JP4025054B2 - Method and apparatus for controlling continuously variable transmission - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a control method and apparatus for a continuously variable transmission mounted on an automobile.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a transmission is provided in a path for transmitting the rotational driving force of an engine, which is a prime mover of an automobile, to wheels. The transmission is provided to convert the output of the engine to the wheel by converting the rotational speed and torque. As a transmission, there are a multistage type that is switched by a driver's manual operation, and a transmission that is switched by automatic control. Further, the gear ratio can be continuously controlled, and a continuously variable transmission called CVT from Continuously Variable Transmission is also used. When a continuously variable transmission is used, it becomes possible to improve exhaust gas and fuel consumption by making full use of engine characteristics. As a continuously variable transmission for a vehicle, a fluid type or a mechanical type is used, and a belt type is used as the mechanical type.
[0003]
FIG. 9 shows a schematic power system of an automobile using the belt-driven continuously variable transmission 1. The continuously variable transmission 1 receives the rotational output of the engine 2 through the torque converter 3 and the forward / reverse clutch 4. The output from the continuously variable transmission 1 is transmitted to wheels 6 serving as drive wheels via a transmission mechanism 5. In the continuously variable transmission 1, a belt 10 is stretched between an input shaft pulley 11 and an output shaft pulley 12 to transmit driving force. The input shaft pulley 11 is attached to the input shaft 13 and has a movable side wheel 14 and a fixed side wheel 15 that sandwich the belt 10. The output shaft pulley 12 is attached to the output shaft 16 and has a movable side wheel 17 and a fixed side wheel 18 that sandwich the belt 10. The movable side wheels 14, 17 and the fixed side wheels 15, 18 are inclined so that the inner side surfaces sandwiching the belt 10 facing each other are narrow in the radial direction and wide in the radial direction. Further, in the movable side wheels 14 and 17, the inner surface can be moved closer to or away from the fixed side wheels 15 and 18 to change the distance between the inner surfaces. The belt 10 has increased radial rigidity so that the belt 10 is pushed outward in the radial direction when the distance between the movable side wheels 14 and 17 and the fixed side wheels 15 and 18 decreases. In order to increase the rigidity, for example, plate members having a predetermined cross-sectional shape are arranged side by side.
[0004]
FIG. 10 shows a schematic cross-sectional configuration of the input shaft pulley 11 of FIG. An oil passage 19 is formed inside the input shaft 13, and hydraulic oil can be guided to the pressurizing chamber 20 formed between the movable member 14 a and the fixed member 14 b of the movable side wheel 14. When the hydraulic pressure in the pressurizing chamber 20 is increased, the movable member 14a is pushed out toward the fixed side wheel 15, the distance between the surface of the movable member 14a and the surface of the fixed side wheel 15 is narrowed, and the belt 10 follows the slope. And pushed outward. That is, the diameter of the portion where the input shaft pulley 11 transmits the driving force to the belt 10 is increased. The output shaft pulley 12 has basically the same configuration as the input shaft pulley 11. Since the length of the belt 10 is constant, when the pressure on the movable side wheel 17 is weakened on the output shaft pulley 12 side, the belt 10 moves radially inward along the slope. As a result, the diameter of the portion that transmits the driving force from the belt 10 to the output shaft pulley 12 is reduced. The gear ratio increases between the input shaft 13 and the fixed shaft 16. When the hydraulic pressure in the pressurizing chamber 20 decreases, the diameter of the portion where the input shaft pulley 11 transmits the driving force to the belt 10 decreases, and the diameter of the portion where the driving force is transmitted from the belt 10 to the output shaft pulley 12 increases. Thus, the gear ratio becomes small.
[0005]
Therefore, in the belt-driven continuously variable transmission 1 as shown in FIG. 9, the gear ratio is controlled by changing the substantial diameter of the pulley that drives the belt 10 when the hydraulic oil enters and exits the input shaft pulley 11. be able to. Further, in the output shaft pulley 12, the hydraulic pressure for narrowing the belt 10 may be controlled so that torque transmission can be effectively performed by the belt 10.
[0006]
[Problems to be solved by the invention]
The continuously variable transmission 1 as shown in FIG. 9 controls so that the hydraulic pressure on the input shaft pulley 11 side is weakened when the traveling speed of the vehicle is low, the substantial diameter is reduced, and the gear ratio is increased. If the hydraulic pressure is too weak due to the structure of the continuously variable transmission 1, the hydraulic oil flows out from the pressurizing chamber 20, the pressure sandwiching the belt 10 is weakened, and the belt 10 is bent. For this reason, when it is determined that the vehicle is stopped, a slight pressure is applied to the input shaft pulley 11 in order to prevent the belt 10 from being bent. When the belt 10 is bent, the belt slip easily occurs when the driving force is transmitted from the input shaft pulley 11 to the belt 10 or the driving force is transmitted from the belt 10 to the output shaft pulley 12. Transmission loss will increase.
[0007]
However, the current speed detection method cannot distinguish between a state where the vehicle is completely stopped and a state where the vehicle is moving at a low speed of, for example, 5 km / h or less. When it is determined that the vehicle is stopped when the vehicle is in a low speed state and pressure is applied to the input shaft pulley 11 to prevent the belt 10 from bending as described above, the pressure applied to the pulley is low. Even if it exists, if the state where pressure is applied continues for a long time, the belt 10 is pushed outward in the radial direction, the gear ratio becomes small, and it becomes substantially the same as when shifting up to the high gear side. If the belt 10 is shifted to the high gear side by the input shaft pulley 11 and is substantially shifted up, the driving force is insufficient when accelerating from the low speed state to the high speed side.
[0008]
If the vehicle is in a completely stopped state, the phenomenon of shifting up does not occur even when pressure is applied to the input shaft pulley 11.
[0009]
  An object of the present invention is to provide a control method and apparatus for a continuously variable transmission that can appropriately secure driving force during acceleration while preventing belt slip at low vehicle speeds.
[0010]
[Means for Solving the Problems]
  The present invention is provided in a rotational driving force transmission path from a prime mover of a vehicle to wheels, a belt is stretched between an input shaft pulley and an output shaft pulley, and the ratio of the diameter of the portion where the belt is hooked is determined as the ratio between the input shaft and the output shaft. In the control method of a continuously variable transmission that can change step by step with a shaft,
  In a low vehicle speed state where the vehicle speed is lower than a predetermined reference low speed, the input shaft pulley is controlled so that the pressure to pinch the belt increases and decreases alternately.And
  The control in which the pressure for pinching the belt is alternately increased and decreased is controlled such that when a predetermined delay time elapses, the input shaft pulley continues the pressure for pinching the belt while the pressure for pinching the belt increases. SwitchThis is a control method for a continuously variable transmission.
[0011]
  According to the present invention, the continuously variable transmission is provided in the rotational driving force transmission path from the prime mover of the vehicle to the wheels, the belt is stretched between the input shaft pulley and the output shaft pulley, The gear ratio can be changed steplessly by changing the ratio of the diameters between the input shaft and the output shaft. When the vehicle speed is lower than the standard low vehicle speed, the belt is controlled so that the pressure that pinches the belt increases and weakens alternately. Therefore, the high gear that becomes a problem with the control that only increases the pressure that pinches the belt. Shifting to the side is less likely to occur, and the driving force when accelerating can be ensured appropriately. Since it is not the control which makes the pressure which pinches | interposes a belt weaken, it can prevent that a belt bends and slips.
  Further, after the delay time has elapsed, the control is changed so that the pressure at which the input shaft pulley pinches the belt is continued in a state in which the pressure at which the belt is pinched increases, so that the belt can be reliably prevented from bending.
[0012]
  The present inventionIs provided in the rotational driving force transmission path from the motor to the wheels of the vehicle, the belt is stretched between the input shaft pulley and the output shaft pulley, and the ratio of the diameter of the portion where the belt is hung is determined between the input shaft and the output shaft. In the control method of the continuously variable transmission that can change the gear ratio steplessly by changing
  In a low vehicle speed state in which the vehicle speed is lower than a predetermined reference low speed, the input shaft pulley is controlled to alternately repeat the state in which the pressure to pinch the belt is increased and the state in which the pressure is weakened,
  Control that alternately repeats the state in which the pressure sandwiching the belt is increased and the state in which the pressure is decreased is detected that the vehicle has stopped.And the control to continue the pressure with which the input shaft pulley pinches the belt while the pressure with which the belt is pinched increases.It is characterized byA control method for a continuously variable transmission..
[0013]
  According to the present invention,The continuously variable transmission is provided in the rotational driving force transmission path from the motor to the wheels of the vehicle, and a belt is stretched between the input shaft pulley and the output shaft pulley, and the ratio of the diameter of the portion where the belt is engaged is determined by the input shaft. And the output shaft, the gear ratio can be changed steplessly. When the vehicle speed is lower than the standard low vehicle speed, the belt is controlled so that the pressure that pinches the belt increases and weakens alternately. Therefore, the high gear that becomes a problem with the control that only increases the pressure that pinches the belt. Shifting to the side is less likely to occur, and the driving force when accelerating can be ensured appropriately. Since it is not the control which makes the pressure which pinches | interposes a belt weaken, it can prevent that a belt bends and slips.
  Also, when the vehicle stops, the control is changed so that the pressure at which the input shaft pulley pinches the belt is continued in a state in which the pressure at which the belt is pinched increases, thus reliably preventing the belt from bending.be able to.
[0014]
Further, in the present invention, the duration of the state in which the pressure sandwiching the belt is increased or decreased is the temperature of the hydraulic oil for controlling the continuously variable transmission, the opening of the accelerator pedal, the opening of the throttle valve, the output torque of the prime mover, It is characterized by being switched by at least one factor of a group of factors consisting of input torque to the input shaft pulley or a gear ratio.
[0015]
According to the present invention, the change in viscosity due to the temperature difference of the hydraulic oil for controlling the continuously variable transmission, the depression state of the accelerator pedal, the degree of opening of the throttle, the output torque of the engine, the input torque to the continuously variable transmission, Depending on factors such as the gear ratio of the stepped transmission, the duration of the state in which the pressure pinching the belt is increased or decreased is changed, so that belt slippage is prevented at low vehicle speeds and the driving force during acceleration is made appropriate. Control can be performed reliably.
[0016]
  The pressure for pinching the belt is switched according to a factor for switching the duration time during which the pressure for pinching the belt increases or decreases.It is characterized by.
[0024]
The present invention also detects the slope of the change in the vehicle speed,
At least one parameter of the reference low speed, the pressure, the duration, or the delay time is corrected based on the detected slope of the vehicle speed.
[0025]
According to the present invention, by detecting the inclination of the change in the vehicle speed, the deceleration corresponding to the inclination is known, and it is possible to distinguish between a sudden stop with a large inclination or a gentle stop with a small inclination. Since at least one parameter of the reference low speed, pressure, duration, or delay time is corrected according to the distinction, appropriate control can be performed.
[0026]
Further, the present invention is based on the hydraulic oil outflow characteristics in the continuously variable transmission,
At least one parameter of the reference low speed, the pressure, the duration, or the delay time is corrected.
[0027]
  According to the present invention, at least one parameter of the reference low speed, the pressure, the duration, or the delay time is set according to characteristics such as a flow rate and pressure at which hydraulic fluid flows out from the pressurizing chamber of the continuously variable transmission. Therefore, control suitable for the continuously variable transmission to be controlled can be performed.
  Further, the present invention is provided in a rotational driving force transmission path from a motor to a wheel of a vehicle, a belt is stretched between an input shaft pulley and an output shaft pulley, and a ratio of diameters of portions where the belt is hung is defined as an input shaft. In the control device for a continuously variable transmission that can be changed steplessly by changing it with the output shaft,
  In a low vehicle speed state in which the vehicle speed is lower than a predetermined reference low speed, the input shaft pulley is controlled to alternately repeat the state in which the pressure to pinch the belt is increased and the state in which the pressure is weakened,
  The control in which the pressure for pinching the belt is alternately increased and decreased is controlled such that when a predetermined delay time elapses, the input shaft pulley continues the pressure for pinching the belt while the pressure for pinching the belt increases. A control device for a continuously variable transmission characterized by switching.
  Further, the present invention is provided in a rotational driving force transmission path from a motor to a wheel of a vehicle, a belt is stretched between an input shaft pulley and an output shaft pulley, and a ratio of diameters of portions where the belt is hung is defined as an input shaft. In the control device for a continuously variable transmission that can be changed steplessly by changing it with the output shaft,
  In a low vehicle speed state in which the vehicle speed is lower than a predetermined reference low speed, the input shaft pulley is controlled to alternately repeat the state in which the pressure to pinch the belt is increased and the state in which the pressure is weakened,
  The control in which the pressure to pinch the belt is alternately increased and weakened is repeated, and when the vehicle is detected to stop, the pressure at which the input shaft pulley pinches the belt continues with the pressure to pinch the belt intensified. The control device for the continuously variable transmission is characterized in that the control is switched to control.
  In addition, parameters such as duration, pressure, reference low speed, etc. are continuously variable to which this control is applied.MachineIf control is performed according to characteristics (characteristics such as pressure and flow rate at which hydraulic oil flows out from the pressurizing chamber), more appropriate control is achieved.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic system configuration for controlling a continuously variable transmission according to an embodiment of the present invention. The continuously variable transmission 21 is mounted on a vehicle and is provided in a path for transmitting the output of the engine 22 as a prime mover to the wheels 26. A driving force is transmitted from the engine 22 to the continuously variable transmission 21 through a configuration equivalent to the torque converter 3 and the forward / reverse clutch 4 shown in FIG. The continuously variable transmission 21 converts the rotational speed and driving torque of the driving force in accordance with the gear ratio, and outputs it to drive the wheels 26 and the like.
[0029]
The continuously variable transmission 21 of the present embodiment is equivalent to the continuously variable transmission 1 of FIG. 9, and the belt 30 is stretched between the input shaft pulley 31 and the output shaft pulley 32 to transmit the driving force. Is called. The input shaft pulley 31 is attached to the input shaft 33 and has a movable side wheel 34 and a fixed side wheel 35 that sandwich the belt 30. The output shaft pulley 32 has a movable side wheel 37 and a fixed side wheel 38 that are attached to the output shaft 36 and sandwich the belt 30. The movable side wheels 34 and 37 and the fixed side wheels 35 and 38 face each other and sandwich the belt 30. Each inner side surface is inclined so that the interval between the inner side surfaces facing each other is narrower in the radial direction and wider in the radial direction. Further, in the movable side wheels 34 and 47, as in FIG. 10, the inner surface can be moved closer to or away from the fixed side wheels 35 and 38 to change the distance between the inner surfaces.
[0030]
For controlling the continuously variable transmission 21, pressure control means 40 is provided. The pressure control means 40 controls the pressure of the hydraulic oil sent to the input shaft pulley 31 and the output shaft pulley 32 via the hydraulic valves 41 and 42, respectively. Shift control for the input shaft pulley 31 is performed by controlling the hydraulic valve 41 from the shift control means 43 via the pressure control means 40. Further, the belt narrow pressure hydraulic control for the output shaft pulley 32 is performed by controlling the hydraulic valve 42 from the shift control means 43.
In the pressure control means 40 of this embodiment, the speed determination means 45 for inputting the vehicle speed, which is the traveling speed of the vehicle measured by the vehicle speedometer 44, determines that the vehicle speed is a low speed of about several km / h or less, for example. Sometimes, the hydraulic pressure for narrowing the belt 30 with the input shaft pulley 31 is controlled via the hydraulic valves 41 and 42. The pressure control means 40, the shift control means 43, and the speed determination means 45 are realized by program control of a microcomputer, and are mounted on a vehicle as an electronic control unit that is abbreviated as ECU from the Electronic Control Unit, or a part thereof. The
[0031]
A timer 50 is connected to the pressure control means 40, and information about time can be obtained. Outputs from the oil temperature gauge 51, the accelerator pedal opening sensor 52, the throttle opening sensor 53, the engine torque sensor 54, and the input shaft torque sensor 55 are also input to the pressure control means 40, respectively.
[0032]
FIG. 2 shows a pressure control procedure in the embodiment of FIG. Control is started from step a0, and in step a1, the speed determination means 45 determines whether or not the vehicle speed is a low vehicle speed equal to or lower than the reference low vehicle speed. When it is determined that the vehicle speed exceeds the reference low vehicle speed, normal control, that is, gear ratio control on the input shaft pulley 31 side and narrow pressure hydraulic control on the output shaft pulley 32 side are performed in step a2. Step a1 and step a2 are repeated until it is determined at step a1 that the vehicle speed is lower than the low vehicle speed. When it is determined in step a1 that the vehicle speed is equal to or lower than the low vehicle speed, the process proceeds to step a3, where pressure is increased to increase the hydraulic oil pressure. In step a4, a fixed duration is set in the timer 50 and waits for the duration to elapse. If a certain continuation time elapses in step a4, the pressure increase is finished in step a5, and further a lapse of a certain continuation time is waited in step a6. In step a7, it is determined whether or not the vehicle is stopped. When it is determined that the vehicle is not stopped, the process returns to step a1. When it is determined in step a7 that the vehicle is completely stopped, the control is terminated in step a8.
[0033]
The determination of the complete stop of the vehicle is made, for example, when the operation lever of the automatic transmission is operated to the P range for parking, or when the operation lever is operated to the N range of the neutral position and the brake pedal is depressed. It can be considered to be performed when a state in which the vehicle speed indicates 0 is detected.
[0034]
FIG. 3 shows an example of control according to the present embodiment. At time t0 when the vehicle speed decreases and becomes equal to or lower than a reference low vehicle speed of 5 km / h, for example, the hydraulic pressure of the input shaft pulley 31 is increased and the pressure sandwiching the belt 30 is increased. At time t1 when a certain duration has elapsed, the pressure is decreased. When increasing the pressure, control is performed to send hydraulic oil. When the pressure is decreased, the control oil is not controlled and includes the operation of causing the hydraulic oil to flow out and the pressure to decrease. Further, the pressure is increased at time t2 when a certain duration has elapsed. Thereafter, the control of decreasing the pressure at time t3 and increasing the pressure at time t4 is repeated. The duration for increasing the pressure and the duration for decreasing the pressure can be the same or different.
[0035]
That is, the continuously variable transmission 21 according to the present embodiment is provided in a rotational driving force transmission path from the engine 22 that is a prime mover of the vehicle to the wheels 26, and the belt 30 is hung between the input shaft pulley 31 and the output shaft pulley 32. The ratio of the diameter of the portion on which the belt 30 is passed is changed between the input shaft 33 and the output shaft 36, and the gear ratio can be changed steplessly. The pressure control means 40 is configured such that the input shaft pulley 31 sandwiches the belt 30 in a low vehicle speed state where the vehicle speed is lower than a reference low speed determined in advance, for example, about 5 km / h, such as 5 km / h. The pressure is controlled to alternately repeat the increasing state and the decreasing state. As a result, the shift up to the high gear side, which is a problem in the control that only increases the pressure sandwiching the belt 30, is less likely to occur. Since it is not the control which only weakens the pressure which pinches | interposes the belt 30, it can also prevent that the belt 30 bends and a slip arises.
[0036]
By continuing the state of increasing the pressure sandwiching the belt 30 for a predetermined duration, it is possible to reliably prevent the belt 30 from slipping. By continuing the state of weakening the pressure sandwiching the belt 30 for a predetermined duration, it is possible to reliably prevent the belt 30 from shifting up to the high gear side.
[0037]
This duration includes the temperature of the hydraulic fluid for controlling the continuously variable transmission 21, the opening degree of the accelerator pedal of the vehicle, the opening degree of the throttle of the engine 22, the output torque of the engine 22, the input torque to the input shaft pulley 31, Alternatively, the switching can be performed by at least one factor in the group of factors including the gear ratio. Viscosity change due to temperature difference of hydraulic oil for controlling the continuously variable transmission 21, accelerator pedal depression state, throttle opening, output torque of the engine 22, input torque to the continuously variable transmission 21, continuously variable transmission Depending on factors such as the gear ratio of the machine 21, the duration of the state in which the pressure sandwiching the belt 30 is increased or decreased is changed, so that belt slippage is prevented at low vehicle speeds and the driving force during acceleration is made appropriate. Control can be performed reliably.
[0038]
The duration time can also be set as a two-dimensional map interpolation value based on two factors selected from the aforementioned group of factors. If the duration time is set as a two-dimensional map interpolation value based on two factors, the pressure of the belt 30 can be controlled by appropriately reflecting the two factors.
[0039]
Further, the pressure sandwiching the belt 30 can be switched according to a factor for switching the duration time. If not only the duration for increasing or decreasing the pressure sandwiching the belt 30 but also the pressure is switched, more appropriate control can be performed according to the factor.
[0040]
If parameters such as duration, pressure, and reference low speed are controlled according to the characteristics of the continuously variable transmission 21 to which this control is applied (characteristics such as pressure and flow rate at which hydraulic oil flows out from the pressurizing chamber) Furthermore, it becomes appropriate control.
[0041]
FIG. 4 shows a schematic system configuration for controlling a continuously variable transmission according to another embodiment of the present invention. In this embodiment, parts corresponding to those of the embodiment of FIG. 1 are denoted by the same reference numerals, and redundant description is omitted. In the present embodiment, a pressure control means 60 is provided for controlling the continuously variable transmission 21. The pressure control means 60 is the same as the pressure control means 40 of FIG. 1 in controlling the pressure of the hydraulic oil fed to the input shaft pulley 31 and the output shaft pulley 32 via the hydraulic valves 41 and 42, respectively. It is mounted on the vehicle as an ECU. A timer 50 is connected to the pressure control means 60, and together with an oil temperature gauge 51, an accelerator pedal opening sensor 52, a throttle opening degree sensor 53, and an engine torque sensor 54, a water temperature gauge 61, an outside air temperature gauge 62, and an engine speed meter. The outputs from 63 are also input.
[0042]
FIG. 5 shows a pressure control procedure in the embodiment of FIG. Control is started from step b0, and in step b1, it is determined by the speed determining means 45 whether or not the vehicle speed is a low vehicle speed equal to or lower than the reference low vehicle speed. When it is determined that the vehicle speed exceeds the reference low vehicle speed, normal control, that is, transmission ratio control on the input shaft pulley 31 side and narrow pressure hydraulic control on the output shaft pulley 32 side are performed in step b2. Step b1 and step b2 are repeated until it is determined at step b1 that the vehicle speed is lower than the low vehicle speed. If it is determined in step b1 that the vehicle speed is equal to or lower than the low vehicle speed, the process proceeds to step b3, where the timer 50 starts the delay time counting operation. In step b4, it is determined whether or not the delay time has elapsed. When it is determined that the time has not elapsed, the process proceeds to step b5 to determine whether or not the vehicle speed is in a low vehicle speed state. While the low vehicle speed state continues, step b4 and step b5 are repeated. When it is determined in step b5 that the vehicle speed is not low, for example, when the vehicle speed is increased again, in step b6, the delay time measurement by the timer 50 is stopped, and the normal shift control in step b2 is started. When it is determined in step b4 that the low vehicle speed has continued and the delay time has elapsed, in step b7, pressure is increased to increase the pressure sandwiching the belt 30, and the control is terminated in step b8.
[0043]
FIG. 6 shows an example of control according to the present embodiment. The timer 50 starts to measure the delay time at time t10 when the vehicle speed decreases and becomes equal to or lower than the reference low vehicle speed of 5 km / h, for example. If the low vehicle speed state continues until time t11 when the delay time elapses, the hydraulic pressure of the input shaft pulley 31 is increased after time t11, and the pressure sandwiching the belt 30 is increased.
[0044]
That is, in this embodiment, when the predetermined delay time corresponding to the delay time set in the timer 50 elapses after the vehicle speed becomes lower than the predetermined reference low speed, the input shaft pulley 31 pinches the belt 30. Controls to increase pressure. Since the pressure for sandwiching the belt 30 is controlled so as to increase after a predetermined delay time elapses, a shift up to the high gear side, which is a problem, is less likely to occur due to the control that only increases the pressure for sandwiching the belt 30. Since the pressure sandwiching the belt 30 is increased after the delay time, the belt 30 can be prevented from being bent and slipping.
[0045]
The delay time set in the timer 50 includes the temperature of the hydraulic oil for controlling the continuously variable transmission 21, the temperature of the cooling water of the engine 22 as the prime mover, the temperature of the outside air, the opening degree of the accelerator pedal, the opening degree of the throttle, It is preferable that the switching is performed according to at least one factor selected from the group of factors including the rotational speed region of the engine 22 that is the prime mover and the output torque of the engine 22 that is the prime mover. Viscosity change due to temperature difference of hydraulic oil for control of continuously variable transmission 21, temperature rise state based on coolant temperature of engine 22, intake temperature of engine 22 depending on outside air temperature, accelerator pedal depression state, Depending on factors such as the degree of throttle opening, the rotational speed range to which the rotational speed of the engine 22 belongs, the output torque of the engine 22 and the like, the delay time until the pressure pinching the belt 30 is increased, so the belt slips at low vehicle speeds. It is possible to reliably perform control that prevents the driving force at the time of acceleration and makes it appropriate.
[0046]
The delay time can also be switched according to a plurality of factors selected from the aforementioned group of factors. If the delay time is switched by a combination of a plurality of factors, the delay time can be switched until the pressure sandwiching the belt 30 is increased by appropriately reflecting the plurality of factors.
[0047]
The reference low speed, which is a reference for determining the vehicle speed by the speed determining means 45, is the temperature of the hydraulic oil for controlling the continuously variable transmission 21, the temperature of the coolant of the engine 22, the temperature of the outside air, the opening degree of the accelerator pedal, the throttle May be switched by a combination of at least one factor or a plurality of factors of the opening degree, the rotational speed region of the engine 22, or the output torque of the engine 22. According to these factors, the reference low vehicle speed, which is a reference for the vehicle speed for judging whether or not to increase the pressure sandwiching the belt 30, is changed, so that the belt is prevented from slipping and the driving force during acceleration is controlled appropriately. , You will be able to do it more reliably.
[0048]
Further, if the delay time is controlled in accordance with the characteristics of the continuously variable transmission 21 to which this control is applied (characteristics such as pressure and flow rate at which hydraulic oil flows out from the pressurizing chamber), as in the case of the parameters described above, it is more appropriate. Control.
[0049]
FIG. 7 shows an example of pressure control of hydraulic oil supplied to a continuously variable transmission, which is performed in still another embodiment of the present invention. In the present embodiment, for example, from time t20 when the vehicle speed is equal to or lower than the reference low vehicle speed of 5 km / h, the control in which the hydraulic pressure increases for the time ta and decreases for the time tb is repeated as in the embodiment of FIG. As a result, the hydraulic pressure decreases from time t21 after time ta has elapsed from time t20, and further increases at time t22 when time tb elapses. In the present embodiment, as in the embodiment of FIG. 4, when the delay time tc elapses from the time t20 when the vehicle speed becomes equal to or lower than the reference low vehicle speed, the high hydraulic pressure is maintained.
[0050]
The control of the present embodiment performs the control to repeat the state of high hydraulic pressure and low hydraulic pressure as in the control of the embodiment of FIG. 1, and the hydraulic pressure when a predetermined delay time tc elapses as in the embodiment of FIG. It will hold the high state. In this way, since the two complement each other by combining the controls of the two embodiments,
tb> ta
Also, with respect to the delay time tc, the delay time t11-t10 in FIG.
t11-t10 <tc
It can be. As a result, it is possible to more reliably prevent the belt from being bent or shifted to the high gear side.
[0051]
FIG. 8 shows that the gradient of the change in vehicle speed should be taken into account in the control performed in each embodiment of the present invention. By detecting the inclination of the change in the vehicle speed, it is possible to distinguish between a sudden stop and a gentle stop. In a sudden stop, the vehicle speed is stopped in a short time after the vehicle speed becomes lower than the reference low speed, and in a gradual stop, it takes a long time to stop, so the continuous duration of high oil pressure and low oil pressure, oil pressure, delay time, It is necessary for more appropriate control to correct the reference low speed itself.
[0052]
【The invention's effect】
  As described above, according to the present invention, when the vehicle speed is in a low vehicle speed state lower than the reference low vehicle speed, the pressure to pinch the belt with the input shaft pulley of the continuously variable transmission is alternately repeated between the increasing state and the decreasing state. Therefore, it is possible to prevent the belt from being bent and slipping, while making it difficult to shift up to the high gear side.Further, after the delay time has elapsed, the control is changed so that the pressure at which the input shaft pulley pinches the belt is continued in a state in which the pressure at which the belt is pinched increases, so that the belt can be reliably prevented from bending.
[0053]
  Also according to the invention,Until the vehicle stops, the state in which the pressure sandwiching the belt is increased and the state in which the pressure is decreased are alternately repeated to prevent the belt from slipping while preventing the shift to the high gear side. Also, when the vehicle stops, the control is changed so that the pressure at which the input shaft pulley pinches the belt is continued in a state in which the pressure at which the belt is pinched increases, thus reliably preventing the belt from bending.be able to.
[0054]
  Also according to the invention,Change in viscosity due to temperature difference of hydraulic oil for continuously variable transmission control, accelerator pedal depression, throttle opening, engine output torque, input torque to continuously variable transmission, gear ratio of continuously variable transmission Depending on factors such as, the duration of the state in which the pressure pinching the belt is increased or decreased is changed, so that belt slippage is prevented at low vehicle speeds and the driving force during acceleration is controlled appropriately.be able to.
[0055]
Further, according to the present invention, not only the duration of increasing or decreasing the pressure but also the pressure sandwiching the belt is switched, so that more appropriate control can be performed.
[0056]
Further, according to the present invention, when the vehicle speed becomes low, the control is repeated so that the high pressure state continues after the control that the pressure across the belt is increased and decreased is repeated, so that the shift to the high gear side is performed. And bending of the belt can be reliably prevented.
[0060]
Further, according to the present invention, it is possible to distinguish a deceleration state such as a sudden stop or a gentle stop by detecting the inclination of the change in the vehicle speed, and among the reference low speed, pressure, duration, or delay time Since at least one parameter is corrected, appropriate control can be performed according to the deceleration state.
[0061]
Further, according to the present invention, at least one parameter of the reference low speed, pressure, duration, or delay time is corrected according to the characteristic of the hydraulic oil flowing out from the pressurizing chamber of the continuously variable transmission. Thus, it is possible to perform control suitable for the continuously variable transmission to be controlled.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic system configuration for controlling a continuously variable transmission 21 according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a control procedure of FIG. 1;
FIG. 3 is a time chart showing an example of pressure control in FIG. 1;
FIG. 4 is a block diagram showing a schematic system configuration for controlling the continuously variable transmission 21 according to another embodiment of the present invention.
FIG. 5 is a flowchart showing a control procedure of FIG. 4;
6 is a time chart showing an example of pressure control in FIG. 4;
FIG. 7 is a time chart showing an example of control according to still another embodiment of the present invention.
FIG. 8 is a time chart showing that the inclination of the change in vehicle speed should be taken into account in each embodiment of the present invention.
FIG. 9 is a block diagram showing a schematic configuration of a conventional vehicle driving force transmission system using a continuously variable transmission.
10 is a cross-sectional view showing a schematic configuration of an input shaft pulley 11 of the continuously variable transmission 1 of FIG. 7;
[Explanation of symbols]
21 continuously variable transmission
22 engine
26 wheels
30 belts
31 Input shaft pulley
32 Output shaft pulley
33 Input shaft
34, 37 Movable side wheel
36 Output shaft
40, 60 Pressure control means
41, 42 Hydraulic valve
43 Shift control means
44 Speedometer
45 Speed judging means
50 timer
51 Oil thermometer
52 Accelerator pedal opening sensor
53 Throttle opening sensor
54 Engine torque sensor
55 Input shaft torque sensor
61 Water thermometer
62 Outside temperature thermometer
63 Engine speed meter

Claims (8)

It is provided in the rotational driving force transmission path from the prime mover of the vehicle to the wheel, a belt is stretched between the input shaft pulley and the output shaft pulley, and the ratio of the diameter of the portion where the belt is engaged changes between the input shaft and the output shaft In the control method of a continuously variable transmission that can change the gear ratio steplessly,
In a low vehicle speed state in which the vehicle speed is lower than a predetermined reference low speed, the input shaft pulley is controlled to alternately repeat the state in which the pressure to pinch the belt is increased and the state in which the pressure is weakened,
The control in which the pressure for pinching the belt is alternately increased and decreased is controlled such that when a predetermined delay time elapses, the input shaft pulley continues the pressure for pinching the belt while the pressure for pinching the belt increases. A control method for a continuously variable transmission, characterized by switching. It is provided in the rotational driving force transmission path from the prime mover of the vehicle to the wheel, a belt is stretched between the input shaft pulley and the output shaft pulley, and the ratio of the diameter of the portion where the belt is engaged changes between the input shaft and the output shaft In the control method of a continuously variable transmission that can change the gear ratio steplessly,
In a low vehicle speed state in which the vehicle speed is lower than a predetermined reference low speed, the input shaft pulley is controlled to alternately repeat the state in which the pressure to pinch the belt is increased and the state in which the pressure is weakened,
The control in which the pressure to pinch the belt is alternately increased and weakened is repeated, and when the vehicle is detected to stop, the pressure at which the input shaft pulley pinches the belt continues with the pressure to pinch the belt intensified. A control method for a continuously variable transmission, wherein the control is switched to control.   The duration in which the pressure across the belt increases or decreases is the temperature of the hydraulic oil for controlling the continuously variable transmission, the opening of the accelerator pedal, the opening of the throttle valve, the output torque of the prime mover, and the input shaft pulley. 3. The continuously variable transmission control method according to claim 1, wherein the control is switched by at least one of a group of factors including an input torque or a gear ratio.   4. The continuously variable transmission control method according to claim 3, wherein the pressure for pinching the belt is switched according to a factor for switching a duration of a state in which the pressure for pinching the belt increases or decreases. Detecting the slope of the change in vehicle speed,
5. The method according to claim 3 , wherein at least one parameter of the reference low speed, the pressure, the duration, or the delay time is corrected based on a detected slope of the vehicle speed. Control method of step transmission. Based on hydraulic oil outflow characteristics in the continuously variable transmission,
The reference low speed, the pressure, the duration, or the least one parameter also among the delay time, the control of the continuously variable transmission according to claim 3 or 4 or 5, characterized in that to correct Method. It is provided in the rotational driving force transmission path from the prime mover of the vehicle to the wheel, a belt is stretched between the input shaft pulley and the output shaft pulley, and the ratio of the diameter of the portion where the belt is engaged changes between the input shaft and the output shaft In a control device for a continuously variable transmission that can change the gear ratio steplessly,
In a low vehicle speed state in which the vehicle speed is lower than a predetermined reference low speed, the input shaft pulley is controlled to alternately repeat the state in which the pressure to pinch the belt is increased and the state in which the pressure is weakened,
The control in which the pressure for pinching the belt is alternately increased and decreased is controlled such that when a predetermined delay time elapses, the input shaft pulley continues the pressure for pinching the belt while the pressure for pinching the belt increases. control device for a continuously variable transmission you wherein the switching. It is provided in the rotational driving force transmission path from the prime mover of the vehicle to the wheel, a belt is stretched between the input shaft pulley and the output shaft pulley, and the ratio of the diameter of the portion where the belt is engaged changes between the input shaft and the output shaft In a control device for a continuously variable transmission that can change the gear ratio steplessly,
In a low vehicle speed state in which the vehicle speed is lower than a predetermined reference low speed, the input shaft pulley is controlled to alternately repeat the state in which the pressure to pinch the belt is increased and the state in which the pressure is weakened,
The control in which the pressure to pinch the belt is alternately increased and weakened is repeated, and when the vehicle is detected to stop, the pressure at which the input shaft pulley pinches the belt continues with the pressure to pinch the belt intensified. control device for a continuously variable transmission you characterized by switching the control to be.

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