JP2005195095A - Control device of continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enumerate a learning value most suitable for a driving condition of a continuously variable transmission. <P>SOLUTION: This control device of the continuously variable transmission to learn and correct clamping force in accordance with a learned result by detecting the sliding limiting clamping force and learning a relation of logical clamping force and the sliding limiting clamping force is furnished with a lowering possibility judging means (step S118 and S120) to judge whether it is possible to further lower the clamping force obtained by learning in accordance with the learned result and a re-learning means (step S120) to re-learn the clamping force by the lowering possibility judging means in the case when it is judged possible to lower it. The re-learning means includes a means (step S119) to judge execution of the re-learning in accordance with the learned value which is a relative quantity of the sliding limiting clamping force and the logical clamping force. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control device that controls the clamping pressure of a continuously variable transmission, and more particularly to a device that controls the clamping pressure as low as possible without causing slippage.

  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.

  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.

  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 this purpose, it is necessary to detect the pressure at which slip starts (that is, the slip limit pressure or the limit clamping pressure). Conventionally, slip is detected by various methods, and the slip limit pressure is detected.

For example, Patent Document 1 discloses a transmission having a conical disk pair and a winding transmission node, and the conical disk pair slips by changing a pressing force for sandwiching the winding transmission node. A transmission is described that is configured to determine a limit and adjust the crimping force so as not to exceed the slip limit.
JP 2001-12593 A

  In the invention described in the above-mentioned Patent Document 1, the crimping force of the continuously variable transmission is reduced within a range in which no slip occurs by controlling the crimping force based on the detected slip limit. In addition, the crimping force stores a characteristic field that represents the required crimping force for a specific slip in relation to the rotational speed, torque, gear ratio, and temperature, and is adjusted accordingly. It is going to be done.

  In the conventional method of detecting the slip limit, that is, the limit clamping pressure, for example, the hydraulic pressure is gradually decreased from the hydraulic pressure corresponding to the known crimping force, that is, the clamping pressure, and the hydraulic pressure immediately before the occurrence of the slip is detected as the hydraulic pressure equivalent to the limit clamping pressure. ing. Therefore, the detection result is a differential hydraulic pressure obtained by subtracting the hydraulic pressure equivalent to the critical clamping pressure from the hydraulic pressure equivalent to the theoretical clamping pressure obtained from the input torque when the critical clamping pressure is detected. At this time, as in the invention of Patent Document 1 described above, the detection result of the above-mentioned limit clamping pressure is obtained for each rotation speed, torque, gear ratio, temperature, or friction coefficient between the conical disk pair and the winding transmission node. If a certain differential hydraulic pressure is stored in a characteristic field, that is, a map, the clamping pressure can be accurately set as “theoretical clamping pressure−stored differential hydraulic pressure”.

  However, when the theoretical clamping pressure is low and the centrifugal hydraulic pressure is high, such as when the vehicle is decelerating, the theoretical clamping pressure becomes lower than the limit clamping pressure. Therefore, the differential hydraulic pressure between the theoretical clamping pressure equivalent hydraulic pressure and the limit clamping pressure equivalent hydraulic pressure has a negative value, and an accurate differential hydraulic pressure cannot be obtained.

  In other words, even if the crimping force is lowered and the slip limit is obtained, the desired slip limit state may not occur depending on the running condition, or the slip limit may not be detected accurately due to some disturbance factor. There was a possibility that the pressure-bonding force could not be reduced to improve fuel efficiency.

  The present invention has been made paying attention to the technical problem described above, and detects a state in which the theoretical clamping pressure is higher than the limit clamping pressure, and in such a range, the continuously variable transmission does not slip. It is an object of the present invention to provide a control device that can reduce the clamping pressure as much as possible.

  In order to achieve the above object, the present invention learns the relationship between the theoretical clamping pressure and the slip limit clamping pressure, and starts relearning or detection of the limit clamping pressure based on the learned result. More specifically, the invention of claim 1 detects the slip limit clamping pressure, learns the relationship between the theoretical clamping pressure and the slip limit clamping pressure, and learns and corrects the clamping pressure based on the learned result. In the transmission control device, a reduction possibility determination unit that determines whether or not the pinching pressure obtained by learning can be further reduced based on the learning result, and the pinching pressure by the reduction possibility determination unit. It is a control device characterized by comprising re-learning means for re-learning when it is determined that reduction is possible.

  The invention according to claim 2 is the means according to claim 1, wherein the re-learning means determines that re-learning is executed based on a learning value that is a relative amount between the slip limit holding pressure and the theoretical holding pressure. It is a control device characterized by including.

  The invention according to claim 3 estimates the slip limit clamping pressure, learns the relationship between the theoretical clamping pressure and the estimated slip limit clamping pressure, and learns the clamping pressure obtained by learning based on the learned result. In the control device for the continuously variable transmission to be corrected, the reduction possibility determination means for determining whether or not the clamping pressure obtained by learning can be reduced based on the learning result, and the reduction possibility determination means A control apparatus comprising: a limit clamping pressure detecting unit configured to detect a limit clamping pressure when it is determined that the clamping pressure can be reduced.

  Further, the invention of claim 4 is the invention according to claim 3, wherein the limit clamping pressure detecting means detects the limit clamping pressure based on a learning value that is a relative amount between the estimated slip limit clamping pressure and the theoretical clamping pressure. A control device including means for determining execution.

  According to the first aspect of the present invention, the possibility that the clamping pressure can be reduced is determined based on the relationship between the theoretical clamping pressure and the critical clamping pressure obtained from the estimated input torque, the estimated friction coefficient, and the like. If is high, relearning is performed. In this case, since the clamping pressure can be further reduced, fuel efficiency can be improved. In addition, since the relearning is performed only when the learning value satisfies the predetermined condition, the number of pinch pressure reduction controls accompanying the relearning can be reduced.

  Furthermore, according to the invention of claim 2, the re-learning execution determination is performed based on a learning value that is a relative amount between the sliding clamping pressure and the theoretical clamping pressure. In this case, since the clamping pressure can be further reduced, fuel efficiency can be improved. In addition, since the relearning is performed only when the learning value satisfies the predetermined condition, the number of pinch pressure reduction controls accompanying the relearning can be reduced.

  According to the third aspect of the present invention, the possibility that the clamping pressure can be reduced is determined based on the relationship between the theoretical clamping pressure and the limit clamping pressure. Is done. In this case, since the clamping pressure can be further reduced, fuel efficiency can be improved. Further, since the limit clamping pressure is detected only when the learning value satisfies a predetermined condition, the number of times of clamping pressure reduction control accompanying the detection of the limit clamping pressure can be reduced.

  According to the fourth aspect of the present invention, the execution of the detection of the limit clamping pressure is determined based on the learning value that is the relative amount of the slipping clamping pressure and the theoretical clamping pressure. In this case, since the clamping pressure can be further reduced, fuel efficiency can be improved. Further, since the limit clamping pressure is detected only when the learning value satisfies a predetermined condition, the number of times of clamping pressure reduction control accompanying the detection of the limit clamping pressure can be reduced.

  Next, the present invention will be described based on specific examples. First, an example of a drive system including a power source and a continuously variable transmission targeted in the present invention will be described. FIG. 4 schematically shows an example of a drive system including a belt-type continuously variable transmission 1. 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.

  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 a configuration similar to that of, for example, a conventional torque converter, and includes a pump impeller rotated by the engine 5, a turbine runner disposed to face the pump impeller, and a stator disposed therebetween. The turbine runner is rotated by supplying a spiral flow of fluid generated by a pump impeller to the turbine runner, and torque is transmitted.

  In such torque transmission via 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.

  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. 4, 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 couples the 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.

  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.

  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) corresponding to the target speed ratio. .

  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.

  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, the turbine speed sensor 21 that detects the input speed (the speed of the turbine runner) to the continuously variable transmission 1 and outputs a signal, and the input speed that detects the speed of the drive pulley 13 and outputs the 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.

  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 transmission electronic control unit 25 is configured mainly by a microcomputer as an example, and performs calculations according to a predetermined program based on input data and data stored in advance, and performs various operations such as forward, reverse, or neutral. And the required clamping pressure setting, the gear ratio setting, the engagement / release of the lock-up clutch 3, the slip rotation speed, and the like are executed.

  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 rotation speed (output rotation speed) No is input from the corresponding sensor. An engine electronic control unit (E / G-ECU) 26 for controlling the engine 5 receives a signal of an engine speed Ne, an engine (E / G) load signal, a throttle opening signal, an accelerator pedal (not shown). )), The accelerator opening signal is input.

  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.

  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 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 clamping pressure is as low as possible without causing the belt 17 to slip. It is controlled to become. For example, the belt clamping pressure controls the continuously variable transmission 1 in a so-called unsteady traveling state such as when acceleration / deceleration is performed relatively frequently or when traveling on a rough road with uneven or uneven road surfaces. It is set to a relatively high pressure such as the line pressure that is the total source pressure in the hydraulic system or its correction pressure.

  On the other hand, in steady running conditions such as running on a flat road at a certain speed or above, or in a quasi-steady running condition equivalent to this, the lowest pressure that can transmit input torque without slipping, that is, the limit clamping pressure In order to detect this, the belt clamping pressure is gradually reduced. The belt clamping pressure is set to a belt clamping pressure obtained by adding a predetermined safety factor or a pressure for setting a margin transmission torque for slipping to the detected limit clamping pressure. The belt clamping pressure in the continuously variable transmission is preferably as low as possible within a range where torque can be transmitted without causing slippage.

  In order to detect this critical clamping pressure, the clamping pressure is temporarily reduced to detect slippage, and control is performed to detect the critical clamping pressure, but slipping within a certain region is prevented to prevent excessive slippage. Detection is performed. FIG. 4 is a diagram showing a region where slip detection is performed, and the “limit clamping pressure detection region” on FIG. 4 corresponds to a region where slip detection is possible.

  According to FIG. 4, slip detection is performed within a detection region where the running state is stable. When normal running is performed in this region, the limit clamping pressure becomes smaller than the theoretical clamping pressure, and the detection result of the limit clamping pressure is detected as a difference obtained by subtracting the limit clamping pressure from the theoretical clamping pressure.

  However, when the theoretical clamping pressure is low and the centrifugal hydraulic pressure is high, such as when the vehicle is decelerating, the theoretical clamping pressure becomes lower than the limit clamping pressure even within the detection region. Therefore, the difference between the theoretical clamping pressure and the limit clamping pressure is a negative value.

  In other words, even if the crimping force is lowered to determine the slip limit, the desired slip limit state does not occur depending on the running state, or the slip limit cannot be detected accurately due to some disturbance factor, and an accurate differential oil pressure can be obtained. become unable. In order to detect such a case where the theoretical clamping pressure is smaller than the lower limit clamping pressure, the following control is performed.

  First, it is determined whether or not a control start condition is satisfied (step S101). The control start condition here is during middle-to-high speed cruising, and is a case where all conditions such as not a rough road but a substantially flat road, that is, no sudden change in vehicle speed are satisfied. When the control start condition is not satisfied, a normal clamping pressure is set (step S104).

  When the control start condition is satisfied in step S101, it is determined whether or not the current travel region is an unlearned region (step S102). If a negative determination is made in step S102, that is, if it is not an unlearned region, it is determined that there is already a learning value, and the limiting clamping pressure is calculated using the learning value from the normal clamping pressure, and the clamping pressure is set. (Step S105).

  If the determination in step S102 is affirmative, that is, if it is an unlearned region, it is determined whether or not the limit clamping pressure detection start condition is satisfied (step S103). Here, the limit clamping pressure detection start condition is that the current running state is within the detection region shown in FIG. 4, that the running state is stable, and that the theoretical clamping pressure is greater than the limit clamping pressure. This is the case. Note that if a negative determination is made in step S103, a normal clamping pressure is set (step S104).

  If the determination in step S103 is affirmative, the hydraulic pressure is swept down (step S110). Then, it is determined whether or not the belt has slipped (step S111). If a negative determination is made in step S111, that is, if the belt has not yet slipped, it is determined whether or not the lower limit value of the mechanical hydraulic pressure has been reached (step S131). If a negative determination is made in step S131, that is, if it is determined that the lower limit value of the mechanical hydraulic pressure has not yet been reached, the sweep down is continued (step S110).

  If the determination in step S131 is affirmative, the hydraulic pressure is maintained in that state (step S132), and it is determined whether or not the belt has slipped again in this state (step S133). If a negative determination is made in step S133, that is, if slip is not detected, it is determined whether or not a predetermined time has elapsed with the hydraulic pressure maintained (step S134). If a negative determination is made, the hydraulic pressure is continuously maintained, and the same processing is performed until a predetermined time elapses (steps S132 to S134). For slip detection in step S111 and step S133, for example, a method of comparing the estimated gear ratio during belt slip with an actual gear ratio, a method of monitoring the gear shift speed, or the like can be used as appropriate.

  On the other hand, when a positive determination is made at step S111 or when a positive determination is made at step S133, slip prevention control is performed (step S112). Note that this slip prevention control can be performed by a method of decreasing the engine torque by retarding control or a method of increasing the clamping pressure.

  When the slip prevention control is completed in step S112 or when an affirmative determination is made in step S134, the limit clamping pressure is calculated (step S113). The calculation of the limit clamping pressure is performed by adding the centrifugal oil pressure and the spring force pressing the pulley to the actual hydraulic pressure at the time when the clamping pressure is the lowest or the actual hydraulic pressure at the time of slip detection.

  Further, the method for calculating the slip start time is to store the gear ratio for a predetermined time, estimate the gear ratio when no slip occurs, and the deviation between the estimated gear ratio and the current gear ratio is zero or The time point when the value becomes equal to or less than the predetermined value can be set as the slip start time point.

  When the limit clamping pressure is calculated in step S113, a learning value is calculated (step S114). Here, a value obtained by dividing the limit clamping pressure by the theoretical clamping pressure when the limit clamping pressure is detected is calculated as a learning value.

  When the learning value is calculated in step S114, the hydraulic pressure is increased by a predetermined amount (step S115), and the hydraulic pressure is maintained until a predetermined time elapses (step S116 to step S117).

  Then, the threshold value A is calculated (step S118). The threshold A is stored in advance in a memory in the electronic control device in the form of a map. This is because the appropriate threshold value is affected by the input torque and the friction coefficient between the belt and the sheave, and therefore it is necessary to obtain the threshold value A corresponding to the input torque and the friction coefficient in advance. In step S118, the mapped threshold value is obtained from the current input torque and friction coefficient.

  When the threshold value A is obtained, it is determined whether or not the learning value calculated in step S114 is smaller than the threshold value (step S119). If the determination in step S119 is affirmative, the learning value is stored (step S120), the normal clamping pressure is set based on the learning value (step S121), and this routine is exited.

  On the other hand, if a negative determination is made in step S119, the normal clamping pressure is set without storing the learned value (step S121), and the routine is exited.

  Next, a time-series flow of this control example will be described with reference to a time chart. FIG. 2 is an example of a time chart showing this control example in time series.

  First, the clamping pressure is constant before the control start condition is satisfied (phase 0). Then, when the control start condition is satisfied, the control is started, and the sweep of the hydraulic pressure command is started (corresponding to step S110 at the start of phase 1). Slip detection is always performed during execution of the hydraulic pressure command sweep-down (corresponding to steps S111 to S131 during execution of phase 1).

  When the hydraulic pressure command value reaches the lower limit of lowering without detecting slip (corresponding to step S131 at the start of phase 2), the hydraulic pressure is maintained (corresponding to step S132 during execution of phase 2).

  On the other hand, the actual hydraulic pressure decreases with a delay from the command value, and if no slip occurs during this time, the lower limit clamping pressure is reached (from the end of phase 2 to the start of phase 3; corresponding to step S134). When the actual hydraulic pressure reaches the lower limit clamping pressure, the learning value is calculated and the hydraulic pressure is increased by a predetermined amount (corresponding to step S115, at the start of phase 3). The hydraulic pressure is held for a predetermined time (corresponding to steps S116 to S117 during execution of phase 3). During this time, the threshold value and the learned value are discriminated and the learned value is stored (corresponding to step S116 to step S120 during execution of phase 3), and the normal clamping pressure is set (after phase 4 in step S121). Equivalent).

  The learning value is a value obtained by dividing the limit clamping pressure by the theoretical clamping pressure. Therefore, the smaller the learning value is, the smaller the limit clamping pressure is, which means that there is room for lowering the clamping pressure. Therefore, when a threshold value is set and falls below the threshold value, the learning value is stored assuming that there is room for lowering the clamping pressure. Based on the stored learning value, the holding pressure reduction control is performed.

  That is, relearning is performed when the theoretical clamping pressure is larger than the limit clamping pressure, that is, when the learning value is small. In this case, since the clamping pressure can be further reduced, fuel efficiency can be improved. In addition, since relearning is performed only when the learning value is small, the number of pinch pressure drop controls associated with relearning can be reduced.

In the above embodiment, whether or not to re-learn is determined based on the set threshold,
A learning value may be estimated, and the detection of the limit clamping pressure may be determined based on the estimated learning value. FIG. 3 is a flowchart showing an example of the control.

  First, it is determined whether or not a control start condition is satisfied (step S201). The control start condition here is during middle-to-high speed cruising, and is a case where all conditions such as not a rough road but a substantially flat road, that is, no sudden change in vehicle speed are satisfied. When the control start condition is not satisfied, a normal clamping pressure is set (step S230).

  When the control start condition is satisfied in step S201, it is determined whether or not the current travel region is an unlearned region (step S202). If a negative determination is made in step S202, that is, if it is not an unlearned region, it is determined that there is already a learning value, and the limit clamping pressure is calculated using the learning value from the normal clamping pressure, and the clamping pressure is set. (Step S231).

  If the determination in step S202 is affirmative, that is, if it is an unlearned region, it is determined whether or not the limit clamping pressure detection start condition is satisfied (step S203). Here, the limit clamping pressure detection start condition is that the current running state is within the detection region shown in FIG. 4, that the running state is stable, the lower limit clamping pressure is greater than the limit clamping pressure, etc. This is the case. Note that if a negative determination is made in step S203, a normal clamping pressure is set (step S230).

  If the determination in step S203 is affirmative, an estimated learning value D is calculated (step S204). The estimated learning value D is a value obtained by dividing an estimated limit clamping pressure obtained by adding a spring force for pressing the pulley against the current centrifugal oil pressure and a design value of the minimum oil pressure by the theoretical clamping pressure.

  When the estimated learning value is calculated in step S204, a threshold value B is calculated (step S205). The threshold value B is stored in advance in a memory in the electronic control unit in the form of a map. This is because the appropriate threshold value is influenced by the input torque and the friction coefficient between the belt and the sheave, and therefore it is necessary to obtain the threshold value B corresponding to the input torque and the friction coefficient in advance. Therefore, in this step S205, the mapped threshold value is obtained from the current input torque and friction coefficient.

  When the threshold value B is obtained, it is determined whether or not the estimated learning value calculated in step S204 is smaller than the threshold value (step S206). If the determination in step S206 is affirmative, the hydraulic pressure is swept down (step S207). Then, it is determined whether or not the belt has slipped (step S208). If a negative determination is made in step S208, that is, if the belt has not yet slipped, it is determined whether or not the lower limit value of the mechanical hydraulic pressure has been reached (step S220). If a negative determination is made in step S220, that is, if it is determined that the lower limit value of the mechanical hydraulic pressure has not yet been reached, the sweep down is continued (step S207).

  If the determination in step S220 is affirmative, the hydraulic pressure is maintained in that state (step S221), and it is determined whether or not the belt has slipped again in this state (step S222). If a negative determination is made in step S222, that is, if slip is not detected, it is determined whether or not a predetermined time has elapsed with the hydraulic pressure maintained (step S223). If the determination is negative, the hydraulic pressure is continuously maintained, and the same processing is performed until a predetermined time elapses (steps S221 to S223). For slip detection in step S208 and step S222, for example, a method of comparing the estimated gear ratio with the actual gear ratio, a method of monitoring the gear speed, or the like can be used as appropriate.

  On the other hand, when a positive determination is made in step S208 or when a positive determination is made in step S222, slip prevention control is performed (step S209). For the slip prevention control, a method of retarding the engine to reduce the engine torque, a method of increasing the clamping pressure, or the like can be used.

  When the slip prevention control is completed at step S209 or when an affirmative determination is made at step S223, the limit clamping pressure is calculated (step S210). This limit pinching pressure is calculated by adding the centrifugal oil pressure and the spring force pressing the pulley to the actual oil pressure when the pinching pressure is the lowest or the actual oil pressure at the time of slip detection.

  Further, the method for calculating the slip start time is to store the gear ratio for a predetermined time, estimate the gear ratio when no slip occurs, and the deviation between the estimated gear ratio and the current gear ratio is zero or The time point when the value becomes equal to or less than the predetermined value can be set as the slip start time point.

  When the limit clamping pressure is calculated in step S210, a learning value is calculated (step S211). Here, a value obtained by dividing the limit clamping pressure by the theoretical clamping pressure when the limit clamping pressure is detected is calculated as a learning value.

  When the learning value is calculated in step S211, the hydraulic pressure is increased by a predetermined amount (step S212), and the hydraulic pressure is held until a predetermined time has elapsed (from step S213 to step S214).

  If the predetermined time has elapsed and the determination in step S214 is affirmative, the learning value is stored (step S215), the normal clamping pressure is set based on the learning value (step S216), and the routine is exited. .

  Therefore, when the theoretical clamping pressure is larger than the estimated limit clamping pressure, that is, when the learning value is small, the limit clamping pressure is detected. In this case, since the clamping pressure can be further reduced, fuel efficiency can be improved. In addition, since the limit clamping pressure is detected only when the estimated learning value is large, the number of clamping pressure reduction controls associated with relearning can be reduced.

  Here, the relationship between the above specific example and the present invention will be briefly described. The functional means of steps S118 to S120 correspond to the “decrease possibility judging means” in claim 1, and the functional means of step S120 is This corresponds to “re-learning means” in claim 1. The functional means of step S119 corresponds to “means for determining execution of relearning” in claim 2.

  The functional means in steps S204 to S206 corresponds to the “decrease possibility determination means” in claim 3, and the functional means in step S210 corresponds to “limit clamping pressure detection means” in claim 3. The functional means of step S206 corresponds to “means for determining execution of detection of limit clamping pressure” in claim 4.

  In the present embodiment, the learning value A and the estimated learning value D are values obtained by dividing the limit clamping pressure by the theoretical clamping pressure. However, what is important is that the relative relationship between the limit clamping pressure and the theoretical clamping pressure can be understood. That's fine.

It is a flowchart for demonstrating an example of control by the control apparatus of this invention. It is a time chart for demonstrating an example which calculates a learning value in control by the control apparatus of this invention. It is a flowchart for demonstrating the other example of control by the control apparatus of this invention. It is a figure which shows the area | region which can detect a slip. It is a figure which shows typically an example of the drive system containing the continuously variable transmission made into object by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Continuously variable transmission, 3 ... Lock-up clutch, 5 ... Engine (power source), 13 ... Drive pulley, 14 ... Drive pulley, 15, 16 ... Hydraulic actuator, 17 ... Belt, 20 ... Drive wheel, 25 ... Shift Electronic control unit for machine (CVT-ECU).

Claims (4)

In the control device of the continuously variable transmission that detects the sliding limit clamping pressure, learns the relationship between the theoretical clamping pressure and the sliding limit clamping pressure, and learns and corrects the clamping pressure based on the learned result.
A lower possibility determination means for determining whether or not the clamping pressure obtained by learning can be further reduced based on the learning result;
A control device for a continuously variable transmission, comprising: a re-learning unit that re-learns when it is determined by the reduction possibility determination unit that the pinching pressure can be reduced.   2. The continuously variable transmission according to claim 1, wherein the re-learning means includes means for determining execution of re-learning based on a learning value that is a relative amount of the slip limit holding pressure and the theoretical holding pressure. Machine control device. Control device for continuously variable transmission that estimates slip limit clamping pressure, learns the relationship between theoretical clamping pressure and the estimated slip limit clamping pressure, and learns and corrects the clamping pressure obtained by learning based on the learned result In
A decrease possibility determination means for determining whether or not the clamping pressure obtained by learning can be decreased based on the learning result;
A control device for a continuously variable transmission, comprising: a limit clamping pressure detecting means for detecting a limit clamping pressure when it is determined by the reduction possibility determining means that the clamping pressure can be reduced.   The limit clamping pressure detection means includes means for determining execution of detection of the limit clamping pressure based on a learning value that is a relative amount of the estimated slip limit clamping pressure and the theoretical clamping pressure. 4. The continuously variable transmission control device according to 3.

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