JPH11294572A - Coast-down shift control device for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a shock caused by quick coupling or quick meshing and to allow delicate clutch hydraulic control by temporarily boosting the line pressure outputted so far when such a shift judgment is made that a coast-down shift requiring the switching of a synchronization mechanism should be implemented. SOLUTION: When an ECU 100 makes a shift judgment to conduct a down- shift after the fourth speed stage clutch of a clutch C2 is coupled and the turbine revolving speed becomes the down-shift point of the third speed stage or below from the state before a shift action that the third speed stage clutch of a clutch C1 is released in the coast state, the ECU 100 quickly lowers the duty ratio of the fourth speed stage clutch to release the fourth speed stage clutch. The ECU 100 outputs the oil pressure of the third speed stage clutch at the duty ratio of 100%, then waits at a low duty ratio, and gradually increases the duty ratio. The ECU 100 switches a second synchronization mechanism to a second speed stage position when the elapse of a drain timer is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device suitable for use in performing a coast downshift in a so-called twin clutch type automatic transmission.

[0002]

2. Description of the Related Art Generally, a driver closes a throttle opening,
Alternatively, during a coast close to the closed state, the downshift is executed when the vehicle speed decreases and passes the downshift shift point. Particularly in recent years, automatic transmissions employing a well-known synchronizing mechanism have become widespread in order to prevent gear noise during clutch-to-clutch shifting.

[0003] The synchronizing mechanism is a device that synchronizes the rotational speeds of the two gears with each other by using a well-known friction of a synchro cone when the gear on the output side of the clutch and the gear on the output shaft having different rotational speeds mesh with each other. is there. Then, after synchronization, the gears mesh with each other.

[0004] Since the line pressure is generally set depending on the throttle opening, it is set to a very low value in a situation where a coast downshift is executed. However, if the line pressure (pressing force) is set too low, it may take time to synchronize the gears with each other, or the pressing force for meshing the gears may become insufficient. Conventionally, the line pressure is set to a high value so as not to cause such inconvenience.

[0005]

However, if the line pressure is set to be high, not only a shock due to a sudden engagement occurs when the gears mesh with each other, as described above, It has become necessary to control clutch oil pressure more finely by hydraulic control devices such as duty solenoid valves.Therefore, if the line pressure is too high, such a fine control will be difficult to perform. ing.

Therefore, while there is a demand to keep the line pressure as low as possible, there is a conflicting condition that it is necessary to secure a pressing force enough to completely engage each other when the gears are engaged. Because it has to be met at the same time, the setting was very difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and in a situation where a coast downshift is executed, a sufficient amount of time for synchronizing two gears by a synchronization mechanism after synchronization is obtained. While maintaining the pressing force, it is possible to generate a line pressure that can simultaneously satisfy conflicting requirements such as preventing a shock due to sudden engagement or sudden meshing, and further enabling fine clutch hydraulic pressure control. An object of the present invention is to provide a coast downshift control device for an automatic transmission.

[0008]

According to a first aspect of the present invention, there are provided a plurality of clutches and a plurality of synchronizing mechanisms, and the combination of switching of the synchronizing mechanisms and switching by the plurality of clutch-to-clutches. Means for detecting in a coast down control device of an automatic transmission that executes a down shift from a high speed stage to a low speed stage in a coast state, that there is a shift determination to execute a coast down shift involving switching of the synchronizing mechanism. And means for temporarily increasing the line pressure output up to the time when the synchronizing mechanism is switched when the shift determination is made, thereby solving the above problem.

According to a second aspect of the present invention, during the line pressure increasing period, the duty ratio of the clutch oil pressure on the low speed stage side is changed so as to correspond to the line pressure increasing, whereby the line pressure changes. Even so, it is possible to secure a suitable clutch oil pressure without depending on it.

According to a third aspect of the present invention, the above-mentioned problem is also solved by performing the boosting at the time of switching of the synchronizing mechanism after the latter half of a period in which the turbine speed is changed by the switching. It is.

[0011]

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

FIG. 2 is a diagram schematically showing the overall structure of a twin-clutch four-speed automatic transmission with a torque converter to which the present invention is applied.

In FIG. 2, 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 40 and the second clutch output shaft 50 are connected to the input shaft 30 of the first clutch output disk C1o of the first clutch C1 and the second clutch output disk C2o of the second clutch C2, respectively. Is coaxially connected to the outside.

Also, a sub shaft 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 formed of a first sleeve S2.
The fourth-speed clutch gear G4 fixedly connected to the fourth-speed driven gear O4 or the second-speed clutch fixedly connected to the second-speed driven gear O2, which is moved by the second sleeve actuator ACT2 via the shift fork Y2. 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 is always meshed with the countershaft drive gear Is, and a reverse drive gear IR which is always meshed 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. ) By D3, it is selectively connected 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 thereof. 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. 3A and 3B show engagement states 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 added. FIG. The engagement added by the preselection does not contribute to the transmission of power at that gear.

For example, in the first speed stage, the first clutch C1 is engaged, and the first clutch output shaft 40 connected to the first clutch output disc C1o drives the first speed drive gear I1,
The first speed driven gear O1, which is always meshed with the first speed drive gear I1, rotates together with the third speed drive gear I3, and then the first sleeve S1 is positioned on the first speed clutch gear G1 side. As a result, 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 C2o is engaged with the second clutch output disc C2o.
The second speed, in which the clutch output shaft 50 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 is always meshed with the second speed drive gear I2. When the driven gear O2 rotates and the second sleeve S2 is located on the second speed clutch gear G2 side, 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 C1o is connected to the first clutch output disc C1o.
The clutch output shaft 40 rotates together with the first speed drive gear I1 and the third speed drive gear I3, and the third speed drive gear I1
The third speed driven gear O3, which is always meshed with the third speed gear 3, rotates, and then the first sleeve S1 is located on the third speed clutch gear G3 side as described above, so that the output shaft 7
0 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 C2o is engaged with the second clutch output disc C2o.
The clutch output shaft 50 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 fourth speed always meshes with the fourth speed drive gear I4. When the driven gear O4 rotates and the second sleeve S2 is located on the fourth clutch gear G4 side, the output shaft 70 is connected to the first hub H1,
It rotates together with the first hub H2, and power is transmitted.

At the reverse speed, 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 drives the countershaft. 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 because the third sleeve S3 is located on the reverse clutch gear GR side.
As a result, the first speed driven gear O1 is rotated via the reverse idler gear MR, and then the output shaft 70 is connected to the first hub H1 by the first sleeve S1 being located on the first speed clutch gear G1 side. It rotates together with the second hub 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. C1 is engaged, and the second sleeve S2 is moved so as to be released from engagement with the second speed clutch gear G2.

In this embodiment, as shown in FIG. 3B, the next gear is predicted from the running environment (for example, the vehicle speed) at that time, and the corresponding synchronization mechanism is engaged in advance. Thus, control is performed so as to immediately start the clutch switching control when a shift is determined.

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

The piston is driven by controlling the supply and discharge of hydraulic oil supplied from a hydraulic supply source OP in FIG. 2 to a piston oil chamber, and the first clutch supply hydraulic control valve VC1 and the second clutch supply hydraulic pressure are controlled. The control is performed by finely controlling the control valve VC2 by an electronic control unit (hereinafter referred to as an ECU) 100.

The first sleeve S1 and the first sleeve S
2, 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.
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, since it is necessary to check whether each sleeve has moved to a predetermined position, 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 compute and is connected to the 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
An 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 via the output interface circuit 106, respectively. To send to.

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

FIG. 4 is a time chart showing the control of the coast downshift according to the present invention.

This time chart shows the fourth gear and the second gear.
The duty ratio for the second clutch C2 also serving as the speed stage, the duty ratio for the first clutch C1 serving as the third speed stage and the first speed stage, the turbine rotation speed (= the rotation speed of the transmission input shaft 30) NT, first, The relationship among 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 are shown. For easy understanding, the engine speed NE is shown as being constant here.

In the column of duty ratio and oil pressure in FIG. 4, 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.

In this embodiment, the low-speed side clutch (and the high-speed side clutch) is controlled so that the turbine speed NT is maintained at the engine speed + the predetermined value ΔNT1.

The portion indicated by 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).

When the turbine rotational speed NT falls below the downshift point of the third speed stage from the fourth speed stage in the coasting state (throttle opening is fully closed or almost fully closed), the downshift should be performed. Assuming that a shift has been determined, first, at time t2, the duty ratio of the fourth speed clutch cl4 is sharply reduced to release the fourth speed clutch cl4 (however, it is not yet in the completely released state).

At the same time, the third speed clutch cl3
In order to engage the clutch, the hydraulic pressure of the third speed clutch cl3 is output at a duty ratio of 100% for a period T1 (an operation called a so-called fast quick fill), and the duty ratio is lowered to DL1 from time t3 to stand by. , Then increase by ΔDL1.

The duty ratio DL1 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 a certain time.
However, in this embodiment, in order to maintain the vehicle in the weak engine braking state, the turbine rotation speed NT
The duty ratio of the third-speed clutch (shift output stage side clutch) cl3 is controlled so that the target rotational speed (target value) NTt is set to be higher than the engine rotational speed NE by a predetermined value ΔNT1. I do. That is, at the time t4 when the third speed clutch cl3 starts to have a capacity and the turbine speed NT slightly increases, the duty ratio of the fourth speed clutch cl4 is set to a complete drain (0%) state, and the turbine speed NT is reduced. The duty ratio of the third speed clutch cl3 is feedback controlled so as to maintain the target rotation speed NTt. Therefore, the turbine rotation speed NT is maintained at the target rotation speed NTt and does not increase.

On the other hand, when it is detected that the drain timer T2 started counting from time t4 has elapsed (at time t4).
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 of the second synchro D2 is started after waiting for the drain timer T2 to elapse is that the hydraulic pressure of the fourth speed clutch cl4 has a capacity even if it is small. In such a case, 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, at the time t7, a shift output of 3 → 2 is issued, and the second-speed clutch cl2 (cl2 (a new low-speed side clutch) is output. In order to re-engage the second clutch C2), the duty ratio of the second-speed clutch cl2 is output at 100% for a predetermined time T3 (first quick fill is performed), and then the duty ratio is temporarily set to DL from time t8.
Lower to 1 and wait, then increase by ΔDL1. In this state, the first clutch C1 starts to have a capacity, and the second clutch C1 is increased due to a slight increase in the turbine rotational speed NT.
2 duty ratio decreases (reduction of C2 charge capacity)
Then, the duty ratio of the third speed clutch cl3 (first clutch C1) is set to 0% (complete drain) at time t9.

Similarly to the above, after the time t9, the second-speed clutch cl2 (the second clutch C2) (which has newly become the low-speed side clutch) has the capacity. The control for maintaining NT at the target rotation speed NTt is switched so as to be realized by feedback control of the second speed clutch cl2.

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

When it is confirmed at the time t11 that the switching of the first synchro D1 has been completed, at the time t12, a shift output of 2 → 1 is output, and the first shift stage clutch cl1 (a new low speed stage clutch) is output. After the duty ratio of the first clutch C1) is again set to 100% for the predetermined time T4 (first quick fill is performed) and the duty ratio is set to DL1 (time t13), the duty ratio is increased by .DELTA.DL1. Until C1 starts to have the capacity, the feedback by the second speed clutch cl2 is continued, and the second speed clutch cl2 is completely drained at time t14.

After the time t14, the control for maintaining the turbine rotational speed NT at the target rotational speed NTt is performed by feedback-controlling the duty ratio of the first speed clutch cl1 (first clutch C1) (which is a low speed side clutch). Do.

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 may be feedback controlled so that T decreases at a predetermined reduction speed.

At time t16, the first speed change clutch cl1
Is completely engaged (confirmed by the vehicle speed: the predetermined condition of the coast control is not satisfied or the condition for terminating the course and the down is satisfied), the duty ratio of the first speed clutch cl1 is maintained at 100%, and the vehicle It stops at time t17.

Next, in order to explain the line pressure control which is a feature of the present embodiment, the coast dam shift from the fourth speed to the third speed will be described in more detail with reference to FIG.
Note that the present invention is not limited to the coast downshift from the fourth speed to the third speed, but is applied to the coast downshift and the jump coast downshift for all the speeds.

FIG. 1 shows the fourth speed clutch cl4 (C2).
Duty ratio and its hydraulic pressure, third speed clutch cl3
, The hydraulic pressure of the third speed clutch cl3, the line pressure PL, the turbine rotation speed (= the rotation speed of the transmission input shaft 30) NT, and the synchronous rotation speed D of the fourth speed and the third speed.
9 shows a correlation between K4 and DK3 and a target rotation speed NTt described later. In addition, in order to facilitate understanding similarly to the above, the description will be made assuming that the engine rotation speed NE is constant.

In FIG. 1, the time chart from time t1 to time t5 is the same as the time chart of FIG. 4, so that the description is omitted here to avoid duplication.

When it is detected at time t5 that the hydraulic pressure of the clutch CL4 of the fourth speed is completely drained, the second synchro D2 starts moving toward the second speed. as a result,
At time t51, the second sync D2 is set to the second speed clutch gear G.
2 and the sleeve S2 begin to operate in synchronization.

The operation method is not different from the conventional one, but a well-known synchro cone (not shown) attached to the tip of the second sleeve S2 is connected to the second-speed clutch gear G.
2nd clutch gear G2 due to friction.
And the second sleeve S2 are pressed until they reach the same rotational speed (synchronous). When the rotation speeds become the same (after synchronization), the second speed clutch gear G2 and the gears of the second sleeve S2 (hereinafter referred to as mutual gears) are engaged (engaged) (time t6).

Here, the conventional control setting will be briefly described.

Conventionally, when synchronizing the second-speed clutch gear G2 and the second sleeve S2, it is necessary to secure a sufficient line pressure PL to ensure that the two gears are engaged with each other. They were set at a fairly high value (even at the coast). However, if the line pressure is set higher, naturally not only the hydraulic pressure for the synchro movement but also the clutch hydraulic pressure becomes higher, and there is a problem in that finer controllability is lacking. In addition, there is also a problem that the speed change until the synchronization becomes too fast, so that a shock is easily generated at the time of engagement.

Therefore, in this embodiment, the second sync D
2 operates (the gear ratio on the output side of the clutch starts to change) from time t51 to time t6 at which the gears are synchronized and engaged / completed from time t6.
The line pressure PL is temporarily increased from the previous time t52 to the time t6. That is, before the time t52, the clutch pressure is easily controlled, and the line pressure PL is maintained at a low level so that the speed change does not become abrupt. Temporarily set the line pressure PL so that the necessary sufficient pressing force can be secured.
To increase.

Here, the boosting period of the line pressure PL will be described in more detail.

The method of setting the time t52 (time T5) is set slightly before the strongest pressing force is required when the gears are engaged. In other words, the line pressure is required to be truly increased at the moment when the second speed clutch gear G2 and the second sleeve S2 mesh with each other after the complete synchronization, that is, t61, which is a little after time t6. However, even if a command to increase the line pressure PL is output at the moment when the pressing force is most strongly required, the line pressure PL is not immediately increased due to a delay in hydraulic pressure response.
In other words, the line pressure P slightly before the gears engage with each other
By increasing L, it is possible to stably secure a sufficient pressing force. Specifically, the boost start time t52 is, for example, the rotation speed Lcl of the third clutch cl3 (the first clutch C1).
It is preferable to set the line pressure PL to increase when 3 reaches a rotation speed lower than the synchronous rotation speed of the third speed by a predetermined value ΔLcl3.

On the other hand, as for the end time of the pressure increase of the line pressure PL, if the voltage increase is instructed until time t6 (because there is a response delay), a good voltage increase can be executed as a result.

Note that a timer or the like may be set so that, for example, after a predetermined time has elapsed after the start of engagement, an instruction to increase the line pressure is issued until the completion of engagement is detected.

After the time t6, the command of the line pressure PL is returned to the value before the pressure increase, and is returned to a value that can control the clutch oil pressure more finely again.

Since the control after time t9 has already been described with reference to FIG. 4, the description is omitted here to avoid duplication.

By the way, when a command to temporarily increase the line pressure PL is issued from the time t52 to the time t6, the clutch hydraulic pressure naturally naturally shows a high value. If the clutch oil pressure indicates a high value, the engagement of the clutch is naturally sharpened, which causes a large shift shock.

Therefore, in order to prevent this, during the time T5 from the time t52 to the time t6, the duty ratio of the hydraulic pressure of the third-speed clutch cl3 (the clutch hydraulic pressure of the low-speed stage) temporarily corresponds to the line pressure. To reduce the hydraulic pressure of the third speed clutch cl3 so as not to affect the hydraulic pressure (claim 2).

As described above, this control is executed for all shifts.

Next, FIGS. 5 to 10 show flowcharts for actually executing the shift control shown in FIG. This flowchart is not limited to the above-described coast downshift from the fourth speed to the third speed, and can be adapted.

However, in order to facilitate understanding also in the flowchart, a specific description will be made only for the case where the coast downshift from the fourth gear to the third gear is executed.

The main substantive contents of the control to be executed according to these flowcharts have already been described with reference to FIG.
Therefore, the procedure will be described only briefly according to each flowchart.

As shown in FIG. 5, this series of control flows mainly includes a shift control processing routine (step 001) and a coast down control processing routine (step 002). First, the shift control processing routine (step 001) will be described with reference to FIG.

At step 101 in FIG. 6, the current gear shift decision stage is stored in msftjdg. At step 102, a map search is performed for an upshift point and a downshift point based on the shift position, shift 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 is the drive range, the second speed range,
Alternatively, it means the position of a shift lever such as a reverse range, and the upshift shift point and the downshift shift point are shift thresholds of the output shaft rotation speed that are predetermined on the up and down sides at that time by a map. is there.

In step 103, it is determined whether or not the output shaft rotation speed is higher than the upshift point. If it is determined that the output shaft rotation speed is higher, in step 104, the shift determination step is incremented by one, the up flag is turned on, and the down flag is turned on. Turn off and perform upshift determination. On the other hand, if it is determined in step 103 that the output shaft rotation speed is equal to or less than the upshift point, a determination of downshift is similarly performed in steps 105 and 106.

At step 107, 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. In step 108, a synchro control process described later with reference to FIG. 7 is executed.

Steps 119 to 114 are for controlling the reflection of the shift output of the shift determination stage when the shift inhibition flag is off (step 119). According to this control flow, at time t2, the fourth speed stage → the third speed stage, at time t7
Thus, a procedure for sequentially generating the shift output from the third speed to the second speed and the second speed to the first speed at time t12 is realized.

Next, FIG. 7 shows a subroutine of the synchro control process executed in the large step 108 (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. 3B shows an example of the 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 208 correspond to an operation to be performed when it is confirmed that the operation of switching the synchro position from the fourth speed position to the second speed position is started at time t5 and completed at time t6.

That is, if the synchro is moving (step 204) or the synchro movement prohibition flag is on (step 205) and the synchro movement request flag is on (step 206), the synchro movement timer is cleared (step 207). ), A synchro movement is performed (step 208).

In steps 209 and 210, the period T during which the coast down flag (see FIG. 8, step 314 described later) is on and the gear ratio on the output side of the clutch changes.
6 (time t51 to time t6), step 21
At 1, the high pressure request flag of the line pressure PL is turned on. Step 209 (coast down flag on),
If any of the conditions in 210 (the latter half of the period T6) is not satisfied, the high pressure request flag of the line pressure PL is turned off in step 212. To complete the synchro movement in step 213, the synchro movement completion flag is turned on, the synchro movement in progress flag is turned off in step 214, the synchro judgment is made a synchro output, and the high pressure request flag of the line pressure PL is turned off.

If it is determined in step 213 that the synchro movement has not been completed, the process proceeds to step 215, in which it is determined whether the synchro movement timer is equal to or greater than a predetermined value. This control is continued until the synchronization is completed at 213.

If the value is equal to or more than the predetermined value in step 215, the flow advances to step 216 to determine that the synchro has failed.
The synchro fail flag is turned on, the synchro output is synchro judgment, the synchro judgment is a synchro output, the synchro movement timer is cleared, and the process exits from this control routine.

Next, referring to FIG.
A flowchart relating to a subroutine of the coast down control process of FIG. 5 will be described.

In step 301, it is determined whether a precondition (predetermined condition) for coast downshift control is satisfied. In this embodiment, the following four conditions are set as the preconditions.

1) The D range is selected. 2) The idle contact is turned on. 3) The accelerator opening is equal to or less than a predetermined value (close to zero). 4) The output shaft rotation speed (vehicle speed). Is greater than or equal to a predetermined value (close to zero)

The processing in the case where the precondition is not satisfied is omitted because it has no relation to the present invention. If it is determined that the precondition is satisfied, the process proceeds to step 304, where it is determined whether a flag indicating that the coast is down is on. When the coast down flag is off, the routine proceeds to step 306, where it is determined whether or not a downshift is being performed (whether or not the down flag is on).
If it is not a downshift, the process exits this control routine. If it is a downshift, step 30
Proceeding to step S8, it is determined whether the current shift output is either the second speed or the fourth speed. If the shift output is 2nd
If it is either the first gear or the fourth gear, the routine proceeds to step 310, where the duty ratio duh (on the high speed side) is changed to the duty ratio of the first clutch C1 and the duty ratio dul (on the low speed side). It is defined as the duty ratio of the second clutch C2. If the shift output is neither the second speed stage nor the fourth speed stage, the routine proceeds to step 312, where the duty ratio du is changed to the C1 duty ratio and the duty ratio d.
uh is defined as the C2 duty ratio.

Thereafter, the flow advances to step 314, where DH1
The value of (see time t2 in FIG. 4) is substituted for the duty ratio duh on the high-speed side, and the coast-down flag is turned on.

In step 316, the duty ratio duh is determined by feedback so that the turbine rotational speed NT becomes equal to the engine rotational speed NE + a predetermined value ΔNT1. Here, the reason that the turbine rotational speed is controlled to be NE + ΔNT1 by the duty ratio duh of the high speed stage is that the clutch of the low speed stage has not yet waited for the capacity at this stage.

Thereafter, the routine proceeds to step 324, where it is determined whether or not the first quick fill (for the low speed side clutch) has been completed. Initially, it is determined that it has not been completed, so the process proceeds to step 326, where the first quick fill is performed, and the process returns.

After the return, it is determined in step 304 that the coast-down flag is ON, so that the process proceeds to step 318, where it is determined whether the coast-down ending condition is satisfied. The conditions for ending the coastdown (conditions for canceling the predetermined conditions) are as follows.

1) The shift output stage is the first speed stage. 2) The deviation between the turbine speed NT and the synchronous speed of the first speed stage (output shaft rotation speed × first speed gear ratio) is equal to or less than a predetermined value. Is continuously detected for a predetermined time. 3) The duty ratio of the lower gear (first gear) is equal to or more than a predetermined value.

At this stage, since it is determined that the coast-down ending condition has not been satisfied yet, step 3
20 and the duty ratio duh is set to the predetermined value DH2 (FIG. 1).
At time t4) is determined. If the duty ratio duh is larger than the predetermined value DH2, the routine proceeds to step 316, where NT = NTt = NE + ΔN
The operation of determining the duty ratio duh by feedback so as to reach T1 is continued.

Eventually, when the low speed side (shift output stage side) clutch has the capacity (as a result of the feedback control in step 316), it is determined in step 320 that the duty ratio duh has become smaller than the predetermined value DH2. Therefore, the process proceeds to step 322, where the duty ratio duh is set to 0% (complete drain). After step 322, whether or not the first quick fill has been completed is checked again in step 324. If it is not completed, the process proceeds to step 326 again. If it is confirmed that the process is completed, the process proceeds to step 328 to determine whether or not a timer started after completion of the first quick fill is equal to or more than a predetermined value. . While this timer is less than the predetermined value, the duty ratio dul is maintained at the predetermined value DL1 in step 330. When the timer is equal to or more than the predetermined value (time-up), the process proceeds to step 332 in FIG. 9 to confirm again whether the duty ratio duh is 0%. If it is determined in step 332 that the duty ratio dul of the high-speed stage is not 0%, it is considered that the present time is before t4, t9, or t14 in FIG. The duty ratio dul on the stage side is swept up (gradually increased), and the upper limit guard process is performed in step 338. On the other hand, if it is determined that the duty ratio duh is 0%, it is considered that the duty ratio duh on the high-speed side is completely drained, that is, it is after t4, t9, or t14 in FIG. Proceeding to 334, the turbine rotational speed NT becomes equal to the engine rotational speed NE + the predetermined value ΔN
Dull is determined by feedback so as to be T1.

In step 354, it is determined whether or not the high pressure request flag for the line pressure PL according to the present embodiment is turned on. If the high pressure request flag has been output, the flow advances to step 356 to convert the duty ratio for the line pressure PL. And returned. If the high pressure request flag has not been output in step 354, the process returns.

Here, the line pressure PL in step 426
An example of a procedure for converting the duty ratio of the clutch hydraulic pressure for the high pressure (pressure increase) of FIG.

For example, the pressure PLL before the pressure increase (low pressure) of the line pressure PL is set at 300 kPa, the line pressure (high pressure) PLH at the time of the pressure increase is 700 kPa, and the duty ratio DU is 50%.
Then, the clutch oil pressure Pc becomes T at low pressure line pressure.
Although c = PLL × DU = 150 kPa, Tc = PLH × DU = 350 kPa at high line pressure. Therefore, by converting PLL / PLH to the duty ratio, the high-voltage duty ratio DUH at the time of high pressure is converted to PL.
If L / PLH × DU = 21.4%, the clutch oil pressure becomes Pc = DUH × PLH = 150 kPa, which can be equal to the low pressure line pressure.

[0110]

As described above, according to the present invention, when a shift is determined in a downshift during coasting, when the synchro mechanism is switched, the line pressure output until then is temporarily reduced. By boosting,
It is possible to sufficiently secure the pressing force required for the gear engagement during the clutch shift, and to control the clutch hydraulic pressure more finely, while suppressing a sudden change in the shift during synchronization. Two requirements can be achieved simultaneously.

[Brief description of the drawings]

FIG. 1 is a time chart showing control characteristics when the present invention is applied to a twin clutch type coast downshift.

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

FIG. 3 is a diagram showing an engagement state of each friction engagement device of the automatic transmission and a switching state of a synchronization mechanism.

FIG. 4 is a time chart showing general control characteristics in the coast downshift of FIG. 1;

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 hydraulic pressure subroutine process during coast down in FIG. 5;

[Explanation of symbols]

 C1 ... first clutch C2 ... second clutch NT ... turbine speed 20 ... hydraulic control device 30 ... computer 40 ... various sensor groups D1 to D3 ... synchro (mechanism) NTt ... feedback target rotation speed DK1 to DK4 ... each speed stage Synchronous rotation speed PL… Line pressure

Claims (3)

[Claims] 1. A downshift from a high speed stage to a low speed stage in a coast state by a combination of switching of the synchronization mechanism and switching by the plurality of clutch-to-clutches, comprising a plurality of clutches and a plurality of synchronization mechanisms. Means for detecting that there has been a shift decision to execute a coast downshift involving switching of the synchronizing mechanism; and Means for temporarily increasing the line pressure output so far when the mechanism is switched, and a coast downshift control device for an automatic transmission. 2. The automatic transmission according to claim 1, wherein during the line pressure increasing period, the duty ratio of the clutch oil pressure on the low speed stage side is converted to correspond to the line pressure increasing. Coast downshift control device. 3. The automatic transmission according to claim 1, wherein the boosting is performed at the time of switching of the synchronizing mechanism after a latter half of a period when the gear ratio on the clutch output side is changed by the switching. Coast downshift control device.