JPH11257482A - Shift controller for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ease a shift shock and provide a smooth engine brake by changing a shift point in downshifting in coasting according to the deceleration of a vehicle. SOLUTION: A duty ratio is feedback controlled so that a target rotational speed NTt in which a turbine rotational speed NT is set higher than an engine rotational speed NE by α to maintain the vehicle in a weak engine brake state. The shift point is calculated by taking account of the deceleration of the vehicle. At first, a coasting state is detected so that the complete stop time t17 is estimated according to the deceleration. Secondly, a point on a forth gear synchronous rotational speed DK4 in the time t13 when a second gear synchronous torational speed DK2 and NTt are crossed with each other is set to P0. A 2-1 shift point P21 is a time t12 before the point P0 by such a quantity that the first clutch C1 implements a fast quick fill so as to have a capacity. The shift points P32, P43 are decided based on the shift point P21.

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 suitable for use in performing a downshift during a coast in an automatic transmission for performing a so-called clutch-to-clutch shift.

[0002]

2. Description of the Related Art Generally, during a coast in which a driver closes a throttle opening or makes a driver's throttle lightly separated, a downshift is executed when the vehicle speed decreases and crosses a downshift shift point. Conventionally, shifting is performed at a preset coast-down shifting point. When this coast downshift is realized by a so-called clutch-to-clutch shift, the lowering of the hydraulic pressure of the high-speed side and the raising of the hydraulic pressure of the low-speed side are performed simultaneously to switch the engagement and disengagement of the clutch ( For example, JP-A-6-221347). At this time, the shift is executed in a coast state (a state in which power is transmitted from the wheel side to the engine side: a driven state). By engaging the step-side clutch (low-speed step side), an operation of raising the rotational speed to the synchronous rotation speed is performed.

[0003] However, in order to increase the turbine rotational speed by executing a shift, a time corresponding to the shift time is required. If the vehicle speed decreases during this period due to rapid deceleration, the turbine rotational speed falls below the engine rotational speed. There is a possibility that the driven state is temporarily switched from the driven state to the driving state.

Further, in an automatic transmission having a synchronizing mechanism, if the deceleration is large, there is a possibility that a problem may occur that the vehicle crosses the next shift point before there is not enough time to switch the synchro. .

Therefore, the shift point in this type of coast downshift is designed so that such a problem does not occur even during a certain rapid deceleration in consideration of the shift time and the synchro moving time, and the driven state can always be maintained. The vehicle speed is set higher than the normal shift point.

[0006]

However, if the shift point is set on the high vehicle speed side as described above, there is a possibility that excessive engine braking force will be generated at a low gear after the shift due to coast down. This causes a problem that the occurrence of a shift shock increases.

The present invention has been made in view of such a conventional problem, and alleviates a shift shock by determining a shift point, which has been basically fixed in the past, optimally in accordance with a running state. SUMMARY OF THE INVENTION It is an object of the present invention to provide a shift control device for an automatic transmission capable of obtaining a smooth engine brake.

[0008]

According to a first aspect of the present invention, there is provided a shift control device for an automatic transmission having a plurality of clutches and performing a downshift of a clutch-to-clutch shift according to a shift point during coasting. The object is achieved by providing a means for detecting a speed, and changing the shift point at the time of performing the downshift during the coast in accordance with the deceleration of the vehicle.

According to a second aspect of the present invention, there is provided an automatic transmission having a plurality of clutches and a plurality of synchronizing mechanisms, and performing a clutch-to-clutch shift for performing a downshift according to a shift point during coasting. In a shift control device for an automatic transmission that executes a fast quick fill in which a complete hydraulic pressure supply command is applied to a clutch to be engaged at an early stage of a clutch shift for a predetermined time, when performing the downshift during the coast, the synchronization mechanism moves. Means for calculating the time required for performing the first quick fill, a shift point based on the time required for the synchro to move, and a shift point based on the time required for the first quick fill. Means for selecting a shift point, wherein the downshift during the course is performed according to the selected shift point. By performing shift is obtained by solving the above problems as well.

[0010]

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

FIG. 3 is a diagram schematically showing the entire structure of a twin-clutch four-speed automatic transmission with a torque converter to which the present invention is applied.

In FIG. 3, 1 indicates an engine, 2 indicates a torque converter having a lock-up mechanism, and 3 indicates a twin clutch type automatic transmission.

An output shaft 10 of the engine 1 is connected to a front cover 20 of the torque converter 2. The front cover 20 is connected to a torque converter output shaft 24 via a pump impeller 21 and a turbine 22 connected via a fluid flow, or via a lock-up clutch 23. The output shaft 24 of the torque converter 2
The input shaft (transmission input shaft) 30 of the twin clutch type automatic transmission 3 is integrally rotatably connected. Note that 25
Is a stator and 26 is a one-way clutch.

The input shaft 30 is connected to a first clutch input disk C1i of the first clutch C1 and a second clutch input disk C2i of the second clutch C2.

The first clutch output shaft 4 is connected to the first clutch output disk C1o of the first clutch C1 and the second clutch output disk C2o of the second clutch C2, respectively.
0, the second clutch output shaft 50 is coaxially connected to the outside of the input shaft 30.

A countershaft 60 and an output shaft (transmission output shaft) 7
0 are arranged parallel to these axes.

A second speed drive gear I2, a countershaft drive gear Is, and a fourth speed drive gear I4 are fixedly connected to the second clutch output shaft 50.

On the other hand, the first clutch output shaft 40 has a fourth
A third speed drive gear I3 is fixedly connected to the speed drive gear I4, and a first speed drive gear I1 is fixedly connected to the torque converter 2 side.

The output shaft 70 has a second speed drive gear I2
The second speed driven gear O2 constantly meshing with the fourth speed drive gear I4, the fourth speed driven gear O4 constantly meshing with the third speed drive gear I3, the third speed driven gear O3 constantly meshing with the third speed drive gear I3, and the first speed drive gear I1 constantly. First speed driven gears O1 to be meshed with each other are rotatably mounted.

The first synchro (synchro mechanism) D1 comprises a first hub H1 fixedly connected to the output shaft 70 and a first sleeve S1 mounted on the outer peripheral end thereof so as to be slidable in the axial direction. The first sleeve S1 is connected to the first sleeve actuator AC via a first shift fork Y1.
By moving by T1 and engaging the first speed clutch gear G1 fixedly connected to the first speed driven gear O1 or the third speed clutch gear G3 fixedly connected to the third speed driven gear O3, The first speed driven gear O1 and the third speed driven gear O3 are selectively output shaft 70
Connect to.

Similarly, a second synchro (synchro mechanism) D
2 is a second hub H2 fixedly connected to the output shaft 70;
A second slidably mounted axially on its outer peripheral end
The second sleeve S2 is made up of the first sleeve S2.
The second sleeve clutch ACT2 is moved by the second sleeve actuator ACT2 via the shift fork Y2 and is fixedly connected to the fourth speed driven gear O4 or the second speed clutch G4 fixedly connected to the fourth speed driven gear O4. The fourth speed driven gear O4 and the second speed driven gear O2 are selectively connected to the output shaft 70 by engaging with the gear G2.

The countershaft 60 is provided with a countershaft driven gear Os which constantly meshes with the countershaft drive gear Is, and a reverse drive gear IR which meshes constantly with the first speed drive gear I1 via the idler gear MR. Counter shaft driven gear Os
Is fixedly connected to the countershaft 60 and always rotates integrally with the countershaft 60, but the reverse drive gear IR is rotatably mounted and has a third synchro (a synchro mechanism) disposed between the two gears. ) D3 selectively connects to the counter shaft 60.

The third synchro D3 comprises a third hub H3 fixedly connected to the countershaft 60, and a third sleeve S3 axially slidably mounted on the outer peripheral end of the third hub H3. The sleeve S3 is moved by the third sleeve actuator ACT3 via the third shift fork Y3,
The reverse drive gear IR is selectively rotated integrally with the sub shaft 60 by engaging with a reverse clutch gear GR fixedly connected to the reverse drive gear IR.

FIGS. 4A and 4B show the state of engagement of the first clutch C1, the second clutch C2, the first sleeve S1, the second sleeve S2, and the third sleeve S3 at each speed stage. It is a thing.

The circles indicate the engagement for transmitting the power at the shift speed, and Δ indicates that the preliminary selection for downshifting is performed, and Δ indicates that the preliminary selection for upshifting is performed. FIG. The engagement added by the preselection does not contribute to the transmission of power at that gear.

For example, in the first speed, the first clutch C1 is engaged, and the first clutch output shaft 40 connected to the first clutch output disk C1o is driven together with the first speed drive gear I1 and the third speed drive gear I3. The first-speed driven gear O1, which is always engaged with the first-speed drive gear I1, rotates, and then the first sleeve S1 moves to the first-speed clutch gear G.
By being located on the first side, the output shaft 70 rotates together with the first hub H1 and the second hub H2, and power is transmitted.

In the second speed, the second clutch C2 is engaged, and the second clutch output shaft 50 connected to the second clutch output disc C2o is connected to the second speed drive gear I2, the second clutch output shaft 50, the fourth clutch output shaft. The second speed driven gear O2, which is always meshed with the second speed drive gear I2, rotates together with the second speed drive gear I2 and the countershaft drive gear Is2, and then the second sleeve S2 moves toward the second speed clutch gear G2. , The output shaft 70 is connected to the first hub H1,
It rotates together with the second hub H2, and power is transmitted.

In the third speed, the first clutch C1 is engaged, and the first clutch output shaft 40 connected to the first clutch output disc C1o rotates together with the first speed drive gear I1 and the third speed drive gear I3. , Third speed drive gear I3
The third-speed driven gear O3, which is always meshing with the shaft, rotates,
Next, as described above, since the first sleeve S1 is located on the third speed clutch gear G3 side, the output shaft 70 rotates together with the first hub H1 and the second hub H2, and power is transmitted.

In the fourth speed, the second clutch C2 is engaged, and the second clutch output shaft 50 engaged with the second clutch output disc C2o is connected to the second speed drive gear I2, the second clutch output shaft 50, and the second clutch output shaft 50. The fourth-speed drive gear I4 rotates together with the countershaft drive gear Is, the fourth-speed driven gear O4 always meshing with the fourth-speed drive gear I4 rotates, and then the second sleeve S2 moves to the fourth-speed clutch gear G4. , The output shaft 70 is connected to the first hub H1,
It rotates together with the first hub H2 and power is transmitted.

In the reverse gear, the second clutch C2 is engaged,
The second clutch output shaft 50 connected to the second clutch output disk C2o rotates together with the second speed drive gear I2, the second clutch output shaft 50, the fourth speed drive gear I4, and the countershaft drive gear Is, and the countershaft drive is performed. The countershaft 60 rotates via the countershaft driven gear Os which is always meshed with the gear Is, and the reverse drive gear IR rotates due to the third sleeve S3 being located on the reverse clutch gear GR side. The first speed driven gear O1 is rotated via the reverse idler gear MR, and then the first sleeve S1 is positioned on the first speed clutch gear G1, so that the output shaft 70 is connected to the first hub H1 and the second hub H1. It rotates with H2 and power is transmitted.

For shifting between the shift speeds, the sleeve necessary for completing the transmission path of the shift speed after the shift is moved and engaged, and then one of the clutches used before the shift is engaged. While releasing, the other clutch used after the shift is engaged, and the sleeve that has completed the transmission path of the shift stage before the shift is moved and released.

For example, when shifting from the second gear to the third gear, the first sleeve S1 is moved so as to be engaged with the third clutch gear G3, the second clutch C2 is released, and the first clutch S2 is released. Engage C1 and move the second sleeve S2 out of engagement with the second speed clutch gear G2.

In this embodiment, as shown in FIG. 4B, the next gear is predicted from the running environment (for example, the vehicle speed) at that time, and the corresponding synchronization mechanism is previously engaged. In this way, control is performed so as to immediately start the clutch switching control when a shift is determined (described later).

Control of engagement and disengagement of first clutch C1 and second clutch C2 (clutch-to-clutch switching control)
Are respectively driven by hydraulic pressure on a first clutch / clutch plate (not shown) and a second clutch / clutch plate (not shown) connected to the first clutch input disk C1i and the second clutch input disk C2i, respectively. A first clutch / clutch plate (not shown) connected to the first clutch output disc C1o, a second clutch output disc C2o by a one clutch piston (not shown) and a second clutch piston (not shown);
This is performed by frictionally engaging a clutch / clutch plate (not shown).

The piston is driven by controlling the supply and discharge of hydraulic oil supplied from a hydraulic supply source OP in FIG. 3 to a piston oil chamber. The first clutch supply hydraulic control valve VC1 and the second clutch supply hydraulic pressure are controlled. The control valve VC2 is finely controlled by an electronic control unit (hereinafter referred to as ECU) 100.

The first sleeve S1 and the first sleeve S2
The movement of the third sleeve S3 is performed by the first sleeve actuator ACT1, the second sleeve actuator ACT2, and the third sleeve actuator ACT3, respectively, as described above.

Although a detailed description of the structure of each sleeve actuator is omitted, it is for moving the piston to which the shift fork is connected in a desired direction, and the hydraulic supply source O
This is performed by controlling the supply and discharge of the hydraulic oil supplied from P to the piston oil chambers formed on both sides of the piston.
Therefore, a valve that controls the supply of hydraulic oil to each piston oil chamber and a valve that controls the discharge of hydraulic oil from each piston oil chamber are provided, and the opening and closing of these valves are controlled by the ECU 100.

In the present invention, it is necessary to check whether each sleeve has moved to a predetermined position. Therefore, the first sleeve actuator ACT1, the second sleeve actuator ACT2, and the third sleeve actuator AC
T3 is a first, second and third sleeve position sensors 115a for detecting the position of the sleeve from the movement of the piston,
115b and 115c, the signals of which are
00 to the input interface circuit 101.

The ECU 100 is composed of a digital computer and has an input interface circuit 1
01, ADC (analog-to-digital converter) 102, CP
U (microprocessor) 103, RAM (random access memory) 104, ROM (read only memory)
105 and an output interface circuit 106.

The CPU 103 has a gear position sensor 111 for detecting a gear position and a vehicle speed (rotational speed of a transmission output shaft).
, A throttle opening sensor 113 that outputs a throttle opening, an input shaft rotation speed sensor 114 that detects the rotation speed of the input shaft 30, and a sleeve position provided in each of the aforementioned sleeve actuators. Sleeve position sensors 115a, 115b, 11
The output signal of each sensor such as 5c is input via the input interface circuit 101 or further via the ADC 102.

The CPU 103 calculates the values of the various sensors and R
In order to perform the control of the present invention, which will be described later, from the data stored in the OM 105, a signal for controlling a sleeve actuator for moving each of the sleeves is generated, and a first signal for controlling a clutch of a twin-clutch automatic transmission is provided. A signal for controlling the clutch supply hydraulic control valve VC1 and the second clutch supply hydraulic control valve VC2, and a signal for controlling the lock-up hydraulic control valve VL for controlling the lock-up clutch are generated. To send to.

Next, the contents of the control will be described in detail.

First, a description will be given of an embodiment relating to a downshift during coasting during slow deceleration. FIG. 1 is a time chart showing a method of setting a shift point in the control of a coast downshift during slow deceleration.

In this embodiment, the shift points for all shifts are sequentially determined and changed from the shift points on the lower gear side according to a flowchart described later.

However, here, in order to facilitate understanding,
First, how the coast downshift is performed based on the determined shift point (by the method described later) will be described from the outline of the qualitative work.
Further, the description is simplified by assuming that the engine rotation speed NE is constant.

This time chart shows the fourth gear and the second gear.
The duty ratio for the second clutch C2 serving also as the speed stage, the duty ratio for the first clutch C1 for the third speed stage and the first speed stage, the turbine rotation speed (= the rotation speed of the transmission input shaft 30) NT, It shows the relationship between the switching state of the second synchro D1, D2, the shift output, the engine rotational speed NE, the synchronous rotational speeds DK1, DK2, DK3, DK4 of the respective gears, and the target turbine rotational speed NTt described later.

In the column of duty ratio and oil pressure in FIG. 1, a thick line indicates a duty ratio and a thin line indicates oil pressure. When the duty ratio is 100%, each clutch C1,
100% line pressure is supplied to C2 and the duty ratio is 0
%, The hydraulic pressure of each clutch C1, C2 is completely drained.

As described above, the first clutch C1 also functions as the third-speed clutch cl3 and the first-speed clutch cl1, and the second clutch C2 functions as the fourth-speed clutch cl4. The second stage also functions as the clutch cl2. Hereinafter, for convenience of description, the description will be made by appropriately changing the names.

The portion shown at time t1 at the left end of FIG.
The third speed clutch is completely engaged with the third speed clutch cl4.
This shows a state before the shift operation in which cl3 is completely released (a state where the fourth speed is established).

From the state of the fourth speed stage, in a coast state (a state in which the throttle opening is fully closed or almost fully closed), the turbine rotational speed NT changes to the downshift point P7 (P4) of the third speed stage.
3) When the speed falls below, it is determined that there is a shift to be downshifted. First, at t2, the duty ratio of the fourth speed clutch cl4 is suddenly reduced, and the fourth speed clutch cl4 is released (not completely released). ).

At the same time, the third speed clutch cl3
In which the duty ratio of the third speed clutch cl3 is output at a duty ratio of 100% for a period T1 (an operation called a so-called first quick fill), and thereafter (from time t3) the duty ratio is reduced to DL1. To wait.

The duty ratio DL3 is a value just before the third speed clutch cl3 has a capacity.

Conventionally, the engagement of the third-speed clutch cl3 is started together with the release of the fourth-speed clutch cl4.
The turbine rotation speed NT starts increasing at time t3. In this embodiment, however, the turbine rotation speed NT is maintained to maintain the vehicle in a weak engine braking state.
However, the duty ratio DL1 is controlled so that the target rotation speed NTt is set to be higher than the engine rotation speed NE by a predetermined value α (α> 0). That is, at the time t4 when the turbine rotational speed NT (same as the synchronous rotational speed DK4 of the fourth speed stage at this time) becomes equal to the engine rotational speed NE + the predetermined value α, the duty ratio of the fourth speed stage clutch cl4 is completely drained (0 %), And the feedback control of the duty ratio of the third speed clutch cl3 is performed so that the turbine rotation speed NT maintains the target rotation speed NTt.

On the other hand, if it is detected that the drain timer T2, which has started counting from time t2, has elapsed (at time t2).
5) A command to switch the second synchro D2 from the fourth gear position to the second gear position is issued.

Here, the reason why the switching command for the second synchro D2 is started after waiting for the elapse of the drain timer T2 is that if the fourth speed clutch cl4 has at least some capacity. This is because there is a possibility that the switching of the second synchro D2 may be hindered, and this is prevented. As for the movement of the synchro, the switching is started, moved and completed as soon as possible without any hindrance.

When it is confirmed at the time t6 that the switching of the second synchro D2 has been completed, the second speed clutch cl2 (the second clutch C2) is reengaged at the time t7 for a predetermined time T3. Outputs the duty ratio of the speed clutch cl2 to 100% (performs quick quick fill),
Thereafter, from time t8, the duty ratio is temporarily reduced to DL2 to wait. This state continues until the rotational speed of the clutch C1 (the synchronous rotational speed DK3 of the third speed stage at this time) reaches the target rotational speed NTt, at which time the duty of the third speed stage clutch cl3 (the first clutch C1) is increased. The ratio is 0% (complete drain).

Similarly, after time t9, since the second speed clutch cl2 (second clutch C2) has a capacity, the control for maintaining the turbine speed NT at the target speed NTt thereafter is as follows. This is realized by feedback control of the second speed clutch cl2.

At time t10, the third-speed clutch cl3 (first
When it is detected that the hydraulic pressure of the clutch C1) has been completely drained, switching of the first synchro D1 from the third speed position to the first speed position is started.

When it is confirmed at time t11 that the switching of the first synchro D1 has been completed, at time t12 the duty ratio of the first shift stage clutch cl1 (first clutch C1) is increased again.
The predetermined time T4 is set to 100% (first quick fill is performed), and at time t13, the second speed clutch cl2
When the rotation speed of the (second clutch C2) (synchronous rotation speed DK2 of the second speed stage at this time) reaches the target rotation speed NTt, the second speed stage clutch cl2 is completely drained.

Thus, at time t14, the second clutch C2
Is completely drained and the turbine rotation speed NT
Is maintained at the target rotation speed NTt.
This is performed by feedback-controlling the duty ratio of the speed clutch cl1 (first clutch C1).

After time t15 when the turbine rotation speed NT reaches the target rotation speed NTt, the turbine rotation speed N
The hydraulic pressure of the first-speed clutch cl1 is feedback-controlled so that T decreases at a predetermined reduction speed.

At time t16, the first speed change clutch cl1
Is completely engaged, this control is stopped, the duty ratio of the first-speed clutch cl1 is maintained at 100%, and the vehicle stops at time t17. In addition, as described later,
The time t17 is estimated from the current deceleration to determine the shift point, and does not always coincide with the actual stop time.

Next, at times t2, t7, and t12, a shift command (shift down) is output (shift point is set). How to determine this shift point (which is also a feature of the present invention) Will be described in detail.

Here, the determination of the 4-3 shift point P43 when shifting from the fourth speed to the third speed while traveling at the fourth speed will be described. It should be noted that the same shift point determination method can be used during traveling at the third speed and the second speed.

The 4-3 shift point from the fourth speed to the third speed is calculated based on the synchronous rotation speed DK4 of the fourth speed, that is, taking into account the deceleration of the vehicle.

In this embodiment, in order to determine the 4-3 change point P43 from the fourth gear to the third gear, first, the shift point P21 from the second gear to the first gear 2-1 is determined. 2-1
A 2-1 shift point P32 of the third speed to the second speed is determined based on the shift point P21, and a 4-3 shift of the fourth speed to the third speed is determined based on the 3-2 shift point P32. The point P43 is determined.

FIG. 1 shows how to determine a shift point during slow deceleration, and FIG. 2 shows how to determine a shift point during rapid deceleration.

First, a method of determining a shift point during slow deceleration will be described.

2-1 shift point P21 from second speed to first speed
First detects that the vehicle is in the coasting state, and predicts the time t17 at which the vehicle completely stops according to the deceleration.

Next, a point on the fourth-gear synchronous rotation speed DK4 at time t13 at which the second-gear synchronous rotational speed DK2 intersects with the target rotational speed NTt is defined as P0. Time t at this point P0
Reference numeral 13 denotes a time when the duty ratio of the second speed clutch cl2 (second clutch C2) becomes 0% (drain), and from this time t13, the first speed clutch cl1 (first clutch C1).
Is the point at which feedback control is started.

At time t13 at point P0, the clutch C1 of the first speed stage gradually increases its capacity.
The first shift point P21 is shifted from the point P0 to the first speed clutch cl.
1 (the first clutch C1) must be fast enough to perform the quick quick fill and have the capacity. In other words, the 2-1 shift point P21 is the point P0
At the time t13, the rotation speed .DELTA.NOF that changes to the time at which the first speed clutch cl1 can perform the quick quick fill to have the capacity at the fourth speed speed synchronous rotation speed DK4.
This is time t12 when 1 is added.

Next, how to determine the 3-2 shift point P32 from the third speed to the second speed will be described.

The shift point P32 needs to consider two factors.

Between the 2-1 shift point P21 and the 3-2 shift point P32, it is necessary to move the first synchro D1 from the third gear to the first gear and complete the same. Therefore, the 3-2 shift point P32 must be set before the 2-1 shift point P21 moves by the time the first synchro D1 moves.

In other words, the rotation speed that changes during the time when the first synchro D1 moves (from third gear to first gear) is ΔN
As OS2, a point obtained by adding this .DELTA.NOS2 to the synchronous rotation speed of the fourth speed at the point of the 2-1 shift point P21 is defined as P2.
This point P2 is the first shift point P32 of the third speed to the second speed.
Are considered as candidates.

On the other hand, assuming that a point on the synchronous speed DK4 of the fourth speed stage at time t9 at which the synchronous speed DK3 of the third speed stage intersects the target rotational speed NTt is P3, at this point P3 Since the duty ratio of the second clutch cl3 (first clutch C1) becomes 0%, the shift point P21
Before the point P3, the second-speed clutch
The first quick fill of cl2 (the second clutch C2) must be executed and completed, and the second-speed clutch cl2 must have a capacity. In other words,
The 3-2 speed change point P32 is a point P4 (previously referred to as a point P4 obtained by adding the fourth speed synchronous rotation speed at the point P3 to the rotation speed ΔNOF2 that changes the time required to hold the capacity of the second speed clutch cl3 (second clutch C2)). ) Must be set to (second
Candidate points).

As a result, the 3-2 shift point P32 is changed to the point P
Although two time points, 3 and P4, are considered as candidates, the shift point P32 must satisfy both conditions described above. Therefore, the point P4 close to the current vehicle speed (high vehicle speed side)
Is determined as the 3-2 shift point P32.

In exactly the same way, the fourth gear to the third gear
The third shift point P43 is also determined.

The second synchronization D2 moves from the fourth speed to the second speed at the rotation speed DK4 of the fourth speed at the time of the 3-2 shift point P32 with reference to the 3-2 speed point P32. The point in time at which the rotation speed ΔNOS3 that changes during the time until the start is added is defined as a point P5 (time t3).

The time t4 at which the synchronous rotation speed DK4 of the fourth speed intersects with the target rotation speed NTt is set as a point P6, and from that point P3, the third speed clutch cl3 (the second clutch C1)
) Performs the first quick fill to add the rotation speed ΔNOF3, which changes to the time when the capacity can be held, to the rotation speed DK4 of the fourth speed stage at the point P6.
2)

Similarly to the above, of the points P6 and P7, the point P7 which is closer to the current vehicle speed side (high vehicle speed side) is shifted to the 4-3 shift point P43 of the fourth to third speeds. Set to.

Next, a description will be given of how to determine the shift point when the vehicle is suddenly decelerated as shown in FIG.

The time t'17 is determined to be closer to the current time (left side in the figure) as compared with FIG. 1, but the same as in FIG. Therefore, the synchronization mechanisms D1, D2
Are displayed relatively long.

In the case of sudden deceleration, just like the slow deceleration, first, the 2-1 shift point P'21 is determined, and based on that, the 3-1 shift point P'21 is determined.
The 2 shift point P'32 is determined, and finally, the 3-2 shift point P '
The 4-3 shift point P'43 is determined on the basis of 32.

Shifting from the second speed to the first speed 2-
A description will be given from the determination of the one shift point P'21.

A point on the synchronous speed DK4 of the fourth speed stage at the point where the synchronous speed DK2 of the second speed stage intersects with the target speed NTt is defined as P'0. This time t 'at P'0
Reference numeral 10 denotes a time when the duty ratio of the second speed clutch cl2 is set to 0% (drain), and also a time when the first speed clutch cl1 starts the feedback control. Therefore, as in the case of the slow deceleration, the 2-1 shift point P'21 must be before the point P'0 by the time which can have the capacity after the first quick fill. In other words, the fourth
The point P'1 (time t'9) obtained by adding the rotation speed .DELTA.NOF'1 which changes for the time during which the first speed clutch cl1 can have the capacity to the synchronous speed of the first speed stage is shifted to the 2-1 shift point P'21. And

Next, at the 3-2 shift point P'32 from the third speed to the second speed, it is natural that the first sync D1 has not completed the movement from the third speed to the first speed. Therefore, P'2, which is a point obtained by adding the rotation speed ΔNOS'2 that changes for the time required for the first synchro D1 to move to the turbine rotation speed at the shift point P'21, is given as a candidate.

The point on the fourth-speed synchronous rotation speed DK4 at time t'8 at which the third-speed synchronous rotation speed DK3 intersects the target rotation speed NTt is P'3, and the point P'3 is Let P'4 be the point obtained by adding the rotation speed .DELTA.NOF'2 which changes during the time when the third speed clutch cl3 can perform the quick quick fill to have the capacity to the fourth speed speed synchronous rotation speed DK4.

Here, of the points P'2 and P'4, the point P'2 closer to the current vehicle speed is set as the shift point P'32 from the third speed to the second speed.

The 4-3 shift point P43 at the time of sudden deceleration is determined in exactly the same manner.

That is, in the case of slow deceleration, in most cases (all in the embodiment of FIG. 1) fast quick fill (time)
Although the shift point is determined based on the time based on the above, the shift point is determined based on the movement (time) of the synchro in many cases (all in the embodiment of FIG. 2) during rapid deceleration. . In any case, that is, when determining the shift point depending on the time of the first quick fill, etc.,
Also, when determining the shift point depending on the movement of the synchro, the shift point is ultimately determined depending on the deceleration.

Since the shift point is determined in accordance with the deceleration for both slow deceleration and rapid deceleration, if the deceleration changes even after the shift point has been determined once, the next shift point is accordingly determined. Are sequentially corrected and changed.

Further, the shift point thus obtained is
As will be described later, specifically, it is used after being added to the value of the output shaft rotation speed.

Next, the control flow in this embodiment will be described in detail.

FIG. 5 is a flowchart of the overall shift control, FIG. 6 is a flowchart of a shift control subroutine, FIG. 7 is a flowchart of a synchro control subroutine, and FIG. 8 is a flowchart of a coast down point calculation subroutine. Since the main substantive contents of the control have already been described with reference to FIGS. 1 and 2, only the procedure will be schematically described along each flowchart here.

As shown in FIG. 5, this series of control flow mainly comprises a shift control processing routine (step 001) and a coast down control processing routine (step 002). The coast-down control processing routine (step 002) has already been described in detail prior to the change of the shift point, and is out of the scope of the present invention. Therefore, a detailed description of the control flow will be omitted. With reference to FIGS. 6 to 8, the shift control routine (step 00) will be described.
1) will be described in detail.

In step 101, the current shift determination is made in msft.
In step 102, a map search is performed for an upshift point and a downshift point based on the shift position, shift determination stage, and accelerator opening. Here, the shift determination stage indicates a shift stage obtained as a result of determining at which speed stage the vehicle should be located based on current traveling conditions or traveling conditions. The shift position means a position of a shift lever such as a drive range, a second speed range, or a reverse range, and an upshift point and a downshift point are defined in advance on the up and down sides by a map. Of the output shaft rotation speed.

If it is determined in step 103 that the conditions for the coast downshift are satisfied,
The coast down shift point is calculated (see FIG. 8: described later). In step 104, it is determined whether or not the output shaft rotation speed is higher than the upshift shift point. If it is determined that the output shaft rotation speed is higher, in step 105, the shift determination step is incremented by 1, and the up flag is turned on and the down flag is turned off. And upshift determination. on the other hand,
If it is determined in step 104 that the output shaft rotation speed ≦ upshift point, a downshift is similarly determined in steps 106 and 107.

At step 108, it is determined whether or not the shift determination stage has been changed.
Returning to step 01, the shift determination is updated based on the new shift determination stage. If it has not been changed in step 108, the process proceeds to step 109 to perform a synchro control process (described later with reference to FIG. 7).

Steps 110 to 115 are for controlling the reflection of the shift output of the shift determination stage when the shift inhibition flag is off (step 110). According to this control flow, even when a downshift from the fourth speed to the third speed is determined, the fourth speed → the third speed at time t2.
At time t7, third gear → second gear, at time t12 second gear →
A procedure for sequentially generating the shift output of the first speed is realized.

Next, FIG. 7 shows a subroutine of the synchro control process executed in step 109 (FIG. 6).

In step 201, a map search is performed to determine the synchro position (the position where the synchro mechanism should be finally) based on the shift position, the speed change determination stage, and the output shaft rotation speed. In step 202, it is determined whether or not the synchro position determination obtained as a result is different from the actual synchro position output. If not, in step 203, the synchro movement request flag is turned on and the synchro movement completion flag is turned off. .

FIG. 4B shows an example of a sync position determination map in the D range. For example, when the shift determination stage is the first speed stage, the output shaft rotation speed at that time is divided into a case where the output shaft rotation speed is smaller than No1 and a case where the output shaft rotation speed is larger. In addition to the position, a neutral position is prepared in advance. Output shaft rotation speed is No1
If it is larger, the synchro position is in a state in which the first speed side and the second speed position are selected and connected in advance. This is because when the output shaft rotation speed is higher than No1, there is a high possibility that the subsequent shift is a shift to the second speed. Similarly, when the shift determination stage is the second speed stage, if the output shaft rotation speed at that time is smaller than No2, the synchro position determination is made between the first speed position and the second speed position, and the output shaft rotation speed is No2. If it is larger, the second speed position and the third speed position are determined as “sync position determination”.

Steps 204 to 209 are the same as those in FIG.
In the slow deceleration, the operation of switching the second synchro D2 position from the fourth speed position to the second speed position is started from time t5 and started at time t6.
, And the operation of switching the position of the first synchro D1 from the third-speed position to the first-speed position is started at time t10, and corresponds to the operation to be performed when it is confirmed that the operation has been completed at time t11.

That is, when the synchro movement is being performed (step 204), or when the synchro movement prohibition club is on (step 205) and the synchro movement request flag is on (step 206), the synchro movement is performed (step 20).
7) In step 208, it is determined that the synchro movement has been completed. If the movement is completed, the synchro movement completion flag is turned on and the moving flag is turned off in step 204, and the synchro position judgment is substituted for the synchro position output.

Next, FIG. 8 shows a schematic flow of the coast down shift point calculation subroutine executed in step 103 (FIG. 6).

In FIG. 8, it is determined in step 301 whether the precondition for coast down is satisfied.
In this embodiment, the preconditions for coast down are the following conditions.

1. 1. D range selection 2. Idle contact on 3. The accelerator opening is equal to or less than a predetermined value close to zero. Output shaft rotation speed is equal to or greater than a predetermined value corresponding to the time point of t16 (t'16).

If the above conditions are not satisfied, the process goes to the return step and ends the control.

If the precondition is satisfied, step 3
At 02, the shift point NOF considering the time required for the first quick fill and the like, the shift point NOS considering the synchro movement time are set to 0, and i indicating the shift speed at the time of calculation is set to 2. This is to set a shift point P21 for shifting from the second gear to the first gear first, and to change the gear from the third gear to the second gear.
I = 3 when performing the shift at the first speed, and i = 4 when performing the shift from the fourth speed to the third speed.

At step 303, a match search is performed between the rotation speed ΔNOF changing for the first quick fill + β time using the deceleration of the vehicle as a parameter and the rotation speed ΔNOS changing for the synchronization movement time. Here, it may be calculated directly from the current vehicle speed instead of the map search.

Here, β corresponds to the time from the end of the first quick fill to the time when the corresponding clutch can have a marginal capacity as described above.

At step 304, it is determined whether or not i = 2. At first, since it is 2, at step 306 the coast downshift point NOS considering the synchro movement time is set to 0. Next, at step 307, the following calculation is performed to calculate the coast down shift point NOF in consideration of the first quick fill time. That is, the target rotation speed NTt (= engine rotation speed + predetermined value α) of the feedback is divided by the gear ratio of the speed stage indicated by i (the first gear ratio), and the synchronous rotation speed and the target at the speed stage indicated by i are obtained. An output shaft rotation speed that makes the rotation speeds equal is calculated, and ΔNOF that has been map-searched in step 303 is added to the output shaft rotation speed.

At steps 308 to 310, NOS and N
The larger of the OF (high vehicle speed side) is shifted from the gear i to (i −
Substitute into the NOC of the shift point of the coast down to the shift stage of 1). In step 311, 1 is added to i. In step 312, it is determined whether or not i is equal to or less than the current gear position. If i is equal to or less than the current gear position, the process returns to step 303, where i becomes larger than the current gear position. The processing of steps 303 to 312 is repeatedly performed until this. Here, after the second time, since i = 2, the process proceeds from step 304 to 305, and NOS
C + ΔNOS is substituted. If i is greater than the current gear position in step 312, the NOC is substituted in step 313 for the down point used in the determination in step 106 of FIG.

As described above, since the speed change is performed in the range of the low-speed side synchronous rotation speed> the target rotation speed NTt of the feedback, the turbine rotation speed NT can always be fed back to the target rotation speed, and the predetermined rotation speed can always be obtained. The engine brake can be generated.

When the present invention is applied to an automatic transmission having no synchro mechanism, it is not necessary to consider the moving time of the synchro mechanism when determining the shift point.

[0117]

As described above, according to the present invention, it is not necessary to set the shift point higher than necessary by changing the shift point according to the deceleration of the vehicle.
An excellent effect is obtained in that excessive engine braking due to deceleration is suppressed, shift shock is always suppressed at any deceleration, and a good downshift can be executed.

[Brief description of the drawings]

FIG. 1 is a time chart showing how to change and set a shift point by slow deceleration according to the present invention.

FIG. 2 is a time chart showing how to change and set a shift point due to rapid deceleration according to the present invention.

FIG. 3 is a block diagram schematically showing an automatic transmission for a vehicle to which the present invention is applied;

FIG. 4 is a diagram showing an engagement state of each friction engagement device of the automatic transmission and a switching state of a synchronization mechanism.

FIG. 5 is a flowchart showing control executed by a computer to execute a coast downshift in the automatic transmission.

FIG. 6 is a flowchart showing a shift control processing subroutine in FIG. 5;

FIG. 7 is a flowchart showing a synchro control processing subroutine in FIG. 5;

FIG. 8 is a flowchart showing a coast down shift point calculation subroutine in FIG. 5;

[Explanation of symbols]

C1: First clutch C2: Second clutch NT: Turbine rotation speed NTt: Feedback target rotation speed 30: Computer 40: Various sensor groups NE: Engine rotation speed DK1 to DK4: Synchronous rotation speed of each shift speed ΔNOF: Fast quick Rotation speed that changes for fill time ΔNOS: Rotation speed that changes for synchro movement time

Claims (2)

[Claims] 1. A shift control device for an automatic transmission, comprising: a plurality of clutches; and performing a downshift of a clutch-to-clutch shift according to a shift point during a coast, comprising: means for detecting a deceleration of a vehicle; A shift control device for an automatic transmission, wherein the shift point at the time of shifting is changed according to the deceleration of the vehicle. 2. An automatic transmission having a plurality of clutches and a plurality of synchronizing mechanisms and performing a clutch-to-clutch shift for performing a downshift according to a shift point during a coast, wherein the automatic transmission is engaged in an early stage of the clutch-to-clutch shift. A shift control device for an automatic transmission that executes a fast quick fill that applies a complete hydraulic pressure supply command to a clutch to be performed for a predetermined time, wherein, when performing a downshift during the coast, means for determining a time required for the synchronization mechanism to move; A means for determining a time required for the first quick fill; a shift point based on a time required for the synchro movement; and a means for selecting a shift point on a high vehicle speed side among a shift point based on a time required for the first quick fill. And performing the downshift during the course according to the selected shift point. Transmission control device for an automatic transmission.