JPH06341526A - Speed change control device for automatic transmission - Google Patents

Abstract

PURPOSE:To eliminate shift quality by letting the engaging pressure of each friction engagement means at the engagement side standby at a specified low pressure value before the input revolution speed of the automatic transmission comes up to a synchronizing point for low speeds with a pressure control means operated at the time of a clown shift actuated by a clutch-to-clutch transmission section, and raising the engaging pressure after the revolution speed of the automatic transmission has been synchronized. CONSTITUTION:The automatic transmission for five forward speeds and reverse, which is equipped with a torque converter 111, and main and an auxiliary for a brake 112 and a brake 113 wherein speed change for second speed and third speed is actuated. The engagement/ disengagement of each friction engagement means is executed by controlling a hydraulic control means 20 based on the command from a computer 30 to which output signals from various sensor groups 40 are inputted. When the transmission is controlled by the computer 30 at the time of a down shift by the clutch-to-clutch transmission section, the engaging pressure of each friction engagement means at the engagement side is so controlled as to standby at a specified low pressure value before the input revolution speed of the automatic transmission comes up to a synchronizing point in low speeds, and is also controlled to rise after the aforesaid revolution speed has been synchronized, so that the occurrent of shift quality is thereby prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control device for an automatic transmission which may perform a downshift of a clutch to clutch relating to two friction engagement devices.

[0002]

2. Description of the Related Art When performing a specific shift of an automatic transmission, it is often necessary to simultaneously engage and disengage two friction engagement devices (including a clutch and a brake in a broad sense). So-called clutch to clutch shift).
In this case, if the engagement and disengagement of the friction engagement devices are not properly synchronized, the output shaft torque will drop or the engine will blow up.

For this reason, conventionally, in order to perform such control, a one-way clutch having a function substantially equivalent to that of one friction engagement device is generally provided so that such a problem does not occur. Was considered.

However, in the method of synchronizing the friction engagement devices by using the one-way clutch in this way, the cost increases due to the attachment of the one-way clutch.
In addition, there are problems such as an increase in weight and an occupied space.

In view of such a point, in recent years, against the background of improvements in various sensor technologies and in electronic control technologies for hydraulic control devices, "clutch-to-clutch shift" can be directly executed without using a one-way clutch. Attempts to do so have become active again.

Conventionally, as a technique for controlling the downshift of the clutch-to-clutch, for example, Japanese Patent Publication No. 52-1834.
No. 4 publication discloses that an orifice kick-down valve is used, a governor pressure (which changes according to the vehicle speed) and a spring load are applied to the spool of the orifice kick-down valve so as to face each other. A technique has been proposed in which the supply is performed via a large-diameter orifice, while the supply is performed via a small-diameter orifice at a predetermined vehicle speed or higher. According to this, the frictional engagement device on the engagement side can be engaged to some extent near the point where the input and output rotations are synchronized.

[0007]

However, in this prior art, the supply of the engagement pressure to the friction engagement device on the engagement side depends on the drain opening condition of the throttle opening and the release pressure of the release side friction engagement device. However, since the downshift is executed by only two-step control by switching the orifice depending on the vehicle speed, there is a large deviation from the actual synchronization point, which may cause engine injection or excessive tie-up. was there. That is, since only the governor pressure (vehicle speed) is taken into consideration, it is not possible to properly cope with variations in the actual synchronization of input / output rotation depending on other running conditions. There was a problem.

In view of such circumstances, the applicant first
In Japanese Patent Application No. 3-344123 (unknown), in the downshift of the clutch-to-clutch, the friction adjustment on the engagement side is performed before the input speed of the automatic transmission reaches the synchronization point of the low speed stage by the pressure adjusting means. A technique has been proposed in which the engagement pressure of the device is made to stand by at a predetermined low pressure value, and after it is detected that the synchronization point is reached, the engagement pressure is gradually increased based on the input torque. According to this technique, the engagement pressure can be adjusted from before the synchronization point according to the input rotation, and after the synchronization, the engagement pressure can be increased based on the input torque.
The engagement timing of the engagement-side friction engagement device can be optimized, and the amount of torque transmitted from the release-side friction engagement device to the engagement-side friction engagement device can be optimized.

However, this Japanese Patent Application No. 3-34412
In the technology proposed in No. 3, although the hydraulic pressure on the engagement side can be increased based on the input torque after the synchronization at the low speed stage is detected, the hydraulic pressure decrease on the release side is set uniformly. In reality, there was still the problem that gear shift shock might occur.

That is, according to the above technique, after the synchronization at the low speed stage is detected, the hydraulic pressure on the engagement side is increased according to the input torque, and the hydraulic pressure on the release side is rapidly drained (time lag). However, in the case where the input torque is comparatively small, there is a margin to increase the engagement pressure, so there is no particular problem, but when the input torque is large, Even if an attempt is made to increase the engagement pressure suddenly, the engagement pressure does not rise suddenly, so the hydraulic pressure on the disengagement side relatively decreases too quickly, and as a result, the engine is jetted and the shift feeling is improved. There is a problem that it becomes worse.

To solve this problem, for example, a method of slightly delaying the timing of the rapid decrease of the hydraulic pressure on the release side from the synchronization point of the low speed stage can be considered. However, in the case where the input torque is simply delayed, the release is relatively delayed with respect to the increase in the hydraulic pressure on the engaging side in the region where the input torque is small, and the output shaft torque decreases due to the drag of the friction engaging device on the engaging side. Also, an increase in time lag occurs, and the shift feeling also deteriorates.

The deviation of the balance between the engagement side hydraulic pressure and the release side hydraulic pressure does not depend only on the input torque but also on the oil temperature of the automatic transmission, for example. That is, generally, the oil temperature of an automatic transmission has a high viscosity and a low responsiveness at an extremely low temperature, but the responsiveness tends to increase as the temperature approaches the normal temperature. On the contrary, when the temperature increases from room temperature to high temperature, the viscosity further decreases, and leakage from each part of the hydraulic control device increases, and the throttling effect in the orifice or the like also decreases, making it difficult to increase the hydraulic pressure ( The oil pressure tends to come off easily. Therefore, the proper timing of the hydraulic drain on the release side after the synchronization detection also changes depending on the oil temperature, and if this setting is not properly made, the shift feeling is also deteriorated.

The present invention has been made in view of the above circumstances, and further improves the technique proposed in the above-mentioned Japanese Patent Application No. 3-344123 so that a time lag can be obtained regardless of various running conditions. The purpose is to realize a downshift of a clutch-to-clutch that is small and has a small shift shock.

[0014]

SUMMARY OF THE INVENTION The present invention, as shown in FIG. 1 (A), shows an automatic transmission that may perform a downshift of a clutch-to-clutch related to two friction engagement devices. In the shift control device, a synchronization detecting means for detecting whether or not the input speed of the automatic transmission has reached a low-speed synchronization point, and the synchronization detection means for detecting that the input speed has reached the synchronization point. After that, while increasing the engagement hydraulic pressure of the friction engagement device on the engagement side from a predetermined low pressure value,
A hydraulic pressure control means for decreasing the released hydraulic pressure from a predetermined high pressure value after a predetermined time from the synchronization detection, a means for detecting the input torque of the automatic transmission, and the greater the input torque, the more the synchronization detection of the low speed stage is performed. Means for setting the predetermined time until the hydraulic pressure of the disengagement side frictional engagement device is reduced to a long time is provided to solve the above problems.

Further, the present invention, as shown in FIG. 1 (B), shows a shift control device for an automatic transmission which may execute a downshift of a clutch-to-clutch related to two friction engagement devices. A synchronization detecting means for detecting whether or not the input speed of the automatic transmission has reached the synchronization point of the low speed stage,
After the synchronization detecting means detects that the input rotation speed has reached the synchronization point, the engagement hydraulic pressure of the friction engagement device on the engagement side is increased from a predetermined low pressure value and a predetermined time is elapsed from the synchronization detection. After that, the hydraulic pressure control means for lowering the release hydraulic pressure from a predetermined high pressure value, the means for detecting the oil temperature of the automatic transmission, and the release side from the synchronous detection of the low speed stage depending on the oil temperature of the automatic transmission. By providing the means for setting the predetermined time until the hydraulic pressure of the friction engagement device is reduced,
Similarly, the above problem is solved.

[0016]

In the present invention, when performing downshifting of the clutch-to-clutch, the above-mentioned Japanese Patent Application No. 3-3 is basically used.
The downshift is controlled by the method disclosed in 44123. That is, before the input speed of the automatic transmission reaches the synchronization point of the low speed stage by the pressure adjusting means, the engagement pressure of the frictional engagement device on the engagement side is kept at a predetermined low pressure value, and after the synchronization, the engagement is performed. Increase the pressure.

On the other hand, the release pressure of the friction engagement device on the release side is
Although rapid draining is performed after synchronization, in this case, draining is not performed immediately after synchronization is detected, but is drained "after a predetermined time", and this predetermined time is set according to the input torque. Specifically, the larger the input torque is, the later the completion of the engagement on the engagement side is substantially delayed, and accordingly, the predetermined time is set longer.

On the contrary, when the input torque is small, the engagement on the engagement side proceeds smoothly, so the "predetermined time" is a short time including zero.

Further, when the oil temperature of the automatic transmission is high, the oil pressure on the engagement side is difficult to rise and the oil pressure on the drain side tends to be released earlier. Therefore, the "predetermined time" is set longer than that at room temperature. .

At the time of extremely low temperature, the viscosity of the oil is high, and it is difficult for the oil to drain. Therefore, in this respect, it is better to set the "predetermined time" shorter. Since it takes time for the hydraulic pressure on the engagement side to rise, the "predetermined time" should be set in consideration of the balance with this.

As described above, according to the present invention, the drain timing of the friction engagement device on the disengagement side is optimized in accordance with the input torque or the oil temperature. Therefore, the clutch-to-clutch shift is always executed at a good timing. You will be able to do this.

In the present invention, how to specifically detect the "input torque" of the automatic transmission is not particularly limited. Generally, it is difficult to actually install a torque sensor on the input shaft of an automatic transmission, so parameters such as throttle opening, engine speed, fuel injection amount, etc. are used to estimate the input torque at that time. It is better to adopt the method.

In the case of estimating the input torque based on, for example, the throttle opening, if the control for reducing the engine torque at the time of shifting is adopted, it is the same depending on whether or not this reduction control is actually executed. Since the input torque varies greatly even with the throttle opening, it is preferable to separately detect whether or not the engine torque reduction control is actually executed.

On the other hand, regarding the "oil temperature of the automatic transmission",
When it is difficult to provide the oil temperature sensor, for example, the detection result of the cooling water temperature sensor of the engine may be used instead.

[0025]

Embodiments of the present invention will now be described in detail with reference to the drawings.

First, a concrete example of an automatic transmission to which the present invention is applied is shown by a skeleton in FIG. The automatic transmission 2 includes a torque converter 111, a sub transmission unit 112, and a main transmission unit 113.

The torque converter 111 has a lockup clutch 124. The lockup clutch 124 is provided between a front cover 127 that is integrated with the pump impeller 126 and a member (hub) 129 to which a turbine runner 128 is integrally attached.

A crankshaft (not shown) of the engine 1 is connected to the front cover 127. The input shaft 130 connected to the turbine runner 128 includes an overdrive planetary gear mechanism 13 that constitutes the auxiliary transmission unit 112.
It is connected to one carrier 132.

A clutch C0 and a one-way clutch F0 are provided between the carrier 132 and the sun gear 133 in the planetary gear mechanism 131. The one-way clutch F0 is adapted to be engaged when the sun gear 133 makes a positive rotation relative to the carrier 132 (rotation in the rotation direction of the input shaft 130).

On the other hand, a brake B0 for selectively stopping the rotation of the sun gear 133 is provided. Further, a ring gear 134 which is an output element of the auxiliary transmission section 112 is connected to an intermediate shaft 135 which is an input element of the main transmission section 113.

The sub-transmission unit 112, when the clutch C0 or the one-way clutch F0 is engaged, has the planetary gear mechanism 1
Since the whole 31 rotates integrally, the intermediate shaft 135
Rotates at the same speed as the input shaft 130. Further, in the state where the brake B0 is engaged and the rotation of the sun gear 133 is stopped, the ring gear 134 is accelerated with respect to the input shaft 130 and rotates normally. That is, the subtransmission unit 112 can set switching between high and low.

The main transmission unit 113 has three sets of planetary gear mechanisms 140, 150, 160, and these gear mechanisms 140, 150, 160 are connected as follows.

That is, the sun gear 141 of the first planetary gear mechanism 140 and the sun gear 151 of the second planetary gear mechanism 150 are integrally connected to each other, and the ring gear 143 of the first planetary gear mechanism 140 and the second planetary gear mechanism 150 are connected. Carrier 1
52 and the carrier 162 of the third planetary gear mechanism 160 are connected together. Further, the output shaft 170 is connected to the carrier 162 of the third planetary gear mechanism 160. Further, the ring gear 153 of the second planetary gear mechanism 150 is connected to the sun gear 161 of the third planetary gear mechanism 160.

The gear train of the main transmission unit 113 can set one reverse gear and four forward gears, and clutches and brakes therefor are provided as follows.

That is, the ring gear 153 of the second planetary gear mechanism 150 and the sun gear 161 of the third planetary gear mechanism 160.
A clutch C1 is provided between the intermediate shaft 135 and the intermediate shaft 135, and a clutch C2 is provided between the sun gear 141 of the first planetary gear mechanism 140 and the sun gear 151 of the second planetary gear mechanism 150 and the intermediate shaft 135.

A brake B1 for stopping the rotation of the sun gears 141 and 151 of the first planetary gear mechanism 140 and the second planetary gear mechanism 150 is arranged. Also, these sun gear 1
A one-way clutch F1 and a brake B2 are arranged in series between 41 and 151 and the casing 171.
The one-way clutch F1 is adapted to be engaged when the sun gears 141, 151 try to rotate in the reverse direction (rotation in the direction opposite to the rotation direction of the input shaft 135).

The carrier 142 of the first planetary gear mechanism 140
A brake B3 is provided between the casing and the casing 171. In addition, the ring gear 16 of the third planetary gear mechanism 160
A brake B4 and a one-way clutch F2 as elements for stopping the rotation of No. 3 are arranged in parallel with each other between the casing 171. The one-way clutch F2 is adapted to be engaged when the ring gear 163 tries to rotate in the reverse direction.

In the automatic transmission 2 described above, it is possible to carry out a shift of one reverse speed and five forward speeds as a whole. FIG. 3 shows an engagement operation table of each clutch and brake for setting these shift speeds. In addition, in FIG. 3, a circle mark indicates an engaged state,
● indicates the engaged state when the engine is braked, and the blank indicates the released state.

As is apparent from this figure, the shift between the second speed and the third speed is the clutch-to-clutch shift of the brake B2 and the brake B3.

Engagement or disengagement of each clutch and brake is executed by driving an electromagnetic valve or a linear solenoid in the hydraulic control device 20 based on a command from the computer 30. The computer 30 includes signals from various sensor groups 40, for example, a vehicle speed signal from a vehicle speed sensor 41 (a signal indicating an output shaft rotation speed N0), a throttle opening signal (accelerator opening signal) from a throttle sensor 42, and a pattern select switch. Basic pattern signals such as a pattern select signal from 43 (a signal selected by the driver for driving with emphasis on power, driving with emphasis on fuel consumption, etc.), a shift position signal from the shift position switch 44, and a foot brake signal from the brake switch 45. In addition, the rotational speed signal of the clutch C0 from the C0 sensor 46 is input. Since the rotation speed of the clutch C0 is the same as the turbine rotation speed (the input shaft rotation speed of the automatic transmission) Nt during the shift between the second speed and the third speed, the rotation speed of the clutch C0 is detected. The turbine rotation speed Nt can be grasped.

The specific hydraulic control of the release and engagement of the brakes B2 and B3 is performed by a hydraulic circuit as shown in FIG.

B3 control valve 202 is 2-3
Oil passage L1 from shift valve 201 to brake B3,
It is arranged in L2 in parallel with the orifice 214 with a check ball. In the valve hole 202a of the B3 control valve 202, a port 221 communicating with the oil passage L1 via a large diameter orifice 202b, a port 222 communicating with the oil passage L2, and an input port 223 also communicating with the oil passage L2. A port 224 is provided to which the signal hydraulic pressure regulated by the SLU linear solenoid valve 203 controlled by the control signal from the computer 30 is supplied. Reference numeral 225 is an input port for the signal pressure of the third speed stage, and 226 is a drain port.

The spool 202c of the B3 control valve 202 has a pair of large diameter lands 227, 228 and a small diameter land 229. One end of the large diameter land 228 is in contact with the pressure receiving piston 202e via the spring 202d, and the outer end of the large diameter land 227 receives the supply pressure from the port 223. The outer end of the pressure receiving piston 202e receives the signal pressure from the input rotation signal port 224, and the inner end of the pressure receiving piston 202e receives the signal pressure from the port 225.

On the other hand, the B2 accumulator 204 is connected to an oil passage L3 leading to the brake B2 via an orifice 204a. Therefore, by controlling the back pressure of the B2 accumulator 204 by the accumulator back pressure control device 206, it is possible to adjust the drain pressure of the oil passage L3 even when the brake B2 is released.

In the figure, reference numeral 210 is a B2 orifice control valve for speeding up (first fill) hydraulic pressure supply to the brake B2, and 211 is an upshift from the second speed stage to the third speed stage. 2 to 3, a 2-3 timing valve for adjusting the drain pressure from the brake B2 by a signal from the SLU linear solenoid valve 203 will be described. However, since these are not directly involved in the downshift control which is the subject of the present invention, detailed description will be given. The description of the configuration is omitted.

In the hydraulic control device constructed as described above, in the third speed stage, the drive range pressure D passed through the manual valve (not shown) becomes 1-2 shift valve 21.
It is supplied to the brake B2 via the 2-3 shift valve 201 and the oil passage L3, and as a result, the brake B2 is brought into the engaged state.

Here, a shift solenoid valve (not shown) operates in accordance with the running condition of the vehicle, and the 2-3 shift valve 201 in FIG. 4 moves to the second gear position (the oil passage in the valve is indicated by a solid line). The pressure of the brake B2 starts to be drained from the oil passage L3 through the 2-3 shift valve 201. In this embodiment, the drop of the drain pressure is caused by controlling the back pressure of the B2 accumulator 204 by the accumulator back pressure control device 206 so that the input rotational speed Nt.
Is controlled to be a predetermined ratio.

On the other hand, the drive range pressure D is the brake B3 from the 2-3 shift valve 201 via the oil passages L1 and L2.
Is supplied to. The supply of the hydraulic pressure to the brake B3 and the hydraulic drain of the B2 follow the procedure of the flowcharts shown in FIGS. 5 and 6 (FIG. 6 is a continuation of FIG. 5).

This procedure will be described below with reference to FIGS. 5 and 6.

First, in step 302, the 2-3 shift valve 201 is in the communicating state (brake B) shown by the solid line in FIG. 4 under the control of a shift solenoid valve (not shown).
2 is connected to the drain circuit and brake B3 is connected to the supply circuit).

At this time, as shown in step 304,
Basically, the back pressure of the B2 accumulator 204 is feedback-controlled as described above so that the input speed becomes the target change of the rotational speed, whereby the drain pressure of the brake B2 is feedback-controlled. This feedback control is basically continued until the second speed synchronization is achieved.

At the beginning of this change in the number of revolutions, the spring of the B3 control valve 202 causes the spool 202c.
4 takes the upper half position of FIG. 4, the port 221 communicates with the port 222, and a rapid hydraulic pressure supply through the large orifice 202b causes a piston stroke of the brake B3.
The piston immediately displaces to a position where the friction material can be engaged, so-called "first fill" operation is performed.

In step 306, the signal pressure by the SLU linear solenoid valve 203 supplied to the port 224 of the B3 control valve 202 is controlled to a predetermined low pressure value. That is, the brake B3 is in a standby state in which the supply pressure (hereinafter referred to as B3 pressure) to the brake B3 is kept low so that the brake B3 slightly transmits the torque. This low pressure standby basically prevents a sudden change in rotational speed due to an increase in B3 pressure and excessive tie-up of both brakes B2 and B3. This low-pressure standby state is specifically achieved by draining the excess B3 pressure through the B2 orifice control valve 210 by releasing the port 226 by applying the feedback pressure from the port 223.

In step 308, the synchronization of the second speed is detected in the computer 30 from the change in the rotation speed NCo (input rotation speed Nt) of the clutch Co. Specifically, it is determined whether or not the rotation speed NCo of the clutch Co has become larger than a value obtained by subtracting α from a value No xi2 obtained by multiplying the output shaft rotation speed No by the gear ratio i2 of the second speed. This predetermined value α takes into account the time lag of the rise of the B3 pressure. Until the synchronization of the second speed stage (immediately before) is detected as a result of this comparison, the process returns from step 308 to step 304, and the flow of steps 304 to 308 is repeated.

When the time immediately before the synchronization of the second speed is detected, the input torque Tin is obtained in step 310, and step 31
At 2, the operation of increasing the B3 pressure is performed at an increasing rate according to the input torque Tin. In this embodiment, the input torque Tin is obtained from the throttle opening and the engine speed.

By increasing the B3 pressure, both brakes B2,
B3 is in a state of sharing the torque in cooperation with each other, and a smooth transition to the synchronization point is possible due to the displacement of the torque sharing rate. This state is continued until it is confirmed in step 314 that the second gear is synchronized. The detection of the synchronization here is based on a value (No xi2-a) obtained by subtracting a from the value No xi2 obtained by multiplying the output shaft speed No by the gear ratio i2 of the output shaft rotational speed NCo of the clutch C0. This is done by determining whether or not it has become larger. Here, a is a value considering the dead time of the quick drain of the brake B2.

When the synchronization according to this formula is confirmed, the SLU linear solenoid valve is set to a high output in step 316, the port 221 of the B3 control valve 202 is completely communicated with the port 222, and the brake B3 is released immediately. Meanwhile, in step 318, it is confirmed whether or not the engine torque reduction control during shifting is permitted. This engine torque reduction control during gear shifting has been adopted in many vehicles equipped with an automatic transmission in recent years.By temporarily reducing the engine torque during gear shifting, the load on the friction engagement device is reduced. The gear shift is realized in a short time and with a small gear shift shock. This reduction control is generally prohibited when the cooling water temperature is low, in order to prevent engine misfire and the like.
Further, for example, in the system in which the reduction control is realized by the ignition retard, if the temperature of the exhaust system abnormally rises due to the execution of the ignition retard, it is also prohibited. It is also prohibited when the sensor system for realizing the engine torque reduction control fails. When the engine torque reduction control is prohibited in this way, the actual input torque of the automatic transmission increases significantly even if the throttle opening and the engine speed are the same. As a result, the engagement of the brake B3 tends to be delayed, so in order to prevent engine injection, the routine proceeds to step 320, where the quick drain of the brake B2 is executed after the elapse of the long timer tB.

On the other hand, when the engine torque reduction control is permitted as scheduled, the routine proceeds to step 322, where it is judged if the input torque Tin is larger than a predetermined value k,
When the input torque Tin is smaller than the predetermined value k, the routine proceeds to step 324, where the quick drain of the brake B2 is immediately executed (zero for a predetermined time). On the other hand, if it is determined that the input torque Tin is larger than k, the routine proceeds to step 326, where the rapid drain of the brake B2 is executed after the timer tA has elapsed. Note that tA <tB.

The quick drain of the brake B2 is realized by opening the B2 orifice control valve 210 by supplying the signal pressure from the solenoid valve 213.

FIG. 7 shows the characteristics when the brake B2 is rapidly drained simultaneously with the detection of the synchronization of the second gear, and FIG. 8 shows the quick drain of the brake B2 after a predetermined time from the detection of the synchronization of the second gear. The characteristics of each case are shown below.

In the case where the brake B2 is rapidly drained at the same time when the synchronization of the second speed is detected, good characteristics are obtained when the input torque is small as shown by the solid line, but the input torque is as shown by the broken line. When it is large, the release of the brake B2 proceeds before the brake B3 is completely grasped, so that engine blowing occurs and the output shaft torque fluctuates greatly.

On the other hand, after a predetermined time corresponding to the input torque Tin after the synchronization of the second speed is detected, the brake B2
When the rapid drain is executed, good characteristics can be obtained both when the input torque Tin is small and when it is large.

In the above embodiment, the magnitude of the input torque Tin and the predetermined value k are confirmed in step 324, and the predetermined time (including zero) until the brake B2 is rapidly drained is set accordingly. However, by changing this step to the step of confirming the oil temperature, the predetermined time until the quick drain of the brake B2 can be changed in the same manner depending on the oil temperature. The qualitative tendency at that time is as already described in the section of "action". Of course, it is also possible to confirm both the input torque and the oil temperature, and to set a more detailed "predetermined time".

When the input torque Tin is estimated and detected from the throttle opening and other parameters as in the above embodiment, the vehicle speed (the output shaft rotational speed N of the automatic transmission N is further increased).
Considering the height of o), the quicker the drain is made (the predetermined time is shorter) as the vehicle speed becomes higher, the more detailed control becomes possible. This is because, due to the characteristics of the engine-torque converter, in general, the input torque tends to decrease at higher speeds, and as a result, the engagement of the engagement side frictional engagement device becomes faster, while at higher speeds, the relative torque becomes lower. This is because the rotation of the frictional engagement device on the disengagement side tends to increase and the drag on the disengagement side frictional engagement device tends to increase.

[0065]

As described above, according to the present invention, the drain of the friction engagement device on the disengagement side can be executed at the optimum timing regardless of the input torque, the oil temperature and the like. Therefore, the excellent effect that the downshift of the clutch-to-clutch can be realized more favorably can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the gist of the present invention.

FIG. 2 is a block diagram schematically showing an automatic transmission for a vehicle to which the present invention is applied.

FIG. 3 is a diagram showing an operating state of each friction engagement device of the automatic transmission.

FIG. 4 is a hydraulic circuit diagram in which a portion related to a downshift from the third speed stage to the second speed stage is extracted and shown in the hydraulic control device for the automatic transmission.

FIG. 5 is a flow chart showing a basic control flow of the above-mentioned speed change.

6 is a flowchart showing a continuation of the control flow of FIG.

FIG. 7 is a gear shift characteristic diagram when the brake B2 is rapidly drained at the same time as the second speed gear synchronization detection.

FIG. 8 is a gear shift characteristic diagram when the brake B2 is rapidly drained after waiting for a predetermined time after the second speed synchronization is detected.

[Explanation of symbols]

 B2, B3 ... Brake 20 ... Hydraulic control device 30 ... Computer 40 ... Various sensor parts

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kunihiro Iwatsuki, 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor, Masahiko Ando, 10 Takane, Fujii Town, Aichi Prefecture Aisin Ai In W Co., Ltd. (72) Inventor Yoshihisa Yamamoto 10 Takane, Fujii-cho, Anjo City, Aichi Aisin AW Co., Ltd.

Claims (2)

[Claims] 1. A shift control device for an automatic transmission, which may execute a downshift of a clutch-to-clutch related to two friction engagement devices, wherein an input speed of the automatic transmission reaches a synchronization point of a low speed stage. After detecting that the input rotation speed has reached the synchronization point by the synchronization detection means for detecting whether or not the engagement oil pressure of the engagement side friction engagement device is set to a predetermined low value. From the predetermined value after the synchronization detection, a hydraulic control means for decreasing the released hydraulic pressure from a predetermined high pressure value, a means for detecting the input torque of the automatic transmission, and a higher input torque, the lower the low speed. A shift control device for an automatic transmission, comprising: a unit that sets the predetermined period of time from detection of gear synchronization to reduction of hydraulic pressure of the disengagement side frictional engagement device to a long time. 2. A shift control device for an automatic transmission, which may execute a downshift of a clutch-to-clutch related to two friction engagement devices, wherein an input speed of the automatic transmission reaches a synchronization point of a low speed stage. After detecting that the input rotation speed has reached the synchronization point by the synchronization detection means for detecting whether or not the engagement oil pressure of the engagement side friction engagement device is set to a predetermined low value. From the predetermined high pressure value after a predetermined time from the synchronization detection, a hydraulic pressure control means for detecting the oil temperature of the automatic transmission, and a means for detecting the oil temperature of the automatic transmission. And a means for setting the predetermined time from when the low speed gear is synchronously detected to when the hydraulic pressure of the disengagement side frictional engagement device is lowered, and a shift control device for an automatic transmission, comprising: