JP2002349693A - Torque converter lock-up controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate such a strange feeling that engine revolution lowers despite the acceleration, which the operator feels when a torque converter is relocked up, after it is released during transmission downshift by acceleration. SOLUTION: The lock-up controller lowers a lock-up clutch throw-in pressure (PA-PR) to an initial pressure P1 all at once, by a lock-up clutch release command issued at t1 following acceleration, then gradually lowers it at a previous low speed ΔP1 and further quickly lowers it at a late low speed ΔP2 to make the torque converter slip. After t4, when engine revolutions Ne is increased to a set value (Nt*-α) which is smaller by an allowance αthan the transmission input revolutions Nt*, corresponding to a transmission ratio after the speed change, the lock-up controller controls clutch throw-in pressure (PA-PR), so that Ne is equal to N*; and at t5, when transmission downshift ends and its input revolutions match its revolutions Nt* corresponding to the transmission ratio, after the speed change, the clutch throw-in pressure (PA-PR) is maximized, to complete torque converter relock-up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention appropriately controls a lock-up capacity between input and output elements of a torque converter used in an automatic transmission including a continuously variable transmission at the time of a downshift caused by depression of an accelerator pedal. The present invention relates to a device for performing

[0002]

2. Description of the Related Art Since a torque converter transmits power between input and output elements through a fluid, it performs a torque fluctuation absorbing function and a torque increasing function, but has poor transmission efficiency. For this reason, lock-up type torque converters in which the input / output elements of the torque converter are directly connected by a lock-up clutch are often used today under running conditions that do not require the torque fluctuation absorbing function or the torque increasing function. .

[0003] When driving in a lock-up state by directly depressing an accelerator pedal during driving in a lock-up state in which the input / output elements of the torque converter are directly connected or in driving in a converter area where lock-up should not be performed, When the torque converter is required to increase the torque by depressing the accelerator pedal and the torque converter is kept in the lock-up state, as shown in FIG. 12A, the engine speed Ne is maintained even after the instant t1 when the accelerator pedal is depressed.
(Torque converter input rotation speed) and turbine rotation speed Nt (torque converter output rotation speed) are always the same and the torque converter does not have a torque fluctuation absorbing function or a torque increasing function. The sudden increase in the torsional vibration of the drive system cannot be absorbed and the rattling vibration is generated or the torque is increased as is apparent from the transmission output torque (To) waveform indicated by A in FIG. The lack of torque gives the driver a feeling of lack of torque, so that drivability is impaired.

[0004] This tendency occurs when the driver depresses the accelerator pedal to accelerate after coasting in the lock-up state, or when the accelerator pedal is depressed from the steady running in the lock-up state. This is particularly noticeable when the accelerator pedal is depressed from a state where the torque is relatively small.

Therefore, conventionally, for example, Japanese Unexamined Patent Publication No.
As described in Japanese Unexamined Patent Publication No. 8 (1994) -108, when the accelerator pedal is depressed during traveling in the lock-up state as described above, or when the torque converter is locked up by depressing the accelerator pedal, the accelerator As shown in FIG. 12B, a technique has been proposed for temporarily releasing the lock-up of the torque converter after the instant t1 as shown in FIG. 12B during the downshift accompanying the depression of the pedal. According to this, the engine speed Ne (torque converter input speed) increases after the instant t1 and the turbine speed Nt (torque converter output speed).
And the torque converter has a torque fluctuation absorbing function and a torque increasing function, so that the above-mentioned jerky vibration can be suppressed as clearly seen from the waveform of the transmission output torque To, and the torque increasing function can provide a sense of torque shortage. Can be eliminated.

[0006]

In this case, however, the engine speed is increased as described above due to the re-lock-up that ends the temporary release of the lock-up after the step-down shift and starts at the instant t2 in FIG. Ne is reduced again as shown in FIG. 4B to reach the turbine rotational speed Nt, giving the driver an uncomfortable feeling that the engine rotational speed Ne temporarily decreases even during acceleration due to depression of the accelerator pedal. The problem arises.

On the other hand, if the relock-up start instant t2 is advanced as shown in FIG. 12C in order to prevent the above-mentioned increase in the engine speed and the subsequent decrease, the next time in the second half of the downshift, Since both the transmission input rotation system (in the case of a V-belt type continuously variable transmission, a primary pulley having a large rotation inertia) and the engine are increased in rotational speed, the inertia of the portion where the rotational speed is changed by the shift is large. As a result, the pulling torque due to the inertia torque is generated as is apparent from the transmission output torque (To) waveform at C in FIG. 7, and the shock increases and the feeling of acceleration deteriorates.

According to the first aspect of the present invention, as long as the lock-up is completely released at the time of the step-down shift as described above, the above problem can be avoided regardless of how the subsequent re-lock-up timing is operated. In view of the fact that the torque converter cannot rotate, the lockup capacity is controlled so that the torque converter input rotation speed (engine rotation speed) does not cause the above-described blow-up, and the torque converter is slipped. It is an object of the present invention to propose a lock-up control device for a torque converter which can suppress the jerky vibration and eliminate the torque shortage at the time of a step-down shift without causing such a problem.

According to a second aspect of the present invention, the engine speed is quickly increased at the time of the above-mentioned depression downshift, whereby the acceleration responsiveness required by the depression of the accelerator pedal is reliably realized. An object of the present invention is to propose a lockup control device for a torque converter that is obtained.

According to a third aspect of the present invention, there is provided a continuously variable type of continuously variable target gear ratio for controlling a shift response to an ultimate gear ratio to be finally set in accordance with an operation state. It is an object of the present invention to propose a lock-up control device for a torque converter that can surely exhibit the same operation and effect as the first and second inventions in a transmission.

[0011]

To achieve these objects, a first aspect of the present invention is to provide a lock-up control device for a torque converter. The lock-up control device for a torque converter according to the first aspect of the present invention includes a step-up stage of the automatic transmission during a depression downshift of the automatic transmission accompanying depression of an accelerator pedal. In a torque converter in which the lock-up capacity between the torque converter input / output elements is reduced even in the lock-up region in which the input / output elements of the torque converter should be directly connected to the lock-up state, the torque converter is set to the slip state. The lock-up capacity is controlled so that a converter input rotation speed becomes a transmission input rotation speed corresponding to a post-shift gear ratio of the automatic transmission to generate a slip state of the torque converter. It is.

According to a second aspect of the present invention, in the first aspect of the present invention, when the accelerator pedal is already in a lock-up region when the accelerator pedal is depressed, the lock-up capacity is controlled by the feed-forward control of the torque converter. The number is reduced so as to increase with a predetermined response to near the transmission input speed corresponding to the post-shift gear ratio, and after the decrease, the lock-up capacity is feedback-controlled to reduce the torque converter input speed to the post-shift gear ratio. The transmission input rotation speed is determined so as to correspond to the above.

A third aspect of the present invention is a lock-up control device for a torque converter, wherein the automatic transmission is shifted from moment to moment with a predetermined shift response to a final target gear ratio to be a final target according to an operating condition. 3. The torque converter lock-up control device according to claim 1, wherein the target speed ratio is determined, and the speed is controlled to be the transient target speed ratio. And a transmission input rotation speed corresponding to the attained transmission ratio.

[0014]

The lock-up control device of the torque converter according to the first invention reduces the lock-up capacity between the input and output elements of the torque converter even in the lock-up region during the depression downshift of the automatic transmission accompanying the depression of the accelerator pedal. By causing the torque converter to slip, the torque converter absorbs torque fluctuations and increases torque, which prevents torsional vibration of the drive system due to increased torque when the accelerator pedal is depressed, and reduces the sense of torque shortage. Therefore, drivability can be ensured.

According to the first aspect of the present invention, when the lock-up capacity for generating the slip state of the torque converter is reduced, the input speed of the torque converter corresponds to the post-shift gear ratio of the automatic transmission. Control the lock-up capacity so that
The torque converter input speed does not increase beyond the transmission input speed corresponding to the gear ratio after shifting, and the temporary slip state of the torque converter is terminated and re-locked to perform the torque converter input speed. When the number matches the output speed of the torque converter (input speed of the transmission), the input speed of the torque converter hardly decreases. Therefore, it is possible to solve the above-mentioned uncomfortable feeling that the input speed of the torque converter (the engine speed) is reduced even during acceleration due to depression of the accelerator pedal.

For the same reason, before the downshift is completed, the input speed of the torque converter together with the output speed of the torque converter (the input speed of the transmission) and the input speed of the transmission corresponding to the gear ratio after shifting are changed. And the shift response can be improved.

For the same reason, in the first half of the downshift, the input speed of the torque converter (engine speed)
Has increased to the transmission input speed corresponding to the post-gear transmission ratio, and during the latter half of the downshift, the torque converter input rotation speed (engine speed) has a substantially constant transmission input corresponding to the post-gear transmission ratio. The rotation speed is maintained, and the inertia of the portion where the rotation changes with the shift is reduced, and the retraction shock due to the inertia torque can be reduced, thereby generating the feeling of acceleration as required by depressing the accelerator pedal. be able to.

In the second invention, when the accelerator pedal is already in the lock-up area when the accelerator pedal is depressed, the lock-up capacity is controlled by feedforward control so that the input speed of the torque converter corresponds to the speed ratio after the shift. After the torque converter input rotation speed is increased, the lock-up capacity is reduced to a transmission input rotation speed corresponding to the post-shift gear ratio by feedback control after the torque converter input rotation speed is increased. Decided to be. Therefore, according to the second aspect of the present invention, the input speed of the torque converter (engine speed) at the time of the step-down shift is quickly increased, whereby the speed change response can be enhanced, and the response of the acceleration requested by the stepping down of the accelerator pedal can be achieved. Characteristics can be reliably realized.

According to the third aspect of the invention, the automatic transmission is a continuously variable transmission, and particularly, an instantaneous transient such that the speed is shifted with a predetermined shift response to a final target gear ratio to be a final target according to an operating state. In the case of a continuously variable transmission in which the target gear ratio is determined and the speed is controlled so as to be the transient target gear ratio, the transmission input speed corresponding to the post-gear gear ratio is changed to the transmission input speed corresponding to the above-mentioned ultimate gear ratio. Because it was configured to determine the rotation speed,
Even in a continuously variable transmission of a type in which the target gear ratio continuously changes in order to control the gear shift response to the ultimate gear ratio to be finally targeted according to the operating state, the first invention and the second invention are surely achieved. The same operation and effect as described above can be achieved.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a vehicle power train provided with a torque converter lock-up control device according to an embodiment of the present invention. The power train includes an engine 1, a torque converter 2, and a continuously variable transmission 3.
And The continuously variable transmission 3 receives rotation from the engine 1 via the torque converter 2, changes the input rotation according to the speed ratio, and outputs the speed to wheels (not shown).

The continuously variable transmission 3 is a V-belt type continuously variable transmission described in "Introduction of New Model Nissan March K11 Type Vehicle" issued by Nissan Motor Co., Ltd. in January 1992. Similarly, it is assumed that the speed is controlled so as to achieve the corresponding speed ratio in response to the speed ratio command input to the step motor 5 provided in the control valve body 4. However, in the present embodiment, the gear ratio command is determined by the controller 12 as follows.

Therefore, the controller 12 and the lock-up control of the torque converter 2 which will be described later also have a throttle opening TV representing the required load of the engine.
A signal from the throttle opening sensor 21 for detecting O,
A signal from an engine speed sensor 22 for detecting an engine speed Ne (torque converter input speed), and a turbine runner speed Nt (torque converter output speed).
And a signal from a vehicle speed sensor 24 for detecting the vehicle speed VSP.

The controller 12 retrieves a target input rotation speed (target turbine rotation speed) Nt ^* of the transmission from the throttle opening TVO and the vehicle speed VSP based on the shift map illustrated in FIG. This is the vehicle speed VSP
By dividing by the transmission output rotation speed that is known from the above, the ultimate target gear ratio to be finally obtained is obtained. Then, the controller 12 determines the continuously variable transmission 3 based on the attained speed ratio and the actual speed ratio.
A continuously variable target gear ratio is determined such that the gear is shifted to the attained gear ratio with a predetermined gear response, and this transient target gear ratio is supplied to the step motor 5 as the above gear ratio command, whereby the continuously variable transmission 3 is gear-change-controlled so that the transient target gear ratio is obtained.

Although the torque converter 2 is also well known, its detailed illustration is omitted, but it is connected to a pump impeller as a torque converter input element which is connected to an engine crankshaft and driven by the engine, and to an input shaft of the continuously variable transmission 3. And a lock-up type torque converter having a lock-up clutch 2c for directly connecting between the pump impeller and the turbine runner as schematically shown in FIG.

As shown in FIG. 3, the lock-up clutch 2
fastening force of c is determined by the differential pressure of the apply pressure P _A and the release pressure P _R at the front and rear (lockup clutch engagement pressure), if the apply pressure P _A is lower than the release pressure P _R, the lock-up clutch 2c is When released, the pump impeller and the turbine runner are not connected to each other, and the torque converter 2 functions in a converter state without slip limitation. During this time, the output torque (turbine torque) of the torque converter is determined only by the product of the converter torque due to the fluid transmission and the torque amplification factor t shown in FIG.

The apply pressure when P _A is higher than the release pressure P _R, the lock-up clutch 2 with a force corresponding to the pressure difference
c, the torque converter 2 locks the lock-up capacity (torque) according to the fastening force of the lock-up clutch 2c.
And converter torque and torque amplification factor t shown in FIG.
This function operates in a slip control state in which a torque represented by the sum of the product of the two is output. 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. During this time, the torque converter output torque (turbine torque) is determined only by the lockup capacity (torque) corresponding to the engagement force of the lockup clutch 2c.

Apply pressure P_AAnd release pressure P_RIs
Provided in the control valve body 4 in FIG.
These are determined by the slip control valve 11 shown in FIG.
The slip control valve 11 is the same as that shown in FIG.
Lock controlled by duty controller 12
Up solenoid 13 (control as shown in FIG. 1)
Signal pressure P from the valve body 4)_SAccording to
Apply pressure P_AAnd release pressure P_RControl the
The slip control valve 11 and the lock-up solenoid
The node 13 is a known one described below. That is, first
The lock-up solenoid 13 has a constant pilot pressure P_P
Is driven by the solenoid from the controller 12
As the duty D increases, the signal pressure P _STo increase
I do.

[0028] While the slip control valve 11 in, along with receiving the above signal pressure P _S and the fed-back release pressure P _R in one direction, receives the apply pressure P _A that is the spring force and the feedback of the spring 11a in the other direction , with increasing signal pressure _{P S,} the apply pressure _{P a} and the release pressure _{P R}
It is assumed that the engagement pressure of the lock-up clutch 2c represented by the differential pressure (P _A -P _R ) is changed as shown in FIG.

[0029] Here, the lock-up clutch engagement pressure _{(P A}
−P _R ) is a negative value of P _R > P _A due to torque converter 2
To the converter state. Conversely, when the lock-up clutch engagement pressure (P _A -P _R ) is positive,
As the value increases, the lock-up clutch 2c
Is increased, which means that the slip rotation of the torque converter 2 is greatly limited, and finally the torque converter 2 is brought into the lockup state.

The controller 12 first determines, from the input information, whether the vehicle is operating in the lock-up region or the converter region based on the throttle opening TVO and the vehicle speed VSP. The torque converter 2 is brought into a lockup state or a converter state by fastening or releasing 2c. On the other hand, during traveling in the lock-up state or during traveling in which the lock-up is performed by entering the lock-up area from the converter area by depressing the accelerator pedal, the controller 12 executes the control program shown in FIG. Then, the lock-up control targeted by the present invention is performed as follows.

First, in step S31, if there is a torque increase request due to the depression of the accelerator pedal, and if the lock-up state is maintained, the drive system twists due to a sudden increase in the engine torque during the depression downshift accompanying the torque increase request. From the occurrence of vibration or the feeling of insufficient torque, a determination is made as to whether or not the operating state has been entered in which lockup should be temporarily released. As the lock-up release condition at the time of the torque increase request, for example, the throttle opening TVO is equal to or larger than the set opening TVOs, and the increase amount ΔTVO of the throttle opening TVO during the calculation cycle of the present control program (throttle opening increasing speed) : Accelerator pedal depression speed) becomes equal to or higher than a predetermined speed ΔTVOs.

If the lock-up release condition at the step-down shift is not satisfied, the control is terminated as it is. If the lock-up release condition at the step-down shift is satisfied, at step S32, the lock-up clutch engagement pressure at the time of lock-up release is determined. The initial pressure (lock-up release initial pressure) P1 of (P _A -P _R ) is obtained from the throttle opening TVO immediately before the step-up downshift lock-up release condition is established (when a torque increase is requested) based on the map of FIG. Based on the map of FIG. 7, the lock-up clutch engagement pressure reduction speeds ΔP1 and ΔP2 (lock-up release speeds) in the first and second periods are determined based on the step-down downshift lock-up release condition (when torque increase is required).
, And the lock-up release speed switching determination speed ratio e 'is further determined based on the map of FIG. 9 based on the map shown in FIG. Obtain from TVO.

The lockup release initial pressure P1 shown in FIG.
Is the engagement pressure of the lock-up clutch, which is just before the lock-up clutch 2c does not slip, and the throttle opening TVO (engine required load) immediately before the depressed downshift lock-up release condition is established (when a torque increase is required). The smaller the lock-up clutch engagement pressure is, the lower the lock-up clutch engagement pressure is. As shown in FIG. 6, the lock-up release initial pressure P1 is the throttle opening TVO () immediately before the step-down downshift lock-up release condition is established (when a torque increase is required). The lower the required engine load), the lower the value.

The lock-up clutch engagement pressure drop speeds ΔP1 and ΔP2 (lock-up release speeds) shown in FIG. 7 are the lock-up clutch engagement pressure decrease speeds at which the shock at the time of lock-up release does not become a problem. The smaller the throttle opening TVO (engine required load) immediately before the step-up downshift lock-up release condition is established (when a torque increase is required), the smaller the shock at lock-up release and the quicker lock-up release is possible. From the lock-up clutch engagement pressure drop rates ΔP1 and ΔP2
As shown in FIG. 7, the lock-up release speed increases as the throttle opening TVO (engine required load) immediately before the step-down shift shift lock-up release condition is established (when a torque increase is requested) is smaller.

Here, the lock-up clutch engagement pressure reduction speed ΔP1 in the first half is made slower than the lock-up clutch engagement pressure reduction speed ΔP2 in the second half, thereby preventing a shock at the start of slipping of the lock-up clutch 2c in the first half. However, in the latter period, the deterioration of the acceleration response due to the response delay of the lock-up release is prevented.

The lock-up clutch engagement pressure drop speeds ΔP1 and ΔP2 (lock-up release speeds) in the first and second periods are not given as maps in advance as shown in FIG. When the lock-up release condition is satisfied during a shift (when a torque increase is requested)
The basic deceleration speeds ΔP1 ′ and ΔP2 ′ for each throttle opening TVO (engine required load) immediately before the throttle opening TVO (eg, the accelerator pedal depressing speed ΔTVO as shown in FIG. 8)
It can also be obtained by multiplying the stepping speed coefficient K for each.

The lock-up release speed switching determination speed ratio e ′ shown in FIG. 9 is changed from the lock-up clutch engagement pressure decrease speed ΔP1 in the first half to the lock-up clutch engagement pressure decrease speed ΔP2 in the second half, and the lock-up release speed is changed. A speed ratio that generates a predetermined converter torque to be increased is set as a speed ratio. The smaller the throttle opening TVO (engine required load) immediately before the depressed downshift lock-up release condition is established (when a torque increase is required), the smaller the lock-up clutch 2c is Since the shock at the time of slip is small and the lock-up release speed can be quickly increased, the lock-up release speed switchover determination speed ratio e 'is set as shown in FIG. Throttle opening just before (when torque increase is requested) As VO (required engine load) is small to large.

FIG. In the next step S33 of 5, the lock-up clutch engagement pressure _(P A -P _R) is the lockup release initial pressure P1 to become as lockup solenoid 1
3 is determined and output. Next, in step S34, whether the torque converter speed ratio e has become less than the lock-up release speed switching determination speed ratio e 'or not has determined whether or not the predetermined converter torque has been generated, that is, the lock-up clutch 2c. It is determined whether it is no longer necessary to consider the shock caused by the slip and the lock-up release speed can be increased to ensure responsiveness.

Until the torque converter speed ratio e becomes less than the lock-up release speed switching determination speed ratio e ', the lock-up clutch engagement pressure (P
_A- P _R ) is reduced by the feed-forward control so that the lock-up solenoid 13 decreases at the slow speed ΔP1 in the previous period.
The drive duty D of the lock-up clutch 2c is output by gradually decreasing the drive duty D of the lock-up clutch 2c. If it is determined in step S34 that the torque converter speed ratio e has become less than the lock-up release speed switching determination speed ratio e ', the engine speed Ne is determined in step S36.
Until it is determined that the (torque converter input rotation speed) has increased to a set value (Nt ^* −α) lower than the transmission input rotation speed Nt ^* corresponding to the attained gear ratio (gear ratio after shifting) by a margin α. During this period, in step S37, the lock-up clutch engagement pressure (P _A -P _R ) increases the late high speed ΔP2
The drive duty D of the lock-up solenoid 13 is gradually reduced and output by feedforward control so as to decrease.

In step S36, the engine speed N
e (torque converter input speed) is equal to the set value (Nt ^* -
When it is determined that it has increased to α), this time, step S38
It is determined whether or not the shift has been completed based on whether or not the turbine speed Nt (transmission input speed) matches the transmission input speed Nt ^* corresponding to the attained speed ratio (speed ratio after shift). Until the shift is completed, in step S39, the lock-up solenoid 13 is adjusted so that the engine speed Ne (the input speed of the torque converter) becomes the transmission input speed Nt ^* corresponding to the attained speed ratio (the speed ratio after the speed change).
Is feedback-controlled.

When it is determined in step S38 that the shift has been completed, the drive duty D of the lock-up solenoid 13 is set to the maximum value in step S40, thereby completing the re-lock-up of the torque converter.

The operation of the lock-up control device according to the above embodiment will be described with reference to a time chart shown in FIG. FIG. 11 shows an engine rotation when a torque increase request is made by depressing an accelerator pedal that increases the throttle opening TVO from 0 at an instant t1, and in response to this, a downshift and a lock-up release command are issued. the number Ne (torque converter input rotational speed), turbine speed Nt (torque converter output speed: transmission input revolution speed), transmission output shaft torque to, and when the lock-up clutch engagement pressure (P a _{-P R)} Indicates a series change.

The lock-up clutch engagement pressure (P
_A- P _R ) to the lock-up release initial pressure P1 as shown in the figure.
The lock-up clutch engagement capacity (lock-up capacity) does not immediately become zero due to the setting of the initial pressure P1, but the lock-up clutch 2c
Maintain the fastening state. Thereafter, the lock-up clutch engagement pressure (P _A -P _R ) is gradually reduced by the feed-forward control at the previous reduction rate ΔP1. During this time, instant t
2, the lock-up clutch 2c starts to slip, and the engine speed Ne can be increased as shown in the figure. After the instant t2, the engine speed Ne (torque converter input speed) and the turbine speed Nt (torque converter output speed) are increased. 10), the torque converter speed ratio e becomes smaller than the coupling point CP on the torque converter performance diagram of FIG. 10 and becomes apparent from the increase of the torque amplification factor t in FIG. A converter torque is generated.

[0044] Then, the converter torque is time t3 thereafter determines the torque converter speed ratio e <e 'from reaches a predetermined value, the lock-up clutch engagement pressure by the feed forward control (P A _{-P R)} and late The engine speed Ne (torque converter input rotation speed) reaches the gear shift from the instant t4 when the engine rotation speed Ne (torque converter input rotation speed) increases to the set value (Nt ^* -α) immediately after the reduction speed ΔP2. Feedback control is performed such that the transmission input rotation speed Nt ^* corresponding to the ratio (speed ratio after shifting) is obtained. After that, re-lockup of the torque converter is completed at the shift end instant t5 when the turbine speed Nt (transmission input speed) matches the transmission input speed Nt ^* corresponding to the attained speed ratio (speed change ratio after shifting), The engine speed Ne and the turbine speed Nt are completely matched.

According to the present embodiment, the instant t4
The lock-up clutch engagement pressure in up to (P _A -
P _R) above the feed following effects by forward control is obtained exerts the obtained exerts operational effects described below by feedback control described above of the lock-up clutch engagement pressure at the instant t4 after (P A _{-P R).}

First, the operation and effect of the former feedforward control will be described. First, during the depression downshift of the automatic transmission accompanying the depression of the accelerator pedal (instantaneous t1),
The lock-up clutch engagement pressure (P
_A- P _R ) is further reduced from the initial pressure P1, that is, the lock-up capacity is reduced to bring the torque converter into a slip state, thereby causing a torque fluctuation absorbing function and a torque increasing function of the torque converter. To prevent the torsional (jerky) vibration of the drive system due to an increase in the torque when the pedal is depressed, as is apparent from the output torque (To) waveform in the portion D in FIG. 11, and to ensure the drivability by eliminating the feeling of insufficient torque. Can be.

During this time, a predetermined converter torque T
_CV lockup clutch engagement pressure to time t3 to generate a (P A _{-P R)} not to 0 lockup clutch engagement capacity (lockup capacity) smaller predetermined value than the maximum value (initial pressure P1 equivalent value) If the lock-up clutch engagement pressure (P _A -P _R ) is reduced thereafter, that is, the lock-up clutch engagement capacity (lock-up capacity) is reduced, the engine speed Ne increases. At the instant t2 when the converter torque is generated, the lock-up clutch engagement capacity (lock-up capacity) still exists, and the product of the converter torque and the torque amplification factor t shown in FIG. The turbine torque, which is the sum of the capacities (lock-up capacities), becomes zero between the instants t1 and t2. There.

Accordingly, the torque converter operates at instants t1 to t2.
In this state, torque cannot be transmitted, and a large deceleration shock does not occur due to a sharp drop in the torque converter output torque when the lock-up is released by depressing the accelerator pedal.

Further, after the instant t3 at which the predetermined converter torque is generated, the lock-up clutch engagement pressure (P _A-
In order to speed up the reduction of P _R ), that is, the reduction of the lock-up clutch engagement capacity (lock-up capacity), the lock-up release can be realized in a predetermined time by recovering the lock-up release delay.

As shown in FIG. 9, the lock-up release speed switching determination speed ratio e 'for determining the timing of switching the lock-up release speed as described above is expressed as follows.
Since the throttle opening TVO (engine required load) is set to be larger as the throttle opening TVO (engine required load) immediately before the depressed downshift due to depression of the accelerator pedal is smaller, the engine required load immediately before the depressed downshift lockup release request is smaller. The lower the load required by the engine, the faster the lockup capacity is reduced.The lower the load required by the engine, the slower the release of lockup is. By avoiding this, the above-mentioned effects can be made more remarkable.

Further, the lock-up release initial pressure P1 is
As shown in the figure, since the setting is made smaller as the engine required load immediately before the depressed downshift lock-up release request is smaller, the lock-up clutch is not slipped as the engine required load immediately before the depressed downshift lock-up release request is smaller. This corresponds well to the fact that the lower limit engagement pressure is low, and the lock-up can be released more quickly as the engine required load is smaller, which also unnecessarily delays the lock-up release when the engine required load is small. And the above-mentioned effects can be made more remarkable.

In addition, as shown in FIG. 7 as the lock-up clutch engagement pressure reduction speeds ΔP1 and ΔP2, the reduction of the lock-up capacity at the time of releasing the lock-up is as follows.
As the engine request load immediately before the lock-up release request at the time of the step-down shift is configured to be performed at a higher speed, the shock at the time of lock-up release is smaller as the engine request load immediately before the lock-up release request at the time of the step-down shift is smaller. According to the fact, the lock-up release speed can be prevented from being unnecessarily reduced when the engine load is small, and the above-mentioned operation and effect can be made more remarkable.

Further, the lock-up capacity is reduced when the lock-up is released by adopting the coefficient K shown in FIG. 8 so that the higher the torque increase request, the higher the speed. Therefore, the torque increase request is high. At the time, that is, when the acceleration request by the driver is strong, the lock-up release due to the decrease in the lock-up capacity can be performed at a high speed, and the acceleration response as requested can be realized, and the above-described operation and effect can be further remarkable. obtain.

Next, to explain the function and effect of the feedback control after the instant t4 in FIG. 11, the lock-up clutch engagement pressure (P _A -P _R ) is reduced so that the torque converter is kept in the slip state at the time of the downshift. At this time, the lock-up clutch engagement pressure (P _A ) is set such that the engine speed Ne (torque converter input speed) becomes the transmission input speed Nt ^* corresponding to the attained speed ratio (speed change ratio after shifting) of the continuously variable transmission. −P _R ), as is apparent from the waveform of the engine speed Ne in the portion E in FIG. 11, the input speed of the torque converter corresponds to the attained speed ratio (speed ratio after shifting). The rotational speed does not increase beyond Nt ^* , and the torque converter temporarily slips at t5 at the end of the downshift. Is terminated and re-locked up, the torque converter input rotation speed hardly decreases when the torque converter input rotation speed matches the torque converter output rotation speed (transmission input rotation speed). Therefore,
It is possible to eliminate a sense of incongruity that the torque converter input rotation speed (engine rotation speed) is reduced even during acceleration due to depression of the accelerator pedal.

For the same reason, before the above-mentioned downshift is completed, the input speed of the torque converter and the output speed of the torque converter (transmission input speed) correspond to the ultimate speed ratio (speed ratio after shifting). Transmission input rotation speed N
t ^* , and the shift response can be improved.

Further, for the same reason, in the first half of the downshifting up to the instant t4, the torque converter input rotation speed (engine rotation speed) first increases to the transmission input rotation speed Nt ^* corresponding to the post-shift gear ratio. Thus, during the second half of the downshift after the instant t5, the input speed of the torque converter (engine speed) is maintained at a substantially constant transmission input speed corresponding to the gear ratio after the shift, and the rotational speed changes with the shift. The inertia of the portion where the acceleration occurs is reduced, and the retraction shock due to the inertia torque can be reduced, and the acceleration feeling required by depressing the accelerator pedal can be generated.

[0057] Although the case of FIG. 11 is the case, the case was already lockup area at the time t1 the accelerator pedal, the lock-up clutch engagement pressure (P _A -P _R)
By feedforward control, the engine speed Ne
(Torque converter input rotation speed) is decreased so as to increase with a predetermined response to near the transmission input rotation speed Nt ^* corresponding to the gear ratio after shifting, and after the torque converter input rotation speed increases, the lock-up clutch engagement pressure ( P _A −
P _R ), the input speed of the transmission is adjusted by the feedback control so that the input speed of the torque converter corresponds to the speed ratio after shifting.
Since it is determined to be t ^* , the input speed of the torque converter (the engine speed Ne) at the time of the step-down shift is quickly increased, whereby the speed change response can be enhanced, and the request by depressing the accelerator pedal can be obtained. Acceleration responsiveness can be reliably achieved. In this case, the input speed of the torque converter (the engine speed N
e) The pulling torque due to the inertia torque tends to increase due to the rapid rise of the torque. However, since the output torque increases due to the increase in the engine rotation, the pulling torque is offset by the torque. There is no such thing as

As in the illustrated embodiment,
An automatic transmission is a continuously variable transmission 3, and an instantaneous transient target gear ratio is determined such that the gear is shifted with a predetermined gear shift response to an ultimate gear ratio to be a final target, particularly according to an operating state;
In the case of a continuously variable transmission whose speed is controlled to be at the transient target gear ratio, the transmission input rotation speed Nt ^* corresponding to the post-gear transmission gear ratio is determined as the transmission input rotation speed corresponding to the attained gear ratio. I do. In this case, even in a continuously variable transmission of a type in which the target gear ratio continuously changes in order to control the gear shift response to the ultimate gear ratio to be finally targeted in accordance with the driving state, the above-described various types are surely ensured. The effect can be achieved as well.

In the above description, as shown in FIG. 11, the instant t when the lock-up release command is issued at the time of the step-down shift is issued.
The operation in the case where the lock-up region is already described in FIG. 1 has been described. However, when the torque converter is locked up by entering the lock-up region by depressing the accelerator pedal before the instant t1. Of course, the lock-up release control at the time of the step-down shift can be similarly applied.

In the above description, the control is performed while monitoring the engine speed Ne (the input speed of the torque converter). Since it can be regarded as constant, it is substantially equivalent to monitoring the gear ratio, and it goes without saying that control may be performed according to the gear ratio. Further, in the above description, the case where the continuously variable transmission 3 is used as the automatic transmission has been described. However, the same control can be performed when the automatic transmission is a stepped type, and the gear ratio corresponding to the gear after the shift is set. The transmission input rotation speed Nt ^* corresponding to the post-gear transmission ratio may be obtained from the post-gear transmission ratio and the vehicle speed VSP.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing a power train of a vehicle including a lock-up control device according to an embodiment of the present invention, together with a shift control system thereof.

FIG. 2 is a diagram showing a shift pattern of a continuously variable transmission forming the power train.

FIG. 3 is a schematic system diagram showing a lock-up control device according to the embodiment;

FIG. 4 is a diagram showing a relationship between a signal pressure output from a lock-up solenoid and a lock-up clutch engagement pressure in the embodiment.

FIG. 5 is a flowchart showing a lock-up control program at the time of a step-down shift executed by the controller in the embodiment.

FIG. 6 is a change characteristic diagram of a lock-up release initial pressure determined in the embodiment.

FIG. 7 is a change characteristic diagram of a lock-up clutch engagement pressure decreasing speed determined in the embodiment.

FIG. 8 is a change characteristic diagram of a depression speed coefficient for changing a lock-up clutch engagement pressure reduction speed to be determined in the same embodiment according to the depression speed of an accelerator pedal.

FIG. 9 is a change characteristic diagram of a lock-up release speed switching determination speed ratio determined in the embodiment.

FIG. 10 is a torque converter performance diagram showing the relationship between the speed ratio of the torque converter and the torque gain.

FIG. 11 is an operation time chart of lock-up control at the time of a depressed downshift according to the embodiment.

FIG. 12A is an operation time chart used to explain the problem of lock-up control at the time of a step-down shift, and FIG. 12B is an operation time chart when lock-up release is not performed at the time of a step-down shift. 7 is an operation time chart in the case of performing lock-up release at the time of step-down shift, and FIG. 7C is an operation time chart of the case where re-locking after releasing the lock-up at the time of step down shift is advanced.

[Explanation of symbols]

 Reference Signs List 1 engine 2 torque converter 2c lock-up clutch 3 stepless transmission (automatic transmission) 4 control valve body 5 stepping motor for shifting 11 slip control valve 12 controller 13 lock-up solenoid 21 throttle opening sensor 22 engine rotation sensor 23 turbine rotation Sensor 24 Vehicle speed sensor

Claims (3)

[Claims] 1. During a downshift of an automatic transmission caused by depression of an accelerator pedal, the torque converter is turned on even in a lock-up region in which the input and output elements of the torque converter in the preceding stage of the automatic transmission are to be in a lock-up state in which the input and output elements are directly connected. In a torque converter in which the lock-up capacity between output elements is reduced to put the torque converter in a slip state, the input speed of the torque converter is adjusted to the transmission input speed corresponding to the gear ratio after the shift of the automatic transmission. A lock-up control device for a torque converter, wherein the lock-up capacity is controlled to generate a slip state of the torque converter. 2. The system according to claim 1, wherein the lock-up capacity is controlled by feedforward control when the accelerator pedal is already in a lock-up area when the accelerator pedal is depressed.
The input speed of the torque converter is decreased so as to increase with a predetermined response to near the input speed of the transmission corresponding to the gear ratio after the shift, and after the decrease, the input speed of the torque converter is reduced by feedback control. A lock-up control device for a torque converter, wherein the lock-up control device is configured to determine a transmission input rotation speed corresponding to a gear ratio after a gear shift. 3. An instantaneous transient target gear ratio is determined such that the automatic transmission is shifted with a predetermined shift response to an ultimate gear ratio to be a final target according to an operating state. 3. The lockup control device for a torque converter according to claim 1, wherein the transmission is a stepless transmission that is controlled to have a transmission ratio corresponding to the attained transmission ratio. A lock-up control device for a torque converter, wherein the lock-up control device is configured to determine the transmission input rotation speed.