JP3555535B2 - Slip control device for torque converter - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a slip control device for converging a relative rotation between input and output elements of a torque converter used in an automatic transmission or the like, that is, a slip rotation to a target slip rotation by controlling an engagement pressure of a lock-up clutch, and in particular, a vehicle drive. The present invention relates to a slip control technique of a torque converter at the time of switching from a traveling state (a traveling state in which an accelerator pedal is depressed) to a coast traveling state (an inertial traveling state in which an accelerator pedal is released).
[0002]
[Prior art]
Since the torque converter transmits power between input and output elements via a fluid, it performs a torque fluctuation absorbing function and a torque increasing function, but has poor transmission efficiency.
For this reason, a lock-up type torque converter in which the input / output elements of the torque converter are directly connected by a lock-up clutch is often used today under running conditions where the torque fluctuation absorbing function and the torque increasing function are unnecessary. .
Thus, whether the input / output element of the torque converter is brought into the lockup state in which the input / output elements are directly connected by the complete engagement of the lockup clutch (lockup area) or the converter state in which the lockup clutch is released (converter area) With only on / off control, it is necessary to determine the lock-up area so that the problem of muffled noise and vibration does not occur. Therefore, the area that limits the slip rotation of the torque converter is narrow and the transmission efficiency is sufficiently improved. Can not expect.
[0003]
Therefore, the slip control region for limiting the slip rotation of the torque converter in such a manner that the lock-up clutch is in a so-called half-clutch state and the required minimum required torque fluctuation absorbing function and the torque increasing function is secured, There have been proposed many slip control techniques for a torque converter which are set between the lock-up region and the converter region so that the slip rotation can be restricted to a lower vehicle speed.
The slip control technology of the torque converter generally determines a target slip rotation according to running conditions such as the throttle opening of the engine, the vehicle speed, and the operating oil temperature of the automatic transmission. Normally, the engagement force (engagement pressure) of the lock-up clutch is feedback-controlled so that the actual slip rotation of the converter becomes the target slip rotation. According to such slip control, the problem of booming noise and vibration does not occur. It is possible to further reduce the vehicle speed in the slip rotation restriction region and to improve fuel efficiency while avoiding deterioration in drivability.
[0004]
By the way, when starting the slip control for coast running when the vehicle is switched from the drive running state to the coast running state, the transmission direction of the torque converter is changed from the forward direction to the reverse direction by the transition from the drive running to the coast running. Since the oil flow direction in the torque converter is reversed due to the switching, the lock-up clutch is almost completely turned off unless the engagement pressure command value of the lock-up clutch determined in consideration of this is achieved in time with the switching timing. The vehicle is in the released state, and the shift to the coasting slip control state cannot be completed.
[0005]
In order to solve this problem, conventionally, as described in Japanese Patent Application Laid-Open No. 5-87234, when the torque converter is in the converter state in which the lock-up clutch is released immediately before the start of the coasting slip control, the locked state is established. Temporarily increase the engagement pressure of the up clutch to reduce the response delay of the slip control, and adjust the timing at which the transmission direction of the torque converter switches from the forward direction to the reverse direction due to the transition from driving to coasting. There has been proposed a technique capable of starting coast control slip control.
[0006]
On the other hand, according to Japanese Patent Application Laid-Open No. 1-279157, conventionally, regardless of the slip control state of the torque converter immediately before the start of the coasting slip control, the lockup clutch must always be used to start the coasting slip control. There is also proposed a technique in which a torque converter is temporarily brought into a lock-up state or a state close to the lock-up state by increasing a fastening pressure, and then a slip control is started.
[0007]
[Problems to be solved by the invention]
However, as in the former prior art, on condition that the torque converter is in the converter state immediately before the start of the coasting slip control, the engagement pressure of the lock-up clutch is temporarily increased at the start of the coasting slip control. That is, when it is necessary to make a transition from the slip control for drive traveling to the slip control for coast traveling, such as when switching from the drive traveling state to the coast traveling state in the slip control area, the lockup is performed. Since the above operation for temporarily increasing the clutch engagement pressure is not performed at all, the following problem occurs.
[0008]
In other words, if the drive traveling slip control is in a stable control state immediately before the start of the coast traveling slip control, the coast traveling slip control is not performed without temporarily increasing the engagement pressure of the lock-up clutch. Even if the control is started immediately, it is possible to shift to the predetermined slip control, but if the drive travel slip control is not in a stable control state immediately before the start of the coast travel slip control, the lock-up clutch is engaged. If the coasting slip control is immediately started without performing the above operation of temporarily increasing the pressure, the lock-up clutch is almost released once for the above-described reason, and the transition to the coasting slip control state cannot be completed. .
It should be noted that once the lock-up clutch is almost released, even if the engagement pressure is increased to start the engagement of the lock-up clutch, it is difficult to start the engagement.
[0009]
Also, as in the latter conventional technique, regardless of the slip control state of the torque converter immediately before the start of the coasting slip control, the engagement pressure of the lock-up clutch is always increased at the start of the coasting slip control to temporarily stop the torque converter. In the lockup state or a state close to this,
This is the case when the drive slip control is in a stable control state immediately before the start of the coast slip, but the coast slip is performed without temporarily increasing the engagement pressure of the lock-up clutch. Even if the control can be started immediately, even if it is possible to shift to the predetermined slip control, the engagement pressure of the lock-up clutch is increased unnecessarily at the start of the coasting slip control,
When the accelerator pedal is depressed and re-accelerated immediately after the transition from the coast running to the drive running, the re-acceleration becomes that in the lock-up state, the re-acceleration shock increases, and the advantage of slip control is impaired. there were.
[0010]
According to a first aspect of the present invention, there is provided a torque converter slip control device in which slip control at the time of transition from drive running to coast running in a slip control region is performed without any of the above-described problems. The purpose is to propose.
[0011]
According to a second aspect of the present invention, the determination as to whether or not the slip control in drive traveling is in a stable control state, which needs to be performed in the first aspect of the present invention, is simplified by using a calculated value used in the slip control. Another object of the present invention is to propose a torque converter slip control device that can be performed at low cost.
[0012]
A third aspect of the present invention is to provide a slip converter for a torque converter which can more reliably achieve the operation and effect aimed at by the first aspect of the invention.
[0013]
According to a fourth aspect of the present invention, the slip control of the torque converter in which the responsiveness of the coast running slip control is prevented from deteriorating while the operation and effect aimed at by the first invention can be more reliably achieved. The aim is to propose a device.
[0014]
A fifth object of the present invention is to provide a slip converter for a torque converter in which the coasting slip control is not unnecessarily restricted for a long time.
[0015]
[Means for Solving the Problems]
For these purposes, the slip converter of the torque converter according to the first invention firstly comprises:
The actual slip rotation between the input and output elements of the torque converter can be limited by the engagement of the lock-up clutch, and the engagement pressure of the lock-up clutch is controlled so that the actual slip rotation becomes the target slip rotation determined according to the vehicle operating state. Device for performing
When the vehicle is switched from the drive driving state to the coast driving state in the slip control area, if the slip control in the immediately preceding driving was in a stable control state, the coast control slip control is immediately started. If the slip control during the drive travel is not in a stable control state, the engagement pressure of the lock-up clutch is maintained at the final value during the slip control during the immediately preceding drive travel, and the slip state of the torque converter is stabilized. The slip control for coasting is started at the time of the start.
[0016]
The slip control device for a torque converter according to the second invention is the same as the first invention,
It is characterized in that the determination as to whether or not the slip control in the drive traveling is in a stable control state is made based on whether or not a slip rotation deviation between the actual slip rotation and the target slip rotation is equal to or less than a set value. Is what you do.
[0017]
The slip control device for a torque converter according to the third invention is the first or second invention,
When the lock-up clutch engagement pressure is held, a lower limit value is set for the held lock-up clutch engagement pressure.
[0018]
According to a fourth aspect of the present invention, there is provided a torque converter slip control device according to any one of the first to third aspects.
In maintaining the lock-up clutch engagement pressure, an upper limit value is set for the lock-up clutch engagement pressure to be held.
[0019]
The slip control device for a torque converter according to the fifth invention is the slip control device for a torque converter according to any one of the first to fourth inventions,
When the lock-up clutch engagement pressure is held, a time limit is set for the holding time.
[0020]
【The invention's effect】
In the first invention, the slip control device basically controls the engagement pressure of the lock-up clutch so that the actual slip rotation of the torque converter becomes the target slip rotation determined according to the vehicle operating state.
By the way, when the vehicle is switched from the drive traveling state to the coast traveling state in the slip control area and the slip control in the immediately preceding driving traveling is in a stable control state, the coast traveling slip control is immediately started. However, if the slip control in the immediately preceding drive travel is not in a stable control state, the engagement pressure of the lock-up clutch is held at the final value during the slip control in the immediately preceding drive travel.
Then, when the slip state of the torque converter is stabilized, slip control for coasting is started.
[0021]
Therefore, in the first invention, when it is necessary to shift from the drive traveling slip control to the coast traveling slip control by switching from the drive traveling state to the coast traveling state in the slip control region,
However, since the slip control in the immediately preceding drive traveling is not in a stable control state, if the coasting slip control is immediately started, only when the lock-up clutch is almost released as described above,
The start pressure of the coasting slip control is delayed by maintaining the lock-up clutch engagement pressure at the final value during the slip control in the immediately preceding drive running, thereby preventing the lock-up clutch from being almost released. Thus, the shift to the coasting slip control can be enabled.
In addition, according to the first aspect of the invention, the slip control in the immediately preceding drive travel is not in a stable control state, and if the coast control slip control is immediately started, the lock-up clutch is almost released. Only when this occurs, the engagement pressure of the lock-up clutch is maintained to avoid this, so that the engagement pressure is reliably maintained only when it is really necessary. Is not wasted, and the problem of unnecessarily delaying the slip control for coasting does not occur.
[0022]
In the case where the slip control for driving immediately before shifting to the slip control for coasting is in a stable control state and the slip control for coasting can be started immediately even if the slip control for coasting can be started immediately, lock-up is performed. Since the control to keep the clutch engagement pressure at the final value during the slip control in the immediately preceding drive travel is not performed,
At the start of the coasting slip control, the above-described holding of the lock-up clutch engagement pressure is not performed unnecessarily, and the above-described lockdown clutch engagement pressure due to the delay of the coasting slip control due to the holding of the unnecessary lockup clutch engagement pressure is not performed. That is, the problem that a large shock is generated when the accelerator pedal is depressed and reaccelerated immediately after the shift from the coast running to the drive running can be reliably avoided.
[0023]
In the second invention, it is determined whether or not the slip control in the drive traveling is in a stable control state based on whether or not the slip rotation deviation between the actual slip rotation and the target slip rotation of the torque converter is equal to or less than a set value. For,
The determination can be easily and inexpensively performed by diverting the actual slip rotation and the target slip rotation obtained by calculation during the slip control.
[0024]
In the third invention, when the lock-up clutch engagement pressure is held, a lower limit value is set for the held lock-up clutch engagement pressure.
Even when the final value of the lock-up clutch engagement pressure at the time of the slip control during the immediately preceding drive travel is extremely low, the above-described operation and effect of the first invention can be reliably achieved.
[0025]
In the fourth invention, when the lock-up clutch engagement pressure is held, an upper limit value is set for the held lock-up clutch engagement pressure.
Even if the final value of the lock-up clutch engagement pressure at the time of the slip control during the immediately preceding drive travel is extremely high, the above-described effects of the first invention are achieved while preventing the responsiveness of the coast travel slip control from deteriorating. be able to.
[0026]
In the fifth invention, when the lock-up clutch engagement pressure is held, a time limit is set for the holding time.
Even if the slip state of the torque converter is not stabilized for a long time while the lock-up clutch engagement pressure is being held for some reason, the coasting slip control will not be limited beyond the above-mentioned time limit.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a slip control device for a torque converter according to an embodiment of the present invention. Although a detailed illustration of a torque converter 2 is omitted because it is well known, the torque that is coupled to an engine crankshaft and driven by the engine is shown in FIG. It has a pump impeller as a converter input element, a turbine runner as a torque converter output element coupled to an input shaft of a gear transmission mechanism for an automatic transmission, and a lock-up clutch 2c for directly connecting the pump impeller and the turbine runner. Lock-up type torque converter.
[0028]
The fastening force of the lock-up clutch 2c is determined by the applied pressure P before and after that._A  And release pressure P_R  Determined by the differential pressure (lock-up clutch engagement pressure)_A  Is the release pressure P_R  If it is lower than this, the lock-up clutch 2c is released and does not directly connect the pump impeller and the turbine runner, and the torque converter 2 functions in a converter state in which the slip is not limited.
[0029]
Apply pressure P_A  Is the release pressure P_R  If it is higher than this, the lockup clutch 2c is engaged with a force corresponding to the differential pressure, and the torque converter 2 is operated in a slip control state in which the slip is limited according to the engagement force of the lockup clutch 2c.
When the differential pressure becomes larger than the set value, the lock-up clutch 2c is completely engaged, the relative rotation between the pump impeller and the turbine runner is eliminated, and the torque converter 2 functions in the lock-up state.
[0030]
Apply pressure P_A  And release pressure P_R  Are determined by the slip control valve 11. The slip control valve 11 controls the signal pressure P from the lock-up solenoid 13 that is duty-controlled by the controller 12._S  Apply pressure P according to_AAnd release pressure P_R  The slip control valve 11 and the lock-up solenoid 13 are known ones described below.
That is, first, the lock-up solenoid 13 applies a constant pilot pressure P_p  , The signal pressure P increases as the solenoid drive duty D from the controller 12 increases._S  To be higher.
[0031]
On the other hand, the slip control valve 11 controls the signal pressure P_S  And the feedback release pressure P_R  In one direction, the spring force of the spring 11a and the applied pressure P fed back in the other direction._A  And the signal pressure P_S  As the application pressure P_A  And release pressure P_R  Pressure difference between (P_A  -P_R  ) Is changed as shown in FIG.
[0032]
Here, the lock-up clutch engagement pressure (P_A  -P_R  ) Is P_R  > P_A  Means that the torque converter 2 is in a converter state, and conversely, the lock-up clutch engagement pressure (P_A  -P_R  ) Is positive, the larger the value is, the larger the engagement capacity of the lock-up clutch 2c is, and this means that the slip rotation of the torque converter 2 is greatly limited, and finally the torque converter 2 is brought into the lock-up state. I do.
[0033]
A signal from a throttle opening sensor 21 for detecting a throttle opening TVO representing an engine load is provided to the controller 12;
Pump impeller rotation speed ω_IR(A signal from an impeller rotation sensor 22 for detecting the
Turbine runner rotation speed ω_TRA signal from the turbine rotation sensor 23 for detecting
A signal from an oil temperature sensor 24 for detecting a hydraulic oil temperature TEMP of the automatic transmission (torque converter 2),
Transmission output speed (equivalent to vehicle speed) N_O  A signal from the transmission output rotation sensor 25 for detecting
Power supply voltage V_igFrom the power supply voltage sensor 26 for detecting
A signal from the idle switch 27 that is turned on when the accelerator pedal is released is input.
[0034]
Based on the input information, the controller 12 determines the drive duty D of the lock-up solenoid 13 by a control program shown in FIG. 3 and performs a predetermined slip control described in detail below.
First, in steps 31 and 32, the throttle opening TVO and the transmission output speed N_O  Based on the (vehicle speed), it is determined whether the current operation state is an operation in a slip control area, an operation in a lockup area, or an operation in a converter area.
[0035]
If the engine is operating in the converter region, at step 33, the lock-up clutch engagement pressure (P_A  -P_R  ) Becomes a negative value, and outputs a drive duty D to the lock-up solenoid 13 (see FIG. 1) so as to bring the torque converter into the converter state.
If the vehicle is operating in the lock-up region, in step 34, the lock-up clutch engagement pressure (P_A  -P_R  ) Becomes a positive maximum value and outputs a drive duty D to the lock-up solenoid 13 such that the torque converter 2 is locked up.
[0036]
If the vehicle is operating in the slip control region, first, at step 35, it is determined whether the idle switch 27 (see FIG. 1) is ON (coast running state) or OFF (drive running state).
If the idle switch 27 is OFF (drive running state), the slip control for drive running is performed in step 36 as follows.
First, the hydraulic oil temperature TEMP and the turbine runner rotation speed ω_TRAnd the target slip rotation Δω for driving from the throttle opening TVO and the throttle opening TVO_S  And the pump impeller rotation speed ω_IRFrom the turbine runner rotation speed ω_TRIs subtracted from the actual slip rotation Δω of the torque converter 2._R  Is calculated. And this actual slip rotation Δω_R  Is the target slip rotation Δω_S  The drive duty D for matching with the power supply voltage V_igIs output to the lock-up solenoid 13 while performing the slip control for driving.
[0037]
In the next step 37, it is determined whether or not the slip control for driving is in a stable control state as shown in FIG. 4 as follows, and in step 38, the lock-up clutch is engaged during the slip control for driving. The pressure command value is stored one by one.
To explain the determination of FIG. 4, in step 51, first, the target slip rotation Δω_S  And actual slip rotation Δω_R  And the slip rotation deviation Δ between the time t and the instant t in FIG.₁  It is checked whether or not the state is within the set value α%, as in the drive traveling slip control prior to this. Further, the time during this state is determined by the determination time T.₁  Check if it shows more than β% of seconds.
If this condition is satisfied, and in step 52 the pump impeller rotational speed ω_IRIs the instant t in FIG.₁  During the slip control for drive traveling before the set time γ, the state that is equal to or less than the set value γ is set time T₂  When it is determined that the control has continued for more than one second, it is determined in step 53 that the drive traveling slip control is in a stable control state.
Note that the above α, β, γ, T₁  , T₂  Are constants that vary depending on the vehicle specifications, the type of engine, and the difference in the torque converter.
[0038]
However, if even one of the two conditions in steps 51 and 52 is missing, that is, the instant t in FIG.₁  Target slip rotation Δω, as in the drive control slip control prior to_S  And actual slip rotation Δω_R  The slip rotation deviation Δ exceeds the set value α% or is within α%.₁  Less than β% of the second, or the pump impeller rotation speed ω_IRExceeds the set value γ or is less than or equal to γ when the set time T₂  If it has not continued for more than one second, it is determined in step 54 that the drive traveling slip control was not in a stable control state.
[0039]
If it is determined in step 35 that the idle switch 27 is ON (coast running state), in step 39, it is determined whether or not it is the first time to shift from driving to coast running, and control is returned to step 40 only at the first time. By proceeding and checking the determination result in step 37, it is determined whether the slip control for the drive traveling immediately before the transition from the drive traveling to the coast traveling is in a stable control state (slip state of the torque converter is stable). .
[0040]
If the determination is that the vehicle is in a stable state, coast running slip control is performed in step 41 as follows.
First, the hydraulic oil temperature TEMP and the turbine runner rotation speed ω_TRFrom the target slip rotation Δω for coasting_S  And the pump impeller rotation speed ω_IRFrom the turbine runner rotation speed ω_TRIs subtracted from the actual slip rotation Δω of the torque converter 2._R  Is calculated. And this actual slip rotation Δω_R  Is the target slip rotation Δω_S  The drive duty D for matching with the power supply voltage V_igThe output is output to the lock-up solenoid 13 while performing the slip control for coasting while correcting in accordance with the following.
[0041]
If the determination in step 40 is that the vehicle is not in the stable state, the process proceeds to step 42 in which the final state of the slip control for drive traveling, which has been continuously updated in step 38 until immediately before the transition to the coast traveling state. The drive duty D for maintaining the engagement pressure is output to the lock-up solenoid 13 to delay the start of the coasting slip control.
However, in maintaining the final fastening pressure of the slip control for drive traveling as described above, taking into account the case where the final fastening pressure is extremely low or extremely high, the upper limit of the holding pressure as shown in FIG. Set the value and lower limit.
[0042]
In steps 61 and 62 in FIG. 5, it is checked whether the final engagement pressure of the drive traveling slip control exceeds the allowable upper limit value, is lower than the allowable lower limit value, or is a pressure between these upper and lower limit values.
Here, the allowable upper limit value is an upper limit pressure at which a response delay when the coasting slip control is started after the lock-up clutch engagement pressure is maintained does not matter, and the allowable lower limit value is the lock-up clutch engagement pressure. During the holding, the pressure is set to the lower limit pressure at which the lock-up clutch is almost not released (disables the shift to the coasting slip control).
[0043]
When it is determined in step 61 that the final engagement pressure of the drive travel slip control exceeds the allowable upper limit value, in step 63, the holding pressure for maintaining the engagement pressure of the lock-up clutch at the final engagement pressure of the drive travel slip control Is output to the lock-up solenoid 13 to maintain
When it is determined in step 62 that the final engagement pressure of the drive travel slip control is less than the allowable lower limit, in step 64, the holding pressure is used to maintain the engagement pressure of the lock-up clutch at the final engagement pressure of the drive travel slip control. The duty D which keeps the allowable lower limit value is output to the lock-up solenoid 13,
When it is determined in steps 61 and 62 that the final engagement pressure of the drive traveling slip control is between the allowable upper limit and the allowable lower limit, in step 65, the engagement pressure of the lock-up clutch is changed to the final engagement of the drive travel slip control. The duty D to keep the pressure is output to the lock-up solenoid 13.
[0044]
From the drive running to the coast running, after the second time, step 39 selects step 43, where it is checked whether or not the above-described operation of holding the lock-up clutch engagement pressure is being performed.
If the lock-up clutch engagement pressure has been held, then in step 44, it is checked whether a time limit has elapsed since the start of the hold action.
If it is determined in steps 43 and 44 that the holding action of the lock-up clutch engagement pressure is being performed, and if the time limit has not elapsed since the start of the holding action, the torque is determined in step 45. It is checked whether the slip condition of the converter is stable in the same manner as in step 37, that is, as shown in FIG.
If the slip state of the torque converter is not stable, the control proceeds to step 42 to continue the above-described operation of maintaining the lock-up clutch engagement pressure. When the slip state of the torque converter is stabilized, the control proceeds from step 45 to step 41. To start coasting slip control.
[0045]
When the operation of maintaining the lock-up clutch engagement pressure is completed, the process proceeds to step 41 in step 43, and the coasting slip control is continuously performed.
If the holding operation of the lock-up clutch engagement pressure does not end because the slip state of the torque converter is not stable at all times, when the time limit has elapsed from the start of the holding operation, the step 44 shifts the control to the step 41. Since the coasting slip control is started to proceed, there is no adverse effect that the coasting slip control is not started at any time.
[0046]
According to the slip control of the torque converter as described above, the throttle opening TVO during traveling in the slip control region is set to the instant t as shown in FIGS.₁ To explain the case of shifting from drive driving to coast driving with fully closed at
The instant t₁ , That is, the drive traveling slip control immediately before the transition from the drive traveling to the coast traveling is not in the stable control state as shown in FIG. 7 (the slip of the torque converter is stable) (step 40 in FIG. 3).And step 45),
The engagement pressure of the lock-up clutch is held at the final value at the time of the slip control in the immediately preceding drive traveling (step 42) to delay the start of the coast traveling slip control, and the lock-up clutch engagement pressure is maintained (step 42). 42), the slip state of the torque converter is stabilized (step 45)._Two After that, the coasting slip control is started.
[0047]
Under such circumstances, the instant t₁ If the shift from the drive travel slip control to the coast travel slip control is immediately executed, the lock-up clutch is almost released as described above because the slip control in the immediately preceding drive travel is not in a stable control state. The shift to coasting slip control becomes difficult.RoWhile
In the present embodiment,Torque converter slipcontrolUntil the state is stabilized, by holding the engagement pressure of the lock-up clutch at the final value during the slip control in the immediately preceding drive as described above, by delaying the start of the coasting slip control.,It is possible to prevent the lock-up clutch from being almost released, and to reliably shift to the coasting slip control.
Moreover, according to the present embodiment, if the slip control in the immediately preceding drive travel is not in a stable control state, and if the coast travel slip control is immediately started, the lock-up clutch is almost released. Only in this case, since the engagement pressure of the lock-up clutch is maintained to avoid this, the engagement pressure is reliably maintained only when it is really necessary. There is no problem that the slip control for coasting is unnecessarily delayed because it is wasted.
[0048]
Then, the transition instant t to the coasting slip control t₁ The slip control for driving immediately before is in a stable control state as shown in FIG. 6 (step 40).And step 45If it is possible to shift to the predetermined slip control even if the coasting slip control is started immediately, the above control for maintaining the engagement pressure of the lock-up clutch at the final value during the slip control in the immediately preceding drive running is performed. Without performing this, the coasting slip control is immediately started as shown in FIG. 6 (step 41).
At the start of the coasting slip control, the above-described holding of the lock-up clutch engagement pressure is not performed unnecessarily, and the above-described lockdown clutch engagement pressure due to the delay of the coasting slip control due to the holding of the unnecessary lockup clutch engagement pressure is not performed. That is, the problem that a large shock is generated when the accelerator pedal is depressed and reaccelerated immediately after the shift from the coast running to the drive running can be reliably avoided.
[0049]
In the present embodiment, the determination as to whether or not the slip control in the drive traveling is in a stable control state (step 37 in FIG. 3) is performed as described above with reference to FIG. 4 by the actual slip rotation Δω of the torque converter._R  And target slip rotation Δω_S  Is performed depending on whether the slip rotation deviation Δ is less than or equal to the set value (α%),
The determination is based on the actual slip rotation Δω obtained by calculation during the slip control._R  And target slip rotation Δω_S  It can be performed easily and inexpensively by diversion.
[0050]
Further, in the present embodiment, when the coasting slip control is delayed, the lock-up clutch engagement pressure is maintained at the final value during the slip control in the immediately preceding drive running, but the holding pressure is described with reference to FIG. Since the lower limit value and the upper limit value are set as described above, even when the final value of the lock-up clutch engagement pressure is extremely low, the above-described operation and effect that the lock-up clutch can be almost completely released can be solved. Even when the final value of the lock-up clutch engagement pressure is extremely high, the responsiveness of the coasting slip control does not deteriorate.
[0051]
In addition, when the lock-up clutch engagement pressure is held, a time limit is set for the hold time (step 44 in FIG. 3), so that the slip state of the torque converter may be extended for a long time while the lock-up clutch engagement pressure is held for some reason. Even in the case where it is not stable over time, it is possible to eliminate the adverse effect of limiting the coasting slip control beyond the time limit.
[Brief description of the drawings]
FIG. 1 is a schematic system diagram showing a control system of a torque converter including a slip control device according to an embodiment of the present invention.
FIG. 2 is a diagram showing a relationship between a signal pressure from a lock-up solenoid and a lock-up clutch engagement pressure in the embodiment.
FIG. 3 is a flowchart showing slip control executed by a controller in the embodiment.
FIG. 4 is a flowchart showing a program to be performed in the slip control to determine whether or not the drive travel slip control is in a stable state.
FIG. 5 is a flowchart showing a program for determining a holding pressure of a lock-up clutch engagement pressure to be held when shifting to the coasting slip control in the slip control.
FIG. 6 is an operation time chart of the slip control for drive running immediately before the slip control when the slip control is in a stable state.
FIG. 7 is an operation time chart of the slip control for driving immediately before the slip control for the drive traveling is not in a stable state.
[Explanation of symbols]
2 Torque converter
2c Lock-up clutch
11 Slip control valve
12 Controller
13 Lock-up solenoid
21 Throttle opening sensor
22 Impeller rotation sensor
23 Turbine rotation sensor
24 Oil temperature sensor
25 Transmission output rotation sensor
26 Power supply voltage sensor
27 Idle switch

Claims (5)

The actual slip rotation between the input and output elements of the torque converter can be limited by the engagement of the lock-up clutch, and the engagement pressure of the lock-up clutch is controlled so that the actual slip rotation becomes the target slip rotation determined according to the vehicle operating state. Device for performing
When the vehicle is switched from the drive driving state to the coast driving state in the slip control area, if the slip control in the immediately preceding driving was in a stable control state, the coast control slip control is immediately started. If the slip control during the drive travel is not in a stable control state, the engagement pressure of the lock-up clutch is maintained at the final value during the slip control during the immediately preceding drive travel, and the slip state of the torque converter is stabilized. A slip control device for a torque converter, characterized in that the slip control for coasting is started when the slip control is performed. 2. The configuration according to claim 1, wherein the determination as to whether or not the slip control in the drive traveling is in a stable control state is performed based on whether or not a slip rotation deviation between the actual slip rotation and the target slip rotation is equal to or less than a set value. A slip control device for a torque converter. 3. The torque converter slip control device according to claim 1, wherein a lower limit value is set for the lock-up clutch engagement pressure to be held when the lock-up clutch engagement pressure is held. The slip control device for a torque converter according to any one of claims 1 to 3, wherein an upper limit value is set for the lock-up clutch engagement pressure to be held when the lock-up clutch engagement pressure is held. The slip control device for a torque converter according to any one of claims 1 to 4, wherein, when the lock-up clutch engagement pressure is held, a time limit is set for the holding time.

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