JP2000097331A - Automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress worsening of shift quality by properly deciding a timing of a start/completion of control of an inertia phase. SOLUTION: In upshift, at a point of time t2 when a change gear ratio (r) monitored at a process of gear shifting is synchronized with a reference change gear ratio R2' lower than a change gear ratio R2 before gear shifting, control of an inertia phase is started. At a point of time (a time t4) when a state (times t3 and t4) that a change gear ratio (r) is synchronized with a change gear ratio R3 to be reached through gear shifting is continued for a time longer than a decision time, control of the inertial phase is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic transmission, and more particularly, to a timing determination for inertia phase control.

[0002]

2. Description of the Related Art In general, shift control in an automatic transmission proceeds in the order of shift start control, torque phase control, inertia phase control, and shift end control. Generally, in the inertia phase, the speed ratio calculated from the turbine speed (the speed of the input shaft of the transmission) and the output speed (the speed of the output side of the transmission) is increased toward the speed ratio after the speed change. This is a phase that changes over time.

Conventionally, the timing of the inertia phase control is determined as follows. First, the start determination of the inertia phase control will be described. In the control prior to the execution of the inertia phase control, the hydraulic pressure of the disengagement side clutch and brake (hereinafter, these are referred to as engagement elements) is reduced, and slight slippage is generated in the engagement elements. This state is called so-called engine blowing, and the speed ratio is slightly larger than the speed ratio before the speed change. Thereafter, the supply of the hydraulic pressure to the engagement element on the engagement side is started. When the hydraulic pressure on the engagement side increases to some extent, the gear ratio starts to decrease. And
When the speed ratio matches the speed ratio before the speed change, the inertia phase control is started.

On the other hand, conventionally, the end determination of the inertia phase control is performed as follows. In the inertia phase control, as the engagement control on the engagement side advances, the gear ratio becomes
It gradually decreases during an upshift and gradually increases during a downshift. Then, the inertia phase control ends when the speed ratio matches a speed ratio to be achieved by the speed change (a speed ratio at a subsequent stage).

[0005]

The above-mentioned conventional timing determination is based on whether or not the gear ratio matches a predetermined gear ratio (a start judgment is a gear ratio before a gear shift, and an end judgment is a gear ratio after a gear shift). It was done. Such a determination is based on the assumption that a change in the gear ratio occurs only depending on a change in the engagement state of the engagement element. Certainly, the gear ratio changes mainly due to the progress of the engagement control. However,
The gear ratio may change due to a change in the engine speed other than the engagement state. For this reason, a case may occur in which the gear ratio matches the predetermined gear ratio due to other factors even though the engagement element is not in the desired state.

Further, after the inertia phase control is completed, a hydraulic control is generally performed such that the hydraulic pressure on the engagement side is increased to a maximum pressure at a stretch. Therefore, even though the engagement element on the engagement side is in an incompletely engaged state, the inertia phase control is terminated and the hydraulic pressure on the engagement side is rapidly changed.
The engagement element on the engagement side suddenly changes from an incomplete engagement state to a complete engagement state. As a result, a shift shock occurs, which deteriorates the shift quality.

As described above, in the prior art, the timing of the inertia phase control is determined when the actual speed ratio matches a predetermined speed ratio, so that the engagement element may not be in the expected state. In some cases, it is determined that the inertia phase control starts / ends.

SUMMARY OF THE INVENTION It is an object of the present invention to suppress the deterioration of the shift quality by accurately determining the timing of the inertia phase control.

[0009]

According to a first aspect of the present invention, there is provided an automatic transmission for transmitting a driving force to an input shaft receiving a driving force from a driving engine and wheels. An output shaft, a plurality of engagement elements for setting a power transmission characteristic between the input shaft and the output shaft, detection means for detecting the number of rotations of the input shaft and the number of rotations of the output shaft; Control means for controlling the engagement, the control means comprising:
In the upshift, when the speed ratio calculated based on the rotation speed of the input shaft and the rotation speed of the output shaft detected by the detection unit is synchronized with a reference speed ratio smaller than the speed ratio before the speed change, the inertia phase control is performed. And an automatic transmission that terminates the inertia phase control when the calculated speed ratio is synchronized with the speed ratio to be attained by the speed change for a determination time or more.

According to a second aspect of the present invention, in an automatic transmission, an input shaft for receiving a driving force from a driving engine, an output shaft for transmitting a driving force to wheels, and an output shaft between the input shaft and the output shaft. A plurality of engagement elements for setting the power transmission characteristic of the input shaft, detection means for detecting the rotation speed of the input shaft and the rotation speed of the output shaft, and control means for controlling the release and engagement of the engagement element, The control means is configured to control the speed ratio calculated based on the rotation speed of the input shaft and the rotation speed of the output shaft detected by the detection unit in an upshift, when the speed ratio is synchronized with a reference speed ratio smaller than the speed ratio before the speed change. In addition, an automatic transmission for starting inertia phase control is provided.

In the first and second aspects, it is preferable that the reference gear ratio is changed according to the rotation speed of the output shaft or the input shaft.

Further, a third aspect of the present invention provides an automatic transmission, comprising: an input shaft receiving driving force from a driving engine;
An output shaft for transmitting a driving force to the wheels, a plurality of engagement elements for setting a power transmission characteristic between the input shaft and the output shaft, and a detecting unit for detecting a rotation speed of the input shaft and a rotation speed of the output shaft; Control means for controlling the disengagement and engagement of the engagement element, the control means, the speed ratio calculated based on the rotation speed of the input shaft and the rotation speed of the output shaft detected by the detection means, Provided is an automatic transmission that ends inertia phase control when a state synchronized with a gear ratio to be reached by gear shifting continues for a determination time or more.

Here, it is preferable that the determination time is set shorter in a downshift than in an upshift.

[0014]

FIG. 1 is a diagram showing a schematic structure of an automatic transmission (AT) as an example. The driving force from the crankshaft 9 of the engine is transmitted to a turbine shaft 11 of the transmission via a torque converter 10. Turbine shaft 1 as input shaft of transmission
1 is connected to the sun gear of the rear planetary 2.
On the other hand, a reduction drive shaft 12 as an output shaft of the transmission is connected to a ring gear of the front planetary 1 and a planetary carrier of the rear planetary 2. Each member (sun gear, planetary carrier, ring gear) in the two planetary gears 1 and 2 has three multi-plate clutches (reverse clutch 3,
High clutch 5, low clutch 6), two multi-plate brakes (2 & 4 brake 4, low & reverse brake 7),
It is connected to the low one-way clutch 8. These engagement elements (clutch, brake) are selectively engaged or released in accordance with the shift speed. As a result, the transmission can perform four forward speeds and one reverse speed.

FIG. 2 is a table showing a relationship between a shift position and an engagement state of an engagement element in the transmission. In this table, a circle indicates that the corresponding engaging element is engaged, and a blank indicates that it is released.
Further, the mark ◎ indicates that the engagement is performed only during the corresponding driving. In this transmission, a clutch-to-clutch shift is performed except for a shift between the first and second speeds. The clutch-to-clutch shift is a shift in which the front-stage engagement element is released and at the same time the rear-stage engagement element is engaged. On the other hand, in the shift between the first speed and the second speed in which the low one-way clutch 8 operates, the shift is achieved only by the engagement control of the 2 & 4 brake 4.

FIG. 3 is an explanatory view showing the overall control mechanism of the automatic transmission. This control mechanism mainly includes an engine 21, a transmission mechanism 22, a hydraulic control mechanism 23, and an electronic control unit (ECU) 24. Engine 2
1 is transmitted to the reduction drive shaft 12 via the torque converter 10, the turbine shaft 11, and the transmission mechanism 22. The torque of the shaft 12 is transmitted to a differential gear 16 via a drive pinion shaft 15 to drive the front wheels.

The throttle opening sensor S1 is connected to the engine 2
1 is a sensor for detecting the throttle opening θ.
The engine speed sensor S2 is a sensor that detects the speed of the crankshaft 9, that is, the engine speed ωE. The turbine speed sensor S3 is a sensor for detecting the speed ω1 of the turbine shaft 11. The output rotation speed sensor S4 is a sensor that detects the rotation speed ω5 of the reduction drive shaft 12 (the output shaft in the present embodiment). As a sensor for detecting these rotation speeds, for example, an electromagnetic pickup may be used.

The oil pump 36 in the hydraulic control mechanism 23
Discharges the control oil sucked from the oil pan 37. The control oil adjusted to a predetermined oil pressure by the regulator valve 38 includes five linear solenoid valves 31, 32, 3
3, 34, 35. Here, a linear solenoid valve is provided for each engagement element. Each linear solenoid valve controls the engagement element corresponding to the linear solenoid valve directly and linearly (a continuous control amount is generated according to the current value) in accordance with the current value from the hydraulic control circuit 51. A system in which a solenoid valve is provided for each engagement element and the engagement of each engagement element is directly controlled by a corresponding valve is generally called direct AT.

FIG. 4 is a sectional view showing the structure of the linear solenoid valve. The magnetic field generated by the electromagnet in response to the control current moves the spool valve, thereby connecting the supply port and the output port. In the direct AT system using a linear solenoid valve, the hydraulic pressure can be adjusted linearly according to the control current. Further, it is not necessary to use an accumulator required for the duty solenoid valve. Therefore, in the direct AT system using the linear solenoid valve, high-precision hydraulic control that does not cause an interlock or a feeling of thrust can be performed by controlling the current supplied to the linear solenoid valve.
In this embodiment, a normally-high valve that supplies the maximum control pressure when the current is 0 is used as the linear solenoid valve. FIG.
5 is a table showing the relationship between the shift speed and the open / closed state of each linear solenoid valve.

Incidentally, instead of the direct AT system, it is also possible to use a conventional hydraulic circuit combining a duty solenoid valve and a switching valve. However, in the present embodiment that requires accurate control of the hydraulic pressure, it may be preferable to use the direct AT.

The ECU 24 includes a CPU 41, a ROM 42,
It comprises a RAM 43, an input circuit 44, and an output circuit 45. The target turbine speed ωr is stored in the ROM 42.
Is stored with respect to a target pattern that is a reference for calculating the target pattern. The signals output from the sensors S1, S2, S3, S4 are input to the input circuit 44. CP
U41 performs a calculation for controlling the hydraulic pressure of the engagement element according to the information from these sensors. The control information as the calculation result is output to the hydraulic control circuit 51 via the output circuit 45. The hydraulic control circuit 51 obtains a current value for operating each linear solenoid valve based on a control signal from the output circuit 45, and supplies the current value to each linear solenoid valve.

(End determination at the time of upshift) Hereinafter, the end determination at the time of the upshift will be described by exemplifying a shift from the second speed to the third speed. However, this is merely an example, and the present invention can naturally be applied to other shifts. FIG. 6 is a timing chart relating to the gear ratio r and the engagement side hydraulic pressure PH in the 2-3 shift (upshift). FIG. 7 is a flowchart of the end determination of the inertia phase control. The flowchart in FIG.
It is repeatedly executed at intervals of 0 ms.

First, in phase 1 of FIG. 6, the hydraulic pressure PD of the 2 & 4 brake 4 in the engaged state is gradually reduced. As a result, a slight slippage (approximately 2% increase with respect to the gear ratio R2 before shifting) occurs in the brake 4. This slip can be detected as a change in the gear ratio r. Then, the gear ratio r is R2 (second gear ratio) × 1.
Until the value of 02 rises, the hydraulic pressure PD on the release side is reduced. The time t1 in FIG. 6 is the time at which such an increase in the speed ratio r has occurred. The gear ratio r is the turbine speed ω1 detected by the turbine speed sensor S3.
Is divided by the output rotation speed ω5 detected by the output rotation speed sensor S4, and is calculated by the CPU 41.

Next, after time t1, hydraulic control is performed so that the generated slip is maintained (that is, the speed ratio r maintains a slightly increased value). That is, the hydraulic pressure PD of the 2 & 4 brake 4 on the disengagement side is further reduced, and at the same time, the hydraulic pressure PH of the high clutch 5 on the engagement side is gradually increased. An inertia flag F indicating the execution of the inertia phase control is set to 0 as an initial value. Therefore,
During the phase 1 phase, step 1 in FIG.
By the determination of 0, the procedure after step 11 is not executed.

Eventually, when the hydraulic pressure PH of the high clutch 5 increases and the torque of the clutch 5 increases, the sensor S
The gear ratio r calculated from the information from S3 and S4 gradually decreases. Then, the gear ratio r is equal to the reference gear ratio R2 '.
At the point of time (time t2) synchronized with, phase 1 ends and the phase shifts to phase 2. That is, the inertia flag F is set from 0 to 1.

Here, the reference speed ratio R2 'is a value slightly smaller than the speed ratio R2 before the speed change. FIG. 11 is an enlarged view of a change in the gear ratio in Phase 1 of FIG.
The speed ratio r is slightly larger than the speed ratio R2 before the speed change due to the slip generated by the engagement element on the release side in the phase 1. When the engagement element is slipping, the speed ratio r is not constant, but actually fluctuates as shown in FIG. In this case, the speed ratio R before the speed change is temporarily set due to the change in the speed ratio.
2 (time t2 'at this time). According to the conventional method, when the speed ratio r matches the speed ratio R2, it is determined that the control of the phase 2, that is, the inertia phase control is started, so the inertia phase control is started at the time t2 '. Originally, the control to be started at time t2 is started at time t2 'when the disengagement-side engagement control has not sufficiently proceeded, so that such erroneous determination may deteriorate the shift quality.

Therefore, the reference speed ratio R2 ', which is slightly smaller than the speed ratio R2 before the speed change, is used as a reference for judging the start of the inertia phase control. When the speed ratio r is synchronized with the reference speed ratio R2', the inertia phase control is started. Has started. It is theoretically possible that a change in the gear ratio r caused by a factor other than the state of the engagement element (for example, a change due to the engine state or the follow-up control of the gear ratio) may be equal to or smaller than the gear ratio R2. There is no. The speed ratio r becomes smaller than the speed ratio R2 only when the engagement control proceeds. Therefore,
If the start determination is made using the reference speed ratio R2 ', it is possible to shift to the inertia phase control in a state where the engagement control has proceeded appropriately.

The start determination based on the reference gear ratio R2 'smaller than the gear ratio R2 is different from the case where the gear ratio R2 is used.
Start of inertia phase control is delayed. Therefore, it is important to appropriately set the reference speed ratio R2 'in consideration of both controllability and shift quality. Therefore, it is preferable to change the reference speed ratio R2 'according to the output rotational speed (may be the turbine rotational speed). For example, it may be set as follows.

The value obtained by subtracting the correction amount ΔR from the speed ratio R2 before the speed change is used as the reference speed ratio R2 '. FIG. 12 is a diagram illustrating a method of setting the reference gear ratio. Correction amount ΔR
When the output rotation speed ω5 at the time of receiving the upshift command is lower than the reference rotation speed Nc, a value that increases linearly with the rotation speed ω5 is used. In other words, in terms of the gear ratio, this is to set a correction amount so that the gear ratio is constant. On the other hand, when the output rotational speed ω5 is equal to or higher than the reference rotational speed Nc, a value is set such that the rotational speed is constant.

In the control of phase 2 (inertia phase control), the inertia flag F is set to 1 at time t2.
Until is set to 0 again, the procedure after step 11 in the flowchart of FIG. 7 is executed.

First, the turbine speed ω1 is detected by the sensor S3 (step 11), and the output speed ω1
5 is detected by the sensor S4 (step 12). In step 13, the CPU 41 calculates the gear ratio r (= ω1 / ω5) based on the information from these sensors. Then, it is determined whether or not the calculated speed ratio r is synchronized with the speed ratio to be achieved by the speed change (speed ratio R3 of the third speed). Here, the synchronization means a case where the speed ratio r is a value within a predetermined range (for example, ± 1%) around the speed ratio R3 after shifting. Time t2
Immediately after the above, since the speed ratio r is larger than the speed ratio R3, the process proceeds to the return according to the judgment of step 13.

In the inertia phase control, the release side 2 &
While setting the hydraulic pressure PD of the 4 brake 4 to the minimum hydraulic pressure,
The hydraulic pressure PH of the high clutch 5 on the engagement side is increased. As a result, the gear ratio r gradually decreases. Eventually, when the speed ratio r synchronizes with the speed ratio R3 (time t3 at that time), the steps after step 14 are executed according to the judgment of step 13. In step 14, 1 is added to the counter value CT. This counter value CT is
This is for counting the time during which the gear ratios are kept synchronized (that is, the time during which the gear ratio r is synchronized with the gear ratio R3 after gear shifting). The initial value of the counter value CT is 0
Therefore, the counter value CT is set to 1 by executing step 14 immediately after the time t3. Next, at step 15, the counter value CT is set to the judgment time CT1.
Is determined. This determination time CT
1 may be set to 15 as an example (that is, since the flowchart is executed every 10 ms, the determination time is 15).
0 ms). Since the current counter value CT is 1, the process proceeds from step 15 to return.

As can be seen from the change in the speed ratio r as shown in FIG. 6, after the time t3, the speed ratio r becomes equal to the speed ratio R.
It is smaller than 3. If the gear ratio r only temporarily coincides with the gear ratio R3, step 1
According to the synchronous judgment of 3, the counting of the counter value CT is stopped, and the content is reset (step 18). Then proceed to return.

Thereafter, when the speed ratio r increases and synchronizes again with R3 (time t4), the counter value CT is set from 0 to 1 according to the synchronization judgment in step 13 (step 14), and the synchronization continuation time Is counted. Time t4
After that, the state where the gear ratio r is synchronized with the gear ratio R3 continues. Therefore, Steps 10 to 15 (No in Step 15) are repeatedly executed in 10 ms, and the counter value CT is incremented. When the counter value CT finally reaches the determination time CT1 (= 15), the counter value CT is reset (step 1).
6), the inertia flag F is set to 0. Thus, the inertia phase control ends.

Finally, phase 3 is executed. In this phase, the hydraulic pressure PH of the high clutch 5 on the engagement side is changed to the maximum pressure. Thus, a series of shift procedures in the upshift ends.

Between time t3 and time t4 in FIG.
The reason why the case where the gear ratio r decreases to the gear ratio R3 or less may occur will be described. Due to an error in the linear solenoid valve 33 corresponding to the high clutch 5, a delay in hydraulic response, or the like, the change in the hydraulic pressure PH on the engagement side should change (see FIG. 6).
(A broken line in the engagement-side hydraulic pressure (PH)) and a different change (a solid line in the engagement-side hydraulic pressure (PH) in 6), albeit to some extent. Specifically, the actual transition of the hydraulic pressure often lags behind the ideal transition, that is, the set transition. As a result, the engagement control may not be progressing as expected by the engagement element. If the reduction of the gear ratio r depends only on the engagement state of the engagement element, the change in the gear ratio r becomes slower in accordance with the delay of the hydraulic pressure response on the engagement side. However, in practice, the change in the gear ratio r is not caused solely by the engagement control on the engagement side. In the case of an upshift of power-off, the engine speed drops (the engine speed decreases toward the neutral speed). Number decreases). As a result, despite the delay in the engagement control, the speed ratio r is reduced by R2
May be consistent with At the time when the gear ratios match due to the drop in the engine speed (time t3
FIG. 9 shows the change of the gear ratio when the inertia phase control is ended and the shift end control (phase 3) is started.
Shown in As can be seen from this figure, the engagement side oil pressure PH sharply increases after a delay time corresponding to the oil pressure response delay from time t3. Such a sudden change in the gear ratio r causes a gear shift shock, which is a factor of deteriorating the shift quality.

Therefore, in the present embodiment, the state in which the speed ratio r is synchronized with the speed ratio R3 to be achieved by this speed change is determined by the inertia phase when the determination time (150 ms (10 ms × 15) in this embodiment) has elapsed. The control is terminated. In other words, the end is not determined simply by the gear ratio r being equal to the gear ratio R, and the determination is made in consideration of the period during which the synchronization is continued. More specifically, the inertia phase control is not terminated unless the synchronization is continued as in the case of the gear ratio r at the time t3. As a result, when the speed ratio r is temporarily synchronized with the speed ratio R3 on the subsequent stage due to a drop in the engine speed, the inertia phase control is continued. And, like the synchronization of the gear ratio at time t4,
Only when the engagement element on the engagement side is sufficiently engaged, the control is terminated. Therefore, the occurrence of a shift shock can be suppressed. As described above, by monitoring the time during which the gear ratios are synchronized, it is possible to appropriately determine the end of the inertia phase control, and it is possible to suppress a gear shift shock that may occur in the related art.

In the above description, the fact that the time during which the synchronization has continued coincides with the determination time is used as the determination criterion for the inertia phase control. However, for the purpose of the present invention, this may be extended, and the termination criterion may be that the synchronization has continued for the determination time or longer.

(End Determination at Downshift) A similar case may occur in downshift. FIG. 8 is a timing chart relating to the gear ratio and the engagement side hydraulic pressure in the 3-2 shift (downshift) in the present embodiment. The flowchart for determining the end of the inertia phase control in this case is the same as that shown in FIG. 8 except that the speed ratio R2 in step 13 is changed.

FIG. 10 shows the hydraulic pressure PD of the 2 & 4 brake 4 on the engaged side when downshifting with power on.
6 is a timing chart for explaining a change of the gear ratio. If the actual oil pressure is lower than the set value for the engagement oil pressure PD, the engine may blow up due to power-on. As a result, the speed ratio r increases, and the speed ratio r may be synchronized with the speed ratio R2 after the speed change (time t3 in FIG. 10). In such a case, if the inertia phase control is terminated, the gear ratio r suddenly changes to R2 for the same reason as described in the case of the upshift, and a gear shift shock occurs. obtain.

Therefore, as shown in FIG. 8, when the state in which the speed ratio r is synchronized with the speed ratio R2 after the shift continues for a determination time (for example, CT1 = 10, ie, 100 ms), the inertia phase control is terminated. To do it. As a result, when the gear ratio is synchronized by the rising of the engine (time t3 in FIG. 8), the control does not shift to the shift end control, so that the occurrence of the shift shock can be suppressed.

The value of the determination time CT1 is set shorter in the downshift than in the upshift.
The same value may be set. However, it is preferable to shorten the downshift determination time from the viewpoint of shift quality. As described above, in the inertia phase control of the upshift, the hydraulic pressure on the engagement side is controlled, and the release side is set to the minimum pressure. Therefore, even during the inertia phase control, if the state where the gear ratio is synchronized with the gear ratio after the gear shift continues, the state is the same as the control after the gear shift. As a result, in order to accurately determine the end of the inertia phase control, even if the set value of the determination time at the end of the shift is slightly increased, there is no problem from the viewpoint of the shift quality. On the other hand, in the inertia phase control in the power-on downshift, the hydraulic pressure on the release side is controlled, and the hydraulic pressure on the engagement side is increased in the latter half of this control. Then, when the end of the inertia phase control is determined, the release side is set to the minimum hydraulic pressure, and the engagement side hydraulic pressure is set to the maximum pressure to completely engage the engagement side engagement element. Therefore, if the set value of the house change time at the end of the shift is increased, an interlock may occur due to the hydraulic pressure on both the engagement side and the release side. Therefore, it is not preferable to make the determination time at the end of the shift too long.
For the above reasons, it is effective to make the downshift determination time shorter than that of the upshift.

[0043]

As described above, according to the present invention, the start / end timing of the inertia phase control can be accurately determined, and the deterioration of the shift quality due to the erroneous determination that may occur in the prior art can be suppressed. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic structure of a main part in an automatic transmission according to an embodiment.

FIG. 2 is a table showing a relationship between a shift position and an engagement state of an engagement element.

FIG. 3 is an explanatory view showing the entire control mechanism of the automatic transmission.

FIG. 4 is a sectional view showing the structure of a linear solenoid valve.

FIG. 5 is a table showing a relationship between a shift speed and an open / close state of each linear solenoid valve.

FIG. 6 is a timing chart relating to a gear ratio and an engagement-side hydraulic pressure in a 2-3 shift (upshift).

FIG. 7 is a flowchart for determining the end of inertia phase control.

FIG. 8 is a timing chart regarding a gear ratio and an engagement side hydraulic pressure in a 2-3 shift (downshift).

FIG. 9 is a timing chart for explaining changes in the supply hydraulic pressure of the engagement-side engagement element and the actual gear ratio when the upshift is performed with the power off.

FIG. 10 is a timing chart for explaining changes in the supply hydraulic pressure of the engagement-side engagement element and the actual gear ratio when downshifting with power-on.

FIG. 11 is an enlarged view of a change in a gear ratio in phase 1 of FIG. 6;

FIG. 12 is a diagram illustrating a method of setting a reference gear ratio.

[Explanation of symbols]

1 front planetary, 2 rear planetary, 3 reverse clutch, 4 2 & 4 brake, 5 high clutch, 6 low clutch, 7 low & reverse brake,
8 low one way clutch, 9 crankshaft,
10 Torque converter, 11 Turbine shaft, 1
2 reduction drive shaft, 15 drive pinion shaft, 16 differential gear, 21
Engine, 22 transmission mechanism, 23 hydraulic control mechanism, 24
ECU, 31, 32, 33, 34, 35 Linear solenoid valve, 36 oil pump, 37 oil pan, 38 regulator valve, 41 CPU, 42
ROM, 43 RAM, 44 input circuit, 45 output circuit, 51 hydraulic control circuit, S1 throttle opening sensor, S2 engine speed sensor, S3 turbine speed sensor, S4 output speed sensor

Claims (5)

[Claims] In an automatic transmission, an input shaft for receiving a driving force from a driving engine, an output shaft for transmitting a driving force to wheels, and a power transmission characteristic between the input shaft and the output shaft are set. A plurality of engagement elements; a detection unit configured to detect the number of rotations of the input shaft and the number of rotations of the output shaft; and a control unit configured to control release and engagement of the engagement element. In the upshift, when the speed ratio calculated based on the speed of the input shaft and the speed of the output shaft detected by the detection unit is synchronized with a reference speed ratio smaller than the speed ratio before the speed change. Automatically starting the inertia phase control and terminating the inertia phase control when a state in which the calculated speed ratio is synchronized with a speed ratio to be reached by the shift continues for a determination time or more. transmission. 2. An automatic transmission, comprising: an input shaft for receiving a driving force from a driving engine; an output shaft for transmitting a driving force to wheels; and a power transmission characteristic between the input shaft and the output shaft. A plurality of engagement elements; a detection unit configured to detect the number of rotations of the input shaft and the number of rotations of the output shaft; and a control unit configured to control release and engagement of the engagement element. In the upshift, when the speed ratio calculated based on the speed of the input shaft and the speed of the output shaft detected by the detection unit is synchronized with a reference speed ratio smaller than the speed ratio before the speed change. Automatic transmission, wherein inertia phase control is started. 3. The automatic transmission according to claim 1, wherein the reference gear ratio is changed according to a rotation speed of the output shaft or the input shaft. 4. An automatic transmission, wherein an input shaft for receiving a driving force from a driving engine, an output shaft for transmitting a driving force to wheels, and a power transmission characteristic between the input shaft and the output shaft are set. A plurality of engagement elements; a detection unit configured to detect the number of rotations of the input shaft and the number of rotations of the output shaft; and a control unit configured to control release and engagement of the engagement element. The speed ratio calculated based on the rotation speed of the input shaft and the rotation speed of the output shaft detected by the detection means, if the state synchronized with the speed ratio to be reached by shifting continues for a determination time or more, An automatic transmission characterized by terminating inertia phase control. 5. The automatic transmission according to claim 4, wherein the determination time is set shorter in a downshift than in an upshift.