JP3417265B2 - 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, particularly when stepping on a road surface having a low coefficient of friction such as an icy snow road surface or a wet tile road surface. Alternatively, the present invention relates to a control device for a continuously variable transmission suitable for suppressing a change in vehicle behavior during braking.

[0002]

2. Description of the Related Art Generally, in a conventional continuously variable transmission of belt type or toroidal type, a speed change pattern for controlling the speed change ratio is, for example, as shown in Japanese Patent Application Laid-Open No. 4-203665. The shift pattern is controlled within the shift ratio control region corresponding to the shift select position by using the valve opening (hereinafter referred to as the throttle opening) as a variable. That is, in the case of forward traveling, when the normal traveling range (generally referred to as D range) is selected as the shift select position, the normal traveling gear ratio control area (that is, the D range gear ratio area) suitable for normal traveling is provided. In addition, if the engine brake range (generally referred to as L range, S (2) range) is selected,
An engine brake gear ratio control region (that is, an L range, which has a minimum gear ratio larger than the normal traveling gear ratio control region)
Within the S (2) range gear ratio range), the gear shift pattern of the continuously variable transmission is controlled according to the vehicle speed and the throttle opening.

Generally, when the accelerator pedal is released and the vehicle speed is at a certain level, such as when the engine brake is operating, that is, the throttle opening is fully closed and the engine speed is When the value is equal to or more than the predetermined value, it is determined that it is not necessary to supply fuel to the engine, and fuel cut is performed to stop fuel supply to the engine for the purpose of improving fuel efficiency or preventing catalyst heating. Has become.

[0004]

However, in the above-mentioned conventional control apparatus for a continuously variable transmission, for example, in a state where the normal driving range is selected, the friction coefficient of the road surface such as ice and snow road surface or wet asphalt road surface is changed. When driving on a low low μ road surface, when the accelerator is operated from the coast running condition with the accelerator pedal released, the friction coefficient between the tire and the road surface is small, but it is equivalent to the high μ road surface. As a result, the driving force of (1) acts, and the driving force tends to be excessive, which may cause wheel spin.
Further, in the accelerator pedal released state, the fuel cut is normally performed when the vehicle is running at a predetermined engine speed or higher, so the accelerator pedal is depressed from the state where the negative engine torque is applied by the fuel cut. Then, since the engine torque is generated after the inertia torque of the engine is accelerated, the fluctuation of the engine torque becomes large and the vehicle behavior becomes unstable.

Further, even if the accelerator pedal is released and the deceleration effect due to engine braking is expected when the vehicle is traveling on a high μ road surface to a low μ road surface, it is a low μ road surface, and Since the gear ratio of the continuously variable transmission is controlled to the minimum gear ratio in the normal driving range gear ratio region, the deceleration effect by the engine brake is small. Therefore, the frequency of brake operation and select down increases, and the vehicle behavior becomes unstable accordingly, and especially on a low μ road surface, unstable vehicle behavior leads to vehicle behavior change. It is desirable to be done.

Therefore, the present invention has been made by paying attention to the above-mentioned conventional problems, and it is possible to suppress the behavior change of the vehicle at the time of accelerator pedal operation or braking, especially on a low μ road surface. An object of the present invention is to provide a control device for a continuously variable transmission.

In order to achieve the above object, the control device for a continuously variable transmission according to a first aspect of the invention does not operate in a predetermined gear ratio control region so that the gear ratio becomes the minimum gear ratio at least when the throttle opening is fully closed. And a fuel supply stop means for stopping fuel supply to the engine when the throttle opening is fully closed and the engine speed is equal to or higher than a predetermined value. In a control device for a continuously variable transmission, a road surface friction coefficient state detecting means for detecting a road surface friction coefficient state while the vehicle is running, and the fuel supply when the road surface friction coefficient state detecting means detects a low friction road surface state. Low friction road surface adjusting means for prohibiting the stop of fuel supply by the stopping means and changing the minimum speed ratio of the speed ratio control region to the maximum speed ratio side, and a vehicle speed detecting means for detecting the vehicle speed.
And the low-friction road surface adjusting means is configured so that the vehicle speed is
The larger the value, the smaller the change range of the minimum gear ratio.
The feature is that it grows.

According to the first aspect of the present invention, the shift control means controls the shift of the continuously variable transmission within a predetermined gear ratio control region based on the throttle opening, the vehicle speed, etc., and at least the throttle opening is fully closed. When the vehicle is in the state, the gear ratio of the continuously variable transmission is controlled to the minimum gear ratio within the gear ratio control region, and an appropriate gear ratio suitable for the running state of the vehicle is set according to the throttle opening or the vehicle speed. . When the throttle opening is fully closed and the engine speed is equal to or higher than a predetermined value, such as when the engine brake is operating,
When it is judged that it is not necessary to supply the fuel to the engine, the fuel supply stopping means stops the fuel supply to the engine, thereby improving the fuel consumption.

Then, for example, when the driver has instructed the snow mode in which the speed change control of the continuously variable transmission is performed in the speed change ratio control region suitable for traveling on a low friction road surface such as a snow road, When it is detected by the road surface friction coefficient state detecting means that the vehicle is traveling on a low friction road surface, such as when it is detected that the wheels are slipping based on the speed difference of the wheel speeds, the low friction road surface adjusting means. By
The stop of the fuel supply to the engine by the fuel supply stopping means is prohibited, and the minimum gear ratio in the gear ratio control region is changed to the maximum gear ratio side.

That is, when the accelerator pedal is opened for the purpose of applying the engine brake, the minimum speed ratio in the predetermined speed ratio control region is set as the speed ratio of the continuously variable transmission by the speed change control means. It is difficult to obtain a braking effect by engine braking in the state where the gear ratio is controlled. As a result, the frequency of braking operations may increase, which may cause changes in vehicle behavior.However, when the road surface has low friction, the minimum gear ratio is changed to the maximum gear ratio side and fuel supply is stopped. Since the stop of the fuel supply to the engine by the means is prohibited, the gear ratio of the continuously variable transmission is changed to a gear ratio larger than the minimum gear ratio to obtain the braking effect by the engine brake and the fuel supply is stopped. the engine brake by the continuously performed it without becomes too strong is avoided, by increasing the gear ratio of the continuously variable transmission in the state that caused a certain degree of engine torque, deceleration effect by moderate engine braking Will be obtained.

Further, when the engine brake is applied and the pedal is depressed again, the fuel supply is stopped when the throttle opening is fully closed and the engine speed is equal to or higher than a predetermined value. Since the fuel supply to the engine is stopped by the means, the engine torque on the negative side acts, and if the accelerator pedal is depressed from this state, the engine torque is generated after the inertia torque is accelerated. Therefore, the fluctuation of the engine torque becomes large and the vehicle behavior becomes unstable. However, when the road surface is low μ, stopping the supply of fuel to the engine is prohibited, so the engine will start up from a state where some engine torque is generated.
The engine torque smoothly rises in response to the depression of the accelerator pedal, the fluctuation of the engine torque is suppressed, and the vehicle behavior is stabilized.

[0012] At this time, the low-friction surface for adjusting means, the greater the vehicle speed detected by the vehicle speed detecting means, so as to reduce the variation range of the minimum speed ratio.

[0013] that is, as the vehicle speed is high, because reduction effect of the engine brake is increased, a minimum speed ratio as the vehicle speed is less more then changed to the maximum speed ratio side, as change width than the higher vehicle speed increases decreases by varying <br/> further the minimum speed ratio, so that the change of the minimum speed ratio is performed in accordance with the reduction effect of engine braking according to the vehicle speed, only effect of the engine brake is avoided.

Further, the control device for the continuously variable transmission according to the second aspect of the invention is at least when the throttle opening is fully closed.
A continuously variable transmission in a predetermined gear ratio control range so that a gear ratio is obtained.
Shift control means for performing shift control of the
Is fully closed and the engine speed is equal to or higher than a specified value.
Fuel supply stop hand that stops the fuel supply to the engine when
In a control device for a continuously variable transmission including
Road friction coefficient status to detect road friction coefficient status during running
The detection means and the driver open the accelerator pedal
To the coast running condition that expects engine braking effect
Coast running state detection means for detecting whether or not there is,
The road friction coefficient state detection means detects a low friction road surface state.
In addition, the coast running state detection means is
When it is detected that the fuel supply is stopped,
Prohibiting the stop of fuel supply due to
Adjustment for low friction road surface that changes the minimum gear ratio to the maximum gear ratio side
Means and are provided. This claim 2
In the invention according to the above aspect, the shift control means is used to open the throttle.
Change within a predetermined gear ratio control range based on vehicle speed, vehicle speed, etc.
The speed change gear is controlled and at least the throttle opening is fully closed.
When in the state, the speed ratio of the continuously variable transmission is controlled by the speed ratio control.
It is controlled to the minimum gear ratio within the range and throttle opening or
An appropriate gear ratio suitable for the running state of the vehicle depending on the vehicle speed etc.
Is set. Also, like when the engine brake is operating
The throttle opening is fully closed and the engine speed is
If it is above the specified value, fuel is supplied to the engine.
If it is determined that there is no need to
Fuel supply to gin is stopped, which improves fuel economy
Etc. And, for example, low
A continuously variable transmission in a gear ratio control range suitable for running on frictional road surfaces
The snow mode that controls the gear shifting of the
Or when there is a speed difference between the front and rear wheels.
When it is detected that the wheels are slipping based on
For example, traveling on a low friction road surface by means of road surface friction coefficient state detection
Is detected, and the driver
Expect engine braking effect with the dull open
Low is detected when coasting is detected.
Friction road surface adjusting means, fuel supply stopping means
Stopping the fuel supply to the engine is prohibited, and the gear ratio is
The minimum gear ratio in the control region is changed to the maximum gear ratio side. One
The accelerator pedal for the purpose of operating the engine brake.
When the dull is opened, the gear change control means
The minimum gear ratio in the gear ratio control area of
Is set, but in the state where it is controlled to the minimum gear ratio
It is difficult to obtain the braking effect of engine braking
It As a result, the frequency of brake operations will increase and
Low friction road surface that may cause both behavior changes
It is detected that the vehicle is in the state of running and is in the coasting state.
Sometimes, the minimum gear ratio is changed to the maximum gear ratio side,
In addition, stopping the fuel supply to the engine by the fuel supply stopping means.
Stopping is prohibited, so the gear ratio of the continuously variable transmission is the minimum gear ratio.
Engine braking changed to a gear ratio greater than
The braking effect can be obtained and the fuel supply is not stopped
By continuing to
It is avoided that it becomes too much, and some engine torque
Increase the gear ratio of the continuously variable transmission with
By, the deceleration effect by moderate engine braking is
Will be obtained. Also, apply the engine brake.
In case of pressing down again from the state
Indicates that the throttle opening is fully closed and the engine is rotating.
If the number is equal to or greater than the predetermined value, the fuel supply stop means
The fuel supply to the engine has been stopped,
Engine torque will be applied, and from this state
When the accelerator pedal is depressed, the inertia shuttle
Engine torque is generated after acceleration of the engine
Because the gin torque fluctuation becomes large, the vehicle behavior becomes unstable.
Become. However, if the road surface is low μ, the engine
Since it is prohibited to stop the fuel supply to the
Do not stand up from the state where gin torque is generated.
Therefore, it smoothly responds to the depression of the accelerator pedal.
The engine torque rises and the engine torque changes
The vehicle behavior is suppressed and stabilized. Further, according to claim 3,
In the continuously variable transmission control device, the low-friction road surface adjusting means sets the maximum gear ratio in the gear ratio control area to the minimum gear ratio side when the road surface friction coefficient state detecting means detects a low friction road surface state. It is characterized by being changed.

According to the third aspect of the present invention, when the road surface on which the vehicle is traveling is in a low friction road surface state, the low friction road surface adjusting means causes the maximum gear ratio in the gear ratio control region to be
The value is changed to a value with a smaller gear ratio on the minimum gear ratio side.

Therefore, on a low μ road surface, an ordinary high μ
When the gear ratio is controlled in the same way as when driving on the road surface, for example, when the accelerator is stepped on, a driving force equivalent to that on the high μ road surface acts on the low μ road surface, and the driving force acts. The vehicle may spin due to excess, but if the vehicle is traveling on low μ road surface, the maximum gear ratio should be
Ri it is so arranged to change to a small value of the variable speed ratio, is the driving force even when subjected to an accelerator operation in the low μ road surface inhibitory, possibility of the vehicle spinning is reduced.

[0017]

According to the controller of the continuously variable transmission according to the first aspect of the present invention, when the low friction road surface condition is detected,
The low friction road surface adjusting means prohibits the fuel supply stopping means from stopping the fuel supply to the engine, and changes the minimum gear ratio in the gear ratio control region to a large gear ratio on the maximum gear ratio side. The deceleration effect by the engine brake can be appropriately obtained, the vehicle behavior at the time of re-depressing can be stabilized, and the behavior variation of the vehicle on the low friction road surface can be suppressed.

Further, at this time, when the minimum friction ratio of the gear ratio control region is changed by the low friction road surface adjusting means, the change width is set to become smaller as the vehicle speed becomes higher. It is possible to obtain the deceleration effect by appropriate engine braking.

Further, according to the control device for the continuously variable transmission according to the second aspect, the low friction road surface state is detected and the coast running is performed.
Low friction road surface adjustment when it is detected that
Fuel to the engine by means for stopping fuel supply
Prohibition of the supply of fuel, and the minimum change in the gear ratio control range.
Change the speed ratio to a larger gear ratio on the maximum gear ratio side.
Therefore, the deceleration effect by the engine brake is moderately obtained.
It is possible to reduce the vehicle behavior when
The vehicle behavior can be changed on low-friction road surfaces.
The movement can be suppressed. Furthermore, according to claim 3,
According to the control device for the disconnection transmission, when the low friction road surface state is detected, the maximum gear ratio in the gear ratio control region is changed to a smaller gear ratio on the minimum gear ratio side. When the accelerator pedal is operated, the driving force can be prevented from being excessively applied, and the vehicle behavior can be prevented from becoming unstable.

[0020]

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 brake range for operating the engine brake as a shift select position for forward traveling. D which is the normal driving range in the select position
When the range is selected, it is within the normal traveling gear ratio control region (D range gear ratio region) suitable for normal traveling, and when the S range which is the engine brake range is selected, the normal traveling gear ratio is selected. Engine brake range control range (S with a minimum gear ratio larger than the control range)
Within the range gear ratio range), by setting the target input shaft rotation speed according to the vehicle speed and the throttle opening, respectively,
Controls the gear ratio of a continuously variable transmission.

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, and a final reduction gear 8 as shown in FIG. 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 to change the tilt angles of the transmission rollers 15 and 16 with respect to the input / output disks 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 41 for detecting VO, an input shaft rotation speed sensor 42 for detecting the rotation speed of the input disk 11 of the toroidal type continuously variable transmission 6, and an output shaft rotation speed sensor 43 for detecting the rotation speed of the output disk 13. The selector switch 44 that outputs a select signal FD = 1 when the D range, which is a normal running range, is selected by a select lever (not shown), and a shift in a snow mode running pattern for low friction road surfaces such as snow roads and sand roads A snow mode switch 45 that outputs a detection signal SW _SNOW = 1 when a snow mode for instructing control is selected, an engine speed sensor 46 that detects the speed of the output shaft of the engine 10, a front wheel side speed and a rear wheel side. A front wheel rotation speed sensor 47 for detecting the rotation speed,
At least a rear wheel rotation speed sensor 48 is provided and provided at appropriate places.

Of these, the throttle opening sensor 41 is
The throttle opening of the engine 10 is detected as a voltage signal, and the depression amount of the accelerator pedal is divided in stages, and the depression amount of the accelerator pedal is "0", that is, the throttle opening equivalent to that. the minimum value TVO _MIN case but it is fully closed, the depression amount of the accelerator pedal is maximum, i.e., the same maximum value TVO where equivalent throttle opening is fully open _MAX
As an analog signal TV according to this throttle opening
O is 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.

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 input speed that should be achieved in
Calculate the gear ratio C to be achieved by the idal type continuously variable transmission mechanism 6
Set the step required to achieve this gear ratio C.
Motor control signal S for driving the motor 22_MLive
Generated and output to the motor drive circuit 32, and the engine
A snow mode flag F, which will be described later, is sent to the control device 50._SNOW
Is output.

The motor drive circuit 32 converts the input motor control signal S _M into a drive signal for the step motor 22 and outputs it. Next, the gear ratio control process executed by the arithmetic processing unit 31b of the microcomputer 31 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 this flowchart does not include steps for communication, but the maps, programs, predetermined arithmetic expressions, etc. necessary for the arithmetic processing are stored in the ROM of the storage device 31c.
It is assumed that the calculated value and each information value that are read from the memory at any time and obtained by the calculation are stored in the RAM of the storage device 31c at any time.

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, and 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 , the selector position signal FD from the selector switch 44, the front wheel side rotational speed N _F and the rear wheel side rotational speed N _R from the front wheel side and rear wheel side rotational speed sensors 47, 48 are read.
Next, in step S2, the vehicle speed V _SP is calculated from the output shaft rotation speed No 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 continuously variable transmission 6 is calculated from the engine torque Te and the torque converter ratio t (e) according to the following equation (2). The torque converter ratio t (e) is calculated from the input shaft speed Nt and the engine speed Ne according to the following equation (3).

Tin = Te × t (e) (2) t (e) = Ne / Nt (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 or not, that is, the driver is traveling in a snow mode traveling pattern. It is determined whether or not it is instructed (step S11). And if SW _SNOW = 1 then
In step S12, the snow mode flag F _{SNOW
Is set} to F _SNOW = 1 and the process 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 the shift determination processing is executed. In this shift determination process, it is determined whether the D range, which is the normal traveling range, is selected based on whether the selector position signal FD from the selector switch 44 is FD = 1, and the D range is selected. If not, for example, if the S range is selected, the target gear ratio Ct corresponding to the gear shift select position is set in the same manner as the process for setting the normal target gear ratio.

On the other hand, when the D range is selected, the flowchart of FIG. 6 is executed, and first, step S
21. Based on the vehicle speed V _SP and the throttle opening TVO,
The target input shaft speed TNt is set in the control map of FIG.

Here, the control map shown in FIG.
It is equivalent to a general control map of a normal shift pattern in which _SP is the horizontal axis, target input shaft speed TNt is the vertical axis, and throttle opening TVO is a parameter, and a straight line passing through the origin has a constant gear ratio. You can think of it. Then, for example, the straight line having the largest inclination in the entire region of the gear shift pattern has the largest reduction ratio of the entire vehicle, that is, the maximum gear ratio C
Represents _MAX, most slope small straight reduction ratio smallest reversed, that is, represents the minimum speed ratio C _MIN. And, even at the same vehicle speed V _SP , the accelerator pedal depression amount is large and the throttle opening TVO is large.
For example, it is necessary to increase the rotational speed of the engine and increase its output torque because the load required for the engine is large due to running load such as uphill roads and head wind resistance because acceleration is required. With the throttle opening TVO detected by the throttle opening sensor 41 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 smaller than a certain threshold value control start threshold value, the gear ratio is the maximum gear ratio C
Set to _MAX .

Within the D range gear ratio range from the minimum gear ratio C _MIN to the maximum gear ratio C _MAX , the target input shaft speed TN is set according to the throttle opening TVO and the vehicle speed V _SP.
t is set.

Next, in step S22, the target input shaft speeds TNt _MAX and TNt corresponding to the maximum and minimum possible gear ratios are determined based on whether or not the snow mode flag F _SNOW = 1. Set _MIN from the control map in FIG. That is, when a snow mode flag F _SNOW = 0, the maximum speed ratio C _MAX and the minimum speed ratio C _{MI N}
As shown by the solid line in the control map of FIG. 7, the maximum and minimum values of the gear ratio in the D range gear ratio area are set as they are as the maximum gear ratio and the minimum gear ratio.

On the other hand, when the snow mode flag F _SNOW = 1, in the process of step S22, the maximum gear ratio C _MAX is set to the minimum gear ratio C _MIN side, as indicated by the broken line in the control map of FIG. _Is limited to the maximum speed ratio C _SMAX in the snow mode with a small speed ratio, and the minimum speed ratio C _{MIN is set} to the minimum speed ratio C _SMIN in the snow mode with a higher speed ratio on the maximum speed ratio side C _MAX. Limit the maximum gear ratio C _{SMAX in the} snow mode and the minimum gear ratio C in the snow mode.
_{Set SMIN} as the maximum gear ratio and the minimum gear ratio. That is, when the snow mode flag F _SNOW = 1, low μ
It can be regarded as traveling on the road surface, and when the accelerator pedal is depressed while traveling on this low μ road surface, a driving force equivalent to that on the high μ road surface is generated on the low μ road surface. The driving force may be too strong for. Therefore, in order to avoid this, the maximum speed ratio C _MAX is limited to the maximum speed ratio C _SMAX in the snow mode in which the speed ratio is smaller than this, and the driving force is suppressed.

Further, when the engine brake is applied, that is, when the throttle opening is fully closed, the gear ratio is controlled to the minimum gear ratio C _MIN .
It is difficult to obtain the braking effect of the engine brake. In order to avoid this, the minimum gear ratio C _MIN is limited to the minimum gear ratio C _SMIN in the snow mode in which the gear ratio is larger than this to improve the braking effect by engine braking.

[0046] Then, the process proceeds to step S23, the target input shaft rotational speed TNT obtained in step S21, the maximum and maximum TNT _MAX and minimum target input shaft rotational speed corresponding to the minimum speed ratio determined in step S22 The value is limited to a value within the range of TNt _MIN , and the target revolution speed TNt ^* is set. That is, when the target input shaft rotation speed TNt exceeds the maximum value TNt _MAX of the target input shaft rotation speed (TNt> TNt).
_MAX ) is reached target speed TNt ^* = TNt _MAX, and when the target input shaft speed TNt is smaller than the minimum target input shaft speed TNt _MIN (TNt <TNt _MIN ), the target target speed TNt is reached. ^* = TNt _MIN , and the target input shaft rotation speed TNt is the maximum value TNt of the target input shaft rotation speed.
If it is within the range of _MAX and the minimum value TNt _MIN , the reaching target rotation speed TNt ^* = TNt is set.

Then, the process proceeds to step S24, 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 S25, 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, the routine proceeds to step S26, where the target gear ratio Ct is calculated according to the following equation (5) based on the first-order lag target rotation speed Nt (k) calculated at step S25 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 processing, the step motor 22 cannot instantaneously achieve the target position, so that the control speed is regulated. As shown in the flowchart of FIG. 8, first, in step S31, the control map of FIG. Based on the target gear ratio Ct and the estimated input torque Tin set in the processing of step S4 based on the above, the actual target gear ratio C ^* considering torque shift compensation is set. 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 or not 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. Then, the process ends and the process returns to the main program.

On the other hand, if it is determined in step S35 that the temporary target step number STP 'is not larger than the actual target step number STP ^* (STP'≤STP ^* ), then step S35.
In step 38, the temporary target step number STP 'is set as the motor control signal S _M. Then, the process ends and the process returns to the main program.

In addition, at the 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
Set as. Then, the process ends and the main program
Return to Lamb.

On the other hand, in the process of step S40, if the temporary target step number STP 'is smaller than the actual target step number STP ^* (STP'<STP ^* ), 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 completed, the process proceeds to step S6, and the motor control signal S _M set in the shift process of FIG. The snow mode flag F _SNOW set in the process of FIG. 5 is output to the engine control device 50 while being output to the drive circuit 32. Then, the shift control processing is ended, and thereafter, the above processing is repeatedly executed at a predetermined sampling cycle.

The engine control device 50 controls, for example, the fuel injection amount, the ignition timing, etc. according to the engine load, the vehicle speed, etc., and controls the rotation state of the engine 10 to the optimum state according to the running state of the vehicle. Further, when the engine brake is actuated, the throttle opening is fully closed, and the engine speed is a predetermined value determined by the engine coolant temperature, vehicle speed, or the like, for example, the fuel return speed shown by the one-dot chain line in FIG. When the engine speed is equal to or higher than the fuel cut speed that is higher than N _FC, it is determined that it is not necessary to perform combustion supply to the engine 10, and fuel is supplied to the engine 10 until the engine speed falls below the fuel return speed N _FC. The fuel cut processing is performed during deceleration to stop. At this time, when the snow mode flag F _SNOW input from the control unit 30 is F _SNOW = 1, the fuel cut processing during deceleration is not performed. That is, as shown in the flowchart of FIG. 11, first, it is determined whether or not the snow mode flag F _SNOW = 0 (step S51). If F _SNOW = 0, it is determined that the snow mode is not in the snow mode. Then, the fuel cut processing during deceleration is executed based on the throttle opening and the engine speed,
When the predetermined condition is satisfied, the fuel supply to the engine 10 is stopped (step S52).

On the other hand, when the snow mode flag is F _SNOW = 1, that is, in the snow mode, even if the predetermined condition in the fuel cut processing during deceleration is satisfied, the engine 1
The fuel supply to 0 is not stopped (step S53).

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 D range suitable for normal traveling is selected as the gear shift select position.

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 processing is executed (step S3). At this time, since the vehicle is traveling on a high μ road surface, the driver instructs traveling in a snow mode traveling pattern for a low friction road surface. If not, the detection signal SW _SNOW of the snow mode switch 45 = 0
Becomes Further, since the vehicle is traveling on a high μ road surface and the wheels are not slipping, the snow mode flag F _SNOW is F.
It is set as _SNOW = 0. Next, the shift determination process of step S4 is executed, and in this case, the D range is selected. Therefore, in the control map of FIG. 7, the D range gear ratio region is determined based on the vehicle speed V _SP and the throttle opening TVO. The target input shaft speed TNt is set from the inside, 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 S
5) The motor control signal S _M calculated and set by this is output to the motor drive circuit 32. A drive signal according to the motor control signal S _M is supplied from the motor drive circuit 32 to the step motor 22, so that the step motor 22 moves and the control valve 21 operates according to the moving direction of the step motor 22. , By this, the transmission roller 15,
When 16 moves, it is controlled to a predetermined gear ratio.

Next, from this state, also on the high μ road surface, it is assumed that the state shifts to the coasting state, that is, the coasting state in which the depression of the brake pedal and the depression of the accelerator pedal are released without changing the shift select position. . In this coasting state, since the accelerator pedal is released, the gear shift control is performed so that it becomes the minimum gear ratio C _{MIN in} the D range gear ratio region of the control map of FIG. 7.

When the accelerator pedal is depressed from this state, the throttle opening becomes large, so that, for example, the maximum gear ratio C _MAX is set as the gear ratio, and gear change control is performed in accordance with this. By means of this, an appropriate acceleration force is given and good acceleration is achieved.

On the other hand, when the vehicle is traveling on a high-μ road surface to a low-μ road surface, it is detected that the vehicle is in the automatic snow mode from the slip state based on the rotation speed difference between the front wheel side and the rear wheel side. And the snow mode flag is F _SNOW =
Set to 1. Alternatively, since the vehicle travels on a low μ road surface, the driver instructs the vehicle to travel in the snow mode traveling pattern, whereby the snow mode flag is set to F _SNOW = 1. Therefore, in the control map of FIG. 7, the range that the gear ratio can take is from C _MAX to C
_{From the} D range gear ratio range, which is the range of _MIN , the range is limited to the maximum gear ratio C _{SM AX} and the minimum gear ratio C _{S MIN in} the snow mode.

When the accelerator pedal is opened in this state in anticipation of the deceleration effect of the engine brake, the throttle opening becomes fully closed.
In the control map of, the minimum gear ratio C in the snow mode
_SMIN will be set as the gear ratio. The minimum gear ratio C _{SMIN in} this snow mode is the normal minimum gear ratio C _{MI N}
Since the gear ratio is set to a larger value, the continuously variable transmission is controlled to have a larger gear ratio.

At this time, assuming that the engine speed is equal to or higher than the fuel cut speed and does not fall below the fuel return speed N _FC , when the throttle opening is fully closed, the engine control device 50 Fuel is cut to the engine 10. In this case, however, since the snow mode flag F _SNOW is F _SNOW = 1, fuel cut is prohibited and fuel cut is not performed.

Therefore, when the engine brake is applied, the fuel is not cut and a certain amount of engine torque is generated to prevent the engine brake from tending to operate excessively as the gear ratio increases. , On a low μ road surface, an appropriate braking effect by engine braking can be obtained.

Therefore, an appropriate braking effect by the engine brake can be obtained even on a low μ road surface, so that the frequency of performing the brake operation or the select down operation is reduced, and the behavior change accompanying this is suppressed. In particular, since the behavior change on the low μ road surface is suppressed, the running stability on the low μ road surface can be improved.

When the accelerator pedal is depressed while the vehicle is coasting on this low μ road surface, and the throttle opening becomes maximum, the snow mode flag F _SNOW is F _SNOW = 1. , Fig. 7
In the control map, the maximum value of the gear ratio is the maximum gear ratio C _{SMAX in the} snow mode, and the gear ratio of the continuously variable transmission is controlled so as to be the maximum gear ratio C _SMAX . At this time, since the maximum gear ratio C _SMAX is smaller than the maximum gear ratio C _MAX in the normal D range gear ratio region, a high μ
The driving force generated in comparison with the road surface is suppressed. Therefore, since a smaller driving force is generated on the low μ road surface as compared with the high μ road surface, the vehicle behavior does not become unstable due to the excessive driving force.

Further, at this time, since the fuel cut is not performed during the coast running state, there is little variation in the engine torque even when the coast running state is shifted to the acceleration state. That is, as shown in FIG. 12, the engine torque Te with respect to the engine speed Ne is compared with the engine torque Te when the throttle opening shown by the solid line is in the fully closed state and fuel cut is performed, and the throttle shown by the broken line is shown. The engine torque Te is larger when the opening is fully closed and fuel cut is not performed.

Therefore, when the accelerator pedal is depressed from the coast running state and the fuel is cut, the engine torque Te on the negative side acts in the coast running state as shown in FIG. 13 (a). When the accelerator pedal is depressed in this state, the inertia torque needs to be accelerated, so that the engine torque Te is temporarily reduced. Then, after that, the engine torque Te is generated according to the depression of the accelerator pedal,
A step ΔTe will be generated.

In comparison with this, when the fuel cut is not performed, as shown in FIG. 13 (b), the engine torque Te is on the positive side even in the coast running state, so the accelerator pedal is depressed. In this case, the pull-in does not occur, and the step ΔTe ′ of the engine torque Te is reduced.

Therefore, such engine torque T
The drive torque in the propeller shaft generated when "e" occurs is shown in Fig. 14 (a) when the fuel cut is performed.
As shown in, the pull-in similarly occurs in proportion to the engine torque Te, and then the drive torque increases. On the other hand, when the fuel cut is not performed, since the engine torque Te is not pulled in, a certain amount of drive torque is output even in the coast state, and then the accelerator It smoothly increases in response to a pedal depression operation, and the maximum gear ratio is changed to a smaller value, so that a step in driving torque is suppressed and acceleration is performed in a state where the vehicle behavior is stable. It will be. Also,
It can be seen that the engine braking torque, which is the difference between the road surface rotational drive force, which is the drive force for the road surface to rotate the wheels, and the drive torque, which is indicated by the broken line in the figure, can be obtained to some extent.

Therefore, when the accelerator pedal is depressed from the coast running on a low μ road surface, the pull-in due to the inertia torque is reduced, and the maximum gear ratio is changed to a smaller value to obtain an appropriate driving force. As a result, the driving force fluctuation is suppressed, and the change in the vehicle behavior accompanying it is suppressed. In particular, the change in the vehicle behavior on a low μ road surface can be suppressed, and the running stability of the vehicle can be suppressed. It is possible to improve the sex.

In the above embodiment, the case where the minimum gear ratio is uniformly changed to C _SMIN on the maximum gear ratio side when the snow mode flag is F _SNOW = 1 has been described. For example, as shown in FIG. 15, the change range may be made smaller as the vehicle speed increases. That is, as the vehicle speed increases, the gear ratio C _{MI N}
The gear ratio may be set to have a small difference with. By doing so, the deceleration effect of normal engine braking increases as the vehicle speed increases, so by changing the change range of the gear ratio according to the vehicle speed, the appropriate degree of engine braking can be adjusted according to the running condition of the vehicle. It is possible to obtain various braking effects.

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.

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.

Here, the D range gear ratio region corresponds to the gear ratio control region, the gear shift determination process of step S4 of FIG. 3 corresponds to the gear shift control means, the engine control device 50 corresponds to the fuel supply stopping means, The snow mode determination process of step S3 of FIG. 3 corresponds to the road surface friction coefficient state detecting means, and when the snow mode flag F _SNOW = 1 in steps S22 and S23 of FIG. 6 and step S51 of FIG. 11, step S53. The process of executing (1) corresponds to the low friction road surface adjusting means, and the process of detecting the vehicle speed in step S2 of FIG. 3 corresponds to the vehicle speed detecting 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 control map showing the correspondence between the vehicle speed V _SP and the target input shaft rotation speed TNt with 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 flowchart showing an example of a processing procedure of fuel cut processing during deceleration in the engine control device.

FIG. 12 is an engine torque map when fuel is cut and when fuel is not cut.

FIG. 13 is an explanatory diagram illustrating a change state of engine torque when the accelerator pedal is operated from the coast running state.

FIG. 14 is an explanatory diagram illustrating a change state of drive torque of the propeller shaft when the accelerator pedal is operated from the coast running state.

FIG. 15 is another example of the control map of FIG. 7.

[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 50 Engine control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI F16H 61/02 F16H 61/02 // F16H 59:24 59:24 59:66 59:66 (56) References JP-A-2 -144233 (JP, A) JP 64-87844 (JP, A) JP 63-167041 (JP, A) JP 62-295762 (JP, A) JP 58-85747 (JP, A) ) JP-A-2-211354 (JP, A) JP-A-63-68428 (JP, A) JP-A-2-3734 (JP, A) JP-A-3-92665 (JP, A) JP-A-7- 280053 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60K 41/00-41/28 B60T ⁷ /12-7/22 B60T 8/32-8/96 F02D 29/00 -29/06 F02D 41/00-41/40 F02D 43/00-45/00

Claims (3)

(57) [Claims] 1. A shift control means for performing shift control of a continuously variable transmission in a predetermined gear ratio control region so that a minimum gear ratio is obtained at least when the throttle opening is fully closed, and the throttle opening is fully closed. In a control device for a continuously variable transmission, which comprises a fuel supply stopping means for stopping fuel supply to the engine when the engine speed is equal to or higher than a predetermined value, The road surface friction coefficient state detecting means for detecting, and when the road surface friction coefficient state detecting means detects a low friction road surface state, prohibits stop of fuel supply by the fuel supply stopping means and minimizes the gear ratio in the gear ratio control region. To a maximum gear ratio side, a low friction road surface adjusting means, and a vehicle speed detecting means for detecting a vehicle speed, wherein the low friction road surface adjusting means is configured such that the minimum gear ratio increases as the vehicle speed increases. Control system for a continuously variable transmission, characterized in that is adapted to reduce the change width. 2. The throttle opening is at least fully closed.
In order to achieve the minimum gear ratio,
A shift control means for controlling the shift of the multi-speed transmission;
Torr opening is fully closed and engine speed is a specified value
When the above is the case, the fuel supply that stops the fuel supply to the engine
In a control device for a continuously variable transmission including a power supply stopping means,
hand, Road friction coefficient that detects the road friction coefficient state while the vehicle is running
The number state detection means and the driver releases the accelerator pedal.
Running with the engine braking effect expected in the normal state
Coast running condition detection hand that detects whether or not
Dan, The road friction coefficient state detection means detects a low friction road surface state.
In addition, the coast running state detection means is
When it is detected that the fuel supply is stopped,
Prohibiting the stop of fuel supply due to
Adjustment for low friction road surface that changes the minimum gear ratio to the maximum gear ratio side
And a control device for a continuously variable transmission, comprising:
Place 3. The low friction road surface adjusting means changes the maximum gear ratio of the gear ratio control region to the minimum gear ratio side when the road surface friction coefficient state detecting means detects a low friction road surface state. Claim 1 or 2 characterized in that
Is a control device for a continuously variable transmission according to 2 .