JP2017048888A - Slip control device of lockup clutch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of an engagement shock caused by an abrupt decrease of actual differential rotation while suppressing the pick-up of an input side rotation number by feedback control based on differential rotation at the acceleration of a vehicle.SOLUTION: When a deviation ΔSN between actual differential rotation SNr and target differential rotation SNt is not smaller than a determination value α, and a reduction degree of the deviation ΔSN reaches a determination value β or larger in the case that chip-in acceleration is determined, actual differential rotation SNr1 at that time is set at the target differential rotation SNt, a feedback control value becomes zero once, an increase of clutch torque is thereby suppressed, and the generation of an engagement shock of a lockup clutch caused by an abrupt decrease of the actual differential rotation SNr is prevented. Furthermore, since the clutch torque is feedback-controlled on the basis of normal target differential rotation SNt2 until the reduction degree of the deviation ΔSN reaches the determination value β or larger, the pick-up of an engine rotation number NE is suppressed at the chip-in acceleration, and a direct feeling related to drive force responsiveness is properly secured.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a slip-up control device for a lock-up clutch, and more particularly to a technique for feedback-controlling clutch torque so that an actual differential rotation between an input side rotational speed and an output side rotational speed matches a target differential rotation.

  The present invention relates to a vehicle power transmission device including a fluid transmission device having a lock-up clutch (direct coupling clutch), and is an actual difference that is an actual rotational speed difference between an input side rotational speed and an output side rotational speed of the fluid transmission device. There is known a slip control device that feedback-controls the clutch torque of the lockup clutch so that the rotation matches the target differential rotation (see Patent Document 1).

JP 2014-2119030 A

  However, when the vehicle is accelerating, such as during tip-in acceleration, where the accelerator pedal is suddenly depressed greatly during driven driving (inertia driving or deceleration driving) and switches to driving driving, the actual differential rotation becomes the target differential rotation. If there is a large deviation from the clutch torque, the clutch torque increases in accordance with the deviation, and then the actual differential rotation decreases rapidly, resulting in an overshoot that becomes smaller than the target differential rotation, and the lockup clutch is temporarily engaged. May cause shock. To prevent this, it may be possible to temporarily release the lock-up clutch during vehicle acceleration, but the input side rotational speed of the engine or the like blows up, impairing the direct feeling (driving force responsiveness) and reducing the fuel consumption. There is a risk of getting worse.

  The present invention has been made against the background of the above circumstances. The object of the present invention is to suppress the increase of the input side rotational speed by feedback control based on the differential rotation at the time of vehicle acceleration, while the actual differential rotation is abrupt. This is to prevent the occurrence of engagement shock due to the decrease.

  The present invention relates to a vehicle power transmission device including a fluid transmission device having a lock-up clutch, and an actual difference that is an actual rotational speed difference between an input side rotational speed and an output side rotational speed of the fluid transmission device. In the slip control device that feedback-controls the clutch torque of the lockup clutch so that the rotation coincides with the target differential rotation, a deviation between the actual differential rotation and the target differential rotation is determined in advance during vehicle acceleration. As described above, when the degree of change in which the deviation decreases is equal to or greater than a predetermined determination value β, the target differential rotation is brought close to the actual differential rotation at that time.

  In such a lock-up clutch slip control device, when the deviation between the actual differential rotation and the target differential rotation is equal to or greater than the determination value α and the degree of change in which the deviation decreases is equal to or greater than the determination value β, the actual differential rotation at that time Since the target differential rotation is brought close to the increase, the clutch torque increase due to feedback control based on these deviations is suppressed or reduced, so that the lockup clutch engagement shock due to the sudden decrease in the actual differential rotation is prevented. The In addition, the clutch torque is feedback-controlled based on the normal target differential rotation until the degree of change in which the deviation between the actual differential rotation and the target differential rotation decreases is equal to or greater than the determination value β. The number is suppressed from being blown up, and a direct feeling regarding the driving force response is appropriately ensured.

1 is a block diagram of a vehicle power transmission device having a slip control device for a lock-up clutch according to an embodiment of the present invention. FIG. 2 is a flowchart for specifically explaining a function of a vehicle acceleration target difference rotation setting unit in FIG. 1. FIG. FIG. 3 is an example of a time chart showing changes in an actual differential rotation SNr, a target differential rotation SNt, a feedback control value (FB control value), and the like when the target differential rotation SNt is set according to the flowchart of FIG. 2. It is an example of the time chart which shows the change of the actual difference rotation SNr and the target difference rotation SNt in the conventional apparatus which is not provided with the target difference rotation setting part at the time of vehicle acceleration.

  The present invention is suitably applied to an engine-driven vehicle including an engine that generates power by combustion of fuel such as an internal combustion engine as a driving force source, but is applied to a hybrid vehicle including an electric motor as a driving force source. Can also be applied. A torque converter is preferably used as the fluid transmission device, but a fluid coupling or the like can also be employed.

  The present invention is preferably applied to slip-up clutch slip control at the time of tip-in acceleration in which the accelerator pedal is suddenly greatly depressed during driving and switches to driving, but the slip-up control of the lock-up clutch is performed. The present invention can also be applied to the case where the accelerator pedal is suddenly depressed greatly during driving and the vehicle accelerates rapidly, or the vehicle is started and accelerated from a stopped state. The lockup clutch does not always need to be slip-controlled, and is switched to three states, for example, full engagement, slip engagement, and release according to predetermined engagement release conditions. The slip control is executed at a low vehicle speed, for example, and a predetermined target differential rotation is determined in advance depending on whether it is driven or driven, but the target differential rotation is changed continuously or stepwise according to the driving state. You can also.

  During vehicle acceleration, such as during chip-in acceleration, if the deviation between the actual differential rotation and the target differential rotation is greater than or equal to the criterion value α and the degree of change in which the deviation decreases is greater than or equal to the criterion value β, the target differential rotation is An increase in clutch torque that is brought close to the actual differential rotation and feedback-controlled based on such deviation is suppressed or reduced. For example, if the target differential rotation is matched with the actual differential rotation, the deviation becomes 0. Therefore, the feedback control value (change amount with respect to the immediately preceding clutch torque) becomes 0, the change in clutch torque becomes 0, and the target differential rotation The clutch torque can be reduced by increasing the value to be larger than the actual difference rotation. However, when the present invention is implemented, it is sufficient that the value is at least closer to the actual difference rotation than the normal target difference rotation. Further, for the subsequent target differential rotation, the actual differential rotation is reduced to the normal target differential rotation without causing an engagement shock while preventing the input rotational speed from rising. It is desirable to return continuously or stepwise.

  In the present invention, when at least the deviation between the actual differential rotation and the target differential rotation is greater than or equal to the determination value α and the degree of change in which the deviation decreases is greater than or equal to the determination value β during vehicle acceleration, the target differential rotation is For example, if the deviation between the actual difference rotation and the target difference rotation once exceeds the determination value α, the deviation decreases after the value falls below the determination value α. Even when the degree of change becomes equal to or greater than the determination value β, various modes are possible, such as making it possible to bring the target differential rotation closer to the actual differential rotation at that time.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram including a control system of a vehicle power transmission device 10 to which the present invention is applied. A driving force output from an engine 12 is transmitted to an automatic transmission 16 via a torque converter 14. It is transmitted to the driving wheel through a differential gear device that does not. The engine 12 is a driving force source, and is an internal combustion engine such as a gasoline engine that generates power by burning fuel. The torque converter 14 includes a pump impeller 20 connected to a crankshaft 18 of the engine 12 and a turbine impeller 24 connected to a turbine shaft 22 serving as an input shaft of the automatic transmission 16, and is generated by the engine 12. This is a fluid transmission device that transmits the generated driving force to the automatic transmission 16 via a fluid. The automatic transmission 16 is a stepped transmission such as a planetary gear type or a continuously variable transmission such as a belt type.

  The torque converter 14 includes a lock-up clutch 30 that can directly connect the pump impeller 20 and the turbine impeller 24. The lock-up clutch 30 is configured so that the friction material provided in the turbine impeller 24 is moved to the front by the differential pressure ΔP (Pon−Poff) between the hydraulic pressure Pon in the engagement side oil chamber 32 and the hydraulic pressure Poff in the release side oil chamber 34. This is a hydraulic friction engagement clutch that is frictionally engaged with the cover 36. Then, when the differential pressure ΔP, that is, the hydraulic pressures Pon and Poff are regulated by the hydraulic pressure control circuit 38, the lockup clutch 30 is (a) a lockup off state in which the differential pressure ΔP is made negative and released. (B) A slip state in which the differential pressure ΔP is set to zero or more to be in a semi-engaged state, and (c) a lock-up on state (directly connected state) in which the differential pressure ΔP is set to a maximum value and is fully engaged. The three states are controlled. The differential pressure P corresponds to the clutch torque. The torque converter 14 is substantially symmetrical with respect to the center line, and the lower half of the center line is omitted in FIG.

  The vehicle power transmission device 10 includes an electronic control device 40 as a controller for performing engagement release control of the lockup clutch 30. The electronic control unit 40 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. The pressure difference ΔP is regulated by controlling a switching valve and a pressure regulating valve provided in the hydraulic control circuit 38, and the lock-up clutch 32 is locked in the lock-up off state, the slip state, and the lock-up. Control to any of the ON states. The electronic control unit 40 includes an engine speed sensor 42, a turbine speed sensor 44, an output speed sensor 46, and a throttle valve opening sensor 48 from the engine speed NE, the turbine speed NT, and the output speed corresponding to the vehicle speed V, respectively. In addition to the number Nout and a signal indicating the throttle valve opening θth of the engine 12, various signals necessary for control are supplied. Then, for example, the engagement / release state of the lockup clutch 30 is switched according to a lockup switching map set in advance using the vehicle operating state such as the output rotation speed Nout and the throttle valve opening θth as parameters. For example, when the vehicle speed is lower than a predetermined vehicle speed, the lockup clutch 30 is controlled to the slip state.

  The electronic control unit 40 functionally includes an L / U clutch slip control unit 50 and a vehicle acceleration target difference rotation setting unit 52 in relation to the slip control of the lockup clutch 30. The L / U clutch slip control unit 50 controls the lock-up clutch 30 to be in a predetermined slip state, and includes an engine speed NE that is an input side speed and a turbine speed NT that is an output side speed. The actual torque difference SNr (= NE−NT), which is the actual speed difference between the clutch torques according to their deviation ΔSN (= SNr−SNt) so as to coincide with a predetermined target difference rotation SNt. That is, the differential pressure ΔP is feedback controlled. In the present embodiment, the target differential rotation SNt is separately set to predetermined values SNt1 and SNt2 depending on whether the actual differential rotation SNr is negative, that is, driven driving with NE <NT, or the actual differential rotation SNr is positive, that is, driving driving with NE> NT. Is stipulated. In the time chart of FIG. 3, the time before the time t2 is the time when the vehicle is driven and a negative constant value SNt1 is determined as the target differential rotation SNt, and the time after the time t2 is the time when the vehicle is driving and the time t2 to t3. And after time t4, a positive constant value SNt2 is determined as the target differential rotation SNt.

  The target differential rotation setting unit 52 at the time of vehicle acceleration sets a target differential rotation SNt that is different from the normal time under a certain condition at the time of chip-in acceleration in which the accelerator pedal is suddenly depressed greatly during driven driving to switch to driving driving. Specifically, signal processing is executed according to steps S1 to S6 (hereinafter simply referred to as S1 to S6) in the flowchart of FIG. When the target differential rotation SNt is set by the vehicle acceleration target differential rotation setting unit 52, the L / U clutch slip control unit 50 sets the target differential rotation SNt set by the vehicle acceleration target differential rotation SNt. Based on this, the clutch torque feedback control is executed.

  In S1 of FIG. 2, whether or not the tip-in acceleration is performed depends on, for example, whether or not the driving travel (NE <NT) is switched to the driving travel (NE> NT) based on the engine speed NE and the turbine speed NT. to decide. The fact that the accelerator operation amount or the throttle valve opening degree θth is at a rapid acceleration such as a predetermined value or more can be added to the conditions for tip-in acceleration. If it is determined in S1 that chip-in acceleration has occurred, S2 and subsequent steps are executed. The time chart of FIG. 3 shows changes in the actual differential rotation SNr, the target differential rotation SNt, the clutch torque feedback control value (FB control value), etc., when the target differential rotation SNt is set during tip-in acceleration according to the flowchart of FIG. This is an example of a time chart showing the case where the accelerator pedal is greatly depressed at time t1 during the driven travel, and the driven travel is switched to the drive travel at time t2 and the determination of S1 becomes YES (positive). is there.

  In S2, it is determined whether or not the deviation ΔSN between the actual differential rotation SNr and the target differential rotation SNt is greater than or equal to a predetermined determination value α. The determination value α is a smaller value than the deviation ΔSN that may cause an engagement shock due to a rapid decrease in the actual difference rotation SNr if feedback control by the normal target difference rotation SNt is continued as it is. Set by Further, in S3, it is determined whether or not the degree of decrease, which is the degree of change in which the deviation ΔSN decreases, is equal to or greater than a predetermined determination value β. If the degree of decrease is smaller than that, if the feedback control based on the normal target differential rotation SNt is stopped, the degree of decrease may cause the engine rotation NE to blow up or the direct feeling of driving force responsiveness to be impaired. It is a larger value and is set by experiment, simulation, or the like. As the degree of decrease of the deviation ΔSN, for example, a change rate (gradient) at which the deviation ΔSN decreases is appropriate, but a decrease amount per unit time such as a control cycle time can also be used. If both S2 and S3 are determined to be YES, that is, if ΔSN ≧ α and the degree of decrease in ΔSN ≧ β, S4 and subsequent steps are executed, but if either determination is NO (negative) S6 is executed. In S6, it is determined whether or not a predetermined stop condition is satisfied. If the stop condition is satisfied, the series of control is stopped and the process ends. If the stop condition is not satisfied, S2 and subsequent steps are repeated. Run. The stop condition is, for example, when the elapsed time after the tip-in acceleration determination in S1 becomes a predetermined time or more, when the accelerator operation amount or the throttle valve opening θth becomes a predetermined value or less, or when the vehicle is driven. This is the case.

  In S4 executed when ΔSN ≧ α and the degree of decrease of ΔSN ≧ β, the actual differential rotation SNr1 at that time is set as the target differential rotation SNt. The time t3 in FIG. 3 is the time when ΔSN ≧ α and the degree of decrease of ΔSN ≧ β, and S4 is executed and the target differential rotation SNt is changed to the same value as the actual differential rotation SNr1, and the actual differential rotation SNr And the target differential rotation SNt = 0, the feedback control value (SB control value) based on the deviation ΔSN once becomes zero. In subsequent S5, the target differential rotation SNt is continuously and smoothly decreased according to a predetermined change pattern so that the target differential rotation SNt becomes the same value as the normal target differential rotation SNt2 during driving. As the change pattern at this time, for example, a non-linear pattern in which the rate of change gradually decreases as shown in FIG. 3 is suitable, but various modes such as a linear decrease at a constant rate of change are possible. Further, the change pattern and change rate of the target differential rotation SNt may be set based on the actual differential rotation SNr1 and the like. Times t3 to t4 in FIG. 3 are times when the target differential rotation SNt is gradually decreased in S5, and the actual differential rotation SNr is smoothly changed following the change of the target differential rotation SNt. In FIG. 3, the actual differential rotation SNr is smaller than the target differential rotation SNt over substantially the entire time period t3 to t4, but the actual differential rotation SNr straddles the target differential rotation SNt vertically depending on the response of feedback control. In some cases, the angle converges so as to substantially match the target differential rotation SNt.

  In such a lock-up clutch slip control device of this embodiment, when it is determined that the tip-in acceleration, the deviation ΔSN between the actual differential rotation SNr and the target differential rotation SNt is greater than or equal to the determination value α, and the deviation ΔSN When the degree of decrease in the value becomes equal to or larger than the determination value β, the actual differential rotation SNr1 at that time is set to the target differential rotation SNt, and thus the feedback control value based on the deviation ΔSN once becomes 0 and the increase in the clutch torque is suppressed. Is done. For this reason, the engagement shock of the lockup clutch 30 due to the rapid decrease of the actual difference rotation SNr is prevented. FIG. 4 is an example of a time chart showing changes in the actual differential rotation SNr and the target differential rotation SNt in a conventional apparatus that does not include the target differential rotation setting unit 52 at the time of vehicle acceleration, and shows a predetermined target differential rotation SNt2. In this case, the feedback control is continuously performed, and the deviation ΔSN is positive until the time ta when the actual differential rotation SNr becomes equal to the target differential rotation SNt2, that is, the feedback control value is positive, and the clutch is controlled according to the deviation ΔSN. Since the torque is increased, the actual differential rotation SNr is decreased (overshoot) beyond the target differential rotation SNt2, and an engagement shock may occur.

  In this embodiment, the clutch torque is feedback-controlled based on the normal target differential rotation SNt2 until the decrease degree of the deviation ΔSN becomes equal to or greater than the determination value β, so that the engine speed NE is increased at the time of tip-in acceleration. In addition, the direct feeling related to the driving force responsiveness is appropriately secured.

  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.

  DESCRIPTION OF SYMBOLS 10: Power transmission device for vehicles 14: Torque converter (fluid transmission device) 30: Lock-up clutch 40: Electronic control device 50: L / U clutch slip control part 52: Target difference rotation setting part at the time of vehicle acceleration NE: Engine rotation Number (input side rotational speed) NT: turbine rotational speed (output side rotational speed) SNr: actual differential rotational speed SNt: target differential rotational speed ΔSN: deviation α: deviation judgment value β: deviation reduction degree judgment value

Claims (1)

In regard to a vehicle power transmission device including a fluid transmission device having a lock-up clutch, an actual differential rotation, which is an actual rotational speed difference between an input-side rotational speed and an output-side rotational speed of the fluid transmission device, is a target difference. In the slip control device that feedback-controls the clutch torque of the lockup clutch so as to coincide with the rotation,
When the deviation between the actual difference rotation and the target difference rotation is greater than or equal to a predetermined determination value α and the degree of change in which the deviation decreases is equal to or greater than a predetermined determination value β during vehicle acceleration, the actual difference at that time A slip control device for a lockup clutch, wherein the target differential rotation is brought close to rotation.

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