JPH0676827B2 - Torque converter slip control device - Google Patents

Description

The present invention relates to a torque converter that is used by inserting it into a power transmission system such as an automatic transmission, and more particularly, a slip control type torque converter capable of limiting relative rotation (slip) between its input and output elements. The present invention relates to a slip control device.

A normal torque converter drives an output element (usually a turbine runner) through a working fluid swirled by an input element (usually a pump impeller) driven by a prime mover, and transmits power, so that a torque increasing function and Although the torque fluctuation absorbing function can be obtained, relative rotation between the input and output elements (slip of the torque converter) cannot be avoided, resulting in poor power transmission efficiency.

Therefore, depending on the operating state of the prime mover, the slip,
A slip control type torque converter is being put into practical use in which the power transmission efficiency is improved by limiting the torque increase function and the torque fluctuation absorbing function to the minimum necessary.

This type of torque converter is constructed by connecting a normal torque converter mechanically directly between its input and output elements, or by adding a lockup clutch for appropriately adjusting this direct connection. Then, in the operating state of the prime mover corresponding to the converter area of the torque converter, this is made to function in the converter state in which the slip of the torque converter is not limited by releasing the lockup clutch,
In the operating condition of the prime mover corresponding to the torque converter lock-up region, this is activated in the lock-up condition where the torque converter slip becomes zero due to the complete coupling of the lock-up clutch. By controlling the coupling force of the lockup clutch, the slip amount of the torque converter is made to function in the slip limited state so as to reach the target value.

By the way, in the case of performing the slip control of the torque converter, conventionally, for example, a device as disclosed in JP-A-57-33253 is used. This device discriminates whether the operating condition of the prime mover is in the converter region, the lockup region or the slip control region, and if it is the former two, the control value is set to the corresponding limit value and the torque converter is set. Is operated in the converter state or the lockup state, and the latter field multiplication control value is set to a value such that the torque converter slip amount becomes the target slip amount, and the slip amount of the torque converter is fed back controlled while operating in the slip limited state.

However, in such a slip control device, there is a large difference between the control value in the converter region or the lockup region and the control value in the slip control region, and when the former two regions move to the latter region, the torque converter slip amount is set to the target slip amount. It takes a long time to reach the amount, and in combination with the response delay of the feedback control, the followability of the slip control is poor, and the initial torque converter slip amount of the slip control once exceeds the target slip amount. The so-called control overshoot brought to the value was generated, and the control was inaccurate.

Therefore, in the conventional slip control device, particularly when it is used for an automatic transmission for a vehicle, the torque converter is frequently changed between the converter state or the lockup state and the slip control state in accordance with the frequent acceleration / deceleration of the vehicle. Since it is necessary to make the torque converter slip amount deviate from the target value in the slip control state, it takes a long time. If the slip amount is too large compared to the target value, the fuel consumption is worsened due to the increase in the number of rotations of the prime mover and the noise is increased, and the original effect of the slip control type torque converter is largely lost. If too much, the torque increasing function and the torque fluctuation absorbing function of the torque converter are impaired, resulting in deterioration of power performance and vibration.

The present invention, even if the torque converter in the converter region or the lockup region is set to the converter state or the lockup state, holds the control value, and when the slip control is restarted, the control value is used while being corrected to a value commensurate with the target slip amount. If so, it is possible to solve the problem of the conventional device that causes poor control followability or control overshoot, and it is possible to accurately control the torque converter slip amount to the target value even when shifting to the slip control region, It is an object of the present invention to provide a slip control device for a torque converter that embodies this idea from the viewpoint that the fuel economy of the prime mover will not deteriorate, the noise will increase, or the power performance will not deteriorate or vibrate. To do.

By the way, in such control, the control value is often similar at the end of the previous slip control and at the time of restarting the slip control this time. At the time of restart, the torque converter slips insufficiently to generate vibration, and smooth restart of slip control cannot be guaranteed.

An object of the present invention is to solve the problem in this respect as well, and to ensure smooth restart of slip control.

For this purpose, the slip control device of the present invention, as shown in FIG. 1, includes a transmission path for transmitting the power from the prime mover a to the output shaft c via the torque converter b, and a lockup clutch d to which the power is appropriately coupled. It also has a transmission path directly transmitted to the output shaft c through the lockup clutch d in the operating state of the prime mover a corresponding to the converter region of the torque converter b, and the lockup clutch d of the prime mover a corresponding to the lockup region of the torque converter b is released. The lockup clutch d is completely connected in the operating state, and the lockup clutch d is calculated by the difference between the slip amount of the torque converter b and the target slip amount in the operating state of the prime mover a corresponding to the slip control region of the torque converter b. A slip control means e for eliminating the difference between the two slip amounts by performing connection control according to the obtained slip control value. In a slip control type torque converter, the slip control is such that the calculation of the slip control value is stopped in the converter region or the lockup region, and the slip control value is held immediately before the transition from the slip control region to the converter region or the lockup region. The value holding means f and the slip control value obtained by correcting the slip control value held by this means by a certain amount in the slip amount increasing direction are slips accompanying the transition from the converter area or the lockup area to the slip control area. Slip control initial value correction means g for setting a control initial value when control is restarted is provided.

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 2 is an embodiment showing a slip control device of the present invention together with a slip control type torque converter for an automatic transmission to be controlled by the slip control device, in which 1 is an engine as a prime mover,
2 The crank shaft, 3 is a flywheel, 4 is a slip control type torque converter, and 5 is a gear transmission mechanism. The torque converter 4 includes a pump impeller (input element) 4a coupled to the crankshaft 2 via a flywheel 3 and driven by an engine, a turbine runner (output element) 4b facing the pump impeller 4a, and a stator (reaction element) 4c. Of 3
Composed of elements, turbine runner 4b and torque converter 4
Drivingly coupled to the output shaft (input shaft of the gear transmission 5) 7 of
The stator 4c is placed on the hollow fixed shaft 9 via the one-way clutch 8. The torque converter 4 supplies working fluid in the direction of the arrow α to the internal converter chamber 10 and eliminates this working fluid in the direction of the arrow β, and at the same time, a pressure holding valve (not shown) provided in the middle of the converter chamber 10 The inside is maintained at a pressure (converter pressure) P _C below a certain value. Thus, as described above, the engine driven pump impeller 4a stirs the internal working fluid, collides it with the turbine runner 4b, and then causes it to flow to the stator 4c, while increasing the torque of the turbine runner 4b under the reaction force of the stator 4c. While rotating. Therefore, the motive power from the engine 1 is the torque converter 4, the input shaft 9, and the transmission mechanism 5.
It is transmitted to the drive wheels via the, and the vehicle can be driven.

Further, the torque converter 4 is provided with a lockup clutch 11 in order to make a slip control type capable of limiting the slip (relative rotation between the input element 4a and the output element 4b), which is mounted on the output shaft 7 via the torsion damper 12. Is connected to the converter chamber 10 and is axially movable on the output shaft.
Separately, the lockup chamber 13 is set in the torque converter 4. The lockup clutch 11 responds to the difference between the converter pressure P _C in the converter chamber 10 and the lockup pressure P _{L / u} in the lockup chamber 13 to the left in the figure, and the force corresponding to the pressure difference causes an input / output element. The slip of the torque converter 4 can be limited by drivingly connecting 4a and 4b.

The lock-up pressure P _{L / u} is adjusted by the slip control valve 14, but this valve is connected to the lock-up chamber 13 at port 14a.
And a drain port 14c for guiding the converter pressure P _C , and when the spool 14d is in the neutral position shown in the figure, the port 14a is cut off from both ports 14b, 14c.
When 14d goes right in the figure, the port 14a is made to communicate with the port 14b, and when spool 14d goes left in the figure, the port 14a is made to communicate with the port 14c. Then, the spool 14d passes through the orifice 15 and the lockup pressure P acting on the right end in the figure.
_In response to the differential pressure between _{L / u} and the control pressure P _S acting on the left end face in the figure, the control pressure P _S is created as follows. That is, a reference pressure (line pressure in the case of an automatic transmission) P _L that controls the shifting of the transmission mechanism 5 is supplied from one end 16a of the control pressure generation circuit 16, and this line pressure is passed through the orifices 17 and 18 to the other circuits of the circuit 16. By draining from the end 16b and determining the drain amount by the duty-controlled solenoid valve 19, a control pressure P is applied between the orifices 17 and 18.
You can create _S.

The solenoid valve 19 is in a normal state, and the plunger 19b is moved leftward in the figure by the spring 19a, thereby closing the drain opening end 16b of the circuit 16, and the plunger 1b is closed each time the solenoid 19c is energized.
9b is in the rightward position shown and opens the drain opening end 16b,
The above drains are allowed. The energization of the solenoid 19c is duty-controlled so that the energization of the solenoid 19c is performed during the pulse width (on-time) of the pulse signal from the slip control computer 20 as shown in FIGS. 3 (a) and 3 (b). As shown in FIG. 3 (a), when the duty (%) is small, the solenoid valve 19 takes a short time to open the drain opening end 16b. Therefore, the control pressure P _S is the line as shown in FIG.
Equal to P _L. Further, as the duty (%) becomes larger as shown in FIG. 3 (b), the solenoid valve 19 opens the drain opening end 16b for a long time, so that the control pressure P _S gradually increases as shown in FIG. It decreases, and finally becomes a constant value determined by the opening area difference between the orifices 17 and 18.

In FIG. 2, as the control pressure P _S becomes higher, this control pressure causes the spool 14d to move to the right as shown in FIG. 5 (a) so that the port 14a gradually increases in communication with the port 14b, and the lockup pressure P _{L / u} is gradually increased as shown in FIG. 6 with the relation of P _{L / u} = k · P _S (where k is a constant), and finally converter pressure P _C
It is a constant value corresponding to. Then, as the control pressure P _S becomes lower, the lock-up pressure P _{L / u on} the end face of the spool 14d on the opposite side to the action thereof causes the spool 14d to move leftward as shown in FIG. 5 (b) and the port 14a to the port 14c. The lock-up pressure P _{L / u} is made to communicate with each other and has the same relationship as the above, and is gradually reduced to the opposite, and finally becomes zero. And the slip control valve 14
When the lockup pressure P _{L / u} becomes a value corresponding to the control pressure P _S , the spool 14d is returned to the neutral position shown in FIG. 2, and the lockup pressure P _{L / u} is kept at the value at this time, and this lockup pressure is maintained. It can be controlled by the control pressure P _S.

By the way, the control pressure P _S with respect to the magnitude of the duty (%)
The change characteristic of is as shown in FIG. 4, and from this and the control pressure (P _S ) -lock up pressure (P _{L / u} ) characteristics shown in FIG.
The change characteristic of the lockup pressure P _{L / u} with respect to the magnitude of the duty is as shown in FIG.

The slip control computer 20 is operated by the power source + V, and the gear position signal Sg from the gear position sensor regarding the selected gear position of the speed change mechanism 5 and the engine speed (rotation speed of the input element 4a) signal Sir from the engine speed sensor 21. , A signal Sor related to the output speed of the speed change mechanism 5 from the output speed sensor 22 and a signal S _TH related to the engine throttle opening from the throttle opening sensor 23, and the duty of the solenoid valve 19 is calculated based on these calculation results. Take control.

For this purpose, the computer 20 has a microprocessor unit (MPU) 24, a random access memory (RAM) 25, and a read-only memory (RO) as shown in FIG.
M) 26 and an input / output interface circuit (I / O) 27. The MPU 24 reads the signals from the sensors 6 and 21 to 23 via the I / O 27 and outputs the above calculation result to the drive circuit 28 via the I / O 27 to control the duty of the solenoid valve 19. Since the signals Sir and Sor are pulse signals, a counter for counting the number of these pulses, and since the signal S _TH is an analog signal, an A / D converter for converting it into a digital signal, Further, since the above calculation result is a binary value, a counter for converting this into a duty control pulse signal is incorporated.

The MPU 24 executes the control program shown in FIGS. 9 and 10 stored in the ROM 26 to control the solenoid valve 19 for duty, and controls the lockup pressure P _{L / u} according to the duty as shown in FIG. 7 to control the lockup clutch. Operate 11

JOB1 shown in FIG. 9 is a timing routine, and JOB2 shown in FIG.
This is for measuring a predetermined time used when executing the control routine. The routine shown in FIG. 9 is repeatedly executed at regular intervals of, for example, 65 ms, and at each repetition, the register named a timer is incremented by one step in the slip 30, and this register is incremented by one step. It is cleared as described later in the control routine. In the next slip 31, whether the difference between the content of the register and the predetermined value stored in the ROM 26 is zero or less or less than zero, that is, whether a certain time (65 ms × predetermined value) has elapsed after the register is cleared Determine whether or not. If the content of the register is equal to or greater than the predetermined value and the above-mentioned certain time has elapsed, the control proceeds to step 32, where the content of the register is maintained at the predetermined value, and the flag F2 is reset to 06 (reset in the next step). If the content is less than a predetermined value and within the above fixed time, the slip 31 selects the slip 34 and sets the flag F2 to 1. Thus, if F2 = 0, a fixed time elapses after clearing the register. If F2 = 1, it means that it is within a certain time after clearing the register.

The control routine shown in FIG. 10 is also executed, for example, at regular intervals of 100 ms, and first, at step 40, the engine speed (the engine speed of the pump impeller 4a) N _E is calculated. For this calculation, the MPU 24 uses the engine speed signal Sir from the sensor 21, but since this signal is a pulse signal, the count value of the counter in the I / O 27 is held in the register for each pulse input, and the The engine rotation period N _E is calculated by calculating the engine rotation cycle by obtaining the difference between the numerical values.

In the next step 41, the output speed N ₀ of the gear transmission 5 is calculated. In this calculation, the MPU 24 uses the gear speed change mechanism output rotation speed signal Sor from the sensor 22. Since this signal is also a pulse signal, the same processing as that for obtaining the engine speed N _E is performed and the output of the gear speed change mechanism 5 is output. The number of revolutions N ₀ is calculated.

In the next step 42, the MPU 24 reads the selected gear position of the gear transmission 5 from the signal Sg from the sensor 6 and determines the gear ratio of the gear transmission 5 from this gear position. Next step
At 43, the rotational speed of the torque coverter output shaft 7 (rotational speed of the turbine runner 4b) _NT is calculated from the speed change gear ratio and the rotational speed of the speed change gear mechanism obtained at the slip 41, and at the next step 44, from the sensor 23. Engine throttle opening signal S
_{Based on TH} , this is converted into a digital signal by the A / D converter in I / O27 and the throttle opening T _H is read.

Next, the control proceeds to step 45, where the engine 1 receives the torque converter from the engine speed N _E and the throttle opening T _H based on the torque converter control diagram stored in the ROM 26 and corresponding to FIG. 11. It is determined which operation mode the 4 should be in. In FIG. 11, A / T is a converter area in which the torque converter 4 should be in a converter state in which slip limiting is not performed, and L / u is the torque converter 4
Is a lock-up region in which the torque converter 4 should not be slipped, and SLiP is a slip region in which the torque converter 4 should be slip-controlled. In the SLiP region, the slip amount of the torque converter 4 should be kept constant (target slip amount).

If the engine 1 is operating in the SLiP region, control proceeds from slip 45 to slip 46, where engine speed (rotation speed of pump impeller 4a) N _E and torque converter output shaft speed (turbine runner 4b). Number of rotations) N _T Difference from N _T N _E
The slip amount of the torque converter 4 is obtained from -N _T , and how much the slip amount is different from the target slip amount is calculated. Next, the control proceeds to the slip 47, where the integral value (slip control value) of the above error is calculated as follows: i _NEW = i _OLD = Ki · E And the integrated value i _NEW is stored in the register.

In the next step 48, the integral value i _NEW is written in the output register, and then the flag F1 is reset to 0 in the slip 49. Next, the control proceeds to step 50, the binary data of the output register is converted into a pulse signal by the counter in the I / O27, and this pulse signal is supplied from the I / O27 to the drive circuit 28, whereby the solenoid valve is operated. 19 can be controlled by the duty (%) so as to eliminate the error.

Thus, the solenoid valve 19 during operation of the engine 1 in the SLiP region reduces the lockup pressure P _{L / u} by the duty control when the torque converter 4 slips too much from the target slip amount, and the torque converter 4 sets the target. If the slip amount is less than or equal to the slip amount, increase it. Therefore, as is apparent from FIG. 7, the torque converter 4 is controlled so that the slip amount is decreased by the decrease of the lockup pressure P _{L / u} in the former case, and the lockup pressure P is decreased in the latter case.
It is controlled to increase the slip amount by increasing _{L / u} ,
As a result, the slip amount of the torque converter 4 can be maintained at the target slip amount.

By the way, depending on the result of the slip 45 determination, the engine 1 is
If the operation is in the T or L / u range, the step 45 selects the slip 51, and it is determined here whether the flag F1 is 0 or 1. Last time the above-mentioned slip control was executed, and if the flag F1 was reset at step 49 (if the transition from SLiP area to A / T or L / u area,
Since F1 = 0, step 51 selects step 52,
Here, it is determined whether the flag F2 is 0 or 1. The flag F2 is set to 0,1 as described above with reference to FIG. 9, but now
Since the predetermined time has elapsed since the timer (register) described above with reference to FIG. 9 has been reset in the slip 54, which will be described later, the slip 52 selects the step 53 by F2 = 0. Step 53 corresponds to the slip control value holding means and the slip control initial value correction means in the present invention, and in this step 53, the integrated value calculated in step 47 is held at the time of transition to the region, and the held integrated value is a constant value. Is subtracted to correct the integrated value, and the integrated value is stored again in the register to be used as the initial value of the slip control at the time of starting the next slip control. Next, the control advances to step 54 to reset the timer (register) described with reference to FIG. 9 to 0, at which time the flag F2 is set to 1 at step 34 in FIG. In the next step 55, the flag F1 is set to 1, and control is passed to slip 56.

At step 56, it is determined whether the A / T area or the L / u area,
In the A / T area, the lower limit of integration is written in the output register in step 57, and in the L / u area, the upper limit of integration is written in the output register in step 58. Control is step 57 or 58
To step 50, the binary data of the output register
It is converted into a pulse signal by the counter in O27, and this pulse signal is supplied from the I / O27 to the solenoid valve 19 via the drive circuit 28. By the way, the integral lower limit value and the integral upper limit value make the duty 0% and 100% respectively, and the lockup pressure P _{L / u} is the same as the converter pressure P _C in the A / T region as shown in FIG. The torque converter 4 to the converter state in the A / T region as required,
It can be locked up in the _{L / u} region.

By the way, when the determination result of step 51 is F1 = 1,
That is, if the previous time was also in the A / T or L / u area, step 51
Since the flag F1 has already been set to 1, the slip 51 bypasses the steps 52 to 55 and selects the slip 56 to keep the torque converter 4 in the converter state or the lockup state by the above control. Or, as long as the L / u region continues, the integration value correction and slip 54 in step 53
Do not reset the timer (register) again.

Also, once returning to the SLiP area and again to the A / T or L / u area, step 51 selects step 52 again, but if the area transition occurs within the predetermined time described above with reference to FIG. Since F2 is still 1, step 52 bypasses slips 53-55 and selects step 56. Therefore, also in this case, even if the torque converter 4 is set to the converter state or the lockup state as required, the integral value correction at step 53 and the timer (register) reset at step 54 are not performed.

FIG. 12 shows a change with time of the integrated value output when the operating state of the engine 1 changes among the A / T region, the L / u region, and the SLiP region. Will be briefly described. In addition, as for FIG. 12, from the SLiP region at an instant t ₁ ,
A / T area, instant t ₂ to ALiT area to SLiP area, instant t ₃
From SLiP region to L / u region, instant t ₄ from L / u region to SLiP region, instant t ₅ from SLiP region to A / T region, instant t ₆ from A / T region to SLiP region, instant t ₇ shows the operation mode when the operating state of the engine 1 changes from the SLiP region to the A / T region, and from the A / T region to the SLiP region at the instant t ₈ , respectively.
In the T and L / u regions, the integrated value output becomes the lower limit value and the upper limit value, respectively, and in the SLiP region, the integrated value output is an intermediate value for keeping the torque converter slip amount at the target value (it varies depending on the operating state of the engine 1) Becomes

When transiting from the SLiP area to the A / T area or the L / u area (t ₁ , t ₅ or t ₃ ), bypass the integral value calculation routine for step control consisting of steps 46 to 49 and proceed to steps 51 to 58. As a result, the calculation of the integrated value is stopped, and the calculation result of the integrated value is set to a constant value Δ in the slip 53.
Only i (see FIG. 12) is subtracted and corrected. However, this integral correction is performed only when the flag F1 is used to shift from the SLiP region to the A / T or L / u region, and by using the flag F2 within a predetermined time T (see FIG. 12) from the shift. It is performed only once, and the integral value correction is not performed at other times.

Then, when returning from the A / T or L / u region to the SLiP region (t ₂ , t ₆
Or t ₄ ), the slip control of the torque converter 4 is started by the above-mentioned correction integral value, but the difference id of the correction integral value with respect to the target integral value output for making the torque converter slip amount the target slip amount id (Fig. 12). (See) is small,
The followability of the slip control can be improved, and since the control overshoot does not occur, the slip control can be performed accurately and stably. Moreover, since the integrated value is corrected by subtraction, the corrected integrated value deviates in the A / T direction from the target integrated value, and the torque converter 4 at the start of the slip control may vibrate due to insufficient slip. This allows smooth restarting of slip control. In addition, correction of the integrated value is performed for a predetermined time T
Since it is performed only once within, for example, the instants t _{5 to} t _{8 in} FIG.
In the case where the area is frequently changed between the A / T area and the SLiP area as in the interval, it is possible to prevent the integral value correction from being performed at the instant t ₇ , and the integral value output unnecessarily decreases. It is possible to prevent the above-mentioned action result of the above from being impaired.

In the above embodiment, the slip control is performed by the integral value calculation in step 47. In this step, the PID calculation based on the error E between the torque converter slip amount and the target slip amount is performed, and the slip value is calculated by the calculated value. It may be controlled. This PID calculation is i _NEW = i _OLD + Ki ・ E _NEW out = i _NEW ＋ K _P・ E + K _D (E _NEW −E _OLD ) However, in this example, it is preferable to correct only the integrated value in the same manner as in the above embodiment. It should be noted that if K _P and K _D are set to 0, it becomes the same as the above embodiment.

Thus, the slip control device of the present invention sets the torque converter in the converter state or the lockup state in the converter region or the lockup region as described above, but the slip control value (in the above example, the integral value or the PID operation value) is the converter state or the lockup value. Instead of using the value for the state, hold it, and use the corrected slip control value obtained by correcting the held slip control value by a fixed amount Δi in the slip amount increasing direction as the initial value when the slip control is restarted. Therefore, it is possible to improve the followability of the slip control as described above and to improve the accuracy of the slip control, and it is possible to eliminate the concern that the torque converter will vibrate due to insufficient slip when the slip control is restarted. it can.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a slip control device of the present invention, FIG. 2 is a system diagram showing an embodiment of the present invention device, and FIGS. 3 (a) and 3 (b) are respectively for slip control in the device of the present invention. A time chart showing a change situation of the duty output by the computer, FIG. 4 is a characteristic diagram of change in control pressure with respect to the duty, FIG. 5 (a) and FIG. 5 (b) are operation explanatory diagrams of the slip control valve, and FIG. Is a characteristic diagram of the change of the lockup pressure with respect to the control pressure, FIG. 7 is a characteristic diagram of the change of the lockup pressure with respect to the duty, FIG. 8 is a block diagram of the slip control computer, and FIGS. 9 and 10 are respectively the slip control computer. Fig. 11 is a flow chart showing a control program of the torque converter, Fig. 11 is a control region diagram of the torque converter according to the operating state of the engine, and Fig. 12 is a computer for slip control. Is a time chart showing a change with time of the integrated value output. 1 ... Engine (motor a) 4 ... Torque converter (b) 5 ... Gear shifting mechanism, 6 ... Gear position sensor 7 ... Torque converter output shaft (c) 10 ... Converter chamber, 11 ... Lockup Clutch (d) 13 …… Lockup chamber 14 …… Slip control valve, 16 …… Control pressure generating circuit 19 …… Solenoid valve 20 …… Slip control computer 21 …… Engine speed sensor 22 …… Gear transmission mechanism output rotation Number sensor 23 …… Engine throttle opening sensor 24 …… Microprocessor unit (MPU) 25 …… Random access memory (RAM) 26 …… Read-only memory (ROM) 27 …… I / O interface circuit (I / O) 28 ... Drive circuit, e ... Slip control means f ... Slip control value holding means g ... Slip control initial value correction means

Claims (2)

[Claims] 1. A torque converter having both a transmission path for transmitting power from a prime mover to an output shaft via a torque converter and a transmission path for directly transmitting the power to the output shaft via a lockup clutch that is appropriately coupled. The lockup clutch is released in the operating state of the prime mover corresponding to the converter region of the torque converter, and the lockup clutch is completely connected in the operating state of the prime mover corresponding to the lockup region of the torque converter to correspond to the slip control region of the torque converter. In the operating state of the prime mover, the lockup clutch is coupled and controlled by a slip control value obtained by calculation based on the difference between the slip amount of the torque converter and the target slip amount, and slip control means for eliminating the difference between the two slip amounts is provided. In a slip control type torque converter, the converter area Alternatively, a slip control value holding unit that stops the calculation of the slip control value in the lockup region and holds the slip control value immediately before the transition from the slip control region to the converter region or the lockup region, and a slip control value holding unit held by this unit Initialized slip control where the corrected slip control value obtained by correcting the slip control value by a certain amount in the slip amount increasing direction is used as the control initial value when the slip control is restarted with the transition from the converter area or the lockup area to the slip control area. A slip control device for a torque converter, comprising: a value correcting means. 2. The slip control device for a torque converter according to claim 1, wherein the slip control initial value correction means performs the correction only once within a fixed time.