JP2008014254A - Control system of automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control system of an automatic transmission by which a gear is downshifted in a short time without causing a transmission shock. <P>SOLUTION: In the downshift of the automatic transmission, rotational speed of the input shaft of the transmission is increased by operating a means for increasing the rotation which increases engine output torque by increasingly correcting a throttle opening angle. In the operation of the rotational speed-increasing means, time required for an actual rotational speed of the input shaft to reach a command input rotational-speed is predicted, and the operation of the rotational speed-increasing means is continued until the predicted time reaches a time less than a threshold. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an automatic transmission control device, and more particularly to a technique for reducing a shift shock during downshifting.

Japanese Patent Application Laid-Open No. H10-260260 discloses that a shift shock associated with a downshift is reduced by increasing the engine output torque by controlling the throttle opening when the automatic transmission is downshifted.
JP 2004-137907 A

However, the end timing of the engine output torque increase control at the time of the conventional downshift is set at the start of engagement of the gear clutch after the downshift (at the start of the increase in turbine rotation), so the engine rotation speed (speed change) The input shaft rotation speed of the machine could not be sufficiently increased, and there was a possibility of giving the driver a feeling of extension during the shift.
The present invention has been made in view of the above problems, and at the time of downshift, control for positively increasing the input shaft rotation speed of the transmission is executed for as long a time as possible without generating a shift shock. The purpose is to shorten the shift time.

Therefore, the invention according to claim 1 is directed to a control device for an automatic transmission that operates rotation increasing means for increasing the input shaft rotation speed when the automatic transmission is downshifted. A time until the shaft rotational speed is reached is predicted, and the operation of the rotation raising means is stopped based on the predicted time.
According to the above invention, the time required for the actual input shaft rotational speed to increase to the target input shaft rotational speed after the shift from that time is sequentially predicted, and the operation of the rotation increasing means is stopped based on the predicted time. Determine whether or not.

Therefore, the operation of the rotation raising means can be stopped at a fixed timing before the actual input shaft rotation speed reaches the target input shaft rotation speed after the shift, and it is avoided that the rotation raising means is kept operating excessively. However, it is possible to shorten the shift time by operating the rotation raising means for as long as possible.
The target on-axis rotation speed after the shift can be estimated from the shift stage (gear ratio) after the downshift and the vehicle speed at that time.

According to the second aspect of the present invention, it is necessary to reach the target input shaft rotation speed after the shift from the target input shaft rotation speed after the shift, the actual input shaft rotation speed, and the change speed of the actual input shaft rotation speed. The time is predicted, and when the predicted time becomes less than the threshold, the operation of the rotation raising means is stopped.
According to the above invention, the time required for changing the rotational speed difference between the target input shaft rotational speed after the shift and the actual input shaft rotational speed is obtained based on the change speed of the input shaft rotational speed at that time. The time required for the actual input shaft rotational speed to reach the post-shift target input shaft rotational speed from that point is predicted.

Then, when the time required to reach the predicted target on-axis rotation speed becomes less than the threshold value, the operation of the rotation raising means is stopped.
Therefore, since the operation of the rotation increasing means can be continued until a predetermined time before reaching the target input shaft rotation speed, the increase of the input shaft rotation speed is accelerated and the downshift is performed while avoiding the occurrence of a shift shock. Time can be shortened.

The invention according to claim 3 is characterized in that the threshold value is variably set according to the temperature and / or oil pressure of the hydraulic oil of the automatic transmission.
According to the above invention, in response to the difference in the response of the speed change operation depending on the temperature of the hydraulic oil of the automatic transmission, when the time to reach the target input shaft rotational speed is reached, Change whether to stop operation.

  Further, since the hydraulic pressure (line pressure) of the automatic transmission is generally controlled to a pressure corresponding to the running state (for example, the input shaft torque of the automatic transmission), the running state (for example, automatic) determined from the hydraulic pressure (line pressure). Depending on the difference in shift shock reduction request due to the difference in the input shaft torque of the transmission, etc., it is changed how long it takes to reach the target input shaft rotational speed when the operation of the rotation raising means is stopped.

  Therefore, the operation of the rotation raising means can be stopped at an optimal timing according to the temperature and / or hydraulic pressure of the hydraulic oil of the automatic transmission, and the hydraulic oil temperature (responsiveness of the shift operation) and hydraulic pressure (input shaft) Even if the conditions of (torque) are different, it is possible to shorten the shift time to the maximum by speeding up the rotation while reducing the shift shock.

Embodiments of the present invention will be described below.
FIG. 1 shows a power train system for a vehicle including a control device for an automatic transmission according to the present invention.
In FIG. 1, torque generated by an engine (internal combustion engine) 1 mounted on a vehicle is transmitted to driving wheels (not shown) via an automatic transmission 2.

The intake pipe 11 of the engine 1 is provided with an electric throttle 12 that opens and closes a butterfly throttle valve with a throttle motor, and the electric throttle 12 is controlled by an engine control unit (ECU) 13. The output torque of the engine 1 is controlled.
The automatic transmission 2 includes a torque converter 21 whose pump side is connected to the output shaft of the engine 1, a gear-type transmission 22 connected to the turbine side of the torque converter 21, and each of the transmissions 22. And a hydraulic control mechanism 23 that performs an engagement / release operation of a speed change element (such as a clutch).

The hydraulic control mechanism 23 controls the hydraulic pressure applied to the various speed change elements with a solenoid so as to switch the engagement / release state of the various speed change elements so that the gear position can be switched from the first speed to the fourth speed. It has become.
The hydraulic control mechanism 23 is controlled by an automatic transmission control unit 24 (ATCU).

The engine control unit 13 and the automatic transmission control unit 24 each include a microcomputer, and are configured to be able to communicate with each other via a communication line 31.
In addition, detection signals from various sensors are input to the control units 13 and 24.

The various sensors include an accelerator opening sensor 51 that detects an accelerator pedal depression amount APO operated by a vehicle driver, a crank angle sensor 52 that outputs a signal synchronized with the rotation of the crankshaft of the engine 1, and the automatic A vehicle speed sensor 53 that detects a vehicle traveling speed (vehicle speed) VSP from rotation of an output shaft of the transmission 2; a turbine sensor 54 that detects a turbine rotational speed Nt of the torque converter 21 (an input shaft rotational speed of the transmission 22); An air flow meter 55 for detecting the intake air flow rate of the engine 1 is provided.

Information detected by the various sensors and various control information are shared by the engine control unit 13 and the automatic transmission control unit 24 by mutual communication via the communication line 31, and coordinated control by the control units 13 and 24 is performed. Is possible.
In the automatic transmission mode, the automatic transmission control unit 24 determines the target gear position according to the accelerator opening APO and the vehicle speed VSP, and in the manual transmission mode, the automatic transmission control unit 24 determines the target transmission speed according to the driver's shift lever operation. When the actual shift speed at that time is different from the target shift speed, the generation of a shift request is determined, and the hydraulic control mechanism 23 (solenoid) is controlled to shift to the target shift speed.

Also, when downshifting during deceleration, etc., the engine rotation (input shaft rotational speed of the transmission 22) is blown up, and the shift is completed in synchronization with the rotational speed that matches the gear position after the downshift. By doing so, the engine control unit 13 and the automatic transmission control unit 24 perform the control for reducing the shift shock in cooperation with each other.
The flowchart of FIG. 2 shows the details of the control for reducing the shift shock during the downshift.

The routine shown in the flowchart of FIG. 2 is executed every predetermined minute time Δt. First, in step S11, the latest value Ntnew of the turbine rotational speed Nt detected by the turbine sensor 54 and the turbine rotational speed at the previous execution of this routine are executed. A change speed ΔNt (ΔNt = (Ntnew−Ntold) / Δt) of the turbine rotational speed Nt is calculated from Ntold.
When the turbine sensor 54 is not provided, the engine rotation speed detected by the crank angle sensor 52 can be used instead of the turbine rotation speed.

In step S12, for example, it is determined whether or not the target shift speed is changed to a lower speed side with a decrease in the vehicle speed, and a downshift request is being generated.
If the downshift determination is not in progress, the control for reducing the shift shock is unnecessary, and the routine is terminated as it is.
On the other hand, if downshift determination is in progress, the process proceeds to step S13 and subsequent steps to execute control for reducing shift shock.

When the downshift determination is made, normal shift control is performed. For example, when downshifting from the 3rd speed to the 2nd speed, as shown in FIG. The fastening pressure is reduced stepwise and then gradually reduced.
In step S13, from the current vehicle speed VSP detected by the vehicle speed sensor 53 and the target gear position (the gear ratio after the downshift) in the current downshift, the turbine rotational speed NtD (the target on-axis rotation after the shift) after the shift. Speed).

In step S14, the deviation between the turbine rotational speed NtD after the shift and the current turbine rotational speed Nt is divided by the change speed ΔNt, so that the turbine rotational speed Nt reaches the turbine rotational speed NtD after the shift from the present time. The time tc required to do is predicted (tc = (NtD−Nt) / ΔNt).
In step S15, it is determined whether the time tc is less than a threshold th.

When the time tc is equal to or greater than the threshold th, it still takes time for the actual turbine rotation speed Nt to reach the turbine rotation speed NtD after the shift, and control for increasing the turbine rotation speed Nt is continued. Thus, it is determined that the shift time can be shortened, and the process proceeds to step S16.
On the other hand, when the time tc is less than the threshold value th, the time until the actual turbine rotation speed Nt reaches the turbine rotation speed NtD after the shift is short, and control for increasing the turbine rotation speed Nt after the present time. Is stopped, the control for increasing the turbine rotation is continued excessively. On the contrary, it is determined that there is a possibility of increasing the shift shock, and the routine proceeds to step S18.

Here, the threshold value th may be a fixed value stored in advance. Of the hydraulic oil (ATF) temperature, the line pressure (input shaft torque of the transmission), and the change speed ΔNt of the automatic transmission 2. It can be variably set according to at least one.
When the temperature of the hydraulic oil (ATF) of the automatic transmission 2 is high and the viscosity of the hydraulic oil (ATF) is low, the hydraulic control mechanism 23 can operate with a high response, and when the temperature is low In comparison, the shift can be completed in a short time.

Therefore, even if the operation of the rotation raising means is stopped after sufficiently approaching the turbine rotational speed NtD after the shift, the shift can be completed smoothly from the rotation state at that time.
On the other hand, when the temperature of the hydraulic oil (ATF) of the automatic transmission 2 is low and the viscosity is high, it takes time to complete the gear shift. Therefore, after the turbine rotation speed Nt has sufficiently approached the turbine rotation speed NtD after the shift. If the operation of the rotation raising means is stopped, the rotation speed is greatly lowered, and then the rotation rise is promoted by the shift operation, which may cause a large shift shock.

Therefore, in this embodiment, the higher the operating oil (ATF) temperature is, the shorter the threshold th is changed (see FIG. 3), and when the operating oil (ATF) temperature is higher, the turbine rotational speed NtD after the shift is changed. Then, the operation of the rotation raising means is stopped.
In addition, when the line pressure is set to be relatively low because the input shaft torque of the transmission 22 is low, the driver is sensitive to shock because there is no large torque change, but the transmission 22 When the line pressure is set to be relatively high because the input shaft torque is high, the driver tends to allow a shock because it is a condition that a large torque change can occur.

Therefore, the lower the line pressure (input shaft torque), the longer the threshold th (see FIG. 4), so that the control for increasing the turbine rotation is stopped earlier, thereby increasing the shift time. However, the shift shock will be reduced.
Furthermore, the faster the change rate ΔNt, the higher the possibility of excessively increasing the turbine rotation, so the threshold th is changed greatly.

In step S16, by increasing corrects the target throttle opening TVO from the value TVO _AC corresponding to the normal accelerator opening degree to a predetermined value TVO _D, the engine output torque by increasing the intake air amount of the engine 1 The engine rotation (the input shaft rotation speed of the transmission 22) is blown up.
The increase correction of the engine output torque by the increase correction of the throttle opening TVO corresponds to the rotation increasing means in this embodiment.

In the increase correction of the throttle opening TVO, the opening correction amount (torque increase amount) can be feedback controlled based on the target turbine rotation speed, and the opening correction amount (torque increase amount) It can be variably set based on the engine speed at the time and the gear position after the shift.
Further, when the intake air amount of the engine is controlled by the opening characteristic (opening / closing timing and / or lift amount) of the intake valve, the intake valve opening characteristic is changed to the intake air amount instead of the correction control of the throttle opening TVO. Can be corrected in the direction of increasing.

Further, the rotation increasing means is not limited to a means for increasing and correcting the intake air amount. For example, the rotation increasing means may be a means for increasing the engine output torque by correcting the air-fuel ratio or the ignition timing, or the transmission 22. Can be temporarily neutralized or shifted to a lower speed than the gear position after downshifting to increase the rotation.
And these rotation raising means may be operated independently, and a plurality of rotation raising means can be combined and operated simultaneously or with a time difference set.

In the control for setting the neutral state to increase the rotation, it is not necessary to reduce the transmission torque capacity of each transmission element of the transmission 22 to 0 to achieve the complete neutral state, or control toward the neutral state, or The transmission torque capacity may be reduced by switching to a state close to neutral.
As described above, when the rotation increasing means is operated and the time tc predicted to reach the turbine rotational speed NtD after the shift at the increasing speed at this time becomes less than the threshold th, the process proceeds from step S16 to step S17.

In step S17, processing for stopping the operation of the rotation raising means is executed. That is, when the throttle opening TVO is corrected to increase, the throttle opening TVO (engine output torque) is returned to the normal value based on the accelerator opening and the like, and the increase correction of the engine output torque is stopped.
In the next step S18, when the turbine rotational speed Nt coincides with the turbine rotational speed NtD, the hydraulic pressure is changed stepwise to achieve the hydraulic state after the downshift, and the shift operation is completed.

The time tc can be gradually changed from the time when the time tc becomes less than the threshold th to the hydraulic pressure command value after the shift at the time tc.
FIG. 5 shows a state during a downshift from the third speed to the second speed.
Increasing the換Ru cut the target shift speed third speed to the second speed by the vehicle speed decreases due to the deceleration in which the accelerator is fully closed, the target throttle opening TVO from the fully closed corresponding to the accelerator opening degree to a predetermined value TVO _D The rotation raising means for increasing the engine output torque is operated to increase the input shaft rotation speed (turbine rotation speed) of the transmission 22.

When the turbine rotational speed (the input shaft rotational speed of the transmission 22) starts to increase with the engine output torque increased, the time tc required for the actual turbine rotational speed Nt to reach the turbine rotational speed NtD. Until the time tc becomes less than the threshold value th, the engine output torque increasing state (the operating state of the rotation increasing means) is maintained.
When the time tc becomes less than the threshold th, the target throttle opening TVO is returned to the fully closed state corresponding to the accelerator opening (fully closed) at that time, and the third speed pressure (the friction engagement element at the third speed) is returned. The downshift from the 3rd speed to the 2nd speed is completed by stepwise decreasing the fastening pressure) from the current hydraulic pressure to the minimum value (0).

  As described above, the time tc required for the turbine rotational speed Nt (input shaft rotational speed) to reach the post-shift turbine rotational speed NtD is predicted from that point, and the rotation is continued until the time tc becomes less than the threshold th. If the operation of the ascending means is continued, the operation of the rotating ascending means can be continued as long as possible while avoiding a shift shock due to excessive operation of the rotating ascending means being continued. .

Accordingly, the turbine rotation speed Nt (input shaft rotation speed of the transmission 22) can be increased to the turbine rotation speed NtD after shifting (target input shaft rotation speed after shifting) at an early stage, thereby shortening the shifting time. (See FIG. 5).
Next, inventions other than those described in the claims that can be grasped from the above-described embodiment will be described together with the effects thereof.
(A) The automatic transmission according to any one of claims 1 to 3, wherein the rotation raising means is means for increasing engine output torque by increasing and correcting an intake air amount of the engine. Control device.

According to the above-described invention, for example, by increasing the throttle opening of the engine to increase the intake air amount of the engine, the engine output torque is increased, and the input shaft rotational speed of the transmission is positively increased during the downshift.
Therefore, it is possible to easily increase the input shaft rotation speed of the transmission during downshifting. (B) The rotation raising means is means for temporarily setting the speed of the transmission to a speed lower than the target speed or in a neutral state. The automatic transmission control device according to one of the above.

According to the above invention, during downshifting, the external load of the engine is reduced by temporarily shifting to a gear position that is lower than the target gear position of the downshift, or by temporarily setting to a neutral state. Increase the rotational speed of the input shaft.
Therefore, the input shaft rotation speed can be increased also by controlling the transmission. For example, with the increase correction of the intake air amount of the engine, the speed is shifted to a speed lower than the target speed or the neutral state. By doing so, it is possible to further increase the input shaft rotation speed.
(C) The control device for an automatic transmission according to claim 3, wherein the threshold is changed to be shorter as the temperature of the hydraulic oil is higher.

According to the above invention, since the temperature of the hydraulic oil is high and the viscosity of the hydraulic oil is low, the speed change operation can be completed in a short time under conditions where the automatic transmission can operate with good response. The operation of the rotation raising means is stopped after the time until the speed reaches the target on-axis rotation speed after shifting becomes shorter than that at low temperature.
Therefore, when the temperature of the hydraulic oil is high, it is possible to operate the rotation raising means for a longer time and further reduce the speed change time.
(D) The control apparatus for an automatic transmission according to claim 3, wherein the threshold value is changed to be shorter as the hydraulic pressure is higher.

  According to the above invention, for example, when the hydraulic pressure (line pressure) is set high because the input shaft torque is large, the tolerance for the shift shock is relatively high. Therefore, the shift time can be shortened by shortening the threshold value. On the other hand, when the hydraulic pressure (line pressure) is set low because the input shaft torque is low, the tolerance for shift shock is relatively low. It is made to advance so that the shift shock can be sufficiently suppressed.

  Therefore, the shift time can be shortened as much as possible without causing a shift shock that causes discomfort to the driver.

1 is a configuration diagram showing a power train system for a vehicle according to an embodiment of the present invention. The flowchart which shows the control at the time of the downshift in embodiment. The diagram which shows the correlation with the threshold value th and ATF temperature in embodiment. The diagram which shows the correlation with the threshold value th and line pressure in embodiment. The time chart for demonstrating the control at the time of the downshift of the 3rd speed-> 2nd speed in embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Automatic transmission, 11 ... Intake pipe, 12 ... Electric throttle, 13 ... Engine control unit (ECU), 21 ... Torque converter, 22 ... Transmission, 23 ... Hydraulic control mechanism, 24 ... Automatic transmission Machine control unit (ATCU), 51 ... accelerator opening sensor, 52 ... crank angle sensor, 53 ... vehicle speed sensor, 54 ... turbine sensor

Claims (3)

In the automatic transmission control device that operates the rotation raising means for raising the input shaft rotation speed during the downshift of the automatic transmission,
Control of an automatic transmission characterized by predicting a time until an actual input shaft rotational speed reaches a target input shaft rotational speed after shifting and stopping the operation of the rotation raising means based on the predicted time apparatus. The time required to reach the target input shaft rotation speed after the shift is sequentially predicted from the target input shaft rotation speed after the shift, the actual input shaft rotation speed, and the change speed of the actual input shaft rotation speed. 2. The control apparatus for an automatic transmission according to claim 1, wherein when the predicted time becomes less than a threshold, the operation of the rotation raising means is stopped. 3. The control apparatus for an automatic transmission according to claim 2, wherein the threshold value is variably set according to a temperature and / or a hydraulic pressure of hydraulic oil of the automatic transmission.

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