JP2005172078A - Lock-up control device for torque converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid an engine stall when rapidly reducing speed while coasting in a locked-up state. <P>SOLUTION: A torque converter between the engine and an automatic transmission is equipped with a lock-up clutch, and the fastening differential pressure becomes a low coast lock-up differential pressure during coasting. When an idle switch is ON and traveling is shifted to coasting, a lock-up release rotational frequency DLURPM is highly corrected over a predetermined amount of time T. When the engine speed is less than the lock-up release rotational frequency DLURP, the L/U flag becomes ON on the engine side, and L/U flag on the transmission side becomes OFF, and the fastening differential pressure is released. At time t3, by delay of oil pressure, the clutch is released, and then the engine speed reaches a fuel cut recover speed TNR. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a lockup control device for bringing a torque converter used by being inserted into a transmission system of an automatic transmission into a lockup state in which input and output elements are directly connected to each other. ) In relation to control of the lockup clutch engagement differential pressure.

  Since the torque converter performs power transmission between the input / output elements via the fluid, the torque converter performs a torque fluctuation absorbing function and a torque increasing function, but has a low transmission efficiency. Therefore, a lock-up type torque converter having a lock-up clutch that can be in a lock-up state in which input / output elements are directly connected is frequently used today.

  In vehicles equipped with such a lock-up type torque converter, when the accelerator opening is fully closed and coasting is performed, a lock-up state (especially a coast lock-up) is mainly used to reduce fuel consumption. In this coast lock-up state, the lock-up clutch engagement differential pressure applied to the lock-up clutch is maintained at a high differential pressure similar to that during normal lock-up. If this happens, when the wheel is locked due to sudden deceleration from the inertia running state, the release of the lock-up is delayed, and there is a possibility that engine stall may occur due to the locked wheel.

  For such a problem, Patent Document 1 discloses that a lockup clutch engagement differential pressure in a coast lockup state is lower than a normal lockup differential pressure for a lockup in a steady running state or slow acceleration. A technique for providing a coast lock-up differential pressure is disclosed.

For example, as illustrated in FIG. 2, the lockup clutch engagement differential pressure in steady running, that is, the normal-time lockup differential pressure is given as a large differential pressure that is close to the maximum differential pressure in order to avoid slipping of the lockup clutch. It is done. On the other hand, after the accelerator opening (for example, the accelerator pedal opening) is fully closed (for example, the idle switch is ON) and coasting is carried out, coast lock is sufficiently low as long as no judder of the lock-up clutch occurs. Controlled by differential pressure up. At the same time as the idle switch is turned ON, the differential pressure is changed stepwise to a slightly higher differential pressure than the final target coast lockup differential pressure, and then gradually decreased to finally the coast lockup differential pressure. And
JP-A-11-182672

  However, since the characteristic indicated by the solid line in FIG. 2 is the target value of the lockup clutch engagement differential pressure, and the actual oil pressure change occurs later than this, the lockup clutch actually acting on the lockup clutch After the idle switch is turned on, the engagement differential pressure decreases with a delay from the target, for example, as indicated by a broken line. Accordingly, in the period indicated by the region B in the figure, the lockup clutch engagement differential pressure is higher than the desired coast lockup differential pressure, so that if the vehicle stops and the wheels are locked due to sudden deceleration within this period, the engine There is a risk of stalling.

  According to the present invention, engine stall due to sudden deceleration during inertia running as described above is avoided by temporarily changing the lockup release rotational speed.

  That is, according to the present invention, in a predetermined steady running state of the vehicle, the torque converter is in a lockup state in which the input / output elements are directly connected by the lockup clutch, and in the inertial running state in which the accelerator opening is fully closed. The engagement differential pressure acting on the lock-up clutch is in a lock-up state in which the coast lock-up differential pressure is lower than the normal lock-up differential pressure in the normal running state, and the engine speed is equal to or less than a predetermined lock-up release speed. In the torque converter lock-up control device that releases the lock-up state when it becomes, the lock-up release speed is corrected to be high for a predetermined time after the accelerator opening is switched from the non-fully closed state to the fully closed state. It is characterized by doing.

  If the accelerator opening is fully closed while the vehicle is traveling in the lock-up state and the coasting state is shifted, the lock-up clutch engagement differential pressure is reduced from the normal lock-up differential pressure to the coast lock-up differential pressure. At the same time, the lockup release rotational speed is corrected to be high for a predetermined time. Then, when a predetermined time has elapsed, the rotation speed decreases to a predetermined lockup release rotational speed. In addition, when the engine speed decreases due to coasting and becomes equal to or lower than the lockup release speed, the lockup state is released. That is, the lockup clutch engagement differential pressure is released.

  Here, assuming that the engine speed has suddenly decreased in the lock-up state due to sudden deceleration immediately after the accelerator opening is fully closed, the lock-up release speed corrected to a high speed as described above. Release of the lock-up clutch engagement differential pressure is started at an early stage when the pressure reaches. Therefore, the lockup clutch is actually released before the engine speed decreases excessively, and the engine stall accompanying the wheel lock is avoided.

  On the other hand, if a certain amount of time has passed since the accelerator opening was fully closed, the lockup clutch engagement differential pressure has decreased to the predetermined coast lockup differential pressure, so normal lockup release rotation Even if the lock-up state continues until the number decreases, the lock-up clutch is released immediately after reaching the lock-up release speed, and the engine speed is not excessively reduced.

  The correction amount of the lockup release rotational speed is preferably set according to the normal lockup differential pressure when the accelerator opening is switched from the non-fully closed state to the fully closed state. In other words, the higher the previous normal lockup differential pressure, the higher the actual differential pressure during the transition to the coast lockup differential pressure. It is desirable to start unlocking earlier.

  It is desirable that the correction amount of the lockup release rotational speed is set so as to correspond to the maximum value of the normal lockup differential pressure. In this way, even if the correction amount is always a constant value, it is possible to reliably avoid engine stall.

  In addition, the length of time for performing the above-described correction of the lockup release rotation speed may be a fixed value, but the normal lockup when the accelerator opening is switched from the non-fully closed state to the fully closed state. It is desirable to set according to the differential pressure. In other words, the higher the previous normal lockup differential pressure, the longer the delay time until shifting to the coast lockup differential pressure. Is desirable.

  In the present invention, the engine fuel supply is stopped (so-called fuel cut) in the inertial running state where the accelerator opening is fully closed, and the engine speed is equal to or lower than a predetermined fuel cut recovery speed. A fuel cut control means for resuming fuel supply can be provided, and the lockup release rotational speed can be set as a value obtained by adding a predetermined margin rotational speed to the fuel cut recovery rotational speed.

  The fuel cut control means, for example, executes the fuel supply stop of the engine on the condition that the engine speed when the accelerator opening is fully closed is equal to or higher than a predetermined fuel cut-in speed. Although configured, in such a case, the lock-up release rotation speed after correction may be limited so as not to exceed the fuel cut-in rotation speed. That is, the upper limit of the lockup release rotational speed is limited to the fuel cut-in rotational speed or less. By limiting in this way, the fuel cut is more reliably executed in the lock-up state at the time of deceleration, which is advantageous in terms of fuel consumption. It should be noted that it is more preferable to limit the lockup release rotational speed only when the deceleration of the vehicle is small.

  According to the present invention, even if a sudden deceleration occurs immediately after the accelerator opening is fully closed and the vehicle shifts to coasting in the lock-up state, the lock-up release is performed before the engine speed decreases excessively. This completes the engine stall due to the wheel lock.

  FIG. 1 is a configuration explanatory view showing a system configuration of a lockup control device according to the present invention, in which a crankshaft of an engine 1 is connected to an automatic transmission 2 via a torque converter 3 as a vehicle drive system. ing. In this embodiment, the automatic transmission 2 is, for example, a 5-speed stepped transmission provided with a planetary gear type auxiliary transmission mechanism, but it is of course possible to combine it with a continuously variable transmission such as a belt type. . The automatic transmission 2 has a known configuration, and includes a hydraulic circuit unit 4 constituting an oil passage for switching various fastening elements and a plurality of solenoid valves 6 that perform hydraulic control thereof in response to control signals. Thus, gear shifting is performed by a control signal from the transmission controller 7 in accordance with the driving state (mainly vehicle speed and accelerator pedal opening).

  The torque converter 3 includes a lockup clutch 3 a that can directly connect a pump impeller as an input element and a turbine as an output element. The lockup clutch 3 a is continuously controlled by duty control of the lockup solenoid 5. Is engaged / released in accordance with a differential pressure (lockup clutch engagement differential pressure) between an apply pressure and a release pressure that are variably controlled.

  In this embodiment, an engine controller 14 for performing various controls such as fuel injection and ignition of the engine 1 is provided separately from the transmission controller 7. However, the engine controller 14, the transmission controller 7, Transmits / receives necessary signals to each other. As sensors, an accelerator opening sensor 8 that detects the opening of the accelerator pedal of the vehicle, a vehicle speed sensor 9 that detects the vehicle speed, an engine speed sensor 10 that detects the rotation speed of the engine 1, and a turbine rotation of the torque converter 3 The turbine speed sensor 11 that detects the number (that is, the speed of the input shaft of the automatic transmission 2), the brake switch 12 that indicates the depression of the brake pedal of the vehicle, and the throttle valve (not shown) of the engine 1 are fully closed. An idle switch 13 indicating that this is the case, and a water temperature sensor 15 for detecting the cooling water temperature of the engine 1 are provided. In this embodiment, it is determined that the accelerator opening is fully closed when the idle switch 13 is ON. However, a similar determination may be made from the detection signal of the accelerator opening sensor 8.

  Next, the control of the lockup clutch 3a in the above configuration will be described.

  As described above, the differential pressure applied to the lock-up clutch 3a, that is, the lock-up clutch engagement differential pressure, can be variably controlled by the duty control of the lock-up solenoid 5, whereby the torque converter 3 is locked up and unlocked. The state can be switched, that is, the engagement / release of the lock-up clutch 3a can be switched, and at the same time, an appropriate lock-up clutch engagement differential pressure can be obtained even with the same lock-up control. Basically, as shown in FIG. 2, in the lock-up state when the vehicle is traveling in a steady running state or a slow acceleration state, the maximum differential pressure is almost set to avoid slipping of the lock-up clutch 3a. It is given as a near large differential pressure (normally lock-up differential pressure P1). On the other hand, while the idle switch 13 is ON and coasting, the transmission torque required for the lockup clutch 3a is small, and from the viewpoint of reducing the hydraulic response delay for the subsequent lockup release command, The pressure is controlled to a sufficiently low differential pressure (coast lockup differential pressure P2) as long as judder of the up clutch does not occur. More specifically, at the same time when the idle switch 13 is turned on, the differential pressure is changed stepwise to a slightly higher pressure than the final target value, the coast lock-up differential pressure P2, and then gradually decreased to the final target value. Specifically, the coast lockup differential pressure P2 is set. As described above, the actual differential pressure changes as shown by the broken line due to the response delay of the hydraulic pressure. The A region in the figure shows the period when the coast lock-up differential pressure P2 has converged, and the B region is the period in which a differential pressure still larger than the target coast lock-up differential pressure P2 still remains.

  Next, lock-up and fuel cut during deceleration will be described with reference to FIG.

  FIG. 3 illustrates a case where the brake pedal is depressed (the brake switch 12 is turned on) immediately after the driver releases the accelerator pedal and the idle switch 13 is turned on. A decrease in engine speed and turbine speed indicates a relatively slow deceleration state. Further, in this example, it is assumed that the engine speed is higher than a predetermined fuel cut-in speed at the start of deceleration, and a predetermined delay time (F / C delay) has elapsed after the idle switch 13 is turned on. The fuel cut of the engine 1 is executed from the time when it has elapsed. The F / C flag in the figure indicates that this fuel cut is being executed. At the start of deceleration, the lock-up clutch 3a is in a lock-up state, and coasting is performed with the lock-up state. The L / U flag indicates that the transmission controller 7 is controlling as a lock-up state. As described above, when the idle switch 13 is turned on, the lockup differential pressure is controlled to decrease toward the coast lockup differential pressure P2. The L / U prohibition flag is a signal on the engine controller 14 side, and a lockup prohibition signal is output from the engine controller 14 side to the transmission controller 7 side while the flag is ON. At the start of deceleration in the figure, the L / U prohibition flag is OFF.

  “TNR” in the figure indicates the fuel cut recovery rotational speed at which the fuel supply is resumed. In the illustrated example, it is, for example, about 900 rpm. The fuel cut-in rotation speed TNJC and the fuel cut recovery rotation speed TNR are set according to the coolant temperature detected by the water temperature sensor 15, as shown in FIG.

  “DLURPM” is the lockup release rotation speed, and the lockup release is performed when the engine rotation speed is equal to or lower than the lockup release rotation speed DLURPM. This lockup release rotational speed DLLUPM is set as a value obtained by adding a predetermined margin rotational speed MR to the fuel cut recovery rotational speed TNR at that time. The margin rotational speed MR takes into account a response delay at the time of unlocking, and is, for example, a value of about 50 to 75 rpm.

  As shown in the figure, since the vehicle is coasting with fuel cut and the brake pedal is depressed, the engine speed gradually decreases with the turbine speed, and eventually, at the point indicated by a circle (time t1), Reach the lockup release speed DLRUPM. At this time, the L / U prohibition flag of the engine controller 14 is turned ON, and a lockup prohibition signal is output to the transmission controller 7. In response to this lockup prohibition signal, the transmission controller 7 turns off the L / U flag at time t2 and starts the lockup release, that is, the release of the lockup clutch engagement differential pressure via the lockup solenoid 5.

  When the actual lock-up clutch 3a is disengaged from the reversal of the L / U flag to OFF, there is a delay in the hydraulic system or the like, and the engine speed and the turbine speed are separated at time t3. That is, the period from t2 to t3 is a period during which the lock-up clutch 3a is dragged. At time t4, the engine speed reaches the fuel cut recovery speed TNR, the F / C flag is turned OFF, and the fuel supply to the engine 1 is resumed. Note that the resumption of fuel supply is when the difference between the engine speed and the turbine speed exceeds a predetermined value (determination of actual lockup release), or the engine speed falls below the fuel cut recovery speed TNR. The case is initiated by any of the conditions.

  In the example of FIG. 3, at the stage of time t2, the above-described region A is reached, and the lockup clutch engagement differential pressure is sufficiently reduced to the predetermined coast lockup differential pressure P2. The actual disconnection is performed quickly and no engine stall occurs.

  On the other hand, if the driver depresses the brake pedal strongly, for example, when a large deceleration occurs in the above-described region B, the engine speed may drop sharply in the locked-up state, possibly causing an engine stall. . Therefore, in the present invention, as shown in the figure, the lockup release rotational speed DLURPM is corrected to be high for a predetermined time after the idle switch 13 is turned on. Specifically, the margin rotation speed MR is corrected to be high, and thereby the lockup release rotation speed DLURPM is temporarily set to be high. In the slow deceleration as in the example of FIG. 3, the correction of the lockup release rotational speed DLRUPM does not affect the behavior of each part.

  4 and 5 show time charts in the case of the rapid deceleration in the B region as described above. In particular, FIG. 4 shows the case where the correction of the lockup release rotational speed DLURPM of the present invention is not performed. FIG. 5 shows an example when the lockup release rotational speed DLURPM of the present invention is corrected.

  First, FIG. 4 will be described. In the example of FIG. 4, after the idle switch 13 is turned on, the driver decelerates rapidly, for example, when the driver depresses the brake pedal strongly. Decreases to the lockup release rotational speed DLRPM. At this time, the L / U prohibition flag of the engine controller 14 is turned ON, and a lockup prohibition signal is output to the transmission controller 7. In response to this lockup prohibition signal, the transmission controller 7 turns off the L / U flag at time t2 and starts the lockup release, that is, the release of the lockup clutch engagement differential pressure via the lockup solenoid 5. However, at this stage, as described above, the lockup clutch engagement differential pressure is not sufficiently reduced to the predetermined coast lockup differential pressure P2, and the actual engagement differential pressure is relatively high. There is a large delay from the reversal of the L / U flag to OFF until the actual release of the lockup clutch 3a, and the lockup clutch 3a is dragged until time t3. Then, before this time t3, the engine speed reaches the fuel cut recovery speed TNR at time t4, the F / C flag is turned OFF, and the fuel supply of the engine 1 is resumed.

  Therefore, the engine speed may be lower than the fuel cut recovery speed TNR in the locked-up state, and engine stall may occur. In addition, there is a problem that a large torque shock occurs as a result of resuming the fuel supply in the lock-up state.

  On the other hand, in the example of FIG. 5, the engine speed rapidly decreases and reaches the lockup release rotational speed DLURPM during the period in which the lockup release rotational speed DLURPM is corrected to be high. The time point (time t1) at which the L / U prohibition flag is turned ON is relatively earlier than in the case of FIG. With this L / U prohibition flag, a lockup prohibition signal is output to the transmission controller 7, and the transmission controller 7 receives this lockup prohibition signal. At time t2, the L / U flag is turned OFF, and the lockup solenoid 5 Then, the lockup release, that is, the release of the lockup clutch engagement differential pressure is started.

  When the actual lockup clutch 3a is disengaged from the reverse of the L / U flag to OFF, there is a relatively large delay as in the case of FIG. 4, but since the lockup prohibition signal is output early, the engine speed and At the stage of time t3 when the turbine speed actually deviates, the engine speed is still higher than the fuel cut recovery speed TNR. At time t4, the engine speed reaches the fuel cut recovery speed TNR, the F / C flag is turned OFF, and fuel supply to the engine 1 is resumed. Therefore, in this case, the lockup is actually released before the fuel cut recovery speed TNR is reached, so that an excessive decrease in the engine speed is avoided and the fuel supply is resumed in the lockup released state. Torque shock is avoided.

  Next, specific control processing will be described based on the flowcharts of FIGS.

  FIG. 7 shows a routine of a timer calculation process for setting a time T for performing correction from the starting point of inertial running, and this routine is repeatedly executed at regular time intervals (for example, every 10 ms). First, in step 1, the state of the idle switch 13 is read. In step 2, it is determined whether the idle switch 13 is ON. If the idle switch 13 is OFF, the process proceeds to step 3 to clear the timer value. If the idle switch 13 is ON, the process proceeds to step 4 to determine whether the idle switch 13 was also ON in the previous time. If NO here, it means that the idle switch 13 has been reversed from OFF to ON, so the process proceeds to step 5 to obtain a correction time T corresponding to the lock-up clutch engagement differential pressure at that time, and this is set to the timer. Is set as the initial value T. The initial value T is set to a larger value as the lockup clutch engagement differential pressure at that time is larger. In step 6, the state of the idle switch 13 (whether it is ON or OFF) is stored.

  If “YES” in the step 4, the inertial running is continued, so the process proceeds to a step 7, and the timer value is gradually subtracted from the initial value T. As will be described later, the lockup release rotational speed DLURPM is corrected until the value of the timer becomes zero.

  FIG. 8 shows a margin rotation speed calculation processing routine for obtaining a correction amount of the lockup release rotation speed DLURPM, more specifically, a value of the margin rotation speed MR. This routine is also repeatedly executed at regular intervals (for example, every 10 ms). First, at step 11, the basic margin rotational speed MR and timer values at that time are read. Next, at step 12, the correction amount ΔMR of the margin rotational speed MR is set according to the lockup clutch engagement differential pressure at that time (when the idle switch 13 is reversed from OFF to ON). The correction amount ΔMR is set to a larger value as the lockup clutch engagement differential pressure is larger. Since the maximum value that the lockup clutch engagement differential pressure can take is determined in advance, the largest value corresponding to the maximum engagement differential pressure may be set as the correction amount ΔMR. Next, in step 13, it is determined whether the timer value is not 0. If the timer value has not reached 0, the process proceeds to step 14 to obtain a value obtained by adding the correction amount ΔMR to the basic margin rotation speed MR. It is set as the margin rotation speed MR after correction. As will be described later, the corrected margin rotational speed MR may be limited by an upper limit value.

  FIG. 9 shows a routine for performing arithmetic processing for outputting a lockup prohibition signal. This routine is also repeatedly executed at regular intervals (for example, every 10 ms). First, at step 21, the engine speed, the state of the idle switch 13, the cooling water temperature, the fuel cut recovery rotational speed TNR, the margin rotational speed MR, etc. are read, and at step 22, it is determined whether or not the idle switch 13 is ON. . If the idle switch 13 is OFF, the process proceeds to step 23 to determine whether the coolant temperature is lower than a predetermined value A. The predetermined value A is determined from the viewpoint of ensuring the performance of an exhaust gas purification system using a catalyst (not shown). If the water temperature is lower than the predetermined value A, the lockup is not performed, and the lockup is performed in step 24. Prohibit signal is output.

  If it is determined in step 22 that the idle switch 13 is ON, the process proceeds to step 25 to determine whether the coolant temperature is lower than the predetermined value B. The predetermined value B is determined from the viewpoint of the stability of the engine 1. If the water temperature is lower than the predetermined value B, lockup is not performed and a lockup prohibition signal is output in step 24. If the water temperature is equal to or higher than the predetermined value B, the process proceeds to step 26, and the rotation speed obtained by adding the margin rotation speed MR to the fuel cut recovery rotation speed TNR, that is, the lockup release rotation speed DLRUPM is compared with the engine rotation speed at that time. To do. If the engine speed is lower than the lockup release speed DLRUPM, the routine proceeds to step 24 where a lockup prohibition signal is output.

  By the processing shown in the above flowchart, as described with reference to FIG. 5, the lockup release rotational speed DLLUPM is set higher by the correction amount ΔMR for a predetermined time T after the idle switch 13 is turned on, and the actual engine speed When the number falls below the lockup release rotational speed DLRPM, the lockup release is started.

  Next, an embodiment in which the upper limit of the margin rotation speed MR corrected in step 14 is limited will be described with reference to FIGS.

  FIG. 10 shows a routine of processing for obtaining the upper limit value of the margin rotation speed MR. This routine is also repeatedly executed at regular intervals (for example, every 10 ms). In step 31, the fuel cut recovery rotation speed TNR and the fuel cut-in rotation speed TNJC are read from the characteristic map shown in FIG. 6, and in step 32, the difference between them (TNJC-TNR) is calculated as the margin rotation speed upper limit. Value.

  FIG. 11 shows a margin rotation speed calculation process routine similar to that in FIG. 8, and the processes in steps 11 to 14 are not particularly different from those in FIG. 8 described above. That is, in step 11, the basic margin rotational speed MR, the margin rotational speed upper limit value, and the timer value at that time are read, and in step 12, the correction amount ΔMR of the margin rotational speed MR is set to the lockup clutch engagement difference at that time. Set according to pressure. Next, in step 13, it is determined whether the timer value is not 0. If the timer value has not reached 0, the process proceeds to step 14 to obtain a value obtained by adding the correction amount ΔMR to the basic margin rotation speed MR. It is set as the margin rotation speed MR after correction. In this embodiment, it is determined in step 15 whether the corrected margin rotational speed MR exceeds the margin rotational speed upper limit value. If the margin rotational speed upper limit value is less than the margin rotational speed upper limit value, the corrected value in step 14 is used as it is. . On the other hand, if it exceeds the margin rotation speed upper limit value, the routine proceeds to step 16, where the margin rotation speed upper limit value is used as the margin rotation speed MR.

  As a result of such processing, as shown in FIG. 12, even if the lockup release rotational speed DLLUPM is obtained as indicated by a broken line by adding the correction amount ΔMR, the fuel cut-in rotational speed TNJC is indicated by a solid line. The fuel cut-in speed TNJC is not exceeded. By limiting in this way, the fuel cut is more reliably executed in the lock-up state at the time of deceleration, which is advantageous in terms of fuel consumption. Note that it is more preferable to determine the deceleration of the vehicle and add the upper limit of the margin rotational speed MR only when the deceleration is small.

Explanatory drawing which shows the system configuration | structure of the lockup control apparatus which concerns on this invention. The time chart which shows the change of lockup clutch fastening differential pressure when it transfers to inertial running. The time chart which shows the rotation speed change etc. at the time of slow deceleration. The time chart which shows the rotation speed change at the time of sudden deceleration when not performing correction | amendment of this invention. The time chart which shows the rotation speed change at the time of sudden deceleration at the time of performing correction | amendment of this invention. The characteristic diagram of fuel cut-in rotation speed TNJC and fuel cut recovery rotation speed TNR. The flowchart which shows the routine of a timer calculation process. The flowchart which shows the routine of the calculation process of margin rotation speed MR. The flowchart which shows the routine of the output process of a lockup prohibition signal. The flowchart of the process which calculates | requires a margin rotation speed upper limit. FIG. 9 is a flowchart similar to FIG. 8 showing an embodiment in which the upper limit of the margin rotation speed MR is limited. The time chart which shows the example which restrict | limited the upper limit of the margin rotation speed MR.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Automatic transmission 3 ... Torque converter 3a ... Lock-up clutch 7 ... Transmission controller 14 ... Engine controller

Claims (6)

In the predetermined steady state of the vehicle, the torque converter is in a lockup state in which the input / output elements are directly connected by the lockup clutch, and in the inertial state in which the accelerator opening is fully closed, the torque converter acts on the lockup clutch. Lock-up when the engagement differential pressure is set to the lock-up state with a coast lock-up differential pressure lower than the normal-time lock-up differential pressure in the steady running state, and the engine speed is equal to or lower than the predetermined lock-up release speed. In the torque converter lock-up control device for releasing the state,
A lockup control device for a torque converter, wherein the lockup release rotational speed is corrected to be high for a predetermined time after the accelerator opening is switched from a non-fully closed state to a fully closed state.   2. The correction amount of the lockup release rotational speed is set according to a normal lockup differential pressure when the accelerator opening is switched from a non-fully closed state to a fully closed state. A lockup control device for a torque converter according to claim 1.   The lockup control device for a torque converter according to claim 1, wherein the correction amount of the lockup release rotational speed is set so as to correspond to the maximum value of the normal lockup differential pressure.   The length of time for performing the above-described correction of the lockup release rotational speed is set according to the normal lockup differential pressure when the accelerator opening is switched from the non-fully closed state to the fully closed state. The lockup control device for a torque converter according to any one of claims 1 to 3.   Fuel cut control means for stopping the fuel supply of the engine when the accelerator opening is fully closed and stopping the fuel supply when the engine speed falls below a predetermined fuel cut recovery speed. 5. The torque converter lockup according to claim 1, wherein the lockup release rotational speed is set as a value obtained by adding a predetermined margin rotational speed to the fuel cut recovery rotational speed. Control device. The fuel cut control means is configured to execute engine fuel supply stop on condition that the engine speed when the accelerator opening is fully closed is equal to or higher than a predetermined fuel cut-in speed. 6. The lockup control device for a torque converter according to claim 5, wherein the corrected lockup release rotational speed is limited so as not to exceed the fuel cut-in rotational speed.

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