JP2008014421A - Automatic transmission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic transmission control device for actualizing down-shifting in a short time with no shift shock. <P>SOLUTION: During the down-shifting of an automatic transmission, when a turbine rotating speed (an input shaft rotating speed) starts rising, the speed of the hydraulic control of a friction engaging element is changed over to be higher. Then, when a time which may be required until a turbine rotating speed after shift is reached is shorter to be a predetermined time, the speed of the hydraulic control of the friction engaging element is changed over to be lower. When the turbine rotating speed reaches the turbine rotating speed after shift, the hydraulic pressure of the friction engaging element is stepwisely changed into a condition after shift. <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

By the way, in the control of the engagement pressure (hydraulic pressure) of the friction engagement element for shifting performed in parallel with the control for increasing the engine output torque, the engagement pressure changes rapidly to the engagement pressure corresponding to the gear position after the downshift. By doing so, the shift time can be shortened, but an excessively fast change in the engagement pressure causes a shift shock.
For this reason, conventionally, the change speed of the engagement pressure (hydraulic pressure) has to be set relatively slow in consideration of the allowance so that the shift shock does not occur even if the conditions are different. There was a problem that it could not be shortened sufficiently.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an automatic transmission control device capable of performing engagement pressure (hydraulic pressure) control capable of shortening the shift time to the maximum while avoiding the occurrence of a shift shock during downshifting. The purpose is to provide.

Therefore, the invention according to claim 1 sequentially predicts the time until the actual input shaft rotation speed reaches the target input shaft rotation speed after the shift at the time of downshift, and based on the predicted time, the friction coefficient for the shift is determined. It is characterized by changing the speed of the engagement / release control of the joint element.
According to the above invention, when the actual input shaft rotation speed changes toward the target input shaft rotation speed after the shift as the shift progresses, the time until the target input shaft rotation speed is reached from the current time is sequentially determined. By predicting the state of progress of the shift, the speed of the engagement / release control of the frictional engagement element for shifting, that is, the changing speed of the engagement pressure (hydraulic pressure) of the frictional engagement element is determined according to the progress state. change.

Therefore, the optimum control speed can be set according to the progress of the shift, and the shift shock can be reduced and the shift time can be reduced at a high level.
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, when the predicted time until the target on-axis rotation speed after the shift is reached is shortened to a predetermined time, the speed at which the shift frictional engagement element moves toward the engaged state after the shift is set. It is characterized by loosening.

According to the above invention, when the actual input shaft rotational speed is sufficiently close to the target input shaft rotational speed and the time required to reach the target is shortened to the predetermined time (the target input shaft rotational speed after the predetermined time). When it is predicted that the speed change frictional engagement element will be engaged or released, the speed at which the speed change frictional engagement element is engaged or released (speed toward the engaged state after the speed change) is made slower than before.
Therefore, until the actual input shaft rotation speed is sufficiently close to the target input shaft rotation speed, the engagement / release of the frictional engagement element is rapidly advanced to shorten the shift time while reaching the target input shaft rotation speed. The shift shock can be reduced by delaying the engagement / release of the frictional engagement element immediately before the friction engagement element is engaged.

In order to slow down the speed toward the engaged state after shifting, the change speed in the same direction as before is slowed, the change is stopped, and the change is temporarily changed in the reverse direction. Is included.
According to a third aspect of the present invention, when the actual input shaft rotation speed starts increasing, the speed of the frictional engagement element for speed change is increased toward the engaged state after the speed change, and then the predicted time is set to a predetermined time. When the speed becomes shorter, the speed of the speed change frictional engagement element is reduced at the speed toward the engaged state after the speed change.

According to the above invention, when the actual input shaft rotation speed starts to increase, it is determined that a substantial downshift (gear ratio change) has started, and the shift frictional engagement element is engaged after the shift (engaged) (Or release) faster than before.
As the shift proceeds, the predicted time until the actual input shaft rotation speed reaches the target input shaft rotation speed after the shift is shortened, and it is predicted that the target input shaft rotation speed will be reached after a predetermined time. At this point, the speed of the speed change frictional engagement element toward the engaged state (fastened or released) after the speed change is made slower than before.

  Accordingly, it is possible to prevent the occurrence of a shock by avoiding a sudden change in the gear ratio at the start of the change of the gear ratio and at the completion of the change, and to reduce the shift time by speeding up the change in the gear ratio.

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 a fastening / release operation of a speed change element (a friction engagement 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. First, in step S1, for example, the target gear stage is changed to a lower speed side as the vehicle speed decreases, and a downshift request is generated. It is determined whether it is in a state.
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 S2 and subsequent steps to execute control for reducing shift shock.
When the downshift determination is made, shift control (engagement / release control of the frictional engagement element for shift) is started. For example, when downshifting from the 3rd speed to the 2nd speed, as shown in FIG. After the third speed pressure (the engagement pressure of the frictional engagement element at the third speed) is decreased stepwise, control is performed to decrease it at a predetermined speed.

In step S2, 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 (see FIG. 3).
The predetermined value TVO _D may be variably set based on such transmission type and vehicle speed.

In step S3, it is determined whether or not the turbine rotation speed Nt (input shaft rotation speed) detected by the turbine sensor 54 has started to increase with the actual shift start (gear ratio change).
Specifically, the latest value Ntnew of the turbine rotation speed Nt detected by the turbine sensor 54.
And a time point at which the difference (change speed) between the turbine rotation speed Ntold and the turbine rotation speed Ntold before a predetermined time becomes equal to or higher than a predetermined value is determined as the rising start time.

If it is detected in step S3 that the increase in turbine rotational speed Nt has started, the process proceeds to step S4.
In step S4, the target throttle opening TVO is returned to the fully closed state corresponding to the accelerator opening (fully closed) at that time, thereby canceling the engine output torque increase control for the downshift (see FIG. 3). ).

In the next step S5, the speed of reduction of the 3rd speed pressure (release control speed) is switched to a speed faster than before, and the gradual decrease of the 3rd speed pressure is continued.
That is, after the third speed pressure is decreased stepwise to a predetermined value in response to a downshift request, the third speed pressure is decreased at the first speed, and when the start of an increase in the turbine rotational speed Nt is detected, Thereafter, the third speed pressure (engagement pressure) is decreased and changed at a second speed higher than the first speed.

In step S6, 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 rotation speed NtD (the target on-axis rotation after the shift) after the shift. Speed).
Further, in step S6, the difference between the turbine rotational speed NtD after the shift and the current turbine rotational speed Nt is divided by the change speed ΔNt of the current turbine rotational speed Nt, so that the turbine rotational speed Nt is A time tc required to reach the turbine rotational speed NtD after the shift is sequentially predicted every time this routine is executed (tc = (NtD−Nt) / ΔNt).

In step S7, it is determined whether or not the predicted time tc is less than a threshold th (predetermined time).
When the time tc is equal to or greater than the threshold value th, it still takes time for the actual turbine rotation speed Nt to reach the turbine rotation speed NtD after the shift. Therefore, by returning to step S6, the third speed pressure is relatively high. The current release control state that is decreasing and changing at the speed is continued as it is.

On the other hand, when the predicted 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 the third speed pressure is decreased and changed at a higher speed after the current time. If it continues, it will be judged that there exists a possibility of generating a shock, and it progresses to step S8.
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 the turbine rotation after the shift Even if the control is switched after approaching the speed NtD, it is possible to avoid the occurrence of a response delay, and the shift time can be further shortened by lengthening the period for controlling the frictional engagement element for shifting at a high speed as much as possible.

Therefore, in the present embodiment, the higher the operating oil (ATF) temperature, the shorter the threshold th is changed (see FIG. 4). When the operating oil (ATF) temperature is high, the turbine rotational speed NtD after the shift is increased. The speed of the engagement / release control of the friction engagement element is changed after approaching.
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) is, the longer the threshold th is (see FIG. 5), and the speed of the engagement / release control of the friction engagement element is switched earlier so that the speed change time becomes longer. 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 S8, the third speed pressure is maintained at the pressure at which the predicted time tc is determined to be less than the threshold th, or the comparison before the predicted time tc is determined to be less than the threshold th. The release control speed is switched so as to decrease at a speed slower than the fast decrease speed (see FIG. 3).
In addition, when it is determined that the predicted time tc is less than the threshold th, the control may be temporarily switched to the direction in which the friction engagement element is fastened (the direction in which the hydraulic pressure is increased) to delay the progress of the release. it can.

That is, when it is determined that the predicted time tc is less than the threshold value th, the speed of control (release control) toward the release state of the frictional engagement element for shifting is reduced, and in this state, the turbine rotation speed Nt is set to the target turbine speed. The rotational speed NtD is reached.
The control speed after the time point when the predicted time tc becomes less than the threshold th may be the same as the control speed in the control period before the increase change in the turbine rotation speed is detected.

In step S9, it is determined whether or not the turbine rotation speed Nt has reached the turbine rotation speed NtD after the shift.
When the turbine rotational speed Nt reaches the shifted turbine rotational speed NtD, the process proceeds to step S10, the third speed pressure is lowered to the minimum value stepwise to complete the release control, and the third speed → second speed downshift is performed. End.

  According to the above embodiment, since the speed of release control for shifting is increased from when the turbine rotation speed Nt starts to change until it approaches the turbine rotation speed NtD after the shift, the shift time is shortened. When the turbine rotation speed NtD after shifting is approached, the release control speed is reduced more than before, and the increase (gear ratio change) of the turbine rotation speed NtD is slowed down. it can.

  In the above embodiment, the case where the downshift is performed by the release control (hydraulic pressure decrease control) is taken as an example. However, even when the downshift is performed by the engagement control, the turbine rotation speed Nt starts to increase. Until the turbine rotational speed NtD after shifting is approached, the speed of the engagement control (hydraulic increase speed) for shifting is increased, and when the turbine rotational speed NtD after shifting is approached, the speed of the engagement control is higher than before. By relaxing (hydraulic pressure increasing speed), the same effect can be obtained.

  In the above embodiment, the end of the engine output increase is the time when the turbine rotation speed Nt starts to increase, but the end of the engine output increase can also be determined from the predicted time tc. When the time tc becomes less than the threshold th, it is possible to slow down the engagement / release control for downshifting and cancel the engine output increase (throttle opening increase correction) at the same time.

Further, the means for increasing the engine speed is not limited to increasing the engine output torque by correcting the increase in the throttle opening, but the engine output torque can be increased by correcting the air-fuel ratio, the ignition timing, and the like.
Furthermore, in the above embodiment, the control speed is switched when the predicted time tc becomes less than the threshold th. However, the predicted time tc is compared with a plurality of thresholds, and the control speed is switched based on the predicted time tc. It can be performed at multiple timings.

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) a rotation increasing means for increasing the input shaft rotation speed of the automatic transmission at the time of the downshift, and changing the speed of the engagement / release control of the frictional engagement element for shifting based on the predicted time; The control device for an automatic transmission according to any one of claims 1 to 3, wherein the operation / stop of the rotation raising means is controlled based on the predicted time.

According to the above invention, the operation / stop of the means for increasing the input shaft rotational speed of the automatic transmission by increasing the engine output torque or the like until the actual input shaft rotational speed reaches the target input shaft rotational speed after the shift. Control is based on the predicted time.
Accordingly, it is possible to set an optimum control speed according to the progress of the shift, and to effectively increase the rotation according to the progress of the shift.
(B) The control apparatus for an automatic transmission according to claim 2 or 3, wherein the predetermined time is changed according to a temperature and / or a hydraulic pressure of hydraulic oil of the automatic transmission.

According to the above invention, the control speed is reduced when the time required to reach the target input shaft rotational speed is reached in response to the difference in response of the speed change operation depending on the temperature of the hydraulic fluid of the automatic transmission. To change.
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). The amount of time required to reach the target input shaft rotation speed is changed depending on the difference in shift shock reduction demand due to the difference in the input shaft torque) of the transmission.

Therefore, the control speed of the frictional engagement element for shifting can be reduced at an optimal timing according to the temperature and / or hydraulic pressure of the hydraulic oil of the automatic transmission.
(C) The control apparatus for an automatic transmission according to (b), wherein the predetermined time is changed to be shorter as the temperature of the hydraulic oil of the automatic transmission 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 actual input shaft rotational speed is the target after the shift under the condition that the automatic transmission can operate with good response and can reduce the hydraulic pressure change. The control speed is relaxed after the time until the on-axis rotation speed is reached is shorter than that at low temperatures, and the control speed is continued as fast as possible to shorten the shift time.
(D) The control apparatus for an automatic transmission according to claim (b), wherein the predetermined time is changed shorter as the hydraulic pressure in the automatic transmission 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, so the shift time is shortened by shortening the predetermined time. 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 gradually advanced so that the shift shock can be sufficiently suppressed.

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 time chart for demonstrating the control at the time of the downshift of the 3rd speed-> 2nd speed 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.

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)

When the automatic transmission downshifts, the time until the actual input shaft rotation speed reaches the target input shaft rotation speed after shifting is sequentially predicted, and the engagement / release of the frictional engagement element for shifting is performed based on the predicted time. A control device for an automatic transmission, characterized by changing a control speed. 2. The control device for an automatic transmission according to claim 1, wherein when the predicted time is shortened to a predetermined time, the speed of the speed change frictional engagement element is decreased. At the time when the actual input shaft rotation speed starts increasing, the shift friction engagement element increases the speed toward the engaged state after the shift, and then when the predicted time is shortened to a predetermined time, 2. The control apparatus for an automatic transmission according to claim 1, wherein the speed-change friction engagement element reduces a speed toward a fastening state after the speed change.

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