JP4039180B2 - Control device for continuously variable transmission for vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a continuously variable transmission for a vehicle, and more particularly to an improvement of a control device that changes a frictional force for transmitting power according to a state of a traveling path.
[0002]
[Prior art]
2. Description of the Related Art A vehicle is known in which a continuously variable transmission that transmits power via a frictional force is disposed on a power transmission path between a driving power source and driving wheels. As one aspect of such a continuously variable transmission, a belt type having (a) an input-side variable pulley and an output-side variable pulley having variable effective diameters, and (b) a transmission belt wound around these variable pulleys. There is a continuously variable transmission, and in such a belt-type continuously variable transmission, power is transmitted via a frictional force between the transmission belt and the variable pulley, and a gear ratio and a belt are changed according to the driving state of the vehicle. The clamping pressure is controlled. The belt clamping pressure corresponds to the frictional force between the transmission belt and the variable pulley, and if slippage occurs between them, the durability (life) decreases due to wear, but the belt clamping pressure is more than necessary. If it is too high, the power loss increases and the fuel consumption and exhaust gas deteriorate. Therefore, control is performed in accordance with the input torque to the continuously variable transmission, that is, the engine torque so as to be as small as possible without causing slip.
[0003]
By the way, when the driving wheel repeatedly spins and grips on a bad road, a large reverse input torque acts from the road surface side when gripping, and slipping may occur between the transmission belt and the variable pulley. is there. Therefore, a technique has been developed that can prevent slippage on such a rough road with certainty, and reduce the power loss by minimizing the belt clamping pressure on a flat road where reverse input torque hardly acts. For example, a control device for a continuously variable transmission for a vehicle described in the specification of Japanese Patent Application Laid-Open No. 2001-254814 and the like. According to such a control device, for example, car navigation information including travel route information is obtained from a navigation system. It is determined whether the current road and the near future road are flat roads or bad roads based on the travel road information. In the case of bad roads, the belt clamp of the belt type continuously variable transmission is compared with the flat road. By selecting a map for rough roads with high pressure, it is possible to reliably avoid slippage of the transmission belt due to unevenness of the road surface on the rough roads, while greatly reducing the belt clamping pressure on flat roads. Reduce loss.
[0004]
However, not all vehicles are equipped with a navigation system, and it may be difficult to determine the state of the road. Therefore, the belt clamping pressure is generally determined according to a relationship stored in advance in a controller or the like that controls the continuously variable transmission.
[0005]
[Problems to be solved by the invention]
FIG. 11 is a diagram illustrating an example of a relationship between input torque and belt clamping pressure used for controlling a conventional continuously variable transmission. As shown in this figure, a conventional continuously variable transmission control device is, for example, an input torque T_INThe basic value Fb (T of the belt clamping pressure determined according to_IN) And input torque T_INThe theoretical value of the belt clamping pressure Ft (T_IN) Fixed margin value C₀Was compared with a value obtained by uniformly adding the two, and the larger one was adopted as the belt clamping pressure. That is, the continuously variable transmission is controlled using the relationship indicated by the solid line in the figure. Here, the input torque T_INIs the predetermined torque T_boThe above-mentioned fixed margin value C when₀Is used when the engine torque is low and the input torque T_INCompared to the reverse input torque T from the road surface_LThis is because slippage is likely to occur between the transmission belt and the variable pulley, and the fixed margin C₀Is the expected reverse input torque T_LUsually, it is determined in advance based on the maximum value of. As a result, although slipping is prevented, the belt clamping pressure becomes higher than necessary, which causes power loss.
[0006]
The present invention has been made against the background of the above circumstances, and its object is to provide a necessary and sufficient friction that does not cause slippage between the transmission belt and the variable pulley when the input torque is relatively small. An object of the present invention is to provide a control device for a continuously variable transmission for a vehicle that reduces power loss as much as possible by adopting force.
[0007]
[Means for Solving the Problems]
  In order to achieve such an object, the gist of the present invention is that it is disposed in a power transmission path between a driving power source and driving wheels in a vehicle to transmit power through frictional force and A continuously variable transmission control device capable of controlling frictional force,A margin value calculation that calculates a margin value to be added to the theoretical value of the driving friction force for driving the continuously variable transmission according to the vehicle speed and the gear ratio so that the margin value increases as the vehicle speed increases. Means, a frictional force calculating means for calculating the driving frictional force using the marginal value calculated by the marginal value calculating means, and the stepless step through the driving frictional force calculated by the frictional force calculating means. Frictional force control means for controlling the transmission to driveIt is characterized by this.
[0008]
【The invention's effect】
  This way,A margin value calculating means for calculating a margin value for adding to the theoretical value of the driving friction force for driving the continuously variable transmission according to the vehicle speed and the gear ratio so that the margin value increases as the vehicle speed increases. A friction force calculating means for calculating the driving friction force using the margin value calculated by the margin value calculating means, and the continuously variable transmission via the driving friction force calculated by the friction force calculating means. The frictional force control means for controlling the machine to drive, the theoretical value of the driving frictional force is the lower limit of the frictional force that does not cause slippage between the transmission belt and the variable pulley. A necessary and sufficient driving frictional force is calculated by the frictional force calculating unit by adding the smallest possible marginal value calculated by the marginal value calculating unit, and the frictional force controlling unit Wherein through such driving frictional force can be controlled to the continuously variable transmission is driven. That is,Control of a continuously variable transmission for a vehicle that reduces power loss as much as possible by adopting necessary and sufficient frictional force that does not cause slippage between the transmission belt and variable pulley when the input torque is relatively small An apparatus can be provided.
[0010]
Other aspects of the invention
  herePreferably, the frictional force calculating means adds the margin value to the basic value of the driving frictional force determined to be always larger than the theoretical value of the driving frictional force and the theoretical value of the driving frictional force. The value is compared, and the larger one is calculated as the driving frictional force. In this way, for example, when the input torque is relatively large, the basic value of the driving friction force is used, and when the input torque is relatively small, a value obtained by adding the margin value to the theoretical value of the driving friction force is used as the driving friction force. As a result, there is an advantage that a necessary and sufficient driving friction force corresponding to the driving state of the continuously variable transmission is calculated while ensuring a value equal to or higher than the basic value of the driving friction force.
[0011]
Preferably, the theoretical value and the basic value of the driving frictional force are determined according to the input torque to the continuously variable transmission. In this way, the theoretical value of the driving friction force, which is the lower limit value of the frictional force that does not cause slip between the transmission belt and the variable pulley, and the basic value of the driving frictional force corresponding thereto are unified. There is an advantage that it is determined.
[0012]
【Example】
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
FIG. 1 is a skeleton diagram of a vehicle drive device 10 to which the present invention is applied. The vehicle drive device 10 is of a horizontal type and is suitably employed in an FF (front engine / front drive) type vehicle, and includes an engine 12 as an internal combustion engine used as a driving power source. The output of the engine 12 is transmitted from the torque converter 14 to the differential gear device 22 via the forward / reverse switching device 16, the belt-type continuously variable transmission (CVT) 18, and the reduction gear 20, and a pair of left and right drive wheels. 24.
[0014]
The torque converter 14 includes a pump impeller 28 connected to the crankshaft of the engine 12 and a turbine impeller 26 connected to the forward / reverse switching device 16 via a turbine shaft 30 via a fluid. Power transmission. Further, a lock-up clutch 32 is provided between the turbine impeller 26 and the pump impeller 28 so that they can be integrally connected to be integrally rotated.
[0015]
The forward / reverse switching device 16 is constituted by a double pinion type planetary gear device, the turbine shaft 30 of the torque converter 14 is connected to a sun gear 16s, and the input shaft 34 of the continuously variable transmission 18 is a carrier 16c. It is connected to. When the clutch 36 disposed between the sun gear 16s and the carrier 16c is engaged, the forward / reverse switching device 16 is rotated integrally so that the turbine shaft 30 is directly connected to the input shaft 34, and the forward direction. Is transmitted to the pair of drive wheels 24. When the brake 40 disposed between the ring gear 16r and the housing 38 is engaged and the clutch 36 is released, the input shaft 34 is rotated in the reverse direction with respect to the turbine shaft 30 to move backward. Is transmitted to the pair of drive wheels 24.
[0016]
The continuously variable transmission 18 includes an input side variable pulley 42 having a variable effective diameter provided on the input shaft 34, an output side variable pulley 46 having a variable effective diameter provided on the output shaft 44, and the input side. A transmission belt 48 wound around the variable pulley 42 and the output-side variable pulley 46 is provided, and power is transmitted through a frictional force between the variable pulleys 42 and 46 and the transmission belt 48. Each of the variable pulleys 42 and 46 has a variable V-groove width and includes a hydraulic cylinder. The hydraulic pressure of the hydraulic cylinder of the input-side variable pulley 42 is controlled by a transmission control circuit 66 described later. The V-groove width of both variable pulleys 42 and 46 is changed to change the engagement diameter (effective diameter) R of the transmission belt 48, and the gear ratio γ (= input-side rotational speed N)._IN/ Output side rotational speed N_OUT) Is continuously changed. Specifically, as shown in FIG. 4, the accelerator operation amount θ representing the driver's requested output_ACCAnd vehicle speed V (output side rotational speed N_OUTTo the target rotation speed N from a predetermined map_AIMAnd the actual input side rotational speed N_INIs the target rotational speed N_AIMThe hydraulic pressure of the hydraulic cylinder of the input-side variable pulley 42 is feedback-controlled so as to match the above. Note that γ in FIG._maxIs the maximum gear ratio, γ_minIs the minimum gear ratio.
[0017]
FIG. 2 is a block diagram illustrating a control system of the continuously variable transmission 18. The controller 50 shown in this figure is configured to include a microcomputer, and performs speed change control of the continuously variable transmission 18 by performing signal processing in accordance with a program stored in advance in a ROM while utilizing a temporary storage function of a RAM. And an accelerator operation amount sensor 52, an engine rotation speed sensor 54, a vehicle speed sensor 56, an input side rotation speed sensor 58, an oil temperature sensor 60, and a hydraulic pressure sensor 62, respectively._ACC, Engine speed N_E, Vehicle speed V (specifically, the rotational speed N of the output shaft 44)_OUT), Input side rotational speed N_IN, Oil temperature T of hydraulic circuit₀, Hydraulic P₀Is supplied.
[0018]
FIG. 3 is a diagram illustrating an example of a clamping pressure control circuit 64 that controls the clamping pressure of the transmission belt 48. As shown in this figure, the hydraulic oil pumped up from the oil tank 70 by the pump 68 is supplied to the linear solenoid valve 72 and also to the hydraulic cylinder of the output side variable pulley 46 via the clamping pressure control valve 74. The The linear solenoid valve 72 continuously adjusts the hydraulic pressure of the hydraulic oil supplied from the pump 68 when the excitation current is continuously controlled by the controller 50, so that the control pressure P_SIs output to the clamping pressure control valve 74, and the hydraulic pressure of the hydraulic oil supplied from the clamping pressure control valve 74 to the hydraulic cylinder of the output-side variable pulley 46 is the control pressure P._SThe belt clamping pressure, that is, the frictional force between the variable pulleys 42 and 46 and the transmission belt 48 is increased.
[0019]
The linear solenoid valve 72 also has a control pressure P when the cutback valve 76 is ON._SIs supplied to the feedback chamber 78, while the control pressure P is applied when the cutback valve 76 is OFF._SIs cut off and the feedback chamber 78 is opened to the atmosphere. When the cutback valve 76 is ON, the control pressure P is higher than when the cutback valve 76 is OFF._SIs switched to the low pressure side. Here, the cutback valve 76 receives a signal pressure P from a solenoid valve (not shown) when the lockup clutch 32 of the torque converter 14 is ON (engaged)._ONIs switched to ON by being supplied.
[0020]
FIG. 5 is a block diagram illustrating functions related to the control of the belt clamping pressure provided in the controller 50. As shown in this figure, the controller 50 is functionally provided with a margin value calculating means 80, a belt clamping pressure calculating means 82, and a belt clamping pressure control means 84, and according to the flowchart shown in FIG. Specifically, the hydraulic pressure of the hydraulic cylinder of the output side variable pulley 46 is controlled. Steps S1 and S2 in FIG. 10 are executed by the margin value calculation means 80, step S3 is executed by the belt clamping pressure calculation means 82, and step S4 is executed by the belt clamping pressure control means 84. The belt clamping pressure uniquely determines the driving frictional force of the continuously variable transmission 18. The belt clamping pressure calculating means 82 is the frictional force calculating means, and the belt clamping pressure control means 84 is the frictional force control. It corresponds to each means.
[0021]
In the present embodiment, the hydraulic pressure of the hydraulic cylinder of the output side variable pulley 46 is such that the input torque T at a constant gear ratio γ as shown in FIG. 6, for example, does not cause the transmission belt 48 to slip._INThe pressure regulation is controlled by the controller 50 and the clamping pressure control circuit 64 using the relationship between the belt clamping force and the belt clamping pressure. That is, the input torque T_INThe basic value Fb (T of the belt clamping pressure determined according to_IN) And input torque T_INThe theoretical value of the belt clamping pressure Ft (T_IN) And a value obtained by adding a margin value C (V, γ) determined according to the vehicle speed V and the gear ratio γ, whichever is larger is adopted as the belt clamping pressure, and the transmission belt 48 is the belt. It is controlled so as to be driven by the clamping pressure. The clamping pressure of the transmission belt 48 is determined according to the hydraulic pressure of the hydraulic cylinder of the output side variable pulley 46, and the driving frictional force of the continuously variable transmission 18 is determined. The basic value Fb (T_IN) And the theoretical value Ft (T_IN) Are functions of the gear ratio γ, but are omitted on the assumption that the gear ratio is constant.
[0022]
Theoretical value of the belt clamping pressure Ft (T_IN) And the basic value Fb (T_IN) Is the input torque T to the continuously variable transmission 18._INSpecifically, the input torque T_IN, The friction coefficient μ, the belt engagement diameter R of the input side variable pulley 42, and the pulley area A, the belt clamping pressure P expressed basically by the following equation 1_BFor example, when the constant α is 1.0, the theoretical value Ft (T_IN) With α being 1.25 is the basic value Fb (T_IN) Respectively. The input torque T_INAnd the belt engagement diameter R are the accelerator operation amount θ, respectively._ACCAnd the gear ratio γ. Further, the theoretical value Ft (T_IN) Is a lower limit value of the belt clamping pressure that does not cause slippage between the transmission belt 48 and the variable pulleys 42 and 46, and the basic value Fb (T_IN) Is the theoretical value Ft (T_IN) Is a practical value determined so as to be always larger than.
[0023]
[Formula 1]
P_B= (T_IN/ Μ ・ R ・ A) × α
[0024]
Here, the margin value C (V, γ) is determined based on the vehicle speed V of the vehicle and the speed ratio γ of the continuously variable transmission 18 based on the correspondence stored in advance in the control device or the like. The inventors of the present invention describe a road surface input torque (reverse input torque) T input from the road surface side when the driving wheel 24 spins or grips._LAs a result of continuing research for the purpose of obtaining the value from other parameters, the road surface input torque T_LHas been found to change according to the vehicle speed V and the gear ratio γ. FIG. 8 shows the vehicle speed V and the road surface input torque T._L9 is a graph showing an example of the relationship between the transmission ratio γ and the road surface input torque T of the continuously variable transmission._LIt is a graph which shows an example of this relationship. As shown in these figures, the road surface input torque T_LIncreases as the vehicle speed V increases, and decreases as the speed ratio γ increases.
[0025]
FIG. 7 is a table showing an example of a correspondence relationship between the vehicle speed V and the gear ratio γ and the margin value C (V, γ). The V, γ-C matrix 86 shown in FIG. 7 has a margin value C (V, γ) and a theoretical value Ft (T_IN)) Is determined in advance based on test results so that the necessary and sufficient belt clamping pressure according to the road surface condition is obtained, and is stored in the ROM of the controller 50 or the like. As described above, the vehicle speed V and the gear ratio γ are determined by the road surface input torque T_LTherefore, the margin value C (V, γ) using them as variables reflects the state of the road surface on which the vehicle travels.
[0026]
The flowchart of FIG. 10 is repeatedly executed at a predetermined cycle time. First, in step S1, the input side rotational speed N is passed through the input side rotational speed sensor 58 and the vehicle speed sensor 56._INFurther, parameters such as the vehicle speed V are read, and the gear ratio γ of the continuously variable transmission 18 is calculated from these values. In addition, the accelerator operation amount θ read through the accelerator operation amount sensor 52._ACCTo input torque T_INIs calculated. Next, in step S2, the theoretical value Ft (T_IN7) stored in the controller 50 based on the vehicle speed V and the gear ratio γ obtained in step 1 above. Derived from the matrix 86.
[0027]
Next, in step S3, a necessary and sufficient belt clamping pressure corresponding to the road surface condition is calculated using the margin value C (V, γ) derived in step S2. For example, the basic value Fb (T_IN) And the theoretical value Ft (T_IN) And a value obtained by adding a margin value C (V, γ), and the larger one is calculated as the necessary and sufficient belt clamping pressure. That is, when the margin value C (V, γ) takes the value indicated by the central chain line in FIG. 6, the relationship indicated by the solid line is employed as the belt clamping pressure.
[0028]
In the last step S4, the hydraulic current of the output-side variable pulley 46 is controlled by controlling the exciting current of the linear solenoid valve 72 of the clamping pressure control circuit 64 in accordance with the belt clamping pressure calculated in step S3. Controls the hydraulic pressure of the cylinder. Strictly speaking, this pressure regulation control is the accelerator operation amount θ._ACCIn addition to the gear ratio γ, the oil temperature T of the hydraulic circuit₀And hydraulic pressure P₀It is done using information such as. As described above, the frictional force of the transmission belt 48 of the continuously variable transmission 18 is changed as needed to take a necessary and sufficient value according to the road surface condition.
[0029]
Thus, according to the present embodiment, the reverse input torque T from the travel path_LThe belt clamping pressure as small as possible adapted to the road surface condition is calculated on the basis of the vehicle speed V of the vehicle that changes in accordance with the speed ratio γ of the continuously variable transmission 18, and the driving frictional force corresponding to the belt clamping pressure. The continuously variable transmission 18 can be controlled to be driven via the input torque T_INIs a continuously variable transmission for a vehicle that reduces power loss as much as possible by employing a necessary and sufficient frictional force that does not cause slippage between the transmission belt 48 and the variable pulleys 42 and 46 when the transmission belt 48 is relatively small. A machine control device can be provided.
[0030]
Further, the theoretical value Ft (T_INThe margin value C (V, γ) to be added to the vehicle speed V and the gear ratio γ, and the margin value C (V calculated by the margin value calculation unit 80). , Γ) to calculate a necessary and sufficient belt clamping pressure 82, and the continuously variable transmission 18 is driven via the belt clamping pressure calculated by the belt clamping pressure calculation means 82. Since the belt clamping pressure control means 84 is controlled in this manner, the belt clamping pressure theory is a lower limit value of the belt clamping pressure that does not cause slippage between the transmission belt 48 and the variable pulleys 42 and 46. Value Ft (T_IN) Is added with the smallest possible margin value C (V, γ) calculated by the margin value calculating means 80, so that the belt clamping pressure calculating means 82 calculates a necessary and sufficient belt clamping pressure. There is an advantage that the continuously variable transmission 18 can be controlled to be driven by the belt clamping pressure control means 84 through the belt clamping pressure.
[0031]
In addition, the belt clamping pressure calculating means 82 is a theoretical value Ft (T_IN) Is a basic value Fb (T_IN) And the theoretical value Ft (T_IN) To the value obtained by adding the margin value C (V, γ), and the greater one is calculated as the necessary and sufficient belt clamping pressure._INIs relatively large, the basic value Fb (T_IN) Is relatively small, the theoretical value Ft (T_IN) Is added to the margin value C (V, γ) as the belt clamping pressure, so that the basic value Fb (T_INThere is an advantage that a necessary and sufficient belt clamping pressure corresponding to the driving state of the continuously variable transmission 18 is calculated while ensuring the above values.
[0032]
Further, the theoretical value Ft (T_IN) And the basic value Fb (T_IN) Is the input torque T to the continuously variable transmission 18._INTherefore, the theoretical value Ft (T) of the belt clamping pressure, which is the lower limit value of the belt clamping pressure that does not cause slippage between the transmission belt 48 and the variable pulleys 42 and 46._IN) And the corresponding basic value Fb (T of the belt clamping pressure)_IN) Is centrally determined.
[0033]
As mentioned above, although the suitable Example of this invention was described in detail based on drawing, this invention is not limited to this, Furthermore, it implements in another aspect.
[0034]
For example, although not particularly mentioned in the above-described embodiments, the driving power source may be various types such as an internal combustion engine such as a gasoline engine or a diesel engine that operates by combustion of fuel, or an electric motor that operates by electric energy. A power source is appropriately employed.
[0035]
The continuously variable transmission 18 is a belt-type continuously variable transmission having an input-side variable pulley and an output-side variable pulley with variable effective diameters, and a transmission belt wound around these variable pulleys. Any other type of continuously variable transmission, such as a toroidal continuously variable transmission, may be used as long as it is a continuously variable transmission that can transmit power and control the frictional force through frictional force. Absent.
[0036]
In the continuously variable transmission 18, the frictional force such as the belt clamping pressure of the transmission belt 48 is controlled by hydraulic control such as a hydraulic cylinder. However, the frictional force is controlled by torque control of the electric motor. It is also possible to adopt various modes.
[0037]
Further, the belt clamping pressure calculating means 82 is configured to generate a basic value Fb (T_IN) And the theoretical value Ft (T_IN) And the value obtained by adding the margin value C (V, γ) as needed, and the larger one is calculated as the necessary and sufficient belt clamping pressure._INIn the range of 100 Nm or less, the theoretical value Ft (T_IN) To which the margin value C (V, γ) is added may be adopted as the belt clamping pressure.
[0038]
Although not exemplified one by one, the present invention is implemented with various modifications within the scope not departing from the gist thereof.
[Brief description of the drawings]
FIG. 1 is a skeleton diagram of a vehicle drive device to which the present invention is applied.
2 is a block diagram illustrating a control system of a continuously variable transmission in the vehicle drive device of FIG. 1; FIG.
FIG. 3 is a circuit diagram showing a specific example of a clamping pressure control circuit provided in the controller of FIG. 2;
4 is a target rotational speed N in the shift control of the continuously variable transmission of FIG. 1;_AIMIt is a figure which shows an example of the shift map used when calculating | requiring.
FIG. 5 is a block diagram for explaining functions related to control of belt clamping pressure provided in the controller of FIG. 2;
6 is a graph showing the relationship between input torque and belt clamping pressure used for controlling the continuously variable transmission of FIG. 1; FIG.
7 is a table showing an example of a V, γ-C matrix stored in the controller of FIG. 2;
FIG. 8 is a graph showing an example of the relationship between the vehicle speed of the vehicle and the road surface input torque.
FIG. 9 is a graph showing an example of a relationship between a gear ratio of a continuously variable transmission and road surface input torque.
10 is a flowchart illustrating specific contents of signal processing executed by each function of FIG. 5;
FIG. 11 is a graph showing the relationship between input torque and belt clamping pressure used for controlling a conventional continuously variable transmission.
[Explanation of symbols]
12: Engine (power source)
18: Continuously variable transmission
24: Drive wheel
80: margin value calculation means
82: Belt clamping pressure calculation means (friction force calculation means)
84: Belt clamping pressure control means (friction force control means)
C (V, γ): margin value
Fb (T_IN): Basic value of belt clamping pressure (Basic value of driving friction force)
Ft (T_IN): Theoretical value of belt clamping pressure (theoretical value of driving frictional force)
T_IN: Input torque
V: Vehicle speed
γ: Gear ratio

Claims (3)

A control device for a continuously variable transmission that is disposed in a power transmission path between a driving power source and driving wheels in a vehicle and that can transmit power through frictional force and control the frictional force,
A margin value calculation for calculating a margin value to be added to the theoretical value of the driving friction force for driving the continuously variable transmission according to the vehicle speed and the gear ratio so that the margin value increases as the vehicle speed increases. Means,
Friction force calculating means for calculating the driving friction force using the margin value calculated by the margin value calculating means;
Friction force control means for controlling to drive the continuously variable transmission via the driving friction force calculated by the friction force calculation means;
And it is one having the control device for a vehicle continuously variable transmission according to claim. The frictional force calculating means compares a basic value of the driving frictional force determined to be always larger than the theoretical value of the driving frictional force and a value obtained by adding the margin value to the theoretical value of the driving frictional force. The control device for a continuously variable transmission for a vehicle according to claim 1 , wherein the larger one is calculated as the driving frictional force. 3. The control device for a continuously variable transmission for a vehicle according to claim 2 , wherein the theoretical value and the basic value of the driving frictional force are determined according to an input torque to the continuously variable transmission.

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