JP3199017B2 - Lockup control device for torque converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lock-up control device for a torque converter, and more particularly to a lock-up control technology for a torque converter when the line pressure is reduced in accordance with the operating oil temperature of an automatic transmission combined with the torque converter. It is about.

[0002]

2. Description of the Related Art Since a torque converter transmits power between input and output elements via an internal working fluid, it can smoothly transmit power by a torque fluctuation absorbing function, and can also obtain a torque increasing function. In this automatic transmission, a torque converter is used in a transmission system.

[0003] However, the torque converter cannot avoid relative rotation between input and output elements, that is, slip, and has poor transmission efficiency and poor fuel economy of the engine. Therefore, in a relatively high vehicle speed range where the torque fluctuation absorbing function and the torque increasing function are unnecessary, the input / output elements are directly connected by the lock-up clutch, and the torque converter is directly connected from the normal converter state to the input / output elements. Lock-up type torque converters that can be brought into a locked-up state are often used.

Here, it is customary to switch the transmission state between the lock-up state of the torque converter and the converter state by switching the supply direction of the torque converter operating pressure, and usually, When the torque converter operating pressure flows from the apply chamber on the front side in the fastening direction of the lock-up clutch to the release chamber on the opposite side, of the apply chamber and the release chamber on both sides of the lock-up clutch, When the torque converter is locked by the dynamic pressure to lock up the torque converter and the operating pressure of the torque converter flows in the opposite direction, the lock-up clutch is released by the dynamic pressure to put the torque converter in the converter state. It is a target.

On the other hand, in an automatic transmission combined with the above-described torque converter, a plurality of clutches, brakes, and other frictional engagement elements are selectively engaged with a line pressure to shift to a predetermined gear. At this time, if the viscosity of the hydraulic oil of the automatic transmission becomes extremely low due to extremely low temperature of less than −10 ° C. and the viscosity becomes abnormally high, the delay in the shift response due to the engagement delay of the friction engagement element increases, Since the early wear of the engagement element causes a decrease in durability, the line pressure should be lower at low temperatures than at other normal temperatures, so that the engagement delay of the friction engagement elements does not become a problem even at the low temperature. For example, Nissan Motor Co., Ltd. (1987)
This is known as described on page I-24 of "RE4R01A Automatic Transmission Maintenance Manual" (A261C07) issued in March.

[0006] This known technique is like shown in (f) in FIG. 6, at a low temperature of less than hydraulic fluid temperature T _{AT F} is the set temperature of the automatic transmission (e.g., -10 ° C as described above), ( during cold flag fLAG _ATF as shown in a) is up to instant t ₁ is 1, and the instant t ₂ after, the higher low-temperature target line pressure P _LH exemplified the line pressure P _L in FIG. 5, The instant t _{1 to} t ₂ at which the transmission hydraulic oil temperature T _ATF is equal to or higher than the set temperature and the low temperature flag FLAG _ATF is set to 0
Between, is that to lower the normal-temperature target line pressure P _LL exemplified the line pressure P _L in FIG.

[0007]

However, the aforementioned torque
The converter operating pressure should be created using the line pressure as the source pressure.
Normal, so if the line pressure changes as above
The operating pressure of the torque converter
Inevitable. Here, the transmission operating oil temperature T_ATFIs the low temperature range
The temperature t in FIG. ₁Shown in (f)
Line pressure P_LIs the target line pressure P for low temperature_LHFrom room temperature
Target line pressure P_LLConsidering a sudden drop to
In this case, the operating pressure of the torque converter also suddenly drops.
Will be down.

By the way, in the converter state of the torque converter, the operating pressure of the torque converter flows from the release chamber to the apply chamber. Therefore, the sudden decrease in the operating pressure of the torque converter first causes a pressure drop in the release chamber. The pressure in the apply chamber is reduced. This because, instant t momentarily ₁ becomes lower than the pressure of the pressure release chamber apply chamber, even though the locking torque converter to the instantaneously moment a converter region should not lock up the torque converter in FIG. 6 There was a problem that the passengers were raised, giving shock and discomfort to the occupants.

A first object of the present invention is to propose a lockup control device for a torque converter which has solved the above problem.

Another object of the first invention is to prevent the operation for solving the above problem from being performed wastefully.

A second object of the present invention is to provide a lock-up control device for a torque converter which can solve the above-mentioned problem without changing the hydraulic circuit itself.

A third object of the present invention is to allow an operation for solving the above problem to be appropriately performed according to a shift mode of the automatic transmission.

[0013]

To achieve these objects, first, a lockup control device for a torque converter according to a first aspect of the present invention provides a target line pressure for low temperature when a hydraulic oil temperature of an automatic transmission is lower than a set temperature. Lock-up in which the input and output elements of the torque converter are directly connected by switching the supply direction of the operating pressure of the torque converter that uses the line pressure that is the target line pressure for the normal temperature at the normal temperature above the set temperature as the base pressure. And a converter state in which the power transmission state can be switched between the state and the converter state in which the direct connection is released, in the torque converter capable of switching the transmission state, from the low-temperature target line pressure having a high line pressure to the low-temperature target line pressure having a low line pressure. The time change ratio of the torque converter operating pressure due to the change is
When the torque converter is in the converter state, the torque converter is reduced, and the decrease in the temporal change rate of the torque converter operating pressure is prohibited when the torque converter is in the lock-up state.

According to a second aspect of the present invention, in the lock-up control device for a torque converter according to the first aspect, a time change ratio from the low-temperature target line pressure having a high line pressure to the low-temperature target line pressure having a low line pressure is reduced. Thus, the torque converter operating pressure is configured to reduce the temporal change ratio.

In a third aspect of the present invention, the lock-up control device for a torque converter according to the second aspect, wherein the degree of decrease in the time change rate of the line pressure is set to be greater in the manual transmission mode of the automatic transmission than in the automatic transmission mode. It is a feature.

[0016]

According to the first aspect of the invention, the line pressure is set to a high low-temperature target line pressure when the hydraulic oil temperature of the automatic transmission is lower than the set temperature, and to a low normal-temperature target line pressure when the normal oil temperature is higher than the set temperature. Is done. On the other hand, the torque converter receives the supply of the torque converter operating pressure using the line pressure as the source pressure and performs power transmission via the working fluid.At this time, by switching the supply direction of the torque converter operating pressure, the torque converter The transmission state is switched between a lockup state in which the input / output elements are directly connected and a converter state in which the direct connection is released.

In the first aspect of the present invention, when the line pressure is changed from the higher target line pressure for low temperature to the lower target line pressure for normal temperature, the operating pressure of the torque converter is reduced. When the torque converter is in the converter state, the rate of change with time when the torque converter is in operation is reduced. According to the control for decreasing the time change ratio of the torque converter operating pressure, it is possible to avoid a sudden change in the differential pressure before and after the lock-up clutch for performing the switching of the transmission state. Despite being in the converter region, it is possible to prevent a problem that the torque converter is momentarily locked up to give a shock or an uncomfortable feeling to the occupant.

Further, in the first invention, the reduction of the time change rate of the operating pressure of the torque converter, which is performed as described above, is prohibited when the torque converter is in the lock-up state. In other words, the torque converter operates in the lock-up state of the torque converter, which does not cause a problem that the torque converter is momentarily locked up even though the converter is in the converter range immediately at the start of the decrease of the line pressure according to the temperature. It is possible to eliminate waste of performing control to decrease the time change ratio of the pressure.

According to a second aspect of the present invention, the time change rate of the line pressure when the line pressure is lowered from the higher target line pressure for low temperature to the lower target line pressure for normal temperature is reduced to thereby operate the torque converter. Since the time change ratio of the pressure is reduced, the above-described problem can be solved only by matching the content of the line pressure control to the above, so that no change in the hydraulic circuit itself is required, and cost is reduced. It is very advantageous.

When the line pressure is raised from the target line pressure for normal temperature to the target line pressure for low temperature, the rate of change of the line pressure with time is not controlled to decrease as described above. Is quickly completed, and the sudden change in the operating pressure of the torque converter causes a sudden change in the differential pressure across the lock-up clutch.However, in this case, the lock-up clutch is urged in the release direction, and the torque converter is locked up for a moment. There is no problem of being compromised. Rather, by quickly increasing the line pressure from the normal-temperature target line pressure to the low-temperature target line pressure, it is possible to eliminate adverse effects on the shift shock for the following reasons.

That is, the automatic transmission is designed by determining the shift timing and the like so that the shift shock is most effectively reduced between the target line pressure for normal temperature and the target line pressure for low temperature. If a shift is performed during a change transition period in which the pressure changes between the pressure and the low-temperature target line pressure, the shift shock cannot be reduced as designed.
In this regard, as described above, in the second invention in which the line pressure is rapidly increased from the target line pressure for normal temperature to the target line pressure for low temperature, the change time of the line pressure is shorter, and the line pressure change transition period is shorter. In the second invention, the intended purpose can be achieved while avoiding the adverse effect on the shift shock.

In addition, as described above with respect to the first invention, when the lock-up state is established, useless reduction control of the time change ratio of the torque converter operating pressure is prohibited, and particularly, as in the second invention, the torque converter operating pressure is reduced. In the control in which the time change rate is reduced by manipulating the time change rate of the line pressure, the line pressure can be rapidly reduced to the target line pressure after the change. The probability of occurrence can be kept small, and the adverse effect on the shift shock which is particularly noticeable due to the lock-up state can be reliably avoided.

In consideration of the fact that the line pressure is changed at a very low temperature in accordance with the temperature, even if the lock-up is temporarily released to prevent a shock at the time of gear shifting, the operation is not performed. Due to the high viscosity of the oil, it is inevitable that the lock-up release delay will occur, and the shift may be performed in the lock-up state. Therefore, as described above, the line pressure is promptly reduced to the changed target line pressure. I confirmed that the significance of obtaining was great.

In the third aspect of the present invention, the degree of decrease in the time change rate of the line pressure is made larger in the manual transmission mode of the automatic transmission than in the automatic transmission mode. The solution to the problem of lock-up malfunction at the time of a decrease in speed will be given priority over shortening the transient period of the line pressure decrease and keeping the probability of shifting occurring during this period low, and the following operational effects will be obtained. Can be. In other words, in the manual shift mode, since the shift is based on the driver's intention, the driver expects a shift shock, and the transition period of the decrease in the line pressure is long, and the probability of shifting during this period increases. Although this does not make the driver feel uncomfortable, the lockup due to a malfunction is uncomfortable because the driver does not expect this. By the way, in the third aspect of the invention, the priority is given to solving the problem relating to the malfunction of the lock-up when the line pressure is lowered according to the temperature, so that the latter can be surely eliminated.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a lock-up control device for a torque converter according to an embodiment of the present invention.
A lock-up torque converter 1 is shown together with a line pressure control system of the automatic transmission.

The torque converter 1 is inserted between an engine (not shown) and an automatic transmission and used to transfer torque between the two. Therefore, the torque converter 1 includes a pump impeller 1a as an input element that is drivingly coupled to an engine crankshaft, a turbine runner 1b as an output element that is disposed opposite to the driving impeller and is coupled to an input shaft of an automatic transmission, It is assumed that the stator 1c, which acts between the input / output elements 1a and 1b and increases the torque, is a well-known basic element.
The torque converter 1 transmits power between the input / output elements 1a and 1b through the internal working fluid while absorbing torque fluctuation (in a converter state), and during this time, performs an output torque increasing action under the reaction force of the stator 1c.

The torque converter 1 further includes a lock-up clutch 1c which rotates together with the turbine runner 1b. Usually, the hydraulic oil supplied from the circuit 2 to the release chamber 1e is removed to the circuit 3 through the apply chamber 1f. The lock-up clutch 1c is moved to the right in FIG.
The converter is operated in a converter state in which the connection between a and 1b is not directly connected by the lock-up clutch 1c. During this time, the torque converter 1 can perform smooth power transmission while performing the torque fluctuation absorbing function and the output torque increasing function.

In a relatively high vehicle speed region (lock-up region) where the torque fluctuation absorbing function and the torque increasing function are not required, the operating oil supplied from the circuit 3 to the apply chamber 1f is supplied to the circuit 2 via the release chamber 1e. By eliminating
The lock-up clutch 1c is moved to the left in FIG.
A function between a and 1b is performed in a lockup state in which the lockup clutch 1c is directly connected to the lockup clutch 1c, thereby improving transmission efficiency.

Next, a system for switching the oil flow direction to the torque converter 1 as described above and performing lockup control of the torque converter will be described. This system has a lock-up control valve 10 as a main component, and the lock-up control valve 10 is provided via circuits 2 and 3 connected to a release chamber 1e and an application chamber 1f.

Here, the lock-up control valve 10 is connected to the plug 1
1 and the spool 12 are provided in a coaxial butting relationship, and both are elastically supported at the rightmost position shown in the drawing by a common spring 13 acting on the side of the spool 12. In this elastic position, the plug 11 disconnects the circuit 2 to the release chamber 1 e from the drain port 14 and communicates with the port 15, and the spool 12 disconnects the circuit 3 to the apply chamber 1 f from the port 16 to the cooler circuit 17. It shall be understood.

When the lock-up control pressure P _L is supplied to the chamber 18, the plug 11 is urged to the left in FIG. 1 by the lock-up control pressure P _L , and against the spring 13 together with the spool 12. It shall be pushed to the same direction limit position. In such a pushing position, the plug 11 disconnects the circuit 2 to the release chamber 1 e from the port 15 and communicates with the drain port 14, and the spool 12 disconnects the circuit 3 to the apply chamber 1 f from the cooler circuit 17 and connects to the port 16. It shall be understood.

As a pressure source for engaging and releasing the lock-up clutch 1d, an oil pump 23, which is also a pressure source for an automatic transmission, is provided, and hydraulic oil from the oil pump 23 is discharged to a circuit 24. Hydraulic fluid to the circuit 24, by a known pressure regulator valve 30, details pressurized be described later adjusted to a predetermined line pressure P _L, also known the line pressure P _L from the pressure regulator valve 30 as a source pressure by the torque converter regulator valve 31 produces a constant pressure below the torque converter operating pressure P _TC. The torque converter operating pressure _PTC is supplied to a circuit 32, which, on the other hand,
Ports 15 and 16, and to the cooler circuit 17 via the orifice 33.

Furthermore the line pressure circuit 24, provided in connection with the known pilot valve 41, the pilot valve 41 is assumed to output the line pressure circuit 24 to the circuit 42 by a constant pilot pressure P _p. Lock-up solenoid 4
3 normally drains the circuit 44 to set the lock-up control pressure P _L to 0 and sets the lock-up control valve 10 to the state shown in the figure, but when the lock-up signal _SL is input, the pilot pressure of the circuit 42 and outputs the P _p in the circuit 44 to generate a lockup control pressure P _L, which was supplied to the chamber 18 of the lock-up control valve 10 plugs 11 and the spool 12
To the left in the figure against the spring 13.

The pressure regulator valve 30, which functions to regulates the line pressure P _L of the circuit 24 to a value corresponding to the spring force of the spring 30a, the spring force of the spring 30a by modifier pressure P _m to the chamber 30b shall be arbitrarily increase the line pressure P _L increases the. This because, the provided line pressure solenoid 45 that is duty-controlled to arbitrarily changed by generating a modifier pressure P _m, the line pressure solenoid 45 is driven by the line pressure control duty D _PL, D _PL = 0% , The modifier pressure circuit 46 is drained and the modifier pressure P _m
To 0, and as a result, the pressure regulator valve 3
By setting the line pressure P _L to the minimum value by setting the zero spring 30a to the minimum spring force, the modifier pressure circuit 46 is connected to the pilot pressure circuit 42 with a large opening as the line pressure control duty D _PL increases. increasing the a pressure P _m, as a result, it is assumed to increase the line pressure P _L by increasing the spring force of the spring 30a in the pressure regulator valve 30.

Next, the lock-up control operation of the torque converter 1 in the hydraulic control system shown in FIG. 1 will be described. When the torque converter 1 is set to the converter state,
The lock-up control signal _SL is not output. In this case the lock-up control valve 10 is in the illustrated state from the lock-up control pressure P _L does not occur within the chamber 18, the circuit 32
Torque converter operation pressure P _TC port 15, flows into the release chamber 1e through the circuit 2, is then removed from the apply chamber 1f through the circuit 3 and the cooler circuit 17. Therefore, the torque converter 1 is in a released state in which the lock-up clutch 1d is displaced rightward in FIG.
Power transmission can be performed in a converter state in which a and 1b are not directly connected.

Put torque converter 1 in lock-up state
The lock-up control signal S _LOutput by
Lockup control pressure P from the solenoid 43 to the circuit 44_LDepart
Let it live. At this time, the lock-up control valve 10 is
Lock-up control pressure P_LPlug 11 and switch
The pool 12 is moved to the limit position opposite to the illustrated position against the spring 13.
It will be pushed. Here, the torque converter of the circuit 32
Operating pressure P_TCIs the apply chamber via port 16 and circuit 3
1f, and then from the release chamber 1e to the circuit 2 and
Rejected via drain port 14. Therefore, torque control
The barter 1 moves the lock-up clutch 1d to the left in FIG.
In the displaced fastening state, the input / output elements 1a and 1b
Power can be transmitted in a lock-up state that is not directly connected
it can.

The lock-up control signal S _L to the solenoid 43 and the line pressure control duty D _PL to the solenoid 45 are controlled by the controller 51.
Therefore, the controller 51 sends a signal from an oil temperature sensor 52 that detects the operating oil temperature T _ATF of the automatic transmission, a signal from a gear position sensor 53 that detects the selected gear stage _GP of the automatic transmission, and the vehicle speed. A signal from the vehicle speed sensor 54 for detecting the VSP, a signal from the throttle opening sensor 55 for detecting the throttle opening TVO of the engine, and whether the driver is in the automatic shifting (D) range in the automatic shifting mode. And a signal from a range sensor 56 for detecting whether the manual shift mode is set to the manual shift (M) range.

The controller 51 performs lockup control of the torque converter 1 based on FIG. 2 and line pressure control of the automatic transmission based on FIGS. 3 and 4 based on the input information. First, the lock-up control of FIG. 2 will be described.
_{Based on P} , the vehicle speed VSP, and the throttle opening TVO, a lock-up determination for determining whether the input / output element of the torque converter 1 is in an operation state in a lock-up region in which it should be directly connected or in a converter region in which it should not be directly connected Do. In step 62, it is checked whether or not the result of the determination is in the lock-up area. If the result is not the lock-up area but the converter area, the lock-up control signal _SL is not output in step 63, so that the torque converter 1 is operated. while the converter state by the lock-up flag fLAG _L to indicate that a relevant converter state to 0, if the lock-up region, by outputting the lock-up control signal S _L at step 64, a torque converter 1 while the lock-up state by the action, to 1 lockup flag fLAG _L to indicate that a the lockup state.

Next, the line pressure control shown in FIGS. 3 and 4 will be described.
_{The ATF} determines whether the line pressure P _L is to be increased to avoid a delay in the shift operation, that is, a low temperature lower than a set temperature (here, −10 °) or a normal temperature higher than the set temperature. If the temperature is not low, in step 72, the low temperature flag FLAG _{ATF is set} to 0 so as to indicate that the transmission working oil temperature T _ATF is normal temperature, and if the transmission operating oil temperature T _ATF is low, step 73
At low temperature flag FLAG
_{Set ATF} to 1.

In FIG. 4, the low-temperature flag FLAG
_ATF and lock-up flag FLAG _L in FIG.
Based on, it controls the line pressure P _L to as follows. First, at step 81, the lock-up flag FLAG _L
It is determined whether the torque converter 1 is currently in the lockup state or the converter state based on whether or not is 1. If the converter is in the converter state, it is determined in step 82 whether the transmission operating oil temperature T _ATF is in a normal temperature range equal to or higher than the set temperature (−10 °) or not, based on whether the low temperature flag FLAG _ATF is 0 or not. It is determined whether the temperature is in a low temperature range below.

In the normal temperature range, a low target line pressure _PLL for normal temperature corresponding to the throttle opening TVO is retrieved from the target line pressure map in FIG. 5 in a step 83, and in a low temperature range, the target in FIG. after searching high target line pressure P _LH of low-temperature corresponding to the throttle opening TVO from the line pressure map at step 85, the line pressure to the line pressure P _L to the high target line pressure P _LH of for the low temperature The control duty _DPL is obtained and output to the line pressure solenoid 45.

At step 82, it is determined that the temperature is within the normal temperature range.
83: Low target line pressure P for normal temperature _LLAfter searching for,
In step 86, the previous low temperature flag FLAG_ATFBut
Whether it was 1 or not, that is, from the low temperature range to the normal temperature range.
High target line pressure P for low temperature target line pressure_LHFrom room temperature
Target line pressure P for_LLThe instant t in FIG. 6 changed to ₁
Is determined. Target line due to the temperature rise
If the pressure has changed from high to low, go to step 87.
Line pressure P_LTo P as shown in FIG._LHFrom
ΔP_LLine pressure control on solenoid 45 so that it gradually decreases
Duty D_PLAnd in step 88,
This duty D_PLTo line pressure P_LBut low eyes for normal temperature
Standard line pressure P_LLStep 8 until it is determined that
7, the line pressure P_LIn FIG. 6 (b).
As shown by α, high target line pressure P for low temperature_LHFrom Δ
P_LGradually lower target line pressure for normal temperature
P_LLTo.

If it is determined in step 88 that the line pressure P _L has decreased to the low target line pressure P _LL for normal temperature,
In step 89, and outputs the line pressure control duty D _PL to maintain the line pressure P _L to the lower target line pressure P _LL of a the ambient temperature to the line pressure solenoid 45. In step 86, the previous low temperature flag FLAG _ATF
If There is determined that no one, that is, when determining that the previous was also normal temperature range advances the control skips step 87 and 88 to step 89, low target line pressure P of a cold line pressure P _L Maintain at _LL .

According to the above line pressure control, step 8
1 to 83, 86 to 88, the transmission hydraulic oil temperature rises from the low temperature range to the normal temperature range, and the low temperature flag FLAG _ATF
Changes from 1 to 0 in response to the line pressure P _L
Is reduced from the high target line pressure P _LH for low temperature to the low target line pressure P _LL for normal temperature.
If There is converter state, since the time rate of change of the line pressure P _L and to reduce as indicated with α in FIG. 6 (b), to the original pressure of the line pressure P _L, decreases with this The time change rate of the torque converter operating pressure P _TC (see FIG. 1) also becomes gradual, and in the converter state, the pressure in the release chamber 1e to which the torque converter operating pressure P _TC is supplied suddenly drops, and the apply chamber 1f It can be prevented that the pressure difference with the pressure in the inside suddenly increases, and therefore, the lock-up clutch 1d is temporarily engaged. Therefore, the torque converter is momentarily locked up in spite of being in the converter region at the moment when the line pressure starts to drop due to the transition from the low temperature region to the normal temperature region, giving a shock or an uncomfortable feeling to the occupant. Generation can be prevented.

[0045] In the above it was decided to reduce the time rate of change of the line pressure P _L as indicated with α in Fig. 6 (b), but of course, directly a time rate of change of torque converter operation pressure P _TC Needless to say, the intended purpose can be achieved by lowering in a similar manner. However, it to reduce the time rate of change of the line pressure P _L, the line pressure control of the content can achieve the purpose only to sign above, thus changing the hydraulic circuit itself is advantageously not require any is there.

The line pressure control when the torque converter 1 is in the converter state is described above.
In 1, when the torque converter 1 from the lock-up flag FLAG _L is determined to be a lock-up state, the line pressure control in the following manner. That is, in step 90, depending on whether or not the low-temperature flag FLAG _ATF is 0, the transmission operating oil temperature T _ATF is in a normal temperature range equal to or higher than the set temperature (−10 °) or in a low temperature range lower than the set temperature (−10 °). It is determined whether there is.

In the normal temperature range, at step 91, the target curve
Normal temperature corresponding to the throttle opening TVO from the in-pressure map
Target line pressure P for_LLAnd then step 8
At 9, the line pressure P_LIs the target line pressure P_LLNasu
Line pressure control duty D _PLIs output to the solenoid 45
And line pressure P_LThe target line pressure P for room temperature
_LLLine pressure control is performed. Low temperature in step 90
If it is determined that the area is the area, at step 84
Added throttle opening TVO from standard line pressure map
High target line pressure P for low temperature_LHSearch, then step
In step 85, the line pressure P_LThe low temperature for high goals
Line pressure P_LHPressure control duty D to make_PL
Is output to the line pressure solenoid 45, and the line pressure P_LOne
High target line pressure P for low temperature_LHLine pressure control
I do.

[0048] Such According line pressure control in the lockup state, ambient temperature and line pressure P _L in response from the low-temperature high target line pressure P _LH for transmission hydraulic oil temperature rises to normal temperature range from low temperature range instant t ₁ and雖of Figure 6 to lower the lower target line pressure P _LL of use also, the line pressure P _L becomes possible to reduce at once as shown by β in FIG. (c), the present invention is to solve the problem In other words, the lockup of the torque converter does not cause a problem that the torque converter is momentarily locked up even though the converter is in the converter range immediately when the line pressure starts to drop due to the transition from the low temperature range to the normal temperature range. In this state, it is possible to prevent unnecessary reduction control of the line pressure time change ratio, and at the same time, it is possible to expect the following effects.

[0049] That is, by prohibiting Such decrease control time rate of change of the waste line pressure in the lock-up state, the target after quickly changed as indicated the line pressure P _L in β in FIG. 6 (c) The line pressure can be reduced to _PLL ,
The probability of a shift occurring during the transition period of the line pressure change can be kept small, and the adverse effect on the shift shock which is particularly conspicuous due to the lock-up state can be reliably avoided.
Considering that the fact that the line pressure P _L is changed at a very low temperature (−10 ° C. in the above case) in accordance with the transition from the low temperature range to the normal temperature range, it is necessary to temporarily change the line pressure P _L to prevent a shock during shifting. Even if it is something that unlocks the lock-up,
Because of the high viscosity of the hydraulic oil, it is inevitable that the lock-up release delay occurs, and the shift may be performed in the lock-up state. Therefore, as described above, the target line pressure P _LL immediately after the line pressure is changed is changed. The significance of being able to reduce to is significant.

In any case, according to this embodiment, as shown in FIGS. 6 (b) and 6 (c), the line pressure changes in response to the shift of the transmission operating oil temperature from the normal temperature range to the low temperature range. P
The _L in the instant t ₂ to increase the low-temperature high target line pressure P _LH from a low target line pressure P _LL of a normal temperature, since it does not perform the reduction control of the time rate of change of the line pressure, increase in the line pressure Is quickly completed, and the sudden change in the torque converter operating pressure _PTC causes the lock-up clutch 1d
Is also suddenly changes the differential pressure, this sudden change, because those which pressure increase the release chamber 1e in the converter state, it is possible to bias the lockup clutch 1d in release direction, the torque converter is instantaneously t ₂ There is no problem of being locked up.

Rather, the target line pressure P for normal temperature of the line pressure
By quickly completing the increase from _LL to the low-temperature target line pressure P _LH , it is possible to eliminate the adverse effect on the shift shock for the following reasons. In other words, the automatic transmission is designed by determining the shift timing and the like so that the shift shock is most effectively reduced by using the target line pressure for normal temperature P _LL and the target line pressure for low temperature P _LH . If a shift is performed during a change transition period that is a value between the target line pressure and the low-temperature target line pressure, the shift shock cannot be reduced as designed. In this regard, in the present embodiment, as described above, in which the line pressure is promptly increased from the room temperature target line pressure to the low temperature target line pressure,
Since the change time of the line pressure is short, the probability that the shift is performed during the transition period of the change of the line pressure can be kept low,
It is possible to avoid an adverse effect on the shift shock.

[0052] Incidentally, as shown in FIG. 6 (d), depending on the shift mode detected by the range sensor 56 in FIG. 1, the lowering degree of the time rate of change of the line pressure P _L at the instant t ₁ in FIG. 6, the automatic transmission In the (D) mode, the same as the above α,
In the manual transmission (M) mode of the automatic transmission, it is preferable to make it larger than in the automatic transmission (D) mode as shown by γ. In this case, the manual shift (M) mode, the problem solving relates to malfunction of a lock-up in reducing instant t ₁ of line pressure in response to transition from a low temperature range to ordinary temperature range, the decrease transition of the line pressure It can be prioritized over keeping it shorter to reduce the probability of shifting during this period, and the following operational effects can be obtained. That is, manual shifting (M)
In the mode, the driver expects a shift shock because the shift is based on the driver's intention, and the shift is likely to occur during the long transition period of the line pressure drop and the shift is likely to occur during this period. Even if a shock occurs, it does not make you feel uncomfortable, but lock-up due to malfunction is uncomfortable because the driver does not expect this. By the way, in the embodiment shown in FIG. 6 (d), in the manual shift (M) mode, priority is given to solving the problem relating to the malfunction of lock-up when the line pressure decreases in response to the shift from the low temperature range to the normal temperature range. With this configuration, it is possible to surely eliminate the discomfort of the latter.

As shown in FIG. 6E, FIG.
In the reduction control α of time rate of change of the line pressure P _L at the instant t ₁ corresponding to the shift mode, gamma, respectively, and to execute only the converter state in view of the aforementioned facts ranging purposes, the lockup state β as shown, so as not to perform reduction control time rate of change of the line pressure P _L, it can be made to effects of the above can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing a lockup control device of a torque converter according to an embodiment of the present invention, together with a line pressure control system of an automatic transmission.

FIG. 2 is a flowchart showing a lockup control program executed by a controller in the embodiment.

FIG. 3 is a flowchart showing a program for determining whether the operating oil temperature of the automatic transmission is in a low temperature range below a set temperature or in a normal temperature range above a set temperature.

FIG. 4 is a flowchart showing a line pressure control program executed by a controller in the embodiment.

FIG. 5 is a change characteristic diagram of a target line pressure targeted in the line pressure control.

FIG. 6 is a line pressure change time chart when the line pressure is changed from a high target line pressure for low temperature to a low target line pressure for normal temperature, and then changed in the opposite direction.
Low temperature flag F indicating whether the transmission operating oil temperature is in a low-tone range or a normal-temperature range
5B shows a change in LAG _ATF , and FIG.
(C) illustrates a second line pressure control mode according to the present invention, (d) illustrates a third line pressure control mode according to the present invention, and (e) illustrates a line pressure control mode according to the present invention. 9 shows a fourth line pressure control mode according to the present invention, and FIG. 9 (f) shows a conventional line pressure control example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Torque converter 1a Pump impeller (torque converter input element) 1b Turbine runner (torque converter output element) 1c Stator 1d Lock-up clutch 1e Release chamber 1f Apply chamber 10 Lock-up control valve 11 Plug 12 Spool 23 Oil pump 24 Line pressure circuit 31 Torque converter regulator valve 32 Torque converter operating pressure circuit 33 Orifice 41 Pilot valve 42 Pilot pressure circuit 43 Lock-up solenoid 44 Lock-up control pressure circuit 45 Line pressure solenoid 46 Line pressure control pressure circuit 51 Controller 52 Transmission oil temperature sensor 53 Transmission Step sensor 54 Vehicle speed sensor 55 Throttle opening sensor 56 Range sensor

Claims (3)

(57) [Claims] When the hydraulic oil temperature of the automatic transmission is lower than a set temperature, the line pressure is set to a high low-temperature target line pressure, and when the operating oil temperature is equal to or higher than the set temperature, the line pressure is set to a low normal-temperature target line pressure. By switching the supply direction of the torque converter operating pressure, the torque capable of switching the transmission state between a lockup state in which the torque converter input / output elements are directly connected and a converter state in which the direct connection is released. In the converter, the time change rate of the torque converter operating pressure due to the change from the high line pressure low-temperature target line pressure to the low line pressure target line pressure for normal temperature decreases when the torque converter is in the converter state. The torque converter operating pressure is prevented from decreasing over time when the torque converter is in a lock-up state. Torque converter lock-up control device, characterized in that the. 2. The time change of the torque converter operating pressure according to claim 1, wherein a time change ratio from the high-temperature target line pressure having a high line pressure to the low-temperature target line pressure having a low line pressure is reduced. A lock-up control device for a torque converter, characterized in that the ratio is reduced. 3. The lock-up control device for a torque converter according to claim 2, wherein the degree of decrease in the time change rate of the line pressure is greater in a manual shift mode of the automatic transmission than in an automatic shift mode.