JP2003314683A - Control device for vehicular continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the increasing amount of holding pressure force preventing a slip by lowering input torque to an continuously variable transmission at the time of shifting reversing the rotating direction of the continuously variable transmission. <P>SOLUTION: In this control device for a vehicular continuously variable transmission, a backward/forward movement switching mechanism switching a backward/forward state by a friction engaging device, and a torque converter having a lockup clutch are coupled in series in an input side. Transfer torque is changed according to a load holding a transfer member mediating transferring of torque between an input side member and an output side member by each member. The control device for the vehicular continuously variable transmission comprises a backward/forward movement switching means (steps S8, S10) detecting that the backward/forward movement switching mechanism is switched in a direction opposite to a traveling direction, and a torque amplification reducing means (a step S1) reducing a torque amplification rate of the torque converter when it is detected that the backward/forward movement switching mechanism is switched in the direction opposite to a traveling direction. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a continuously variable transmission such as a belt type continuously variable transmission or a traction type continuously variable transmission, and more particularly, a torque converter and a forward / reverse switching mechanism connected in series to an input side. And a control device for the continuously variable transmission.

[0002]

2. Description of the Related Art Conventionally known continuously variable transmissions for vehicles have a transmission member such as a belt or a power roller that mediates the transmission of torque, disposed between an input side member and an output side member. By continuously changing the torque transmission parts of the transmission member and the input member and the output member, the gear ratio is continuously changed. However,
Unlike a gear-type transmission, the transmission direction of torque cannot be reversed, so a forward / reverse switching mechanism is separately provided.

Further, in the above continuously variable transmission, it is necessary that the torque transmitting surface is a highly accurate and smooth curved surface.
Therefore, there is a strong demand to prevent slippage of the transmission member and wear associated therewith. A factor that causes slippage of a transmission member such as a belt is a rapid change in torque that acts on the continuously variable transmission, and one example thereof is that by operating the forward / reverse switching mechanism, the operating direction of the output torque, that is, This is a case where the direction of the input torque of the continuously variable transmission is reversed. In particular,
When the forward / reverse switching mechanism is switched so that the vehicle travels or moves in the direction opposite to the traveling or moving direction, the torque acting on the continuously variable transmission increases.

Conventionally, in order to prevent the continuously variable transmission from slipping due to reversing the rotation direction of the continuously variable transmission by operating the forward / reverse switching mechanism, the tension of the belt is kept for a predetermined period. During that period, devices are known that are configured to be relatively high. That is, Japanese Patent No. 2626257
In the invention described in the publication, when the rotation direction of the variable pulley in the belt type continuously variable transmission is reversed, only a part of the block forming the belt is involved in the transmission of the torque. During the period when the transmission torque is reduced, the clamping pressure for clamping the belt is increased to increase the tension of the belt, thereby preventing the transitional slippage of the belt.

[0005]

By the way, one of the advantages of using a continuously variable transmission is that the speed ratio is set according to the running state of the vehicle or the required state of the driving force, and so on. The number of revolutions can be set to the number of revolutions at which the fuel consumption is optimum. Therefore, the shift control of the continuously variable transmission is generally performed automatically instead of manually, and the clutch release operation is not required even when the vehicle is stopped accordingly. In order to eliminate the requirement, a fluid type torque converter is also used.

Further, in this type of torque converter, since power is transmitted through fluid, unavoidable slip occurs, which causes insufficient power transmission efficiency and deteriorates fuel efficiency of the vehicle. There are cases. In order to avoid such an inconvenience, a lock-up clutch that directly mechanically connects an input member (for example, pump impeller) and an output member (for example, turbine runner) of the torque converter is provided. If the lockup clutch is engaged, the original function of the torque converter will not occur, and the fluctuation of the input torque will be transmitted to the output side as it is, and the vibration and noise will be deteriorated. Then, it is common to release the lockup clutch.

Also in the inventions described in the above publications,
The torque converter with the lock-up clutch described above is also used. Therefore, the lock-up clutch is released at a low vehicle speed such that the forward / reverse switching mechanism is operated to reverse the output direction. Therefore, the torque amplified by the torque converter acts on the continuously variable transmission, and the belt clamping pressure must be increased in consideration of the amplified amount of the torque. That is, in the above conventional invention, since the belt clamping pressure or the belt tension becomes large when the direction of the torque is reversed by the forward / reverse switching mechanism, the belt can be prevented from slipping, but the durability of the belt is deteriorated. May occur.

The present invention has been made by paying attention to the above technical problem, and when the forward and reverse movements are switched, the torque acting on the continuously variable transmission is reduced to easily and surely slip. An object is to provide a control device that can be avoided.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention sets the torque amplification factor of a torque converter connected in series to the input side of a continuously variable transmission to a forward or reverse direction. It is characterized in that it is configured so as to be lowered when switching is performed. More specifically, in the invention of claim 1, the forward / reverse switching mechanism for switching the forward / backward state by switching the engaged / released state of the friction engagement device, and the torque converter having the lockup clutch are input side. Continuously variable transmission for a vehicle in which the transmission torque changes in accordance with the load sandwiching the transmission member that mediates the transmission of torque between the input-side member and the output-side member between the respective members. In the control device of the machine,
Forward / reverse switching detection means for detecting that the forward / reverse switching mechanism has been switched so as to travel in a direction opposite to the traveling direction at a predetermined vehicle speed or higher, and at that time or higher at a predetermined vehicle speed or higher. Torque amplification reducing means for reducing the torque amplification factor of the torque converter when the forward / reverse switching detecting means detects that the forward / reverse switching mechanism is switched so as to travel in a direction opposite to the traveling direction. It is a control device characterized by comprising.

Therefore, in the first aspect of the present invention, when the forward / reverse switching mechanism is switched so that the vehicle travels in the direction opposite to the traveling or moving direction while the vehicle is traveling or moving, the torque is changed. The torque amplification factor of the converter is reduced, and as a result, the torque input to the continuously variable transmission is reduced. Therefore, even if the clamping pressure of the transmission member such as the belt or the power roller is increased in order to prevent the continuously variable transmission from slipping, the amount of increase in the clamping force may be small due to the decrease in the input torque.

According to a second aspect of the present invention, the torque amplification reducing means according to the first aspect of the present invention includes lockup control means for controlling the lockup clutch to a weak engagement state in which an engagement force is weaker than full engagement. It is a control device characterized by including.

Therefore, in the second aspect of the present invention, the lockup clutch is weakly engaged to suppress relative rotation between the input side member and the output side member in the torque converter, resulting in an increase in the speed ratio. Along with this, the torque ratio (torque amplification rate) decreases. Therefore, the torque input to the continuously variable transmission is reduced. Further, since the lockup clutch is not completely engaged, relative rotation between the input side member and the output side member of the torque converter is allowed, so that the rotation speed of the power source is excessive even at low vehicle speed. Therefore, even if the power source is an internal combustion engine, the stall is avoided.

Further, according to the invention of claim 3, in the structure of claim 1 or 2, the forward-reverse switching mechanism is switched so that the vehicle travels in a direction opposite to a traveling direction at that time in a state of a predetermined vehicle speed or more. Engagement force reducing means for reducing the engagement force of the frictional engagement device in the forward / reverse switching mechanism when it is detected by the forward / reverse switching mechanism as compared with the case where switching by the forward / reverse switching mechanism is not detected. The control device further comprises:

Therefore, according to the third aspect of the present invention, the torque amplification factor in the torque converter is reduced to reduce the torque input to the continuously variable transmission, and the friction engagement device in the forward-reverse switching mechanism is engaged. Since the resultant force decreases and the transmission torque decreases, the torque input to the continuously variable transmission decreases in accordance with the decrease in the transmission torque. Also,
Since the fluctuation amount of the torque due to the switching operation of the forward / reverse switching mechanism is suppressed, the torque that acts on the continuously variable transmission due to the inertial force is suppressed.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described based on specific examples. First, a drive mechanism of a vehicle and a control system thereof which are the subject of the present invention will be described. FIG. 2 schematically shows a drive mechanism including a belt type continuously variable transmission 1 as a transmission. The machine 1 is connected to a power source 5 via a forward / reverse switching mechanism 2 and a torque converter 4 with a lockup clutch 3.

The power source 5 is composed of an internal combustion engine, or an internal combustion engine and an electric motor, and is essentially a drive member that generates power for traveling. The output of the internal combustion engine can be electrically controlled by, for example, retarding the ignition timing or controlling an electronic throttle valve. In the following description, the power source 5 will be referred to as the engine 5.

The torque converter 4 has the same structure as the conventional torque converter, and includes a pump impeller rotated by the engine 5, a turbine runner arranged to face the pump impeller, and a stator arranged therebetween. And is configured to rotate the turbine runner and transmit torque by supplying the spiral flow of the fluid generated by the pump impeller to the turbine runner. The stator applies reaction torque by changing the direction of the fluid in a state where the ratio of the input rotation speed to the output rotation speed (speed ratio) is small, and generally, a predetermined torque is applied via a one-way clutch. Although it is connected to a fixed part of the stator, the stator can be configured to be held by a predetermined fixed part through a friction clutch. In that case,
The reaction torque can be reduced by controlling the slippage of the friction clutch, and the torque amplification factor in the torque converter can be reduced.

In the transmission of torque through such a fluid, an unavoidable slip occurs between the pump impeller and the turbine runner, which causes a reduction in power transmission efficiency. Therefore, a member on the input side such as the pump impeller. A lock-up clutch 3 is provided for directly connecting an output side member such as a turbine runner. The lockup clutch 3 is configured to be controlled by hydraulic pressure, and is controlled to be in a completely engaged state, a completely released state, and a slip state which is an intermediate state between these states, and the slip rotation speed thereof is appropriately controlled. You can do it.

The forward / reverse switching mechanism 2 is a mechanism adopted because the rotation direction of the engine 5 is limited to one direction, and outputs the input torque as it is and reverses the output. Is configured to. In the example shown in FIG. 2, a double pinion type planetary gear mechanism is adopted as the forward / reverse switching mechanism 2. That is, the ring gear 7 is arranged concentrically with the sun gear 6, and the pinion gear 8 meshed with the sun gear 6 and the pinion gear 9 meshed with the pinion gear 8 and the ring gear 7 are arranged between the sun gear 6 and the ring gear 7. The pinion gears 8 and 9 are rotatably and revolvably held by the carrier 10. A forward clutch 11 that integrally connects the two rotating elements (specifically, the sun gear 6 and the carrier 10) is provided, and by selectively fixing the ring gear 7, the direction of the output torque is obtained. A reverse brake 12 for reversing is provided. The clutch 11 and the brake 12 are friction engagement devices, and are, for example, wet multi-plate clutches or brakes.

The continuously variable transmission 1 has the same structure as a conventionally known belt type continuously variable transmission, and each of a drive pulley 13 and a driven pulley 14 arranged in parallel to each other is
It is composed of a fixed sheave and a movable sheave that is moved back and forth in the axial direction by hydraulic actuators 15 and 16. Therefore, the groove width of each pulley 13, 14 changes by moving the movable sheave in the axial direction, and accordingly, the winding radius of the belt 17 wound around each pulley 13, 14 (the effective diameter of the pulleys 13, 14). ) Changes continuously, and the gear ratio changes continuously. Then, the drive pulley 13 is used for the forward / reverse switching mechanism 2
Is connected to a carrier 10 which is an output element in.

The hydraulic actuator 16 of the driven pulley 14 receives hydraulic pressure (line pressure or its correction pressure) corresponding to the torque input to the continuously variable transmission 1 via a hydraulic pump and a hydraulic control device (not shown). Is being supplied. Therefore, each sheave in the driven pulley 14 sandwiches the belt 17 so that tension is applied to the belt 17 and a clamping pressure (contact pressure) between the pulleys 13 and 14 and the belt 17 is secured. . On the other hand, the hydraulic actuator 15 in the drive pulley 13
Is supplied with pressure oil according to the gear ratio to be set, and the groove width (effective diameter) is set according to the target gear ratio.

The driven pulley 14 is connected to a differential 19 via a gear pair 18, and the differential 19 outputs torque to the drive wheels 20. Therefore, in the above drive mechanism, the torque converter 4 with the lockup clutch 3 and the forward / reverse switching mechanism 2 are connected in series to the input side of the continuously variable transmission 1.

Various sensors are provided to detect the operating state (running state) of the vehicle in which the continuously variable transmission 1 and the engine 5 are mounted. That is, a turbine rotation speed sensor 21 that detects the input rotation speed (rotation speed of the turbine runner) to the continuously variable transmission 1 and outputs a signal, and an input rotation speed that detects the rotation speed of the drive pulley 13 and outputs a signal. A sensor 22, an output rotation speed sensor 23 that detects the rotation speed of the driven pulley 14 and outputs a signal, and a wheel speed sensor 24 that detects the rotation speed of the drive wheel 20 and outputs a signal are provided. Also, although not particularly shown,
Accelerator opening sensor that detects the amount of depression of the accelerator pedal and outputs a signal, throttle opening sensor that detects the opening of the throttle valve and outputs a signal, brake sensor that outputs a signal when the brake pedal is depressed Etc. are provided.

Control of engagement / release of the forward clutch 11 and the reverse brake 12 and the belt 17
An electronic control unit (CVT-ECU) 25 for a transmission is provided to control the clamping pressure of the gear, the gear ratio, and the lockup clutch 3. The electronic control unit 25 is mainly composed of a microcomputer as an example, performs an operation in accordance with a predetermined program based on input data and previously stored data, and performs various states such as forward and reverse or neutral. The required clamping force setting, the gear ratio setting, the engagement / disengagement of the lockup clutch 3, and the slip rotation speed are controlled.

Here, an example of the data (signal) input to the electronic control unit 25 for the transmission will be described. The continuously variable transmission 1
Of the input rotation speed Nin, the output rotation speed N of the continuously variable transmission 1
Signals of o are input from the corresponding sensors (not shown). Further, from an engine electronic control unit (E / G-ECU) 26 that controls the engine 5, an engine speed Ne signal, an engine (E / G) load signal, a throttle opening signal, an accelerator pedal (not shown). No)
The accelerator opening signal, which is the amount of depression of the pedal, is input.

Further, a shift device 27 is connected to the continuously variable transmission 1 and the transmission electronic control device 25. The shift device 27 is a device for manually selecting a traveling position (traveling range) such as parking, reverse, neutral, drive, and brake, and is operated by operating a lever or operating a switch. , The valves (not shown) of the hydraulic device are switched, or an electric signal is output.

When the shift device 27 is configured to select the traveling range by operating the lever, the traveling positions are set to parking P, reverse R, neutral N, drive D as shown in FIG. 3 as an example. ,
The brakes B are arranged in this order. The parking range is a range for setting the vehicle in a stopped state, and is controlled so that output torque is not generated. The reverse range is a range for causing the vehicle to travel in the reverse direction, in which the forward clutch 11 is released and the reverse brake 12 is engaged. Further, the neutral range is a range for setting a neutral state in which no output torque is generated, and the forward clutch 11 and the reverse brake 12 are released. Further, the drive range is a range for traveling forward, the forward clutch 11 is engaged, and the reverse brake 12 is released. The brake range is a range for applying engine braking in a forward traveling state, and the gear ratio is maintained at a predetermined gear ratio on the low speed side (a relatively large gear ratio).

With the shift device 27 having such a configuration, so-called garage shift is possible. This garage shift is a shift operation in which forward and backward movements are repeated within a short period of time, and is based on a continuous shift operation of D → N → R or the opposite continuous shift operation of R → N → D. It is gear shifting.

According to the continuously variable transmission 1, the engine speed, which is the input speed, can be changed steplessly (in other words, continuously).
Since it can be controlled, the fuel economy of a vehicle equipped with this can be improved. For example, the target drive force is obtained based on the required drive amount represented by the accelerator opening degree and the vehicle speed, and the target output required to obtain the target drive force is obtained based on the target drive force and the vehicle speed. The engine speed for obtaining the target output with the optimum fuel economy is obtained based on a map prepared in advance, and the gear ratio is controlled so as to become the engine speed.

In order not to impair such an advantage of improving fuel economy, the power transmission efficiency of the continuously variable transmission 1 is controlled to a good state. Specifically, the torque capacity of the continuously variable transmission 1, that is, the belt clamping pressure can be transmitted to the target torque determined based on the engine torque, and the belt clamping pressure is as low as possible within a range where the belt 17 does not slip. Controlled.

On the other hand, when the direction of the torque input to the continuously variable transmission 1 is reversed by performing the switching operation of the forward / reverse switching mechanism 2, the traveling or traveling of the continuously variable transmission 1 is performed especially at a predetermined vehicle speed. When the forward / reverse switching mechanism 2 is switched so as to travel or move in the direction opposite to the moving direction, the torque input to the continuously variable transmission 1 increases by the inertia torque. Therefore, at the time of such range switching, the following control is executed in order to reduce the torque input to the continuously variable transmission 1 to suppress the slip of the belt 17 and the increase in the belt clamping pressure. To be done.

FIG. 1 is a flow chart for explaining an example of control executed by the control device according to the present invention, and the routine shown here is executed every predetermined short time. First, it is determined whether or not the shift device 27 has performed a shift operation from the drive range to the neutral range (step S1). This can be determined based on the position signal output from the shift device 27. When the affirmative determination is made in step S1 due to the execution of the shift operation, the fact that the N → D shift has been executed is stored (step S2), and then the routine exits.

On the contrary, if the determination in step S1 is negative, it is determined whether or not the shift operation from the reverse range to the neutral range has been executed (step S3). This can be determined based on the position signal output from the shift device 27.
When the affirmative determination is made in step S3 due to the execution of the shift operation, after the fact that the R → N shift has been executed is stored (step S4), the routine exits.

Next, it is determined whether or not the switching control from the neutral range to the reverse range is being performed (whether or not the N → R shift control is being performed) (step S5). This is because whether or not the shift device 27 is operated to switch from the neutral range to the reverse range, and accordingly, the engagement control of the reverse brake 12 and the control of the continuously variable transmission 1 described above are started. This is a judgment step. Therefore, if the N → R shift has not been executed immediately before, the judgment is negative.

If the determination in step S5 is negative,
It is determined whether or not the shift operation from the neutral range to the reverse range has been executed (step S6). N
→ When the R shift operation is performed and thus the determination in step S6 is affirmative, the hydraulic control for setting the reverse range is started (step S
7). Specifically, it is a control for supplying hydraulic pressure to the reverse brake 12 so that the reverse brake 12 in the released state is gradually engaged. Further, it is a control for setting the clamping pressure of the belt 17 in the continuously variable transmission 1 to a predetermined pressure.

Thereafter, D → by step S2 described above
It is determined whether or not N shifts are stored (step S
8). If the determination in step S8 is affirmative, the N → R shift detected in step S6 is D
→ N shifts are consecutive shift operations, so D
→ N → R consecutive shifts have been executed. Therefore, in that case, the D → N → R shift is stored, and the D → N shift is erased (step S9).

Then, it is judged whether or not the vehicle is traveling, that is, whether or not the vehicle is traveling at or above a predetermined vehicle speed (step S10). This determination is a determination as to whether the direction of the shift operation is opposite to the traveling direction (moving direction) of the vehicle. Therefore, in this case, since the vehicle is in the reverse range, the vehicle moves forward in step S10. It is determined whether or not it is. When the determination in step S10 is affirmative, the continuously variable transmission 1 is rotating in the forward direction, but the reverse range torque is applied to the continuously variable transmission 1 by shifting to the reverse range. Is input, and the rotation direction of the continuously variable transmission 1 is reversed.

As a result, a large torque acts on the continuously variable transmission 1, so that the belt clamping pressure for clamping the belt 17 with the driven pulley 14 is the clamping pressure during the normal shift from the neutral range to the reverse range ( P1 (N →
R)) is set to a higher pressure (P1 (D → N → R)), and an instruction for weak engagement to engage the lockup clutch (L / U) 3 with an engagement force lower than full engagement is issued. (Step S11). If the determination in step S10 is negative, the rotation direction of the continuously variable transmission 1 is not reversed, so the control of step S11 is not executed.

When the lockup clutch 3 is controlled to be in the weakly engaged state, a part of the torque input to the torque converter 4 is transmitted to the output side via the lockup clutch 3. As a result, the ratio (speed ratio) between the rotation speed of the input-side member and the rotation speed of the output-side rotating member in the torque converter 4 increases, and the torque ratio (torque amplification factor) decreases. Therefore, by performing the control of step S11, the torque acting on the continuously variable transmission 1 when the drive range is continuously shifted to the reverse range is reduced.

Then, it is judged whether or not the engagement of the reverse brake 12 is completed (step S12). this is,
The determination may be made by a timer, or by detecting the hydraulic pressure, and further the determination may be made based on the number of rotations of a predetermined rotating member.

If the negative determination is made in step S12 because the reverse brake 12 is not completely engaged, that is, if the reverse brake 12 is in the transitional engagement state, the drive range to the reverse range is reached. It is determined whether there is a memory of consecutive shifts to (step S
13). In the case described here, since the storage is performed in the above step S9, step S1
It is judged positively in 3. As a result, the clutch hydraulic pressure is corrected (step S14).

The clutch hydraulic pressure is the forward / reverse switching mechanism 2
It is the hydraulic pressure for engaging the friction engagement device in step 1 above, and is the hydraulic pressure for engaging the reverse brake 12 when shifting to the reverse range. Therefore, in the example described here, the brake oil pressure P2 (D → N → R) is the oil pressure P when shifting from the normal neutral range to the reverse range.
It is corrected to a lower pressure than 2 (N → R).

Therefore, since the engagement pressure of the reverse brake 12 is low, the torque transmitted here is limited,
As a result, the input torque of the continuously variable transmission 1 is suppressed. Moreover, since the reverse brake 12 does not suddenly engage, a shock is avoided. If the determination in step S13 is negative, it means that the shift from the normal neutral range to the reverse range is being performed, so the control of step S14 is not executed.

The above step S13 or step S
After the control of 14, it is determined whether or not the accelerator pedal is depressed, that is, whether or not the accelerator is ON (step S15). When the determination in step S15 is affirmative, the control for controlling the electronic throttle valve (electric slot) in the closing direction to reduce the torque is started (step S16). When the output torque of the engine 5 increases in a state where the reverse brake 12 is not completely engaged, its rotation speed increases, and the rotation speed is reduced as the reverse brake 12 is completely engaged. This is to prevent the inertia torque and the shock resulting from it due to such a rotation change. In addition, when a negative determination is made in step S15 because the accelerator pedal is not depressed, the control in step S16 is not executed.

In the state where the N → R shift control is executed in this way, a negative determination is made in steps S1 and S3, and an affirmative determination is made in step S5. Therefore, during the control of the N → R shift, it is sequentially determined whether or not the engagement of the reverse brake 12 is completed. Then, when the engagement of the reverse brake 12 is completed and the determination in step S12 is affirmative, return control from torque down by starting the throttle of the electronic throttle valve is started (step S17). That is, the forcible torque reduction by the electronic throttle valve is ended.

Thereafter, it is determined whether or not the accelerator pedal is depressed during the engagement control of the reverse brake 12, that is, whether or not the accelerator is turned on (step S1).
8). When the determination in step S18 is affirmative, it is determined whether the elapsed time from the completion of engagement of the reverse brake 12 has reached a predetermined time (step S1).
9).

If a negative determination is made in step S19, that is, if the predetermined time has not elapsed from the complete engagement of the reverse brake 12, the clutch hydraulic pressure calculated from the input torque (the reverse brake 12 is The engagement hydraulic pressure) is output (step S20). This is to prevent the belt 17 from slipping due to the inertia torque. The input torque is the output torque of the engine 5 or the torque converter 4
It can be obtained based on the torque ratio at.

On the other hand, since the accelerator ON operation was not performed during the engagement control of the reverse brake 12, step S18
If the answer is negative, and the reverse brake 12
If a positive determination is made in step S19 after the completion of the engagement of the clutch, the clutch hydraulic pressure (brake hydraulic pressure) calculated from the input torque and the clutch hydraulic pressure (brake hydraulic pressure) calculated from the required belt clamping pressure. Of the above, the higher hydraulic pressure is output (step S21). Here, the required belt clamping pressure is a pressure that is set so that the belt 17 does not slip based on the engine torque, the torque expected to be input from the driving wheel side, and the like.

Then, termination control is executed (step S22). That is, the hydraulic control during the N → R shift is ended, the pressure control of the belt clamping pressure started in step S11 is ended, the memory of the D → N → R shift is erased, and the lock started in step S11. The weak engagement control of the up clutch 3 is ended.

If a negative determination is made in step S8, the hydraulic control for switching from the neutral range to the reverse range is started, but D
→ Since there is no memory of N shifts, shift control from the normal neutral range to the reverse range is performed. That is, the process immediately proceeds to step S12, and it is determined whether or not the engagement of the reverse brake 12 is completed.

On the other hand, if a negative determination is made in step S6 because the shift from the neutral range to the reverse range has not been performed, it is determined whether or not the shift control from the neutral range to the drive range is being performed. (Step S23). When a negative determination is made in step S23, it is determined whether or not a shift operation from the neutral range to the drive range has been executed (step S24). If a negative determination is made in step S24, it means that no shift operation has been executed, so this routine is exited without performing any particular control.

On the other hand, if the shift operation from the neutral range to the drive range is executed and the determination in step S24 is affirmative, and the control associated therewith has been started and is being controlled, step S23. If the determination is affirmative, the control similar to the above-described steps S7 to S22 for setting the river range is executed as the control for setting the drive range (step S25).

Specifically, when the hydraulic control at the N → D shift is started and the memory of the R → N shift is stored, the R → N shift is performed.
The → D shift is stored and the R → N shift is erased, and it is determined whether or not the vehicle is traveling in reverse. When there is no memory of the R → N shift and when the vehicle is not traveling in reverse, it is determined whether or not the engagement of the forward clutch 11 is completed. On the other hand, when the vehicle is traveling backward, the control for increasing the belt clamping pressure is started, and the control for weakly engaging the lockup clutch 3 is instructed.

If the engagement of the forward clutch 11 is not completed, it is judged whether or not there is a memory of R->N-> D shift.
After the engagement pressure is corrected to be reduced, and if the memory is not stored, it is immediately determined whether or not the accelerator is ON. If the accelerator is ON, the torque down control by the electronic throttle valve is started, and then the routine is exited. If the accelerator is not ON, the routine is immediately exited.

On the other hand, when the engagement of the forward clutch 11 is completed, the torque down control by the electronic throttle valve is restored, and if the accelerator is ON during the engagement control, the engagement is completed. During the predetermined time, the clutch hydraulic pressure calculated from the input torque is output. On the other hand, when the accelerator is not turned on during the engagement control, and after a predetermined time has elapsed from the completion of the engagement, the clutch hydraulic pressure calculated from the input torque and the clutch hydraulic pressure calculated from the required belt clamping pressure. The higher oil pressure is output, and then the end control is executed.

Therefore, according to the control shown in FIG. 1, when the vehicle is traveling and the vehicle is shifted to the range for traveling in the direction opposite to the traveling direction, the lock built in the torque converter 4 is set. The up clutch 3 is controlled to the weak engagement state. Therefore, since the torque amplification factor of the torque converter 4 is reduced, the torque input to the continuously variable transmission 1 is smaller than that when the lockup clutch 3 is not weakly engaged. Therefore, even if the rotation direction of the continuously variable transmission 1 is reversed as the range is switched, the input torque is reduced and the belt 17
It is possible to suppress the increase width of the belt clamping pressure that is increased to prevent the slipping of the belt. As a result, it is possible to prevent the belt 17 from slipping and at the same time suppress the increase in the tension of the belt 17 and improve its durability. Furthermore, since the increase of the clamping force of the belt 17 is suppressed, the power transmission efficiency of the continuously variable transmission 1 does not decrease, and as a result, the deterioration of fuel consumption can be prevented or suppressed.

Further, the lockup clutch 3 is weakly engaged to allow relative rotation between the input side member and the output side member. Therefore, even if the vehicle speed is considerably reduced, it is possible to prevent or suppress the significant decrease in the rotation speed of the engine 5, and thus the engine stall can be prevented.

Further, in the control shown in FIG. 1, the clutch hydraulic pressure, that is, the engagement pressure of the reverse brake 12 or the forward clutch 11 is corrected to be reduced, so that the torque input to the continuously variable transmission 1 is corrected to be reduced. The torque is limited according to the clutch oil pressure. Therefore, also in this respect, the input torque of the continuously variable transmission 1 can be suppressed, and the slip of the belt 17 and the deterioration of durability can be prevented. In addition to this, since the engaging pressure of the reverse brake 12 and the forward clutch 11 to be engaged is low, it is possible to suppress or prevent the torque fluctuation, that is, the shock due to the engagement of these friction engagement devices. .

In the control shown in FIG. 1, the engine 5
If the operation to increase the output of the engine occurs during the engagement control of the reverse brake 12 or the forward clutch 11, the engine torque is forcibly reduced, so that the engagement of these brakes and clutches is completed. A shock can be prevented or suppressed by reducing the amount of torque fluctuation at the time point. Further, when the rotation direction of the continuously variable transmission 1 is reversed, the belt clamping pressure is increased as compared with other normal cases, so that the belt 17 can be prevented from slipping.

The relationship between the above-described specific example and the present invention will be briefly described. The functional means of steps S8 and S10 shown in FIG. 1 correspond to the forward / reverse switching detecting means of the present invention. The functional means of step S11 is
This corresponds to the torque amplification reducing means of the present invention, and the functional means of step S14 corresponds to the engaging force reducing means of the present invention.

An example of the present invention has been described above. However, the present invention is not limited to the above-described specific example, and the continuously variable transmission is not limited to the belt type continuously variable transmission and is of a traction type (toroidal type). It may be a gear transmission. Further, the lock-up clutch 3 may be temporarily engaged completely instead of being transiently weakly engaged as described above.
In this invention, the engagement side may be controlled. Further, the means for reducing the torque amplification factor of the torque converter is not limited to the means for controlling the lockup clutch in the engagement direction, but is also the means for rotating the stator to reduce the reaction torque, such as the means shown in the above specific examples. It may have a different configuration. The structure of the forward / reverse switching mechanism in the present invention is not limited to the structure shown in the above specific example, and an appropriate structure can be used as necessary.

[0062]

As described above, according to the first aspect of the invention, when the shift in which the rotation direction of the continuously variable transmission is reversed is executed, the torque amplification factor in the torque converter is reduced. Since the input torque of the continuously variable transmission is reduced, it is possible to suppress the increase width (increased amount) of the clamping force for preventing slipping of transmission members such as belts, and as a result, the durability of the continuously variable transmission is reduced Can be prevented.

According to the second aspect of the present invention, the torque amplification factor of the torque converter can be reduced to reduce the input torque of the continuously variable transmission, and the input side member and the output side of the torque converter can be reduced. By allowing relative rotation with respect to the member described above, the engine stall can be avoided because the rotational speed of the power source is not excessively reduced even at a low vehicle speed.

Further, according to the invention of claim 3, in addition to reducing the torque amplification factor in the torque converter to reduce the torque input to the continuously variable transmission, the friction engagement device in the forward / reverse switching mechanism is also reduced. As the transmission torque is reduced by lowering the engagement force of, the torque input to the continuously variable transmission can be reduced according to the reduction in the transmission torque, and the switching operation of the forward / reverse switching mechanism can be performed. Since the variation amount of the accompanying torque is suppressed, the torque acting on the continuously variable transmission due to the inertial force can be suppressed.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining a control example by a control device of the present invention.

FIG. 2 is a skeleton diagram showing an example of a drive mechanism including a continuously variable transmission which is a target of the present invention.

FIG. 3 is a diagram showing an example of an array of shift positions.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Continuously variable transmission, 2 ... Forward / backward switching mechanism, 3 ... Lockup clutch, 4 ... Torque converter, 11 ... Forward clutch, 12 ... Reverse braking, 25 ... Transmission electronic control device, 27 ... Shift device .

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F16H 61/02 F16H 61/02 // F16H 59:08 59:08 59:44 59:44 F term (reference) ) 3J053 CA03 CB12 CB21 DA11 DA23 EA01 3J552 MA07 MA08 MA12 MA26 NA01 NB01 PA12 PA13 PA61 RA22 SA07 UA01 UA02 UA04 VA62W VB01W

Claims (3)

[Claims] 1. A forward / reverse switching mechanism for switching a forward / backward state by switching an engaged / released state of a friction engagement device, and a torque converter having a lockup clutch are connected in series to an input side, and an input is provided. In a control device for a continuously variable transmission for a vehicle, the transmission torque of which changes depending on the pressure that sandwiches a transmission member that mediates the transmission of torque between a member on the output side and a member on the output side, Forward / reverse switching detection means for detecting that the forward / reverse switching mechanism has been switched so as to travel in a direction opposite to the traveling direction at the vehicle speed and above, and traveling at that time at a predetermined vehicle speed and above The torque amplification factor of the torque converter when the forward / reverse switching detecting means detects that the forward / reverse switching mechanism is switched to travel in the direction opposite to the direction. Control device for a continuously variable transmission for a vehicle, characterized by comprising a torque amplification reducing means reduces. 2. The vehicle according to claim 1, wherein the torque amplification reducing means includes lockup control means for controlling the lockup clutch to a weak engagement state in which an engagement force is weaker than full engagement. Control device for continuously variable transmission for automobiles. 3. The forward / reverse switching detecting means detects that the forward / reverse switching mechanism is switched so as to travel in a direction opposite to the traveling direction at that time when the vehicle speed is equal to or higher than a predetermined vehicle speed. The engagement force reducing means for reducing the engagement force of the frictional engagement device in the forward / reverse switching mechanism as compared with the case where the switching in the forward / reverse switching mechanism is not detected is further provided. A control device for a continuously variable transmission for a vehicle as described above.