JP3463527B2 - Control device for continuously variable transmission - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a continuously variable transmission mounted on a vehicle, and particularly to a steering effect on a road surface having a low friction coefficient such as an ice and snow road surface or a wet tile road surface. The present invention relates to a control device for a continuously variable transmission, which is suitable for ensuring a braking distance.

[0002]

2. Description of the Related Art Generally, in a belt type or toroidal type conventional continuously variable transmission, a gear shift pattern for controlling the gear ratio is a vehicle speed and an opening of a throttle valve (hereinafter referred to as a throttle opening). Is used as a variable to control the shift pattern in the shift ratio control region corresponding to each select position. For example, "New model car manual (K11-1) N
As described in "ISSAN March K11 type vehicle", when traveling forward, if the D range, which is the normal traveling range, is selected from the select positions provided in the select operation device, Suitable normal traveling gear ratio control area (that is, D range gear ratio area)
In addition, when the Ds range which is the engine brake range is selected, the engine brake gear ratio control is limited to the minimum gear ratio limit value of which the minimum gear ratio is larger than the normal traveling gear ratio control region. Area (ie Ds
Within the range gear ratio range, the gear ratio of the continuously variable transmission according to the vehicle speed and the throttle opening is controlled.

Then, on a high μ road surface such as a normal dry asphalt road surface or a concrete road surface, in order to reduce the vehicle speed by engine braking, with the accelerator pedal depressed, the D range to the Ds range or 2 If the so-called select down operation is performed after shifting the select position to the range 1 and the range 1, when the accelerator pedal is released, that is, when the throttle opening is reduced, the select position is still When in the D range, the smallest gear ratio in the D range gear ratio region is set, and when the select position shifts to the Ds range from this state, the gear ratio is forcibly changed to the smallest gear ratio in the Ds range gear ratio region. It is set.

[0004]

However, in the above-mentioned conventional control apparatus for a continuously variable transmission, when a select down operation such as shifting from the D range to the Ds range is performed, the range of each of the above ranges is changed. Since the setting of the minimum gear ratio in the gear ratio region is different, the gear ratio of the continuously variable transmission is changed and set so as to rapidly increase.
As a result, the engine back torque, that is, the engine brake, acts on the wheels as a large braking force. Therefore, when this operation is performed on snowy roads, wet asphalt roads, etc., the friction coefficient between the tire and the road surface is also small, so strong engine braking, that is, braking force, works on low μ road surfaces. Then, there is an unsolved problem that the wheels tend to lock and the behavior of the vehicle changes greatly.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and particularly, to stabilize the behavior of the vehicle when the engine brake is operated by the select down operation on the low μ road surface. It is an object of the present invention to provide a control device for a continuously variable transmission capable of achieving the above.

[0006]

In order to achieve the above object, a control device for a continuously variable transmission according to a first aspect of the present invention comprises a selecting means capable of selecting at least a normal traveling range and a required engine braking range, and the selecting means. When the normal drive range is selected by the means, the normal speed control means for performing the speed change control of the continuously variable transmission in the normal travel speed ratio control region suitable for the normal running, and when the engine braking range required by the selecting means is selected A continuously variable transmission including: engine brake control means for performing shift control of the continuously variable transmission in the engine brake gear ratio control area in which the minimum gear ratio in the normal traveling gear ratio control area is limited to a large value on the maximum gear ratio side. In the control device, the snow mode switch selected by the driver's operation and the input for estimating the input torque input to the continuously variable transmission. A torque estimating means, and being driven cars
And in a state where the main engine braking range by the select means is selected, the estimated torque of the snow mode switch is selected and the input torque estimating means when less than the predetermined value, the engine braking transmission ratio control region And a gear ratio control region changing means for changing the minimum gear ratio limit value to the minimum gear ratio side in the normal traveling gear ratio control region.

In the invention according to claim 1, the driving traveling
Medium, when the engine braking required is selected by the selecting means, when the snow mode switch is not selected, that is, when the road surface has a high friction coefficient, or when input to the continuously variable transmission estimated by the input torque estimating means. When the estimated torque is larger than the predetermined value, the minimum gear ratio in the engine brake gear ratio control region is maintained in a state of being limited to a large value, so that a large engine brake can be generated.

However, when the vehicle is driving and the engine braking range is selected by the selecting means, the snow mode switch is selected and the continuously variable transmission estimated by the input torque estimating means is selected. When the estimated torque input to the machine is smaller than a predetermined value, the minimum gear ratio limit value of the engine brake gear ratio control region is smaller than the minimum gear ratio when traveling on the high friction coefficient road surface by the gear ratio control region changing means. The gear ratio is changed to a predetermined gear ratio with a smaller gear ratio.

Therefore, since the braking force by the engine braking acting on the wheels is reduced, the tendency of the wheels to lock is suppressed even when the vehicle is traveling on a road surface having a low friction coefficient, and the steering stability is improved. Reserved.

[0010]

[0011]

Further, since the estimated torque of the input torque estimating means is smaller than a predetermined value during driving and the minimum gear ratio is changed only when the driving force is considered to be small, slipping due to upshifting is promoted. Is avoided.

That is, when the vehicle is driving and the engine brake range is selected, and the output torque of the engine is relatively large and the engine speed is limited to the minimum gear ratio in the engine brake range, the snow mode switch is selected and the engine brake is selected. When the minimum gear ratio limit value of the gear ratio control region is changed to a smaller gear ratio by the gear ratio control region changing means, this is upshifted, and with the release of the inertia torque of the continuously variable transmission. It will further promote slip.

Further, a control device for a continuously variable transmission according to a second aspect of the present invention includes a selecting means capable of selecting at least a normal traveling range and an engine braking range, and a normal traveling when the normal traveling range is selected by the selecting means. A normal speed change control means for performing speed change control of a continuously variable transmission in a suitable normal travel speed ratio control area, and a minimum speed ratio in the normal speed speed change ratio control area when the engine braking range required by the selecting means is selected. A controller for a continuously variable transmission including engine brake control means for performing gear shift control of the continuously variable transmission in an engine brake gear ratio control region limited to a large value on the maximum gear ratio side, and is selected by a driver's operation. A snow mode switch, throttle opening detection means for detecting the throttle opening, and the throttle opening detection
Throttle opening and engine speed detected by output means
Estimate the input torque input to the continuously variable transmission based on
The input torque estimating means for driving, the driving mode and the engine braking range required by the selecting means are selected, and the snow mode switch is selected.
When the estimated torque estimated by the input torque estimating means is smaller than a predetermined value, a shift for changing the minimum speed ratio limit value in the engine brake speed ratio control region to the minimum speed ratio side in the normal traveling speed ratio control region. And a ratio control area changing means.

According to the second aspect of the present invention, drive traveling is performed.
In a state in which a main engine brake by the select means is selected, when the snow mode switch is in the high friction coefficient road surface state or when not selected, or the throttle opening and detected by the throttle opening detection means
Estimated by the input torque estimation means based on the engine speed
When the estimated torque input to the continuously variable transmission is larger than the predetermined value, the minimum gear ratio in the engine brake gear ratio control region is maintained at a large value, so that a large engine brake may be generated. it can. However, when the vehicle is driving and the engine braking range required is selected by the selecting means, the snow mode switch is selected and the input torque estimating means estimates it.
When the determined estimated torque is smaller than the predetermined value, the gear ratio control region changing means causes the minimum gear ratio limit value of the engine brake gear ratio control region to be higher than the minimum gear ratio when the road surface travels with the high friction coefficient. Is changed to a predetermined gear ratio.

Therefore, since the braking force by the engine brake acting on the wheels is reduced, the wheels tend to lock even when the snow mode switch is selected, that is, the vehicle is traveling on a road surface having a low friction coefficient. It is suppressed and the steering stability is secured. The engine braking range is selected, the throttle opening is relatively large knob
When the output torque of the engine is large and the gear ratio is limited to the minimum gear ratio in the engine brake range, the snow mode switch is selected and the minimum gear ratio in the engine brake range is smaller by the gear ratio control area changing means. When the gear ratio is changed, this will be upshifted, further promoting slippage with the release of the inertia torque of the continuously variable transmission, but the estimated torque is smaller than the predetermined value Since the minimum gear ratio is changed only when the force seems to be small, it is possible to prevent the slip from being promoted.

Further, a control device for a continuously variable transmission according to a third aspect of the present invention is characterized in that at least a normal traveling range and an engine braking required range are selected, and a normal traveling range is selected when the normal traveling range is selected by the selecting means. A normal speed change control means for performing speed change control of a continuously variable transmission in a suitable normal travel speed ratio control area, and a minimum speed ratio in the normal speed speed change ratio control area when the engine braking range required by the selecting means is selected. Engine brake control means for performing shift control of a continuously variable transmission in an engine brake gear ratio control region limited to a large value on the maximum gear ratio side, a first throttle controlled according to a depression amount of an accelerator pedal, and the accelerator. A control device for a continuously variable transmission, comprising: a second throttle that is controlled independently of the depression amount of a pedal; A snow mode switch that is selected by the operation of the driver, a first throttle opening detection means and the second throttle opening detection means for detecting the first throttle and the second throttle of the throttle opening, ejection
While the vehicle is traveling dynamically and the selecting means selects the engine braking range, the snow mode switch is selected and the first throttle opening detecting means and the second throttle opening detecting means detect the snow mode switch. A gear ratio control region changing means for changing the minimum gear ratio limit value of the engine brake gear ratio control region to the minimum gear ratio side in the normal traveling gear ratio control region when any one of the values is smaller than a predetermined value. And are provided.

According to the third aspect of the present invention, the first throttle controlled according to the depression amount of the accelerator pedal and the second throttle controlled independently of the throttle are provided. The throttle opening of the throttle is controlled, for example, by reducing the output of the engine according to the slip state of the driving wheels,
Appropriate driving force control is performed according to the running state of the vehicle.
During driving, when the engine braking required is selected by the selecting means and the snow mode switch is not selected, that is, when the road surface has a high friction coefficient, or when the first and second throttles are opened. When any one of the throttle opening degrees detected by the degree detecting means is not smaller than a predetermined value, the minimum gear ratio in the engine brake gear ratio control region is maintained at a large value, so that a large engine brake is maintained. Can occur. However, while driving, the selecting means selects the engine brake range, the snow mode switch is selected, that is, the road surface has a low friction coefficient, and the first and second throttle opening detecting means are used. When at least one of the detected values of is smaller than the predetermined value, the gear ratio control area changing unit causes the minimum gear ratio limit value of the engine brake gear ratio control area to be smaller than the minimum gear ratio when the vehicle is traveling on the high friction coefficient road surface. Is also changed to a predetermined gear ratio with a small gear ratio.

Therefore, since the braking force of the engine brake acting on the wheels is reduced, the tendency of the wheels to lock is suppressed even when the vehicle is traveling on a road surface having a low friction coefficient, and steering stability is improved. Reserved. Also drive
While the vehicle is running, the engine brake range is selected, the throttle opening is relatively large, and the gear ratio is limited to the minimum gear ratio in the engine brake gear ratio control range, the snow mode switch is selected and the engine brake gear ratio is selected. When the minimum gear ratio in the control region is changed to a smaller gear ratio by the gear ratio control region changing means, this is upshifted, and slip is further promoted as the inertia torque of the continuously variable transmission is released. However, the throttle opening of the first throttle that is controlled according to the depression amount of the accelerator pedal that governs the output torque of the engine, and the throttle opening of the second throttle that is controlled independently of the first throttle. Only one of the throttle opening is smaller than a predetermined value and the driving force seems to be small. Since emission Jin change of the minimum gear ratio of the braking range is performed, is avoided slip is promoted. Further, in the control device for a continuously variable transmission according to claim 4, the gear ratio control area changing means is configured to, when the selection of the snow mode switch is released, change the minimum gear ratio of the engine brake gear ratio control area. The feature is that the limit value is returned to the original value.
In the invention according to claim 4, when the snow mode switch is selected and the predetermined condition is satisfied, the minimum gear ratio limit value of the engine brake gear ratio control region is set to the predetermined gear ratio by the gear ratio control region changing means. Although the value is slightly changed, when the selection of the snow mode switch is released, the change of the minimum gear ratio limit value is also released, and the engine brake gear ratio control area returns to the original area. Therefore, when the road surface state shifts from a low friction coefficient road surface to a high friction coefficient road surface, the minimum gear ratio in the engine brake gear ratio control area is maintained at a large value.

[0020]

According to the control device for a continuously variable transmission according to the first aspect of the present invention, the vehicle is driving on a low friction coefficient road surface ,
Moreover, when the input torque input to the continuously variable transmission is smaller than the predetermined value, the minimum gear ratio limit value in the engine brake gear ratio control area is set to a smaller value, so that the low friction coefficient road surface is set. Even when the engine braking range is selected instead of the normal driving range, the braking force due to the engine braking acting on the wheels is reduced compared to when traveling on a road surface with a high friction coefficient, so it is strong on a road surface with a low friction coefficient. It is possible to prevent the wheels from tending to lock due to the engine brake acting, maintain running stability, and secure a braking distance.
Further, when the vehicle is traveling on a low friction coefficient road surface and the input torque input to the continuously variable transmission is smaller than a predetermined value, the minimum gear ratio limit value in the engine brake gear ratio control region is changed. Therefore, it is possible to prevent the slip from being accelerated due to the change of the minimum gear ratio in the engine brake gear ratio control region.

[0021]

Further, according to the control apparatus for a continuously variable transmission according to claim 2, being driven traveling road surface has a low friction coefficient, and the throttle opening detected by the throttle opening detection means
To the continuously variable transmission estimated from the engine speed and engine speed
When the force torque is smaller than the specified value, the minimum gear ratio limit value in the engine brake gear ratio control area is set to a smaller value.Therefore, on the low friction coefficient road surface, the normal running range is replaced by the engine brake range. Even when is selected, the braking force due to the engine braking acting on the wheels is reduced compared to when traveling on a road surface with a high coefficient of friction. It is possible to suppress the tendency of the wheels to lock, maintain traveling stability, and secure a braking distance. It also drives on low-friction coefficient road surfaces.
While the vehicle is running , and when the estimated input torque of the continuously variable transmission is smaller than the predetermined value, the minimum gear ratio limit value in the engine brake gear ratio control region is changed.
It is possible to prevent the slip from being accelerated due to the change of the minimum gear ratio in the engine brake gear ratio control region.

Further, according to the control device for a continuously variable transmission according to a third aspect of the present invention, the first frictional coefficient detecting means detects that the vehicle is driving on a low friction coefficient road surface and is detected by the first and second throttle opening degree detecting means. When any of the detected throttle opening of the second throttle and the second throttle opening is smaller than a predetermined value, the minimum gear ratio limit value in the engine brake gear ratio control region is set to a smaller value, and thus the low value is set to a low value. Friction coefficient Even when the engine braking range is selected instead of the normal driving range on the road surface, the braking force due to the engine braking acting on the wheels is reduced compared to when traveling on a road surface with a high friction coefficient, so low friction It is possible to suppress the tendency of the wheels to lock due to strong engine braking on the road surface, maintain running stability and secure a braking distance. . It also drives on low-friction coefficient road surfaces.
When the vehicle is in the process of traveling and one of the detected throttle opening degrees of the first and second throttles detected by the first and second throttle opening degree detecting means is smaller than a predetermined value, the engine brake gear ratio Since the minimum gear ratio limit value in the control region is changed, the driving force that changes according to the first and second throttles is appropriately estimated to change the minimum gear ratio in the engine brake gear ratio control region. Along with this, it is possible to accurately prevent the slip from being promoted. Further, according to the control device for a continuously variable transmission according to the fourth aspect, when the snow mode switch is deselected, the changed minimum gear ratio limit value in the engine brake gear ratio control region is returned to the original value. Therefore, when the low friction coefficient road surface state is changed to the high friction coefficient road surface state, it is possible to return the state in which the minimum gear ratio in the engine brake gear ratio control region is limited to a large value.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an example when the present invention is applied to a toroidal type continuously variable transmission.

The continuously variable transmission mounted on the vehicle in this embodiment is provided with at least a normal traveling range and an engine braking range for operating the engine brake, as a shift select position for forward traveling. When the D range, which is the normal traveling range, is selected as the shift select position by operating the select lever (selecting means) not shown, the normal traveling gear ratio control region (D
Within the range gear ratio range), and within the engine brake gear ratio control region (S range gear ratio region) when the S range, which is the engine braking range required, is selected,
The gear ratio of the continuously variable transmission is controlled by setting the target input shaft speed according to the vehicle speed and the throttle opening.

As shown in FIG. 1, the power transmission mechanism of this continuously variable transmission has a torque converter 2, a forward / reverse switching mechanism 4, a toroidal type continuously variable transmission 6, a final reduction gear 8 and the like. The rotation of the output shaft (not shown) of the engine 10 can be transmitted to the left and right drive wheels 9 at a predetermined gear ratio and rotation direction. The output side of the torque converter 2 connected to the output shaft of the engine 10 is connected to a rotary shaft (not shown) of the forward / reverse switching mechanism 4, and the drive shaft is controlled by controlling the forward / reverse switching mechanism 4. The rotation direction of can be changed to the forward forward direction or the reverse backward direction. A fluid coupling may be adopted for the torque converter 2.

As shown in FIG. 1, the toroidal type continuously variable transmission 6 has input disks 11 and 12 which rotate integrally with the rotary shaft of the forward / reverse switching mechanism 4, and the input disk 11 concerned.
And an output disk 13 disposed between the input disk 11 and the output disk 13, and a pair of transmission rollers 15 provided between the input disk 11 and the output disk 13 for transmitting the rotational force therebetween, and the output disk 13 provided between the input disk 12 and the output disk 13. And a pair of transmission rollers 16 for transmitting the rotational force therebetween.

Here, the contact surfaces of the input disks 11 and 12 and the output disk 13 with the transmission rollers 15 and 16 are formed as toroidal surfaces, and the transmission rollers 15 and 16 are tilted with respect to the input disks 11 and 12 and the output disk 13. By changing the angle, the rotational speed ratio between the input disks 11 and 12 and the output disk 13 can be continuously changed.

The tilt angles of the transmission rollers 15 and 16 with respect to the input disks 11 and 12 and the output disk 13 are controlled by the hydraulic control device 20. As shown in FIG. 2, the hydraulic control device 20 includes a control valve 21 having a spool 21b slidably arranged in a valve body 21a.
And a step motor 22 for moving the spool 21b of the control valve 21 via a rack and pinion mechanism,
One piston rod is provided with a hydraulic cylinder 23 connected to a rotating shaft of a support mechanism 17 that rotatably supports the transmission rollers 15 and 16, and a precess cam surface attached to the tip of the other piston rod of the hydraulic cylinder 23. And a L-shaped link 25 having one end engaged with the cam surface of the recess cam 24 and the other end engaged with a protruding piece 21c formed on the valve body 21a of the control valve 21.

The line pressure PL is supplied to the input port Ps of the control valve 21, and the input / output ports Po1 and Po2 are supplied.
Respectively through the hydraulic piping to the piston 2 of the hydraulic cylinder 23.
It is connected to the pressure chambers 23b and 23c defined by 3a. Reference numeral 26 is a return spring that returns the valve body 21a to the neutral position.

Therefore, the spool 21b of the control valve 21 is moved to the right in response to, for example, clockwise rotation of the step motor 22, whereby a predetermined line pressure PL is applied to the pressure chamber 23b of the hydraulic cylinder 23 via the input / output port Po1. And the pressure oil in the pressure chamber 23c is returned to the tank via the input / output port Po2 and the drain port P _D. Therefore, the piston 23a moves downward, and the support mechanism 17 that supports the transmission roller 15 is moved downward from the neutral position.

Therefore, when the precess cam 24 is also moved downward, the control valve 2 is moved through the L-shaped link 25.
When the valve body 21a of No. 1 moves to the right, the input / output port P
o1 and Po2 are closed, and at the same time, the transmission roller 1
The precess cam 2 is started by the start of tilting of 5 and 16.
4 rotates, and accordingly, the valve body 21a is further moved to the right, and contrary to the above, the line pressure PL is applied to the input / output port Po2.
Is supplied, the support mechanism 17 is returned to the neutral position, the precess cam 24 is raised, and the valve body 2
1a is moved to the left to close the input / output ports Po1 and Po2, and the tilt angles of the transmission rollers 15 and 16 are set to the step motor 2.
The angle is changed according to the number of steps of 2.

The step motor 22 is driven and controlled by the control unit 30, so that the tilt angles of the transmission rollers 15 and 16 with respect to the input / output disks are changed in accordance with the number of steps of the step motor 22. The number of steps of the motor 22 and the gear ratio uniquely correspond to each other.

On the other hand, the vehicle is configured with a rotary potentiometer or the like and has a throttle opening T of the engine 10.
A throttle opening sensor (throttle opening detection means) 41 for detecting VO, and an input shaft rotation speed sensor 4 for detecting the rotation speed of the input disk 11 of the toroidal type continuously variable transmission 6.
2. When the output shaft rotation speed sensor 43 for detecting the rotation speed of the output disk 13 and the D range which is a normal traveling range are selected by the select lever (not shown), the select signal FD
Is output as a logical value "1", and when the S range which is the engine braking range required is selected, the select signal FS
Selector switch 44 for outputting as a logical value "1",
A snow mode switch 45 for outputting a detection signal SW _SNOW as a logical value "1" when the snow mode for instructing shift control in a snow mode traveling pattern for a low friction road surface such as a snow road or a sand road is selected, and the engine 10 At least an engine speed sensor 46 for detecting the speed of the output shaft of the engine, a front wheel speed sensor 47 for detecting the front wheel speed and a rear wheel speed, and a rear wheel speed sensor 48 are provided at appropriate positions. Has been.

Of these, the throttle opening sensor 41 is
The throttle opening of the engine 10 is detected as a voltage signal, and the accelerator pedal depression amount is "0".
That is, the minimum value TVO _MIN is set when the equivalent throttle opening is fully closed, and the maximum value TVO _MIN is set when the accelerator pedal is fully depressed, that is, when the equivalent throttle opening is fully opened. as _MAX, for example, an analog signal TVO corresponding to the throttle opening between these minimum TVO _{MI N} and the maximum value TVO _MAX is configured to be output.

Then, the control unit 30
Is a microcomputer 31 for performing arithmetic processing for gear ratio control and other gear shift function control, which will be described later, and a motor drive circuit 3 for driving the step motor 22.
2 is provided. The microcomputer 31
Is an input interface circuit 31a having an A / D conversion function for reading signals from the respective sensors, an arithmetic processing unit 31b composed of a microprocessor unit MPU, etc., and a storage device having ROM, RAM, etc. 31c and an output interface circuit 31d having a D / A conversion function and the like.

Then, with this microcomputer 31
Is, for example, a calculation process for gear ratio control described later.
Therefore, the throttle opening sensor 41 opens the throttle.
Degree TVO and output shaft speed from output speed sensor 43
Vehicle speed V calculated based on No _SP, D range is selected
Whether or not the S range is selected,
Continuously variable transmission based on whether or not the
Calculate the target input shaft speed to be achieved in
Calculate the gear ratio C to be achieved by the toroidal type continuously variable transmission 6
Output and set the required gear ratio to achieve this gear ratio C.
Motor control signal S for driving the up motor 22_MTo
It is generated and output to the motor drive circuit 32.

Further, the motor drive circuit 32 outputs the motor control signal S _M output from the microcomputer 31,
The step motor 22 is converted into a drive signal and output.
Next, the arithmetic processing unit 3 of the microcomputer 31
The gear ratio control process executed in 1b will be described with reference to the flowchart shown in FIG. This arithmetic processing is executed by a timer interrupt for each sampling period of about 10 msec. It should be noted that although no particular steps are provided for communication in this flowchart, maps, programs, predetermined arithmetic expressions, etc. required for arithmetic processing are read from the ROM of the storage device 31c at any time, and calculations obtained by arithmetic operations are performed. Values and each information value are stored in the storage device 3 as needed.
It shall be stored in the RAM 1c.

In this gear ratio control process, first, in step S1, the throttle opening TVO from the throttle opening sensor 41, the engine speed Ne from the engine speed sensor 46, the input shaft from the input shaft speed sensor 42. Rotational speed Nt, output shaft rotational speed N from the output shaft rotational speed sensor 43
o, detection signal S from the snow mode switch 45
W _SNOW , selector position signals FD and FS from the selector switch 44, front wheel side and rear wheel side rotation speed sensors 47, 4
The front wheel side rotation speed N _F and the rear wheel side rotation speed N _{R from 8} are read. Next, in step S2, the output shaft rotation speed N
The vehicle speed V _SP is calculated from o based on the following equation (1). A in the equation is a conversion coefficient.

V _SP = No × A (1) Further, based on the engine speed Ne and the throttle opening TVO, the engine speed Ne and the engine torque Te are shown in FIG. 4 with the throttle opening TVO as parameters. The engine torque Te is calculated from the control map showing the correspondence between Then, the estimated input torque Tin of the toroidal type continuously variable transmission 6 is calculated from the engine torque Te and the torque converter ratio t (e) according to the following equation (2).
It should be noted that the torque converter ratio t (e) is equal to the input shaft rotation speed N.
It is calculated from t and the engine speed Ne according to the following equation (3).

Tin = Te × t (e) (2) t (e) = Nt / Ne (3) Next, in step S3, the snow mode determination process is executed. In this snow mode determination processing, as shown in the flowchart of FIG. 5, first, whether the detection signal SW _SNOW from the snow mode switch 45 is SW _SNOW = 1, that is, the snow mode traveling pattern is selected by the driver. It is determined whether or not (step S1
1). If SW _SNOW = 1, the process proceeds to step S12 and the snow mode flag F _{SNOW is set} to F _SNOW.
= 1 and the processing is terminated, and the process returns to the main program.

On the other hand, if SW _SNOW = 1 is not set in step S11, the process proceeds to step S13, and it is determined whether or not the vehicle is slipping based on the difference between the front wheel side rotational speed N _F and the rear wheel side rotational speed N _R. Or whether the vehicle is in the automatic snow mode suitable for traveling in the snow mode traveling pattern, that is, whether or not the vehicle is traveling on a low μ road surface, based on a change in the wheel speed of the driving wheels. If it is the automatic snow mode, the process proceeds to step S12. On the other hand, if it is not in the automatic snow mode, the process proceeds to step S14, the snow mode flag F _{SNOW is set} to F _SNOW = 0, the process ends, and the process returns to the main program.

Returning to the flowchart of FIG. 3, when the snow mode determination processing is completed in the processing of step S3, the process proceeds to step S4, and shift determination processing is executed. In this gear shift determination process, as shown in the flowchart of FIG. 6, first, in step S21, the target is selected from within the D range gear ratio region described later in the gear shift control map of FIG. 7 based on the vehicle speed V _SP and the throttle opening TVO. The input shaft speed TNt is set.

Here, the shift control map shown in FIG. 7 is equivalent to a general control map of a normal shift pattern in which the vehicle speed V _SP is the horizontal axis, the target input shaft speed TNt is the vertical axis, and the throttle opening TVO is a parameter. Therefore, it can be considered that a straight line passing through the origin and having a constant inclination has a constant gear ratio. Then, for example, the straight line having the largest inclination in the entire region of the shift pattern has the largest reduction ratio of the entire vehicle, that is, the maximum gear ratio C _MAX, while the straight line having the smallest inclination has the smallest reduction ratio, that is, the minimum gear ratio. It represents the ratio C _MIN .
Even if the vehicle speed is equal to V _SP , the large depression amount of the accelerator pedal and the large throttle opening TVO demand the engine due to, for example, an acceleration force or a traveling load such as an uphill road or a headwind resistance. Since the load applied is large, it is necessary to increase the rotational speed of the engine to increase its output torque. Therefore, the throttle opening TV detected by the throttle opening sensor 41 is
With O as a parameter, the larger the throttle opening TVO, the larger the target input shaft rotation speed TNt is set. In the region where the vehicle speed V _SP is lower than a certain threshold value for controlling the gear ratio, the gear ratio is set to the maximum gear ratio C _MAX .

When the D range is selected by the select lever, the throttle opening TVO and the vehicle speed are set within the D range gear ratio region including the range from the minimum gear ratio C _MIN to the maximum gear ratio C _MAX. The target input shaft rotation speed TNt is set according to V _SP . When the S range is selected with the select lever and the snow mode flag F _SNOW is F _SNOW = 0, the minimum value of the gear ratio that can be taken is the minimum value in the D range shown by the solid line in FIG. 7. The S range minimum gear ratio (minimum gear ratio limit value) C indicated by the broken line, which has a gear ratio larger than the gear ratio C _MIN
The target input shaft rotational speed TNt is set within the S range gear ratio region that is limited to _SMIN and is in the range from the maximum gear ratio C _MAX to the S range minimum gear ratio C _SMIN .

On the other hand, the S range is selected with the select lever, and the snow mode flag F _SNOW is F.
_In the case of _SNOW = 1, the minimum value of the gear ratio that can be taken is larger than the minimum gear ratio C _MIN in the D range and smaller than the S range minimum gear ratio C _SMIN . S range snow mode gear ratio range limited to the S range snow mode minimum gear ratio C _SMIN-SNOW and shown in FIG. 7 from the maximum gear ratio C _MAX to the S range snow mode minimum gear ratio C _SMIN-SNOW The target input shaft rotation speed TNt is set therein.

Next, steps S21 to S22
Then, it is determined whether or not the S range is selected by the select lever, that is, whether the selector position signal FS = 1 and FD = 0. If the S range is selected, the process proceeds to step S22a.
Then, the estimated input torque calculated in the process of step S2 in FIG.
It is necessary for the Tin to promote the preset slip.
Whether it is smaller than the threshold value Tth predicted to be avoided
To determine. Then, when Tin <Tth,
, The process proceeds to step S23, the vehicle speed V _SP and step S3
Based on the snow mode flag F _SNOW set in the process of step S1, the limiter value TNt _LIM of the target input shaft speed is retrieved from the shift control map of FIG. That is, when the snow mode flag F _SNOW is F _SNOW = 1 the minimum gear ratio is limited to the S range snow mode minimum gear ratio C _SMIN-SNOW , and when the snow mode flag F _SNOW = 0, S Since the range minimum speed ratio C _SMIN is limited, the snow mode flag F is _calculated from the speed change control map of FIG.
Depending on whether _SNOW is 1, the S range minimum gear ratio C
_SMIN or S range Snow mode Minimum gear ratio C _SMIN-SNOW
Limiter value T according to the current vehicle speed V _SP for realizing
Search Nt _LIM . Then, the process proceeds to step S24
It On the other hand, in step S22a, Tin <Tth
If not, the process proceeds to step S23a and the snow
Set the flag F _SNOW to F _SNOW = 0 and set the minimum gear ratio to
S range minimum gear ratio C _SMIN limited to S range minimum gear ratio
Limited in accordance with the current vehicle speed V _SP for achieving specific C _SMIN
The TN value LTNt _LIM . Then, step S24
Move to.

In step S24, step S21
The larger one of the target input shaft speed TNt obtained in step S1 and the limiter value TNt _LIM obtained in step S23 is set as the reached target speed TNt ^* .

On the other hand, if the S range is not selected in the process of step S22, the process proceeds to step S25 and the target input shaft rotation speed T obtained in the process of step S21.
Nt is set as the reaching target speed TNt ^* .

When the reaching target revolution speed TNt ^* is set in step S24 or S25, next, step S
26, and the time constant Kr is set according to, for example, the vehicle characteristics. The time constant Kr is a weighting factor for reflecting the first-order lag target rotation speed Nt (k-1) described later on the reaching target rotation speed TNt ^* , and is set to a value satisfying 0 <Kr <1. . Incidentally, the time constant Kr be a fixed value, may be reduced to "1" to "0" in response to an increase in the vehicle speed when the vehicle speed V _SP is equal to or larger than a predetermined vehicle speed.

Next, in step S27, the primary delay target rotation speed Nt (k) is calculated based on the following equation (4). Nt (k) = [TNt ^* + Nt (k−1) × Kr] / (Kr + 1) (4) Note that Nt (k−1) in the equation is saved in a predetermined storage area when the shift control process is executed last time. This is the first-order lag target rotation speed at the time of the previous calculation.

Next, in step S28, the target speed ratio Ct is calculated according to the following equation (5) based on the first-order lag target rotation speed Nt (k) calculated in step S27 and the output shaft rotation speed No. To calculate. Then, the process ends and the process returns to the main program.

Ct = Nt (k) / No (5) Returning to FIG. 3, when the shift determination process is completed in the process of step S4, the process proceeds to step S5 and the shift process is executed. In this shift process, the control speed is defined because the step motor 22 cannot instantaneously achieve the target position. As shown in the flowchart of FIG. 8, first, in step S31, the process in step S4 is performed. Based on the set target gear ratio Ct and the estimated input torque Tin, the actual target gear ratio C ^* considering torque shift compensation is set based on the control map of FIG. Next, the process proceeds to step S32 and corresponds to this actual target gear ratio C ^* ,
The actual target step number STP ^* , which is the step number of the step motor 22, is obtained from the control map shown in FIG. 10, which shows the correspondence between the actual target gear ratio C ^* and the step number STP of the step motor 22.

Next, in step S33, it is determined whether the actual target step number STP ^* obtained in step S32 is smaller than the current step number STP _NOW of the step motor 22. And the current number of steps STP
_{If the} actual target step number STP ^* is not smaller than _NOW (STP ^* ≧ STP _NOW ), the process proceeds to step S34, and the unit step amount ΔSTP is set to the current step number S.
It is added to TP _NOW to calculate the provisional target step number STP '.

Next, in step S35, it is determined whether the temporary target step number STP 'is larger than the actual target step number STP ^* , and the temporary target step number STP' is larger than the actual target step number STP ^*. If it is larger, the process proceeds to step S36 and the actual target step number STP ^* is set as the motor control signal S _M. And step S
In step 37, the motor control signal S _M is output to the motor drive circuit 32, the processing is terminated, and the process returns to the main program.

On the other hand, in the process of step S35, if the provisional target step number STP 'is not larger than the actual target step number STP ^* (STP'≤STP ^* ), step S35.
38, the provisional target step number STP 'is set as the motor control signal S _M , and the process proceeds to step S37.

Further, in the processing of step S33, the current step
Number of STP_NOWIs the actual target number of steps STP^*Greater than
If not, the process proceeds to step S39 and the current step number S
TP _NOWThe unit step amount ΔSTP is subtracted from
The standard step number STP 'is calculated. Then, step S
40, and the provisional target step number STP ′ is changed to the actual target step.
Number of steps STP^*Is smaller than ST, and ST
P '<STP^*If not, move to step S41
Then, the temporary target step number STP ′ is set to the motor control signal S_M
Is set, and the process proceeds to step S37.

On the other hand, if the temporary target step number STP 'is smaller than the actual target step number STP ^* (STP'<STP ^* ) in the process of step S40, step S36.
Move to.

In this way, when the shift process of FIG. 6, that is, the process of step S5 of FIG. 3 is finished, the shift control process is finished, and thereafter, the above processes are repeatedly executed at a predetermined sampling cycle.

Next, the operation of the above embodiment will be described.
Now, on a high μ road surface such as a dry asphalt road surface or concrete road surface where a sufficient coefficient of friction with the tire is maintained, the accelerator pedal is depressed to drive the vehicle normally at a constant speed or in an accelerated state. It is assumed that the select position is maintained in the D range suitable for normal running.

In the control unit 30, as shown in FIG.
Shift control processing of is executed at a predetermined sampling cycle,
Detection values from various sensors are read (step S
1), based on these, vehicle speed V _SP and estimated input torque T
in is calculated (step S2).

First, the snow mode determination process is executed (step S3). At this time, since the vehicle is traveling on a high μ road surface, the driver must select the snow mode traveling pattern for a low friction road surface. Then, the detection signal SW _SNOW of the snow mode switch 45 becomes 0, and
Since the vehicle is traveling on a high μ road surface and the wheels have not slipped, the snow mode flag F _SNOW is set as F _SNOW = 0. Next, the shift determination process of step S4 is executed, and in this case, the D range is selected.
In the shift control map of 1, the target input shaft rotation speed TNt is set from within the D range gear ratio region based on the vehicle speed V _SP and the throttle opening TVO, and the target gear ratio Ct is set based on this. Then, the gear shift process is executed based on the target gear ratio Ct (step S5), the motor control signal S _M calculated and set by this is output to the motor drive circuit 32, and the drive signal corresponding to the motor control signal S _M is output. Is supplied to the step motor 22, the step motor 22 moves, the control valve 21 operates in accordance with the moving direction of the step motor 22, and the transmission rollers 15 and 16 move accordingly, whereby a predetermined speed change is performed. Controlled by the ratio.

Next, it is assumed that, on this high μ road surface as well, a coasting state, that is, a coasting state in which the depression of the brake pedal and the depression of the accelerator pedal are released without changing the select position, is assumed. In this coasting state, since the select position is in the D range, the gear ratio is set within the D range gear ratio region of the gear shift control map of FIG. 7, and in this case, the accelerator pedal is released. The speed change control is performed so that the speed change ratio of the continuously variable transmission 6 becomes the minimum speed change ratio C _MIN in the D range.

From this state, if the S range, which is the engine brake range, is selected in place of the D range of the normal running range in order to apply the back torque due to the engine brake to each wheel as a braking force, in the shift determination process of FIG. , S range is selected, snow mode flag F
_{Since SNOW} = 0, the target input shaft rotation based on the speed change control map of FIG. 7 is obtained from the speed change control map of FIG. 7 based on the vehicle speed V _SP and the snow mode flag F _SNOW set in the process of step S3. The number limiter value TNt _LIM is retrieved. That is, the snow mode flag F _SNOW is F _SNOW =
When it is 0, the limiter value TNt _LIM that realizes the S range minimum gear ratio C _SMIN is set, and this limiter value T
Nt _LIM is compared with the target input shaft speed TNt selected from the D range speed ratio region, in this case the speed TNt that achieves the D range minimum speed ratio C _MIN . At this time, the S range minimum speed ratio C _SMIN is set so that the speed ratio becomes larger than the D range minimum speed ratio C _MIN.
Limiter value to achieve a range minimum speed ratio C _SMIN TNT
_LIM is set as the reaching target speed TNt ^* , and the shift control of the continuously variable transmission 6 is performed so as to realize the S range minimum gear ratio C _SMIN . That is, the gear ratio is from the minimum gear ratio C _MIN in the D range to the minimum gear ratio C in the S range.
_By being controlled to _SMIN , the back torque of the engine brake effectively acts as the braking force on the drive wheels, and the vehicle deceleration effect can be obtained.

On the other hand, when the vehicle is running on a low μ road surface where a sufficient friction coefficient state cannot be obtained between the vehicle and a tire such as a wet asphalt road surface or ice snow road surface, the D range which is a normal running range is selected. It is assumed that after releasing the accelerator pedal, the S range, which is the engine braking range, is selected instead of the D range. In this case,
When the D range is selected, the gear ratio is set within the D range gear ratio region in the gear shift control map of FIG. 7, and then the accelerator pedal is released to set D
Shift control is performed so that the minimum speed ratio C _MIN in the range is _achieved . Further, when the S range is selected instead of the D range from this state, since the vehicle is traveling on a low μ road surface in this case, the slip state based on the rotational speed difference between the front wheel side and the rear wheel side is changed to In the process of step S13 of FIG. 5, the automatic snow mode is detected and the snow mode flag F _SNOW = 1 is set. Alternatively, since the vehicle travels on a low μ road surface, the driver instructs the snow mode traveling pattern, whereby the snow mode flag F _SNOW = 1 is set.

Therefore, in the shift control map of FIG.
Minimum gear ratio C _SMIN-SNOW in S range snow mode
Since the limiter value TNt _LIM corresponding to is set and this is set as the target revolution speed TNt ^* , the minimum gear ratio is limited to the S range snow mode minimum gear ratio C _SMIN-SNOW , and the gear ratio is the D range. From the minimum gear ratio C _MIN to S
It will be changed to the minimum gear ratio C _SMIN-SNOW in the range snow mode. In this case, the minimum speed ratio C _SMIN-SNOW of S-range snow mode, the minimum speed ratio of S-range C _SMIN
Since the braking force is set to a smaller value, a braking force smaller than the braking force by the engine brake at the normal minimum speed ratio C _SMIN in the S range is applied to the drive wheels.

After that, when the vehicle shifts from the low μ road surface to the high μ road surface and the snow mode running pattern is released, the snow mode flag becomes F _SNOW = 0, so the minimum value of the gear ratio is the normal S range. _Is limited to the minimum gear ratio C _SMIN .

Therefore, when the braking force by the strong engine brake acts on the drive wheels on the low μ road surface, the wheels tend to lock, but the vehicle runs on the low μ road surface in the S range where the engine brake acts. In this case, the minimum value that can be taken as the gear ratio is limited to be smaller than when traveling on a high μ road surface so that a smaller braking force due to engine braking acts on the road surface on a high μ road surface. Even when the S range is selected on the μ road surface, it is possible to avoid the tendency of the drive wheels to lock due to an appropriate engine brake being applied, and while ensuring the steering effect, the engine brakes control the drive wheels. It is possible to exert power to shorten the braking distance.

Further , in the above embodiment, the snow mode flag is set to F _SNOW = 1 by determining that the automatic snow mode is in effect by detecting slippage based on the front and rear wheel speeds or changing the speed of the drive wheels. because in so doing, for example, in S range while running at low throttle opening, when the scan no mode shift pattern is instructed,
The minimum gear ratio is _changed from the minimum gear ratio C _SMIN in the S range to the minimum gear ratio C _SMIN-SNOW having a smaller gear ratio, and further upshifting is performed while the wheels are slipping. Then, the slip is further promoted.

[0070]

However, the flow of the shift determination process of FIG.
-As shown in the chart, S range is selected, and
Estimated input torque T calculated in the process of step S2 of FIG.
Only when in is smaller than a threshold value Tth predicted to be able to avoid promoting a preset slip and the snow mode flag F _SNOW = 1 is set, the minimum value of the gear ratio is set to the S range snow mode minimum. The gear ratio is limited to C _SMIN-SNOW . Therefore, it is possible to prevent the slip from being accelerated due to the change of the minimum gear ratio , and
The traveling stability can be ensured more reliably.

In this case, when the estimated input torque Tin is smaller than the threshold value Tth, the minimum gear ratio in the S range is limited. However, the present invention is not limited to this. For example, the throttle opening is larger than a predetermined value. When it is small, the minimum gear ratio in the S range may be limited,
Even in this case, the same effect can be obtained.

Further, the control device for a continuously variable transmission according to the present invention is provided with an accelerator pedal 6 as shown in FIG.
A main throttle valve (first throttle) 62 whose opening is adjusted according to the amount of depression of 1, and a step motor 63 or the like as an actuator separately from this, and the opening is adjusted and controlled by the rotation angle according to the number of steps. And a sub-throttle valve (second throttle) 64 for detecting the wheel speed of each wheel.
It is applied to a vehicle having a driving force control function that controls the driving force to the driving wheels by controlling the opening degree of the sub-throttle valve 64 based on the slip state detected based on the detection value of It is also possible to do so. In this case, since the actual opening of the throttle is controlled by either the main throttle valve 62 or the sub-throttle valve 64, a throttle opening sensor (first throttle valve) for detecting the depression amount of the accelerator pedal 61 (first throttle The opening value of the main throttle valve 62 based on the detection value of the opening detection means 41 and the detection value of the sub throttle opening sensor (second throttle opening detection means) 65 for detecting the throttle opening of the sub throttle valve 64. If the minimum gear ratio in the S range is limited when the throttle opening degree of any of the above is smaller than the predetermined value, the same effect as the above embodiment can be obtained, and
It is possible to prevent the slip from being accelerated due to the change of the minimum gear ratio.

In the above embodiment, the half toroidal type continuously variable transmission 6 is applied as the continuously variable transmission, but the present invention is not limited to this, and the full toroidal type continuously variable transmission is used. The present invention can also be applied to a belt type continuously variable transmission in which a V belt is stretched between a primary pulley and a secondary pulley.

In the above embodiment, the case where the valve body 21a of the shift control valve 21 and the spool 21b are moved relative to each other has been described, but the present invention is not limited to this, and the valve body 21a has a cylindrical shape. By moving the sleeve of No. 2 by the precess cam 24, the same effect as above can be obtained.

Further, in the above embodiment, the case where the control unit is constructed by the microcomputer has been described, but the present invention is not limited to this, and it goes without saying that an electronic circuit such as an arithmetic circuit may be combined. Yes.

Further, in the above embodiment, the case where the torque shift compensation is performed in step S31 has been described, but this may be omitted. Further, in the shift process of FIG. 8, the open-loop control process is performed, but for example, the input shaft rotation speed Nt from the input shaft rotation speed sensor 42 and the output shaft rotation speed No from the output shaft rotation speed sensor 43 are set. The current actual gear ratio Cp (= Nt / No) may be calculated from the above, and the feedback control process may be performed based on this.

In the above embodiment, the vehicle having the D range as the normal traveling range and the S range as the engine braking range is explained. However, for example, the D range as the normal traveling range and the gear ratio It is also possible to apply to a vehicle provided with a large normal 1 range (L range) or 2 ranges, and in this case, gear shifting in the 1 range (L range) or 2 range during traveling on a low μ road surface. If you set the ratio to a larger value,
It is possible to obtain the same effects as those of the above embodiment.

Here, in the processing of step S22 of FIG.
When it is determined that the range is not selected, the gear ratio is set according to the target target rotation speed TNt ^* set in the process of step S25, and the process of controlling the gear ratio based on this corresponds to normal gear shift control means. It is determined that the S range is selected in the process of step S22 of step S2 and step S2.
3, the process of setting the gear ratio in accordance with the target revolution speed TNt ^* set in the process of S24 and controlling the gear ratio based on this corresponds to the engine brake control means, and the processes of steps S23 and S24 of FIG. It corresponds to the gear ratio control area changing means, and the processing of step S2 of FIG. 3 corresponds to the input torque estimating means.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a control device for a continuously variable transmission according to the present invention.

FIG. 2 is an explanatory diagram showing a schematic configuration of a hydraulic control device.

FIG. 3 is a flowchart showing an example of a processing procedure of shift control processing.

FIG. 4 is a control map showing a correspondence between an engine speed Ne and an engine torque Te with a throttle opening TVO as a parameter.

FIG. 5 is a flowchart showing an example of a processing procedure of snow mode determination processing.

FIG. 6 is a flowchart showing an example of a processing procedure of a shift determination processing.

FIG. 7 is a shift control map showing the correspondence between the vehicle speed V _SP and the target input shaft rotation speed TNt using the throttle opening TVO as a parameter.

FIG. 8 is a flowchart showing an example of a processing procedure of a shift process.

FIG. 9 is a control map showing the correspondence between the target gear ratio Ct and the actual target gear ratio C ^* with the input torque Tin as a parameter.

FIG. 10 is a control map showing the correspondence between the actual target gear ratio C ^* and the step number STP of the step motor.

FIG. 11 is a diagram illustrating a control device for a continuously variable transmission according to the present invention .
Provide explanations when applied to vehicles with power control function
FIG.

[Explanation of symbols]

6 Toroidal type continuously variable transmission 9 wheels 10 engine 11,12 Input disk 13 Output disc 15, 16 Transmission roller 20 Hydraulic control device 21 Control valve 22 step motor 23 Hydraulic cylinder 24 Precessum 25 L-shaped link 30 control unit 32 motor drive circuit 41 Throttle opening sensor 42 Input shaft speed sensor 43 Output shaft speed sensor 45 snow mode switch 46 Engine speed sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI F16H 59:66 F16H 59:66 (56) References JP-A-8-285061 (JP, A) JP-A-7-217712 (JP , A) JP 4-183645 (JP, A) JP 2-144233 (JP, A) JP 2-117443 (JP, A) JP 2-3375 (JP, A) JP 1-218932 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F16H 59/00-61/12 F16H 61/16-61/24 F16H 63/40-63/48

Claims (4)

(57) [Claims] 1. A continuously variable transmission in a normal traveling gear ratio control region suitable for normal traveling when a normal traveling range and an engine braking required range are selected, and a normal traveling range is selected by the selecting means. And a normal gear shift control means for performing the gear shift control, and an engine brake gear ratio in which the minimum gear ratio in the normal traveling gear ratio control region is limited to a large value on the maximum gear ratio side when the engine braking range required by the selecting means is selected. In a control device for a continuously variable transmission including engine brake control means for performing shift control of the continuously variable transmission in a control area, a snow mode switch selected by a driver's operation and input to the continuously variable transmission. an input torque estimating means for estimating the input torque is being driven traveling and main engine brake Len in the select means Is selected and the snow mode switch is selected and the estimated torque of the input torque estimation means is smaller than a predetermined value, the minimum speed ratio limit value in the engine brake speed ratio control region is set to the normal travel. A control device for a continuously variable transmission, comprising: a gear ratio control region changing means for changing the gear ratio control region to a minimum gear ratio side. 2. A continuously variable transmission in a normal traveling gear ratio control region suitable for normal traveling when a normal traveling range and an engine braking required range are selected at least, and a normal traveling range is selected by the selecting means. And a normal gear shift control means for performing the gear shift control, and an engine brake gear ratio in which the minimum gear ratio in the normal traveling gear ratio control region is limited to a large value on the maximum gear ratio side when the engine braking range required by the selecting means is selected. In a control device for a continuously variable transmission equipped with engine brake control means for controlling the transmission of the continuously variable transmission in a control area, a snow mode switch selected by a driver's operation and a throttle opening for detecting a throttle opening. The detection means and the throttle opening detected by the throttle opening detection means.
Input to the continuously variable transmission based on engine speed and engine speed.
Input torque estimating means for estimating the input torque , and the snow mode switch selected and the input torque estimating means inferred by the input torque estimating means while the vehicle is driving and the engine braking range is selected by the selecting means.
And a gear ratio control region changing means for changing the minimum gear ratio limit value of the engine brake gear ratio control region to the minimum gear ratio side in the normal traveling gear ratio control region when the determined estimated torque is smaller than a predetermined value. A control device for a continuously variable transmission, comprising: 3. A continuously variable transmission in a normal traveling gear ratio control region suitable for normal traveling when at least a normal traveling range and an engine braking required range are selected, and a normal traveling range is selected by the selecting means. And a normal gear shift control means for performing the gear shift control, and an engine brake gear ratio in which the minimum gear ratio in the normal traveling gear ratio control region is limited to a large value on the maximum gear ratio side when the engine braking range required by the selecting means is selected. The engine brake control means for controlling the shift of the continuously variable transmission in the control region, the first throttle controlled according to the depression amount of the accelerator pedal, and the second throttle controlled regardless of the depression amount of the accelerator pedal. In a control device for a continuously variable transmission equipped with a throttle, a snow mode switch selected by a driver's operation. A first throttle opening detecting means and a second throttle opening detecting means for detecting the throttle opening of the first throttle and the second throttle, and the driving means and the selecting means. With the engine braking range required selected, the snow mode switch is selected, and one of the detection values of the first throttle opening detection means and the second throttle opening detection means is greater than a predetermined value. And a gear ratio control region changing means for changing the minimum gear ratio limit value of the engine brake gear ratio control region to the side of the minimum gear ratio in the normal traveling gear ratio control region. Gearbox control device. 4. The gear ratio control area changing means returns the changed minimum gear ratio limit value of the engine brake gear ratio control area to the original value when the selection of the snow mode switch is released. The control device for a continuously variable transmission according to any one of claims 1 to 3, wherein: