JP3089930B2 - Transmission control device for automatic transmission - Google Patents

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 used in an automobile or the like, and more particularly to a technique for reducing a shift shock at the time of kick down during extremely low speed running.

[0002]

2. Description of the Related Art In an automatic transmission for an automobile, a transmission mechanism using a planetary gear is generally used, and a sun gear or a planetary gear is provided by a hydraulic friction engagement element such as a hydraulic wet multi-plate clutch or brake, a hydraulic band type brake, or the like. A desired gear is obtained by re-gripping the carrier or the like.

In recent automatic transmissions, an electronic control unit (ECU) that performs feedback control of an electromagnetic valve for hydraulic control by an electronic control unit (ECU) to engage and disengage a hydraulic friction engagement element has been increased. ing. In such an automatic transmission, the shift control is performed based on a shift map using the throttle opening and the vehicle speed as parameters. That is, a shift command is output when the operating state crosses the downshift line or the upshift line on the shift map, and the solenoid valve is feedback-controlled in accordance with the shift command and supplied to the coupling-side hydraulic friction engagement element. The working hydraulic pressure or the working hydraulic pressure discharged from the release side hydraulic friction engagement element is adjusted.

[0004] Generally, feedback control is performed such that the rate of change of the turbine speed (input shaft speed) in the speed change process matches the target rate of change. For example, JP-A-4-25
In the hydraulic circuit of the automatic transmission described in Japanese Unexamined Patent Publication No. 662, the hydraulic pressure is discharged through the 2-3 shift valve 82 and the orifice 86 as shown in FIG. The clutch 31) is released to gradually increase the turbine speed, and when the turbine speed reaches the synchronous speed, the full pressure is supplied to the apply chamber 64 of the kick down servo 61 via the 1-2 shift valve 71. By the coupling side frictional engagement element (kick down brake 34)
Is engaged. At this time, if the rate of change of the turbine speed becomes higher than the target rate of change (that is, if the turbine starts to blow up), it is necessary to operate the front clutch 31 again to the engagement side, so that the third gear is set. Front clutch 31 to establish and kickdown brake 3 to establish second speed
Release oil chamber 6 of kick down servo 61 that drives 4
5 is communicated with communication oil passages 81 and 88 and the supply oil pressure of the kick down servo 61 to the apply oil chamber 64 is controlled, so that the release oil chamber 65 and the communication oil passages 81 and 88 are controlled.
The front clutch 31 is re-engaged by utilizing the remaining pressure inside.

In the above-mentioned automatic transmission, if the driving state changes to the second speed range while the vehicle is traveling at the fourth speed, a downshift to the second speed is commanded. Is impossible due to the structure of the hydraulic circuit.
A procedure is adopted in which a shift to the second speed is performed after the speed is established. In this case, first, in the 4-3 downshift, the supply hydraulic pressure of the kickdown servo 61 to the release oil chamber 65 is controlled by feedback control to release the kickdown brake 34 and engage the front clutch 31. The third gear is achieved.

Thereafter, the 3-2 downshift is executed continuously. As described above, this control is performed by controlling the hydraulic pressure supplied to the apply oil chamber 64 by the kick down servo 61, thereby controlling the front clutch. The discharge of the hydraulic pressure from 31 is controlled. By the way, in the 3-2 downshift, in order to feedback-control the oil pressure supplied to the apply oil chamber 64, the piston 66 needs to be completely returned. It takes about 0.7 seconds to completely release.

For this reason, 3-3 immediately after the 4-3 downshift.
In the 2-downshift, conventionally, open loop control is executed instead of feedback control. As shown in the graph of FIG. 11, this open-loop control is performed by turning off the electric switch (kick-down servo switch 69) that operates immediately before the engagement position of the kick-down servo 61.
When the F signal is input (point e in the figure), the solenoid valve for driving the kick-down servo 61 is driven at a predetermined duty ratio for a fixed time (t4), and thereafter (point f in the figure), the duty is gradually reduced. By reducing the ratio, the synchronization determination time (g in the figure, g
), The operation of the solenoid valve is stopped. As a result, the hydraulic pressure of the front clutch 31 rises again via the release oil chamber 65 of the kick down servo 61 and the residual pressure in the communication oil passages 81 and 88 immediately before the kick down brake 34 is engaged. As a result, the front clutch 31 is again operated to the engagement side to be in a so-called half-clutch state,
While the turbine speed is prevented from rising, the kickdown brake 34 can be engaged at full pressure at the time of synchronization determination at which the turbine speed is equivalent to the second speed.

[0008]

However, even with the above-described open loop control, the release control of the front clutch 31 may not be smoothly performed at a very low turbine speed. That is, in such a case, the difference in the synchronous turbine speed between the third speed stage and the second speed stage is of course very small, and after the kick-down servo switch 69 outputs the OFF signal, In short, synchronization is determined in a short time. If the response of the piston 66 in the kick down servo 61 is poor,
After the synchronization judgment, the kick-down servo switch 69
In some cases, the F signal was output. As a result, the kick-down brake 34 is also connected at full pressure in a state where the release control of the front clutch 31 can be hardly or not performed, so that there is a possibility that a so-called interlock state occurs and a large shift shock occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a shift control device for an automatic transmission which reduces shift shock at the time of kick down during extremely low speed running.

[0010]

SUMMARY OF THE INVENTION Therefore, a shift control device for an automatic transmission according to the present invention has the following objects.
A first frictional engagement element that establishes a first gear , a second frictional engagement element that establishes a second gear that is lower than the first gear, and a third frictional element that establishes a higher gear than the first gear. From the gear
During the downshift to the second speed, downshift command means for outputting a downshift command from the first speed to the second speed engages the second frictional engagement element. an engagement condition detecting means for outputting an engagement immediately before the signal at the time when a state immediately before, when said vehicle speed when the downshift command detection is equal to or less than a predetermined value, the first friction Kosugakari from the time of the engagement immediately before the signal input After supplying a predetermined hydraulic pressure to the combined element for a predetermined time, the second
Characterized in that comprises a hydraulic control means for engaging and supplies the maximum oil pressure to the frictional Kosugakarigo element.

[0011]

According to the shift control device of the present invention, the third shift stage is changed to the third shift stage.
During the downshift to the 2nd gear, from the 1st gear
If the vehicle speed is equal to or lower than a predetermined value when downshifting to the second gear, the first gear is established immediately before the second frictional engagement element that establishes the second gear is engaged at full pressure. A predetermined oil pressure is supplied to one friction engagement element for a predetermined time. As a result, the shift can be completed without performing the synchronization determination, so that the shift shock during the engagement does not occur.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. In the description of the embodiments, the same members as those of the above-described conventional device are denoted by the same reference numerals. FIG. 1 shows a schematic configuration of a power plant of a passenger car to which a shift control device according to the present invention is applied. In the figure, an automatic transmission 2 is connected to the rear end of the engine 1, and the output of the engine 1 is transmitted to drive wheels (not shown) via the automatic transmission 2. The automatic transmission 2 includes a torque converter 3, a transmission main body 4, and a hydraulic controller 5, and the controller 5 is driven and controlled by an ECU (electronic control unit) 6. The transmission body 4 incorporates a hydraulic friction engagement element such as a hydraulic clutch and a hydraulic brake in addition to the planetary gear mechanism 30. The hydraulic controller 5
Contains a plurality of solenoid valves duty-driven by the ECU 6 in addition to a hydraulic circuit formed integrally.

On the other hand, the ECU 6 includes an input / output device (not shown), a storage device (RAM, BURAM, ROM, etc.), a central processing unit (CPU), a timer counter, and the like.
On its input side, an NE sensor 7 for detecting the engine speed NE, a throttle sensor 8 for detecting the opening degree θTH of the throttle valve, an NT sensor 9 for detecting the turbine speed NT of the torque converter 3, and an output shaft rotation of the transmission. A NO sensor 10 for detecting the number NO and a kick down servo switch 69 for detecting the piston position of the kick down servo are connected. The ECU 6 is connected to various sensors and switches such as an inhibitor switch for detecting the position of the shift speed and an oil temperature sensor for detecting the operating oil temperature, in addition to these sensors. Not shown because it is not directly related.

FIG. 2 schematically shows the torque converter 3 and the gear train in the transmission main body 4. As shown in this figure, the torque converter 3 includes the casing 2
0, a pump 21, a stator 22, a turbine 23 and the like. The pump 21 is connected to a crankshaft 24 of the engine 1 via a casing 20. The stator 22 is held by a casing 26 of the transmission main body 4 via a one-way clutch 25, and the turbine 24 is connected to an input shaft 27 of the transmission main body 4.

In the transmission body 4, in addition to the planetary gear mechanism 30, three sets of clutches 31, 32, 33, two sets of brakes 34, 35, and one set of one-way clutch 36 are provided. . The planetary gear mechanism 30 includes a ring gear 37, a long pinion 38, a short pinion 39, a pinion carrier 40 that rotatably supports these pinions 38, 39, a front sun gear 41, and a rear sun gear 42. The ring gear 37 is connected to the output shaft 43, and the front sun gear 41 is connected to the kick down drum 44,
It is connected to the input shaft 27 via the front clutch 31. The rear sun gear 42 is connected to the input shaft 27 via the rear clutch 32, and the kick down drum 44 is connected to the casing 26 via the kick down brake 34. Further, the pinion carrier 40 is fixed to the casing 26 via a low-reverse brake 35 and a one-way clutch 36 provided together, and the input shaft 27 via a fourth-speed clutch 33 provided at the rear end of the casing 26. Linked to

The rotational torque of the input shaft 27 is transmitted to the output shaft 43 via the planetary gear mechanism 30, and further transmitted from the output gear 45 fixed to the output shaft 43 to the driven gear 47 via the idle gear 46. You. And the driven gear 47
The power is transmitted to a differential unit 51 that drives left and right axles 50 via a helical gear 49 fixed to a transfer shaft 48 integral with the transmission shaft 48. The casing 26 is provided with an NT sensor 9 for detecting a turbine speed NT via an input shaft 27 and an NO sensor 10 for detecting an output shaft speed NO via a driven gear 47.

FIG. 3 shows only a portion of the shift hydraulic control device that drives and controls the front clutch 31 and the kick down brake 34. The overall configuration and operation of the shift hydraulic control device of the present embodiment are described in
The description of other clutches and brakes is omitted since it is already known in Japanese Patent No. 6258. As shown in FIG. 3, the kick down brake 34 includes a brake band 60 wound around the kick down drum 44.
And a kick-down servo 61 for driving the brake band 60. Kickdown servo 61
Is a housing 63 having a stepped cylinder bore 62
And a stepped piston 66 which is slidably fitted into the cylinder hole 62 and divides the cylinder hole 62 into an apply oil chamber 64 and a release oil chamber 65. The actuator includes an actuator rod 67 projecting toward the band 60 and having an end in contact with the brake band 60, and a return spring 68 for urging the piston 66 in a direction to separate the actuator rod 67 from the brake band 60.
The pressure receiving area of the piston 65 is smaller on the apply side than on the release side because the apply oil chamber 64 is defined by the step of the piston 65 itself.

In FIG. 3, reference numeral 69 denotes a kick-down servo switch mounted on the housing 63,
The position of No. 6 is detected and a signal is output. This signal is turned on when the piston 66 moves to the right in the drawing, that is, when the brake band 60 releases the kick-down drum 44, the piston 66, that is, the actuator rod 67 moves to the left, and the brake band 60 kicks down. It is turned off immediately before the drum 44 is locked.

Apply oil chamber 6 of kick down servo 61
4 is connected to a 1-2 shift valve 71 via an oil passage 70, and the 1-2 shift valve 71 is further connected to a shift control valve 73 via an oil passage 72. 1-2 shift valve 7
1 is driven and controlled by a control oil pressure from a switching valve (not shown), the spool 71a moves to the left end in the figure to shut off the oil passage 70 and the oil passage 72 in the first speed, and The spool 71a moves to the right end as shown in FIG.
And the oil passage 72. The shift control valve 73 is
Depending on the position of the spool 73a, the oil passage 72 is
5 (OFF state in the figure) or the oil passage 72
Is connected to the line pressure oil passage 76 (ON state). A control oil passage 77 is connected to the shift control valve 73. When the control oil pressure supplied from the control oil passage 77 urges the spool 73 a, the spool 73 a is turned on to turn on the oil passage 72 and the line pressure oil passage. And 76.

A normally closed solenoid valve 80 having an oil discharge port 79 driven by the ECU 6 is connected to the control oil passage 77 via an oil passage 78. And the solenoid valve 8
When 0 is turned on, the control oil pressure is discharged from the oil discharge port 79, the oil passage 72 communicates with the oil discharge port 75 of the shift control valve 73, and the operation in the apply oil chamber 64 via the oil passages 70, 72. The oil is discharged from the oil discharge port 75.
When the solenoid valve 80 is turned off, the shift control valve 73 is turned on by the control oil pressure, and the oil passage 7 is turned off.
2 is communicated with a line pressure oil passage 76, and hydraulic oil is supplied into the apply oil chamber 64 via oil passages 72 and 70.

On the other hand, a 2-3 shift valve 82 is connected to a release oil chamber 65 of the kick down servo 61 via an oil passage 81. The 2-3 shift valve 82 is driven and controlled by a control oil pressure from a switching valve (not shown), and at the second speed stage, the spool 82a moves to the left end shown to communicate the oil passage 81 with the discharge oil passage 84, At the time of the speed stage, the spool 82a moves to the left end in the drawing, and the oil passage 81 communicates with the oil passage 85 connected to the oil passage 70. The discharge oil passage 84 and the oil passage 85 have orifices 86 and 87, respectively.
The discharge and supply of hydraulic oil are performed gradually. An oil passage 88 communicating with an apply oil chamber (not shown) of the front clutch 31 is connected to the oil passage 81, and the same hydraulic pressure is used for the release oil chamber 65 of the kick down servo 61 and the apply oil chamber of the front clutch 31. Works.

In the transmission 2 of this embodiment, as shown in the engagement table of Table 1, each clutch or brake is engaged or released to achieve four forward speeds and one reverse speed. I do. In Table 1, ○ indicates the engaged state, and ● indicates the locked state of the one-way clutch. The engagement states in the first to fourth gears in the table are all in the drive range.

[0023]

[Table 1]

That is, in the first gear, the rear clutch 32
Engages the rear sun gear 42 with the input shaft 27,
In the power-on state, the one-way clutch 36 locks the pinion carrier 40 to the casing 24. In the second speed, the front sun gear 41 is locked to the casing 26 via the kick down drum 44 by the kick down brake 34 while the rear clutch 32 is engaged. At the third speed, the front clutch 31 is also engaged while the rear clutch 32 is engaged, so that the planetary gear mechanism 30 is directly connected. At this time, the fourth speed clutch 33 is also engaged in preparation for shifting to the next fourth speed. In the fourth speed, the front clutch 31 and the rear clutch 32 are released, and the kick-down brake 34 is engaged again to lock the front sun gear 41 by the fourth speed clutch 33 and to input the pinion carrier 40. The shaft 27 is engaged. Further, in the reverse gear, the front clutch 31 is engaged to couple the front sun gear 41 to the input shaft 27, and the low reverse brake 35 is engaged to fix the pinion carrier 40 to the casing 26.

Next, the operation of this embodiment will be described. In the automatic transmission according to the present embodiment as well, when a downshift command to the second speed is output during traveling at the fourth speed, the same as in the conventional apparatus, once
A procedure for establishing the second gear and then shifting to the second gear is adopted. That is, first, in the 4-3 downshift, the front clutch 31 and the rear clutch 32 are engaged while releasing the kick down brake 34 to achieve the third speed. Thereafter, the kick down brake 34 is engaged while the front clutch 31 is released in the 3-2 downshift to achieve the second speed. This operation is performed by using the front clutch 31 and the kick down brake 34 shown in FIG.
Is considered as follows. In the present embodiment, the first speed is the third speed and the second speed is the second speed. Similarly, the first frictional engagement element is a front clutch 31 and the second frictional engagement element is a kick down brake 34.

In the fourth speed, the solenoid valve 80 is not energized (duty 0%), so the spool 73a of the shift control valve 73
Moves rightward in the figure, the spool 71a of the 1-2 shift valve 71 is at the right end as shown, and the spool 82a of the 2-3 shift valve 82 is at the left end as shown,
The release oil chamber 65 of the front clutch 31 and the kick down servo 61 is released and the kick down servo 6 is released.
An oil passage 76 and a shift control valve 7 are connected to the first apply oil chamber 64.
3, line pressure is supplied via the oil passage 72, the 1-2 shift valve 71, and the oil passage 70.

When downshifting from fourth gear to third gear, the ECU 6 controls a switching valve (not shown) to perform 2-3 shifting.
The spool 82a of the shift valve 82 is moved to the right end in the figure. Then, the oil passage 88 and the oil passage 81 are communicated with the oil passage 85, and the oil passages 72 and 70 are connected to the release oil chamber 65 of the kick down servo 61 and the apply oil chamber of the front clutch 31.
Hydraulic fluid is supplied. As a result, in the kick down servo 61, the piston 66 moves toward the apply oil chamber 64 due to the difference in the pressure receiving area and the spring force of the return spring 68, and the kick down drum 44 is locked by the brake band 60. The kick-down brake 34 is released and the front clutch 31 is engaged, and the third speed is established. (At this time, the oil pressure is still supplied to the apply oil chamber 64 of the kick-down servo 61.) At this time, the electromagnetic valve 80 is feedback-controlled to drive the shift control valve 73, so that the oil passage 72 The inflowing line pressure can be reduced to a desired pressure, and the feeling during a downshift can be controlled. Further, even after the release of the kick-down brake 34 and the engagement of the front clutch 31 to establish the third speed, the operating oil is continuously supplied to the release oil chamber 65 of the kick-down servo 61 for a predetermined time. Piston 6 after elapse
6 returns to the apply oil chamber 64 side.

On the other hand, when performing a downshift from the third speed to the second speed, the ECU 6 controls a switching valve (not shown) to move the spool 82a of the 2-3 shift valve 82 to the left end side again as shown. Then, the oil passage 88 and the oil passage 81 communicate with the discharge oil passage 84, and the working oil is discharged from the apply oil chamber of the front clutch 31 and the release oil chamber 65 of the kickdown servo 61. As a result, the front clutch 3
In the kick down servo 61, the hydraulic oil introduced into the apply oil chamber 64 via the oil passages 72 and 70 causes the piston 66 to release the piston 66 in the release oil chamber 6.
The brake band 60 which has moved to the fifth side and is pressed by the actuator rod 67 integral with the piston 66 locks the kickdown drum 44, and the second speed is established.
The operation oil is gradually discharged by the orifice 86 provided in the discharge oil passage 84, and also in this case, the feedback during the downshift can be controlled by feedback-controlling the solenoid valve 80.

Hereinafter, the procedure of the shift control according to the present invention will be described with reference to the flowcharts of FIGS. A downshift from the fourth gear to the third gear (4-3 shift) is performed during traveling, and when the downshift is completed, the shift control main routine in FIG. 4 is started. When control is started, E
First, in step S1, the CU 6 determines whether a downshift (3-2 shift) command to the second speed is output. If this determination is negative (NO), the ECU 6 proceeds to step S2, and determines whether an upshift command to the fourth gear is output this time. If the determination is affirmative (YES), the process proceeds to step S3 to execute an upshift subroutine from the third speed to the fourth speed, and if NO, returns to step S1 to repeat the control. .

If the determination in step S1 is YES, that is, if a 3-2 shift command is output,
In step S4, the ECU 6 outputs the 3-2 shift command to t1 seconds after the completion of the 4-3 shift (0.7 seconds in this embodiment).
It is determined whether or not it has been performed within. This determination confirms that the hydraulic oil has been supplied to the release oil chamber 65 of the kick down servo 61 and the piston 66 has completely returned. If this determination is NO, the ECU 6 proceeds to step S5 and executes a 3-2 feedback control subroutine.

Hereinafter, the 3-2 feedback control subroutine will be described with reference to FIGS. 5 to 7. First, the relationship between the turbine speed and the drive duty ratio of the solenoid valve 80 will be described with reference to FIG. . If a downshift (3-2 shift) command to the second gear is output during traveling in the third gear, the EC
U6 first moves the 2-3 shift valve 82 to the left end as shown to discharge hydraulic oil from the apply oil chamber of the front clutch 31 and the release oil chamber 65 of the kick-down servo 61, while the solenoid valve 80 Is controlled as shown in the graph of FIG. That is, from the point of time of inputting the 3-2 shift command (ss point in FIG. 10), the ECU 6 firstly sets t2.
Solenoid valve 80 with a relatively low duty ratio DU2 over seconds.
Drive. This is for the following reason.

That is, the piston 66 is in a stopped state until the 3-2 shift command is output, and the static friction coefficient acts between the piston 66 and the cylinder hole 62. If you try to move the piston 66 from this state,
It does not move easily due to a large coefficient of static friction. Therefore,
By supplying a relatively high oil pressure to the apply chamber 64 by outputting the duty ratio DU2 for t2 seconds, the coefficient of friction acting between the piston 66 and the cylinder bore 62 can be calculated as the static friction coefficient as the dynamic friction coefficient (dynamic friction coefficient <static friction coefficient). Coefficient) to improve the movement of the piston 66.

When t 2 seconds have elapsed (point a in FIG. 10)
Therefore, after outputting the relatively high duty ratio DU3, the ECU 6 drives the solenoid valve 80 while gradually increasing the drive duty ratio. Then, a relatively low hydraulic pressure corresponding to the duty ratio DU3 is supplied to the apply oil chamber 64,
The piston 66 gradually moves to the release oil chamber 65 side.
When the front clutch 31 is gradually released and the actual turbine speed NT becomes larger than the third-gear synchronous turbine speed NTC3 by a threshold value NTB1 (point b in FIG. 10), the ECU 6 The ratio DU4 is output, and the drive duty ratio of the solenoid valve 80 is feedback-controlled so that the actual change rate NTR 'of the turbine speed falls within a predetermined range. That is, the feedback control of the supply hydraulic pressure to the apply oil chamber 64 is also performed on the front clutch 31 in the same manner, and the discharge oil passage 8 is controlled.
The disengagement state of the front clutch 31 is controlled by the balance with the amount discharged from the front clutch 6.

Next, the ECU 6 calculates the actual turbine speed NT.
From the second speed stage synchronous turbine speed NTC2 by a threshold value NTB2 (synchronization determination time point c in FIG. 10), the actual change rate NTR 'of the turbine speed becomes -10 rpm / s.
The feedback control is continued for t3 seconds so as to be 0 rpm / s, and thereafter (point d in FIG. 10), the drive duty ratio of the solenoid valve 80 is set to 0, and the kickdown brake 34 is operated at full pressure.
Is engaged. Here, the reason why the feedback control is continued for t3 seconds after the synchronization determination will be described.

That is, at the synchronization determination point (point c), there is still some margin in the kick-down stroke. If the duty ratio is set to 0% and the full pressure is supplied, the piston 66 moves rapidly over the extra stroke. After that, the kick down drum 44 is suddenly grasped, and a shift shock occurs. Therefore, during t3 seconds after the synchronization determination, the feedback control is continued so that the actual rate of change NTR 'of the turbine speed becomes substantially zero, thereby suppressing an increase in the turbine speed and increasing the synchronous speed of the second speed stage. In addition to converging to the vicinity, a surplus stroke is eliminated so that a shift shock does not occur even when full pressure is applied.

Next, the procedure of the 3-2 feedback control will be described with reference to FIGS. When the 3-2 feedback control is started, the ECU 6 first detects in step S10 in FIG. 5 a predetermined time (180 ms in the present embodiment) before the control start time (ss point in FIG. 10) and sets the RA.
It is determined whether or not the throttle opening θTH stored in M is larger than a predetermined value (15% in this embodiment). This is to determine whether the 3-2 shift is kick down or on down. If this determination is YES, it is recognized that the vehicle is in the on down state, and in steps S11 and S12,
The duty ratios D3O / D and D4O / D, which are relatively small, are substituted for the duty ratios DU3 and DU4, respectively. If the determination in step S10 is NO, it is recognized that the kick-down state is established, and steps S13 and S14 are performed.
Then, relatively large duty ratios D3K / D and D4K / D for kickdown are substituted for the duty ratios DU3 and DU4, respectively.

The duty ratio D3O / D for on-down,
D4O / D is the duty ratio for kickdown D3K / D, D4K
The reason why the value is set smaller than / D is as follows.
If the driver suddenly depresses the throttle pedal while traveling on a flat road with the throttle valve being almost fully closed, a shift command is output rapidly across the downshift line on the shift map, so-called kickdown is performed. . Also,
When the throttle pedal is further depressed from a state in which the throttle pedal is depressed to a certain extent while traveling on an uphill road, a shift command is also output across the downshift line, and a so-called power-on downshift (hereinafter referred to as on-down) is performed. Done. Comparing the engine torque (acceleration force) at the time of both shifts, the engine speed is relatively small in the case of kick-down because the rise of the engine speed is delayed, and the engine speed is already somewhat high in the case of on-down. Because it is relatively large.

Therefore, when the solenoid valve is driven at the same duty ratio as that at the time of kick down at the time of on-down to release the disengagement-side friction engagement element, the oil pressure is excessively released from the disengagement-side friction engagement element, and further, the engine is disengaged. Since the torque is large, the turbine blows up instantaneously, which may cause a large shift shock when the engagement-side friction engagement element is engaged. Conversely, if the duty ratio is set to a value suitable for on-down, the release of the hydraulic pressure from the disengagement side frictional engagement element is delayed, and the disengagement side frictional engagement element and the engagement side frictional engagement element are simultaneously engaged. In addition, there is a problem that the planetary gear mechanism becomes inoperable, that is, a so-called interlock phenomenon occurs and a shock occurs. Therefore, the on-down duty ratio D
3O / D and D4O / D have the duty ratio D3K /
Setting these values smaller than D and D4K / D eliminates these problems.

Thereafter, the ECU 6 proceeds to step S15.
Then, the duty ratio DU2 is output, and the solenoid valve 80 is driven for t2 seconds to improve the movement of the piston 66 as described above. Next, the ECU 6 outputs the duty ratio DU3 in step S16 to drive the solenoid valve 80, and in step S16
At 17, it is determined whether or not NT ≧ NTC3 + NTB1, that is, whether or not the actual turbine speed NT has started to rise from the third-gear-stage synchronous turbine speed NTC3 by releasing the front clutch 31. The third-speed synchronous turbine speed NTC3 is calculated by multiplying the output shaft speed NO by the third-speed gear ratio.

If the determination in step S17 is NO, the ECU 6 adds a predetermined value α to the duty ratio DU3 in step S18, and then proceeds to step S16 to drive the solenoid valve 80. By repeating the processing in step S18, the supplied hydraulic pressure gradually decreases, and the front clutch 31 is driven to the release side. At this time, since the duty ratio D3O / D is relatively small at the time of on-down, the hydraulic pressure supplied to the front clutch 31 is made high so as to correspond to the engine torque, and the rapid rise of the turbine 23 is prevented. Also, at the time of kick down, the duty ratio D3K / D is relatively large, so the hydraulic pressure supplied to the front clutch 31 is low, and the turbine speed N
T rises quickly.

On the other hand, if the determination in step S17 is YES, the ECU 6 proceeds to step S19 in FIG. 6, outputs the duty ratio DU4, and drives the solenoid valve 80. At this time, the duty ratio D4K / D
Is relatively small, the hydraulic pressure supplied to the front clutch 31 is high enough to cope with the engine torque, and the rapid rise of the turbine 23 is prevented. Also, at the time of kick down, the duty ratio D4K / D is relatively large, so that the hydraulic pressure supplied to the front clutch 31 is low, and the turbine speed NT rapidly rises.

Next, the ECU 6 determines in step S20 that NT
It is determined whether or not ≧ NTC2−NTB2 holds, that is, whether or not the actual turbine speed NT has started to reach the second speed synchronous turbine speed NTC2. Here, NTB2 is a synchronization determination threshold value. If this determination is NO, E
The CU 6 proceeds to step S21, where the turbine rotational speed NT
It is determined whether or not the rate of change NTR ′ is equal to or higher than the upper limit threshold value NTO1 ′ before synchronization determination (60 rpm / s in the present embodiment).
If it is ES, the duty ratio D
The predetermined value β is subtracted from U4, the hydraulic pressure is increased, and the engagement of the front clutch 31 is strengthened. If this determination is NO, the ECU 6 determines in step S23 that the rate of change NTR 'is equal to the lower limit threshold NTO2' before synchronization determination (30 rpm in the present embodiment).
/ S) is determined. If the determination is YES, the ECU 6 proceeds to step S24.
Then, a predetermined value β is added to the duty ratio DU4 to lower the hydraulic pressure and weaken the engagement of the front clutch 31. Further, if the determination in step S23 is NO, in step S25, the ECU 6 maintains the engagement state of the front clutch 31 while keeping the duty ratio DU4 unchanged.

On the other hand, if the determination in step S20 is YES, that is, if the actual turbine speed NT starts to reach the second speed synchronous turbine speed NTC2, the ECU 6
Shifts to step S26 in FIG. 7, and starts the built-in timer T. Next, in step S27, the ECU 6 determines whether or not t3 seconds have elapsed after the start of the timer T, and proceeds to step S28 if NO.

In step S28, the ECU 6 determines whether or not the rate of change NTR 'of the turbine speed NT is equal to or greater than an upper limit threshold value NTO3'(<NTO1', in this embodiment, 0 rpm / s) after the synchronization determination. If YES, the predetermined value γ is subtracted from the duty ratio DU4 in step S29, and the hydraulic pressure is increased to increase the engagement of the front clutch 31. Also,
If this determination is NO, the ECU 6 determines in step S30 that the rate of change NTR 'is equal to the lower limit threshold NTO4' after the synchronization determination.
(<NTO2 ', in this embodiment, -10 rpm / s). If this determination is YES, the ECU 6 adds a predetermined value γ (≦ β) to the duty ratio DU4 in step S31, reduces the hydraulic pressure, and weakens the engagement of the front clutch 31. Further, step S3
If the determination at 0 is NO, the ECU 6 keeps the engagement state of the front clutch 31 while keeping the duty ratio DU4 at step S32. After the elapse of t3 seconds after the start of the timer T, the determination in step S27 is YE
When S is reached, the ECU 6 proceeds to step S33, stops driving the electromagnetic valve 80, and ends the feedback control.
Thereby, the apply oil chamber 6 of the kick down servo 61
4, the kick down brake 34 completely locks the kick down drum 44, and the shift is completed. still. The time t3 at which the timer T finishes counting up is set longer than the time required until the kickdown brake 34 is engaged. That is, as described above, the piston 66 of the kick down servo 61 makes a full stroke during the time t3 from the time of the synchronization determination, and at this time the full pressure is supplied, so that the complete locking can be performed without a shift shock. .

If the determination in step S4 of FIG. 4 is YES, that is, if the 3-2 shift command is issued within t1 seconds (0.7 seconds in this embodiment) after the end of 4-3 shift, The ECU 6 then determines in step S6 whether the current vehicle speed V is lower than a predetermined value VL (20 km / h in this embodiment). If this determination is NO, step S7
Then, during normal driving shown in the flowchart of FIG.
2. Execute the open loop control subroutine. In this subroutine, the ECU 6 drives the switching valve (not shown) to move the spool 82a of the 2-3 shift valve 82 to the left end as shown, and applies the apply oil chamber of the front clutch 31 and the release oil chamber 65 of the kickdown servo 61. , While the hydraulic oil is discharged, the solenoid valve 80 is controlled as shown in the graph of FIG. That is, when the piston 66 of the kick-down servo 61 moves and the OFF signal of the kick-down servo switch 69 is input (point e in FIG. 11), the solenoid valve 80 is turned on at a predetermined duty ratio Dd1 for a predetermined time t4. And then (point f in FIG. 11)
The drive duty ratio is gradually reduced, the drive of the solenoid valve 80 is stopped at the time of the synchronization determination (point g in FIG. 11), and the kickdown brake 34 is engaged at full pressure.

During normal running 3-2 When the open loop control is started, the ECU 6 first determines in step S40 in FIG. 8 whether or not an OFF signal has been input from the kick down servo switch 69. , This determination is repeated and the process stands by. When the determination in step S40 is YES, that is, when the brake band 60 is in a state immediately before locking the kickdown drum 44, the process proceeds to step S41 to start the timer T1.

Next, the ECU 6 determines in step S42 that NT
While monitoring whether or not ≧ NTC2−NTB2, that is, whether or not the actual turbine speed NT has started to synchronize with the second speed turbine speed NTC2, the determination in step S42 is NO.
In step S44, the ECU 6 outputs a predetermined duty ratio Dd1 to drive the solenoid valve 80. next,
In step S45, it is determined whether or not t4 seconds (160 ms in this embodiment) has elapsed after the start of the timer T1.
In the case of O, the process returns to step S42 to repeat the processing. If the determination in step S42 is YES before the elapse of t4 seconds, the drive of the solenoid valve 80 is stopped in step S43 to stop the control, and the full pressure is supplied to the kick down servo 61 to change the gear. Terminate.

If t4 seconds have elapsed after the start of the timer T1 and the determination in step S45 is YES, the ECU 6 proceeds to step S46, and determines again whether NT≥NTC2-NTB2. The determination in step S46 is N
If it is O, the duty ratio Dd is determined in step S47.
By subtracting the predetermined value d from 1 and increasing the hydraulic pressure of the kick down servo 61 to the apply oil chamber 64, the kick down brake 3
4. Enhance engagement. This process is repeatedly performed, and the hydraulic pressure is increased at a constant rate. When the result of the determination in step S46 is YES and the time reaches the synchronization determination time, the ECU
In step S46, the solenoid valve 80 is stopped in step S46, the full pressure is supplied to the kick down servo 61, and the shift is completed.

On the other hand, the determination in step S6 of FIG.
S, that is, when the current vehicle speed V is lower than the predetermined value VL,
In step S8, the ECU 6 executes an extremely low speed 3-2 open loop control subroutine shown in the flowchart of FIG. In this subroutine, the ECU 6
Operates the switching valve (not shown) as in the other cases,
As shown, the spool 82a of the shift valve 82 is moved to the left end to discharge the operating oil from the apply oil chamber of the front clutch 31 and the release oil chamber 65 of the kick down servo 61, while the solenoid valve 80 is moved to the position shown in FIG. Is controlled as shown in the graph of FIG. That is, when the OFF signal of the kick down servo switch 69 is input (h in FIG. 12).
(Point), the solenoid valve 80 is driven at a predetermined duty ratio Dd2 for a predetermined time, and thereafter (point i in FIG. 12)
The drive duty ratio of 0 is set to 0, and the kickdown brake 34 is engaged at full pressure.

When extremely low speed 3-2 open loop control is started, the ECU 6 first determines in step S50 in FIG. 9 whether or not an OFF signal has been input from the kick down servo switch 69. , This determination is repeated and the process stands by. Then, if the determination in step S50 is YES, that is, if the brake band 60 is in a state immediately before locking the kickdown drum 44,
In step S51, the timer T2 is started. Next, the ECU 6 determines in step S52 a predetermined duty ratio D
The solenoid valve 80 is driven by outputting d2 (40% in this embodiment). Next, in step S53, it is determined whether or not t5 seconds (150 ms in this embodiment) has elapsed after the start of the timer T2, and if NO, the process returns to step S52 to repeat the processing.

If t5 seconds have elapsed after the start of the timer T1 and the determination in step S53 is YES, the ECU 6 proceeds to step S54, resets the timer T2,
In step S55, the solenoid valve 80 is stopped, the full pressure is supplied to the kick down servo 61, and the shift is completed. At extremely low speeds, the absolute value of the turbine speed NT itself is small.
It has been confirmed by experiments by the inventors that the synchronous rotation is reached before the elapse of t5 seconds from the start of the timer T1.

In this control, since no synchronization judgment is made,
The release control of the front clutch 31 is performed unconditionally over a predetermined time. Therefore, even when the turbine speed NT reaches the synchronization determination speed in a very short time after the kick-down servo switch 69 outputs the OFF signal, the kick-down brake is performed with the turbine speed NT rising. 34 is prevented from being connected at full pressure, and the occurrence of a shift shock is prevented.

Embodiments of the present invention are not limited to the above embodiment. For example, in the above embodiment, the present invention is applied to the downshift from the third gear to the second gear, but the present invention is applied to other downshifts such as the fourth gear to the third gear or the second gear to the first gear. May be applied. In addition, the start condition of the 3-2 open loop control subroutine at an extremely low speed is determined not by the vehicle speed itself but by a predetermined value (for example, 500
rpm) or less.

[0054]

As described above in detail, according to the shift control device of the present invention, the shift from the third shift stage to the second shift stage is performed.
During downshifting, shift from the first gear to the second gear
When the vehicle speed is equal to or lower than a predetermined value when downshifting, the first friction engagement element that establishes the first shift speed immediately before engaging the second friction engagement element that establishes the second shift speed at full pressure. The first frictional engagement element is controlled to the half-clutch state even when the turbine speed reaches the synchronous speed in a very short time, so that the turbine speed can be increased. Is prevented, and shift shock at the time of engagement is prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a power plant to which a shift control device according to the present invention is applied.

FIG. 2 is a skeleton diagram showing a gear train in a transmission main body.

FIG. 3 is a control hydraulic circuit diagram of a front clutch and a kick down brake.

FIG. 4 is a flowchart illustrating a shift control main routine according to the present embodiment.

FIG. 5 is a flowchart showing a 3-2 feedback control subroutine.

FIG. 6 is a flowchart showing a 3-2 feedback control subroutine.

FIG. 7 is a flowchart showing a 3-2 feedback control subroutine.

FIG. 8 is a flowchart showing a 3-2 open loop control subroutine during normal running.

FIG. 9 is a flowchart showing a 3-2 open loop control subroutine at an extremely low speed.

FIG. 10 is a graph showing the relationship between the turbine speed and the solenoid valve drive duty ratio in 3-2 feedback control.

FIG. 11 is a graph showing the relationship between the turbine speed and the solenoid valve drive duty ratio in 3-2 open loop control during normal running.

FIG. 12 is a graph showing a relationship between a turbine speed and a solenoid valve drive duty ratio in 3-2 open loop control at an extremely low speed.

[Explanation of symbols]

 Reference Signs List 1 engine 2 transmission 4 transmission body 5 controller 6 ECU 7 NE sensor 8 throttle sensor 9 NT sensor 10 NO sensor 31 front clutch 34 kick down brake 61 kick down servo 66 piston 69 kick down servo switch 71 1-2 shift valve 73 Shift control valve 73 80 solenoid valve 82 2-3 shift valve

Continued on the front page (72) Inventor Shoji Nakamura 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Yoichi Furuichi 5-33-8 Shiba 5-chome, Minato-ku, Tokyo Mitsubishi (56) References JP-A-5-263910 (JP, A) JP-A-2-46360 (JP, A) JP-A-63-67454 (JP, A) JP-A-62-49065 (JP, A) JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F16H 59/00-61/12 F16H 61/16-61/24 F16H 63/40-63/48

Claims (2)

(57) [Claims] A first frictional engagement element that establishes a first shift speed; and a second frictional engagement element that establishes a second shift speed lower than the first shift speed.
A friction engagement element; and a second shift stage from a third shift speed higher than the first shift speed.
Time during downshift to gear speed, the downshift command means from the first shift stage and outputs the down-shift command to the second speed stage, said second frictional engaging element becomes engaged state immediately before An engagement state detecting means for outputting a signal immediately before engagement at a time when the vehicle speed at the time of detecting the downshift command is equal to or lower than a predetermined value; And a hydraulic pressure control means for supplying a maximum hydraulic pressure to the second frictional engagement element so as to engage the second frictional engagement element after supplying the hydraulic pressure over a period of time. 2. The method according to claim 1, wherein the downshift from the first gear to the second gear is performed during a downshift from the third gear to the second gear and under a predetermined condition. 2. The shift control of the automatic transmission according to claim 1 , wherein the hydraulic pressure supplied to the one friction engagement element is feedback-controlled so that a change rate of the input shaft rotation speed matches a predetermined target change rate. apparatus.