JPH07243526A - Lockup control device of torque converter - Google Patents

Abstract

PURPOSE:To reduce the lockup engaging shock and shorten the delay in lockup engagement by setting the initial value of the release pressure controlling target value for an electronic actuator while study control is performed in accordance with the engagement-associate conditions such as the apply pressure. CONSTITUTION:The release pressure Pr led from a lockup control valve 20 to a torque converter 14 is controlled by a lockup solenoid 24, and the engaging capacity of a lockup clutch is control led. A controller 30 executes the specified control program on the basis of the engine speed Ne, turbine revolving speed Nt, degree of throttle opening Two, oil temp. (t), and car speed Vsp which are given by sensors 31-36, determines the initial value of the release pressure controlling target value, and gives the duty ratio D to tame lockup solenoid 24 wherein D is obtained by correcting the duty ratio D1 determined from the initial value with the battery voltage Vr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lockup control device for a torque converter.

[0002]

2. Description of the Related Art As a conventional example of a lockup control device for a torque converter, there is, for example, one disclosed in Japanese Patent Laid-Open No. 3-292461. This conventional example includes a lockup clutch capable of engaging the pump impeller side and the turbine runner side of the torque converter, and the engagement pressure of the lockup clutch is controlled by an electric actuator (solenoid) to control the release pressure. It is configured to be controlled by.

Further, in this conventional example, when a lockup engagement command is issued, a drive signal (duty) obtained by adding a value corresponding to the slip of the lockup clutch at that time to the initial value of the release pressure control target value. Ratio) to the electric actuator for lockup control and
A correction is made to increase or decrease the initial value according to the length of the delay time from the start of the output of the drive signal until the slip of the lockup clutch actually changes.

[0004]

It is necessary to optimize the initial value so that the lock-up engagement time is shortened as much as possible and a shock is not generated at the lock-up engagement as much as possible. However, in the above-mentioned conventional example, as described above, the initial value of the drive signal output to the electric actuator in response to the lock-up engagement command is changed so that the slip of the lock-up clutch actually changes from the start of the output of the drive signal. Since it is corrected by performing learning control based on the delay only until the delay, it includes parameters that constantly change according to operating conditions such as line pressure and engine oil temperature, and parameters that change over time such as solenoid supply voltage. In order to consider all the influences of the engagement involvement conditions on the above initial values, it is necessary to correct each parameter by the same learning control, and a complicated learning logic is required to obtain an appropriate initial value. . In addition, a lot of traveling distance (a lot of time) is required until the proper initial value is obtained by the learning control, during which lockup engagement shock occurs or engagement time becomes long and lockup is delayed. Therefore, there is a fear that the fuel efficiency will be deteriorated.

An object of the present invention is to solve the above-mentioned problems by setting an initial value of a release pressure control target value of an electric actuator in accordance with an engagement condition such as an apply pressure.

[0006]

To this end, according to the structure of claim 1 of the present invention, the pump impeller side rotating with the output shaft of the engine and the turbine runner side rotating with the input shaft of the automatic transmission are fastened. A lock-up control of a torque converter, which comprises a lock-up clutch capable of controlling the release pressure applied to the lock-up clutch by an electric actuator so as to control the engagement capacity of the lock-up clutch. In the device, when an engagement command for the lockup clutch is issued, an initial value setting means for setting an initial value of the release pressure control target value according to an engagement condition based on a driving condition of the vehicle or a change over time, and the initial value setting means. Drive signal output means for outputting a drive signal determined based on a value to the electric actuator; It is characterized in that formed by equipped.

According to a second aspect of the present invention, the initial value setting means has an apply pressure detecting means for detecting or estimating the apply pressure, and the third aspect of the present invention is configured. The initial value setting means has a line pressure detecting means for detecting or estimating the line pressure. According to a fourth aspect of the present invention, the initial value setting means detects the engine oil temperature. A fifth aspect of the present invention is characterized in that the initial value setting means has a supply voltage detection means for detecting a supply voltage to the electric actuator. . Further, in the configuration of claim 6 of the present invention, the initial value setting means sets the initial value of the release pressure control target value to be lower as the lockup engagement side pressure obtained by the apply pressure detection means is lower. The structure of claim 7 of the present invention is characterized in that, in the structure of each of the above claims, the initial value of the release pressure control target value is continuously updated after the start of lock-up engagement. .

[0008]

According to the first aspect of the present invention, when the engagement pressure of the lockup clutch of the torque converter is controlled by controlling the release pressure by the electric actuator, the initial value setting means sets the lockup. When the clutch engagement command is issued, the initial value of the release pressure control target value is set according to the engagement condition based on the driving situation of the vehicle and the change over time, so the initial value changes according to the driving situation. The initial value is appropriate considering the influence of parameters and parameters that change over time.

According to the present invention, the initial value setting means is an apply pressure detecting means for detecting or estimating the apply pressure, and a line pressure detecting means for detecting or estimating the line pressure. Release pressure control set by the initial value setting means, since one or more of an oil temperature detecting means for detecting an engine oil temperature and a supply voltage detecting means for detecting a supply voltage to the electric actuator are included. The initial value of the target value is a proper initial value in consideration of the influence of the parameter that changes according to the driving situation and the parameter that changes with time, which are obtained in each claim.

Further, in the structure of claim 6 of the present invention, the initial value setting means lowers the initial value of the release pressure control target value as the lock-up engagement side pressure obtained by the apply pressure detection means is lower. Since it is set, the initial value of the release pressure control target value set by the initial value setting means is
It becomes an appropriate initial value according to the lock-up engagement side pressure.

Further, in the structure of claim 7 of the present invention, the initial value of the release pressure control target value set by the initial value setting means is continuously updated even after the start of the lockup engagement, so the lockup engagement is performed. It becomes an appropriate initial value according to the change in the driving situation.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of a lock-up control device for a torque converter and a hydraulic circuit to which the lock-up control device is applied according to a first embodiment of the present invention, in which 1 denotes a pressure source. A similar example of this hydraulic circuit is Nissan Motor Co., Ltd.
"RE4R02A Automatic Transmission Maintenance Manual".

The pressure source 1 includes an oil pump, a pressure regulator valve, a pilot valve and the like, and a line pressure P having a throttle pressure and an R range pressure as command pressures.
_L , pilot pressure Ppi, and torque converter pressure Pt are generated. In the pressure source 1, the pilot pressure oil passage 2 for supplying the pilot pressure Ppi is connected to the lockup control valve 20 and the lockup solenoid 24 via the orifice 13, the lockup signal pressure oil passage 23, and the oil passage 3 It is connected to the lockup control valve 20 via. Further, the torque converter pressure oil passage 10 that supplies the torque converter pressure Pt is
The torque converter relief valve 21 and the oil passage 22 are connected to the lockup control valve 20, and the lockup control valve 20 is connected to the release side of the torque converter 14 via the release pressure oil passage 6. An oil passage 4 that guides the drain from the release side is connected between the pressure source 1 and the torque converter relief valve 21.

The lockup control valve 20 comprises a spool 20a, a plug 20b and a spring 20c, and is connected to the Apply side of the torque converter 14 via the Apply pressure oil passage 5 in addition to the above. The illustrated ports of the lockup control valve 20 are connected to the oil cooler 12 and the rear lubrication system via the orifices 9, 15, 16 and the lubricating oil passage 11, respectively.

Next, a control circuit for performing lockup control in the hydraulic circuit will be described. This control circuit is a control unit 30 that controls lock-up control.
An oil temperature sensor (oil temperature detecting means) 31 for detecting an engine oil temperature t, a throttle sensor 32 for detecting a throttle opening Tvo, an engine speed sensor 33 for detecting an engine speed Ne, and a turbine speed. It comprises a turbine rotation speed sensor 34 for detecting Nt, a vehicle speed sensor 35 for detecting a vehicle speed Vsp, and a battery voltage sensor (supply voltage detecting means) 36 for detecting a battery voltage Vb. The control unit 30 executes the control programs of FIGS. 2 and 3 based on the input signals Ne, Nt, Tvo, t, Vsp, and Vb from the above-mentioned sensors to release the target release pressure control target of the present invention. Lockup control including optimization by learning control of the initial value is performed.

FIG. 2 is a flowchart showing a control program for lock-up control which is repeatedly executed by the control unit 30 at predetermined intervals. In FIG. 2, first, in step 102, N is detected from the sensors 31 to 35.
e, Nt, Tvo, t, Vsp are read, step 104
Then, the slip rotation speed Ns in the previous processing routine is set to OL.
After updating to DNs, in step 106, the current slip rotation speed Ns is calculated by Ns = | Ne-Nt |.

At the next step 108, the current vehicle speed Vsp
Is the predetermined vehicle speed (the lockup clutch engagement allowable vehicle speed) V
Determine whether _LU is exceeded. Vsp ≦ in this judgment
If _VLU is NO, the lockup flag F is cleared (F = 0) in step 109 and the processing routine of this time is ended. If Vsp> _VLU is YES, the lockup flag F is set in step 110. It is determined whether it is 0 or not. In this determination, if F = 0, YES, steps 112 to 1
18 is executed, and if F = 1 NO, step 112
The processing of ~ 118 is skipped.

In step 112, the flag F is set (F = 1), and in step 114, the coefficient k is obtained as a function f1 (t) of the oil temperature t (may be obtained as a function of the viscosity coefficient of hydraulic oil). At the same time, the line pressure P _L is obtained as a function f2 (Tvo) of the throttle opening Tvo. Then
In step 116, the apply pressure Pa is set to the coefficient k and the line pressure P.
_{The value} is obtained as the product of _L and the initial value d ₀ of the duty ratio D for the lockup solenoid 24 is set by the function f3 (Pa) of the apply pressure Pa in step 118. For this setting, for example, the lower the apply pressure Pa obtained in step 116 is, the lower the initial value d ₀ is set. The step 112 functions as an apply pressure detecting means, the step 114 functions as a line pressure detecting means, and the step 118 functions as an initial value setting means.

In the next step 120, the above step 1
The deviation e between the actual slip rotation speed Ns obtained in 06 and the preset target slip rotation speed Nsobj is obtained, and step 1
In step 22, the I used for feedback control is obtained by adding the product of the feedback coefficients Ki and e to I in the previous processing routine. In step 124, the duty ratio (command value) D ₁ for the lockup solenoid 24 is set to D ₁
= Kp × e + I + d ₀ . However, Kp is a feedback coefficient.

At the next step 126, the duty ratio D is corrected by the subroutine of FIG. That is,
In step 132 of FIG. 3, the battery voltage (constant voltage) Vr is read from the battery voltage sensor 36, and step 134
Then, the deviation from the reference voltage V (voltage decrease) Vε is Vε = V
-Vr, and in step 136, the voltage fluctuation correction amount Δd of the duty ratio is calculated by Δd = KVε. Here, K is a correction coefficient. Then, in step 138, the voltage variation correction amount Δ is added to the duty ratio D ₁ previously set by a factor other than the voltage variation by D = D ₁ + Δd.
The corrected duty ratio D is determined by adding d. Then, returning to FIG. 2, in the next step 128, the corrected duty ratio D is output to the lockup solenoid 24. The step 128 functions as drive signal output means.

Next, the operation of this embodiment will be described. In the above hydraulic circuit, the pressure source 1 controls the line pressure so that a required amount can be obtained by the throttle pressure generated according to the throttle opening Tvo. When the line pressure does not reach the predetermined line pressure, the opening areas of the line pressure oil passage and the torque converter pressure oil passage 10 decrease, and as a result, the amount of oil supplied to the torque converter and the lubricating system decreases. Increase the line pressure to a specified value. Pressure source 1
When the discharge flow rate of the oil pump (not shown) has a sufficient margin with respect to the discharge flow rate for obtaining the required amount of the line pressure, the torque converter pressure oil passage 10 opens sufficiently to the line pressure oil passage. A stable state is reached at the pressure adjustment position.

The lockup solenoid 24 outputs a lockup signal pressure Psig according to the duty ratio D,
It is designed to lower the release pressure of the torque converter as the duty ratio increases. The lockup control valve 20 reduces the lockup control valve supply pressure of the torque converter pressure oil passage 22 in accordance with the output pressure (lockup signal pressure Psig) of the lockup solenoid 24, thereby releasing the release pressure oil passage 6
However, the release pressure Pr cannot be controlled to be equal to or higher than the lockup control valve supply pressure of the torque converter pressure oil passage 22 in the torque converter pressure oil passage 22. The dead zone of release pressure control changes.

When the duty ratio falls within the dead zone, the target release pressure cannot be obtained in the duty ratio control. Therefore, the spool 20a of the lockup control valve has a lockup solenoid signal acting on its left end. The release pressure P acting on the right end of the plug 20b is the resultant force of the pressure Psig and the force of the spring 20b (the force that pushes the spool 20a to the right).
Since the combined force of the force due to r and the force due to the constant pilot pressure Ppi acting on the shoulder portion of the plug 20b (the force pushing the spool 20a to the left) is exceeded, the spool 20a is positioned at the stroke end in the right direction. The apply pressure oil passage 5 is connected to the lubricating oil passage 11.

On the other hand, when the duty ratio is reduced from the dead zone, the release pressure control target value and the lockup control valve supply pressure become equal to each other.
The spool 20a and the plug 20b are positioned at the pressure adjusting position. In this state, the apply pressure oil passage 5 is connected to the torque converter pressure oil passage 22 by the spool 20a. Therefore, when the duty ratio is equal to or less than the above duty ratio, the release pressure Pr is controlled according to the output pressure of the lockup solenoid 24.
When the duty ratio becomes 0 or more, the force pushing the spool 20a to the left becomes larger, so the spool 20a is positioned at the stroke end in the left direction.
The release pressure oil passage 6 is completely connected to the drain port 20d.

In the above, the duty ratio and the hydraulic pressure of each part
(Apply pressure Pa, release pressure Pr, lockup signal
The relationship with the pressure Psig) is as shown in the characteristic diagram of FIG.
That is, the apply pressure Pa and the release pressure pr are
When the supply pressure of the pull-up control valve is the maximum value P1
Is the characteristic of the solid line, and when the minimum value P2 is the characteristic of the dotted line
Become. The transmission torque of the lockup clutch is (Pa-P
proportional to r), the lockup control valve supply pressure
Is the maximum value P1, the duty ratio is d ₁ More than
When transmission torque is generated,
If the trawl valve supply pressure is at the minimum value P2,
Tee ratio is d₂ Transmission torque can be generated only when
Becomes

By the way, in order to smoothly perform the lock-up engagement so as not to deteriorate the lock-up engagement shock characteristic, the engine speed Ne and the turbine speed Nt are determined.
It is common practice to perform feedback control so that the slip rotation speed calculated from the difference between the two follows a predetermined slip target value. In this general feedback control, the initial value of the duty ratio is d ₁ or less. However, if the PI control for lock-up engagement is performed using the initial value of d ₁ or less when the apply pressure Pa is low, a low control constant necessary to prevent a lock-up engagement shock must be used. As a result, it takes a very long time to lock up. Therefore, it is required to correct the above initial value to a proper value by learning control.
In this embodiment, in consideration of the fact that the apply pressure Pa changes according to various engagement involvement conditions, learning control is performed comprehensively for each engagement engagement condition.

For example, in the hydraulic circuit of FIG. 1, the pressure source 1 to the torque converter pressure oil passage 10, the torque converter relief valve 21, and the torque converter pressure oil passage 22.
It is considered that the apply pressure Pa drops from the line pressure P _{L by the} amount of the pressure loss because the lubricating system hydraulic oil flows through the path that guides the hydraulic oil to the lockup control valve 20 via. That is, step 114 in FIG.
In order to reflect the rate of decrease from the line pressure in the apply pressure in step 116, the Apply pressure Pa is Pa = k.multidot. It is calculated (estimated) by P _L, and based on the obtained apply pressure (estimated value) Pa, step 11
In step 8, the initial value d ₀ of the release pressure control target value is set to d ₀ = f3
Since it is set to (Pa), this d ₀ is the maximum duty ratio that does not generate the lockup fastening force. Therefore, by the lockup control using the optimized initial value, it becomes possible to perform the lockup engagement in the shortest engagement time that does not cause an engagement shock.

Further, the judgment in step 108 of FIG. 2 is YE.
When S (when the vehicle speed Vsp exceeds the lockup allowable vehicle speed V _LU; during lockup judgment), the control first is the step 110 becomes to YES, the control second and subsequent N
Since it becomes O and steps 112 to 118 are skipped, the initial value d ₀ of the first control is the lockup release judgment after the lockup engagement judgment (the judgment in step 108 is N
Not updated until O) is done. Therefore, step 1
The duty ratio D ₁ obtained at 24 is not changed by other engaging conditions other than the feedback constant during the lockup engagement, and the control stability is not adversely affected. However, once the lockup release determination is made, the flag F is cleared (F = 0) in step 109, so that the next time the lockup engagement determination is made, the initial value d ₀ is again set according to the situation.
Is set, lock-up engagement can be performed without a large response delay or lock-up engagement shock.

By the way, the optimization of the initial value is based on the assumption that the battery voltage, which is the voltage supplied to the lockup solenoid 24, maintains a constant value. As shown in, the output characteristic of the duty ratio (ON duty ratio) changes. For this reason, even if the duty ratio is the same, the actual lockup solenoid output pressure varies depending on the battery voltage, and the lockup engagement shock characteristic deteriorates. On the other hand, in the present embodiment, by executing the control program of FIG. 3, the voltage variation correction amount Δd of the duty ratio is obtained according to the deviation Vε of the battery voltage Yr from the reference voltage V, and the duty ratio ( Command value)
Is corrected, the influence of the voltage fluctuation is canceled and a proper initial value is obtained.

FIG. 6 is a flow chart showing a control program for lock-up control by the control unit in the second embodiment of the present invention. In this second embodiment,
The point that the initial value d ₀ is directly obtained from the line pressure (or the throttle opening Tvo that determines the apply pressure) and the oil temperature without performing the process for obtaining the apply pressure to determine the initial value d ₀ This is different from the first embodiment. Due to this change, steps 110 to 118 of the control program of FIG. 2 of the first embodiment are replaced with step 150 of FIG. 6, and step 109 following NO in step 108 of FIG. 2 is deleted in FIG. There is.

[0031] In FIG. 6, when the lockup judgment (Vsp> V _LU) is made in step 108, the next step 150, searching a map, not shown, based on the throttle opening Tvo and fluid temperature t Initial value d
_{Since 0} is obtained and the other steps are the same as those in FIG. 2, description thereof will be omitted. In the above, the map showing the initial value by the line pressure (throttle opening) and the oil temperature is used. However, the line pressure by using the map showing the initial value only by the line pressure without using the oil temperature is used. A sufficient effect can be obtained even if the map is searched only by itself. Further, instead of the line pressure or the throttle opening, a shift stage may be used to represent a map that represents an initial value. Further, as the line pressure, when a system in which the line pressure is controlled by a controller and an electronically controlled hydraulic actuator is used, the line pressure control target value determined in the controller may be used.

In the second embodiment, during lock-up fastening,
The initial value d ₀ is constantly updated according to the operating conditions. That is, the initial value d ₀ is changed according to the throttle opening change due to the accelerator depression within a range that does not affect the lockup engagement determination in step 108 of FIG. 6, and the initial value change corresponding to the line pressure change is performed. Since the output duty ratio of the lock-up solenoid is changed, lock-up control can be continuously performed even when the lock-up engaging force rapidly increases due to a sudden increase in the apply pressure. Therefore, it is possible to further reduce the lock-up engagement shock according to the change in the operating condition after the lock-up engagement determination.

FIG. 7 is a diagram showing the configuration of a lockup control device for a torque converter and a hydraulic circuit to which the same is applied according to a third embodiment of the present invention. In the configuration of the third embodiment, a hydraulic sensor 37 for detecting the apply pressure of the apply pressure oil passage 5 is added to the configuration of the first embodiment.

FIG. 8 is a flow chart showing a control program for lockup control by the control unit in the third embodiment of the present invention. In this third embodiment,
In step 160 corresponding to step 102 in FIG. 2, the apply pressure Pa is added as the data to be read, and the throttle opening Tvo and the oil temperature t are deleted because they are no longer needed. Furthermore, the apply pressure Pa existing in FIG. The steps 114 and 116 for obtaining the pressure are deleted, and the other steps are the same as those in FIG.

This third embodiment is based on step 160 in FIG.
Since the apply pressure Pa is directly read in, the initial value d ₀ can be obtained in step 118 without estimating the apply pressure, and the control logic is simplified. Moreover, since the apply pressure is directly detected, the initial value can be determined with high accuracy, and the lock-up engagement delay can be further shortened.

[0036]

As described above, according to the first aspect of the present invention, the initial value setting means is used when the engagement capacity of the lockup clutch of the torque converter is controlled by controlling the release pressure by the electric actuator. , When the lock-up clutch engagement command is issued,
The initial value of the release pressure control target value is set according to the vehicle operating condition and the engagement-related conditions based on the change over time, so the initial value considers the influence of parameters that change according to operating conditions and parameters that change over time. It is a proper initial value. Therefore, by the lockup control using the optimized initial value, it becomes possible to perform the lockup engagement in the shortest engagement time that does not cause an engagement shock.

In the second to fifth aspects of the present invention, the initial value setting means is an apply pressure detecting means for detecting or estimating the apply pressure, and a line pressure detecting means for detecting or estimating the line pressure. Release pressure control set by the initial value setting means, since one or more of an oil temperature detecting means for detecting an engine oil temperature and a supply voltage detecting means for detecting a supply voltage to the electric actuator are included. The initial value of the target value is a proper initial value in consideration of the influence of the parameter that changes according to the driving situation and the parameter that changes with time, which are obtained in each claim. Therefore, by the lockup control using the optimized initial value, it becomes possible to perform the lockup engagement in the shortest engagement time that does not cause an engagement shock.

Further, in the structure of claim 6 of the present invention, the initial value setting means lowers the initial value of the release pressure control target value as the lockup engagement side pressure obtained by the apply pressure detection means is lower. Since it is set, the initial value of the release pressure control target value set by the initial value setting means is
It becomes an appropriate initial value according to the lock-up engagement side pressure. Therefore, by the lockup control using the optimized initial value, it becomes possible to perform the lockup engagement in the shortest engagement time that does not cause an engagement shock.

Further, in the configuration of claim 7 of the present invention, the initial value of the release pressure control target value set by the initial value setting means is continuously updated even after the start of the lockup engagement, so the lockup engagement is performed. It becomes an appropriate initial value according to the change in the driving situation. Therefore, by the lockup control using the optimized initial value, it becomes possible to perform the lockup engagement in the shortest engagement time that does not cause an engagement shock.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a lockup control device for a torque converter and a hydraulic circuit to which the lockup control device is applied according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a control program of lockup control executed by a control unit in the same example.

FIG. 3 is a flowchart showing a control program for correction of an initial value of a release pressure control target value by a battery voltage, which is executed by a control unit in the same example.

FIG. 4 is a characteristic diagram showing a relationship between a duty ratio, an apply pressure, a release pressure, and a lockup signal pressure in the same example.

FIG. 5 is a characteristic diagram showing a battery voltage-duty ratio output characteristic in the same example.

FIG. 6 is a flowchart showing a control program for lockup control by a control unit in the second embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a lockup control device for a torque converter and a hydraulic circuit to which the lockup control device is applied according to a third embodiment of the present invention.

FIG. 8 is a flowchart showing a control program for lockup control by a control unit in the third embodiment of the present invention.

[Explanation of reference numerals] 1 pressure source 2 pilot pressure oil passage 5 apply pressure oil passage 6 release pressure oil passage 10 torque converter pressure oil passage 14 torque converter 20 lock-up control valve 20a spool 20b plug 20c spring 21 torque converter relief valve 22 torque Converter pressure oil passage 23 Lock-up signal pressure oil passage 24 Lock-up solenoid (electric actuator) 30 Control unit 31 Oil temperature sensor 32 Throttle sensor 33 Engine rotation speed sensor 34 Turbine rotation speed sensor 35 Vehicle speed sensor 36 Battery voltage sensor 37 Hydraulic pressure sensor

Claims (7)

[Claims] 1. A lock-up clutch capable of engaging a pump impeller side rotating with an output shaft of an engine and a turbine runner side rotating with an input shaft of an automatic transmission, wherein the lock-up clutch is released by an electric actuator. In a lock-up control device for a torque converter that controls the engagement capacity of the lock-up clutch by controlling the release pressure that acts in the direction of driving the vehicle, when the lock-up clutch engagement command is issued, the vehicle operation is Initial value setting means for setting the initial value of the release pressure control target value in accordance with the engagement involvement condition based on the situation and changes over time, and a drive signal output for outputting a drive signal determined based on the initial value to the electric actuator And a lock for a torque converter, comprising: -Up control device. 2. The lockup control device for a torque converter according to claim 1, wherein the initial value setting means has an apply pressure detecting means for detecting or estimating the apply pressure. 3. The lockup control device for a torque converter according to claim 1, wherein the initial value setting means has a line pressure detection means for detecting or estimating the line pressure. 4. The lockup control device for a torque converter according to claim 1, wherein the initial value setting means includes an oil temperature detecting means for detecting an engine oil temperature. 5. The torque converter according to claim 1, wherein the initial value setting means has a supply voltage detecting means for detecting a supply voltage to the electric actuator. Lockup control device. 6. The initial value setting means sets a lower initial value of the release pressure control target value as the lockup engagement side pressure obtained by the apply pressure detection means is lower. 5. The lockup control device for a torque converter according to any one of items 1 to 5. 7. The initial value of the release pressure control target value is
7. The lockup control device for a torque converter according to claim 1, wherein the lockup control is continued even after the start of lockup engagement.