JP2010286040A - Lock-up control device for automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve fuel consumption by shortening a time required for fastening a lock-up clutch. <P>SOLUTION: In this lock-up control device for an automatic transmission comprising the lock-up clutch which can directly connect the input and output elements of a torque converter interposed between an engine and the automatic transmission and a lock-up control means which switches the lock-up clutch to a released state or fastened state by controlling the pressure difference of the lock-up clutch, the lock-up control means comprises an initial pressure estimation means S34 which estimates an initial pressure being a differential pressure at a time when the lock-up clutch starts fastening, and differential pressure holding means S23, S24 which bring the lock-up clutch into a released state by holding the differential pressure at a holding pressure which is a differential pressure equal to or lower than the initial pressure and higher than the lowest pressure of the differential pressure. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to control of a differential pressure of a lockup clutch in an automatic transmission.

  The torque converter interposed between the engine and the automatic transmission includes a lockup clutch that can directly connect the input side and the output side. The lock-up clutch is controlled so as to be engaged when the vehicle operating state defined based on the vehicle speed and the throttle opening is in a predetermined region, and thereby the driving force from the engine to the automatic transmission is controlled. Transmission efficiency can be improved and fuel consumption can be improved.

  In Patent Document 1, when the lockup clutch engagement condition is satisfied, the differential pressure of the lockup clutch is temporarily increased to the initial engagement pressure, and then gradually increased at a predetermined time change rate. Are listed.

Japanese Patent Laid-Open No. 11-37279

  However, since the differential pressure is kept at the lowest pressure when the lockup clutch is in the released state in the above-described conventional technology, the differential pressure increases from the lowest pressure state when the lockup clutch is shifted to the engaged state again. Therefore, the time required for fastening becomes longer. Therefore, there is a problem in that the time required until the engagement is lengthened, the engagement is delayed, and the effect of improving the fuel consumption is suppressed.

  An object of the present invention is to improve the fuel consumption by shortening the time required until the lockup clutch is engaged.

  The present invention relates to a lockup clutch capable of directly connecting between input and output elements of a torque converter interposed between an engine and an automatic transmission, and the lockup clutch is released by controlling a differential pressure of the lockup clutch. Alternatively, in an automatic transmission lockup control device including a lockup control unit that switches to an engaged state, the lockup control unit estimates an initial pressure that is a differential pressure at a point in time when the lockup clutch starts to be engaged. And a differential pressure holding means for releasing the lock-up clutch by holding the differential pressure at a holding pressure that is equal to or lower than the initial pressure and higher than the lowest differential pressure. To do.

  The present invention also provides a lockup control method for an automatic transmission comprising a lockup clutch capable of directly connecting input / output elements of a torque converter interposed between the engine and the automatic transmission. By switching the lockup clutch to the released state or the engaged state by controlling the step, and the step of switching includes the step of estimating an initial pressure that is a differential pressure at the time when the lockup clutch starts to be engaged, And holding the lock-up clutch in a disengaged state by holding at a holding pressure that is equal to or lower than the initial pressure and higher than the lowest differential pressure.

  According to the present invention, when the release of the lockup clutch is determined, the differential pressure is held at a holding pressure higher than the minimum pressure, so that the hydraulic pressure can be increased more quickly when the lockup clutch is subsequently determined to be engaged. Accordingly, the time required to engage the lock-up clutch can be shortened accordingly. Therefore, since the driving | running | working area | region where a vehicle drive | works with a lockup state expands, a fuel consumption can be improved.

It is a schematic block diagram which shows the structure of the lockup control apparatus of the automatic transmission in this embodiment. It is a flowchart which shows control of the lockup control apparatus of the automatic transmission in this embodiment. It is a table which shows the relationship between a vehicle speed and the amount of accelerator pedal operation, and a lockup area | region. It is a flowchart which shows the setting control of an initial pressure. It is a time chart which shows the effect | action of the lockup control apparatus of the automatic transmission in this embodiment. It is a time chart which shows the effect | action of the lockup control apparatus of the automatic transmission in this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a lockup control device for an automatic transmission according to this embodiment. The torque converter 1 is interposed between the engine 2 and the automatic transmission 3 and transmits the driving force of the engine 2 to the automatic transmission 3 via a fluid. In the torque converter 1, a pump impeller 5 connected to the output shaft 4 of the engine 2 and a turbine runner 7 connected to the input shaft 6 of the automatic transmission 3 are arranged to face each other. When the pump impeller 5 rotates with the rotation of the engine 2, the fluid (ATF) filled in the torque converter 1 flows, whereby the turbine runner 7 rotates.

  A lockup clutch 8 that is connected to the input shaft 6 of the transmission and rotates together with the turbine runner 7 is connected to the output shaft 4 of the engine 2 and is provided inside the front cover 9 that is integral with the pump impeller 5. When the lock-up clutch 8 is fastened to the pump impeller 5, the input element and the output element of the torque converter 1 are directly connected to each other, so that the relative rotation is eliminated and a complete lock-up state is established. Further, when the input element and the output element are put in a semi-fastened state, a slip lock-up state is generated in which slip occurs between the input element and the output element. When the lockup clutch 8 is completely released, the unlocked state is established.

  A torque converter apply pressure PA and a torque converter release pressure PR are respectively supplied from both sides of the lockup clutch 8 from the hydraulic circuit 20, and the lockup clutch 8 has a differential pressure between the torque converter apply pressure PA and the torque converter release pressure PR. Acts in the axial direction accordingly. The lockup clutch 8 is completely released when the differential pressure is the lowest and the unlocked state, and is engaged when the differential pressure is the highest and the fully locked up state.

  The controller 10 receives the accelerator pedal operation amount, the brake on / off state, the vehicle speed, and the selector lever select position signal from the accelerator pedal operation amount sensor 11, the brake sensor 12, the vehicle speed sensor 13, and the inhibitor switch 14, respectively. The differential pressure command value of the lockup clutch 8 is calculated based on the above, and this differential pressure command value is instructed to the hydraulic circuit 20 that controls the hydraulic pressure supplied to the lockup clutch 8.

  Hereinafter, control performed by the controller will be described. FIG. 2 is a flowchart showing lockup clutch control of the automatic transmission according to this embodiment.

  In step S11, the vehicle speed and the accelerator pedal operation amount are read.

  In step S12, it is determined whether it is a lock-up area. If it is determined that it is in the lock-up region, the process proceeds to step S14. If it is determined that it is not in the lock-up region, the process proceeds to step S13, and the lock-up clutch 8 is shifted to the released state. Note that the details of the release control of the lockup clutch 8 have been conventionally performed, and thus the description thereof is omitted here.

  Whether or not it is a lock-up area is determined according to the map shown in FIG. That is, in FIG. 3, when the driving state defined based on the vehicle speed and the accelerator pedal operation amount is in the lockup region, it is determined that the vehicle is in the lockup region.

  In step S14, the differential pressure is increased to the initial pressure. The initial pressure is a differential pressure at the time when the lockup clutch 8 starts to be engaged, and is set in advance separately from this flow. The initial pressure setting method will be described later.

  In step S15, the differential pressure is gradually increased. The increasing range (gradient) of the differential pressure is set to a value that does not cause a shock due to the sudden engagement of the lockup clutch 8, and is set to increase as the throttle opening (accelerator pedal operation amount) increases.

  In step S16, it is determined whether or not the differential pressure is greater than or equal to a predetermined pressure. If it is determined that the differential pressure is equal to or higher than the predetermined pressure, the process proceeds to step S18. If it is determined that the differential pressure is lower than the predetermined pressure, the process proceeds to step S17. The predetermined pressure is a value at which it can be determined that the lock-up clutch 8 is completely engaged, and is obtained in advance through experiments or the like.

  In step S17, it is determined whether or not the differential rotation is equal to or less than a predetermined rotation. If it is determined that the differential rotation is equal to or less than the predetermined rotation, the process proceeds to step S18. If it is determined that the differential rotation is higher than the predetermined rotation, the process returns to step S19. The differential rotation is a relative rotation speed between the pump impeller 5 and the turbine runner 7, and the predetermined rotation is a value that can be determined that the lock-up clutch 8 is completely engaged, and is obtained in advance through experiments or the like.

  In step S18, the differential pressure is increased stepwise to the maximum pressure, and the process ends. The maximum pressure is a maximum value of the differential pressure that can be set, whereby the lock-up clutch 8 is completely engaged.

  In step S19, it is determined whether the vehicle is decelerating rapidly. If it is determined that the vehicle is suddenly decelerating, the process proceeds to step S20, the differential pressure is reduced stepwise to the lowest pressure, and the process is terminated. Regarding the determination of sudden deceleration, for example, the acceleration (deceleration) of the vehicle is detected, and it is determined that the vehicle is suddenly decelerating when the acceleration becomes a predetermined value or less (deceleration is a predetermined value or more). Further, the minimum pressure is the lowest value of the differential pressure that can be set, and the lockup clutch 8 is thereby unlocked.

  On the other hand, if it is determined that the deceleration is not abrupt, the process proceeds to step S21 to determine whether or not the accelerator is off. If it is determined that the accelerator is off, the process proceeds to step S22. If it is determined that the accelerator is not off, the process returns to step S15 to further increase the differential pressure gradually. The accelerator off is determined in a situation where the driver returns the accelerator pedal. For example, it is determined when the accelerator pedal operation amount becomes zero or a predetermined low value.

  In step S22, it is determined whether or not the differential pressure is equal to or lower than a determination pressure. When it is determined that the differential pressure is equal to or lower than the determination pressure, the process proceeds to step S23, and when it is determined that the differential pressure is higher than the determination pressure, the process proceeds to step S26. The determination pressure is a value at which it can be determined that the engagement of the lockup clutch 8 has progressed to some extent after the gradual increase of the differential pressure is started in step S15, and is determined in advance by an experiment or the like.

  In step S23, the differential pressure is gradually reduced. The reduction range of the differential pressure is set to a value that does not cause a shock caused by the sudden release of the lockup clutch 8 and is obtained in advance by an experiment or the like.

  In step S24, it is determined whether or not the differential pressure is equal to or lower than the holding pressure. If it is determined that the differential pressure is equal to or lower than the holding pressure, the process is terminated. If it is determined that the differential pressure is higher than the holding pressure, the process proceeds to step S25. The holding pressure is a differential pressure for holding the lockup clutch 8 in the unlocked state, and is set to a pressure lower than the initial pressure by a predetermined amount and higher than the minimum pressure.

  In step S25, it is determined whether or not the vehicle has stopped. If it is determined that the vehicle has stopped, the process proceeds to step S20 to reduce the differential pressure to the lowest pressure, and if it is determined that the vehicle has not stopped, the process returns to step S23 to further decrease the differential pressure gradually. Whether or not the vehicle has stopped is determined by, for example, the vehicle speed becoming zero or extremely low.

  On the other hand, if it is determined in step S22 that the differential pressure is greater than the determination pressure, the process proceeds to step S26 and coast lockup control is performed. The coast lockup control is a control for setting the lockup clutch 8 in a slip lockup state during coasting. The coast lock-up control is a control that has been conventionally performed, and thus detailed description thereof is omitted.

  In the above control, if it is determined that the region is in the lockup region, the differential pressure is increased to the initial pressure in step S14, and then the differential pressure is gradually increased by repeating steps S15 to S17 (hereinafter, this control is referred to as “control”). "Smooth-on control"). When the lockup clutch 8 is engaged, a shock is generated due to a driving force step, so that the shock can be mitigated by gradually increasing the differential pressure by smooth-on control.

  Further, if the rapid deceleration is determined in step S19 during the smooth-on control, the smooth-on control is stopped and the differential pressure is reduced stepwise to the lowest pressure. If the vehicle is suddenly decelerated, the vehicle is likely to stop. If the lock-up clutch 8 is in the engaged state or the slip state when the vehicle is stopped, engine stall occurs. To prevent this, the differential pressure is stepped during sudden deceleration. The lockup clutch 8 is released rapidly.

  If the accelerator-off is determined in step S21 during the smooth-on control, the differential pressure is gradually reduced by stopping the smooth-on control and repeating steps S23 and S24 (hereinafter, this control is referred to as “ Smooth off control ”). When the lock-up clutch 8 is released, a shock is generated due to a step difference in driving force. Therefore, the shock is alleviated by gradually reducing the differential pressure by smooth-off control.

  Next, the initial pressure setting method used in step S14 will be described with reference to the flowchart of FIG.

  In step S31, it is determined whether or not the vehicle is stopped with the D range and the brake on. If it is determined that the vehicle is stopped with the D range and the brake on, the process proceeds to step S32, and if it is determined that the condition is not satisfied, the process is terminated.

  In step S32, the differential pressure is gradually increased. When this step is executed, the vehicle is stopped with the D range and the brake on, so if the differential pressure is increased too much, engine stall may occur. Therefore, the increase range of the differential pressure is set to a value that can prevent engine stall due to sudden engagement of the lockup clutch 8.

  In step S33, it is determined whether the rotational speed of the engine 2 has decreased or whether the torque of the engine 2 has increased. If it is determined that the engine rotation speed has decreased or the engine torque has increased, the process proceeds to step S34. If it is determined that the engine rotation speed and the engine torque have not changed, the process returns to step S32 to gradually increase the differential pressure again.

  In step S34, the differential pressure at this point is set as the initial pressure, and the process is terminated.

  As described above, when the differential pressure is gradually increased while the vehicle is stopped with the D range and the brake on, the lockup clutch 8 comes into contact with the pump impeller 5 and starts to be engaged at a certain time. At this time, since the vehicle is forcibly stopped by the brake, the engine speed decreases. Further, the engine is controlled so as to increase the engine torque in order to stabilize idle rotation when a decrease in engine rotation speed is detected. Therefore, when it is determined that the engine rotational speed has decreased or the engine torque has increased, it can be estimated that the lockup clutch 8 has started to be engaged, and the differential pressure at this point is set as the initial pressure.

  Next, the operation of this embodiment will be described with reference to FIGS.

  5 and 6 are time charts showing the operation of the automatic transmission lock-up control device according to this embodiment. In FIG. 5, (a) shows the throttle opening, (b) shows the vehicle speed, and (c) shows the differential pressure. In FIG. 6, (a) shows the throttle opening, (b) shows the operating state of the brake, (c) shows the vehicle speed, and (d) shows the differential pressure.

  First, with reference to FIG. 5, a description will be given of a case where accelerator-off is determined during the smooth-on control and the process proceeds to the smooth-off control.

  At time t1, when the accelerator pedal is depressed, the throttle opening increases, and the vehicle speed increases accordingly.

  At time t2, when the driving state defined based on the accelerator pedal operation amount and the vehicle speed enters the lockup region, the differential pressure increases stepwise to the initial pressure and then gradually increases.

  At time t3, the throttle opening is suddenly reduced by the driver returning the accelerator pedal. At this time, it is determined that the accelerator is off, and since the differential pressure is lower than the determination pressure, the differential pressure is gradually decreased, and when the pressure decreases to the holding pressure, the reduction of the differential pressure is finished, and the differential pressure is changed to the holding pressure. Retained.

  At time t4, when the accelerator pedal is depressed again, the throttle opening increases, and the vehicle speed increases accordingly.

  At time t5, when the driving state defined based on the accelerator pedal operation amount and the vehicle speed enters the lockup region, the differential pressure gradually increases from the holding pressure to the initial pressure and then gradually increases. At this time, since the differential pressure increases from the holding pressure to the initial pressure, the time required to engage the lock-up clutch 8 can be increased earlier than when increasing from the minimum pressure to the initial pressure. It can be shortened.

  When the differential pressure becomes equal to or higher than the predetermined pressure at time t6, the differential pressure increases stepwise up to the maximum pressure.

  Next, with reference to FIG. 6, the case where the vehicle is suddenly decelerated by the operation of the brake during the smooth-on control will be described.

  While the vehicle is accelerating, at time t1, the differential pressure increases stepwise to the initial pressure and then gradually increases as the driving state defined based on the accelerator pedal operation amount and the vehicle speed enters the lockup region. Go.

  Thereafter, when the driver returns the accelerator pedal and further depresses the brake pedal, the vehicle decelerates rapidly. Thereby, since it is determined that the vehicle is suddenly decelerated at time t2, the differential pressure is lowered stepwise to the lowest pressure. In this way, when the vehicle decelerates suddenly, the differential pressure is suddenly reduced to the lowest pressure instead of the holding pressure, so that the lockup clutch 8 can be reliably shifted to the released state, and engine stall is prevented. Can do.

  As described above, in the present embodiment, when it is determined that the lock-up clutch 8 is released due to the accelerator being off, the differential pressure is gradually reduced to a holding pressure higher than the minimum pressure. In some cases, the hydraulic pressure can be increased more quickly, and the time required to engage the lockup clutch 8 can be shortened accordingly. Therefore, since the driving | running | working area | region where a vehicle drive | works with a lockup state expands, a fuel consumption can be improved. (Corresponding to claims 1 and 6)

  In addition, when the D-range and the brake are on, the differential pressure is gradually increased while the vehicle is stopped, and when the engine speed decreases or the engine torque increases, the differential pressure at that time is set as the initial pressure. Also, an appropriate initial pressure can be set for each individual. Therefore, for example, the engine stall can be prevented from occurring by setting the initial pressure higher than the actual pressure. (Corresponding to claim 2)

  Further, when it is determined that the lock-up clutch 8 is released due to the accelerator off during the smooth-on control, the differential pressure is gradually reduced to a holding pressure higher than the minimum pressure, so that the hydraulic pressure is increased faster when the lock-up clutch 8 is re-engaged. Accordingly, the time required until the lockup clutch 8 is engaged can be shortened accordingly. For example, when the driver repeatedly turns the accelerator pedal on and off at low vehicle speeds, it is highly likely that the lockup clutch 8 is released and then immediately engaged, so the differential pressure is held at the holding pressure. As a result, the time required until the lockup clutch 8 is reengaged can be shortened. Thereby, the driving | running | working area | region where a vehicle drive | works in a lockup state can further be expanded, and a fuel consumption can be improved. (Corresponding to claim 3)

  Further, when the vehicle suddenly decelerates during smooth-on control, the differential pressure is reduced to the minimum pressure instead of the holding pressure, so that the lockup clutch 8 can be released quickly and reliably during sudden deceleration, and sudden deceleration Occurrence of engine stall at the time can be prevented. (Corresponding to claim 4)

  Further, although there is hysteresis between the increase side and the decrease side of the differential pressure, the holding pressure is set to a differential pressure that is lower than the initial pressure by a predetermined amount. Therefore, when the differential pressure is reduced to the holding pressure, the lockup clutch 8 is It can be surely released. (Corresponding to claim 5)

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea.

  For example, in the present embodiment, the differential pressure is held at the holding pressure when it is determined that the accelerator is off during the smooth-on control, but the present invention is not limited to this. The pressure may be held at a holding pressure. The pump pressure can be reduced as the differential pressure while the vehicle is stopped, and the engagement time of the lockup clutch can be shortened as the pressure difference is high. Therefore, the differential pressure is appropriately set in consideration of the reduction of the pump loss and the shortening of the engagement time.

  In the present embodiment, the smooth pedal control is performed when it is determined that the accelerator pedal is released and the accelerator pedal is off during the smooth on control. However, the condition for the smooth off control is limited to this. A condition other than the accelerator off may be used as the determination condition.

DESCRIPTION OF SYMBOLS 1 Torque converter 2 Engine 3 Automatic transmission 8 Lockup clutch 10 Controller S15 Smooth lockup fastening means S19 Rapid deceleration determination means S20 Rapid deceleration lockup release means S23, S24 Differential pressure holding means S34 Initial pressure estimation means

Claims (6)

A lockup clutch capable of directly connecting between input and output elements of a torque converter interposed between the engine and the automatic transmission;
Lockup control means for switching the lockup clutch to a disengaged state or an engaged state by controlling a differential pressure of the lockup clutch;
In an automatic transmission lockup control device comprising:
The lock-up control means includes
An initial pressure estimating means for estimating an initial pressure which is a differential pressure at the time when the lock-up clutch starts to be engaged;
Differential pressure holding means for releasing the lock-up clutch by holding the differential pressure at a holding pressure that is equal to or lower than the initial pressure and higher than the lowest differential pressure;
A lockup control device for an automatic transmission, comprising:   The initial pressure estimating means gradually increases the differential pressure from the minimum pressure while the vehicle is stopped, and estimates that the differential pressure when the engine rotational speed or the engine torque changes is the initial pressure. The lockup control device for an automatic transmission according to claim 1. The lock-up control means includes
Comprising a smooth lockup fastening means for gradually switching the lockup clutch to a fastening state by gradually increasing the differential pressure;
The differential pressure holding means, when the differential pressure is gradually increased by the smooth lockup fastening means, when the predetermined condition is satisfied and the lockup clutch is released, the differential pressure is changed to the holding pressure. The lockup control device for an automatic transmission according to claim 1 or 2, wherein The lock-up control means includes
Sudden deceleration determination means for determining that the vehicle is rapidly decelerating when the deceleration of the vehicle is higher than a predetermined deceleration;
When the sudden deceleration determining means determines that the vehicle is rapidly decelerating, the differential pressure holding means is prohibited from holding the differential pressure, and the differential pressure is reduced stepwise to the minimum pressure. A sudden deceleration deceleration lock-up release means for switching the lock-up clutch to a released state at
The lockup control device for an automatic transmission according to any one of claims 1 to 3, further comprising:   The lockup control device for an automatic transmission according to any one of claims 1 to 4, wherein the holding pressure is set to a differential pressure lower than the initial pressure by a predetermined amount. In a lockup control method for an automatic transmission including a lockup clutch capable of directly connecting between input and output elements of a torque converter interposed between the engine and the automatic transmission,
The step of switching the lockup clutch to the released state or the engaged state by controlling the differential pressure of the lockup clutch,
The switching step includes
Estimating an initial pressure which is a differential pressure at the time when the lock-up clutch starts to be engaged;
Holding the differential pressure at a holding pressure that is equal to or lower than the initial pressure and higher than a minimum pressure of the differential pressure, thereby bringing the lock-up clutch into a released state;
A lockup control method for an automatic transmission, comprising:

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