydraulic circuit unit 10 Automatic transmission controller (transmission control means)
10A transmission control unit (transmission control means)
10B Lock-up control unit (lock-up control means)
10C estimation unit (estimation means)
10D downshift delay unit (downshift delay means)
Reference Signs List 20 lock-up clutch 100 engine controller (engine control means)

Claims (8)

During coasting with the engine in a no-load state, the torque converter is locked up and fuel cut to stop supplying fuel to the engine is performed. During the fuel cut, the engine speed is reduced by fuel recovery. When the number of revolutions is reduced, the fuel cut is terminated and the fuel is supplied to the engine.
A control device for controlling an automatic transmission having the torque converter and a stepped automatic transmission mechanism to which rotation from the engine is input via the torque converter,
During the fuel cut, when the turbine speed of the torque converter decreases to a downshift speed, a downshift request is determined, and shift control means for performing downshift control of the automatic transmission mechanism by changing a friction engagement element is provided. Prepared,
The control device for an automatic transmission according to claim 1, wherein the shift control means performs the fuel recovery with priority to the downshift control when the downshift and the fuel recovery are estimated to overlap. The shift control means,
When determining the downshift request, estimating means for estimating whether or not the fuel recovery is started during the downshift when the downshift control is performed;
When the estimating unit estimates that the fuel recovery is performed during the downshift, the estimating unit has a downshift delay unit that delays the start of the downshift control until the fuel recovery is completed. The control device for an automatic transmission according to claim 1. 3. The control device for an automatic transmission according to claim 2 , wherein the estimating unit estimates whether or not the fuel recovery is started before an inertia phase during the downshift is started. 4. The downshift delay means delays the start of the downshift control until the turbine speed can be expected to not exceed the engine speed even after the downshift is performed and the downshift is completed. The control device for an automatic transmission according to claim 2 or 3, wherein: The control device for an automatic transmission according to claim 4, wherein the downshift delay means delays the start of the downshift control until the engine rotation is stabilized after the completion of the fuel recovery. When the engine speed falls below the lockup release rotation speed, the engine further includes a lockup control unit that releases a lockup clutch of the torque converter,
The control device for an automatic transmission according to any one of claims 2 to 5, wherein the lock-up release rotation speed is set to a value higher than a fuel recovery rotation speed. The lock-up control means, when the estimating means determines that the downshift is completed before the start of the fuel recovery, temporarily reduces the lock-up release rotation speed to the fuel recovery rotation speed. A control device for an automatic transmission according to claim 6. The estimating means estimates whether or not the fuel recovery is started by determining whether or not the engine speed is lower than the lock-up release speed by the time the inertia phase during the downshift is started. The control device for an automatic transmission according to claim 6 or 7, wherein:

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