JP2011208754A - Control device for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for a lock-up clutch, suppressing influence of a hysteresis of a solenoid, without giving a driver a sense of discomfort.SOLUTION: In the control device for a lock-up clutch, after a vehicular running condition is moved from drive running to coast running and when engine torque is a predetermined value or less, a command differential pressure is temporarily decreased to suppress the influence of hysteresis generated in the solenoid, and then the command differential pressure is returned to be predetermined command differential pressure.

Description

  The present invention relates to a lockup clutch control device for an automatic transmission having a lockup clutch.

  Conventionally, as disclosed in Patent Document 1, when reducing the energization amount of a solenoid to a predetermined value, a technique is known in which the energization amount of the solenoid is set to zero for a predetermined time and then increased to a predetermined value. . This suppresses the occurrence of hysteresis in the thrust generated by the linear solenoid when the energization amount increases and decreases. Patent Document 2 discloses a technique for reducing the lock-up clutch capacity to a predetermined capacity when the accelerator opening is zero, as control of a lock-up clutch of a vehicle that performs fuel cut during coasting. It has been.

Japanese Patent No. 2657316 JP 2006-125629 A

However, in the technique in which Patent Document 2 is combined with Patent Document 1 described above, when the accelerator opening becomes 0, if the energizing amount to the solenoid that controls the lockup capacity is set to 0, the engine speed is increased and the operation is performed. There is a risk of discomfort. That is, as described in Patent Document 2, a predetermined cut-in delay time is provided from the time when the accelerator opening becomes 0 to the start of fuel cut, thereby reducing the torque step at the start of fuel cut. The engine torque when the degree becomes zero is positive. If the energization amount of the solenoid for controlling the lockup capacity is set to 0 when the engine torque is positive, the lockup capacity is reduced, the engine load becomes insufficient, and the engine rotation is blown up.
The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a control device for a lockup clutch that suppresses the influence of the hysteresis of the solenoid and does not give the driver a sense of incongruity.

  In order to achieve the above object, according to the present invention, in the control device for the lock-up clutch, the command difference is detected when the vehicle running state has shifted from drive running to coast running and the engine torque is equal to or less than a predetermined value. The pressure is temporarily reduced to suppress the effect of hysteresis generated in the solenoid, and then the command differential pressure is returned to a predetermined command differential pressure.

  Therefore, it is possible to control the lockup clutch capacity in the coasting state with high accuracy by suppressing the influence of hysteresis generated in the solenoid, and to minimize the command differential pressure of the lockup clutch when the engine torque is larger than the predetermined value. It is possible to prevent the engine rotation from being generated without increasing the pressure.

1 is a schematic diagram showing a power train of Example 1. FIG. It is a characteristic view showing the hysteresis characteristic of a lockup solenoid. 3 is a flowchart illustrating a coast slip lockup control process according to the first embodiment. 3 is a time chart illustrating coast slip lockup control according to the first embodiment.

  FIG. 1 is a schematic diagram showing a power train of the first embodiment. The engine 1, which is a power source, is controlled in its operating state by the engine controller 200, and in addition to the throttle opening, ignition timing, etc., fuel is injected from the fuel injection device 10a to generate positive torque, and torque from the engine Is unnecessary (hereinafter referred to as fuel cut), a predetermined engine braking force, that is, a negative torque is generated. The control related to the fuel cut will be described later. Torque generated in the engine 1 is output from the engine output shaft 1a. A torque converter 2 that performs torque amplification is connected to the engine output shaft 1a, and an automatic transmission 3 that achieves a plurality of shift stages is connected to a transmission input shaft 2a that outputs driving force from the torque converter 2. Yes.

  The torque converter 2 includes a pump impeller 21 welded in a converter cover 20 that rotates integrally with the engine output shaft 1a, a stator 22 fixedly supported on a transmission case via a one-way clutch OWC, and a transmission input shaft 2a. A turbine runner 23 that rotates integrally with the transmission input shaft 2a, and a lock-up clutch 24 that rotates together with the transmission input shaft 2a and is fitted to allow axial movement.

  The lock-up clutch 24 is spline-fitted to the end of the transmission input shaft 2a, and is attached so as to be able to stroke in the axial direction and transmit only a force in the rotational direction. The lockup clutch 24 has a release pressure chamber 24a disposed on the axial front engine side and an apply pressure chamber 24b disposed on the axial rear automatic transmission side. The release pressure chamber 24a and the apply pressure Stroke in the axial direction by the differential pressure with the chamber 24b. As a result, a frictional force is generated between the lockup clutch 24 and the converter cover 20 to achieve three states: a completely engaged state, a slip engaged state, and a completely released state.

  In the fully engaged state, the engine output shaft 1a and the transmission input shaft 2a are directly connected, and the driving force output from the engine 1 is input to the automatic transmission 3 as it is. In the slip engagement state, the driving force is transmitted from the turbine runner 23 to the transmission input shaft 2a by the torque amplification action of the torque converter 2, and the transmission input shaft 2a is driven by the frictional engagement force of the lockup clutch 24. A predetermined driving force is transmitted from the route to the route through which the force is transmitted. In the fully released state, only the torque amplification action of the torque converter 2 functions, and all the driving force is transmitted from the turbine runner 23 to the transmission input shaft 2a.

  The automatic transmission 3 is a stepped automatic transmission, and is configured to be able to achieve a plurality of shift speeds by engaging and releasing a plurality of frictional engagement elements. When a certain gear stage is achieved, the first frictional engagement element is engaged and the second frictional engagement element is released. When the shift command is output, the first friction engagement element is released and the second friction engagement element is engaged, so-called change gear shift is performed to achieve a plurality of shift stages. The number of the first friction engagement elements and the second friction engagement elements may be one or a plurality, and two or more shift stages may be achieved. The driving force output from the automatic transmission 3 drives the drive wheels 4 from the output shaft 3a via the differential mechanism DEF.

  Below the automatic transmission 3, a control valve unit 5 that regulates the control pressure based on a command signal from the AT controller 100 is provided. The control valve unit 5 is provided with a plurality of pressure regulator valves, shift valves, manual valves, fastening pressure regulating valves, lockup solenoids 5a, and the like, and regulates the hydraulic pressure as appropriate to supply control pressure to necessary places. When an engagement / disengagement command for the lockup clutch 24 is output from the controller 100, the lockup solenoid 5a is a so-called linear solenoid, and by changing the amount of current supplied to the lockup solenoid 5a, the release pressure chamber 24a is entered. The release pressure PR to be supplied is lowered, the apply pressure PA to be supplied to the apply pressure chamber 24b is increased, and the lock-up clutch 24 is completely engaged, slipped and completely released. When a shift command is output, the hydraulic pressure of the first frictional engagement element in the automatic transmission 3 is decreased and the hydraulic pressure of the second frictional engagement element is increased.

  The AT controller 100 includes an accelerator pedal opening sensor 11 that detects an accelerator pedal opening that is a driver's accelerator pedal operation amount, a throttle opening sensor 12 that detects a throttle opening of the engine 1, and a transmission output shaft. 3a, the vehicle speed sensor 13 for detecting the vehicle speed by multiplying a predetermined final reduction ratio and the tire radius, the inhibitor switch 14 for detecting the shift lever position operated by the driver, and the rotation of the turbine runner 23. The engine speed information 15 and the engine speed information supplied from the engine controller 200 side are input. In the controller 100, the engagement state of the lock-up clutch 24, the shift state of the automatic transmission 3, and the like are controlled based on these input sensor signals.

  The engine controller 200 executes fuel cut when the throttle opening detected by the throttle opening sensor 12 is zero. Here, the fuel cut is a control for stopping the fuel injection from the fuel injection device 10a when a travel state in which the accelerator opening is 0 as in coastal travel and no torque needs to be output from the engine side is detected. It is. When the engine 1 shifts from a drive state in which positive torque is output to fuel cut, cut-in delay control is executed. In the cut-in delay control, when the throttle opening becomes 0, the engine torque is gradually reduced over a predetermined time (the fuel injection amount is gradually reduced) to suppress a shock caused by engine torque fluctuation. Thereafter, a predetermined engine braking force is generated by performing fuel cut. Hereinafter, this predetermined time is described as a cut-in delay time.

  The automatic transmission 3 according to the first embodiment shifts from the complete lockup state to the slip lockup state at the time of shifting from the pre-shift speed stage in the complete lockup state to the post-shift stage speed in the complete lockup state. Execute, and then transition to the full lockup state. This suppresses shift shocks and the like.

  Further, not only at the time of shifting but also at the time of non-shifting, the vehicle shifts to a slip lock-up state during coasting. That is, when the driver releases the accelerator pedal and the throttle opening is set to 0, the vehicle shifts to the coasting state. At this time, in order to prevent excessive engine braking force and torque fluctuation in the drive wheels, the process shifts to slip lock-up control, and after first setting the lock-up command differential pressure initial value, Slip amount feedback control is performed so that Specifically, the lockup command differential pressure is determined based on the deviation between the engine speed and the turbine speed, and the current value corresponding to the lockup differential pressure command is output to the lockup solenoid 5a. The differential pressure between the hydraulic pressure in the pressure chamber 24a and the hydraulic pressure in the apply pressure chamber 24b is controlled to control the slip amount.

  Here, the value of the lockup command differential pressure initial value at the start of control is important. If this initial value is too large, a sufficient slip amount cannot be obtained, and complete fastening is performed, and torque fluctuations are easily transmitted. Further, if the initial value is too small, the slip amount becomes excessive, and a feeling of torque loss is generated. Therefore, this initial value is controlled by learning control so that the slip amount becomes an appropriate value. The learning control process for the lockup command differential pressure initial value is not particularly described because a known technique may be applied as appropriate.

  On the other hand, in the lockup clutch 24, the hysteresis cancellation control is executed. FIG. 2 is a characteristic diagram showing the hysteresis characteristic of the lockup solenoid. When the current value of the lock-up solenoid 5a is increased, the differential pressure increases through the lower line, and when the current value is decreased, the differential pressure decreases through the upper line. As described above, when the differential pressure is controlled by the lock-up solenoid 5a, there is a hysteresis characteristic in which different differential pressures are generated even when the current is increased and when the current is decreased. For example, suppose that it is desired to obtain the differential pressure Pα when the current value is increased to obtain ID and control is performed at point D to obtain the differential pressure PD. When the current is rising, the differential pressure Pα can be obtained by Iα. However, due to the hysteresis characteristic, even if the pressure is actually decreased from ID to Iα, the differential pressure PE becomes higher than the differential pressure Pα. Similarly, in the case of point A where the current value is increased to IA and the differential pressure PA is obtained, if the differential pressure Pα is set to Iα, the differential pressure PB is higher than the differential pressure Pα. In other words, when trying to obtain the differential pressure Pα, the current value needs to be IC when at point A, and the current value needs to be IF when at point D. Thus, storing various current values in order to obtain the same differential pressure depending on the state is very complicated and complicated in terms of control.

  Therefore, hiss cancellation control is executed. His cancel control is to reduce the current value to zero, wait for a predetermined time (his cancel time), cancel the residual magnetic field, and increase the current value along the lower characteristics shown in FIG. This is control for obtaining a desired differential pressure. In this embodiment, the current value of the lockup solenoid 5a is set to zero. However, if the polarity of the lockup solenoid 5a is reversed, the current value may be increased to the maximum value.

  When it is determined that the vehicle has traveled during coasting, cut-in delay control is executed in advance on the engine side in order to smoothly perform fuel cut. That is, positive torque is output from the engine until the cut-in delay time elapses. If hysteresis cancellation control is performed at this timing, the command differential pressure is too low, and the engine speed increases due to insufficient engine load, which may give the driver a sense of discomfort. This phenomenon is particularly noticeable when shifting from high-torque driving to coasting. Therefore, even if it is determined that the vehicle is in a coasting state, execution of the hysteresis cancellation control is prohibited and the engine torque becomes less than the predetermined value during the time when the engine torque is considered to be equal to or greater than the predetermined value by the cut-in delay control. At that time, the hysteresis cancellation control is started. Note that when the engine torque becomes negative, the lockup command differential pressure is reduced and at the same time the hysteresis cancellation control is performed, the engine torque is reduced without passing through the slip engagement state, and torque fluctuations are caused by the driving wheel. Needless to say, it is necessary to achieve the slip engagement state when the engine torque is positive.

(Coast slip lock-up control process)
FIG. 3 is a flowchart illustrating a coast slip lockup control process according to the first embodiment.
In step S1, it is determined whether or not the coasting state has been reached. If it is determined that the coasting state has been reached, the process proceeds to step S2, and otherwise the control flow is terminated.
In step S2, the delay timer starts counting up.
In step S3, the lockup command differential pressure is set to the lockup command differential pressure initial value P1. While the cut-in delay control is being performed, the engine torque is gradually reduced by a predetermined time constant until the differential pressure command value becomes P1 in parallel with the engine torque being gradually reduced.

In step S4, it is determined whether or not the delay timer value is longer than a delay time T1 at which it can be determined that the engine torque has reached a sufficiently small value (substantially zero). In step S5, the lockup command differential pressure is maintained otherwise.
In step S5, the delay timer is reset.
In step S6, the cancel timer starts counting up.
In step S7, the lockup command differential pressure is set to the lowest value (history cancel control).
In step S8, it is determined whether or not the cancel timer value has exceeded a predetermined time T2 required for the hysteresis cancel control. If it has elapsed, the process proceeds to step S9. Otherwise, the process returns to step S7 to return to the lockup command difference. Maintain pressure at minimum.

In step S9, the cancel timer is reset.
In step S10, the lockup command differential pressure is set to P2 higher than P1. Here, the reason for setting P2 higher than P1 will be described. As described above, the hysteresis cancellation operation is started when the lockup command differential pressure is set to P1 and the engine torque becomes substantially zero. As a result, the hysteresis canceling operation is performed earlier while suppressing the increase in the engine speed, and the influence of the hysteresis generated in the solenoid can be eliminated earlier. At this time, since the hysteresis canceling operation starts when the engine torque is substantially zero, the “absolute value” of the engine torque when returning to the predetermined command differential pressure after the minimum pressure is reached is the value at the time when the minimum pressure is reached. It becomes larger than the absolute value of engine torque. Accordingly, when returning to the minimum pressure, if the pressure difference is returned to the same differential pressure as the initial differential pressure P1, the lockup clutch capacity is insufficient with respect to the absolute value of the engine torque, and the slip amount of the lockup clutch increases. End up. Therefore, by optimizing the slip amount of the lockup clutch by returning to the differential pressure P2 higher than the initial differential pressure P1 is measured.
In step S11, slip amount feedback control is executed so that the lock-up slip amount becomes the target slip amount.

FIG. 4 is a time chart showing coast slip lock-up control according to the first embodiment.
When the driver releases the accelerator pedal at time t1, the throttle opening is closed and the coasting state is entered. At this time, the engine controller 200 performs cut-in delay control, and the engine torque gradually decreases over a cut-in delay time. In parallel with this engine-side control, the AT controller 100 sets a lockup command initial differential pressure P1 that is a coast capacity learning value as a lockup command differential pressure, and gradually lockup command differential pressure by a predetermined time constant. Decreases.

When the cut-in delay time elapses at time t2, it is determined that the engine torque has become substantially zero, and hysteresis cancellation control is started. Therefore, the lockup command differential pressure is set to the lowest pressure, and the hysteresis cancel timer starts counting up.
At time t3, when the engine controller 200 sufficiently reduces the engine torque, fuel cut is executed, and the engine torque starts to generate negative torque.
At time t4, when the hysteresis cancellation time necessary for eliminating the residual magnetic field has elapsed after setting to the minimum pressure by the hysteresis cancellation control, the coast capacity learning value P2 (> P1) is set as the command differential pressure. An initial value of the feedback control is given, and the command differential pressure is controlled so that the target slip amount is obtained by the feedback control. At this time, since P2 is set to a value higher than P1, even if the engine braking force is increased, excessive slip does not occur, and the target slip amount in feedback control can be quickly converged. it can.

As described above, the effects listed below can be obtained in the first embodiment.
(1) It is possible to fasten the engine 1 that can be fuel cut during coasting of the vehicle, the torque converter 2 interposed between the engine 1 and the automatic transmission 3, and the impeller side and the turbine side of the torque converter 2 The lockup clutch 24, the AT controller 100 (lockup clutch control means) for controlling the command differential pressure of the lockup clutch 24 in accordance with the driving state of the vehicle, and the torque of the engine 1 is determined to be equal to or less than a predetermined value Step S4: When the travel state of the delay timer (determination means) and the vehicle shifts from the drive travel in which the lockup clutch 24 is slip-engaged to the coast travel, the lockup command differential pressure is changed to a predetermined initial differential pressure. Step S3 (initial differential pressure control means) to reduce to P1, and the vehicle running state is coasting from drive running Step S7 (history canceling control means) for temporarily reducing the lockup command differential pressure to the lowest pressure when it is determined in step S4 that the engine torque is equal to or lower than the predetermined value after the transition to the line. Steps S8 and S10 (command differential pressure return means) for returning the lockup command differential pressure to the predetermined command differential pressure P2 after the lockup command differential pressure is temporarily reduced to the minimum pressure in step S7, Have

When shifting to coasting, the command differential pressure of the lockup clutch 24 is reduced to a predetermined lockup initial differential pressure P1, and when it is determined that the engine torque is equal to or less than a predetermined value, the lockup command differential pressure is reduced to the minimum. By temporarily reducing the pressure to a predetermined command differential pressure, it is possible to control the lockup clutch capacity in a coasting state with high accuracy by suppressing the influence of hysteresis generated in the lockup solenoid 5a. . Further, since the command differential pressure is reduced to the lowest pressure after the engine torque becomes lower than the predetermined value, it is possible to suppress the engine speed from rising.
In other words, the command differential pressure of the lockup clutch 24 is reduced to the predetermined initial differential pressure without reducing it to the lowest pressure until it is determined that the engine torque is equal to or lower than the predetermined value. While avoiding the occurrence of complete engagement shock, the engine speed can be suppressed and when the engine torque is determined to be lower than the predetermined value, the command differential pressure of the lockup clutch 24 is temporarily reduced to the minimum pressure. By doing so, the influence of the hysteresis generated in the solenoid can be suppressed, and the lockup clutch capacity control in the coasting state can be executed with high accuracy.
Note that when the command pressure of the lock-up clutch 24 is temporarily set to the maximum pressure, an attempt is made to suppress the influence of hysteresis generated in the solenoid, the command pressure of the lock-up clutch 24 becomes the maximum pressure so that the lock-up clutch 24 Will be completely fastened, and the engine stall avoidance performance during sudden deceleration will be reduced. Therefore, by temporarily reducing the command differential pressure of the lock-up clutch 24 to the minimum pressure, the influence of hysteresis generated in the solenoid is suppressed.

  (2) Step S4 (determination means) determines that the engine torque is below a predetermined value when the delay timer value has elapsed (when the engine torque is substantially zero), and step S10 (command differential pressure return means) ) Returns the command differential pressure P2 to a predetermined command differential pressure greater than the initial differential pressure P1.

  Since hysteresis cancellation control is started when the engine torque becomes substantially zero, the hysteresis canceling operation is performed earlier while suppressing the increase in engine speed, thereby eliminating the effects of hysteresis generated in the solenoid at an early stage. be able to. Since the hysteresis canceling operation is started when the engine torque is substantially zero, the absolute value of the engine torque when returning to the predetermined command differential pressure after the minimum pressure is reached is the absolute value of the engine torque at the time when the minimum pressure is reached. It will be larger than the value. Therefore, when returning to the minimum pressure, if the pressure difference is returned to the same differential pressure as the initial differential pressure, the capacity of the lockup clutch is insufficient with respect to the absolute value of the engine torque, and the slip amount becomes large. Therefore, the slip amount of the lockup clutch 24 can be set to an appropriate amount by returning to the command differential pressure P2 larger than the initial differential pressure P1.

  Although the first embodiment has been described above, the present invention is not limited to the configuration of the embodiment, and other configurations are also included in the present invention.

  For example, in the first embodiment, the engine torque is determined to be substantially zero (below the predetermined value) when a predetermined time has elapsed since the transition from the drive travel to the coast travel. However, the present invention is not limited to this. However, it may be anything that can determine that the engine torque is substantially zero (predetermined value or less), such as a sensor that detects the engine torque.

  In the first embodiment, the command differential pressure is reduced to P1 with a predetermined time constant. However, the present invention is not limited to this. For example, the command differential pressure is decreased with a predetermined gradient, step by step when a certain time elapses. What is necessary is just to reduce the command differential pressure of the lockup clutch before the start of the hysteresis cancellation control, such as a reduction or a reduction with a predetermined profile so as to correspond to a reduction profile of the engine torque.

DESCRIPTION OF SYMBOLS 1 Engine 2 Torque converter 3 Automatic transmission 5 Control valve unit 11 Accelerator pedal opening sensor 12 Throttle opening sensor 13 Vehicle speed sensor 15 Turbine speed sensor 24 Lock-up clutch 100 AT controller

Claims (3)

An engine that can cut fuel when the vehicle is running on the coast,
A torque converter interposed between the engine and the automatic transmission;
A lockup clutch capable of fastening the impeller side and the turbine side of the torque converter;
Lock-up clutch control means for controlling the command differential pressure of the lock-up clutch according to the driving state of the vehicle;
Determining means for determining that the torque of the engine is equal to or less than a predetermined value;
An initial differential pressure control means for reducing the command differential pressure to a predetermined initial differential pressure when the vehicle travel state shifts from drive travel where the lock-up clutch is slip-engaged to coast travel;
The command differential pressure is temporarily reduced to the lowest pressure when the vehicle travel state has shifted from the drive travel to the coast travel and the determination means determines that the engine torque is equal to or less than a predetermined value. His cancel control means to reduce,
Command differential pressure return means for returning the command differential pressure to a predetermined command differential pressure after the command differential pressure is temporarily reduced to the minimum pressure by the hysteresis cancellation control means;
A lockup clutch control device comprising: In the lockup clutch control device according to claim 1,
The hysteresis canceling means temporarily reduces the command pressure to a minimum pressure by setting a current value of a linear solenoid that controls a differential pressure of the lockup clutch to zero or a maximum value. Up clutch control device. In the lockup clutch control device according to claim 1 or 2,
The determination means determines that the engine torque is equal to or less than a predetermined value when the engine torque is substantially zero;
The command differential pressure return means returns the command differential pressure to the predetermined command differential pressure that is larger than the initial differential pressure.

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