JP4411858B2 - Control device for continuously variable transmission - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a continuously variable transmission capable of continuously changing a gear ratio, and more particularly to a control device for optimizing a clamping pressure for setting a torque capacity of a continuously variable transmission. .
[0002]
[Prior art]
The belt-type continuously variable transmission and the traction-type continuously variable transmission transmit torque using the frictional force between the belt and the pulley and the shearing force of the traction oil between the disk and the roller. Therefore, the torque capacity of these continuously variable transmissions is set according to the pressure acting on the location where the torque is transmitted.
[0003]
The above-mentioned pressure in a continuously variable transmission is referred to as pinching pressure. Increasing the pinching pressure can increase the torque capacity and avoid slipping, but on the other hand, more power than necessary to generate high pressure. There are inconveniences such as consumption or reduction in power transmission efficiency. Therefore, in general, the clamping pressure is set as low as possible within a range in which unintended slip does not occur.
[0004]
For example, in a vehicle equipped with a continuously variable transmission, the engine speed can be controlled by the continuously variable transmission to improve fuel efficiency. In order to improve the transmission efficiency as much as possible, the clamping pressure is controlled to be set as low as possible within a range where no slip occurs. For that purpose, it is necessary to detect the pressure at which slip starts (that is, the slip limit pressure), and conventionally, slip is detected by various methods, and the slip limit pressure is detected.
[0005]
As a device for detecting the slip, Patent Document 1 compares the actual speed ratio change rate with the theoretical speed ratio change rate, and if the actual speed ratio change rate is larger than the theoretical speed ratio change rate, the slip is generated. An apparatus is described which is configured to detect and increase the line pressure (the original pressure of the entire hydraulic apparatus that controls the transmission) based on the detection result.
[0006]
Patent Document 2 describes a method for determining a slip limit by changing a pressure-bonding force when conditions regarding a transmitted force, a speed, a transmission ratio, or a combination thereof are at least substantially constant.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 6-11022 (Abstract)
[Patent Document 2]
JP 2001-12593 A (Claims 1, 2, 6, 7)
[0008]
[Problems to be solved by the invention]
The theoretical gear ratio change rate described in the above-mentioned Patent Document 1 represents the tendency of change in the gear ratio up to the current time point. When belt slip occurs, the tendency of change in the gear ratio continues. As a result, there is a difference between the actual gear ratio change rate and the theoretical gear ratio change rate, and slip is detected by the comparison. Therefore, the slip is detected based on the state of the so-called past gear ratio before the current time. The same slip detection can be performed by estimating the current gear ratio and its changing speed based on the past gear ratio, and comparing the estimated value with the actual value.
[0009]
However, it is common to detect the slippage of a continuously variable transmission while the vehicle on which the continuously variable transmission is running is running. In this case, acceleration / deceleration is slightly caused by the road surface condition or the vehicle flow condition. Is done. If such acceleration / deceleration occurs, if slip is detected by comparison with values obtained from past data such as the above estimated values, a change in the gear ratio due to shift may be erroneously determined as slippage. There is.
[0010]
The present invention has been made paying attention to the above technical problem, and an object of the present invention is to provide a control device capable of accurately determining or detecting slipping and limit clamping pressure.
[0011]
[Means for Solving the Problem and Action]
  In order to achieve the above object, the present inventionIf the current gear ratio or gear ratio change speed is estimated from the previous gear ratio or gear ratio change speed, and slip is judged based on the estimated value, there is noWhen the required amount of downshift for the step transmission is large, the slip determination is not performed. More specifically, the invention of claim 1 is a gear shift prior to the current time point.Ratio or speed ratio change speed estimated based on the current speed changeEstimated value of speed ratio or gear ratio change speed and current gear ratio or speed change speedThe actual value of degree andIn the control device for a continuously variable transmission that determines slip by comparing the above, the estimation is performed when the required downshift amount for increasing the transmission ratio of the continuously variable transmission is large.For comparison between the actual value and the valueIt is a control device characterized by comprising slip determination stopping means for preventing the determination of slip based on.
[0012]
  Therefore, in the invention of claim 1, the past speed change is performed.Ratio and gear ratio change speedOn the basis of this, an estimated value of the gear ratio and the gear ratio changing speed is obtained, and the estimated value is compared with the current gear ratio and the gear ratio changing speed (that is, their actual values) to determine the slip of the continuously variable transmission. Is determined. If the downshift amount in the process of obtaining the estimated value or comparing the estimated value and the actual value or the downshift required amount that causes the downshift is large, the above estimation is performed. Slip determination based on the value is stopped. As a result, it is possible to avoid erroneously determining the change in the gear ratio and the gear ratio change speed accompanying the downshift as slipping, and the slip judgment accuracy is improved.
[0013]
  The invention of claim 2In a continuously variable transmission control device for determining slip by comparing an estimated value of a gear ratio or a gear ratio change speed based on a gear ratio before the current time point with a gear ratio or a gear ratio change speed at the current time point A slip determination stopping means for preventing the determination of slip based on the estimated value when a required downshift amount for increasing the transmission ratio of the continuously variable transmission is large;A slip determination means for determining the slip by reducing a clamping pressure for setting a torque capacity of the continuously variable transmission, a clamping pressure increasing means for gradually increasing the clamping pressure after the determination of the slip, and the slip Input torque control means for gradually reducing the input torque to the continuously variable transmission based on the establishment of the determination and then gradually increasing the input torque to complete the return of the input torque almost simultaneously with the convergence of the slip. It is the control apparatus characterized by the above.
[0014]
  Therefore, in the invention of claim 2,Based on the past gear ratio, an estimated value of the gear ratio and the gear ratio change speed is obtained, and the estimated value is compared with the current gear ratio and the gear ratio change speed (that is, their actual values). The slip of the continuously variable transmission is determined. If the downshift amount in the process of obtaining the estimated value or comparing the estimated value and the actual value or the downshift required amount that causes the downshift is large, the above estimation is performed. Slip determination based on the value is stopped. As a result, it is possible to avoid erroneously determining the change in the gear ratio and the gear ratio change speed accompanying the downshift as slipping, and the slip judgment accuracy is improved. Also pinchedWhen slippage due to a decrease in pressure is determined and the slip determination is satisfied, the clamping pressure is restored, the input torque is decreased once, and then gradually increased, and at the same time as the convergence of the slip is decreased. Return of the input torque is completed. As a result, a shock at the time of converging the slip generated by reducing the clamping pressure is prevented.
[0015]
Further, the invention of claim 3 is the invention of claim 2, further comprising limit clamping pressure detecting means for obtaining a limit clamping pressure that balances the input torque based on the clamping pressure at the time when the restoration of the input torque is completed. It is the control apparatus characterized by having.
[0016]
Therefore, in the invention of claim 3, the limit clamping pressure that matches the input torque is obtained based on the restored input torque. As a result, the limit clamping pressure is detected while preventing a shock.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described based on specific examples. First, an example of a drive system including a continuously variable transmission targeted by the present invention will be described. FIG. 3 schematically shows a drive mechanism including a belt type continuously variable transmission 1, and the continuously variable transmission. 1 is connected to a power source 5 via a forward / reverse switching mechanism 2 and a fluid transmission mechanism 4 with a lock-up clutch 3.
[0022]
The power source 5 is composed of an internal combustion engine, or an internal combustion engine and an electric motor, or an electric motor. In the following description, the power source 5 is referred to as the engine 5. The fluid transmission mechanism 4 has, for example, a configuration similar to that of a conventional torque converter, and includes a pump impeller rotated by the engine 5, a turbine runner disposed so as to face the pump impeller, and a stator disposed therebetween. The turbine runner is rotated by supplying a spiral flow of fluid generated by the pump impeller to the turbine runner, and the torque is transmitted.
[0023]
In such torque transmission through the fluid, inevitable slip occurs between the pump impeller and the turbine runner, and this causes a reduction in power transmission efficiency. Therefore, the input member such as the pump impeller and the turbine runner A lock-up clutch 3 that directly connects an output side member such as the above is provided. The lock-up clutch 3 is configured to be controlled by hydraulic pressure, and is controlled to a fully engaged state, a fully released state, and a slip state that is an intermediate state between them, and the slip rotation speed can be appropriately controlled. It has become.
[0024]
The forward / reverse switching mechanism 2 is a mechanism that is employed when the rotational direction of the engine 5 is limited to one direction, and outputs the input torque as it is or reversely outputs it. It is configured. In the example shown in FIG. 3, a double pinion type planetary gear mechanism is employed as the forward / reverse switching mechanism 2. That is, a ring gear 7 is arranged concentrically with the sun gear 6, and a pinion gear 8 meshed with the sun gear 6 and the pinion gear 8 and another pinion gear 9 meshed with the ring gear 7 are arranged between the sun gear 6 and the ring gear 7. The pinion gears 8 and 9 are held by the carrier 10 so as to rotate and revolve freely. A forward clutch 11 that integrally connects two rotating elements (specifically, the sun gear 6 and the carrier 10) is provided, and the direction of the torque that is output by selectively fixing the ring gear 7 There is provided a reverse brake 12 that reverses.
[0025]
The continuously variable transmission 1 has the same configuration as a conventionally known belt-type continuously variable transmission, and each of a driving pulley 13 and a driven pulley 14 arranged in parallel to each other includes a fixed sheave, a hydraulic type The movable sheave is moved back and forth in the axial direction by the actuators 15 and 16. Therefore, the groove width of each pulley 13 and 14 is changed by moving the movable sheave in the axial direction, and accordingly, the winding radius of the belt 17 wound around each pulley 13 and 14 (the effective diameter of the pulleys 13 and 14). ) Changes continuously, and the gear ratio changes steplessly. The drive pulley 13 is connected to a carrier 10 that is an output element in the forward / reverse switching mechanism 2.
[0026]
The hydraulic actuator 16 in the driven pulley 14 is supplied with hydraulic pressure (line pressure or its correction pressure) according to the torque input to the continuously variable transmission 1 via a hydraulic pump and a hydraulic control device (not shown). Yes. Therefore, each sheave in the driven pulley 14 holds the belt 17 so that tension is applied to the belt 17, and a holding pressure (contact pressure) between the pulleys 13, 14 and the belt 17 is ensured. . On the other hand, the hydraulic actuator 15 in the drive pulley 13 is supplied with pressure oil corresponding to the speed ratio to be set, and is set to a groove width (effective diameter or winding diameter) corresponding to the target speed ratio. It has become.
[0027]
The driven pulley 14 is connected to a differential 19 through a gear pair 18, and torque is output from the differential 19 to driving wheels 20. Therefore, in the above drive mechanism, the lockup clutch 3 and the continuously variable transmission 1 are arranged in series between the engine 5 and the drive wheels 20.
[0028]
Various sensors are provided in order to detect the operation state (running state) of the vehicle on which the continuously variable transmission 1 and the engine 5 are mounted. That is, a turbine rotation speed sensor 21 that detects an input rotation speed (rotation speed of the turbine runner) to the continuously variable transmission 1 and outputs a signal, and an input rotation speed that detects the rotation speed of the drive pulley 13 and outputs a signal. A sensor 22, an output rotation speed sensor 23 that detects the rotation speed of the driven pulley 14 and outputs a signal, and a hydraulic pressure sensor 24 that detects the pressure of the hydraulic actuator 16 on the driven pulley 14 side for setting the belt clamping pressure are provided. ing. Although not specifically shown, an accelerator opening sensor that detects a depression amount of the accelerator pedal and outputs a signal, a throttle opening sensor that detects a throttle valve opening and outputs a signal, and a brake pedal are depressed. A brake sensor or the like that outputs a signal in case is provided.
[0029]
A transmission is used to control the engagement / release of the forward clutch 11 and the reverse brake 12, the control of the clamping force of the belt 17, the control of the transmission ratio, and the control of the lockup clutch 3. An electronic control device (CVT-ECU) 25 is provided. The electronic control unit 25 is configured mainly by a microcomputer as an example, performs calculations according to a predetermined program based on input data and data stored in advance, and various states such as forward, reverse, or neutral, Further, it is configured to execute control such as setting of a required clamping pressure, setting of a gear ratio, engagement / release of the lock-up clutch 3, and slip rotation speed.
[0030]
Here, an example of data (signal) input to the transmission electronic control unit 25 is as follows: a signal of the input rotation speed (input rotation speed) Nin of the continuously variable transmission 1 and an output of the continuously variable transmission 1. A signal of the rotational speed (output rotational speed) No is input from the corresponding sensor. An engine electronic control unit (E / G-ECU) 26 that controls the engine 5 receives an engine speed Ne signal, an engine (E / G) load signal, and an accelerator pedal (not shown) depression amount. An accelerator opening signal is input.
[0031]
According to the continuously variable transmission 1, the engine speed, which is the input speed, can be controlled steplessly (in other words, continuously), so that the fuel efficiency of a vehicle equipped with the engine speed can be improved. For example, the target driving force is obtained based on the required driving amount represented by the accelerator opening and the vehicle speed, and the target output necessary to obtain the target driving force is obtained based on the target driving force and the vehicle speed. The engine speed for obtaining the target output with the optimum fuel consumption is obtained based on a map prepared in advance, and the gear ratio is controlled so as to be the engine speed.
[0032]
In order not to impair such an improvement in fuel consumption, the power transmission efficiency in the continuously variable transmission 1 is controlled to a good state. Specifically, the belt clamping pressure as low as possible within a range in which the torque capacity of the continuously variable transmission 1, that is, the belt clamping pressure, can transmit the target torque determined based on the engine torque and the belt 17 does not slip, That is, the clamping pressure is controlled by adding a predetermined pressure to the limit clamping pressure that matches the input torque. Such so-called reduction control of the clamping pressure is executed in a state where the possibility of disturbance is low, specifically, in a state where the vehicle is traveling on a flat good road without particularly accelerating or decelerating, and is traveling on a bad road. In a state where the vehicle is greatly accelerated or decelerated, the clamping pressure is set to a relatively high pressure such as a line pressure.
[0033]
The clamping pressure set by the lowering control is the pressure corresponding to the so-called road surface input that is expected to be input from the output side according to the road surface condition to the limit clamping pressure that can transmit the input torque without causing the slip. The pressure is set to a predetermined pressure that allows for safety against slipping. The predetermined pressure can be set in advance, but the slip limit pressure is influenced by the coefficient of friction and the condition of the lubricating oil, which can change over time, and cannot be uniquely set in advance. Is preferably set.
[0034]
The control device according to the present invention for the continuously variable transmission 1 shown in FIG. 3 is configured to detect slipping and a limit clamping pressure as follows, and to set the clamping pressure based on the detection result. Has been. That is, FIG. 1 is a flowchart showing an example of the control, and this flowchart is repeatedly executed every predetermined short time.
[0035]
In FIG. 1, first, the flag F is determined (step S1). This flag F is set to “1” when the occurrence of slippage in the continuously variable transmission 1 is determined, and is set to “2” when the pinching pressure is increased after the occurrence of slippage is determined. It is a flag and is initially set to “0”.
[0036]
Therefore, at the beginning of the routine of FIG. 1, the determination of “F = 0” is established in step S1, and it is determined whether or not the control precondition is satisfied (step S2). In order to detect the limit clamping pressure, the torque acting on the continuously variable transmission 1 needs to be stable. Therefore, the precondition in step S2 is that the high-speed cruise is being performed while loading on a flat good road. The final correction of the clamping pressure corresponding to the input torque at that time is not completed. The determination of a good road can be made, for example, by the absence of an input determination from the road surface side, and the determination of being in high-speed cruising during road loading is based on, for example, the torque of the driven pulley 14 and the rotational acceleration. I can judge.
[0037]
If a positive determination is made in step S2 because the control precondition is satisfied, a clamping pressure gradual decrease command for gradually decreasing the clamping pressure with a predetermined gradient is output (step S3). This is, for example, control for gradually changing the duty ratio of a duty solenoid valve that controls the hydraulic pressure with respect to the actuator 16 on the driven pulley 14 side.
[0038]
Further, when the control precondition is satisfied, a differential value (or an amount of change from the previous value) of the speed ratio γ is obtained, and the moving average process is performed to calculate the moving average value Δγ (step S4). The average value may be obtained instead of the moving average value. Next, it is determined whether the amount of depression of the accelerator pedal from the current time point to a time before the predetermined time is equal to or less than a predetermined value (step S5). Since the accelerator pedal is depressed to increase the driving force, it is determined in step S5 that a request for increasing the driving force has been made, and in order to increase the driving force, a downshift that lowers the gear ratio is executed. Therefore, in step S5, it is determined whether the downshift amount or the downshift request amount is large or small.
[0039]
If the amount of depression of the accelerator pedal is equal to or less than a predetermined value, the downshift amount or the downshift request amount is small, and if the determination in step S5 is affirmative, the moving average value Δγ before the predetermined time is used. The threshold value for slip determination is corrected (step S6). This is to prevent changes in the gear ratio change speed due to slipping from being taken into the estimated value of the gear ratio change speed, and thus the threshold value is corrected by the average value of the speed ratio change speed in the past specific section. It is good to do.
[0040]
As described above, since data for a predetermined time period or a specific section in the past is used for slip determination, if the gear ratio changes due to a downshift due to an increase in the requested amount of drive, the change in the gear ratio change speed due to the shift and the change due to the slip are It becomes impossible to distinguish. In order to avoid such inconvenience, the determination in step S5 is performed.
[0041]
After the determination threshold value is corrected in step S6, macro slip determination is performed (step S7). In the continuously variable transmission 1, torque is transmitted with inevitable minute slip (so-called micro slip), but slip exceeding this is a cause of mechanical damage of the continuously variable transmission 1 or a decrease in durability. Become. The macro slip is such a slip state. In step S7, the estimated value of the gear ratio and the gear ratio changing speed based on the gear ratio and the gear ratio changing speed before the current time point, and the actual values at the current time point and It is determined whether or not the difference is larger than the corrected threshold value.
[0042]
If a negative determination is made in step S7 because no macro slip has occurred, this routine is temporarily exited. On the contrary, if a positive determination is made in step S7 due to the occurrence of macro slip, that is, if the determination of slip is established, the flag F is set to “1”, and the slip start time and A slip speed is specified (step S8). The slip start time is a time point before the current time point, and the difference between the estimated value of the gear ratio γ or the gear ratio change speed Δγ and one of these actual values is determined in step S7. It is specified as the time when a predetermined value smaller than the value is exceeded. The slip speed is obtained based on the difference between the estimated gear ratio and the actual gear ratio.
[0043]
In addition, when the slip determination is established, a gradual increase command for the clamping pressure (step S9) and an engine torque (Te) down command (step S10) for reducing the input torque are output. The gradual increase of the clamping pressure is control for gradually increasing the clamping pressure with a predetermined gradient. Instead of this gradual increase control of the clamping pressure, control for holding the clamping pressure at the pressure at that time may be executed.
[0044]
Further, the engine torque reduction is executed by, for example, retarding control of the ignition timing of the engine 5, and the amount thereof is an estimated speed change ratio at the time when it is specified that the actual slip has started before the time when the slip determination is established. And a function of a difference Δγ ′ between the estimated speed ratio change speed and the actual speed ratio change speed. Since there is an unavoidable delay in engine torque down control, the engine torque down command may be held for a predetermined time.
[0045]
Next, it is determined whether or not the slip has converged (step S11). Specifically, the determination can be made based on whether or not the difference Δγ ′ between the estimated gear ratio and the actual gear ratio has become equal to or less than a predetermined value set as a criterion.
[0046]
If a negative determination is made in step S11, the slip has not converged, so the routine is temporarily exited. In this case, since the flag F is set to “1”, the determination of “F = 1” is established in step S1, and as a result, the process immediately proceeds to step S9, and the gradually increasing control of the clamping pressure is continued.
[0047]
On the other hand, if the determination is affirmative in step S11 because the slip has converged, the pinching pressure map is corrected (step S12). That is, the clamping pressure to be reduced when the vehicle driving state such as the steady running state is stable is determined as a map according to the input torque and the gear ratio. In step S12, the actual hydraulic pressure at the start of the clamping pressure reduction is determined. The map is corrected with a value obtained by converting the difference from the actual hydraulic pressure when the slip determination is established into a hydraulic pressure command value. More specifically, the necessary clamping pressure is obtained by adding the road surface input-corresponding portion (that is, the pressure that anticipates the predetermined safety) to the limit clamping pressure that is balanced with the pressure at which the slip starts, that is, the input torque, and is mapped according to the necessary clamping pressure Change the value.
[0048]
Since the slip has converged, the return gradient of the clamping pressure is increased (step S13). Further, the flag F is set to “2”, and a command for reducing the engine torque reduction amount to zero is output (step S14). Since the slip has converged, the engine torque down amount obtained by the above-described function becomes zero, but in order to ensure, the command in step S14 is output.
[0049]
  Further, it is determined whether or not the clamping pressure has reached an appropriate level (appropriate pressure) (step S15). If a negative determination is made in step S15, the routine is temporarily exited. In that case, flag F is set to "2"ItSince the determination of “F = 2” is established in step S1, the process immediately proceeds to step S13, and the clamping pressure return control is continued. On the other hand, when a positive determination is made in step S15, the flag F and the temporarily stored (stored) value are cleared to end the control (step S16).
[0050]
If a negative determination is made in step S5 because the amount of depression of the accelerator pedal exceeds a predetermined value, the limit pinching pressure detection control based on the drop of the pinching pressure is stopped at that point. In other words, the stored value is cleared, the return control of the reduced clamping pressure is executed, the clamping pressure corresponding to the input torque region at that time is determined according to the control progress state, and the map value is changed. The
[0051]
That is, the amount of change in the gear ratio increases due to the large amount of downshift required, and this causes an error in slip detection, so control is stopped, but at that time, no slip occurs even if the clamping pressure is reduced. Therefore, the clamping pressure can be reflected in the clamping pressure reduction control in the steady running state or the quasi-steady running state. Therefore, the map value is changed based on the pinching pressure at that time.
[0052]
Changes in the clamping pressure, engine torque, shift command value, etc. when the above control is executed during downshifting are shown in the time chart of FIG. In FIG. 2, the change in the gear ratio and the change speed in the case of upshifting are indicated by broken lines.
[0053]
When the control start condition is satisfied at time A, a command for gradually decreasing the clamping pressure is output, and as a result, the actual clamping pressure starts to decrease after a predetermined time. In the process, a differential value of the gear ratio and a moving average value are obtained. When the accelerator pedal is depressed at a predetermined time B while the pinching pressure is reduced and the accelerator opening is increased, a gear change command is output and the gear ratio changing speed is increased. Control is continued when the change amount ΔPa of the accelerator opening is equal to or less than a predetermined value.
[0054]
When slippage occurs due to a decrease in the clamping pressure (at time C), the actual gear ratio and the actual gear ratio change rate increase, so the difference from these estimated values gradually increases, and the difference exceeds the threshold value. If it exceeds (D point), the determination of slip is established. As a result, a command for gradually increasing the clamping pressure is output, and a command for reducing engine (E / G) torque (input torque) (down command) is output.
[0055]
For example, if the change amount ΔPa of the accelerator opening exceeds a predetermined value during a predetermined time t1 before reaching the time point D, a negative determination is made in step S5 described above, and the control is stopped. Instead of the change amount of the accelerator opening exceeding the predetermined value ΔPa, the current shift command value is greater than or equal to the predetermined value D1 on the downshift side, and the shift command value change amount during the predetermined time t1 is Control may be stopped based on the fact that the value is equal to or greater than the predetermined value ΔD1 on the down side.
[0056]
When engine torque reduction control is executed by ignition timing retardation control, the response is good, so the engine torque immediately decreases, and as a result, the slip tends to converge. That is, the once-increasing gear ratio starts to decrease or stops increasing, and the gear ratio changing speed starts to decrease. Further, the actual clamping pressure starts to increase after a predetermined time from the start of outputting the clamping pressure gradual increase command. This is time E in FIG.
[0057]
Since the actual clamping pressure increases in conjunction with the engine torque reduction control being executed, the slip converges at time F after a predetermined time. As described above, the engine torque reduction amount is set according to the difference between the actual value and the estimated value of the gear ratio or the gear ratio changing speed. When the difference disappears, the engine torque reduction amount becomes zero. In addition, in order to ensure certainty, a command for reducing the engine torque reduction amount to zero is output. As a result, the time when the slip is converged by the gradual increase of the clamping pressure and the time when the engine torque reduction amount becomes zero, that is, the restoration of the clamping pressure and the restoration of the input torque are simultaneously established. At the same time, the gradient of return of the clamping pressure is increased. As a result, the safety against slipping can be quickly improved.
[0058]
According to the control device of the present invention configured to execute the above-described control, the amount of downshift required by the accelerator pedal being depressed in the process of obtaining the estimated value of the gear ratio or the gear ratio change speed. Since the change in the gear ratio due to the downshift becomes a disturbance to the slip determination and causes an erroneous determination, the slip determination control is stopped. In other words, since slip is determined without any erroneous determination factor, slip determination accuracy is improved. Further, by correcting the control amount such as the map value of the clamping pressure based on the clamping pressure at the time of the cancellation, it is possible to improve the accuracy of the so-called reduction control of the clamping pressure.
[0059]
Furthermore, since the slip determination is established and the gradual increase command for the clamping pressure is output, the input torque reduction control is executed at the same time, so that the slip after the slip determination is established can be effectively suppressed or prevented, and the nip pressure is increased. Thus, it is possible to suppress or prevent a shock caused by the inertial force at the time when the slip is converged. Then, by matching the time points of the recovery of the pinching pressure, that is, the convergence of the slip accompanying the increase of the pinching pressure and the return of the input torque, the input torque at that time point and the limit pinching pressure commensurate with it can be obtained. That is, since the engine torque down amount is zero, the engine output torque can be obtained based on the engine load and the like, and the actual clamping pressure at the time when the slip has converged can be known from the output value of the sensor. From the corresponding relationship, the limit clamping pressure can be estimated on the convergence side of the slip.
[0060]
  Here, the relationship between the above specific example and the present invention will be briefly described. The functional means of step S5 described above corresponds to the slip determination stopping means of the present invention, and the functional means of step S7 is the function of the present invention. The functional means in step S9 corresponds to the slip determining means, the clamping pressure increasing means in the present invention, the functional means in step S10 corresponds to the input torque control means in the present invention, and the functional in step S12. The means corresponds to the limit clamping pressure detecting means of the present invention.The
[0061]
Note that the present invention is not limited to the above specific example, and the continuously variable transmission in the present invention may be a toroidal (traction type) continuously variable transmission in addition to the belt-type continuously variable transmission. Further, the present invention can be applied not only to the slip generated by reducing the clamping pressure but also to detecting the slip during the normal operation of the continuously variable transmission. Further, the requested downshift amount in the present invention may be a change amount on the load increase side of the power source, may be a requested amount from a control device that maintains the vehicle speed at a set value, and further, a shift command. It may be the amount of change on the downshift side of the value. The determination of slip in the present invention is a determination of the state of slip, and thus includes not only determination of the start of slip but also determination of a state immediately before the start of slip or a sign of slip.
[0062]
【The invention's effect】
  As explained above, according to the invention of claim 1Change from the gear ratio before the current time point or the speed change speed to the current time point.Obtain an estimate of the speed ratio or speed change ratio, orIs the guessWhen the downshift amount in the process of comparing the constant value with the actual value and the downshift request amount such as the drive request amount that causes the downshift are large, the judgment of slip based on the above estimated value is canceled. Therefore, it is possible to avoid erroneously determining a change in the gear ratio and the gear ratio changing speed associated with the downshift as slipping, thereby improving the slip determination accuracy.
[0063]
  According to the invention of claim 2,The downshift required amount such as the downshift amount in the process of obtaining the estimated value of the gear ratio and the changing speed of the gear ratio, or comparing the estimated value with the actual value, and the requested amount of drive that causes the downshift If it is large, the slip judgment based on the above estimated value is canceled, so that it is possible to avoid erroneously judging the change of the gear ratio and the speed change speed associated with the downshift as slip and improve the slip judgment accuracy. Can also be made smoothSince the return of the input torque is completed almost simultaneously with the convergence of the slip, it is possible to prevent a shock when the slip caused by reducing the clamping pressure is converged.
[0066]
According to the fifth aspect of the present invention, since the clamping pressure reduced to cause the slip is increased with a relatively large gradient after the convergence of the slip, the slip can be prevented from occurring again. At the same time, when the input torque is reduced in order to converge the slip, the input torque can be quickly restored, and as a result, a delay in returning the output torque of the continuously variable transmission can be prevented.
[Brief description of the drawings]
FIG. 1 is a flowchart for explaining an example of control by a control device of the present invention.
FIG. 2 is a time chart when the control of FIG. 1 is executed.
FIG. 3 is a diagram schematically showing an example of a drive mechanism including a continuously variable transmission targeted by the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Continuously variable transmission, 5 ... Engine (power source), 13 ... Drive pulley, 14 ... Driven pulley, 17 ... Belt, 20 ... Drive wheel, 25 ... Electronic control unit for transmission (CVT-ECU), 26 ... Electronic control unit for engine (E / G-ECU).

Claims (3)

The estimated value of the variable speed ratio or gear ratio rate of change of the current time estimated based on the previous gear ratio or speed ratio change rate than the current time point, the actual value of the gear ratio or speed ratio variation speed of the current point in time In a control device for a continuously variable transmission that determines slippage by comparison,
A slip determination stopping means for preventing a slip determination based on a comparison between the estimated value and the actual value when a required downshift amount for increasing the transmission ratio of the continuously variable transmission is large. A control device for a continuously variable transmission. In a control device for a continuously variable transmission that determines slip by comparing an estimated value of a gear ratio or a gear ratio change speed based on a gear ratio before the current time point with a gear ratio or a gear ratio change speed at the current time point,
Slip determination stopping means for preventing the determination of slip based on the estimated value when a required downshift amount for increasing the transmission ratio of the continuously variable transmission is large;
A slippage determination means that determines the slip lowering the clamping pressure to set the torque capacity before Symbol CVT,
Clamping pressure increasing means for gradually increasing the clamping pressure after establishment of the slip determination;
Input torque control means for gradually reducing the input torque for the continuously variable transmission based on the determination of the slip and then gradually increasing the input torque to complete the return of the input torque almost simultaneously with the convergence of the slip. further comprising that has control of the continuously variable transmission you characterized. The continuously variable transmission according to claim 2 , further comprising limit clamping pressure detecting means for obtaining a limit clamping pressure that is balanced with the input torque based on the clamping pressure at the time when the restoration of the input torque is completed. Control device.

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